HIDDEN FACTS

IN
SSCE
BIOLOGY

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 © OTUMUDIA PUBLISHERS LIMITED 2021
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ISBN-978–978-980-559-4
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Preface xii
CHAPTER ONE
1.0. SCIENCE OF LIVING THINGS 1
 Meaning of biology ___________________________________________________________________1
 Branches of biology ___________________________________________________________________1
 Scientific methods of investigation or inquiry in science ____________________________________1
 Controlled experiment ________________________________________________________________2
 Usefulness of biology _________________________________________________________________2
CHAPTER TWO
2.0. RECOGNIZING LIVING THINGS 3
 Characteristics of living things ___________________________________________________________3
 Connecting link between living and non-living thing _________________________________________4
 Organization of life ____________________________________________________________________6
 Advantages of complexity in high organisms _______________________________________________9
 Disadvantages of complexity in higher organism ____________________________________________9
CHAPTER THREE
3.0. CLASSIFICATION OF LIVING THINGS 12
 New system of classification ___________________________________________________________ 12
 Kingdom Monera ____________________________________________________________________ 14
 Kingdom Protista ____________________________________________________________________ 15
 Kingdom Fungi ______________________________________________________________________18
 Kingdom Plantae ____________________________________________________________________ 20
- Botanical classification ____________________________________________________________ 20
- Agricultural classification __________________________________________________________24
- Classification of crops according to life cycle ___________________________________________24
 Kingdom Animalia ___________________________________________________________________28
 Revision exercise ____________________________________________________________________42
CHAPTER FOUR
4.0. THE CELL 44
 Cell as a Living Unit of organisms _______________________________________________________44
 Forms in which living things exist _______________________________________________________44
 Cell structure ________________________________________________________________________51
 Cell structures and its functions _________________________________________________________ 51
 Difference between plant and animal cell _________________________________________________ 59
 Revision exercise ____________________________________________________________________ 61
CHAPTER FIVE
5.0. THE CELL AND ITS ENVIRONMENT 62
 Diffusion ___________________________________________________________________________62
 Osmosis ___________________________________________________________________________ 64
 Haemolysis _________________________________________________________________________68
 Plasmolysis, turgidity and flaccidity _____________________________________________________ 69
 Active transport _____________________________________________________________________ 71
 Revision exercise ____________________________________________________________________72
CHAPTER SIX
6.0. NUTRITION 73
 Types of nutrition ____________________________________________________________________73
 Plant Nutrition (Photosynthesis) _________________________________________________________80
 Adaptations of the leaf for photosynthesis _________________________________________________81
 Materials and conditions necessary for photosynthesis _______________________________________ 82
 Micronutrient and macronutrient ________________________________________________________ 89
 Nutrition in mammals _________________________________________________________________92
 Food Test __________________________________________________________________________ 96
 Enzymes __________________________________________________________________________ 103

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CHAPTER SEVEN
7.0. FEEDING MECHANISM AND DIGESTIVE SYSTEM 109
 Modification and mechanisms of feeding in some animals ___________________________________109
 Mechanisms of feeding in some animals _________________________________________________ 109
 Feeding mechanism (II) ______________________________________________________________ 111
 Mammalian teeth ___________________________________________________________________ 117
 Structural description of the tooth ______________________________________________________ 118
 Care of the mammalian teeth __________________________________________________________ 119
 Digestive system ____________________________________________________________________122
 Alimentary canal of an earthworm ______________________________________________________123
 Alimentary canal of grasshopper or cockroach ____________________________________________ 124
 Alimentary canal of a bird ____________________________________________________________ 125
 Differences between the alimentary canal of a bird and grasshopper ___________________________ 125
 Alimentary canal and Digestion of food in man ____________________________________________126
 Caecum and appendix ________________________________________________________________127
 Revision Exercise ___________________________________________________________________131

CHAPTER EIGHT
8.0. TRANSPORT SYSTEM 132
 Need for transportation _______________________________________________________________132
 Materials for transportation ___________________________________________________________ 134
 Transport in man ____________________________________________________________________134
 The mammalian blood _______________________________________________________________ 135
 Functions of blood __________________________________________________________________ 136
 Blood group _______________________________________________________________________ 137
 The heart __________________________________________________________________________142
 The blood vessels ___________________________________________________________________ 143
 Transport in plants __________________________________________________________________ 148
 Structure of vascular bundle ___________________________________________________________148
 Translocation ______________________________________________________________________ 148
 Transpiration _______________________________________________________________________149
 Mechanisms of transportation in higher plants _____________________________________________150
 Absorption of water and minerals ______________________________________________________ 150
 Transport of water in the xylem tissue ___________________________________________________151
 Transport in plants and animals ________________________________________________________ 155
 Major blood vessels in systematic circulation _____________________________________________ 157
CHAPTER NINE
9.0. RESPIRATORY SYSTEM 159
 Stages of respiration _________________________________________________________________159
 Respiratory structures ________________________________________________________________159
 Mechanism of respiration in insects _____________________________________________________160
 Mechanism respiration in fish _________________________________________________________ 160
 Respiratory system in toad ____________________________________________________________161
 Respiratory system in mammals ________________________________________________________162
 Gaseous exchange in lower animals _____________________________________________________163
 Respiratory systems in plants __________________________________________________________167
 Differences between respiration and photosynthesis ________________________________________ 167
 Types of cellular respiration ___________________________________________________________169
 The Kreb’s cycle (citric acid cycle) _____________________________________________________ 169
 Anaerobic respiration ________________________________________________________________172
 Importance of energy (ATP) released during respiration _____________________________________173
 Experiments on respiration ____________________________________________________________175

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CHAPTER TEN
10.0. EXCRETORY SYSTEM 177
 Excretory organs and excretory products of some organisms _________________________________ 177
 Excretory mechanism in protozoan _____________________________________________________ 177
 Excretory system in flat worms ________________________________________________________ 178
 Excretory mechanism in earthworm _____________________________________________________178
 Mechanism of excretion in insects ______________________________________________________178
 Excretory system in mammals _________________________________________________________ 180
 The kidney ________________________________________________________________________ 180
 Nephron __________________________________________________________________________ 181
 Functions of the kidney ______________________________________________________________ 182
 Similarities between the excretory organ of mammal and earthworm ___________________________183
 Differences between the excretory organ of mammal and earthworm___________________________ 183
 Excretion in plants __________________________________________________________________ 188
 Opening of stomata __________________________________________________________________188
 Differences between excretion in flowering plants and excretion in human ______________________188
 Revision Exercise ___________________________________________________________________189
CHAPTER ELEVEN
11.0. REGULATION OF INTERNAL ENVIRONMENTAL (HOMOEOSTASIS) 191
 Homeostasic organs and substances _____________________________________________________191
 The Kidney ________________________________________________________________________191
 Regulatory function of the kidney ______________________________________________________ 192
 Mechanism of excretion by the kidney ___________________________________________________193
 The Liver _________________________________________________________________________ 196
 Regulatory functions of the liver _______________________________________________________ 197
 Disease of the liver __________________________________________________________________197
 The Skin __________________________________________________________________________ 200
 Functions of the skin _________________________________________________________________200
 Care of the mammalian skin ___________________________________________________________202
 Revision Exercise __________________________________________________________________ 204
12.0. NERVOUS CO-ORDINATION 207
 The nervous system _________________________________________________________________ 207
 The fore brain ______________________________________________________________________208
 The olfactory lobe ___________________________________________________________________208
 The mid brain ______________________________________________________________________ 208
 The hind brain ______________________________________________________________________209
 Medulla oblongata __________________________________________________________________ 209
 Spinal cord ________________________________________________________________________ 211
 The Peripheral Nervous System (PNS) __________________________________________________ 213
 The Sympathetic Nervous System (SNS) _________________________________________________213
 The Neurone _______________________________________________________________________215
 Classification of Neuron ______________________________________________________________216
 Ionic Transmission __________________________________________________________________218
 Reflex and voluntary action ___________________________________________________________ 220
CHAPTER THIRTEEN
13.0. ENDOCRINE GLANDS AND THEIR HORMONES 225
 Characteristics of endocrine glands and hormones _________________________________________ 225
 Pituitary gland ______________________________________________________________________226
 Thyroid gland ______________________________________________________________________228
 Adrenal gland ______________________________________________________________________229
 Parathyroid gland ___________________________________________________________________ 230
 The Pancreas (islets of langarhans) _____________________________________________________ 230
 Ovaries ___________________________________________________________________________ 231

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  Ovary - Corpus Luteum ______________________________________________________________ 231
 Testes ____________________________________________________________________________ 232
 Plant hormones _____________________________________________________________________234
 Auxin ____________________________________________________________________________234
 Gibberellins _______________________________________________________________________ 236
 Abscisic acid _______________________________________________________________________236
 Ethane (Ethylene) ___________________________________________________________________237
 Revision Exercise ___________________________________________________________________237
CHAPTER FOURTEEN
14.0. SENSE ORGAN 238
 Organ of smell _____________________________________________________________________ 238
 Organ of taste ______________________________________________________________________ 239
 Skin as a sense organ ________________________________________________________________ 240
 Oran of hearing _____________________________________________________________________241
 Organ of sight ______________________________________________________________________245
 Mechanism of seeing/image formation __________________________________________________ 247
 Defects of the eye ___________________________________________________________________248
 Correction of short sightedness ________________________________________________________ 248
 Short-sightedness (myopia) ___________________________________________________________ 248
 Long-sightedness (hypermetropia) ______________________________________________________249
 Revision Exercise ___________________________________________________________________254
CHAPTER FIFTEEN
15.0. IRRITABILITY (SENSITIVITY) 256
 Types of response ___________________________________________________________________256
 Differences between nastic (sleep) movement and tropism ___________________________________257
 Experiment to demonstrate phototropism using a potted plant ________________________________ 258
 Experiment to demonstrate genotropism using potted plant and klinostat ________________________258
 Experiment to demonstrate hydrotropism ________________________________________________ 259
CHAPTER SIXTEEN
16.0. SUPPORTING TISSUES IN PLANT 262
 Parenchyma tissue __________________________________________________________________ 262
 Xylem ____________________________________________________________________________262
 Phloem ___________________________________________________________________________ 263
 Mechanism of support in plants ________________________________________________________ 264
 Internal structure of a leaf _____________________________________________________________268
 Tissues and supporting system in animals ________________________________________________ 270
 Forms of skeleton (the skeletal material) _________________________________________________270
 Types of skeleton ___________________________________________________________________ 271
 The skull __________________________________________________________________________273
 Bone of the vertebral column __________________________________________________________274
 Atlas vertebrae _____________________________________________________________________ 274
 Normal cervical vertebra _____________________________________________________________ 275
 The caudal vertebrae _________________________________________________________________277
 Summary of the vertebrae features ______________________________________________________278
 Long bones of the appendicular skeleton _________________________________________________282
 Fore limb __________________________________________________________________________282
 Radius and ulna ____________________________________________________________________ 283
 Metacarpals ________________________________________________________________________283
 Phalanges _________________________________________________________________________ 283
 Hind-limbs ________________________________________________________________________ 284
 Tarsal, metatarsals and phalanges ______________________________________________________ 285
 The pelvic girdle ____________________________________________________________________285
 Joints _____________________________________________________________________________288

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  Muscles ___________________________________________________________________________291
 How muscle interact with bones to bring about movement ___________________________________292
 Revision exercise ___________________________________________________________________293
CHAPTER SEVENTEEN
17.0. MOVEMENT 294
 Movement in amoeba ________________________________________________________________294
 Movement in euglena _______________________________________________________________ 295
 Movement in paramecium ____________________________________________________________ 295
 Movement in hydra __________________________________________________________________296
 Movement in earthworm _____________________________________________________________ 296
 Movement in fish ___________________________________________________________________ 297
 Movement in the adult frog or toad _____________________________________________________ 297
 Movement in bird ___________________________________________________________________298
 Movement in mammal _______________________________________________________________ 298
 Walking in man ____________________________________________________________________ 299
 Revision exercise ___________________________________________________________________ 300
CHAPTER EIGHTEEN
18.0. REPRODUCTION 301
 Forms of asexual reproduction _________________________________________________________301
 Organs used by plants for natural vegetative propagation ___________________________________ 302
 Sexual reproduction _________________________________________________________________ 308
 Conjugation _______________________________________________________________________ 308
 Fertilization _______________________________________________________________________308
 Some important points to note on fertilization ____________________________________________308
 Meiosis ___________________________________________________________________________309
 Advantages of sexual reproduction _____________________________________________________ 312
 Disadvantages of sexual reproduction ___________________________________________________ 312
 Reproduction in unicellular organisms and invertebrates ____________________________________ 316
 Reproduction in Spirogyra ____________________________________________________________ 317
 Conjugation in Rhizopus _____________________________________________________________ 318
 Sexual reproduction in paramecium caudatum ____________________________________________ 319
 Reproduction in earthworm ___________________________________________________________ 319
 Metamorphosis in insects _____________________________________________________________320
 Reproduction in cockroach ___________________________________________________________320
 Reproduction in housefly _____________________________________________________________321
 Complete metamorphosis in butterfly ___________________________________________________321
 Complete metamorphosis in mosquito ___________________________________________________322
 Reproduction in snail ________________________________________________________________324
 Reproductive system of vertebrates _____________________________________________________325
 Reproductive systems in reptile ________________________________________________________325
 Reproductive system in fish ___________________________________________________________326
 Reproductive system in birds __________________________________________________________327
 Structure and function of male reproductive system in human ________________________________327
 Structure and function of the female reproductive system in human ____________________________328
 Sperm cell (male gamete) ____________________________________________________________330
 Structure of the egg (ovum) ___________________________________________________________330
 Development of the egg (oogenesis) and menstrual cycle ____________________________________330
 Comparism of reproduction in fish, amphibian, reptiles, birds and mammals ____________________331
 Fertilization _______________________________________________________________________331
 Implantation of the embryo ___________________________________________________________336
 Placenta ________________________________________________________________________336
 Gestation period __________________________________________________________________337
 Test tube babies ____________________________________________________________________338

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  Reproduction in bryophyte and pteridophyte ______________________________________________339
 Life cycle of a bryophyte _____________________________________________________________339
 Life cycle of pteridophyte _____________________________________________________________339
 Reproductive system in flowering plant __________________________________________________340
 Essential and non-essential parts of a flower ______________________________________________340
 Perianth and perianth segment _________________________________________________________341
 Types of ovary______________________________________________________________________343
 Placentation _______________________________________________________________________347
 Pollination in plant __________________________________________________________________349
 Features that aid self-pollination _______________________________________________________349
 Features that aid cross pollination ______________________________________________________349
 Characteristics of insect pollinated flower ________________________________________________351
 Characteristics of wind pollinated flowers ________________________________________________351
 Agents of pollination (pollinators) ______________________________________________________351
 Development of new seed _____________________________________________________________351
 Development of ovule _______________________________________________________________352
 Development of the pollen grain and fertilization in flowering plants ___________________________352
 Development of plant embryo _________________________________________________________357
 Structure of a seed __________________________________________________________________357
 Structure and germination of seed ______________________________________________________358
 Conditions necessary for germination of seed _____________________________________________360
 Fruit _____________________________________________________________________________362
 Types of fruit ______________________________________________________________________363
 Dispersal of seed and fruits ___________________________________________________________365
 Agents of dispersal of seed and fruits ____________________________________________________366
 Reproductive behaviour ______________________________________________________________373
 Types of courtship behaviour in animal __________________________________________________373
CHAPTER NINETEEN
19.0. GROWTH 377
 Aspect of growth ___________________________________________________________________377
 Types of meristems __________________________________________________________________377
 Cell division (Mitosis) _______________________________________________________________377
 Cell enlargement and differentiation ____________________________________________________379
 Patterns of growth ___________________________________________________________________382
 Primary and secondary growth in plants _________________________________________________383
 Factors affecting growth in plants_______________________________________________________383
 Difference between growth in plants and animals __________________________________________383
 Regulation of growth by hormones _____________________________________________________383
 Hormones of importance in plant _______________________________________________________384
 Growth curve (growth curvature) _______________________________________________________384
CHAPTER TWENTY
20.0. BIOLOGY OF HEREDITY (GENETICS) & VARIATION 387
 Characteristics that can be transmitted in man _____________________________________________387
 How characteristics are transmitted _____________________________________________________ 387
 Meaning of some basic terms in genetics _________________________________________________387
 Mendel’s work in genetics ____________________________________________________________ 390
 Dihybrid inheritance _________________________________________________________________391
 Chromosomes: Basis of Heredity _______________________________________________________399
 Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) __________________________________398
 Differences between DNA and RNA ____________________________________________________400
 Similarities between DNA and RNA ____________________________________________________ 400
 Number of chromosomes ____________________________________________________________ _401
 Probability of genetics _______________________________________________________________ 405

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  Application of probability in genetics ___________________________________________________406
 Sex determination in humans__________________________________________________________411
 Blood types ________________________________________________________________________412
 Uses of the knowledge of genetics ______________________________________________________412
 Variations in population ______________________________________________________________422
 Genetic differences __________________________________________________________________423
 Application of variation ______________________________________________________________427
 Revision Exercise ___________________________________________________________________430
CHAPTER TWENTY ONE
21.0. RELEVANCE OF BIOLOGY IN AGRICULTURE 431
 Classification of plants _______________________________________________________________431
 Kingdom plantae____________________________________________________________________431
 Agricultural classification of plants _____________________________________________________431
 Effect of agricultural activities on ecological activities ______________________________________433
 Pest and diseases of agricultural importance ______________________________________________435
 Pest and parasite of farm animals _______________________________________________________435
 Diseases of farm animals _____________________________________________________________438
 Pest and diseases of crops _____________________________________________________________440
 Disease ___________________________________________________________________________ 441
 Some disease of crops ________________________________________________________________441
 Control of pests _____________________________________________________________________442
 Life cycle of pest ___________________________________________________________________443
 Food production and storage __________________________________________________________445
 Population growth and food supply _____________________________________________________447
CHAPTER TWENTY TWO
22.0. MICROORGANISMS AROUND US AND TOWARDS BETTER HEALTH 448
 Group of microorganisms _____________________________________________________________448
 Concept of culturing _________________________________________________________________452
 Identification of microorganisms _______________________________________________________452
 Microorganisms in our bodies and food __________________________________________________453
 Ways and places through which microorganisms enter the body ______________________________454
 Carrier of microorganisms ____________________________________________________________ 454
 Micro-organisms in action ____________________________________________________________455
 Diseases caused by microorganisms _____________________________________________________456
 Towards better health ________________________________________________________________459
 Vectors and their control _____________________________________________________________462
 Life cycle and habit _________________________________________________________________462
 Public health _______________________________________________________________________468
 Health organizations _________________________________________________________________472
 Revision Exercise ___________________________________________________________________474
CHAPTER TWENTY THREE
23.0. ECOLOGY 476
 Basic Ecological Concept _____________________________________________________________476
 Components of an Ecosystem __________________________________________________________478
 Local biotic community or biomes in Nigeria _____________________________________________480
 Major biomes of the world ____________________________________________________________483
 Aquatic habitat (Marine and Estaurine Habitat) ____________________________________________487
 Marine habitat ______________________________________________________________________487
 Estuarine habitat ____________________________________________________________________491
 Fresh water habitat __________________________________________________________________492
 Terrestrial habits (marsh, forest) _______________________________________________________496
 Marsh habitat ______________________________________________________________________496
 Formation of marshes ________________________________________________________________496

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 Forest ____________________________________________________________________________498
 Adaptation of living organisms to forest habitat ___________________________________________499
 Adaptive features of plants in tropical rain forest __________________________________________ 499
 Grass and Arid Habitat _______________________________________________________________502
 Climate factors affecting grassland habitat _______________________________________________502
 Arid land or desert habitat ____________________________________________________________503
 Adaptive features of plants in arid lands _________________________________________________505
 Population studies by sampling method __________________________________________________507
 Factors that affect population __________________________________________________________509
 Ecological factors common to all habitat _________________________________________________513
 Topographical factor or land surface ____________________________________________________515
 Instruments for measuring ecological factors ______________________________________________516
 Ecological Succession _______________________________________________________________519
 Outcome of succession _______________________________________________________________520
 Types of succession _________________________________________________________________521
 Major communities in a plant succession _________________________________________________523
 Process of succession in abandoned farmland _____________________________________________523
 Overcrowding ______________________________________________________________________524
 Population and population density ______________________________________________________524
 Population density __________________________________________________________________525
 Effects of overcrowding ______________________________________________________________525
 Adaptation/measure to avoid overcrowding _______________________________________________525
 Food shortage ______________________________________________________________________527
 Effects of food shortage ______________________________________________________________527
 Differences between competition and succession __________________________________________528
 Factors affecting a population _________________________________________________________529
 Balance in nature ___________________________________________________________________532
 Family planning and birth control ______________________________________________________532
 Functioning ecosystem _______________________________________________________________534
 Trophic level _______________________________________________________________________535
 Food web _________________________________________________________________________539
 Pyramid of number __________________________________________________________________541
 Pyramid of biomass _________________________________________________________________542
 Pyramid of energy __________________________________________________________________543
 Energy transformation in nature ________________________________________________________546
 Energy loss in the ecosystem and biosphere ______________________________________________547
 Application of both laws to ecological phenomena or event __________________________________548
 Nutrient cycling in nature _____________________________________________________________549
 The carbon cycle ____________________________________________________________________550
 Oxygen cycle ______________________________________________________________________552
 Carbon-oxygen balance ______________________________________________________________552
 Water cycle ________________________________________________________________________552
 Nitrogen cycle ______________________________________________________________________554
 Processes of nitrogen cycling __________________________________________________________554
 Decomposition in nature ______________________________________________________________556
 Ecological management ______________________________________________________________557
 Tolerance _________________________________________________________________________562
 Tolerance range ____________________________________________________________________562
 Adaptation ________________________________________________________________________563
 Pollution __________________________________________________________________________571
 Water pollution _____________________________________________________________________572
 Land pollution ______________________________________________________________________572
 Noise pollution _____________________________________________________________________573

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  Conservation of natural resources ______________________________________________________576
 Problems and difficulties of natural resources conservation __________________________________578
 Ways of ensuring the conservation of natural resources _____________________________________578
 Revision Exercise ___________________________________________________________________584
CHAPTER TWENTY FOUR
24.0. EVOLUTION (HISTORY OF LIFE) 585
 Evidence of evolution _______________________________________________________________585
 Adaptive radiation, convergent and divergent evolution _____________________________________586
 Lamark Theory of Organic Evolution ___________________________________________________587
 Darwin’s Theory of Evolution _________________________________________________________587
 Modern Evolutionary Theory __________________________________________________________587
 Formation of a new specie by isolation __________________________________________________588
 The Outcome of Organic Evolution (Adaptation) __________________________________________594
 Structural adaptation for obtaining food __________________________________________________594
 Structural adaptation for protection and defense ___________________________________________595
 Structural adaptation to attract mate _____________________________________________________595
 Structural adaptation to regulate body temperature _________________________________________596
 Structural adaptation in mammals to regulate body temperature _______________________________596
 Structural adaptation in birds to regulate body temperature ___________________________________596
 Structural adaptation for conserving water in plants ________________________________________596
 Structural adaptation for conserving water in animals _______________________________________596
 Adaptive colouration ________________________________________________________________596
 Behavioural adaption ________________________________________________________________597
 Social animals ______________________________________________________________________598
 Revision Exercise ___________________________________________________________________607
CHAPTER TWENTY FIVE
25.0. FIRST AID 609
 First aider _________________________________________________________________________ 609
 First aid kit ________________________________________________________________________ 609
 Component of a first aid kit/box ________________________________________________________609
 Burns and scalds first aid _____________________________________________________________ 609
 Haemorrhage and bleeding ____________________________________________________________609
 First aid for bleeding _________________________________________________________________609
 Fainting ___________________________________________________________________________610
 First aid for fainting _________________________________________________________________ 610
 Bruise ____________________________________________________________________________ 611
 First aid for bruises ________________________________________________________________ _ 611
 Drowning _________________________________________________________________________ 611
 Artificial respiration ________________________________________________________________ 611
 Dislocation _______________________________________________________________________ 611
 First aid for dislocation ______________________________________________________________ 612
 Drug abuse and its effect _____________________________________________________________ 612
 Exercise __________________________________________________________________________613

BIOLOGY PRACTICAL 614

EXERCISE 644
ALTERNATIVE TO PRACTICAL 650
EXERCISE 694

ANSWERS 702

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 Hidden Facts in SSCE Biology covers the entire SSCE Biology Syllabus including Practical
and Alternative to Practical. The notes, examples and exercises were presented in line with the
expectations of the examiners from students and the current trend of the examination syllabus.

The current expectation of the examiners is that the answers should be brief and straight to the
point. However for the point that Hidden Facts in SSCE Biology is a teach – yourself series, many of the
answers to questions are a bit longer. The purpose is to give the average student a clear understanding even
when there is no teacher to guide him/her.

In many cases, additional notes are added to the answers to explain some hidden facts. In some
cases the notes are instructions and warnings that the students need to adhere to, so as not to lose marks.
Furthermore, at the end of each chapter, exercises are provided to enable student test their understanding on
the just concluded concept.

The aspect on Practical Biology addresses the challenges that Students usually face in Biology
Practical or Alternative to Practical Examination, as a result, a well detailed approach involved in practical
works were outlined in this book, backed up with numerous past questions over the years to help buttress the
required concept .

xii
Science of Living Things
Meaning of biology
Biology is a branch of science that involves the study of living things. The term biology is derived from two Greek
words: BIOS and LOGOS. BIOS means life and LOGOS means to study. Therefore, biology is the study of life.

Branches of biology:
Biology has two branches. These are (i) Botany and (ii) zoology
Botany is the study of plant while zoology is the study of animals.

Scientific methods of investigation or inquiry in science.

The scientific method is a systematic approach used to investigate inquiries that arise from observed natural
phenomena. When a biology student observes living phenomena, the student uses his scientific method to reveal the
mysteries behind the natural phenomena.

The scientific method includes the following:

i. Making observations: This means physical observation of something in the environment. For example, when you
look at shoot of plants growing in sheltered area receiving light from one direction, you will observe that the shoot
appears to grow towards the brighter areas of the shelter.

ii. Put forward a possible hypothesis to account for observations: A hypothesis is a scientific or intelligent guess
made by a scientist in order to account for the natural phenomenon.
For example, from your observation above, you can put forward a theory that says “non-woody shoots of plants
respond to light from one direction by growing towards that light”.

iii. Design and conduct experiments to test the hypothesis. For example, take two similar potted bean seedlings and
water them. They should be labeled A and B. Place pot A in a box with a window cut on one side. Light would
reach the shoot from one direction only. Place pot B in an identical situation but on a klinostat (a turn table that
rotates slowly). This will rotate the plant so that each side of the shoot is exposed to light equally. The seedlings in
pot A and pot B should be examined after two days.
a. The potted plant labeled “A” will bend towards the source of light rays.
b. The seedling in pot B will continue to grow vertically.

Klinostat

NB: One part of the boxes has been removed to show plant
iv. Analyse result and draw conclusion: From the above experimental design, non woody shoots of plants respond to
one-sided lighting by growing toward light. The result analysed may be those of several experiment. The
conclusion is then drawn based on the results of the experiments.

v. Accept, reject or modify hypothesis: The hypothesis may be accepted or rejected or modified based on the result
of experimental design.
If the hypothesis is accepted and proven to be true it becomes a theory (a theory is therefore a tested hypothesis
that has been proven repeatedly correct between the limit of available evidence). It is rejected if the result of the
experiment are not in line or consistent with the hypothesis.

vi. Share the results: The results of this study must be shared with other scientists to enable them test the hypothesis,
verify it and proceed to carry out further investigation and formulate more hypothesis related to the effect of light
and other factors on the various parts of plants. When a theory is tested and proven true extensively, it becomes a
principle or a law.
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Summary of the method of inquiry in science

Example
Define the term biology and list the two main branches
Answer: Biology can be defined as the study of life. It is also defined as the study of plants and animals.
Main branches of biology
i. Botany: which deals with the study of plants
ii. Zoology: which deals with the study of animals.
Example 2
Biology is the study of
A. Animal B. life C. macro-organism D. micro-organism E. plant (2008/1 Neco)
Answer: Life (B) – Biology is derived from two Greek words: BIOS meaning life and LOGOS meaning to study. It is therefore
the study of life. The rest options are examples of living things. Option B is the most appropriate Answer.
Controlled experiments
An experiment must be designed to eliminate all bias so as to avoid making false conclusions. To do this, all factors
affecting the results of the experiment must be kept constant except the one that is being tested – which is known as
the variable. Such experiments are known as controlled experiment.
For example in the experiment to demonstrate that the shoot bend toward the source of light, the variable factor is the
lighting. The experimental plant (i.e. Pot A), was exposed to one-sided lighting while the control (i.e. Pot B), was
exposed to equal light on all its side (through the use of klinostat) all other factors affecting the experiment were kept
constant for both plants.
Usefulness of biology
Biology finds application in the following:
i. Agriculture and horticulture: the application of biology in agriculture has helped to develop better and more
resistant breed of crops. Secondly, it has helped in the development of insecticides, pesticides and herbicides
for the eradication of pests and weeds of crops. It has also led to development of techniques for hastening
ripening of fruits. Fishery and animal husbandry has also improved with the application of biological
knowledge in reproductive cycles.
ii. Medicine, dentistry and veterinary science. The knowledge of biology is applied in the development,
manufacture and use of vaccines and drugs for prevention and cure of diverse diseases including organ
transplant, e.g. kidney transplant.
iii. Food production industries: most food industries apply the knowledge of biology in their production. For
example in the beverage industries, fermentation processes are applied at various level.
iv. Biotechnology which includes fields like genetic engineering and hybridization technology. This technology
is used in producing important cell products such as hormones, vaccine from microorganisms and production
of single cell protein such as yeast.
v. The development of vaccines and drugs for preventing and treating many serious diseases. An adverse effect
of biology is the development of biological weapons. This uses disease causing microbes to attack enemy
troops.

Exercise 1.1
1. The science of life is referred to as
A. anatomy B. biology C. ecology D. phylogeny (2012/1)
2. List the stages involved in scientific method.
3. State 4 usefulness of biology to man.
4. Explain the term controlled experiment.
2
RECOGNIZING LIVING THINGS
Characteristics of Living Things
All organisms except viruses can be classified into two groups namely: Living and non-living things. The following
are the activities which living things normally perform whereas non-living thing cannot perform them.
1. Movement: Animals can move from place to place on their own accord for protection or in search of food and
mates. Higher plant only move certain parts of their body in response to growth or external stimuli (tropism or
nastic movement).
2. Respiration: Living things respire. Respiration is the oxidative breakdown of complex food substances such
as glucose, in the cells to release energy for vital activities. The mitochondria in the living cells are
responsible for the release of energy from food substances. The mitochondria are therefore referred to as the
power house of the cells.
3. Nutrition: Nutrition comprises the processes involved in taking in, digesting, absorbing and utilizing food in
animals. In plants it includes taking of water, carbondioxide and minerals, making food through
photosynthesis, fat and protein synthesis and utilizing food.
4. Irritability (sensitivity): This is the ability of living things to respond to stimuli (e.g. hunger, thirst or pain) in
order to survive. Stimuli could be external e.g. heat, light, water, sound and chemical substances, or internal
e.g. hunger, thirst, pain.
5. Growth: Growth is irreversible increase in size or dry weight as a result of synthesis of new body material,
increase in number of cells, cell enlargement and cell differentiation.
6. Excretion: Living things excrete. Excretion is the removal of waste products of metabolism from inside the
body.
7. Reproduction: Reproduction is the process by which an organism give rise to young ones of its own kind.
8. Death: every organism has a definite and limited period of existence. Death occurs when conditions are
unfavourable for life processes.
9. Competition: Living things tend to struggle for many of the necessities of life in order to survive.
Therefore, organisms usually compete for natural resources such as food, light and space.
10. Adaptation: in order to survive, every organisms possesses the ability to adapt to changes in its environment.
The inability of an organism to do so leads to its extinction.

Differences between plants and animals

Plants Animals
i. Green plants make their own food (i.e. autotrophic) Animals do not make their own food but feed on
plant and other animals. (i.e. heterotrophic)
ii. Plants are fixed i.e they do not move from place to Animals move from place to place i.e
place. They only move some parts of their body e.g locomotion is with the whole body.
root, stem and leaves.
iii. Chlorophyll/chloroplast is present No chlorophyll/chloroplast
iv. Have cell wall made of cellulose No cell wall
v. Plants have no specific organs for respiration, Animals have specific organs for respiration e.g.
excretion or sensitivity. lungs, excretion e.g. kidney, and sensitivity e.g. eye
vi. Growth is unlimited/indefinite; growth is apical or Growth is limited/definite; growth in all parts of
terminal the body.
vii Store carbohydrate as starch. Store carbohydrate as glycogen
viii Their response to stimuli is usually slow/long termed Their response to stimuli is fast/short termed.
ix. Sense organ absent. Sense organ present.

Similarities between plants and animals

1. Both are made up of cells
2. They both respond to stimuli
3. They grow by the process of cell division
4. Both reproduce and have limited life span.
5. Both carry out digestion and excretion.
6. Both undergo nutrition for growth and development.

3
Differences between living things and non living things
Living things Non-living things
i. They have life in them. They are lifeless.
ii. They can feed, excrete, respire, reproduce and respond They cannot carry out any of these function.
to external stimuli
iii. They have limited life span and such they age and die. They have unlimited life span and do not die.
iv. Growth is by assimilation of food substance into the Growth is by external addition of materials to
body, it is internal and nonreversible. the body.
v. They possess some specialize structures such as Movement is as a result of the influence from
muscles, bones, flagella etc. for movement. external force such as wind or current.
vi. Living things cannot exist as one single element as their It is possible for non living things to exist as
various cellular components are made up of different single element.
element and not one particular element.
vii. Examples of living things includes: rat, bird, amoeba, Examples of non-living things includes:
paramecium, fungi, etc. oxygen, stone, sand, water, acid, book etc.

Connecting link between living and non-living things [Virus]

One of the characteristic difference between living and non living things is that living things have life in them while
non living things do not have life in them. There however exist a connecting link between living things and non living
things. Viruses are believed to be this connecting link.
Viruses are non-cellular microscopic organisms which can only be seen with the aid of an electron microscope.
Outside the living cells, a virus appears to be non living and possesses the characteristics of non-living things. They
are normally crystallized but when they enter into the living cells, they become living and loss their crystal-like nature.
It is worthy to note also that viruses contain either RNA or DNA but never both which maybe single or double
stranded. Virus is made up of protein outer shell and inner nucleic acid, this infectious particle is called Virion
Virus that affect bacteria are known as bacteriophage.

Bacteriophage Typical virus SARS – Cov-2

Example
(b) State two features each which viruses have in common with: (i) living things (ii) non-living things (2017/1b)
Answer:
NB: Viruses can act as living and non-living things, depending on whether or not they are inside a living thing.
i. Features in common with living things: (a) They reproduce, (b) They move.
ii. Features in common with non-living things: (a) They can’t move, (b) They can’t respire.
The above is so, because when viruses are in living organisms, they possess all the features (characteristics) of living
thing. And when they are outside living organisms, they possess all the characteristics of non-living thing.
Example
Which of the following is not correct about all living organisms?
A. Response to changes in the surroundings B. Possession of the ability to reproduce
C. Growth through the division of their cells D. Ability to combine carbon dioxide and water to form sugar
E. Elimination of waste products (1992/9 Nov)
Answer: D – This is so because not all living things can combine carbondioxide and water to form sugar. This process
is only possible in plant in the presence of sunlight and chlorophyll. This is known as photosynthesis.
All other option (A, B, C and E) are common to all living thing.
Example
Which of the following is a characteristic of non-living things?
A. growth B. locomotion C. insensitivity D. respiration E. nutrition (1996/1 Nov)
Answer: C – This is so because insensitivity is not a feature of living things.
NB: Don’t confuse irritability (sensitivity) for insensitivity.
4
Example
(a) (i) List all the characteristics of a living organisms.
(ii) Explain briefly the characteristics listed in 1(a)(i) above [2014/1a (i), (ii) adjusted]
Answer:
(ai) The characteristic of living thing can be easily remembered by the mnemonic: MR NIGER CAD
Where: M – Movement
R – Respiration
N – Nutrition
I – Irritability
G – Growth
E – Excretion
R – Reproduction
C – Competition
A – Adaptation
D – Death
(aii) i. Movement: This is the process by which living things move from place to place in search of food, shelter and
mate.
ii. Respiration: Respiration is the oxidative break down of complex food substances such as glucose in the cells
to release energy for vital activities.
NB: The oxidative breakdown of these substances in order to release energy takes place in the mitochondria of
the cells. For this reason, the mitochondrion (singular of mitochondria) is referred to as the “power house of
the cell”.
iii. Nutrition: This is the process by which living things take in, digest, absorb, and assimilate food substances.
iv. Irritability (sensitivity): This is the ability of living things to respond to stimuli (e.g. hunger, thirst or pain) in
order to survive. Stimuli could be external e.g. heat, light, water, sound and chemical substances, or internal
e.g. hunger, thirst, pain.
v. Growth: Growth is irreversible increase in size or dry weight as a result of synthesis of new body material,
increase in number of cells, cell enlargement and cell differentiation.
vi. Excretion: Living things excrete. Excretion is the removal of waste products of metabolism from inside the
body.
vii. Reproduction: Reproduction is the process by which an organism give rise to young ones of its own kind.
viii. Competition: Living things tend to struggle for many of the necessities of life in order to survive. Therefore,
organisms usually compete for natural resources such as food, light and space.
ix. Adaptation: in order to survive, every organisms possesses the ability to adapt to changes in its environment.
The inability of an organism to do so leads to its extinction.
x. Death: every organism has a definite and limited period of existence. Death occurs when conditions are
unfavourable for life processes.
Example
Which of the following is NOT a diagnostic feature of living things?
A. respiration B. crystallisable C. irritability D. adaptation (1999/2 NABTEB)
Answer: B – Crystallisable implies something to be able to form crystals.

Example
A characteristic that can possibly be shared by both living and non-living organisms is
A. locomotion B. irritability C. increase in biomass D. increase in size (2008/2 JAMB)
Answer: D – Both living and non-living things increase in size (grow). The difference is that, while living things
increase in size by the internal accumulation of organic materials, non-living things on the other hand,
increase in size by the external accumulation of inorganic materials.

EXERCISE 2.1
1. When virus is placed in a non-living medium it
A. becomes dehydrated B. forms spores C. forms flagella D. becomes crystallized (1999/3 NABTEB)
2. Which of the following can reproduce by replicating itself in the living cell of a host?
A. fungi B. bacteria C. virus D. algae (2018/33 NABTEB)
3. Viruses are regarded as non-living because they
A. can neither reproduce asexually nor sexually B. cannot survive in their respective
C. do not possess characteristics that can be transmitted from one generation to the next
D. can neither respire nor excrete (1986/1 JAMB)
4. State two features each which viruses have in common with: (i) living things (ii) non-living things (2017/1b)
5
5. Which of the following pairs of vital characteristics is common to all living organisms?
A. Reproduction and increase in size B. Photosynthesis and excretion
C. Respiration and photosynthesis D. Reproduction and respiration (2015/1 Nov)
6. All the following are examples of living things except
A. fish B. crops C. air D. chlamydomonas (2000/1 Nov)
7. All living organisms
A. photosynthesize B. respire C. move D. feed E. transpire (1979/1 JAMB)
8. Living things can perform all of the following except
A. oxidize food to release energy B. show sensitivity to changes in their environment
C. show increase in size and weight D. Store metabolic waste the contractile vacuole of cells
E. move part or the entire body (1994/1 Nov)
9. Which of the following characteristics is exhibited by animals but not by plants?
A. Feeding B. Growth C. Respiration D. Locomotion (2015/2 Nov)
10. Which of the following forms a link between living and non living things?
A. bacterium B. virus C. flowering plant D. fungus (2001/1 NABTEB)
11. bi. Is virus a living or non-living thing? Give two reasons in each case to support your (2017/1bi NABTEB)

Organization of Life:
Organization of life is the existence of life from a single celled organism to a multi-cellular organism with complex
structures that perform different functions. There are four levels of organization of life in organisms. These are:
1. The cell: the cell is defined as the smallest unit of living organisms or a microscopic mass of protoplasm
enclosing the nucleus and bounded on the outside by either the cell wall or cell membrane. The cell in fact, is
the fundamental, structural and functional unit of life of which plants and animals bodies are made.
Examples of organisms in this cellular level are Amoeba, Euglena, Paramecium, Plasmodium,
Chlamydomonas, Trypanosoma etc.
Some single-celled organisms live together in a colony e.g. pandorina and volvox. Some exist as filament
e.g. spirogyra.
2. Tissue: Tissue as defined as a group of similar cells that perform a particular function. Examples of
organisms in this level are hydra, algae, sponges and fungi.

Types of tissues in man:

In man the different types of tissue include;
a. Epithelial tissues: These line and protect the body surface. They help in the formation of the skin.
b. Blood tissue: They transport food and oxygen round the body.
c. Skeletal tissue: They support the body and aid movement.
d. Connective tissue: They bind other tissue together
e. Nerve tissue: They coordinate and transmit nerve impulses.
f. Muscle tissue: It is used for movement

Types of tissues in plant:

In plants, there are different types of tissues which include:
a. Vascular tissue: for transport of food and water in plant. For example the phloem transports manufactured
food from the leaves to other parts of the plant by a process called translocation. They xylem transport
water and mineral salts from the root to the leaves.
b. Strengthening tissues: They give strength and support to the plant body. They include sclerenchyma,
collenchyma, parenchyma etc.
c. Photosynthetic tissues: They are used for manufacturing food.
d. Epithelial tissues: They line and protect the plant surface.
e. Packing tissue: They provide surface for new cells which are used for storage.
3. The organ: This is a group of similar tissue forming a layer in an organism which performs a specific
function. Examples of organs in animals are skin, eyes, ears, stomach, brain, heart, liver, kidney etc. examples
of organs in the plant are onion bulb, root, stems, leaves, flowers, fruits, seed etc.
4. System: this is a group of organ co-ordinated together so as to perform a prime function e.g., the kidney,
ureters, urinary bladder and urethra, constitute excretory system of mammals. Examples of systems in plants
are the root system and shoot system. Example of systems in animals are digestive, reproductive, respiratory,
skeletal, nervous, excretory and circulatory system. The system work together to make up an organism.
6
Example
At what level is Amoeba
A. tissue B. organ C. Cellular D. System E. Filament (1995/1)
Answer: C – Amoeba is a unicellular (single-celled) organism and therefore belongs to the cellular level of organization.
Example
Which of the following is not a tissue found in plants?
A. Epidermis B. Phloem C. Xylem D. Dermis E. Mesophyll. (1995/9)
Answer: D – Options (A, B, C and E) are found in plants. But option D (dermis) is not found in plants. It can only be
found in some animals. It is the layer of the skin just beneath the epidermis of mammals.
N.B: Both plants and animals posses epidermis. The epidermis is an outer protective layer.
Example
4(a)(i) Name the four levels of organization in living organisms
(ii) Explain two of the levels of organizations named in (a)(i) above
(iii) State the level of organization of Euglena, onion bulb and blood (2000/4a i, ii, iii)
Answer:
4ai. The cell, tissue, organ, system
ii. The cell: This is the smallest structural and functional unit of life. Examples: amoeba, plasmodium, euglena,
paramecium, chlamydomonas, etc.
Tissue: This is a group of similar cells that perform a given function. Examples: sponge, hydra, etc.
iii. Euglena → Cell; Onion bulb → organ; blood → tissue
Example
Which of the following is a tissue?
A. Volvox B. Chlamydomonas C. Epidermis D. Paramecium (2001/2)
Answer: C – Chalamydomonas and paramecium exist at the cellular level of life.
Volvox exist as a colony, while epidermis exists as a tissue.
Example
Which of the following represents the correct sequence, from the most simple, to the most complex organizations?
A. Mitochondrion, Muscle, Alimentary canal, Rabbit, Heart, Neuron
B. Mitochondrion, Neuron, Muscle, Heart, Alimentary canal, Rabbit
C. Alimentary canal, Neuron, Muscle, Heart, Rabbit, Mitochondrion
D. Rabbit, Mitochondrion, Heart, Neurone, Alimentrary canal, Muscle. (2002/6)
Answer: B – Before you attempt this question, you must understand the organization of life, starting from the smallest
called cell, followed by tissue, then organ, then system and finaly an organism.
- The mitochondria are organelles of a cell
- The neuron is a nerve cell
- The muscle is a tissue
- The heart is an organ
- The alimentary canal is a system
- The rabbit is an organism.
So, option B is the most orderly arranged option
Example
Which of the following structure is a tissue?
A. Vessel element B. Blood C. Sieve tube element D Erythrocyte (2011/2)
Answer: B – A tissue consists of similar cells organized to perform a particular function. From the above options,
only B (blood) suits the Answer: . The rest options are all singular cells.
N.B: The cellular component of blood are the white blood cells (leucocytes), the red blood cells (erythrocytes), and the
platelets (thrombocytes)
Example
The epidermis of a leaf is considered an example of a tissue because the cells
A. allows sunlight to pass through B. are covered by a waxy cuticle
C. all possess a similar structure and function D. allow water to enter them by osmosis. (2012/2)
Answer: C – A tissue is a group of similar cell that performs a particular (similar) function.
Example
The organism at the organ level of organisation of life is
A. Euglena B. Spirogyra C. Ginger D. Tapeworm (2012/3)
Answer: C –An organ consists of similar tissues that are organized to perform a particular function. e.g the heart,
kidney, rhizomes, bulbs e.t.c. Ginger is an example of a rhizome therefore it is at the organ level of organization.

7
Example
Which of the following organism is the most specialized?
A. Paramecium B. Amoeba C. Spirogyra D. Rhizopus (2014/3)
Answer: D – The most specialized organism is the one at the highest level of organization. From the options listed
above, rhizopus, belongs to the highest level of organization.
Example
What level of organization is Spirogyra?
A. Organ system B. Organ C. Cell D. Tissue (2018/3)
Answer: C – Spirogyra exist in the cellular organization of life but as a filament.
Example
Which of the following is at the cellular level of organisation?
A. Taenia B. Heart C. Euglena D. Bulb E. Kidney (1997/1 Nov)
Answer: C – Euglena exists as a cell, Heart and kidney are organs in animal, Taenia (tape worm) is an organism.
Bulb (e.g. onion) is an organ.
Example
The organisms listed below are unicellular in nature except
A. Paramecium. B. Amoeba. C. Euglena. D. Volvox. E. Chlamydomonas. (1994/3 Nov)
Answer: D – Volvox exists as a colony

EXERCISES 2.2
1. The epidermis of the mammalian skin is an example of a tissue because the cells
A. prevent light from passing through them B. have a similar structure and function
C. prevent excessive loss of water D. are impregnated with keratin (2006/3)
2. Which of the following statements is correct about organs?
A. They are composed of specialized cells B. They perform a certain overall function
C. They are not found in plants D. Unicellular animals have few organs (2006/4)
3. An organism that operates at the cellular level of organization, carries out its physiological activities by using its
A. cell membrane B. organelles C. small size D. plasma membrane (2010/2)
4. Which of the following groups carry out similar functions in living things?
A. vertebral column, chitin, and guard cells B. sclerenchyma, cartilage and chitin
C. tendon, chitin and neuron D. collenchyma, intercellular spaces and blood vessels
E. blood vessels, lymph and shell (1995/6)
5. Which of the following levels of organization in living things is the correct sequence, starting from the complex to
the simplest
A. Tissue → cell → organ → system B. System → organ → tissue → cell
C. Cell → tissue → system → organ D. Cell → tissue → organ → system
E. Organ → system → tissue → cell (1996/1)
6. Which of the following is not an organ?
A. Hair B. Tongue C. Rhizome D. Corn E. Heart (1998/2)
7. At the level of organization, the artery is classified as
A. a tissue B. an organ C. a cell D. a system (2013/2 Nov)
8. Which of the following statements best describes an organ it is a
A. mass of cells usually of the same kind
B. mass of different cells, assembled to perform more functions
C. specialized part of protoplasm D. structure made up of a number of individuals of a particular kind (2004/2 Nov)
9. List two types of tissues in man. [2018/2a(ii) NABTEB]
10. Name two tissues in plants. [2018/3c(ii) NABTEB]
11. Levels of organization include the following EXCEPT
A. tissue B. unicellular C. organ D. multicellular (2001/11 NABTEB)
12. A tissue can best be defined as
A. an aggregate of similar cells B. an aggregate of cells performing a similar function
C. an aggregate of similar cells performing the same function
D. a mixture of different cell typed performing the same function. (1992/2 JAMB)
13. The cells of the yam tuber functioning as a unit could best be described as
A. a colony B. an organ C. a tissue D. a filament E. a system (1996/2 Nov)
8
14. Which of these organisms has a body structure at the tissue level of organization?
A. Amoeba B. Paramecium C. Hydra D. Euglena (2005/4 Nov)
15. (d) State one difference each between Hydra and the mammals with respect to:
(i) level of organization (1991/1d(i) Nov)
16. Which of the following is the youngest plant tissues?
A. meristem B. phloem C. epidermis D. xylem (1997/3 JAMB)
17. Which of the following is an organ?
A. guard cell B. liver C. xylem bundle D. blood (1999/6 JAMB)
18. An Amoeba and an unlaid chicken egg are
A. organelles B. Animal tissues C. organisms D. Single cells (2002/3 JAMB)
19. What is the level of organization of an onion bulb?
A. Tissue B. Organ C. Systemic D. Organismal (2009/1 JAMB)
20. Which of the following is the simplest living organism?
A. paramecium B. virus C. Amoeba D. chlamydomonas (2013/12 JAMB)
21. The lowest level of organization in living organisms is
A. system B. tissue C. organ D. cell (2014/4 JAMB)
22. Which of the following is the most complex according to their cellular level of organization?
A. Euglena B. Hydra C. Heart D. Hair (2014/5 JAMB)

Advantages of complexity in higher organisms

i. It leads to cellular differentiation. As a result of complexity, group of similar cells are differentiated to form
tissues that carry out similar function.
ii. It leads to internal structural specialization: This is when the group of similar cells or tissues become
specialized to carry out one or more function.
iii. Mutual interdependence between component cells: There is a division of labour among the component cells.
iv. Complexity leads to efficiency: complexity makes higher organisms to be efficient in carrying out life
processes.
v. The increased biological efficiency has enable multicellular organisms to survive in different habitats.
vi. Complexity leads to increase in size: This is because there is space between cells for growth.
vii. Complexity increases adaption to environment: Complexity make higher organisms to adapt to adverse
conditions within the environment.
viii. Reproduction in complex organism does not lead to the disintegration of the parents. Specialized reproductive
parts (testis and ovaries) are only involved. But in unicellular organisms, the entire parent or parents are
involved in reproduction leading to their disintegration.
ix. Due to specialization and efficiency of tissues, organs and systems, complex organisms have longer life span
than unicellular organisms.

Disadvantages of complexity in higher organisms

i. Inability of individual cells to exist on their own: In complexity, cells lose their independence and become
increasingly dependent on one another’s activities.
ii. Unicellular organisms have a large surface area to volume ratio, whereas multicellular organisms have a small
surface area to volume ratio; thus movement of substances by diffusion is not efficient in multicellular
organisms. Therefore, complex organisms have developed transport systems. However, if there is any defect
in this system, the organisms may be endangered.
iii. Complexity leads to slower rate of expulsion of waste product from cells due to their small surface area to volume ratio.
iv. Difficulties in reproduction: complexity leads to difficulties in reproduction in higher organisms.
v. Complexity leads to decrease in ability to regenerate.
vi. The proper coordination of the activities of the various tissues, organs and system necessary in multicellular
organisms may be hindered if such coordination is poor or impaired.

Example
Which of the following statements about complexity of organization in organisms is not true?
A. It enables the organisms to perform specialized tasks B. It enables the organisms to adapt to their environment
C. Body functions are limited and restricted to specific conditions D. It enhances the organism’s efficiency
E. All parts of the organism work in a coordinated fashion for the benefit of the organism (1998/2 Nov)
Answer: C – All other options (A, B, D and E) are true and they are advantages of complexity in higher organism.

9
Example
State two advantages of complex structural organization in higher organism (1996/1a)
Answer: - It leads to more efficiency., It leads to increase of size.
Example
Below is a list of the levels of organization in organisms. Use it to Answer: questions 4 and 5.
I. TISSUE II. SYSTEM III. CELL IV. ORGAN
The correct sequence of the levels in an increasing order of complexity is
A. I, II, III, IV B. III, I, IV, II C. III, IV, I, II D. IV, III, I, II E. IV, I, II, III (1992/4)
Answer: B – Increasing order of complexity mean that one should start listing from the simple to the complex.
That is;
→ III
complexity
Decreasing

Cell
complexity
Increasing
Tissue → I
Organ → IV
System → II

EXERCISE 2:3
1. 4(b) Give four advantages of complexity of organization in higher organizations
(c)(i) State one advantage Amoeba has over a cell of a lizard, in relation to their levels of organization
(ii) Give two reasons for the advantage. (2000/4b & c (i), (ii)
2. Differentiation and specialization in multicellular organisms is necessary because
A. the volume surface area ratio of the organisms is low B. it allows for division of labour among the cells
C. there is a definite arrangement of cells D. cells have different shapes and sizes (2019/5 NABTEB)
3. Which of these could be regarded as an advantage of complexity in higher organisms
A. There is no cellular differentiation B. Cellular differentiation leads to loss of independence of the cells
C. Complexity stops at cellular differentiation only
D. Cellular differentiation leads to internal structural specialization (1995/2)
4a. State 3 advantages of complexity in higher organisms.
b. State 2 disadvantages of complexity in higher organisms.

10
CLASSIFICATIONS OF LIVING THINGS

Classification of Living things

Classification is the science of arranging living things into groups based on structural, genetic or cellular organization.
Classification is also called taxonomy.
Living things are first grouped into kingdoms. The kingdoms are further divided into phyla or division. Phyla are
divided into smaller groups called classes. Each class is further divided into orders. Orders are further divided into
families. Families are divided into genera (singular genus).

11
A genus is broken into species.
Specie is a population of related organisms that can interbreed within themselves to produce fertile offspring. A genus
is a group of closely related species. A family is a group of genera that are closely related. An order is a group of
related families. A class is a group of related orders. A phylum is a group of related classes. A kingdom is a group of
related phyla.

Scientifically, every living thing has two names. The first name is the generic name which starts with a capital letter
and the second name is the specific name which starts with a small letter. For example, Homo Sapiens (man), Musca
domestica (housefly) etc.
The system of giving two names to an organisms is known as binomial nomenclature and it was developed by a
Swedish botanist, Carolus Linnaeus (1707-1778). He is the father of taxonomy.
Using the following headings: Kingdom, phylum, sub-phylum, class, order, family, genus and species,
Man can be classified as follows:
Kingdom - Animalia (Animal)
Phylum - Chordata (possesses notochord)
Sub-Phylum - Vertebrata (animals that posseses backbone)
Class - Mammalia (possesses mammary gland)
Order - Primate (having well-developed hands and feet for grasping)
Family - Hominidae (man-like apes, primitive man and modern man)
Genus - Homo (primitive and modern man)
Species - Homo sapiens (well developed brain)
New system of classification
Linnaeus placed all living organisms into two kingdoms, plant and animal. In this method, many one – celled
organisms could not fit in properly. Therefore, most biologist favour the placing of all living organisms into five
kingdoms: 1.Monera, 2.Protista, 3.Fungi, 4.Plantae, 5.Animalia

Pteridophyte e.g ferns

Spermatophyta Gymnosperm e.g. conifers

Angiosperm

NB: The new system of classification was introduced by Margulis and Schwatz in 1982.

12
Example
In the binomial system of naming organisms, the second name is called the
A. scientific name B. common name C. generic name D. specific name. (2008/1)
Answer: D – The first name is the generic name which usually starts with a capital letter. The second name is the
specific name usually starts with a small letter.
Example
The scientist who introduced binomial nomenclature in the classification of organisms was
A. Charles Darwin B. Carolus Linnaeus C. John Ray D. Louis Pasteur (2018/1)
Answer: B – Carolus Linnaeus a Swedish botanist was the one who introduced the binomial nomenclature. He is also
known as the father of taxonomy.
Charles Darwin is a British naturalist who developed a theory of evolution and natural selection.
Louis Pasteur is a French biologist who discovered the principles of pasteurization, vaccination and microbial
fermentation. He is also known as father of microbiology.
John Ray is a English naturalist who formulated the fundamental principles of plant classification into Cryptogams,
monocotyledons and dicotyledonous.
Example
In biology, keys are used to
A. classify organisms B. describe organisms C. identify organisms D. evaluate organism (2006/3 Nov)
Answer: C- In biology, keys are used to identify organisms

Example
The lowest unit of classification is the
A. kingdom B. class C. phylum D. species (2016/29, JAMB)
Answer: D – Hierarchy of classification is as follows:

Exercises 3.1
1. The arrangement of organisms into kingdom, phylum, class, order, family, genius and species is called
A. taxonomy B. theory C. scientific-method D. hierarchy (1999/7 NABTEB)
2. The similarity among organisms belonging to the group will be least within each
A. order B. family C. species D. kingdom (2003/4 JAMB)
3. In terms of the number of individuals, which of the following taxanomy is most inclusive?
A. Order B. Family C. Class D. Species (2008/1 JAMB)
4. In which of the following levels of classification are the members most similar?
A. Order B. Genius C. Species D. Phylum. (2013/1)
5. 1(a)(i) What is classification of living things?
(ii) Name the scientists that developed the Binomial system of classification
(iii) State three reasons why it is necessary to classify living things
(iv) List seven major groups into which Taxononimists classify living things in order of hierarchy. (2017/1a)
6. The branch of biology that deals with the principles of classification of organisms is known as
A. biological index B. nomenclature C. taxonomy D. ecology (2011/1)
7. Which of the following groups embraces the rest?
A. Class B. Kingdom C. Phylum D. Species (2005/1)

13
Kingdom Monera (Prokaryotes)
They are very small organisms i.e. microscopic. They are single – celled, motile or non-motile organisms. This
kingdom consists of two main phyla viz; The phylum Schizophyta (the bacteria) and the phylum cyanophyta (the blue
green algae). The monerans have the following characteristics.
i. They lack organized DNA – That is their DNA is scattered in the cytoplasm and not located in the nucleus.
ii. They are microscopic and single-celled organisms.
iii. They lack definite nucleus (i.e. they are prokaryotic)
iv. Their cells lack cell organelles such as mitochondria, chloroplasts endoplasmic reticulum, etc.
v. They are motile or non-motile organisms.
vi. The cell walls lack cellulose. The cell walls are made of protein and fatty materials.
vii. They feed autotrophically or heterotrophically.
viii. Reproduction is strictly asexual by binary fission in schizophyta and cell division in cyanophytes. Examples
are bacteria and photosynthetic blue green bacterium (Anabaena) formally known as blue-green algae.
A typical structure of bacteria

A bacteria cell consists of a mass of protoplasm surrounded by a cell wall. In some types of bacteria, the cell wall is
covered on the outside with a slimy substance. The slimy layer (capsule) helps to protect the bacteria cell from
dehydration and also helps the cell to stick to the surface of its host or food.
There is a definite cytoplasm bounded inside by plasma membrane and outside by the cell wall. The cell membrane is
thrown into folds called mesosomes. The mesosomes contain various enzymes. Some motile ones have whip like
structures called flagella which enable them to move about in water. The cytoplasmic fluids contain granules and
ribosomes. The bacteria have no well organized nucleus. They have nuclear material (nucleoid) without a nuclear
membrane. The DNA is concentrated in the nucleoid. Most bacteria reproduce by binary fission (a type of asexual
reproduction). Bacteria are of great economic importance. Harmful bacteria cause diseases in plant and animals,
including human. Useful bacteria bring about decay and improve soil fertility. Bacteria are also used in industrial
processes.
NB: Cyano bacteria (Blue green algae) are found mainly in fresh water, and in damp Places on land. They contain
chlorophyll and as such are able to produce their own food. The chlorophyll is not present in chloroplast but is
dispersed as particles throughout the cytoplasm. Blue green algae can exist as single cells or as colonies composed of
clumps or long chains of nearly identical cells held together in slimy sheaths. Example of blue green algae include
Nostoc, Oscillatoria and Anabaena.
Bacteria have different forms and shape, those that are spherical or round are known as cocci (singular-coccus), those
that are rod-shaped are called Bacilli (singular-bacillus), those that are spirally twisted are known as spirilla (singular-
spirillum) while those that are comma-shaped are known as vibrio e.g. Vibrio cholera.

Example
Which of the following is not true about a bacterial colony growing on an agar plate?
A. They are visible without the aid of the microscope B. Bacterial cells found in one colony often belong to one species
C. Different colonies have different colours D. Only one species of bacterial colony can grow on a culture (1989/56)
Answer: A- Bacteria are microscopic in nature i.e. they are not visible to the unaided eyes.

Example
A bacterial cell differs from eukaryotic cell by having no
A. cell wall B. nuclear membrane C. nuclear material D. cell membrane (2003/4)
Answer: B – Bacteria cells lack a nuclear membrane, hence they are called prokaryotes.

14
Example
The diagrams below are illustrations of biological structures. Study them and Answer: questions 2

2. Which of the following statements is correct?

A. B needs A and other living things to reproduce B. A and B cannot exist together in a parasitic relationship
C. A needs B to function properly in its environment D. The relationship between A and B is usually mutual
3. The strand of nucleic acid structure B is
A. injected into a host cell during feeding. B. Either DNA or RNA. C enclosed by the nucleus
D. combined molecules of DNA and RNA 2020/2-3 (PC1)
Answer:
NB: Before attempting these questions you must be able to recognize what cells are represented by the diagram. From
the diagram, it is clear that “A” is prokaryotic (bacteria) cell, because it is void of organelles such as mitochondria,
chloroplasts, endoplasmic reticulum etc. and “B” is a viral cell because it appearance is like a crystal. Also remember
that a virus is made up of a protein outer shell and an inner nucleic acid. So, let’s Answer: the question.
2: A – This is so because viruses need to be inside other living organisms (e.g. bacteria, plants and animals) in order
for them to carryout life process such as reproduction, respiration etc.
3: B – This is because a virus can only possess either RNA or DNA and never both.

Exercise 3.2:
1. An organism with no membrane-bounded organ in its cell, belongs to the kingdom
A. Protista B. Monera C. Animalia D. Plantae. (2011/2 Nov)
2. Which of the following statements is not correct about bacteria?
A. Bacteria in the intestine of man digest cellulose.
B. They are used in the process of making cheese, vinegar and silage
C. Bacteria are used in tanning, curing of tobacco and tea
D. They aid the process of fermentation in the baking industry
E. They are used in the treatment plants for water purification. (1992/55 Nov)
3. Bacteria multiply rapidly by means of
A. budding B. fragmentation C. binary fission D. spore formation (1999/27 JAMB)
4. The bacteria type that are arranged in chains are the
A. Staphylococci B. Clostridia C. Streptococci D. Bacilli (2008/7 JAMB)

Kingdom Protista (Eukaryotes)

The protists are unicellular organisms. They are made up of eukaryotic cells in which the cell structure is complex
with a well-defined nucleus. They have many structures called organelles which carry out specific functions. Many of
them move about by using hair like structures called flagella and cilia, or by forming pseudopodia, often known as
“false feet”.
This kingdom is divided into:
(i) Phylum protophyta which are plant like, having cellulose cell walls and organelles called chloroplast.
Examples are Chlamydomonas and Chlorella found in fresh water and diatoms found in fresh water and in the
sea. Diatoms have hard silica coats.
(ii) Phylum protozoa: some protists are ‘animal-like’ because they feed on ready-made food and have no cellulose
cell walls. Examples are Amoeba and Paramecium.
NB: Euglena viridis is a protists that shows both plant-like and ‘animal-like’ features. Some of its animal-like
characteristics includes: Possession of flagellum for locomotion, presence of contractile vacuole for excretion,
possession of eyespot which responds to light, presence of gullet for passage of food, plasma membrane called pellicle
and ability to carry out holozoic nutrition in the absence of light. While it plant-like characteristics includes:
possession of chloroplast and ability to photosynthesize in the presence of light, possession of pyrenoid and storage of
starch in form of paramylum granules.
Some protist reproduce by simply dividing into two daughter cells, many; however, reproduce sexually, i.e. produce
gametes which fuse to form a zygote.

15
Characteristics of Protista
 They have well organized DNA in the nucleus bounded by nuclear membrane. Hence they are called eukaryotic
organisms.
 They are unicellular organisms
 They are motile and non motile organisms
 They reproduce either asexually or sexually. Examples are amoeba, euglena, chlamydomonas, spirogyra,
plasmodium, chlorella and fucus.

Chlamydomonas (Phylum protophyta: ‘plant like’ ) Euglena (animal and plant like)

Amoeba (Phylum protozoa:‘animal-like’) Paramecium

Example
Which of the following features of paramecium is not an advancement over amoeba? The possession of
A. definite shape B. cilia C. oral groove D. nucleus. (1999/2)
Answer: D – Nucleus is present in both paramecium and amoeba and so possession of nucleus in paramecium is not
an advancement over amoeba since amoeba possesses a nucleus also.
Example
Which of the following indicates that Euglena is a plant?
A. Conspicuous “eye” spot B. Presence of gullet C. Limited movement D. Presence of starch grains. (2001/1)
Answer: D – This is so, because plants store their food as starch and animals store their food as glycogen.
All other options (A, B and C) are typical of animals.
Example
Euglena can be classified as an animal because of the possession of
A. nucleus B. cytoplasm C. cell wall D. pellicle (2011/6)
Answer: D - Animal-like features of Euglena:
 Presence of flagellum for locomotion
 Presence of eye spot to respond to light (the eyes spot do not form images)
 Presence gullet and a food reservoir
 Presence of contractile vacuole for excretion and osmoregulation.
 Presence of pellicle

16
Example
Which of the following organisms is not a protozoan?
A. Amoeba B. Ascaris C. Plasmodium D. Paramecium (2015/1)
Answer: B – Ascaris is a nematode (round worms). All other options are protozoans.
Example
The organism that can carry out both autotrophic and heterotrophic modes of nutrition is
A. Chlamydomonas B. Eudorina C. Euglena D. Spirogyra (2017/7)
Answer: C – Euglena can carry out autotrophic mode of nutrition in the presence of light. And when light is absent,
it carries out Heterotrophic mode of nutrition.
Example
A structural similarity between Paramecium and Amoeba is the presence of
A. one food vacuole. B. two contractile vacuoles C. two nuclei D. one gullet (2019/3)
Answer: A - both Amoeba and paramecium possesses one food vacuole.
Example
Which of these organisms is a protozoan?
A. hydra B. mucor C. paramecium D. spirogyra E. volvox (2005/3 Neco Nov)
Answer: C – Hydra is a coelenterate (cnidarian) spirogyra and volvox are lower plants, mucor is a fungus.
Example
One characteristic feature of Chlamydomonas is
A. its star-shaped chloroplast B. the presence of pseudopodia C. its cup-shaped chloroplast
D. the presence of nucleus in its cell. (2011/4 Nov)
Answer: C – chlamydomonas is unique by its cup-shaped chloroplast.

Example
Amoeba, Euglena and paramecium belong to the protozoa group because they are
A. unicellular and microscopic B. found in the same habitat C. most parasitic
D. mostly aquatic E. free-living (1996/3 Nov)
Answer: A – They are all unicellular and microscopic.
Example
Euglena may be classified as a plant because it has
A. chloroplast B. a gullet C. a pellicle D. a flagellum (1999/5 NABTEB)
Answer: A – Chloroplast (Plant-like features of Euglena: Possession of chlorophyll for photosynthesis, Possession of
pyrenoid stores food as starch granules)
Example
Which of the following organisms has chloroplast?
A. amoeba B. mucor C. spirogyra D. paramecium (2017/3 NABTEB)
Answer: C – Spirogyra is a lower plant. Mucor is a fungi. Paramecium and amoeba are protozoans

EXERCISE 3.3
1. Which of the following features of Euglena is found only in animals?
A. Paramylum granules B. Flagellum C. Pellicle D. Pyrenoid (1987/2 JAMB)
2. Spirogyra, euglena and chlamydommas share many characteristics EXCEPT
A. nutrition B. reproduction C. mobility D. irritability (1988/7 JAMB)
3. A plant-like feature in Euglena is the
A. gullet B. large vacuole C. pellicle D. pigment spot (2004/45 JAMB)
4. A blue-green alga is not a protophyte because
A. it is aquatic B. its cells are prokaryotic C. it cannot move D. it is not a green plant. (2009/7 JAMB)
5. A feature that qualifies Euglena as a plant is
A. presence of gullet B. possession of flagella C. possession of chloroplast D. presence of pellicle (2017/2 NABTEB)

17
Kingdom, fungi (eukaryotes)
They are mainly non-motile organisms except slime-mould: They are composed usually of thread-like structure or
hyphae containing many nuclei. The hyphae can also branch out and create a large network called a mycelium. There
are two main types of hyphae. Viz “septate” hypha which have cross walls that separate individual cells. An example
of a fungi that possess this type of hyphae is the mushroom and “Ceonocytic”or “aseptate”hypha which do not have
cross walls but appears as one long continuous cell e.g. mucor and rhizopus.
Members include mushrooms, toadstools, bread mould and slime-mould. They do not contain chlorophyll, most of
them are saprophytes. The fungi and bacteria are important decomposers. They grow on logs, dead leaves, fruits,
bread and leathers. Some are parasites causing diseases to both plants and animals. Fungi reproduce rapidly by spore
(asexual reproduction)
The spores are released into the surrounding air, and when condition is favourable, they germinate and grow. Fungi
also reproduce sexually. A typical unicellular fungi is yeast.
Characteristic of Fungi
1. They are non green plants and lack chlorophyll. Nutrition is therefore heterotrophic. Food is digested outside
the body and digested soluble food is absorbed into the body by diffusion.
2. Tropical simple multicellular organisms.
3. Their bodies are not differentiated into root, stem and leaves.
4. They are mostly non-motile organisms composed of thread like multinucleate hyphae collectively known as
mycelium.
5. They reproduce by means of spores.
6. They store Carbohydrates as glycogen and not starch.
7. The cell wall is made of chitin and not cellulose.

Examples are mucor, rhizopus, mushroom and slime mould.

Sporangiophore

Fungi (Bread mould) Mushroom

NB: Fungi sometimes can be involved in complex relationship with the root of higher plants, this is known as
mycorrhizae. It can also be involved in a relationship with an algae/cyano bacteria this relationship is otherwise
known as lichen.

Differences between prokaryotic cell and eukaryotic cell

Prokaryotic cell Eukaryotic cell
i. The DNA is not enclosed within nuclear membrane and it The DNA is enclosed within nuclear membrane
is circular and naked. and restricted to nucleus and is not naked.
ii. Cell division is usually carried out by binary fission and Cell division is by mitosis, meiosis or both.
conjugation in some.
iii. Absence of endoplasmic reticulum Endoplasmic reticulum are present
iv. Cell wall is made up of protein and polysaccharide Cell wall is made of cellulose in plants and algae,
chitin in fungi. No cell wall in animals.
v. Mitochondria are absent Mitochondria are present
vi. Chloroplast for photosynthesis are absent Chloroplast are present for photosynthesis in plant

Example
Which of the following is not true of Rhizopus or mucor? It
A. manufactures its own food B. has non-septate hyphae
C. undergoes sexual and asexual reproduction D. bears spores in sporangia. (2003/6)
Answer: A – They can’t manufacture their own food because they lack chloroplast

18
Example
Which of the following characteristics do fungi share in common with animals?
A. presence of digestive tract B. movement from one place to another
C. storage of carbohydrates as glycogen D. movement of centrioles during cell division (2010/6)
Answer: C – Animals store carbohydrates as glycogen while plants store carbohydrates as starch.
Fungi stores carbohydrates as glycogen
Example
Which one of the following options is not true for Mucor or Rhizopus? It
A. grows on moist dead organic matter B. is a plant C. has cellulose cell wall
D. reproduces asexually by producing spores E. has no chlorophyll (1979/12 JAMB)
Answer: C – Mucor and rhizopus are examples of fungi and the cell wall of fungi is made of chitin and not cellulose.
Characteristics of fungi: Ɵ They are decomposers – i.e. they feed on moist dead organic matter.
Ɵ They lack chlorophyll. Ɵ They are non-motile. Ɵ They possess cell wall made of chitin.
Ɵ They store their food as glycogen Ɵ They are both multicellular and unicellular
Example
In rhizopus, carbohydrates is stored in the form of
A. glucose B. paramylon C. glycogen D. starch E. oil (1983/43 JAMB)
Answer: C – Rhizopus is a fungus and one of the characteristics of fungi is that they store their food as glycogen.
Example
Which of the following is no true of mucor? It
A. contains chlorophyll B. grows saprophytically C. bears spores in sporangium
D. consists of hyphae E. reproduces by conjugation (1985/7 JAMB)
Answer: A – Mucor is a fungus and fungi lack chlorophyll. All other option (B – E) are typical characteristics of mucor (fungi).
Example
An organism found on a bare rock surfaces has features of algae and fungi. The organism is
A. epiphyte B. a lichen C. a bryophyte D. A fern (1987/9 JAMB)
Answer: B – A lichen. A symbiotic relationship between an algae and a fungus.
 An epiphyte is a plant that grows on the surface of another plant and derives its moisture and nutrients from the
air, rain, water or from debris accumulating around it.
 Bryophyte is an example of non-vascular plant.
 Fern is a vascular plant that does not produce seed nor flower.
Example
A multinucleate body without internal cell boundaries is characteristic of
A. bryophytes B. fungi C. algae D. gymnosperms (1989/6 JAMB)
Answer: B – Some fungi posses non-septate hyphae which are multinucleated and have no internal cell boundaries.

EXERCISE 3.4
1. Which of the following are non-green plants?
A. Euglena B. Fungi C. Spirogyra D. Angiosperms (1991/4 JAMB)
2. Fungi are heterotrophic because they
A. have no leaves B. lack roots C. are filamentous D. lack chlorophyll (1992/12 JAMB)
3. The most common characteristic of the fungal hyphae is the possession of
A. cell-like partitions formed by crosswalls B. cell-like compartments with one nucleus each
C. cell walls that are both rigid and chitinous D. a multicellula cycellium the substrate (2004/41 JAMB)
4. The hyphal wall of fungi is rigid owing to the presence of
A. cellulose B. cell wall C. chitin D. lignin. (2005/38 JAMB)
5. The importance of the association to the fungus that it obtains
A. a partner for reproduction B. anchorage from the algae
C. oxygen a carbohydrates from the algae D. water and mine salts from the algae (2006/47 JAMB)
6. The fungi are a distinct group of eukaryotes mainly because they have
A. spores B. no chlorophyll C. many fruiting bodies D. sexual and asexual reproduction (2012/7 JAMB)
7. Fungi are referred to as heterotrophs because they
A. are filamentous B. lack chlorophyll C. have mycellum D. lack roots (2013/21 JAMB)

19
Kingdom Plantae (Eukaryotes)
The green plants belong to this kingdom. Plants are non-motile multicellular organisms whose cells have cellulose cell
walls and chloroplast.
The chlorophyll in the chloroplast enable plants to make their own food by photosynthesis. Members include mosses,
ferns, pines, oil palm.

Characteristics
i. They are multicellular non-motile organisms.
ii. Their cells are bounded by rigid cellulose cell walls, external to the cell membrane.
iii. They contain chlorophyll used for photosynthesis.
iv. They store carbohydrates as starch or sucrose.

Classification of plants
Classification of plants is the act of placing plants into groups based on their common features. The branch of biology
concerned with identifying, naming and classifying plants is called plant taxonomy.
The kingdom plantae (plants) according to RH Whittaker 1969 refers to the multicellular photosynthetic eukaryotes
with well-developed tissues. They are adapted to terrestrial and aquatic habitats. Plants are commonly classified based
on the following three techniques.
i. Botanical classification
ii. Agricultural classification
iii. Classification based on life cycle.

Botanical Classification
Botanical classification is based on the structural complexity of plants and their life history. This uses the bionomial
system of nomenclature in which every plants is given two names i.e. generic (genus) name and specific (species).
The most recent botanical classification of plants is based on four divisions which include;
i. Thallophyta (Algae)
ii. Bryophyte
iii. Pteridophyta
iv. Spermatophyte (Angiospermophyta or angiospermatophyta)

Thallophyta
These are mostly aquatic green plants that have filamentous or thalloid bodies devoid of roots, stem or leave e.g.
algae.
Characteristics
i. They are simple plant without roots, stem and leaves.
ii. Some are unicellular e.g. chlamydomonas while other are multicellular e.g. spirogyra.
iii. They are mostly aquatic with a few on damp soils and shady places. Examples includes volvox,
diatoms,sargassum and spirogyra.
iv. All algae have chlorophyll. Some have blue, yellow brown and red pigments which mask the chlorophyll.
v. They have no specialized reproductive organs or cells but can exhibit sexual and asexual means of
reproduction. Examples include the single free-living algae like: spirogyra, volvox, seaweeds.
Note: Fungi might also be classified under the thallophytes but it has already been treated as a separate kingdom

Spirogyra Volvox
20
Bryophyta (liverwort and mosses)
These are simple plants that commonly grow in damp places on land. They possess simple leaves and rhizoids in place
of roots e.g. moss and liverwort.
Characteristics of Bryophyta
i. They are non-vascular multicellular organisms.
ii. They have chlorophyll as the only photosynthetic pigment.
iii. They are terrestrial but live in moist environment.
iv. Their body is differentiated into stem like and leaf-like structure.
v. They lack true roots, stems and leaves. They lack vascular tissues and therefore unable to transport food and
other materials round the body.
vi. The leaves of some are spirally arranged on the stem.
vii. Asexual reproduction is by spore while-sexual reproduction is by gamete. Water is needed for sexual
reproduction hence they are regarded as the amphibians of the plant kingdom.
viii. Some are in thalloid form e.g. liverwort and moss.

Moss Liverwort

Pteridophyta (ferns)
These are the vascular non-flowering spore producing plants. They possess vascular tissues for conducting water and
food. They are known as land plants e.g. fern and club moss.
Characteristics
i. The body is differentiated into true roots, stems and leaves with well developed vascular bundles comprising
xylem and phloem. The young leaves are coiled.
ii. The stem is a rhizome.
iii. Reproduction is by means of spores.
iv. Asexual reproductive organ consist of sori while sexual reproductive organ is a heart – shaped prothallus.
v. Water is needed for sexual reproduction (prothallus) as the sperms need water to swim to the egg.
vi. They are mainly terrestrial with few aquatic members. Examples includes Dryopteris, Cyclosorus,
Platycerium and Phymatodes which are terrestrial while Nephrolepis, Salvinia, and Azolla are aquatic
members.
Note: The bryophyte and pteridophyte both undergo an alternation of generation between a haploid gametophyte
stage and a diploid sporophyte stage. In the bryophyte the gametophyte is dominant but in the fern, the sporophyte
stage is dominant.

Fern
21
Spermatophyta
These are vascular seed bearing plants having well-developed roots, stem and leaves. Their seeds develop from
embryos e.g. all seed plants such as mango, orange, palm fruit etc.
Spermatophyte is divided into two types;
i. Gymnosperm – non flowering plant that produce seed.
ii. Angiosperm – flowering plants that produce seed.
Angiosperms are further divided into two types: a. Monocotyledons – those with one seed leaf.
b. Dicotyledons – those with two seed leaves.

Gymnosperm – non flowering plant that produce seed.

These are non-flowering plants. Their seeds are not enclosed in an ovary or fruit. They exposed on the surface of a
leaf – like structure
Characteristics of Gymnosperm
i. They are large plant with well developed vascular bundles, with true roots, stem and leaves.
ii. Their leaves are green in colour, small, scaly and needle-like.
iii. They have cones where naked seed are formed because there is no ovary. Fruit is not formed.
iv. They are terrestrial in habitat. Example include whistling pine (casuarina sp.) and cycas.
Examples of Gymnosperm

22
Angiosperm – flowering plants that produce seed. They are further divided into two types:
a. Monocotyledons
b. Dicotyledons
Seed Cotyledons are structures that provide energy for for the young plant; monocots have one cotyledon while dicot
have two cotyledons
Note: Double fertilization which is a complex fertilization mechanism involving the joining of a female gametophyte
with two male gamete (sperm) is present only in flowering plants/angiosperm.

Characteristics of Angiosperm
i. They possess true flowers for sexual reproduction.
ii. They possess well developed true root, stems and leaves.
iii. They have well developed vascular bundles.
iv. Seeds and fruits are produced after fertilization. Seed are enclosed in an ovary.
v. They are terrestrial but few are aquatic. Examples are oil palm tree, goat-weed, orange tree, mango tree, guava
tree and maize.
Difference between Dicotyledon and Monocotyledon
Dicotyledon Monocotyledon
1. Flowers occurs in parts of fours or fives. Flowers occurs in parts of threes.
2. Embryo consists of two cotyledons. Embryo is made up of one cotyledon.
3. Leaves are net veined. Leaves are parallel veined.
4. Tap root present. Possess fibrous root.
5. Vascular bundles occur in rings in the stem structure. Vascular bundles scattered in the stem structure.
6. Secondary growth occurs. Absence of secondary growth.

23
Agricultural Classification of Plants
In this classification, plants are classified according to the main food substances existing in them or according to
economic uses.
i. Cereal: These are grain crops grown mainly for their seeds which are very rich in carbohydrate e.g. rice, maize,
millet, guinea corn (sorghum) wheat, oat, barley.
ii. Legumes (pulses): These crops have nodules or swelling in their roots. They are rich in proteins. They include
cowpea, soya bean, groundnut, pigeon, pea and Mucuna.
iii. Root tuber: These are crops grown primarily for the food stored in their swollen roots e.g. cassava, carrot and
sweet potatoes.
iv. Stem tuber – These are underground stem which are swollen with food reserve e.g. cocoyam, irish potato and yam.
v. Vegetable crop – These are plants grown chiefly as vegetables e.g. cabbage, carrot, egg plants, lettuce, okra,
onions, spinach, tomato, green (Amaranthus spp), flute pumpkin. They are rich in vitamins and minerals.
vi. Fruit crops: These are crops grown for their fruits and supply vitamin, minerals and sugar. Examples includes
orange, mango, guava, pineapple, pawpaw, banana, cashew, avocado pear etc.
vii. Beverage crops: These are grown for use as beverage drinks or a source of refreshment. They supply minerals to
the body examples are cocoa, coffee and tea.
viii. Oil crops – The seeds or fruits of these crops are rich in oils and fats. Examples include oil palm, groundnut,
cotton, coconut, shea butter and sunflower.
ix. Latex crops: These crops produce milky fluid called latex. The latex is used for various industrial purposes such
as making of tyres, tubes and plates. A good example of latex crop is rubber (Hevea brasiliensis) other examples
are Ficus elastica, Funtumia elastica (lagos rubber) and Landolphia owariensis.
x. Fibre crops – These supply ropes and threads for textile industry. The crops include cotton, sisal hemp, jute,
guinea hemp, baobab, sorrel plant etc.
xi. Spice crop: These are crops which are used in flavouring foods. Example include ginger, onions, pepper, thyme
xii. Stimulants: These are crops that produce substances used as stimulant for medical purposes. Examples are
cocaine plant kola, lime, indian hemp or marijuana and Neem plant.
xiii. Forage crops: These crops are grown for feeding farm animals. They consist mainly of legumes and grasses.
Examples are guinea grass, elephant grass, gamba grass, Centrosema, Calapogonium, Stylosantes etc.
xiv. Nuts: These are crops whose fruits consist of hard shells that enclose fleshy part which are edible. Examples are
coconut, cashew and oil palm.
xv. Wood crops: Some trees provide hardwood, which is used mainly for making furniture or building materials
e.g. ebony, mahogany and iroko (Chlorophora excelsa) some tree yield softwood used for wood pulp and paper,
as well as for buildings.

Classification of crops according to life cycle

On the basis of their life cycle, plants are classified into the following.
i. Annual crops: These are plants that complete their life cycle in one year (one growing season). They germinate,
grow, mature, produce seed and die within one year. They include maize, yam, groundnut, rice, beans, millet, jute,
flour, soughum, etc.
ii. Biennial crops: These are crops which complete their life cycle in two years. The first year is for growth and
storage of food while the second year is for reproduction maturity and death. Examples are pineapple, cocoyam,
cassava, plantain, carrot, onions, ginger, cabbage, radish, turnip and sugar beet.
iii. Perennial crops: These are crops that take three or more years to complete their life cycle. They are mainly tree
crops and include cocoa, rubber, mango, oil palm and orange. Most of the perennials shed their leaves once a year
and are called deciduous evergreen.

Example
One important characteristic of green plants is that they
A. possess specialized sense organs B. are usually motile
C. are autotrophic D. respond slowly to stimuli. (2005/7)
Answer: C – green plant can manufacture their own food through the process of photosynthesis, hence they are called autotroph.
Example
The order of evolutionary trend in plants is
A. Bryophyta, Thallophyta, Pteridophyta and Spermatophyta
B. Thallophyta, Bryophyta, Pteridophyta and Spermatophyta
C. Spermatophyta, Pteridophyta, Bryophyta and Thallophyta
D. Bryophyta, Pteridophyta, Spermatophyta and Thallophyta (2008/60)
Answer: B – By “evolutionary trend”, they mean that one should arrange the plant classification from simplest to most complex.

24
Example
Which of the following characteristics features is not associated with monocotyledonous plants?
A. Well differentiated sepals and petals B. Presence of fibrous root system
C. Presence of narrow leaves D. Floral parts are in multiples of three. (2015/19)
Answer: A – Monocotyledonous plants do not have well differentiated sepals and petals.
Example
Gymnosperms bear naked seeds because they lack
A. Ovary B. Colourful flowers C. Pollen grains D. Stigma (2016/2)
Answer: A – In Angiosperms, seeds are enclosed in an ovary but in Gymnosperms seeds are borne naked on cones as
they lack ovary.
Example
One of the similarities between algae and mosses is their possession of
A. chlorophyll B. stem C. leaves D. roots. (1999/5)
Answer: A – Chlorophyll is a common characteristics of all green-plant.
Stem, leaves, and roots are found in higher plant (e.g. spermatophytes)
Example
The classes of plants the root system is diagrams I and II below represent respectively are

A. dicotyledoneae and Monocotyledoneae B. Monocotyledoneae and Dicotyledoneae

C. Dicotyledonaea and Dicotyledoneae D. Monocotyledoneae and Monocotyledoneae (2019/4)
Answer: A – Dicotyledonous plants have tap roots, while monocotyledonous plants have fibrous root.
Example
Which of the following characteristics is that of a plant?
A. Absence of chlorophyll B. Immediate response to stimuli
C. Carbohydrate is stored as glycogen D. Presence of large vacuoles in cells (2020/1 PC1)
Answer: D – Plant cells are characterized by the presence of large vacuoles. All other option (A to C) are features of animals.
Example
Which of these organisms are NOT autotrophs?
A. algae B. ferns C. fungi D. grasses (2005/20 Neco Nov)
Answer: C – Fungi are not autotrophs because they lack chlorophyll and hence, they cannot manufacture their own food.
Example
Which of the following is a bryophyte?
A. Bladder wort B. fly trap C. liver wort D. pitcher E. sundew (2018/10 Neco)
Answer: C – Liver wort is a bryophyte. All other options (A, B, D and E) are carnivorous plants.
Example
Plants are classified into the following classes except
A. Bryophyta B. coelentrata C. pteridophyta D. spermatophyta E. thallophyta (2014/2 Neco)
Answer: B – Coelenterata is a phylum belonging to the the animal kingdom.
Example
Bryophytes are different from spermatophytes because they
A. live in moist habitats B. reproduce sexually and asexually C. have small leaves D. have no vascular tissues (2019/1 NABTEB)
Answer: D – Bryophytes are non-vascular green-plants i.e they have no vascular tisues.
Example
Which of these best describes the flower of a dicotyledonous plant?
A. the petals and sepals do not wither after formation of the fruit B. the petals and sepals form part of the fruit
C. the petals and sepal occur in four, five or multiples of four or five
D. the petals and sepals are well coloured (1999/12 NABTEB)
Answer: C – In Dicotyledonous plants, the petals and sepals are arranged in fours or five or multiples of four or five
but in monocotyledonous plants, the petals and sepals are arranged in threes or multiples of three.

25
Example
1a. State Three characteristics of ferns. (1999/1a NABTEB)
Answer:
i. Reproduction is by means of spores.
ii. Water is needed for sexual reproduction (prothallus) as the sperms need water to swim to the egg.
iii. The stem is a rhizome
Example
One common feature of the fungi, algae, mosses and ferns is that they
A. are photosynthetic B. show alternation of generation
C. reproduce by means of conjugation D. can survive dry conditions E. have no seeds (1981/39 JAMB)
Answer: E – They are all seedless/ non-seed producing.
Example
Mosses, liverworts and ferns can be grouped because they
A. are all aquatic plants B. all grow in desserts
C. are seedless plants D. have undifferentiated plant bodies (1984/3 JAMB)
Answer: C – They are all seedless plants.
Example
Spirogyra and Mucor can be grouped together as Thallophyta because
A. they are unicellular organisms B. their pores could be dispersed by wind
C. there are capable of independent lives D. they reproduce sexually only
E. their bodies are made up of thallus and filaments alternatively (1984/4 JAMB)
Answer: E – This is so because during their growth process, they alternate from thallus to filaments.
Example
Which of the following is seed bearing?
A Mosses B. Whistling pine C. Algal filaments D. Liverwort E. Fern fronds (1985/3 JAMB)
Answer: B - Whistling pine is a spermatophyte (seed bearing plants)
Example
In lower plants like mosses, the structure which performs the function of roots of higher plants is called
A. root hairs B. rhizoids C. rootlets D. hyphae E. thalli (1985/10 JAMB)
Answer: B – Rhizoids are root-like structures on the underside of the thallus in some lower plants. They provide
anchorage to the plant and help in conducting water. This is a similar function to the roots of higher plants.
Example
Which of the following has cones?
A. Angiosperm B. Gymnosperm C. Pteridophyte D. Bryophyte (1986/4 JAMB)
Answer: B – Gymnosperm are plants that have cones in which naked seeds are formed.
Example
In a plant exhibiting alternation of generations the diploid multicellular stage is known as
A. gametophyte B. spermatophyte C. holophyte D. sporophyte (1987/4 JAMB)
Answer: D – sporophyte phase is a phase in the life cycle of lower plants that is diploid . It is the asexual stage
Example
A characteristics that distinguishes bryophytes from flowering plants is the
A. possession of true stems and leaves B. ability to reproduce asexually
C. absence of vascular tissues D. ability to grow in moist habitats (1987/5 JAMB)
Answer: C – Bryophyte are non-vascular plants but flowering plants are vascular.
Example
In most true ferns sporangia are grouped into
A. indusium B. fronds C. prothalli D. sori (1987/10 JAMB) Answer: D – Sori

EXERCISE 3.5
1. In the reproduction of mosses, water is essential because
A. they live in moist habitats B. they cannot reproduce without water
C. the male gametes must swim to fertilize the ovum D. they produce spores (1987/11 JAMB)
2. The term “thallophyta” refers to
A. ferns and mosses B. algae and fungi C. mosses and liverwort D. fungi and ferns (1988/3 JAMB)
3. The prothallus of a ferns is equivalent to the gametophye generation of a moss because it
A. is conspicuous B. has rhizoids C. bears sexual organs D is multicellular (1988/8 JAMB)
26
4. A multinucleate body without internal cell boundaries is characteristic of
A. bryophytes B. fungi C. algae D. gymnosperms (1989/6 JAMB)
5. The algae, bryophytes and pteridophytes are similar in that they
A. are seed weeds B. have no vascular tissues
C. require moisture for fertilization D. are microscopic plants (1990/5 JAMB)
6. The spores of ferns are dispersed by
A. wind B. water C. insects D. explosive mechanism (1990/6 JAMB)
7. In bryophytes, sex organs are produced in the
A. gametophyte B. rhizoid C. protonema D. sporophyte (1990/7 JAMB)
8. Angiosperms and gymnosperms belong to the plant group known as
A. schizophyta B. bryophita C. pteridophyta D. spermatophyte (1991/3 JAMB)
9. Which of the following are non-green plants?
A. Euglena B. Fungi C. Spirogyra D. Angiosperms (1991/4 JAMB)
10. Which of the following are differentiated into true roots, stems and leaves?
A. Algae B. Schizophyta C. Pteridophyta D. Bryophyta (1991/6 JAMB)
11. The annulus of fern sporangium helps in
A. spore dispersal B. conduction of mineral salts
C. Trapping of light energy D. transportation of water. (1991/8 JAMB)

12. Which of the following correctly summarizes the life cycle of a fern plant?
A. Spore → prothallus → thallus → sporangium
B. Male and female gametangia → Zygospore → sporanglum → spores
C. Spore → thallus → spermatozoa + ovum → sporangium
D. Prothallus → spermatozoid + egg cell → leaf plant → sporangium → spore (1992/3 JAMB)
13. Production of naked seeds is a distinctive feature of the group of plants called
A. grasses B. conifers C. legumes D. palms (1993/2 JAMB)
14. In which of these features do bryophytes differ from pteridophytes?
A. Absence of flower B. Alternation of generation
C. Dependence on water for reproduction D. Presence of a vascular system. (1993/3 JAMB)
15. Which of the following organs or cell components are common to both the sporophyte and the gametophyte of a fern
A. Rhizoids B. Roots C. Chloroplasts D. Leaves (1993/4 JAMB)
16. Which is the correct order in an evolutionary sequence for the following plant groups?
A. Bacteria → ferns → algae → moses → seed plants
B. Bacteria → ferns → moses → algae → seed plan
C. Bacteria → algae → moses → fern → seed plants
D. Bacteria → moses → algae ferns → seed plants. (1994/5 JAMB)
17. Green plants are distinguished from other living organisms by their ability to
A. make use of water B. make use of oxygen
C. respond to sunlight D. manufacture their own food. (1994/3 JAMB)
18. Which of the following perform similar functions?
A. Ascospores and ascocarp B. Antherozoids and rhizoids
C. Sorus and indusium D. Strobili and inflorescence (1997/7 JAMB)
19. The order in which organic evolution has progressed in plants is
A. thallophyta, schizophyta, bryophyta, pteridophta and spermatophyta
B. bryophyta, pteridophyta, spermatopyta, thallopthya and schizophyta
C. pteridophyta, spermatophyta, thallophyta, schizophyta and bryophyta
D. schizophyta, thalophyta, bryophyta, pteridophyta and spermatophyta (2000/4 JAMB)
20. Which of the following groups is the most advanced?
A. Pteridophytes B. Bryophytes C. Thallophytes D. Gymnosperms. (2001/5 JAMB)
21. Most monocots are easily recognized by their
A. short leaves with petioles B. long and sword-like leaves
C. long and palm-like leaves D. short leaves with many veinlets. (2001/6 JAMB)
22. One distinctive feature in the life history of liverworts is that they exhibit
A. vegetative reproduction B. Alternation of generation
C. sexual reproduction D. asexual reproduction (2003/6 JAMB)
27
23. The absence of special food and water-conducting systems restricts the body size in
A. liverworts, mosses and ferns B. the thallophytes and the pteridophytes
C. algae, liverworts and mosses D. the bryophytes and the pteridophytes (2004/47 JAMB)
24. Angiosperms and gymnosperms belong to the class
A. spermatophyte B. bryophyte C. schizophyta D. pteridophyta (2005/43 JAMB)
25. The dominant phase in the life cycle of a bryophyte is the
A. gametangium B. sporophyte C. gametophyte D. prothallus (2006/33 JAMB)
26. The evidence that supports the advancement of ferns over moses is derived from
A. comparative anatomy B. molecular records
C. biochemical similarities D. physiological records (2006/34 JAMB)
27. The dominant phase in the life cycle of a fern is the
A. gametophyte B. prothallus C. sporophyte D. antheridium (2010/4 JAMB)
28. Seed plants are divided into
A. angiosperms and gymnosperms B. monocotyledons and dicotyledons
C. thallophytes and bryophytes D. tracheophytes and ferns (2011/4 JAMB)
29. Plants that show secondary growth are usually found among the
A. thallophytes B. pteridophytes C. monocotyledons D. dicotyledons (2012/6 JAMB)
30. Double fertilization is a unique feature of
A. angiosperms B. bryophytes C. pteriophytes D. algae (2019/6 JAMB)
31. A wide pith with a ring of conducting tissue is characteristic of the root of
A. sunflower B. maize C. bean D. okra (1991/16 JAMB)

Kingdom Animalia (Eukaryotes)

This kingdom is made up of invertebrates and vertebrates. The first eight phyla of the animal kingdom are
invertebrate, they are animals without backbone and internal skeleton (endoskeleton). The invertebrates comprises of
the following phyla.
i. Phylum porifera (sponges)
ii. Coelenterate (cnidaria and hydra)
iii. Platyhelminthes (flat worm)
iv. Nematoda (round worm)
v. Annelida (sequined worm e.g. earthworm)
vi. Mollusca (e.g. snail)
vii. Echinodermata (e.g. star fish and sea cucumber)
viii. Arthropoda (e.g insects, centipede, ant etc)

The vertebrates belong to the phylum chordata. They are characterized by the presence of a backbone or simple pre-
backbone structure called notochord.

Characteristics of the animal kingdom

i. They are all multicellular organisms and motile
ii. DNA is located in nucleus enclosed with nuclear membrane.
iii. The cells have no cell walls.
iv. They possess nervous system except the sponges.
v. They possess true tissues except the sponges.
vi. The possess heterotrophic mode of feeding.

Phylum Porifera (sponges)

The sponges contain tiny pores that are basic structures in their functional activity. They are the most primitive in the
animal kingdom. They are multicellular i.e cellular level of organisaion, sessile (i.e. they do not move but water
current moves through them) aquatic organisms. They are diploblastic (i.e. composed of two cell layers).
Reproduction is both asexual (by budding) and sexual (by production of gametes).
Characteristics
i. They are all aquatic, mostly marine; a few are fresh water forms.
ii. Many of them have branches and a variety of body forms such as vase – like and globular structures.
iii. Most are radially symmetrical, while a few are asymmetrical.
iv. They are multicellular organisms.
v. Their bodies have many pores.

28
A = Scypha; B = Leucosolenia; C = Syconoid sea sponge

Phylum coelenterata: These are multicellular animals with two body layer (diplobastic). That is tissue–level of
organization. They are mostly aquatic. Example are sea anemone, jelly fish, hydra and coral.
Characteristics
i. They are entirely aquatic with some in fresh water but majority are found in marine water.
ii. They are radially symmetrical.
iii. They are mostly of two basic forms polyps and medusa.
iv. Exoskeleton is made of chitinous, calcerous or proteinaceous components.
v. They possess stinging cells called nematocyst.
vi. They have two distinct body layer (diplobastic) ectoderm and endoderm, separated by a middle layer called
mesogloea.
vii. They have only one body cavity called enteron.
viii. There is only one opening called mouth to the outside world. No anus.
ix. Mouth is surrounded by tentacles.
x. Asexual reproduction is by budding.
Examples are Obelia, Hydra, sea anemone, Physalia etc.

Cross section of Hydra (showing two layers cells) Hydra

29
Phylum Platyhelminthes (flatworm): These animals have dorsoventrally flattened bodies, hence they are also called
flatworms. They have no body cavity. They have, alimentary canal. Some are free living e.g planaria which live in
ponds and streams while others are parasitic in nature such fluke and tapeworms.
Characteristics
i. They are bilaterally symmetrical
ii. They are multicellular flatworms.
iii. They do not have body cavity (acoelomate)
iv. They are hermaphrodites and reproduce sexually.
v. They possess alimentary canal with highly branched diverticula. No anus.
vi. Some are free living e.g. planaria while others are parasitic e.g. liver fluke and tapeworms.
vii. They have three germ layers (triploblastic)

Fluke Tape worm

Phylum nematode (roundworm)

They are thread like and cylindrical without body cavity. Their alimentary canal has, two openings, the mouth and the
anus. Many of them are parasites e.g roundworm, hookworm, threadworm and guinea worms, Filaria etc.
Characteristics
i. They have soft cylindrical and slender bodies pointed at both ends.
ii. Body is not segmented.
iii. They have alimentary canal with both mouth and anus.
iv. They are bilaterally symmetrical
v. They are mainly parasitic but few are free living.
vi. They have false body cavity (pseudocoelomates)

30
Phylum Annelida (segmented worms)
This phylum comprises of the segmented worms such as earthworm and leech. They are metamerically segmented (i.e.
segmentation is both external and internal).
Characteristics
i. The body is segmented.
ii. The body is long and cylindrical.
iii. They possess true body cavity (coelomates) with a distinct head.
iv. The alimentary canal has two openings, the mouth and the anus.
v. They reproduce sexually and many are hermaphrodites.
Examples are earthworm, leech, tubeworm etc.

Earthworm Leech
Phylum Mollusca
Molluscs possess soft, non-segmented bodies with tentacles. Some have shells e.g snails, mussels, and squid whereas
others have no shells e.g slug and have internal shell such as octopus and sefia.
Characteristics
i. They have soft unsegemented body.
ii. Tentacles are present in most members.
iii. The body of most of them are covered with shells e.g. land snail (Achatina) while others are not e.g. octopus
and squid. The major mineral present in their shell is calcium.
iv. The eyes and tentacles are used for sensitivity. Examples are squid, mussel, periwinkles, snails, oyster,
octopus, slug.
v. Essentially they breathe through skin and gills situated in the palatial cavity but most land snails have a mantle
cavity within which there is a lung and breath through the pneumostome or the breathing pores.

Snail

31
Phylum Echinodermata
Echinoderms have spiny skin. Most of them are radially symmetrical and star shaped. They are all aquatic. Example
are sea cucumber, starfish, bristle star, sea urchin.
Characteristics
i. They are all marine organisms.
ii. They are radially symmetrical in adult but bilaterally symmetrical in larvae.
iii. Most of them are star shaped.
iv. They are triploblastic animals i.e. they have three body layer.
v. They possess tough spiny and calcareous exosketeton.

Star Fish

Phylum Arthropoda
This is the most successful phylum in term of diversity and also the largest present in the animal kingdom, it is divided
into the following classes:
1. Crustacea e.g. crab, crayfish, lobsters
2. Insecta e.g. cockroach, butterfly, housefly
3. Arachnida e.g. scorpion, mites, ticks, spider
4. Myriapoda e.g. centipede and millipede (diplopoda and chilopoda)
Characteristics
i. They have segmented body.
ii. Presence of jointed appendages which are used for feeding, movement, reproduction and irritability they
exhibit moulting or ecdysis (shedding of exoskeleton at intervals for growth).
iii. They are triploblastic (have three body layers).
iv. They are coelomates (have true body cavity)
v. Terrestrial and aquatic form present.
vi. They have bilaterally symmetrical bodies.
vii. Their bodies are usually divided into three regions (head, thorax and abdomen) but in some the head and
thorax are fused forming a cephalothorax.
Crustacea e.g. crab, crayfish, lobsters

Prawn(form of crayfish) Crab

32
Insectea e.g. cockroach, butterfly, housefly

Arachnida e.g. scorpion, mites, ticks

Scorpion Spider

Myriapoda e.g. centipede and millipede

Millipede Centipede

Differences between crustaceans, insects and arachnids

Features Crustaceans e.g. crabs Insect e.g. cockroach Arachnid e.g spider
Body division 2 i.e Cephalothorax and 3. i.e. head, thorax, and abdomen 2 i.e. prosoma and
abdomen opisthoma
Wings Absent Present Absent
Antenna 2 pairs A pair None
Eye A pair of stalked eyes A pair of compound Eight simple eyes
Walking legs 5 pairs of jointed legs 3 pairs of jointed legs 4 pairs of jointed legs
Respiratory organs Gills Trachea Lung books

33
Vertebrates
General characteristics of vertebrates (chordate)
1. They possess skeletons made up of cartilages or bones
2. They are bilaterally symmetrical
3. Thee body is divided into head, trunk and tails
4. The have two pair of limbs
5. They have well developed central nervous system with brain and spinal cords.
6. They have well developed sense organs.
7. They have efficient excretory organs
8. They have a closed blood system made up of a heart and muscular blood vessels.

Vertebrates are divided into five classes:

i. Pisces
ii. Amphibian
iii. Reptilia
iv. Aves
v. Mammalian

Characteristics of Pisces (i.e. bony fishes or osteichthtyes)

1. They are aquatic animals
2. The skin is covered by scales but few are without scales
3. They have fins which are used for movement in water.
4. They are poikilothermic or cold blooded animals
5. They have gills which are used for gaseous exchange
6. They have lateral lines or system used for detection of vibration and pressure in water
7. They have swim bladder which enables them to maintain buoyancy in water.
8. Reproduction is sexual and they have external type of fertilization
9. They are oviparous animals, i.e. the lay eggs which develop to adult stage outside the body of the adult female fish.
10. They have a two-chambered heart.

Bony fish (Tilapia)

Amphibian (characteristics)
1. They are poikilothermic or cold blooded animals
2. They have two pairs of limbs-forelimbs and hind limbs. There is presence of webbed toes in hind limbs.
3. They possess moist, soft skin without scales
4. Fertilisation is external
5. The young ones (tadpoles) are herbivores while adults are carnivores
6. They have poison glands on their skin which are used for defence.
7. The heart is two chambered in larva stage and three chambered in adult.
8. Breathing is by gills in larva stage and lungs, skin and mouth in the adult stage.
9. They do not show parental care e.g. toad, frog, salamander, etc.

Toad frog

34
Reptilia (characteristics)
1. They are poikilothermic or cold blooded
2. They have dry skin covered with scale
3. They have two pairs of limbs except snakes
4. Some are aquatic e.g. crocodile and turtle while others are terrestrial animals e.g. snakes and lizards.
5. They have lungs used for gaseous exchange.
6. Reproduction is sexual and fertilization is internal
7. They have oviparous mode of reproduction. I.e. the female lay fertilized eggs.
8. They have homodont dentition
9. The heart is three chambered except crocodile with four chambered heart.
10. They do not show parental care.

Lizard

Snake

Characteristics of aves
1. They are homoiothermic or warm blood animals
2. Their body is covered with feathers except the legs and the feet, which are covered with scales.
3. Their forelimbs are modified as wings for flight
4. The mouth is modified into horny toothless beak or bill
5. Their bones are porous light and in some cases filled with air
6. Their bodies are supported by two hind limbs
7. They use lungs for respiration
8. They exhibit oviparous mode of reproduction
9. The heart is four chambered
10. They show parental care for the young ones. E.g. pigeon, domestic fowl, ducks, ostrich, etc.

Cock Duck Hen

35
Mammalia (characteristic)
1. They are homoeothermic (warm blooded animals)
2. Their bodies are covered with hairs.
3. They have heterodont dentition, that is they have different sets of teeth.
4. They use lungs for gaseous exchange
5. They possess mammary gland which produce milk in adult females.
6. They are viviparous i.e. the young are born at an advanced stage of development. However, the monotremes lay
eggs which hatch into young ones that are nourished by milk secreted by mammary gland.
7. The heart is four chambered
8. Most possesses four limbs for locomotion
9. They have a well-developed brain
10. They show parental care.
Examples includes bats, man, cat, dog, rat, sheep etc.

Rat
Example
Which of the following depicts the external features of a rat as mammal?
A. Long intestine and tall B. Diaphragm and lungs
C. Milk and sweat production D. Fur and whispers (2002/5)
Answer: D – Fur is a hairy coat covering the external surface of some mammals (e.g. rat). Whiskers are long
protecting hairs at the sides of the mouth of some mammals (e.g. cat, rat etc)
Example
Hydra is able to perform all the following functions except
A. feeding B. movement C. photosynthesis D. egestion (2004/2)
Answer: C – Hydra is an animal and all animals lack chlorophyll hence can’t photosynthesize
Example
The group mollusca is characterized by the presence of
A. jointed appendages B. star-shaped bodies C. backbones D. soft, non-segmented bodies. (2005/2)
Answer: D – Mollusca possess soft, non-segmented bodies.
Example
Which of the following organisms is not classified as an animal?
A. Amoeba B. Paramacium C. Euglena D. Obelia (2010/1)
Answer: C – Euglena shares characteristics with both plants and animals.
All other options (A, B and D) belong to the animal kingdom
Example
The diagram below is an illustration of a crocodile. Use it to Answer: question 7 and 8

Which of the labelled parts enable the animal to stay under water most of the time?
A. I, IV, and V B. I, II and V C. I, III, and IV D. III, IV and V (2015/7)
Answer: B – Transparent eyelid (I), Eyes at the top of the head (II) and Nostril at the top of the nose (V),
help crocodile to see and breath while it is under water.
36
Example
Two characteristics features of the class to which the crocodile belongs are labelled
A. I and II B. III and IV C. II and IV D. II and V (2015/8)
Answer: B – Crocodile belongs to a class called reptilian. This class is characterized by the presence of scaly skin
and homodont dentition.
Example
The diagram below is an illustration of an Arthropod. Study it and Answer: question 4

The Arthropod in the diagram is not an insect because it

A. has a big head which is almost equal to the “thorax” B. has eight legs and no wings
C. does not have visible abdomen D. has head, thorax and abdomen (2017/4)
Answer: B – Insects possess three (3) pairs of legs. i.e. six legs
Example
Which of the following statements is true about arthropods?
A. prothorax bears only legs B. mesothorax bears only legs
C. metathorax bears only wings D. prothorax bears only wings (2018/2)
Answer: A – The prothorax bears only legs while the mesothorax and metathorax bear both legs and wings.
Example
The major mineral present in the shell of Molluscs?
A. copper B. sodium C. iron D. calcium (2019/25)
Answer: D – Calcium occur in form of calcium carbonate in the shell of moluscs.

Example
The information below is a list of features possessed by organisms. Use it to Answer: questions 4 to 6.
I - Segmented body
II - Coelom
III - Seta
IV - Chitin
The feature not possessed by Arthropods is
A. I B. II C. III D. IV (2020/4 PC1)
Answer: C – Seta is a feature in annelids and not arthropods
The feature common to both Arthropods and Annelids is
A. I B. II C. III D. IV (2020/5 PC1)
Answer: B – Arthropods and Annelids are coelomate, i.e. they possess true body cavity
The feature possessed by Annelids only is
A. I B. II C. III D. IV. (2020/6 PC1)
Answer: C – seta is present in annelids but not in arthropods
Example
The least complex of the following invertebrates is the
A. Coelenterate B. Annelid C. Mollusa D. Arthropod (2020/7 PC1)
Answer: A:
Increasing advancement

- Porifera (sponges)
- Coelenterate (cnidaria)
- Platyhelminthis (flat worms)
- Nematode (round worms)
- Annelid (segmented worms)
- Mollusca
- Echinodermata
- Arthropoda

37
Example
Which of the following characteristics is exhibited by animals but not by plants?
A. Feeding B. Growth C. Respiration D. Locomotion (2005/2 Nov)
Answer: D – Locomotion is the displacement of a whole organism from one place to another.
Plants only move parts of their body.
Example
Which of the following statements is not true of Hydra? It has
A. both mouth and anus B. stinging cells C. ectodermal and endothermal tissues D. radial symmetry (2005/3 Nov)
Answer: B – Hydra has only one opening called the mouth. Other options (A, C and D) are characteristics of hydra.

Example
A centipede differs from an earthworm in
A. having a segmented body B. being a herbivore
C. having jointed appendages on every segment D. having a definite anterior end (2004/1 Nov)
Answer: C – Centipede belongs to the phylum arthropoda and this phylum is characterized by the presence of joint
appendages on each of their body segment which they use for feeding movement, reproduction, and irritability.
Earthworm belongs to the phylum annelida and they are characterized by the presence of segmented body that lacks
joint appendages.
Example
The mouth-like Structure of Hydra is the
A. endoderm B. enteron C. hypostome D. endoblast (2004/3 Nov)
Answer: C – Hypostome are mouth-like structures in hydra.
Example
Which of these is an amphibian?
A. fish B. lizard C. rat D. snake E. toad (2018/7 Neco)
Answer: E – Toads and frogs belong to the class Amphibia. Snake and lizard belong to the class Reptilia.
Rat belongs to the class mammals.
Example
(ii) Give two characteristics of a reptile (2018/3c(ii) Neco)
Answer: They are poikilothermic or cold blooded, They have dry skin covered with scale

Example
Earth worm is an example of
A. Annelid B. coelenterate C. mollusca D. nermatode E. platyhelminthis (2014/4 Neco)
Answer: A – Earth worm is an example of annelid. Other examples of Annelids are leech, tubeworm etc.
Example
Which of these organisms is a protozoan?
A. hydra B. mucor C. paramecium D. spirogyra E. volvox (2005/3 Neco)
Answer: C – Paramecium, is an example of a protozoa. Spirogyra and volvox are lower plants, mucor is a fungus,
hydra is an example of organisms that belong to the phylum coelenterate (cnidarians)
Example
Spider belongs to which of the following classes in the phylum arthropoda?
A. arachnida B. chilopoda C. crustacean D. insect E. myriapoda (2008/6 Neco)
Answer: A – In the phylum Arthropoda, Spider belongs to the class arachnida. Other examples of arthropods that
belong to the class arachnida includes scorpions, ticks, mites, harvestman e.t.c
Example
The most successful group of invertebrates are
A. arthropods B. annelids C. mollusca D. nematodes (2019/3 NABTEB)
Answer: A – Arthropods are the most successful group of invertebrates
Example
Which of these animals is radially symmetrical?
A. squid B. hydra C. snail D. cockroach (2019/6 NABTEB)
Answer: B – Hydra belong to the phylum coelenterate (cnidrian) and they are radially symmetrical.
Other examples are: Sea anemone, jelly fish, coral etc.
Example
Roundworm belongs to the phylum
A. Nematoda B. Annelida C. Platyhelminthes D. Coelenterata (2001/31 NABTEB)
Answer: A – Nematoda are also called round worms.
38
Example
Which of these is NOT a bird
A. Pigeon B. Dove C. Ostrich D. Bat (2001/32 NABTEB)
Answer: D – Bats belong to the class mammalia this is because they possess characteristics such as:
 Presence of mammary glands.
 Presence of fur
 They are viviparous i.e. they give birth to their young ones alive.
The above characteristics pertains to mammals and are not found in birds.

Example
Cockroach belongs to the phylum
A. Arthropoda B. Platyhelminthes C. Vertebrata D. Echinodermata (2001/35 NABTEB)
Answer: A – Cockroach is an insect, hence it is under the phylum Arthropodsa.
Example
4a. State FIVE peculiar characteristic of mammals.
bi. Give THREE distinctive features of Arthropod
ii. Name the major groups of Arthropods with examples (1999/4a, b(i) & (ii) NABTEB)
Answer:
4a. i. They are homoeothermic i.e. warm blooded animals
ii. They have furs or hair
iii. They have heterodont dentition
iv. They show parental care
v. They possess four (4) chambered heart
bii. i. Insecta e.g. cockroach, housefly, butterfly etc.
bi. i. They possess segmented body. ii. Crustacean e.g. crab, crayfish, lobster etc.
ii. They are triploblastic (have three body layers) iii. Arachnida e.g. scorpion, mites, ticks
iii. They are bilaterally symmetrical iv. Myriapoda e.g. centipede and millipede
Example
Land snail belongs to the phylum
A. annelida B. arthropoda C. Echinodermata D. Mollusca E. nermatoda (2018/15 Neco)
Answer: D – Land snai; belongs to the phylim mollusca Other examples of molluscs includes mussels, squid, etc.
Example
Some of the features of an animal are scales, teeth, nares and backbone. The animal is likely to be a
A. toad B. bird C. lizard D. rat E. bat (1980/6 JAMB)
Answer: C – Presence of scales, teeth, nares and backbone best describes reptiles. Examples of reptiles are lizard,
snake, crocodile etc.
Example
Which of these animals is NOT metamerically segmented?
A. Tapeworm B. Earthworm C. Centipede D. Crayfish E. Shark (1982/3 JAMB)
Answer: E – From the listed options, it is only shark that doesn’t show Metameric segmentation. Metameric
segmentation is mostly found in Annelids and Arthropods. Earthworm is an annelid while centipede and crayfish are
arthropods. Although tapeworm (a platyhelminth) is neither an arthropod nor annelid, it however exhibits a false
metameric segmentation
Example
Which of the following structures is NOT found in the female agama lizard?
A. Pre-anal pads B. Eardrum C. Gular fold D. Nasal scale E. Nuchal chest (1983/6 JAMB)
Answer: E – The nuchal crest is an elevated ridge of tissue along the back of the neck of male agama lizard.
Example
Exoskeleton is NOT found in the
A. maggot B. mosquito larva C. earthworm D. caterpillar E. termite (1984/15 JAMB)
Answer: C – Exoskeleton is a characteristic possessed by arthropods. Earthworm lacks exoskeleton as it is not an
arthropod.
Example
A centipede differs from a millipede by it’s
A. colour B. numerous abdominal segments
C. paired legs on each abdominal segment D. poison claws E. cylindrical body (1983/23 JAMB)
Answer: D – Centipedes have poison claws but millipedes in contrast, do not have poison claws.
Note: Millipedes have two sets of legs (paired legs) per segment but centipedes have one set of legs per
segment. So, option C is wrong because centipede is the reference and not millipede.
39
Example
Which of the following invertebrates do NOT possess antennae
A. Centipede B. Crustacean C. Millipede D. Insect E. Spider (1984/5 JAMB)
Answer: E – Arachnids (e.g. spiders and ticks) do not have antenna
Example
Spirogyra and Mucor can be grouped together as Thallophyta because
A. they are unicellular organisms B. their pores could be dispersed by wind
C. there are capable of independent lives D. they reproduce sexually only
E. their bodies are made up of thallus and filaments alternatively (1984/4 JAMB)
Answer: E – Their bodies are made of thallus and filaments alternatively
Example
The male cockroach differs from the female by having
A. mandibles B. a pair of styles C. spiracles D. a pair of cerci (1986/11 JAMB)
Answer: B – Male cockroaches have a pair cerci and a pair of styles (needle like structures) below the cerci
while female cockroaches have only a pair of cerci but lack the style.
Example
Hydra removes undigested food by
A. passing it through the anus B. passing it through the mouth
C. means of a contractile vacuole D. egesting it through the body surface (1990/3 JAMB)
Answer: B – Hydra have only one body opening which is the mouth. Food goes in and out of their body through the mouth
Example
Sting – cells are normally found in
A. Flatworms B. Hydra C. Snails D. paramecium (1991/5 JAMB)
Answer: B – Phylum coelenterate (cnidaria) is characterized by the presence of sting-cells.
Example
In the earthworm, the cocoon is secreted by the
A. chaeta B. prostomium C. peristomium D. clitellum (1991/10 JAMB)
Answer: D – The clitellum is a specialized body segment in earthworm that secretes cocoon.
Example
The function of maxillipeds in the crayfish is to aid
A. walking B. swimming C. feeding D. respiration (1991/11 JAMB)
Answer: C – Maxillipeds are modified appendages used for feeding
Example
The respiratory organ in the land snail is the
A. radula B. mantle C. tentacle D. foot (1991/12 JAMB)
Answer: B – Mantle in land snail is used as a respiratory organ, the radula is used for feeding, the tentacle is used for
of olfactory orientation and search for food.
Example
The essential structural difference between Hydra and tapeworm is that while Hydra
A. has tentacles, tapeworm parasitic B. is diploblastic, tapeworm is triploblastic
C. has a mouth, tapeworm feeds by suckers D. has mesoderm tapeworm has mesogloea (1992/5 JAMB)
Answer: B - Platythelminthes (e.g. tapeworm) are triploblastic (have three body layers) while
coelenterates (e.g. hydra) are diploblastic (have two body layers)

EXERCISE 3.6
1. Annelids differ from nematodes in that they
A. exhibit bilateral symmetry B. are triploblastic
C. are metametrically segmented D. possess complete digestive system (1997/6 JAMB)
2. In snails, the hard calcareous shells are secreted by the
A. radula B. ctenidium C. pneumostome D. mantle (1998/4 JAMB)
3. The ability of the cockroach to live in cracks and crevices is enchanced by the possession of
A. wings and segmented body B. compound eyes
C. claws on the legs D. dorso-ventrally flattened body (1998/7 JAMB)
4. The group of arthropods that has no antennae is the
A. crustacean B. chilopoda C. arachnida D. diplopoda (1999/4 JAMB)

40
5. The possession of scales, laying of eggs with shells and bony structure of the head are characteristics shared
by
A. birds and reptiles B. fishes and birds
C. reptiles and fishes D. birds and mollusks (1999/3 JAMB)
6. A characteristic of vertebrates that is unique to mammals is
A. the presence of pentadactyl limb B. the possession of scrotum
C. parental care D. pulmonary circulation (2000/1 JAMB)
7. The most recently evolved structure in animals is the
A. feather B. ciclium C. scale D. hair (2000/2 JAMB)
8. Amphibians are normally found
A. on dry land and water B. in water and on moist land
C. on moist land D. in water. (2001/2 JAMB)
9. The joint structure in insects that bears organs which are sensitive to touch, smell and vibration is the
A. maxilla B. labium C. antenna D. abdomen. (2001/4 JAMB)
10. Water fleas, wood lice and barnacles belong to the group
A. arachnida B. crustacea C. insecta D. chilopoda (2001/7 JAMB)
11. Hermaphroditic reproduction can be found among the
A. annelids and molluscs B. Pisces and amphibians
C. coelentetrates and platyhelminthes D. arthropods and nematodes (2003/5 JAMB)
12. A peculiar characteristic of mammals is that they
A. have lungs B. have sebaceous glands C. are warm-blooded D. have teeth. (2004/48 JAMB)
13. Insects are considered the most successful among the invertebrates because they
A. have wings for flight B. possess exoskeletons
C. possess the ability to change their forms
D. Survive in various environmental conditions (2004/49 JAMB)

I. Rattus rattus
II. Agama agama
III. Bufo regularis
IV. Tilapia Zilli.
14. The order of evolutionary advancement of the above vertebrates is
A. IV, III, II, I B. II, III, IV, I C. I, IV, III, II D. I, II, III, IV (2005/39 JAMB)
15. The leech and the earthworm belong to the
A. arachnids B. annelids C. crustaceans D. mollusca (2005/46 JAMB)
16. Which of the following vertebrates has the most simple structured heart?
A. Reptile B. Fish C. Mammal D. Amphibian (2006/35 JAMB)

Use the diagram below to Answer: questions 36 and 37

17. A unique characteristic that distinguishes the class of vertebrates represented from other vertebrates is the
presence of
A. two pairs of limbs B. scales on the lower legs
C. a pair of wings D. a covering of feathers (2006/36 JAMB)
18. The structures used for offence and defence and defence are labelled
A. I and IV B. I and II C. II and III D. II and IV (2006/37 JAMB)
19. One primitive feature of the coelenterates is the possession of
A. a dorsal mouth B. radial symmetry C. bilateral symmetry D. a false foot (2006/38 JAMB)
41
20. A characteristic that best exemplifies the evolutional advancement of mammals over other vertebrates in the
A. viviparous mode of reproduction B. possession of paired limbs
C. terrestrial mode of life D. possession of a heart. (2006/39 JAMB)
21. The most abundant group of organisms in the animal kingdom is
A. Mammalia B. Aves C. Annelida D. Insecta (2008/8 JAMB)
22. Parental care is exhibited by
A. toads B. snails C. earthworms D. birds (2010/5 JAMB)
23. In which of the following groups of vertebrates is parental care mostly exhibited?
A. Amphibia B. Aves C. Mammalia D. Reptilla (2011/5 JAMB)
24. Which of the following is most advanced in the evolutionary tread of animals?
A. Liverfluke B. Earthworm C. Snail D. Cockroach (2012/4 JAMB)
25. An arthropod that is destructive at the early stage of its life cycle is
A. butterfly B. mosquito C. bee D. millipede (2012/8 JAMB)
26. An animal body that can be cut along its axis in any plane to give two identical parts is said to be
A. radially symmetrical B. bilaterally symmetrical C. asymmetrical D. symmetrical (2012/9 JAMB)
27. Which of the following possess mammillary gland?
A. Dogfish B. Whale C. Shark D. Catfish (2012/10 JAMB)
28. Which of the following describes a characteristic of arthropods?
A. The organism finds it easy to grow freely B. The organism has a pair of jointed appendages
C. The body is not divided into a number of segments D. The body is covered by chitin (2013/8 JAMB)
29. The chitin in the exoskeleton of many arthropods is strengthened by
A. Lipids B. proteins C. calcium compounds D. organic salts (2013/31 JAMB)
30. The first vertebrates to venture out of water and live on land are the
A. Pisces B. Amphibians C. Reptiles D. Aves. (2016/37 JAMB)
31. A common characteristic found among the crustaceans is the possession of
A. a pair of antennae B. a pair of walking legs of each segment
C. Four pairs of walking legs on the cephalothorax D. two pairs of antennae. (2016/43 JAMB)
32. In which of the following groups of invertebrates are flagella cilia found
A. annelids B. protists C. coelenterates D. Anthropoids. (2016/44 JAMB)
33. The following organisms are hermaphrodites EXCEPT
A. snail B. taenia C. schistosomia D. earthworm (2019/10 JAMB)

34. Which of the following phyla have members with both internal and external segmentation?
A. platyhelminthes B. nematode C. annelid D. mollusca (2019/12 JAMB)
35. State one difference each between Hydra and mammals with respect to:
(i) level of organization; (ii) symmetry; (iii) number of body layers. (1991/1d)
36. Which of the following lacks chaetae, tentacles and antennae.
A. Snail B. Crab C. Millipede D. Earthworm (1986/7 JAMB)

REVISION EXERCISE
1. A virus can sometimes be regarded as a living organism because it
A. causes disease in plants and animals B. exists in a variety of shapes
C. reproduces in living cells D. is easily visible with the aid of an electron microscope. (2005/3)
2. A major difference between plants and animals only
A. there is free movement in animals while this is limited in plants
B. there is indefinite growth in animals only
C. animals consume inorganic materials as food, while plants consume organic materials
D. animals give up carbon-dioxide as a waste product of respiration while plants do not. (2005/4)
3. A serious disadvantage of complexity in higher organisms is
A. a high demand for food and energy B. ability to function in many specialized roles
C. little amount of energy dissipated in functioning D. specialization of parts of the body. (2005/8)
4. The following life processes are common to both plants and animals except
A. respiration B. growth C. reproduction D. photosynthesis (2006/1)

42
5. Which of the following features does not necessarily place Paramecium at a higher level of organisation over
Amoeba?
A. Presence of cilia B. Absence of pseudopodia
C. Presence of micro and meganuclei D. Presence of more than one food vacuole. (2008/2)
6. (b) In a tabular form, state four differences between plants and animals (2014/1b)
7. Which of the following groups of animals do not possess a nervous system?
A. Porifera B. Cnidaria C. Platyhelmintthes D. Nematodia (2017/1)
8. Plants are similar to animals in
A. possessing well developed excretory organs B. carrying out tissue respiration
C. moving from place to place D. synthesizing their own food
E. bringing their young one alive (1990/1 June Health Science)
9. Which of the following pairs of vital characteristics is common to all living organisms?
A. Reproduction and increase in size B. Photosynthesis and excretion
C. Respiration and photosynthesis D. Reproduction and respiration (2005/1 Nov)
10. One of the roles played by proteins in the human body is that they
A. act as solvents B. act as an insulator
C. repair damaged tissues D. are the main source of energy (2005/34 Nov)
11. Which of these organisms exhibit both plant and animal features?
A. amoeba B. Euglena C. Mucor D. Paramecium E. Spirogyra (2007/1 Nov)
12. Which of the following distinguishes a plant from an animal?
A. ability to live B. ability to respire
C. ability to display sensitivity D. presence of chlorophyll (2001/2 NABTEB)
\\\\\\\

13. 1.(a) Draw a large labelled diagram of a named unicellular organism that behaves like a plant as well as an
animal.
(b) What characteristics do the organism possess that make it live like:
i. A plant? ii. An animal?
(c) Why is virus classified as a living thing? (2001/1a, b, c NABTEB)
14. bi. Is virus a living or non-living thing? Give two reasons in each case to support your Answer: .
ii. Draw and label (8-10)cm long of an euglena (2017/1b (i) & (ii) NABTEB)
15. Asexual reproduction does NOT occur in
A. Mucor, Spirogyra and Paramecium B. Penicillium, paramecium and Amoeba
C. Mucor, Rhizopus and Penicillium D. Amoeba, Spirogyra and Mucor
E. Rhizopus, Ascaris and Amoeba (1984/34 JAMB)
16. The algae, bryophytes and pteridophytes are similar in that they
A. are seed weeds B. have no vascular tissues
C. require moisture for fertilization D. are microscopic plants (1990/5 JAMB)
17. In which of the following organisms would glycogen be stored?
A. Spirogyra B. Chlamydomonas C. Rattus D. Magnifera (1993/6 JAMB)

43
The Cell
Cell as a Living Unit of Organisms
The cell is the basic structural and functional unit of all living organism. The protoplasm is the organized complex
material of which living cells are made.
The cell is regarded as the basic unit of all living things because it can carry out all life activities such as feeding,
reproduction, excretion, growth, adaptation, etc.
Unicellular organisms are made up of one cell e.g. amoeba, paramecium, chlamydomonas, euglena, etc.
An organism may consist of many cells, such organism is said to be multicellular. E.g. hydra, earthworms, birds, man,
Talinum(water leaf), mangos, egg cell e.t.c

Some facts to note:

i. The smallest cell is Mycoplasma (a bacteria).
ii. The largest cell is an egg cell of an ostrich.
iii. The longest cell is the nerve cell.
iv. The largest cell in the human body is the female ovum.
v. The smallest cell in the human body is the male gamete (sperm cell)

Example
Amoeba can be compared with a multicellular organism because it
A. has ability to perform all functions of a complex organism B. undergoes sexual reproduction
C. possesses large cells within its endoplasm D. has ability to synthesize glucose from raw materials (2000/3 Nov)
Answer: A – Amoeba can perform all the life function of multicellular organisms by the working together of different
organelles. N.B: Organelles in unicellular organisms are equivalent to organs in multicellular organisms.
Example
The largest single cell in living organisms is the
A. sperm cell B. unfertilized egg of a bird C. bacterium cell D. fat cell (2005/5 Nov)
Answer: B – The unfertilized eggs of a bird is the largest single cell in living organism. Mycoplasma (a bacteria) is the
smallest single cell organism. The sperm cell is the smallest single cell in the human body. The nerve cell is the longest cell in the
human body. The female ovum is the largest cell in the human body.
Example
The cell is a functional unit of living organisms because
A. multicellular organisms are made up of cells
B. all the cells in a multicellular organism function as a single cell
C. the function of a multicellular organization is the sum total of the functions of its constituent cells
D. the function of a single cell is superior to that of the multicellular organism
E. the cells of a multicellular organism are similar in structure. (1991/1)
Answer: C – The collective functions of individual cell determines the overall function of a whole organism, hence it
is the functional unit of living organisms.

Forms in which living things exist.

Living things exist as:
i. Independent organism i.e. free living unicellular organism e.g. amoeba, paramecium, euglena
ii. Colony e.g. volvox, eudorina, pandorina, sponges
iii. Filament e.g. spirogyra, zygnema, ulothrix, chladophora
iv. As part of another living organism e.g. cheek cell, onion cell, epidermal cell, parenchyma cell

44
Independent organisms
Amoeba
Amoeba proteus is the simplest heterotrophic unicellular organism, having no definite shape. It has the ability to alter
its shape by extending and retracting of its pseudopods (amoeboid movement). Its internal content consists of a
nucleus and a cytoplasm. The cytoplasm is divided into a non-granular outer layer called ectoplasm and a granular
inner layer called endoplasm

Amoeba

Functions of labeled parts

i. Pseudopodium: used for movement, used for food capture
ii. Ectoplasm: ectoplasm forms pseudopodia for movement and food capture, exchange of gases
iii. Contractile vacuole: it excretes wastes liquid such as dissolved ammonia (for osmoregulation)
iv. Food vacuole: it stores food and it is the site of food digestion
v. Nucleus: control directly or indirectly most of the cellular activities, it carries chromosomes which are
hereditary units, it initiates cell division.

Paramecium
Paramecium caudatum is a slipper shaped organisms with a pointed posterior end and a blunt anterior end. It has two
nuclei (mega and micro nuclei).The micronuclei which is the smallest controls sexual reproduction and the macro
nucleus controls the other activities of the cell. The two contractile vacuoles (anterior and posterior) are for excretion
and osmo-regulation.

Paramecium
Functions of labeled parts:
i. The two contractile vacuoles are for osmo-regulation and excretion.
ii. Food vacuole is responsible for digestion.
iii. The micro nucleus controls sexual reproduction.
iv. Mega nucleus controls other (non-reproductive) activities of the cell.
v. Cilia is used for movement.
vi. Trichocyst is used for trapping preys/offense and defense.
vii. Pellicle helps paramecium maintain a definite shape.
viii. The gullet helps to form food vacuoles as they are been collected.

45
Euglena
Euglena viridis is a unicellular protist that shows both “plant-like” and “animal-like” features. Some of its animal-like
characteristics includes: Possession of flagellum for locomotion, presence of contractile vacuole for excretion,
possession of eyespot which responds to light, presence of gullet for passage of food, plasma membrane called pellicle
and ability to carry out holozoic nutrition in the absence of light. While its plant-like characteristics include:
possession of chloroplast and ability to photosynthesize in the presence of light, possession of pyrenoid and storage of
starch in form of paramylum granules.

Euglena

Function of labeled parts:

i. Flagellum: For movement.
ii. Gullet: For ingestion of food.
iii. Contractile vacuole: For osmoregulation.
iv. Pellicle: For Euglenoid movement
v. Chloroplast: For photosynthesis
vi. Eyespot: Its for response to light stimulus.

Chlamydomonas
Chlamydomonas reinhardtii also called the green yeast due to its shape and size. It is another organism that shares
both the characteristics of plants and animals. Some of its animal characteristics includes: presence of flagella for
locomotion, contractile vacuole for osmo-regulation and eyespot that responds to light. Its plant characteristics
includes: presence of chloroplast, storage of carbohydrate as starch and the presence of a hemicellulose cell wall.

Chlamydomonas

46
Functions of labelled parts:
i. Contractile vacuole: For osmo-regulation or excretion.
ii. Eyespot: Helps it to respond to light stimulus.
iii. Chloroplast: Contains chlorophyll for photosynthesis.
iv. Pyrenoid: Helps to store starch
v. Flagellum: For locomotion

COLONY
A colony consists of several similar cells united by protoplasmic strands with each cell having its own nucleus and
flagellum. In some colonies, individual cells can exist independently e.g. Eudorina, while in others, individual cells
cannot exist independently e.g. volvox.

Volvox colony

FILAMENT
Cells can also exist as filaments in which similar cells join end to end to form unbranched filaments, with each cell
functioning independently. Hence they are seen as multicellular e.g spirogyra, oscillatoria, ulothrix, zygnema e.t.c.

Spirogyra filament
Function of some labelled parts
1. Chloroplast-contains chlorophyll for photosynthesis
2. Pyrenoid: Protein piles up in the pyrenoid and starch is deposited around it also
3. Cell wall: Consist of an inner layer of cellulose and an outer layer of pectin which is responsible for its
slippery nature

Differences between colonial and filamentous organisms

Colonial Organisms Filamentous Organisms
i. Intercellular wall absent. Intercellular wall present.
ii. Identical cell form a mass and are held together Identical cell form end to end arrangement in linear
by cytoplasmic strands. form.
iii. Cells are dependent physiological and there is Cells are not dependent and there is no division of
division of labour. labour.
iv. Examples of colonial organisms includes: Examples of filamentous organisms includes:
Volvox, pandorina and eudorina spyrogira, zygnema, oscillatoria

47
AS PART OF A LIVING ORGANISM
Cell forms the basic building block of all organisms, several cells of one kind interconnecting with one another and
performing a shared function are known as tissues and when these tissues combine to perform a particular function,
they are called organs, several organs make up a system and several system that function together form an organism
like an earthworm, crocodile etc.

Cheek cell

NB: When cells become specialized to carry out specific functions, their structural and chemical content also becomes
modified .Specialized cells cannot exist on their own unlike simple cells like the chlamydomonas and amoeba.

Example
Spirogyra is regarded as a multicellular plant because
A. its cell are linked together by cytoplasmic strands B. its cells are joined to form organs
C. the cylindrical cells are linked end to end D. the filaments consist of one cell only
E. it is an alga containing large vacuoles. (1991/3)
Answer: C – The cylindrical cells of spirogyra are linked end to end.
Example
Which of the following organisms exists as a filament?
A. Euglena B. Amoeba C. Volvox D. Paramecium E. Spirogyra (1994/12)
Answer: E – Euglena, amoeba and paramecium exist as free living single cells. Volvox exists as a colony. Spirogyra
exist as filament, hence it is the appropriate answer to this question.
Example
Use the diagram below to answer questions 11 and 12

The organisms shown lives in the

A. air B. marsh C. ocean D. pond E. soil (2008/11 Neco)
Answer : C – Euglena lives in fresh water (e.g. pond and lake)
The structure labeled C is used for
A. excretion B. irritability C. locomotion D. nutrition E. respiration (2008/12 Neco)
Answer : D – “C’ represents the chloroplast and it is used for nutrition.
Example
Which of the following organisms is one-celled and free living?
A. Volvox B. Spirogyra C. Rhizopus D. Chylamydomonas E. Hydra (1995/3)
Answer: D – Chlamydomonas are free-living single cell organisms. Other options (A-C) are multicellular organisms.

48
Example
(b) (i) List two differences between colonial organisms and filamentous organisms
(ii) Give one example each of a colonial organism and a filamentous organism (1996/1b i, ii)
Answer:
(b) i. - In colonial organisms, intercellular wall is absent while in filamentous organisms, intercellular wall is present.
- In colonial organism, identical cells are held together by cytoplasmic strands while in filamentous organism,
identical cells are joined end to end
(b) ii.- Example of colonial organism is volvox.
- Example of filamentous organism is spirogyra.
Example
Use the diagram below to Answer: questions 2 to 4

The structure represented in the diagram above is

A. a colony B. a tissue C. a filament D. a pseudopodium E. an organ (1997/2)
Answer: C – The structure is a spirogyra and spirogyra exists as a filament.
Example
The part labeled I in the diagram is the
A. cytoplasm B. chloroplast C. chlorophyll D. nucleus E. cell wall (1997/3)
Answer: B – It is chloroplast. NB: Chlorophyll is located inside the chloroplast.
Example
What is the function of the part labeled II in the diagram? It
A. manufactures food B. protects the chloroplast
C. produces protein D. suspends the nucleus E. digests starch (1997/4)
Answer: D – It suspends the nucleus.
Example
The cell is a functional unit of living organisms because
A. multicellular organisms are made up of cells
B. all the cells in a multicellular organism function as a single cell
C. the function of a multicellular organism is the sum total of the functions of its constituent cells
D. the function of a single cell is superior to that of the multicellular organism
E. the cells of a multicellular organism are similar in structure. (1991/1)
Answer: C – The function of a multicellular organism is the sum total of its consistuent cells
Example
The main similarity between unicellular and multicellular organisms is that both
A. perform all life activities B. exist as filaments C. are plants D. exist as colonies (2005/6)
Answer: A – Both unicellular and multicellular organisms have the ability to perform all life function.
Example
Which of the following pairs of organisms exist as colonies?
A. Obelia and Euglena B. Pandorina and Volvox
C. Chlamydomonas and Amoeba D. Hydra and Spirogyra (2005/11)
Answer: B – Pandorina and volvox are existing as colonies.
Example
In which of the following multicellular organisms is interdependence
of cells maintained?
A. Spirogyra B. Volvox C. Eudorina D. Pandorina. (2012/5)
Answer: B – In volvox, similar cells are held together by cytoplasmic strands, hence, they are interdependence.

49
EXERCISES 4.1
1. Spirogyra is regarded as a multicellular plant because
A. the cylindrical cells are linked end to end B. its cell are linked together by cytoplasmic strands
C. its cells are large D. it is an algae containing a large vacuole. (2013/4)
2. The following organisms have structures for movement except
A. Amoeba B. Spirogyra C. Volvox D. Paramecium. (2015/4)

3. Which of the following traits is not a characteristic of organisms that exist as colony?
A. there is division of labour B. cells form a mass C. All cells are physiologically independent
D. Cells are linked by cytoplasmic material (2020/8 PC1)
4. The organelle which eliminates water from the body of protozoa is
A. plasma membrane B. contractile vacuole C. cell wall D. protoplasm E. nucleus. (1991/2 Nov)
5. The organisms listed below are unicellular in nature except
A. Paramecium B. Amoeba C. Euglena D. Volvox E. Chlamydomonas (1994/4 Nov)
6. The difference between Euglena and Amoeba is that
A. Amoeba can move from place to place while Euglena cannot B. Euglena can photosynthesize
C. Euglena has a rigid cell membrane D. Euglena only feeds holozoically
E. Contractile vacuole is present only in Amoeba. (1994/9 Nov)
7. An organism that is one-celled is likely to be a
A. coelentera B. protozoa C. nematoda D. mould E. fern (1998/3 Nov)
8. Which of the following cannot exist as a free living organism?
A. Amoeba B. chlamydomonas C. Paramecium D. Plasmodium E. Euglena (1997/2 Nov)
9. Which of the following organisms has both plant and animal-like characteristics?
A. amoeba B. euglena C. pandorina D. paramecium E. volvox (2014/1 Neco)

10. 1(a) State four forms in which living cells exist giving one example of each form.
(b) Make a diagram, (8 – 10)cm long, of chlamydomonas and label the diagram fully.
(c) State: (i) two disadvantages and (ii) two advantages a unicellular organism has over a multicellular
organism. (2019/1a, b, c NABTEB)
11. An example of unicellular organisms is
A. amoeba B. hydra C. spirogyra D. volvox (2017/4 NABTEB)
12. Which of the following organisms is multicellular?
A. Amoeba B. Euglena C. Chlamydomonas D. Spirogyra (2014/8 JAMB)

13. (i) Make a labeled diagram 8cm to 10cm long of the Euglena
(ii) List three animal like features and two plant like features of Euglena (2003/4c i, ii)
14. 2(a). Draw a well labeled diagram (8-10 cm) of a paramecium. (2005/2a Neco)

Use the diagram below to answer questions 37 and 38

15. The organelle responsible for sexual reproduction is

A. IV B. I C. II D. III (2015/37 JAMB)
16. The part labelled IV is responsible for
A. respiration B. ingestion C. locomotion D. osmoregulation (2015/38 JAMB)

50
 Use the diagram below to answer questions 2 and 3

17. The part labeled II is the

A. basal granule B. contractile vacuole C. nucleus D. eyespot (2014/2 JAMB)
18. The part responsible for photosynthesis is labelled
A. I B. II C. III D. IV (2014/3 JAMB)

CELL STRUCTURE
Cell Theory: The Cell Theory States as Follows
i. All living things are made up of a cell or cells
ii. The cell is the structural and functional unit of all living things
iii. New cells arise from pre-existing cells by cell division

Contribution of scientist to the cell theory

i. Robert Hooke: In 1665, Robert Hooke, a British scientist, examined thin slices of cork tissues under the
compound microscope and found that the cork consisted of many neatly arranged little chambers or cavity. He
also noticed that each chamber was enclosed by walls similar to the cell of a honey comb. Thus he named the
chamber cells. Hooke did not, however, realize that a cell has content, since he did not examine a thin slice of
living plant or animal.
ii. Felix Dujardin: In 1835, Dujardin, a French biologist, examined thin slice of living plant under much
improved microscope and discovered that the cells have content. He named the content sarcode, later named
protoplasm by purkinje in 1839.
iii. Purkinje was the first scientist to name the cell content as protoplasm in 1839.
iv. Mathias Schleiden: In 1838, Matthias Schleiden, a German botanist, carried out an extensive study on the
structure of plants and concluded that plants were composed of cells.
v. Theodor Schwann: In 1839, Theodor Schwann, a German zoologist examined bits of animals under a
microscope and observed that animals were composed of cells.
vi. Rudolf Virchow: In 1855 Rudolf Virchow, a German biologist stated that all cells come from cells i.e. cell
arises from pre-existing cells by cell division.

CELL STRUCTURES AND FUNCTIONS

Plant cell
51
 Typical animal cell

The cell is composed of cytoplasm and nucleus (protoplasm)

A. The cytoplasm is semi-fluid and consists of endoplasmic reticulum, mitochondria, lysosomes, ribosomes,
Golgi apparatus, centrosomes and vacuole which are all bounded by the cell membrane.
The major functions of the cytoplasm are:
i. All living substances including nucleus are suspended in the semi-fluid cytoplasm.
ii. The streaming of the content of the cytoplasm brings about inter-change of materials between the
organelles within the cytoplasm.
B. The cell wall: This is the non-living outer boundary of the cell made up of cellulose. It has tiny pores or
openings through which nutrients pass from one cell to another. The cell wall is absent in animal cells.
The cell walls functions include:
i. Giving rigidity to cell and the plant as a whole.
ii. It allows free passage of materials
C. Endoplasmic reticulum: This is a system of canal found abundantly in the cytoplasm. There are two types of
endoplasmic reticulum; rough and smooth. Ribosomes are attached to the surfaces of rough endoplasmic
reticulum. Rough endoplasmic reticulum packs and transports proteins made by ribosomes through the
channels from one part of the cell to another. Smooth endoplasmic reticulum is involved in liquid and steroid
synthesis, packaging and transport.
The major function of the rough endoplasmic reticulum (ER) includes the following.
i. They help in the formation of enzymes and protein.
ii. The transport metabolic products within cytoplasm and nucleus.
iii. They assist in the formation of nuclear membrane during nuclear division.
iv. They interconnect the organelles of the cell.
v. They provide surface for the attachment of ribosomes.
Functions of smooth endoplasmic reticulum ER
i. It makes liquids (fat molecules)
ii. The enzymes of the smooth endoplasmic reticulum (SER) in the liver detoxificate drugs such as
morphine and codeine.
D. Cell membrane (plasma membrane): This is a thin flexible layer that surrounds the entire cytoplasm. It
prevents the cell content from escaping. It also controls the materials which are allowed to enter or leave the
cell, i.e. it is selectively permeable.
E. Ribosomes: Ribosomes are round bodies that are found free in the cytoplasm or attached to endoplasmic
reticulum. Ribosomes are the sites of protein synthesis. They contain large amount of ribonucleic acid (RNA).
F. Mitochondria: These are tiny rod-shaped bodies (or sausage shaped) or granules surrounded by double
membrane layer. They are more concentrated in very active cells such as the liver cells.

52
 Functions of mitochondria includes the following:
i. They are the centre of cellular respiration in which food substances are oxidized to release energy for the
activities of the cells, hence it is refers to as the power house of the cell.
ii. Mitochondria contain enzymes and deoxyribonucleic acid (DNA). The enzymes carryout oxidative
phosphorylation of adenosine diphosphate (ADP) to adensine triphosphate (ATP).
iii. The DNA helps to code the synthesis of protein in mitochondria membranes.

G. Lysosomes: These are small round sacs that contain digestive enzymes which break down structures and
substances.
The major functions of the lysosome are:
i. The destroy worn out parts of the cells by discharging enzymes into them and clearing the area for a
new healthy cell to grow.
ii. They discharge enzymes to degenerated tissues causing the breakdown of the cells
iii. Enzyme released by lysosome destroys bacteria cells.

H. Golgi apparatus (bodies): They are found in group as flat tubes or threads. They are absent in mature sperms
and red blood cells.
Functions includes:
i. They help in distributing proteins made by the cells
ii. They help in the manufacture of lysosomes
iii. They help in the formation of membrane of endoplasmic reticulum and production of cellulose cell wall.

I. The Centriole:
The centriole are found mostly in animal cells. They are absent in plant cell except for some few algae and fungi.
Functions include:
i. They provide spindle fibres to which chromosomes are attached during cell division.
ii. They help in the formation of cilia and flagella

J. Plastids in plant cell

i. Chloroplast: This occurs only in green plant. It contains a pigment called chloroplast. It is the site of
photosynthesis.
ii. Leucoplast: These are colorless plastids mainly for storage of starch and liquids.
iii. Chlomoplast: These plastids may contain different colours. The colours of petals of flower are due to
these plastids.

K. Vacuoles:
Vacuoles are mainly found in plant cell. They are very large in plant cells but in animal cells, they are usually
small or absent. A vacuole is surrounded by a membrane called tonoplast and is filled with water, minerals
salts, sugar and pigments called cell sap.
Functions of vacuoles include the following:
i. The cell sap is osmotic in function
ii. It stores nutrients and waste products
iii. It contains food reserves such as sucrose and minerals
iv. Contain tannins and alkaloids which prevent herbivores animals from eating plants with such chemicals.
v. Vacuoles sometimes contain colour pigments called anthocyanin which gives coloration to flowers,
fruits, leaves and buds.

L. Nucleus
The nucleus is bounded by a thin nuclear membrane which separates it from the cytoplasm. The nuclear
membrane has many tiny pores or pits. The pits allow substances to go in and out to the nucleus. The nucleus
contains a small spherical body called nucleolus and chromatin materials which condense during cell division
into chromosomes (hereditary units). The fluids inside the nucleus is called nucleoplasm and the
chromosomes are made up of DNA (deoxyribonucleic acid).
The functions of the nucleus includes:
i. It controls directly or indirectly most of the activities of a living cell.
ii. The nucleus carries chromosomes on which hereditary materials (genes) are coded.
iii. The DNA in chromosomes gives information for the manufacture of the proteins in the cell.
iv. The nucleus produces several kinds of RNA which are passed out of the nucleus to the cytoplasm to
manufacture protein.
NB: DNA does not pass out of the nucleus.
The red blood cell in man lacks nucleus

53
Example
The part of the cell that stores acid is
A. nucleolus B. nuclear membrane C. chromosome. D. nuclear pore. (2020/43 PC1)
Answer: C – Chromosome is made up of DNA (deoxyribonucleic acid)
Example
Animal cells are different from plant cells because animal cells have
A. definite cell wall B. large vacuoles C. centrioles D. chloroplasts (2002/4)
Answer: C – centrioles play a role during cell division. It is only found in animal cells. All other options (A, B & D)
are characteristic of plants cell.
Example
Which of the following structures controls the activities of the living cell?
A. Nucleus B. Centrosome C. chloroplast D. Golgi body E. Mitochondrion (1990/2)
Answer: A – The nucleus controls all activities of the cell. It is more or less the brain of the cell.
Example
Most of the energy in the cell is produced in the
A. mitochondrion B. lysosome C. plastid D. Golgi apparatus E. cytoplasm. (1990/3)
Answer: A – The mitochondrion is the organelle where cellular respiration takes place. It is also known as the power
house of the cell.
Example
The structure in the cell that controls the movement of substances in and out of the cell is the
A. cytoplasmic membrane B. nuclear membrane C. cytoplasm
D. protoplasm E. endoplasm (1990/4)
Answer: A – The cytoplasmic membrane (cell membrane or plasmalemma or plasma membrane), is a thin flexible
layer that surrounds the entire cytoplasm. It controls the movement of materials in and out of the cell.
Example
The first scientist to describe the cell was
A. Theodor Schwann B. Felix Dujardin C. Robert Hooke
D. Charles Darwin E. Matthias Schleiden (1993/3)
Answer: C–The first scientist to describe the cell was Robert Hooke in 1665
Example
Which of the following cells are not regarded as specialized?
A. Sperm cells B. Root tip cells C. Muscle cells D. Somatic cells (2011/3)
Answer: D– somatic cells are not specialized cells
Example
Which of the following structures differentiates an animal cell from a plant cell?
A. Ribosomes B. Cell membrane C. Chloroplast D. Mitochondrion E. Iysosome (1990/5)
Answer: C – Chloroplast is only found in plant cells. Options A, B, D and E are common to both plants and animals.
Example
Which of the following is not true of the nucleus of a living cell? It contains
A. chromosomes B. nucleolus C. nucleoplasm D. chromatids E. ribosomes. (1992/6)
Answer: E – Ribosome is an organelle located in the cytoplasm just like the nucleus. Other options (A to D) are
constituents of the nucleus.
Example
The cell membrane consists of
A. carbohydrates and lipids B. Vitamins and proteins C. lipids and proteins
D. water and sugar E. starch and cellulose. (1992/7)
Answer: C – All cell membranes are made up of lipids (e.g. phospholipids) and proteins
Example
Which of the following is not likely to be found in the cell of a ripe tomato fruit?
A. Plastids B. Chlorophyll C. Cellulose cell wall D. Mitochondrion E. Mineral salts. (1992/8)
Answer: B – When fruits get ripened, their chlorophyll breaks down.
Example
In which of the following parts of a cell is the chromosome found?
A. Nucleus B. Golgi body C. Cytoplasm D. Cell membrane E. Cell wall (1993/4)
Answer: A – The chromosomes are found inside the nucleolus of the nucleus.

54
Example
The cell membrane of a cell is said to be semi-permeable because
A. it allows only large molecular substances to pass through it into the cell
B. it is actively involved in energy production in the cell
C. it actively allows all substances to pass through it by diffusion
D. it is actively selective in allowing substances through it
E. fatty acids are only the building blocks of the membrane (1995/12)
Answer: D – The cell membrane is active selective in allowing substances to pass through it.
Example
Which of the following is not a cell organelle?
A. Golgi body B. Nucleus C. Fat droplets D. Ribosome E. Endoplasmic reticulum (1996/3)
Answer: C – Fat droplet is an example of cell inclusions. Cell inclusions are various nutrients or pigments that can be
found within the cell, but do not have activity like cell organelles. Other examples of cell inclusion are: glycogen,
lipids, melanin etc.
Example
Which of the following organelles helps to remove excess water from cells?
A. Mitochondrion B. Ribosome C. Contractile vacuole D. Golgi vacuole E. Nucleus (1997/5)
Answer: C – The contractile vacuole helps in osmo-regulation (removal of excess water).
Example
All the following organelles have membranes except
A. nucleus B. vacuole C. cell membrane D. cell wall (2000/4)
Answer: D – The cell wall is the outer most part of the cell. Organelles are usually present I nside the cytoplasm of
the cell. Examples of membrane bounded organelles are: nucleus, endoplasmic reticulum, golgi apperatus,
mitochondria, plastids, lysosomes and vacuoles.
Example
The unit contained in a cell structure responsible for changes in form and shape of organisms is called
A. mitochondria B. gene C. ribosome D. lysosome. (2000/6)
Answer: B – Genes determine the kind of proteins that are synthesized in an organism. Proteins are body building
molecules. Genes therefore can then indirectly regulate changes in form and shape of an organism by synthesizing
specific proteins.
Example
The presence of a large member of mitochondria in a cell indicates that
A. it has little cytoplasmic content B. the cell is very active C. the cell is dormant D. the respiration is poor. (2000/8)
Answer: B – Mitochondria help in cellular respiration which leads to the production of energy. So more mitochondria
leads to more energy which invariably increase activity.
Example
Use the diagram below to Answer: questions 3 and 4

The structure that produces ATP is labeled

A. VII B. V C. VI D. I (2001/3)
Answer: A – Label “VII” is the mitochondria that produce ATP. NB: ATP is the energy currency of the cell.
The structure labeled V is the
A. cell wall B. nucleus C. endoplasmic reticulum D. mitochondrion (2001/4)
Answer: A – Structure “V” is the cell wall.
Example
The major function of the cell membrane is that it
A. delimits the cytoplasm B. synthesizes protein
C. breaks down worn-out organelles D. is the site for photosynthesis. (2001/5)
Answer: A – The cell membrane give well defined boundary to the cell i.e. it delimits the cytoplasm
55
Example
Which of the following statements about ribosomes is not correct? Ribosomes are
A. are responsible for protein synthesis B. contain a large amount of ribonucleic acid (RNA)
C. release enzymes for the digestion of bacteria D. are attached to endoplasmic reticulum. (2003/2)
Answer: C – Ribosomes do not release enzyme for the digestion of bacteria. This function is carried out by the
Lysosome. All other options (A, B and D) are the functions of the ribosome.
Example
The protoplasm of a living cell is made up of the nucleus and
A. vacuole B. cytoplasm C. cell wall D. cell sap. (2003/3)
Answer: B – The protoplasm is equal to nucleus + cytoplasm.
Example
(d) (i)Name one organelle in a living cell that produces enzymes (2003/1di) Answer: Lysosome
Example
The nucleus controls the activities of the cell because it
A. synthesizes hormone B. is like a brain in the cell
C. uses DNA to synthesize enzymes which are used in a cell metabolism
D. sends out nervous impulses to ensure the functioning of the cytoplasm (2004/5)
Answer: C – The nucleus houses the DNA which regulate the synthesis of proteins (enzymes) which are used in cell metabolism.
Example
Which of the following parts of a cell is not an organelle?
A. Food vacuole B. Mitochondrion C. Cell wall D. Nucleus (2006/6)
Answer: C – The cell wall is the outer most part of the cell. Organelles are usually present inside the cytoplasm of the
cell. Examples of cell organelles are: the nucleus, endoplasmic reticulum, golgi apparatus, mitochondria, plastids,
lysosomes and vacuoles.
Example
The organelle involved in the transport of substances within a cell is
A. Golgi body B. endoplasmic reticulum C. ribosome D. mitochondrion. (2007/6)
Answer: B – The Endoplasmic reticulum (ER), forms the transport system of the cell.
Example
The living material of the cell consists of
A. nucleus and cytoplasm B. cytoplasm and vacuole
C. cytoplasm and cell membrane D. nucleus and cell membrane. (2008/3)
Answer: A – The protoplasm (nucleus and cytoplasm) is the living component of the cell.
Example
The organelle which eliminates water from the body of a protozoan is the
A. plasma membrane B. contractile vacuole C. nucleus D. cell wall (2010/3)
Answer: B – The contractile vacuole helps in osmo-regulation (removal of excess water).
Example
Which of the following cell types has the least number of mitochondria?
A. Cardiac cells of the heart B. Cells of the cornified layer
C. Muscle cells of the bladder D. Muscle cells of the diaphragm (2010/4)
Answer: B – Cells of cornified layer are those found on the dead layer of the skin, they do not engage in much
activities that require much energy. Therefore they have the least number of mitochondria from the under-listed options
Example
Which of the following cell inclusions can destroy organelles?
A. Centriole B. Ribosome C. Lysosome D. Mitochondrion (2014/5)
Answer: C – The lysosome contains enzymes that help to breakdown worn out organelles.
Example
DNA formation is associated with
A. Golgi bodies B. lysosomes C. mitochrondria D. nucleus (2016/3)
Answer: D – The nucleus houses the DNA.
Example
Which of the following structures will not be found in the nucleus of a cell?
A. DNA B. Nucleolus C. Lysosome D. Centriole (2019/1)
Answer: C – Lysosome is an organelle in the cytoplasm of a cell. NB: Centriole is located near the nuclear
membrane.

56
Exercise 4.2
1. Which of these organelles of the human cell is concerned with the release of energy from food?
A. Ribosome B. Golgi bodies C. Mitochondria D. Nucleoplasm E. Vacuole (1996/1 Nov Health Sci)
2. The structures found in the cytoplasm of a cell are called
A. organelles B. protoplasm C. nuclei D. endoplasm (2003/1 Nov Health Sci)
3. The function of ribosomes in cell is for
A. lipid storage B. mechanical support C. protein synthesis D. starch synthesis E. transport of materials (2014/41 Neco)
4. The aerobic stage of cellular respiration takes place in the
A. cytoplasm B. nucleus C. protoplasm D. mitochondrion E. ribosome (1992/10 Nov)
5. Which cellular component is essentially composed of DNA?
A. lysosome B. centrosome C. chromosome D. chlorophyll (2006/5 Nov)
6. The cell organelle which is physically and functionally associated with the endoplasmic reticulum is the
A. lysosome B. golgi body C. ribosome D. mitochondrion (2006/6 Nov)
7. Which of the following organelles stores food in plants?
A. mitochondrion B. Golgi body C. Endoplasmic reticulum D. plastid (2006/7 Nov)
8. Which of the following cell organelles serves as the site for energy production?
A. Golgi apparatus B. endoplasmic reticulum C. nucleolus D. mitochondrion (2013/3 Nov)
9. One function of the cell membrane is to
A. offer protection against mechanical injury B. give definite shape to the cell
C. regulate the movement of substances to and from the cell D. provides a site for chemical processes (2013/4 Nov)
10. Which of the following organic molecules constitute the nucleus of a living organism
A. RNA and ATP B. DNA and ATP C. ATP and AMP D. RNA and DNA (2004/4 Nov)
11. On which structures are genes located in the nucleus?
A. Nuclear membrane B. Nucleolus C. Chromosome D. Nucleoplasm (2004/52 Nov)
12. 4.(a) What is a cell membrane?
(b)(i) Name four organelles bounded by membranes.
(ii) State the function of the membranes in the organelles you have named (2004/4a, bi, ii Nov)
13. (b) Make a large labelled diagram of a typical plant cell. (1991/1b Nov)
14. The structure in the plant cell which is selectively permeable to materials moving in and out of the cell is the
A. cell wall B. cell membrane C. vacuole D. nucleus (2019/7 PC2)
15. The cell wall of plants is rigid due to the presence of
A. cambium B. cellulose C. cortex D. chloroplast E. phloem (2018/2 Neco)
16. Which of the following cell organelles traps sunlight energy in plant?
A. chloroplast B. endoplasmic reticulum C. Mitochondrion D. Ribosome E. vacuole (2018/4 Neco)
17. Which of the following is not present in the nucleus of the cell?
A. chromosome B. chromatin C. gene D. mitochondrion E. nucleolus (2014/5 Neco)
18. Which of the following mammalian cells has no nucleus?
A. muscles B. nerve cell C. red blood cell D. white blood cell (2005/7 Nov)
19. Which of the following does a virus have in common with animal cell?
A. Nucleus B. DNA C. Glycogen D. Cytoplasm (2019/7 NABTEB)
20. Which of the following is the function of the nucleus of a cell?
A. it is where most reactions occur B. it is involved in the release of energy during respiration
C. it controls all chemical activities within the cell
D. it stores and modifies substances made by the endoplasmic recticulum (2018/3 NABTEB)
21. In which part of a cell is the chromosome located?
A. Mitochondrion B. Cytoplasm C. Nucleus D. Golgi body (2001/6 NABTEB)
22. The part of the cell concerned with transmission of characters from parents to offspring
A. cytoplasm B. nucleus C. mitochondria D. food vacuole (1999/8 NABTEB)
23. The part of the cell solely responsible for respiration is the
A. nucleus B. nucleolus C. mitochondria
D. golgi apparatus E. endoplasmic reticulum (1980/27 JAMB)
24. Where is energy produced in a cell
A. Nucleus B. Nucleolus C. Lysosomes D. Chloroplast E. Mitochondria (1982/41 JAMB)

57
25. The function of endoplasmic reticulum is
A. protein synthesis B. intracellular transport of material
C. digestion and destruction of foreign bodies D. production of energy from glucose (1987/1 JAMB)
26. Which of the following structures is common to Euglena, White blood cell and Amoeba
A. Vacuole B. Cell wall C. Cilia D. Cell membrane (1988/2 JAMB)
27. The organelle involved in tissue respiration is the
A. endoplasmic reticulum B. ribosome C. golgi bodies D. mitochondrion (1992/1 JAMB)
28. Which of the following organelles are likely to be present in cells that are actively respiring and
photosynthesizing?
A. Nucleus and centrioles B. Mitocondria and chloroplasts
C. Lysosomes, and ribosomes D. Golgi apparatus and endoplasmic reticulum. (1995/2 JAMB)
29. The vacuole of a plant cell is
A. a large empty space B. smaller than that of an animal cell C. filled with air
D. an ordinary vacuum E. surrounded by a membrane (1980/4 JAMB)
30. The structure that most commonly identified in all living cells under the light microscope of the
A. mitochondrion B. chloroplast C. nucleus D. ribosome (1999/5 JAMB)
31. The cell component that is present in a prokaryotic cell is the
A. ribosome B. mitochondrion C. chloroplast D. nuclear envelope (2003/9 JAMB)
32. Which of the following is NOT a function of the nucleus of a cell?
A. It controls the life processes of the cell B. It translates genetic information for the manufacture of proteins
C. It stores and carries hereditary information D. It is a reservoir of energy for the cell. (2010/3 JAMB)
Use the diagram below to Answer: questions 2 and 3

33. The part labelled IV is the

A. mitochondrion B. cell wall C. endoplasmic reticulum D. nucleus (2012/3 JAMB)
34. The organelles present in cells that are actively respiring and photosynthesizing are
A. lysosome and ribosomes B. Golgi apparatus and endoplasmic reticulum
C. nucleus and centrioles D. mitochondria and chloroplast (2013/4 JAMB)
Use the diagram below to Answer: questions 33 and 34

35. The cell organelle solely responsible for respiration is the

A. nucleus B. nucleolus C. endoplasmic reticulum D. mitochondrion (2015/33 JAMB)

36. The organelle responsible for hereditary is

A. IV B. I C. II D. III

37. (b) Make a large labelled diagram of a typical animal cell (1991/1b) adjusted
38. Which of the following cell organelles is the site for the production of ATP?
A. Lysosome B. Nucleus C. Mitochondria D. Ribosome (2017/5)

58
Difference between plant and animal cell

Plant cell Animal cell

1 Cellulose cell wall is present Cellulose cell wall absent
2 Chloroplast present Chloroplast absent
3 A large central vacuole present Small vacuole may be present or absent
4 Centrioles absent Centriole present
5 Cytoplasm is pushed towards edge of wall Cytoplasm spread throughout the cell
6 Starch granules present Glycogen granules present
7 It is usually rectangular and definite in shape It is spherical and has no definite shape
Example
(c) List three ways in which a typical plant cell differs from a typical animal cell (1991/1c)
Answer:
i. The cell wall is made of cellulose.
ii. They possess chloroplast.
iii. They lack centrioles.
Example
Which of the following is a similarity between a typical animal cell and a typical plant cell? Presence of
A. cellulose cell wall B. chlorophyll C. centrally – placed nucleus D. cell membrane E. large vacuole (1993/2)
Answer: D – All cell (plant and animal) have cell membrane.
Example
One of the differences between plant and animal cells is that in plants
A. cells have less distinct outline but animal cells have distinct outline
B. cell wall is made of cellulose, but animal cell wall is made of chitin
C. large vacuoles are absent, but present in animals D. plastids are absent, but present in animals
E. carbohydrates are stored as starch, but as glycogen in animals (1995/4)
Answer: E – Plants store carbohydrates as starch and animals store carbohydrates as glycogen
Example
Which of the following characteristics differentiates a palisade cell from a liver cell? The possession of
A. a cell wall and cytoplasm B. a vacuole and a nucleus
C. non-cell membrane and chloroplast D. a cell wall and chloroplast. (2002/1)
Answer: D – Palisade cells are part of the cells that collectively make up the mesophyll tissue of plant leaves. A liver
cell is found in the liver of animals. A cell wall and presence of chloroplast are typical characteristic of plant cell;
hence option D is the most appropriate option.
Example
Which of the following organisms has both plant and animal-like features
A. Paramecium B. Euglena C. Amoeba D. Spirogyra (2002/2)
Answer: B – Euglena share characteristics with both plant and animals. Spirogyra is a multicellular green plant while
amoeba and paramecium are protozoans.
Example
Which part of a plant cell contains cellulose?
A. Vacuole B. Cytoplasm C. Cell wall D. Chloroplast (2002/3)
Answer: C – Plants cell wall is made of cellulose.
Example
Animal cells are different from plant cells because animal cells have
A. definite cell wall B. large vacuoles C. centrioles D. chloroplasts (2002/4)
Answer: B – Centrioles are only found in animal cells.
Example
Which of these organelles is common to both plant and animal cells?
A. Chloroplast B. Centriole C. Mitochondrion D. Pyrenoid (2006/2)
Answer: C – The mitochondria are the organelles that produce energy for the cell. Energy is needed by all cells, hence
all cell (plant and animals) have mitochondria.

59
Example
(c)(i) In a tabular form, state three differences between a plant cell and animal cell
(ii) State three similarities between a plant cell and an animal cell. (2016/1c i, ii)
Answer:
ci. Plant Cell Animal Cell
1. Cellulose cell wall is present. Cellulose cell wall is absent.
2. They possess chloroplast. Chloroplast is absent.
3. They store food as starch. They store food as glycogen.

cii. 1. Both plant cell and animal cell have nucleus.

2. Both plant cell and animal cell have cell membrane.
3. They both have mitochondria for energy production.
Example
The organelles that synthesize carbohydrates in plant cell are
A. chromoplasts B. ribosomes C. mitochondria D. chloroplasts E. leucoplasts (1992/4 Nov)
Answer: D – Chloroplast contain chlorophyll that carryout photosynthesis which leads to the formation of
carbohydrate.
Example
Which of the following structure can be found only in plant cells?
A. myomerefibre B. Plastid C. Nucleolus D. Cell vacuole E. Mitochondrion (1992/5 Nov)
Answer: B – Plastid is a site where important compound (e.g. starch) are manufacture and stored in plants.
Example
The structure found in both plant and animal cells is the
A. cell membrane B. cell wall C. large vacuole D. chloroplast (2000/8 Nov)
Answer: A – Cell membrane is common to both plants and animals cells.

EXERCISE 4.3
1. Which of the following structures is found in animal cells?
A. Cell wall B. Ribosome C. Middle lamella D. Pyrenoids (2011/1 Nov)
2. A major difference between onion cells and cheek cells is that
A. Cheek cells are irregular in shape B. onion cells are spherical in shape
C. cheek cells are not edible D. onion cells contain glycogen (2002/3 Nov)
3. 4.(a) (i) Give four similarities between plant and animal cells
(ii) Make a labeled diagram 8-10 cm long of a typical plant cell (2002/4ai, ii Nov)
4. Which of the following organelles differentiates a plant from an animal cell?
A. Cell membrane B. Cellulose C. Nucleus D. Cytoplasm E. Mitochondrion (1998/1 Nov)
5. Plant cells differ from animal cell in their possession of
A. large vacuoles B. ribosomes C. cytoplasm D. nucleus E. nucleic acids (1994/2 Nov)
6. (ii)In a tabular form, state five differences between plant and animal cells (2018/3aii Neco)
7. Which of these combinations is common to plant and animal cells?
A. Centriole, middle lamella, golgi bodies, mitochondrion
B. Cytoplasm, sap vacuole, starch grains, leucoplasts
C. Plasma membranes, chromosomes, mitochondria, lysosomes
D. Nucleus, nucleolus, cellulose cell wall, endoplasmic reticulum
E. Cytoplasm, centriole, cellulose cell wall, nucleolus (1982/2 JAMB)
8. The membrane surrounding the vacuole in a plant cell is called the
A. plasmalemma B. tonoplast C. nuclear membrane D. endoplasmic reticulum (1994/1 JAMB)
9. The structures found only in plant cells are
A. cell wall and chloroplast B. cell membrane and lysosome
C. chromatin and nucleolus D. cell membrane and cytoplasm (2002/8 JAMB)
10. The organelle common to both plant and animal cells is the
A. chloroplast B. centriole C. plasmalemma D. cell wall (2005/45 JAMB)
11. The cell of an onion bulb can be differentiated from a cheek cell by the presence of
A. plasmalemma B. chloroplast C. cell wall D. nucleus (2008/3 JAMB)
60
 REVISION EXERCISE
1. Which of the following cells are not regarded as specialized?
A. Sperm cells B. Root tip cells C. Muscle cells D. Somatic cells (2011/3)
2. Which of the following pair of cells carry out the same function?
A. Cheek cell and red blood cell B. Spermatozoan and ovum
C. Palisade cell and epidermal cell D. Root tip cell and guard cell (2011/4)
3. Cells that utilizes a lot of energy are characterized by the presence of a large number of
A. vacuoles B. mitochondria C. endoplasmic reticulum D. ribosomes (2011/8)
4. The resolution of a microscopic refers to its power to
A. increase an object’s apparent size B. distinguish clearly between two objects
C. scan the surface of an object D. focus on an object. (2013/25)
5. The cells and tissues of the nose, throat, chest diaphragm and lungs form the
A. circulatory system B. respiratory system C. transport system D. digestive system (2016/13)
6. The red blood cell is also called
A. phagocyte B. thrombocyte C. lymphocyte D. erythrocyte E. fibrinogen (1996/4 Nov Health Science)
7. In which of the following cell organelles does glycolysis occur?
A. cytoplasm B. lysosome C. mitochondrion D. nucleus E. ribosome (2005/7 Neco Nov)
8. State: (i) Two disadvantages and
(ii) Two advantages a unicellular organism has over a multicellular organism (2005/1c Nov)

61
The cell and its environment
The environment of a cell is its total surrounding. A unicellular organism is surrounded by the medium in which it
lives e.g. water, air, soil, or in the case of a parasite a part of a living organism.
In multicellular organisms, each cell is surrounded by other cells and some tissue.

Importance of the Cells Environment

1. The tissue fluid or water around a cell provides its food substances and oxygen.
2. The tissue fluid or water around a cell keeps the cell moist and prevents it from drying up.
3. The environment of a cell provides a medium into which excretory products from the cell are deposited.
4. The tissue fluid acts as a buffer around the cells
5. It provides a medium in which some chemical reactions take place.

Exchange of Materials between Cell and Its Environment

A cell exchange materials with its surrounding environment. The materials exchanged include
i. Food materials (nutrients)
ii. Gases (oxygen, carbondioxide)
iii. Excretory substances
iv. Water.

The biophysical processes involved in the exchange of materials include diffusion, osmosis, active transport,
plasmolysis, turgidity, haemolysis and crenation.

Diffusion
Diffusion is the process by which molecules of substances such as liquid and gases move randomly from a region of
higher concentration to a region of lower concentration through the medium of air or liquid until there is an even
distributions of the molecules (uniformity of concentration gradient).

N.B: Gases can diffuse through air or liquid, liquids can diffuse through other liquids, vapour can diffuse from
aromatic solid compounds through the air, solid molecules can diffuse through liquids if they are dissolvable in such
liquids. The foul smell from a dead rat and the pleasant smell from air freshener spread through a room by diffusion.
The ability of ink molecules to move in water is also brought about by diffusion.

Factors that affect the diffusion of substances

i. Surface area – Large surface area will allow more molecules of substances to diffuse. i.e. Diffusion increases as
the surface area increases.
ii. Temperature: Increase in temperature increases the movement of molecules and diffusion rate while decrease in
temperature slowdown movement of molecules and diffusion rate.
iii. Size of the molecules or particle: The smaller molecules will diffuse faster than large molecules.
iv. Presence of concentration gradient: When the concentration of substances is high, the rate of movement of
molecules will increase; molecules move from a region of higher concentration to a region of lower concentration
leading to an increase in the rate of diffusion.
v. State or nature of the diffusing substance: Gases diffuses faster than liquids and liquid diffuse faster than solid.
vi. Shaking or stirring.

Importance of diffusion to living thing

i. Gaseous exchange involving oxygen and carbondioxide between a cell and its environment during respiration
occur by diffusion.
ii. Movement of mineral salts through the cell walls of plants for metabolic process occurs by diffusion.
iii. Removal of some excretory products from cells occurs by diffusion
iv. Absorption of digested food into the intestinal wall occurs by diffusion
v. Translocation of food in the phloem involves diffusion
vi. Carbondioxide from the air diffuses into the cells of green leaves for photosynthesis
vii. Exchange of materials between mother and foetus occur by diffusion
viii. Digested food enters saprophytic plants such as mucor by diffusion
N.B: Earthworm uses diffusion as their principal method of gaseous exchange.

62
Example
The mechanism of gaseous exchange in living organisms is essentially by
A. osmosis B. inhalation C. diffusion D. exhalation E. breathing. (1991/4)
Answer: C – Diffusion is the movement of fluid (gas or liquid) from a region of higher concentration to a region of
lower concentration until they are evenly distributed. Exchange of gases (O2 and CO2) in the lungs is done through
diffusion. NB: Breathing is the process of moving air into (inhalation) and out (exhalation) of the lungs.
Example
Which of the following statements is correct about diffusion?
A. It involves the movement of water molecules only
B. Molecules move from a region of higher concentration to a region of lower concentration
C. Differentially permeable membrane must be present for diffusion to occur
D. It involves the movement of only solute molecules into the Bowman's capsule
E. It occurs when a solute can no longer dissolve in a solvent (1991/5)
Answer: B – In Diffusion, molecules move from a region of higher concentration to a region of lower concentration
until they are evenly distributed.
Example
Carbon dioxide enters the stomata during photosynthesis through the process known as
A. osmosis B. active transport C. diffusion D. inhalation E. ventilation (1995/5)
Answer: C – Carbon-dioxide and oxygen enters and leaves the body of flowering plants through the stomata and
lenticels by the process of diffusion.
Example
Which of the following processes occurs by diffusion?
A. Reabsorption of water in kidney tubules B. Entry of water into the cytoplasm of unicellular animals
C. Absorption of water in the large intestines D. Exchange of nutrients between a mother and a foetus
E. Movement of water in and out of living cells (1997/6)
Answer: D – Exchange of nutrients between a mother and a feotus occur through diffusion.
N.B: The movement of water is often time done through osmosis.
Example
The process by which a drop of ink spreads uniformly in a beaker of water is called
A. absorption B. osmosis C. plasmolysis D. diffusion (2004/6)
Answer: D – Diffusion is the movement of fluid (gas or liquid) from a region of higher concentration to a region of
lower concentration until they are evenly distributed.
Example
Which of the following processes involves diffusion?
A. Opening and closing of the stomata pores B. Turgidity of herbaceous plants
C. absorption of water through the root hairs D. absoption of digested food into the villi (2010/7)
Answer: D – Digested food are absorbed into the villi of the small intestine by diffusion.
Example
Steady spread of the unpleasant odour from dead rat is a physical process called
A. cyclosis B. diffusion C. osmosis D. plasmolysis (2000/10 Nov)
Answer: B – Spreading of a gas or liquid, in order to achieve uniformity is usually done through the process of diffusion.
Example
A major reason why tilapia fish survives well in fresh water habitat than in a bowl filled with tap water is that
A. it cannot move around in the bowl B. dissolved oxygen in the fresh water will diffuse into the gills
C. it will starve inside the bowl D. its gills will be affected by chemicals in the tap water (2000/9 Nov)
Answer: B – Dissolve oxygen in the fresh water will diffuse into the gills more than that of tap water.

EXERCISE 5.1
1. The smell of perfume perceived from a distance is made possible by the process of
A. osmosis B. haemolysis C. cyclosis D. diffusion. (2011/7 Nov)
2. An example of diffusion in living organisms is the
A. shrinking of a cell in hypertonic solution B. passage of water from the soil into the root hair
C. bursting of erythrocytes in a hypotonic solution
D. passage of digested food from the villi into the blood (2013/5 Nov)

63
3. Which of the following statements is correct about diffusion?
A. It involves the movement of water molecules only
B. Molecules move from a region of higher concentration to a region of lower concentration
C. Differentially permeable membrane must be present for diffusion to occur
D. It involves the movement of only solute molecules into the Bowman’s capsule
E. It occurs when a solute can no longer dissolve in a solvent. (1991/5 Nov)
4. The movement of substances by diffusion stops when
A. there is uniformity in the concentration gradient B. there is high temperature
C. the concentration gradient is higher on one side D. the molecular size is large (2019/8 PC2)
5. Which of the following processes occurs by diffusion?
A. Entry of water into the cytoplasm of a unicellular animals B. Absorption of water in the large intestine
C. Exchange of nutrients between a mother and the foetus
D. Movement of water in and out of living cell. (2019/10 NABTEB)
6. The following are factors that affect the rate of diffusion EXCEPT
A. the state of matter B. the size of molecules C. temperature D. light (2001/12 NABTEB)
7. Movement of water from the soil to the plant root occurs as a result of
A. differences in concentration of soil water and cell sap B. presence of living organisms in the soil
C. non- aeration of the soil D. diffusion of mineral salts between soil particles
E. too much water in the plant root (1998/14 Nov)
8. Which of the following uses diffusion as the principal method of gaseous exchange?
A. Grasshopper B. Rat C. Lizard D. Earthworm (2015/3 JAMB)

Osmosis
Osmosis can be defined as the diffusion of water molecules across semi-permeable membrane. Osmosis can also be
defined as the movement of water molecules from a region of low concentration of solute to a region of high
concentration of solute through a semi-permeable membrane separating the two solutions until equilibrium is attained.
The solution which loses water in osmosis is said to by hypotonic and the solution that gains water is said to be
hypertonic.
When a state of equilibrium is established, the solution is said to be isotonic i.e there is no gain nor loss of water.
Solution A Solution B
(Concentrated solution containing a low (Dilute solution containing a high
concentration of water molecules.) concentration of water molecules.)

Big solute Small solute

molecule (Salt) molecule

Small water
molecule Semi-Permeable
membrane

Net movement of water molecules

Diagram showing equilibrium and arrows indicating water movement

From the above diagram, it can be seen that that solution A has a very high concentration of solute dissolved in it and
solution B has smaller amount of solute dissolved in it. This means that the solution A with higher concentration of
solute has a smaller amount of water left for dissolution of more solute while the solution B with lower concentration
of solute has more water available. Therefore, the solution B above has a higher concentration of water than solution
A. Since this two solutions are separated by a semi-permeable membrane water molecules will move from solution B
into solution A through the Semi-permeable membrane.

Any given solution has a certain amount of osmotic pressure. The osmotic pressure of pure distilled water is zero (0).
The higher the amount of solute dissolved in a solution, the higher the osmotic pressure of that solution.

From the above solutions, the osmotic pressure of solution A is higher than the osmotic pressure of Solution B.
Osmotic pressure is the pressure developed by a more concentrated solution such as sugar or salt solution when water
moves into it through a semi-permeable membrane. It can also be defined as the pressure required to stop water from
diffusing through a membrane by osmosis.

64
Therefore, osmosis can also be defined as the movement of water molecules from a region of lower osmotic pressure
to a region of higher osmotic pressure though a semi-permeable membrane.
A semi-permeable membrane has a very tiny pore which can permit the free movement of smaller molecules like that
of water across it. Molecules larger than water molecules cannot freely pass through.
As water is been drawn into solution A from solution B, the osmotic pressure of A is slowly being reduced. A time
will come when the osmotic pressure of solution A equals the osmotic pressure of solution B. At this time,
the two solutions have reached an osmotic equilibrium. When two solutions are in equilibrium, the rate of the
movement of water from A to B equals the rate of movement from B to A.

Importance of osmosis in living organisms

i. Plants absorb water from the soil into the root hair cells by osmosis.
ii. Water moves from one cell into another in plant and animal by osmosis
iii. Opening and closing of stomata takes place when guard cells take up or lose water by osmosis
iv. Cells in animals and plants take up water by osmosis to keep them turgid.
v. Re-absorption of water in the colon of animals occur by osmosis
vi. The re-absorption of water in the kidney tubules of mammals is by osmosis.

Differences between diffusion and osmosis

Diffusion Osmosis
Involves the movement of molecules of gases, liquids Involve the movement of molecule of water only
and solids
Movement of molecules need not occur through a semi- The water molecules always pass through a semi-permeable
permeable membrane. membrane
Molecules diffuse into any space accessible to them. Water molecules move between two solution of different
osmotic pressure leading to the establishment of osmotic
equilibrium.

Experiment on Osmosis
Aim: Experiment to demonstrate osmosis using yam tuber as living plant material.
Materials needed: Two thick slices of yam, strong salt solution, distilled water, A trough
Method: Two thick slices of yam tuber A and B are obtained and their “Skin” peeled off. A large cavity is made in the
middle of each. A strong solution of salt is kept in yam tuber A and the salt solution is marked T1. Yam tuber B is left
without salt solution to serve as a control experiment. They are both kept in a trough containing distilled water as
shown in the diagram below, and allowed to stand for some hours.

A B
N

Results: After some hours, it is observed that salt solution in tuber A has risen to level T2 while no water enters the
yam tuber B.
Conclusion: The salt solution in yam tuber A has a higher osmotic concentration than the water in the trough and
exerted a higher osmotic pressure on the water. The water with lower osmotic concentration move through the cells of
the yam which act as semi-permeable membrane to the cavity of the yam. Hence, there is a rise of the salt solution. In
yam tuber B, water could not be drawn into its cavity because it contains no salt solution and the cells of the yam have
lower osmotic concentration and osmotic pressure than the water in the trough.

Example
Four cells with osmotic potential equivalent to that of 3% salt solution were immersed respectively in solutions of
different concentrations labeled as follows:
I = 4% salt solution; II = 6% salt solution; III = 1% salt solution; IV = 10% salt solution; V = 5% salt solution
Which of the solutions will cause an increase in osmotic pressure within the cell?
A. I B. II C. III D. IV E. V (1989/2)
Answer: C – This is because the osmotic potential of the cell (3% salt solution) is greater than that of solution III
which is 1% of salt solution. This will result in water flowing into the cell and hence, increases osmotic pressure.

65
Example
Which of the following statements is not true of osmotic process?
A. There must be a selectively permeable membrane
B. The two solutions must be of different concentrations initially
C. It involves only the movement of water molecules
D. Equilibrium is reached when there is equal distribution of water molecules
E. The two solutions are of equal concentration at the beginning of the experiment (1989/3)
Answer: E – At the beginning of osmotic process, the two solutions are not of equal concentration but rather they
must be of different concentration.
Example
Osmosis can be defined as diffusion of
A. atoms and molecules through a membrane to an area of higher concentration
B. water molecules from a dilute solution to a concentrated solution across a permeable membrane
C. water molecules from a dilute solution to a concentrated solution through a semi-permeable membrane
D. perspiration and excretion. (1992/9)
Answer: C – Osmosis is actually the diffusion of water molecule from dilute solution (less solute concentration) to a
concentrated solution (more solute concentration) through a semi-permeable membrane.
Example
In which of the following yam tissues will osmosis occur?
A. Boiled and peeled B. Raw and peeled C. Boiled and unpeeled D. Roasted and peeled (2014/6)
Answer: B – Raw and peeled yam can act as a semi-permeable membrane; but a boiled or roasted yam either peeled
or unpeeled has lost the ability to act as a semi-permeable membrane.
Example
Which of the following substances pass through the root cell membrane by osmosis?
A. Cell sap B. Carbon dioxide C. Oxygen D. Water (2005/14)
Answer: D – Water move from the soil into the root cell through osmosis.
Example
Use the diagram below to Answer: questions 5 to 7.

After an hour, the level of water in the thistle funnel will

A. rise B. fall C. remain the same D. double (2009/5)
Answer: A – This is a typical experiment that illustrates Osmosis. Osmosis is the movement of solvent (e.g. water)
from a region of less solute concentration to a region of more solute concentration, through a semi-permeable
membrane.
In the above experiment the distilled water which is the less concentrated solute solution, moves through the semi-permeabale
membrane into the sugar solution which is the more concentrated solute solution. As a result of this, the water level of the sugar
solution in the thistle funnel will rise.
Example
The experiment above is used to demonstrate the process of
A. transportation B. water culture C. diffusion D. osmosis. (2009/6) Answer: D - Osmosis
Example
1a. (i) Define the term osmosis
(ii) State two conditions necessary for osmosis to occur (2014/1a i, ii Neco)
Answer:
1a. i. Osmosis is defined as the diffusion of water molecules across a semi-permeable membrane. It can also be
defined as the movement of water molecules from a region of low solute concentration to a region of high
solute concentration through a semi-permeable membrane separating the two solution until equilibrium is
reached.
ii. 1. There must be a semi-permeable membrane.
2. The two solutions must be of different concentrations initially.

66
Example
(b) Describe an experiment to demonstrate osmosis using a non-living material. (2000/3b Nov)
Answer:
Aim: To demonstrate osmosis using non living material.
Method: A piece of cellophane is tied over to the mouth of a thistle funnel carefully and tightly. The cup of the thistle
funnel is filled with sugar solution while the beaker contains water. The funnel side carrying the semi-permeable
membrane (cellophane) is immersed into the beaker of water. The experiment is left for one day. The control
experiment is similarly arranged but instead of filling the funnel with sugar solution, it is filled with water.

Result: After a few hours the level of liquid (water) in the funnel has risen from its original mark. There is no rise in the
level of water in the funnel of the control experiment.
Conclusion: Water has moved through the semi-permeable membrane cellophane to the sugar solution by osmosis.
Example
(c) Give two differences between osmosis and diffusion. (2000/3c Nov)
Answer: 1. Osmosis requires a semi-permeable membrane in order for it to take place. Diffusion does not require a
semi-permeable membrane before it can take place.
2. Osmosis involves only liquid (water), diffusion involves both liquid and gas.

EXERCISE 5.2
1. An important difference between osmosis and diffusion is that
A. the presence of a membrane is essential for osmosis to occur
B. diffusion occurs in the atmosphere while osmosis occur in the cell
C. osmosis is a faster process D. osmosis occurs in aquatic plants while diffusion occurs in aquatic animals
E. a semi-permeable membrane is necessary in diffusion only (1995/5 Nov)
2. 4a. Define the following terms: 1. Diffusion 2. Osmosis 3. Plasmolysis (2018/4a Neco)
3. Which of the following correctly defines osmosis?
A. movement of molecules from the region of higher concentration to the region of lower concentration
B. movement of molecules from the region of lower concentration to a region of higher concentration
C. movement of molecules aided by energy
D. movement of water molecules from a region of lower concentration solution to a region of higher
concentration solution through a semi permeable membrane. (2001/13 NABTEB)
4. Two important process involved in the absorption and transport of materials in plants are
A. flaccidity and turgidity B. diffusion and plasmolysis
C. plasmolysis and capillarity D. osmosis and diffusion. (2016/30 JAMB)

Use the figure below to Answer: questions 25 and 26.

5. After 30 minutes, the level of sugar solution in the above figure will
A. rise in X only B. rise in Y only C. be the same in X and Y D. fall in Y (1991/25 JAMB)
6. The process by which water moves from X to Y through the semi-permeable membrane is called
A. diffusion B. osmosis C. active diffusion D. osmoregulation (1991/26 JAMB)
67
7. Which of the following results is to be expected if the set-up is left for several hours?
A. Movement of water from the salt solution into the yam B. Decrease in the volume of water inside the yam
C. Decrease in the size of the yam D. Movement of the salt solution into the water. (2004/24 JAMB)
8. Yam is used in this set-up because it
A. is a plant material B. acts as a storage organ
C. acts as a semi permeable membrane D. is permeable to the salt solution. (2004/25 JAMB)

Haemolysis
This refers to the bursting of red blood cells in the plasma due to excessive intake of water (i.e. high turgor pressure).
Normally, the blood plasma and the red blood corpuscles (RBC) are isotonic (i.e both the RBC and the plasma have
the same osmotic concentration).
If for some reasons, the concentration of salt in the plasma falls (hypotonic), water will enter into the red blood cell by
osmosis (endosmosis) through the cell membrane. Continuous absorption of water into the cell will make the cells
very turgid and eventually burst.

Haemolysis leads to anemia which may eventually cause death if ignored. Animal cells have no cellulose cell wall to
resist turgidity hence the bursting.

One the other hand, if the concentration of salt in the plasma is higher (hypertonic) water leaves the red blood cells by
osmosis (exosmosis). The red blood cell will shrink. The shrinking of the red blood cells is called crenation.
Example
(ii) Mention three conditions that may cause haemolysis. (2000/6b (ii)
Answer:
i. Low concentration of solute in the blood plasma.
ii. High concentration of solute in the red blood cell cytoplasm.
iii. Defect in the red blood cell membrane.
Example
A major reason why the red blood cell can survive in the blood is that the
A. blood plasma and the red blood cells are isotonic B. red blood cells are hypotonic to the plasma
C. the red blood cells are hypotonic to the plasma D. the red blood cells receive digested nutrients. (2001/8)
Answer: A – The red blood cell will survive in the blood if the blood plasma and the red blood are isotonic, i.e. the
solute concentration of the red blood cell cytoplasm and that of the blood plasma are the same. But in a situation
where the solute concentration in the cytoplasm of the red blood cell is higher than that of the blood plasma, the red
blood cell will absorb water from the plasma and swell until it finally burst (haemolysis). When the solute
concentration of the cytoplasm of the red blood cell is lesser than that of the plasma, the red blood cell will shrink
(crenation).
Example
A red blood cells hemolysis when placed in a hypotonic solution because
A. it contains hemoglobin B. the cytoplasm is less dense
C. the cell lacks a wall D. its pigment has a high affinity for water. (2001/10)
Answer: B – When placed in a hypotonic solution, red blood cell cytoplasm appear less dense because of it low solute
as compared that of the hypotonic solution. Hence, the red blood cell will be haemolyzed.
Example
Haemolysis occurs when red blood cells
A. and blood plasma are isotonic B. are hypotonic and blood plasma hypertonic
C. are hypertonic and blood plasma hypotonic D. are weaker in concentration than blood plasma (2004/6 Nov)
Answer: C – Haemolysis occurs when the blood cells are hypertonic (at a higher concentration) and the blood plasma
are hypotonic (at a lower concentration).

EXERCISE 5.3
1. Haemolysis of the red blood cells occurs when blood is
A. put in hypotonic solution B. put in liquid nitrogen
C. put in isotonic solution D. put in concentrated salt solution. E. collected in a container. (1995/9 Nov)
2. (ii) Explain what will occur when red blood cell is placed in a hypertonic salt solution. (2018/1c (ii) NABTEB)
3. A red blood cell in isotonic solution
A. becomes turgid B. remains unchanged C. becomes plasmolysed D. becomes diffused (2001/38 NABTEB)

68
4. The process by which a red blood cell placed in distilled water absorbs water until it bursts and releases its
contents into the surrounding is known as
A. osmosis B. plasmolysis C. turgidity D. haemolysis (1994/18 JAMB)
5. If amoeba is placed in a salt solution, the contractile vacuoles would
A. be bursting more frequently B. be more numerous
C. be formed less frequently D. grow bigger before they burst (2011/5)

6. 6(a) Explain the term osmosis

(b) (ii) Mention three conditions that may cause haemolysis. (2000/6a, bii)

Plasmolysis, Turgidity and Flaccidity

Plasmolysis can be defined as the shrinkage of vacuole and pulling away of the cytoplasmic linings from the cell wall
when a plant cell is placed in more concentrated salt solution.
When a plant cell is placed in a more concentrated salt or sugar solution than that of the cell sap, water is lost by
osmosis (exosmosis). As a result of water loss, vacuole shrinks and the cytoplasmic linings are pulled from the cell
wall. The space between the cell wall and cytoplasm becomes filed with concentrated solution. The cell becomes
flaccid or plasmolysed. This process is also known as crenation in animals. Plasmolysis can lead to wilting or death in
plants

A plasmolyzed plant cell

On the other hand, when the plasmolysed cell is placed in water or pure water, H2O moves into the cell sap by
osmosis, (endosmosis) because the cell sap in the vacuole is more concentrated. The vacuole increases in volume and
distends towards the cytoplasm and cell wall.
The cell wall distends until no further distension. At this point, the cell is said to be turgid and the process is called
turgidity.

A turgid plant cell

Plasmolysis can lead to the death of the cells if allowed for a long time. Crops planted in a very salty soil will fail to
survive due to the effect of plasmolysis.
Importance of turgidity
i. Some plant cells such as parenchyma cells can perform a supporting function only when they are turgid, e.g.
the lamina of leaf is always flat because of the turgid mesophyll cells.
ii. Turgidity helps animals cells to retain their shape.
iii. All cells carry out their physiological processes effectively when they contain sufficient water and are turgid.

Flaccidity
This is the condition in which plants lose water to their surroundings faster than they can absorb; it results in the
withdrawal of water from the vacuoles. When the rate of transpiration is faster that the rate of water absorption by the
root of a plant, cells of the plant become flaccid and the plants droop or wilt. Plants usually experience flaccidity when
there is drought. Flaccidity makes plants become weak limp and soft and so they drop.
69
Example

Which of the labeled structures in the diagram will shrink when plasmolysis occurs?
AI B. II C. III D. IV (2000/18)

Answer: A – During plasmolysis, the protoplasm and the plasma membrane shrink away from the cell wall due to loss
of water.
Example
The condition shown in the above diagram is due
A. conversion of starch to sugar B. conversion of sugar to starch
C. excess water in structure labeled I D. presence of carbondioxide in the structure labeled I. (2000/19)
Answer: C– The condition shown in the above diagram is known as turgidity and it is as a result of excess water in
the structure labeled 1
Example
Which of the following solutions will induce the condition shown in the diagram?
A. Hypertonic solution B. Hypotonic solution C. Isotonic solution D. Distilled water. (2000/20)
Answer: B – The condition shown is known as turgidity and it occurs when a cell is placed in a less concentrated
(hypotonic) solution than itself
Example
Which of the following statements defines plasmolysis?
A. Shrinking of a plant cell in a solution B. Shrinking away of cytoplasm from an animal cell membrane
C. Shrinking away of the cytoplasm from the plant cell wall
D. Shrinking of the vacuole and leaving the cytoplasm attached to the cell wall (2005/15)
Answer: C – Plasmolysis is the shrinkage of vacuole and pulling away of the cytoplasmic linings from the cell wall
when a plant cell is placed in a more concentrated salt (hypertonic) solution.
Example
When a spirogyra filament is placed in a concentrated salt solution for 30 minutes, the cell would become
A. plasmolysed B. turgid C. shortened D. elongated (2015/6)
Answer: A – The spirogyra cell will plasmolyze
Example
Turgor pressure occurs in a cell when the
A. volume of its cell sap increases B. cell loses water to its environment
C. volume of cell decreases D. cell is put in an isotonic solution. (1999/11)
Answer: A – Turgor pressure is the force within the cell that pushes the cytoplasmic membrane against its cell wall.
This force is caused by excess fluid in the cytoplasmic membrane. Hence, increase in the volume of cell sap will cause
turgor pressure to occur.
Example
Turgidity in the cell of plant does not easily lead to bursting of the cell because the
A. cell membrane can resist the turgidity B. large vacuole contained in the cell, can continuously take in water
C. cellulose cell wall can resist the turgidity D. cytoplasm is jelly-like (2001/39)
Answer: C – The cellulose cell wall in plant cells resist the turgidity.

EXERCISE 5.4
1. Which of the following statements best explains why an animal cell will burst if it is placed in water?
A. The animal cell cannot hold much water B. The animal cell becomes too turgid
C. Water will enter the cell and it will swell and burst because it lacks a cell wall
D. The animal cell is too thin to resist water pressure as water continuous to enter (2005/10 Nov)
2. (a) (i) Describe an experiment to show the effect of plasmolysis on a fresh filament of spirogyra
(ii) How can the process be reversed (2000/3a (i), (ii)

70
3. A cell is said to be turgid when
A. its content exert pressure on the cell wall B. the cell wall ruptures C. it is put in hypertonic solution
D. the cell wall loses sap E. water flows out from the cell to another cell (1998/16 Nov)
4. Which of the following can cause shrinkage of living cells?
A. isotonic solution B. deionized water C. hypertonic solution D. hypotonic solution (2019/8 NABTEB)
5. 1(a) Define: i. Exosmosis ii. Plasmolysis (2018/19 (i), (ii) NABTEB)
6. The filaments of spirogyra were put into equal volumes of sugar solutions X and Y. After 5 minutes,
filaments from solution X had their cell contents rounded up while those from Y were unaffected. The
experiment shows that
A. solution X was stronger than Y B. solution Y was stronger X
C. Spirogyra used up the sugar in solution X
D. Solution X is good for stimulating sexual reproduction in Spirogyra
E. Solution Y was less contaminated than X (1980/31 JAMB)
7. When a spirogyra cell is immersed in a salt solution more concentrated than its cell sap, it
A. remains uncharged B. takes up water and bursts
C. absorbs a little water D. loses water and shrivels E. becomes turgid (1983/47 JAMB)

Active transport
This is a process whereby molecules pass across a semi-permeable membrane of a living cell against the concentration
gradient. It involves the expenditure of energy (ATP). Active transport is characteristics of all actively respiring cells,
such cells contain numerous mitochondria. Examples of living activities involving ACTIVE transport includes:
i. Selective reabsorption of glucose, amino acid, and sodium in the nephron of the kidney during urine
formation.
ii. Movements of sodium ions out of the nerve cell in the course of transmitting nerve impulses.

Factors that can affect active transport in living cells are:

i. Temperature: The lower the temperature, the slower the molecules moving across the membrane.
ii. High oxygen concentration: Any factor that will inhibit respiration will also inhibit active transport.

Example
(c) What role do the following processes play in the activities of a living cell?
(i) osmosis; (ii) diffusion? (1988/1c)
Answer:
i. Osmosis:
- Plant absorbs water from the soil into the root hair cells by osmosis.
- Water moves from one cell into another in plant and animals by osmosis.
- Opening and closing of stomata takes place when guard cells take up or lose water by osmosis.
ii. Diffusion:
- Gaseous exchange involving oxygen and carbondioxide between a cell and its environment during
respiration occur by diffusion.
- Absorption of digested of food into the intestinal cells occurs by diffusion.
- Removal of some excretory products occur by diffusion.
Example
In active transport, molecules move against a concentration gradient, therefore,
A. molecules move from a region of low concentration to a region of high concentration
B. molecules move from a region of high concentration to a region of low concentration
C. the concentration gradient has little effect on the movement of molecules
D. molecules force their way through special channels. (2005/13)
Answer: A – Active transport involves the movement of molecules from a region of low concentration to a region of
high concentration (i.e. against concentration gradient) by the use of energy.

Example
Which of the following environmental conditions is ideal for plant cells to remain turgid?
A. Hot, dry weather B. Windy weather C. Cold, dry weather D. Cool, humid weather (2006/10)
Answer: D – Plant cells are more like to remain turgid in a cool and humid weather condition because there will not
be water loss through the process of transpiration.

71
Example
Which of the following processes does not contribute towards growth?
A. Cell division B. Cell enlargement C. cell differentiation D. Cell plasmolysis (2006/11)
Answer: D – Cell plasmolysis is not a process that favours growth. All other options (A to C) are stages of cell
growth.

EXERCISE 5.5
1. Which of the following processes takes place when a plant cell is put in a hypotonic solution?
A. Water moves into the cell and the cell bursts B. Water leaves the cell and the cell becomes flabby
C. Water moves into the cell and the cell becomes turgid D. The cell becomes plasmolysed. (2007/7)
2. The mechanism of opening and closing of stomata in plants is based on
A. turgidity and diffusion B. turgidity and flaccidity
C. osmosis and diffusion D. diffusion and flaccidity (2010/8)
3. Active transport can be defined as the movement of
A. substances from a region of high concentration to a region of low concentration
B. substance from a region of low concentration to a region of high concentration across a living cell membrane
C. substance across a living cell membrane using energy from the cell
D. movement of molecules in a medium. (2014/14)
4. Which of the following processes is not applicable to the reaction of a cell to the Concentration of a liquid
medium?
A. Osmosis B. Haemolysis C. Diffusion D. Plasmolysis E. Radiation (1992/7 Nov)

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Nutrition
Feeding or Nutrition
This is the supply of vital materials or nutrients to the cells of an organism for growth, respiration reproduction and
other activities that pertains to life. Food is the source of nutrient which supplies energy to the cells to carry out
metabolic activities.
Nutrition is one of the characteristics of living things. It is the process by which organisms obtain and utilize materials
from external environment for metabolic activities such as respiration, growth, excretion and reproduction.
Metabolism refers to all the chemical processes associated with living organisms. It is divided into two parts namely:
catabolism and anabolism.
Catabolic processes are those activities which result in complex substances being reduced or decomposed into simple
ones with the release of energy which become available to the organisms. On the other hand, anabolic processes are
those processes which results in the building up of complex substances with the absorption or storage of energy.
Metabolic reactions are controlled by enzymes.

Types of Nutrition
i. Autotrophic nutrition (Autotrophy)
ii. Heterotrophic nutrition (Heterotrophy)

Autotrophic Nutrition
This is a type of feeding in which an organism manufactures its own food.
There are two types of autotrophic nutrition namely:
i. Photosynthetic nutrition (Holophytic)
ii. Chemosynthetic nutrition

In Photosynthetic nutrition, the green plants manufacture their own food from simple inorganic substances using
sunlight as external source of energy in the presence of carbondioxide, water and chlorophyll.
𝑠𝑢𝑛𝑙𝑖𝑔ℎ𝑡
6CO2 + 6H2O 𝑐ℎ𝑙𝑜𝑟𝑜𝑝ℎ𝑦𝑙𝑙
C6H12O6 + 6O2

On the other hand, Chemosynthetic nutrition involves the manufacture of food from simple inorganic substances
such as carbondioxide (CO2), water (H2O) and hydrogen sulphide (H2S) using energy released during chemical
reaction. Hence the process is called chemosynthesis. For example, sulphur bacteria can synthesize its own food by
oxidizing hydrogen sulphide around to produce energy.
𝑠𝑢𝑙𝑝ℎ𝑢𝑟 𝑏𝑎𝑐𝑡𝑒𝑟𝑖𝑎
2H2S + O2 → 2S + 2H2O + chemical energy
The chemical energy is capable of bringing about the combination of hydrogen sulphide and Co2 in the soil to form
sugar, water and sulphur.
𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙
12H2S + 6Co2 𝑒𝑛𝑒𝑟𝑔𝑦
C6H12O6 + 6H2O + 12S
From the simple sugar other food substances such as protein, oil and vitamins are manufactured.

Another example of chemosynthesis is given below:

𝑛𝑖𝑡𝑟𝑜𝑠𝑜𝑚𝑜𝑛𝑎𝑠
2NH3 + 3O2 → 2HNO2 + 2H2O + chemical energy

2HNO2 + O2 2HNO3 + chemical energy.

The energy released is used to combine water and carbon IV oxide to form sugar.
𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙
6CO2 + H2O 𝑒𝑛𝑒𝑟𝑔𝑦
C6H12O6.

73
Hetrotrophic Nutrition
This is a form of nutrition in which the organisms depend on other organisms for its food requirement.
All animals and plant that lack chlorophyll (fungi, bacteria, few parasitic flowering plants) are examples of
heterotrophs:
There are four main types of heterotrophic nutrition namely:
(i) Holozoic (ii) saprophytic (iii) symbiotic (iv) parasitic
i. Holozoic Nutrition
In this type, food is obtained as a solid organic material, eaten, digested, and absorbed into the body.
Holozoic animals developed different efficient digestive systems to digest solid food materials into simple materials
for absorption into the body. Holozoic animals include:
a. Herbivores, which feed on plants materials e.g. sheep, cow, horses e.t.c.
b. Carnivores, which feed on flesh and bones of other animals e.g. leopard, dog e.t.c. Carnivores that
hunt living animals (prey) for food are known as predators, while those that feed only on dead animals
are known as scavengers .
c. Omnivores, which feed on both plants and other animals e.g. man.

ii. Saprophytic Nutrition

In this type, non-green plant feed on dead and decaying organic matter. Enzymes are secreted on the substrate to
digest it and the soluble products are absorbed. Digestion takes place outside the body of the organism (extracellular
digestion). Such organisms are called saprophytes. Examples include most fungi e.g. mucor, mushroom, and yeast
and bacteria.

iii. Symbiotic Nutrition:

In this type, two organisms of different species live together and they benefit from each other. Example of this is the
association between an alga and a fungus in lichen. The fungus provides moisture, mineral salts and support for the
alga while the alga manufactures food by photosynthesis for the fungus and itself. Another example is found in the
hermit crab and sea anemone. Another is herbivorous animal and cellulose – digesting bacteria that live in the caecum
and colon of herbivores.

iv. Parasitic nutrition:

In this type of nutrition, one organism obtains food from another organisms and during the feeding process, one of the
organisms is harmed and does not benefit. The organisms gaining food, protection and shelter is called parasite while
the organisms being harmed is called host. This type of association is called parasitism. Some parasites live on the
surface of their host and are called ectoparasite. Examples are lice, tick, bed-bugs, fleas, and mite.
Parasite that live inside the body of their hosts are called endoparasite. Example of endoparasite are Plasmodium,
hookworm, Ascaris, tapeworm, and liver fluke. These endoparasite, have special adaptation that enable them to live
within their hosts. For example, tapeworm has four suckers on its head/scolex which are supported by hooks that help
it to fasten itself unto the wall of the small intestine of its host. The long and tape-like body consists of a series of
proglottides which provides a large surface area for absorption of digested food by diffusion.

Tape worm

74
Apart from animal parasites which have been mentioned, there also exists some parasitic plants. Examples of
some parasitic plants include dodder plant (cassytha filiformis) and mistletoe. They obtain their nourishment by
developing special organs called haustoria (suckers) which are sent to the host vascular bundles.

Dodder plant A section through a host stem and dodder stem

Adaptation of parasites includes:

i. Presence of organs of attachment e.g. hooks and sucker in tapeworm and haustoria in mistletoe
ii. Simple body structure, since they do not have to search for their food e.g. round worm
iii. Resistance to digestion e.g intestinal worms like round worms
iv. Production of large numbers of eggs or young to ensure survival and the infection of new hosts e.g. tapeworm.
v. The existence of an intermediate host, in some cases e.g. malaria parasite (Plasmodium), guinea – worm.

Carnivorous mode of nutrition in plants

Carnivorous plants have green leaves and are able to manufacture their own food/carry out photosynthesis. They have
root to absorb water and mineral salts from the soil. They usually grow in places with little nitrogenous salts and use
insects/other small animals as source of nitrogen. They have devices/modified leaves with high colour/scents/sugary
liquid/sticky wet surface for attracting and trapping insects. Once the insect is trapped the plant secretes enzymes to
kill and digest it. The soluble nitrogenous compounds are absorbed/assimilated by the plants. Carnivorous plants are
also called insectivorous plants
Name of carnivorous plants: Butterwort/Pinguicula, bladderwort/Utricularia, sundew/Drosera,
venus flytrap/Dionaea, pitcher plant/Nepenthes/sarracenia.

Venus fly trap Pitcher plant

Note: There are some plants that grows upon the surface of another plant without causing harm to such plant. These
plants are known as epiphytes. Examples include mosses and orchids. They do not grow haustoria and therefore not
parasitic.

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Example
A plant which grows on another plant without apparent harm to the host plant is called
A parasite B. an epiphyte C. saprophyte D. a predator E. a hermaphrodite (1978/1 JAMB)
Answer: B – An epiphyte is a plant that grows on another plant and depends on it for support but not food. An
epiphyte do not cause any harm to it host plant.
Example
Rhizopus (or Mucor) obtains its food from dead organic matter extracellularly. It is said to be
A. a facultative parasite B. a saprophyte C. an obligate parasite D. a commensal E. an autotroph (1978/25 JAMB)
Answer: B – A saprophyte is an organism (e.g. fungi) that grows on and derives it nourishment from dead or decaying
organic matter.
Example
The mode of nutrition in which digestion is extra cellular is
A. holophytic B. parasitic C. holozoic D. saphrophytic (1990/17 JAMB)
Answer: D – In saprophytic nutrition, digestion is done extracellularly i.e. the organism (the saprophyte) secrete
digestive enzyme on the decaying or dead matter and then absorbed the digested substance through it cell walls.
Example
The mode of nutrition exhibited by a tapeworm is
A. saprophytic B. parasitic C. holozoic D. symbiotic (2002/23 JAMB)
Answer: B – Tapeworm are parasitic i.e. they feed at the expense of the host.
Example
The mode of nutrition of sundew and bladderwort can be described as
A. autotrophic B. saprophytic C. holozoic D. chemosynthetic (2010/15 JAMB)
Answer: C – Sundew and bladderwort are carnivourous plants. They possess special structures which they use to trap
and digest insects. This makes them holozoic in nature.
Example
Fungi are referred to as heterotrophs because they
A. are filamentous B. lack chlorophyll C. have mycellum D. lack roots (2013/21 JAMB)
Answer: B – Fungi lack chlorophyll and are unable to manufacture their own food. This makes them depend on other
organism for their food (heterotrophic).
Example
An example of a parasitic protozoan is
A. Paramecium B. Plasmodium C. Euglena D. Chlamydomonas (2013/22 JAMB)
Answer: B – Plasmodium is a parasite carried by mosquitoes and are transferred to human, when a mosquito carrying
it feeds on human blood. The plasmodium feeds on the haemoglobin of the red blood cells and during the process
releases toxins that cause malaria in human.
Example
Which of the following is an example of parasitism?
A. A squirrel living in an abandoned nest of a bird B. Mistletoe growing on an orange tree
C. Fungi growing on a dead tree branch D. Cattle egrets taking tasks from the body of cattle (2015/29 JAMB)
Answer: B – Mistletoe is a parasitic plant that derives it nutrients from its host plant and invariable harm the plant.
Example
Autotrophic nutrition may be defined in terms of food obtained
A. from other orgnaisms in exchange for some products B. by the breakdown of complex substances
C. by an organisms utilizing its own store of energy
D. by synthesizing simple substances using energy from an external source
E. in a synthesized form from other living organism (1988/ 31)
Answer: D – Autotrophic nutrition is one in which an organism can manufacture it own food by making use of energy
from external source (e.g. sun).
Example
Autotrophs are also described as
A. consumers B. decomposers C. carnivores D. producers E. herbivores. (1989/20)
Answer: D – Autotrophs are also known as producers, while hetrotrophs are known as consumers.
Example
Which of the following is not an example of a heterotrophic mode of nutrition?
A. Symbiosis B. Parasitism C. Commensalism D. Holophytism E. Saprophytism (1992/38)
Answer: D – Holophytism is an example of autrophic nutrition in which plant obtain their food by making use of in-
organic material.

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Example
What type of relationship exits in the large intestine of a sheep, between bacteria and sheep
A. Symbiosis B. Commensalism C. Predation D. Parasitism E. Saprophytism (1996/38)
Answer: A – Symbiosis is an association between two organisms in which both of them benefit from it. The bacteria
in the intestine of the sheep gain shelter and protection and helps the sheep to digest cellulose.
Example
1(a) Explain the terms (i) Parasitism (ii) Commensalism;
(b) Mention (i) one fungal parasite of a plant and its host (2002/1a, b)
Answer:
1a. i. Parasitism: This is a a relationship between species, in which one organism (the parasite) lives on or in
another organism (the host), causing it harm.
ii. Commensalism: This is an association between two organism in which one benefits and the other derives
neither benefits nor harm.
1bi. Fungi: Cryphonectria parasitica; Host: Chestnut tree.
Example
The type of nutrition shown by spirogyra is
A. symbiosis B. holophytic C. holozoic D. chemosynthetic (2003/34)
Answer: B – Holophytic nutrition is a type of autotrophic nutrition in which organism (plants) make use of inorganic
material to manufacture their own food. NB: Holozoic nutrition is a type of hetrotrophic nutrition.

Example
Which of the following protozoans feeds parasitically?
A. Paramecium B. Chlamydomonas C. Plasmodium D. Euglena (2007/35)
Answer: C - The plasmodium feeds on the haemoglobin of the red blood cells and during the process releases toxins
that cause malaria in human.
Example
8(a) Explain the following modes of nutrition which occur in plants:
(i) Autotrophic (ii) Chemosynthetic (iii) Carnivorous
(b) Give one example each of a plant which undergoes the modes of nutrition listed in 8(a) above (2008/8a–8b)
Answer:
8a. i. Autotrophic – This is a process in which organism manufacture their own food from in organic materials such
as water, carbondioxide and mineral salts in the presence of sunlight or chemical as a source of energy.
ii. Chemosynthesis – This is a type of autotrophic nutrition in which organism manufacture their food from
simple inorganic substances such as CO2, H2O and hydrogen sulphide using energy released during chemical
reaction
iii. Carnivorous: This is a kind of nutrition in which plants derive some or most of their nutrients (but not energy,
which they derive from photosynthesis) from trapping and digesting insects.
8b. i. Autotrophic nutrition – e.g. orange tree
ii. Chemosynthesis – e.g. sulphur bacteria, ferroxidans
iii. Carnivorous – e.g. sundew
Example
State two distinguishing features each of (i) epiphytes (ii) parasites (2010/2b)
Answer:
i. Epiphytes:
- They are mostly found on the body of their host plant.
- They do not cause harm to their host plant.
ii. Parasites:
- They live in or on the body of their host.
- They cause harm to their host.
Example
Give two examples of parasitic plants (2010/2c)
Answer: 1. Sundew; 2. Bladderwort
Example
The association between two organisms in which one of the organisms gains and the other loses is referred to as
A. saprophytism B. commensalism C. mutualism D. parasitism (2016/24)
Answer: D – Parasitism: This is a symbiotic relationship between species, in which one organism (the parasite) lives
on or in another organism (the host), causing it harm.

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Example
The examples of autotrophic organisms include the following except
A. Euglena B. Chlamydomonas C. Hydra D. Spirogyra (2006/35)
Answer: C – Hydra is an animal, it feed heterotrophically. All other options (A, B and D) are autotrophs.
Example
Which of the following organisms feeds both autotrophically and heterotrophically?
A. Hydra B. Paramecium C. Mucor D. Euglena (2006/36)
Answer: D – Euglena is an organism that has characteristics of both plant and animal. It has chlorophyll which is used
for photosynthesis in the present of light and in the absence of light, it switches to heterotrophic mode of nutrition.
Example
A characteristic feature of plant parasites is the
A. possession of holdfast B. possession of rhizoids
C. development of hanging roots D. development of haustoria (2014/25)
Answer: D – Haustoria is a projection from the root of a parasitic plant which enables it to penetrate the tissues of its
host and absorb nutrients from it.
Example
6(f) Name three organisms that carry out holozoic mode of nutrition (2016/6f)
Answer:
Cow, Lion and Bird
Example
3b. (i) State three adaptive features of parasites. (ii) State two effects of parasites on their hosts.
c. (i) What are saprophytes? (ii) Give four examples of saprophytes. (2019/3b, 3c)
Answer:
3b. i. - Development of piercing device that enables them to invade the tissue of the host.
- Production of enzymes that helps to digest the host tissue.
- Possession of reduced body size in order to occupy the niche in the internal or external surface of the host.
ii. - Deprive the host of nutrients.
- Kill the host in the process of feeding.
c. i. Saprophytes are organisms that live and feed on dead and decaying organic matter.
ii. Mushroom, mold, earthworm, mucor
Example
The raw materials required by green plants for the manufacture of foods are
A. liquid substances B. inorganic substances C. organic materials D. solid materials (2019/28 PCE)
Answer: B – Plants make use of inorganic materials such as CO2, and H2O in the presence of chlorophyll and sunlight
to manufacture their food.
Example
Insectivorous plants are commonly found
A. in marshy areas B. on soil deficient in magnesium
C. at the edge of forests D. on soils deficient in nitrogen (2000/40 Nov)
Answer: D – Insectivorous (carnivourous) plants are found in nitrogen deficient soil; for this reason, they trap insects
and other small animals in order to derive nitrogen and nutrient from them.

EXERCISE 6.1
1. 7(a) Define the following terms:
(i) Parasitism; (ii) Saprophytism; (iii) Symbiosis, giving one example of each.
(b) Describe the external features of a named animal ecto-parasite and how the features adapt it to its
mode of life. (2011/ 7a, b)
2. Which of the following plants is a parasite?
A. cassytha B. Algae C. sundew D. mushroom E. Chlamydomonas (1998/38 Nov)
3. 1(c) List FIVE types of nutrition. (2005/1c Neco Nov)
4. Which of these organisms are NOT autotrophs?
A. algae B. ferns C. fungi D. grasses E. (2005/20 Neco Nov)
5. Which of the following is an autotrophic mode of nutrition?
A. holozoic B. parasitic C. photosynthesis D. saprophytic E. symbiotic (2007/57 Neco)
6. Which of the following mods of nutrition is autotrophic?
A. holophytic B. holozoic C. parasitic D. saprophytic E. symbiotic (2008/9 Neco)
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7. The mode of nutrition in mushroom is
A. autotrophic B. epiphytic C. parasitic D. saprophytic E. symbiotic (2018/31 Neco)
8. Rhizopus is a saprophyte because it
A. feeds on decaying organic matter B. absorbs nutrients from living plants
C. lives symbiotically with an alga D. feeds on microscopic organisms (2001/3 NABTEB)
9. Autotrophic mode of feeding is a characteristic of
A. algae B. fungus C. bacterium D. protozoan (2017/14 NABTEB)
10. Which of the following structural features adapts Drosera (Sundew) to its carnivorous mode of nutrition?
A. Long root with glandular hairs B. Club-shaped glandular hairs on leaves
C. Prominent lenticels on the stem D. Broad leaves with long species
E. Wide stomata under the leaves. (1994/54)
11. Which of the following organisms is not considered as a parasitic plant?
A. Cassytha B. Rhizopus C. Dodder D. Mistletoe (2006/34)
12. (b) Describe the mode of nutrition in a named carnivorous plant (2014/3b)
Study the diagram below and use it to Answer: questions 32 to 34

13. The mode of nutrition of the plant in the diagram is

A. photosynthesis and chemosynthesis B. saprophytic and carnivorous
C. photosynthesis and carnivorous D. chemosynthetic and saprophytic. (2015/32)
14. The structure labeled I is
A. a pitcher B. an onion C. a flower D. a tendric (2015/33)
15. In which type of soil is the plant found? Soil that is
A. poorly aerated B. water logged C. exposed D. nitrogen deficient (2015/34)
16. b. (i) State three adaptive features of parasites. (ii) State two effects of parasites on their hosts. (2019/3bi, ii)
17. Which of the following plants is a parasite?
A. cassytha B. Algae C. sundew D. mushroom E. Chlamydomonas (1998/38 Nov)
18. (ii) Parasitic feeding in tapeworm. (1995/1cii Nov)
19. If an organism obtains its food by means of haustoria, it is said to be
A. holophytic B. heterophytic C. saprophytic D. parasitic (2019/38 NABTEB)
20. The parts used by the tapeworm to fasten itself to the host’s intestine are the
A. neck and suckers B. hooks and suckers C. rostellum and suckers
D. young proglottis and neck E. rostellum, hooks and suckers (1984/23 JAMB)
21. In the tapeworm, the suckers on the scolex are used for
A. sucking the blood of the hosts B. holding fast to the hosts C. reproduction D. locomotion (1990/12 JAMB)
22. Insectivorous plants trap and kill their prey to derive
A. phosphorus B. calcium C. nitrogen D. zinc (2008/15 JAMB)
23. Which of the following is an example of a carnivorous plant?
A. Hydra B. Bladderwort C. Yeast D. Spirogyra (2009/15 JAMB)
24. The mode of nutrition of sundew and bladderwort can be described as
A. autotrophic B. saprophytic C. holozoic D. chemosynthetic (2010/15 JAMB)

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Use the diagram below to Answer: questions 6 and 7

25. The organs for attachment to the lining of the host’s intestine are labelled
A. I and II B. I and III C. II and III D. III and IV (2014/6 JAMB)
26. The young proglottid is represented by
A. I B. II C. III D. IV (2014/7 JAMB)
27. Chemosynthetic organisms are capable of manufacturing their food from simple inorganic substances
through the process of
A. oxidation B. denitrification C. reduction D. phosphorylation (2010/25 JAMB)
28. Plants that have special devices for trapping and digesting insects
A. carnivorous B. symbiotic C. parasitic D. saprophytic (2013/19 JAMB)
29. Which is NOT a carnivorous plant?
A. bladderwort B. dodder plant C. drosera D. pitcher plant E. Venus flytrap (2001/22 Neco)

PLANT NUTRITION
Photosynthesis
This is the process by which green plants (autotrophs) manufacture food (organic compound) from carbondioxide and
water using energy absorbed from the sunlight by the chlorophyll with the help of enzymes, while oxygen is liberated
as a by-product.
light and chlorophyll
6CO2 + 6H2O         C6H12O6 + 6O6↑ + E
The first stable product of photosynthesis is a simple sugar (glucose).
Although all the green part (areas that contains chlorophyll) of a plant can carryout photosynthesis, the leaves are the
primary photosynthetic organs. The major site of a leaf where photosynthesis occurs is the palisade mesophyll. This is
because:
(i) It contains more chloroplast/chlorophyll than the spongy layer/other parts of the leaf.
(ii) Palisade cells are located just beneath the upper epidermis where the chlorphyll could absorb more sunlight.

NOTE: Apart from chlorophyll, there are some other pigment which are capable of absorbing sunlight energy.
Examples includes: carotenoids (orange in colour), xantophylls (yellow colour) and antocyanin (bluish green), these
are accessory pigment and are masked by the chlorophyll (green) which is the main photosynthetic pigment, but
usually becomes visible when leaves fall and die.

The transverse section of a leaf showing chloroplast containing chlorophyll

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Adaptations of the leaf for photosynthesis
i. The broad leaf lamella: Provides large surface for absorption of sufficient light.
ii. Stomata: Allows carbon-dioxide to diffuse into the leaf and oxygen to diffuse out.
iii. Epidermis: It is thin and transparent to allow more light reach the palisade cells.
iv. Palisade Cells: It contains many chloroplast to absorb all the available light.
v. Thin lamella: Provides short distance for carbon-dioxide to diffuse into leaf cells.
vi. Thin cuticle made of wax: Protect the leaf from infection and prevent water loss without blocking out light.
vii. Xylem: This specialized tissue transports water into the leaves for photosynthesis.
viii. Phloem: Transports manufactured food to other parts of the plant.
ix. Network of veins: Supports the leaf and transports water, mineral ions and sucrose (sugar).
x. Chlorophyll: Absorbs sunlight energy and transfers it into chemical energy.

The process of photosynthesis is divided into two phases namely: (i) light reaction;
(ii) dark reaction

1. Light reaction
This takes place only in the light. The light reaction is divided into four steps:
Step I: Chlorophyll is energized: The chlorophyll absorbs sunlight energy and become energized.
Step II: Photolysis of water: The energy absorbed by the chlorophyll is used to split water molecule into
hydrogen ion (H+) and hydroxyl (OH-) ion.
𝐿𝑖𝑔ℎ𝑡 𝑒𝑛𝑒𝑟𝑔𝑦
H2O 𝑐ℎ𝑙𝑜𝑟𝑜𝑝ℎ𝑦𝑙𝑙
> H+ + OH-
The hydroxide ion (OH-) gives up its negative electron to the chlorophyll molecules and form water and oxygen.
𝐿𝑖𝑔ℎ𝑡
4H2O 𝑐ℎ𝑙𝑜𝑟𝑜𝑝ℎ𝑦𝑙𝑙
> 4H+ + 4OH-

4(OH-) 2H2O + O2↑ Oxygen is given up as a by-product.

Step III: Hydrogen is transferred by NADP (Nicotinamide adenine di-nucleotide phosphate). The hydrogen atom
released during photolysis of water is picked up by coenzyme (NADP). This is to prevent the escape of hydrogen
atom from the cell or recombining with oxygen to form water.
NADP when reduced becomes NADPH2 and serves as electron carrier of hydrogen ions.

Step IV: Formation of ATP (Adenosine triphosphate). Chloroplast contains ADP (Adenosine di-phosphate, an
energy carrier). The extra energy not used in the splitting of water molecules is released to ADP to form ATP which is
used in the dark reaction.
The light reactions take place in the grana (granium singular form) of the chloroplast.

Major products of light-dependent stage of Importance of the product

photosynthesis
i. ATP (Adenosine triphosphate)/energy To generate energy for the dark stage reaction
ii. H+ (hydrogen ion) Combines with NADP to form NADPH2
(2H+ + NADP   NADPH2)
iii. OH- (hydroxyl ion) Forms water and oxygen gas which are released as by-
product (OH– → H2O; O2 gas)
iv. NADPH2 (reduced nicotinamide adenine To generate hydrogen ion/to reduce carbondioxide/CO2
dinucleotide phosphate) to form carbohydrate in the dark stage.
v. Oxygen gas (O2) Given off into the atmosphere for animals/other
organism to use for respiration.

2. Dark Reaction (Calvin cycle)

This reaction does not require light energy. Carbondioxide is reduced by combining with two atoms of hydrogen
provided by a coenzyme (NADPH2) to form sugars after undergoing a series of stepwise reactions. Each step is
controlled by a specific enzyme. The energy needed for formation of sugar is provided by ATP from light reaction.
The dark reactions take place in the stroma of the chloroplasts.
enzymes
6CO2 + 12H2 → C6H12O6 + 6H2O
6H2O + 6CO2 → C6H12O6 + 6O2

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Materials and conditions necessary for photosynthesis
The materials needed for photosynthesis are water, carbon IV oxide, light energy, suitable temperature and
chlorophyll.
Factors that affects the rate of photosynthesis:
i. External factors: light intensity/sunlight, carbon dioxide concentration, temperature, pollution, water.
ii. Internal factors: Hormones, chlorophyll or presence of chlorophyll/chloroplast, enzymes, number/state of stomata

Evidence of photosynthesis
The first main product of photosynthesis is glucose. It is immediately converted into starch for storage. The presence
of starch in the leaves thercfore show that photosynthesis has occurred.
Some plants, especially monocotyledons do not change their sugar into starch. If such leaves are tested for starch, a
negative result will be obtained. In such plants, parts of the foods synthesized are converted to soluble forms and
carried in the phloem vessels to storage organs.
Fate of food manufactured by green plants
Glucose is the first stable product of photosynthesis. Manufactured food/glucose is translocated to various parts of the
plant through the phloem. This can be combined with other elements such as nitrogen and sulphur to form proteins for
growth. It can be converted to starch and stored. It is used in respiration/metabolic activities or broken down into
carbondioxide and water to produce energy; other products like lipids and cellulose can also be manufactured from
glucose.

Importance of photosynthesis
i. Green plants manufacture their food through photosynthesis.
ii. All other organisms depend on this process as their ultimate source of energy because they feed on plants
directly or indirectly.
iii. Carbon atoms present in the organic molecules of organisms are derived from CO2 of the atmosphere either
directly during photosynthesis by autotrophs or indirectly. Heterotrophs use organic molecules formed during
photosynthesis.
iv. Photosynthesis helps to purify the environment by removing carbondioxide from the environment and adding
oxygen to it. It maintains a fairly constant concentration of the oxygen and carbondioxide in the atmosphere.

Experiment to test for starch in a leaf

Aim: To test for starch in a leaf.
Materials: A fresh green leaf, bunsen burner, tripod stand, test tube, petri dish, beakers, water, iodine solution,
forceps, / dropping pipette and alcohol.

Testing for starch

Method:
1. Pluck a fresh green leaf, from plant in the sunlight.
2. Boil the leaf in water for 5 minutes to kill the protoplasm, inactivate enzymes and burst any starch grains
present.
3. Place the leaf in a tube about one-third full with 70% alcohol. Place the tube in a water bath and warm the
water gently until the alcohol begins to simmer. The alcohol will decolourise the leaf.
4. Dip the leaf in warm water to soften it.
5. Place the leaf on a petri dish containing dilute iodine solution for 5 minutes.

Observation: If starch is present in the leaf, it will turn blue black.

Conclusion: This shows that the leaf has photosynthesized.
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An experiment to demonstrate that oxygen is released by green plants during photosynthesis.
Aim: To show that oxygen is released during photosynthesis
Apparatus: Two beakers (1 litre), water plant, glowing splint, water, funnels (two) and two test tubes.
Method: The water plant is placed in a beaker containing the fresh water and is covered with an inverted funnel and
labeled A. The same thing is done with a control experiment labeled B, only that while A is exposed to sunlight, B is
covered with a cardboard paper. Leave them for some time.

Test tube A Test tube B

Experiment to demonstrate that oxygen is released during photosynthesis.

Observation: Bubble of gas is noticed in experiment A. On passing a glowing splint at the test tube end of A, it
rekindled. No bubbles were noticed in B and it could not rekindle a glowing splint.
Conclusion: The gas that evolved in A is oxygen since it was able to rekindle a glowing splint. This confirms that
oxygen is produced during photosynthesis.

Experiment to show that green plants require sunlight for photosynthesis

Method: Take a potted plant that is well watered, de-starch the leaves by keeping the plant in a dark cupboard at least
for 24 hours/overnight. Test leaf sample of the plant for starch. The result is negative/yellowish brown colour which
shows the absence of starch.

A leaf of this plant is partially covered with black paper on which a design/pattern is cut and the plant is then exposed
to sunlight for 4-6 hours. Re-test the leaves from both plants for starch.

Areas of leaf not

Affected with iodine

Experiment to show that green plants require sunlight for photosynthesis

Observation: The covered leaf part shows brown colouration, while exposed leaf part shows blue-black colouration

Results: Starch is present in the area of leaf exposed to sunlight but absent in the leaf part covered with black paper.

Conclusion: The area of the leaf exposed to sunlight gave a positive iodine test, indicating that sunlight is necessary
for photosynthesis.

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Experiment to show that water is needed for photosynthesis
Aim: To show that water is needed for photosynthesis
Apparatus: Alkaline pyrogallol solution, a conical flask, retort stand and split cork.
Method: Take a potted plant and de-starch it by keeping it in the dark room for 24 hours. A leaf of the de-starched
potted plant is enclosed in a conical flask containing alkaline pyrogallol solution (this solution absorbs water). The
other leaves serves as control. Place the setup outside under bright sunlight for about 6-8 hours. Detach the
experimental and control leaf from the plant and test for starch.
Observation: The experimental leaf turns yellowish brown (negative test for starch) while the control turns blue black
(positive test for starch) upon testing for starch
Conclusion: This shows that water is needed for photosynthesis

Example
The oxygen given off during photosynthesis process is derived from
A. sunlight B. chlorophyll C. carbon dioxide D. atmosphere E. water (1978/3 JAMB)
Answer: E – oxygen give off during photosynthesis is derived from the splitting of water.
Example
Which of these is a direct photosynthetic product?
A. Glucose B. Starch C. Protein D. Fats E. Latex (1978/34 JAMB)
Answer: A – Glucose is a direct product of photosynthesis.
Example
Alkaline pyrogallol was used in an experiment. That experiment must have been connected with
A. excretion B. germination C. transpiration D. digestion E. photosynthesis (1979/23 JAMB)
Answer: E – Alkaline pyrogallol is used to test for the importance of water to photosynthesis.
Example
The major site of photosynthesis in the leaf is the
A. Palisade parenchyma B. mesophyll parenchyma C. upper epidermis D. lower epidermis (1992/13 JAMB)
Answer: A – Palisade parenchyma is the major site for photosynthesis because it contains high concentration of chloroplast.
Example
The manufacture of carbohydrates by plants takes place only in
A. the leaves B. the green stems C. chlorophyllous part D. flowering plants (1998/12 JAMB)
Answer: C – Chlorophyllous part means any part of the plant that has chlorophyll and is exposed to sunlight. This can
be the leaf stem or flower.
Example
The dark reaction of photosynthesis involves
A. fixation of carbon (iv) oxide to give a six-carbon sugar B. Fixation of carbon (iv) oxide with the help of oxygen
C. use of carbon (iv) oxide to produce glucose using ATP
D. fixation of carbon (iv) oxide on chlorophyll using hydrogen (1999/16 JAMB)
Answer: C – The dark reaction of photosynthesis involves the use of carbon-dioxide to produce glucose using energy (ATP).

Example
During the manufacture of food by plants, which of the following organisms use energy from the sun
A. Anaebena B. Sulfur bacteria C. Nitrosomonas sp D. Nitrobacter sp (2013/16 JAMB)
Answer: A – Anaebena is a photosynthetic organism i.e .it uses sunlight as it source of energy to make it food. All
other options (B to D) are chemosynthetic i.e. they use energy derive from chemical reaction to generate their food.

Example
The photosynthetic pigments include
A. chloroplast and cytochromes B. melanin and hemoglobin
C. chlorophyll and carotenoids D. carotenoids and hemoglobin (2015/25 JAMB)
Answer: C – Chlorophyll is a green photosynthetic pigment and carotenoid is an orange photosynthetic pigment.
Example
When testing for the presence of starch in a leaf, the reason for dipping the decolorized leaf in hot water is to
A. detect the starch B. kill the leaf C. soften the leaf D. remove the chlorophyll (2017/10 JAMB)
Answer: C – It is to soften the top leaf.

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Example
The process that takes place in the dark stage of photosynthesis is
A. oxidation of water B. photolysis of water
C. oxidation of carbon(IV) oxide D. reduction of carbon (IV) oxide (2017/14 JAMB)
Answer: D – In dark reaction, carbon(iv)oxide is reduced by hydrogen supplied by NADPH2 to form glucose.
Example
Which of the following does not occur during photosynthesis?
A. Energy from sunlight is absorbed B. carbondioxide is evolved
C. glucose is synthesized D. oxygen is given off E. water is split. (1988/ 26)
Answer: B – Carbondioxide is not evolved but rather it is absorbed through the stomata during photosynthesis. All
other options (A, C, D and E) occur during photosynthesis.
Example
Even though some flowering plants contain accessory pigments which give them colours they will contain the pigment
A. melanin B. chlorophyll C. xanthrophyll D. carotene E. chlorocruorin (1988/ 27)
Answer: B – Chlorophyll is the main pigment for photosynthesis. Hence, even though some flowering plants contain
accessory pigments that give them colouration, they will also contain chlorophyll.
Example
In photosynthesis, the following processes are part of the light reaction except
A. transfer of radiant energy which reduces a co-factor B. absorption of radiant energy by chlorophyll
C. utilization of the energy in the electron transfer chain a form ATP
D. formation of glucose using energy from NADPH E splitting of water into its component parts. (1989/21)
Answer: D – Formation of glucose using energy from NADPH2 is a process that takes place in dark reaction. All
other options (A, B, C and E) are processes that take place in light reaction.
Example
Describe an experiment to demonstrate that oxygen is released by green plants during photosynthesis. (1990/1c)
Answer:
Aim: To show that oxygen is released by green plants during photosynthesis.
Apparatus: Two beaker (1 litre), water plant, glowing splint, water, funnels and test tubes.
Method: The water plant is placed in a beaker containing fresh water and it is covered with an inverted funnel
and labeled A. The same thing is done with a control experiment labeled B only that while A is
exposed to sunlight, B is covered with cardboard paper. They are left for some time.
Observation: Bubbles of gas would be noticed in experiment A on passing a glowing splint at the tube and A, it
rekindled. No bubbles were noticed in B and it couldn’t rekindle a glowing splint.
Conclusion: The gas that evolved in A is oxygen since it was able to rekindle a glowing splint. This confirms that
oxygen is released by green plants during photosynthesis.
Example
During which of the following processes is food for animals produced?
A. Photosynthesis B. Respiration C. Nutrition D. Digestion E. Transpiration (1991/27)
Answer: A – Animals feed on plant directed or indirectly. Plant produce food by photosynthesis, hence, animals food
are produced indirectly by photosynthesis.
Example
The following are necessary for photosynthesis to take place except
A. chlorophyll B. water C. carbondioxide D. light E. oxygen (1992/35)
Answer: E – Oxygen is a product of the process of photosynthesis, so it is not needed for it to occur.
All other options (A to D) are essential for photosynthesis to occur.
Example
Use the diagram below to Answer: questions 21

The experimental set-up can be used to demonstrate that

A. photosynthesis occurs in the leaves of plants B. light is necessary for photosynthesis
C. carbon (IV) oxide is necessary for photosynthesis D. oxygen is necessary for photosynthesis (2002/21 JAMB)
Answer: C – Caustic soda solution absorbs carbondioxide. Hence, the above experimental setup is used to
demonstrate the importance of carbondioxide in photosynthesis.
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Example
All animals are dependent on green plants because plants
A. shelter them from excessive heat from the sun B. give them protection from enemies
C. are used for building houses and furniture D. beautify their surroundings
E. manufacture food for animals. (1994/1)
Answer: E – Plants manufacture food for animals through photosynthesis.
Example
The principal organ for the manufacture of food in autotrophy is the
A. root hair B. growing root C. Mature fruit D. green leaf. (2016/10 JAMB)
Answer: D – The green leaf contains chlorophyll hence, it is the principal organ where photosynthesis takes place.
Example
At the end of photosynthesis, the green leaf is tested for starch and not glucose, because
A. the glucose is used up immediately to provide energy for the needs of the leaf
B. the glucose formed is immediately converted to starch C. starch is stored only in leaves
D. there are no chemicals for glucose test in leaves E. it is easy to test for starch (1995/29)
Answer: B – Glucose formed during photosynthesis is converted to starch.
Example
Which of the following equations is not associated with photosynthesis?
A. H2O → H + OH B. C6 H12 O6 → 2C2H2OH + 2CO2 C. CO2 + [4H] → CH2O + H2O
D. 4[OH] → 2H2O + O2 E. 6CO2 + 6H2 → OC6H12O + 6O2 (1995/30)
Answer: B – In photosynthesis, glucose (C6H12O6) is never broken down rather, it is formed.
Example
Which of the following conditions is not necessary for photosynthesis to occur in plants?
A. There must be light B. The must be Xylem tissue used to conduct water
C. There must be chlorophyll to trap radiant energy D. Carbon dioxide must be present
E. Water must be present (1995/32)
Answer: B – Xylem tissue are not necessary for photosynthesis to take place. This is seen in lower plants (e.g.
mosses) which have no xylem tissues and yet carry out the process of photosynthesis.
Example
1(a) (i) Name the two stages involved in photosynthesis
(ii) Write an equation to represent the first stage of photosynthesis (1998/1a)
Answer: Light energy
1a. i. Light reaction stage ii. 4H2O Chlorophyll 4H+ + 4OH-
Dark reaction stage 4(OH-) → 2H2O + O2
Example
During photosynthesis, light energy is always absorbed by the
A. shoot B. water C. chlorophyll D. enzyme (1999/29)
Answer: C – The chlorophyll help to absorb energy during photosynthesis.
Example
Which of the following is an evidence of photosynthesis?
A. Absorption of light B. Formation of starch
C. Availability of carbon dioxide D. Splitting of water molecules (2001/37)
Answer: B – The formation of starch is an evidence of photosynthesis.
Example
Which of the following is considered to be the first product of photosynthesis?
A. Protein B. Energized chlorophyll C. Hydroxyl ions D. Starch (2003/30)
Answer: D – Starch is the storage form of glucose in plant.
Example
Which of the following pairs of organisms are photosynthetic?
A. Amoeba and Paramedium B. Volvox and Rhizopus
C. Chlamydomonas and Euglena D. Nostoc and Plasmodium (2005/10)
Answer: C – Chlamydomonas and Euglena posses chlorophyll, hence they are photosynthetic.
Example
In testing for starch in a leaf, the leaf is boiled in alcohol to
A. kill the cells. B. soften the leaf. C. enable chemicals penetrate the leaf D. decolourise the leaf. (2007/25)
Answer: D – The leaf is boiled in alcohol in order to decolorize it.
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Example
The main raw materials required for photosynthesis are
A. oxygen and water B. oxygen and carbon dioxide
C. oxygen and chlorophyll D. carbon dioxide and water (2012/27)
Answer: D – Carbon dioxide and water

EXERCISE 6.2
1. The first step in the process of photosynthesis is the
A. activation of chlorophyll B. formation of water
C. reduction of carbon dioxide D. formation of sugar. (2020/23 PC1)
2. The source of energy required by plants during food production is
A. photosynthesis B. chlorophyll C. sunlight D. microorganisms. (2018/21)
3. 2(a) Name the gases involved in the photosynthesis of a plant.
(b) State one role each of the gases named in (a). (2018/2a-2b)
4. Which of the following statements about photosynthesis is not true?
A. Plants can photosynthesize without an increase in dry weight
B. Carbon dioxide is absorbed by the leaves in bright light
C. Oxygen produced during photosynthesis is from the breakdown of water
D. Photosynthesis occurs in green plants. (2011/27)
5. The conversion of glucose to starch in the leaf during the day principally
A. enables photosynthesis B. prevent osmotic problems
C. enables the leaf to store the starch D. enables glues to be used up (2011/30)
6. 2(a) What is photosynthesis?
(b) List: (i) four external factors (ii) two internal factors that affect the rate of photosynthesis
(c) (i) List the major products of the light dependent stage of photosynthesis
(ii) State the importance of each of the products listed in 2(c)(i) above (2013/2a - c)
7. 2(a) Explain how the leaf of a flowering plant is adapted for photosynthesis (2015/2a)
8. Which of the following processes are associated with photosynthesis?
I. Energy from sunlight is absorbed II. Carbon dioxide is evolved
III. Oxygen is given off IV. Glucose is synthesized
A. I and II only B. I, III and IV C. I, II, III and IV (2017/24)
9. Outline the procedure used for testing for starch in a leaf (2017/2d)
10. Which of these sentences is not true about the following chemical equation?
Light
2H2O + CO2 (CH2O) + H2O + O2
Chloroplast
A. It represent; the photolysis of water
B. The low molecular weight compounds are used to synthesize a high molecular weight compound
C. The reaction must take place in the presence of sunlight and chlorophyll
D. A gas is given off during the process E. It represents the net reaction of photosynthesis. (1994/32 Nov)
11. In a plant, photosynthesis generally takes place in the
A. leaves only B. stems only C. roots only D. flowers only E. green parts only. (1995/30 Nov)
12. 1(a) Describe an experiment to show that light is necessary for photosynthesis (1996/1a Nov)
13. Which of these statements is not correct about photosynthesis?
A. The first process is photolysis of water B. the dark reaction involves the fixing of carbon
C. it is an exothermic reaction D. it can take place in the stem of certain plants
E. the first soluble product is glucose (1996/31 Nov)
14. The first stage of the process of photosynthesis is the
A. Formation of chlorophyll B. reduction of carbon(IV)oxide
C. splitting of water molecules D. colouration of leaves E. synthesis of enzymes (1996/32 Nov)
15. During photosynthesis energy from the sun is converted to
A. heat energy B. chemical energy C. electrical energy D. so energy E. kinetic energy (1997/31 Nov)
16. The oxygen given off during photosynthesis is produced from
A. H2O B. CH2O C. Na2CO3 D. CO2 E. C2H5OH (1997/32 Nov)

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17. The light energy absorbed by chlorophyll is used in the leaf to
A. split water molecules B. convert water to glucose in the leaf
C. form carbonic acid from carbon dioxide D. release energy from starch stored in leaf
E. increase the rate at which simple sugars are formed (1998/37 Nov)
Light
4H2O 4H+ + 4(OH)–
Chloroplast
18. The above equation represents
A. photosynthesis B. photolysis of water C. dehydration of water D. nutrition in plants (1999/38 Nov)
19. Which of the following statements is not true about photosynthesis?
A. Glucose is a product of photosynthesis B. energy is released during the formation of glucose in plant cells
C. oxygen is a by-product of photosynthesis
D. it purifies the atmosphere by the constant removal of carbon dioxide (2000/30 Nov)
sunlight
20. The equation 6H2O + 6CO2 chlorophyl
C6H12O6+ 6O2 represents
A. reproduction B. nutrition C. respiration D. excretion (2002/28 Nov)
21. (c) (i) Define photosynthesis
(ii) Mention one way by which the process is beneficial to life (2002/3c Nov)
22. The structure of the plant responsible for the trapping of sun energy is
A. chlorophyll B. stomata C. epidermis D. xylem (2006/28 Nov)
23. 3.(a) State four conditions necessary for photosynthesis
(b) Describe what happens in the dark phase of photosynthesis
(c) How are the products of photosynthesis utilized by plants and animals? (2006/3a, 3b, 3c Nov)
A leaf attached to a plant with partly covered with a strip of paper and left outside. After twenty-four(24) hours, it
was tested for starch using iodine. The diagrams below are illustrations of the leaf before and after it was tested for
starch. Use the diagram to answer questions 24 to 26

24. The function of number 5 in the experiment is to eliminate

A. carbon dioxide B. oxygen C. lightrays D. water (2011/25 Nov)
25. Which parts of the leaf tested positive for starch at the end of the experiment?
A. 1, 2, 3 and 4 B. 1, 2, 3 and 6 C. 1, 2, 4 and 5 D. 1, 2, 5 and 6 (2011/26 Nov)
26. The title which could be given to the above experiment is
A. starch is formed after photosynthesis B. water is necessary for photos
C. sunlight is necessary for photosynthesis D. carbon dioxide is necessary for photosynthesis (2011/28 Nov)
27. The raw materials required by green plants for the manufacture of foods are
A. liquid substances B. inorganic substances
C. organic materials D. solid materials (2019/24 PC2)
28. Which of the following factors does not affect the rate of photosynthesis?
A. light intensity B. oxygen concentration
C. temperature D. concentration of carbon dioxide (2020/24 PC 1)
29. Name the TWO stages of photosynthesis (2007/1a ii Neco)
30. 1(a) Give one function each of the following in photosynthesis: i. Sunlight ii. Chlorophyll
(b) Mention four structural adaptations of leaf for photosynthesis (2008/1a & b Neco)
31. Which of the following cell organelles traps sunlight energy in plant?
A. chloroplast B. endoplasmic reticulum C. Mitochondrion
D. Ribosome E. vacuole (2018/4 Neco)
32. The following conditions are necessary for photosynthesis except
A. carbon(iv)oxide B. chlorophyll C. light energy D. oxygen E. water (2018/5 Neco)
33. Explain the importance of photosynthesis as an illustration of interdependence between green plants and
animals. (2001/6c NABTEB)

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34. The process of splitting water into its components during photosynthesis is called
A. auolysis B. chemolysis C. photolysis D. hydrolysis (2017/10 NABTEB)
35. 2ai. List five conditions necessary for photosynthesis.
ii. Describe an experiment to show that light is necessary for photosynthesis. (2017/2a i & ii NABTEB)
36. 2(a) Describe an experiment to show that green plants require sunlight for photosynthesis.
(b) State three other conditions necessary for photosynthesis.
(c) State the site of a dicotyledonous leaf where photosynthesis occurs and give three reasons for this.
(d) Explain the fate of food manufactured by green plants. (2019/2a, b, c, d NABTEB)
37. One major difference between plant and animal nutrition is the ability of plants to synthesize
A. food for plants and animals B. water for plants C. water for animals D. food for plants only. (2018/22)

Micronutrient and Macronutrient

Micronutrient are mineral salts required by living organisms in small quantities, whereas, macronutrient are required in large
quantities. Macronutrient includes the following: nitrogen, phosphorus, sulphur, potassium, magnesium, calcium, iron, carbon,
hydrogen and oxygen.

Carbon enters the plant in combination with oxygen as carbon(IV)oxide (CO2) molecules. It is used for synthesis of
carbohydrates, protein, fat and complexes of these or as respiratory substances for the supply of energy. Hydrogen enters the
plants in combination with oxygen as water molecule (H 2O). H2O is used for oxidation and reduction processes. Hydrogen ion
maintains acid-base balance of cell fluid. Oxygen enters the plant as CO2 or H2O, and as molecular oxygen from the atmosphere.
It is used for aerobic respiration.

Nitrogen is obtained as nitrogenous compound in soil solution. Nitrogen is used for amino acid formation and protein and other
nitrogenous compound. Phosphorus is absorbed from the soil solution in the form of phosphate ion. It serves as buffer in the cell
sap. It is also used in formation of coenzymes and adenine phosphate. Sulphur is absorbed from the soil solution as sulphate ions.
Sulphur is contained in amino acids such as cystine, cysteine and methionine. It may be used in chlorophyll formation.

Potassium is absorbed as potassium (K +) ion. Potassium is important in protein synthesis, chlorophyll formation and in carbon
assimilation.

Magnesium is absorbed as magnesium ion. It is used for chlorophyll formation. It is a catalyst in glycolytic reactions.

Calcium is absorbed as calcium ion Ca2+. It is used for plant cell formation.
Iron is absorbed as iron II or Iron III ions. (Fe 2+ or Fe3+). It is essential part of respiratory enzyme and chlorophyll.

Micronutrient include boron, manganese, zinc, copper, molybdenum, chlorine, vanadium, cobalt and silicon.

Boron is necessary for development of apical meristems, translocation of sugar and uptake of calcium. It is absorbed from the soil
as borate ion (BO2-). Manganese is absorbed as manganese ion (Mn2+). It is present in green plants and associated with the
respiratory enzyme system. Zinc is absorb as Zn2+ and is a constituent of the enzyme carbohydrate.

Copper is absorbed as Cu2+ and is involved in respiratory processes.

Molybdenum is essential for normal growth in some plants when the only form of nitrogen available is nitrate.

Macronutrient Function in plant (i.e. importance) Deficiency

1. Magnesium Formation of chlorophyll Poor growth
Activation of coenzymes and Chlorosis.
Promotion of growth.
2. Calcium Formation of cell wall. Stunted growth.
Activation of some enzymes. Death of terminal bud.
Gives rigidity to plant. Poor root development.
3. Iron Formation of chlorophyll. Poor growth.
Formation of protein. Leaves turn yellow.
4. Nitrogen Proper root development Stunted growth and chlorosis
Protein synthesis. (yellow leaves).
Nucleic acid synthesis. Poor flower and fruit formation.
Component of chlorophyll and enzymes.
5. Phosphorus Formation of ATP, DNA and RNA. Stunted growth, poor root
Stem and root formation. development.
Coenzyme and protein formation.
6. Sulphur Protein synthesis Stunted growth, chlorosis.
7. Potassium Protein synthesis. Leaf margin turns yellow and
Cell membrane formation. brown.
Activate respiration and photosynthesis. Premature death.
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 Micronutrient Function in plant (i.e. importance) Deficiency
1. Manganese Activates enzymes involved in cellular respiration and photosynthesis. Death of shoot.
2. Zinc Necessary for the synthesis of the starting material (tryptophan) of Poor growth.
auxin.
2. Activates some enzymes.
3. Play a role in the synthesis of proteins.
3. Copper 1. Component of respiratory enzymes Poor growth
2. Present in materials which act as electron carrier for chlorophyll.
4. Boron 1. translocation of sugar and calcium 1. Poor growth.
2. Poor growth of pollen tube.
5. Molybdenum 1. Necessary for nitrogen fixation by nitrogen fixing bacteria. Poor growth.
2. Activates the enzymes that reduces nitrate to nitrate.
6. Chlorine Necessary for oxygen release during photosynthesis. May affect growth.
7. Nickel Necessary for nitrogen metabolism. Stunted growth and chlorosis.
8. Silicon For cell wall formation. May affect growth.

Example
Which of these elements is required by plants in small quantities only?
A. Boron B. Nitrogen C. Phosphorus D. Magnesium E. Potassium (1978/33 JAMB)
Answer: A – Boron is a micronutrient. Micronutrients are those elements that plants require in small quantities for
their normal growth and functioning. Other examples include: manganese, zinc, copper, molybdenum etc.

Example
Which of the following elements are necessary for the formation of chlorophyll in a plant?
A. magnesium and iron B. Calcium and potassium
D. potassium and Sulphur E. phosphorus and potassium (1983/10 JAMB)
Answer: A – Magnesium and iron are necessary for the formation of chlorophyll.

Example
Which of these is a trace element?
A. Iron B. Copper C. Calcium D. Sulphur (1986/15 JAMB)
Answer: B – Trace element are also known as micronutrient. Copper is a micro element.

Example
In demonstrating the importance of mineral elements in plants, the culture bottle must be darkened to
A. prevent algal growth in culture solution B. allow root growth
C. prevent breakdown of mineral elements D. prevent photosynthesis in the root (1987/17 JAMB)
Answer: A – The culturing bottle must be darkened in order to prevent the growth of algal in the culturing solution.

Example
Interveinal chlorsis is normally associated with the deficiency of
A. magnesium B. potassium C. amino acid D. starch (1993/14 JAMB)
Answer: A – Magnesium is a macronutrient; and it deficiency leads to chlorosis of the leaves.

Example
In a water culture experiment, a plant showed poor growth and yellowing of the leaves. These may be due to
deficiency of
A. copper B. iron C. magnesium D. calcium (1998/13 JAMB)
Answer: C – Yellowing of leaves is a result of deficiency of magnesium. This condition is also known as chlorosis.

Example
Which of the following is not regarded as a micro-nutrient or trace element for plant growth?
A. Phosphorus B. Zinc C. Boron D. Silicon E. Molybdenum (1988/28)
Answer: A – Phosphorus is a macronutrient.

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Example
In a water culture experiment a plant showed poor growth and yellowing of the leaves. These symptoms were
probably due to the absence of
A. calcium B. phosphorus C. iron D. zinc E. copper (1988/29)
Answer: C – Iron is importance in the formation of chlorophyll, it deficiency will lead to yellowing of leaf.
Example
In a water culture experiment, the culture solution in a transparent beaker turned green. What precaution should have
been taken to prevent the culture solution from turning green?
A. Changing the culture solution regularly B. Increasing the number of times the culture is aerated
C. Covering the transparent beaker with black cloth D. Adding warm alcohol to bleach the green color
E. Sterilizing the beaker in a hot oven before use (1996/27)
Answer: C – The culturing bottle must be darkened in order to prevent the growth of algal in the culturing solution
Example
Which of the following groups consists of only micro-nutrients?
A. Molybdonum, Sulphur and Copper B. Boron, Zinc and Calcium
C. Manganese, Molybdenum and Zinc D. Magnesium, Phosphorus and Manganese. (2000/31)
Answer: C – Manganese, molybdenum and zinc are all microelement.
Example
The deficiency of manganese in plants results in
A. death of shoot B. leaves turning yellow C. stunted growth D. poor root development. (2004/27)
Answer: A – The deficiency of manganese in plants leads to death of shoot.
Example
Macronutrients essential for the synthesis of chlorophyll include:
A. iron and potassium. B. iron and magnesium C. magnesium and calcium. D. magnesium and potassium. (2007/27)
Answer: A – Magnesium and iron are necessary for the formation of chlorophyll.
Example
Which of the following elements is not a macro-nutrient required by plants?
A. Potassium B. iron C. Magnesium D. Manganese E. Phosphorus (1992/34 Nov)
Answer: D – Manganese is a microelement required by plant. It is not a macro element.

EXERCISE 6.3
1. Which of the following is not a macro-nutrient for plant growth?
A. Nitrogen B. molybdenum C. calcium D. magnesium (2000/31 Nov)
2. Which of the following plant nutrients is a micro element?
A. copper B. nitrogen C. magnesium D. phosphorus (2006/29 Nov)
3. Which element is a microelement?
A. iron B. magnesium C. manganese D. phosphorus E. potassium (2001/23 Neco)
4. All these are trace elements EXCEPT
A. boron B. copper C. manganese D. magnesium E. cobalt (2005/22 Neco Nov)
5. Which of the following is not a micronutrient?
A. boron B. molybdenum C. phosphorus D. silicon E. zinc (2014/22 Neco)
6. A micro nutrient is a nutrient needed by
A. plants in large quantity B. both plants and animals
C. animals only D. plants in small quantity (2001/14 NABTEB)
7. b. State four micro and macro nutrients necessary for plant growth (2017/2b NABTEB)
8. Which of the following groups contains only macro-nutrients?
A. phosphorus, nitrogen and molybdenum B. manganese, copper and zinc
C. Boron, Sulphur and iron D. calcium, magnesium and potassium (2018/18 NABTEB)
9. A solution which contains all the required elements in their correct proportions is known as a
A. culture medium B. growth medium
C. complete culture solution D. nutrient solution (2018/19 NABTEB)
10. Which of the following is not true about a potted plant left in the laboratory for one week without watering?
A. the cells of the plant will be turgid B. There will be wilting of the plant
C. the leaves are likely to turn yellow D. The plant will not take in enough nutrients. (2018/20 NABTEB)
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Nutrition in mammals
Food Substances
Food is any substance which serves as source of energy or is used to build up the body cells for growth, or to repair
the body tissues.

Food materials are used to make new protoplasm, new body materials, new cells and hence bring about growth. Food
is broken down during respiration to produce energy for various vital activities. Food substances are used to synthesis
materials for the repair of damaged parts and for repair of wear and tear. Feeding consists of ingestion, digestion,
absorption and Digestion

Classes of Food Substances

i. Carbohydrates
ii. Proteins
iii. Vitamins
iv. Lipids (fats and oils)
v. Mineral salts
vi. Water
vii. Roughages and dietary fibre

Carbohydrates
Carbohydrates are substances composed of carbon, hydrogen and oxygen, with the number of hydrogen atoms twice
the number of oxygen atoms in each molecule, the ratio of hydrogen to oxygen is 2:1
The main sources of carbohydrates include yam, rice, maize, millet, guinea corn, potatoes, bread, garri e.t.c

Types of Carbohydrates
1. Monosaccharides (Simple Sugars): Monosaccharide (simple sugar): They have a general formula of CnH2nOn.
Examples are glucose (C6H12O6), fructose (C6H12O6), galactose (C6H12O6). Ribose (C5H10O5) and deoxyribose are
pentose (five carbon) sugar used in the formation of nucleic acids. They are called reducing sugars.

2. Dissaccharides
These contain two units of simple sugar and are represented by the formula C12H22O11. Examples are sucrose,
maltose and lactose (they may also be referred to as non – reducing sugar).
 H 2O
Glucose + glucose   Maltose
 H 2O
Glucose + galactose  Lactose
 H 2O
Glucose + fructose   Sucrose
Sucrose occurs in sugar cane stem, in ripe sweet fruits and in storage roots like sugar beets and carrots. Lactose is
found in milk of mammals. Maltose is found in malted cereals and sprouting grains

3. Polysaccharides (complex sugar): These consist of more than two simple sugar or several simple sugars joined
together. They are represented by the general formula (C6H10O5) n, where n represents a large number. Examples
are starch, cellulose, glycogen and chitin. Excess carbohydrates are stored in the muscles and liver and it can be
reconverted to glucose during starvation.

Importance of Carbohydrates
1. Carbohydrates provide energy required by animals for their daily activities.
2. It provides heat, during its oxidation, used in maintaining the body temperature.
3. Carbohydrates are also used to build certain body parts e.g. exoskeleton of arthropods.
4. Mucus, an important lubricant in the body is composed of carbohydrates.

Lipids (Fats and Oils)

Fats and oils consists of carbon, hydrogen and oxygen only, but the proportion of oxygen to hydrogen atoms in a
molecule of fat and oil is less than that in a carbohydrate molecule. Lipids require more oxygen and yield more energy
than carbohydrates per unit mass oxidized. Fats and oils are similar in chemical composition, being esters formed from
fatty acids and glycerol. Fat are solid at room temperature while oils are liquid. Sources of fats and oils are butter,
margarine, animal fat, cocoa butter, milk, egg yolk, groundnut, palm, corn, cod liver, olive oils.

Uses of Lipids in Animal’s Body

1. Lipids are oxidized during respiration to provide energy and heat when there is acute shortage of carbohydrates
into the body as a food store.
2. Fat is stored under the skin and around organs such as the kidneys to insulate and reduce heat loss from the body.

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Protein
Proteins are complex molecules and are made up of smaller units called amino acids. Proteins have to be digested to
amino acids before they are absorbed in the bodies of animals. The breakdown of proteins during digestion takes place
in the following stages
Protein → peptone → polypeptides →amino acids.

Protein is composed of carbon, hydrogen, oxygen, and nitrogen and sometimes phosphorous and sulphur.
Animal sources of proteins are milk egg, fish, cheese, meat and chicken while plant sources are beans (cowpea),
groundnut, soya bean e.t.c.

Importance of Protein
1. Proteins are used for the growth of young ones.
2. It is used for the repair of worn out tissues or cells.
3. It aids reproduction.
4. It is used for the production of hormones.
5. It is used for the production of enzymes.
6. It is used for tissue and cell formation (body building).

Consequences of protein deficiency

The consequence of protein deficiency in an adult is normally illness but in children, it affects their general
appearance. The child will have retarded or stunted growth, loss of weight, swollen legs, distended or swollen stomach
or kwashiorkor, ruptured or cracked/split skin, pale body or skin colour, hair becomes reddish brown and legs appear
thin.

Mineral Salts
Mineral salts are normally present in food. They enter food substances through the mineral salts absorbed by plants.
Also mineral salts enter the body through drinking water and in other ways, such as addition of salts to processed
foods. Only sodium chloride is deliberately added to the food because it is required by the body in large quantities. A
lack of the necessary mineral salts leads to ill health and in certain cases, deficiency diseases.

Minerals required by humans:

Mineral Sources/daily need Functions Deficiency symptoms
1. Calcium Milk, cheese, egg, fish, fruit, 1. Bone and teeth formation and 1. Rickets in
green vegetables, almonds (1g) development children
2. For blood clotting 2. Osteomalacia or
3. Normal functioning of heart and softening of
nervous system and normal bone
contraction of muscles 3. Tooth decay
2. Phosphorous Fish, egg, milk, cheese, shellfish, 1. For strong development of teeth 1. Rickets
and wheat (1.5g) and bone 2. Osteomalacia
2. Forms part of DNA and RNA 3. Tooth decay
3. For respiration
3. Magnesium Leafy vegetables, nuts, seafoods, 1. A major component of bones Weakness, depression
milk, meat (350mg) 2. Activate glycolytic enzymes in and disturbance in
muscles muscles contraction
3. Needed for utilization of iron
4. Potassium All natural food and fruits (2mg) 1. Functioning of the muscles Leads to muscle
2. Transmission of impulses in nerves paralysis
5. Sodium Added to food as sodium chloride, 1. Maintain the correct osmotic Dehydration, muscles
milk, natural foods such as egg pressure of the body fluid cramps, kidney failure.
meat (5 – 8g) 2. Component of blood plasma
Note : Excess causes
3. Needed in the transmission of oedema and
impulses in nerves, sensory cells
hypertension
and muscles and for normal cell
membrane permeability
6. Chlorine Salt, natural food (3g) 1. Maintain correct osmotic pressure of Muscles cramp
body fluid (excess causes
oedema)

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 Mineral Sources/daily need Functions Deficiency symptoms
7. Iron Unripe plantain, liver, eggs, green Formation of Structural and functional Anaemia
vegetable, kidney, beans, meat component of haemoglobin in red blood
(10mg) cells, myoglobin in muscles cells and
enzyme (cytochromes) involved in cell
respiration
8. Sulphur Bean, fish, meat, egg Necessary for formation of hair, nail and Poor growth
some proteins
9. Iodine Sea food (0.1mg) Needed for the synthesis of the thyroid Goiter, poor growth
hormone
For normal reproduction in mammals
10. Nitrogen Protein Necessary for formation of protoplasm Poor growth
Repair of cells and tissues
11. Copper Meat, liver, egg, milk, vegetable For formation of haemoglobin Anemia
(1mg)
12. Manganese Meat, liver, egg, milk, vegetable For formation of haemoglobin and Anemia
(3mg) enzyme action
13. Fluorine Milk, water and food substances Hardens bone and teeth Decaying of teeth
(trace)
14. Cobalt Meats For haemoglobin formation Pernicious Anemia

Vitamins
Vitamins are food substances required by the body in some amounts. They are not energy producing food. They are
biocatalyst (i.e. they promote chemical reactions in the body). They protect the body from diseases, hence in their
absence, the body suffers from deficiency diseases. Some vitamins form part of compounds called coenzymes, which
help enzymes to act. Vitamins are grouped into two main classes.
1. Fat Soluble Vitamins: These are vitamins that are soluble only in fats. E.g. vitamins A, D, E and K.
2. Water Soluble Vitamins: These are soluble in water e.g. vitamin B complex and vitamin C. some members
of vitamin B-complex are vitamin B1, B2, B3 B5 B6, B12, Folic acid e.t.c

Vitamins Required by Human

S/N Vitamins Function Deficiency Sources/Daily Needs
FAT SOLUBULE VITAMINS
1. A (retinol) Needed for proper functioning of Skin becomes flaky (horny fish liver oil, milk, egg yolk,
epithelial tissues such as skin, and dry), night blindness and green and yellow vegetables,
mucous membrane, needed for xerophthalmia (can lead to fruits (1.5mg)
vision in dim light, essential for permanent blindness)
normal growth and it is a
component of visual pigments
2. D (calciferol) Increases absorption of calcium Rickets in children (poor bone Fish – liver oil, egg yolk, butter
and phosphorous in the intestine, and teeth formation), softening (synthesized in skin when
calcification and hardening of of bones in adults exposed to sun’s ultraviolet
bones rays (0.01mg)

3. E (tocopherol) Protects fatty acids and cell Sterility in some animals and Leafy vegetables, seeds, eggs,
membranes from oxidation death of embryo milk, magarine (15mg)
For normal functioning of the Weak muscle and destruction
reproductive organs of liver cells

4. K (phylloquinone) Assist blood clotting (i.e. Slow clotting of blood leading Liver, vegetables (made by
synthesis of blood clotting to severe bleeding from cuts intestinal bacteria (0.03mg)
factor)

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 WATER SOLUBLE VITAMINS
5. Vitamin B1 (thiamine) Needed for synthesis of Beri–beri, Muscle becomes Whole grains, legumes, yeast,
coenzymes involved in weak, Paralysis, stunted beans, liver, rice bran (1.0mg)
cellular respiration growth.
6. Vitamin B2 Helps in the formation of Sore-mouth, soreness of Milk, yeast, egg, liver, kidney,
(Riboflavin) coenzymes involved in throat, skin cracking, anemia, leafy vegetables, meat,
respiration dermatitis, weakness or mushrooms, almond (1.1 –
fatigue. 1.6mg)

7. Vitamin B3 (Niacin, Formation of coenzymes Pellagra (scaly pigmented Yeast, liver, milk, egg, whole
Nicotinic Acid) involved in cellular skin, sore mouth and tongue, grain, fish, green vegetable,
C6H5NO2 respiration. It helps the body nervous disorders) cereal grains (niacin is also
to use protein and fats and it produced in the body from
keeps the skin, hair and tryptophan, which is found in
nervous system healthy protein containing food)
Men: 16mg
Women: 14mg
Pregnant women: 18mg
Breast feeding women: 17mg
8. Vitamin B5 Formation of coenzymes Disorder of nervous system Yeast, egg, rice bran, liver,
(pantothenic acid) involved in cellular and gut, burning feet, kidney broccoli, peanuts, fish,
C9H17NO5 respiration required to insommia, fatigue, depression chicken, milk, yogurt, sweet
synthesize and metabolize potatoes, avocado, legume,
proteins, carbohydrates, fats mushroom, shell fish, whole
e.t.c. grains (10mg)

9. Vitamin B6 Formation of enzymes Anemia, diarrhea, skin rashes, Yeast, egg, cereals, pork,
(pyridoxine) involved in synthesis of crack and sore lips, glossy poultry such as chicken or
amino acid tongue, weakened immune turkey, fish, bread, whole
function, Tingling an pain in grains, cereals such as oatmeal
hands and feet e.t.c and brown rice – vegetables,
soya – beans (2mg)

10. Vitamin B12 Formation of red bloods cells Pernicious anemia Kidney, liver, fish, milk (3mg)
(cyano-cobalamin)
11. Folic acid Formation of red blood cells Anaemeia Leafy vegetables, liver (0.5mg)

12. Vitamin C Required for healthy Scurvy (swelling of joints and Fresh citrus fruits, pawpaw,
(Ascorbic acid) connective tissues, bones and gums), loosening of teeth, guava, fresh leafy green
dentine, may help to resist haemorrhages of the skin and vegetables.
infection membranes

Water
Water is regarded as a food substance. Although it does not by itself provides energy, it is used for body building and
it is so important that an animal may die sooner without water than without energy giving food. Water is made of two
elements, hydrogen and oxygen.

Importance of Water
1. Water is required for metabolic activities in the body.
2. It is necessary for the digestion of food.
3. It can be used for the maintenance of body temperature.
4. Water is the component of plant and animals (e.g. water forms about 75% of man’s body).
5. It acts as a solvent for soluble food substances in digestion.
6. It acts as a medium of transportation of nutrients.
7. It constitutes a greater part of the blood.
8. It aids the excretion of metabolic waste products from the body e.g. urine.
9. It helps to maintain the osmotic content of the body tissues.
10. It is the basis of body secretion from endocrine glands.

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Roughages
Roughages consist of indigestible fibre materials derived from vegetables, fruits, carbohydrates and proteins.
Roughages provide bulk of the intestinal content there by stimulating the movement of bowels. Lack of roughages can
cause constipation.

Diet
Diet is a collective name for all the food that a person normally eats. Diet varies from one geographical area to another
(because food items are localized), from one family to another (because of economic status) and from one individual
to another (because of food preferences).

Balanced Diet
A balanced diet is one that contain adequate amount of all the classes of food namely carbohydrates, lipids, protein,
mineral salts, vitamins and water in the right proportion to meet the body’s requirement for growth, repair and
maintenance.
The amount of these classes of food substances varies according to age, mass, sex, activity or type of work engaged in
and climate.
Balance diet is important to the body in the following ways
1. It makes us healthy and by so doing makes us to be resistant to diseases
2. It encourages growth and normal development of the body
3. It also provides energy needed for normal activities
4. Balance diet prevents malnutrition or deficiency diseases. Lack of some food substances e.g. protein in diet
can cause a nutritional disease called kwashiorkor in children which is characterized by a very big head,
narrow neck, big, swollen and shiny stomach, flat buttocks and very slender and narrow legs

Food Test
Tests for carbohydrates
i. To test for simple reducing sugar (e.g glucose and fructose): Mix equal amount of glucose and fehling’s
(or benedicts|) solutions in a test tube and place the test tube in a boiling water bath. After some time an
orange red precipitate is formed. This confirms the presence of a reducing sugar.
ii. To test for complex sugar or non reducing sugar (e.g sucrose, maltose or lactose): Add dilute
hydrochloric acid to a solution of a complex sugar in a test tube. Place the test tube in a boiling water bath.
The acid hydrolyses the complex sugar to simple sugars. The fehling’s test is then carried out on the simple
sugars that are formed. To do this, add a few drops of dilute caustic soda first to neutralize the excess acid.
Then, add an equal amount of fehling’s solution and place the test tube in a boiling water bath. An orange –
red precipitate is obtained.
iii. To test for starch: A boiled starch solution turns blue – black when a few drops of iodine solutions are added
to it.

To Test for Proteins

i. Biuret Test: To a small amount of albumen or meat extract in a test tube, add a few drops of water and 1cm 3
of dilute solution hydroxide. Then carefully add 1% copper II sulphate solution, drop by drop, shaking the
solution thoroughly after each drop. A violet colour is produced by a protein solution and a pink colour by a
peptone solution.
ii. Millon’s test: Add million’s reagent to a colloidal solution of a protein in a test tube and heat it. A deep red
colour or precipitate appears. This shows presence of protein.
Note: Millon’s reagent is made by resolving metallic mecury (Hg) in nitrous acid (HNO 2) and dissolving in
water.
iii. Xanthoproteic reaction: To a protein solution, carefully add a few drops of concentrated nitric acid. A white
precipitate forms, which turns yellow on heating. Cool the contents and add a few drops of ammonia solution.
The colour of the precipitate deepens to orange.

To Test for Fat

i. Sudan III test: Add a few drops of Sudan III solution to some oil or mashed food containing fats and oil.
A red coloration is obtained. On boiling this, a black precipitate is formed.
ii. Translucent white paper mark: The presence of a translucent spot when a drop of oil is placed on a white
paper or a food substance is rubbed against a white paper and the paper held against any source of light is a
positive test for the presence of fat.
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Example
Which of the following helps in maintain the proper function of the eye?
A. Iodine B. Vitamin D C. Calcium D. Amino acids E. Vitamin A (1998/23 Health Sci Nov)
Answer: E – Vitamin “A” helps in maintaining proper functioning of the eye.
Example
When fat is stained with Sudan III it gives a
A. white colour B. green colour C. blue colour D. red colour E. brown colour (1998/27 Health Sci Nov)
Answer: D – When fat is stained with sudden II, it gives a red coloration.
Example
Vitamin B1 helps to
A. prevent night blindness B. prevent scurvy C. control the oxidation of glucose in the cells
D. develop strong teeth and bones E. build prothrombin for clotting of blood (1998/28 Health Sci Nov)
Answer: C – Vitamin B1 helps in the synthesis of coenzymes involved in cellular respiration i.e. the oxidation of
glucose in the cells.
Example
Rickets is caused by lack of vitamin
A. K B. E C. D D. B (2003/14 Health Sci Nov) Answer: C – Lack of vitamin D causes rickets
Example
Which of the following is the richest source of Vitamin C?
A. Palm oil B. Liver C. Egg D. Citrus fruits (2003/26 Health Sci Nov)
Answer: D – Citrus fruits e.g orange, are rich in vitamin C
Example
Who amongst the following scientist discovered vitamins?
A. Frederick Hopkins B. Adeniji-Jones C. Ronald Ross D. Adewale Omololu (2003/36 Health Sci Nov)
Answer: A – Frederick Hopkins was an English scientist who was awarded the noble prize for the discovery of vitamins.
Example
Scurvy results from a deficiency of
A. Vitamin A B. Vitamin C C. Vitamin D D. Vitamin E E. Vitamin K (1996/26 Health Sci)
Answer: B – Deficiency in vitamin C causes scurvy.
Example
Which of the following is mostly required by a pregnant woman?
A. Starch B. Water C. Proteins D. Minerals E. Vitamins (1996/27 Health Sci)
Answer: E – Vitamins are important for the development of foetus in pregnant women. They help also to prevent
some birth defects.
Example
Fats and oils are utilized by the body of mammals for the
A. production of sweat B. manufacture of vitamins C. formation of protoplasm
D. clotting of blood E. provision of energy (1990/19 Health Sci)
Answer: E – Fat and oil (lipids) are the main sources of energy in the body.
Example
Lack of iodine in the body may cause
A. beriberi B. muscle cramps C. rashes D. goiter E. anemia (1990/49 Health Sci.)
Answer: D – Lack of iodine in the body lend to the formation of goiter.
Example
Lack of niacin causes
A. beri-beri B. scurvy C. pellagra D. anaemia (2000/6 Health Sci Nov)
Answer: C – Niacin is also known as Vitamin B3. Lack of it causes pellagra (scaly pigmented skin)
Example
It is important to include iron in the diet because it is essential for the production of
A. hormone B. haemoglobin C. enzyme D. antibody (2000/7 Health Sci Nov)
Answer: B – Iron is very important for the formation of haemoglobin of red blood cells.
Example
An individual who takes a lot of palm oil is not likely to suffer from
A. kwashiorkor B. night blindness C. scurvy D. pellagra (2000/26Health Sci Nov)
Answer: B – Palm oil is a good source of Vitamin A. Night blindness result from the deficiency for Vitamin A.

97
Example
Human beings require vitamins in their diet because vitamins
A. contain carbohydrates and fats B. prevent kwashiorkor C. digest proteins in the body
D. digest proteins in the body E. influence many important chemical processes in the body. (1980/8 JAMB)
Answer: E – Vitamins influence many important chemical processes in the body.
Example
In testing for glucose the necessary reagent and the condition under which the reagent reacts best are
A. Fehling’s reagent, in the cold B. Million’s reagent, boiled
C. Fehling’s reagent in acid medium, heated D. Iodine solution, boiled
E. Fehling’s reagent in neutral or alkaline medium, boiled (1980/18 JAMB)
Answer: E – The reagent will react best when Fehlings reagent is in neutral or alkaline medium and boiled.
Example
If Benedict’s solution gives a positive result in a food test, the food contains
A. sugar B. Protein C. oil D. fat E. cellulose (1981/30 JAMB)
Answer: A – Benedict’s solution give a positive result in a food that contains reducing sugars.
Example
The deficiency of Vitamin D leads to
A. scurvy B. pellagra C. rickets D. beriberi E. polio (1981/40 JAMB)
Answer: C – Rickets results from the deficiency of Vitamin D.
NB: Scurvy results from the deficiency of Vitamin C.
Pellagra results from the deficiency of Vitamin B3 (Niacin).
Beri-beri results from the deficiency of Vitamin B1 (Thiamine).
Polio is caused by a virus called poliovirus.
Example
Which of these substances is likely to be deficient in the diet of a person having goiter?
A. Potassium B. Calcium C. Iodine D. Sodium E. Phosphorus (1981/41 JAMB)
Answer: C – Deficiency in iodine causes goiter.
Example
Kwashiorkor is caused by severe deficiency of
A. water B. oil C. drugs D. proteins (1982/6 JAMB) Answer: D – Deficiency in protein causes kwashiorkor.
Example
Fehling’s solution will readily change colour from blue to reddish colour when it is
A. mixed with sugar solution in the cold B. warmed or heated by itself
C. mixed with reducing sugar in the cold D. warmed or heated with a complex solution
E. warmed with a solution of reducing sugars (1984/35 JAMB)
Answer: E – Fehling’s solution will change from blue to reddish colour when it is warmed with a solution of reducing sugars.
Example
In addition to the high calories derived from fats and oils, they are
A. used in producing new cells B. necessary for enzyme formation
C. used as insulators from cold D. required for growth (1986/19 JAMB)
Answer: C – Fats and oil also serves as insulators from cold.
Example
The extract from a food substance reacting with sodium hydroxide and copper sulphate solutions will produce violet to
purple coloration if
A. fats are present B. carbohydrates is present C. protein is present D. reducing sugar is present (1986/20 JAMB)
Answer: C – Sodium hydroxide and copper sulphate solution is also known as biuret reagent. This is used to test for
the presence of protein. It turns violet to purple when the test is positive
Example
The vitamin which is important in the formation of the retina pigment is
A. vitamin A B. vitamin B C. vitamin C D. vitamin D (1987/18 JAMB)
Answer: A – Vitamin A is import for the formation of the retina pigment of the eye. Also Vitamin “A” helps in
maintaining proper functioning of the eye.
Example
Which of the following food substances will produce a brick-red colour when warmed with Benedict’s solution
A. Glucose B. Starch C. Egg white D. Maltose (1990/19 JAMB)
Answer: A – Glucose is a reducing sugar. It turns brick-red, when warmed with Benedict’s solution.

98
Example
The element common to protein, carbohydrate and lipid is
A. hydrogen B. sulphur C. nitrogen D. phosphorus (1991/21 JAMB)
Answer: A – Hydrogen, carbon and oxygen are common elements to protein, carbohydrate and lipids.
Example
Which vitamin plays and important role in blood clotting?
A. Vitamin A B. Vitamin K C. Vitamin B12 D. Vitamin C (1995/13 JAMB)
Answer: B – Vitamin K plays an important role in the blood clothing process.
Example
The richest sources of vitamin A are
A. palm oil and groundnut oil B. palm oil and carrots C. rice and groundnut oil D. oranges and carrot (1999/19 JAMB)
Answer: A – Palm oil and groundnut oil are rich sources of Vitamin A.
Example
Which of the following contains a reducing sugar?
A. milk B. cassava C. grape fruit D. bean E. plantain (1998/41)
Answer: B – Cassava contains starch which is made up of many units of glucose (a reducing sugar).
Example
The complex energy-rich organic matter which living organisms need for life is
A. water B. air C. food D. Mineral salt (2017/23)
Answer: C – Food is the energy-rich organic matter which living organism need for life.
Example
The greatest amount of energy will be obtained by the oxidation of 100kg of
A. meat B. biscuits C. sugar D. butter (2000/12 JAMB)
Answer: D – Butter is a fat; fats provide more energy than carbohydrates; carbohydrate provides more energy then protein.
Example
A disease that results from lack of iodine diet of human is
A. beri beri B. scurvy C. rickets D. goiter (2016/11 JAMB)
Answer: D – Deficiency in iodine causes goiter. Lack of iodine in the body leads to the formation of goiter.
Example
Mammals requires roughage in their food to
A. provide energy B. slow down aging C. Ease digestion D. prevent disease. (2016/26 JAMB)
Answer: C – Roughages provide bulk of the intestinal content and there by stimulate the movement of the bowels. In
other words, they help to ease digestion.
Example
The importance of a balanced diet is to
A. maintain constant size of an animal B. provide good taste in the food
C. increase the effectiveness of digestion D. provide good health for an individual. (1999/33)
Answer: D – Balance diet provides good health for an individual.
Example
Vitamin C which is water soluble is
A. cabalamine B. pyridoxine C. ascorbic acid D. riboflavin. (2000/35) Ans: C – Vitamin C is also known as ascorbic acid.
Example
Vitamin E is concerned with
A. bone formation B. reproduction C. normal growth D. formation of red blood cells (2000/39)
Answer: B – Vitamin E is concerned with reproduction.
Example
Members of the vitamin B complex are
A. water – soluble B. fat-soluble C. water insoluble D. generally insoluble (2000/37)
Answer: A – Vitamin B complex are water soluble vitamins.
NB: Vitamin C is also a water soluble vitamin. Vitamin A, D, E and K are fat soluble.
Example
A balanced meal for an adult person may consists of
A. two pieces of chicken, four balls of bean cake, two eggs and two cups of tea with milk
B. four slices of bread, one bowl of pap, two oranges and two bananas
C. four slices of yam and stew, two pieces of beef, one cup of tea with milk and two oranges
D. a plate of beans, two pieces of meat, two eggs, one cup of tea with milk and two organs. (2000/40)
Answer: C – This is because only option c contains literally all the food classes.
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Example
Mammals require a relatively high amount of carbohydrates because
A. they maintain the weight of the body B. they are required for growth
C. they initiate enzyme production D. they yield energy for activities (2000/42)
Answer: D – Carbohydrate yield energy for activities.
Example
Which of the following statements about water in human is not correct? It
A. plays an important role in temperature regulation B. acts as solvent for substances conveyed around the body
C. plays a role in the formation of vitamin D D. is needed for many life processes. (2003/29)
Answer: C – Water does not play any role in the formation of vitamin D.
Example
When a food substance gives a purple colour on the addition of sodium hydroxide and a drop of copper sulphate, then
the food substance is likely to contain
A. carbohydrates B. fat C. protein D. sugar (2002/31)
Answer: C – Sodium hydroxide and copper sulphate solution is also known as biuret reagent. This is used to test for
the presence of protein. It turns violet to purple when the test is positive.
Example
Which of the following essential substances is contained in vegetables?
A. Chlorophyll B. Glucose C. Mineral salts D. Carbon dioxide (2003/32)
Answer: C – Mineral salts are obtained from vegetable.
Example
A solution which contains all the required elements in their correct proportions is known as a
A. culture nutrient B. grown medium C. complete culture solution D. nutrient solution (2004/26)
Answer: C – Complete culture solution contains cell required elements in the correct proportions.
Example
The deficiency of vitamin D and calcium ions in the diet of a human causes
A. anaemia B. night—blindness C. Kwashiokor D. rickets (2004/29)
Answer: D – The deficiency of Vitamin D and calcium ions result in rickets.
Example
In a test for non-reducing sugars like sucrose, what is the significance of adding dilute hydrochloric acid to the
original sugar solution? To
A. hydrolyse the non-reducing sugar B. accelerate the rate of the reaction
C. stabilize the medium. D. sterilize the solution (2007/29)
Answer: A – Dilute hydrochloric acid helps to hydrolyze the non-reducing sugar.
Example
The colour that is associated with a positive iodine test is
A. brown B. red C. blue-black D. yellow (2007/30)
Answer: C – Iodine is used to test for the presence of starch. When this test is positive, a blue-black colouration appears.
Example
Which of the following food substances gives the least amount of calories?
A. Rice B. Groundnuts C. Cabbage D. Egg yolk (2008/25)
Answer: C – Cabbage is a vegetable that provides the body with mineral salts, vitamin and roughages only; Hence, it
gives the least amount of energy.
Example
In a Biuret test, some proteins was mixed with sodium hydroxide solution. Which of the following chemicals should
be added to the mixture for a positive result?
A. Mercurous nitrate B. Copper sulphate C. Sodium carbonate D. Silver nitrate (2014/24)
Answer: B – Copper sulphate and Sodium hydroxide solution is also known as biuret reagent. This is used to test for
the presence of protein.
Example
By what process is starch converted into maltose?
A. Hydrolysis B. Condensation C. Translocation D. Photosynthesis (2018/23)
Answer: A – Hydrolysis is the splitting of large molecules into smaller ones by the aids of water. The hydrolysis of
starch by the enzyme diastase (amylase) gives maltose

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EXERCISE 6.4
1. Pepsin is secreted as an inactive precursor called pepsinogen because
A. pepsin as an enzyme is quickly destroyed by the alkaline food from the mouth.
B. all digestive enzymes pass through a precursor stage.
C. pepsin is a proteolytic enzyme and might attack the stomach tissues.
D. pepsin is not required in large quantities. (2009/29)
2. Which of the following substances is not complex carbohydrate?
A. Glycogen B. Cellulose C. Starch D. Glucose (2013/31)
3. A meal consisting of yam and a lot vegetables is not balanced because it does not contain
A. carbohydrates B. proteins C. vitamins D. minerals (2014/23)
4. A man suffering from obesity must avoid meals containing
A. margarine and butter B. rice and bear C. carrots and oranges D. beef and fish (2010/26) `

The table below shows the percentage composition of fat and protein in six different meat types. Study it and
Answer: questions 2(a) to 2(d).
Meat type Fat (%) Protein (%)
A 07.2 21.3
B 25.3 10.6
C 20.0 22.5
D 03.1 28.2
E 12.6 17.3
F 13.2 14.3
5. 2a. (i) Which two of the meat types may be recommended for an obese patient?
(ii) State one reason for the Answer: in 2(a)(i)
b. (i) Which two of the meat types would provide the most energy?
(ii) State two reasons for the Answer: in 2(b)(i).
c. (i) Which three of the meat types could be recommended for a child suffering from kwashiorkor?
(ii) State one reason for the Answer: in 2(c)(i).
d. Which of the meat types would most likely be suitable for:
(i) an active teenager; (ii) a 70 -year old human?

e. Which other class of food provides energy?

f. State three uses of fat in the human body.
g. Describe briefly the procedure for testing for fat in a meat sample using a piece of white paper.
(2019/2)
6. In which of the following organic compound is the hydrogen-oxygen ratio equal to 2:1?
A. Proteins B. Carbohydrates C. Lipids D. Vitamins (2010/25)

7. Equal volumes of Fehling’s solution A and B were added to a food substance and on heating, a brick-red
precipitate was formed. This indicated that the food substance contained
A. proteins B. reducing sugar C. starch D. fattyacid E. amino acid (1992/32 Nov)
8. Pellagra can be prevented by taking food rich in
A. vitamin A B. vitamin B C. vitamin D D. calcium E. iodine (1991/31 Nov)
9. In testing for a reducing sugar, the food substance is usually warmed with
A. sulphuric acid B. Millon’s reagent
C. Sudan III D. Benedict’s solution E. Sodium hydroxide (1991/32 Nov)
10. (b) (i) What is a balanced diet?
(ii) State two importance of a balanced diet (1996/1b i, ii Nov)
11. The deficiency disease known as beri-beri can result from lack of vitamin
A. B12 B. K C. B6 D. A E. B1 (1996/33 Nov)
12. When cobalt chloride paper is used to test for the presence of water the colour change is usually from
A. pink to blue B. blue to pink C. blue to white D. white to blue E. pink to white (1997/33 Nov)
13. The food substance containing the elements hydrogen and oxygen only is
A. vitamin B. protein C. water D. fats and oil E. carbohydrate (1997/35 Nov)
14. For which of the following classes of food is the Biuret test used?
A. carbohydrates B. protein C. fats D. mineral salts E. vitamin (1998/34 Nov)

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15. Lipase is produced in the
A. liver and duodenum B. pancreas and large intestine
C. liver and gall bladder D. ileum and pancreas E. ileum and gall bladder (1998/36 Nov)
16. A deficiency of vitamin c in the diet causes
A. ricket B. scurvy C. cretinism D. goiter (1999/3 Nov)
17. In preparing a balanced diet for a particular person all the following factors must be considered except the
person’s
A. level of activity B. age C. state of health D. rice (1999/8 Nov)
18. A diet that contains all the six classes of food in the correct proportion is
A. a primary food substance B. a food for convalescing C. a nourishing diet D. a balanced diet (2000/32 Nov)
19. Vitamin E promotes
A. bone formation B. fertility C. good vision D. body weight formation (2000/35 Nov)

20. The energy value of food is expressed in terms of

A. grammes per body weight B. degrees centigrade
C. kilojoules D. pounds pressure per metre (2000/37 Nov)
21. Which of the following food substances contains vitamin E?
A. apple fruit B. cassava root C. yeast powder D. Egg yolk (2002/30 Nov)
22. A disorder caused by deficiency of iodine in the body is known as
A. anaemia B. diabetes C. cretinism D. goiter (2002/31 Nov)
23. A white on warming, resulting from a food sample being warmed after the addition of Millon’s reagent
confirms the presence of
A. protein B. reducing sugar C. fat D. starch (2004/26 Nov)
24. In the test for starch the leaf is immersed in alcohol in order to
A. make the starch soluble B. remove the chlorophyll
C. soften the tissues D. expose the starch grains (2006/31 Nov)
25. A patient’s blood was unable to clot on time so the doctor advised him to take more of vitamin
A. C B. D CE D. K. (2011/29 Nov)
26. A person suffering from exophthalmic goitre would have all of the following symptoms except
A. bleeding gums B. nervousness C. swollen neck D. sluggishness (2011/30 Nov)

27. Which of the following groups of food substances serves as the best source of vitamin A?
A. fish liver oil, milk and palm oil B. leafy vegetables, eggs and grains
C. yeast, soya beans and sorghum D. rice, bran, kidney and citrus fruits (2013/28 Nov)
28. A man whose lips often cracks lacks
A. vitamin B B. vitamin K C. vitamin C D. vitamin A (2013/29 Nov)
29. The end point of protein digestion is
A. fatty acids B. amino acids C. glucose D. glycerol (2013/30 Nov)
30. Which of the following substances in not correctly paired with its deficiency disease?
A. water-constipation B. fibre-diarrhoea C. proteins-kwashiorkor D. vitamin C-scurvy (2019/26 PC 2)
31. The food substance that is lacking in the diet of a person who passes hard faeces is
A. starch B. roughage C. protein D. fats (2020/21 PC 1)
32. Which of the following reagents is used to test for starch?
A. Millon’s reagent B. Benedict’s solution C. Iodine solution D. Fehling’s solution (2020/22 PC 1)

33. Protein deficiency in the diet of children can cause a disease called
A. beri-beri B. kwashiorkor C. pellagra D. rickets E. scurvy (2005/28 Neco Nov)
34. 3(a) i. What is a balanced diet?
ii. List FOUR constituents of a balanced diet. (2007/3a (i), (ii) Neco)
35. A little food substance in a test tube plus million’s reagent when heated, tests for the presence of
A. Fats and oil B. simple sugars C. starch D. Mineral salts E. protein (2007/42 Neco)
36. Fat and oil are also known as
A. amino acids B. fatty acids C. glycerol D. lipids E. carbohydrates (2018/33 Neco)

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37. The deficiency of proteins in a developing child results in
A. beriberi B. kwashiorkor C. night blindness D. rickets E. scurvy (2018/54 Neco)
38. Acute vitamin A deficiency in children results in
A. night blindness B. kwashiorkor C. beriri D. ricket (1999/34 NABTEB)

39. 3ai. What is balanced diet?

ii. State three importance of balanced diet to man
b. Describe how to test for fat in groundnut seed (2017/3a & 3b NABTEB)
40. 4(a) What is a balanced diet?
(b)(i) Name four classes of food other than proteins.
(ii) Give one example of food substance for each class named.
(c)(i) State three functions of proteins in humans.
(ii) Describe the appearance of a child with protein deficiency. (2019/4a, b, c NABTEB)

Enzymes
Enzymes: Enzymes are biochemical catalyst which speed up or slow down the rate of metabolic reactions including
digestion.
Characteristics of Enzymes
1. Enzymes are soluble
2. Enzymes are protein. Some enzymes require a coenzyme to activate them (note:coenzyme are non proteins).
3. An enzyme is specific in action
4. Enzymes are organic catalyst. They have the ability to speed up chemical reactions in the body, but they
cannot start a reaction.
5. Reactions catalyzed by enzymes are usually reversible, and the enzymes catalyzes the reaction in either
direction depending on the conditions.
6. An enzyme act best within a narrow range of temperature (35- 40°C), optimum at 37°C.
7. Enzyme act best at a particular narrow range of pH.
8. Enzymes are usually denatured by heat above 60°C.
9. A small amount of enzymes can catalyze the reaction of a large amount of substrate
10. A digestive enzyme acts extracellularly (in the alimentary canal)
11. Enzymes can be inactivated by inhibitors. (examples of inhibitor are cyanide and mercury)
12. In some cases, a digestive enzymes is secreted in an inactive form. They remain inactive until it mixes with
the activator which is usually secreted by another organ.

Classification of Enzymes
Most digestive enzymes are hydrolysing enzymes.
Digestive enzymes are classified according to the type of food (substrate) they digest or act on.
S/N Enzymes Food Digested Examples
1. Amylases Carbohydrate Ptyalin, amylopsin, sucrase, lactase,
maltase
2. Lipases Lipids (fats and oil) Steapsin
3. Proteases Proteins Pepsin, trypsin, erepsin,renin
4. Celluloses Cellulose cellulase

Importance/Roles of Enzymes
Enzymes are organic catalysts of protein origin produced by living cell which help to speed up or slow down the rate
of chemical reactions but remain chemically unchanged at the end of the reaction. The importance/role of enzymes
includes:
1. Enzymes help in breaking down proteins in foods into amino acid
2. They breakdown fats and oils into fatty acids and glycerol
3. They help in breaking down of carbohydrates into glucose, fructose and galactose.
4. They aid the absorption of digested food through the addition of water to the food.

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Enzymes, sources, location, substrate acted upon and effect on products
S/N Enzyme Source Location Substrate acted upon Effect/products
1. Ptyalin Salivary Mouth Cooked starch Partial hydrolysis of starch to
maltose
2. Rennin Gastric gland Stomach Proteins It coagulates or curdle milk protein
3. Pepsin Gastric gland Stomach Protein It converts proteins to peptones
4. Amylase Pancreas Duodenum Starch It converts starch to maltose
5. Trypsin Pancreas Duodenum Protein or Peptone It converts proteins or peptone to
polypeptide
6. Lipase Pancreas Duodenum Fats and oils it converts lipid to fatty acid and
glycerol
7. Erepsin Succus Small intestine Polypeptides and Amino acid
entericus peptone
8. Lipase Succus Small intestine Fat and oil Fatty acid and glycerol
entericus
9. Maltose Succus Small intestine Maltose Converts maltose to glucose
entericus
10. Sucrase Succus Small intestine Sucrose Converts sucrose to glucose and
entercius fructose
11. Lactose Succus Small intestine Lactose It converts lactose to glucose and
entericus galactose
NOTE: Enzymes located in the mouth, pancreas and small intestine work best in an alkaline medium while those of the stomach works best in
acidic medium. An interesting fact is that nature has done its part by providing the various region of the human gut with its proper PH for
effective working of these enzymes.

Example
Which of the following statements is true?
A. ptyalin acts on proteins to give amino acid B. lactase acts on maltose to give amino acid
C. pepsin acts on proteins to give peptide D. peptide acts on starch to give maltose (1999/35)
Answer: C- Ptyalin acts on starch to convert it to maltose. Lactose coagulates milk protein. Pepsin acts on protein to
give peptones. The correct option is c.
Example
3(a) Define enzymes (b) State six characteristics of enzymes. (2005/3a, b)
Enzymes are biological catalyst which speed up or slow down the rate of metabolic reactions.
b. Characteristics of enzymes: - Enzymes are proteinous in nature. - Enzymes are soluble.
- Enzymes are specific in action. - Enzymes are organic catalysis
- Enzyme are sensitive to temperature. - Enzyme are sensitive to PH
Example
If an enzyme works best in an acid medium, in which of the following parts of the human gut is the pH best for
enzyme activities? In the
A. ileum, pH 9.0 B. stomach, pH 2.0 C. duodenum, pH 7.0 D. mouth cavity; pH 8.0 (2006/33)
Answer: B – The Stomach is the only part in the human gut that has acidic medium.
Example
Enzymes can be inactivated by certain chemical substances in the body called
A. catalysts B. inhibitors C. substrates D. activators (2007/31)
Answer: B – Inhibitors inactivate or inhibit enzymes.
Example
Which of the following enzymes is not one of the main classes of enzymes?
A. Sucrase B. Amylases C. Proteases D. Lipases (2007/32)
Answer: A – Sucrase is under amylases, hence, it is no among the main classes of enzymes.
Example
Use the following equations to Answer: question 33.
I – Boiled saliva + starch → X
II – Fresh saliva + starch → Y
What substances do X and Y represent?
A. X = Maltose and Y = Sugar B. X = Starch and Y = Maltose
C. X = Sugar and Y = Starch D. X = Maltose and Y = Starch (2007/33)
Answer: B – A boiled saliva has lost it enzymatic properties, this is because enzymes are sensitive to temperature. A
fresh saliva still retains it enzymatic properties. Hence, boil saliva + starch will produce starch. Fresh saliva + starch
will produce maltose. NB: Saliva contains the enzyme ptyalin which converts starch to maltose.

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Example
Which of the following enzymes does not belong to proteases?
A. Sucrase B. Pepsin C. Trypsin D. Erepsin (2007/34)
Answer: A – Sucrase is an example of amylases. All other option (B to D) are examples of proteases.
Example
(c) In a tabular form, state the source, substrate and end products of the following enzymes:
(i) ptyalin: (ii) pepsin; (iii) lipase. (2007/2c)
Answer:
Enzyme Source Substrate End product
Ptyalin Saliva Starch Maltose
Pepsin Gastric gland Protein Peptones
Lipase Succus entericus Fat and oil Fatty acid and glycerol
Example
Which of the following food substances is incorrectly linked to its enzyme?
A. Protein – trypsin B. Fat – lipase C. Sucrose – pepsin D. Starch – amylase (2010/28)
Answer: C – Sucrose is catalyzed by sucrase.
Example
Which of the following pH values is the best for the action of the enzymes – renin and pepsin in the stomach?
A. pH2 B. pH7 C. pH8 D. pH9 (2010/29)
Answer: A – The stomach is the only part in the human gut that has acidic medium
Example
Which of the following enzymes is active in the deudonum?
A. Pepsin B. Renin C. Trypsin D. Amylase (2011/33)
Answer: C – Trypsin is active in the duodenum, renin and pepsin are active in the stomach, while amylase is active in
the mouth.
Example
Which of the following structures produces the greatest variety of digestive enzymes?
A. Salivary Glands C. Stomach B. Pancreas D. Colon (2011/35)
Answer: B – The pancreas produces three (3) enzyme (amylase, trypsin and lipase). The salivary gland produces only
one (ptyalin). The colon does not produce any enzyme. The stomach produces two enzymes (rennin and pepsin).
Example
Which of the following digestive enzymes would be greatly affected if the liver fails to produce bile?
A. Amylase B. Cellulase C. Lipase D. Protease (2012/34)
Answer: C – Lipase helps to digest fat and oil. Bile also helps in the digestion of fat and oil. If the liver fails to
produce bile, the digestion of fat and oil will be affected.
Example
The name of the enzyme that catalyses the conversion of glucose-6-phosphate at the beginning of glycolysis is
A. phosphor-fructokinase B. glucose isomerase C. hexokinase D. glucose-6-kinases (2013/29)
Answer: C – Hexokinase catalyses glucose to glucose-6-phosphate.
Example
(iii) Name three digestive enzymes found in the small intestine and state one function of each (2018/2biii Neco)
Answer: Erepsin – Converts polypeptides and peptones to amino acid.
Maltase – Converts maltose to glucose.
Sucrase – converts sucrose to glucose and fructose.
Example
Which of the following enzymes requires acidic medium to function?
A. Amylase B. repsin C. maltose D. pepsin E. ptyalin (2005/35 Neco)
Answer: D – Pepsin is found in the stomach which is the only part of the gut that is an acidic medium.
Example
The enzyme pepsin acts in the
A. Large intestine B. mouth C. oesophagus D. small intestine E. stomach (2005/42 Neco)
Answer: B – Pepsin is found in the stomach which is the only part of the gut that is an acidic medium.
Example
Which of these is not an inhibitor of enzymatic action?
A. Cyanides B. Co-enzymes C. Lead D. Mercury (2004/27 Nov)
Answer: B – Coenzymes are small molecules that help enzyme to catalyze the substrate. All other options (A, C and D) are inhibitors.

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Example
Enzymes are
A. destroyed in metabolic reactions B. inorganic trace elements
C. carbohydrate compounds D. protein compounds (2004/28 Nov)
Answer: D – Enzymes are protein compound.
Example
Which of the following is not a characteristic feature of enzymes?
A. being specific in action B. can be denatured
C. speed up chemical reactions D. cannot breakdown cellulose E. being soluble (1998/35 Nov)
Answer: D – Cellulase is an enzyme that breaks down cellulose therefore enzymes can breakdown cellulose
Example
Which of the following organelles stores digestive enzymes?
A. centrosome B. Golgi body C. lysosome D. ribosome (2000/6 Nov)
Answer: C – Lysosome contains hydrolytic enzymes, which it uses to digest worn-out parts of the cell.
Example
Which of the following is not a characteristic of enzymes?
A. they are protein which are activated by co-enzymes B. they are specific and can act only on specific substrates
C. they are organic catalysts D. their reactions are irreversible (2000/38 Nov)
Answer: D – Enzymatic reaction are usually reversible.
Example
The enzyme that coagulates the protein in milk is
A. Pepsin B. Trypsin C. Amylase D. Rennin E. ptyalin (1992/36 Nov)
Answer: D – Renin is found in the stomach and it helps in coagulating milk.
Example
Which of the following organelles secrets hydrolytic enzymes?
A. endoplasmic reticulum B. contractile vacuole C. nucleus D. lysosome (2005/8 Nov)
Answer: D – Lysosome contains hydrolytic enzymes, which it uses to digest worn-out parts of the cell.
Example
(d)(i) Name one organelle in a living cell that produces enzymes.
(ii) Mention two enzymes that act on protein. (2019/4di-ii NABTEB)
Answer: 4di. Lysosome ii. Trypsin and Pepsin
Example
Which of the following characteristics of enzymes is correct? They
A. are not specific in their actions B. act on mineral salts
C. work both in acid and alkaline medium D. work under very high temperature
E. slow down chemical reactions (1990/10 Health Science Nov)
Answer: C – Enzymes can work both in acidic and alkalinic medium.
Example
Which of the following enzymes functions best in an acidic medium?
A. Trypsin B. Ptyalin C. Renin D. Lipase (2003/9 Health Science Nov)
Answer: C – Renin is found in the stomach which is the only acidic part of the gut.
Example
Which of these is not an enzyme?
A. Pepsin B. Gastrin C. Amylase D. Chymotrypsin E. Trypsin (1979/13 JAMB)
Answer: B – Gastrin is a hormone. All other options (A, C, D and E) are enzymes.
Example
Milk protein is hydrolysed by
A. rennin B. amylase C. lipase D. lactase (1981/18 JAMB)
Answer: A – Renin is found in the stomach and it helps to coagulate milk.
Example
In the enzymic reactions starch Amylase
  sugar starch is referred as the
A. substrate B. product C. enzyme
D. enzyme-substrate complex E. reaction mixture (1982/22 JAMB)
Answer: A – Starch is the substrate. Amylase is the enzyme while sugar is the product.

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EXERCISE 6.5
1. The pancreatic juice contains the enzymes amylopsin,
A. pepsin and tryposinogen B. renin and steapsin
C. steapsin and trypsinogen D. steapsin and ptyalin (1989/19 JAMB)
2. The organ which secretes digestive enzymes as well as a hormone is the
A. liver B. salivary gland C. pancreas D. spleen (1990/20 JAMB)
3. Which enzymes are contained in the pancreatic juice?
A. Ptyalin, lipase and pepsin B. Maltase, crepsin and trypsin
C. Rennin, sucrase and lipase D. Amylase, lipase and trypsin (1992/22 JAMB)
4. The breakdown of fats and oils into simpler absorbable compounds is catalyzed by the group of enzymes
called
A. hydrolases B. Amylases C. peptidases D. lipases (2004/32 JAMB)
5. The pancreas secrets enzymes for the digestion of
A. fats, proteins and carbohydrates B. fats, vitamins and cellulose
C. fats, carbohydrates and vitamins D. proteins, cellulose and minerals (2007/26 JAMB)
6. Which of the following statements is NOT true of enzymes? They
A. are proteins B. need cofactors to active them C. are sensitive to hydrogen ion concentration
D. are specific in their action E. can withstand high temperatures (1984/13 JAMB)
Use the information below to Answer: 19 and 20.
I. Test tube containing cane sugar and water.
II. Test tube containing cane sugar and diluted acid.
III. Test tube containing cane sugar and its degrading enzymes
7. In which of the test tubes will glucose be detected after complete hydrolysis?
A. II and III only B. I only C. I, II and III D. I and II only (2011/19 JAMB)
8. Which of the following is a catalyst?
A. Hormone B. Fibrinogen C. Insulin D. Enzyme (2003/30 Health Sci Nov)
9. Which of the following characteristics of enzymes is correct? They
A. are not specific in their actions B. act on mineral salts
C. work both in acid and alkaline medium D. work under very high temperature
E. slow down chemical reactions (1990/10 Health Sci June)
10. All of the following are digestive enzymes except
A. bile B. lipase C. maltase D. pepsin E. ptyalin (1981/24 JAMB)

11. The activity of ptyalin is likely to decrease with an increase in the concentration of
A. oxygen B. starch C. protein D. acid (1994/16 JAMB)
12. The enzyme invertase will hydrolyze sucrose to give
A. maltose and glucose B. glycerol and fatty acid C. glucose and fructose
D. mannose and galactose (2001/18 JAMB)

13. The optimum temperature for the action of most enzymes is

A. 35oC B. 40oC C. 37oC D. 73oC E. 50oC (1996/34 Nov)

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 The graph below shows the amount of starch hydrolyzed over a period of time at three different
temperatures. Use the graph to Answer: questions 36 and 37

14. What is the volume of starch hydrolysed at the 10th minute when the temperature of the medium is 15oC?
A. 30cm3 B. 10cm3 C. 40cm3 D. 20cm3 E. 15cm3 (1996/36 Nov)
15. Which of the following is the correct deduction that can be made from the graph?
A. In this experiment 25oC is the best observed temperature for ptyalin activity
B. in general 25oC is the optimum temperature for ptyalin activity
C. in this experiment, 45oC is a better temperature than 15oC
D. temperature did not seem to have an effect on ptyalin activity
E. ptyalin acts bet at 25oC at pH 8.0 (1996/37 Nov)
16. The enzyme that is present in the saliva is
A. rennin B. lipase C. pepsin D. ptyalin (2013/18 JAMB)
17. Which of the following enzymes is active in the deudonum?
A. Pepsin B. Renin C. Trypsin D. Amylase (2011/33)
18. Which of the following structures produces the greatest variety of digestive enzymes?
A. Salivary Glands B. Pancreas C. Stomach D. Colon (2011/35)
19. Organic substrates produced by living cells which are involved in metabolic reactions are called
A. hormones B. auxins C. enzymes D. juices (2000/39 Nov)
20. Which of the following organelles stores digestive enzymes?
A. centrosome B. Golgi body C. lysosome D. ribosome (2000/6 Nov)
21. Which of these is not an inhibitor of enzymatic action?
A. Cyanides B. Co-enzymes C. Lead D. Mercury (2004/27 Nov)
22. The food substance acted upon by enzymes in the human stomach is
A. carbohydrate B. mineral salts C. proteins D. simple sugar (2019/27 PCE)
23. The two digestive enzymes that work in an acid medium are
A. Amylase and pepsin B. lipase and renin
C. maltase and renin D. pepsin and renin E. Trypsin and lipase (2007/36 Neco)
24. (d)(i) Name one organelle in a living cell that produces enzymes.
(ii) Mention two enzymes that act on protein. (2019/4d NABTEB)

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Feeding Mechanism and Digestive System
Modification and Mechanisms of Feeding in some Animals
Modification in Feeding Habit
The competition for food would be too keen and many animals would die of starvation if all animals were to feed on
one type of food. To avoid this, many animals have adopted different ways of feeding which are classified as:
1. Herbivores 2. Carnivores 3. Omnivores 4. Scavengers
1. Herbivores (plant eaters): These are animals that feed on grasses and vegetables. Examples of herbivores are
goats, sheep, rabbit, antelope, deer, squirrel and elephant. Tilapia and crab are also herbivores.
2. Carnivores: These are animals that feed on flesh and bones of other animals. Carnivores that feed on insects
are said to be insectivorous while piscivorous carnivores are those that feed on fish. Examples of carnivores
are lion, dog, cat, foxes, tiger, fish (lates niloticus (niger perch), Gymnarchus niloticus) toad and reptiles
(snake, lizards wall geckos).
Mammalian carnivores are characterized by well developed dentition, large canines and a pair of carnassials
teeth. These are adapted for stabbing their preys, cutting and crushing meat and bones.
3. Omnivores: Omnivores feed on both plants and animals. Examples are man, pigs, rats, cat, fish (Claria spp),
domestic fowl.
4. Scavengers: These are animals that feed on dead or decaying plants and animal matters. Example of
scavengers are vultures, earthworm, African river prawn and snails.
Vulture eats dead animals, earthworm eats dead plants remains, prawn eats dead animals in the river and
snails eat dead plants remains.

Mechanisms of feeding in some animal

1. Absorbing mechanisms e.g. tape worm: The tapeworm is an endoparasite which carries out parasitic feeding
on its host i.e. man. It has no mouth but absorbs digested food from the intestine of its host. The body of the
tapeworm is modified and adapted for parasitic feeding as follows:
i. The alimentary canal is absent hence food is absorbed through its entire body surface.
ii. The tape worm has hooks and suckers which are used for attachment to the intestine of the host to
void dislodgement.
iii. The body has thick cuticle which resists digestive enzymes of the host.
iv. The flat body surface of the tape worm provides a large surface area of the absorption of the already
digested food.
v. The cuticle of the body surface is used also for absorption of food.

2. Biting and chewing mechanisms e.g. grasshopper or cockroach:

Labrum Maxillae
Iupper jaw)

The mouth parts of a grasshopper

The grasshopper or cockroach has mouth parts adapted for biting and chewing. These insects have four mouth part which are:
i. Labrum or upper lip: This prevents the food from falling off the mouth.
ii. Mandibles: The pair of mandibles are heavy toothed and jaw-like structure used for cutting and
chewing food materials.
iii. Maxillae: The pair of maxillae are biting blades. The maxillae breaks down the food which the
mandible have chewed into the smaller particles.
iv. Labium or lower lip prevent the wastage of food from the mouth.
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3. Sucking mechanisms: Sucking mechanisms is observed in mosquito, butterfly and housefly. These insects
have different modification of mouth parts adapted for feeding on food through the mechanisms of sucking.

Mouth part of a mosquito

The mosquito possesses the following adaptation for sucking:

i. It possess a piercing mouth part called proboscis used for sucking the blood of man and animals.
ii. The mouthparts altogether form a strong stylet capable of penetrating the skin to suck blood.
iii. The stylet except the labium is sharp and pointed to ease penetration into the skin.
iv. The mouth can produce saliva to prevent clotting of blood while it is being sucked in.
v. The labium can be folded easily so as to allow the stylet perform its work of penetration of the skin in orderto
suck blood.

The butterfly mouthparts are modified for sucking as follows:

i. It possesses a long, coiled proboscis used for sucking nectars of flowers.
ii. It is capable to recoiling the long proboscis under its head when not in use.
iii. There is the non-functioning of the other mouth parts due to the type of food taken by the insect.

Mouth part of butterfly

The housefly has the following modification for sucking liquid food materials:
i. The housefly possesses enlarged labella which are sucking structures for liquid food.
ii. The housefly feed on solid food e.g. sugar by pouring out the saliva to change the food to liquid.
iii. It has a sucking mechanism called sponging in which the mouth is placed on the liquid food and it
will start to rush into the mouth.
iv. The labella have fine channels which aid rapid absorption of liquid food into the mouth.

Labium (proboscis)

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4. Grinding Mechanism: This is common in mammals such as man, cattle, sheep, goat, horses, camel, rabbit,
elephant etc. These animals grind their food before swallowing. The grinding is aided by the presence of hard
and strong teeth made up of enamel and dentine. The grinding mechanism in these animals include:
i. Possession of different sets of teeth to grind food.
ii. The teeth are hard and strong to withstand biting, chewing or grinding and cracking of food.
iii. They possess incisors which are sharp with flat edges used for cutting off bits of food.
iv. They have pointed canine teeth which are used for tearing food.
v. There is presence of premolars and molars with undulating and wide surfaces used for grinding of
food.
vi. There is absence of front teeth (incisors) in sheep (a herbivores) this is a special adaptation which
helps to grip the grasses during feeding by animals.

5. Trapping and absorbing mechanism: This is common among the insectivorous or carnivorous plants such
as bladder worts and sundew. Bladderwort and sundew have structures which enable them to adapt to this
mode of feeding. This include:
i. Sundew undergoes nastic movement in response to touch from the body of insects thus trapping
insects.
ii. The sundew leaf has long hairs which carry digestive glands.
iii. Insects on landing on these hair causes other hairs to curl over the insect and cover it.
iv. The sundew is capable of secreting a fluid rich in enzyme to digest the insect externally.
v. The protein so synthesized is easily absorbed by the carnivorous plant into its body.

Feeding Mechanism (II)

Different feeding habit can be found in various organisms, some of these includes:
1. Filter feeding 2. Fluid feeding 3. Insect feeding 4. Parasitic feeding 5. Saprophytic feeding

Filter Feeding:
Some aquatic animals feed on microscopic organisms called planktons. There are two types of planktons, the
zooplankton (microscopic animals) and the phytoplankton (microscopic plants) examples of the filter feeders are
mosquito larva and Tilapia galilaea.

Filter feeding in mosquito larva:

The mouth part of mosquito larva have jaws and two ciliated mouth brushes. The larva uses the mouth brushes to
create current of water. The mouth brushes filter off the planktons and other particles from the water and sweep them
into the mouth, then to the oesophagus and to other parts of the alimentary canal for digestion and absorption into the
body.

Mouth part of mosquito larva

Filter feeding in tilapia galilaea:

Tilapia galilaea feeds by filtering its food (plankton) through the gill rakers. When the floor of the mouth is lowered,
water containing plankton is drawn into the mouth and at the same time the opercula are closed. When the mouth is
raised, the gill rakers filter off the plankton and direct them to the oesophagus. From the oesophagus, the food goes to
the stomach and small intestine where digestive enzymes are secreted and digested food is absorbed.

111
 Tilapia fish showing the operculum opened
Fluid feeding:
Some animals feed on fluid substance gotten from other animals or plants. If the food is solid, it has to be converted
into liquid form before it is sucked into the gut.

Examples of fluid feeders are housefly (Musca domestica), adult female anopheles mosquito and adult butterfly.

Mouth part of a housefly

The labella assume different positions depending upon the type of food. If the food substance is a moderately thick
liquid such as pus and syrup, the head of the labella is raised off the food so that the pseudotracheal surface can rest on
the pus or syrup. The food is then sucked into the pseudotrachea and then to the food canal by capillary action.

Mouth part of housefly showing head of labella raised

Feeding mechanism in female anopheles mosquito:

The mosquito possesses a piercing mouthparts called the proboscis which they use for sucking the blood of man and
animals. The mouth parts form a strong, stylet capable of penetrating the skin to suck blood. The mouth can produce
saliva to prevent clotting of blood while it is being sucked in.

Butterfly:
The butterfly feeds on liquid food like nectars of flowers. It has its mouthparts modified for sucking due to the
presence of long proboscis.

Parasitic feeding:
This is the type of feeding that is carried out by plants and animals parasite. A parasite is a small organism that lives in
or on another large organism (host) from which it obtains food without contributing anything in return.During feeding
process the host is harmed. Example of parasites are tick, lice, flea, ascaris, hook worm etc.

Saprophytic feeding:
Saprophytic feeding habit is carried out by plant that lack chlorophyll that is non-green plants. They feed on dead
decaying organic matter. Examples are Rhizopus and mushroom. The rhizoids (false roots) of these plants secrete
digestive enzymes from their cells to the dead matter.
The digestion of dead organic matter takes place outside the cells of saprophytic plants. The digested food substance
are absorbed by the cells through diffusion. Digestion is therefore extracellular.

Feeding in protozoa and hydra:

In protozoa, there is no alimentary system. They are aquatic in nature and feed on small microscopic organism.
Examples of protozoa are amoeba and paramecium.

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Feeding in amoeba
Amoeba proteus feed on microscopic organisms smaller than itself or decay food substances found in matter.

Feeding mechanism in Amoeba proteus

Feeding in paramecium
Paramecium sets up a water current with its cilia which carry food particles in the water into its gullet, and hence the
food enters its cytoplasm.

Feeding in paramecium

Feeding in hydra
Hydra is a carnivore that feed on tiny animals. It waits quietly until a prey brushes against one of its tentacles and then
immediately, discharges the stinging cells on its tentacles which injects poison into the prey and paralyses it. The
tentacle coils around the prey and push it into the mouth.

The whole prey passes into the gut cavity. Extra-celluar digestion occurs by the secretion of digestive enzymes on it
before the food is pushed into the food vacuole for intracellular digestion to occur.

Feeding mechanism in hydra

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Feeding in mammals
Young mammals feed on their mother’s milk. Adult mammals have different feeding habits. Mammals have different
feeding habit, some are herbivores, others are carnivore and omnivores
In reptiles and other animals all the teeth are alike (homodont dentition). In mammals there are four kinds of teeth
(heterodont dentition).

Kind of teeth:
1. Incisor for cutting
2. Canines for tearing
3. Premolar for grinding or chewing
4. Molar for grinding

Mammals have two successive sets of teeth.

1. The milk teeth (dentition) found in young children and
2. Permanent dentition in adult.
Note: The molar only occur in permanent dentition.

Dental formula
The dental formula is the summary of the number of each kind of teeth in one half of the upper and lower jaw. The
dental formula of different mammal is given below

2 1 2 3
Man = I 2 C 1 PM 2 M 3
2 0 3 3
Rabbit = I 1 C 0 PM 2 M 3
3 1 4 2
Dog = I 3 C 1 PM 4 M 3
0 0 3 3
Sheep = I 3 C 1 PM 3 M 3
Example
The mode of nutrition which describes feeding habit in animal is
A. autotrophic B. holozoic C. holophytic D. saprophytic E. photosynthetic (1998/35)
Answer: B – Animals generally ingest their food (solid or liquid). This makes them holozoic in feeding.
Example
Which of the following plants is a carnivore
A. Desmodium B. Sundew C. Mushroom D. Platycerium E. Liverwort (1998/39)
Answer: B – Sundew is a carnivorous plant i.e. it traps and digest small animals such as insects. Other example of
carnivorous plants are: pitcher plant, bladderwort etc.
Example
Organisms that feed essentially on plants within any ecosystem may be referred to as
A. carnivores B. herbivores C. saprophytes D. omnivores (2006/43)
Answer: B – Herbivores generally feed on plants.
NB: Carnivores feed on flesh (animals). omnivores feed on both plants and flesh (animals), saprophytes feeds on dead and decaying matter.
Example
Which of the following features of the tadpole indicates that the animal is herbivorous? Possession of
A. operculum B. muscular tail C. long coiled intestine D. internal gills (2007/36)
Answer: C - Herbivores usually have long coiled intestine that facilities digestion.
Example
Analysis of the gut content of an animal showed that it contained small pieces of bone, seeds, roughage and insects.
The animal is likely to be a/an
A. carnivore B. herbivore C. insectivore D. omnivore (2008/26)
Answer: D – Omnivore feed on both plants and animals. From the question, bone and insect are animals component
of the food, seeds and roughage are plant component of the food.
Example
A herbivore cannot feed on a piece of meat because it has no
A. incisors to cut the meat B. canine to tear up the meat
C. premolars to grind the meat D. molars to mash the meat (2010/31)
Answer: B – Herbivores generally lack canine which is used for tearing flesh.

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Example
Amoeba engulfs food particles by means of its
A. contractile vacuole B. cytoplasmic membrane C. food vacuoles D. nucleus E. pseudopodia (2008/5 Neco)
Answer: E – Amoeba engulfs food particles by means of its Pseudopodia which is a cytoplasmic projection. This
structure is also used for locomotion.
Example
(b) Describe the process of feeding in: (i) Hydra (ii) Amoeba (1988/2c)
Answer:
i. Hydra: It feeds on tiny animals. It waits quietly until a prey brushes against one of its tentacles. Immediately, the
straying cells on its tentacle are discharged in order to paralyze the prey. The tentacles then coils around the prey and
push it into the gut where digestion begins.
ii. Amoeba: It feeds on microscopic organisms such as single-celled algae and bacteria. When the amoeba encounters
a prey, its cytoplasm flows around the prey and engulfs it. This is done with a water drop to form a food vacuole. The
cytoplasm secretes digestive enzymes into the food vacuole where digestion takes place.
Example
Hydra feeds by
A. Digesting its food extracellularly B. Absorbing food digested by other organisms
C. Symbiotic association D. Masticating the food particles
E. Synthesizing its food chemically (1998/40)
Answer: A – Hydra digest its food extracellularly by secreting digestive enzymes into it prey before pushing it into its gut.
Example
Which of these is not correct about the tsetse fly and mosquito? They
A. harbor protozoa as disease agents B. possesses piercing and sucking mouth parts
C. have intermediate hosts D. inject disease-causing organisms into the blood stream (2001/52)
Answer: C – Tsetse fly and mosquito are vectors (carriers of disease causing organisms) and do not have intermediate host.
Example
Which of the following features enables the tapeworm to live successfully in the small intestine of human?
A. Hooks and suckers for strong attachment B. a long neck for forming young proglottis
C. the absence of segmentation and appendages D. Possession of flame cells for excretion (2004/39)
Answer: A – Tape worm attaches firmly to the wall of the small intestine by its hook and sucker. This prevents it
from been eroded away through faeces.

Example
An example of a saprophytic relationship is a/an
A. vulture feeding on decaying meat B. mushroom growing on decaying vegetation
C. boy eating stale food D. earthworm feeding on decaying vegetation (2010/50)
Answer: B – Saprophytes are plants that feed on dead and decaying organic matter.
NB: Animals that feeds on dead and decaying matter are called scavengers. E.g. vultures, snail etc.
Example
c. (i) What are saprophytes? (ii) Give four examples of saprophytes. (2019/3ci, ii)
Answer: i. Saprophytes are organism that obtain their nutrients from dead and decaying organic matter.
ii. Mushroom, Mucor, Molds and yeast.
Example
The mouth parts of mosquito are adapted for
A. piercing and chewing B. cutting and sucking
C. biting and filtering D. biting and licking E. piercing and sucking (2007/7 Neco)
Answer: E – Mosquito mouth parts are adapted for piercing and sucking.
Example
The association existing between tapeworm and man is
A. holozoic B. parasitic C. predatory D. saprophytic E. symbiotic (2007/47 Neco)
Answer: B – The association between tapeworm and man is parasitic. In this association, the tapeworm is the parasite
and man is the host.
Example
Mention two differences between the modes of feeding in spirogyra and rhizopus. (2014/4aii Neco)
Answer:
1. Spirogyra makes uses of sunlight to manufacture its food, rhizopus does not make use of sunlight to
manufacture it food.
2. Spirogyra carries out photosynthetic mode of feeding rhizopus carriers out saprophytic mode of feeding.

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Example
An example of saprophyte is
A. drosera B. ultricularia C. dodder D. mushroom (2013/31 Nov)
Answer: D – Mushroom is a saprophyte.
NB: Drosera (Sundew) and Ultricularia (bladder wort) are carnivorous plant. Dodder is a parasitic plant.
Example
Which of the following mouth parts of the insect is used for cutting and crushing plant materials for food?
A. Labrum B. Labium C. Hypopharynx D. Mandible E. Maxillae (1995/36 Nov)
Answer: D – The mandible is the largest and most robust mouth part of chew in insect. Its function is typically to
grasp, crush, or cut the insects food

EXERCISE 7.1
Use the diagram below to Answer: Question 29-31

1. The parts labeled I, II and III respectively are:

A. mouth, intestine and tail B. operculum, gills and tail
C. cement gland, intestine and tail D. operculum, intestine and tail (1999/29 Nov)
2. What mode of feeding does the part labeled II in the diagram indicate?
A. herbivorous B. carnivorous C. omnivorous D. insectivorous (1999/30 Nov)
3. What stage will the organism develop, into immediately after this stage?
A. internal gill stage B. young larva stage
C. yolk in a string of jelly stage D. External gill stage (1999/31 Nov)
4. 7(a) Define the following terms:
(i) parasitism; (ii) saprophytism; (iii) symbiosis, giving one example of each.
(b) Describe the external features of a named animal ecto-parasite and how the features adapt it to its
mode of life. (2011/7a, b Nov)
5. An organism that feeds on algae is said to be
A. holozoic B. parasitic C. holophytic D. saprophytic (2005/37 Nov)
6. Rhizopus is a saprophyte because it
A. feeds on decaying organic matter B. absorbs nutrients from living plants
C. lives symbiotically with an alga D. feeds on microscopic organisms (2001/3 NABTEB)
7. Which of the following organisms is well adapted for filter feeding?
A. Cockroach B. Grasshopper C. Mosquito larva D. Ant (2018/45 NABTEB)
8. A green plant growing in a compost pit is feeding
A. holozoically B. parasitically C. saprophytically D. holophytically (1980/26 JAMB)
9. A tapeworm has no alimentary canal because
A. it is autotrophic B. it does not feed C. it has no enzymes
D. its body absorbs digested food E. the suckers on the scolex suck blood (1982/13 JAMB)
10. In Rhizopus, carbohydrates is stored in the form of
A. glucose B. paramylon C. glycogen D. starch E. oil (1983/43 JAMB)
11. The mouth parts of the housefly are adapted for
A. lapping and sponging B. sucking and chewing C. piercing and sucking
D. chewing and lapping E. biting and chewing (1984/1 JAMB)
12. Which of the following adapts an insect for feeding?
A. suitable mouth parts B. paired antennae C. segmented body D. jointed appendages (2016/5 JAMB)
13. The mode of feeding in Amoeba and Hydra is
A. heterotrophic B. holophytic C. autotrophic D. symbiotic (2001/8 JAMB)

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Mammalian Teeth
Dentition:
Dentition refers to the number, arrangement and conformation of teeth in an organism. There are two main types of
dentition.
i. Homodont
ii. Heterodont dentition

1. Homodont Detention: In this type of dentition, the organisms have same type of teeth. No set of teeth is
special for any function. All the teeth are same shape, size and have same functions. Example of homodont
dentition is found in fishes, amphibians and reptiles.

2. Heterodont Dentition: In this type of dentition, the organism possesses teeth of different shapes, sizes and
functions. Example of organisms having heterodont dentition are mammals e.g rabbit, man, dog, cattle etc.
The mammals generally have four different types of teeth. These are incisors, canines, premolars and molars.
Mammals again have different set of teeth. These are milk teeth and permanent teeth.

Milk Teeth: This is the set of teeth possessed by the young ones that is children in the case of human and is
made up of the incisors, canine and premolar teeth (i.e. without the molar ). It is common among the young
ones and may number up to twenty (20). They later fall off, to be replaced by the permanent teeth.

Permanent Teeth: This is the set of teeth possessed by adult mammals and are usually four types. These are
incisors, canine, premolar and molar teeth. They remain till old age and may number up to 32 in man.

Types of teeth/adaptation to feeding

There are four types of teeth in mammals, these are incisors, canine, premolars and molars
1. Incisors: These are located in the front of the jaw. They are flat, chisel – shaped with a sharp edge used for
cutting and holding to the prey so that they do not escape.

2. Canine: Canine are found next to incisor. They are sharp and pointed at the tips. They are used for tearing
flesh and catching the prey.

3. Premolars: These are located next at the back of the jaw following the canines. They have large, ridged flat
surfaces used for grinding and chewing of food.

4. Molars: They are located at the extreme back of the jaws. They are closely packed with rigged surfaces. They
are used for chewing and grinding of food.

Vertical Section of the Mammalian Tooth

N.B: In carnivores, the last upper premolar and first lower molar are enlarged and are called carnassials teeth. They are used
for cutting large pieces of meat, breaking, grinding and chewing of bones and tendons.

Dental Formula: The dental formula is a summary of the number of teeth of each kind of teeth in one half of the
upper and lower jaw. The dental formula of adult human is:
(upper−jaw) 2 1 2 3
I C PM M = 16 × 2 = 32
(lower−jaw) 2 1 2 3

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This means that in the right or left half of the upper jaw, a man has 2 incisors, 1 canine, 2 premolar, and 3 molars. The
same is true of the other half of the lower jaw. The total number of teeth in an adult human is 32.
The dental formula of some other mammals are:
2 0 3 3
Rabbit = I 1 C 0 Pm 2 M 3 = 14 × 2 = 28
3 1 4 3
Dog = I 3 C 1 Pm 4 M 2 = 21 × 2 = 42
0 0 3 3
Cow/Goat/Sheep = I 3 C 1 Pm 3 M 3 = 16 × 2 = 32

Structural Description of the Tooth

The human tooth is divided into three different parts:
 Crown – This is the visible portion of the tooth. It covers nearly two-thirds of the total tooth structure. The crown
lies above the gums (gingiva).
 Neck – This is the small and narrow portion lying between the crown and root of the tooth.
 Root – It consists of one-third of the tooth and is deeply seated inside the bone supporting the tooth. This part of
the tooth lies below the gums and is usually not visible in healthy teeth.

Human teeth are composed of multiple layers of both hard and soft tissue. Enamel, dentine, and cementum are
harder sections, whereas pulp is the softer portion of tooth.
The centre of the tooth consists of a pulp cavity. The pulp cavity contains blood vessels and nerves which are
extremely sensitive to heat and cold. The dentine encloses the pulp cavity and it is hard and bone-like. The dentine
contains some living cytoplasm. A thin layer of cement covers the dentine in the root region. The cement is in turn
covered by the periodontal membrane which fixes the tooth to the jaw bone.The enamel is a white layer that covers
the dentine. Enamel is the hardest material made by animals. It protects the pulp and dentine within.
Enamel surrounds the crown and acts as a protective covering. It varies in thickness in different parts of the tooth. It is
thickest at the cuspal region of the molars and premolars. The thinnest enamel is at the neck of the tooth.
The enamel color ranges from yellow to grayish white, and generally reflects the degree of mineralization and staining
on tooth surfaces.
Composition of Enamel
Enamel is formed by the ameloblast cells and it is the hardest substance of the human body due to high percentage of
mineral salts in crystalline state.
Enamel consists of 95% to 98% inorganic and 1% organic substances, with water constituting 1% to 4% of the
enamel.
Adaptation of the teeth of some mammals
Mammals Dentine formula Incisors Canines Molar Premolar
Carnivore 3 1 4 3 Small and pointed Long sharp curved and Cusped, blunt with flat Flattened surface
𝐼 , 𝐶 , 𝑃𝑀 , 𝑀
e.g. Dog 3 1 4 2 for cutting flesh and pointed, for holding surface for cutting and with cusp pointed
= 21 × 2 = 42 for defence. prey and for attack and grinding. and sharp.
defence.
Herbivore 2 0 3 3 Long and flattened Absent, creating a Broad and ridges for Large and ridged for
I ,C ,P ,M
e.g. Rabbit 1 0 2 3 like chisel for wide space called cutting and grinding. cutting and grinding.
= 14 × 2 = 28 cutting of grasses. diastema.
Omnivore 2 1 2 3 Broad, sharp and Sharp and bluntly Broad with four or five Broad with two
𝐼 , 𝐶 , 𝑃𝑀 , 𝑀
e.g. Man 2 1 2 3 flattened like chisel pointed for cutting, cusps for chewing and cusps for chewing
= 16 × 2 = 32 for cutting. biting and tearing. grinding of food. and grinding food.

Carnivorous teeth set with pronounced canine Herbivrous teeth set with pronounced incisor and molars

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Care of the mammalian teeth
The teeth is usually prone to decay because germs easily grow on food particles left in the teeth after a meal. The part
of the teeth which is first damaged in tooth decay is the enamel thereafter the dentine is affected and subsequently the
sensory nerve of the pulp cavity are exposed leading to tooth ache. Some of the ways to care for the mammalian teeth
inorder to prevent tooth decay includes:
1. Regularly washing of the teeth with fluoride tooth paste at least twice a day.
2. Washing/rinsing of mouth after every meal.
3. Eating of tooth healthy foods (food that easily stick to teeth should be avoided).
4. Frequent checkups by visiting the dentist.
5. Washing of artificial teeth by germicide after each meal.
6. Using of dental sealants (a sealant is a protective plastic coating applied to chewing surface of back teeth).

Example
(c) Explain briefly how the dentition of herbivores is adapted for feeding. (2016/2c)
Answer:
- Elongate/curved incisors; for cutting grass.
- Thick horny pad, against which the lower incisor bit.
- Presence of diastema; allows tongue to roll the cropped grass.
- Broad surface of the molars; used for grinding grass.
Example
1 Carnassial teeth are found in
A. dog B. cow C. goat D. man E. sheep (2018/40 Neco)
Answer: A – Carnassial teeth are mostly found in carnivores. They use it to tear flesh and break bones. Examples of
carnivores are: dog, lion, tiger etc.
Example
5a. (i) Define dentition; (ii) List four types of teeth in man (2014/5ai – ii Neco)
Answer:
i. Dentition is defined as the numbering, arrangement and conformation of teeth in an organisms.
ii. Incisors, canine, premolars, molars
Example
Teeth that grow indefinitely can be found in
A. man B. camel C. shark D. rabbit E. pig (1998/39 Nov)
Answer: D – The incisors of rabbit are rootless and can grow indefinitely.
Example
A prominent carnivorous feature in an animal is the possession of
A. incisors B. molar C. diastema D. premolars E. canine (1997/37 Nov)
Answer: E – Carnivorous animals posses well developed canine which they use in tearing flesh.
Example
Which of these conditions will not prevent tooth decay?
A. Eating too many sweets B. eating hard and fibrous food stuff
C. keeping the teeth free from food particles D. visiting the dentist regularly
E. having evenly spaced teeth (2000/2a Nov)
Answer: A – Eating too many sweets will not prevent tooth decay.
Example
Which of the following statements is true of the periodontal membrane of a tooth? It
A. produces the dentine B. is fastened firmly to the jawbone by cement
C. is embedded in the pulp cavity D. attaches the cement to the jaw bone (2005/38 Nov)
Answer: D – The cement is in covered by the periodontal membrane which fixes the tooth to the jaw bone
Example
The best method of cleaning the teeth is
A. brushing the teeth from inside to outside B. using the brush in an up and down motion
C. brushing the teeth from outside to inside D. moving the brush from side to side (2000/8 Health Science Nov)
Answer: B – The best method of cleaning the teeth is using the brush in an up and down motion.
Example
The kind of teeth used for tearing food materials is the
A. fang B. canine C. premolar D. carnassial E. incisor (1981/8 JAMB)
Answer: B – Canine is used in tearing flesh.

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Example
5(a)i. Describe the structure of a mammalian tooth?
ii. Name the types of teeth and their functions. (2001/5ai-ii NABTEB)
Answer:
i. A tooth consists of enamel, dentine, cementum and pulp tissue. The part of the tooth expose to the oral cavity
is called the crown, and the part of the tooth below the crown is called the root. The part between the crown
and root of the tooth is called the neck.
ii. Incisors – Used for cutting and holding prey.
Canine – Used for tearing flesh and catching prey.
Premolars – Used for grinding and chewing food.
Molars – Used for chewing and grinding food.
Example

The diagram above represents the skull and lower jaw of

A. a fruit eating reptile B. a herbivorous mammal
C. a carnivorous mammal D. an insectivorous reptile (2002/33 Nov)
Answer: C - a carnivorous mammal (because of the pronounced canine teeth IV)
Example
The types of teeth which enable the animal to feed efficiently on its main diet labelled
A. I and III only B. I and IV C. II and III only D. III and IV only (2002/34 Nov)
Answer: D. III and IV only
Example
Which of the labeled teeth is incisor?
A. II B. III C. IV D. V (2002/35 Nov)
Answer: D. V (incisor is the starting point of teeth)
Example
The part of the tooth which contains blood vessels is the
A. cement B. pulp C. enamel D. dentine E. jaw bone (1998/7 Health Science Nov)
Answer: B – The pulp contains nerve, blood vessels and connective tissue.
Example
In which of the following dental disorders does the jaw bones supporting the taste waste away?
A. Overlapping B. Gingivitis C. Periodontitis D. Dental carries E. Mottling (1996/39 Health Science Nov)
Answer: C – Periodontitis is a serious gum disease that damage the soft tissues and the jaw bone.

Example
Which of the following is not a part of a tooth?
A. cement B. gum C. enamel D. Pulp cavity (2003/8 Health Science Nov)
Answer: B – The gum is not a part of the tooth. All other options (A, C and D) are parts of the tooth.
Example
(c) State five measures by which tooth decay can be prevented (2003/4c Health Science Nov)
Answer:
- Regularly washing of the teeth with fluoride tooth paste at least twice a day.
- Washing/rinsing of the mouth after every meal.
- Eating of tooth health foods.
- Frequently cheek ups by visiting the dentist.
- Using of dental sealants.

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Example
Use the diagram below too Answer: questions 14 and 15

The part that is similar to bone is labelled

A. IV B. III C. II D. I Answer: C – The dentine is the part of the tooth that is similar to bone.
The parts labelled I and II constitute the
A. crown B. neck C. Root D. gum (1997/14 & 15 JAMB)
Answer: A – I and II constitute the crown of the tooth.
Example
Rodents gnaw on food with their
A. chisel-like front teeth B. Molar teeth C. strong jaws D. flat ridged teeth (2004/11 JAMB)
Answer: A – Rodent gnaw on food with the chisel-like front teeth. These chisel-like front teeth are the incisors.

EXERCISE 7.2
Use the figure below to Answer: questions 16 and 17

1. Which of the structure is the molar?

A. 1 B. 2 C. 3 D. 4 (2019/16 JAMB)
2. What is the function of 3?
A. cutting of large pieces of food B. seizure and tearing of prey
C. grinding of food D. tearing of flesh only (2019/17 JAMB)
3. (a) Make a labelled diagram of the vertical section of the mammalian tooth (1995/1a)
4. Which of the following parts of the tooth is first damaged during dental decay?
A. Cement B. Enamel C. Dentine D. Root E. Gum (1997/33)
The diagrams below are illustrations of the dentition of an organism. Study them and Answer: questions
26 to 28.

5. The dentition belongs to a

A. rabbit B. cat C. frog D. man (2017/26)
6. The function of the teeth labeled X is for
A. biting and grasping B. chewing and grinding
C. tearing and grasping D chewing and tearing (2017/27)
7. The teeth which are absent in the young of the organisms are labeled
A. W B. X C. Y D. Z (2017/28)
8. The dental formula i 3/3, cl/1, pm 4/4, m2/3 represents that of a
A. cat B. dog C. man D. rabbit E. sheep (2008/47 Neco)

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9. Which of the following statements about the dentition of man is INCORRECT? Man has
A. more molars than incisors B. the diastema
C. the same number of teeth on upper and lower jaws D. a total of thirty-two teeth
E. a total of six molars (1983/46 JAMB)
10. The presence of a diastema in the jawbone indicates that the mammal lacks the teeth suitable for
A. tearing B. chewing C. cutting
D. chewing and tearing E. cutting and grinding (1984/36 JAMB)
11. Evidence that a tooth is a living part of the mammalian body can be found within the
A. gum B. pulp cavity C. cement D. enamel (1986/22 JAMB)
12. If an animal has diastema, it would NOT possess
A. incisors B. cannines C. premolar D. molars (1988/18 JAMB)
13. Which of the following animals has homodont dentition?
A. Rat B. Man C. Lizard D. Pigeon (1990/10 JAMB)
14. The crown of the mammalian tooth is covered with
A. cement B. dentine C. caries D. enamel (1991/22 JAMB)
15. The dental formula 13/3CI/1pm4/4m2/3 is that of a
A. goat B. rabbit C. man D. dog (1994/14 JAMB)
2 0 3 3
16. I C PM M : The dental formula above represents that of
1 0 2 3
A. a carnivore B. a herbivore C. an ominivore D. a dentrius feeder (2014/14 JAMB)
17. In a tabular form, state the sources, substances and products of the following enzymes:
(i) ptyalin (ii) lipase (iii) lipase (2007/2ci, ii, iii).
18. Define detention (Neco 2014/5a)
19. State three characteristics of enzymes. [1998/1(di)]
20. Which food type yields the most energy during respiration?
A. protein B. starch C. fat D. sugar (Nov. 2005/32)
21. An infant suffering from kwashiorkor can be cured if fed on food rich in
A. carbohydrates B. proteins C. fats D. roughages (Nov. 2005/33)
22. One of the roles played by proteins in human body is that they
A. act as solvent B. act as insulators C. repairs damaged tissues
D. are the main sources of energy (Nov. 2005/34)
23. Which of the following would you use to test for a simple reducing sugar?
A. Benedict’s solution B. Biuret test C. million’s test D. Sudan III solution (NABTEB 1999/35)
24. Fat and oil are also known as
A. amino acids B. fatty acids C. glycerol D. lipids E. carbohydrates (Neco/2018/33)
25. Describe how to test for fat in groundnut seed. (NABTEB 2017/3b)
26. State three functions of proteins in humans
Describe the appearance of a child with deficiency (NABTEB 2019/4c)

27. Which of the following substances is not complex carbohydrate?

A. glycogen B. cellulose C. starch D. glucose (2013/31)

Digestive System
Digestive system or alimentary canals are complex system developed by multicellular organisms to break complex
foods into simpler forms.
Types of Alimentary Tracts
There are two types of alimentary tracts:
1. Incomplete tracts
2. Complete tracts
Incomplete digestive tract has only one opening to the outside. This opening is called the mouth which serves for
ingestion and egestion.
Coelenterate (e.g. hydra) and flat worm (e.g. planaria) are typical examples of animals with incomplete digestive tracts.
On the other hand, complete digestive tracts have two openings called mouth and anus. The mouth is used for
ingestion while the anus is used for egestion. Examples of animals with complete digestive tract or system are
earthworm, birds, goat etc.

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One major advantage of complete digestive tract over incomplete one is that the incoming food does not mix with
outgoing undigested food materials. In complete digestive tracts, different portion of the tract become specialized to
perform different function.
Alimentary canal of planaria

Planaria has a digestive tract consisting of a mouth placed ventrally, a muscular pharynx and an intestine. The pharynx
leads to the intestine and it is protruded from the mouth when attacking a prey. The intestine has 3 (three) main
branches:
i. An anterior branch pointing forward and
ii. Two Posterior branches pointing toward the tail end
These main branches give rise to extensive lateral diverticular (branches) thus forming a gastro vascular cavity
(anterior and posterior cavity) which is lined with phagocytic cells, glandular storage cells and gland cells.
Planarians feed on small animals such as crustaceans, nematodes and insects (They are carnivorous free living worm).
They capture their prey by wrapping them in mucus gland and suck them bit by bit into the gastro vascular cavity
through the muscular pharynx. The sucked food is digested by the phagocytic cells and distributed by diffusion to
other parts of its body. Digestion is intracellular. The gastro-vascular cavity is extensively branched giving it a large
surface area for absorption.
Alimentary canal of earthworm

The alimentary canal of earthworm runs along the length of the body from mouth to anus between the first and last
segment (complete alimentary canal). It is made up of mouth, buccal cavity, pharynx, oesophagus, crop, gizzard,
intestine and anus. The mouth is the first segment called peristomium and its covered by prostomium, which is
sensory in nature. The muscular pharynx acts as a suction pump, enabling the mouth to suck in food. The prostomium
helps to arrange the food for ingestion. The muscular pharynx leads to the oesophagus. In the pharynx glandular cells
that secrete mucin (which makes the food soft) and protein digesting enzymes into the pharyngeal cavity are present.
This starts the digestion of protein. The crop acts as a temporary storage chamber and connects the oesophagus with
the gizzard. The gizzard contains small stones which the earthworm eats and uses them to grind the food into small
particles. The gizzard connects the crops with the intestine.

The intestine is the longest part of the alimentary canal. It secretes digestive enzyme which digest various types of
food. The intestinal wall contains blood vessels which aids in the absorption and transportation of the digested food to
the rest part of the body. The intestine terminates as the anus in the last segment called anal segment.

Advancement of alimentary canal of earthworm over that of flat worm(planaria):

1. Alimentary canal of earthworm has two openings, the mouth and anus (complete alimentary canal) while that of
the flatworm has only one opening (incomplete alimentary canal).
2. The earthworm possesses a muscular gizzard in which food particles are grinded into smaller bits. The gizzard is
absent in planarians.
3. The intestine of the earthworm is not branched and this enables efficient digestion and absorption of food. But in
the planarians, the intestine has three main branches which give rise to other sub-branches (diverticular)
4. In the earthworm, food is absorbed by the blood, but in flatworms, food is absorbed by diffusion.
5. The crop which is a temporary storage organ for food is present in the earthworm but absent in planarians.
123
Example
The absence of alimentary canal in the parasitic flatworm can be attributed to the fact that
A. its body does not feed B. it has no enzymes
C. its body absorbs digested food D. it has suckers on the scolex (2013/45)
Answer: C – Parasitic flatworms absorb digested food through their body.

EXERCISE 7.3

1. What is the name of the part labeled I?

A. oesophagus B. Nephridium C. Pharynx D. Intestine E. Crop (1991/28 Nov)
2. What is the name of the structure labelled III?
A. Gizzard B. Crop C. Heart D. Seminal vesicle E. Coelom (1991/29 Nov)
3. What is the function of the part labeled IV?
A. Production of sperm B. Temporary storage of food C. Mechanical grinding of food
D. Pumping blood all over the body. E. Producing cocoon for the eggs (1991/30 Nov)

Alimentary canal of grasshopper or cockroach

The grasshopper feeds on green vegetable (a herbivore) and the cockroach feeds on household materials like books,
sugar etc. The alimentary of these insects are divided into three main regions which are the foregut, midgut and
hindgut.
The foregut consists of mouth cavity, pharynx, oesophagus, crop and gizzard. The mouth cavity is a small space
which is surrounded by mouth part such as mandible, maxillae and labium. Food is crushed and acted upon by
salivary secretion in the mouth. The mouth opens into the pharynx which leads into the oesophagus. The oesophagus
is a tubular passage that leads into a temporary storage structure called crop. The food is later taken into the gizzard
(proventriculus) for grinding.
The midgut is also known as the stomach. At the junction of the midgut and foregut finger-like projections known as
caeca secretes digestive juices which aid in digestion and absorption of food in the mid gut.
The hindgut is differentiated into three parts i.e. anterior ileum, a middle colon and posterior rectum. Absorption of
water occurs at the hindgut. The hindgut terminates at the anus.
Various parts of alimentary canal of an insect
Gut Part of gut
Fore gut Mouth, mouth cavity, pharynx, oesophagus, crop, gizzard
Mid gut Stomach
Hind gut Intestine (ileum, colon and rectum), anus

Alimentary Canal of a Cockroach

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Alimentary canal of a bird:
The alimentary canal (or digestive system) of a bird include the beak, mouth, pharynx, oesophagus, crop, the
proventriculus, gizzard, intestine, caecum, rectum and anus. Teeth is absent in the bird but the beak can pick up
food such as fruits, grains etc.

Alimentary canal of a bird

During feeding in the bird, the food are picked up by the beak, and are moved from the mouth to the crop through a
muscular passage known as oesophagus. In the crop the food is stored temporarily, acted upon by some fermenting
bacteria and later moved to the proventriculus where digestive enzymes are secreted on the food. The proventriculus
contains glands that secrete digestive enzymes like pepsin and amylase and as such it is often referred to as glandular
stomach.
The proventiculus leads to the gizzard. The actual grinding of the food takes place in the gizzard with the aid of stone
particles thus it is referred to as grindular stomach. From the gizzard, the food moves to the duodenum and the
intestine for further absorption and digestion. Undigested food particles passes through the caeca to the rectum and
finally to the anus (cloaca) where they are egested from the body. The faeces and urine are removed from the body at
the same time.
Differences between the alimentary canal of a bird and grasshopper.
Birds Grasshoppers/cockroach
1. Tongue present in the mouth. Tongue is absent.
2. Mouth is modified into beak. Mouth is modified into mandible and maxillae for chewing
and grinding.
3. Duodenum present. Duodenum is absent.
4. Alimentary canal is long. It has relatively short alimentary canal
5. Hind gut terminates in the cloaca and not The hind gut terminates in anus and it is distinct from
distinct from reproductive opening reproductive tracts.
6. Absence of Malpighian tubules Malphigian tubules are attached to the alimentary canal.
7. Pancreas present. Pancreas is absent
Similarities between the alimentary canal of bird and grasshopper/cockroach
1. Both have narrow oesophagus.
2. Crop is found in both organisms.
3. Muscular gizzard is present in both.
4. There is presence of caecum in both
5. Presence of mid gut is in both organisms.
Example
The part of the alimentary system of a bird where grinding of maize occurs is the
A. crop B. stomach C. gizzard D. cloaca E. rectum. (1991/34)
Answer: C – The gizzard of birds contains small stones which help to grind food (e.g. maize)

EXERCISE 7.4
1. Which part of the alimentary canal of birds is adapted to crushing of food?
A. Crop B. Gizzard C. Oesophagus D. Pharynx E. Midgut (1995/35 Nov)
2. A humming bird is able to feed on nectar because its beak is
A. short, slender and ridged B. short, strong and conical
C. long, slender and slightly curved D. long, wide and slightly curved (2017/31)
3. State four similarities and four differences between the alimentary canal of a bird and a cockroach (2013/3c Nov)
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Alimentary Canal and Digestion of food in Man
The alimentary canal of man include the mouth, oesophagus, stomach, duodenum, small intestine or ileum, appendix,
large intestine or colon, rectum and anus.
In the mouth, the teeth, salivary gland and tongue can be found. The teeth has several functions some of which
includes cutting and grinding of food into smaller fraction and exposing large area of food for enzymes to act on
them. The tongue rolls the food into bolus and allows the food to mix with saliva (which contains ptyalin).The tongue
also enhances movement of food in the mouth and swallowing of food into the gullet or oesophagus. The tongue also
plays a vital function in production of speech (sound)

rectum

The alimentary canal of man

The salivary gland consists of three major pairs which are parotid glands (on the insides of cheeks), submandibular
gland (on the floor of the mouth) and sublingual glands(under the tongue).it produces saliva which contain water,
mucin and an enzyme called ptyalin. The ptyalin helps to break starch into maltose. Mucin acts as a lubricant for
chewed food and to ease swallowing, it makes the chewed food stick together like a round mass (bolus). Dry food
substances are been dissolved by the watery portion of the saliva. The saliva is slightly alkaline and this enables it to
dissolve the acids released by the bacteria which ferments leftover food particles between the teeth
The oesaphagus acts as a passage way from the mouth to the stomach. Through a peristaltic movement, swallowed
food passes through the oesphagus into the stomach.
The stomach stores food temporarily for about 3-4 hrs before it is released at regular intervals into the duodenum by
the opening of the pyloric sphincter. In the stomach, the gastric gland secretes juice which contains two enzymes renin
and pepsin.
The renin acts on milk (coagulates the milk into curdle) by converting soluble caseinogen into insoluble casein while
the pepsin breaks down proteins to peptones. These two enzymes works best in an acidic medium. The gastric gland
also secretes hydrochloric acid which kills some stomach bacteria and creates the appropriate medium for the effective
working of these enzymes.
The muscular contraction of the stomach wall helps to churn the food thus allowing for the mixture of digestive juices
with the swallowed food. As a result of this churning movement, the food is converted into a semi-liquid state called
chyme. In the duodenum, digestion of food also takes place. The pancreas which secretes pancreatic juice that
contains three enzymes is located in the duodenum. These enzymes are:
Amylase: That converts starch to maltose.
Lipase: Which converts fat and oil to fatty acids and glycerol
Trypsin: That converts proteins and peptone to polypeptides.

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The pancreatic juice which is alkaline, provides an alkaline medium for enzymes. Present also in the pancreas is the
islets of langerhans which secrete two hormones (insulin and glucagon). Insulin is secreted when there is excess
glucose in blood and glucagon is secreted when there is less glucose. The liver secretes a greenish alkaline liquid
called bile. Bile is stored in the gall bladder and helps in the digestion of fat and oil by the process of emulsification
(i.e. breaking down fats into tiny droplets). At the end of digestion in the duodenum, the food called chyle passes to
the ileum (small intestine). Chyle is in liquid form.
The small intestine (ileum) is found between the duodenum and the large intestine. Two key events that takes place in
the small intestine are Digestion and absorption of digested food.
The intestinal wall secretes intestinal juice which contains the following enzymes: lipase, erepsin, maltase, sucrose
and lactase.
Lipase: Converts fat and oil to fatty acid
Erepsin: Converts polypeptides to amino acid
Maltose: Converts maltose to two unit of glucose
Sucrose: Convert sucrose to glucose and fructose
Lactase: Converts lactose to glucose and galactose
In man digestion of food ends in the small intestine.
Absorption of digested food
Absorption of food is defined as the diffusion of digested food through the wall of small intestine(villi) into the blood
stream. The end product of digestion of food (amino acids, glucose, fatty acids and glycerol) are absorbed in the small
intestine by tiny finger-like structures called villi (singular villus).

A villus
Adaptation of small intestine for absorption
The long and coiled nature of the small intestine gives it a large surface area. The presence of folds and furrow
together with the numerous villi found in the small intestine also creates a large surface area for the absorption of
digested food. The inner surface or epithelium of each villus is thin, thus allowing the absorption of the end products
by either diffusion or active transport through it. The glucose and amino acids are easily absorbed by blood capillaries
through the epithelium(containing micro villi) and carried to the liver by the herpatic portal vein. While the fatty acid
and glycerol enters the lacteal where they are carried through the lymph vessels which eventually empty their contents
into the blood vessels near the heart. The blood then carries the fat and other food materials to various parts of the
body where they are needed.

Caecum and Appendix

The functions of caecum and appendix are not well known but the caecum usually contains some bacteria which aid
minor digestion of cellulose. Some vitamin K and B complex are partially synthesized in this region.

Large Intestine: The undigested food are passed into the colon or large intestine. Absorption of water takes place at
this point and this helps to concentrate the waste product into faeces. The faeces is passed into the rectum and
eventually out of the body through the anus.
Example
Which of the following is not an adaptation of the small intestine for absorption of digested food? The
A. villi are well supplied with blood and lymph vessels B. villi are numerous and thin-walled
C. small intestine has large surface area D. small intestine is long and coiled
E. small intestine leads into the large intestine (1989/22)
Answer: E – The small intestine leads into the large intestine is a correct statement, but it is not an adaptation of the
small intestine for absorption of food. All other options (A – D) are adaptation of the small intestine for absorption of
digested food.
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 Example
2(a) Describe the general arrangement of the viscera of a named mammal. (1994/2a)
Answer: The general arrangement of the Viscera of Rat – The general arrangement of the viscera of rat reveals
that the diaphragm divides the trunk into two unequal parts, these are; the upper thoracic cavity and the lower
abdominal cavity. The thoracic cavity is enclosed by the ribs inside which the heart and the lungs are situated. The
gullet runs down behind the buccal cavity through the whole length of the thoracic cavity. The liver lies below the
diaphragm which overlaps a large portion of the stomach. The stomach leads to the small intestine, the small intestine
leads to the large intestine which form the caecum at one end and continues to form the rectum at the other end which
finally terminates at the anus. Very close to the stomach are the pancreas and spleen. A pair of kidneys are situated at
the posterior portion of the abdominal cavity. In male, the male part of the vas deferens is seen at the posterior region
in close position with the bladder and ureter. In female, ovaries lie near the kidney and the oviducts lead to the uterus
which is in the lower part of the abdominal cavity.
Note: viscera means the internal organs in the main cavity of the body; though in this question, this diagram is not required

Internal organs of a rat

Example
(b) Describe the role of the following in mammalian nutrition: (i) teeth; (ii) tongue; (iii) saliva (iv) stomach (1995/1b)
Answer:
i. Teeth: These help to break large food particles into smaller ones before swallowing.
ii. Tongue: It helps to roll the food in the mouth into bolus and allows the food to mix with saliva.
iii. Saliva: It helps in moistening the food and allows for easy swallowing.
iv. Stomach: It helps to hold food while the food is being mixed with enzymes that are found in the stomach.

Example
The pancreatic duct opens into the
A. caecum B. colon C. ileum D. duodenum E. oesophagus (1998/37)
Answer: D – The pancreatic duct opens into the duodenum.
Example
(c) Describe the role of pancreatic juice in the digestion of carbohydrates and proteins in a mammal.
(d) In what form is carbohydrate stored in (i) animals (ii) plants
(e) Describe the saprophytic nutrition of Rhizopus (2005/3c-e)
Answer:
c. The pancreatic juice provide the alkaline medium for the enzymes which it contains. These enzyme operate in
the duodenum. The enzymes are amylase – this converts carbohydrate to maltose; and trypsin – this converts
protein to peptone or polypeptide.
di. Carbohydrate is stored in animals as glycogen.
ii. Carbohydrate is stored in plant as starch.

e. Rhizopus is found growing on dead and decaying organic matter. It secretes enzymes which digest the organic
compounds present in the dead and decaying matter. After these compounds are digested extra-cellularly, it absorb the
products into the hypha through the cell wall.

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Example
2(a) Describe briefly the role of stomach in digestion (2012/2a)
Answer: The stomach helps to hold food; during the time of holding food, it secretes enzymes that help to digest food.
Example
The function of the villi in the alimentary canal is to
A. secrete gastric juice B. curdle milk C. emulsify fat D. increase the surface area for absorption (2016/25)
Answer: D – The function of the villi is to increase the area of absorption.
Example
Which of the following structures is not an organ of the digestive system?
A. Oesophagus B. Pancreas C. Stomach D. Kidney (2016/26)
Answer: D – The kidney is an excretory organ and not a digestive organ .
Example
2(a) In sequence, name the organs that constitute the alimentary canal of humans
(b) State: (i) three structural differences;
(ii) three structural similarities between the alimentary canal of a bird and human.
(d) State two roles of the pancreas in digestion. (2016/2a, c, d)
Answer:
2a. Organs that constitute the alimentary canal of humans: bii. - They both have mouth.
- Mouth or buccal cavity - They both have oesophagus.
- Oesophagus or gullet - They both have stomach.
- Stomach
- Duodenum d. - It produces pancreatic amylase which
- Ileum or jejunum or small intestine converts starch to maltose.
- Caecum or colon or large intestine - It produces trypsin which converts
- Rectum protein to peptone or polypeptones.

bi. Bird Human

- Beak present Beak absent
- Teeth is absent Teeth is present
- Crop is present Crop is absent

Example
(c) (i) Describe what happens to a meal of bread and fried egg from the mouth to the stomach of man. (1996/1ci Nov)
Answer: In the mouth, saliva adds moisture, while the teeth tear and grind the bread and friend egg into small pieces.
The saliva contains the enzyme amylase which breaks down the starch present in the food. The tongue helps to roll the
food into small ball called bolus which is then swallowed. The swallowed food passes through the oesophagus and
enters into the stomach. In the stomach, the food is mixed with enzymes found in the stomach. There enzymes found
in the stomach, break down the protein contents of the food before passing it on to the duodenum.
Example
(d) List four disorders of the alimentary canal of humans. (2013/3d Nov)
Answer: Peptic ulcer, Gastritis , Constipation and Gastroenteritis

Example

Use the diagram below to Answer: questions 25-27

The part labeled I in the diagram is called
A. bile duct B. duodenum C. gall bladder D. liver E. sphincter (2005/25 Neco Nov)
Answer: C – The part labeled I is the gall bladder.
Example
Which of the labeled parts secretes the hormone that converts excess glucose to glycogen?
A. I B. II C. III D. IV E. V (2005/26 Neco Nov)
Answer: E – The part labeled V is the pancreas which secretes insulin that convert excess glucose to glycogen.
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Example
Villi are finger-like structures found in the
A. large intestine B. rectum C. small intestine D. stomach E. tongue (2018/24 Neco)
Answer: C – Villi are finger-like projections/structures found in the small intestine.
Example
The enzyme pepsin acts in the
A. Large intestine B. mouth C. oesophagus D. small intestine E. stomach (2005/42 Neco)
Answer: E – Pepsin acts in the stomach.
Example
(c) State two functions of each of the following parts of the digestive system: i. Mouth ii. Stomach iii. Duodenum (2008/1c Neco)
Answer:
i. Mouth: The mouth houses the teeth, tongue and salivary glands which play important roles in digestion.
ii. Stomach: Helps to hold food and mix the food with the enzyme that are found in it.
iii. Duodenum: It receives secreted enzymes from the pancreas. It also receives partially digested food from the stomach.
Example
Which of the following systems in the body is associated with peristalsis?
A. digestive system B. respiratory system C. circulatory system D. locomotory system (2013/33 Nov)
Answer: A – Peristalsis is the contraction of muscle tissue that helps to move food particles down the gut. Peristalsis
is also associated with digestion.

Example
(c) State three functions each of the following structures during digestion:
(i) Pancreas (ii) Salivary gland (2000/2c Nov)
Answer:
i. Pancreas:
- Produces amylase which converts starch to maltose.
- Produces lipase which converts fats and oil to fatty acid and glycerol.
- Produces trypsin which converts protein to peptones or polypeptide.
ii. Salivary gland Secrete saliva that:
- Moisturizes food in the mouth.
- Contain amylase that breaks down starch to maltose.
- Helps to lubricate the passage way of food.
Example
Which of the following is the correct sequence in protein digestion?
A. amino acids→peptones→proteins B. proteins→amino acids→peptones
C. peptones→proteins→amino acids D. proteins→peptones→amino acids (2006/30 Nov)
Answer: D. Proteins→peptones→amino acid is the correct sequence in protein digestion.
Example
At the end of digestion, food nutrients are absorbed into the ileum in the following forms except
A. starch as glucose B. protein as amino acids
C. fat as fatty acids and glycerol D. roughage as cellulose (2006/33 Nov)
Answer: D – Roughage is not broken down neither is it absorb in the small intestine. It forms the bulk of faeces.
Example
Which of the following statements is correct about peristalsis? It
A. is a voluntary action B. is an involuntary action
C. is a conditioned reflex action D. occurs only in humans (2005/25 Nov)
Answer: B – Peristalsis is an involuntary constriction and relaxation of the muscles of the gut, that creates a wave-like
movements which push the contents of the gut downward. It occurs in both humans and other animals.
Example
Which of the following organs produces bile in humans?
A. Spleen B. liver C. stomach D. pancreas (2002/32 Nov)
Answer: B – Bile is produced in the liver and stored in the gall bladder.
Example
Which of the following is a function of bile?
A. digests lipids B. break down starch C. reduces the acidity in the chyme
D. stops the action of the acid in the duodenum E. accelerates hydrolysis of water in cells (1998/32 Health Science Nov)
Answer: A – Bile helps to break down fat

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EXERCISE 7.5
1. Emulsification of fat is the
A. digestion of fat into glycerol B. conversion of glycerol into energy
C. breakdown of fat into small globules D. conversion of fat into a form which can be absorbed
E. assimilation of digested fat (1990/4 Health Science Nov)
2. In man, carbohydrates is stored in the liver as
A. starch B. amino acid C. sugar D. glycogen E. cellulose (1990/20 Health Science)
3. Digested fats reach the blood stream through the
A. walls of the stomach B. islets of Langerhans C. capillaries of the villi
D. walls of large intestine E. lacteals of the lymphatic system (1990/21 Health Science)
4. The chemical breakdown of food substances into soluble forms which are easily absorbed into the blood stream is known
as
A. absorption B. peristalsis C. digestion D. assimilation E. ingestion (1990/22 Health Science)
Study the list below and use it to Answer: questions 11 to 13
I - Mouth IV - Ileum
II - Oesophagus V - Stomach
III - Rectum VI - Duodenum
5. The correct path taken by a piece of meat passing through the alimentary canal is
A. I → II → IV → V → VI → III B. I → II → V → VI → IV → III
C. I → III → II → IV → V → VI D. I → II → IV → III → V → VI (2003/11 Health Science Nov)
6. In which of the structures does absorption of digested food take place?
A. I B. II C. III D. IV (2003/12 Health Science Nov)
7. The pyloric sphincter is located between
A. V and VI B. II and V C. III and IV D. I and II (2003/13 Health Science Nov)
8. Which of the following organs produces bile?
A. Gall bladder B. Pancreas C. Spleen D. Liver E. Stomach (1980/9 JAMB)
9. Which of the following food substances is digested in the stomach?
A. Carbohydrates B. Fats and oils C. Fats and proteins
D. Proteins E. Carbohydrates and fats (1980/15 JAMB)
10. The removal of a man pancreas by surgical operation can affect only the digestion of
A. starch B. starch, protein and fats C. oils and fats
D. proteins E. carbohydrates and fats (1984/22 JAMB)
11. Partially digested food ready to leave the stomach is referred to as
A. chyme B. curd C. glycogen D. paste E. roughage (1985/17 JAMB)
12. The three important organs that are situated close to the stomach are
A. kidney, liver and gall bladder B. pancreas, liver and kidney
C. liver, kidney and spleen D. gall bladder, pancreas and spleen (1986/21 JAMB)
13. If the gall bladder of a mammal is damaged, which of the following will be most seriously affected?
A. Glycolysis B. Digestion of starch
C. Digestion of fats and oils D. Digestion of proteins (1988/19 JAMB)
14. Which of the following will be first digested if ingested at the same time?
A. Cooked beans B. Cooked rice C. Cod liver oil D. Roasted beef (1988/20 JAMB)
15. The villus in the small intestine is significant because it
A. increases the surface area for absorption B. increases the surface area for digestion
C. assists in mixing digested food D. assists in filtering undigested food (1990/21 JAMB)

16. In which of the following organisms would glycogen be stored?

A. Spirogyra B. Chlamydomonas C. Rattus D. Magnifera (1993/6 JAMB)
17. The organ located within the duodenal loop in the mammal is the
A. liver B. gall bladder C. pancreas D. spleen (2002/17 JAMB)
18. The part of the human gut that has an acidic content is the
A. stomach B. duodenum C. ileum D. colon (2010/26 JAMB)
19. One of the accessory organs of the digestive system is the
A. kidney B. spleen C. liver D. lung (2019/14 JAMB)
20. In the alimentary system of a bird, the function of teeth is carried out by the
A. crop B. beak C. gizzard D. tongue (2008/18 JAMB)
21. Make a diagram 8cm_10cm long of a longitudinal section of a villus and label fully. (2014/2c)
22. Make a diagram 8 – 10cm long to show the relative position of the following organs in the mammalian gut: (i) stomach
(ii) pancreas (iii) liver (iv) gall bladder (v) duodenum and label fully (2011/2a)
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TRANSPORT SYSTEM
Transport system
Living cells are always surrounded by a watery environment (tissue fluid). Materials flow between the cell and its
environment mainly by diffusion and osmosis.
Diffusion is defined as the process by which molecules of substances move from a region of higher concentration to a
region of lower concentration of the molecules. Diffusion occurs through gases, liquid and solids but the rate of
diffusion of molecules through gases, liquid and solids varies. Molecules in gaseous state diffuse faster than those in
liquid, while those in liquid state diffuse faster than those in solid state.
Osmosis is the movement of water molecules from a dilute solution into a concentrated solution through a semi –
permeable membrane. It is also defined as the movement of water molecules from a low osmotic concentration
through a semi – permeable membrane.

Need for transportation

In small or unicellular organism such as amoeba or paramecium, substances can move to all parts of the body by
diffusion because of:
(i) The small size of their body
(ii) The short distances moved by materials.
(iii) The surface area to volume ratio is large.
But in a large organism such as a human being, the surface area to volume ratio is small and the materials have to
move long distances therefore, there is need for a transport system.
When we talk about transport, we are talking about movement of substances. The transport system is responsible for
the movement of food and oxygen to all tissues, expulsion of waste products of metabolism and movement of
hormones from ductless glands to target organs. In the transport system, materials are usually dissolved in liquid form
before they are carried.

Example
In unicellular organisms, essential nutrients can be transported directly to all parts of their body by the process of
diffusion only because unicellular organisms have
A. a large surface area to volume ratio B. a large volume to surface area ratio C. permeable cell membrane
D. outer membrane made of cellulose E. their body always immersed in the nutrient material (1988/2)
Answer: A – Unicellular organisms have large surface area to volume ratio, hence they have the ability to transport
nutrient and other substances directly throughout their body by simple diffusion.
Example
Which of the following explains the need for transport system in large mammals?
A. The area to volume ratio in large animals is high
B. The area to volume ratio diminishes with large size
C. Diffusion as an adequate means of transport is lacking
D. Large animal have internal fluid which contains different types of cells
E. Large animals have four-chambered heart. (1992/13)
Answer: B – Large mammals have very small surface area to volume ratio, hence the need for transport system.

Example
One major difference between osmosis and diffusion is that diffusion
A. does not need a semi-permeable membrane B. does not take place in living tissues
C. takes place only in a liquid medium D. takes place membrane
E. cannot be demonstrated experimentally (1998/3)
Answer: A – Diffusion does not require a semi-permeable membrane before it can occur but osmosis does.
Example
Which of the following statements is incorrect about diffusion?
A. It involves degradation of soluble particles in solvents B. It occurs mainly in gaseous and liquid media
C. No membrane is needed to effect the movement of molecules
D. Molecules move from region of lower concentration to that of higher concentration (2000/9)
Answer: D – In diffusion, molecules move from a region of higher concentration to a region of lower concentration,
hence option D is incorrect.

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Example
Which of the following organisms has the largest surface area-to-volume ratio?
A. Man B. Earthworm C. Amoeba D. Grasshopper (2000/12)
Answer: C – Amoeba is the smallest of all the organisms mentioned in the option; hence it has the largest surface area
to volume ratio. NB: Surface area to volume ratio decreases with increase in size of organism.
Example
Diffusion is most effective in living organisms, when the surface area is
A. large and the thickness is also large B. Small while the thickness is large
C. large while the thickness is small D. the same as it thickness (2002/12)
Answer: C – Diffusion will be most effective in organisms whose surface area is large and thickness is small.
Example
Which of the following processes involves diffusion?
A. Opening and closing of the stomata pores B. Turgidity of herbaceous plants
C. Absorption of water through the root hairs D. Absorption of digested food into the villi (2010/7)
Answer: D – Absorption of digested food into the villi is done by diffusion. All other options (A to C) are carried out
by osmosis.
Example
(c) What role do the following processes play in the activities of a living cell: (i) osmosis; (ii) diffusion? (1988/1c)
Answer:
i. Osmosis:
- It helps to transport water from one cell to another.
- It helps to transport substance dissolved in water from one cell to another.
- Plant cells absorb water from the ground through the root by osmosis.
ii. Diffusion:
- It helps in the exchange of gases between cells and their environment.
- It helps in the transport of chemical substances from one cell to another.
Example
An example of osmosis in plants is the
A. movement of water through the xylem B. loss of water vapour from the stomata
C. translocation of food through the phloem D. absorption of water from the soil by the root (2017/6)
Answer: D – Absorption of water from the soil by the root is done by the process of osmosis.

EXERCISE 8.1
1. The following are factors that affect the rate of diffusion EXCEPT
A. the state of matter B. the size of molecules C. temperature D. light (2001/12 NABTEB)
2. (b)i. Define Osmosis (2001/3b NABTEB)
3. The major difference between osmosis and diffusion is that in osmosis
A. cells take up nutrients and water B. oxygen and water move from one part of the organism to another
C. carbon dioxide and water are eliminated from the organism
D. water moves through the cell membrane (2011/6 Nov)
4. The movement of substances by diffusion stops when
A. there is uniformity in the concentration gradient B. there is high temperature
C. the concentration gradient is higher on one side D. the molecular size is large (2019/8 Nov)
5. Unicellular organisms transport essential nutrients directly to all parts of their bodies by the process of
diffusion because they have
A. a large volume to surface area ratio B. a large surface area to volume ratio
C. their bodies immersed in the nutrients D. their outer membrane made of cellulose (1998/16 JAMB)

133
Materials for transportation
The materials transported in living organisms include water, digested foods, gases, excretory products, hormones,
auxins and other materials such as vitamins, antibodies e.t.c.
Excretory products: Excretory products are produced in body cells by respiration except urea which is produced
during deamination in liver. They are carried in solution in blood and they are carried to the lungs, kidney, skin and
liver.
Gas: is taken in from air through respiratory surface and all cells of the body.
Food materials: Food materials are digested in the intestine and are carried by lymphatic and blood system to all cell
of the body.
Hormones: are produced by endocrine glands and carried in lymphatic and blood system to target organs or tissues.
Anti – bodies: Antibodies are produced in white blood corpuscles and are carried in true or colloidal solution in blood
to all parts of the body.
Media of transportation
In living things there is a life long process of continuous exchange of materials within the cells in the body and
between the entire organism and the environment. Exchange of these materials is through some media.
The media of transportation in living things are:
Cytoplasm, Body fluid ,Blood and lymph ,Cell sap, Latex and Water
Cytoplasm in cells: The environment (habitat) of unicellular plants and animals is majorly aquatic and as such, their
bodies are constantly bathed by the water present in this Habitat. Dissolved oxygen and nutrients present in this water
enter into the cells of this organism by diffusion. Upon entering the cells, these substances are transported to all parts
of the cell by the process of “cytoplasmic streaming”. Waste products of metabolism also leave the cells by simple
diffusion. Example of some unicellular organisms that use this medium of cytoplasmic streaming includes amoeba,
paramecium and euglena.
Body fluid in the invertebrate
The body fluids of invertebrates, serve as their medium of transport. This body fluid which bathes various cells of the
invertebrate body as it flows, transports food, oxygen and waste product of metabolism to their respective destination.
In the invertebrates, excretory organs lie in the coelom and are bathed by the body fluid called coelomic fluid.
Note: Open circulatory system might be found in some invertebrate like insects and mollusks. In open circulatory
system, blood flows freely through cavities since there are no vessels to conduct the blood. A typical example is found
in the insects where blood flow is only in one direction into space called haemocoels which are found in the body
cavity.
Blood and lymph
Blood and lymph are important media of transportation in the higher animals. Blood moves through blood vessels like
the artery, veins and capillaries while lymph moves through the lymphatic vessels. An example of a lymphatic vessels
is the lacteal which transports fatty acids and glycerol. Lymph nodes which produce white blood cells are found at
some certain point in the lymphatic vessels. Lymph has no red blood cell.
Cell sap or latex
Plants use either the cell sap or latex as their transport medium. The solution present in cell sap of plants is usually
concentrated than the incoming solution and the concentration of cell sap in the upper part of plant is greater than that
below. This concentration difference enables the cell sap to serve as transport media in plants.
Latex which is an excretory product in some plants contains fluids. It is also used as a transport medium.
Transport in man
Transport system in man comprises of
1. A circulatory fluid (blood)
2. A pumping organ (the heart) and
3. A system of closed vessels (arteries, veins and capillaries)

Example
The medium in which dissolved nutrients are transported in the body of vertebrates is called
A. latex B. urine C. cell sap D. blood E. haemoglobin (1992/19)
Answer: D – The blood is the medium of transport in vertebrates. NB: Cell sap and latex are media of transport in plants.
Example
Which of the following is the medium of transportation of nutrients within unicellular organisms?
A. Blood B. Serum C. Protoplasm D. Plasma E. Lymph (1993/10)
Answer: C – The protoplasm consists of the cytoplasm and the nucleus. The cytoplasm is the medium of transport in
unicellular organisms.
134
Example
(c) List four materials transported in the bodies of flowering plants. (2005/1c)
Answer: Water, sugar, mineral salt and amino acids.

EXERCISE 8.2
1. The medium of transportation in higher plants is
A. Cell sap B. cytoplasmic fluid C. phloem D. water E. xylem (2005/41 Neco)
2. Transportation media in organisms do not include
A. Latex B. cytoplasm C. synovial fluid D. cell sap E. blood (1996/12 Nov)
3. Which of the following is not a medium of transportation in living organisms?
A. Cytoplasm B. Cell sap C. Bones D. Lymph E. Blood (1997/8 Nov)

The mammalian blood

Blood is a fluid tissue made up of about 55% fluid called plasma and 45% cells. The cells/corpuscles includes:
1. Red blood cells (erythrocytes)
2. White blood cells (leucocytes)
3. Platelets (thrombocytes)

The plasma: The plasma consists of about 90% water, and 10% of dissolved substance which includes: glucose,
amino acid, carbon (IV) oxide salts, blood protein such as albumens, globulins and fibrinogen, hormones, antibodies
and excretory waste products. It is the fluid portion of the blood.
Function: It transport the substances that are dissolved in it as well as the cell that float in it.

Red blood cells (Erythrocytes)

The red blood cells (erythrocytes) are very small in size but numerous in quantity. They are disc shaped and have an
elastic nature.

Red blood cell

One cubic litre of blood has about 4.2-5 million red blood cells. They lack nucleus and have a normal life span of
about 120 days (4 months) before they are destroyed by the liver. The erythrocytes is produced in the bone marrow of
long bones. The red colour of the cells is due to the presence of iron compound called haemoglobin.
Functions
Haemoglobin in the red blood cells transport oxygen from the lungs to the body cells. Haemogobin combines readily
with oxygen to form oxy-haemoglobin in the lungs.

White blood corpuscles (Leucocytes)

White blood cells (leucocytes) are larger in size that red blood cells. They are amoeboid in shape, non elastic,

White blood cells

colourless and nucleated (contain nucleus). They are larger than red blood cells in diameter but fewer in numbers than
the red blood cells (about 4,300-10,800) They are made in the red bone marrow, the lymph nodes or the spleen. They
lack haemoglobin pigment and do not carry oxygen. They are capable of living for months

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There are three major types of white cells.
1. Granulocytes: These are phagocytes i.e they are able to ingest foreign cells such as bacteria, viruses and other
parasites. They are found in the lymphatic system and are account for 60% of the entire white blood cell. The
process of ingestion of foreign substances is known as phagocytosis. The three form of granulocytes are the
neutrophils, eosinophils and basophils.
2. Lymphocytes: The lymphocytes produce antibodies and are made in the lymph glands. They help to regulate
the body’s immune system.
3. Monocytes: These are produced in the bone marrow. They develop into macrophages which are also
phagocytic.
Note: Lymphocytes and monocytes are both agranular (they lack cytoplasmic granules) while the granulocytes are granular.
Functions
The white blood cells defend the body against disease by ingesting the bacteria and virus that cause various diseases.

Blood platelets (Thrombocytes)

The blood platelet are tiny, irregular cell fragments which lack nucleus. They are formed in the bone marrow. Platelets
are few in number and smaller in size than the red blood cell. They contain thromboplastin which aid blood clotting.

Blood platelets
Functions: Platelets enable clotting of blood.
Note: In some persons, blood doesn’t clot easily, this condition is referred to as haemophilia. Haemophilia is a hereditary disease
which is sex-linked. Females are the carriers. Individual with this disease lacks the enzyme thrombokinase.

Lymph
Lymph is a clear and colourless fluid which flows in one direction along lymphatic vessels by the action of the body
muscles. The lymphatic vessels connect to the subclavian vein located on either side of the neck. Some swellings
which resemble the shape of a bean do exist in groups along the lymph vessels especially in the neck, groin and armpit
and are called lymph nodes.
The lymphatic system is second to the circulatory system but it ends blindly.
Functions of lymph
1. Body defence.
2. Absorption of fatty acids and glycerol: The lymphatic system such as the lacteal is associated with the
absorption of fatty acids and glycerol.

Functions of blood
The blood carries out some important functions, it is the transport medium which carries various substances from one
part of the body to another. It also protects the body against disease causing micro – organism and also helps in
regulating body temperature. The function of the blood is described below under three major aspects:
a. Transport of substances
I. Oxygen from the lung is transported by the red corpuscles in form of oxy-haemoglobin to living body cells
where it is used for respiration. Carbon dioxide produced in the respiring body cells is carried by the red
corpuscles to the lungs where it is excreted.
II. Digested food substances like amino acids, glucose, fatty acids and glycerol are carried from the ileum to
body tissues for use or storage.
III. Hormones are carried in the blood from the ductless or endocrine glands, where they are produced to organs
or tissues which they affect.

b. Body protection
IV. The blood defends the body against the attack of pathogen. Thus, the phagocytes destroy any invading germs
and poisonous material while the lymphocytes produce antibodies which render foreign bodies in the blood
harmless.
V. The blood protects the body from too much bleeding by clotting (coagulation) whenever minor cuts and
wounds occur.

c. Body regulation
VI. For body temperature regulation, the blood distributes heat produced by the liver and muscles throughout the
body. While excess heat is lost mainly through the skin.
VII. The blood keeps constant the amount of water and mineral salts in the body (osmoregulation).
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Blood group
The blood group in man is determined by the presence or absence of two substances known as antigens and
antibodies. Antibodies are proteins found in plasma, they are part of the body’s natural defense system. They help to
recognize the presence of foreign substances such as germs and alert the immune system which destroys them.
Antigens are proteins molecules found on the surface of red blood cells. In human, there are four types of blood group,
these are: A, B, AB and O.

Blood group Substance on cell Substance in plasma

A Antigen A Antibody B
B Antigen B Antibody A
AB Antigen A and B No antibody
O No antigen Antibody A and B

In blood transfusion, the effect of the recipient’s plasma on the donors erythrocytes is considered. The plasma of the
donor is usually too small to have any effect on the recipient’s erythrocytes. Agglutination which is the clumping
together of antigens with the corresponding antibodies in the plasma of incompatible blood group will occur if blood
transfusion is not done appropriately (using a compatible blood group).

Blood group compatibility

Recipient blood Antibodies present in Donor’s blood group
group plasma A B AB O
A B  × × 
B A ×  × 
AB None    
O A and B × × × 
= compatible
× = not compatible

Example
Which of the following blood components has the greatest affinity for oxygen and carbondioxide?
A. blood plasma B. leucocytes C. thrombocytes D. erythrocytes E. lymphocytes (1988/12)
Answer: D – Erythrocytes (red blood cells) contain haemoglobin which has high affinity for oxygen and
carbon(iv)oxide and helps in their transportation.
Example
Blood in mammals transports oxygen because it contains the pigment called
A. haemoglobin B. chlorocruorin C. melanin D. haemocyanin E. haemoerythrin (1989/6)
Answer: A – Haemoglobin is a pigment that gives the red blood cell it red colouration. It helps in the transportation of oxygen.
Example
Thrombocytes are blood cells responsible for initiating
A. phagocytosis of bacteria B. synthesis of ribosomes C. clotting of the blood
D. immunity to certain infectious diseases E. removal of carbondioxide from tissues (1990/51)
Answer: C – Thrombocytes (blood platelets) helps in blood clotting.
Example
Which of the following is not correct about blood platelets? They
A. are also known as thrombocytes B. have no nucleus C. are formed in the red bone marrow
D. neutralize the toxins in the blood E. help in clotting of blood (1992/15)
Answer: D – Blood platelets helps in clotting process of the blood.
NB: Neutralization of toxins in the blood is carried out by the white blood cells (leucocytes).
Example
Which of the following blood group(s) is/are the universal donor(s)?
A. O B. A C. B D. AB E. AB and O (1994/16)
Answer: A – Blood group O is the universal donor, i.e. it can donate blood to individual of all other group groups.
NB: Blood AB group is the universal acceptor, i.e. it can accept blood from individuals of other blood groups.
Example
The function of the human red blood cells is to
A. make antibodies B. carry oxygen C. absorb heat D. destroy bacteria. (2003/12)
Answer: B – The red blood cells helps to transport oxygen across the body tissues.

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Example
Which of the following constitutes the cellular components of the mammalian blood?
I. haemoglobin II. Erythrocytes III. Leucocytes IV. Platelets
A. I, II and III only B. I, III and IV only C. II, III and IV only D. I, II, III and IV (2003/14)
Answer: C – Erythrocytes (red blood cells), leucocytes (white blood cells) and platelets (thrombocytes) are the
cellular components of the blood.
Example
Which of the following is more concentrated to the blood within the renal artery that the blood within the renal vein?
A. Urea B. Red blood cells C. Glucose D. Protein E. White blood cells (1996/13)
Answer: A – Urea is excreted through the kidneys. Renal artery carries blood containing high concentration of urea
into the kidney which extracts it out of the blood and expels it through urine. The renal vein carries blood that has less
concentration of urea.
Example
Which of the following is not a function of the blood?
A. Maintenance of body temperature B. Formation of clot C. Distribution of bile
D. Transportation of excretory materials E. Distribution of hormones (1998/10)
Answer: C – Bile is no transported by the blood; but rather it is secreted directly into the digestive tract by the gall
bladder. All other options (A, B, D and E) are transported by the blood.
Example
A major reason why the red blood cells can survive in the blood is that the
A. blood plasma and the red blood cells are isotonic B. red blood cells are hypotonic to the plasma
C. the red blood cells are hypotonic to the plasma D. the red blood cells receive digested nutrients. (2001/8)
Answer: A – The red blood cells can survive in the blood because they are isotonic with the blood plasma, i.e. the
solute concentration in the blood plasma and the cytoplasm of the red blood cells are the same.
Example
Which of the following statements is true about blood groupings?
A. Group AB can donate to all other groups B. Group O are universal recipients
C. Group A has A antigen in its plasma D. Group O has no antigen (2001/15)
Answer: D – Blood group O has no antigen; hence individual with blood group O can transfer blood to individuals of
all other blood groups. They are known as universal donor.
Example
Which of the following is not a constituent of blood plasma?
A. Proteins B. Mineral salts C. Water D. Platelets (2001/16)
Answer: D – Platelets are among the cellular component of the blood. All other options (A to C) are components of the plasma.
Example
3(a) List the main constituent of mammalian blood (b) State two functions of each constituent (2002/3a, b)
Answer:
a. Cellular component and Plasma
b. Cellular component: Plasma:
- Helps to transport oxygen. - Help to transport waste.
- Helps in blood clothing. - Serve as a medium to transport the cellular component.

Example
The hepatic portal vein is often heavily loaded with food-nutrients because it carries blood
A. directly from the heart B. from the liver to the heart
C. from the small intestine to the liver D. from the liver to join the posterior vena cava (2004/13)
Answer: C – The hepatic portal vein carries blood from the small intestine to the liver.
NB: The hepatic portal vein is the only vein that starts and ends in capillaries.
Example
(b) State eight functions of blood in mammals. (2005/1b)
Answer:
- Helps to transport oxygen from the lungs to the other parts of the body.
- Helps to transport carbon(iv)oxide from the body tissues to the lungs.
- Helps to transport digested food from the small intestine to other parts of the body.
- Helps to transport hormones from one part of the body to another.
- Defends the body against attack of pathogens.
- Protects the body from too much bleeding by clotting whenever minor cut and wounds occur.
- Regulates body temperature.
- Helps in osmoregulation.
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Example
Which of these statements about white blood cells is true? They
A. aid clotting of blood B. carry oxygen round the body
C. are the most numerous blood cells D. are large nucleated cells (2007/13)
Answer: D – White blood cells are large and nucleated.
NB: Mature red blood cells have no nucleus. Blood platelet have no nucleus.
Example
A person with blood group O can be given blood from persons who have blood belonging to
A. group O only B. group A only C. groups A and O D. groups A, B and O (2010/47)
Answer: A – Individuals of blood group O can only receive blood from individuals of blood group O. But these
individuals can transfer blood to individuals of all other blood groups.
Example
Which of the following statements is true about ABO blood group system?
A. Antigens are located on the surface of white blood cells B. Antibodies are located in the blood plasma
C. Antibodies are located on the surface of red blood cells D. Antigens are located in the blood plasma (2012/51)
Answer: B – Antibodies are located in blood plasma.
NB: Antigens are found attached to the surface of red blood cells.
Example
(d) State the features of red blood cells and how these features adapt the cell to perform its function. (2012/1d)
Answer:
- They contain haemoglobin which combines with oxygen.
- They lack nucleus; this makes them have more space for haemoglobin.
- They are small and elastic. This enables them to move through narrow openings.
Example
Individuals with blood group AB can donate blood to individuals with blood group(s)
A. A and B B. A and O C. AB only D. O only. (2019/42)
Answer: C – Individuals of blood group AB can only donate blood to individual in the same blood group.
Example
The defective cells involved in sickle-cell anaemia disease are
A. phagocytes B. lymphocytes C. erythrocytes D. thrombocytes (2008/51)
Answer: C – Sickle cell anaemia results when the erythrocytes (red blood cells) are not properly shaped; i.e. the
appear sickled-shaped.
Example
Which of the following is NOT a function of the blood?
A. the red blood cell produce antibodies
B. the white blood ingest and destroy harmful micro-organism that enter the body
C. blood is a medium of transportation D. blood distribute heat to all parts of the body (1999/37 NABTEB)
Answer: A – The red blood cell don’t produce antibodies.
Example
Agglutination occurs in blood transfusion when the
A. donor and the recipient belong to the same blood group B. donor and the recipient belong to different races
C. antigens and antibodies in the donor and the recipient react
D. same antibodies from donor and recipient fuse together. (2018/29 NABTEB)
Answer: C – Agglutination will occur when antigens and antibodies of donor and the recipient react.
NB: Whenever same antigen and antibodies come together, agglutination will occur. E.g. Antigen A + Antibody A =
Agglutination, Antigen B+ Antibody B = Agglutination.
- Individuals of blood group A, have A- antigens and B- antibodies.
- Individuals of blood group B have B- antigens and A- antibodies.
- Individual of blood group AB have A and B- antigens but lack antibodies.
- Individuals of blood group O have no antigens but have A and B- antibodies.
- Antibodies are found moving freely in the blood plasma.
- In blood transfusion, the blood plasma of the donor has no effect on the recipient.

Example
Haemorrhage is caused due to the deficiency of vitamin
A. A B. C C. D D. E E. K (2018/51 Neco)
Answer: E – Vitamin K helps in blood clotting.

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Example
The part of the blood responsible for clotting is called
A. erythrocytes B. lymphocytes C. monocytes D. phagocytes E. thrombocytes (2005/9 Neco Nov)
Answer: E – The thrombocyte (blood platelet) is responsible for blood clothing.
Example
Which of the following best explains why blood group AB individuals are universal recipients?
A. They have b antigens in their blood B. There is no agglutination when their blood is transfused
C. They have both A and B antibodies in their blood D. Their antigens do not react chemically
E. They lack antibodies in their blood (1990/24 Health Science Nov)
Answer: E – Individuals with blood group AB have no antibodies in their blood plasma, hence they can receive blood
from any other blood group individuals.
Example
The oxygen-carrying capacity of the blood is enhanced by the
A. volume of oxygen which can dissolve in plasma B. hemoglobin which can combine with oxygen
C. red blood corpuscles which have short life span D. volume of oxygen present in the lungs
E. number of white blood cells in the blood (1990/25 Health Science Nov)
Answer: B – The oxygen carry capacity of the blood is enhanced by the number of haemoglobin that can combine with oxygen.
Example
The formation of antibody is associated with
A. thrombin B. vitamin K C. white blood cells D. fibrinogen E. serum (1990/27 Health Science Nov)
Answer: C – White blood cells are responsible for the production of antibodies.
Example
Platelets are associated with
A. clotting mechanism B. phagocytic activity C. formation of antibodies
D. oxygen transport E. detoxication (1990/29 Health Science Nov)
Answer: A – The platelets help in blood clotting.
Example
Which of the following blood groups is a universal recipient?
A. A B. B C. AB D. O E. AO (2007/41 Neco)
Answer: C – Individuals with blood group AB are universal recipients.
Example
Which component of the blood transports digested food materials?
A. Blood plasma B. platelets C. erythrocytes D. Leucocytes E. lymphocytes (1996/11 Nov)
Answer: A – Blood plasma helps in the transport of digested food materials.
Example
Which of the following statements is not correct about the lymph? It
A. contains red blood cells and platelets B. is transported in vessels C. helps to transport oxygen and food
D. contains white blood c and platelets E. is in continuous circulation in the body (1997/7 Nov)
Answer: A – The lymph contains all blood components except the red blood cells.
Example
b. Write short notes on the following terms: i. Transpiration – pull ii. Diffusion (1999/3b Nov)
Answer:
i. Transpiration pull is a biological process in which the force of pull is produced inside the xylem tissue. This
force helps in the upward movement of water into the xylem vessels, the water is transported to the leaves
where it is lost as vapour through the process of transpiration.
ii. Diffusion is the movement of fluid (gas or liquid) from a region of high concentration to a region of low
concentration until equilibrium is reached.

EXERCISE 8.3
1. Which of the following substances are removed from the blood by all cells?
A. metabolic waste and digested food B. Water and toxins C. water and oxygen
D. digested food and hormones E. Carbon dioxide and metabolic waste (1998/11 Nov)
2. Which of the following occurs when there is a fresh wound in the mammalian skin?
A. Blood cease to reach the cut surface
B. More white blood cells are produced to prevent the entry of disease causing bacteria
C. Fibrinogen is converted to fibrin which traps blood cells and prevent loss of blood
D. Haemoglobin reacts with the atmospheric oxygen to form oxyhaemoglobin
E. Lymph reacts with atmospheric carbon dioxide to form lymphocytes (1998/12 Nov)
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3. Red blood cells are manufactured in the
A. spleen B. lacteals C. pancreas D. cartilage E. bone marrow (1996/3 Health Science Nov)
4. The red blood cell is also called
A. phagocyte B. thrombocyte C. lymphocyte D. erythrocyte E. fibrinogen (1996/4 Health Science Nov)
5. Which of the following systems function as intermediary between the blood and the tissue cells?
A. Nervous system B. Skeletal system C. Excretory system
D. Lymphatic system E. Digestive system (1996/5 Health Science Nov)
6. Failure of the blood to clot is called
A. leukemia B. septicaemia C. anaemia D. haemorrhage E. haemophilia (1996/14 Health Science Nov)
7. The fluid that surrounds the body is known as
A. water B. sebum C. lymph D. serum E. semen (1998/13 Nov)
8. (b) State five functions of the mammalian blood (1998/1b Nov)
9. 2(a) State three differences between blood and lymph. (b) List five functions of blood (2004/2a, b Nov)
10. (b)(i) Copy and complete the table below to indicate the corresponding antigen in the red blood cells (RBC)
and antibody in plasma of each blood group.
Blood Group Antigen in RBC Antibody in Plasma
A
B
AB
O
(ii) What is the importance of Blood Group in humans?
(iii) Why is it dangerous to transfer blood from one person to another without a preliminary test? (2004/8b i-iii Nov)
11. Which of the following materials is not needed when carrying out blood test?
A. Anti-serum B. Ethanol C. sharp needle D. phenylthiocarbamide (PTC) (2002/51 Nov)
12. 1 (a) Name the components of mammalian blood
(b) State five functions of the mammalian blood (2002/1a, b Nov)
13. Individuals with blood group AB can donate blood to individuals with blood group(s)
A. A and B B. A and O C. AB only D. O only (2013/49 Nov)
14. Which of the following is NOT a function of mammalian blood?
A. Engulfing bacteria B. Production of hormones C. Transportation of urea
D. Distribution of heat E. Transporting glucose (1982/31 JAMB)
15. Which of the following statements is NOT true of mammalian erythrocytes?
A. They have hemoglobin B. They appear yellow when looked at singly
C. They are disc shaped D. The cells are more numerous than leucocytes
E. They have nuclei at maturity (1983/11 JAMB)
16. Blood platelets are important because they
A. are amoeboid and nucleated B. produce antitoxins C. produce antibodies
D. digest harmful bacteria E. release thrombin for blood clotting (1985/20 JAMB)
17. One cubic centimeter of lymph is richer than an equal volume of blood in
A. erythrocytes B. leucocytes C. amino acid D. glucose (1987/21 JAMB)
18. Aged erythrocytes are destroyed in the
A. pancreas B. liver C. lymph nodes D. kidney (1989/20 JAMB)
19. Fibrinogen and prothrombin play important roles in the
A. deamination of proteins B. clotting of blood
C. detoxication of substances D. storage of vitamins (1991/27 JAMB)
20. Which of the following is NOT involved in the transport of substances in the body?
A. lymph B. plasma C. leucocytes D. erythrocytes (1995/15 JAMB)
21. In adult mammalian blood, the cells which lack nuclei are the
A. erythrocytes B. lymphocytes C. leucocytes D. phagocytes (1998/18 JAMB)
22. Serum differs from blood plasma because it
A. contains blood cells and fibrinogen B. contains soluble food and minerals salts
C. lacks blood cells and albumin D. lacks blood protein and fibrinogen (2000/16 JAMB)
23. The mammalian vein which starts with and ends in a capillary network is the
A. pulmonary vein B. mesenteric vein D. renal vein D. hepatic portal vein (2006/16 JAMB)
141
24. The blood component that has the greatest affinity for oxygen is the
A. lymphocytes B. leucocytes C. erythrocytes D. thrombocytes (2010/31 JAMB)
25. Which of the following is true of leucocytes?
A. They are most numerous and ramify all cells B. They are large and nucleated
C. They are involved in blood clotting D. They are respiratory pigments (2011/13 JAMB)
26. Which blood cells are involved in the immune response of vertebrates?
A. Phagocytes B. Lymphocytes C. Erythrocytes D. Monocytes (2013/23 JAMB)

The heart
The human heart is a conical, hollow, muscular organ which works continuously through the life of a person. It is
about the size of a clenched fist.
The heart lies in the chest just behind the breast bone and between the two lungs. The heart has four chambers: two
upper thin wall atria or auricle and two lower thick–walled ventricle. A thick interventricular septum divides the
heart longitudinally into two sides, right and left. The right atrium (auricle) communicates with the right ventricle
below it by an opening guarded by the tricuspid valve. This valves prevents wrong flow of blood by ensuring that
blood flows only in one direction. On the left portion of the heart, the biscupid (mitral) valve plays similar role as the
tricuspid does on the right. The biscuspid valve has two cusps while the triscuspid valve has three cusps. They are
attached to the ventricular wall below by the chordae tendinae which prevents them from upward projection into the
atrium during ventricular contraction.
There is no communication between the right and left sides of the heart, therefore, the heart functions as a double
pump. Deoxygenated blood enters the heart through a major vein called vena cava into the right atrium, passes
through the tricuspid valve into the right ventricle and pumped to the lungs by the right side of the heart in the
pulmonary circulation for oxygenation . The left side pumps oxygenated blood through aorta to all parts of the body in
the systemic circulation. The heart is made up of cardiac muscles (the only involuntary muscle that has striations). The
muscles are not attached to the bone or any hard structures. The ventricles are thicker and firmer than the auricles
because they pump blood to greater distance.
The heart is an involuntary organ (its function is not under the control of the will). The beat of the mammalian heart is
initiated by the sino – atrial node(pace maker) which generate nerve impulses that spread to the atrioventricular
node(av node) ,where the impulses are amplified and spread to other region of the heart by the purkinje fibres. The
rate of the beat is controlled by the nervous system (Medulla oblongata).
The sino–auricular (atria) node receives fibres from the vagus nerve (parasympathetic nerve) and the sympathetic
nerve of the autonomic nervous system. The vagus of the parasympathetic nerve slows the rate of heartbeat while the
sympathetic fibres accelerates it.
The heartbeat occurs in two stages which are the diastole and systole. The diastole stage is the first stage and involves
the contraction of the auricles, while the systole stage is the second stage and involves contraction of the ventricles.
The rate of heartbeat in an adult human being is 72 times per minute.

The mammalian heart

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The blood vessels
Blood flows into the heart and away from it is by means of some special tubes called blood vessels. Although the three
major type of blood vessels in the body are arteries capillaries and veins, other divisions exist and are very vital for
transport. The blood vessels start with the artery leaving the left ventricle of the heart, as the main artery or aorta. The
superior vena cava and inferior vena are the two major veins that return blood to the right atrium of the heart, with the
superior vena cava draining blood from the head and fore limbs while the inferior vena cava drains blood from the
hind limbs and trunk.
The exact flow of blood from the heart to the cells and back to the heart goes thus:

HEART → ARTERIES →ARTERIOLES → CAPILLARIES →CELLS → VENULES→ VEIN→HEART

Although arteries contains oxygenated blood and veins contain deoxygenated blood, the Pulmonary artery however
contains deoxygenated blood while pulmonary veins contain oxygenated blood. It should also be noted that the
hepartic portal vein is the only major vessel or vein that starts and ends with capillaries

Structure of arteries, vein and capillaries

Difference between arteries, veins and capillaries

Arteries Veins Capillaries
1 Elastic, thick, muscular walls Walls are thin and less elastic One cell layer thick
2 Blood flow at high pressure Blood flow at low pressure. Blood flows is under the pressure from
arteries.
3 Carry oxygenated blood away from the Return de – oxygenated blood to the Carry de – oxygenated blood and
heart. heart. oxygenated blood.
4 Walls have thick layer of muscle. Walls have thin layer of muscle. One cell layer thick.
5 Usually lack valves except aorta and Valves usually present. No valves present.
pulmonary artery.
6 Pulmonary artery carries deoxygenated Pulmonary veins bring oxygenated Carry deoxygenated blood from
blood away from the heart of the lungs. blood from the lungs into the left pulmonary artery and oxygenated
‘auricle of the heart’. blood from the pulmonary vein.
7 Low blood volume. Increased blood volume. High blood volume
8 Blood flows in pulses. Blood flows smoothly No pulse in blood flow.
9 Arteries blood is bright Vein blood is dark red.

Example
The bicuspid valve is located between the
A. left auricle and left ventricle B. aorta and the left ventricle
C. superior vena cava and the inferior vena cava D. right auricle and the superior vena cava
E. right auricle and the right ventricle (1988/10)
Answer: A – The bicuspid valve is located between the left auricle and the left ventricle.
Example
The pulmonary artery caries
A. deoxygenated blood from the right ventricle to the lungs B. oxygenated blood from the right ventricle to the lungs
C. oxygenated blood from the left ventricle to the right auricle
D. deoxygenated blood from the left ventricle to the right auricle
E. oxygenated blood from the lungs to the right auricle (1988/11)
Answer: A – The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
NB: The pulmonary artery is the only artery that carries deoxygenated blood.

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Example
Blood moves through the arteries under high pressure because of the
A. absence of valves B. wide lumen C. thin layer of elastic tissue
D. thick layer of muscle and elastic tissue (2006/12 Nov)
Answer: D – Blood moves through the arteries under high pressure because of their thick layer of muscles and elastic
tissue.
Example
Tissue fluid is formed by the blood plasma
A. after passing through the blood capillaries B. when present in the veins
C. when it enters into the lymphatic vessels D. when it enters into the arteries (2000/17 Nov)
Answer: A – Tissue fluid is the fluid between cells. It is outside the blood vessel. It is formed when some of the blood
plasma escapes through the blood capillaries.
Example
(c) State three differences between an artery and a vein. (1998/1c Nov)
Answer:
i. An artery has a thick and elastic muscular wall while a vein has a thin and less elastic muscular wall.
ii. Blood flows at high pressure in an artery while in a vein, blood flows at low pressure.
iii. An artery carried blood away from the heart while a vein carries blood to the heart.
Example
Which of the following is a characteristic of arteries?
A. Possessing thin walls B. Contain valves C. Ending as capillaries D. Permeable to nutrients (2004/10 Nov)
Answer: C – Arteries usually end as capillaries.
NB: Veins usually start from capillaries.
Example
Which of the following blood vessels carries oxygenated blood into the heart?
A. Pulmonary vein B. Serum C. Protoplasm D. Plasma E. Lymph (1993/11)
Answer: A – The pulmonary vein carries oxygenated blood from the lungs to the heart.
NB: The pulmonary vein is the only vein that carries oxygenated blood.
Example
Filtered blood from the kidney is carried back to the circulatory system through the
A. hepatic portal vein B. renal artery C. renal vein D. pulmonary vein E. vena cava (1997/14)
Answer: C – The renal vein carries filtered blood from the kidney back to the circulatory system.
Example
A difference between the auricle and the ventricle of the mammalian heart is that the
A. ventricles carry deoxygenated blood B. ventricles do not have outlets C. auricles have no valves
D. walls of the ventricles are less muscular than that of the auricles
E. walls of the ventricles are more muscular than that of the auricles. (1998/12)
Answer: E – The muscular walls of the ventricles are thicker than the muscular walls of the auricles.
Example
Which of the following heart structures is best adapted to cope with double circulation?
A. One auricle and one ventricle B. Two auricles and none ventricle
C. Two auricles and partially divided ventricle D. Two auricles and two ventricles (2006/14)
Answer: D – Two auricles and two ventricles are best adapted for double circulation.
Example
The ventricles of the mammalian heart have thicker muscular walls than the auricles because the
A. ventricles are large B. ventricles receive more blood
C. ventricles pump blood to longer distances D. auricles have smaller capacity (2006/16)
Answer: C – Ventricles of the mammalian heart have thicker muscular walls than the auricles because the ventricles
pump blood to longer distances.
Example
Which of the following statements is not correct about the mammalian heart?
A. Oxygenated blood enters the left auricle from the pulmonary vein
B. The walls of the ventricle are thicker than those of the auricle
C. Blood passes from the right ventricle to the left auricle through the aorta
D. The tricuspid valve prevents the back flow of blood into the right auricle (2013/12)
Answer: C – Blood does not pass from the right ventricle to the left auricle through the aorta. Therefore option c is
not correct.

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Example
The hepatic portal vein is often heavily loaded with food-nutrients because it carries blood
A. directly from the heart B. from the liver to the heart
C. from the small intestine to the liver D. from the liver to join the posterior vena cava (2018/14 NABTEB)
Answer: C – The hepatic portal vein carries blood from the small intestine to the liver.
Example
4.(a) State one function of each of the following structures: (i) Arteries; (ii) Capillaries; (iii) Veins (2018/4a NABTEB)
Answer:
i. Arteries: Carry blood from the heart to other parts of the body.
ii. Capillaries: Connect the arteries with the veins.
iii. Veins carry blood from other parts of the body to the heart.

Example
Which of the following statements is correct about blood transfusion? A patient with blood group
A. B can receive blood from groups B, AB and O B. A can receive blood from groups A, AB and O
C. AB can receive blood from groups AB, A, B and O D. O can receive blood from groups O, A, B and AB
E. A can receive blood from groups B, AB and O (1998/10 Health Science Nov)
Answer: C – Blood group AB is a universal recipient, i.e. it can receive blood from blood group A, B, AB and O.
Example
Which of the following is not a disorder of the circulatory system?
A. Varicose vein B. Arteriosclerosis C. Leukemia D. Arthritis E. Coronary thrombiosis (1998/11 Health Science Nov)
Answer: D – Arthritis is a disorder of the joint.
Example
The blood vessel that supplies blood rich in digested food to the liver is the
A. hepatic artery B. hepatic portal artery
C. hepatic portal vein D. hepatic vein E. renal artery (2001/9 Neco)
Answer: C – The hepatic portal vein conveys blood rich in food-nutrients from the small intestine to the liver.
Example
All these statements are correct about a vein except that it
A. Carries blood to the heart B. contains blood at low temperature
C. has no valve D. possess fairly thick walls E. usually carries de-oxygenated blood (2005/51 Neco)
Answer: C – Vein usually possesses valves.
Example
Which of the following organs receives blood from an artery and a vien?
A. heart B. kidney C. large intestine D. liver E. small intestine (2005/4 Neco Nov)
Answer: A – The heart receives blood from coronary artery and pulmonary vien.
Example
The blood vessel which carries blood containing nitrogenous wastes to the kidney is the
A. pulmonary artery B. pulmonary vein C. renal artery D. renal vein E. vena cava (2005/5 Neco Nov)
Answer: C – The renal artery conveys blood containing nitrogenous wastes from the circulatory system to the kidney.
Example
De-oxygenated blood from the upper part of the body enters the heart via the
A. Inferior vena cava B. pulmonary artery C. pulmonary vein
D. subelavian vien E. superior vena cava (2005/12 Neco Nov)
Answer: E – Deoxygenated blood from the upper part of the body enters the heart via the superior vena cava.
Example
In which of the following vessels will a drug injected into the upper arm enters the heart?
A. Inferiorvenacava B. Superior vena cava C. Renal artery D. Pulmonary artery (2011/11 Nov)
Answer: B – The superior vena cava drains deoxygenated blood from the head and upper limb to the heart.
Example
The ‘Lub’ sound of the heartbeat is due to the flapping close of the
A. semilunar and bicuspid valves B. tricuspid and bicuspid valves
C. bicuspid and vena cava valves D. semilunar and tricuspid valves (2011/16 Nov)
Answer: B – The first heart sound (lub) occurs due to the closure of the Atrioventricular (tricuspid and bicuspid)
valves. NB: The second heart sound (dub) is due to the closure of the semilunar valves.

145
Example
In the mammalian heart the left ventricle is thicker than the right ventricle because it
A. sustains great pressure being on the left side of the body B. receives blood directly from the lung
C. is nearer the surface of the body D. pumps blood to all parts of the body (1999/12 Nov)
Answer: D – The left ventricle is thicker than the right ventricle because it pumps blood to all parts of the body except
the lungs.
Example
De-oxygenated blood from the head region first enters the heart through the
A. right auricle B. right ventricle C. left auricle D. left ventricle (2000/18 Nov)
Answer: A – Deoxygenated blood from the head region first enters the heart through the right auricle.
Example
A damage to the veins of a person causes
A. blood to ooze out in different directions B. ejection of blood under high pressure
C. blood to flow out under low pressure D. blood to clot inside the vein (2000/20 Nov)
Answer: C – When the vein of a person is damage, blood flows out under low pressure. NB: Blood in the vein are
always under low pressure.
Example
The heart is divided into the right and left halves by the
A. tricuspid valve B. bicuspid valve C. septum D. semilunar valve E. chordae tendinae (1997/6 Nov)
Answer: C – The septum is a muscular wall that separate the heart into right and left halves.
Example
(d) Name the major blood vessel which supplies each of the following with blood:
(i) Lung, (ii) Liver, (iii) Small intestine (2004/2d Nov)
Answer:
i. Lung – Supplied by the pulmonary artery.
ii. Liver – Supplied by the hepatic artery and the hepatic portal vein.
iii. Small intestine – Supplied by the superior mesenteric artery.
Example
The blood vessel which carries blood away from the right ventricle of the heart is
A. pulmonary artery B. superior vena cava
C. pulmonary vein D. inferior vena cava (2003/16 Health Science Nov)
Answer: A – The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
Example
Which of the following is correct about the transverse section of a vein, when compared with that of an artery?
A. The lumen of a vein is wider than that of an artery B. The endothelium of the vein is thinner than that of an artery
C. There are more smooth muscles in a vein than in an artery D. There are valves in veins but not in artery (1999/15)
Answer: D - Veins usually possess valves.
NB: The only arteries that possess valves are the pulmonary artery and the aorta.
Example
The reason why the flow of blood through the capillaries is very slow is
A. because the walls of capillaries are very thin B. to avoid high-blood pressure
C. to ensure that the individual does not get dizzy D. to allow adequate time for exchange of materials (2009/15)
Answer: D – The slow movement of blood in the capillaries is to allow for the adequate time for exchange of
materials between the blood and the body tissue.
Example
Which of the following features is not characteristic of arteries? Arteries
A. possess valves at intervals throughout their length B. have thick, muscular and elastic walls
C. carry blood away from the heart D. transport oxygenated blood with the exception of the pulmonary artery (2009/16)
Answer: A – Arteries do not possess valves except for the pulmonary artery and aorta.

146
EXERCISE 8.4
1. Make a labeled diagram, 8- 10cm long, to show the longitudinal section of the mammalian heart (2002/1c Nov)
2. The pulmonary vein carries
A. oxygenated blood from right ventricle to the lungs B. oxygenated blood from the lungs to the left auricle
C. deoxygenated blood from the lungs to the right auricle D. oxygenated blood from the lungs to the right auricle
E. deoxygenated blood from the right ventricle to the lungs (1991/10 Nov)
3. Which of the following adapts the aorta to the high pressure of the blood from the heart?
A. Thin walls B. Fragile membrane
C. Thick elastic walls D. Stiff walls E. Narrow lumen (1991/33 Nov)
4. Which of these vessels associated with the heart contains the most oxygenated blood?
A. pulmonary artery B. pulmonary vein C. anterior vena cava D. posterior vena cava (2005/18 Nov)
5. Which of the following blood vessels carries the richest supply of oxygen in man?
A. Renal vein B. Pulmonary artery C. Renal artery D. Vena cava E. Pulmonary vein (1990/26 Health Sci Nov)
6. Which of the following explains why the ventricles of the heart are more muscular than the auricles?
A. The ventricles store blood whereas auricles do not
B. Ventricles are responsible for pumping blood into the main artery
C. Ventricles are thickened by the presence of the valves D. Ventricles are bigger than the auricles
E. The cells of the ventricles absorb more fluid (1990/28 Health Science Nov)
7. Which of the following is not a symptom of coronary thrombosis
A. Shortness of breath B. Low pulse rate C. Unconsciousness
D. High body temperature E. Severe sweating (1990/30 Health Science Nov)
8. The symptom of varicose veins is
A. Profuse sweating B. Sleeplessness C. Hemorrhage
D. Tiredness E. Swelling of veins along lower limbs (1990/31 Health Science Nov)
9. The vein which returns blood from the head and arms to the heart is called
A. aorta B. inferior vena cava C. superior vena cava
D. pulmonary vein E. pulmonary artery (1985/19 JAMB)
10. The aperture between the left auricle and the left ventricle is guarded by the
A. auricular valve B. tricuspid valve C. ventricular valve D. bicuspid valve (1986/25 JAMB)
11. The blood vessel which carries blood from the alimentary canal to the liver is the
A. hepatic artery B. hepatic vein C. hepatic portal vein D. mesenteric artery (1992/15 JAMB)
12. The heart of the adult frog consists of
A. two auricles and two ventricles B. one auricle and one ventricle
C. two ventricles and one auricle D. one ventricle and two auricles (1998/17 JAMB)
13. The chamber of the mammalian heart with the thickest wall is the
A. right ventricle B. left ventricle C. right auricle D. left auricle (2000/15 JAMB)
14. The surface of an alveolus in a mammal is well supplied with tiny blood vessels known as
A. arteries B. Capillaries C. venules D. arterioles (2004/21 JAMB)
15. The organ situated in the pericardial cavity of mammal is the
A. heart B. liver C. stomach D. spleen (2006/7 JAMB)
Use the diagram below to Answer: questions 29 and 30.

16. Oxygenated blood is pumped to the entire body from the part labelled
A. IV B. III C. II D. I (2007/29 JAMB)
17. The part labelled I is the
A. pulmonary artery B. vena cava C. aorta D. bicuspid valve (2007/30 JAMB)
18. The primary structure responsible for pumping blood for circulation through the mammalian circulatory
systems is the
A. veins B. right auricle C. arteries D. left ventricle (2010/17 JAMB)
147
19. The blood circulatory system of vertebrates consist of
A. heart, arteries, capillaries and veins B. heart, aorta, capillaries and veins
C. heart, aorta, arteries and veins D. heart, vena cava, arteries and veins (2013/24 JAMB)
20. Which of the following helps in the clotting of blood?
A. Red blood cells B. White blood cells C. Plasma D. Platelets (2013/26 JAMB)
21. Which of the following forms about 55% of the volume of the blood in man?
A. Leucocytes B. platelets C. plasma D. Erythrocyte (2013/27 JAMB)
22. The blood vessel which carries blood from the alimentary canal to the liver is the
A. hepatic artery B. hepatic vein C. hepatic portal vein D. mesenteric artery (2019/20 JAMB)

Transport in plants
The major materials transported within plants are gases such as carbon (iv) oxide (CO2) and oxygen O2),water,
mineral salts, manufactured food and essential chemicals such as hormones and pigments.
The media of transport are plants saps, cell sap and cytoplasm. Plant sap includes the fluids in the vascular tissues and
latex tubes. The sap in vascular tissue is composed of 98% water and complex mixtures of organic and inorganic
solutes. The solutes include nutrients such as sugars, proteins, amino acids, mineral salts, citric acid and tartaric acid.
Pigments like anthocyanins and flavones can be found also in the solutes. Plants saps are acidic. Latex and milky
substance rich in plant food is found in latex tubes.
The function of the cell sap is for the uptake of water from the soil by the root hairs and its transport to the vascular
tissues in the root. It also works in the diffusion of gases within the plant body.

Structures of vascular bundle

The vascular tissues are grouped together in bundles within the plant body. The vascular tissues of plants are made up
of a network of long tubes called vascular bundles. They are called veins in leaves. They consist mainly of xylem and
phloem tissues. But in the root of dicotyledonous, a layer of cambium cells exist between the xylem and phloem
tissues. Hence, vascular bundle are food in the roots, stem and leaves of flowering plants. The xylem tissue transports
water and mineral salts from the root to all plants parts, whereas the phloem tissue transport soluble manufactured
foods to different part of the plant.

Monocot Dicot
vascular bundles vascular bundle in a
scattered in stem distinct ring of the stem

Translocation
Translocation is the process by which manufactured food substances are transported from where they are
manufactured (leaves) to tissues where they are needed. The tissue through which manufactured food are transported,
is known as the phloem.

Substances translocated in plants include sugar, glucose or carbohydrates, oil, resins, fatty acids, proteins or amino
acids, alkaloids(steroids) and hormones.

The functions of these translocated substances include.

(i) Proteins or amino acids are used for building up new tissues.
(ii) Sugar, glucose or carbohydrate provides energy for synthetic process.
(iii) Oil provides energy.
(iv) Alkaloids, resins and steroids are protective in function and prevent herbivores from eating the plants as they
are all waste products in plants.

148
Experiment to show that translocation takes place through the phloem tissue
Materials required: Two plants marked A and B,
Procedure: The knife is used to remove the bark and phloem round one of the trees mark A while only the bark of the
one marked B is removed. This tree marked B serves as the control experiment. The plants are left for about 2 weeks.

After the expiration of the two to four weeks, it will be observed that swelling begins to appear gradually in the bark
along the ring in plant A but no swelling in that of B. the swelling in A is due to the accumulation of food substances
which have passed down through the phloem from the leaves. After a long period of time, tree A will finally die
because the root cannot obtain food manufactured in the leaves.
Conclusion
Phloem is the tissue through which manufactured food substances are translocated.

Transpiration
Transpiration is the removal of excess water from plants into the atmosphere in form of water vapour through different
parts of the plant shoot. This is carried out through the following.
(i) The stomata in the leaves and is called stomata transpiration.
(ii) The lenticels in the stem and is called lenticellular transpiration and the
(iii) Cuticle of the leaf surface and this is called cuticular transpiration.

Note: The greatest amount of transpiration occurs through the stomata.

Factors affecting the rate of transpiration
(1) Light: High light intensity results in high rate of photosynthesis and consequently leads to increase in
temperature, this give rise to high rate of transpiration and vice – versa.
(2) Soil water: The higher the level of soil water the higher the rate of absorption and so the rate of transpiration
and vice versa.
(3) The size of the stomata pores: When stomata opens due to turgidity of the guard cells, transpiration takes
place while flaccidity of the cell causes the guard cells to close and prevent transpiration from taking place.
(4) Humidity: The higher the humidity of the atmosphere the slower the rate of transpiration while the lower the
humidity the higher the rate of transpiration.
(5) Wind :The higher the rate of wind, the higher the rate of transpiration, and the lower the rate of wind the
lower the rate of transpiration
(6) Temperature: Increase in temperature gives rise to high rate of transpiration while low temperature gives rise
to low rate of transpiration.

Importance of transpiration to plant

(1) It removes excess water from the plant.
(2) It enables plants to absorb water and mineral salts from the soil.
(3) Transpiration cools the plants.
(4) It facilitates the movement of soil water.

149
Experiment to show transpiration in plants
Materials required: Bell jar, leafy plants, polythene bag, plastic sheet, oil layer, droplet of liquid, beaker, glass sheet
and Vaseline paste.
Dip a leafy plant (twig) in a beaker of water and cover the surface with oil to prevent evaporation of water into the jar.
Airtight all joint point and place the set up on a glass sheet with a bell jar inverted over the plant. All joints are greased
with Vaseline paste to prevent gaseous water entry into the bell jar. The whole set up is placed in the sunlight for
about two to five (2 – 5) hours. In the control experiment, plant without leaves is used.

Observation
It is observed that droplets of liquid are seen on the inner surface of the bell jar in the main experiment while no liquid
droplet is seen in the control experiment. The liquid is then collected and tested with blue cobalt chloride paper which
turns pink; showing that the liquid droplet is water.

Conclusion
Green plants undergo transpiration.

Mechanism of transportation in higher plants

In aquatic unicellular and simple multicellular plants, gases enter and leave their cells by diffusion. Water enter the
cells by osmosis whereas manufactured foods and waste are transported by diffusion.

In higher plants (flowering plants) gas absorption is mainly through stomata in the leaves and lenticels in the stems,
while minerals salts are absorbed through the root system. In plants, movement of gases is by diffusion, while the
vascular tissues are responsible for transporting water, mineral salts and soluble foods.

A B

The distribution of vascular bundle in the A. Root B. Stem

Absorption of water and minerals

Direct contact exists between the soil water and young root hairs of flowering plants. The concentration of cell sap in
the root hairs is greater than that in the soil water; this makes it possible for water to pass from the soil into the root
hairs by osmosis. The cell membrane functions as a selectively permeable barrier which allows soil water to pass
through into the vacuole of root hairs. The extra water raises the turgor pressure of the vacuole or reduces the osmotic
pressure thereby forcing water out into the cell walls towards the cortex. A lower turgor or higher osmotic pressure is
found in the cell which is next to the root hair cell, thus making water to pass into it through osmosis. As a result of
this pressure difference, the water absorbed will be able to get to the xylem vessel.

150
Transport of water in the xylem tissue
Transport of water in the xylem tissue is due to the following processes.

1. Root pressure and suction pressure: The difference in osmotic pressure between the cell sap and the
concentration of soil nutrients creates a root pressure which is most active under the conditions of high
humidity and low temperature. The cell sap being more concentrated tends to draw up the nutrient. There is an
unbroken column of water between the water in the soil and the water in the leaves known as the transpiration
stream. The root pressure cannot account for water rise to the top of very tall plants.

When water evaporates through the stomata of leaves (transpiration), a suction pressure which is the total
force by which the cell absorbs water from its surrounding is created. By this pressure, the movement of water
from the soil to the xylem tissues through the root hairs is achieved. The xylem vessels are capillary tubes and
movement of water through them is via capillary force which ensures that the water column remains
unbroken.

2. Capillary action: The upward flow of water through the xylem is by capillary action. The xylem vessels
extending from the roots to the leaves forms very fine capillary tubes as a result of capillary action which is
due to the attraction between the water molecules and the walls of the xylem vessels.

3. Transpiration pull: The continuous flow of water from the roots to the leaves forms the transpiration stream.
The force which causes the upward movement of water to the top of very tall trees is created on the leaf as a
result of evaporation through the stomata during the day, this force is known as transpiration pull. As water
evaporates from the leaf cells and as more sugar is produced through photosynthesis, the osmotic pressure in
the leaf cells increases with respect to that in the xylem cells. This osmotic pressure causes more water to flow
into the leaf cells from the xylem vessels, causing a pull on the water column in the vessels. The overall effect
is that water is drawn up into the plant from the soil.

Example
The diagram illustrates an experimental set-up. Use it to Answer: questions 16 and 17.

The part labelled I is

A. a micro-organism B. a developing insect C. a water droplet D. an oil droplet E. a soil particle
Answer: C – The experiment set up is done to show that the phenomenon of transpiration occur in the leaves. The
label I represents water droplet as a result of transpiration.
The function of the part labeled II is to
A. prevent the entry of insects into the soil B. prevent the entry of light into the soil
C. Prevent light from shining on the delicate roots D. Prevent evaporation from the soul
E. Make the container air tight. (1992/16-17)
Answer: D – The labeled II is a bag used to cover the soil in order to prevent water lost through evaporation from the soil.
Example
Which of the following can be used to determine the loss of water vapour from the leaves of plants?
A. Hydrated copper sulphate B. Blue litmus paper C. Red litmus paper
D. Blue cobalt chloride paper E. Lead acetate paper (1992/18)
Answer: D – Blue cobalt chloride paper is used to test for the presence of water. If the test is positive, it turns pink.
Example
Which of the following structures transports water from the roots to the leaves?
A. Phloem B. Cambium C. Pericycle D. Xylem E. Cortex (1997/25)
Answer: D – The xylem transports water from the root to the leaves of a plant.
Example
Excessive loss of water from leaves is prevented by the
A. vascular bundle B. cuticle C. midrib D. parenchyma E. mesophyll (1998/48)
Answer: B – The cuticles of the leaves helps to prevent excess water loss.

151
Example
The removal of all the phloem tissues of the stem of a plant close to the root system for a long period of time is likely
to
A. provide more energy to the roots B. accumulate more starch in the roots
C. cause the underground roots to develop buds D. cause the plant to wither (2011/29)
Answer: D – The phloem is the vascular bundle that helps to transport food manufactured in the leaves to other parts
of the plant; hence, when the phloem is removed, the plant is likely to wither.
Example
The xylem is used for
A. transportation B. absorption C. transpiration D. translocation (2017/35 NABTEB)
Answer: A – The xylem is used for the transportation of water and mineral salt.
NB: - Absorption is carried out by the root.
- Transpiration is carried out by the leaves.
- Translocation is carried out by the phloem.
Example
The tissue which carries organic food site to all other parts of the plant is called the
A. Cambium B. Epidermis C. phloem Sclerenchyma E. xylem (2001/7 Neco)
Answer: C – The phloem helps to transport manufactured food from the leaves to other parts of the plant.
Example
ii. Name one material transported by the xylem in plants (2005/1bii Neco)
Answer: Water.
Example
Movement of water from the soil to the plant root occurs as a result of
A. differences in concentration of soil water and cell sap B. presence of living organisms in the soil
C. non- aeration of the soil D. diffusion of mineral salts between soil particles
E. too much water in the plant root (1998/14 Nov)
Answer: A – The difference in concentration of soil water and the cell sap of the root will cause water to move from
the soil into the root by the process of osmosis.
Example
The loss of water vapour through the aerial part of the plant to the atmosphere is called
A. respiration B. guttation C. osmoregulation D. transpiration E. diffusion (1989/11)
Answer: C – Transpiration is the removal of water from the plant in form of vapour.
NB: The removal of water in form of droplets though the hydathodes (small pores) of the leaf margin is called GUTTATION.
Example
The upward movement of the sap in the xylem vessel is brought about by
A. transpiration stream B. guttation C. capillarity D. osmosis E. cohesion (1989/12)
Answer: C – Capillarity is the tendency of liquid (sap) to rise and fall in the narrow tube (xylem) as a result of surface
tension. Therefore sap moves upward in the xylem through capillarity.
Example
The translocation of food materials in plants takes place in the
A. xylem B. cambium C. phloem D. parenchyma E. sclerenchyma (1989/24)
Answer: C – Phloem helps to transport (translocate) manufactured food from the leaves to other parts of the plant.
Example
Which of the following is used to measure the rate of water uptake in plants?
A. Potometer B. Hydrometer C. Hygrometer D. Aspirator (2002/14)
Answer: A – A potometer is used to measure the rate of water uptake by a plant shoot.
 Hydrometer is used to measure density or specific gravity.
 Hygrometer is used to measure humidity.
Example
Which of the following will cause wilting in plant?
A. Humidity B. Coldness C. Adequate soil water D. Excessive transpiration (2002/7)
Answer: D – Excessive transpiration will cause wilting in plant.
Example
The process by which plants convey food material to different parts of the body is called
A. nutrition B. absorption C. circulation D. translocation (2001/17)
Answer: D – Translocation is the movement of manufactured food from the leaves of the plant to the other parts of
the plant via the phloem.
152
Example
Transpiration in plants results in the
A. closure of the stomata at night B. continuous streaming of water through the plant
C. pale, green coloration of portions of the leaves D. opening of stoma (2003/15)
Answer: B – Transpiration results in the continuous streaming of water through the plant. In other words it allows for
the continuous movement of water through the xylem.
Example
2(a) What is transpiration?
(b)(i) Name two types of transpiration.
(ii) List two factors which affect the rate of transpiration.
(c) Describe the mechanisms of opening and closing of the stomata.
(d) State: (i) two similarities and (ii) two differences between transpiration and sweating. (2008/2a-d)
Answer:
a. Transpiration is the removal of excess water from the plants into the atmosphere in form of water vapour
through different parts of the plant shoot.
bi. - Stomata transpiration. , - Lenticellular transpiration. ii. - Light, - Wind
c. The mechanism of the closing and opening of the stomata depends on the presence and absence of sugar in the
guard cells.
During the day, the guard cells which contain chloroplast manufacture sugar. When the concentration of the
sugar in the guard cells is high, water begins to flow into the guard cells through the process of osmosis. This
makes the volume and turgidity of the guard cells to increase and also cause their thin outer walls to stretch
more than their thick inner wall. In this condition the stomata opens.
During the night, the concentration of the sugar falls and water begins to flow out of the guard cells by the
process of osmosis. This makes the volume and turgidity of the guard cells to decrease and then become
flaccid. In this condition the stomata closes.
di. - Both involve loss of water from the body of organisms.
- Both process result in cooling.
ii. - Transpiration occurs in plant while sweating occurs in animals.
- Transpiration occurs only during the day, while sweating occurs both day and night.
Example
Which of the following factors is likely to increase the rate of transpiration in plants?
A. Reduction in the number surface area per unit surface area B. Increase in humidity around the leaves of plants
C. An increase in leaf surface area to volume D. Removal of leaves from plant (2013/28)
Answer: C – An increase in the surface area to volume of the leaf will increase the rate of transpiration.
Example
The movement of food in soluble form within the vascular bundles to all parts the plant is known as
A. diffusion B. evaporation C. transportation D. translocation E. transpiration (2001/8 Neco)
Answer: D – Translocation is the movement of manufactured food from the leaves to other parts of the plant.
Example
The instrument used to measure the rate of transpiration in plants is called a/an
A. anemometer B. barometer C. hydrometer D. potometer E. photometer (2001/10 Neco)
Answer: D – Potometer is used to measure transpiration in plant. It is also used to measure the rate of water uplake
from the soil.
Example
(b) Explain the following terms (i) active transport (ii) transpiration
(c) State four ways by which plants can reduce high rate of transpiration (2012/1b, c)
Answer:
1bi. Active Transport: This is the movement of molecules from a region of lower concentration a region of higher
concentration (against concentration gradient) across a membrane with the use of energy.
ii. Transpiration: This is the removal of water in form of vapour from different parts of the plant shoot.

c. - Closure of stoma during the day.

- Reduction in the size of the leaf.
- Development of thick cuticle.
- Dropping of leaves in the dry season.

153
EXERCISE 8.5
1. (d) (i) Name the tissues responsible for the transportation of materials in plants
(ii) State the main material carried by one of the tissue you have named in d(i) above (2002/1d Nov)
2. (c) State: (i) Two functions of xylem tissues (ii) One function of phloem tissues (2013/1ci-ii Nov)
3. An herbaceous plant is placed in a solution with red dye for about two hours, which tissue is likely to be
stained red?
A. phloem B. Xylem C. Cambium D. Epidermis (2005/16 Nov)
4. The processes that bring the movement of water from the soil through the roots to the leaves of a tree can be
represented as
A. Osmosis→root pressure→transpiration B. diffusion→root pressure→transpiration
C. Transpiration →root pressure→osmosis D. Osmosis→root pressure →diffusion (2005/17 Nov)

1
2
3
4
5

5. Which of the labelled tissues in Fig 3 is responsible for the transport of mineral salts and water in a living
plant?
A. 1 B. 2 C. 3 D. 4 E. 5 (1981/10 JAMB)
6. In woody plants, gases and water vapor are transported across the stems by the
A. xylem fibres B. medullary rays C. sieve tubes
D. phloem fibres E. phloem parenchyma (1983/12 JAMB)
7. If the phloem of a healthy plant is killed by heat treatment the
A. upward movement of salts will cease B. food manufactured in the leaves will accumulate
C. whole plant will die immediately D. leaves of the plant will become yellow (1988/21 JAMB)
8. Manufactured food in the plant is transported through the
A. xylem B. phloem C. cambium D. cortex (1993/13 JAMB)
9. If water that has been coloured red is poured at the base of a wilting plant, it will appear as a red stain in the
cells of the
A. Phloem B. Parenchyma C. xylem D. epidermis (2003/14 JAMB)
Use the diagram beside to Answer: questions 19 and 20

Arrows represent directional movement of materials

10. Transportation in the xylem is represented by
A. I B. II C. III D. IV (2012/19 JAMB)
11. The arrow labelled II represents the
A. release of oxygen B. intake of carbon(IV)oxide
C. movement of photosynthesis D. movement of nutrients (2012/20 JAMB)
12. A plant tissue that carry water and mineral salts is the
A cambium B. xylem C. cortex D. phloem (2013/25 JAMB)
13. The respective tissues that transport water and manufactured food in plants are
A. xylem and phloem B. phloem and tracheid
C. phloem and xylem D. xylem and tracheid (2017/26 JAMB)

14. (d) i. Name three parts of plants actively involved in transpiration

ii. State three factors that affect transpiration (2008/2d i, ii Neco)

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15. (b)(i) Define translocation in plants.
(ii) Describe the ringing experiment to demonstrate translocation in plants. (2011/2b i, ii Nov)
16. In an experiment to demonstrate transpiration which of the following reagents is used?
A. Cobalt chloride paper B. pyrogallic acid
C. Fehling’s solutions A and B D. Benedict’s solution (2005/20 Nov)
17. The rate of transpiration of a leafy shoot would be highest under
A. damp, cold, still air B. damp, warm, moving air C. dry, warm, moving air
D. dry, cold, moving air E. dry, warm, still air (1981/21 JAMB)
18. A major limitation in the use of the potometer for measuring the rate transpiration is that
A. it is made of breakable glass material B. It is measures the rate of water intake
C. it measures the rate of water loss through the stern only
D. the movement of the air bubble in the poto-meter cannot be timed accurately (1986/26 JAMB)
Use the diagram below to Answer: questions 12 and 13

19. The experiment is used to demonstrate that

A. transpiration occurs through the leaves B. Plants lose water through guttation
C. leaves are important to photosynthesis D. water is necessary for photosynthesis. (2003/12 JAMB)
20. In the experiment, the layer of oil serves to prevent water loss by
A. osmosis B. transpiration C. evaporation D. guttation (2003/13 JAMB)
21. Movement of minerals and chemical components within a plant occurs during
A. osmosis B. translocation C. transpiration D. diffusion (2013/17 JAMB)
22. Water in plants is removed as water vapour through the process of
A. evaporation B. transpiration C. diffusion D. osmosis (2014/19 JAMB)
23. Which is the correct order of water loss from the leaf?
1. Mesophyll 2. Veins 3. Substomatal cavity 4. Stomata
A. 3→2→1→4 B. 2→3→1→4 C. 2→1→3→4 D. 1→2→3→4 (1986/24 JAMB)

Transport in plants and animals

Similarities between transport in plants and animals

1. Diffusion plays a major role in transportation in both plants and animals.
2. Liquid medium is needed for transportation in both plants and animals.
3. In both, materials are transported in dissolved form.
4. Tubular vessels are necessary in plants and animals.

Differences between transport in plants and animals

Plants Animal
1. The transport vessels consist of non-living cells The transport vessels consist of different living cells.
2. Cell sap is the medium of transportation. Blood is the medium of transportation.
3. Root pressure/transpiration pull generates force for Heart generates the forces for transportation of
transportation of materials. materials.
4. Nutrients are transported through different vessels Nutrients are transported in the same vessels.
(xylem and phloem)

Mechanism of transportation in unicellular organisms

In unicellular organisms, there is continuous streaming of movement of the cytoplasm. This movement circulate
materials within one – cell body. In amoeba for example, the cytoplasm stream from rear to the front of the organism
along the direction of its movement.
In paramecium, the continuous circular movement of the cytoplasm brings about the distribution of materials such as
food, oxygen, CO2 e.t.c. within its body. The circular movement is called cyclosis.
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Mechanism of transportation in simple multicellular organism
Hydra is a simple multicellular organism with two body layer. The body encloses a huge gut cavity called enteron.
Movement of the gut wall draw water into the gut and cause digested food and oxygen within it to circulate. This
enables the cell lining the gut to absorb the materials. Some cells in the gut have flagella. The whipping movement of
the flagella also helps to circulate the materials in the gut.
In flatworms (e.g. tapeworm), there is a thin and flat head so that the surface area to volume ratio is large. In addition,
the gut branches extensively throughout the body. These features enable sufficient food and oxygen to diffuse into all
the body cells. A branched excretory system is present to collect and get rid of waste products from the body. As in
hydra, movements of the body wall aid the transportation of waste products out of the body.

Mechanism of transport in insects and mollusks

In insects and mollusca, there is an open circulatory system which enables them to transport materials within the body.
In the open circulatory system, the heart pumps blood out into a blood vessel which branches and open into spaces in
the body cavity called haemocoel. The organs and tissues are bathed in blood and exchange of materials occurs
between the body cells and the blood. Blood in the spaces eventually flows into vessels leading to the heart. Valves in
the heart and blood vessels only allow the blood to flow in one direction. In the open system, the distribution of blood
to the various body parts is poorly controlled.

Mechanisms of transportation in higher animals

In higher animals, like the mammals, the blood is made to circulate round the body by the pumping action of the heart
through the blood vessels like arteries, vein and capillaries. All mammals have double circulation.
In double circulation, the blood passes through the heart twice every time it makes one complete movement round the
body. The double circulation are (1) pulmonary circulation and (2) Systemic circulation
In pulmonary circulation, blood is carried from the right ventricles of the heart to the lungs through pulmonary artery
and taken back to the heart through the pulmonary vein. The role of this circulation is to oxygenate the blood and
remove CO2 from the blood in the lungs. It also prevents mixing of deoxygenated and oxygenated blood, and allows
only oxygen rich blood to enter into systemic and coronary circulation
In systemic circulation, oxygenated blood is carried from the left ventricles to all body parts except the lungs through
the arteries and back to the heart through veins. The role of the systemic circulation is to transport products of
digestion, oxygen, water, hormones and other substances to all parts of the body and collect excretory products like
water, urea, CO2, mineral salts e.t.c. from the cells of the body to organs that will excrete them.
The heart like other organs has a blood supply. This is called coronary circulation in which coronary arteries, which
branch from the aorta near the heart, carries blood to the heart muscle. The flow is called coronary circulation.

Double circulation in man

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Major blood vessels in systematic circulation
a. Arteries:
1. Right and left carotid arteries: They supply the head, the brain, the face. Right carotid artery gives a
branch to the right arm as the right subclavian artery.
2. The right and left subclavian artery: They supply the right and left arm respectively.
3. Phrenic arteries: They supply the ribs.
4. Mesenteric arteries: Branches into the gastric, splenic and intestinal artery which supplies the stomach,
spleen and intestine respectively.
5. Renal arteries: They supply the kidney.
6. Genital arteries: These are the testicular and ovarian arteries and they supply the testes in male and the
ovaries in female.
7. Abdominal arteries: These are the iliac and femoral arteries, they supply the thigh and legs respectively.

b. Veins:
1. Right and left Jugular veins: They drain the blood from the head, the neck and the face into the superior
vena cava.
2. The right and left subclavian vein: They drain blood from the fore limbs into the superior cava also by
joining the jugular vein.
3. Every other vein from the rest part of the body are drained into inferior vena cava, these includes, the
hepatic vein (from the liver), renal vein (from the kidney), phrenic vein (from the ribs and intercostals
muscle etc)

Example
In which of the following is cilia not associated with movement or transport of materials?
A. Fallopian tube funnel B. Ectoplasm of paramecium C. Lining of the mammalian trachea
D. Mammalian alimentary canal E. Oral groove of paramecium (1989/7)
Answer: D – Movement in the alimentary canal of mammals is achieved through peristalsis and not through ciliary
action. All other options (A, B, C and E) are associated with cilia.
Example
Oxygenated blood from the lungs is carried to the left auricle of the heart through the
A. pulmonary vein B. pulmonary artery C. hepatic portal vein
D. renal portal vein E. superior vena cava (1992/14)
Answer: A – The pulmonary vein carries oxygenated blood from the lungs to the left auricle of the heart.
Example
Which of the following statements about the lymphatic system is not correct?
A. The lymph vessels are always larger in size than the arteries B. The flow of lymph is assisted by general muscular movement
C. Lymph flows only in one direction due to the presence of valves D. Lymph is emptied into the blood circulatory system through a vein
E. Lymph node becomes swollen during serious infections (1996/14)
Answer: A – Lymph vessels are not always larger in size the arteries.
Example
Which of the following statements about the circulation of blood is not correct?
A. Deoxygenated blood flows in the heart through the vena cavae B. Blood is pumped out of the heart through the aorta
C. Oxygenated blood from the lungs is carried to the left auricle D. The oxygenated blood enters the lungs through the pulmonary vein
E. Ventricles contract to pump blood into the aorta (1998/11)
Answer: D – Oxygenated blood leaves the lungs through the pulmonary vein.
Example
The pulmonary circulation involves movement of the blood to and from the
A. brain B. kidneys C. liver D. lungs (2012/9)
Answer: D – Pulmonary circulation involves the movement of blood from the heart to the lungs and from the lungs to
the heart.
Example
c. (i) Define pulmonary circulation. (ii)Mention three components of the blood (2014/2c i-ii Neco)
Answer:
i. Pulmonary circulation is the movement of blood between the heart and the lungs via the pulmonary artery and vein.
ii. Plasma , Red blood cells (Erythrocytes) . White blood cells (Leucocytes)

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Example
(b) Describe the changes that take place in the composition of human blood as it passes through the:
(i) lungs (ii) liver (iii) kidneys (2018/4b NABTEB)
Answer:
i. Lung – Oxygen is added, carbon(iv)oxide is removed, water is removed.
ii. Liver – Urea is added to the blood, hormonal level is reduced, glucose level is reduced, worn out erythrocyte
are removed from the blood.
iii. Kidneys – Water, urea, some glucose, mineral salt are reduced from the blood.
Example
Oxygenated blood from the lungs is carried to the
A. right auricle B. right ventricle C. left ventricle D. left auricle E. vena cava (1992/15 Nov)
Answer: D – Oxygenated blood from the lungs is carried to the left auricle of the heart.
Example
Urea is transported in the plasma of the human blood from the
A. intestines to the kidney B. liver to the pancreas C. lungs to the liver D. liver to the kidney (2005/21 Nov)
Answer: D – Urea is transported from the liver to the kidney.

EXERCISE 8.6
1. The world owes its knowledge of the system of blood circulation to the discovery by
A. Alexander Fleming B. Gowland Hopkins C. William Harvey
D. Anthony Van Leeuwenhoek E. Joseph Lister (1990/54 Health Science Nov)
2. A carbohydrate molecule in the blood in the right ventricle of the heart is pumped into the cell of the toe of
man. Which of these structures is it unlikely to pass through en-route?
A. Pulmonary artery B. Lungs C. Heart D. Liver E. Aorta (1978/43 JAMB)
3. Blood circulation in a mammal is said to be double because
A. it passes twice through the heart in a complete circuit B. it moves in both arteries and veins
C. it circulates in both the heart and other organs D. the heart contain auricles and ventricles (1986/23 JAMB)
4. A circulatory system that does not allow mixing of oxygenated and de-oxygenated blood in mammalian heart
is referred to as
A. open B. haemodoelic C. single D. closed (1994/21 JAMB)
5. Unicellular organisms transport essential nutrients directly to all parts of their bodies by the process of
diffusion because they have
A. a large volume to surface area ratio B. a large surface area to volume ratio
C. their bodies immersed in the nutrients D. their outer membrane made of cellulose (1998/16 JAMB)
6. The lymphatic system of mammals rejoins the blood circulatory system at the
A. hepatic vein B. subclavian vein C. renal vein D. common iliac vein (1999/22 JAMB)
7. Salts and water are absorbed in the roots and transported to the leaves by
A. diffusion through the xylem tissues B. osmosis through the phloem tissues
C. diffusion through the phloem tissue D. osmosis through the xylem tissues (2001/27 JAMB)
8. The only vein that carries pure oxygenated blood is the
A. sciatic vein B. hepatic vein C. renal vein D. pulmonary vein (2005/14 JAMB)
9. Which of the following describes the sequence of blood flow from the heart to a tissue?
A. Heart → artery → arteriole → tissue B. Heart → vein → venule → tissue
C. Heart → venule → vein → tissue D. Heart → arteriole → artery → tissue (2009/19 JAMB)
10. Circulation of blood to all parts of the body except the lungs is through
A. the pulmonary artery B. systemic circulation
C. the lymphatic system D. pulmonary circulation (2010/18 JAMB)

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RESPIRATORY SYSTEM
Respiration is defined as a process by which glucose is broken down in the cell by a series of reaction controlled by
enzymes to release energy which is needed for specific and important activities in living organism. The oxygen (O 2),
we breathe in is used to break down the food molecules so that the energy in the food can be released for various
activities. Carbon dioxide (CO2), water (H2O) and alcohol are also released but depending on whether oxygen is used
or not for the respiration.

Stages of respiration
There are two stages of respiration.
1. External respiration (breathing): It is the process by which gases are exchanged (by diffusion) between the
environment and the respiratory organs of living organisms. It is also called gaseous exchange and involves
the entry of oxygen and exit of carbondioxide from the cell.
2. Internal (tissue) respiration: This is also known as cellular respiration. It is the process whereby organic
food substances within the cells (mostly in mitochondria) are oxidized, leading to the release of energy,
carbon dioxide and water. Before oxidation, energy is stored in food substances as potential energy but this is
later converted into kinetic energy which will be used for work after oxidation.
Internal respiration can be represented by the following equation:
C6H12O6 + 6O2 → 6H2O + 6CO2 + Energy
The sole aim of respiration is to provide energy which the body needs for various life processes.

RESPIRATORY STRUCTURES
Respiratory system consists of organs or structures for the exchange of oxygen required for oxidation and carbon-
dioxide (CO2) produced by respiration. The taking in of oxygen and giving out of Carbon-dioxide is called gaseous
exchange or breathing.

Characteristics of respiratory surface/organs

1. The respiratory organs has a large surface area through which gaseous exchange takes place by diffusion.
2. The respiratory surface is usually moist, so that gases can dissolve in the moisture on the surface and then
diffuse into or out of the organ as the case may be.
3. The respiratory surface is supplied with a large number of blood capillaries so that gaseous exchange can take
place, between the blood in the capillaries and the air or water in contact with the respiratory surface.
4. There is a thin layer of cells separating the blood capillaries and the respiratory surface so that diffusion
distance between the respiratory surface and the blood is short.
5. Respiratory surface are permeable, so that oxygen and CO2 can pass freely.
6. Respiratory surface must have adequate supply of transport medium e.g. blood

Types of respiratory systems

Respiratory system consists of specific structures and organs which are used for gaseous exchange in plants and
animals. Different respiratory structures can be found in various organisms, depending on their types, complexity, size
and habitat in which they are found.

Different organisms and their Respiratory structures

Organisms Respiratory structure/ organ
1 Unicellular organisms e.g. amoeba and paramecium Body surface
2 Hydra and tapeworm Cell membrane
3 Earthworm Wet skin or moist body surface
4 Fishes e.g. tilapia Gills
5. Arthropod e.g. insects Tracheal system / spiracle
6 Arachnids e.g. spiders Lung books
7 Tadpoles Gills
9 Amphibians e.g. adult told Mouth (buccal cavity) skin and lungs
11 Mammals, Reptiles, Aves (birds) Lungs
12. Flowering plants Stomata(on leaves) and lenticels(on stem)
Example
Respiration in amoeba is through the
A. contractile vacuole by the process of diffusion B. foods vacuole by cyclosis
C. exchange of gases between its vascular system and the cytoplasm
D. body surface by the process of diffusion E. nucleus and the environment (1996/4 Nov)
Answer: D – Amoeba respires through it body surface by the process of diffusion. This is because it has a larger
surface area to volume ratio.
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Example
The mechanism of gaseous exchange in living organisms is essentially by
A. osmosis B. inhalation C. diffusion D. exhalation E. breathing (1991/4)
Answer: C – Gaseous exchange is achieved by the process of diffusion.
Example
The conditions that ensure successful exchange of gases in multicellular organisms include the following except
A. concentration gradient across the respiratory surface B. presence of thin membrane as the respiratory surface
C. last transportation of absorbed gases D. presence of large surface area of the respiratory organ
E. presence of small, dry surface area of the respiratory organ (1993/12)
Answer: E – Respiratory surface’s are usually moist. Therefore the Presence of small, dry surface area of the
respiratory organ will not aid the exchange of gases in multicellular organisms.
Example
8 (a)(i) Briefly explain the term respiration.
(ii) Name the two types of respiration and write a balanced equation to summarize each of them. (2006/8ai-ii)
Answer:
8ai. Respiration is the process by which living things oxidizes organic substance or food, with or without the use
of oxygen, to release energy for metabolic activities of the body.
ii. - Aerobic respiration: 𝐶6 𝐻12 𝑂6 + 6𝑂2 → 6𝐻2 𝑂 + 6𝐶𝑂2 + 𝐸𝑛𝑒𝑟𝑔𝑦
- Anaerobic respiration: 𝐶6 𝐻12 𝑂6 → 𝐶2 𝐻5 𝑂𝐻 + 𝐶𝑂2 + 𝐸𝑛𝑒𝑟𝑔𝑦
Example
(c) State four characteristic features associated with respiratory structures (2013/1c)
Answer:
i. They have large surface arc. ii. Their surfaces are usually moist. iii. They are highly vascularized.
iv. They have thin layer of cells separating the blood capillaries and the respiratory surface.

EXERCISE 9.1
1. (a) (i) What is respiration? (1996/1a Health Science Nov)
2. Explain why simple diffusion is an efficient means of gaseous exchange in lower organisms. (2018/1b NABTEB)
3. Respiration is an essential life process providing the cells with
A. oxygen B. sugar C. energy D. carbon dioxide (2002/9 Nov)
4. In the adult frog gaseous exchange takes place through the
A. buccal cavity, skin and lungs B. buccal cavity, skin and spiracles
C. gills, skin and buccal cavity D. tympanic membrane, lungs and gills (2008/11, 2013/13)
5. Lungs and gills are used for respiration in
A. bats B. birds C. insects D. man E. newts (2007/14 Neco)
6. Exchange of gases takes place through the following structures except
A. Lenticel B. gills C. kidney D. body surface E. lungs (1996/14 Nov)
7. Mention three characteristics of respiratory surfaces. (2002/7c Health Science Nov)

Mechanism of respiration in insects

Insect breathe by means of tracheae. These are a system of branched tubes which extend to the internal organs and
tissues of the body. The trachea open to the outside through spiracles which are segmentally arranged one on each side
of the body. An insect breathe by contracting and relaxing the abdominal muscles. When it contracts, its abdominal
cavity decreases in a dorsal ventral direction and the pressure in it increases. This forces air out of the tracheal system
through the spiracles. When the abdominal muscles relax, the abdomen turns to its normal volume and pressure in it
decreases. This causes air to move through the spiracles into the tracheae.
Mechanism of respiration in fish (Tilapia fish)
Tilapia is an example of a bony fish that uses gills for gaseous exchange.
When the gill covers are closed, the mouth is opened and the floor of the mouth is lowered, water rushes into the
mouth. When the mouth is closed, the gill covers are opened, and the floor of the mouth is raised, water flows out
through the gill opening, bathing the gill filament.
As water flow over the gill filaments, there is gaseous exchange. Oxygen dissolved in the water diffuse into the blood
of the capillaries in the gill filaments, while CO2 diffuses from the blood into the water.

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Respiratory system in toad
In the tadpole stage, the respiratory organ is the gill and they carry out gaseous exchange in a manner similar to that of
the fish. The adult toad/frog uses three respiratory surfaces.
1. Skin
2. Mouth/buccal cavity
3. Lungs

Gaseous exchange in toad through the skin (cutaneous respiration)

The skin of the toad is kept moist by mucus secreted by some glands in the skin. There are many blood capillaries in
the skin. Oxygen in the air dissolves in the moisture on the skin and then diffuses into the blood capillaries in the skin.
Carbondioxide (CO2) diffuses from the blood in the blood capillaries through the moisture on the skin into the air.
This method of breathing is used when the toad is in water or in land, if the skin is moist.

Gaseous exchange through the mouth/Buccal Cavity

The toad lowers the floor of its mouth and opens the nostrils. Air is drawn into the large mouth cavity through the
nostril, the surface of the mouth cavity is moist and mucus membrane lining the mouth is supplied with numerous
blood capillaries. Gaseous exchange takes place between the air in the mouth and the blood in the capillaries.
The toad raises the floor of the mouth and the air in the mouth goes out through the nostrils. This method of breathing
is used on land.

Gaseous exchange through the lungs

The toad closes the glottis, open the nostrils and lowers the floor of its mouth. Air enters through the nostrils into the
mouth. The toad closes the nostrils, open the glottis and raises the floor of the mouth, air then passes into the lungs.
Oxygen dissolves in the moist lining of the lungs and then diffuses into the blood capillaries in the lungs.
Carbon(iv)oxide diffuses from the blood into the lungs. The reverse of the process leads to breathing out.

Example
Which of the following structures is associated with respiration in insects
A. Air sac B. Spiracle C. Lung D. Alveolus E. Gill (1997/10)
Answer: B – The insects use spiracle for gaseous exchange.
Example
Which part of the gill of fish is involved in gaseous exchange?
A. Gill slits B. Gill bars C. Gill covers D. Gill filaments (2001/18)
Answer: D – Gaseous exchange takes place in the gill filaments of the gill of fish.
Example
Fish cannot survive on land because it has
A. body covered with scales B. a streamlined body C. no lungs D. no walking appendages (2003/40)
Answer: C – Fish cannot survive on land because it has no lungs which are adapted for breathing on land.
Example
Which of the following organs are used for gaseous exchange in mature toad?
A. Gills, lungs and eardrum B. Lungs, mouth and eardrum C. Mouth, skin and gills D. Skin, lungs and mouth (2013/13)
Answer: D – A mature toad can exchange gases through the skin, lungs and mouth.
Example
A grasshopper respire by means of its
A. book lungs B. trachea tubes C. antennae D. lungs (2019/19 NABTEB)
Answer: B – A grasshopper respires by means of its trachea tube. This tube is opened to the outside through the
spiracle.
Example
The excretory product common to all insects is
A. water B. bile C. uric acid D. ammonia (2019/21 NABTEB)
Answer: C – Uric acid is an excretory product common to all insects.
Example
Respiration in amoeba is through the
A. contractile vacuole by the process of diffusion B. foods vacuole by cyclosis
C. exchange of gases between its vascular system and the cytoplasm
D. body surface by the process of diffusion E. nucleus and the environment (1996/4 Nov)
Answer: D – Amoeba respires through it body surface by the process of diffusion. This is because it has a larger
surface area to volume ratio.

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EXERCISE 9.2
1. The structure in insects which has the same function as the stoma in plants is
A. Spiracle B. Malpighian tubule C. antenna D. trochanter E. flame cell (1996/13 Nov)
2. Which of the following organs is not part of the respiratory system in fish?
A. mouth B. pharynx C. Gills D. Gill cover (2013/16 Nov)
3. 4. (a) (i) List five excretory organs found in living organisms.
(ii) Give one example of an organism in which each type is found.
(b) (i) State two ways in which the excretory organ of earthworm is similar to that of mammal (1991/4a, b Nov)
4. What is the name of the respiratory organ of the crab?
A. Tubules B. Trachea C. Spiracles D. Lungs E. Gills (1981/22 JAMB)
5. A grasshopper respires by means of it’s
A. lung-books B. gills C. lungs D. antennae E. tracheal tubes (1982/14 JAMB)
6. When an operculate fish breathes, it takes in water through the
A. mouth and also passes it through the same way B. mouth and passes it through the operculum
C. operculum and passes it through the nostrils D. operculum and passes it through the nostrils
E. nostrils and passes it through the operculum (1982/27 JAMB)
7. In which of the following vertebrates does the skin function as a respiratory surface?
A. Rat B. Lizard C. Fish D. Frog (1995/8 JAMB)
8. The sequence of the one-way gaseous exchange mechanism in a fish is
A. gills → operculum→ mouth B. mouth → operculum → gills
C. mouth → gills → operculum D. operculum → gills → mouth (2011/26 JAMB)
9. Which of the following has the most primitive respiratory system?
A. Insect B. Fish C. Snail D. Mouse (2015/1 JAMB)
10. Which of the following uses diffusion as the principal method of gaseous exchange?
A. Grasshopper B. Rat C. Lizard D. Earthworm (2015/3 JAMB)

Respiratory system in Mammals

Land animals exposed to the atmosphere have dry body coverings. Gaseous exchange cannot occur through such
surfaces. As a result, these animals have evolved a suitable respiratory structure.
Mammals have the most complex respiratory system. The main gaseous exchange organs are a pair of lungs enclosed
in the thorax and connected to the air outside by a series of branched tubes and pathways.

The Human Respiratory System

The components of respiratory system in mammals are:

1. Nose
2. Pharynx
3. Larynx (voice box)
4. Trachea
5. Bronchi
6. Lungs
As seen in the diagram above.
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Nose and mouth: The nose has two air passages called nostrils. The lining of the nostril secretes mucus which keeps
them moist. The nostrils also have hairs for filtering air. The nose and mouth helps to warm and moisten in-coming
air.

Pharynx: The pharynx continues from the mouth and the nose and it leads to the oesophagus (gullet) and larynx
(voice box). Food goes into the gullet and air into the trachea. The entrance into the lungs has flap of tissue called the
epiglottis. This closes the opening (glottis) when the individual is eating thus preventing particles of food from falling
into the trachea and causing fits of cough.

Larynx (voice box)

The larynx is short and made of strong cartilage. Air enters the trachea through the larynx.

Bronchi: The bronchi are made of rings and cartilages. The right and left bronchi, branches into bronchioles. The
bronchioles in turn lead into air sacs. An air sac is made up of a cluster of alveoli. The walls of the air sacs are very
thin and elastic. Through these thin walls, exchange of gases takes place between the air sac and capillaries.

Lungs – The lungs are spongy consisting mainly of bronchioles, air sacs, network of blood vessels and capillaries
bound together by connective tissues.

The lungs occupy the thoracic cavity from the shoulder to the diaphragm except the area occupied by the trachea,
gullet, blood vessels and heart.

Each lung is surrounded by an elastic membrane (pleural membrane) and so it can stretch.

Mechanism of breathing in man

Breathing occurs in two phase called inhalation (breathing in) and exhalation (breathing out). These two events
occurs as a result of movement of the ribs, diaphragm, sternum and intercostal muscles.

Inhalation: this is the breathing in of oxygen, it is also called inspiration. During inspiration, the thoracic cavity
increases in volume, the diaphragm contracts and becomes flattened, the intercostal muscles contract while the ribs
move upwards and outwards. As the sternum projects forward; there is an increase in the volume and decrease in the
pressure of thoracic cavity. Air is then forced from outside into the lungs through the air passage (nose, treachea,
bronchus and bronchioles).

Exhalation (expiration): This is the breathing out of air (carbondioxide and water vapour) into the atmosphere, in
expiration, the following event occur:
1. The intercostal muscles relax, while the ribs cage is lowered.
2. The diaphragm relaxes and returns to its original dome – shaped position.
3. The thoracic cavity volume decreases while the lungs shrink.
4. The lung air pressure increases and a lot of air is expelled from the lungs through the air passage.

A film of moisture covers the lining of each alveolus. The oxygen concentration in the blood capillaries of the alveoli
is less than that in the cavity of the alveoli. As a result, oxygen in the air, spaces of the alveoli dissolves in the film of
moisture and diffuses through the capillary walls into the red blood corpuscles, where it readily combines with the
haemoglobin. The capillaries, form the pulmonary veins which returns the oxygenated blood to the left auricle of the
heart. From here, it is transported round the body. The oxygen is used in the body cells for respiration, whereas
carbon(IV)oxide, energy and water are produced.

Gaseous exchange in lower animals

In lower animals like Amoeba, paramecium and earthworm, diffusion occurs through membrane or body surface.
Oxygen that dissolves in water diffuses into the body while carbon dioxide goes out of the body through the entire
body surface. The cell membrane acts as a respiratory surface. Gaseous exchange in unicellular organism is by
diffusion. The earthworm uses its body surface because it has moist skin.

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Example
Use the diagram below to Answer: questions 5 to 8.

The pat labeled VII is the

A. pleural cavity B. lung C. rib D. diaphragm E. intercostals muscle (1993/5)
Answer: D – The part labeled VII is the diaphragm.
The part labeled I is the
A epiglottis B. larynx C. oesophagus D. trachea E. bronchus (1993/6)
Answer: B – The part labeled I is the larynx.
Exchange of gases takes place in the air sacs contained in the part labelled
A. I B. II C. IV D. V E. VI (1993/7)
Answer: C – The part labeled IV is the lung. Which contain air spaces for gaseous exchange.
During the process of breathing, volume and pressure changes occur as a result of the movement of the parts labeled
A. I and II B. II and IV C. III and VII D. IV and V E. VI and VII (1993/8)
Answer: C – The movement of the ribs (III) and the diaphragm (VII) during the process of breathing results in the
changes in volume and pressure of the lungs.
Example
Rabbits cannot survive in an aquatic habitat because they have
A. fore and hind limbs B. no gills C. no fins D. no scales (2003/44)
Answer: B – Rabbits cannot survive in aquatic habitat because they have no gills. Gils are adapted for breathing under water.
Example
(b) Outline the mechanisms involved in: (i) inhalation; (ii) exhalation in human beings. (2006/8b)
Answer:
i. During inhalation: ii. During Exhalation:
- The external intercostals muscles contract. - External intercostals muscles relax.
- The internal intercostals muscles relax. - Internal intercostals muscles contract.
- The ribs move upward and out-wards. - Ribs move downward and inwards.
- The diaphragm contracts and becomes flattened. - Diaphragm relaxes and become dome-shaped.
- The volume of the thoracic cavity increase. - Volume of the thoracic cavity decreases.
- Air pressure decreases. - Air pressure increase.
- Air rushes into the lungs from the atmosphere. - Air is forced out of the lungs to the atmosphere.
Example
Inhaled air is made warm and moist in the
A. epiglottis B. nasal cavity C trachea D. mouth (2011/14)
Answer: B – Inhaled air is made warm and moist in the nasal cavity.
Note: Paranasal sinuses surrounding the nasal cavity are lined with mucosa. The mucosa lining the paranasal sinuses help to
warm and humidify the air we inhale.
Example
Which of the following structures is not involved in respiration?
A. Lung books B. Mouth C. Stomach D. Trachea (2011/15)
Answer:
C – The stomach is not involved in respiration. It is a part of the digestive system.
Example
Which of the following statements about the diaphragm of a mammal is not correct? It
A. separates the thorax and the abdomen B. is a thick layer of muscle
C. is made of epithelial cells D. is part of the human respiratory apparatus (2013/15)
Answer: C – The diaphragm is not made of epithelial cells. It is a c-shaped structure of muscles and fibrous tissue.
Hence, option C is not correct.

164
Example
The diagram above are parts of a human lung. Which of the labeled parts is diagram Z taken from?
A. II B.III C. IV D V (2012/13)
Answer: C. aveoli is in the lungs
Example
(a) (i) What is respiration?
(b) In a tabular form, state four differences between gaseous exchange and aerobic respiration (2013/1a, b, c)
Answer:
a. Respiration is the process by which living things oxidizes organic substance or food nutrients to release
energy for metabolic activities of the body with or without oxygen.
b. Gaseous Exchange Aerobic Respiration
Oxygen simply moves into the organism and CO2 moves out Oxygen is used to oxidize glucose
It is a physical process It is a Chemical process
No energy is released Energy is released
No enzyme is involved Enzymes are involved

Example
The exchange of gases between the environment and the respiratory organs of vertebrates is referred to as
A. inhalation B. respiration C. expiration D. breathing (2016/14)
Answer: D – Breathing is the exchange of gases between the environment and the respiratory organs.
NB: Breathing involves:
- Inhalation: Forcing air into the respiratory organ.
- Exhalation: Forcing air out of the respiratory organ.
Example
Which of the following actions does not occur during exhalation in man?
A. Thoracic cavity decreases in volume B. Diaphragm flattens
C. Ribs move down and in D. Air pressure increases in the thoracic cavity (2017/12)
Answer: B – Diaphragm becomes dome-shaped during exhalation.
NB: The diaphragm flatten during inhalation.
Example
Which of the following is the correct sequence of the parts of the respiratory systems?
A. Nostril→larynx→lungs→bronchus B. Nostril→larynx→bronchus→trachea
C. Nostril→bronchus→trachea→larynx D. Nostril→trachea→bronchus→lungs
E. Nostril→bronchus→lungs→trachea (1998/8 Health Science Nov)
Answer: D – The sequence of the respiratory system is:
Nose (Nostril) → Pharynx (throat) → Larynx (voice box) → Trachea (wind pipe) → Bronchi → Lungs

Example
(b) State two function each of the following organs in relation to respiration:
(i) Nostril (ii) Diaphragm (1996/1b, Health Science Nov)
Answer:
bi. Nostril:
- It helps to filter air.
- It helps to warm the inhaled air.
ii. Diaphragm
- It contracts and flattens to create vacuum which pulls air into the lungs.
- It relaxes and becomes dome-shaped to force air out of the lungs.

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EXERCISE 9.3
1. The part of the mammalian respiratory tract located after the pharynx is the
A. bronchus B. bronchiole C. larynx D. tracheal (2020/13 PCI)
2. Which of the following terms is used to describe the breathing movement during which the ribs are drawn
upwards and outwards?
A. Expiration B. Oxygenation C. Inspiration D. Anaerobic respiration E. Internal respiration (1992/13 Nov)
3. Which of the following statements best describes breathing?
A. the removal of carbon dioxide from the lungs B. the absorption of oxygen from air in the lungs
C. the taking of air into the lungs and expelling it
D. the absorption of oxygen and the loss of carbon dioxide (2006/10 Nov)
4. The movement of the diaphragm is characteristic of gaseous exchange in
A. insects B. fish C. toad D. mammals E. plants (1994/18 Nov)
5. 1(a)(i) What is external respiration? (ii) List the structures involved in breathing in mammals.
(b) (i) Describe briefly rho process of inspiration in a mammal.
(ii) State the structures for gaseous exchange in plant. toad, fish and insects. (1997/1a, b Nov)
6. The diaphgram which is dome shaped is flattened during inspiration by
A. the pressure exerted by the heart on it B. the contraction of muscles of the abdomen
C. contraction of its own fibres D. contraction of the intercostal muscles
E. the pressure exerted by the abdominal organs (1995/21 Nov)
7. The upper part of the trachea in mammals is called
A. palate B. epiglottis C. larynx D. glottis E. bronchus (1991/11 Nov)
8. During the inspiration process of breathing in man, which of the following events takes place?
A. Diaphragm becomes dome-shaped B. Intercostal muscles relax C. rib cage is lowered
D. sternum moves forward E. volume of the thorax decreases (2007/13 Neco)
9. Which of the following statements is TRUE of inhalation of air by man?
A. The ribs are not raised B. Diaphragm is raised C. Intercostal muscles relax
D. Pressure of the thoracic cavity increases E. Size of thoracic cavity increases (1982/38 JAMB)

10. Which of the following movements occur during exhalation?

A. The diaphragm and intercostal muscles relax B. The thoracic cavity increases in volume
C. The diaphragm and intercostal muscles contract
D. The diaphragm contracts and the intercostal muscled relax (1998/19 JAMB)
11. Which of the following is true about inspiration in mammals?
A. Intercostal muscles relax and ribs are lowered B. intercostal muscles contract, ribs move forwards
C diaphragm relaxes and returns to its dome-shaped position
D. volume of thorax decreases and pressure in the lungs increase
E. sternum moves backwards (1994/15 Nov)
12. Which of the following is the correct passage of air into the lungs?
A. Mouth→bronchus→brinchiole→lungs B. Nose→trachea→bronchus→lungs
C. Mouth→alveolus→brionchole→lungs D. Nose→brionchiole→trachea→lungs
E. Nose→trachea→brionchole→lungs (1996/13 Health Science Nov)

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Respiratory Systems in Plants
Plants do not have special respiratory organs for gaseous exchange. Gases move in and out of the plants through the
stomata and lenticels.
Stomata are very thin openings found in the epidermis of leaves and stems of seedlings. Each stoma (singular) is
surrounded by two bean shaped cells called guard cells. The guard cells have chloroplasts. The opening and closing of
the stomata are controlled by the guard cells.

opening and closing stomata

Mechanism of gaseous exchange through the stomata and lenticels

Gaseous exchange in plants is by stomata on the leaves and lenticels found on the stems.
Completely submerged aquatic plants like algae and floating aquatic plants like water lettuce exchange gases by
diffusion all over their body surface or through the stomata in their leaves
Terrestrial plants exchange gases mainly through the stomata in their leaves, lenticels in their stems and through the
roots (from air spaces in the soil particles around the roots)
Stomata have been observed to open during the day and close at night. Therefore, light intensity is seen as a major
factor controlling stomata movement (opening and closing of the stomata).
Other factors associated with stomata movement are water balance of plants and concentration of carbon (IV) oxide in
the surrounding air.
Wilting plants close their stomata: low concentration of carbon (IV) oxide causes stomata to open whereas high
concentration of carbon (IV) oxide causes the stomata to close.
The osmotic pressure within the guard cells also plays a role in the opening and closing of the stomata. When the
osmotic pressure is high, the guard cells become turgid and as a result of which the stomata pore opens. When the
pressure is low, the guard cells become flaccid and the pore is closed.
In general, the movement of gases and water vapour in and out of the leaves is controlled by the opening and closing
of the stomata.
The lenticels are breathing pores that permits the exchange of gasses between the environment and the internal tissues
of plants. They are always open in contrast to stomata which regulates their extent of opening. Lenticels are found on
the epidermis of different plant organs such as the stem, petiole and fruits.

Differences between respiration and photosynthesis

Respiration Photosynthesis
1. Respiration occurs in every living cells Photosynthesis occurs only in autotrophs.
2. Respiration releases energy Photosynthesis makes use of energy
3. Respiration results in a decrease in weight It results in an increase in weight
4. High energy containing food i.e. O2 and Low energy substances like CO2 and H2O are used.
carbohydrate are used.
5. Food substances are broken down Food substances are built up (i.e. anabolism)
(i.e. catabolism)

Example
(b) Describe briefly the process of gaseous exchange in the shoot system of flowering plants. (1993/2b)
Answer: In the shoot of flowering plants, gaseous exchange takes place through the stomata of the leaves and the
lenticels of the stem. The stomata are thin pores found mostly on the lower epidermis of the leaves. These pores are
enclosed by guard cells which change in volume due to osmotic pressure caused by the concentration of sugar in it.
When this osmotic pressure is high, the guard cells become turgid, thus making the stomata to open. The opened
stomata allows for the exchange of gases between the plant and its environment. The stomata close when the guard
cells become flaccid due to fall in the osmotic pressure. In summary, exchange of gases in and out of the plant, is
controlled by the opening and closing of the stomata.
Example
Which of the following structures would carry out respiration? A
A. germinating cowpea B. decolourized leaf C. dry leaf D. boiled cowpea (2018/11)
Answer: A – A germinating cowpea contains cells that are actively dividing, hence, needs energy that is produced through respiration
167
Example
The diagram below represents a section of the stem of a plant. Use it to Answer: question 11 and 12

Which of the labeled parts is made up of dead cells?

A. III and IV B. I, II and IV C. IV and V D. II and III E. II and IV
Answer: E – Label II (the bark) and label IV (the xylem) are made up of dead cells.
The part labelled I in the diagram is called
A. stoma B. epidermis C. lenticel D. cortex E. parenchyma. (1997/11-12)
Answer: C – The label I represents the lenticels of the stem.
Example
c. State FIVE differences between respiration and photosynthesis. (1999/2c NABTEB)
Answer:
- Respiration occurs in every living cells while photosynthesis occurs only in cells that have chlorophyll.
- Respiration releases energy while photosynthesis make use of energy.
- Respiration results in a decrease in weight while photosynthesis results in an increase in weight.
- High energy containing food i.e. O2 and carbohydrate are used while photosynthesis uses low energy substances like CO2 and water.
- Respiration is a catabolic process while photosynthesis is an anabolic process.

Example
In the above diagram (fig. 1) the cell which controls the opening and closing of stomata pore is
A. 1 B. 2 C. 3 D. 4 E. 5 (1979/36 JAMB)
Answer: E – Label “5” is the guard cell, and it controls the opening and closing of the stomata.
Example
In plants, respiration occurs in
A. mesophyll cells only B. the root only C. the stomata and lenticels only D. all living cells. (2005/22)
Answer: D – Respiration takes place in all living cells of a plant. This is true because cell living cells of a plant need energy for
their metabolic activities. This energy is produced through the process of respiration.
NB: Don’t confuse exchange of gases which takes places in the stomata and lenticels with respiration which occur inside the cells.
Example
Heat produced in tissue respiration in plants is
A. a chemical form of energy B. the main form of energy
C. a useful form of energy D. the only form of energy (2019/18 NABTEB)
Answer: A – Heat produced in tissue respiration in plants is a chemical form of energy.

EXERCISE 9.4
1. The flow of carbon dioxide and water in and out of the mesophyll layer of a leaf is controlled by
A. chloroplast B. lenticels C. air spaces D. guard cell (2020/11 PC1)
2. (c) Describe the mechanism of opening and closing of the stomata. (1991/4c Nov)
3. The function of lenticels is
A. to remove excess water in the plant B. to absorb water from the atmosphere
C. for gaseous exchange D. to absorb light E. to store food (1978/11 JAMB)
4. The absence of stomata shows that a leaf may be
A. from a floating plant B. from a submerged plant C. variegated
D. from a terrestrial plant E. from a parasitic green plant (1982/50 JAMB)
5. During respiration, air circulates round plant tissues via the
A. lenticels B. stomata C. guard cells D. intercellular spaces (1995/17 JAMB)

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Cellular Respiration
Respiration is the process by which assimilated simple sugar is broken down in a step wise series of chemical reaction
to produce energy. Carbondioxide and water are released as by – products during respiration.
Cellular respiration is the process whereby food substance are oxidized in the cells (particularly in the mitochondria)
to release chemical energy in the form of ATP for work.
C6H12O6 + 6O2 enzymes
  6CO2 + 6H2O + 38ATP

Types of cellular respiration (Aerobic Respiration & Anaerobic Respiration)

Aerobic Respiration
In this type of cellular respiration, oxygen is utilized in the oxidation of a sugar molecule (usually glucose within the
cell ), with the release of energy, carbon(IV)oxide and water. This type of respiration is commonly carried out by
most living things.
C6H12O6 + 6O2 enzymes
  6CO2 + 6H2O + 38ATP
Energy is stored in the cell in the form of adenosine triphosphate (ATP)
The first stage of aerobic respiration takes place in the cytoplasm and is referred to as glycolysis. Glycolysis is the
series of reactions in respiration by which glucose is incompletely broken down to pyruvic acid in the cytoplasm.
C6H12O6 + 6O2  2CH3COCOOH + 2H2 + 2ATP (energy)
enzymes
cytoplasm

The second phase or stage that follows glycolysis is referred to as the Kreb’s cycle or citric acid cycle. This is when
the pyruvic acid is completely broken down to form CO2 and water. The Kreb’s cycle takes place in the presence of
oxygen and during this phase further energy is released as shown in the equation below:
2CH3COCOOH + 2H2 + 6O2 → 6CO2 + 6H2O + 36ATP

The Kreb’s cycle (citric acid cycle)

The kreb’s cycle consist of a series of chemical reactions proceeding step by step in a cyclic manner under aerobic
conditions. The cycle was first worked out by H.A Kreb an English Biochemist in 1943. In the cycle, each reaction is
regulated by specific respiratory enzymes. The Kreb’s cycle takes place in the mitochondria.
The overall reaction of glycolysis and kreb’s cycle is represented by an equation.
C6H12O6 + 6O2 → 6CO2 + 6H2O + 38ATP (energy)

Outline of Glycolysis Kreb cycle outline (citric acid)

NB: If sufficient oxygen is available, each molecule of pyruvic acid (pyruvate) is oxidized to remove one molecule of carbon (IV)oxide
(decarboxylation) forming one molecule of acetic acid. The acetic acid combines with a co-enzyme called coenzyme A to form acetyl COA. The
acetyl COA then enters the citric acid or krebs cycle. Acetyl-coA combine with oxaloacetic acid to form citric acid (a 6 carbon acid).

169
Example
Aerobic respiration in the cell takes place in the
A. Cytoplasm B. lysosome C. nucleus D. mitochondrion (2011/3 Nov)
Answer: D – Aerobic respiration occurs in the mitochondria of the cell.
NB: Anaerobic respiration takes place in the cytoplasm of the cell.
Example
In cellular respiration, energy is stored in form of
A. chemical energy B. adenosine triphosphate ATP
C. Adenosine diphosphate ADP D. solar energy (2001/17 NABTEB)
Answer: B – In cellular respiration, energy is stored in form of adenosine triphosphate (ATP).
Example
Cellular respiration occurs in the
A. chloroplast B. endoplasmic reticulum C. food vacuole D. mitochondrion E. nucleus (2018/11 Neco)
Answer: D – Cellular respiration takes place in the mitochondrion of a cell.
Example
The part of the cell solely responsible for respiration is the
A. nucleus B. nucleolus C. mitochondria D. golgi apparatus E. endoplasmic reticulum (1980/27 JAMB)
Answer: C – Mitochondria is the part of the cell solely responsible for respiration.
Example
The gas produced during tissue respiration can be identified by using
A. calcium hydroxide B. copper sulphate C. calcium carbonate D. sodium hydroxide (2001/16 JAMB)
Answer: A – The gas produced during respiration is carbon(iv)oxide. This gas reacts with a solution of calcium
hydroxide (Ca(OH)2) to form a white precipitate (appears milky) of calcium carbonate. Hence, the gas produced
during cellular/tissue respiration can be identified by using calcium hydroxide (Ca(OH)2).
Example
Tissue respiration is important for the
A. release of energy for body use B. Absorption of oxygen into the alveoli
C. exhalation of carbon (IV) oxide from lungs D. Release of carbon (IV) oxide into the lungs (2002/31 JAMB)
Answer: A – Cellular/Tissue respiration is important for the release of energy for the body’s use.
Example
1(a) Describe briefly the process involved in the breakdown of glucose in the cell of living organisms to produce
energy (ATP).
(b) State two conditions under which glycogen can be converted to glucose to produce energy (1990/1a, b)
Answer:
1a. The process involved in the breakdown of glucose in living cells occurs in two stages. These stages include:
i. Anaerobic Stage: In this stage, glucose is broken down into pyruvate through series of enzymatic
reactions by the process of glycolysis. In this stage, oxygen is absent. This stage produces two
molecules of ATP for each of the glucose molecule broken down. This stage takes place in the
cytoplasm of the cell.
ii. Aerobic Stage: This stage occurs in the mitochondria of the cell. Here, pyruvate under the influence of
enzymes is oxidized to Acetyl COA with the release of carbon(iv)oxide. The Acetyl COA enters the
citric acid cycle (kreb cycle) where series of changes take place and oxygen combines with Hydrogen
to form water. In this stage, a lot of energy is produced in form of ATP.
Overall reaction can be summarized in the chemical equation below:
𝐶6 𝐻12 𝑂6 + 6𝑂2 → 6𝐶𝑂2 + 6𝐻2 𝑂 + 𝑒𝑛𝑒𝑟𝑔𝑦 (𝐴𝑇𝑃)
Example
Kreb’s cycle occurs in the
A. mitochondria B. cytoplasm C. nucleus D. ribosomes (2011/25)
Answer: A – Kreb Cycle (citric acid cycle) takes place in the mitochondria.
Example
The equation below represents the process of glycolysis Glucose + ATP heterokina
  se
 X + ADP X in the equation
represents
A. glucose diphosphate B. glucose phosphate C. glucose triphosphate D. fructose phosphate (2011/28)
Answer: B – “X” in the equation represents glucose phosphate.

170
EXERCISE 9.5
1. The process whereby sugar is broken down in the tissue to release energy is known as
A. assimilation B. digestion C. breathing D. oxidation E. aerobic respiration (1990/34 Health Science Nov)
2. Glycolysis involves
A. oxidation of fats and oil B. deamination of amino acid
C. oxidation of glucose D. fermentation of glucose (2001/25 NABTEB)
3. Kreb’s circle occurs in the
A. mitochondria B. cytoplasm C. nucleus D. ribosomes (2019/20 NABTEB)
4. Aerobic respiration in the cell takes place in the
A. cytoplasm B. lysosome C. nucleus D. mitochondrion (2011/8 Nov)
5. The Krebs’ Cycle usually starts with
A. acetyl coenzyme B. oxoglutanic acid C. lactic acid D. citric acid (1999/6 Nov)
6. Which of the following is true of aerobic respiration in a cell?
A. Oxygen is given off as a by-product B. Energy, carbon dioxide and water are given off.
C. Lactic acid and energy are released D. Carbon dioxide, lactic acid and energy are formed
E. Alcohol, carbon dioxide and energy are formed. (1994/6 Nov)
7. Glycolysis is best described as
A. splitting of glucose in the presence of oxygen B. anaerobic respiration of starch
C. fermentation of starch. D. splitting of glucose in the absence of oxygen (1994/7 Nov)
The diagram below represents the pathways of glycolysis. Study the diagram and use it to Answer: Questions 6 and 7.

8. Which of the following will be formed at stage III?

A. Acetyldehyde B. Acetic acid C. Lactic acid D. Ethyl alcohol E. Glucose (1995/6 Nov)
9. Which of the following stages shows the pathway that goes directly to the Krebs cycle after the formation of
pyruvic acid?
A. I B. II C. III D. IV E. V (1995/7 Nov)
10. Which statement about aerobic respiration is NOT correct?
A. Carbon dioxide is used up B. food substances are broken down
C. occurs in every living cell D. oxygen is used up
E. takes place throughout the day (2001/3 Neco)
11. The end product of glycolysis in plants and animals is
A. pyruvic acid B. citric acid C. aspartic acid D. malic acid (1995/16 JAMB)

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Anaerobic Respiration
In this type of cellular respiration, glucose is broken down inside the cell in the absence of oxygen, giving
carbon(IV)oxide, alcohol and 2ATP as products.
C6H12O → C2H5OH + 2CO2 + energy (2ATP)
Glucose ethyl alcohol
Examples of organisms that undergo anaerobic respiration are yeast, bacteria, fungi and endoparasites such as
tapeworm and roundworm.
The anaerobic respiration of yeast is referred to as alcoholic fermentation. In this process, the glucose is first
converted to pyruvic acid. The pyruvic acid is then reduced to ethanol by the acceptance of hydrogen from NADH.
1st step
C6H12O6 Glycolysis
  2CH3COCOOH+2H2 + 2ATP
NAD
Pryuvic Acid

nd
2 step
CH3COCOOH + 2NADH → 2CH3CH2OH + CO2 + 2NAD+
(pryuvic acid) (ethylalcohol)

Lactic acid fermentation: In this type of fermentation, no carbon(IV)oxide is given off. Instead, pyruvic acid
combines with hydrogen from NADH to produce lactic acid as shown below.
CH3COCOOH + 2NADH → CH3CHOHCOOH + 2NAD+
Pyruvic acid lactic acid

Lactic acid fermentation occur in the cell of human when there is not enough oxygen available for aerobic stages of
respiration. Lactic acid fermentation also occurs in some bacteria which live in anaerobic habitat such as the bottom of
ponds and sea. It occurs in the muscles of man and animals after a very fast race or strenuous exercise. During such
exercises, enough oxygen is not supplied to the exercising muscle for complete oxidation of glucose to release CO2,
H2O and energy. Instead lactic acid and a little energy are released. As the lactic acid accumulates, the increase in the
level of acidity in the muscles causes muscle fatigue and cramps. The athlete recovers when oxygen is carried to the
muscle cells later to oxidize the lactic acid to pyruvic acid and the pyruvic acid is oxidized by the supplied oxygen to
give carbon(iv)oxide, water and energy.

Oxygen Debt: The oxygen needed to oxidize lactic acid to pyruvic acid and from pyruvic acid to CO 2, H2O and
chemical energy is known as oxygen debt. When athletes for example undergoes strenuous exercises there is a built up
of lactic acid and this causes muscles to ache. Oxygen is needed to get rid of this lactic acid. The oxygen needed for
this purpose is what is known as oxygen debt. Some of the activities that can result to oxygen debt includes: running,
boxing, swimming etc.

Residual air: This is the amount of air that remains in the lungs after expiration or exhalation. It is that portion of the
air which cannot be expelled even by the most violent respiratory effort, it is important because it prevents the lungs
from collapsing and enables more oxygen to diffuse into the blood streams during inspiration or inhalation.

The process involved in the breakdown of glucose in the cell of living organisms to produce energy (ATP)
(i) Anaerobic process: the glucose is broken down in a series of step-wise reaction into pyruvic acid (a three
carbon compound) in the presence of the enzyme hexokinase. This process takes place in the absence of
oxygen and is referred to as anaerobic glycolysis. Energy is gained (2 ATP). The pyruvic acid is further
decarb-oxylated to acetyl fragments (two carbon compound).

(ii) Aerobic process: In the mitochondria, the acetyl group CH3CO becomes attached giving acetyl COA and
carbon(IV)oxide is liberated (after the reaction of pyruvic acid with coenzyme A). acetyl COA enters the kreb
cycle (also called the citric acid cycle) and undergoes a series of changes whereby oxygen and hydrogen
combine to form water. ATP (Adenosine triphosphate) molecule are generated from ADP (Adenosine
diphosphate) and phosphate.
C6H12O6 → 6CO2 + 6H2O + Energy (ATP)

In yeast cells, glucose is broken down into ethanol, carbon (IV) oxide and energy (in the absence of oxygen).
C6H12O6 energy
 2C2H5OH + 2CO2 + Energy.

During strenuous exercise, where oxygen in the muscles are so depleted, pyruvic acid is converted to lactic
acid. This is further oxidized to liberate energy.

172
Condition under which glycogen can be converted to glucose to produce energy
(i) During exercise when the body must have used up the available glucose in the tissues.
(ii) When the glucose level is low due to starvation, or as a result of sickness, or due to fasting. Or
(iii) When the adrenalin level is high which would have consumed the available glucose due to fright or anger.

Important of energy (ATP) released during respiration:

(i) ATP is used for work such as swimming, running, flying, heart beat, blood pressure, talking etc.
(ii) Transmission of nerve impulses or messages requires energy (ATP)
(iii) ATP is used to produce heat to keep the body warm in warm blooded animals.
(iv) Electric fish (Malapterurus electricus) converts ATP into electrical energy which form electric current used
for capturing of their prey and also for defence.
(v) ATP is used for active transport.
(vi) ATP is used to produce light in some animals such as fireflies.
(vii) ATP is used for the synthesis of proteins, starch, cellulose, fat and oil.
(viii) ATP provides energy used for cell division.

Example
The process of anaerobic respiration of yeast in sugar solution is known as
A. oxidation B. fermentation C. tissue respiration D. alcohol production E. decomposition (1991/6)
Answer: B – Fermentation is the anaerobic break down of sugar by micro-organisms such as yeast to produce energy
and alcohol.
Example
During anaerobic respiration in skeletal muscles, pyruvic acid is
A. reduced to lactic acid B. oxidized to ethanol C. oxidized to lactic acid D. reduced to water (1999/7)
Answer: A – In the absence of oxygen, pyruvic acid in skeletal muscles is reduced to lactic acid.
Example
When a mammal respires aneaerobically for a long time
A. pyruvic acid is converted into acetyl COA B. more energy is released from fats in the body
C. lactic acid accumulates in the muscles D. the Kreb’s cycle is fully completed. (2000/16)
Answer: C – When a mammal respires anaerobically for a long time, lactic acid begins to accumulate in the muscle.
Example
Which of the following is not a product of fermentation of glucose?
A. Energy B. Alcohol C. Lactic acid D. Carbon dioxide (2001/19)
Answer: C – In the fermentation of glucose by yeast, lactic acid is not a product.
Example
The products of respiration are
A. nitrogen and water B. nitrogen and carbon dioxide C. water and oxygen D. carbon dioxide and water (2004/14)
Answer: D – The products of respiration are carbon(iv)oxide water and energy.
Example
The role of ATP include all the following activities except
A. provision of energy to do work in living organisms B. transmission of nerve impulse
C. keeping the body warm in homothermic animals D. producing water during aerobic respiration (2005/17)
Answer: D – Producing water during aerobic respiration is not a role of ATP. All other options (A – C)) are roles of
ATP.
Example
Anaerobic respiration results in the production of
A. more energy than aerobic respiration B. no energy
C. an equal amount of energy to aerobic respiration D. less energy than aerobic respiration. (2013/10)
Answer: D – Anaerobic respiration produces less energy as compared to aerobic respiration.

EXERCISE 9.6
1. 1(a) Write the chemical equation for each of the following processes: (i) Anaerobic respiration
(ii) Anaerobic respiration in plants (iii) Anaerobic respiration in animals. (2010/1ai, ii, iii)
2. Muscle fatigue in the body of an athlete is due to
A. low pH B. high oxygen content
C. accumulation of lactic acid D. accumulation of carbonic acid (2019/10)

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3. When the human body is engaged in every strenuous physical exercise, the blood sugar is broken down into
energy and
A. carbon dioxide B. lactic acid C. glycogen D. ethanol (2002/10 Nov)
4. Lactic acid is produced in the human body when there is
A. lack of exercise B. presence of citric acid C. absence of oxygen D. lack of lipid (2020/10 PC1)
5. (c) State two differences between aerobic and anaerobic respiration.(1997/1c Nov)
6. The process of anaerobic respiration of yeast in sugar solution is known as
A. oxidation B. fermentation C. tissue respiration D. alcohol production E. decomposition (1991/6 Nov)
7. The anaerobic process of respiration occurs in the
A. cytoplasm B. endoplasmic reticulum C. mitochondrion D. nucleus E. ribosomes (2007/16 Neco)
8. The part of the cell solely responsible for respiration is the
A. nucleus B. nucleolus C. mitochondria D. golgi apparatus E. endoplasmic reticulum (1980/27 JAMB)
9. Anaerobic respiration in yeast produces
A. carbon dioxide and ethanol B. carbon dioxide and water C. carbon dioxide and oxygen
D. carbon dioxide and glucose E. ethanol and water (1984/18 JAMB)
10. The equation that can be used to summarize the process of anaerobic breakdown of sugar is
A. C6H12O6 → 2C2H2OH + 2CO B. 6CO2 + 6H20 → C6H12O + 6O2
C. C6H12O6 + 6CO + 6H2O + energy D. C6H12O6 → 2C2H5OH + 2CO2 + energy (1986/28 JAMB)

(i) Differences between aerobic respiration and anaerobic respiration

Aerobic respiration Anaerobic respiration
1 It requires oxygen Oxygen is not required
2 It produces high amount of energy (38 ATP) per molecule of It produces less amount of energy (2 ATP) per molecule of
glucose glucose.
3 Occur in most plants and animal cells. Occur in some bacteria, fungi and cells of the muscles of
animals.
4 CO2 and H2O are the by-products. CO2 and alcohol or lactic acid are the by-products.
5 Sugar (glucose) is oxidized completely Sugar is partially oxidized.
Glucose glycolysis
  pyruvic acid  O2
CO2 + H2O + 38ATP Glucose glycolysis
  pyruvic acid → CO2 + C2H5OH + 2ATP

Anabolisms: This refers to the synthesis of complex substances from simpler ones by the living things. The complex substances
are used to produce body tissue.

(ii) Differences between gaseous exchange and aerobic respiration

Gaseous exchange Aerobic respiration
1. Oxygen simply moves into the organisms and Oxygen is used to oxidize glucose
CO2 move out
2. Process takes place outside the cells Process takes place inside the cells
3. It is a physical process It is a chemical process
4. No energy is released Energy is released
5. No enzymes involved Enzymes are involved.

Usefulness of Food:
i. The food supplies energy when oxidized in the cell.
ii. The food is used for growth. Growth occurs when anabolic process proceed at a faster rate than catabolic process.
iii. Food is used to synthesis enzymes and hormones needed for good health.

Similarities between aerobic and anaerobic respiration.

(i) Both occur in the mitochondria of plants and animal cells.
(ii) Both involve the breakdown of simple sugar (glycolysis) to pyruvic acid.
(iii) Both convert pyruvic acid to energy called ATP.
(iv) Respiratory enzymes and coenzymes are involved on both cases.
(v) Carbon(IV)oxide is the by-product of both, except latic acid fermentation which does not produce Co2.
(vi) Both reactions produce by-products.

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 Experiments on Respiration
EXPERIMENT 1
Aim: To show that carbon (IV) oxide is given out by rat (mammal)

Materials: Three gas jars, a conical flask, caustic soda, lime water, small rat and delivery tube.

Method: The experiment is set up as shown below

Observation; Any CO2 in the air entering the apparatus is removed by caustic soda in the first gas jar. This is
confirmed by the lime water in the second gas jar, which means that flask containing the rat is free of carbon IV oxide.
After a short time, the lime water in the third gas jar began to turn milky indicating that the air reaching it contains
CO2. The CO2 must have been produced by the small rat.

EXPERIMENT 2
Aim: To demonstrate anaerobic respiration in yeast.
Materials: Two conical flask, fresh palm wine, Two rubber bungs, paraffin, and delivery tube.
Method: Obtain two conical flask and label A and B. put about 25cm3 of fresh palm wine containing yeast in flask A
while some lime water as put in flask B. Connect the two conical flask with delivery tube. Keep the flask containing
palm wine at a temperature of about 21oC.
Observation: After about 60 minutes, the palm wine started bubbling (fermenting). The gas bubbles were seen to be
escaping through the delivery tube to the lime water in flask B. The lime water turns milky, showing that the gas is
carbon IV Oxide.
Conclusion: This shows that yeast respire anaerobically (in the presence of oxygen).

Example
In which of the following processes is carbondioxide not given out
A. Respiration in plant B. Decay of organism C. Burning of Organic matter
D. Burning of fuels E. during photosynthesis (1993/36)
Answer: E – Carbon(iv)oxide is used up during photosynthesis. In all other options (A to D) carbon(iv)oxide is given off.
Example
Which of the following cell organelles is the site for production of ATP.
A. Lysosome B. nucleus C. mitochondria D. ribosome (2017/5)
Answer: C – ATP is produced in the mitochondria.
Example
3(a) List five classes of food other than carbohydrates
(b) Explain why glucose is taken by an athlete ready for a race rather than corn meal. (2000/3a, b)
Answer:
3a. Protein, fat & oil, mineral salt, vitamin and water.
b. Glucose is taken by an athlete ready for a race rather than corn meal because glucose is the simplest form of
carbohydrate and when taken, it does not have to go through the process of digestion which consumes time,
rather it is absorbed directly in the small intestine and taken into the blood stream where it assimilated and
oxidized by the athlete body cells to produce energy for the athlete. This process takes place within a short
period of time. A corn meal on the other hand, is a complex carbohydrate which requires a series of digestive
processes that starts from the mouth and ends in the small intestine. This takes more time to produce energy
need to be used by the athlete.

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Example
Which food type yields the most energy during respiration?
A. protein B. starch C. fat D. sugar (2005/32 Nov)
Answer: C – Fat produces more energy than other food type/classes.
Example
In palm wine, yeasts as a
A. carrier B. culturing agent C. preservative D. catalyst E. sweetening agent (1997/49)
Answer: D – Yeast acts as catalyst in palm wine. It converts the sugar in palm wine to carbon(iv)oxide and alcohol.
Example

The lime water in container C turned milky because

A. carbon dioxide was produced by plant B during respiration B. carbon dioxide entered C through the filter pump
C. oxygen reacts with lime water to produce milkiness D. soda lime did not remove carbon dioxide from air
E. the delivery tubes were not well connected (1980/35 JAMB)
Answer: A – Carbon(iv)oxide is capable of turning lime water milky, hence carbon(iv)oxide produced by the plant in
container “B” during respiration turned the lime water in container “C” milky.

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Excretory System
Every organism gets rid of the waste products of metabolism from its body cell or cells. This is because waste
products tend to be harmful if not removed from the body.
Excretion is the process by which an organism removes or eliminates from its body, waste products of metabolism
such as carbon-dioxide, nitrogenous substances and unwanted substances such as excess water.

Excretory organs and excretory products of some organisms

Organisms Excretory organs Main excretory products
1. Protozoa e.g. amoeba Contractile vacuole, by diffusion Carbon dioxide, ammonium salts, water.
2 Flat worms e.g. tapeworm Flame cells Water, urea, carbondioxide
3 Earthworms Nephridia Water, urea, carbondioxide
4. Insects Malphighian tubules Uric acid, carbon dioxide, water.
5. Fresh water fish Gills, kidneys Carbon dioxide, water, urea
6. Amphibians e.g. toad Skin, lungs, mouth, kidneys Carbon dioxide, water vapour, uric acid.
7. Reptiles Lungs, kidneys Carbon(iv)oxide, H2O, uric acid
8. Mammals Lungs, Skin, Kidney, liver Carbon(iv)oxide, water vapour, urea, salts
9. Flowering plants Stomata, Lenticels and leaves Water Vapour, Oxygen, carbondioxide,
alkaloids, tannins, resins.
10. Crustaceans Green gland, antennal gland and Uric acid, carbon dioxide, water.
maxillary gland

Example
4(a)(i) List five excretory organs found in living organisms.
(ii) Give one example of an organism in which each type is found (1991/4ai-ii)
Answer:
4ai. Contractile vacuole, flame cell, nephrida, malpighian tubule, kidneys.
ii. - Contractile vacuole e.g. Amoeba
- Flame cell e.g. Tapeworm
- Nephridia e.g. Earthworm
- Malpighian tubule e.g. Grasshopper
- Kidneys e.g. Rabbit
Example
3(a) (i) Define excretion (2002/3ai Nov)
Answer: Excretion is the process by which an organism get rid or removes from its body, waste product of
metabolism such as carbon(iv)oxide, nitrogenous substances and unwanted substances such as excess water.

Excretory mechanism in protozoan

The contractile vacuole is the excretory organ of the protozoa. The contractile vacuole is a specialized type of vacuole
that regulates the quantity of waste in the cell by expelling out excess water from the cell. The osmotic pressure within
the cytoplasm of protozoa cell is higher than that of the surrounding water. Water from the surrounding flows through
the semi-permeable membrane of their cell into the cytoplasm. As water flows, inside the cytoplasm, a contractile
vacuole is formed, which expels water when it gets to maximum size by contracting.

The membrane of the contractile vacuole reunites with the cell membrane after expulsion. The growth (water
gathering) and contraction (water expulsion) of the contractile vacuole and periodical excretion of carbondioxide and
ammonia is by diffusion through cell membrane.

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Excretory system in flat worms
Flame cells are found in flatworms such as Schistoma and tapeworms. The flame cells consist of two canals with
network of duct (tubules). The two canals open on the dorsal surface of the body by excretory pores. Each flame cell is
a bulb cavity and funnel shaped. Projecting down from the cell lumen is a brush of long cilia. The cell lumen ends up
as narrow tube called duct. The beating of the cilia resembles a flame. Flame cells remove waste from flatworms
through filtration in the manner similar to the kidney in mammals.

The flame cell of planaria

Excretory mechanism in Earthworm
The main waste materials in earthworm are carbondioxide and nitrogen waste. The excretory organ of the earthworm
is the nephridium (plural nephridia). The Nephridia are present in each segment of the earthworm body except for the
first three and the last segment. All nephridia have the same plan with each consisting of five portion namely
nephrostome, narrow tube, middle tube, wide tube and muscular tube. The nephrostome which is ciliated and funnel
shaped, leads to the exterior through an opening called nephridiopore. Each nephrostome is situated in the body cavity
of one segment while the rest coiled part of the nephridia are located in the body cavity of the segment behind it.
Coelomic fluid (containing useful materials like glucose and waste material) are drawn along the nephridia tube by the
beating action of the cilia. Useful materials are reabsorbed by the walls of the nephridia tubes as they are well supplied
by blood capillaries. The unabsorbed waste substances are collected as urine in the muscular bladder where they are
stored temporarily before it is discharged to the exterior through nephridiopore.
Carbon(iv)oxide is excreted from the body by diffusion through the moist body surface.

Mechanism of excretion in Insects

The malpighian tubule is the excretory organ in the insects. It is located between its midgut and rectum. The
malpighian tubule is made of two parts. The distal/free end which floats in the haemocoel and the proximal end which
opens into the gut.
At the distal end, nitrogenous waste products and water are absorbed from the heamocoel, in which they were
liberated. Conversion of these wastes into uric acid and reabsorption of water also takes place as the nitrogen waste
moves along the malpighian tubules towards the proximal end. Also in the hind gut, more water is absorbed by the
rectal glands. The absorption and reabsorption of water from these waste make them concentrated. The urine and
faeces that leaves the body is almost a dry solid.

Malpighian tubule of cockroach

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Example
The organelle which eliminates water from the body of protozoa is
A. plasma membrane B. contractile vacuole C. cell wall D. protoplasm E. nucleus (1991/2)
Answer: B – Contractile vacuole is the organelle that eliminates excess water from the body of protozoa.
Example
(b) (i) State two ways in which the excretory organ of earthworm is similar to that of mammals
(ii) Give three differences between them (1991/4bi, ii)
Answer:
bi. Similarities of the excretory system of earthworm and that of mammals:
- Both are well supplied with blood.
- Both excrete urea and water.
ii. Differences between them:
- The excretory organ of earthworm is made up of ciliated tubule which in mammals there is no ciliated
tubule.
- The excretory organ of earthworm is segmentally arranged while that of mammal is not segmentally
arranged.
- In earthworm, each unit of excretion of organ discharges directly outside the body while in mammals, the
units are united and discharge through a single duct.

Example
Which of the following structures functions as an excretory system found in flatworm?
A. Contractile vacuole B. Nephridium C. Flame cell D. Malphighian tubule E. Kidney (1993/14)
Answer: C – The Flame cell is the excretory organ of flat worms.
Example
(a) Describe the process of osmoregulation in (i) A named unicellular organism (1996/2ai)
Answer:
ai: The process of osmoregulation in Euglena: The Euglena uses contractile vacuole to carry out the process of
osmoregulation. Its cytoplasm is hypertonic to its environment; therefore water enters it by osmosis. To
prevent it from becoming turgid and burst, the contractile vacuole constantly get rid of the excess water out of
the cell, thereby maintain a balance of water with the euglena.
Example
Excretion in paramecium sp. is by diffusion because
A. its habitat is water and moist places B. it has simple, small and few internal organs
C. it has a large surface area to volume ratio D. it has a large efficient meganucleus (2010/10)
Answer: C – Excretion in paramecium is by diffusion through it entire body surface because it has a large surface area
to volume ratio.

EXERCISE 10.1
1. (c) Make a diagram 8 – 10cm long of a flame cell and label fully. (2010/1c)
2. The excretory product in protozoans is
A. amino acid B. uric acid C. ammonia D. urea (2014/1)
3. (ii) Name four excretory organs in animals. (2002/3aii Nov)
4. The excretory organ in insects is the
A. Kidney B. Malpighian tubule C. flame cell D. skin (2020/14 PC1)
5. The organelle which eliminates water from the body of protozoa is
A. plasma membrane B. contractile vacuole C. cell wall D. protoplasm E. nucleus (1991/2 Nov)
6. a. Name the excretory organs of the following organisms:
i. Flat worm; ii. Paramecium; (1999/2ai, ii Nov)
7. The structure responsible for excretion inn tape worm is called?
A. cell membrane B. contractile vacuole C. flame cell D. Malpighian tubule E. nephridum (2018/30 Neco)
8. What is the function of the contractile vacuole in paramecium?
A. Produces enzymes B. Gets rid of excreta C. Stores and digests food
D. Gets rid of excess water E. Controls movement (1981/13 JAMB)
9. The nephridia in the earthworm forms part of the
A. reproductive system B. respiratory system C. circulatory system D. excretory system (1990/14 JAMB)
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10. Flame cells are the
A. excretory system of worms B. excretory and respiratory systems of flatworms
C. secretory system of flatworms D. excretory system of flatworms (1993/8 JAMB)
11. The excretory structure in the earthworm is the
A. malphighian tubule B. flame cell C. nephridium D. kidney (1995/18 JAMB)
12. Which of the following is a waste product of an insect?
A. Alkaloids B. Uric acid C. Sweat D. Mucilage (2013/29 JAMB)
13. In which of the following groups of animal is the Malphigian tubule found?
A. Lizards, snakes and frogs B. Crickets, houseflies and grasshoppers
C. Millipedes, centripedes and scorpions D. Earthworms, roundworms and flatworms (1998/20 JAMB)

Excretory System in Mammals

There are four types of excretory organs used by mammals. These are lungs, skin, liver and kidney but the major
excretory organs in mammals are the kidney.
Excretory organs Materials excreted
lungs Carbon dioxide and water
Skin Sweat (containing water salts and urea)
Liver Bilirubin (a bile pigment), derived from decomposition of
haemoglobin
Kidneys Water, mineral salts, urea, uric acid and creatinine

The Kidneys
Kidneys are the organs responsible for the excretion of all nitrogenous wastes from the body and also responsible for
the osmoregulation of the blood and body fluid.

The human excretory system

Structure of kidney
There are two kidneys present in the abdominal wall(left and right). The right kidney is slightly lower in position than
the left one. Each kidney has a bean-shaped, appears dark red in colour and kept in position by fibrous capsule and fats
surrounding it. The adrenal gland lies at the top of each kidney. Each kidney is joined with renal artery, renal vein and
ureter. The renal artery carries oxygenated blood to the kidney while renal vein carries away deoxygenated blood.
Ureter carries urine to the urinary bladder.

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When a kidney is cut vertically, it consists of three portions, cortex, medulla and pelvis.

The vertical section of a kidney

Cortex: This forms the outer layer. It consists of malpighian bodies and tubules. The renal artery and veins forms
capillaries in the malpighian capsule.

Medulla: This is the inner layer and it consist of uriniferous tubules. The medulla forms inward projections of about
15-16 pyramids and it is through these pyramids that the uriniferous tubules open into the pelvis

Pelvis: This leads into the ureter. Ureter leads into the urinary bladder and the urinary bladder leads into the
urethra. The structure responsible for the formation of urine is the nephron (kidney tubule). Each kidney consists of
about one million nephrons. The nephron is otherwise known as the functional unit of the kidney.
Note: The urethra is shared by both the excretory and reproductive system

Nephron
Nephron
The nephron is the basic functional unit of the kidney. A nephron is made up of a cup-shaped Bowman’s capsule and a
long coiled uriniferous tubule. The Bowman’s capsule is supplied with a branch of renal artery (an arferent arteriole)
which divides several times and forms tiny branches called capillaries .These capillaries unite at one end to form the
efferent arteriole. This network of capillaries is called glomerulus. The walls of the glomerulus and Bowman’s capsule
have tiny pores which allows molecules to pass through. The body of the kidney is made up of the Bowman’s capsule
and glomerulus. The nephron consists of three portions namely:
i. First (proximal) convoluted tubule
ii. Loop of henle and
iii. Second (distal) convoluted tubule.
The first con-voluted tubule joins the Bowman’s capsule anteriorly and the loop of Henly posteriorly. The loop of
henle leads into the second convuluted tubule which in turn joins the main collecting duct. The efferent arteriole forms
a network of capillaries over the surface of the uriniferous tubule as it leaves the glomerulus

Formation and discharge of urine by the kidney

The cells of the liver are responsible for changing all nitrogenous waste into urea. The urea is carried to the kidneys by
the renal artery. Blood under high pressure flows into the Bowman’s capsule through a branch of renal artery (afferent
arteriole).This high pressure, allows substances of low molecular weight to pass through the tiny pores of the
glomerulus and Bowman’s capsule by a process called ultrafiltration. In this process substances of large molecular
size do not pass through the glomerulus but rather remains in the blood.
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Substances that flow into the Bowman’s capsule include urea, glucose, water, mineral salts, vitamins, hormones and
amino acid. The fluid in the Bowman’s capsule is called glomerular filtrate. This glomerular filtrate passes through
into the proximal convoluted tubule where they are reabsorbed into the body. A process called ultrafiltration.
After the reabsorption, the filtrate passes into the loop of henle where exchange of ions take place. This is where the
final reabsorption of water takes place. The longer the loop of henle, the more efficient the reabsorption of water. The
filtrate continues its journey to the distal convoluted tubule and collecting duct where further reabsorption of water
and salts takes place. After the reabsorption, the fluid in the kidney tubule is called urine. The collecting ducts then
empty the urine into the pelvis. From the pelvis, the ureter passes the urine into the urinary bladder where it is stored
for sometime and later discharged through the urethra to the outside world.
Note: Those substance that cannot pass through the glomerulus remain in the blood e.g blood cells and plasma
proteins like prothrombin and fibrinogen

Function of the kidney

1. Excretion
The removal of waste products of metabolism from the body. As discussed above.
2. Osmoregulation (Water balance in the body)
The process by which the amount of water to mineral salt in the body fluids of a living organisms is balanced is
known as osmoregulation.
In scenarios such as vigorous exercise like running, boxing e.t.c, water is lost from the body via sweating. The water
content in the body reduces as a result of this water loss. The body will need to conserve water in other to prevent
damage to the body cells due to loss of water. Osmoreceptor in the hypothalamus found in the brain, detect changes in
the osmotic pressure in the blood as the water content of the blood falls. The pituitary gland is stimulated to release
more ADH (Anti-Diuretic-Hormone) into the blood. This makes the walls of the kidney tubules more permeable to
water and so more water is reabsorbed into the blood by osmosis. Less water is then lost from the body through the
bladder as concentrated urine.
On the other hand, when there is too much water in the body, the osmoreceptors in the hypothalamus of the brain are
stimulated to release less Anti Diuretic Hormone into the blood thus making the walls of the kidney less permeable to
water and so less water is reabsorbed into the body by osmosis. Large quantity of water is then present in the urine
which is passed out from the bladder as diluted urine.
Also, when the weather is cold, urination is very frequent because little or no water is released through the skin by
sweating.
NOTE: The hormone which tells the kidney how much water to conserve is known as Antidiurectic hormone (ADH). It is also
known as Arginine vasopressin. ADH constantly regulates and balances the amount of water in the blood. IT is made by the
hypothalamus of the brain and stored in the posterior pituitary gland.

3. Acid Base Balance (PH)

The pH of human blood is between 7.3 and 7.4. A range that is below or above this is dangerous to the body. The
body fluids contain small amount of acid which is gotten from food and carbonic acids gotten during respiration when
carbon(iv)oxide combines with cell water. If the acid content of the blood get higher, the distal convoluted tubules
reabsorb more hydroxyl ions (OH-) from the urine and more hydrogen ions (H+) are excreted with the urine. Likewise,
if the hydroxyl ion content of the blood gets higher, less hydrogen ions are produced by the cells of the distal
convoluted tubules while more hydroxyl ions are produced and excreted with the urine. In this way, the acid base
balance of the body is maintained.

4. Kidney maintains the osmotic pressure of the blood.

Diseases of the kidney

Kidney diseases are as follows: i. Nephritis ii. Kidney stone iii. Diuresis

Nephritis: This is the condition known as inflamed kidney and it is as a result of infection in the throat, ears, nose etc.
The poison produced by the germs when carried by the blood to the kidneys damage the glomeruli. This causes the
glomeruli to inflame and be more permeable than normal. Other effects includes puffiness in the face, swollen kidney,
dizziness, fatigue, high blood pressure, back pain, headache, fever etc.

Prevention/cure
i. All food items must be properly washed or cooked.
ii. Drinking water must pass through proper purification process before consumption.
iii. Dialysis machine (artificial kidney) for filtering out waste could be used by a professional etc.

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Kidney stone: This results when tiny solids like calcium phosphate find their way into the nephron and become too
large to the extent of blockingf the nephrons . This disturbs the free flow of urine, causes severe abdominal pains and
also increases the blood pressure.
Some of the remedies to these disease includes:
i. Drinking of sufficient water and other fluid such as fruit juices in other to flush out unwanted waste product
ii. Intake of food containing calcium should be limited.
iii. Usage of prescribed drugs from qualified medical doctor.
iv. In extreme cases, surgery might be done to remove the stone.

Similarities between the excretory organ of mammal and earthworm

1. Both filter their excretory product.
2. Both reabsorb useful materials in the tubule.
3. Both excrete urea.
4. Both possess bladder for temporary storage of excretory products.
5. Both are made of network of long coil tube.
Differences between the excretory organ of mammal and earthworm
S/N Earthworm Mammals
1. Each segment has its own pair of excretory organ Nephrons unite form a main collecting tubule which
called nephridia which carries waste products outside empties into the renal pelvis and is discharged
the body. through single opening.
2. Nephridia are arranged in each segment. Nephrons are not arranged in segments.
3. The funnel is ciliated. The funnel is not ciliated.

Example
Which of the following statements on urine production is not correct?
A. concentrated urine is produced under the control of antidiuretic hormone
B. The total volume of urine produced depends on the need for water excretion
C. if there is an excess intake of water, dilute urine is excreted
D. if there is a shortage of water in the body the volume of urine produced decreases
E. in the presence of antidiuretic hormone dilute urine is produced. (1988/16)
Answer: A – The presence of anti-diuretic hormone leads to the formation of concentrated urine. Anti-diuretic
hormone signals the kidney to reabsorb more water from the filtrate in the tubules into the capillaries around the
tubule, thereby producing more concentrated urine.
Example
Which of the following performs the same function as the contractile vacuoles of a unicellular organism?
A. Kidney B. Alimentary canal C. Liver D. Pancreas E. Bladder (1994/20)
Answer: A – The kidney helps in osmoregulation in higher animals just as the contractile vacuole helps in
osmoregulation in unicellular organism.
Example
Which of the following is the correct route for the movement of materials through the kidney?
A. Glomerulus Bowman’s capsule Loop of Henle Collecting tubule Pelvis
B. Glomerulus Loop of Henle Collecting tubule Bowman’s capsule Pelvis
C. Pelvis Bowman’s capsule Glomerulus Loop of Henle Collecting tubule
D. Bowman’s capsule Glomerulus Loop of Henle Collecting tubule Pelvis
E. Bowman’s capsule Loop of Henle Glomerulus Collecting tubule Pelvis (1989/4)
Answer: A – The route of materials through the kidney is:
Glomerulus → Bownman’s Capsule → Descending Tubule → Loop of Henle → Ascending tubule → Collecting duct → Pelvis
Example
The mechanism by which useful materials in the glomerular filtrate are taken back into the blood is known as
A. filtration B. reabsorption C. haemolysis D. osmosis E. dialysis (1990/21)
Answer: B – The mechanism by which useful materials in the glomerular filtrate are taking into the blood is known as
selective reabsorption.
Example
The cup-shaped part of the Bowman’s capsule contains the
A. nephridium B. glomerulus C. loop of Henle D. nephron E. convoluted tubule (1990/23)
Answer: B – The cup shaped part of the bowman’s capsule contains the glomerulus. The glomerulus is a cluster of
capillaries.

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Example
Kidney stone is a disease of the kidney that results in the
A. blockage of the tubules by solid particles B. passing out useful materials of the body fluid with urine
C. presence of large quantity of water in urine D. passing out hormones in urine
E. prevention of urine production (1991/13)
Answer: A – Kidney stone results in the blockage of the tubules by solid particles. These solid particles are hard
collections of salt and mineral often made up of calcium and uric acid.
Example
Ultra filtration process at the Bowman’s capsule is facilitated by
A. the volume of water in the blood B. the high concentration of urea in the blood of the bowman’s capsule
C. the differential blood pressure between blood pressure between the glomerulus and the bowman capsule
D. the differential blood volume between the glomerulus and the Bowman’s capsule
E. heavy weight of the urea, water, glucose and amino acids in the Bowman’s capsule. (1995/60)
Answer: C – ultra filtration process at the bowman’s capsule is facilitated by the differential blood pressure between
the glomerulus and the bowman’s capsule.
Example
Which of the following is more concentrated to the blood within the renal artery that the blood within the renal vein?
A. Urea B. Red blood cells C. Glucose D. Protein E. White blood cells (1996/13)
Answer: A – Urea is more concentrated in the blood within the renal artery as compared to the blood within the renal
vein. This is because, the renal artery carries blood that is highly concentrated with urea from the abdominal aorta to
the kidney which helps to filter out urea from the blood, hence, making the blood going into the renal vein to have
little or no concentration of urea.
Example
Which of these is not a function of the kidney?
A. Production of urine B. Maintenance of acid-base balance in the body C. Osmo-regulation
D. Removal of urea E. Production of bile (1998/17)
Answer: E – Kidney does not produce bile. Bile production is the function of the liver
Example
In which part of the kidney does ultrafiltration take place?
A. Bowman’s capsule B. Distal convoluted tubule C. Proximal convoluted tubule
D. Collecting duct E. Afferent arteriole (1998/18)
Answer: A – Ultrafiltration takes place in the bowman’s capsule
Example
The glomerular filtrate contains the following substances except
A. water B. urea C. blood corpuscles D. Glucose (2003/18)
Answer: C – The glomerular filtrate does not contain blood corpuscles. NB: The glomerular filtrate contains water,
glucose, amino acids, salts and urea.
Example
The Malpighian body of the mammalian kidney is made up of
A. Cortex and Medulla B. Bowman's Capsule and loop of Henle
C. Glomerulus and Bowman's capsule D. Pelvis and Pyramid (2007/15)
Answer: C – The malpighian body of the kidney is made up of the glomerulus and the bowman’s capsule.
Example
Which of the following organisms has kidney as their excretory organ?
A. Fishes, amphibians, birds, man B. Fishes, amphibians, annelids, insects
C. Fishes, reptiles, birds, tapeworms D. Fishes, protozoans, amphibians, man (2009/18)
Answer: A – Fishes, amphibians, birds and man have kidney. NB: All vertebrates have kidney.
Example
The excretory system in mammals consists of the following parts except
A. two kidneys B. two ureters C. two bladders D. one urethra (2010/15)
Answer: C – Mammals usually have one bladder.
Example
More sweat is produced during muscular exercises because
A. the contracting muscles produce water B. fermentation occurs in muscles
C. the temperature of the body rises D. the muscles fatigues (2011/17)
Answer: C – More sweat will be produced during muscular exercises because the temperature of the body rises. This
is in order to cool the body.

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Example
A substance present in the glomerular filtrate in the mammalian kidney is
A. glucose B. fibrinogen C. albumen D. blood platelets (2013/16)
Answer: A – Some amount of glucose is present in the glomerular filtrate.
Example
Which part of the nephron is associated with ultra-filtration?
A. Distal convoluted tubule B. Proximal convoluted tubule
C. Collecting duct D. Bowman’s capsule (2013/19)
Answer: D – The Bowman’s capsule is involved in ultra filtration process of the kidney.
Example
Water and salts are both from the human body in
A. breath and sweat B. breath and urine C. breath, urine and sweat D. sweat and urine (2015/9)
Answer: D – The sweat and urine contain water and salt.
Example
Which of the following substances is not usually present in the urine of a healthy person?
A. Urea B. Mineral salts C. Glucose D. Water (2016/10)
Answer: C – In the urine of a healthy person, glucose is not always absent.
Example
The diagram below is an illustration of the urinary tubule in a mammal. Study it and Answer: questions 14 to 15.

The part which contains the lowest concentration of urea is labeled

A. I B. II C. III D. IV
Answer: C – The labeled III point to the efferent arteriole which contain less concentration of urea. This is because good amount
of urea has been filtered out from the blood in the glomerulus before the blood enters the efferent arteriole.
Which of the following substances is greater in concentration in the part labelled IV when compared to that of the part
labeled I?
A. Lipid B. Glucose C. Urea D. Uric acid (2017/14-15)
Answer: C – The part labeled IV is the collecting duct. It contains great amount of urea and water.
Example
Deamination of amino acids in the liver produces
A. blood sugar B. glycogen C. bile D. urea (2017/16)
Answer: D – Urea is a product obtained from the deamination of proteins in the liver.
Example
Which of the following substances is not an excretory product of animals?
A. Carbon dioxide B. Urea C. Sweat D. Oxygen (2018/12)
Answer: D – Oxygen is not an excretory product in animals. it is used to cellular/tissue respiration in animals.
Example
The process by which nitrogen is removed from amino acid and converted into urea is known as
A. emulsification B. glycolysis C. deamination D. detoxication (2003/10 Health Science Nov)
Answer: C – Deamination is the removal of an amino group (a nitrogen) from an amino acid and its conversion into
urea. The process takes place in the liver.
Example
Which of the following glands is located at the top of the kidneys?
A. Thyroid gland B. Adrenal gland C. Pituitary gland D. Parathyroid gland (2003/25 Health Science Nov)
Answer: B – The adrenal gland is located at the top of the kidneys.
Example
Which of the following will not be reabsorbed by the uriniferous tubule?
A. Mineral salts B. Water C. Urea D. Glucose E. Protein (1990/37 Nov Health Science)
Answer: C – Urea is a metabolic waste product and will not be reabsorbed in the uriniferous tubule.

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Example
Which of the following processes eliminates non-metabolic waste products from the body of man?
A. Urination B. Panting C. Sweating D. Defecation E. breathing (1990/5 Health Science Nov)
Answer: D – Defecation is the process of eliminating solid or semi-solid waste materials (faeces) from the digestive
tract via the anus. This does not involve the removal of metabolic waste.
Example
The conversion of excess amino acids into urea in man is carried out by the
A. kidney B. liver C. skin D. small intestine E. pancreas (1990/17 Health Science Nov)
Answer: B – The conversion of excess amino acids into urea (deamination) is carried out in the liver.
Example
Into which part of the kidney are waste materials filtered under pressure?
A. Pyramid B. Ureter C. Bowman’s capsule D. Medulla E. Tubules (1990/36 Health Science Nov)
Answer: C – Waste materials are filtered under pressure into the Bowmen’s capsule of the kidney.

EXERCISE 10.2
1. Which of the following is not involved in the process of excretion of nitrogenous waste in the human body?
A. Selective reabsorption takes place B. A lot of liquid is required for the process
C. It removes toxic substances from the cells D. It keeps the environmental temperature of the cells constant
E. It occurs in the kidney (1990/39 Health Science Nov)
2. Water is re-absorbed by the uriniferous tubules into the blood in order to
A. maintain water balance in the tissues B. prevent frequent urination
C. increases the volume of blood D. replace water loss by sweating
E. replace metabolic water (1990/41 Health Science Nov)
3. Which of the following does not perform the function of excretion?
A. contractile vacuole B. skin C. Malpighian tubule D. Flagellum (2018/32 NABTEB)
4. Which of the following best describes the function of the leaf in flowering plants?
A. absorption of water vapour B. manufacture of food substance through photosynthesis
C. excretion of waste products D. transpiration of water vapour (1999/16 NABTEB)
5. Which of the following explains what happens to excess amino acid in the body of mammals? It is
A. stored in the liver B. broken down in the liver C. Converted into urea in the kidney
D. stored as bile in the liver E. stored in the blood (1992/11 Nov)
6. Excretory products in mammals do not include
A. urea B. mineralsalts C. carbon dioxide D. ammonia E. water (1992/12 Nov)
7. Which of the following statements is correct?
A. Excretory structures of organisms vary in complexity B. Urine is the only excretory product of animals
C. Nephridium is the excretory organ in insects D. in insects, the malpighian tubules takes part in feeding only
E. In plants, carbon dioxide and water are excreted through the lenticel only (1994/19 Nov)
8. Which of the following is an example of excretion in mammals? The
A. voiding of waste of digested food through the anus B. release of digestive enzymes into the stomach
C. removal of urea by the kidney D. release of hormones from glands (2004/9 Nov)
9. The following are functions of the liver except
A. deamination of excess amino acids and proteins B. excretion of bile pigments
C. manufacture of blood plasma D. production of heat E. storage of vitamins and minerals (2008/22 Neco)
10. The following are kidney diseases except
A. diuresis B. hepatisis C. kidney stones D. nephritis E. oedema (2008/23 Neco)
11. The network of blood capillaries in the kidney capsule is referred to as
A. capsule B. glomerulus C. pelvis D. pyramid E. ureter (2008/51 Neco)
12. Which of these is NOT an excretory product?
A. faeces B. salts C. sweat D. urine E. water (2007/9 Neco)
13. Which is NOT a kidney disease?
A. cirrhosis B. kidney stones C. nephritis D. uraemia E. Wilm’s tumor (2001/15 Neco)
14. The following are animal excretory products EXCEPT
A. ammonia B. carbondioxide C. tannins D. urea E. urea (2005/21 Neco Nov)
15. Which of these products obtained from analyzing sweat from the skin is not an excretory product?
A. water B. Salts C. Dust D. Urea E. Urates (1978/47 JAMB)
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16. Which of the following is not an excretory organ?
A. Lungs B. Kidney C. Leaf D. Large intestine E. Skin (1979/16 JAMB)
17. Which one of the following parts of the mammalian body is most closely associated with the production of
urine?
A. Malpighian capsule B. Urinary bladder C. Ureter D. Vas deferens E. Urethra (1980/22 JAMB)

18. The kidneys of all vertebrates act as osmoregulators. This means that they
A. keep the composition of the plasma constant B. regulate osmotic processes
C. control the volume of blood entering the kidneys D. decrease the osmotic pressure of blood
E. increase the osmotic pressure of the blood (1983/14 JAMB)
Use the diagram below to Answer: questions 17 and 18

19. In mammals, reabsorption of salt takes place in

A. I B. II C. III D. IV (2000/17 JAMB)
20. The parts labeled I and II make up the
A. glomerulus B. Bowman’s capsule C. Malphighian body D. convoluted tubules (2000/18 JAMB)
21. The urinary tubules of the kidney function through
A. ultrafiltration and selective reabsorption B. active transport and cytoplasmic streaming
C. osmosis and diffusion D. Active transport and osmosis (2005/7 JAMB)

22. Excess water in plants is excreted as water vapour and droplets respectively through
A. transpiration and guttation B. respiration and guttation
C. guttation and condensation D. Photosynthesis and guttation (2005/11 JAMB)
23. 4(a) List three functions of the kidney
(b) Make a labeled diagram of the mammalian kidney tubule (nephron) (1989/4a-b)

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Excretion in Plants
Plants have no special excretory organs. Waste materials are disposed through various parts of plant. The excretory
products in plants include carbon-dioxide, oxygen, tannis, acids, resins, mucilage, latex, alkaloids, oils, gum and
anthocyanin. The main excretory organs of flowering plants are the stomata in the leaves and lenticels in the stem.

Opening of stomata
The opening and closing of the stomata depends on the turgidity of the guard cells.

During the day, manufactured food increases the concentration of cell sap which enables water to move into the
epidermal cell of the guard cells by osmosis. The guard cells become turgid. This in turn makes the cell wall to open.
At night, when photosynthesis has ceased, the sugar in the guard cells is converted into starch. The concentration of
the cell sap of the guard cells is lower than epidermal cells. Water now moves from the guard cells to the epidermal
cells. This enables the cell wall to close.

Opening and closing of the stomata

Differences between excretion in flowering plants and excretion in humans

Flowering plants Humans
Excretory organ is not definite Have definite excretory organs like liver, kidney and skin.
Releases tannins, alkaloids, resins, gums etc as waste products Sweat, urea, urine, salts etc. are released as waste products.
Excretory products are in small quantities. Excretory products are released in large quantities.
Excretory products are released in slower rate. Excretory products are released in a faster rate.
Some of the Excretory products released are stored. Most of the Excretory products are removed completely.
Excretory products like carbondioxide, oxygen and water Products like uric acid, urea can’t be reused.
vapour can be re-used.
Excretory products are produced from simple organic products are produced from complex organic molecules.
molecules.

Example
(c) Describe the mechanism of opening and closing of the stomata. (1991/4c)
Answer: The opening and closing of the stomata is regulated by the guard cells. When the solute concentration of the
guard cells is high as a result of buildup of sugar through the process of photosynthesis, water begins to flow from
neighbouring cells into the guard cells by osmosis. This makes the volume and turgidity of the guard cells to increase.
When this happens, the thin outer walls of the guard cells stretch more than the thicker inner walls causing the stomata
to open. When the solute concentration of the guard cells is low especially at night, water begins to flow out of the
guard cells by osmosis. This causes the volume and turgidity of the guard cells to decrease and the guard cells become
flaccid, then the stomata pore closes.
Example
Use the diagram below to Answer: questions 13 to 15

The function of the part labeled I is

A. controlling water loss B. trapping solar energy C. absorbing water
D. guard cell E. epidermal cell
Answer: B – The part Labeled I points to the chloroplast of the guard cell which traps solar energy.

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The part labeled II is the
A. stoma B. palisade cell C. spongy cell D. guard cell E. Epidermal cell
Answer: A – The part Labeled II point to the stoma (pore) between two guard cells.
The structure that will be stained blue-black by iodine is labelled
A. I B. II C. III D. IV E. V (1995/13-15)
Answer: A – The part Labeled I points to the chloroplast. Starch is stored in the stroma of chloroplast. The chloroplast
will be stained blue-black by iodine because it contains starch.
Example
Which of these is not an excretory product of a plant?
A. Tannin B. Gum C. Alkaloid D. Sweat E. Anthocyanin (1998/16)
Answer: D – Sweat is an excretory product of animals not plants.
Example
Study the information below. Use it to Answer: question 9
In an experiment to study the rate of water loss in plants, leaves of a potted plant were tested as follows:
I. Upper surface covered with Vaseline II. Lower surface covered with Vaseline
III. Both surfaces covered with Vaseline IV. None of the leaf surfaces covered
Indicate in a descending order, the rate of water loss from the leaves
A. I, II, III and IV B. II, I III and IV C. III, II, I and IV D. IV, I, II and III (2002/9)
Answer: D – The descending order of water lost will be: IV, I, II and III. This is because stomata is more on the lower
surface of the leaves than the upper surface of the leaves and when Vaseline is applied, it block the stomata. NB:
Stomata is the pore of the leaf that allows for water loss.
Example
The opening of the guard cells of the epidermis in plants is by the process of
A. osmosis B. diffusion C. active transport D. transpiration (2013/8)
Answer: A – The opening of the guard cells of the epidermis in plant is by the process of osmosis.
Example
Excretory products in plants responsible for the decolouration of flowers are called
A. alkaloids B. tannins C. anthocyanins D. resins (2019/13)
Answer: C – Anthocyanins are the excretory products of plants that decolourises flowers.
Example
Which of the following is not an excretory product of plants?
A. Quinine B. Tannin C. Latex D. Cytosol (2018/42 NABTEB)
Answer: D – The cytosol is the fluid part of the cytoplasm within which various organelles and particles of the cell
are suspended. It is not a waste product of plants.
Example
a (iii) Give two examples of each, of excretory products in plants and animals. (2002/3aiii Nov)
Answer:
Excretory products of plants: Excretory products of animals:
- Tannin - Urea
- Anthocyanin - Carbon(iv)oxide

Example
What is not an excretory product of plants?
A. cocaine B. oxygen C. quinine D. tannins E. sap (2001/2 Neco)
Answer: E – Sap is the fluid transported in the xylem or phloem of a plant. This fluid is useful to the plant as it
contains; water, mineral salts or nutrients.

EXERCISE 10.3
1. The amount of water lost from a leaf can be detected using
A. lime-water B. red litmus paper C. blue litmus paper
D. blue cobalt chloride paper (1980/49 JAMB)
2. Which is the correct order of water loss from the leaf?
1. Mesophyll
2. Veins
3. Substomatal cavity
4. Stomata
A. 3→2→1→4 B. 2→3→1→4 C. 2→1→3→4 D. 1→2→3→4 (1988/23 JAMB)
189
3. Which of the following is a plant excretory product?
A. Oil B. Cytokinin C. Resin D. Amino Acids (1991/29 JAMB)
4. The opening and closing of the stoma are regulated by
A. transpiration B. respiration C. diffusion D. osmosis (2007/24 JAMB)
5. Excretory products responsible for the red, purple and blue colours of flowers are called
A. alkaloids B. tannins C. anthocyanins D. resins (1990/24 JAMB)
6. Which of the following waste products in plants is excreted through the stomata and lenticels?
A. Carbon dioxide B. Alkaloids C. Tannis D. Anthocyanins (1994/22 JAMB)
7. The waste product of plants used in conversion of hid of leather is
A. gum B. alkaloid C. tannin D. resin (2007/31 JAMB)
8. Water in plants is removed as water vapour through the process of
A. evaporation B. transpiration C. diffusion D. osmosis (2014/19 JAMB)

9. b i. In a tabular form, state four similarities in structure between the skin of man and the leaf of a plant.
ii. Mention five functions of the liver
c i. Name the waste product common to insects, reptiles and birds.
ii. Mention one hormone that controls reabsorption of water in man. (1999/2b-c Nov)
10. 2(a) Draw a well labeled diagram (8-10cm long) of the nephron
(b) State two importance of excretion in mammals
(c) Name two excretory structures each in: (i) Lower Animals (ii) Higher Animals (2008/2a-c Neco)

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Regulation of Internal Environmental (Homoeostasis)
Homeostasis is the process of maintaining a steady internal environment. The cells of multicellular organisms are
bathed in body fluids such as blood, lymph and intercellular (or tissue) fluid. This internal environment must be kept
fairly constant for the health, growth and efficient functioning of the cells.
An organism regulates its internal environment and keeps it in a steady state by constantly adjusting any changes in
the physical and chemical conditions of its body fluids. These conditions include temperature, osmotic pressure and
concentration of dissolved substances in the body fluids such as CO2, O2 and urea, food substances (glucose, amino
acids etc) and ions (Na, K, Chlorine e.t.c)

Homeostasic Organs and Substances

Homeostasis takes place at all level of “Organization of life”. In unicellular organisms such as amoeba and
paramecium, the contractile vacuole which is used for osmo-regulation, performs the function of homeostasis. In
higher animals, such as mammals special organs have been developed to carry out this homeostasic process. The main
organs and substances involved in homeostasis in mammals are;
1. Kidney
2. Liver
3. Skin
4. Hormones (substances secreted by endocrine glands)
Although these organs and hormones play an important role in homeostasis, the brain has overall control over
homeostasis processes in the body
Example
Which of the following describe a condition of constant internal environment of the body?
A. Synthesis B. Osmosis C. Hydrolysis D. Homeostasis E. Diffusion (1996/36 Health Science Nov)
Answer: D – Homeostasis is the process of maintaining a steady/constant internal environment.
Example
The ability of organisms to maintain a constant internal environment is known as
A. diuresis B. homeostasis C. dialysis D. endosmosis (2019/24 NABTEB)
Answer: B – The ability for an organism to maintain a constant internal environment is homeostasis.

EXERCISE 11.1
1. The control of water and salt requirements of the body in order to maintain a stable internal environment is
known as
A. osmosis B. excretion C. plasmolysis D. ultrafiltration E. homeostasis (1994/52)
2. The process of maintaining a steady internal environment is known as
A. osmoregulation B. equilibration C. homeostasis D. plasmolysis (2019/14)

THE KIDNEY
Mammals have two kidneys attached to the dorsal wall of the abdominal cavity. Each of the kidneys lies on either side
of the vertebral column. At the top of each kidney lies the adrenal gland
A kidney is bean – shaped and reddish – brown in colour.
A vertical section shows three part.
1. The cortex on the outside.
2. The medulla, the inner zone, which projects in form of a pyramid into the pelvis
3. The pelvis, a cavity which leads into the ureter.
The kidney consists of numerous units each called a kidney tubule or nephron (urinary tubule).

Cortex

The longitudinal section of a kidney

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Regulatory function of the kidney
1. OSMOREGULATION
Osmoregulation is the control of the concentration of substances in the blood and body fluid by regulating the amount
of water and salts in them. When there is excess water in the blood, the kidney under the influence of a hormone
known as antidiuretic hormone or vasopressin, excretes more water so that the amount of water in the blood returns to
a required level. When the blood contains less water than its optimal, it minimizes the excretion of water from the
glomerular filtrate.

2. REGULATION OF SALT CONCENTRATION IN THE BODY

Salts exist in the blood in the form of ions. The kidney controls the concentration of various ions in the blood by
excreting more of the ions which are excess and excreting little (or none) of the ions in short supply.

3. REGULATION OF ACID – BASE BALANCE

When the blood is acidic, the kidneys excrete acid radicals so as to restore the balance. If the blood is basic, the kidney
excretes more basic ions than usual, to restore the acidic – base balance.

4. The kidney excretes urea to keep the body free from this waste product

5. The kidney helps to maintain the osmotic pressure.

NEPHRON (KIDNEY/URINARY TUBULE )

The nephron is the functional unit of the kidney. Each urinary tubule begins in the cortex as a cup – like structure
called the Bowman’s capsule. The capsule opens into a short coiled tube called proximal convoluted tubule. It
straightens out as it passes into the medulla, where it makes a U – shaped loop, the Henle’s loop before re – entering
the cortex. In the cortex, the tubule becomes coiled again to form the distal convoluted tubules. The tubule bends once
more and completes its course in the medulla.
The tubule widens as it approaches the pelvis. The tubule pours its content into the main collecting ducts which
eventually join up and open into the pelvis at the apices of the pyramids.
The tubules are closely associated with several networks of blood capillaries. The renal artery branches in the kidney.
Each branch breaks into a mass of blood capillaries in the Bowman’s capsule. The knot of the capillaries is called
glomerulus. The capsule and glomerulus forms the malpighian capsule or body.

A Nephron

malpighian capsule

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MECHANISM OF EXCRETION BY THE KIDNEY
Blood that enters glomerulus from different arteriole is pressured. As this happens, water, urea, mineral salts, sugar
and other wastes present in the blood are filtered into the capsule by a process called ultra – filtration
The filtrate known as glomerular filtrate then passes into the proximal tubule where reabsorption of some useful
materials like water, glucose, amino acid, vitamins, hormones and salts (e.g. chloride, hydrogen trioxocarbonateIV,
tetraoxophosphateV and tetraoxosulphateIV of sodium, potassium and calcium) takes place. This re-absorption called
selective re-absorption prevents the loss of useful substances from the blood stream.
In the distal portion of the tubules, more water is re-absorbed into the blood stream so that the resulting fluid called
urine, becomes very concentrated. The urine then trickles down the ureter and collects in the urinary bladder. Usually,
the sphinter muscles at the base of the urinary bladder relaxes so that the urine is expelled through the urethra

Diseases of the Kidney

1. NEPHRITIS
This is a medical term which refers to inflammation of the kidneys. In this disease, the glomeruli i.e. blood vessels
becomes inflamed so that ultra – filtration is incomplete. The result of this is that it may lead to the passing out of
much useful materials of body fluid with urine. This disease is caused by Streptococcus infection of the throat, ear,
Effects
1. Glomeruli become inflamed, making them more permeable than normal.
2. Kidney becomes swollen.
3. Puffiness in the face.
4. Watery swelling in the feet and ankles.
5. Dizziness, fatigue, high blood pressure, convulsion, back pain, headache, fever and vomiting may result.
6. Protein and blood cells pass into the urine.
Remedies
1. All food items must be properly washed and well cooked
2. Drinking water must be properly boiled and filtered
3. Dialysis machine can be used to filter out the waste. This is very expensive

2. KIDNEY STONE
This is a condition in which the nephrons i.e. kidney tubules are blocked. This is caused by some tiny solid (e.g.
calcium phosphate) present in urine which are not very soluble. These solids are precipitated under certain conditions
in the nephron into kidney stone. When the kidney stones become too large, they block the free flow of urine.
Effects
1. Difficulty in passing out urine
2. Severe abdominal pains
3. High blood pressure may occur
Remedies
1. Drink sufficient water and other fluids such as fruits juices especially during hot weather so as to prevent the
urine from becoming concentrated. Over concentrated urine may lead to precipitation of kidney stones
2. Avoid food items that are hard to digest.
3. Avoid excessive intake of food containing calcium.
4. Prophylactic drugs can be used to dissolve the stones.
5. SURGERY: If the usage of drugs fail, surgery can be carried out to remove the stones.

3. DIURESIS
This is a condition in which there is removal of excess watery urine from the body through the kidneys. This situation
occurs when the kidney tubules fails to re-absorb water from the glomerular-filtrate, back to the blood. It is caused by:
a. Diseases such as Diabeties insipidus and pituitary disease.
b. Lack of a hormone called aldostetrone causing excess sodium ions to be excreted.
c. Drinking excessive alcohol.
d. Drugs such as lasix when given to patients suffering from oedema can cause diuresis.
e. Heart failure, renal failure and kwashiorkor also causes diuresis.
Effects
1. Thirst and dehydration results due to excess removal of the body fluid.
2. High blood pressure may occur.
3. It leads to loss of serum electrolytes from the body.
4. Loss of appetite, weakness, fatigues and nausea. Death eventually results, if not treated.

193
Remedies
1. Do not use fan and air conditioners in cold weather.
2. Avoid excessive drinking of alcohol.
3. Diabetic patient should be treated with insulin.
4. Those who lack ADH and aldoestrone should be treated.
5. Kidney transplant.

4. OEDEMA/DROPSY
This is a condition in which some part of the body becomes swollen because so much water is retained within the
blood. Oedema may be caused when the cells of the kidney tubules are unable to absorb water from the blood into the
tubules
Effect
Swelling of feet and ankle is noticed.
Remedy
Oedema may be treated with drug therapy.

Example
Which of the following is not correct about the kidney of man? It
A. helps to remove waste products from the body B. controls the amount of water in the blood
C. facilities the dilution of urea from urine D. removes the undigested liquid food materials from the body
E. consists of uriniferous tubules (1990/38 June Health Science)
Answer: D – The kidney does not remove the undigested liquid food materials from the body. All other options (A, B,
C and E) are true about the kidney of a man.
Example
Water is re-absorbed by the uriniferous tubules into the blood in order to
A. maintain water balance in the tissues B. prevent frequent urination C. increases the volume of blood
D. replace water loss by sweating E. replace metabolic water (1990/41 June Health Science)
Answer: A – Water is reabsorbed by the uriniferous tubules into the blood in order to maintain water balance in the tissues.
Example
Malfunctioning of the kidneys causes
A. loss of appetite B. accumulation of nitrogenous wastes in the body C. difficulty in defecating
D. impairment in digestion E. low oxygen intake (1998/13 Nov Health Science)
Answer: B – The malfunction of the kidneys will cause accumulation of nitrogenous waste in the body.
Example
A condition in which the kidney tubules do not absorb water from the glomerular filtrate into the blood is called
A. diuresis B. nephritis C. hepatitis D. kidney stones (2002/19 Nov)
Answer: A – Diuresis is a condition in which the kidney tubules do not re-absorb water from the glomerular filtrate
into the blood.
Example
2(a) Outline the effects and remedies of the following:
(i) Kidney stone (ii) Infective hepatitis (1998/2ai, ii Nov)
Answer:
i. Effects of kidney stone: ii. Effect of ineffective hepatitis:
- Difficulty in passing out urine. - Loss of appetite.
- Severe abdominal pain. - Nausea.
- High blood pressure may occur. - Weakness
- Eye and skin turn yellow.
Remedies to kidney stone: Remedies to ineffective hepatitis:
- Drinking enough water. - Eating of fruit and vegetable
- Avoiding food items that are hard to digest. -Water should be boiled and filtered before drinking.
- Avoiding excessive intake of food containing calcium. -A medical doctor should be consulted.
- Prophylactic drugs can be used to dissolve the stone.
- Surgery can be carried out to remove the stone.
Example
Ultra-filtration takes place in the
A. medulla B. pelvis C. pyramid D. convoluted tubule E. Bowman’s capsule (1997/16 Nov)
Answer: E – Ultra filtration takes place in the Bowman’s capsule of the nephron.

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Example
Mention one hormone that controls reabsorption of water in man. (1999/2cii Nov)
Answer: Anti Diuretic Hormone (ADH)
Example
The effect of the vessels leaving the Bowman’s capsule being narrower in diameter than the vessels enter the capsule is
A. Formation of concentrated urine B. slowing down the rate of heart beat
C. causing kidney damage D. building up blood pressure in the capsule E. increasing the rate of deamination (1996/16 Nov)
Answer: D – The effect of the blood vessels leaving the Bowman’s capsule being narrow in diameter than the vessels entering the
capsule is to build up blood pressure in the capsule.
Example
Under which of the following conditions will urine output from the kidneys most likely to reduce?
A. a cold weather B. a hot day C. soon after a drink of water D. soon after a big meal (2013/18 Nov)
Answer: B – The urine output of the kidney will likely be reduced during a hot day. This is because some of the waste
products excreted through the kidney will now be expelled through sweating.
Example
What is NOT a kidney disease?
A. cirrhosis B. kidney stones C. nephritis D. uraemia E. Wilm’s tumor (2001/15 Neco)
Answer: A – Cirrhosis is a disease of the liver.
Example
The main constituents of glomerular filtrate are
A. blood and water B. blood and urea C. glucose and water D. salt and blood E. water and urea (2008/26 Neco)
Answer: E – The main constituents of the glomerular filtrate are water and urea.
Example
Which of the following are components of glomerular filtrate?
A. All the components of blood except mineral salts B. Water and Salt only
C. All the components of blood except plasma protein and cells D. Plasma proteins, red and white blood cells
E. Blood cells, amino acid, salts and nitrogenous wastes (1990/20)
Answer: C – The components of the glomerular filtrate consists of all components of the blood except plasma protein
and cell.
EXERCISE 11.2
1. The cup-shaped part of the Bowman’s capsule contains the
A. nephridium B. glomerulus C. loop of Henle D. nephron E. convoluted tubule (1990/23)
2. Kidney stone is a disease of the kidney that results in the
A. blockage of the tubules by solid particles B. passing out useful materials of the body fluid with urine
C. presence of large quantity of water in urine D. passing out hormones in urine
E. prevention of urine production (1991/13)
3. Which of these is not a function of the kidney?
A. Production of urine B. Maintenance of acid-base balance in the body
C. Osmo-regulation D. Removal of urea E. Production of bile ( 1998/17)
4. Glomerular filtrate contains
A. no glucose B. amino acids C. no proteins D. urea (1999/17)
5. The glomerular filtrate contains the following substances except
A. water B. urea C. blood corpuscles D. Glucose (2003/18)
6. The Malpighian body of the mammalian kidney is made up of
A. Cortex and Medulla. B. Bowman's Capsule and loop of Henle
C. Glomerulus and Bowman's capsule. D. Pelvis and Pyramid (2007/15)
7. The process of regulating the amount of water and solutes in the body fluids is called
A. osmosis B. diffusion C. osmoregulation D. homeostasis (2008/12)
8. Ultrafiltration in the kidney takes place in the
A. renal vein B. medulla C. loop of Henle D. Bowman’s capsule (2018/14)
9. c. Explain briefly the following diseases: (i) hepatitis: (ii) kidney stones (2019/6ci, ii)
10. Which of the following statements about the mammalian kidney is false?
A. The glomerulus is formed by a branch of the renal artery
B. The glomerulus is a part of urinferous tubules
C. The Bowman’s capsule is in the cortex of the kidney
D. The urinferous tubules are richly supplied with blood vessels
E. The glomerulus is lodged in the Bowman’s capsule (1979/19 JAMB)
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11. The kidneys of all vertebrates act as osmoregulators. This means that they
A. keep the composition of the plasma constant B. regulate osmotic processes
C. control the volume of blood entering the kidneys D. decrease the osmotic pressure of blood
E. increase the osmotic pressure of the blood (1983/14 JAMB)
Use the diagram below to Answer: questions 26 and 27

12. Bowman’s capsules are located in the part labelled

A. 1 B. 2 C. 3 D. 4 E. 5 (1985/26 JAMB)
13. The function of the loop Henle is to
A. increase the flow of urine B. concentrate amino acids in the kidney tissue
C. concentrate sodium chloride in the medulla of the kidney D. increase the volume of urine (1987/24 JAMB)
14. The urinary tubules of the kidney function through
A. ultrafiltration and selective reabsorption B. active transport and cytoplasmic streaming
C. osmosis and diffusion D. Active transport and osmosis (2005/7 JAMB)
15. In the mammalian kidney, the Bowman’s capsule is located in the
A. ureter B. pelvis C. cortex D. medulla (2008/21 JAMB)
16. Which of the following organs regulates the levels of water, salts, hydrogen ions and urea in the mammalian
blood?
A. Kidney B. Bladder C. Colon D. Liver (2011/25 JAMB)
17. Make a label diagram 10cm-12cm long of the longitudinal section of the mammalian kidney (2004/2c Nov)

THE LIVER
The liver and the kidney can be regarded as the two main important organs concerned with the regulation or
maintenance of a constant internal environment i.e. homeostasis
The liver is the largest organ in the body. It is dark red and spongy. It has an excellent supply of blood, receiving more
blood per unit time than any other organ. In fact, it has been calculated that the blood flow through the liver is well
above a liter per minute. The liver derives its blood supply from
1. The hepatic artery which brings oxygenated blood from the dorsal aorta.
2. The hepatic portal vein which brings blood rich in food materials from the small intestine.
3
As much as 4 of the blood reaching the liver does so through the hepatic portal vein. The liver has four main lobes.
1. Caudate lobe
2. Left lobe
3. Right lobe
4. Median lobe

The underside of the right lobe has a gall bladder which contains liquid called bile. The bile duct is attached to the gall
bladder which leads from the liver to the duodenum. The hepatic vein carries blood away from the liver while the
hepatic portal vein supplies blood rich in products such as glucose, amino acid, lipids, plasma protein, urea, CO 2 e.t.c.
to the liver. These products are shed into the hepatic vein.

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 The liver
The liver is a dark red region lying in the cavity of the diaphragm and overlapping to some extent with the stomach. It
is made up of lobes. The gall bladder is a transparent, ovoid sac which is embedded in one of the liver lobes. The bile
is produced by the liver and then stored in the gall bladder. The bile is an alkaline fluid and green in colour. Its colour
is derived largely from breakdown products of the red pigment in decomposing red blood cells. The gall bladder is
connected to the proximal arm (i.e. first part) of the duodenum. The bile contains organic bile salt and sodium
carbonate which partly neutralizes the acid chyme from the stomach. The bile also emulsifies fats to facilitate their
rapid digestion.

Regulatory Functions of the Liver

1. BLOOD SUGAR CONSTANT: The liver regulates the sugar level by converting excess glucose in the blood to
glycogen in the presence of insulin which is secreted by the pancreas. When blood glucose falls below normal,
the liver converts glycogen into glucose in the presence of glucagon secreted by the pancreas
2. DEAMINATION OF PROTEINS: Excess amino acids are deaminated in the liver. The nitrogenous wastes
from the breakdown of protoplasm is formed into urea which passes into the blood stream for transport to the kidney
3. Manufacture of bile
4. Manufacture of fibrinogen (from amino acid) used for the clotting of blood
5. It removes cholesterol from the blood
6. The numerous metabolic activity of the liver produces heat which is distributed to all parts of the body by blood
circulation thus, regulating body temperature.
7. It prepares fat for use as a source of energy
8. Stores vitamin B12
9. Store iron
10. Detoxification: Detoxification is the process by which toxic substance are made inactive. This happens in the
liver. Some of the substances that are detoxified in the liver include drugs and medicine, food preservatives,
poisonous substance produced as a result of bacteria action in the large intestine and pollutants present in water.
11. Manufacture of foetal red blood: The red blood cells of embryo are manufactured by their liver

Diseases of the Liver

1. Infectious Hepatitis (Catarrhal Jaundice)
This is caused by a virus. The virus causes destruction and inflammation of the liver. As a result of this, the glycogen
cannot be stored nor converted into glucose in the liver.
Effects Remedies
1. Loss of appetite 1. Fruits and vegetables should be properly washed with clean water.
2. Nausea 2. Water should be boiled and filtered.
3. Weakness 3. Consult a medical doctor.
4. Eye and skin turns yellow

2. GALL STONE
This is caused by over concentration of the bile leading to solidification of substance and consequently blocking the
bile duct and preventing small intestine. Gall stone can be removed by surgery. Also cholesterol in the bile crystallizes
to form stones. Over weight and high concentration of bilirubin in the bile are also causes of this disease.
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Effects Remedies
1. Abdominal pains, 1. Drinking sufficient water or fruit juices.
2. Indigestion, nausea and vomiting 2. Reduction of cholesterol intake.
3. Signs of jaundice (yellow eyes and skin); 3. Avoid over weight.
this may lead to cancer of the liver.

3. Cancer of the Liver

This is caused by dietary deficiency. Cancer cells from other part of the body can affect the liver cells.
The effects of cancer of the liver
1. Indigestion 2. Loss of weight 3. Weakness 4. Anaemia 5. Jaundice 6. Frequent chill
Remedies
1. Sufficient rest and care.
2. Eating balanced diet.
3. Consult a medical doctor.
4. Regular medical examination at least once a year.
5. Cancer cell can be removed by surgery. Cancer cell can also be killed by radiation.
4. Diabetes Mellitus
When the liver is unable to convert excess glucose in the blood to glycogen, diabetes result. The failure of the liver to
do this conversion happens when the hormone insulin is not produced by the pancreas. It may be controlled by the use
of drugs. The patient may be given regular doses of insulin injection intravenously, throughout life.

5. Cirrhosis of the Liver

This is a serious liver disease in which the damaged liver cells become replaced by dead and useless fibrous tissue.
Because of this, the liver is very firm and irregular. This is caused by excessive drinking of alcohol over a long period
of time.
Effects Remedies
1. It results to general weakness of the body. 1. Patients should avoid alcoholic drink.
2. It leads to loss of appetite. 2. Surgery may be done on the patient
3. It can lead to death. 3. Transplanting of the liver may be carried out.

Example
If bile is discovered in a patient’s blood, which of the following organs is likely to be affected?
A. pancreas B. Heart C. Spleen D. Liver (2000/5 Nov Health Science)
Answer: D – The liver produces bile which is stored in the gall bladder. Hence, if bile is found in the blood, the liver
is likely to be affected.
Example
Which of the following is a disease of the liver?
A. Scurvy B. Epilepsy C. Influenza D. Cirrhosis E. Arthritis (1998/12 Nov Health Science)
Answer: D – Cirrhosis is a serious disease of the liver in which the damage liver cells become replaced by dead and
fibrous tissue. Note that:
- Scurvy is a condition that results from the deficiency of Vitamin C.
- Epilepsy is a neurological disorder.
- Influenza is a viral infection of the respiratory system.
- Arthritis is the inflammation of the joint.
Example
Which of the following would result when a man’s liver is damaged?
A. His urinary bladder can be overworked B. All his white blood cells would be destroyed
C. Excess amino acids would remain in the blood D. He cannot maintain a constant body temperature
E. Digestion of carbohydrate will be affected (1990/14 Nov Health Science)
Answer: C – When a man’s liver is damaged, excess amino acid would remain in the blood. This is because the liver
helps to breakdown excess amino acid into urea which excreted by the kidney.
Example
Which of the following is not a function of the liver?
A. Secretion of ptyalin B. Production of blood cells in early life
C. Storage of glucose as glycogen (1996/11 Nov Health Science)
Answer: A – Secretion of ptyalin is done by the salivary gland of the mouth. All other options (B, C) are functions of the liver.

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Example
The following are the activities of the liver except
A. production of heat B. manufacture of bile C. detoxication of alcohol and drugs
D. maintenance of osmotic balance E. deamination of excess nitrogenous substances (1991/14 Nov)
Answer: D – The liver is not involved in the maintenance of osmotic balance.
Example
Infective hepatitis is a disease of the
A. heart B. kidney C. liver D. stomach E. pancreas (1991/15 Nov)
Answer: C – Infective hepatitis is a disease of the liver.
Example
ii. Mention five functions of the liver (1999/2bii Nov)
Answer: Regulation of blood sugar level. Deamination of excess protein. Manufacturing of bile.
Storage of vitamin. Production of blood in infants.
Example
Which of the following occurs in the liver?
A. deamination of amino acids B. storage of bile
C. manufacture of red blood cells D. production of gastric juice (2006/16 Nov)
Answer: A – Deamination of amino acid occurs in the liver. NB: Bile is produced in the liver and stored in the gall bladder.
Example
3a.(i) Name three diseases of a liver. (2018/3ai Neco)
Answer: Infectious Hepatitis, Gall stone and Cirrhosis
Example
The following are functions of the liver except
A. deamination of excess amino acids and proteins B. excretion of bile pigments
C. manufacture of blood plasma D. production of heat E. storage of vitamins and minerals (2008/22 Neco)
Answer: C – The liver does not manufacture blood plasma.
Example
Deamination is the process during which
A. excess amino acid is broken down into ammonia and a ketoacid
B. fats and oils are converted into an emulsion for absorption
C. excess glucose is converted and stored as glycogen in the liver
D. glycogen is reconverted into glucose through the action of glucagon
E. excess amino is converted into proteins (1988/15)
Answer: A – Deamination is the process during which excess amino acid is broken down into ammonia and ketoacid.

EXERCISE 11.3
1. The following are the activities of the liver except
A. production of heat B. manufacture of bile C. detoxication of alcohol and drugs
D. maintenance of osmotic balance E. deamination of excess nitrogenous substances (1991/14)
2. Infective hepatitis is a disease of the
A. heart B. kidney C. liver D. stomach E. pancreas (1991/15)
3. Which of the following organs is associated with deamination of proteins?
A. Lung B. Stomach C. Kidney D. Liver E. Heart (1993/15)
4. The process whereby poisonous compounds are made harmless in the liver is called
A. deamination B. glycolysis C. dehydration D. detoxification E. denitrification (1994/37)
5. Which of the following organs is concerned with detoxication of harmful compounds?
A. Kidney B. Lungs C. Gall bladder D. Liver E. Pancreas (1998/19)
6. Which of the following is not a function of the liver in mammals?
A. Storage of some vitamins B. Conversion of glycogen into glucose
C. Deamination of excess nitrogenous substances D. Filtration (1999/18)
7. The organs constantly in touch with the liver are
A. pancreas, colon and caecum B. duodenum and stomach
C. ileum, stomach and colon D. stomach and gall bladder (2000/22)
8. The following functions are associated with the liver except
A. regulation of blood sugar B. production of heat
C. production of fibrinogen D. production of vitamin D (2001/24)

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9. (b) State four functions which the liver of a patient suffering from cancer of the liver will not
be able to perform. (2010/1b)
10. Which of the following is NOT a function of the liver?
A. Regulation of blood sugar B. storage of iron C. Formation of bile
D. Breakdown of excess amino acids E. Excretion of urea from the blood (1981/15 JAMB)
11. Urea is produced in the
A. liver B. bladder C. spleen D. kidneys E. gall bladder (1983/48 JAMB)
12. The process of deamination is essential for the
A. digestion of protein B. secretion of bile C. formation of urea D. formation of antibody (1997/21 JAMB)
13. Regulation of blood sugar level takes place in the
A. pancreas B. ileum C. liver D. kidney (1998/15 JAMB)

The Skin
The mammalian skin is the largest organ of the body. It consists of two main parts:
i. Epidermis
ii. Dermis
The epidermis is the outer layer of the skin. It is made up of three layers. These are:
1. Cornified layer
2. Granular layer
3. Malpighian layer

Human Skin
The cells which are present in the outer most layer of the epidermis are dead cells. The dead cells are located in the
horny or cornified layer of the epidermis. The second layer is the granular layer whose cells are progressively more
alive. Beneath the granular layer is the malpighian layer. The cells of the malpighian layer are very much alive. This
malpighian cells produce cells that replace the cells of the upper layer of the epidermis. The malpighian cells also
secrete melanin. The melanin is the pigment that gives skin its colour. Black people have more melanin pigments than
white people. Melanin pigment is absent in albinos. There is also the presence of nerves ending which are used to
respond to stimulus.

Keratin which is a protein substance is also present in the skin. The keratin confers toughness and flexibility on the
skin. The melanin helps to prevent the entrance of ultraviolet rays which can lead to destruction of cells of the skin,
thus resulting in skin cancer.
The dermis contains sweat glands, root of the hair that project out of the skin surface, sebaceous gland, erector
muscles, blood vessels and sensory cells as well as fat cells.

Functions of the Skin

The important functions of the skin include:
1. Protection
The skin protects the body by forming barrier between external environment and the tissue below it thus
preventing the body from mechanical injuries, ultraviolet rays of the sun, harmful bacteria that want to invade
tissue and desiccation by acting as water proof.
2. Excretion
The skin excretes excess water, mineral salts and some nitrogenous wastes through the sweat glands as sweat.

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3. Sensitivity
Different sense receptors which are sensitive to various stimuli are present on the skin. Some of the
environmental stimuli the skin responds to include change in temperature, pain, cold, and pressure.
4. Production and Storage of Vitamin D
The skin is able to manufacture Vitamin D by using infra-red rays from the sunlight.
5. Production of Milk
The mammary glands in mammals are modification of the skin. They produce milk which are used to feed the
young ones.
6. Storage of Food
Fats which form an insulating layer are stored under the dermis of the mammalian skin.

7. Regulation of Body Temperature

Vertebrates can be classified into two different categories based on their body temperatures. These are the
poikilotherms and homoitherms. In the poikilothermic vertebrates, body temperature is never constant as it
varies with the temperature of the environment e.g the fishes, amphibians and reptiles. While in the
homoitherms their body temperature doesn’t vary with the environmental temperature but remains constant
e.g mammals and birds.
The mammalian skin helps to regulate the body temperature in specific ways.

a. On a cold day: On a cold day, a mammal is able to keep its body temperature constant. A fall in body
temperature as a result of a fall in environmental temperatures stimulates the following processes inorder
to conserve heat and maintain the body temperature at 37 degree Celsius or 98.4 degree Fahrenheit
i. Vasoconstriction
The capillaries near the skin surface constrict while those in the deeper layer dilate, resulting in lesser flow of blood
to the skin surface and less production of sweat by the sweat glands so that heat loss is greatly reduced. As a result
of this occurrence, people appear pale when the weather is cold.
ii. Raising of Hairs
The erector muscles contracts to raise the hairs and trap out more air; since air is a bad conductor of heat, the layer
of air next to the skin act as an insulator and prevent heat loss from the body.
iii. Increasing Metabolic Rate
The body increases in metabolic rate especially that of the liver, to produce more heat. Shivering is also aimed at
increasing the body’s metabolic rate. Physical activities such as clapping and running in cold day help to produce
body heat.
iv. Behavioural Changes
Wearing of wollen clothing, jacket, coat and stocks help to conserve heat. Many mammals keep their body by
staying in nests and huddling into a ball to reduce surface areas

b. On a hot day: On a hot day, mammals keep their temperature constant. They get rid of excess body
heat by the following:
i. Vasodilation
The capillaries near the skin surface dilate while those in the deeper layers of the skin constrict. As a result of this,
more blood flows near the surface of the skin so that the heat is lost through conduction, convection and radiation to
the environment.
ii. Sweating
In human, the sweat gland becomes active and produces a large amount of sweat that flow out onto the surface of
the skin. As the sweat evaporates, heat from the body is used up therefore cooling the body.
iii. Lowering of Hairs
In a hairy mammal, the hair erector muscle relaxes, causing the hair to lie flat on the skin surfaces. This force out
most of the air trapped among the hairs. Without this insulating layer, the animal loses more heat from the body
iv. Decreasing Metabolic Rate
The body slows down its activities to reduce the metabolic rate. This reduces the heat released by metabolic
reactions hence heat production within the body is reduced.
v. Behavioural Changes
Human beings wear light clothes that are light coloured. Many mammals keep cool by staying in the shade
NOTE: Inability of the skin to maintain a constant temperature during hot and cold weather are known as hyperthermia and hypothermia
respectively. Both of these conditions can lead to death

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 Care of the Mammalian Skin
1. Regular Cleaning
The skin should be cleaned (washed) regularly at least once a day with soap and water to remove dirt.
2. Eating of Balanced Diet
A balanced diet containing vitamins A and B2 (riboflavin) should be taken to keep the skin healthy.
3. Dressing of Wounds
Wounds and cuts should be cleaned regularly to get rid of dirt and then dressed with antiseptic to prevent
infection from entering such opening.
4. Exposure to Fresh Air
The skin should be exposed to fresh air and sunlight regularly.
4. Proper Treatment of Skin Diseases
Skin diseases should be reported to qualified doctor/dermatologist for proper treatment. Example of some skin
diseases includes rashes, eczema, chicken pox, e.t.c
5. Wearing of Clean Clothes
Wear clean, light and loose clothes for free circulation of air round the body. Dirty clothes and heavy clothes
causes discomfort, rashes and fungi infection of the skin.
6. Use Of Good Moisturizing Cream to Keep the Skin Moist
Bleaching creams should not be used at all as this causes skin infection and cancer. It destroys the menlanin
pigment and the skin in general.
7. Regular Exercise
The body should be exercised regularly to remove sweat and keep the skin healthy

Example
The following are ways of caring for the mammalian skin except
A. eating balanced diet B. exposing the skin to adequate sunlight C. using skin toning cream
D. using moisturizing cream to prevent drying E. washing the skin with clean water and soap (2005/33 Neco)
Answer: C – Using skin toning cream is not a way of caring for our skin.
Example
The mammalian skin can insulate the body from cold because it has
A. epidermal cells B. nerve endings C. the subcutaneous fatty layer
D. sebaceous gland E. malpighian layer (1992/27)
Answer: C – The subcutaneous fatty layer of the skin helps to insulate the body from cold.
Example
Which of the following takes place when a person’s body temperature rises about 37°c
A. sweating and vasoconstriction B. panting and vasoconstriction
C. sweating and vasodilatation D. panting and vasodilatations (2005/24)
Answer: C – When a person’s body temperature rises above 37oC, the person begins to sweat and the blood vessels
supplying the skin dilate, so as to restore the body temperature back to normal. Hence sweating and vasodilatation
takes place when a person’s body temperature rises above 37oC.
Example
The hair on the human skin will stand erect when the person is
A. in-air conditioned room B. strolling in the sun C. taking a hot drink D. doing strenuous exercises (2012/20)
Answer: A – The hair on the human skin will stand erect when a person is in an air condition room so as to reduce
heat loss.
Example
Which of the following processes will not conserve body heat?
A. shivering B. vasoconstriction C. perspiration D. erection of body hair (2006/17 Neco)
Answer: C – Perspiration is another word for sweat. Sweating results in heat loss.
Example
When the hairs on the skin stands on end, developing some air they are performing the function of
A. radiation B. conduction C. insulation D. vasoconstriction E. sensation (1996/19 Nov)
Answer: C – When the hairs on the skin stand on end, they are performing the function of insulation, i.e. preventing
heat loss.

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Example
State the function of the following parts of the mammalian skin: (i) Erector muscle (ii) Sweat gland (2007/2b Neco)
Answer:
i. Erector muscle – This helps to regulate the position of the hair.
ii. Sweat gland – Helps in sweat production.
Example
State the advantage of sweating to mammals. (2001/2b NABTEB).
Answer:
- Sweating helps to excrete waste.
- Sweating helps in thermoregulation of the body.

Example
The colour of the skin is due to the
A. secretions of the sweat gland B. secretions of the sebaceous gland
C. deposition of fat in the adipose tissue D. blood vessels in the dermis
E. pigments below the epidermis (1990/35 June Health Science)
Answer: E – The colour of the skin is due to the pigments (Melanin) below the epidermis of the skin.
Example
Which of the following is not correct about the skin?
A. It contain network of nerves B. It is sensitive to touch C. It is sensitive to cold
D. It may contain pigment E. The secretion from sebaceous gland keeps the skin cool (1990/40Health Science)
Answer: E – The secretion from sebaceous gland is called sebum. This lubricates the skin to protect it against friction
and makes it more impervious to moisture. It does not keep the skin cool.
Example
Which of the following is the function of shivering in man? It
A. aids the growth of the hair on the skin B. helps in raising body temperature
C. helps in reducing body temperature D. enables the skin to respire actively
E. dilates the blood vessel (1990/51 June Health Science)
Answer: B – Shivering is man helps in raising the body’s temperature.
Example
The involuntary shivering which occurs in mammals as a response to reduced body helps the animal in heat
A. loss B. generation C. conservation D. gain from the outside (2004/14 Nov)
Answer: B – The involuntary shivering in mammals helps them to generate heat.
Example
The following structures are present in the skin except
A. sweat gland B. horny layer C. renal tube D. sebaceous gland (2002/20 Nov)
Answer: C – Renal tube is found in the kidney.
Example
Which of the following parts of the human skin is not associated with temperature regulation?
A. sweat gland B. fatty acid C. hair shaft D. Erector muscle E. sebaceous gland (1998/17 Nov)
Answer: E – The sebaceous gland produces sebum which helps to lubricate the skin. This does not take part in
temperature regulation.
Example
In hot weather, the body of a mammal can be cooled through
A. shivering B. vasoconstriction C. hair standing on end D. relaxation of erector muscles (2013/17 Nov)
Answer: D – In hot weather the body of a mammal can be cooled through relaxation of erector muscles.
Example
Which of the following structures of the mammalian skin is associated with excretion?
A. sweat glands B. erector muscles C. hair shaft D. adipose tissue (2013/22 Nov)
Answer: A – The sweat glands help to produce sweat which contains excretory products of various sorts.
Example
In the mammalian skin, melanin and keratin are contained in the
A. sebaceous gland B. sweat gland C. subcutaneous layer D. Malpighian layer (2019/23 NABTEB)
Answer: D – Melanin and keratin are contained in the malpighian layer of the skin.

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EXERCISE 11.4
1. The following are ways of caring for the mammalian skin except
A. Eating balanced diet B. exposing the skin to adequate sunlight C. using skin toning creams
D. using moisturizing creams to prevent drying E. washing the skin with clean water and soap (2005/33 Neco)
2. The pigment in the malphigian layer responsible for skin colouration is known as
A. haemoglobin B. haemocyanin C. chlorocruorin D. haemoerythrin E. melanin (1988/17)
3. The mammalian skin can insulate the body from cold because it has
A. epidermal cells B. nerve endings C. the subcutaneous fatty layer
D. sebaceous glands E. the malpighian (1992/27)
4. In cold condition, the mammalian body reacts in the following ways except
A. shivering of the body B. dilation of the capillaries supplying blood to the skin
C. constriction of blood capillaries D. increased rate of chemical changes in the body (2003/17)
5. (b) Describe how the mammalian skin can regulate the body temperature in a hot room. (1996/2b)
6. Which of the following conditions will cause a decrease in body temperature?
A. Increased metabolism B. Shivering C. Vasoconstriction of capillaries of the skin
D. Relaxation of the erector muscles (2000/21)
7. Which of these is NOT a function of the mammalian skin?
A. Protection against bacterial infection B. Excretion of wastes and water
C. Production of vitamin D when exposed to light D. Production of pigments to reduce temperature
E. Regulation of body temperature (1978/32 JAMB)
8. In mammals, the function of the sebaceous gland is to
A. produce sweat B. secrete sodium chloride C. secrete water
D. produce an oily substance E. manufacture vitamin D for the skin (1985/24 JAMB)
9. In the mammalian skin, melanin and keratin are contained in the
A. sebaceous gland B. sweat gland C. subcutaneous layer D. Malpighian layer (1986/31 JAMB)
10. The skin through the sweat glands function as
A. an excretory organ B a respiratory organ C. a sensory organ D. a protective organ (1988/25 JAMB)
Use the diagram below to Answer: question 29 and 30

11. The part labeled III is for

A. protection B. insulation C. lubrication D. growth (1999/29 JAMB)
12. The structure labeled II is known as
A. sweat gland B. lymph vessel C. blood vessel D. nerve ending (1999/30 JAMB)
13. The part of the mammalian skin involved in temperature regulation is the
A. sweat gland B. hair papilla C. hair follicle D. sebaceous gland (2006/29 JAMB)

REVISION EXERCISES
1. 1(a) Explain the following terms: (ii) deamination; (iii) detoxification (2000/1ai, ii Health Science Nov)
2. (c) How does the mammalian body respond to low water content? (2011/8c Nov)
3. (b) (i) What is homoeostasis?
(ii) Explain how the level of sugar in the mammalian blood is maintained (2002/3b Nov)
4. What physiological term can be used to describe the regulation of the body temperature of the lizard?
A. homeostatsis B. osmoregulation C. homoithermy D. poikilothermy (2017/25 NABTEB)
5. Which of the following structural features in animals does not affect control of body temperature?
A. Scales B. Skin C. Fur D. Capillaries E. Feathers (1994/51)
6. (a) Describe the process of osmoregulation in:
(i) A named unicellular organism (ii) man (1996/2ai & ii)
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7. Which of the following conditions will cause a decrease in body temperature?
A. Increased B. Shivering C. Vasoconstriction of capillaries of the skin
D. Relaxation of the erector muscles (2000/21)
8. The body temperature of a mammal has to be maintained at a fairly constant level because
A. excessive heat is continually lost by the body to the environment
B. their body temperature is always higher than that of the environment
C. evaporation of sweat cools the body
D. metabolic activities function best at certain temperature (2004/16)
9. An organism which maintains a constant temperature irrespective of environmental temperature fluctuation is
A. an insect B. a mammal C. an amphibian D. a fish (2006/20)
10. Which of the statements below is valid?
A. The bird's blood was always warmer than that of the lizard
B. The body temperature of the bird varied less than that of the lizard during changes in environmental temperature
C. The body temperature of the bird remained constant despite changes in environmental temperature
D. The body temperature of the lizard was always close to that of the environmental temperature (2009/19)
11. Which of the following organs regulates the amount of amino acids and glucose in the body?
A. Kidney B. Liver C. Pancreas D. Spleen E. Stomach (1985/25 JAMB)
12. Cold blooded animals are referred to as
A. poikilothermi B. homoeothermic C. polythermic D. homoestatic (1993/49 JAMB)
13. Birds maintain their body temperature with the help of their
A. blood which maintains constant temperature B. feathers which cover the body
C. skin which conserves moisture
D. veins which transport fluid of constant temperature to all body tissues (1995/9 JAMB)
14. Water loss is regulated in plants and animals by both the
A. scales and skin B. scales and the hair
C. thick leaves and the feathers D. leathery cuticle and the feathers (1997/46 JAMB)
15. Which of the following is a homeostatic response in humans?
A. Yawning owing to tiredness B. Withdrawing the hand from a hot object
C. Shivering in a cold environment D. The mouth getting watery when food is sighted. (2005/8 JAMB)
16. The oil substance that lubricates the mammalian hair to keep it flexible and water repellent is secreted by the
A. seat glands B. sebaceous gland C. fatty cells D. granular layer (2010/21 JAMB)
17. An example of poikilothermic organisms is a
A. rabbit B. bird C. lizard D. cockroach (2014/48 JAMB)
18. The following homeostasis mechanisms are carried out by mammals except
A. excretion B. osmoregulation C. PH regulation D. reproduction E. thermo regulation (Neco 2018/49)
19. The control of water and salt requirements of the body in order to maintain a stable internal environment is known as
A. osmosis B. excretion C. plasmolysis D. ultra filtration E. homeostasis (1994/52)
20. The maintenance of a constant internal environment in an organism is known as
A. homeostasis B. homoiothermy C. dieresis D. dialysis (2016/15)
21. An example of homeostasis in living organisms is
A. cooling effect resulting from evaporation of water from the body surface
B. root hairs of a plant growing towards a source of light
C. changing of the body colour of chameleon to maintain the colour of the foliage on which it is resting
D. the release of phosphorous into the phloem of a plant growing in a phosphorous deficient soil. (2018/13)
22. Homeostasis can be defined as the
A. ability of the internal environment to change if the external environment changes
B. constancy of the internal environment despite changes in the external environment
C. removal of excess materials from the internal environment
D. control of materials entering the internal environment. (2005/22 Nov).
23. Which of these is not a function of the kidney?
A. production of urine B. maintenance of acid base balance in the body
C. osmosis regulation D. removal of urea E. production of bile (1998/17)
24. In which part of the kidney does ultra filtration takes place?
A. Bowman’s capsule B. distal convoluted tubule C. proximal convoluted tubule
D. collecting duct E. afferent arteriole (1998/18)
25. Which organ removes the largest quantity of water from the blood?
A. lung B. intestine C. kidney D. skin (2003/16
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26. When a person’s urine contains a high concentration of urea, it could be the result of
A. a drop in body temperature B. having diabetes mellitus
C. eating a meal rich in protein D. drinking a large amount of water (2004/7)
27. A substance present in the glomerular filtrate in the mammalian kidney is
A. glucose B. fibrongen C. albumen D. blood platelets (2018/16)
28. The process whereby poisonous compounds are made harmless in the liver is called
A. cleamination B. glycolysis C. dehydration D. detoxification E. denitrification (1994/37)
29. Which of the following process occurs in the liver?
A. deamination of amino acids B. storage of bile C. manufacture of red blood cells
D. production of gastric juice (2000/16 Neco)
30. Describe the process of osmoregulation in
a. A named unicellular organism b. Man (1996/2a)
31. Describe how the kidney carries out two of its functions. (1996/2a)
32. List two diseases of the liver ii. State the effects of the disease on human body (2011/2b)
33. Briefly explain how the level of sugar in the mammalian blood can be regulated. (2012/2c)
34. Explain briefly the following diseases (i) hepatitis (ii) kidney stones. (2019/6c)
35. Make a well labeled diagram of the vertical section through the mammalian skin (1992/1c)

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Nervous Co-ordination
In complex animals different organ system which are specialized for a particular function are present. For effective
functioning of the body, these organ system must work together as a team. This is what is meant by co-ordination.
Co-ordination is defend as the process in which one or more tissues or organs interact and complement the function of
each other in other to maintain the homeostasis of the body.
Two communication system works together to bring about co-ordination. These are:
1. Hormonal (endocrine glands) systems
2. The nervous system
The hypothalamus of the brain forms the important link between these two systems.
The Nervous System
The nervous system of a mammal consists of brain, spinal cord & nerves. It is divided into two parts.
1. The central nervous system.
2. The peripheral nervous system.
Example
Co-ordination and regulation of body activities in mammals are achieved by the
A. nerves only B. hormones only C. nerves and muscles D. nerves and hormones (2014/3 JAMB)
Answer: D – Co-ordination and regulation of body activities in mammals are achieved by the nerves and hormones.
Example
Co-ordination is achieved in the body of mammals through the action of the
A. endocrine and nervous systems B. skeletal and nervous systems C. muscular and nervous systems
D. circulatory and nervous systems E. skeletal, muscular and nervous systems (1988/18)
Answer: A – Co-ordination is achieved in the body of mammals through the action of the endocrine and nervous
systems.

EXERCISE 12.1
1. The central nervous system in humans is made up of the
A. brain, medulla oblongata and nerves B. brain, spinal cord and cranial nerves
C. brain and spinal nerves D. brain and spinal cord. (2006/22)
2. 2. (a) Name the main system responsible for coordination in mammal
(b) State: (i) Three similarities;
(ii) Four differences in the functioning of the system named in 2(a) above (2006/2a&b Nov)

The Central Nervous System

The central nervous system is composed of the brain, enclosed in the cranium (brain box) and the spinal cord which
runs down the center of the vertebrae column (back bone).

The Brain
The mammalian brain is divided into three (3) main parts
1. The fore brain.
2. The mid brain.
3. The hind brains.

The dorsal view of the brain of rabbit Dorsal view of the human brain
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Vertical view of the human brain The vertical section of human brain

The Fore Brain

The fore brain is also called the prosencephalon. It consists of the cerebrum, olfactory lobes, thalamus and
hypothalamus.

Cerebrum
The largest part of the brain is the cerebrum. The cerebrum is divided by a deep furrow (median fissure) into two
halves called cerebral hemisphere. A bond of fibres called Corpus callosum, connect and protect these two halves. The
outer surface of the cerebrum known as cerebral cortex or grey matter is folded in irregular pattern or convolution to
increase its surface area. The inner part of the cerebral cortex is known as white matter as it contains nerve fibres that
are white in colour.
 The outer part of the cerebrum is known as grey matter because it consists of grey cell bodies of neurones.
Functions of the cerebrum
1. It controls all voluntary action e.g. movement of parts of the body and ability to speak.
2. It is the seat of consciousness, intelligence, memory judgment, learning, imagination.
3. It is responsible for the collection of information from sense organs and the storage of such information for
later use.

The Olfactory Lobe

These are pair of small structures located anteriorly on the cerebrum. They receive sensory impulses of smell from the
olfactory organ and make the animal conscious of the odour in its environment.

Thalamus
These are two oval structures located above the mid brain and contain some mass of grey matter.
1. It is the center of sensation of pain, touch, taste and anger. It contains grey matter.
2. The thalamus also direct sensory impulses from the lower parts of the brain and spinal cord to the approximate
parts of the cerebrum.
3. Acts as an impotent relay centre by relaying motor impulses from the cerebrum to the spinal cord.

The Hypothalamus
It is found just below the thalamus. It is connected to the pituitary gland and contains reflex centres linked to the
autonomic nervous system.
Functions
1. It regulates the body temperature, water balance sleep and blood pressure.
2. It is the control centre for appetite.
3. It controls speech
4. It is the seat of aggression and anger.
5. It controls hormone secretion from the pituitary gland.

The Mid Brain

The mid brain is also called the mesencephalon. It is a short region connecting the forebrain to the hindbrain. It
consists of the optic lobes which are responsible for sight/vision. It controls some reflexes concerned with detection of
sound (hearing)

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The Hind Brain
The hindbrain is also called the rhombencephalon. It consists of the cerebellum, medulla oblongata and pons varolii.

Cerebellum
The cerebellum is sometime called small brain. It consists of two hemispheres. The surface is covered with grey
matter while the inner side is composed of white matter. It is connected to the semi – circular canals of the ear and
receives impulses from it through vestibular nerves fibre. It also controls some reflexes concerned with detection of
sound (hearing).
Functions of Cerebellum
1. It controls the actions of muscle in voluntary responses such as walking, talking and sitting. Damage to the
cerebellum might cause jerky unco-ordinated movement.
2. It controls and co-ordinates body posture/balance.

Medulla Oblongata
This connects the cerebellum to the spinal cord. It is the posterior portion of the brain that continues into the spinal
cord. Unlike the cerebrum and cerebellum, this part of the brain has an outer region of white matter and an inner
region of grey matter.
Note: It is in the medulla oblongata that the right and left motor fibres from the brain cross over each other, so that the
left hemisphere controls the right side and the right hemisphere controls the left side of the body.
Function of Medulla Oblongata
1. It controls respiration, heart – beat, dilation and contraction of artery (i.e. regulate blood pressure).
2. It controls digestive movement and movement of intestine, secretion of many glands e.g. secretion of saliva.
3. Involuntary actions such as laughing, coughing, yawning and blinking of eyes are also controlled by the
medulla oblongata.

Pon Varolii
The two halves of the cerebellum and the cerebrum are connected to the medulla oblongata by a thick bundle of nerve
fibre known as pon varoli.
Functions
It carries impulses from one hemisphere of the cerebellum to the other thereby coordinating muscular movement in the
two sides of the body.

Example
The part of the mammalian brain responsible for maintaining balance is the
A. medulla oblongata B. olfactory lobe C. cerebellum D. cerebrum E. frontal lobe (1983/16 JAMB)
Answer: C – The cerebellum is the part of the brain that is responsible for maintenance of balance or body posture.
Example
If an animal is very active and has a good muscular control, it is likely to have well developed.
A. olfactory lobes B. cerebral hemispheres C. optic lobes D. cerebellum E. spinal cord (1984/31 JAMB)
Answer: D – The cerebellum is responsible for the control of voluntary muscular actions. So, an active animal with a
good muscular control is likely to have a well developed cerebellum.
Example
The part of the brain that controls heart beat and breathing is the
A. olfactory lobe B. cerebellum C. cerebral hemisphere D. medullar oblongata (1994/29 JAMB)
Answer: D – The medulla oblongata is the part of the brain that controls heartbeat and breathing.
Example
The part of the brain that regulates most biological cycles is termed as
A. olfactory lobe B. optic lobe C. medulla oblongata D. pineal body (1997/31 JAMB)
Answer: C – The medulla oblongata is the part of the brain that controls/regulates most of the biological cycles.
Example
Which of the following parts of the mammalian brain is involved in taking the decision to run rather than walk?
A. Cerebellum B. Medulla oblongata C. Cranial nerves D. Mid brain E. Cerebrum. (1990/26)
Answer: E – The cerebrum is the seat of consciousness. It is the part of the brain where decisions are made.
Example
The nerves that arise from the brain are known as
A. Spinal nerves B. sacral nerves C. cranial neurons C. optic nerves (2000/24)
Answer: C– The nerves that arise from the brain are known as cranial nerves (neurons)
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Example
The part of the brain responsible for the control of voluntary movement and interpretation of sensations is the
A. cerebrum B. cerebellum C. optic lobe D. medulla oblongata E. olfactory lobe (1991/21)
Answer: A–The Cerebrum is the part of the brain responsible for the control of voluntary movement and
interpretation of sensation.
Example
What part of the brain is concerned with the regulation of the heart beat, body temperature and breathing rate?
A. Cerebellum B. Medulla C. Cerebrum D. Olfactory lobe E. Cortex (1992/26)
Answer: B – The medulla oblongata is the part of the brain responsible for the regulation of heart-beat, body
temperature and breathing rate.
Example
The medulla oblongata controls all the following except
A. heart beat B. breathing rate C. blood pressure D. balance and posture (1999/20)
Answer: D – Balance and posture are controlled by the cerebellum.
Example
If the cerebellum of a person is slightly damaged, which of the following will be impaired?
A. Vision B. Walking C. Breathing D. Digestion (2002/21)
Answer: B– The cerebellum controls the actions of muscle in voluntary responses such as walking. Hence, if
the cerebellum of a person is slightly damaged, walking will be impaired
Example
The part of the nervous system that interprets blinking of the eye is the
A. spinal cord B. cerebrum C. hind brain D. olfactory lobe (2003/20)
Answer: C – The hind brain interprets blinking of the eye.
Note: The hind brain consists of three parts namely: cerebellum, medulla oblongata and pons varolli. The medulla
oblongata controls involuntary actions and blinking of the eye is an involuntary action. Other involuntary actions
include respiration, coughing, yawning etc.
Example
7(a) Name three main parts of the human brain
(b) State the functions of the following: (i) Cerebellum (ii) Hypothalamus (iii) Medulla Oblongata (2003/7a & b)
Answer:
7a. Fore brain, mid brain, hind brain.
bi. Cerebellum:
- Controls and co-ordinates body posture/balance.
- Controls the actions of muscle in voluntary responses such as walking, talking and sitting.
ii. Hypothalamus
- It regulates body temperature.
- It is the control centre for appetite.
- It is the seat of aggression and anger.
- It controls hormone secretion from the pituitary gland.
iii. Medulla oblongata
- It controls respiration, heartbeat, and dilation and contraction of artery.
- It controls digestive movement and movement of the intestine.
- It controls involuntary actions such as laughing, coughing, yawning and blinking of the eye.

EXERCISE 12.2
1. The diagram below is an illustration of the side left side of the human cerebrum

The part labeled X controls

A. general memory B. speech C. sight D. respiratory functions (2014/15)

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 The diagram below is an illustration of a human brain. Study it and Answer: questions 16 and 17.

2. The part labelled I is the

A. olfactory lobe B. cerebellum C. cerebrum D. Medulla oblongata (2019/16)
3. The function of the part labelled II is that is controls
A. posture and balance of body B. all voluntary actions
C. temperature and appetite D. many involuntary actions (2019/17)
4. Which of the following organs is responsible for controlling the body temperature regulation and water
balance in mammals?
A. Kidney B. Hypothalamus C. Parathyroid D. Adrenal E. Thymus (1988/14)
5. Make a large labeled diagram of (10-12)cm long of the dorsal view of a mammalian brain. (2017/4a NABTEB)
6. The part of the mammalian brain responsible for maintaining balance is the
A. medulla oblongata B. cerebellum C. optic lobe D. olfactory lobe (2019/26 NABTEB)
7. Part of the brain that controls blood pressure is called
A. cerebellum B. cerebrum C. corpus callosum D. medulla oblongata E. pons varolli (2018/50 Neco)
8. Which of the following is not a part of the mammalian brain?
A. cerebellum B. cerebrum C. olfactory lobe D. spinal cord E. thalamus (2018/26 Neco)

9. Which of the following is impaired if the cerebellum is damaged?

A. breathing B. digestion C. swallowing D. vision E. walking (2014/59 Neco)
10. The central nervous system is made up of which of the following pairs?
A. Brain and spinal cord B. brain and nerves C. spinal cord and systematic nervoussystem
D. parasympathetic and systematic nervous systems E. brain and cerebrum (2007/56 Neco)
11. Which part of the mammalian brain regulates the maintenance of body equilibrium?
A Olfactory lobes B. Optic lobes C. Cerebrum D. Cerebellum E. Medulla oblongata (1992/23 Nov)
12. The part of the brain that controls sleep is
A. hypothalamus B. cerebellum C. optic lobe D. medulla oblongata E. pineal body (1998/21 Nov)
13. 4. (a) Make a large labeled diagram of the brain of a rabbit/man (1998/4a Nov)
14. 4.(b) Give two functions each of the brain (1998/4b Nov)
15. Which of the following is not the function of the mid-brain of man?
A. For passage of nerve fibers B. Linking the olfactory lobe with the cerebellum
C. Controlling the sense of hearing D. Controlling respiratory actions
E. Controlling the sense of sight (1990/47 Nov Health Science)
16. The largest part of the human brain is the
A. medulla oblongata B. midbrain C. cerebrum D. cerebellum E. hind brain (1998/20 Nov Health Science)

Spinal Cord
The spinal cord consists of thousands of neurone clustered to form a cylinder of the nervous tissues. The spinal cord is
the continuation of the brain. It occupies the neural canal of the vertebral column. It is protected by the bones of the
vertebral column but passes through the neural canal.
The spinal cord is protected by three layers of meninges namely; dura matter (out layer), arachnoid matter (middle
layer) and pia matter (inner layer). A narrow canal, the spinal canal, runs down the centre of the cord. It is filled with
a fluid, the cebrospinal fluid.

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 Central
Canal

Transverse Section of Spinal Cord

The diagram shows that:

1. White matter is on the outer portion of the spinal cord: It contains the axon of sensory and motor neurons.
2. Grey matter is H – shaped and it is in the inner part of the spinal cord. It contains intermediate neurons and
cell body of motor neurons.
NOTE: The grey matter is divided into anterior and posterior horn
3. Central canal is a hole in the central of the spinal cord. It contains cerebrospinal fluid.
4. Pia matter is a membrane that surrounds the spinal cord and contain blood vessel. Other outer membranes are
arachnoid matter and Dura matter. The pia matter, arachnoid and Dura matter are also called layer of
meaninges and they protect the spinal cord.
Each spinal nerve before attaching to the spinal cord divides into dorsal root and ventral root. The dorsal root contains
sensory neurons and before it enters the spinal cord it forms a ganglion containing cell bodies of sensory neurons. The
dorsal root carries impulses (i.e. messages) from the body to the spinal cord. The vertical root contains motor neurons
and carries impulses away from the spinal cord to the body.
Functions of the Spinal Cord
1. It sends impulses (messages) to the brain and carries responses from the brain to the muscles.
2. It is the seat of reflex (involuntary) actions.

Example
Use the figure below to Answer: questions 33 to 34

All the cell bodies in the spinal cord are found in

A. 1 B. 2 C. 3 D. 4
Answer: C – Label “3” points to the grey matter of the spinal cord. This portion contains all the cell body of neurons
in the spinal cord.
In a reflex action, impulse flows from
A. 1 to 2 B. 2 to 1 C. 4 to 1 D. 4 to 2 (1990/33-34 JAMB)
Answer: A – In a reflex action impulse flows from sensory neuron (1) to interneuron (2) then to motor neuron (4)
Example
The function of the spinal cord is to
A. stand the body structure erect B. control involuntary actions
C. Transmits impulses to the brain D. regulates developmental changes (2016/36 JAMB)
Answer: C – The function of the spinal cord is to transmit impulses to the brain.

Example
The region that controls most of the unconsciously processes of a mammalian body is the
A. cerebellum B. cerebrum C. spinal cord D. medulla oblongata (1989/35 JAMB)
Answer: C – The spinal cord is the region that controls most of the unconscious (reflex) process of the mammalian body.

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Example
Which the following structures occupies the neural canal of the vertebral column?
A. cerebellum B. hypothalamus C. medulla oblongata D. spinal cord (2004/19)
Answer: D – The spinal cord (Medulla spinalis) occupies the neural canal of the vertebral column

EXERCISE 12.3
Study the diagram below and use it to Answer: questions 17 and 18

1. The part labeled II in the diagram is the

A. central canal B. grey matter C. spinal cord D. dorsal root E. vertebraterial canal. (1997/17)
2. Which of the labeled parts is filled with cerebrospinal fluid?
A. V and I B. V only C. III only D. II and I E. I only (1997/18)
3. Which of the following is NOT a part of the spinal cord?
A. central canal B. dorsal fissure C. grey matter D. pineal body E. white matter (2005/8 Neco Nov)
4. Which of the following structures is directly connected to the spinal cord?
A. Cerebellum B. Olfactorylobe C. Pituitary D. Cerebral hemisphere E. Medulla oblongata (1997/19 Nov)
5. (a) Explain what may happen if any of the following parts of the body is damaged:
(iii) spinal cord; (1996/2(a) iii Health Science)

The Peripheral Nervous System (PNS)

The peripheral nervous system includes all nerves outside the brain and spinal cord. These are the sensory nerves
which lead from all parts of the body to the central nervous system and the motor nerves running from the central
nervous system to all parts of the body.
There are two types of peripheral nerves:
1. Spinal nerves – These are nerves which are connected to the spinal cord. The spinal nerves serve the receptors
and effectors in other body parts.
2. Cranial nerves – These are nerves that are connected to the brain. The cranial nerves are associated mainly
with the receptors and effectors in the head.
There are also two types of peripheral nervous systems
a. Somatic nervous systems
b. Autonomic nervous systems
The somatic nervous system (SNS) primarily senses the external environment and controls voluntary activities in which decision
and commands come from the cerebral cortex of the brain. It deals with mainly external stimuli and their responses. The somatic
nervous system (SNS) is made up of 12 pairs of cranial nerves in the head and 31 pairs of spinal nerves in the body of man. Of the
12 cranial nerves, the optic and olfactory nerves, consists only of sensory fibres. The remaining 10 pairs and the 31 pairs of spinal
nerves contain both sensory and motor nerve fibres which conduct impulses from sense receptors to the spinal cord or brain and
from there to effectors.
The autonomic nervous system (ANS) is the part of the peripheral nervous system that controls involuntary actions such as the
rate of heartbeat, breathing, digestion, sweating etc inside the body. The system consists of sensory and motor nerves which
connect the brain or the spinal cord to internal organs such as heart, liver and alimentary canal.
Differences between somatic nervous system and autonomic nervous system
Somatic nervous system Autonomic nervous system
1. It affects skeletal muscles It affects glands, cardiac muscles and smooth muscles
2. Body activities are mainly voluntary Activities are mainly involuntary
3. It always stimulates effectors It may stimulates or inhibit effectors
The autonomic nervous system consists of two parts:
1. Sympathetic nervous system 2. Parasympathetic nervous system
Sympathetic Nervous System (SNS)
The sympathetic nervous system consists of nerves which connect internal organs to the thoracic and lumbar areas of
the spinal cord. It stimulates many parts of the body for necessary action in time of danger. During this process, a
hormone, adrenaline may be released.
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Function of Sympathetic Nervous System
1. It accelerate the heart beat. 6. It dilates the iris.
2. It slows gut movement. 7. It dilates the bronchioles.
3. It raises the blood pressure. 8. It causes the relaxing of bladder muscles.
4. It inhibits the secretion of salivary glands. 9. It contracts bladder and anal sphincter.
5. It constricts arteries.

The Parasympathetic Nervous System

The parasympathetic nervous system consists of nerves which connect internal organs to the 10 th cranial nerve and the
sacral region of the spinal cord. This system stimulates the same organs as the sympathetic system but its action is
opposite to the sympathetic nervous system.
Functions of Parasympathetic Nervous System
1. It slows down heart beat. 6. It constricts iris.
2. It speeds up gut movement. 7. It constricts the bronchioles.
3. It lowers the blood pressure. 8. It causes the contraction of the bladder muscle.
4. It stimulates the secretion of salivary glands. 9. It relaxes the bladder and sphincter.
5. It dilates arteries.

The PNS and SNS

Example
The nerves that arise from the brain are known as
A. spinal nerves B. sacral nerves C. cranial nerves D. optic nerves (2000/24)
Answer: C – The nerves that arise from the brain are called cranal nerves.
NB: The nerves that arise from the spinal cord are called spinal nerves.
Example
The following are functions of sympathetic nervous system except
A. Dilation of pupil of eye B. inhibition of salivary secretion C. reduction of blood pressure
D. reduction of urine output E. stimulation of ejaculation (2018/48 Neco)
Answer: C – The reduction of blood pressure is the function of the parasympathetic nervous system.
Example
The autonomic nervous system comprises
A. sympathetic and parasympathetic B. cranial and sacral nerves
C. brain and cranial nerves D. spinal cord and spinal nerves (1989/53)
Answer: A – The autonomic nervous system comprises the sympathetic and the parasympathetic nervous systems.

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Example
The autonomic nervous system consists of neurons that control the
A. voluntary muscles B. heart beat C. tongue D. hands (2012/27 JAMB)
Answer: B – The autonomic nervous system consist of nerves that controls involuntary actions such as the heartbeat.

EXERCISE 12.4
1. Which of the following specialized structures are stimulated by touch, pressure, pain, heat and cold?
A. Receptors B. Synapse C. Cell bodies D. Myelin sheath E. Relay neurons (1988/23)
2. The autonomic nervous system comprises
A. sympathetic and parasympathetic systems B. cranial and sacral nerves
C. brain and cranial nerves D. spinal cord and spinal nerves E. brain and spinal nerves (1989/53)
3. The following are functions of sympathetic nervous system except
A. dilation of pupil of eye B. inhibition of saliva secretion
C. reduction of blood pressure D. reduction of urine output E. stimulation of ejaculation (2018/48 Neco)

THE NEURONE
The nervous system consists of millions of neurons (nerve cell). The neuron/nerve cell is the basic unit of nervous
system that is responsible for the transmission of impulses within the body. The neuron is the structural and functional
unit of the nervous system.
The neurone/nerve cell consists of three main parts: the cell body, Dendron and the axon. Some nerve cells have
Dendron.
1. The cell body – Consist of nucleus and cytoplasm. Present in the cytoplasm are nissl’s granules which are rich
in RNA and help to manufacture protein.
2. Dendrites – These are short cytoplasmic filaments that conduct impulses (messages) to the cell body.
3. The axon – The axon is also known as the nerve fibre. It is that portion of the nerve cell (neuron) which
carries impulses away from the cell body. Most axons of vertebrates are enclosed in a myelin sheath, which
increases the speed of impulse transmission. Axons with myelin sheath are said to be myelinated, while those
without myelin sheath are unmyelinated. Myelin sheath are covered with neurilemma. The neurilemma are
part of another cell called schwan cells and not part of the neuron. At intervals, myelin sheaths are interrupted
by constrictions known as node of ranvier.
4. Dendron – This is a long fibre which conduct impulse from a synapse to the cell body.

Synapse
Where two nerves meet is a nerve junction called synapse. At a synapse, the motor end – plate of the axon joins with
the dendrite of the following neurone but the two nerve cells do not touch each other. They leave a gap called synaptic
gap.

Neurone

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CLASSIFICATION OF NEURONE
There are three types of neurons.
1. Sensory (afferent) neurone.
2. Motor (efferent) neurone.
3. Intermediate (association) neurone

1. Sensory/Afferent Neurone
Transmits impulses from the sensory cell towards the central nervous system (spinal cord and brain). The
dendrites are connected to the sensory cells while the axon is connected to other neurones.

2. Motor/Efferent Neurone
The motor neurone transmits impulses away from the central nervous system to the effector organ e.g.
muscles and glands. The dendrites are connected to an intermediate neurone while the axon is connected to an
effector.

3. Intermediate/Relay/Association/Connector Neurone
The intermediate neurone joins the sensory neurone with the motor neurone. That is, it transmits impulses
from one nerurone to the other within the central nervous system. Both their dendrites and axon are connected
to other neurones.

Example
Use the diagram below to Answer: questions 26 and 27

The structure can be found in the

A. peripheral and central nervous systems B. peripheral nervous system only
C. sympathetic and parasympathetic nervous systems D. central nervous system (2003/26 JAMB)
Answer: A– The structure in the diagram above is known as the neuron. It is the basic unit of the nervous
system and it is found in both the central nervous system and the peripheral nervous system
The point marked I is referred to as
A. myelin sheath B. dendrites C. node of ranvier D. axon (2003/27 JAMB)
Answer: C– The part labeled I is known as the node of ranvier

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Example

The diagram represents

A. sensory neurone B. relay neurone C. afferent neurone D. motor neurone
Answer: D – The diagram is a typical example of a motor neuron (efferent neuron)

Example
Use Diagram to answer question 21-22 The actual label

The cell body in the diagram is labeled

A. I B. II C. III D. IV E. V (1998/21 )
Answer: A– from the diagram above, the cell body I the part labeled I
The function of the part labeled II in the diagram is to
A. transmit impulse from one end of the cell to the other B. manufacture food of the cell
C. protect the axon D. produce energy for the cell E. detect electrical impulses (1998/22 )
Answer: C- insulate electrical impulses i.e protecting the axon where electrical impulses passes
Example
Neurones that receive stimuli from the body or internal organs are called
A. sensory neurons neurones B. efferent neurons C. motor neurones D. relay neurones (1992/31 JAMB)
Answer: A – Neurons that receive stimuli from the body or internal organs are called sensory neurons (afferent neurons)
Example
Each neurone consists of the following structures except
A. cell body B. dendrites C. axon D. white matter (2000/26)
Answer: D – White matter is not a part of the neuron. A typical neuron consists of; a cell body, dendrites and an axon.
Example
Impulses are conducted towards the nerve cell through the
A. myelin sheath B. Dendron C. axons D. synaptic node (2012/17)
Answer: B – Impulses are conducted towards the nerve cell through the Dendron.
Note: Impulses are conducted away from the nerve cell through the Axon
Example
The spaces between neurons through which impulses cross by means of chemical reaction are called
A. axons B. ganglia C. synapses D. dendrites E. pia matter (1989/49)
Answer: C – A Synapse is the space between neurons through which impulses cross by means of chemical reaction.
Example
The neuron that transmits impulses directly from sensory cells is called
A. an afferent neuron B. an efferent neuron C. a relay neuron D. a peripheral neuron (2007/21)
Answer: A – Neurons that transmit impulses directly from sensory cells are called afferent neurons (sensory neurons)
Example
The neurone that relay the message of effector organs are called
A. efferent neurons B. intermediate neurones C. afferent neurones D. spinal nerves (2000/25)
Answer: A – The neurons that relay the massage of effort or organs are called efferent neurons.
NB: To relay a message means to carry a message towards something.

EXERCISE 12.5
1. The smallest branches on the cell body of a neurone are called
A. dendrites B. dendrons C. ganglia D. Schwan cells (2007/20)
2. A neurone that transmits impulses directly from sensory cells is called
A. an afferent neurone B. an efferent neurone C. a relay neurone D. a peripheral neurone (2007/21)
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3. Which of the following neurons may not have myelin shealth?
A. Effector cells B. Intermediate neurons C. Motor neurons D. Sensory neurons (2011/18)

4. 3b(ii) Name THREE types of neurones.

(iii) State ONE function of each of the named neurons. (2005/3b ii, iii Neco Nov)
5. Which of the following is an effector?
A. spinal cord B. brain C. blood D. muscle (2019/27 NABTEB)
6. Which of the following is the correct sequence of a nerve impulse?
A. axon → Dendron → terminal branch → cell body B. cell body → Dendron → terminal branch → axon
C. Dendron → cell body → axon → terminal branch
D. terminal branch → axon → cell body → dendron (2006/21 Nov)
7. (c) Make a drawing, 10 to 12 cm long, of a motor neurone and label it fully (2006/2c Nov)
8. The neurone is the functional unit of the
A. kidney B. heart C. brain D. liver (2020/17 PC1)
9. 1a. With the aid of a labeled diagram 10cm – 12cm long, describe the structure of a neurone.
b. Name the three types of neurones and give the function of each (1999/1a & b Nov)
10. Which of the following is not correct about nerve cells?
A. The axons relay impulses from the body cells B. The cell body is always found at the end of the neurone
C. Each neuron has a cell body D. The dendrites of on neuron transmit impulses to the cell body (2002/22 Nov)
11. Nerves that carry messages to the brain are described as
A. relay nerves B. afferent nerves C. connector nerves
D. motor nerves E. synapse (1998/19 Nov Health Science)
12. The part of the neuron that receives stimulus first is the
A. axon B. synapse C. cell body D. grey matter E. dendrite (1998/21 Nov Health Science)

Ionic Transmission
The transmission of impulses along a neuron is by electrochemical means, this means that it involves both electrical
and chemical transmission. The mechanism of transmission of impulses through a nerve fibre is in three phases.
1. Resting potential.
2. Action potential.
3. Depolarization.
The transmission of nerve impulses involves fibre transmission which is electrical and transmission through synapse
which is chemical.
1. Resting potential: The resting potential is the stage when no impulse is passing through the fibre. A nerve
fibre is electrically polarized (i.e. has positive charges) with a net positive charge outside and a net negative
charge inside the cell membrane. There are more potassium ions inside than outside and more sodium ions
outside than inside the membrane. In this state where no impulse is passing through, the fibre is said to be at
resting potential.

Three stages in the electrical transmission of an impulse along an axon

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2. Action potential: When a dendrite receives a stimulus, the beginning of the axon is stimulated and becomes
temporarily depolarized by the inward flow of sodium ions and the out ward flow of potassium ions. This
stimulates the adjacent part of the axon which in turn becomes depolarized. As this continues, depolarization
occurs from one end of the axon to the other. The nerve fibre is said to be at an action potential.
3. Repolarization phase: Before the ontset of repolarization phase, the inner side of the membrane of the nerve fibre is
electropositive relative to the outside. Soon, after the transmission of the impulse, the resting potential is re-established.
The transmission of nerve impulse is unidirectional and obeys the all – or none law which state that if the intensity of the
stimulus is below a definite threshold, the nerve fibre is not stimulated at all. If the stimulus is up to or above the
threshold, the nerve fibre is stimulated to a full action potential.
4. Transmission of impulse by chemical means: Transmission of nerve impulses across a synapse is chemical.
When a nerve impulse reaches the end of an axon, the synaptic knobs at the tips of the end – plate fibres
secrete a chemical substance called acetyl choline.
Acetylcholine diffuses across the synaptic gap and stimulates the dendrites of the post synaptic neuron. The
second neurone continues the transmission of impulse. An enzyme called cholinesterase renders the
acetylocholine inactive, therefore preventing it from accumulating at the synaptic gap.
Functions of Neurone/Nerve Cells
1. It conduct impulses to the brain (sensory neurone).
2. The intermediate neurones integrate the reflex actions.
3. The autonomic nerves helps to keep us active.
4. Motor neurones conduct impulses to the sense organs.
5. Neurones enable us to be aware of our environment.

Example
In a mammal, stimulus is transferred from the receptor muscle to the central nervous system through the
A. motor neurons B. effector muscles C. Dendrites D. sensory neurons E. synapses (1985/40 JAMB)
Answer: D – Stimulus is transferred from the receptor muscle to the central nervous system through the sensory
neurons (afferent neurons).
Example
Which of the following ions is involved in the conduction of the nerve impulse?
A. Ca2+ B. K+ C. H+ D. Mg2+ (1995/30 JAMB)
Answer: B. K+ (potassium ion) is one of the ions involved in the conduction of nerve impulse. NB: The other ion is Na+
Example
The two key cations involved in the action potential of nervous transmissions are
A. Na+ and K+ B. Na+ and Fe2+ C. Fe2+ and Mg2+ D. Mg2+ and K+ (2004/22 JAMB)
Answer: A – The two key cations involved in the action potential of nervous transmissions are Na+ and K+.
Example
The transmission of impulses along a nerve fibre is characterized by
A. hormonal and temperature changes B. electrical and ionic changes
C. hormonal changes D. electrostatic changes (2008/28 JAMB)
Answer: B – The transmission of impulses along a nerve fibre is characterized by electrical and ionic changes.
Example
When an axon is at rest, the concentration of ions on either side of the membrane are different. Which of the following
is correct about the concentrations of ions on either side of the membrane?
A. There is an excess of potassium ions inside the axon and an excess of sodium ions outside
B. The inside of the axon becomes positively charged while the outside is negatively charged
C. There is an excess of sodium ions on the inner side of the axon
D. Chloride and potassium ions begin to move across the membrane
E. Calcium ions accumulate on the inner side of the axon (1993/17)
Answer: A – In a resting membrane, there is an excess of potassium ions inside the axon and an excess of sodium ions
Example
Which of the following statements about the response of neurons to stimulus is correct?
A. Neurons respond to stimulus of any strength B. Neurons respond to all stimuli applied in rapid succession
C. Neurons respond more rapidly during the absolute refractory period
D. Intensity of stimulus must reach a threshold value before the neurons can be excited (2018/16)
Answer: D – Intensity of stimulus must reach a threshold value before the neurons can be excited. This is the all-or-
none principle. Option D is the correct option.

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EXERCISE 12.6
1. (c) Describe the mechanism of transmission of impulses through a nerve fibre. (1994/3c)
2. (a) What is a receptor? (b) Describe the general features common to all receptors (2002/2a & b)

3. b. Briefly describe the mechanism of transmission of impulses by neurone (2017/4b NABTEB)

4. Through which means are impulses transmitted across a synapse?
A. chemical B. electrical C. electromagnetic D. magnetic E. physical (2005/16 Neco Nov)
5. Which of the following statements about the transmission of messages within the nerve cell is correct? It
A. proceeds in both directions along a nerve axon
B. Involves both electrical impulses and chemical transmissions
C. is slower via a myelinated axon than a non-myelinated axon
D. relies on the active transport of a neurotransmitter across a neurone (2019/17 PC2)

Reflex and Voluntary Action

Reflex Action (Involuntary)
Reflex action is a rapid/autonomic/quick response to stimuli which are not consciously controlled by the brain.
Characteristics of Reflex Action
1. It is a quick response 4. It involves minimum member of nerve cells
2. It is not under the control of will i.e. autonomic 5. It ends at the spinal cord
3. It is not planned
Examples of Reflex Actions
Examples of reflex/involuntary actions are blinking of eyes, peristalsis, coughing, sneezing, salivation, withdrawal of
hand from a hot object and secretion of glands.

Voluntary Actions
Voluntary actions are responses to stimuli that are consciously controlled by the brain.
Characteristics of Voluntary Actions
1. It involves prolong response.
2. It involves many nerve cells.
3. Its response is controlled by the brain.
4. It response to a particular stimulus may vary.
Examples of Voluntary Actions
Example of voluntary actions includes singing, driving, walking, writing, dancing, eating, running, reading and typing.

Simple reflex arc

A simple reflex arc is the simplest pathway in the nervous system by which a stimulus is received and a response is made.
A reflex arc consists of the following parts:
1. Sensory cells/Receptor organ: These cells receive the stimulus.
2. Afferent neurone/Sensory neuron: This transmits nerve impulses from the sensory cells to the spinal cord or
brain.
3. Intermediate neurone: This conducts nerve impulses from the afferent to the efferent neurone.
4. Efferent neurone: Th is transmits impulses from the intermediate neurone to the effector.
5. Effector (muscle/gland): This takes action.

Simple reflex arc

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Conditioned Reflex
Conditioned reflex is a learned response after birth. Once they are acquired, they can be performed without thinking
about them. Most of our behaviors are conditioned reflexes. Examples of conditioned reflexes are walking, driving,
reading, writing, swimming e.t.c. It takes a fairly long time to learn each of these skills. But once they have been
mastered, they are performed very fast and efficiently without the individual thinking about them i.e they become
habits.
A Russian biologist, Ivan Pavlov demonstrated the concept of conditioned reflex in 1902 with an experiment carried
out on dog. Naturally when food is placed before a hungry dog, the sight and smell of the food causes saliva to flow in
the mouth of the dog.
In the experiment, Pavlov rang a bell each time food was ready for the dog. After a long time of giving food with the
ringing of the bell, the dog became conditioned to the sound of the bell. Pavlov observed after sometime, that when
the bell was rung the dog still salivated. The dog has been conditioned to the sight and smell of food and sound of the
bell. Any of the stimulus (such as sight, smell or sound of bell) could stimulate salivation.
Training of domestic animals such as dogs, cats, horses is based on conditioning. The animals learn to associate
spoken command or sound of whistles.

Unconditioned Reflexes
Unconditioned reflexes are reflexes a person is born with e.g Withdrawing of hand/leg from a sharp object

Differences between reflex actions and voluntary actions

Reflex actions Voluntary actions
1. They have their actions in the hind brain or spinal cord. They have their actions in the forebrain.
2. The response to stimuli happens unconsciously and not Response to stimuli is usually controlled i.e. it is done
consciously. consciously.
3. Most of the reflex action are inborn and are not learnt. Most of the voluntary actions are learnt.
4. The response to stimuli happens automatically and The response to stimuli is not automatic. It is a little delayed.
quickly.
5. Few neurons are involved in the path of nervous impulses, Many neurons are involved making it a longer path.
making the path shorter.
6. Some reflex actions can be converted to voluntary actions. Voluntary actions cannot be converted to reflex.
7. Examples of reflex actions are blinking of eyes, Examples of voluntary actions are singing, driving, walking,
peristalsis, coughing, sneezing, salivation, withdrawal of writing, dancing, eating, running, reading, and typing.
hand from a hot object and secretion of glands.

In summary, the organization of the nervous system is given schematically below:

Example
Which of the following actions is not a voluntary action?
A. stealing B. sneezing C. fighting D. cheating (2016/17)
Answer: B – Sneezing is not a voluntary action i.e. it is done outside of our will/unconsciously.
Example
Which of the following action is not a conditioned reflex?
A. walking B. blinking of eyes C. driving a vehicle D. swimming. (2019/28 NABTEB)
Answer: B – Blinking of the eye is not a conditional reflex.
Example
Which of the following action is not a simple reflex action?
A. knee jerk B. blinking of the eye C. withdrawal of hand from hot object
D. reading a book E. contraction of the iris
Answer: D – Reading a book is not a simple reflex action because it is done with our consciousness.
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Example
The simplest form of nervous pathway which links receptors with effectors is known as the
A. relay neurone B. reflex arc C. motor nerves D. sensory nerves (2000/27)
Answer: B – The reflex are in the simplest pathway which link receptors with effectors.
Example
Reading the verdict of a case by a judge or magistrate is an example of
A. a reflex action B. an instinct C. a conditioned reflex D. a voluntary action (2005/26)
Answer: D – Reading is a voluntary action.
Example
Which of the following processes is not an example of a reflex action?
A. Blinking of the eye B. Reading C. Beating of the heart D. Sneezing (2008/19)
Answer: B – Reading is a voluntary action. i.e it is done with our consciousness and will.
Example
The passage of nerve impulse across a synapse is facilitated by the secretion of
A. acetylcholine B. thyroxine C. insulin D. progesterone (2008/17)
Answer: A – Acetyl choline is the neuro-transmitter that passes nerve impulse across synapses.
Example
Which of the following is an effector organ
A. Tongue B. Skin C. Nose bridge D. Ear glands (2011/19)
Answer: B – The skin is an effector organ. An effector organ is one that is capable of responding to a stimulus from a
nerve.
Example
The following are all examples of a simple reflex action, except
A. swallowing B. sneezing C. walking D. blinking (2012/16)
Answer: C – Walking is not a reflex action.
Example
Which of the following sequences is the correct route of the transmission of impulses along a reflex arc?
A. Receptor  sensory neurone  synapse intermediate neurone  synapse  motor neurone  effector
B. Receptor  motor neurone  synapse  intermediate neurone  synapse  sensory neurone  effector
C. Effector  intermediate neurone  synapse  motor neurone  synapse  sensory neurone  receptor
D. Effector  motor neurone  synapse  sensory neurone  synapse  intermediate neurone  receptor (2017/18)
Answer: A – The correct route of the transmission of impulses along a reflex are:
Receptor  sensory neurone  synapse intermediate neurone  synapse  motor neurone  effector
Example
The legs of an accident victim with a fractured vertebra column and injured spinal cord could not be raised because
A. impulses from receptors in the legs cannot travel to the brain
B. impulses from the brain cannot travel to the legs
C. chemical substances will be released at synapses in the central nervous system
D. reflex actions cannot take place in the legs (2014/13)
Answer: B – The legs of an accident victim with a fractured vertebra column and injured spinal cord cannot be raised
because impulses from the brain cannot travel to the legs. This is true because impulse form the brain must pass
through spinal cord before it gets to the leg.
Example
(b)i. Describe the path of a reflex action.
ii. State FOUR differences between reflex action and voluntary action (2001/5b(i) & (ii) NABTEB)
Answer:
i. Impulses move from stimulated sensory cells or receptor organ to the afferent neuron (sensory neuron). From
here, they pass through the synapse between the efferent neuron and the intermediate neuron into the
intermediate neuron. Then they pass from the intermediate neuron into the synapse between the intermediate
neuron and the efferent neuron (motor neuron). From there they enter the motor neuron which passes them to
the effector or muscles.
In summary:
Receptor organ →afferent neuron→ synapse→ intermediate neuron→ synapse → efferent neuron →effector
ii. Difference between reflex action and voluntary action:
- Reflex actions are inborn and not learnt while voluntary actions are learnt.
- Reflex actions are done without consciousness while voluntary actions are done with consciousness.
- Reflex actions are automatic and quick while voluntary actions are not automatic and quick.
- Some reflex actions can be converted to voluntary actions but Voluntary actions cannot be converted to reflex actions

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Example
Which of the following is an effector?
A. spinal cord B. brain C. blood D. muscle (2019/27 NABTEB)
Answer: D – Muscle is a effector organ.
Example
The following are involved in reflex action except
A. brain cells B. intermediate neuron C. motor neuron D. receptor E. sensory neuron (2008/50 Neco)
Answer: A – Brain cells are not involved in reflex action.
Example
What is NOT a reflex action?
A. blinking of an eye B. jerking of the knee C. learning D. salivating E. sneezing (2001/16 Neco)
Answer: C – Learning is not a reflex action because it is done with the forebrain.
Example
The part of the nervous system which controls voluntary actions is the
A. cerebellum B. cerebrum C. medulla oblongata D. spinal cord E. thalamus (2007/39 Neco)
Answer: B – The cerebrum is the part of the brain that controls voluntary action.
Example
Which of the following statements about a reflex action is correct?
A. nerve impulses are transmitted faster to the brain B. the action is intentional
C. impulses that pass along motor nerves are blocked D. the reaction is quick and automatic (2013/20 Nov)
Answer: D – In reflex action, the reaction is quick and automatic.
Example
Reflex actions do not have to be
A. Interpreted B. learnt C. effected D. sensed E. translated as impulse (1996/18 Nov)
Answer: B – Reflex actions do not have to be learnt.
Example
Which of the following statements about reflex action is correct?
A. Reflexes are controlled by the brain B. Impulses end at the spinal cord
C. Response involves reasoning D. Response is delayed
E. Response is voluntary (1997/20 Nov)
Answer: B – In reflex action, impulses end at the spinal cord and are not transmitted to the brain.
Example
Which of the following is a voluntary action?
A. sneezing B. knee jerking C. walking D. Blinking of eyes (2000/22 Nov)
Answer: C – Walking is a voluntary action.
Example
Which of the following actions is not a conditioned reflexed
A. walking B. dancing C. blinking of eyes D. driving a vehicle E. swimming (1998/22 Nov)
Answer: C – Blinking of the eyes is not a conditioned reflex. A condition reflex is a learned response from birth and
once they are learnt, they can be performed without thinking about them.
Example
The following are examples of reflex action except
A. blinking of the eye B. yawning C. sneezing D. knee jerk E. eating (1998/18 Nov Health Science)
Answer: E – Eating is not a reflex action.
Example
Which of the following is not a voluntary action?
A. Sleeping B. Dancing C. Climbing D. Singing (2000/19 Nov Health Science)
Answer: A – Sleeping is not a voluntary action.

EXERCISE 12.7
1. A fundamental similarity between nervous and hormonal system is that both
A. involve chemical transmission B. have widespread effects
C. shed chemical into the blood stream D. evoke rapid responses (1989/34 JAMB)
2. Nervous control differs from hormonal control in that the former
A. produces short-term changes B. has no specific pathway
C. involves only chemical transmission D. is a slower process (2004/31 JAMB)

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3. The brain and spinal cord make up the
A. peripheral nervous system B. autonomic nervous system C. central nervous system
D. somatic nervous system E. sympathetic nervous system (1990/27)
4. Which of the following parts of the mammalian brain is involved in taking the decision to run rather than
walk?
A. cerebellum B. medulla oblongata C. cranial nerve D. mid brain E. cerebrum (1990/26)
5. If the cerebellum of a person is slightly damaged, which part of the following will be impaired
A. vision B. walking C. breathing D. digestion (2002/21).
6. The part of the nervous system that interprets blinking of the eye is the
A. spinal cord B. cerebrum C. hind brain D. olfactory lobe (2003/20)
7. Which of the following structures occupies the neural canal of the vertebral column?
A. cerebellum B. hypothalamus C. medulla oblongata D. spinal cord (2004/19)
8. Which of the following is not a part of the mammalian brain?
A. cerebellum B. cerebrum C. olfactory lobe D. spinal cord E. thalamus (2018/26 Neco)
9. Which of the following is an example of a reflex action?
A. sneezing B. biting C. dancing D. singing E. talking (1997/19)
10. Which of these actions is not a reflex action?
A. peristalsis B. sneezing C. laughing D. coughing E. eye blinking (1997/20 Nov.)
11. Which of the following is the correct route of transmission of impulses along a reflex arc?
A. Receptor→sensory neurone→synapse→intermediate neurone→synapse→motor neurone→ effector
B. Receptor → motor neurone → synapse → sensory neurone → effector
C. Receptor→synapse→sensory neurone→intermediate neurone→synapse→effector→motor neurone
D. effector→motor neurone→synapse→sensory neurone→synapse intermediate neurone→receptor (1995/20)
12. The smallest branches on the cell body of a neurone are called
A. dendrites B. Dendron C. ganglia D. schwan cells (2007/20)
13. Which of the following neurones may not have myelin sheath?
A. effector cells B. intermediate neurone C. motor neurone D. sensory neurone (2011/18)
14. The legs of an accident victim with a fractured vertebra column and injured spinal cord could not be raised
because
A. impulses from receptors in the leg cannot travel to the brain
B. impulses from the brain cannot travel to the legs
C. chemical substances will be released at synapses in the central nervous system
D. reflex actions cannot take place in the legs (2014/13)
15. The following are involved in reflex action except
A. brain cells B. intermediate neurones C. motor neurones D. receptor E. sensory neurons (2008/50 Neco)
16. Which of the following is the correct sequence of nerve impulse?
A. Axon → Dendron → terminal branch → cell body
B. Cell body → Dendron → terminal branch → axon
C. Dendron → cell body → axon → terminal branch
D. Terminal branch → axon → cell body → Dendron (2006/21 Nov)
17. State the functions of the following
i. Cerebrum ii. Hypothalamus iii. Medulla oblongata iv. Cerebellum (2003/7b / 2009/1d)
18. Make a large labeled diagram of the brain of a rabbit/man. (1998/4a Nov.)
19. Briefly describe the mechanism of transmission of impulses by neurone. (2017/4b NABTEB)

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Endocrine Glands and their Hormones
Co-ordination is making the different parts of an organism to work together effectively or for increased efficiency.
One way of achieving co-ordination is by the secretion of endocrine glands called hormones. Hormones are chemical
substances produced in minute quantities in one part of an organism and transported to the site of action where they
exert specific effect to control body metabolism. Animal hormones are secreted by glands known as endocrine glands
or ductless glands. They are called ductless gland because they do not have ducts through which their secretions can
be channeled but rather their secretions are poured directly into the blood stream by diffusion. The hormone secreted
by endocrine gland is defined as a chemical substance produced in one specific part of an organism which brings
about effect in another part of the organisms. The hormone helps to co-ordinate the functions of the body.

The endocrine glands include the pituitary gland, thyroid gland, parathyroid, thymus gland and adrenal gland.
Endocrine glands also occur in the walls of the stomach and small intestine as well as the pancreas and gonad (i.e.
ovaries and testes). These glands mentioned above, makes up the endocrine system.

Characteristics of endocrine glands and hormones

1. The endocrine glands have no duct.
2. Hormones are carried in the blood streams from ductless glands where they are secreted, to other parts where
they exert their effect.
3. A ductless gland may be stimulated to secrete either by nervous system, or by the presence of a specific
substance such as food.
4. Each hormones stimulate only specific organs or cells but has no effect or action on other part of the body.
5. The nature of action of a hormone is to change the metabolic activity of the target cells.
6. The effect of a hormone is slow compared with the effect stimulated by the nervous system.
7. The effect of a hormone persists for a longer time when compared with the effects of nervous co-ordination
which is concerned with changes over a short time.
8. Correct functioning of the endocrine glands promotes good physical, mental and emotional health.

Differences between hormonal coordination and nervous coordination

Hormonal co-ordination Nervous co-ordination
1. Message are carried chemically by blood stream. Message are electrically and chemically carried by nerves.
2. Response to stimulus is slower (adrenaline being an Response to stimulus is faster
exception)
3. Since it is poured into the blood, it is carried to any Nerve impulses are transmitted to a particular location by a particular
part of the body. set of neurons.
4. Hormonal responses are usually widespread. Target Responses may be localized. Sometimes one type of muscle may be
is far away from site of production. affected.
5. Responses may last for a long time, for example, Responses are short-lived. For example, the contraction and
growth and sexual maturity are long term responses relaxation of muscles.
of hormones.
6. Their secretions, actions and responses are Their actions and response are under voluntary actions.
controlled by involuntary actions.
7. Present in both plants and animals. Present only in animals.

Similarities between hormonal coordination and nervous coordination

1. Hormonal and nervous system provide means of communication within the body of an organism.
2. Both transmit messages when triggered by a stimulus.
3. The nerve effector of nervous system is similar to target organs of hormones.
4. In some cases, both evoke the same responses. For example, the hormone adrenaline when released into the
blood accelerates the beating of the heart, the pupils of the eye dilate, the arterioles constrict, etc. the
sympathetic nerves do the same.
5. Once the action is completed, both cease to act.

Example
Mention four characteristics of hormones (2002/6a Nov Health Science)
Answer:
- They are produced from ductless gland.
- They are transported through the blood stream.
- Each hormone stimulates only specific organs or cells.
- Their effects are slow compared with the effects caused by the nervous system.

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Example
The endocrine gland secretes
A. antibodies B. antigens C. antitoxins D. hormones (2017/39 NABTEB)
Answer: D – Hormones are secreted by the endocrine glands.
Example
A fundamental similarity between nervous and hormonal system is that both
A. involve chemical transmission B. have widespread effects
C. shed chemical into the blood stream D. evoke rapid responses (1989/34 JAMB)
Answer: A – A fundament similarity between nervous and hormonal system is that both involve chemical
transmission.

EXERCISE 13.1
1. The mammalian endocrine system is responsible for
A. transmitting impulses B. regulating body temperature
C. regulating osmotic pressure of blood D. chemical co-ordination (2019/9 JAMB)
2. Which of the following statements is correct of hormones? Hormones are
A. secreted into blood through ducts B. secreted directly into the blood stream
C. Inactive chemical substances in the blood stream E. secreted at the site of the target organs (1988/19)
3. Hormones are transported around the mammalian body by
A. water B. nerves C. blood D. osmosis E. diffusion (1995/18)
4. 7. (a) What is a hormone? (2006/7a)
5. Which of the following statements is not true about hormones?
A. Hormones are manufactured in ductless glands and poured straight into the blood stream
B. Hormones are carried by the blood plasma to the required target organs
C. Hormonal responses are usually swift, instant and electrical
D. Once the effects of hormones are over, they are inactivated and excreted from the body (2008/14)

Location of various glands in the body

PITUITARY GLAND
The pituitary gland is located at the base of the mid brain. It produces about twelve hormones, some of which are
concerned with the stimulation and inhibition of the endocrine glands. The hormones which are secreted by this gland
include:
a. GROWTH HORMONE (SOMATOTROPIN): This hormone is concerned with the normal growth in an
animal. In humans, over secretion of this hormone causes gigantism, a condition in which the long bones of
the body lengthen abnormally.
Under secretion of the growth hormone (pituitrin) results in the formation of dwarfs i.e. abnormally short
persons.The growth stimulating hormone promotes the growth of the bones and muscles. If the secretion
increases suddenly after adult life has been reached, a condition known as Acromegaly results. In this case, a
person who has been previously normal develops a coarse skin, a large nose, thick lips and huge hands and
feet.
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 b. PROLACTIN: This hormone is secreted by the pituitary gland. This hormone stimulates and control milk
production by mammary glands.
c. OXYTOCIN (PITOCIN): This is also secreted by the pituitary gland. Its major function is to control the
flow of milk in the mammary gland and contraction of uterine wall
d. ANTI-DIURETIC HORMONE (VASOPRESSIN): This hormone is secreted by the pituitary gland. Its
function is to stimulate the kidney tubule to re-absorb water from the glomerular filtrate.
e. TROPIC HORMONE: This is secreted by the piturary gland. It stimulates or control all other endocrine
glands in the body. For this reason, the pituitary gland is called a master gland.

Example
When the secretion of the hormone A.D.H (antidiuretic hormone) is suppressed by the post- pituitary gland, the urine
produced will be
A. more and very watery B. small and reddish C. isotonic to blood D. retained in the bladder (2002/16 Nov)
Answer: A – When antidiuretic hormone is suppressed, the urine produced will be more and very watery. This will
results because, ADH is responsible for the re-absorption of water from the glomerular filtrate into the surrounding
blood vessels.
Example
The pituitary is regarded as the master gland because
A. it is located in the brain B. its secretions are the most numerous C. its secretions control other endocrine glands
D it is the biggest endocrine gland E. it controls the activities of the brain (1991/16 Nov)
Answer: C – The pituitary is regarded as the master gland because its secretions control other endocrine glands.
Example
Pituitary gland is very important in the body because it
A. is located in the brain B. secrets insulin
C. secrets hormones directly into the blood D. controls the activities of other endocrine glands (1999/21 Nov)
Answer: D – The pituitary gland is very important in the body because it controls the activities of other endocrine
glands.
Example
Which of the following glands is called the master gland?
A. Parathyroid gland B. Adrenal gland C. Thyroid gland D. Pituitary gland (2020/16 PC1)
Answer: D – The pituitary gland is also called the master gland.
Example
In which part of the human body does the secretion of the growth hormone occur?
A. gonads B. waist region C. neck region D. head region (2000/26 JAMB)
Answer: D – Secretion of growth hormone occurs in the pituitary gland which is located at the head region.

EXERCISE 13.2
1. If a nursing mother is not producing enough milk, her hormonal system is probably deficient in
A. Insulin B. thyroxin C. prolactin D. testosterone (2004/28 JAMB)
2. The gland that is found just below the hypothalamus is the
A. parathyroid B. adrenal C. pituitary D. thyroid (2013/34 JAMB)
3. The absence of anti-diuretic hormone in human result in
A. decreasing dehydration B. drastic dehydration
C. eliminating dehydration D. increasing dehydration (2013/37 JAMB)
4. The early removal of the pituitary gland in animals may cause
A. ceasation of growth B. gigantism C. poor mental development
D. goitre E. inability to digest food (1997/15)
5. (d) State five functions of the pituitary gland. (2007/1d)
6. Which of the following conditions would result in a decrease in the production of antidiuretic hormone?
A. Abnormally high blood sugar level B. Drinking large quantity of water
C. Increase in osmotic pressure of blood D. Period of strenuous exercises (2013/20)

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THYROID GLAND:
This gland is located in the posterior part of the pharynx or anterior region of the neck. It secretes a hormone called
thyroxin. Thyroxine contains iodine. Thyroxin speed up the rate of most body activities namely, body metabolism and
particularly aerobic respiration. Secondly, it stimulates mental and physical growth and development in young
animals; it also controls metamorphosis in tadpole.

Under secretion of this hormone in man causes cretinism (which is a kind of defective development in which the
person is dwarfed). Under secretion of this hormone may also cause:
1. Poor physical and mental development in children.
2. Sluggishness and excessive weight in adult( a condition referred to as myxedema).
3. Sexual activities are hinder.
4. In insects and amphibians, under secretion slow down metamorphosis.
Over secretion of thyroxine by the thyroid gland is accompanied by:
1. Enlargement of the gland (Exophthalmic goiter)
2. Voracious appetite
3. Over activity
4. High rate of heart burn
5. Wasting away of the tissues of the body
6. General restlessness as well as protrusion of the eye balls

It is important to note that when there is a deficiency of iodine in the diet, the thyroid gland enlarges in order to
compensate for the deficiency. This results in the formation of Hyperplastic goiter.

Example
Hyposecretion of thyroxin in infants causes
A. cretinism B. rickets C. goiter D. dwarfism E. kwashiorkor (1998/17 Nov Health Science)
Answer: A – Cretinism is a condition that is characterized by defective development and learning difficulties. It
results from the deficiency of thyroxin (Hyposecretion of thyroxin).
Example
A person suffering from exophthalmic goitre would have all of the following symptoms except
A. bleeding gums B. nervousness C. swollen neck D. sluggishness (2011/30 Nov)
Answer: A – Bleeding gums is not a symptom of exophthalmic goiter.
Example
Over secretion of thyroxin is likely to lead to
A. thinness of body B. sluggishness C. cretinism in infants D. reduced metabolism E. dwarfism (1991/18 Nov)
Answer: A – Over secretion of thyroxin is likely to lead to thinness of the body i.e loss of weight. This is as a result of
wasting away of the body tissue.
Example
Which of the following hormones will increase the growth rate of tadpole?
A. insulin B. adrenalin C. thyroxin D. oxytocin (1999/19 Nov)
Answer: C – The growth rate of tadpole is controlled by thyroxin secretion

EXERCISE 13.3
1. Excessive thyroxine secretion causes
A. hyperactivity B. hypoactivity C. isoactivity D. metamorphosis E. sensitivity (2007/17 Neco)
2. Under secretion of thyroxine before maturity causes an abnormality known as
A. cretinism B. gigantism C. dwarfism D. myxedema E. obesity (2001/27 Neco)
3. The over secretion of thyroxin in man results in
A. decreased rate of metabolism B. increased rate of metabolism
C. poor sexual and mental development D. increase muscular tone (2017/40 NABTEB)
4. Iodine is needed by a patient suffering from a malfunctioning of the
A. salivary gland B. thyroid gland C. adrenal gland D. sebaceous gland (1999/19)
5. The thyroid gland is located at the base of the
A. midbrain B. kidney C. neck D. liver (2018/15)
6. State three effect of over secretion and under secretion of thyroxin on mammals. (2008/7c).

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ADRENAL GLAND:
They are located above the kidney and they produce a hormone called Adrenalin. The adrenal gland consists of
peripheral cortex which produces some hormone called corticosterones. The cortex also produce small amount of
hormones which controls the development of secondary sexual characteristics.
The adrenalin is produced by the medulla portion of the gland: fright, anger, stress, danger are stimuli of the gland for
hormone production . Some actions of adrenaline are given below:
1. Adrenalin stimulates the liver to converts glycogen to sugar (glucose) thereby increasing the blood sugar level
2. It also increases muscular power and resistance to fatigue
3. It increase the rate of heartbeat and breathing.
4. It prepares the body for emergency
5. It is associated with fear and anxiety
Adrenalin is sometimes referred to as emergency hormone.
The effects of over-secretion include over anxiety, over excitement, rise in blood pressure and heartbeat, dilation of
pupils, erection of hairs, heavy breathing, profuse sweating e.t.c.
Effects of under secretion include low blood pressure and heartbeat, slow response to emergency, lack of energy,
weakness and tiredness.

Example
Which of the following activities does not occur in the body when a person is afraid?
A. The rate of heart beat increases B. Adrenalin is released into the blood C. The hormone thyroxin is secreted
D. There is sudden rise in body temperature E. The nervous system is stimulated (1990/48 Nov Health Science)
Answer: C – Fear does not trigger the release of thyroxin. All other options (A, B, D and E) are activities that occur
when a person is afraid.
Example
Which of these is not a function of adrenalin?
A. sudden death B. conversion of glucose to glycogen C. Quickening of heart beat
D. profuse sweating E. increased excitement (1998/19 Nov)
Answer: B – Adrenalin stimulates the liver to convert glycogen to glucose. Conversion of glucose to glycogen is not the function
of adrenalin.
Example
Which of the following hormones causes anxiety?
A. Thyroxin B. progesterone C. insulin D. adrenaline (1999/20 Nov)
Answer: D – Adrenaline is the hormone horme that causes anxiety.
Example
Adrenaline is referred to as an “emergency hormone” because it stimulates
A. water reabsorption by kidneys B. release of glucose to the muscles
C. glycogen synthesize in the liver D. absorption of glucose by the liver (2006/19 Nov)
Answer: B – Adrenaline is referred to as an emergency hormone because it stimulates the release of glucose to the muscle.
Example
Which of the following is responsible for the increased heart beat of a boy who saw a python? Increased production of
A. adrenaline B. insulin C. pituitrin D. thyroxin (2000/23)
Answer: A – Adrenaline is also known as fright hormone. Hence, increase the heart beat of a boy who saw a python would be
initiated by increase in the production of adrenalin.

EXERCISE 13.4
1. Adrenalin is considered as a hormone for “fright and flight” because it
A. controls the fluid content of body B. is used in protein metabolism
C. plays a role in the pH balance of the body fluids D. prepares the body for action (2002/18)
2. Which of the following lands secretes a substance into the blood stream of a frightened person?
A. Adrenal glands B. Salivary glands C. Gastric glands D. Parathyroid glands (2005/25)
3. (b) Outline the role played by adrenaline in an emergency. (2006/7b)
4. Which of the following actions is not a function of adrenalin? It increases
A. body blood sugar by conversion of liver glycogen into glucose
B. muscular power and resistance to fatigue
C. the rate of heart beat D. the dilation of the pupils of the eye (2008/15)
5. Increasing adrenaline content of the blood would be expected to decrease the flow of blood to the
A. liver B. Heart C. lungs D. brain (2012/15)
6. (b) A student suddenly stepped on a big snake, he cried for help and ran away
(i) Name the hormone produced in the body for the reaction
(ii) in which part of the human is the hormone named in 1(a)(i) produced?
(iii) State five changes that must have taken place as a result of the hormone named in 1(a)(i) (2015/1bi-iii)
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PARATHYROID GLAND
This is located in the anterior part of the neck, near the thyroid gland (back surface of thyroid lobes). It secretes a
hormone called parathormone. The hormone maintains or controls the normal level of calcium and phosphate ions in
the body (blood).
Over secretion of parathormone causes softening of bones and increased loss of phosphate (i.e. Hyper- calcaemia:
bones become fragile, soft and prone to fracture). Under secretion causes tetany and hypocalcaemia (muscle spasm
and uncontrollable muscles activity).

The Pancreas (Islets of Langerhans)

This is located in the loop of the duodenum below and behind the stomach (pelvis region). The islet of langerhans are
group of cells in pancreas that secrete the hormones called insulin and glucagon.
The insulin regulate the amount of glucose in the blood by stimulating the liver to convert glucose to glycogen,
thereby lowering the blood sugar level. The glycogen which is formed is then stored in the liver and muscle
Insulin also helps muscle to oxidize sugar during respiration. It also removes sugar from the blood streams by causing
the cells to convert more of the sugar into fat.
Deficiency of the hormones give rise to diabetes mellitus, a disease due to too much sugar being present in the blood.
This results in loss of glucose in urine, excessive urination, great thirst and weakness. Over secretion causes blood
sugar to fall below normal.
When blood sugar is low, the hormone glucagon stimulates the liver and muscles cells to reconvert glycogen to
glucose for oxidation, there by releasing energy.

Example
The blood-sugar level of the body is regulated by
A. thyroxin B. insulin C. adrenalin D. iodine (2000/30 Nov Health Science)
Answer: B – Insulin regulates the blood sugar level by converting excess glucose (sugar) into glycogen which is
stored in the muscles and the liver.
Example
Which of the following is a sign of diabetes mellitus?
A. Urine being yellow in colour B. presence of salt in urine
C. presence of sugar in urine D. presence of protein in urine (2000/44 Nov Health Science)
Answer: C – Presence of sugar in urine is a sign of diabetes mellitus. Diabetes mellitus is a condition that results from
the deficiency of insulin.
Example
Which of the following organs produces insulin?
A. Kidney B. Thyroid C. Ovaries D. Adrenal gland E. Pancreas (1997/18 Nov)
Answer: E – Insulin is produced in the pancreas.
Example
The gland that secretes the hormone glucagon is ….. gland
A. Adrenal B. endocrine C. pancreas D. pituitary E. thyroid (2005/32 Neco)
Answer: C – The pancreas is the gland that produces glucagon.
NB: Glucagon antagonizes the effect of insulin.
Example
Insulin deficiency causes a disease called
A. diabetes B. goitre C. ricket D. scurvy (2014/7 Neco)
Answer: A – Insulin deficiency causes diabetes. Diabetes mellitus is a condition that results from the deficiency of
insulin.
Example
A gland in the human body secretes two hormones, one of which causes a disease called diabetes when there is a
deficiency. Which of these organs produces the hormones?
A. Spleen B. parathyroid C. Adrenal body D. Thyroid E. pancreas (1979/28 JAMB)
Answer: E – The pancreas produces both insulin which when deficient causes diabetes and glucagon.
Example
The organ which secretes digestive enzymes as well as a hormone is the
A. liver B. salivary gland C. pancreas D. spleen (1990/20 JAMB)
Answer: C – The pancreas has both digestive and endocrine function.

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EXERCISE 13.5
1. Which of the following produces both hormones and enzymes?
A. Ileum B. Pancreas C. Gall bladder D. Kidney (2006/14 JAMB)
2. Which of the following is not a function of insulin?
A. Accelerates the rate at which glucose is converted to glycogen B. Promotes the uptake of glucose by tissues
C. Regulate the amount of glucose in the blood D. Accelerates the absorption of glucose of the glomerulus
E. Stimulates muscles to oxidize glucose (1995/19)
3. Which of the following diseases results from the deficiency of insulin?
A. Cretinism B. Goiter C. Beriberi D. Diabetes (1999/3)
4. Which hormonal deficiency is likely to cause an accumulation of reducing sugar in the urine?
A. thyroxine B. insulin C. secretin D. testosterone (2004/18)
5. Which of the following conditions is responsible for the presence of sugar in the blood of diabetic patients?
A. High intake of carbohydrates B. Low production of insulin
C. Low intake of carbohydrates D. High Production of insulin (2006/21)
6. The presence of glucose in the urine of a patient is an indication of malfunctioning of the
A. pancreas B. gall bladder C. liver D. spleen (2008/13)
7. Which of the following organs is responsible for the production of insulin?
A. Spleen B. Adrenal gland C. Thyroid gland D. Pancreas (2016/16)
8. Deficiency in insulin could lead to
A. cirrhosis B. hepatitis C. diabetes D. nephritis (2019/22)
9. Which of the following is the function of the hormone in the Islets of Langerhans?
A. is used in protein metabolism B. is involved in sugar synthesis
C. aids the rate at which glucose is converted to glycogen D. controls the fluid content of the body
E. plays a role in the pH balance of the body fluid (1989/5)

Ovaries
The ovaries are attached to the dorsal wall of the abdomen (pelvis region). The ovaries produce oestrogen. The stimuli
of the ovaries responsible for production of oestrogen are pituitary gland and ovary development

The function of the oestrogen includes:

1. Stimulates the development of female secondary sex characteristics e.g breast development,
appearance of hair on the pubic area and armpit.
2. Control menstrual cycle and development of mammary glands.
3. Promotion of sexual urge: Over secretion causes abnormal urge for sex.

Deficiency/under secretion results in

1. Poor development of reproductive system.
2. Decline in female secondary sex characteristics.

Ovary – Corpus Luteum

This is located in the pelvis region. It produces the hormone progesterone (the stimulus for hormone production is
ovulation).
The functions of the hormones include:
1. Prepares and maintains the lining of the uterus after ovulation.
2. Aids implantation of the fertilized eggs in the walls of the uterus.
3. Development of breasts during the later month of pregnancy.
Over secretion causes violent muscle contractions of the uterine wall before birth or at birth,. This may lead to the
death of embryo
Deficiency/under secretion results in
1. Irregular menstrual cycle
2. Poor development of mammary glands
3. Abortion of fertilized eggs

Note: Progesterone is referred to as pregnancy hormone. It inhibits ovulation and prevent the uterus from contracting.

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Example
Which of the following hormones does not control the menstrual cycle?
A. follicle stimulating hormone (FSH) B. luteinizing hormone (LH)
C. ostrogen D. progesterone E. prolactin (2014/32 Neco)
Answer: E – Prolactin is a hormone that stimulates the production and secretion of milk. It does not control menstrual cycle.
Example
Oestrogen is a hormone that is synthesized in the
A. ovaries B. testes C. anterior pituitary D. adrenal cortex (2013/38)
Answer: A – Oestrogen is synthesized in the ovaries.
Example
The hormone that promotes secondary sexual characteristics in female is
A. insulin B. thyroxin C. testosterone D. oxytocin E. oestrogen (1998/20)
Answer: E – Oestrogen is the hormone that promotes secondary sexual characteristics in females.

TESTES
The testes are located in the scrotum and they produce male hormone called testosterone and androsterone. (The
stimuli of the gland is the tropic hormone (tropin) from pituitary gland and testes development). Testosterone
stimulates appearance of secondary sexual characteristics in male at puberty e.g. hair in armpit and pubic areas,
development of beard, moustaches, deep voice and thick muscles. Testosterone also stimulates the production of
sperm by the testes.
Over secretion of testosterone results in excessive development of sexual organs and secondary sexual characters such
as abnormal urge for sex.
Under secretion causes under development of sexual organs and decline of male secondary sex characteristics.
Note: Androsterone is a steroid hormone that is, a breakdown product of testosterone. It is less active than
testosterone. They are responsible for typical male sexual characteristics.

Example
Testosterone is secreted by
A. pituitary gland B. prostate gland C. testes D. ovary (2000/24 Nov health Science)
Answer: C – The testes secrete testosterone.
Example
The hormone responsible for the development of secondary sexual characteristics in boys is
A. testosterone B. oestrogen C. progesterone D. adrenalin (2003/2 Nov health Science)
Answer: A – Testosterone is the hormone responsible for the development of secondary sexual characteristics in
males (boys).
Example
In humans, which of the following pairs of hormones correspond to male and female respectively?
A. Oestrogen and adrenalin B. Progesterone and testosterone
C. Testosterone and oestrogen D. Adrenalin and progesterone (2002/20)
Answer: C – Testosterone corresponds to male while oestrogen corresponds to female.
NB: In questions like this, always take note of the way the words come after each other. E.g. male and female
respectively is not the same thing as female and male respectively.

EXERCISE 13.6
1. Which of the following glands is located at the top of the kidneys?
A. Thyroid gland B. Adrenal gland C. Pituitary gland D. Parathyroid gland (2003/25 Nov Health Science)

2. 3(a) (i) What are endocrine glands?

(ii) State the specific locations of the pituitary, adrenal and thyroid glands in the body.
(b) Explain the process of blood sugar regulation in the body. (1996/3a, b Nov Health Science)
3. (c) Name three animal hormones and their functions. (1997/2c Nov)
4. Which of the following hormones is responsible for the reabsorption of water along the kidney tubules
A. Insulin B. Adrenalin C. Oxytocin D. Prolactin E. Antidiuretic (1994/14 Nov)

232
Use the diagram below to Answer: questions 27 and 28

5. A hormone secreted at IV serves to

A. make the body react to emergencies B. Lower blood glucose level
C. raise the level of calcium ions in the blood D. Facilitate the development of facial hairs (2002/27 JAMB)
6. The gland usually found in the position labeled I is the
A. pancreatic B. pituitary C. thyroid D. adrenal (2002/28 JAMB)
7. Nervous control differs from hormonal control in that the former
A. produces short-term changes B. has no specific pathway
C. involves only chemical transmission D. is a slower process (2004/31 JAMB)
8. One basic similarity between nervous and endocrine systems is that they both
A. produce widespread effects B. transmit very fast impulses
C. involve the use of chemical substances D. produce precise and short-lived effects (2006/6 JAMB)

Use the diagram below to Answer: questions 21 and 22.

9. Insulin is produced by the endocrine organ labelled

A. IV B. III C. II D. I (2007/21 JAMB)
10. The function of the structure labelled I is to
A. stimulate the development of secondary sexual characters B. prepare the body for any emergency
C. maintain proper glucose concentration in the blood
D. regulate the activities of other endocrine glands (2007/22 JAMB)
11. Thyroxine and adrenalin are examples of hormones which control
A. blood grouping B. tongue rolling C. behavioural patterns D. colour variation (2010/44 JAMB)
12. Co-ordination and regulation of body activities in mammals are achieved by the
A. nerves only B. hormones only C. nerves and muscles D. nerves and hormones (2014/23 JAMB)
13. The gland directly affecting metabolic rate of growth and development is known as
A. adrenal gland B. thyroid gland C. mammalian gland D. parathyroid gland (2019/24 JAMB)
14. Which of the following glands also serves as an exocrine gland?
A. Ovary B. Pancreas C. Adrenal D. Thyroid (2017/17)
15. Which of the following statements is not true about hormones?
A. Their responses are voluntary B. They may affect more than one target organ
C. They are chemical messengers in animals D. They are transported by the blood to the target organs (2019/15)

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16. (c) In a tabular form, list five differences between hormonal co-ordination and nervous co-ordination. (2006/7c)
17. Copy and complete the table below on endocrine glands and their functions (2011/1c)
S/N Endocrine glands Hormone produced Function
1. Thyroid
2. Insulin
3. Development of secondary sexual
characteristics of females

18. Which of the following statements is correct of hormones? Hormones are

A. secreted into blood through ducts B. secreted directly into the blood stream
C. inactive chemical substances in the blood stream D. non-specific in their mode of action
E. secreted at the sight of the target organs (1988/19)
19. Which of the following endocrine glands is a master gland?
A. pituitary gland B. urea C. blood corpuscles D. glucose (2003/19)
20. Which hormonal deficiency is likely to cause an accumulation of reducing sugar in urine?
A. thyroxin B. insulin C. secretion D. testosterone (2004/18)
21. Which of the following conditions would result in a decrease in the production of anti dieretic hormone?
A. abnormally high sugar level B. drinking large quantities of water
C. increase in osmotic pressure of blood D. period of strenuous exercise (2013/20)

PLANT HORMONES
Plant hormones are chemical substance produced in one part of the body of plants and transported to another part
where they exert their effects. They are similar to animal hormone in that they are:
1. Only needed in small amount to bring about effects
2. Produced in one part of the body and transported to another part where they exert their effects

Plant hormones are not produced in tissues specialized only for their production. Their effects are also more general.
In contrast, animal hormones are produced in specific glands and bring about very specific responses in specific target
organs.
Plant hormones usually stimulate or inhibit growth in the target tissues in response to external stimuli such as light,
temperature, gravity e.t.c. The responses of plant hormones are usually much slower than those of animal hormones.
Example of hormones in plants include
1. Auxin
2. Gibberellins
3. Cytokinins
4. Abscisic acid
5. Ethane (ethylene)

AUXIN
The most important natural auxin manufactured in plants is indoleacetic acid (IAA). It is produced at the apices of
shoot, developing leaves, flowers, fruits cambial cells and root tips.

ROLE OF AUXINS
Auxins are regarded as growth regulators or growth hormones as they play vital roles in growth initiation,
stimulation, and inhibition. The most important naturally auxin is indoleacetic acid (IAA) it is produced at the
apices of shoots and transported in one direction away from the tip. Auxins influence all three aspect of growth and
development i.e. cell division, cell elongation and cell differentiation. Some of its function includes:
1. It promotes normal stem growth in plants especially herbs. It stimulates cell elongation by softening the cell wall.
This enables the cells to stretch as their protoplasm swells and increase in amount. Auxins influence the growth
of stem to light (phototropism).
Similarly it also causes the growth of roots towards the force of gravity
2. It stimulates the development of lateral and adventitious root for increased water and mineral absorption. This
brings about rooting in stem cutting.
3. It stimulates the vascular cambium to divide and increase the production of secondary vascular tissues
(increase in width of stem).
4. It induces cells to differentiate into xylem, to increase water and mineral transport and to provide support.
5. It promotes the development of fruits.
6. Auxin inhibits growth of lateral buds, a phenomenon known as apical dominance. It also inhibits abscission.
Abscission is a process by which a leaf, fruit or any other plant organ falls from the plant naturally.
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Experiment to demonstrate the influence of auxins on the growth of plant shoots
Apparatus: Two young seedlings, jelly strip (soluble) and insoluble strip.
Method: Get two young seedlings and insert at their tips (coleoptiles) one with the soluble jelly strip and the other
with the insoluble which is the control experiment. Allow them to stay for about 5 – 7 days.
Observation: The seedlings with the soluble jelly strip will be able to grow, while the one with the insoluble strip will
not grow.
Conclusion: The insoluble strip will not allow the movement of growth hormone (auxin) downwards. Therefore there
will be no growth. The soluble jelly strip will allow the diffusion of auxin and here growth will occur

Experiment to demonstrate the effect of auxins on the growing tip (coleoptiles) of maize seedlings
Apparatus: Three beakers, maize seedlings, black box with hole on one side to allow light and aluminum foil
Method: Two maize seeds are germinated in each of the three labeled beaker x, y, z. The coleoptiles tips of two of the
maize seedlings in x are covered with an aluminum foil. In beaker y, the coleoptiles tips are cut off while that of z is
left as control.
The three beakers xyz are placed in the black box near a window with the hole facing the source of light for some days
Results:
The coleoptiles tips of beaker x do not bend
The coleoptiles tips of beaker y do not bend
The coleoptiles tips of beaker z bend towards the source of light
Conclusion
There is no bending in beaker x because the coleoptiles tips is prevented from receiving light. There is no bending in
beaker y because the coleoptiles tips that produce auxins are cut off.
There is bending in beaker z which is the control towards light because of the uneven distribution of auxins. Light
inhibits auxin production.
The side receiving light receives little auxins while the side that is not receiving light has a lot of auxins there by
causing the bending.

Modern Applications of Auxins in Agriculture

1. Weed control: Synthetic auxin called 2, 4-D is used as a selective weed killer (herbicide) 2, 4-D is 2, 4 -
Dichloropenhenoxy acetic acid. 2, 4-Trichlorophenol acetic acid is used to kill woody seedlings and weeds.
2. Synthetic auxin Naphthalene acetic acid (NAA) is sprayed on flowering fruit trees to stimulate fruit development.
In some species, it causes the flowers to develop into fruits without fertilization (Parthenocarpy)
3. Auxins are used for preserving yam and potatoes for a very long time
4. Auxins are applied to delay harvesting of fruits if the price at such time are not favorable
5. Auxins are used to promote root growth in stem cuttings
6. Synthetic auxins are used to knit together parts of plant after grafting, by inducing wound tissue formation .
7. Auxins are used to ripen fruits like tomatoes, artificially and uniformly when needed
Example
(b) List three uses of auxin in agriculture (1994/3b)
Answer: As weed control , For stimulating fruit development , For promoting root growth in stem cutting.
Example
Which of the following is not a function of auxins?
A. Early ripening of fruits B. killing of fungal parasites C. promoting terminal growth in plants
D. Stimulating growth of lateral branches E. Encouraging formation of adventitious roots (1998/20 Nov)
Answer: D – Auxins inhibit the growth of lateral buds (branches), a phenomenon known as apical dominance
Example
In which of the following parts of plants are auxins produced?
A. In the petals of flowers B. At the petals of leaves C. In the epidermis of roots arid stems
D. In the sclerenchyma tissues of roots and stems E. At the apical regions of roots and shoots (1992/23 Nov)
Answer: E- Auxins are produced in the shoot apices. They are also produced in the root tips of plants

EXERCISE 13.7
1. Which plant hormone inhibits the development of lateral buds in plants?
A. abscisic acid B. auxins C. cytokinins D. florigen E. gibberellins (2001/14 Neco)
2. The following are plant hormones, except
A. auxins B. cytokinnis C. ethylene D. gibberellins E. thyroxin (2014/26 Neco)
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3. The hormones that regulate plant growth are
A. ethylene and auxins B. auxin and gibberellins
C. cytokinins and abscisic acid D. ethylene and gibberellins (2017/2 JAMB)
4. Auxins are produced in the
A. petiole of leaves B. parenchyma of roots and shoots C. epidermis of roots and shoots
D. apical regions of roots and shoots E. sclerenchyma tissues of roots and shoots (1988/21)
5. A high concentration of auxin in the root will
A. inhibit growth B. stimulate growth C. not affect growth
D. cause the root to rot E. reduce water absorption (1997/16)
6. Plant hormones include the following except
A. insulin B. auxin C. cytokinin D. gibberelin (2008/16)
7. What happens to a plant if the shoot tip is cut off and replaced by an algae block containing auxin? It will
A. stop growing B. grow rapidly C. continue to grow normally D. die completely (2013/9)

GIBBERELLINS:
These hormones are found in root and stem apices. They promote growth by stimulating both cell elongation and cell
division.Glibberellin together with auxin play a major role in controlling stem elongation in most plants especially
shrubs and trees. Other roles of gliberellin include:
a. Inducing dormant seeds to germinate.
b. Causing dormant axillary buds to grow.
c. Increasing fruit size.
d. Stimulate some biennial plants to flower during their first year of growth.

Example
Which of the following growth activities in plants is brought about by gibberellins?
A. rapid cell division B. trophic response C. main stem elongation D. cell elongation (2000/27 JAMB)
Answer: C – Gibberellins induce stem enlongation.
Example
The hormones that regulate plant growth are
A. ethylene and auxins B. auxin and gibberellins
C. cytokinins and abscisic acid D. ethylene and gibberellins (2017/2 JAMB)
Answer: B – Auxin together with gibberellins regulate plant growth.

CYTOKININS
They are produced in root. They are also growth promoting hormones like auxins and gibberrllin. Their roles include:
1. Breaking seed dormancy in some seed.
2. Promote flowering in some plants.
3. Promote fruit development in some plants.
4. Help to delay ageing in plant organs (i.e. cause delay in leaf senescence).
5. Unlike auxin, cytokinins stimulate lateral bud to grow into branches.
6. Inhibit primary root growth.
7. Promote lateral root growth.
8. Promote stem growth by cell division in apical meristem and cambium.
Together with auxin, they stimulate cell division so that stem and root grow normally

ABSCISIC ACID
This hormone is produced in mature green leaves, fruits and root caps. It is a growth inhibitor whose effects generally
opposed those of auxins, gibberellins and cytokinins
The role include:
1. Suppresses the growth of buds.
2. Induces dormancy (important when environmental conditions are unfavourable).
3. Brings about ageing in leaves.
4. Promotes abscission.
5. Control opening and closing of stomata (important during periods of water storage). The effect of
abscisic acid enables plant to withstand severe environmental conditions.

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Example
Which of the following hormones is used to prevent stored potatoes from sprouting?
A. Auxin B. Cytokinin C. Ethylene D. Abseisic acid (2011/17 Nov)
Answer: D – Abscisic acid induces dormancy i.e. prevents seed from sprouting.
Example
A farmer who wants to keep seeds for three years before planting and wants to prevent them from sprouting uses
A. auxin B. gibberellins C. abscisin D. cytokinins (2015/16)
Answer: C – Abscisin (abscisic acid) induces seed dormancy i.e. prevents seed from sprouting

ETHENE (ETHYLENE)
This hydrocarbon is produced in leaves, stem and young fruits
The roles includes:
1. Retarding lateral bud development (auxin prevents lateral buds from growing by inducing the
formation of ethene around them)
2. It hastens the ripening of fruits
3. Promotes flowering in pineapple
4. Inhibits stem growth (notably during physiological stress)
5. Inhibits root growth
REVISION EXERCISE
1. (b) Make a large labeled diagram of an outline of a man and indicate the location of the following glands.
(i) Adrenal (ii) Pancreas (iii) Thyroid (iv) Pituitary (v) Ovaries (1998/2b Nov)
2. (c) State one effect each, of over secretion and deficiency of
(i) Thyroxin (ii) Adrenalin (iii) Insulin (iv) oestrogen (1998/2c Nov)
3. 5b. What is hormone?
c. Name THREE hormones and in each case state:
i. Where the hormone is produced?
ii. ONE function of each hormone
iii. ONE effect of the deficiency of each hormone. (1999/5b, c NABTEB)
4. Fruit enlargement can be induced by spraying young ovary with
A. cytokinin, absiscic acid and ethylene B. gibberellin, ethylene and abscisic acid
C. auxin, absidic acid and ethylene D. auxin, cytokinin and gibberellin (1989/33 JAMB)
5. The gland directly affecting metabolic rate, growth and development is known as
A. adrenal gland B. thyroid gland C. mammary gland D. parathyroid growth (1995/27 JAMB)
6. The most important plant hormone is
A. cytokinin B. abscisic acid C. auxin D. gibberellin (2013/35 JAMB)
7. (b) State three functions each of (i) insulin (ii) auxins (1992/4bi, ii)
8. (d) Name three animal hormones and two plant hormones. (2006/7d)
9. (d) Name one appropriate hormone each responsible for the following conditions in plants;
(i) ripening of fruits; (ii) breaking dormancy in seeds; (iii) weed control; (iv) leaf fall (2010/1d)
10. (c) Name two hormones each involved in: (i) Plant growth; (ii) animal growth.
(d) State the effects of the hormones named in 8(c)above. (2009/8ci, ii, d)
11. Plant hormones include the following except
A. insulin B. auxin C. cytokinin D. gibberelin (2008/16)
12. The following are plant hormones except
A. auxins B. cytokinins C. ethylene D. thyroxine E. gibberellins (Neco 2014/2b)
13. A high concentration of auxin in the root will
A. inhibit growth B. stimulate growth C. not affect growth
D. cause the root to rot E. reduce water absorption (1997/16)
14. Which of the following is not a function of auxins?
A. early ripening of fruits B. killing of fungal parasites
C. promoting terminal growth in plants D. stimulating growth of lateral branches
E. encouraging formation of adventitious roots (1998/20 Nov.)
15. In which of the following parts of plants can auxin be found in highest concentration
A. flower B. lenticels C. mibrib D. petiole D. shoot apex (2007/54 Neco)
16. List three uses of auxin in agriculture. (1991/3b)
17. Define the term hormones
Name one plant hormones
State two effects of plant hormones. (1998/2d)
18. Name two plant hormones other than auxins. (2001/4c)

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Sense Organs
A sense organ is a group of specialized cells, tissues or receptors which are able to receive, perceive or detect stimulus
and transmit information, impulses and messages to the central nervous system.
Most cells in the body are sensitive to stimuli but some cells are specialized to detect only a particular type of
stimulus. They are called sensory cell or sensory receptors. There are four groups of sensory receptors.
(1) Mechanoreceptor (2) Chemoreceptor (3) Thermoreceptor and (4) Photoreceptor
There are five sense organs in human body. These sense organs are eye, ear, nose, tongue and skin. These organs and
their functions are:
1. Nose for smell.
2. Tongue for sense or taste.
3. Skin is the sense of touch, pain, heat, cold and pressure.
4. Ear is the sense of hearing and balance.
5. Eye is the sense of sight.
Each of these organs has nerve endings which receive impulses and relay them to the central nervous system.

Organ of smell
The organ of smell is the nose (olfactory organ). This is linked to the brain by the olfactory nerves. The sensory cells
in the nose are stimulated by substances dissolved in the moist mucus membrane covering the inside of the nostrils.
The upper portion of the nasal chambers has many sensory nerve cells. The sensory nerve endings join together to
form an olfactory nerve that goes to the olfactory lobe of the brain.
When chemical substances carried in the air passes through the nostrils, their molecules dissolves in the moist
membrane and stimulates the sensory nerve endings which join together to form an olfactory nerve that passes to the
cerebrum of the brain. The brain then interpretes the chemical impulses and the sensation of smell is produced.
Sensory nerves of smell that are exposed to a particular odour over a period of time, becomes sensitive or conditioned
to that odour and are unable to respond to it.
The sense of smell in man is poor and limited compared to other animals.

Functions of the organ of smell

1. It helps in avoiding bad and poisonous food.
2. Smell of burning food or leakage of cooking gas can be detected and immediate actions are taken to remedy
the situation.
3. Animals depend on smell greatly to help them locate food, mate and escape from their predator.
4. Unfamiliar and dangerous odour such as those from wild animals can be detected and avoided.
5. Trained dogs are used to trail criminals by detecting the odour left by criminals. Also, after moving long
distances, dogs are able to find their way back home by relying on their organ of smell.
6. The nasal mucus contains lysozymes which kill bacteria and viruses.
Defects of the organ of smell
People who cannot detect a particular odour are suffering from anosmia; it is possible that the olfactory portion of
their cerebral cortex may have been damaged resulting in this defects.

Example
What is a sense organ? (2000/1a)
Answer: A sense organ is a group of specialized cells, tissue or receptors which is able to receive, perceive or detect
stimulus and transmit information, impulses and messages to the central nervous system.
Example
List the principal sense organs in mammals and state their functions. (1992/1a)
Answer:
Nose – for smell. Tongue – for taste. Skin – As a sense of touch, pain, heat, cold and pressure.
Ear – For hearing and balance. Eye – For sight or vision.
Example
Explain briefly the process of perceiving smell in humans. (2017/6a)
Answer: Chemical substances (odours) are carried in the air that passes through the nasal cavity. These chemical
substances (odours) dissolve in the moist membrane lining the nasal cavity. Then, the sensory cells which are present
in the nasal cavity are stimulated, and impulses are formed. These impulses travel through the olfactory nerves into the
brain. The brain interprets these impulses and smell is perceived.
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EXERCISE 14.1
1. If the mucus in the air track of mammals dry up and the hairs in the nostrils are removed
A. impure air would be breathed into their lungs
B. the speed of air movement into their lungs would increase
C. breathing air into their lungs would be difficult D. more air would be taken into the lungs. (2006/27)
2. A person had an accident that affected the skull but not the nose and later lost the sense of smell. The accident
must have affected the
A. nose by extension B. olfactory lobes of the brain
C. passage from the nose to the brain D. part of the skull near the nose. (2015/17)
3. The olfactory organs are responsible for the sense of
A. taste B. smell C. touch D. balance (2000/21 Health Science)

Organs of taste
The organ of taste is the tongue. Sensory cells of taste which open to the surface of the tongue by a pore, can be found
on the tiny swellings located on the exposed surface of the tongue. These sensory cells are grouped into taste buds
and are connected by fine sensory nerves to the brain which gives information on what is tasted.

The tongue is sensitive to four (4) Primary tastes these are (1) sweet (2) sour (3) salt (4) bitter

The tongue
Four primary areas of taste
The back of the tongue is sensitive to bitter stimuli, the sides of the tongue are sensitive to salt and sour stimuli while
the tip is sensitive to sweet sensation.

It is an established fact that the tongue can also detect alkaline taste, texture of food and its temperature.

Factors that affect taste by the tongue

1. The hotness and coldness of the food being tasted. .
2. The quantity of food being chewed at the same time.
3. When the nostril are closed or opened when chewing the food.
4. The tasters health condition.

Example
Which of the following parts of the tongue does not correspond to the taste indicated against it?
A. Tip-sweet B. Centre-salt C. Back-sour D. Side-sour E. Back-bitter (1990/30)
Answer: C – The back of the tongue is for bitter taste not sour.
Example
Which of the following parts of the tongue is sensitive to sugar
A. Tip B. Back C. Right side D. Left side E. Under surface (1992/28)
Answer: A – The tip of the tongue is sensitive to sweet (sugar).

EXERCISE 14.2
1. The groups of sensory cells found on the upper surface of the tongue are called
A. ampullae B. taste buds C. nerve cells D. somatic cells E. tactile cells (1993/18)
2. 1(b) Explain how bitter taste is detected in humans (2011/1b)

3. The sensory cells found on the upper surface of the tongue are
A. ampullae B. nerve cells C. taste buds D. somatic cells (2020/18 PCI)

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Skin as a sense organ
In the dermis of skin, there are five sense receptors namely touch, pressure, pain, heat and cold. Their sensory nerve
endings are unevenly distributed in the skin.

The vertical section of the mammalian skin

Pain – The pain receptors when stimulated give rise to the sensation of pain.
Touch (Meissners corpuscle) – If you prick your skin with a needle, you will feel touch sensation. Also sense of
touch is greatly developed in the finger tips of blind people which help them to identify objects and for reading
Braille.
Temperature – There are two temperaure receptors in the skin. These are heat and cold receptors. The heat receptor
detects heat while the cold receptor detects cold. These two receptors make us aware of temperature changes.
Pressure (Pacinia corpuscle) – Receptors that respond to pressure are located deep in the skin. They respond to very
heavy touch.
Example
Which of the following structures are stimulated by touch, pressure, pain, heat and cold?
A. receptors B. snynapse C. cell bodies D. myelin sheath E. relay neurons (1988/23)
Answer: A – Receptors are structures that are stimulated by pressure, pain, heat and cold. These receptors are mostly
found in the skin.
Example
Which of the following stimuli are not perceived through the skin of mammals?
A. Light B. Pressure C. Pain D. Heat E. Cold (1990/29)
Answer: A – Photorecptors (receptors that detect light) are not present in the skin, hence, light can’t be perceive by
the mammalian skin.
Example
The human skin is regarded as a sense organ because it
A. separates the body from the outside world B. protects the body from cold and heat
C. regulates the water content of the body D. has an outer layer of dead cells E. has nerve endings. (1991/20)
Answer: E – The human skin is regarded as a sense organ because it has nerve endings which can be stimulated by
changes in the external environment.
Example
The mammalian skin can insulate the body from cold because it has
A. epidermal cells B. nerve endings C. the subcutaneous fatty layer
D. sebaceous glands E. the malpighian (1992/27)
Answer: C – The mammalian skin can insulate the body from cold because it has subcutaneous fatty layer which
serve as insulator.
Example
Protection of the body cells of mammals against ultra-violet rays of the sun is brought about by
A. keratin B. melanin C. sebum D. scales (2007/22)
Answer: B – Melanin is a skin pigment that protects the skin or body cells of mammals against the ultra-violet rays of the sun.
NB: Melanin is also responsible for the colour of the skin and hair of mammals.
Keratin is a fibrous structural protein that forms hair, nails, horn, hoofs, wool and feathers of animals. It also forms protective
barrier in the skin. Sebum is an oily substance produced by the sebaceous gland. It helps to lubricate the skin and protects it
against friction.
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Example
The hair on the human skin will stand erect when the person is
A. in an air-conditioned room B. strolling in the sun C. taking a hot drink D. doing strenuous exercise (2012/20)
Answer: A – The hair on the human skin will stand erect when the person is in an air-conditioned room. This happens
in order to conserve heat.
Example
6(c) (i) State three ways of caring for the mammalian skin
(ii) List three stimuli to which mammalian skin is sensitive (2016/6c i; & ii)
Answer:
i. Ways of caring: ii. Stimuli to which mammalian skin is sensitive:
- Avoiding excess exposure to ultra-violet rays. - Touch
- Engage in regular exercise. - Pressure
- Moisturizing the skin with lotion. - Heat and cold.

EXERCISE 14.3
1. The part of the mammalian skin involved in temperature regulation is the
A. sweat gland B. hair papilla C. hair follicle D. sebaceous gland (2006/29 JAMB)

2. The following structures are present in the skin except

A. sweat gland B. horny layer C. renal tube D. sebaceous gland (2020/20 Nov)

3. When the hairs on the skin stands on end, enveloping some air, they are just performing the function of
A. Radiation B. conduction C. insulation D. vasoconstriction E. sensation (1996/19 Nov)
4. Explain briefly the role of the skin as a sensory organ (2013/8a Nov)
5. Which of the following is not correct about the skin?
A. It contain network of nerves B. It is sensitive to touch C. It is sensitive to cold
D. It may contain pigment E. The secretion from sebaceous gland keeps the skin cool (1990/40 Health Science)
6. In the human skin, the nerve endings sensitive to touch can be found
A. in the epidermis B. within cornified layer C. below the malphigian layer
D. in the sebaceous glands E. above the cornified layer (1990/51 Health Science June)
7. Make a large labeled diagram of vertical section through the mammalian skin. (1992/21c)

Organ of hearing (ear)

The mammalian ear is the sense organ that carries out the function of hearing and balancing. It is divided into three
region namely external ear (outer ear), middle ear (tympanic cavity) and the inner ear (labyrinth).

The vertical section of the mammalian ear

Outer ear
The external or outer ear consists of the pinna (auricle), external auditory canal or ear tube and tympanic membrane
(ear drum).
1. Pinna: The pinna is made of soft cartilage covered by skin. It is flexible and only found in mammals.
Function
It collects sound waves and directs them into the auditory meaitus. It detects the direction of sound waves.

2. External auditory canal or ear tube: It is a narrow passage which contains wax producing glands. It
contains fine hairs which prevent tiny insects, dust and germs from entering the ear.

3. Tympanic membrane/Ear drum: It is found at the end of the ear tube. It separates the outer ear from the
middle ear. It helps to transmit sound waves from the outer ear to the middle ear.

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Middle ear
The middle ear is also known as the tympanic cavity, it consist of the ear ossicles and the Eustachian tube.
Ear ossicles: These are held in place by muscles. They include
I. Malleus/hammer which is attached to the tympanic membrane. It receives vibrations from the tympanic membrane and
transmits this to incus
II. Incus/anvil which connects the malleus at one end and stops at the other end.
III. Stapes/stirrup: This is the smallest bone in the body .It fits into the oval window which opens to the inner ear.
These three ossicles form a moveable bridge linking the outer and inner ears. A second membrane, the round window
connects the middle ear with inner ear.
The ossicles transmit vibrations (sound) across the tympanic membrane to the oval window. They also magnify the pressure on
the oval window several times.

Eustachian tube: The Eustachian tube is a narrow tube found in the middle ear. It is connected to the back of the pharynx. The
Eustachian tube helps to equalize the air pressure in the middle ear. Equalized pressure, is needed for the proper transfer of sound
waves. The Eustachian tube allows air from the surroundings to enter or leave the middle ear so that the air pressure on both sides
of the ear drums is equal.

Inner ear
The inner ear contains a complex bony passage called labyrinth filled with a fluid called perilymph. There is also a
membranous labyrinth filled with another fluid called endolymph. These form two important sensory structures.
1. The cochlea which is the organ for hearing and
2. The semicircular canals (containing three parts), utriculus and sacculus which are concerned with balance.
The three semicircular canals are attached to the utriculus. Each semicircular canal at the point of its attachment to the
utriculus, is swollen to form the ampulla, which contains sensitive cells. The cochlea arises from the sacculus. It is a hollow
structure coiled like a snail’s shell.
Cochlea is concerned with the organ of hearing. The cochlea is internally divided into three chambers by two membrane which
run along the length. The cells which are sensitive to vibrations called hair cells are arranged on the lower membrane of the
middle chamber of the cochlea. These sensitive cells form the organ of corti.

Functions of the ear

The ear performs two major functions.
1. Hearing.
2. Maintenance of balance.

Mechanism of hearing
For hearing to take place, sound waves entering the outer ear, travels through the external auditory canal until they reach the
tympanic membrane, where they cause the membrane and the attached chain of auditory (ear) ossicles to vibrate. The vibration
of the auditory ossicles (malleus, incus and stapes) helps to amplify the sound. The round oval window (Fenestra ovalis
rotunda) also vibrates, passing the waves into the cavity of the inner ear or cochlea where the perilymph vibrates and transmit the
waves in the cochlea, causing the endolymph of the cochlea to vibrate. The vibrations are then transmitted across the organ of
corti/sensory nerve cell. These vibrations, actually stimulates the organ of corti which sets up impulses that in turn, stimulates
the auditory nerve cells which then transmit the impulses to the brain for interpretation by the auditory lobes of the brain into
the different sounds we hear.

Maintenance of Balance
Mechanism involved in maintenance of balance
Head movement in any direction affects the fluid (endolymph) in the corresponding semicircular canals (horizontal, posterior
and superior canal) which are at the right angle to each other. This forces the sensory cells in the ampulla to set up impulses
through the auditory nerve to the brain for interpretation. The brain relays impulses to the body muscles for balancing the position
of the body.

Ampullae

Structure of the internal ear

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Care of the ears
1. The ear should be cleaned regularly with cotton wool.
2. Avoid the use of sharp objects for the ear.
3. Avoid blows on the ear. So that the tympanic membrance/ear drum is not damaged.
4. Use protective ear muffs when working under conditions of high noise level
5. Avoid area of high noise for a long period of time to prevent deafness.
6. Consult medical doctor if there is ear problem.

Deafness
Deafness is the inability to hear. It may be temporary or permanent. It is usually due to.
1. Damage to the tympanic membrane.
2. Stapes hardening and fusing with oval window so that it cannot vibrate.
3. Blocking of the ear canal by wax.
4. Blocking of the Eustachian tube.
5. Infection of the middle and inner ear.
6. Damage to the sensory cells in the cochlea.
7. Constant exposure to loud noises.

Example
A boy spins round several times and stops. He loses balance as he attempt to walk. A possible explanation for this
could be
A. high pressure in the ear fluid B. too much air pressure in the middle ear
C. continuous movement of the fluid in the inner ear D. rotation of the semi-circular canals (2006/22 Nov)
Answer: The loss of balance results from the continous movement of the fluid in the inner ear.
Example
2(b) Describe the mechanism of hearing in mammals
(c) State two ways of caring for the ear. (1991/2b-c)
Answer
b. Sound waves enters the outer ear and travel through the external auditory canal until they reach the tympanic
membrane, causing the membrane and the attached chain of auditory ossicles to vibrate. The vibrations of the
auditory ossicles help to amplify the sound. The round oval window also vibrates passing the waves into the
cavity of the inner ear (cochlea) where the perilymph vibrates and transmits the waves in the cochlea,
causing the endolymph of the cochlea to vibrate. The vibrations are transmitted across the organ of corti
(sensory nerve cell). Impulses are set up which stimulates the auditory cells which then transmit the impulses
to the brain for interpretation.

c. Ways of caring for the ear:

- Regular cleaning of the ear with cotton wool.
- Avoid blows on the ear.
Example
The organ which is sensitive to smell in a cockroach is the
A. nostril B. pedipalp C. antenna D. mandible E. anal circus (1992/29)
Answer: C – The antenna is the organ of smell in cockroaches.
Example
Which pair of structures contributes to balance in mammals?
A. Utriculus and Sacculus B. Malleus and Stapes C. Saculus and cochlea
D. Utriculus and pinna E. Fenestra ovalis and sacculus (1994/46)
Answer: A – The utriculus and sacculus are structures which are concerned with balance in mammals. They are
found in the inner ear.
Example
The organ responsible for equalizing air pressure in the ear is the
A. sacculs B. utriculus C. Eustachian tube D. ampulla E. air ossicle (1998/23)
Answer: C – Eustachian tube is the organ responsible for equalizing air pressure in the ear.
Example
The structure of the ear that is responsible for balancing is the
A. semi-circular canals B. pinna C. auditory nerve D. fenestra ovalis (2002/22)
Answer: A – The semi-circular canals are structures of the ear responsible for balancing.
NB: It does this function along side with the utriculus and sacculus.

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Example
The part of the ear in mammals responsible for the detection of sound is the
A. utriculus B. tympanum C. cochlea D. semi-circular canal (2006/23)
Answer: C – The cochlea is the part of the ear responsible for sound detection.
Example
The ear pinna is strengthened by
A. blood pressure B. cartilage C. bone D. turgor pressure (2010/17)
Answer: B – The pinna (part of the outer ear) is supported by cartilage.
Example
The inability to maintain proper balance of the body in humans may be due to a defect in the
A. cochlea B. Eustachian tube C. semi-circular canals D. oval window (2014/17)
Answer: C – Defect in the semi-circular canals will result in the inability to maintain proper balance of the body in
humans.
Example
The function of the ossicles (maleus, incus and stapes) in the mammalian ear is the
A. transmission of vibrations B. regulation of pressures C. support of the inner ear
D. maintenance of balance during motion E. secretion of oil (1983/39 JAMB)
Answer: A – The function of the ossicles in mammals is to transmit vibration from the tympanic membrane to the
inner ear.
Example
The sequence of ear ossicles from the fenestra ovalis is
A. malleus, incus and stapes B. malleus, stapes and incus
C. staples, incus and malleus D. stapes, malleus and incus (1987/37 JAMB)
Answer: C – The sequence of the ear ossicles from the fenestra ovalis is:
Stape (stirrup) → incus (anvil) → malleus (hammer). NB: Fenestra ovalis is also known as oval window
Example
Which path does sound entering the human ear follow?
A. Oval window → ossicles → ear drum B. Ear drum → oval window → ossicles
C. Ear drum → ossicles → oval window D. Ossicles → eardrum → oval window (1993/32 JAMB)
Answer: C – Sound enters the human ear through: Ear Drum → Ossicles → Oval window.
Example
The inner ear contains two main organs, namely the
A. eardrum and Eustachian tube B. oval window and oscicles
C. cochlea and semi-circular canals D. pinna and cochlea (2000/24 JAMB)
Answer: C – The inner contains cochlea and semi-circular canals.
Example
The Eustachian tube of the mammalian ear leads from the
A. outer ear B. middle ear to the cholera C. outer ear to the pharynx D. middle ear to the pharynx (2002/24 Nov)
Answer: D – The Eustachian tube of the mammalian ear leads from the middle ear to the pharynx.
Example
The semicircular canals are located in the
A. outer ear B. middle ear C. inner ear D. ossicles E. tympanum (1998/24 Nov)
Answer: C – The semi-circular canals are located in the inner ear.

EXERCISE 14.4
1. Which of the following structures of the mammalian ear is affected when a person turns round several times?
A. Ampulla B. semicircular canals C. Tympanum D. Pinna E. Ear ossicles (1998/25 Nov)
2. The main function of the Eustachian tube is to
A. remove dirt from the ear B. equalize the pressure of the middle ear with the atmosphere
C. serve as a passage for nerves from the middle ear D. balance the body in space
E. collect sound waves into the canal (1995/24 Nov)
3. The inner ear contains
A. liquid and three small bones B. cochlea and its associated nerve endings
C. air and three small bones D. ciliated cells only E. liquid (1995/25 Nov)
4. Which part of the ear is responsible for the maintenance of balance?
A. Ossicles B. Tympanic membrane C. Eustachian tube
D. Semicircular canals E. Cochlea (1991/22 Nov)
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5. 2. (a) Make a labelled diagram to show the internal structure of the mammalian ear.
(b) Describe the mechanism of hearing in mammals.
(c) State two ways of caring for the ear. (1991/2a – c Nov)
6. The ear ossicle closes to the oval window is
A. stapes B. malleus C. incus D. anvil (2019/19 PC2)
7. Which of the following has no remedy?
A. damaged cochlea B. damaged pinna C. infected tympanum D. infected ossicles (1999/28 Nov)
8. Which of the following structures is not a part of the ear?
A. Incus B. malleus C. cochlea D. suspensory ligament E. Eustachian tube (1996/20 Nov)
9. The part of the ear which contains nerve cells sensitive to sound vibrations is the
A. cochlea B. ampulla C. tympanum D. malleus (2017/24 NABTEB)
10. Describe the mechanism of hearing in man. (2005/4a Neco)
11. 2(a) Make a labeled diagram (8-10cm) of a typical section of the human ear.
(b) Which of the labeled parts are responsible for:
(i) Transmission of sound waves to the inner ear.
(ii) Maintenances of balance
(iii) Sending sound impulse to the brain (2005/2a-b Neco Nov)
12. The external part of the human ear is called
A. anvil B. cochlea C. eardrum D. hammer E. pinna (2014/53 Neco)
13. Which of the following pairs indicate the functions of the cochlea and the semi-circular canals?
A. Smelling and hearing B. Hearing and collection of sound waves C. Equalizing pressure and balance
D. Hearing and balance E. Equalizing pressure and smelling (1990/50 Health Science June)
14. Auditory defect can be caused by
A. air pollution B. dirty environment C. noise pollution D. poor nutrition (2003/32 Health Science Nov)
15. Describe the process of hearing. (2003/1b Health Science Nov)
16. Which of the following is the correct sequence in hearing a sound?
A. Outer ear → brain → semi-circular canals → cochlea
B. Outer ear → semi-circular canals → brain → cochlea
C. Brain → cochlea → outer ear → semi-circular canals
D. Brain → cochlea → semi-circular canals → outer ear
E. Outer ear → semi-circular canals → cochlea → brain (1998/22 Health Science Nov)
17. Make a labelled diagram to show the internal structure of the mammalian ear (1991/2a)

The organ of sight

The organ of sight is the eye. Each eye is a spherical organ known as the eyeball.

The protective structures of the eye include eye socket, eyelids, eye lashes, tears glands and conjunctiva. The eye is
housed in a protective cavity called the eye socket.

The eye is cleaned by tears from the tears gland (lacrimal gland) located in the front part of the socket. The eye is a
hollow, spherical organ consisting of three layers which are the outer layer (consisting of sclera and cornea), middle
layer which is called choroid and the inner layer called retina.

The various component of the eye and their functions are given below:
1. The sclerotic layer which is the white part of the eye: It is the outermost layer of the eye. It is a thick,
fibrous connective tissue forming the white of the eye.
Functions
(i) It protects the eye and maintains the shape of the eyeball. The sclerotic layer bulges out in front to
form a transparent and convex tissue called cornea.

2. Cornea
(i) It supports and protects the inner parts of the eye
(ii) It bends the light rays to bring them to a focus on the retina.

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3. The choroid of middle layer: This layer is dark in colour due to presence of black pigments. It is well
supplied with blood vessels (vascularized).
Functions
(i) The black pigments absorb light rays therefore preventing internal reflection of light.
(ii) It supplies food and oxygen to other parts of the eye especially the retina.

The longitudinal/vertical section of the human eye

4. Conjunctiva: It is a thin tough transparent membrane which lines the inside of the eyelids and provides a
covering to the sclera.
Functions
(i) It allows the passage of light into the eye.
(ii) It serves as a protective shield to the innermost delicate structures.
(iii) It provides lubrication for the eye by the production of mucus and tears

5. Optic nerve: Optic nerve is found at back of the sclerotic layer. It penetrates the choroid and retina at a point
known as blind spot which is devoid of light sensitive cells.
Functions
(i) Optic nerve transmits sensory impulses to the brain.
(ii) It transmits impulses from the brain.

6. Iris: The iris has a radial and circular muscle fibre. The iris controls the amount of light passing through the eye.

7. Pupil: The pupil is the aperture/opening through the iris.

Functions
(i) It regulates the amount of light rays entering the eye. When bright light shines on the eye, circular
muscles of the iris contract, making the pupil small. Therefore reducing the amount of light entering
the eye.

8. Ciliary muscle and suspensory ligaments

(i) Changes in contraction of the ciliary muscle alter the focal length of the eye.
(ii) It brings about proper accommodation of eye.

9. Lens: It is a transparent bi – convex elastic structure which is held in position by suspensory ligaments.
Functions
(i) It refract light rays that enter the eye.
(ii) It makes fine adjustment to focus the image of an object on the retina.
10. Retina: The retina is the innermost layer of the eyeball. It is the part of the eye that is sensitive to light. It is
vascularized, pigmented and elastic. Images formed on it are always inverted and smaller than the real object.
There are two types of sensory cells in the retina (1) cones (2) rods

Cones: These are cells in the retina that are sensitive to colour vision and high light intensities. They do not
respond to dim light.

Rods: They distinguish only black and white colours. They are sensitive to all light intensities, bright and dim light.

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 Function of the retina
(i) Images are formed on the retina.
(ii) Retina is used to detect colours of objects.
(iii) Light ray come to focus on retina

11. Yellow spot (fovea centralis)

This is the most sensitive part of the retina. From the yellow spot, the fullest visual information is sent to the brain.

12. Blind spot

The blind spot is found also on the retina. It is the point where the cells are not sensitive to light. The optic
nerve goes out of the eye ball to the brain from the blind spot.
Function
1. It marks the point where optic nerve leave the eye to the brain.

13. Aqueous humour: The aqueous humour is a transparent, watering liquid which fills the space between the
cornea and the lens. The liquid is made up of solutions of proteins, sugars and salts in water.
Function
(i) It refract lights into the retina.
(ii) It maintains the spherical shape of the eye.

14. Vitreous humour: This is a transparent, jelly – like liquid which fills the space between the lens and the
retina. It is wider than the aqueous humour. It also contains solutions of proteins, sugars and salts in water.
Functions of vitreous humour
(i) It refracts light rays onto the retina.
(ii) It maintains the spherical shape of the eye like the aqeous humour.

Functions of the eyes

The eye performs two major functions these are:
1. Image formation.
2. Accommodation.

Mechanism of seeing/image formation

Light rays from an object enters the eye through the cornea. The light rays are refracted (bent) by the convex cornea
and passed through the aqueous humour which further bends the light rays and focuses them on the retina, especially
the yellow spot. As the light rays passes through the vitreous humour, bending of light rays occur again. The light
ray reaching the retina stimulates the rods and cones to form an inverted image on the retina.

The inverted image on the retina is smaller than the actual size of the object. Impulses are sent through the optic nerve
to the optic lobes of the brain. From the optic lobes, the image is sent to the visual centre of the cerebral hemisphere
where the actual size and colour of the image are interpreted correctly.
Conjunctiva → cornea → aqueous humour → lens → vitreous humour → retina → optic nerve → brain.

Accommodation of the lens

Accommodation is the ability of the human eyes to focus for and near objects on the retina. It is brought about by the
contraction and relaxation of the ciliary muscles.

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Near object
In order to see a near object clearly.
1. The ciliary muscle contract and become thicker and fatter.
2. The suspensory ligaments relaxes their tension (slacken) on the lens.
3. The lens assumes a more convex shape.
4. The focal length of the lens is reduced. Under this condition, the eye is able to focus the image of near objects
on the retina.

Near object
Light from near object is focus on the retina by thick and flat lens.

Far object
In order to see a distant object clearly.
1. The ciliary muscle is relaxed.
2. The suspensory ligaments pull tightly on the lens therefore stretching the lens to be thin, flat and less convex.
3. The focal length of the lens is increased.
4. The convex lens assumes a near flat shape.
Under these conditions, the eye is able to focus the image of distant objects on the retina.

Far object
Light from far object is focused on the retina by thin and flat lens.
Defects of the eye
1. Short –sightedness/myopia.
2. Long – sightedness/hypermetropia
3. Astigmatism
4. Presbyopia
These defects are mainly caused by excessive eye strain and old age.
Other eye defects include: 1. Colour blindness 2. Night blindness 3. Cataract 4.Conjuctiviatis 5. Xerophthalmia

Short – sightedness (myopia): Short sightedness (myopia) is a condition where the eyeball is too long or the cornea
is too curved. Parallel rays of light from a distant object are brought to focus by cornea and lens at a point in front of
retina. A short sighted person can only see object near but cannot see distant object clearly.

Image is formed before the retina and the eye ball is too long

Correction of short sightedness

The defect can be corrected by using concave lens which diverge (bend light ray outwards) parallel light from distant
objects before falling on the eyeball, and therefore focusing on the retina.

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Long – sightedness (hypermetropia)
Long – sightedness is a condition in which parallel light rays from near objects are brought to a focus behind the
retina. The eye can see distant objects clearly but not near by objects. This is caused because the eyeball too short or
the lens is too flat.

Correction
Hypermetropia can be corrected by using convex lens. Eye-glasses which converges (to bend inward) light rays before
falling on the eyeball and thus focusing them on the retina.

Astigmatism: This is caused by uneven (unequal) curvature of the cornea or lens. The rays of light are brought to
focus at different points on the retina. This causes the image to be blurred.
Correction
It can be corrected by using cylindrical lens or lenses with compensating uneven surface.

Presbyopia: This defect comes with old age. The power of the lens to accommodate is reduced due to less elasticity
of the lens or hardened ciliary muscles.
Correction
Wearing bi-focal galsses (lens) in which one part is for near vision and the other is for distant vision.

NOTE: Bi-focal glasses are glasses with two distinct optical powers.
Astigmatism can also be corrected by a special surgery technique known as “REFRACTIVE SURGERY”

Colour blindness: This is the inability of a person to distinguish one colour from the other. For example if the red
sensitive cone is lacking, the person will not be able to identify a red colour. He will perceive red colour as green.
Colour blindness is an inherited sex – linked characteristics showing up in males.
Cataract: This occurs mainly in old people. The lens becomes cloudy and so the person cannot see clearly.
Correction
By removing the affected lens and either:
1. Replace it with a plastic one or
2. Providing spectacles with suitable lens.

Nightblindness: This people cannot see clearly in dim light. It may be due to deficiency of vitamin A which is used
to make rhodopsin.

Xeropthalmia: is also caused by vitamin A deficiency. It can lead to blindness.

Why a person in a dark room is dazzled for some seconds when he is suddenly exposed to bright sunlight
In a dark room, the iris contracts, the pupil dilates (widely opened) to let in more light. On sudden exposure to bright
sunlight, the pupil which is still wide opened, lets in too much light which bleaches the pigment of the rod cells. This
causes the dazzling sensation experienced when someone in a darkroom is suddenly exposed to bright light.

The iris muscle gradually relaxes within a few seconds and the pupil gradually constricts to control the entry of the
required amount of light for vision to return to normal.

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Example
Which of the following is the function of the iris of the mammalian eye?
A. closes and opens the eye B. absorbs dangerous rays from sunlight
C. regulates the amount of light entering the eye D. bringing light rays to focus on the retina (2003/23)
Answer: C – The iris regulates the amount of light entering the eyes.
Example
The most sensitive part of the retina is called
A. blind spot B. conjunctiva C. fovea centralis D. choroid coat E. sclerotic coat. (1996/18)
Answer: C - The fovea centralis (yellow spot) is the most sensitive part of the retina.
Example
Use the diagram below to Answer: questions 17 to 19.

The light – sensitive layer is labelled

A. I B. III C. IV D. VI E. VII
Answer: B – Label III points to the retina which is the light sensitive layer of the eyes.
The greatest concentration of light receptors is found in the part labeled
A. VI B. V C. IV D. III E. I
Answer: B – Label V points to the fovea centralis which has the greatest concentration of light receptors.
The aqueous humour is represented by the part labeled
A. I B. II C. III D. VI E. VII (1989/17-19)
Answer: B – Label II points to the aqueous humour of the eye.
Example
List four structures that protect the eye from injury. (2019/5ci NABTEB).
Answer: Eye socket , Eye lashes, Eye glands and Conjunctiva
Example
Use the diagram below to Answer: questions 19 and 20

Which type of eye defect is illustrated in the diagram above?

A. Hypermetropia B. Myopia C. Cataract D. Astigmatism E. Glaucoma.
Answer: A – Hypermetropia (long sightedness) is characterized by the formation of image behind the retina.
This defect can be corrected by the use of
A. convex lens B. concave lens C. cylindrical lens
D. surgical operation E. biconcave lens (1993/19-20)
Answer: A – A convex lens (a converging lens) is used for the correction of hypermetropia.
Example
When a person moves from darkroom into bright light, the pupil becomes
A. red B. larger C. white D. smaller (2004/22)
Answer: D – When a person moves from a darkroom into a bright light, the pupil of the eye becomes smaller so as to
reduce the intensity of light entering into the eye.
Example
Which of the following parts of the eye is sensitive to light?
A. Retina B. Cornea C. Choroid layer D. Optic nerves (2000/28)
Answer: A – Retina is the part of the eye that is sensitive to light.
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Example

The part labeled IV, V and VI respectively are

A. ciliary body, optic nerve and yellow spot B. blind spot, optic nerve and suspensory ligament
C. vitreous humour, yellow spot and optic nerve D. blind spot, optic nerve and pupil
E. yellow spot, retina and choroid layer.
Answer: C– vitreous humour, yellow spot and optic nerve
The light ray entering the eye goes through the following route
A. II, III, I, IV B. II, I, VII, III, V C. II, I, III, IV, V D. V, IV, III, I, II E. I, VII, III, IV, V
Answer: C– II, I, III, IV, V
Which of the follwiong structures are adjusted in focusing the image of a near distant or near object on the retina?
A. I & II B. II & III C. III & VII D. IV & V E. V and VII (1993/29 – 31)
Answer: C– III & VII
Example
The eye defects that is corrected by a diverging lens is
A. long – sightedness B. short sightedness C. astigmatism D. presbyopia (2019/29 NABTEB)
Answer: B – Short sightedness can be corrected by using a diverging lens (concave lens).
Example
In long – sightedness, the image of a near object is focused
A. in front of the retina B. behind the retina C. on the yellow spot D. on the blind spot (2013/21 Nov)
Answer: B – In long sightedness, images are formed behind the retina.
Astigmatism can be corrected by
A. convex lens B. cylindrical lens C. concave lens D. plane lens (1999/27 Nov.)
Answer: B – Astigmatism is corrected by the use of a cylindrical lens.
Example
The layer of light-sensitive cells in the human eye is called the
A. cornea B. sclerotic layer C. retina D. conjunctiva (2003/22)
Answer: C – The retina is the layer of light sensitive cells in the human eye.
Example
Which of the following best explains why it is difficult to see clearly in dim light?
A. Initially the eyes cannot operate when the light is dim B. The choroid reflect all the light that enters the eye
C. Too little light reaches the retina and so the cones may not be stimulated at all
D. Dim light causes the pupil to close up so that not much light enters the eye (2005/12)
Answer: C – It is difficult to see in dim light because too little light reaches the retina and this may cause the cones
not to be stimulated at all.
Example
The function of the convex lens in the correction of eyes defects is to
A. diverge light rays from far objects to focus image on the retina
B. converge light rays to focus image behind the retina
C. converge light rays to focus the image before the retina
D. converge light rays from far objects to focus their image on the retina (2012/18)
Answer: D – The function of convex lens in correction of eye defect is to converge light rays from objects, before
they fall on the eye ball thus focusing their images on the retina.
Example
Which of the following practices may lead to infection of the eye? Use of
A. contact lenses B. convex lenses C. biconcave lenses D. concave lenses (2018/17)
Answer: A – The use of contact lens may lead to infection of the eye.
NB: Contact lens is one that is placed directly on the surface of the eye in order to correct eye defects.

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Example
Use the diagram below to Answer: question 16 only

The diagram above is an illustration of

A. normal sight B. short sightedness
C. correction of long sightedness D. correction of short sightedness. (2014/16)
Answer: C – The diagram is a illustration of correction of long-sightedness (hypermetropia). This is so because of
the presence of a converging lens (convex lens).
Example
Ability of the human eye to focus images accurately on the retina is called
A. astigmatism B. myopia C. adjustment D. accommodation. (2015/18)
Answer: D – Accommodation is the ability of the human eye to focus images accurately on the retina.

Example
Biconcave lenses are used in the correction of an eye defect called
A. myopia B. colour blindness C. old age D. hypermetropia E. weakening of ciliary muscles (1980/36 JAMB)
Answer: A – Biconcave lenses are used to correct myopia (short sightedness)
Example
The parts of the mammalian eye that strongly bend light rays are the
A. cornea and the lens B. cornea and aqueous humor C. cornea and vitreous humor
D. lens and aqueous humor E. lens and vitreous humor (1982/25 JAMB)
Answer: E – The lens and vitreous humour are parts of the mammalian eye that strongly bend light rays.
Example
When the ciliary muscle of the eye contracts, the eye lens
A. bulges B. contracts C. rotates D. flattens E. is rounded (1979/17 JAMB)
Answer: E – When the ciliary muscle of the eye contracts, the lens becomes more spherical (rounded).
Example
The vitamin which is important in the formation of the retina pigment is
A. vitamin A B. vitamin B C. vitamin C D. vitamin D (1987/18 JAMB)
Answer: A – Vitamin A is important for the formation of the retina pigments.
Example
Short-sightedness can be corrected by lenses which are
A. convex B. concave C. piano-convex D. biconvex (2000/25 JAMB)
Answer: B – Short sightedness can be corrected by concave lens. (diverging lens)
Example

The eye defect illustrated is

A. myopia B. hypermetropia C. astigmatism D. cataract (2009/27 JAMB)
Answer: B – hypermetropia
Example
The function of the correcting lens is to
A. diverge incoming rays B. converge incoming rays
C. reflect incoming rays D. screen incoming rays (2009/28 JAMB)
Answer: B – converge incoming rays

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EXERCISE 14.5
1. The eye defect that rises because the corneas is not curved smoothly is
A. astigmatism B. shortsightedness C. long sightedness D. presbyopia (2015/28 JAMB)
Use the diagram below to Answer: questions 33 and 34

2. Image is formed on the structure labeled

A. A B. B C. C D. D E. E (2008/33 Neco)
3. In myopia, the image is formed
A. behind A B. behind B C. in front of B D. in front of C E. on D (2008/34 Neco)
4. The cells which receive the stimulus of light and enable the eyes to perform the function of vision, are found
in the
A. cornea B. choroid C. retina D. sclera (2004/19 Nov)
5. A situation where the image is formed behind the retina is referred to as
A. myopia B. hypermetropia C. astigmatism D. presbyopia (2004/20 Nov)
6. The term Accommodation of the eye means
A. altering the focal length of the eye lens B. adapting to different light intensities
C. judging distance D. distinguishing between different colours (2002/23 Nov)
7. The eye condition in which light rays from near objects are brought to a focus behind the retina is
A. myopia B. hypermetropia C. presbyopia D. astigmatism E. conjunctivitis (1998/23 Nov)
8. Which of the following is not a part of the mammalian eye?
A. ampulla B. choroid C. pupil D. conjunctiva (2000/24 Nov)
9. When the eyeball is too short, the eye defect that occurs is
A. hypermetropia B. myopia C. astigmatism D. presbyopia (2000/25 Nov)
10. Which of the following parts of the eye is not involved in image formation?
A. Retina B. Lens C. Pupil D. Yellow spot E. Blind spot (1997/22 Nov)
11. Astigmatism can be corrected by
A. convex lens B. cylindrical lens C. concave lens D. plane lens (1999/27 Nov)
12. Which of these structures is not associated with sight?
A. ciliary muscle B. suspensory ligament C. blind spot D. stapes (1999/26 Nov)
13. If the distances between the cornea and retina is too short the person will
A. see only distant objects clearly B. see only very bright colours
C. have larger images formed on the retina D. have the image formed on the yellow spot (1999/25 Nov)
14. When the radial muscles of the iris are in a relaxed state, the pupil becomes
A. larger and adapted for a dim-light vision B. narrower and adapted for bright-light vision
C. closed completely for the eye to rest D. pale in colour (2006/23 Nov)
15. In long sightedness the image of a near object is focused
A. in front of the retina B. behind the retina C. on the yellow spot D. on the blind spot (2013/21 Nov)
16. The eye defects that is corrected by a diverging lens is
A. long sightedness B. short sightedness C. astigmatism D. presbyopia (2019/29 NABTEB)
17. When a person moves from dark room into bright light the pupil becomes
A. red B. larger C. white D. smaller (2019/30 NABTEB)
18. The opening through which light enters the eye is called
A. cornea B. iris C. lens D. pupil (2019/31 NABTEB)
19. 5(a) What is a sensory cell?
(b) State one function each of the following parts of the mammalian eye:
(i) lens (ii) vitreous humour (iii) optic nerve
(c) (i) List four structures that protect the eye from injury.
(ii) Explain briefly how each of these structures perform its function.
(d) Explain why a person in a dark room is dazzled for some seconds when he is suddenly exposed to
bright sunlight. (2019/5a-d NABTEB)

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20. The altering of the shape of the lens in order to see objects at varying distances is termed
A. accommodation B. conjunctivitis C. focusing
D. long-sightedness E. shortsightedness (2005/32 Neco (Nov)
21. The vitreous humour in the human eye assists in …….. of objects
A. Contraction B. conversion C. reflection D. refraction E. retention (2005/20 Neco)

Use the diagram above to Answer: questions 13 and 14

22. The part that helps to control the amount of light entering the eye is labeled
A. I B. II C. III D. IV E. V [2005/13 Neco (Nov) ]
23. The part through which impulses are sent to the brain is marked
A. I B. II C. III D. IV E. V (2005/14 Neco (Nov)
24. The condition in which light rays from near objects are brought to focus behind the retina is
A. myopia B. hypermetropia C. presbyopia D. astigmatism E. accommodation (2007/35 Neco)
25. The opening through which light enters the eye is called
A. cornea B. iris C. lens D. pupils E. retina (2014/37 Neco)
26. c.(i) Name three defects of the human eye (2014/3c(i) Neco)
27. The part that supplies food and oxygen to the eye is
A. choroids B. cornea C. lens D. pupil E. retina (2018/44 Neco)

28. The disorder caused by the formation of an opaque substance on the lens of the eye and which hinders vision
is known as
A. cataract B. myopia C. conjunctivitis D. presbyopia E. glaucoma (1990/52 Health Science June)
29. Myopia can be corrected by
A. wearing concave lens B. wearing convex lens C. wearing cylindrical lens
D. taking more of vitamin A tablets E. taking more of mineral salts (1990/53 Health Science June)
30. A converging lens is used to correct
A. astigmatism B. night blindness C. myopia D. long sight (2003/22 Health Science Nov)
Use the diagram below to Answer: questions 37 and 38

A lens
31. Which type of lens is illustrated in the diagram above
A. Convex lens B. Concave lens C. Hollow lens D. Plain lens E. Bifocal lens (1998/37 Health Science Nov)
32. The type of lens illustrated in the diagram above is used to correct
A. astigmatism B. presbyopia C. glaucoma D. short sight E. conjunctivitis (1998/38 Health Science Nov)

REVISION EXERCISE
1. Which of the following is not a sense organ
A. skin B. mouth C. eye D. tongue E. nose (1996/21 Nov., 2000/23 Nov.).
2. The sensory cell found on the upper surface of the tongue are
A. impulse B. nerve cells C. taste buds D. somatic cells (2019/18)
3. A person who fails to detect the bitter taste of a substance swallowed is more likely to have
A. dead taste buds on the tongue B. avoids the substance from contracting the back of his/her tongue
C. fewer taste bud on the tongue D. swallowed the substances without any water (2001/44)

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4. The human skin is regarded as a sense organ because it
A. seperates the body from the outside world B. protects the body from cold and heat
C. regulates the water content of the body D. has an outer layer of dead cells E. has nerve endings (1991/20)
5. Which of the following sensation may not be detected by the skin
A. touch B. pressure C. stress D. pain (2008/21)
6. Which of the following structures of the mammalian ear is affected when a person turns round several times
A. ampula B. semi-circular canals C. tympanum D. pinna E. ear ossiccles (1998/25)
7. Which of the following structure is not part of the ear?
A. incus B. malleus C. cochlea D. suspensory ligament E. Eustachian tube (1996/20 Nov)
8. The semi-circular canals are located in the
A. outer ear B. middle ear C. inner ear D. ossiccles E. tympanum. (1998/24 Nov)
9. Which pair of structures contributes to balance in mammals?
A. utriculus & sacculus B. malleus and stapes C. sacculus and stapes
D. utriculus and pinna E. fenestra ovales and saccules. (1994/46)
10. The following are directly involved in transmission of sound waves to the brain except
A. ear drum B. auditory meatus C. auditory ossicles
D. Eustachian tube E. cochlea (1995/22, 2005/26 Neco)
11. The part of the ear in mammals responsible for the detecton of sound is the?
A. utriculus B. tympanum C. cochlea D. semi-circular canal (2006/23).
12. The inability to maintain proper balance of the body in humans may be due to a defect in the
A. cochlea B. Eustachian tube C. semi-circular canals D. oval window (2014/7).
13. The cells which receive the stimuli of light and enable the eyes to perform the function of vision are found in
the
A. cornea B. iris C. retina D. sclera (20004/19 Nov)
14. Which of this structure is not associated with sight?
A. ciliary muscles B. suspensory ligament C. blind spot D. stapes (1999/26 Nov.)
15. The ability of the eye to alter the focal length of the lens with regard to the distance of the object from the eye,
is known as
A. binocular vision B. nocturnal vision C. distortion D. accommodation E. focusing (1994/26, 2002/23 Nov)
16. Which of the following parts of the eyes is not involved in image formation?
A. retina B. lens C. pupil D. yellow spot E. blind spot (1997/22)
17. Which of the following is not part of the mammalian eye?
A. ampulla B. choroid C. pupil D. conjunctiva (2000/24)
18. When a person moves from darkroom into bright light the pupil become
A. red B. larger C. white D. smaller (2019/30 NABTEB).
19. The opening through which light enters the eye is called
A. cornea B. iris C. lens D. pupils (2019/37 NABTEB)
20. Spectacles with convex lenses correct long – sightedness by
A. converging the light rays before they enter the eye
B. diverging the light rays before they enter the eye
C. reducing light intensity before it enters the eye D. increasing the light intensity before it enters the eye (2009/23)
21. When viewing an object that is close to the human eye, the
A. eye lens becomes thin B. ciliary muscles relax
C. suspensory ligament become tant D. eye lens becomes fat (2017/19).
22. To focus on a distant object, the ciliary muscle of the eye
A. contracts and they eye lens get thicker B. relaxes and the eye lens get thinner
C. contracts and the eye lens get thinner D. relaxes and the eye lens get thicker (2019/18)
23. The relationship between the retina and the brain is similar to that between the
A. cochlea and the auditory nerve B. cochlea and brain
C. cochlea and the semi-circular canals D. ear drum and the brain (2010/18)
24. Which of the following is a characteristic of sense organs? They
A. respond to external stimuli B. are very sensitive to sound
C. function without the brain D. function best under low temperature (2003/21 Health Sci. Nov)

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Irritability (Sensitivity)
The ability that living organisms have to respond to changes in their environment is known as irritability (sensitivity).
Environmental changes could be internal or external. Examples of external environmental changes include change in
temperature and light intensity while example of an internal environmental change is change in PH.

Types of Response
The three major types of responses are: i. Tactic (or taxis) ii. Nastic iii. Tropic movement

i. Taxis or tactic movement (responses) is a type of directional responses or movement in which a whole
organism moves from one place to another in response to external stimuli such as light, temperature, water and certain
chemicals. Movement or response is either positive or negative.
Example of tactic movement are (1) Thermotaxis (2) Phototaxis (3) Hydrotaxis (4) Chemotaxis (5) Rheotaxis
Thermotaxis: This is the movement of organisms in response to temperature change or heat. Example is snail moving
away from a hot region to a cold region. This is negative thermotaxis.
If the locomotory movement is towards the stimulus, it is positive taxis, if it is away, it is negative taxis. The response
of animals to stimulus of light is called phototaxis. E.g. Euglena moving away from sunlight (negative phototasis),
euglena moving towards the light source (positive phototaxis).
Hydrotaxis: This is the response of the whole organism in response to water or humidity, example is the woodlouse
moving towards areas of high humidity.
Chemotaxis: This is the movement of organism in response to chemical stimuli. Example is amoeba and paramecium
moving away from chemicals (i.e. negative chemotaxis). Another example is sperm cells moving towards chemical
substance produced by eggs (positive chemotaxis) Mosquitoes avoiding repellants (negative chemotaxis).
Rheotaxis: This is the response of organisms to current. For example, many fresh water fish (e.g. tilapia) move
against current.

ii. Nastism or Nastic Movement (Sleeping Movement): Nastism is a type of response in which a part of a plant
moves in a non-directional stimuli such as changes in light intensity, temperature or humidity. The response is non-
directional. Example of nastic movement are:
i. Closing of the morning glory flower when the light intensity is low.
ii. Petals of sunflower which opens in the light and closes in the dark.
iii. The folding of the leaflet of the Mimosa plant when it is touched.
iv. Closing of the leaflets of the flamboyant tree. That is sleeping movement due to low light intensity.
v. Opening of “four O’clock plant at about 4pm daily.
Sleeping movement also occur in the leaves of St. Thomas plant and Cassia. Pinnate and bipinate leaves of many
leguminous plants open and close as a result of changes in temperature, light intensity and humidity of atmosphere.

Example
Nastic movement is
A. response to light stimulus B. non-directional C. directional D. response to internal stimulus (1986/33 JAMB)
Answer: B – Nastic movement is a non directional kind of movement.
Example
Taxism differs from tropism because
A. the whole organism is affected B. it is a directional movement
C. it is a response to multi-directional stimuli D. part of the organism is affected (1988/27 JAMB)
Answer: A – Taxism differ from tropism because the whole organism is affected.
Example
When bacteria swim from cold to warm regions, this is known as
A. positive phototaxis B. negative phototaxis C. positive thermotaxis D. negative chemotaxis (2005/15 JAMB)
Answer: C – The movement of bacteria from a cold region to a warm region is an example of positive thermotaxis movement.
Example
The ability of a living organism to detect and respond to changes in the environment is referred to as
A. irritability B. growth C. taxis D. locomotion (2011/15 JAMB)
Answer: A – Irritability is the ability of a living organisms to detect and respond to changes in the environment. It is
also called sensitivity.

256
Example
The movement response of a cockroach away from a light source can be described as
A. negative phototaxism B. negative phototropism C. positive phototropism D. positive phototaxism (2011/23
JAMB)
Answer: A – The movement of a cockroach away from a light source is a example of negative phototaxis movement
NB: Taxism involves animals while tropism involves plants.
Example
(d) Explain the following terms, giving one examples in each case: (i) Phototaxis (ii) Hydrotaxis
(iii) Chemotaxis (2003/7ci, ii, dii)
Answer:
i. Phototaxis: This is the movement of a whole organisms in response to light. When the organisms move
towards light it is called positive phototaxis while if it moves away from light, it is called negative phototaxis.
E.g. euglena moving toward light source (positive pohtotaxis).
ii. Hydrotaxis: This is the movement of a whole organism in response to water or humidity. It is positive
hydrotaxis when the organism moves towards water or humid area. E.g. the movement of woodlouse towards
area of high humidity.
iii. Chemotaxis: This is the movement of a whole organism in response to chemical stimuli. When an organism
move towards a chemical stimuli; it is known as positive chemotaxis while when it moves away, it is called
negative chemotaxis. E.g. mosquitoes avoiding repellants (negative chemotaxis). The movement of sperm
towards chemical substance produced by the egg (chemotaxis).
Example
(c) What would be observed when a grow1ng seedling is placed horizontally? (2007/1c)
Answer:
- The shoot will bend upwards, show positive phototropism and negative geotropism.
- The root will bend downwards, showing positive geotropism and negative phototropism.

iii. Tropism or Tropic movements: This is a type of response in which a part of a plant moves in response to a
directional stimulus. The direction of the movement is related to that of the stimulus and it is positive if the plant part
grows towards the stimulus and it is negative if the plant part grows away from the stimulus. Tropism are named
according to the stimuli. E.g. phototropism which is a response to light and hydrotropism which is a response to
water. Examples of tropism are:
1. Phototropism: The stimulus here is light. E.g. bending of plant shoot towards light. This is called positive
phototropism. Movement of the root of plants away from light is negative phototropism.
2. Geotropism: The stimulus in this case is gravity. Examples are the shoots of green plants bending away from
gravity which is negative geotropic while roots bend towards gravity and is positively geotropic.
3. Hydrotropism: The stimulus is water. Example is how the roots of plants move towards moisture which is
known a positively hydrotropic and the shoot bends away from moisture and is known as negatively
hydrotropic.
4. Thigmotropism: The stimulus here is touch. Example is how the tendrils of a climbing plant twine around a
support as a positive response to touch while the root grows away from touch as a negative response.

Differences between nastic (sleep) movement and tropism

Nastic/sleeping movement Tropism
1. Movements are reversible (or growth is reversible) Not easily reversible (i.e. growth in tropic movement is
irreversible)
2. Nastic movement is non-directional. It is neither Tropic movement is a directional positive or negative
positive nor negative response response to stimuli
3. Nastic movement can be due to changes in cell Tropic movement is not due to turgor
turgor
4. Nastic movement is not a growth movement Tropic movement involves growth movement.
5. In nastic movement, response to stimuli is very fast. In tropic movement, response is very slow
6. Response are due to changes in temperature, Response are due to water, gravity and chemical
humidity, light intensity or touch.
7. Response does not lead to growth Response lead to growth

257
Experiment to demonstrate phototropism using a potted plant
Materials needed: some cowpea seeds, two small containers, wet soil,
Method: Some cowpea seeds are germinated in two small containers such as milk cans filled with wet soil. As soon as
the first foliage leaves appear, one of the can is kept in a room by the side of a window, and the other is kept outside.
They are then left for about 48 hours.
Results: it would be seen that the shoots of the seedlings placed by the window side bend towards the direction of
light while those on the outside maintain straight stems.
(A) (B)

A. seedling on window: shoot bends towards light

B. Seedling kept outside: shoot maintain straight growth
Conclusion: The side of the shoots receiving light has lower amount of auxin than the other side in the dark. There is
more growth on the side with higher concentration of auxins and little growth on the side receiving light with low
auxin concentration. The unbalance growth causes the shoots to bend to the side where growth is reduced, i.e. towards
the direction of light.

C. Shows shoot before response

D. Shows shoot bending towards light

The Klinostat: This is an instrument used to demonstrate the effect of light and gravity on the growth of plants. it is
made up of a cylinder and an electric motor for a clockwise rotation of the cylinder.

Klinostat

Experiment to demonstrate geotropism using potted plant and klinostat

Materials needed: Some cowpea seeds, small pots, Klinostat.
Method: Sow some cowpea seed in small pots (one seed per pot), klinostat.
After the appearance of the first foliage leaves, the pots are placed in the dark with the seedling in a horizontal
position. The control is a klinostat with a seedling kept working in a horizontal position. The whole set-up is left for
about 24-36 hours.
Results: After 24 hours, the shoot of the seedling in the pot curves and grows vertically upward (away from gravity).
If the soil is carefully washed off and the whole seedling is examined, the root is also seen to have curved and grown
downwards (i.e. towards gravity).

258
The shoot of the working klinostat remains in a horizontal position and does not curve. But if the klinostat is not
rotating (i.e. stationary) then the shoot will curve.

Conclusion: Shoot is negatively geotropic while root is positively geotropic

Hydrotropism: This is the response of roots to the stimulus of water in the soil. Plant roots are positively hydrotropic.

Experiment to demonstrate hydrotropism

Aim: To show that the roots of plant are positively hydrotropic.
Materials required: Two large beakers, water, seedlings, two troughs.
Procedure: Some bean seeds are germinated in moist filter papers in a beaker. Two troughs (A and B) are obtained
and filled with soil to about two-third level. In trough A, at some distance from the center a porous clay pot filled with
water is placed. As soon as the seeds in the beaker germinate, the seedlings with very straight radicles are selected and
transferred into the soil in the different troughs. The soil in trough A is left un-watered and the soil in trough B is well
watered. Seedlings in trough B without a porous clay pot serve as control. The experiment is left for 2 or 3 days after
which the seedlings are carefully removed and examined.

Trough A Trough B
Observation/Result: The roots of seedlings in trough 1 are curved but those in trough B remain straight.
Conclusion: The bending of the roots towards source of water in trough A shows that the roots are positively
hydrotropic. In trough B (control) the roots grows straight downward as water availability is uniform throughout the
soil.

Example
Which of these instruments can be used to perform an experiment on geotropism?
A. Photometer B. Cup anemometer C. Klinostat D. Kymograph E. Sphygmomanometer (1996/8)
Answer: C – Klinostat is a device which is used to study the rate of growth in plant. It uses rotation to negate the
effects of gravitational pull on plant growth and development.
NB. Photometer is a instrument for measuring light intensity.
Cup anemometer is an instrument used to measure the speed and force of wind.
Kymograph is an instrument for recording variations in pressure.
Sphygmomanometer is an instrument for measuring blood pressure .
Example
In a phototropic experiment, young seedlings in a box were subjected to light from one direction. The seedlings
continued to grow erect. Which of the following statements is correct?
A. Only the tip of the seedling received light B. The light was not strong enough
C. The seedlings were rather too young D. The tips of the seedlings may have been covered (1978/44 JAMB)
Answer: A – The seedlings continued to grow erect because only the tip of the seedling received the light.
259
Example
(a) In a tabular form, distinguish between tropic movements and nastic movements.
(b) Explain how light brings about tropic movement in the stem and root of a flowering plant. (2007/1a, b)
Answer:
a. Differences between tropic movements and nastic movements:
Tropic movement Nastic movement
- Movement is not easily reversible. - Movement is reversible
- It is directional. - It is non-directional.
- It is a growth movement. - It does not involve growth.
- It is very slow. - It is very fast.
- It is due to changes in gravity, - It is due to changes in temperature, humidity,
water and chemical. light intensity or touch.
b. In the stem: When light is incidented on the stem of a plant, the auxin is displaced, to the side that is not
directly receiving the light. Due to the increase in auxin concentration in the side not directly receiving the light, there
is rapid growth on that side causing the stem to bend towards the light (positive phototropism).
In the root: The auxin is displaced from the root side that directly receives light, to the other side. This leads to
increase in auxin concentration on the side that is not indirect contact with the light. Due to the increase of auxin
concentration on this side, growth is retarded and the root bends away from the light source (negative phototropism).

Example
Which of these instruments is used to demonstrate the response of roots and shoots to gravity?
A. Klinostat B. Manometer C. Porometer D. Potometer E. Photometer (1981/17 JAMB)
Answer: A – The instruments used to demonstrate the response of roots and shoots to gravity is a Klinostat.
Example
In a positive phototrophic response o f a coleoptile, the region of greatest curvature is brought about by the
A. movement of auxins away from the region of curvature B. even distribution of auxins in all part of the coleoptile
C. inhibition of growth by auxins in the region of smaller curvature D. concentration of auxins in the region of curvature
E. absence of auxins in the coleoptile (1983/37 JAMB)
Answer: D – In a positive phototropic response of a coleoptiles (shoot), the region of greatest curvature is brought about by the
concentration of auxins in the region of the curvature.
Example
An instrument that can be used to demonstrate phototropism and geotropism in plants is the
A. auxanometer B. photometer C. klinostat D. photometer (1986/41 JAMB)
Answer: C – A Klinostat can be used to demonstrate both phototropism and geotropism.
Example
A directional growth movement of a plant part in response to a unilateral stimulus is called
A. tactic movement B. sleeps movement C. locomotion D. tropism E. Phototropism (1998/7 Nov)
Answer: D – Tropism is a directional growth movement of a plant part in response to a unilateral stimulus.
Example
If a germinating seed is attached horizontally on a revolving k1inostat what will be the effect on the seedling after
three days? The
A. plumule will curve vertically upwards while the radicle will curve towards the ground
B. plumule and radicle will not show any curvature
C. radicle will curve towards the ground while the plumule will not show any curvature
D. plumule will curve vertically upwards while the radicle will not show any curvature
E. plumule and the radicle will curve towards the ground (1991/19 Nov)
Answer: B – Plumule and radical will not show any curvature. This is because a klinostat counterfeits the effects of
geotropism and phototropism.
Example
Which of the following statements explains why the illuminated side of the apex of a young shoot bends towards
unilateral source of light?
A. Growth is faster at the dark side B. the illuminated side becomes weak
C. growth is faster at the illuminated side D. the dark side becomes heavier (2013/8 Nov)
Answer: A – The illuminated side of the apex of a young shoot bends towards unilateral source of light because
growth is faster at the dark side.
Example
The response shown by the tips of the root and shoot of a plant to the stimulus of gravity is
A. heptotropism B. phototropism C. hydrotropism D. geotropism (2019/21 JAMB)
Answer: D –The tips of the root and shoot of a plant responds to the stimulus of gravity (geotropism)
260
EXERCISE 15.1
1. The response of plants to the stimulus of touch is called
A. chemotropism B. geotropism C. hydrotropism D. phototropism E. thigmotropism (2018/9 Neco)
2. The response shown by the tips of the root and shoot of a plant to the stimulus of gravity is
A. haptotropism B. phototropism C. hydrotropism D. geotropism (1993/23 JAMB)
3. The tropic movement of parts of plants in response to unidirectional influence of external stimulus can be
explained on the basis of unequal distribution of
A. auxins B. cytokinins C. florigens D. gibberellins (2005/13 Nov)
4. 3(a)(i) Define tropic and nastic movements.
(ii) List four differences between tropic and nastic movements (2019/3ai, ii NABTEB)

5. c(ii) Give two examples of tropism. (2019/3cii NABTEB)

6. Tropic movement may enable plants to
A. grow towards source of water B. escape from predators
C. prevent competition amongst themselves D. become widely dispersed (2013/7 Nov)
7. The bending of a shoot towards the source of light is caused by the
A. increase in auxin on the side away from the source of light
B. decrease in thin on the side away from the source of light C. concentration of auxin at the apex of the shoot
D. movement of auxin away from the region of elongation
E. increase in auxin in the plant generally (1994/21 Nov)
8. Which of the following is the reason for plants bending towards a source of light?
A. a green plant requires light for photosynthesis
B. light slows down elongation of cells on the lighted side
C. concentration of auxin on the shaded side stimulates cell elongation
D. green plants require the stimuli for tropisms (1999/7 Nov)

9. Which of these instruments can be used to perform an experiment on geotropism?

A. Photometer B. Cup anemometer C. Klinostat
D. Kymograph E. Sphygmomanometer (1996/8)
10. 1aii. Describe an experiment to demonstrate the effect of gravity on the roots of plants. (2011/1aii)
11. (c) What would be observed when a growing seedling is placed horizontally? (2007/1c)
12. (c) Describe an experiment to show that plant roots respond positively to gravity. (1992/4c)

The diagrams below are illustrations of an experimental set-up to demonstrate a type of tropic response in plants.
Study them and Answer: questions 7 and 8.

13. The type of response demonstrated is

A. phototropism B. geotropism C. hydrotropism D. thigmotropism

14. The conclusion drawn from the experiment is that

A. shoots of plants are negatively thigmotropic B. shoots of plants are negatively geotropic
C. leaves of plants are positively phototropic D. roots of plants are positively hydrotropic (2018/7-8)

15. (a)i. What is the effect of gravity on plant growth?

ii. Describe an experiment to demonstrate the effect of gravity on the roots of plants. (2011/1ai, ii)

261
SUPPORTING TISSUES IN PLANT
Plants need supporting tissues to remain upright, spread out their branches and hold their leaves in the best positions
for trapping sunlight. The main supporting tissues in plants are parenchyma, collenchymas and sclerenchyma (fibre
and sclereids). The xylem and phloem however have some supporting functions in plants also.

Parenchyma Tissue: This is one of the most common and most abundant plant tissues that occurs in all the organs of
the higher plants. The parenchyma cells occur in cortex, pith, stem, root, leaf mesophyll, succulent storage tissues and
vascular tissues (xylem and phloem). Parenchyma is located just below collenchyma. The parenchyma tissue of root
and most of those in stem are usually colourless and function mainly in storage of food and water. In the leaves and in
some younger parts of the stems, parenchyma cells contain chlorophyll and hence, function mainly in food synthesis.
Functions of Parenchyma
1. It stores food and water.
2. The cells contains chloroplast, hence photosynthesis takes place in parenchyma.
3. It provides and maintains turgidity of the stem.
4. It allows air to diffuse among the cells.
5. When parenchyma cells are less turgid or flaccid, it makes the leaves to drop thereby conserving water for the
plant.

Collenchyma
These tissues are found mainly in the cortex of stems and in leaves. It is the primary supporting tissues for many
herbaceous plants. Collenchymas cells have thick deposit of cellulose in their cell wall, they are living and elongated.
These cells are flexible and this enables the stem, root and leaf to bend without breaking.
Functions
1. It gives the plant strength and mechanical support.
2. It can carry out photosynthesis because it contains chloroplast.
3. It gives resilience and flexibility to plants

Sclerenchyma (fibre and sclereid)

Unlike collenchyma, the cells making up the sclerenchyma tissues are dead cells. There are two types of sclerenchyma
cells. These are the fibres and sclereids. The fibres are elongated, while the sclereids are usually roughly spherical.
They both consist of cell wall that is heavily thickened with deposit of lignin. Lignin is a hard substance with great
tensile and compressional strength. The sole function of sclerenchyma is to assist in providing support and mechanical
strength for the plant.
Functions
1. Fibres are used in the manufacture of twines, rope and textiles.
2. Fibres gives flexibility to plants and prevent them from breaking up easily.
3. Sclereids form the greater part of seed coat (testa) and nut shells, and occur in the bark of tree.
4. Sclerenchyma tissues occur in the vascular tissue, cuticles of roots and stems, where they give rigidity,
hardness and support to plants.

Xylem
The xylem tissue consists of many types of cells, tracheids, vessels, fibre and xylem parenchyma.
Tracheids are dead elongated cells with tapering end walls that is lignified and contains piths that aids the passage of
water and dissolve mineral salt. Tracheids also give strength and support to organs in which they occur. The vessels
help in upward transport of water and mineral salts. They also give strength and support to the plant. The function of
the fibres is for tensile strength and support.
The xylem has two main functions:
1. It conducts water and mineral salts from the roots to the stem and into the leaves, flowers and fruits
2. It supports the plant wherever it exists in a plant.

Example
(c) State: (i) Two functions of xylem tissues (2013/1c(i) Nov)
Answer:
i. Functions of xylem tissues:
- It conducts water and mineral salts from the roots to the stem and into the leaves, flowers and fruits.
- It supports the plant wherever it exist in a plant.

262
Example
Different tissues in plants contribute to the support of the parts as a result of the following characteristics except
A. malleability B. rigidity C. flexibility D. resilience E. hardness (1990/16).
Answer: A – Malleability is a physical property of metals that defines their ability to be hammered, pressed or rolled
into thin sheets without breaking. This is not a characteristics of plant tissues that contribute to support of parts of
plant.
Example
One of the functions of the xylem is
A. strengthening the stem B. manufacturing food C. reducing loss of water
D. conducting manufactured food E. storing unused sugar (1978/4 JAMB)
Answer: A – One of the functions of the xylem is to support and strengthen the stem. The other function is to conduct
water from the root to the rest parts of the plant.
Example
Which of these tissues serves the function of support and water conduction?
A. Parenchyma B. Collenchyma C. Sclerenchyma D. Xylem E. Phloem (1979/3 JAMB)
Answer: D – The xylem serves the function of support and water conduction.

EXERCISE 16.1
1. The following are the functions of supporting tissues in plants except
A. rigidity B. flexibility C. strengthening D. secretory (2000/11)
2. Which of the following tissues are made up of dead cells?
A. Meristematic B. Xylem vessels C. Cambium D. Mesophyll E.Palisade (1982/28 JAMB)
3. The supporting tissue of xylem is most poorly developed in
A. submerged water plants B. Desert plants C. man grove swamp plants D.Grassland plants (2002/39 JAMB)
4. If water that has been coloured red is poured at the base of a wilting plant, it will appear as a red stain in the
cells of the
A. Phloem B. Parenchyma C. xylema D. epidermis (2003/14 JAMB)

Phloem
The phloem is a mixture of living and dead cells which are elongated and tubular. The phloem consists of four types
of cells. These are the “sieve tube”, “companion”, “Phloem parenchyma” and the “phloem schlerenchyma (fibre and
sclerieds)” cells. Both the phloem fibers and sclereids have secondary cell wall that is thickened with lignin .This
makes them strong and water proof.
Functions
The sieve tubes help to transport organic solute (food) while the companion cells work in association with sieve tubes.
The phloem sclerernchyma are mechanical in functioin.

Example
(ii) One function of phloem tissues (2013/1c(ii) Nov)
Answer: It transports manufactured food from the leaves of a plant to the other parts of the plant.
Example
If the bark and phloem tissues of a woody shoot are peeled off by ringing, the whole plant will eventually die because:
A. water does not reach the leaves B. water and salts remain below the ringed portion
C. there is a withdrawal of water from the root by soil D. manufactured food does not reach the roots
E. the roots store too much water. (1980/30 JAMB)
Answer: D – The plant will die because manufactured food does not reach the roots. The phloem helps to transport
manufactured food from the leaves to the rest part of the plant which includes the root, hence, when the phloem is
peeled off, this function can’t be carried out.

EXERCISE 16.2
1. If the phloem of a healthy plant is killed by heat treatment the
A. upward movement of salts will cease B. food manufactured in the leaves will accumulate
C. whole plant will die immediately D. leaves of the plant will become yellow (1988/21 JAMB)
2. The phloem parenchyma is sometimes used for
A. food storage B. supporting the stem C. production of the sieve tube D. transporting water (1994/17 JAMB)

263
Mechanism of Support in Plants
The protective tissues of plants are epidermal cells found on the leaves and stem and piliferous layers in roots. It
prevents the inner cells from injury, infection and water loss. It does not contain chloroplast except in the guard cells
of herbaceous stems like the water leaf. The part between the epidermis and the vascular bundles is the cortex. The
parenchyma consists of large thin walled cells with many air spaces which permit air from the stomata or lenticels to
circulate to all parts. In dicotyledonous stems such as the sunflower, cambium is present between the phloem and
xylem. Cambium cells are constantly dividing cells. This constant division helps to increase the number of cells and
the process involved is known as secondary thickening. Secondary thickening is responsible for the increase in size
of the trunk of many trees.
The pitch is in the central part of the stem and is composed of parenchyma. In herbaceous plants, strength and rigidity
are achieved by a combination of turgor pressure and supporting tissues.
When the cells of the parenchyma tissues are fully expanded with water (turgid) they give rigidity and strength
(hydrostatic support) e.g. talinum, balsam est.
Wood makes stems strong and rigid. It is the wood in the trunks of tree that enables high tree to carry all their
branches, leaves e.t.c and prevent them from being broken into pieces by strong winds. Hence the more wood a stem
has, the more difficult it is to break it up with the hand.
Functions of Supporting Tissues in Plants
1. They give plants their distinct shape
2. They provide rigidity and strength to plant e.g. collenchymas, sclerenchyma and wood
3. They make the stem of herbaceous plants resilient and flexible so that the plants are not broken by the bending
and twisting movements caused by strong winds
4. They protect the delicate parts of the plants body e.g. cambium and phloem vessels

Internal Structure of Herbaceous Stem

The arrangement of tissues in dicot stem is different from that of monocot stem. A section of a dicot stem shows the
following arrangement of tissues from the circumference to the centre

i. Epidermis Outer Cylinder

ii. Cortex, including the endodermis
iii. Pericycle
iv. Vascular bundles Inner cylinder or stele
v. Pith and medulary rays

Stomata and lenticels are found between the epidermal cells. The cortex is made up of collenchymas and
parenchyma. The collenchymas form a strengthening hollow cylinder down the length of the stem. The inner most
layer of the cortex is bound by the endodermis (starch sheath). The pericycle is composed of sclerechyma. It forms
solid strengthening strands that run down the length of the stem. The vascular bundles are arranged in a ring within
the pericycle. Each bundle is made up of phloem, cambium and xylem. The pith consists of thin walled
parenchyma which extends between the vascular bundles as medullary rays.
A transverse section of monocot stems shows an epidermis and a ground tissue with vascular bundles scattered on
it. The vascular bundles are surrounded by sclerenchyma which forms hollow, strengthening cylinders that run down
the length of the stem. Cortex, Pith and Cambium are absent.
The collenchymas, sclerenchyma and xylem are the main supporting tissues in the stem. Turgid parenchyma is an important
supporting tissue in herbaceous stems. In woody stems, secondary xylem or wood is the main supporting tissue.
Ground tissues include all plant tissues except the dermal and vascular tissues. Thus, the cortex, pith and medullary
rays are part of the ground tissues. In monocotyledons, the cambium is absent in the vascular bundle.

Transverse Section of Young dicot stem Transverse Section of a young monocotyledonous

stem e.g maize.
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 Differences between the Internal Structures of Dicot Stem and Monocot Stem
Dicotyledonous stem Monocotyledonous stem
1. Collenchymas are located below epidermis Sclerenchyma are located below epidermis
2. The cortex is wide Cortex is narrow
3. The percicyle is made of sclerenchyma, caps The sclerenchyma is completely surrounded by each vascular
and individual bundles bundle
4. The vascular bundles are few and are arranged The vascular bundles are Numerous scattered all over the ground
in a ring of cambium tissues
5. Cambium is present Cambium is absent
6. Secondary thickening occurs Secondary thickening does not occur
7. Pith is present Pith is absent

Young root of dicotyledonous Transverse Section of a young monocotydedonous

plant in transverse section. root e.g maize.

Internal structure of a herbaceous root

The internal structure of a herbaceous dicot root shows that it is made up of
1. Epiblema/piliferous layer: Which has no cuticle and aid in water absorption.
2. Cortex: Made up of parenchymatous cells and helps to store food and water.
3. Endodermis/casparian strip: Situated between the pericycle and cortex. The endodermis contains starch grains.
4. Pericycle: From which lateral root originate.
5. Vascular bundles (xylem and phloem): Which aid water and food conduction.
The internal structure of a herbaceous monocot root is similar to that of a dicot root with few differences in the
vascular cylinder.
Differences between the internal structure of a dicot root and a monocot stem
Internal structure of a dicot root Internal structure of a monocot root
1. Pith is absent. Pith is large and well developed.
2. Secondary growth occurs leading to the development of No secondary growth and cambium is absent.
cambium and cork cambium.
3. Few phloem bundles are present. Many phloem bundles are present.
4. Has only xylem bundle which is star shaped and Xylem bundles are many and radially arranged.
centrally placed.
5. Xylem vessels are generally angular. Xylem vessels are oval or rounded.

Example
The diagram below represents a cross-section through a monocotyledonous root. Use it to Answer: questions 8 to 10.

The piliferous layer is labeled

A. I B. II C. III D. IV E. V
Answer: A – The label I points to the piliferous layer.
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The xylem is labeled
A. II B. IV C. V D. VI E. VII
Answer: The label V points to the xylem
The part through which manufactured sugar is transported is labelled
A. I B. III C. IV D. VII E. VI (1989/8-10)
Answer: The label VII points to the phloem which is the part through which manufactured sugar is transported

Example
Which of the following pair of tissues is responsible for strengthening the plants?
A. phloem and epidermis B. parenchyma and cambium C. collenchymas and sclerenchyma
D. collenchyma and cambium E. xylem and cambium (1995/8)
Answer: C – Collenchyma and Sclerenchyma are responsible for strengthening the plants.
Example
Which of the following tissues does not offer support in plants?
A. meristem B. sclerenchyma C. collenchymas D. xylem (2003/11)
Answer: A – Meristem is a type of tissue found in plants. it consists of undifferentiated cells capable of cell division.
It does not offer support in plants. all other options (B to D) offer supports in plants.
Example
The stem of young herbaceous plants is kept upright mainly by
A. osmotic pressure B. turgor pressure C. transpiration pull
D. suction pressure E. root pressure (1990/15)
Answer: B – The stems of young herbaceous plants are kept upright by turgor pressure.
Example
Which of the following is not found in the stem and root of monocotyledons?
A. xylem B. cambium C. pith D. cortex E. pericycle (1991/9)
Answer: B – Cambium is not found in the stem and root of monocotyledons.
NB: Cambium is only found in the stems and roots of dicotyledons. It is located between the xylem and phloem
tissues and responsible for the secondary growth of the stems and roots.
Example
The following are the functions of supporting tissues in plant except
A. rigidly B. flexibility C. strengthening D. secretory (2000/11)
Answer: D – Supporting tissues in plant are not secretory in function.
Example
The diagram below illustrates the transverse section of a

A. dicotyledonous root B. monocotyledonous root

C. dicotyledonous stem D. monocotyledonous stem (2017/11)
Answer: C – This is a dicotyledonous stem because the vascular bundles are well arranged around a central pith.
Example
The main difference between the cross sections of dicotyledonous and monocotyledonous stems is that the
dicotyledonous stem has
A. vascular bundles B. a well defined pith C. xylem for water conduction D. a defined epidermal layer (1999/13 NABTEB)
Answer: B – The main difference between the cross sections of dicotyledonous and monocotyledonous stem is that
the dicotyledonous stem has a well defined pith.
Example
Which of the following statements is a function of the root hairs of a plant?
A. manufacturing of plant food B. conduction of mineral salts and water
C. conduction of manufactured food D. conduction of mineral salts only (1999/14 NABTEB)
Answer: B – The root hairs help to conduct water and mineral salts from the soil into the xylem of the plant.
Example
(d) Mention three components of the vascular bundle. (2008/1d Neco) Answer: Xylem, Phloem and Cambium
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Example
Which of the following is not seen in the transverse section of a young monocotyledons stem?
A. parenchyma B. phloem C. xylem D. cambium E. sclerechynma (1991/25)
Answer: D – The young monocotyledonous stem does not have vascular cambium. This is why monocot do not
undergo secondary growth (thickening).
Example
Which of the following does not contribute to the support of a young herbaceous dicotyledonous plant?
A. Turgidity of the parenchyma cells B. Presence of cambium cells
C. Presence of sclerenchyma cells D. Presence of xylem tissue E. Presence of collenchyma cells (1995/17 Nov)
Answer: B – The presence of cambium cells is a young herbaceous dicotyledonous plant does not contribute to its
support. Cambium cells are responsible for secondary growth of the plant.

EXERCISE 16.3
1. 1(ai) State two main functions of roots
(ii) Make a diagram 8-10cm long of the transverse section of the stem of a dicotyledonous plant and label
fully.
(b) In a tabular form, state three differences between the functions of vascular tissues of plans and
skeleton of mammals (2013/1a-b Nov)
2. Which of the following tissues is not found in the stem and root of monocotyledons?
A. Xylem B. Cambium C. Pith D. Cortex E. Pericycle (1991/9 Nov)
3. Which of the following is not seen in the transverse section of a young monocotyledonous stem?
A. Parenchyma B. Phloem C. Xylem D. Cambium E. Sclerenchyma (1991/25 Nov)
4. One significant difference between roots and stem is that
A. branch roots originate in the pericyle while branch stems do not
B. stems are always above the ground while roots are always below the ground
C. stems are positively geotropic while roots are negatively geotropic
D. stems are sometimes used for storage while roots are never so used (1979/49 JAMB)
5. Which of the labelled tissues in Fig 3 is responsible for the transport of mineral salts and water in a living plant?

A. 1 B. 2 C. 3 D. 4 E. 5 (1981/10 JAMB)
6. Root hairs are developed from the
A. root apex B. epidermis of roots C. vascular bundles D. endodermis E. pericycle (1983/1 JAMB)
7. Which of the following is true of the transverse section of a dicot stem?
A. The epidermis is completely encircled by the cortex B. The xylem is more interiorly located than the phloem
C. The cambium lies between the cortex and the vascular bundles
D. The vascular bundles are randomly scattered within the cortex. (2010/11 JAMB)

Use fig. I to Answer: questions 2-4

fig I
8. Which of the following features can be used to identify Fig.I?
A. Position of 7 B. Its circular nature C. Number of 5 D. Presence of 3 E. Width of 2 (1983/2 JAMB)
9. The main function of 6 is to
A. separate 5 from 7 B. produce more of 5 and 7 C. produce cork D. translocate water and mineral salts
E. conduct carbon dioxide to the other parts (1983/3 JAMB)
10. The main function of 4 is to
A. surround the inner tissues B. produce cork C. produce of root hairs
D. produce lateral roots E. produce more of 3 (1983/4 JAMB)

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11. Which of the following statements is NOT true of the pilliferous layer of a root? It
A. has a very thin cuticle B. is the outmost layer of the cortex C. may bear root hairs
D. breaks down as the root ages E. is replaced by cork in old roots (1984/27 JAMB)
12. Which of the following is common to a dicotyledonous stem and a monocotyledonous root?
A. Medullary rays B. Central pith C. Wide cortex D. Narrow cortex E. Pericyclic fibres (1985/13 JAMB)
13. In a dicotyledonous stem, each companion cell is found beside the
A. endodermal cell B. xylem vessel C. sieve tube D. pericyclic fibre (1989/15 JAMB)

Use the diagram below to Answer: questions 24 and 25

14. The function of absorption is performed by the structure labelled

A. IV B. III C. I D. II (2002/24 JAMB)
15. The structure labelled I represents the
A. cortex B. Pericycle C. xylem D. Phloem (2002/25 JAMB)
16. In the internal structure of plants, a wide pith in the center is common to
A. dicot stems and monocot roots B. dicot roots and monocot roots
C. dicot roots and monocot stems D. dicot stems and monocot stems (2004/40 JAMB)
17. In the root vascular system, the stele is directly surrounded by the
A. parenchyma B. endodermis C. pericycle D. Cortex (2005/9 JAMB)

Internal Structure of a Leaf

The internal structure of a leaf consists of three main tissues these are the epidermis (upper and lower), the
mesophyll and vascular bundles.
The leaf is covered with a waxy coat called the cuticle, which prevents it from losing water. The one cell thick upper
and lower epidermis form the outer most layer of the leaf. The lower epidermis has numerous stomata through which
gases and water vapour enters and leave the leaf. Each stomata is surrounded by a pair of bean shaped guard cells
which are able to change their shape thus controlling the opening and closing of the stomata.
The tissue between the upper and lower epidermis is called the mesophyll tissue. The mesophyll tissue consists of the
upper palisade mesophyll and the lower spongy mesophyll. The palisade mesophyll contains numerous
chloroplast and are the main sites of photosynthesis in the leaf. The spongy cells contains fewer chloroplast.
The vascular bundles consists of the mid rib and vein. They form the conductive tissues of the leaf. The vascular
bundles includes the xylem which carry water to the leaf and the phloem which carry soluble food such as sugar away
from the leaf. These conducting tissues enters the leaf through the leaf stalk and pass down the centre of the leaf as a
thick bundle called the mid rib. Smaller bundles of vascular tissues, the veins, branches throughout the leaf lamina.
They form a network pattern in the dicot leaf but in a monocot leaf they are arranged in a parallel pattern.

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Example
Which of the following constitutes the main internal tissue of a leaf?
A. Cuticle B. Mesophyll C. vascular tissue D. Lower epidermis E. Upper epidermis (1989/1)
Answer: B – The main internal tissue of a leaf is composed of mesophyll.
Example
The mesophyll layer of a leaf consists of
A. wax and cutin B. cells with lignified walls
C. irregularly shaped collenchyma cells D. photosynthetic parenchyma cells (2009/27 Nov)
Answer: D – The mesophyll layer of a leaf consist of photosynthetic parachyma cell.

REVISION EXERCISE 16.4

1. Which of the following is not a tissue found in plants?
A. epidermis B. phloem C. xylem D. dermis E. mesophyll (1998/7)
2. Support in young plants is provided by
A. translocation B. guttation C. turgidity D. osmosis (2006/13)
Use the diagram to Answer: questions 4 – 6
I

II

III
IV

3. The above diagram represents

A. longitudinal section of a stem B. longitudinal section of a root C. cross section of a root
D. transverse section of a stem E. longitudinal section of a leaf (1998/7)
4. The part labeled II in the diagram
A. epidermis B. cortex C. phloem D. xylem E. cuticle (1998/8)
5. The part labeled IV in the diagram is the
A. peticycle B. pericycle C. cortex D. xylem (1998/9)
6. Different tissues in plants contribute to the support of the parts as a result of the following characteristics
except
A. malleability B. rigidity C. flexibility D. resilience E. hardness (1990/16)
7. Which of the following groups carry out similar functions in living things?
A. vertebral column, chitin, and guard cells B. sclerenchyma, cartilage and chitin
C. tendon, chitin and neuron D. collenchyma, intercellular spaces and blood vessels
E. blood vessels, lymph and shell (1995/6)
8. Which of the following pairs of tissues is responsible for strengthening the plant?
A. phloem and epidermis B. parenchyma and cambium C. collenchyma and sclerenchyma
D. collenchyma and cambium E. xylem and cambium (1995/8)
9. Which of the following is not a tissue found in plants?
A. Epidermis B. Phloem C. Xylem D. Dermis E. Mesophyll (1995/9)
10. Which of the following plant parts does not perform supportive function?
A. Parenchyma, xylem and colleenchyma B. Epidermis, Sclerenchyma and xylem
C. Parenchyma, collenchymas and sclerenchyma D. Sclerenchyma, xylem and collenchymas (2000/13)

11. Which of the following tissues does not offer support in plants
A. Meristem B. Sclerenchyma C. Collenchyma D. Xylem (2003/11)
12. 2(c) How Is support provided for in each of the following plants?
(i) Herbaceous plants (ii) Woody plants (2005/2c (i) (ii)
13. Which of the following reagents is used to test for the presence of glucose?
A. Fehling’s solution B. Hydrochloric acid C. Iodine solution
D. Million’s reagent E. Sudan III (2005/23 Neco)
14. c. (i) List two types of supporting tissues in plant (2018/3c(i) Neco)

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15. Support in herbaceous plants is provided by means of
A. flexibility B. flaccidity C. turgidity D. cell wall (2006/11 Nov)
16. Which of the following tissues is responsible for support in herbaceous plants?
A. Cambium B. Phloem C. Epidermis D. Parenchyma E. Cuticle (1998/10 Nov)
17. Which of these is not a supporting tissue in plants?
A. Collenchyma B. xylem C. phloem D. cambium E. parenchyma (1996/10 Nov)
18. Which of the following tissues does not function as a supporting tissue?
A. collenchyma B. parenchyma C. cork D. sclerenchyma (2000/15 Nov)

Tissues and Supporting System in Animals

Skeleton: The skeleton is the bony frame work or hard part of the body which provides support, shape and protection
to the soft tissues and organs in animals e.g. the skeleton of a rabbit is its bony frame work.
Biological Significance (Functions) of Skeleton
(1) The skeleton supports the animal and keeps its shape.
(2) It protects fragile but vital structures e.g. the brain.
(3) It provides a base for attachment of muscles
(4) Skeleton helps the animal in movement. This is possible because of the presence of a numerous joint in the skeleton
(5) Helps the animal in respiration especially the rib cage
(6) The skeleton helps to manufacture red and white blood cells. The white blood cells and the red blood cells are
manufactured in the bone marrows of the long bones.
(7) Skeleton helps in the transmission of sound waves e.g. the three small soft and light bones found in the middle
ear (malleus or hammer, incus or anvil, stapes or stirrups) vibrate and transmit sound waves from middle ear
to the inner ear.

Forms of Skeleton (The Skeletal Material)

1. Chitin: This is found in arthropod (such as insects and crustaceans). Chitinous exoskeleton limits the size and
weight of arthropods. Animals with skeleton made up of chitin can grow only by molting

2. Cartilage: These are semi-rigid but flexible connective tissue, devoid of blood vessels and nerves. They are
found in cartilaginous fish, rays, and shark. It is also found in several parts of adult human. Cartilage has several
functions in the human body. Some of them include preventing friction between the bones thus allowing free
movement, forming cushion in the socket of bones such as in hip sockets and glenoid cavity or shoulder. The ear
cartilage keeps the pinna erect so as to collect sound vibrations from the ear. The cartilage of the ribs enhances
breathing mechanism by allowing contraction and expansion of the thorax. In mammals, three different types of
cartilage can be seen. These are:
i. Hyaline cartilage which is presence in trachea, bronchi, protruding part of nose and moveable joints
ii. Elastic cartilage is found in the external ear and epiglottis.
iii. Fibro cartilage is found in the intervertebral disc of the vertebral column

3. Bones: This is found in vertebrates. It contains both living cells and non – living materials such as calcium,
phosphate and calcium carbonate. They often replace cartilage but cartilage never replaces bones. The laying down
of mineral substances in the bones is called ossification. The three bones of the ears are not ossified. They are the
smallest, softest and lightest bones in the body of man. Bones are a type of connective tissues and although bones
appear hard they are however not the hardest substance in the body of mammal. The hardest substance in a
mammalian body is dentine of the tooth.
Bones are classified based on their shapes and length into four groups namely:
i. Long bones e.g. humerus, radius, ulna, femur, tibia, fibula
ii. Short bones e.g. bones of vertebrae column, patella, phalanges, tarsals and metatarsals
iii. Flat bones e.g. scapula, ilium, skull
iv. Irregular bones e.g. malleus, incus and anvil

Example
Which of the following is not a function of the mammalian skeleton? It
A. gives the body its shape B. provides a framework on which internal organs are suspended
C. protects soft and delicate parts of the body D. provides attachment for muscles
E. contracts and relaxes to bring about movement (1990/11)
Answer: E – The mammalian skeleton does not contracts and relaxes to bring about movement.
NB: It is the function of the muscles to contract and relax to bring about movement.

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Example
Which of the following is not a skeletal tissue?
A. Plasma B. Chitin C. Cartilage D. Bone (2013/11) Answer: A – The plasma is not a skeletal tissue.
NB: The plasma is the liquid portion of the blood in which other component float. Options B to D are skeletal tissues.
Example
The following are functions of the skeleton except
A. providing support for the body B. protection of delicate internal organs
C. maintenance of the shape of the body D. providing attachment for muscles
E. controlling growth rate in animals (1991/7)
Answer: E – The skeleton does not control growth rate in animals.

EXERCISE 16.5
1. Which of the following structures is not a skeletal material?
A. chitin B. cartilage C. bone D. muscle (2017/23 NABTEB)
2. The skeleton functions as a
A. stimulus B. protective cover for delicate organs C. reproductive organ D. flagellum (1997/27 NABTEB)
3. The skeleton will perform the following functions except
A. production of blood cells B. destruction of old blood cells
C. protection of delicate organs D. support E. attachment of muscles (1997/5 Nov)
4. The bone is a
A. connective tissue B. simple epithelial tissue
C. columnar epithelial tissue D. fibrous tissue E. nervous tissue (1998/14 Health Science Nov)
5. List four functions of the mammalian skeleton and name a particular part of the skeleton which performs each
of these functions. (2005/2a)

Types of Skeleton
1. Exoskeleton
2. Endo skeleton
3. Hydrostatic skeleton
(1) Exoskeleton (External skeleton): This skeleton occurs on the outside of the animal. Arthropods e.g.
grasshopper, crab, beetles, scorpions, mosquitoes, have exoskeleton. Normally, the muscles of these animals are
attached to the inside of the skeleton. Exoskeleton limits growth and increase in size. Growth is therefore by molting
or ecdysis. The term exoskeleton may also be used to describe such hard parts as hairs, nails, hoofs, feathers and
scales. The snail also has exoskeleton.

(2) Endoskeleton: This is skeleton that is found inside the body of the animal and it is a characteristics of
mammals and other vertebrate. It consists of the bone and cartilage. Examples of animals with endoskeleton are rabbit,
dog, fishes, birds and man. These animals grow by continuous increase in size.

(3) Hydrostatic skeleton (fluid skeleton): Hydro static skeleton consists of liquid which presses outwards
against a muscular body wall. The pressure maintains the shape of the body and supports it. Example of organisms
that has such skeleton includes the earthworm and sea anemones

Parts of the Mammalian Skeleton

The mammalian skeleton is made up of two parts:
1. Axial Skeleton: This is consists of the skull, vertebral column, (backbone), ribcage and sternum.

2. Appendicular skeleton: This is made up of the pectoral girdle, the pelvic girdle and the limb bones. The
girdles connect the appendicular skeleton to the axial skeleton.

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 The Human Skeleton
Example
(ii) Name three types of skeletons found in animals, and in each case name one animal which possesses it. (2006/2a(ii)
Answer: a. Exoskeleton e.g. Grasshopper. b. Endoskeleton e.g. Man. c. Hydroskeleton e.g. Earthworm.
Example
The organisms that has a hydrostatic skeleton is
A. tilapia B. hydra C. mosquito larva D. earthworm (1999/2 JAMB) Ans: D – Earthworm has Hydroskeleton
Example
The process of shedding the exoskeleton of an arthropod is known as
A. ecdysis B. instar formation C. metamorphosis D. tagmosis (2015/13 JAMB)
Answer: A–The process of shedding the exoskeleton of an arthropod is known as ecdysis
Example
The scapula and the ischium are part of the
A. pectoral girdle B. appendicular skeleton C. pelvic girdle D. hind limb (2000/19 JAMB)
Answer: B – The scapular belongs to the pectoral girdle while ischium belongs to the pelvic girdle. The pectoral
girdle and the pelvic girdle together with the limbs attached to them form the appendicular skeleton.
Example
Use the diagram below to Answer: questions 4 and 5

Which of the organisms is characterized by the possession of a chitinous exoskeleton?

A. I B. II C. III D. IV (2008/4 JAMB)
Answer: A – The exoskeleton of cockroach(I) is made up of chitin.
Example
The chitin in the exoskeleton of many arthropods is strengthened by
A. Lipids B. proteins C. calcium compounds D. organic salts (2013/31 JAMB)
Answer: C – The chitin in the exoskeleton of many arthropods is strengthened by calcium compounds.

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Example
Which of the following structures is not a skeletal material?
A. chitin B. cartilage C. bone D. muscle (2018/11 JAMB) Ans: D – The muscle is not a skeletal material.
Example
Which of these is not part of the appendicular skeleton?
A. clavicle B. vertebral column C. scapula D. femur E. humerus (1994/32)
Answer: B – The vertebral column is not part of the appendicular skeleton. It is part of the axial skeleton.
Example
The axial skeleton is made up of the following
A. skull, vertebral column, rib cage and sternum B. limbs and limbs girdle
C. lumbar and thoracic vertebrae D. vertebral column and lumbar vertebrae (2004/10)
Answer: A – The axial skeleton is made up of: The skull, vertebral column, rib cage and sternum.

EXERCISE 16.6
1. The exoskeleton in insects is made up of
A. bone B. cartilage C. chitin D. tendon (2017/7 NABTEB)

2. Exoskeleton is a characteristic feature of

A. amoeba B. earthworm C. hydra D. millipede E. tapeworm (2018/13 Neco)
3. Which of these animals possess an exoskeleton?
A. earthworm B. obelia C. spider D. starfish E. tapeworm (2007/55 Neco)
4. The axial skeleton is composed of the
A. skull and vertebral column B. limbs and girdles C. atlas and axis D. radius and ulna (2010/11)

5. Which of these is not part of the appendicular skeleton?

A. Clavicle B. vertebra Column C. scapular D. Femur (2019/13 NABTEB)

6. Which of the following bones is not a part of axial skeleton?

A. Backbone B. limbs C. ribs D. skull E. sternum (2018/41 Neco)
7. Which of the following is not part of appendicular skeleton?
A. Tibia B. Humerus C. Radius D. Sternum (2003/18 Nov Health Science)
8. The axial skeleton of a mammal does not include the bone of the
A. skull B. tail C. limbs D. back E. neck (1984/39 JAMB)
9. The appendicular skeleton is made up of the
A. limbs B. skull and limbs C. phalanges D. ulna and radius E. girdles and limbs (1985/29 JAMB)

The Skull
The skull consists of two major parts these are the cranium and facial bones. The cranium has a number of individual bones tightly
fitted together at immovable (suture) joints. At birth, many of these joints are not completely fused together as bones leading to a
number of “soft spots” or “fontanelles”. The fontanelles do not completely join until the age of 14-18 months. It is the
fontanelles that enable the head of the baby to pass through the mothers pelvic during delivery.
The main bones making up the cranium include:
1. Frontal bone: Which make up the fore head.
2. Temporal bone: Making up the sides of the cranium.
3. Occipital bone: Forming the base of the cranium.
4. Parietal bone: Which consists of the top and side walls of cranium
It is also important to note the main bones of the face which are the cheek, nasal and jaw bones. The jaw bones consist of the
upper jaw bone(maxilla) which is fused together with the base of cranium and the lower jaw bones(mandible) which is hinged
with the cranium. This alignment of the jaw bones enables the mouth to open and close.

Parietal bone

Front view of the human skull Side view of the human skull

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Bone of the Vertebral Column
The vertebra column (backbone) is made up of 33 short bones, each one is called vertebra.
Functions of the vertebral column:
1. It protects the spinal cord
2. It supports the weight of the body
3. It absorb shock from a fall, jump or blow to the body
4. It enables the body to bend
5. It provides surfaces for attachment of muscles.

The vertebral column consists of the following:

1. Cervical vertebrae
2. Thoracic vertebrae
3. Lumbar vertebrae
4. Sacral vertebrae
5. Caudal vertebrae

Location of and distribution of the vertebrae in some animals

Region of the body Types of vertebrae Number in Rabbit Number in Rat Number in man
Neck Cervical 7 7 7
Chest (Thorax) Thoracic 12 – 13 13 12
Abdomen or waist Lumbar 6–7 6 5
Hip or loin Sacral 3–4 4 5
Tail Caudal 16 27 – 30 4
Total 44 – 47 57 – 60 33

Cervical Vertebrae
At the base of the skull, the vertebral column starts with the cervical vertebrae. The cervical vertebrae are seven in
number in all mammals. The first cervical vertebrae is known as the atlas, while the second is called the axis. The
third to seven bones are the normal cervical bones.
Characteristics of Cervical Vertebrae
1. The Centrum is relatively small.
2. The neural spine is short.
3. The neural canal is relatively large.
4. It has two vertebrarterial canals for the passage of blood vessels.
5. It has two cervical ribs or transverse process.

Atlas Vertebrae
Characteristics of Atlas
1. It has a large neural canal
2. It has rounded and wing – like transverse processes. (i.e flat and broad transverse processes )
3. The neural spine is very short or absent
4. The Centrum is absent
5. It has a vertebrarterial canal for the passage of blood vessels

Functions of the Atlas

It allows the head to nod on it (i.e. permits nodding of head) as it fits into the occipital condoyle of the skull
Articular facet
For dens

Anterior view of Atlas Vertebra Posterior view of Atlas Vertebra

274
Characteristics of Axis Skeleton
1. It has a well developed Centrum
2. It articulates with the atlas through the odontoid process
3. It has a large, flattened neural spine
4. The transverse process is reduced to a pig – like structure
5. It has a vertebrarterial canal

Functions of the Axis

It allows the head to be turned easily (i.e. twisting of the head).

g
Lateral view of the axis vertebra Anterior view of the axis vertebra

Normal Cervical Vertebra:

This includes the 3th, 4th, 5th, 6th and 7th cervical vertebrae. The special feature of normal cervical vertebrae is the
possession of a short bifurcate transverse process.

Anterior view of a normal cervical vertebra Posterior view of a normal cervical vertebra

Characteristics Features of Thoracic Vertebrae

1. Long neural spine
2. Transverse processes have articular facets for movement against the capitular facets and tubercles of the
ribs
3. The neural canal is circular
4. The Centrum has surfaces for articulation with the facets of the capitulum of the ribs

Anterior view of Thoracic Vertebra Lateral view of Thoracic Vertebra

275
 Anterior view of thoracic vertebra showing articulation with ribs
Functioning of Thoracic vertebrae
One of the functions of the thoracic vertebrae is to support the back. Their articulation with the ribs, allows them to
also provide a protective cage around the delicate organs of the thorax, including the heart and lungs.

Characteristics of the Lumbar Vertebrae

1. The Centrum is thick
2. The neural spine is stout
3. The transverse processes are long and broad
4. There are additional articulatory processes (metapophysis and anapophysis)
5. It has well developed pre and post zygapophyses

Anterior view of a Lumbar Vertebra Lateral view of a Lumbar Vertebra

Differences between Cervical and Thoracic Vertebrae

Cervical vertebra Thoracic vertebra
1. Short neural spine Long neural spine present
2. Prominent and bifurcate transverse process Less prominent transverse process
3. Presence of vertebrarterial canal. Absence of vertebrarterial canal.

Differences between Cervical and Lumbar Vertebra

Cervical vertebra Lumbar vertebra
1. Reduced transverse process Long and large transverse process
2. Small neural spine Neural spine broad and massive
3. Wide neural canal Narrow neural canal
4. Vertebrarterial canal present No vertebrarterial canal
5. Centrum small or absent Centrum present and well developed
6. Facet are few Facet are more
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Characteristics of Sacral Vertebrate
1. The bones are usually fused to form a solid mass of bone called sacrum
2. The first sacral vertebrae is bigger than the rest which decreases progressively in size
3. The first sacral vertebrae has a small neural canal
4. It has a large Centrum
5. It has a neural spine which is reduced to a small notch.
6. The first sacral vertebra has a pair of transverse process which is large and wing – like, but the others are
attached to the muscles of the back.

Function
They are joined to the pelvic girdle to provide support rigidity and strength.
N.B: The transverse processes of the first sacral vertebra are broad, and its facet articulate with the ilia of the pelvic
girdle.

Posterior view of the human sacrum Anterior view of the rat sacrum

N.B: The true sacral vertebrae are those whose transverse processes are attached to the ilia of the pelvic girdle.

The Caudal Vertebrae

It is reduced to mass of rectangular bone called Centrum. It has a projection on it for attachment of tail muscle. In
man, the caudal vertebrae is reduced to four bones which are fused together to form a structure called coccyx.
The coccyx is tucked in between the ischium. Hence in man no external tail.
Functions
1. The coccyx stabilizes the rigid pelvic girdle
2. Coccyx houses and protects blood vessels and nerves fibres from under the ischium
3. Supports the tail
Characteristics of Caudal Vertebrae
1. It has no neural spine
2. It has no neural canal
3. It appears as a solid, rectangular mass of bone
4. It has no transverse processes.

Ribs and sternum

The rib cage is formed by 12 pairs of ribs and the sternum. The sternum in humans consist of a single bone, while
that in rabbit is made up of 7 small bones. The ribs articulate with the thoracic vertebrae at the back and curve to the
front to attach, by means of elastic cartilage, to the sternum. However, in humans, only the first ten pairs are attached
to the sternum. The last two pairs remain free and are known as floating ribs. In the rabbit, the last three pairs form
floating ribs.

277
Summary of the vertebrae features

Types of vertebra Distinguishing features

Atlas 1. Very large neural canal.
2. No centrum.
3. A pair of facets for the articulation of the skull to permit nodding of the head.
4. Broad and flattened transverse processes.
5. A pair of vertebrarterial canal.
Axis - Large centrum modified into the odontoid process which makes it possible for the atlas to
rotate on the axis allowing sideways turning of the head.
- A pair of vertebrarterial canal.
- Small transverse processes.
- Large neural spine.
Cervical ● Has a pair of openings for the passage of vertebra arteries known as vertebrarterial canal.
● Short neural spine.
● The transverse processes are flattened and the outer parts divided into two.
They are known as cervical ribs.
Thoracic ♯ Large centrum.
♯ Large neural canal.
♯ Long neural spine which projects upwards and backwards.
♯ Two facets for articulating with a rib.
Lumbar i. Large and thick centrum.
ii. Long neural spine with upward and backward projections.
iii. Long transverse processes developed to provide surfaces for attachment of abdominal
muscles.
Sacral ▬ Fused to form a rigid structure known as sacrum.
▬ Narrow neural canal.
▬ The transverse processes of the first two articulate with the pelvic girdle.
▬ Reduced neural spine.
Caudal ○ They are fused.
○ Resembles a solid mass of stone.
○ No neural spine.
○ No transverse processes.

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Example
Which of the following vertebrae provide articulating surfaces for the ribs?
A. Thoracic B. Lumbar C. Cervical D. Sacral (2006/25)
Answer: A – The thoracic vertebral provide attituculation surfaces for the ribs.
Example
Use the diagram below to Answer: questions 12 and 13.

What type of vertebra is represented in the diagram?

A. Atlas B. Axis C. Cervical vertebra D. Sacrum E. Lumbar vertebra (1990/12)
Answer: E– The type of vertebrae represented by the above figure is the Lumbar vertebra
Example
The structure labeled A represents the
A. transverse process B. neural spine C. neural canal D. centrum E. metapophysis (1990/13)
Answer: C – Label A is the neural canal.
Example
Which of the following statements is not correct about the functions of each group of mammalian vertebrae?
A. Cervical vertebrae support the neck B. Thoracic vertebrae articulate with the ribs
C. Lumbar vertebrae provide attachment for abdominal muscles
D. Sacral vertebrae support the skull and allow nodding and rotating movements
E. Caudal vertebrae support the tail and provide attachment for tail muscle (1990/14)
Answer: D – The sacral vertebrae does not support the skull and does not allow for nodding and rotating movements.
NB: The sacral vertebrae helps to provide support, rigidity and strength to the pelvic girdle.
Example
The thoracic vertebrae differs from all other vertebrae by possession of
A. long neural spine B. odontoid process C. vetebrarterical canal D. large Centrum E. transverse process (1996/9)
Answer: A – The thoracic vertebrae differs from all other vertebrae by the possession of long neural spine.
Example
Study the list below and use it to Answer: questions 10-12
The vertebral column of mammals consists of the following:
i. Lumbar vertebrae ii. Thoracic vertebrae
iii. Caudal vertebrae iv. Cervical vertebrae V. sacral vertebrae
Which of the following are found immediately next to the skull?
A. I B. II C. III D. IV E. V
Answer: D – The cervical vertebrae (iv) is directly next to the skull.
Which of the following articulates the ribs?
A. I B. II C. III D. IV E. V
Answer: B – The thoracic vertebrae (ii) articulate the ribs.
Which of the following articulates the pelvic girdle?
A. V B. IV C. III D. II E. I (1996/10-12)
Answer: A – The sacral vertebrae (v) articulate the pelvic girdle.
Example
Which of the following groups of vertebrae have two branches at the end of their transverse processes?
A. sacral B. throcic C. cervical D. lumbar (2004/9)
Answer: D – The lumbar vertebrae have two branches at the end of their transverse process.
Example
2.(a)(i) Describe three features of a typical vertebra. (2006/2a(i)
Answer:
- Neural canal – For the passage of the spinal cord.
- Centrum – It is a solid piece of bone.
- Neural arch – Forms an arch over the centrum and it surrounds the neural canal.
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Example
The diagram below illustrates a part of the mammalian skeleton. Use it to Answer: questions 13and 14

The part of the mammalian skeleton illustrated in the diagram is the

A. atlas vertebrate B. axis vertebrate C. cervical vertebrate D. thoracic vertebrae
Answer: C – The diagram illustrates a typical cervical vertebrae .
The function of the part labeled I is to
A. provide support to the spinal cord B. provide surface for attachment of the muscle
C. carry the spinal cord D. articulate with adjacent vertebrae (2015/13-14)
Answer: C – The part labeled I helps to carry the spinal cord or it serves as passage for the spinal cord.
Example
Which of these vertebrae has an odontoid process?
A. atlas B. axis C. lumber D. thoratic (2017/41 NABTEB)
Answer: B – The odontoid process is found in the axis (the second cervical vertebra).
NB: The odontoid process is also known as dens.
Example
Which of the following structures occupies the neural canal of the vertebral column?
A. cerebellum B. hypothalamus C. medullar oblongata D. spinal cord (2018/16 NABTEB)
Answer: D – The spinal cord occupies the neural canal.
Example
The main feature that distinguishes a thoracic vertebra from cervical vertebra is the possession of
A. cervical ribs B. long neural spines C. short neural spine D. anapophysis E. neural arch (1998/9 Nov)
Answer: B – The presence of long neural spines distinguishes a thoracic vertebra from a cervical vertebra.
Example
The lumbar of the mammalian skeleton has a well-developed centrum in order to
A. reduce the number of vertebrae B. adequately protect the spinal cord
C. bear the weight of the body D. provide surface for attachment of the transverse process (2013/9 Nov)
Answer: C – The lumbar of the mammalian skeleton has a well-developed centrum in order to bear the weight of the
body.
Example
The main distinguishing features of the axis vertebrae is the presence of
A. Odontoid process B. occipital condyle C. long neural spine
D. prezygapophysis E. vertebraterial canal (1996/8 Nov)
Answer: A – The main distinguishing features of the axis vertebrae is the presence of odontoid process.
Example
Which of these statements is not true about the vertebral column in man? The
A. Column protects the spinal cord B. caudal bones fuse to form coccyx
C. vertebrae provide good examples of synovial joints D. thoracic vertebrae is made up of twelve bones
E. lumbar vertebrae are stout (1996/9 Nov)
Answer: C – Vertebrae joints are not good examples of synovial joints.
NB: The kind of joint that occurs in the vertebrae is cartilaginous joint.
Example
The atlas vertebra distinguished from the other vertebrae by the
A. presence of neural arch B. presence of neural canal
C. presence of odontoid process D. complete absence of neural spine (1992/16 Nov)
Answer: D – Complete absence of neural spine, distinguishes the atlas vertebra from other vertebrae.
Example
The first bone of the vertebral column located in the neck region is called
A. Atlas B. axis C. caudal D. cervical E. thoracic (2001/6 Neco)
Answer: A – The atlas vertebra is the first bone of the vertebral column located in the neck region.

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EXERCISE 16.7
1. A bone with large centrum, neural canal and long spine can be found around the
A. chest B. neck C. skull D. tail E. Milk (2007/32 Nov)
2. The vertebra which has a long neural spine is the
A. lumbar vertebra B. sacral vertebra C. thoracic vertebra D. cervical vertebra (2013/19 Health Sc)
3. Which of the structures listed below is peculiar to the Axis vertebra?
A. Odontoid process B. Anterior zygapophysis C. Posterior – zygapophysis
D. Lateral spine E. Centrum (1979/8 JAMB)
4. The joint between the atlas and axis vertebrae allows for
A. rotary movements only B. up and down or nodding movements only
C. rotary and nodding movements D. no movement at all E. slight movement (1980/14 JAMB)

5. Which of the parts are used to recognize the bone in fig. 2?

A. 1 and 4 B. 2 and 3 C. 3 and 5 D. 1, 2 and 6 E. 4 and 5 (1982/46 JAMB)
6. Which of the following types of vertebrate occur in equal numbers in the rabbit, rat and man?
A. Caudal B. Thoracic C. Lumbar D. Cervical E. sacral (1984/26 JAMB)
7. Two main distinguishing features of the cervical vertebra are the presence of
A. short neural spine and vertebral canal B. prezygapophysis and cervical ribs
C. large centrum and cervical ribs D. vertebraterial canal and large centrum (1986/32 JAMB)
8. Which of the following vertebrae lacks a centrum?
A. Atlas B. Axis C. Thoracic D. Lumbar (1991/31 JAMB)
9. The bone of the neck on which the skull rests is known as the
A. odontoid process B. axis C. atlas D. occipital condyle (1992/21 JAMB)
10. Which of the following is the correct order of the vertebrae along the spinal column?
A. Axis → atlas → thoracic → lumbar → cervical → sacral
B. Atlas → cervical → axis → thoracic → lumbar → sacral
C. Atlas → axis → cervical → thoracic → sacral → lumbar
D. Atlas → cervical → thoracic → lumbar (1993/24 JAMB)
Use the diagram below to Answer: questions 38 and 39.

11. The bones labelled II are called

A. lumbar vertebrae B. thoracic vertebrae
C. cervical vertebrae D. sacral vertebrae (2004/38 JAMB)
12. The type of joint between adjacent bones in the part labelled II is the
A. hinge joint B. ball-and socket joint C. suture joint D. sliding joint (2004/39 JAMB)
13. The unique characteristic of the cervical vertebrate in the presence of
A. large centrum B. long transverse processes
C. zygapophysis D. vertebraterial canal (2006/8 JAMB)

281
 Use the diagram below to Answer: the question that follows

14. The type vertebra represented in the diagrams is

A. Atlas B. Lumbar C. Axis D. Sacrum (2016/49 JAMB)
15. The structure labelled I is
A. centrum B. neural canal C. neural spines D. transverse process (2016/50 JAMB)
16. The vertebrae that allows the skull to nod and rotate are
A. axis and cervical B. atlas and thoracic C. axis and atlas D. atlas and cervical (2017/34 JAMB)

Long Bones of the Appendicular Skeleton

The appendicular skeleton is composed of the pectoral girdle, the pelvic girdle, the fore limbs and hind limbs. The
pectoral girdle consists of scapula or shoulder blade, the clavicle or collar bone and coracoid. In mammals, the scapula
and coracoids are fused to form what is called scapula – coracoid. The scapula is a flat bone. It has one head – like end
with two processes, the coracoid process and acromion with a a deep notch called glenoid fossa or cavity. The rounded
head of humerus fits into the glenoid cavity in a ball and socket joint. Triceps muscles originated at the scapula and
head of humerus.

Anterior view of the scapula of a mammal Posterior view of the scapula of a mammal

Fore Limb
The fore limb is made up of the “humerus” in the upper arm and “ulna and radius” in the lower arm, carpals in the
wrist and phalanges in the digits.

Anterior View of Humerus of Mammal

282
Functions of the Humerus
1. It forms attachment surface for biceps and tricep muscle.
2. The bicipital groove anchors the biceps muscle.
3. It forms the ball and socket at the shoulder.
4. It forms the hinge joint at the elbow.
5. It allows free movement of the arm.

Radius and Ulna

The radius and ulna form the bones in the lower arm. The radius is shorter and lies on top of the ulna. They both form
the sigmoid notch into which the trochlea of humerus fits in the elbow joint.

Anterior View of Radius and Ulna of Mammal

Functions of Radius and Ulna

1. They are the point of attachment for the insertion of the biceps and triceps muscles
2. They provide large surface area for attachment of extensor and flexor muscles of the lower arm
3. The muscles attached to radius and ulna contract and relax to move the hand and digits

Carpals
This comprises of the wrist bone which are eight in number and irregular in shape. The wrist bone are held together by
tough ligament.

Functions
They form a hinge joint which allows for the movement of the hand along one plane.

Metacarpals
These are the bones of the hand. There are five metacarpals in one hand. The thumb has the shortest metacarpal

Functions
1. They form the shape of the hand
2. They provide surface area for the attachment of muscles of the palm

Phalanges
These are the bones of the digit. They are the bones that make up the hands and toes of the foot. Three phalanges can
be seen on each finger and toe with the exception of the thumb and large toe which possess only two. There are a total
of 56 phalanges in the human body with each hand and foot having 14 each.

Functions
1. They support the digit
2. They are used for gripping and holding on to objects
3. They are use for walking in tetrapod animals
4. They bear claw which are used for climbing and digging in some animal such as rat

283
 Carpals, Metacarpals and Phalanges of a Mammal

Hind – Limbs
The hind limb is made up of the femur or thigh bone; tibia and fibula in the leg; the tarsal in the ankle, the metatarsals
of the foot and the phalanges of the digits. The femur is the largest/longest bone of the body.

Functions of the Femur

1. It forms a ball and socket joint with the ilium allowing free movement of hind limbs
2. Forms attachment surface for the thigh muscles
3. The distal end forms a hinge joint with the patella, tibia and fibula

Anterior View of Femur

Functions of Tibia and Fibula

1. Provides large surface area for the attachment of muscles of the leg
2. Muscles that move the foot have their origin attached to the tibia and fibula
3. They form the ankle joint which allows the movements of the foot along the plane

284
 Anterior of the tibia and fibula of a human
Tarsal, Metatarsals and Phalanges
The tarsal are the ankle bones and are eight in number. They are arranged irregularly in two rows. The tarsal provide attachment
surface for the strong muscles of the leg. They form the ankle for the movement for the movement of the foot along one plane.
Muscles for moving the foot and toes are attached to the tarsal
Metatarsals are the foot bone and they are five in number. The metatarsal support the foot used for walking. Secondly, metatarsals
bear phalanges of the toes and support them. Lastly, it provides surface area for the attachment of the foot and toe muscles.
Phalanges are the bones of the digits or toes. The big toes have two phalanges. The remaining four toes have three phalanges each.
The phalanges support the toes used for walking, gripping and digging. Secondly, it provides surface area for the attachment of
muscles of the foot and toes.

The Tarsals, metatarsals and phalanges of a human

The Pelvic Girdle

This consists of ilium (hip bone), ischium and pubis which are fused together on each side of the body as the in-nominate bone.
The three bones are joined together at the pubic symphysis. The distal ends of these bones form a cavity called acetabulum into
which the head of femur fits to form the ball and socket hip joint.

Pelvic girdle of a human Pelvic girdle of a rat

285
Example
Which of the following statements is correct? The
A. Bicep muscle has its origin in the head of the humerus
B. Biceps muscles is inserted in the ulna
C. Tricep muscles originated at the scapula and head of the humerus
D. Ulna is pulled up when biceps relax
E. Radius is the point of insertion of triceps muscles (1995/7)
Answer: C – Tricep muscles originated at the scapular and head of the humerus. All other options (A, B, D and E) are
not correct.
Example
Which of these is not part of the appendicular skeleton?
A. clavicle B. atlas C. scapula D. femur E. humerus (1994/32)
Answer: B – The atlas is not part of the appendicular skeleton. NB: It is part of the axial skeleton
Example

Fig. 1 HUMAN ARM PART OF SKELETON OF HUMAN ARM

The bone labelled X in fig 4 is the
A. Ulna B. fibula C. radius D. humerus E. tibia (1981/18 JAMB)
Answer: D – The bone labeled X is the humerus.
The joint at Y in Fig 4 is
A. ball and socket B. hinge C. pivot D. rivet E. none of the above (1981/19 JAMB)
Answer: B – The joint at Y is a hinge joint
Example
Study the diagram below. Use it to Answer: questions 12-14

Which of the following bones is illustrated in the diagram?

A. Tibia B. Humerus C. Patella D. Scapula (1999/12)
Answer: D – The bone illustrated in the diagram above is the scapula.
Example
The part labelled I in the diagram is for the attachment of
A. ribs B. biceps C. shoulder muscles D. the vertebral column (1999/13)
Answer: C – The Part Labelled I is for the attachment of shoulder muscles
Example
Which of the following bones forms a joint at the point labeled II in the diagram?
A. Humerus B. Sternum C. Radius D. Femur (1999/14)
Answer: A – The humerus forms a joint at the point labeled II.

286
Example
Study the diagram below and use it to Answer: questions 13 to 15

The piece of bone represented in the diagram is found in the

A. pelvic region B. pectoral girdle C. vertebral column D. skull E. thoracic region
Answer: A –The piece of bone represented in the diagram is found in the pelvic region.
The part labeled I is the
A. lumbar B. sacrum C. illium D. pubis E. coccyx
Answer: C – The part labeled I is the ilium
The bone that articulates with the part labeled III is the
A. humerus B. femur C. tibia D. sacrum E. fibula (1989/13-15)
Answer: B – The femur is the bone that is articulated at label III.
Example
Study the diagram below and use it to Answer: questions 7 and 8.

To form a ball and socket joint, the structure labelled I fits into another structure in the scapula called the
A. blade B. glenoidcavity C. olecranon fossa D. patella
Answer: B – Structure labeled I fits into the glenoid cavity present in the scapula.
The structure labelled II is called
A. deltoid ridge B. trochanter C. shaft D. trochlea (2008/7-8)
Answer: C – The structure labeled II is the shaft of the humerus.

EXERCISE 16.8
Use the diagram below to Answer: questions 37 – 39

1. The structure marked V serves as

A. Passage of blood vessels B. passage of nerves C. point of attachment of muscles
D. point of articulation with other bones E. support for the chest (2005/37 Neco)
2. Which of the following bones fits into the structure labeled IV?
A. femur B. Humerus C. ribs D. tibia E. ulna (2005/38 Neco)
3. In which region of the body is the diagram illustrates in Fig.3 found?
A. Abdominal B. chest C. neck D. tail E. waist (2005/39 Neco)
4. 1b. List five types of bones found in the forearm of man. (2018/1b Neco)
287
 Use the diagram below to Answer: questions 16 and 17

5. The bone labeled II in the diagram above is the

A. scapula B. clavicle C. humerus D. femur (2000/16 Nov Health Science)
6. In which of the following parts of the body is the structure illustrated in the diagram above found
A. Elbow B. Hip C. Shoulder D. Leg (2000/17 Nov Health Science)
Uuses the diagram below to answer question 33 – 34

7. The structure labeled II articulates with III to form a

A. sliding joint B. hinge joint C. pivot joint D. ball-and-socket joint (2019/33 JAMB)
8. Which of the bones is the radius?
A. I B. II C. III D. IV (2019/34 JAMB)

Joints
A joint is a regoin of the skeleton where two or more bones articulates each other. The different types of joints are:
immovable joints, slightly movable and moveable joints.

Human knee joint

Immovable joints
Two or more bones are in close contact, but no movement can occur.
Examples of immovable joint includes:
1. Suture joint e.g skull
2. Fused joint e.g sacrum

Slightly movable
In this type of joint the bones are connected by cartilage which allows for s slight movement.
Examples of slightly movable joint includes:
1. Joint of vertebrae column
2. Joint of the hip bones

288
Moveable joints
In this type of joint the opposing bony surface are covered with a layer of cartilage, it allows for some degree of free
movement
Examples of moveable joint include:
1. Hinge joint – permit movement one direction e.g. elbow joint, knee joint, finger joints.
2. Sliding of gilding or double hinge joint which permits movement in two planes e.g. wrist and ankle joints.
3. Ball and socket joint permits movement in all direction e.g. hip joint and shoulder joint
4. Pivot joint which permits rotatory movement e.g. in the neck between the atlas and the axis.

Ball and socket

Example
What kind of joint can be found in the hip and shoulder?
A. hinge joint B. pelvic joint C. elbow joint D. ball and socket joint (1999/29 NABTEB)
Answer: D – Ball and socket joint is found both at the shoulder and the hip.
Example
2(a) (i) What is a joint? (ii) List three types of movable joints and mention one location in the mammalian body of
each type (b)(i) Make a labeled diagram, 8 – 10 cm long, off a typical movable joint. (ii) Explain how the structure of
the joint adapts it to its function. (2004/2ai, ii, iii)
Answer:
2ai. A joint is a region of the skeleton where two or more bones articulate each other.
ii. Types of movable joints:
- Pivot joint located in the neck.
- Ball and socket joint located in the hip.
- Hinge joint located in the elbow.

bi. A well labeled diagram of a typical movable joint:

ii. Cartilage is present in order to reduce friction between the two or more bones that are involved in the joint.
Ligament helps to hold different bones together that are involved in the joint. The synovial membrane secretes
the synovial fluid which helps to lubricate the joint thereby minimizing or reducing friction and shock.

289
Example
(ii) Name four types of joints found in the mammalian skeleton. (2006/2b ii)
Answer: Ball and socket joint, Hinge joint, Gliding joint and Pivot joint.
Example
The longest bone in animal body is the
A. humerus B. scapula C. tibia D. femur (2017/22 NABTEB)
Answer: D – The femur is the longest and strongest bone in the body of animal.
Example
When the lower arm acts as a lever, the fulcrum is located at the
C A. deltoid muscle B. wrist joint C. humerous bone D. elbow joint (2000/20 Nov Health Science)
Answer: D – When the lower arm act as a lever, the fulcrum is located at the elbow joint.

Example
Use the diagram below to Answer: questions 42 and 43

The part labeled II is the

A. bone B. hyaline cartilage C. ligament D. synovial cavity E. synovial membrane (2018/42 Neco)
Answer: C – The label II is the ligament.

EXERCISE 16.9
The diagram below is an illustration of a hinge joint in the mammalian skeleton. Use it to Answer: questions 10
and 11

1. The name of the part labeled II is

A. humerus B. trochlea C. synovial fluid D. olecranon process (2013/10 Nov)
2. The function of the part labeled I is to
A. secrete synovial fluid B. prevent the wearing of body surfaces
C. prevent the wearing of body surfaces D. holds the bone of the joint in position (2013/11 Nov)
3. Friction at a joint is prevented by
A. synovial fluid B. capsule C. tendon D. lymph (2003/20 Nov Health Science)
4. A hinge joint may be found at the
A. shoulder B. hip C. neck D. knee E. wrist (1998/15 Nov Health Science)
5. The two halves of the pelvic girdle are joined together at the
A. pubic symphysis B. ileum C. pubis D. obturactor foremen (2010/33 JAMB)
6. The longest bone in the body is the
A. humerous B. femur C. scapula D. tibia (2018/10 JAMB)

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Muscles
The single celled protozoan ancestors of animals had their weight supported by water and were able to move by cilia
or other simple oraganelles. The evolution of large and more complex organisms (animals) gave need to the
development of support and locomotion system. Animals use their muscle and skeletal system for support, locomotion
and maintaining their shape.

A muscle consist of muscle tissues which contract together to produce a force. There are about 600 muscles in the
human body. Muscles have a range of functions from pumping blood and supporting movement to lifting heavy
weights or giving birth. Muscles causes movement by contracting or relaxing and this movement may be voluntary or
involuntary.

Types of muscles
The three main types of muscles include:

1. Skeletal muscles: These are muscles that are attached to the bones and allow movement. Skeletal muscles are
under our conscious control which is why they are also known as voluntary muscles. Another term used for
this is striated muscles since they look stripped when their tissues are viewed under a microscope. Functions
of voluntary muscles include:
i. Lifting and carrying of weight
ii. Movement of the body in walking, running, jumping etc,
iii. Pulling, pushing and throwing of objects.

(2) Smooth muscles: These are also known as involuntary muscles, since their action happens without our
conscious awareness. Smooth muscles are arranged in layered sheets and are located in various internal
structures including the digestive tract, uterus and blood vessels such as arteries. Function of smooth muscles
includes
i. The smooth muscles in the uterus help a woman to push out her baby.
ii. The smooth muscles in the lungs, helps the air way to expand and contract as necessary.
iii. Smooth muscles move food through the digestive tract.
iv. Smooth muscles determine the flow of blood in the arteries.
v. The smooth muscles in the eye acts to change the size of the iris and the shape of the lens.

(3) Cardiac muscles: This muscle is specific to the heart. The heart contracts and relaxes without our conscious
awareness. Cardiac muscles are also striated. Due to the above facts, cardiac muscles are the intermediate
between the skeletal and involuntary muscles.

Make-up of muscles
Skeletal, smooth and cardiac muscles have very different functions, but they share the same basic composition. A
muscle is made up of thousands of elastic fibres bundled tightly together. Each bundle is wrapped in a thin transparent
membrane called a perimysium. The entire muscle is bounded by a membrane called epimysium. All individual
muscle fibre is made up of blocks of proteins called myofibrils, which contain a specialized protein (myoglobin) and
molecules to provide the oxygen and energy required for muscle contraction.

Fasicle

Cross section of a muscle

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How Muscles Interact with Bones to Bring About Movement
A muscles is attached to a bone by a though fibrous material called tendon. Each muscle has at least two point of
attachment. One point of attachment called the origin is to the bone that does not move. The second point of
attachment called the insertion is to a long bone that moves. Between the origin and the insertion a bone often passes
across a joint. This joint forms a pivot.
When the muscles contracts, it moves the moveable bone closer to the bone that does not moves.

Differences between a Bone and a Cartilage

Bone Cartilage
1. It is hard because it is made up of hard substances It is relatively soft because it is made up of soft substances
2. It is not elastic It is elastic
3. It is composed of mineral salts It is not composed of mineral salt
4. Bone cannot be replaced by a cartilage cartilage can be replaced by a bone
5. Has blood vessels Has no blood vessels in adult

Side View of a Rib

Example
Muscles are attached to bones by means of
A. ligament B. cartilage C. synovial membrane D. tendons E. connective tissue. (1991/8)
Answer: D – Muscles are attached to bones by means of tendons.
Example
(b) Briefly describe how muscles and bones bring about movement at the elbow. (2005/2b)
Answer: The muscles that are involved in the movement at the elbow are the triceps and biceps. When the biceps
muscles contracts, it pulls the radius of the forearm, causing the forearm to flex. At this time, the triceps muscle is
relaxed. When the triceps muscle contracts, it pulls the ulna of the forearm, causing the forearm to extend. At this
time, the biceps muscle is relaxed.
Example
Intercostal muscles are found in the _____ region
A. abdominal B. chest C. head D. limb E. neck (2008/32 Neco)
Answer: B – Intercoastal muscles are found in the chest region. These are muscles between ribs.
Example
(ii) Mention two muscles that bring about movement of a forearm (2018/2b(ii) Neco)
Answer:
- Biceps muscles.
- Triceps muscles.

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EXERCISE 16.10
1. When the biceps muscle of the arm contract, the
A. scapula moves toward the sternum B. triceps muscle also contracts
C. forearm straights D. forearm bends (2000/14 Nov)
2. Muscles are attached to bones by means of
A. ligament B. cartilage C. synovial membrane D. tendons E. connective tissue (1991/8 Nov)

3. A muscle end which is attached to an immovable bone is called

A. insertion B. origin C. deltoid D. triceps E. tendon (1996/17 Nov Health Science)
4. Which of the following types of muscle is found in the heart?
A. Voluntary muscle B. Striped muscle C. Smooth muscle
D. Striated muscle E. Cardiac muscle (1998/16 Nov Health Science)
5. Muscles are indirectly attached to bones by means of
A. ligaments B. membrane C. tendons D. sutures (1990/26 JAMB)

REVISION EXERCISE
1. Which of the following does not function as support in animals?
A. cuticle in arthropods B. scales in birds C. cartilage in mammals
D. body fluid in earthworm E. bones in vertebrates (199/60)
2. Which of the following contains a non – supporting structure in animals?
A. cartilage, bone and pseudopodia B. pellicle, chitin and bone
C. humerus ribs and cartilage D. femur, pellicle and chitin (2001/14)
3. The longest bone in the body is the
A. humerus B. femur C. scapula D. tibia (2009/13).

4. Which of the following part of the skeleton does not have a protective function?
A. ribs B. carpals C. skull D. pelvis (2008/9)
The diagram below illustrates a part of the human skeleton. Study it and Answer: the questions 19 – 21.

5. The diagram represents the bones of the

A. upper arm B. lower arm C. upper leg D. lower leg (2017/19)
6. Which of the labeled parts articulates with the head of the trochlea to form a hinge joint?
A. I B. II C. III D. IV (2017/20)
7. The labeled part that provides surface for the attachment of the triceps is
A. I B. II C. III D. IV (2017/21)
8. Which of the following groups of supporting tissues is found Animals?
A. Parenchyma, collenchyma, sclerenchyma
B. Chitin, cartilage, bone
C. Sclerenchyma, chitin, cartilage
D. Pectoral girdle, pelvic girdle, collenchyma’s
E. Cervical vertebrae, parenchyma chitin (1994/11 Nov)
9. The main function of the compressible cartilage pads in bones is to
A. prevent friction B. provide nutrients
C. produce fluids D. prevent movement (2019/10 PC2)
10. In the lever system, the head rocking on the vertebral column is an example of the
A. first class order B. second class order C. third class order
D. first and second class order E. second and third class order (1996/18 Nov Health Science)
11. Which of the following postural defects is described as the lateral curvature of the spine?
A. Bow leg B. Knock leg C. Scoliosis D. Kyphosis E. Lordosis (1996/19 Nov Health Science)
12. Which of the following parts of the skeleton does not have a protective function?
A. Ribs B. Carpals C. Skull D. Pelvis (2008/9)

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Movement
Movement is the ability to living organisms to migrate from one place to another. Some of the reasons why organisms
move include searching for food, escape from danger, response to stimuli (either positively or negatively) and for the
sake of reproduction. All organisms that can move are equipped with various organelles or organs and mechanisms for
movement.

Cyclosis (Cytoplasmic streaming or Protoplasmic streaming)

Cyclosis can be defined as the streaming of the cytoplasm and its contents within a living cell without deformation of
the external membrane. This streaming might be restricted to a particular region of the cell or it might involve the
whole cytoplasm but in all, substances are transported from one region of the cell to another.

Cytoplasmic streaming
Functions of Cyclosis
1. In the cytoplasm, inter-charge of materials between the organellles in the cell occur partly by cyclosis.
2. The chloroplasts of some plants move independently (when the source of light is altered) by cyclosis thereby
placing their broad surface parallel or perpendicular to the surface of the leaf in order to receive sufficient
sunlight for photosynthesis.
3. The streaming of the food vacuole in paramecium is brought by cyclosis.

Movement in Amoeba: The typical type of movement that an amoeba exhibits is called “amoeba-like movement” or
“Amoeboid movement”.
The formation of pseudopodia and sol-gel transition enables the amoeba to move. Pseudopodia are protuberances
formed from the body of the amoeba. They aid not only in movement but also in capturing preys. In the sol-gel
transition, the cytoplasm present in the cell changes from fluid to solid and vice versa. The fluid state is known as
plasma-sol and solid state is known as plasma-gel hence the name sol-gel. Amoeba is capable of propelling itself
only when its cytoplasm is in fluid (sol) state.

Movement in Amoeba

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Movement in Euglena: Euglena carries out two methods of movement.
(i) Slow creeping (euglenoid) movement.
(ii) Flagella movement.
i. Slow creeping is carried out by gradual change of the shape of the whole cell. In this process, a contractile
wave passes along the body from the anterior end to the posterior end and the animal creeps forward. The
body becomes shorter and widen first at the posterior end. The organism thus progresses slowly

A Slow creeping (euglenoid) movement in Euglena

ii. Flagella movement is the chief means of locomotion in euglena. It takes place by the lashing of the
flagellum. The flagellum draw back water and propel the animal forward rapidly.

Flagella movement in Euglena

Movement in paramecium: Movement in paramecium is brought about by the beating action of its cilia. The cilia
beat in unison against the water current in a particular direction. If for example, the organism wants to move forward,
beating of the cilia will be at an angle in the backward direction. The beating of the cilia can also happen in the reverse
direction and this will also reverse the direction of movement.

Movement of paramecium
Example
State the structure used by each of the following organism for movement?
A. Amoeba B. Euglena C. paramecium (1998/4a practical)
Answer: A. Amoeba: Pseudopodium B. Euglena: Flagellum C.Paramecium: Cilia
Example
Which of the following organelles is used for locomotion in paramecium?
A. Pseudopodium B. Trichocyst C. Cilium D. Pellicle E. Contractile vacuole (1992/5)
Answer: C – The paramecium uses cilium for locomotion. (NB: Cilium is the singular form of cilia)
Example
Euglena moves by the
A. whipping action of its flagellum B. beating of its cilia C. rotating action of the flagella
D. pushing out a jet of water from an organelle E. beating the pseudopodia and cilia simultaneously (1988/1)
Answer: A – Euglena moves by the whipping action of its flagellum
Example
In which of the following is cilia not associated with movement or transport of materials?
A. Fallopian tube funnel B. Ectoplasm of paramecium C. Lining of the mammalian trachea
D. Mammalian alimentary canal E. Oral groove of paramecium (1989/7)
Answer: D – Cilia is not associated with movement or transport of materials in the mammalian alimentary canal.
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Example
The following organisms have structures for movement except
A. Amoeba B. Spirogyra C. Volvox D. Paramecium (2015/4)
Answer: B – Spirogyra does not have any structure for movement.

EXERCISE 17.1
1. The streaming movement of cytoplasm within paramecium is known as
A. transpiration B. digestion C. cyclosis D. osmosis (2018/4)
2. In animals, cilia, flagella, pseudopodia, and chaetae, can be used for
A. reproduction B. fighting enemies C. attachment to plants
D. locomotion E. locating sensation (1980/50 JAMB)
3. One of the features which adapts Paramecium to its environment is the possession of
A. regular shape B. two nuclei C. cilia D. a pellicle (1991/9 JAMB)
4. In which of the following groups of invertebrates are flagella cilia found
A. annelids B. protists C. coelenterates D. Anthropoids (2016/44 JAMB)
5. The structure used for movement in Amoeba is
A. cilia B. pseudopodia C. flagella D. endoplasm (2006/5)

Movement in Hydra: Hydra moves in the following ways.

(1) Swaying: Sometimes Hydra comes to rest on rock or other suitable hard surface in water and fixes itself
temporarily with mucus substances at the basal disc. Even when Hydra is fixed, it is continuously swaying
and this swaying is brought about by the contractile and elongation of the muscles on the sides of the body
and tentacles.
(2) Swimming: By freeing itself from the substratum and with the help of wave-like movement of the tentacles,
hydra is able to swim in water.
(3) Gliding: Alternate contraction and elongation of the muscles of the basal disc results in a gliding movement
of the animal. This type of movement resembles that of a snake.
(4) Looping: In looping, while standing erect, the body first extends and then bends and fixes the tentacles to the
substratum by means of glutinant nematocysts. It then releases the attachment of the basal disc, reattaches
the basal disc near the tentacles and again assumes an upright position by releasing its tentacles.

Stages of loping movement in Hydra

5. Somersaulting: Sometimes instead of Hydra moving the base towards the attached tentacles, the base is
swung right over and beyond the tentacles to achieve a grip on the other side of the tentacles. This is the
somersaulting method of locomotion and it carries Hydra faster.

Stages in somersaulting in Hydra. To be drawn

Movement in Earthworm
Earthworm moves by crawling.
Other examples of animal that move by crawling are snail, and snake. These animals lack limbs and fins and so adopt
crawling movement. The earthworm has chaetae that make crawling easy.

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Movement in Fish
The fish moves by swimming with the fins. There are two kinds of fins: The paired fins which are the pectoral and
pelvic fins and the unpaired fins which are the dorsal, anal and tail (caudal) fins.
The pectoral and pelvic fins (paired fins) are used for slow movement. They are used for balancing and steering.
They also help to act as brakes.
Dorsal fin (unpaired fin) is used as a stabilizer that keep the fish steady.
Anal fin (unpaired fin) also act as stabilizer and help the fish to maintain a straight course. The tail fin is used for
steering during locomotion. The streamlined shape of the body also helps for easy movement through the water.
Most bony fishes are able to maintain their depth without floating upward or sinking because of possession of the swim bladder.
The swim bladder also called air bladder is a buoyancy organ which helps fishes to maintain their specific gravity.

The movement of a fish

Movement in the adult frog or toad
The adult frog or toad moves two ways (i) hopping (ii) swimming.
The body is stream-lined in shape for an efficient swimming. The powerful hind limbs have webbed toes which are
used as paddles. They use the hind-limbs to push the water backward that enable them to move forward. The forelimbs
are without web and are used for steering.
During hopping, the hind-limbs are folded in form of letter Z when the frog is at rest. When the hind limbs are
extended the force pushes the frog forward and upwards. The fore-limbs extend to receive the shock on landing while
the hind-limbs are folded.

The various movement of frog or toad

Movements in Lizard:
(i) Running: Agama carries out short running movements with the head raised from the ground.
(ii) Climbing: The presence of sharp claws on the limbs makes it possible for the lizard to climb walls and trees.
(iii) Press-up (head bobbing): After a fast brief running, the animal stops and carries out “press-up” movement.
(iv) Tail movement: During fighting, the male’s tail moves frequently while the female shows its tail movement
before mating.
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Movements in birds: Most birds move by flying because of the presence of a well-developed wing with flight
feathers. The wings of some birds are modified for swimming e.g. penguin. Birds of the duck family (Anseriformes)
such as duck, goose, heron, grebes use their webbed toes as paddle in water for swimming.

Webbed toes of a duck

Some adaptive features of the flying bird
1. Presence of light and hollow bones which helps to reduce body weight of the bird.
2. Presence of keen vision and nictating membrane which help to remove dirt from the eye.
3. Presence of preen (oil) gland which helps to make the feathers glossy and water proof for easy flight.
4. Possession of powerful pectoral muscles which operates the wings.
5. Possession of a streamlined body shape.
6. Modification of forelimbs into wings with large surface area.
7. The bodies of these birds are completely covered with feathers apart from the lower part of the leg.
Note: There are two classes of feathers, these are the “quill” feathers and the “contour and down” feathers. The quill
feathers are large flat and have barbs. They are found on the wings and tail and used for flight and steering while the
contour feathers are smaller. They are found all over the body and helps to keep the animal warm.

Different feathers found in bird

Movements in Mammal: There are different types of movement in mammals. They include walking, jumping,
running, climbing, swinging, flying, gliding and swimming.
Example of flying mammal is bat
Mammals on land usually move by walking, running, jumping or galloping. Mammals in aquatic habitat move by
swimming and diving. Arboreal animals move by climbing, swinging and jumping from branch to branch or glide
from one tree to another.

Bending and straightening of the elbow joint

The pattern of muscle activity in the movement of the elbow involves set of antagonistic muscles.

The articulation of the humerus with the radius and ulnar forms the elbow joint. In front of the humerus a flexor
muscle (biceps) is attached, while the extensor muscle (triceps) which has a lesser diameter than the flexor muscle
(biceps) is attached at the back of the humerus.

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The contraction of the biceps results in a pull on the radius causing bending of the elbow joint, while the contraction
of the triceps exerts a force on the ulnar, resulting in straightening of the elbow joint. When the biceps contracts, the
triceps relaxes and when the triceps contracts, the biceps relaxes. Since these muscles works together in opposite
direction, they are regarded as antagonistic muscles.

Walking in man
Man is a bipedal mammal. In standing position, the weight of the body is balanced over the two legs, during walking,
the legs and feet aided by the upper limbs (arms) are moved by the contraction and relaxation of skeletal muscles.
From a stationary position a step in walking is taken when:
1. The flexor muscle contracts, thereby pulling the foot upward.
2. The extensor muscle contracts thereby pulling the tibia-fibula forward.
3. The protractor muscle contracts, pulling the femur forward.
4. The extensor muscle contracts, thereby pulling the foot downward.
5. The flexor muscle contracts and the tibia-fibula are pulled backward.
6. The retractor muscle contracts, pulling the femur backward.

Example
List four adaptive features of animals that climb rain forest trees 2003/8a
Answer:
Adaptive features of climbing animals:
1. Presence of a prehensile tails (e.g. monkey) 3. Sticky/adhesive discs on fingers (e.g. geckos)
2. Grasping scales (e.g snake) 4. Grasping pads (e.g. tree frogs)
Long, sharp claws for climbing (e.g. squirrel) Opposable digits (e.g. monkey)
Example
The structure used by fishes to detect the presence and movement of other animals by the vibration they produce is the
A. eye B. nostril C. lateral line D. scales E. fins (1994/24)
Answer: C – Fishes use their lateral line to detect the presence and movement of other animals by the vibration they
produce.
Example
Which of the following statements is true about movement of the forearm? In
A. bending the arm, the biceps relax and the triceps contract
B. bending the arm, the biceps contract and the triceps relax
C. straightening the arm the biceps contract and the triceps relax
D. straightening the arm, both biceps and triceps contract (2005/19)
Answer: B – The biceps contracts and the triceps relax in order to bring about the bending of the hand.

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Example
The following adaptations are associated with the flight of birds except
A. reduced body weight B. streamlined shape C. presence of powerful muscles D. clawed digits (1978/27 JAMB)
Answer: D – Clawed digits are not adaptation which is associated with flight of birds.
NB: They are associated with feeding.
Example
Which of these is NOT associated with the movement of the toad, reptile or birds?
A. Hopping B. Bopping C. Flapping D. Gliding E. Pecking (1978/30 JAMB)
Answer: E – Pecking Is not associated with movement in toad, reptile or birds. ( They are associated with feeding)
Example
Which of these is NOT a part of the feature of a bird?
A. Wing B. Aftershaft C. Inferior umbilicus D. Vane E. Barbule (1978/31 JAMB)
Answer: A – The wing is not a part of the feather of a bird.
Example
The fins making up the limbs of the bony fish are
A. caudal and ventral B. ventral and pelvic C. pelvic and pectoral D. pectoral and dorsal (1986/12 JAMB)
Answer: C – The pectoral and pelvic fins make up the limbs of bony fish.
EXERCISE 17.2
1. A feature which adapts birds to flight is the possession of
A. scaly legs B. light bones C. two walking legs D. a pointed beak (1990/13 JAMB)

2. The set of fins that controls steering, balancing and change of direction and pitch in fish is
A. dorsal and anal B. caudal and dorsal C. pectoral and pelvic D. anal and pelvic (2005/49 JAMB)

3. The feature that makes locomotion in water easy for fish is the
A. scaly body B. slimy body C. streamlined body D. lateral line (2009/10 JAMB)
4. Which of the following types of feathers is used for flight in birds
A. Anvil B. Filoplume C. Covert D. Down (2013/10 JAMB)
5. Which of the following specialized cells is associated with human movement?
A. Muscle cell B. Blood cell C. Nerve cell D. Epithelial cell (2000/2 Health Science Nov)
6. b. With the aid of a labeled diagram, explain how movement is brought about at the elbow joint in man.
(1992/1b Nov)

REVISION EXERCISE
(1) The structure of the cell that control the movement of substance in and out of the cell is the
A. cytoplasmic membrane B. nuclear membrane C. cytoplasm
D. protoplasm E. endoplasm (1990/4)
(2) In which of the following is cilia not associated with the movement or transport of materials?
A. fallopian tube funnel B. ectoplasm of paramecium C. lining of the mammalian trachea
D. mammalian alimentary canal E. oral groove of paramecium (1989/7)

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REPRODUCTION
Reproduction is the ability of living organism to produce new generation of individuals of the same species. It
involves transmission of genetic material from one generation to the next in order to ensure the continuity of life.

The two basic types of reproduction are:

(1) Asexual reproduction: This is reproduction by a single parent without production of gamete. It occurs in
plants and animals.
(2) Sexual reproduction: This is the reproduction that involves the fusion of gametes (male and female) to form
a zygote which develops into a new organism
Types of Asexual reproduction
Types Examples
Binary fission Amoeba, paramecium
Multiple fusion (schizogony) Plasmodium
Budding Hydra, Obelia, yeast
Fragmentation Planaria, sponges, coelenterates
Sporulation Amoeba
Parthenogenesis Aphids, honey bee.

Difference between Asexual reproduction and sexual reproduction

Asexual reproduction Sexual reproduction
1. One parent involved Two parents involved
2. No gamete formed Gametes/sex cells formed
3. Meiosis not involved Meiosis is involved
4. No fertilization/fusion of gametes/sex cells/no Fertilization/fusion of gametes/sex cells occur/zygote
zygote formed formed
5. Offspring identical/no genetic variation Offspring vary genetically
6. Rapid/faster mode of reproduction Slower mode of reproduction
7. More individuals are produced Few individuals are produced

Forms of Asexual Reproduction

The major forms of Asexual reproduction includes (i) Binary Fission (ii) Budding (iii) Spore formation and (iv)
Vegetative Propagation
(1) Binary fission: The division of a parent cell into two or more daughter cells that are identical to the parent is
known as fission. When the division of the parent cell give rise to only two identical daughter cells it is known as
binary fission. Amoeba, paramecium and bacteria reproduce by binary fission. If the organism divides
repeatedly into many daughter cells, the fission is known as multiple fission. Plasmodium reproduce by multiple
fission (schizogony)

Binary Fission in Amoeba

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(2) Budding: This is a form of asexual reproduction in which the parent organism forms an outgrowth (bud) which
then grows into a new organism. The new organism later separates from the parent organisms. This occurs mainly
in yeast and hydra.

Budding in yeast

(3) Spore formation: Spores are asexual reproduction units formed by some lower organisms especially fungi e.g.
Rhizophus, which produces numerous spores in sporangia that are borne at the ends of upright hyphae called
sporangiosphores. When the sporangia become mature, they burst and the spores are dispersed by the wind. If a
spore falls on a suitable substance, it germinates and gives rise to a new mycelium.

Spore formation in Rhizopus

(4) Vegetative Propagation: This involves growing of new plants from any part of an old plant other than the
seed. It is the production of new individuals from the vegetative parts of plants. The vegetative parts of plants
which are involved in this method of reproduction are stems, root and leaves.
There are two types of vegetative reproduction. These are natural vegetative reproduction and artificial
vegetative reproduction.

A. Natural Vegetative reproduction involves the use of natural parts of plants to reproduce and get new
individual. Such parts include stem, leaves and root.

Organs used by plants for natural vegetative propagation

1. Stem tubers: A stem tuber is a swollen branch of the main (aerial) stem of the plant as in irish potato and
yam. Each auxiliary bud on a stem tuber can develop into a new shoot during favourable condition.

Stem tuber of sweet potato

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2. Rhizome: A rhizome is an underground shoot which usually grow horizontally and is swollen with food
reserve. At the terminal buds of rhizomes, roots and shoots are given off as ginger and cana lily.

Rhizome of Cana Lily

3. Bulbs: A bulb is an underground compressed shoot with reduced triangular stem bearing thick fleshy storage
leaves covered externally by brown scale-like leaves. Bulbs are formed from auxiliary and terminal bud as
seen in onions, garlic and lily.

Bulb of onion

4. Corms: These are underground stem that grows in the soil in a vertical manner. They are swollen with food.
Their stems are covered by thin scale leaves. Buds, contractile roots and adventitious roots are present also in
them. Examples include Cocoyam, Gladiolus, Calladium. In Corms, food is manufactured by the leaves and
translocated to the the top of the old corm and stored there. From there, a new corm develops. Contractile
roots helps to hold the corm firmly in the soil there by preventing it from growing to the surface of the soil
while adventitious root are used to absorb water and mineral salts.

Cocoyam corm

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5. Stolons or Runners: A stolon is a stem which grow horizontally on the surface of the ground. They have
buds, scale leaves and adventitious root. Examples are sweet potato, strawberry, passion flower and spear
grass (Impereta cylindrica).

Stolon (stem)
Runners are also called creeping stem and they arise from auxiliary buds and creep on the soil surface. They have
long inter nodes, develop underground roots and new plants (aerial shoot) at the node. Runners separate from the
mother plant through the death of the internodes while the terminal buds continue to grow. Examples are sweet potato,
Axonopus etc.

6. Offset: This is a short, thick horizontal branch which produces a ring of leaves and cluster of roots that form a
new plant. An offset also forms from the leaf axil but it is shorter, stouter and more common in plants with
whorled leaves. Examples are hyacinth and water lettuce (Pistia).

Offset of Water lettuce (Pistia)

7. Suckers: Suckers are short horizontal branches arising from a stem at or slightly below soil surface. They
contain food reserves and grow upward close to the parent plant and form roots at their base. Examples of
sucker are banana sucker, plantain sucker etc.

Sucker of Banana
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8. Adventitious Buds: This buds develops on margins and veins of leaves. They develop into adult plant as soon
as they come in contact with the soil e.g. Bryophyllum.

Adventitious buds on leaf margin of Bryophylum plant

9. Bulbils: These are reproductive buds which develop in the axils of lateral leaves. They are short structure
filled with food reserve. As soon as they mature, they drop off to the ground and form new plant. Example is
wild yam (Dioscorea bulbifera). Bulbils are borne at the base and crown of the compound flower
(inflorescence) as in pineapple.

10. Gemmae: These are special reproductive structures which develop on the leaf, branch or thallus e.g. mosses
and liverworts (Marchantia).

11. Leaf tips: This is noticed in some ferns (walking fern). They have long leaves which bend down and touch
the ground thus forming roots at the tip, leading to the formation of buds which grow into new plants.
Examples are Adiantum caudatum, Camptosorus and Polypodium.

B. Artificial vegetative Propagation: This involves the use of intelligence by man to grow new plants from cut portion of
the vegetative body of an older parent plant. It can be carried out by the following ways.
i. Cutting: This is the process in which the stem of a plant is cut and placed in moist soil to generate a new root system e.g.
cassava, hibiscus, sugar cane etc.
ii. Layering: This is the process which involves bending the stem of a plant to the ground and covering it with soil in other
to generate a new root system and therefore an entirely new plant e.g. tomato, cocoa, cola and coffee
iii. Budding: Budding involves the bringing together of the bud and stock. The bud is taken from a tree that is already
producing or matured. The stock is a young plant of about a year old. During budding, a T – shaped cut or inverted T is
made at about 45cm. from the ground on the stem of the stock plant. The cut shape is slightly raised to expose the
cambium. The bud is carefully slopped into the raised bark and pressed firmly to ensure that the cambia of both bud and
stock unite together. It is then tied with plastic material or any device to hold it in place. e.g. orange, cocoa and rubber
iv. Grafting: Grafting is closely related to budding. In grafting, the stem and leaf structure of a plant is attached to another
plant whose root system is in the ground. The two unite to form a new plant e.g. orange, grape, tangerine etc. The part of
the plant whose root system is on the ground is called the stock while the other plant that is been attached is known as the
scion.
v. Marcotting: The roots grow from the part of a branch at which a ring of tissue has been removed. Example of
marcotting include garden shrubs, mango and lemon.

Layering

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 Stages in marcotting for plants

Stages of budding for plants

Stem grafting

Example
(c) Name the two types of reproduction usually associated with organisms. (1999/1c)
Answer: Sexual Reproduction and Asexual Reproduction
Example
4(a)(i) Define asexual reproduction.
(ii) Name two types of asexual reproduction which occur in animals giving one example in each case. (2005/4ai& ii)
Answer:
4ai. Asexual reproduction is a type of reproduction that involves a single parent without the production of gamete.
ii. Binary fission e.g. Amoeba;
Budding e.g. Hydra.
Example
(b) In a tabular form outline four differences between sexual and asexual reproduction. (2005/4b)
Answer:
Sexual Asexual
- It involves two parents. - It involves a single parent
- It involves the production of gametes. - It does not involve gamete production.
- It involves meiosis. - It does not involve meiosis.
- It leads to genetic variation. - It does not lead to genetic variation.

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Example
Which of the following statements about asexual reproduction is correct? It
A. always involves one parent but the offspring is genetically different from the parent
B. may involve two parents but the offspring is always identical to one parent
C. always involves one parent and the offspring is genetically identical to the parent
D. involves two parents but the offspring is not genetically identical to any of the parents. (2014/9)
Answer: C – Asexual reproduction always involves one parent and the offsprings is genetically identical to the
parent.
Example
Which of the following can be used for vegetative propagation?
A. Ginger stem B. Yam leaf C. Plantain roots D. Sweet potato tuber E. Carrot root (1998/5)
Answer: A – Ginger stem is a rhizome and can be used for vegetative propagation.
Example
Which of the following methods is appropriate for the cultivation of cassava?
A. Budding B. Fragmentation C. Root cutting D. Stem cutting (2011/23)
Answer: D – Stem cutting is appropriate for the propagation of cassava.
Example
A plant that commonly undergoes vegetative propagation by means of leaves is
A. Hibiscus B. Bryophylum C. Crotalaria D. Spirogyra (2015/12)
Answer: B – Bryophylum pinnetum is a plant that can be propagation vegetative by means of the leaves.
Example
These processes are all forms of asexual reproduction except
A. marcotting B. binary fission C. budding D. conjugation (2018/10 NABTEB)
Answer: D – Conjugation is a form of sexual reproduction that involves the transfer of genetic material between to
organisms in direct contact.
Example
Which of the following statements is not true of asexual reproduction in a living organism? It
A. results in the formation of two daughter cells B. involves only division of somatic cells
C. involves fusion of opposite gametes D. involves mitotic division of a cell. (2011/10 Nov)
Answer: C – Asexual reproduction does not involve the fusion of opposite gametes.

Example
(a) What is reproduction? (2013/2a Nov)
Answer:
Reproduction is the ability of living organism to produce new generation of individuals of the same species. it
involves the transmission of genetic material from one generation to another in order to ensure continuity of life.
Example
Banana is vegetatively propagated by
A. stem cutting B. sucker C. marcotting D. layering (2001/22 NABTEB)
Answer: B – Banana just like plantain is propagated by means of sucker.
Example
Which of these plant groups are normally propagated by asexual means
A. Banana, yam, pineapple and cassava B. Yam, cassava, rubber and banana
C. Yam, cassava, orange and banana D. Banana, cashew, coffee and pineapple (1988/31 JAMB)
Answer: A – Banana, yam, pineapple and cassava are normally propagated by asexual means.

EXERCISE 18.1
1. The type of asexual reproduction that is common to both paramecium and protists is
A. sporulation B. fragmentation C. fission D. budding (2011/27 JAMB)
2. The simplest form of reproduction is
A. conjugation B. budding C. spore formation D. binary fission (2017/17 JAMB)
3. In vegetative propagation, which of the following requires part of another part to develop?
A. Scion B. Bulb C. Rhizome D. Sucker (1988/30 JAMB)
4. The elephant grass is propagated vegetatively by means of
A. corns B. bulbis C. suckers D. stolons (1990/32 JAMB)

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5. Vegetative propagation is described as a sexual reproduction because
A. reproductive organs are not involved B. new individuals are not formed
C. many new plants are produced D. there is no exchange of genetic materials. (1991/34 JAMB)
Use the diagram below to Answer: question 28

6. The type of vegetative reproduction illustrated in the diagram beside is

A. grafting B. adventitious bud C. sucker D. aerial layering (1997/28 JAMB)
7. An example of an organ of perennation in plants is
A. petal of a flower B. calyx of a flower C. rhizome D. seed (2014/20 JAMB)

Sexual reproduction
This is the reproduction that involves fusion of gametes (male & females), to form a zygote which develops into a new
organism. Sexual reproduction leads to genetic variation. This provides the basic raw material needed for natural
selection and evolution. Natural selection can lead to speciation. Speciation is the process of formation of new
species. Fusion of gametes can happen in two ways which are the two types of sexual reproduction:
1. Conjugation
2. Fertilization

Conjugation: This can be seen in some lower animals such as mucor, rhizopus, paramecium & spirogyra. In this
process, the nuclear content of one cell is passed to another cell. Spirogyra will be used as a case study.

Process of conjugation in spirogyra (Spirogyra is a filamentous organism)

1. The cells of two filament (conjugants) come to lie side by side.
2. The two opposite cells bring forth protrusions.
3. The protrusions elongate and meet to form the conjugation tube. The gamete also form at the same time.
4. The male gamete migrate through the conjugation tube to meet with the female gamete in the second cell.
5. The cytoplasm of both cell fuse and a thick resistant wall known as zygospore is secreted around it.
6. The cell wall of the parents degenerate, releasing the zygospore.
7. After a while and during favourable condition the outer coats burst and young filaments grow out.

Fertilization: The fusion of a haploid male gamete and a haploid female gamete to form a diploid zygote is called
fertilization. Fertilization can be extenal or internal. External fertilization occurs outside the body of the parent.
Aquatic animals such as toad, frog & fish carry out external fertilization. Internal fertilization occurs inside the body
of the parent. Birds and mammal carry out internal type of fertilization.

In higher plants, male and female gametes are also produced. The flowers are the reproductive units in plants.

The male gametes called pollen grains are produced by the anthers while the female gametes called ovules are
produced by the ovary of the flower. The pollen grains and the ovules fused together during fertilization. The ovules
form the seeds while the ovary becomes the fruit.

Some other important points to note on fertilization

1. Self fertilization: This is when the male and female gamete produced by one parent fuse to form zygote e.g.
tapeworms.
2. Cross fertilization: This is when the male gamete is produced by one parent and the female gamete is
produced by another. During fertilization, these gametes fuse to form the zygote e.g. mammals, birds, lizard.
3. Hermaphorditism: This is when the male gamete and female gamete are found in one parent. E.g. hydra, tape
worm, earthworm and some flowering plants. Hermaphroditism usually lead to self fertilization but to prevent
this some organisms have developed two special mechanisms:
a. Protandry: In which male gametes mature before the female gamete.
b. Protogyny: In which the female gametes mature first before the male gamete.
4. Parthenogenesis: This is the process in which a diploid egg develops without fertilization. This is found in
aphids, wasps, reproduction of drones in bees and in some plants like dandelion.
5. Oviparous reproduction: This is a reproductive mode in which the developing eggs are hatched outside the
body of the parents e.g. most fishes and birds.
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6. Ovoviparous reproduction: In this type of reproduction, fertilization, development and nourishment of the
egg happen inside the body of the parents but in the absence of placenta. These eggs are hatched before or
soon after laying e.g. tse-tse fly, snakes, lizards and snail.
7. Viviparous reproduction: In viviparous reproduction, the embryo is developed inside the body of the parent
(mother) through placenta e.g. females of human, cattle, sheep, goat and monkey.

Meiosis
Meiosis is a type of cell division during spermatogenesis (sperm formation) and oogenesis (egg formation) in which
there is a reduction of chromosomes to half the original number of chromosomes. In human for example, the 46
chromosomes are reduced to 23 during gamete formation. As a result, each sperm or egg contains 23 chromosomes.
The fusion of the sperm and egg gives 46 chromosomes which every human being has.

Stages of meiosis (first meiotic division)

(1) Prophase: There are 3 phases of the prophase stage
i. Early prophase: At this stage chromosome become visible as long threads.

Early prophase

ii. Middle prophase: At this stage homologous chromosomes become thicker, shorter and clearly
visible. Spindle is formed.

Middle prophase

iii. Late prophase: At this stage each chromosomes reproduces a replica of itself and becomes double
stranded. Nuclear membrane starts disappearing. Cross links called chiasmata (singular chiasma) are
formed between chromosomes. The function of the Chiasmata is to hold two homologous
chromosomes together. At this stage also, there is an exchange of genetic materials between
homologous chromosomes. This exchange of genetic materials leads to variation or mutation.

Late prophase

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(2) Metaphase I: At this stage, nuclear membrane gets dissolved in the cytoplasm. Bivalent chromosomes are
arranged at the equator and attached to the spindle by their centromeres.

Metaphase I
(3) Anaphase I: At this stage each member of the bivalent chromosomes moves apart and move towards the
poles of the cell by shortening of the spindle.

Anaphase I

(4) Telophase I: At this stage bivalent chromosomes arrive at the poles of the cell. A new nuclear membrane is
formed around each group of chromosomes. Chromosome uncoils and nucleolus reappears on each nucleus.
The two nuclei have half the number of chromosomes of the parent cell (i.e. reduction division). No cleavage
of cytoplasm takes place. There is a short interphase and during this interphase there is not replication of
D.N.A.

Telophase I

Second meiotic division:

(1) Prophase II: Chromosome in the two nuclei becomes distinct. Centrioles divide, separate and move to the
opposite poles of the cells. Spindles are formed.

Prophase II

(2) Metaphase II: At this stage nuclear membrane gets dissolved in the cytoplasm. Chromosomes become
attached to the spindle by their centromeres. The two chromatids of the chromosomes become more distinct.

Metaphase II

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(3) Anaphase II: At this stage the chromosomes become attached at the centromere and begin to separate and
move to opposite poles.

Anaphase II
(4) Telophase II: At this stage the chromatids arrive at the poles of the cell. Nuclear membranes are reformed to
cover the nucleus. Nucleous reappears in each cell. Spindle fibres disappear in the cytoplasm. Cleavage of
cytoplasm then follows. At the end of second meiotic division, four haploid cells are formed with each cell
having half the number of the mother chromosome i.e haploid(n)

Four daughters cells with half (haploid) number of chromosomes of the parent cell.

The importance of meiosis

1) Meiosis ensures that the fertilized egg has a diploid number of chromosomes (i.e. it brings about reduction
division in gametogenesis).
2) Random assortment of genes during meiosis leads to genetic variation among offspring of same parent.
3) Meiosis can lead to a marked gene changed (mutation) which can also bring about variation among
individuals.

Life processes involving meiosis include

(1) Formation of spermatozoa.
(2) Formation of eggs (or ovum).
(3) Formation of pollen grains in flowering plants.
(4) Formation of ovules in flowering plants.

Similarities between mitosis and meiosis

1) Interphase is the same in mitosis and first meiotic division, but there is however, no interphase between
telophase I and prophase II of meiosis.
2) In both mitosis and meiosis, centrioles divide at interphase. Chromosome also doubles at interphase stage in
both mitosis and meiosis.
3) The dissolvement of nucleolus in the nuclear material takes place at prophase in both mitosis and meiosis.
4) Both involve the formation of spindle fibres in the cytoplasm by the centrioles which divide at interphase.
5) Both mitosis and meiosis leads to the formation of new cells from pre-existing cells through cell division.

Differences between mitosis and meiosis

Mitosis Meiosis
1. Mitosis takes place during growth of body (somatic) Meiosis takes place only in the production of gamete
cell. i.e in reproductive cells.
2. The number of chromosomes produced by parent The number of chromosomes of new cells is half the
are the same with new cell. number in the parent cell (haploid number).
3. There is no crossing over. Crossing over occurs.
4. Mitosis involves only one stage of division. Meiosis involves two stages of division.
5. There is no exchange of materials between There is exchange of materials that result in variation.
chromatids.
6. There is no formation of bivalent. Two whole chromosomes form bivalent.
7. Two daughter cells are formed. Four daughter cells are formed.
8. Short prophase stage Long prophase stage
9. Chiasmata are never formed Chiasmata are formed
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Advantages of sexual reproduction
1) It makes variation to be possible in individual, which enhances survival in a new environment.
2) It leads to the production of hybrids that are desirable.
3) It provides a mechanism for recombination of genetic materials that would have been impossible to come
together.
4) It helps to maintain the chromosome numbers peculiar to each species from generation to generation.
5) It permits speciation (new species formation).
Disadvantages of sexual reproduction
1) In most cases two organisms are needed before reproduction. Therefore the absence of one will prevent
reproduction.
2) Defenseless offspring in animals are produced. Parents have to provide fare and protect them against enemies.
3) The process is slow for an optimum population size to be achieved for organisms that have very long
reproductive cycles.
Example
Which of the following organisms is viviparous?
A. Tapeworm B. Snail C. Sheep D. Grasshopper E. Lizard (1997/28)
Answer: B – Sheep is a viviparous organism. Other examples include goat, man and dog
Note: In viviparous reproduction, the embryo is developed inside the body of the parent (mother) through placenta.
Example
What is the difference between viviparous and oviparous animals?
A. Possession of yolked eggs B. Laying of unfertilized eggs C. Possession of yolkless eggs
D. Protection of eggs from predator E. Laying and brooding of eggs. (1990/33)
Answer: E– Viviparous animals do not lay eggs. They give birth to their young ones alive but in contrast,oviparous
animals lay and brood (incubate) their eggs.
Example
Study the diagram below and use it to Answer: Questions 6 and 7.

What stage of mitotic division is represented in the diagram of the cell illustrated above?
A. Prophase B. Telophase C. Anaphse D. Metaphase E. Interphase.
Answer: A – The stage of mitotic division represented in the diagram is prophase. The prophase is characterized by
chromosome condensation, disappearance of nucleolus and nuclear envelop, and formation of spindle.
This stage of mitosis is characterized by the
A. movement of the chromosomes to the poles B. arrangement of chromosomes on the equatorial plate
C. centromeres moving apart along the spindle D. interaction of the spindles with the chromosomes
E. condensation of chromosomes and formation of spindles. (1988/6-7)
Answer: E – It is characterized by condensation of chromosomes and formation of spindle.
Example
At which of the following stages of cell division can the cell be said to be resting
A. Anaphase B. Telophase C. prophase D. Interphase E. Metaphase (1989/37)
Answer: D – The interphase is also called the resting stage.
Example
All hereditary characters in a cell are passed on from parent-cell to daughter-cell through the process of
A. mitosis B. meiosis C. fertilization D. implantation E. gestation. (1989/39)
Answer: A – All hereditary characters in a cell are passed on from parent cell to daughter cell through the process of
MITOSIS.
Example
At the end of mitosis the number of cells produced from a parent cell is
A. four B. six C. eight D. three E. two (1990/6)
Answer: E – At the end of mitosis, two daughter cells are produced.

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Example
At which of the following stages of mitosis do the two daughter chromosomes separate completely?
A. Early prophase B. Telophase C. Anaphase D. Late Prophase E. Metaphase (1990/8)
Answer: C – At anaphase, daughter chromosome move to opposite poles of the cell.

Example
The diagram below illustrates a stage in mitosis. Use it to Answer: questions 40 and 41.

What stage is illustrated by the diagram?

A. Interphase B. Prophase C. Metaphase D. Anaphase E. Telophase
Answer: C – The stage illustrated by the diagram is the metaphase. This is so because the chromosomes are aligned
at the equatorial region of the cell.
What is the name given to the structure labelled A at this stage of cell division?
A. Chromatin B. Chromosome C. Chromatid D. Gene E. daughter-chromosomes (1989/40-41)
Answer: B – Chromosome.
Example
Below is a drawing of a stage in mitosis. Use it to Answer: questions 9 and 10.

Which of the following processes is not evident from the drawing?

A. Lining up of the chromosomes at the equatorial plate B. Centromere attaching
C. Chromatids held by centromere D. Absence of nuclear membrane E. Chromatids moving to the poles.
Answer: C – Chromatids are not held by the centromere in this drawing.
The stage of mitosis represented in the diagram is known as the
A. telophase B. metaphase C. anaphase D. interphase E. prophase (1990/9-10)
Answer: C – Anaphase, because chromatids have started moving to opposite poles of the cell.
Example
4(a) Explain briefly how the process of meiotic division contributes to variation in a population. (1990/4a)
Answer: Meiotic division contributes to variation in a population in that during the prophase I of meiosis I, a special
phenomenon takes place. This is called crossing over.
During crossing over, homologous pairs of chromosomes join together and from synapsis. In this close association,
the homologous chromosomes exchange genetic materials by the formation of chiasmata. This then results in
chromosomes that are different from that of the parent chromosomes, hence variation in population occurs.
Example
(b) State two differences between mitosis and meiosis
(c) Explain briefly the importance of meiosis and fertilization in the reproduction of organisms. (1993/4b, c)
Answer:
4b. Differences between mitosis and meiosis:
i. Mitosis takes place in somatic cells while meiosis occurs only in gametes producing cells.
ii. There is no crossing over in mitosis while in meiosis, crossing over takes place.
c. Importance of meiosis and fertilization in the reproduction of organisms:
- Meiosis brings about variation among species. it also leads to the production of haploid cells which
serves as gametes.
- Fertilization helps in the restoration of the diploid number of chromosomes in organism. It also helps
to produce new organism through sexual reproduction.

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Example
Which of the following is a difference between mitosis and meiosis?
A. Alignment of chromosomes along the equatorial plane B. Replication of the chromosomes and the cell organelles
C. Pairing of homologous chromosomes D. Formation of spindle fibers
E. Thickening of chromatin threads at prophase (1998/4)
Answer: C – There is no pairing of homologous chromosomes in mitosis, while in meiosis pairing of homologous
chromosomes occurs.
Example
(b)(i) Name the two types of cell divisions
(ii) Give two examples each of life processes involved in each type of the cell divisions (1999/1bi, ii)
Answer:
bi. Mitosis and Meiosis.
ii. Mitosis: - Repair of damaged body parts.
- Formation of hapatocyte (liver cells).
Meiosis: - Formation of sperms (male gametes).
- Formation of ovum (female gametes).
Example
The advantages of sexual reproduction include the following except
A. it allows the formation of new species B. it allows production of desirable traits
C. it permits variation of individuals
D. it provides mean for the variation of chromosome number from generation to generation. (2001/13)
Answer: D – Meosis does not provide means for the variation of chromosome number but rather it helps to maintain
the chromosome numbers peculiar to each species from generation to generation .
Example
Which of the following occurrences is not a feature of meiosis?
A. Formation of four haploid cells B. Two successive nuclear cell divisions
C. Pairing of homologous chromosomes at prophase D. Formation of two diploid cells (2008/53)
Answer: D – The formation of two diploid cells is not a feature of meiosis.
Example
4. (a) Describe the main stages of mitotic division.
(b) State four ways in which mitosis is important to living organisms. (2008/4a, b)
Answer:
4a. Prophase: Anaphase:
- Chromosomes appear as thread like chromatins. - Paired chromatids are pulled to opposite pole of
- Chromosomes condense. the cell.
- Nuclear membrane disappear. - Spindle fibres shorten.
- Nucleolus disappear.
- Spindle fibres formation. Telophase:
- Chromatids finally arrive at the poles.
Metaphase: - Spindle fibres disappear.
- Chromosomes are arranged at the equator of the - Nuclear membrane and nucleolus reappear.
cell by the attachment of the contromeres on the - Cytokinesis occurs.
spindle fibres. - Two daughter cells are formed.

b. Importance of mitosis to living organisms.

- Maintains the diploid number of chromosomes of the cell.
- Promotes cell growth.
- Produces genetically identical offspring which resembles the parents.
Ensures repairs of damage tissues. Serves as basis for asexual reproduction.

Example
Two organelles directly involved in mitotic cell division are
A. nucleus and mitochondrion B. ribosome and nucleus
C. centriole and golgi apparatus D. nucleus and centriole (2009/11)
Answer: D – Nucleus and centriole are directly involved in mitotic cell division.

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Example
The immediate product of meiosis in flowering plants is the
A. sporophyte B. gametophyte C. zygote D. pollen grain (2009/54)
Answer: D – The immediate product of meiosis in flowering plant is pollen grain and ovules.
Example
Cytokinesis of mitosis is a process that ensures that
A. each daughter cell gets the necessary organelles
B. there is distribution of a complete set of genes into each daughter cell
C. daughter cells inherit new genetic combinations
D. worn out organelles are excluded from daughter cells (2009/58)
Answer: B – Cytokinesis of mitosis ensures that there is a distribution of a complete set of genes into each
daughter cell.
Example
The following events occurs during mitosis in a cell
I Chromatids separate
II Chromosomes become visible
III Chromosomes align at the equator
IV Cytoplasm divides (Cytokinesis)
The correct sequence of the events is
A.III, II, IV, I B. II, III, I, IV C. II, III, IV D. II, IV, I, III (2014/8)
Answer: B –The correct sequence of event is: Chromosome condense (prophase) II, chromosome align at the equator
(metaphase) III, chromatids separate (anaphase) I, cytoplasm divides/cytokinesis (telophase) IV.
Example
The diagram below is an illustration of a stage in a biological process.

What stage of cell division is illustrated in the diagram?

A. Prophase B. Metaphase C. Anaphase D. Telophase (2019/5)
Answer:
B – Metaphase. This is so because the chromosomes are aligned at the equator of the cell.

EXERCISE 18.2
1. At which stage of mitosis does each sister chromatid moves to the opposite pole?
A. anaphase B. prophase C. metaphase D. telophase (2001/20 NABTEB)
2. Meiosis in flowering plants occurs in the
A. sporophyte B. embryo C. zygate D. pollen grain (2017/34 NABTEB)
3. During prophase in mitosis
A. chromatin thread condense to become chromosomes
B. chromosomes line up along the equator of the spindle
C. spindle fibres break down D. division of the cytoplasm occur (2018/9 NABTEB)
4. The first stage in the process of mitosis is
A. prophase B. diplotene C. anaphase D. telophase (1999/10 NABTEB)
5. At which of these stages in mitosis are the chromosomes arranged at the equatorial region of the cell?
A. anaphase B. telophase C. metaphase D. prophase (1999/11 NABTEB)
6. During cell division, two strands of chromosome are joined at a point called
A. centromere B. chiasmata C. chromatid D. locus E. spindle (2014/44 Neco)
7. Meiosis involves all the following except
A. exchange of genes B. production of cells with diploid number of chromosomes
C. production of cells haploid number of chromosomes D. production of two daughter cells (2008/53 Neco)

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 Study the diagram below and use it to Answer: questions 42 and 43

8. What stage of mitotic division is represented in the diagram above?

A. anaphase B. early prophase C. interphase D. late prophase E. metaphase (2014/42 Neco)
9. The part labeled I is called
A. centromere B. chromosome C. gene D. nucleus E. spindle (2014/43 Neco)
10. Meiotic cell division results in the
A. Growth of the cell B. Production of chromosomes C. production of gametes
D. Production of two daughter cells E. repair of tissue (2007/22 Neco)
11. Which of these statements best describes metaphase of mitosis
A. The daughter chromatids separate and become mature chromatids
B. the spindle forms and chromosomes become attached at the centre
C. The nuclear membranes disappear and chromosomes thicken
D. Two daughter cells are formed
E. The chromosomes thicken and can be seen as two daughter chromatids (1997/4 Nov)
12. (b) In a tabular form, state six differences between sexual reproduction and a sexual reproduction
(c) State three advantages of sexual reproduction (2013/2b, c Nov)
13. In animals, meiosis comes
A. after fertilization B. after every mitotic division
C. before fertilization D. before every mitotic division (1994/25 JAMB)
14. Which of the following is a major cause of variation among organisms?
A. Inbreeding B. Backcrossing C. Sexual reproduction D. Gene dominance (2008/40 JAMB)
15. The chromosome number of a cell before and after the process of meiosis is conventionally represented as
A. 2n → 2n B. n → n C. n → 2n D. 2n → n (2010/46 JAMB)
16. Cytokinesis of mitosis is a process that ensures that
A. each daughter cell gets the necessary organelles
B. there is distribution of a complete set of genes into each daughter cell
C. daughter cells inherit new genetic combinations
D. worn out organelles are excluded from daughter cells (2018/33 JAMB)
17. The immediate product of meiosis in flowering plants is the
A. sporophyte B. gametophyte C. zygote D. pollen grains (2018/30 JAMB)

18. Which of the following processes occurs in the second phase of meiosis?
A. Homologous chromosomes separate B. Two daughter cells are formed
C. Fertilization occurs D. Segregation of genes occurs. (2012/6)

Reproduction in Unicellular Organisms and Invertebrates

The continuity of life, depends on the ability of living organisms to give rise to new individual of the same species.
This ability is known as reproduction. Reproduction in unicellular organisms and invertebrates happens by both
asexual & sexual means.

Reproduction in amoeba by binary fission

Binary fission involves division of a parent cell into two daughter cells by mitosis. This is seen in amoeba.

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Reproduction in spirogyra
Reproduction in spirogyra is of two types:
1. Asexual (vegetative) reproduction and
2. Sexual (conjugation)

Vegetative reproduction in spirogyra is when a fraction of the parent cell break away to form a new spirogyra. This
known as fragmentation.

Sexual reproduction is very simple in spirogyra. The whole cell may act as a gamete. This may then pair with another
similar whole cell and exchange nuclei. Such process is known as conjugation. Each individual cell is known as
conjugant. Conjugation can also occur in paramecium and rhizopus.
In spirogyra, two spirogyra filament come to lie side by side. Conjugation tubes are formed within them. The cell in
one filament acts as male gametes while those in the other act as female gametes. The male gamete migrates and fuses
with the female gamete to form thick wall zygospores.

Stages of reproduction (conjugation) in spirogyra showing conjugation tube

Example
Which of the following methods of reproduction is common to Paramecium and Amoeba?
A. Conjugation B. Sexual reproduction C. Binary fission D. Budding E. Fragmentation (1990/1)
Answer: C – Binary fusion is common in both paramecium and amoeba.
Example
(b) Name the methods each of asexual and sexual reproduction in spirogyra. (2005/2b Nov)
Answer: Asexual – Fragmentation. Sexual – Conjugation.

EXERCISE 18.3
1. 1(a) Describe the process of conjugation in Spirogyra (2004/1a Nov)
2. Which of the following is NOT true of spirogyra?
A. reproduces by conjugation B. reproduction by fragmentation
C. consists of branched filaments D. consists of unbranched filaments (1986/6 JAMB)

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Conjugation in Rhizopus: This occurs as follow:
i. Sexually compatible mycelia come close together
ii. Short protrusions (progametangia) develop from them and make contact at their tips to form a conjugation
tube.
iii. As these protrusions elongate, they push the parent hyphae apart.
iv. These protrusions enlarge into club-shaped structures whose terminal walls then dissolve.
v. Nuclei from tips of hyphae fuse in a common cytoplasm and form pairs.
vi. The resulting structure enlarges as a thick-walled dormant zygote (the zygospore) which can grow into a new
plant.

Sexual reproduction in rhizopus

Example
Use the diagram below to Answer: questions 44 and 45

The process illustrated is

A. gametogenesis B. sporulation
C. sexual reproduction in spirogyra D. sexual reproduction in Rhizophus (2007/44 JAMB)
Answer: D – The process illustrated is sexual reproduction in rhizopus.
Example
The structure labeled I is the
A. sporangium B. hypha C. zygospore D. conidiophore (2007/45 JAMB)
Answer: C – The structure labeled I is the zygospore.

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Sexual Reproduction in Paramecium Caudatum
This occurs by conjugation.There are different stages

Stage 1: Two individual paramecia get fuses by their oral grooves. In each conjugant, the meganucleus gets dissolved
in the cytoplasm while the micronucleus remains to take part in the mating process.

Stage 2: The micronucleus divides twice by meiosis leading to the formation of four nuclei in each conjugant. Of
these four, three gets dissolved in the cytoplasm of each conjugant. The remaining micronucleus divides unequally
into a smaller micronuclei and a larger micronuclei.

Stage 3: The two conjugant exchanges the smaller micronuclei.

Stage 4: The migratory micronucleus fuses with the stationary micronucleus in each conjugant to form zygote. The
two conjugant separates and are now referred to as ex-conjugant.

Stage 5: The zygote in each ex-conjugant divides thrice to form eight nuclei. Four of the eight nuclei form four
meganuclei while three of the remaining four get dissolved in the cytoplasm. The remaining micronucleus divide
twice to form four micronuclei.

Stage 6: Each ex-conjugant with four meganuclei and four micronuclei divide to form four paramecia. Each
paramecium has one meganucleus and one micronucleus.

Stages of sexual reproduction in paramecium caudatum

NOTE: Asexual means of reproduction in Paramecium is by binary fission.

Example
How many conjugants are involved in the sexual reproduction of paramecium
A. 1 B. 2 C. 4 D. 8 (2004/8)
Answer: B – Two conjugants are involved in the sexual reproduction of paramecium.
NB: A conjugant is one of the pair of organisms involved in conjugation.

Example
During sexual reproduction in paramecium, how many times does the zygote divide to produce eight nuclei?
A. 1 B. 2 C. 3 D. 4 (2011/20)
Answer: C – The zygote divides three (3) times in order to produce eight nuclei.

Reproduction in earthworm
Earthworms are hermaphrodites (monocious) i.e. they contain both male and female reproductive organs. Their
reproductive organs are located on the 9th – 15th segment. The male reproductive system comprises of the testes,
testis sacs, seminal vesicles, prostrate glands and other accessory glands while the female reproductive system
consist of ovaries, oviduct and spermatheca.
Reproduction in earthworm occurs through cross fertilization by copulation. During copulation two earthworms lie
in contact with each other in the opposite direction such that the male genital aperture of one earthworm is near to the
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spermathecal pores of the other earthworm. A seminal groove carries droplets of spermatozoa from the male pore to
the clitellar region, where it collects, and it eventually enters the spermathecae. After copulation the mated
individuals produce cocoons with variable number of fertilized ova, the resistant cocoon are usually deposited near the
soil surface except in dry weather when they are laid in deep layers

Earthworm

Metamorphosis in insects:
Metamorphosis is the series of gradual changes that takes place during the development of an insect from the zygote
(fertilized egg) to the adult stage. There are two types of metamorphosis:
1. Incomplete metamorphosis
2. Complete metamorphosis
In complete metamorphosis, the egg hatches into larva, the larva changes to pupa and pupa finally changes to an
adult. Examples are housefly, mosquito and butterfly.
Egg → Larva → Pupa → Adult
In incomplete metamorphosis the egg hatches into a nymph and then into the adult stage. The pupa stage is absent.
The nymph resembles the adult form except that there are no wings, the gonad are not yet developed and is very small
in size. Examples are cockroach, termite and grasshopper.
Egg → Nymph → Adult
Metamorphosis provides the Juvenile and adult forms to live in different habitats, feed on different kinds of food items
thereby reducing competition for space and food resources. For example, the adult butterfly feeds on nectar of flowers
with its proboscis while the larvae feed on leaves with the help of its mandibles. Moulting is controlled by moulting
hormone (ecdysome).

Difference between incomplete and complete metamorphosis

Incomplete metamorphosis Complete metamorphosis
1. There is no pupa (resting) stage. There is pupa (resting) stage.
2. Nymph similar to the adult is present. No nymph stage
3. No larva stage. Larva stage which is quite different from adult is present.
4. Nymphs and adult feed on the same food items Larvae and adult feed on different food items preventing
leading to competition for food and space. competition for food and space.
5. It involves three stages of development. It involves four stages of development.
6. Examples of incomplete metamorphosis are Examples of complete metamorphosis are Housefly and mosquito
cockroach and grasshopper.

Reproduction in cockroach
This insect undergoes incomplete metamorphosis. A female cockroach lay about 10 to 16 eggs in a horny egg-
case(oothecae). She carries the egg case for some time in her abdominal pouch before depositing it in a safe, dark,
warm place. After 30 – 100 days, the eggs hatch into nymphs which are small, wingless and colourless. They feed,
grow and become brown like the adult, moulting up to about 13 times. In the later instars, the wings appear as wing
pads. In the last instars, the body and wings reach adult size. The cockroach requires 11 to 20 months to develop from
egg to imago. The imago may live for about 3 to 12 months.
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 Metamorphosis in Cockroach

Reproduction in housefly
The housefly undergoes complete metamorphosis with a very short life span, lasting about 3 to 4 weeks only. A
female housefly lays 2 to 7 batches of about 130 eggs each in rotting matter. Within 8 to 72 hours, a whitish worm-
like maggot hatches out. The rotting matter provides the food it feed on as well as the moist and dark environment
that it needs. The maggot feeds and grows rapidly, moulting twice in this case. It reaches a length of about 12mm in
about 5 to 14 days. Then it moves to a dry place to pupate. It shortens and its skin becomes hard and brown to form
the pupal case.
The pupa is an oval, barrel-shaped structure with transverse rings. About 3 to 10 days later, the imago emerges from
the pupal case. To do this, the imago pumps blood into a sac-like organ attached to its head. As the organ inflates, it
presses against the front end of the pupal case causing it to crack. The imago flies off as soon as its wings are dry.
A female housefly takes 2 weeks to become sexually mature and start laying eggs.

Metamorphosis in Housefly

Complete metamorphosis in butterfly

The butterfly passes through a complete metamorphosis. This comprises the egg, larva, pupa and imago.

Metamorphosis in Butterfly

The egg: The female butterfly lays its egg in a small batch on the undersurface of a leaf of a selected plant that will
provide food for the caterpillar. The eggs are shaded from direct rays of sunlight and hidden from view of possible
predators. The egg is coloured blue, green or white according to the species of the butterfly.

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The larva (caterpillar):
The eggs hatch into the larvae in about 10 days. The larvae of a butterfly is called caterpillar. The caterpillar is
worm-like. The body is hairy which makes it to look dirty and unpleasant to eat by predators. It has a cylindrical body
which consists of a head, thorax and abdomen. The head bears a pair of short and segmented antennae, three pairs of
simple eyes (ocelli) and a pair of powerful mandibles. The powerful mandibles help in grinding the egg shell which
serves as the first meal of the larva (caterpillar). Later the larvae feed on the leaves of the plant frequently using the
mandibles to cut and grind leaves for food.

The thorax consists of three segments, each bearing a pair of short jointed true (thoracic) legs for crawling and
attachment to leaves and twigs. The abdomen consists of ten segments each bearing a pair of spiracles. Four pairs of
false legs called prolegs are borne on the third, fourth, fifth and sixth abdominal segments. The last abdominal
segment bears a pair of claspers for attachment. As the larva grows, it moults five times in about one month. After the
fifth moult, the caterpillar spins thread-like silk around itself and become a pupa which is motionless and does not
feed. The pupa of a butterfly is called chrysalis. The pupa land itself on the twig with the silk thread. Internal organs
of the adult are formed at this stage. After the complete formation of the adult organs in about a month or more, the
pupa case split open and a young imago emerges. After resting for about three hours, its wings become fully stretched
and flies away in search of food and mate. The adult butterfly feeds on nectar of flowers with its proboscis.

Economic importance of butterfly

1. It pollinates flowers during its visit to flowers in search of nectar. Pollination brings about fertilization of
flowers leading to production of seeds and fruits hence increase in food production for man.
2. The larva referred to as caterpillar are very destructive to plant. Caterpillars feed greatly on the green leaves
and young stems destroying them during the feeding process.
3. In trying to control the caterpillars, a lot of money is needed to buy chemicals to kill them.

Complete Metamophorsis in Mosquito

Mosquitoes passes through a complete metamorphis which consist of four stages: Egg → Larvae → Pupae → Adult

Egg: The eggs are hatched within 24-72 hours after being layed in water (stagnant).
Larvae: After the hatching process has been completed, the mosquito larvae (wigglers) emerges. They move on the
surface of the water and they feed on various organic materials e.g. bacteria, algae, protozoans and other organic
material using their mouth brushes to take in particles. The amount of time between the larval and the pupal stage
varies dpending on species and weather conditions, it typically lasts a few days. The larvae molts four times,
developing with each successvive molt. During their final molt, they grow about half of an inch longer.

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Pupae: After their final molt, the mosquito larvae develop into the pupal stage. In this stage, the pupae (tumblers)
stays near the surface of the water. They breathe air and they form a pupa casing and they transform to adults while
inside the casing. The pupal stage usually lasts from one to four days depending on species and water temperature.
Adult: When the pupae is fully developed into an adult, the adult mosquito will rest on the water’s surface until its
legs and wings are strong enough to carry it. The complete metamorphosis of a mosquitoes ranges from four days to
one month.
Control and Prevention
1. Remove any source of stagnant water:
2. Keep weeds and other vegetation mowed and cleared to minimize shelter for adult mosquitoes.
3. The use of mosquito net should be adopted to prevent mosquito from biting you.
4. Protective clothing may be used, such as will cover the exposed part of the body, especially after sunset.
5. Paint walls with creosote repels mosquitoes.
6. Fumigation of dwellings with sulphur dioxide is also useful.
Example
In the life history of a butterfly, destruction of crops is caused by the
A. maggot B. nymph C. caterpillar D. pupa (1987/14 JAMB)
Answer: C – Caterpillar feeds on green leaves and stems, hence are destructive to crops.
Example
The butterfly is of great economic importance because
A. of its use in scientific studies B. it sucks nectar from flowers
C it adds to the beauty of the environment D it pollinates flowers of crops and other plants. (1993/12 JAMB)
Answer: D – The butterfly is of great economic importance because it helps to pollinates flower of crops and other
plants.
Example
Which of the following distinguishes a butterfly from a moth?
A. The wings of a butterfly rest horizontally but that of moth rest vertically
B. Both are active during the day C. They have similar antennae
D. The abdomen of moth is fatter than that of a butterfly (2013/9 JAMB)
Answer: D – The abdomen of moth is fatter than that of a butterfly.
NB: The wings of a butterfly rest vertically but that of a moth rest horizontally hence option “A” is not correct
Example
(c) (i) Describe the life history of the housefly.
(ii) State two economic importance of the housefly. (2005/2ci, ii Nov)
Answer:
2ci. Houseflies undergoe complete metamorphosis. The female housefly lays fertilized eggs on decomposing
matter. These eggs then hatch into larvae (maggot) after few hours. The maggots then feed on the organic matter
present in the decomposing matter on which they are found. They grow become about twelve mm in length.This later
contracts to become pupas. After about four days, the pupas metamorphose to become adults (imagos) which are
enclosed by the puparia (brown skin covers). The puparia then tear open allowing the adult houseflies to fly away.
ii. Economic importance of the housefly: - Transmission of disease causing organism.
- Decomposition of dead and decaying organic matter.
Example
Which of the following is common to the mosquito, housefly and blackfly?
A. They undergo complete metamorphosis B. They are parasites of man
C. Their immature stages are aquatic D. Their adults have two pairs of wings (2007/43 JAMB)
Answer: A – All three (mosquito, housefly and blackfly) undergo complete metamorphosis.
Example
The process in which insects undergo conspicuous changes in form and appearance during development is known as
A. ecdysis B. metamorphosis C. aestivation D. migration E. hibernation (1994/5)
Answer: B – Metamorphosis is the process in which insects undergo conspicuous changes in form and appearance
during development.
- Ecdysis is the shedding of exoskeleton in order to permit growth. This is also known as moulting.
- Aestivation is a state of inactivity and metabolic deposition in animals during summer.
- Hibernation is a state of inactivity and metabolic depression in animals during winter.
Example
The following insects undergo incomplete metamorphosis except
A. termite B. cockroach C. butterfly D. locust (2004/23)
Answer: C – butterfly undergoes complete metamorphosis.
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Example
Differences in Metamorphosis in housefly and toad. (2009/8bii)
Answer: The differences between the metamorphosis in housefly and toad are:
Housefly Toad
- Takes place in decomposing organic matter. - Takes place in winter.
- The presence of resting stage/pupal. - No resting stage/pupal.
- Takes shorter time. - Takes longer time.
Example
Parthenogenesis is a type of reproduction that occurs in
A. lizard B. bird C. earthworm D. aphid (2017/36 NABTEB)
Answer: D – Parthenogenesis is a form of reproduction in which an egg develops into an embryo without being
fertilized by a sperm. Aphids, bees and ant often reproduce by parthenogenesis.
Example
The following insects exhibit complete metamorphosis EXCEPT
A. grasshopper B. mosquito C. tsetse fly D. housefly (1999/24 NABTEB)
Answer: A – Grasshopper undergoes incomplete metamorphosis.
Example
Which of these animals exhibits metamorphosis?
A. fish B. fowl C. lizard D. Rat E. toad (2014/34 Neco)
Answer: E – Toad exhibits metamorphosis.

EXERCISE 18.4
1. Which of these insects undergoes incomplete metamorphosis?
A. Beetle B. Butterfly C. Cockroach D. Housefly E. Mosquito (2007/40 Neco)
2. Which of these animals undergo metamorphosis?
A. fish B. fowl C. lizard D. rat E. toad (2018/23 Neco)
3. Incomplete metamorphosis occur in the
A. butterfly B. grasshopper C. mosquito D. housefly (1986/8 JAMB)
4. Which of the following insects undergoes incomplete metamorphosis?
A. Mosquito B. Termite C. Housefly D. Moth (1992/9 JAMB)
5. Which of the following is common to the mosquito, housefly and blackfly
A. They are parasites of man B. Their immature stages are aquatic
C. They undergo complete metamorphosis D. Their adults have two pairs of wings (2015/19 JAMB)

Reproduction in Snail
Generally snails are considered to be hermaphrodites with some few exceptions such as apple snails and periwinkle
which have separate male and female individuals. The land snail is considered sexually mature from one month and a
half to five years but depending on the species. The makeup of the snail includes their reproductive organs on the
bottom of their body. This is close to the front of their body, allowing for easier abilities to mate.
The mating practices of snail allow them to deliver eggs, for new snails to be brought into life at a consistent rate. Two
snails will go through complete mating ritual with each other for about 2 to 12 hours. At the end of the ritual, the pair
will fertilize the eggs in the other. So, both of them will deliver eggs. It is known that a snail can carry up to 100 eggs
at a time. When the eggs are fertilized they will go through a process of growth inside the snail until they are ready to
be delivered. After that both snails lay their eggs and bury them separately inside a small hole made in the top soil in a
cool place. This will allow the eggs to develop without being harmed. The egg takes 2-4 weeks to develop. As soon as
they are hatched, they will immediately move into a survival mode. This is because their shells will still be in a weak
form. Their reaction is to find calcium as soon as they hatch by eating the remaing of their own egg in order to get
extra nutrient. It will take about 3 months for the snail to completely form and look like a miniature version of an adult
snail of their species.
Example
What is sexual reproduction? (2005/2a Nov)
Answer: Sexual reproduction is a type of reproduction that involves the fusion (union) of a male gamete (sperm) and
female gamete (egg) to turn a new individual.

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Example
What is reproduction? (2013/2a Nov)
Answer: Reproduction is the process by which living organism give rise to new individuals of the same species.
EXERCISE 18.5
1. i. Describe the life history of the housefly.
ii. State two economic importance of housefly.
iii. State three methods of control of housefly (2005/2c Nov)

2. Which of the following diagrams represents the larval stage of a housefly?

A. I B. II C. III D. IV E. V (2005/27 Neco)
3. Which of the diagrams represents the nymphal stage?
A. I B. II C. III D. IV E. V (2005/28 Neco)
4. i. Define Metamorphosis.
ii. List the examples of insects that undergo incomplete metamorphosis? (2018/4c)
5. in a housefly the pair of stump-like wings beneath the first pair of wings is called
A. elytron B. halters C. squame D. squamosa E. terga (2007/8 Neco)
6. which of the following insects undergoes complete metamorphosis during development
A. cockroach B. termite C. mosquito D. aphid (1999/56 Nov)

REPRODUCTIVE SYSTEM OF VERTEBRATES

Reproduction is the process by which organisms give rise to new individuals of the same species. There are two main
types of reproduction namely;
1. Sexual reproduction
2. Asexual reproduction

Sexual reproduction:
This is the type of reproduction that involves two individuals usually of opposite sexes. It requires the formation of
gametic cells.
Gamete i.e. sperms and ovum are produced by a reduction division called meiosis. For a new offspring to be formed,
there must be a fusion of gametes. This fusion or union is called fertilization. It may be internal or external and the
result of fertilization is the production of zygote which undergoes growth and development into a new individual.
Conjugation is also a type of fusion or union of sex cells

Advantages of Sexual Reproduction

1. It enables new species formation.
2. It enables variability of individuals.
3. It creates a means for the maintenance of the chromosomes number characteristics of the species from
generation to generation.
4. It allows the production of hybrids for some desirable traits.
5. It allows a mechanism for the recombination of genetic materials that otherwise would not have come
together.

Structures of Male and Female Reproductive System in Reptiles, Fish, Bird and Mammals

Reproductive systems in reptile

The male agama lizard has two testes located in the abdomen, with the right testes a little above the left. The sperms
are carried from the testes to tiny tubes called vas deferens which then passes them to the penis. The penis releases the
sperm into the female for internal fertilization.

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The female reproductive system has two ovaries like the male has two testes. The eggs are released into the abdominal
space and then into the oviduct as a result of some cilia action. The oviduct opens at the posterior end into the cloaca
near the opening of the ureter. As they mate, fertilization takes place internally.

male reproductive organs of agama lizard female reproductive organs of lizard

Reproductive system in fish

All fish have internal sexual organs, and some have evolved external organs as well. The male fish has two testes
which lead to the genital opening. The testes produces sperm. The female fish has two ovaries which produce eggs.
The eggs are discharged into the oviduct which leads to the genital opening. After the production of these gametes, the
next step is fertilization and different species makes use of different method to ensure that fertilization takes place
consistently. Since fish reproduce sexually, if eggs are not fertilized, they don’t produce any young

The mating process of fishes involves the female scaterring the eggs her ovaries have produced into the water and the
male ejecting his sperm into the water in the same general area. The key to the success of this method is scattering lots
of eggs and sperm so that the chances of a sperm finding an egg in the water and fertilizing it are high. From the
above mating process, it is seen that fertilization process in fishes is external .

Male reproductive system of tilapia

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 Female reproductive system of fish
Reproductive system in birds
The male reproductive system of fowl is made up of two testes that are attached to the edge of the kidneys; a sperm
duct leads from each testes to the ureter.Generally, birds lack penis. During copulation, the sperm are transferred from
the male to the female when their cloaca contact. In hens, only the left ovary is functional and fertilization is internal;
the ovary is connected to the outside by the cloaca. Hens lay eggs (oviparous).

Male reproductive system of fowl Female reproductive system of fowl

Internal structure of hen’s egg

Structure of male reproductive system in human

The male reproductive system of man consists of the testes (testis), vasa efferentia, vas deferens (sperm duct), penis
and glands.
A. Testes (singular testis): There are two testes in mammals. Each of them have an oval shape and are housed
in a sac functioning as a thermo-regulator. The sac is the scrotal sac. It protects the sperm from adverse (hot)
temperature.
Functions: 1. The male gamete/sperm are produced in the seminiferous tubules located in the testes.
2. They also produce the male hormone testosterone.

B. Seminiferous Tubules: Inside each testis, are about 1,000 highly coiled tubes called seminiferous tubules.
Functions:
1. Sperm (spermatozoa) are produced in the wall of these tubes through a process known as
spermatogenesis.
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 2. The male sex hormones (testosterone) are produce by the leydig/interstitial cells located between the tubes.

Seminal Vesicle Corpus

Cavernosum

Side view of the male reproductive system in human Front view of the male reproductive system in human
C. Epididymis: This is a long coiled tube found within the testis.
Function:Sperms are temporarily stored until maturity in the epididymis.
D. Prostate Gland: This gland is located a little below the bladder.
Function: It secretes a white milky fluid which helps to neutralize the acidity of the vagina making the sperm
more active.
E. Urethra: This is a narrow tube that extends into the penis and function as a urinogenital organ i.e. It serves
as a passage for both urine and sperm.
Functions: 1. It serves as a passage of sperm into the vagina.
2.It serves as the passage of urine out of the body.
Note: Urine and semen does not pass through the urethra at the same time. This is because a muscular valve
closes the bladder when the penis is erect and it is also impossible for semen to be discharged when there is no
erection (when the penis is limp).
F. Sperm duct (vas deferens):
It is a narrow tube which leads from the epididymis to the seminal vesicle.
Function: It carries sperm from the epididymis to the seminal vesicle.
E. Seminal vesicles:
The seminal vesicles are a pair of sac-like glands responsible for producing majority of the components that
make up the semen. They are located close to the posterior end of the vas deferens.
Function: It secretes part of the seminal fluid.
F. Cowper’s gland: Cowper’s gland is also known as the bulbourethral gland. It located close to the prostate
gland.
Function: It secretes seminal fluid that causes increase in the PH of the female reproductive medium which is
normally acidic.
I. Penis:
This is an organ that runs through the urethra when the penis is erected, it can penetrate the vagina leading to
the release of sperm.
Function: It introduces the sperm into the vagina of the female animal.

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Structures and function of the female reproductive system in human

Side view of the female reproductive system in human Front view of the female reproductive system in human

A. Ovaries: There are two ovaries located in the body of a female mammal. The ovaries are almond shaped and
contain thousand of undeveloped eggs or ova. During the fertile years of the females, one egg is usually
produced every month. The production of eggs by the ovaries stops at about the age of 45-55 years in human a
condition known as menopause.
Functions: 1. The ovaries secrete the female sex hormones called oestrogen and progesterone.
2. Produces gamete cells (egg/ova)
B. Oviduct or fallopian tube: These tubes are about 12cm long. They carries eggs from the ovary to the uterus.
Functions: 1. It allows passage of the egg from the ovary to the uterus.
2. Fertilization occurs in the oviduct.

C. Uterus or womb: The uterus is about 7.5cm long, 5cm wide and 2.5cm thick. It has the shape of an inverted
pear. The outer layer is called myometrium and inner layer is called endometrium.
Functions: 1. This is the place when the foetus/embryo grows and develop.
2. The outer layer (myometrium) contains smooth muscles which help to push the baby out
during delivery by contracting.
D. Cervix: It is the narrow entrance to the uterus from the vagina.
Function: It controls the opening and closing of the vagina during birth.
E. VAGINA: This is also referred to as the birth canal. It is a muscular tube about 8-10cm long containing
elastic tissues, which stretches during child birth to allow passage of the baby and during sexual intercourse
when the penis is placed in it.
Functions: 1. It allows the passage of the foetus during birth.
2 . It receives sperm from penis during sexual intercourse.
F. VULVA: The collective name for all the external part of the female reproductive organ is the “vulva”. These
include the labia majora, labia minora and clitoris.
Functions: 1. Vulva protects the vagina opening.
2. The clitoris helps stimulates the female during sexual intercourse.

Differences between male and female reproductive system (human)

Male System Female System
1. Vas deferens (sperm duct) is present. Vas deferens is absent.
2. Epididymis tube is present. Epididymis tube is absent.
3. Fallopian tube is absent. Fallopian tube is present.
4. Millions of sperms are produced every month. Only one egg or in some few cases two eggs are produced
every month.
5. Sperm are manufactured by testes with outside Eggs are produced by ovaries with body temperature.
temperature.
6. It produces male sexual hormones called testosterone. It produces female sexual hormone called oestrogen and
progesterone.
7. Sperm pass through urethra. Egg passes through the fallopian tube into the uterus.
8. Vagina is absent. Vagina is present.
9. There is no uterus. Uterus is present.
10. Cervix is absent. Cervix is present.
11. The gonads are located outside the body. The gonads are located inside the body.
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 Structure of the sperm cell

Sperm cell (male gamete)

The sperm cell is a single microscopic cell consisting of head, neck, body (middle piece) and tail. It is about 2.5mm in
diameter and 50nm long. The head contains the nucleus with haploid number of chromosomes (23 in humans). The
acrosome, a large lysosome containing hydrolytic enzyme that digest the cell membrane of the female ovum during
fertilization is also found in the head. Attached to the head is the short neck region of the sperm. After the neck is the
body (middle piece) which is enlarged by the presence of many mitochondria arranged around the axial filament. The
mitochondria produces ATP as a source of energy which is used to bring about the beating movement of the tail. The
tail aids swimming of the sperm cells in the semen. The sperm swims at a rate of 1-4mm per minute.

Structure of the egg (ovum)

Structure of the egg (ovum)

The egg is a round single cell, much larger than the sperm. The egg is about 0.1mm in diameter. It consists of nucleus
and cytoplasm. The nucleus with haploid number of chromosomes is in the cytoplasm and is bounded by nuclear
membrane.

The yolky cytoplasm relatively larger than the nucleus is surrounded by a thin plasma membrane, vitelline membranes
and a layer of jelly

Development of the egg (oogenesis) and menstrual cycle

The process involved in the development of the ova/egg is known as oogenesis. The production of eggs in females
begins before birth. At birth, about 200,000 primary oocytes are present in each ovary but only about 400-500 reaches
maturity. The rest degenerate and are absorbed.
Each egg is surrounded by a sac of smaller cells called Graafian follicle. The Graafian follicle increases in size as the
eggs size increases but when the egg reaches maturity, it bursts to release them. Each ovary releases one egg in an
alternate manner. The release of the egg is known as ovulation. Ovulation usually happens at the 14th day after
menstrual flow although it can vary for some individuals.
After ovulation, the Graafian follicle which remains behind in the ovary develops into a yellow body called corpus
lutetum. The corpus lutetum produces two hormones oestrogen and progesterone. The release of progesterone is
associated with a rise in body temperature of the female just after ovulation. The corpus lutetum withers away after 2
weeks of ovulation. The production and release of mature ova, follows a cycle know as the menstrual cycle. Each
cycle takes an average of 28 days. The menstrual cycle which is controlled by hormones, is accompanied by some
series of changes in the reproductive organ of a mature female. Some of these changes includes maturation and release

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of mature ovum from an ovary, thickening and maintenance of the uterine endometrium and break down of the extra
uterine endometrial tissue if fertilization of the ovum and implantation of the embryo do not occur.
Structural differences in the eggs of vertebrates
The eggs of fish are enclosed in small sac, the egg has small yolk and the eggs are small.
The eggs of toads are small and are covered by mucus or gelatinous layer. Therefore the eggs are in strings
The egg of reptile (lizard), birds have shell, shell membrane, yolk and albumen.
The egg shell of bird is harder than that of reptile. The egg shell of lizard is soft, tough and leathery. It absorbs water from the
surrounding soil and increases in size or volume.
Bird’s egg is the largest single animal cell. The egg shell is porous and allows exchange of gases between the egg and its
environment.
Though mammals do not lay eggs, one ovary produces one to ten eggs each with 0.1mm in diameter with vitelline membrane.

Differences between male and female gametes

SPERM EGG (OVUM)
1. Very small with a diameter of 2.5 micron Far larger than sperm with a diameter of 120microns.
2. Divided into head, neck, middle piece and tail Round and not divided into head, middle piece and tail.
3. It is capable of swimming from vagina to the fallopian Not capable of swimming. It is moved by the beating of
tube fallopian tube cilia and muscular contraction of the fallopian
tube
4. Very small cytoplasm present Large cytoplasm present
5. No yolky cytoplasm Yolky cytoplasm present
6. Millions of sperm are released during each ejaculation Only one egg or rarely two eggs are released monthly

Comparism of reproduction in fish, amphibian, reptiles, birds and mammals

s/n Types of Fish Amphibian Reptiles Birds Mammals
vertebrates
1. Time of breeding seasonal seasonal seasonal seasonal seasonal except in
human being
2. Number of eggs very many many few few none except in
laid monotremes that
lay few eggs
3. Mode of external (water) external (water) internal (oviduct) internal (oviduct) internal (oviduct)
fertilization
4. Site where water water holes in earth nest uterus (womb)
embryo is covered with soil
developed
5. Feeding of from yolk and from yolk and from yolk and from yolk and from mother
embryo albumen albumen albumen albumen through placenta
6. Mode of zygote mostly oviparous mostly oviparous mostly oviparous mostly oviparous mostly viviparous
growth
7. Parental/care/type protection by some none in most none in most incubation of protection, feeding
of parental care fish e.g. cases cases eggs, protection, and teaching for a
Oreochromis feeding of the long period
niloticus (mouth young ones until
broider) and none flight is achieved
for some fish
8. Territorial present in some absent present in some present in some present in some
behaviour species species e.g. species e.g. species e.g. baboon
Agama lizard, heron, shrike
crocodile

Fertilization:
Fertilization is the fusion of the haploid sperm nucleus with the haploid egg nucleus to form a diploid cell known as
the zygote.

During copulation/sexual intercourse, sperm is ejaculated into the body of the female. The sperm moves through the
cervix and uterus into the upper part of the oviduct. The movement of the sperm is brought about by the lashing of
their tails and contraction of the vagina, uterus and oviduct wall. It is worthy to note that during ejaculation about
twenty to one hundred and twenty million sperms are released into the vagina but of these numbers only the head of
one sperm penetrates the ovum. The sperm is able to penetrate because of the release of its acrosomal enzymes.
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These enzymes being lytic can dissolve cell walls and membranes thus enabling the sperm cell to penetrate the zona
pellucida of the ovum. The head of the sperm moves into the ovum, leaving its tail behind. The nucleus of the sperm
then fuses with that of the ovum, forming a diploid zygote.

There is a special type of reaction called cortical reaction that happens as soon as the sperm enters an ovum. This
reaction initiates some changes in the zona pellucida of the ovum, thus preventing the penetration of other sperm cell.

The process of fertilization

Example
Use the diagram below to Answer: questions 31 and 32.

The structures labeled III, VI, IV and II respectively represent the

A. uterus cervix, oviduct and ureter B. cervix, oviduct, uterus and ureter
C. oviduct, uterus, ureter and cervix D. vagina, cervix, oviduct and uterus
E. uterus, cervix, ovary and oviduct (1990/31)
Answer: A – III – Uterus; VI – Cervix, IV – Oviduct, II – Ureter.
Example
The gamete is produced in the structure labeled
A. I B. II C. IV D. VI E. V (1990/32)
Answer: E – V is the ovary which produces the female gamete.

Example

The above is the drawing of a mammalian spermatozoa. Use it to Answer: questions 20 to 22

Which of the labelled structures is the nucleus?
A. I B. II C. III D. IV E. V
Answer: B – II: Nucleus.
Which of the labeled structures secretes enzymes which facilitate penetration of the egg?
A. I B. II C. III D. IV E. V
Answer: A – I: Acrosome which secretes enzyme that facilitates penetration of the egg by the sperm.
Which of the following labeled structures is similar to the locomotory structure in euglena
A. I B. II C. III D. IV E. V (1996/20-22)
Answer: E – V: Tail (flagellum)
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Example
During mating, the male toads holds the female with it’s
A. sticky tongue B. jelly C. webbed hind limbs D. nuptial pad E. gummy limbs. (1997/20)
Answer: D – During mating, the male toads holds the female with its nuptial pads.
Example
The testes in male mammals descend into the scrotal sac because
A. there is congestion in the lower B. they run the risk of being destroyed
C. they need special support D. they require a relatively low temperature (2011/21)
Answer: D – The testes of mammals descend into the secretal sac because they require a relative low temperature.
Example
When fertilization occurs that leads to formation of a zygote, which of the following processes take place?
A. The tail of the sperm fuses with the egg cell B. Both tail and head of the sperm fuse with the egg cell
C. The nucleus of the sperm fuses with the egg cell D. The egg cell develops on its own without the sperm (2012/21)
Answer: C – The nucleus of the sperm fuses with the nucleus of the egg.
Example
The product of the union of spermatozoon and an ovum is called
A. meiosis B. zygote C. foetus D. cyst E. gamete (1996/9 Health Science Nov)
Answer: B – Zygote is the product of the union of spermatozoon and an ovum.

Example
Use the diagram below to Answer: questions 23-26

The structure labeled I is the

A. oviduct B. ovary C. uterus D. funnel
Answer: A – Oviduct (I)
In which of the labeled structures does implantation take place?
A. I B. II C. IV D. VI
Answer: C – IV (uterus)
Which of the following indicates the direction of the movements of sperm introduced into the female reproductive
system?
A. III→II→I→IV B. VI→V→IV→I C. V→IV→I→II D. VI→IV→I→III
Answer: B – VI→V→IV→I
Which of the labeled parts is responsible for the release of ripe ovum?
A. VI B. III C. II D. I (1999/23-26)
Answer: B – Ovary (III)
Example
(b) State one function of each of the following:
(i) Nucleus (iii) Vas deferens (iv) Testis (2002/6bi, iii, iv Health Science Nov)
Answer:
i. Nucleus: It carries the genetic material.
ii. Vas Deferens: It conducts sperm from the epididymis to the reminal vesicle.
iii. Testis: Production fo the male gamete (sperm) and production of the male sex hormone.
Example
Testosterone is secreted by
A. pituitary gland B. prostate gland C. testes D. ovary (2000/24 Health Science Nov)
Answer: C – The testes secrete testosterone.

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Example
The diagram below is an illustration of the human sperm.
Study it carefully and Answer: questions 20 and 21.

The part labelled I is the

A. acrosome B. nucleus C. mitochondria D. tail Answer: A – Aerosome.

The function of the part labeled II is to

A. fuse with the ovum during fertilization
B. generate the energy for the sperm to swim to the fallopian tube
C. help the sperm to swim forward
D. dissolve the membrane of the egg during fertilization (2017/20-21)
Answer: C – The function of II (tail) is to help the sperm to move forward.

Example
Which of the following structures serves as exist for both sperm and urine in the male?
A. Sperm duct B. Vas deferens C. Urethra D. Testes E. Seminal vesicle (1996/8 Health Science Nov)
Answer: C – Urethra serves as exit for sperm and urine.

Example
Which of the following secondary sexual characteristics is peculiar to boys?
A. Enlargement of sex organs B. Breaking of voice
C. Growth of pubic hair D. secretion of sex hormones (2000/4 Health Science (Nov)
Answer: B – Breaking of voice is a secondary sexual characteristics found only in males (boys)
Example
Which of the following is not part of the female reproductive system?
A. Ovary B. Fallopian tube C. Urethra D. Uterus E. Vagina (1990/44 Health Science Nov)
Answer: C – The Urethra is not part of the female reproductive system. It is part of the urinary system.
Example
Spermatogenesis and oogenesis are terms used to describe
A. meiosis B. mitosis C. gametophyte D. gametogenesis (2001/18 NABTEB)
Answer: D – Spermatogenesis (formation of male gamete) and oogenesis (formation of female gamete) are terms
used in gametogenesis (formation of gametes).
Example
In male mammal, sperms are in the
A. cowper’s gland B. scrotal sac C. seminal vesicle
D. seminiferous tubules E. vas deferens (2014/9 Neco)
Answer: C – Seminal vesicle helps to store mature sperm.
NB: Seminiferous tubules are sites where sperms are found.
EXERCISE 18.6
1. Infertility in females may be as a result of
A. hairs on the body B. lack of ovulation C. menstrual cycle
D. narrow pelvis E. small breasts (2007/53 Neco)
2. The outer covering of the human ovum is called
A. cell membrane B. nuclear membrane C. plasmallema
D. plasma membrane E. viteline membrane (2005/15 Neco Nov)
3. In mammals, fertilization takes place in the
A. Ovary B. oviduct C. uterus D. vagina E. vulva (2005/50 Neco)
4. Which of the following is not a part of the female reproductive system in mammals?
A. Oviduct B. Uterus C. Epididymis D. Vulva E. Cervix. (1992/28 Nov)

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5. Internal fertilization does not take place in
A. toad B. grasshopper C. bird D. lizard E. rat (1992/29 Nov)
6. Which of the following parts of the male gamete is essential for fertilization?
A. tail B. middle piece C. nucleus D. neck (2000/27 Nov)
7. In human beings, fertilization occurs in the
A. Vagina B. fallopian tube C. cervix D. ovary E. vulva (1996/22 Nov)
8. Which of the following classes of organisms show parental care?
A. Fish, reptile, bird B. insect, bird, mammal C. fish, bird, mammal
D. insect, mammal, toad E. mammal, toad, fish (1996/23 Nov)
9. (a) Draw a large labeled diagram of the female reproductive system of a named mammal (1996/2a Nov)
10. Spermatogenesis in mammals takes place in the
A. vas deferens B. testis C. urethra D. Cowper’s gland (2019/18 Nov)
11. The main function of the seminal vesicle is to
A. produce sperms B. destroy dead sperms C. store mature sperms
D. produce hormone E. discharge sperm (1998/27 Nov)
12. In man, spermatozoa are never found in the
A. testis B. urethra C. epididymis C. prostrate gland E. vas deferens (1982/37 JAMB)
13. Which of the following structures is NOT found in the female agama lizard?
A. Pre-anal pads B. Eardrum C. Gular fold D. Nasal scale E. Nuchal chest (1983/6 JAMB)
Use Fig. 2 to Answer: questions 24 and 25

14. The young chick is formed from

A. 3 B. 3 and 4 C. 1, 3 and 5 D. 2 E. 4 (1984/24 JAMB)
15. Which parts provide food for the developing chick?
A. 2 and 3 B. 4 and 5 C. 3 and 4 D. 2 and 5 E. 1 and 2 (1984/25 JAMB)
16. Fertilization in humans usually takes place in the
A. lower part of the uterus B. upper part of the uterus
C. lower part of oviduct D. upper part of the oviduct (1999/24 JAMB)
Use the diagram below to Answer: questions 12 and 13

17. Birth control by vasectomy is achieved by severing the structure labelled

A. IV B. I C. II D. III (2005/12 JAMB)

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 Use the diagram below to Answer: questions 10 and 11

18. The part labelled IV is for

A. excretion B. nourishment C. protection D. respiration (2006/10 JAMB)

19. The organ through which the embryo receives food, water and oxygen is labelled
A. III B. IV C. II D. I (2006/11 JAMB)
20. The reproductive system of a male mammal is made up of
A. claspers, prostrate gland, sperm duct and vas deferens
B. testis, prostrate gland, sperm duct and vas deferens
C. oviduct, urethra, testis and sperm duct
D. testis, uterus, prostrate gland and sperm duct (2009/25 JAMB)
21. In the male reproductive system of a mammal, sperm is stored in the
A. van deferens B. urethra C. epididymis D. semniferous tubules (2010/24 JAMB)
22. Which of the following possess mammillary gland?
A. Dogfish B. Whale C. Shark D. Catfish (2012/10 JAMB)
23. (a) Make a labelled diagram of the female reproductive organ of a (i) flowering plant (ii) mammal (man)
(b) State the functions of any two of the labelled parts in (a) (i) and (ii) Compare reproduction in mammals,
amphibians and birds with respect to (i) number of eggs produced (ii) method of fertilization (iii) parental
care. (1997/3a-b)

24. (b) List three differences between reproduction in mammals and in amphibians. (1992/2b)
25. In which of the following organisms is parental care manifested?
A. Tilapia B. Toad C. Cockroach D. Snail (2007/23)
26. Viviparity occurs in the
A. mammals B. reptiles C. aves D. amphibians (2001/3 JAMB)
Use the diagrams below to Answer: questions 5

27. Ovoviparity is the type of fertilization exhibited by the organism labelled

A. IV B. III C. II D. I (2002/5 JAMB)

Implantation of the embryo:

As the zygote passes down the oviduct to the uterus, it divides by successive nuclear and cell division into a small ball
of cells by a process called cleavage. On reaching the uterus, it secretes enzyme that dissolves the uterine line
(endometrium). It penetrates the uterine line and gets implanted into the uterine wall. The movement of the zygote
takes about 5-7 days and its enabled by peristaltic contraction of the muscle of the oviduct.
Development of the embryo:
The embryo feed on the yolk of the ovum at the initial stage. When the yolk is exhausted, it feeds on the food
substances in the fluid of the uterine. The embryo then develops placenta and membranes.
Placenta:
Placenta is a disc of vascular tissue formed partly by embroyonic tissue and partly by uterine linining. The embryo
is attached to the placenta by an umbilical cord which contains an artery and a vein.

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Function of the Placenta:
The placenta establishes an intimate connection between the embryo and the mother.
1. The placenta carries oxygen, water and food from the mother’s blood to the embryo’s blood.
2. It removes excretory wastes like urea, salt, carbon dioxide from the embryo’s blood and put it into the
mother’s blood stream for elimination.
3. It produces hormones that enables the mother to adapt to pregnancy
4. The placenta serves the embryo as liver, kidney, lungs, intestine and hormonal gland.
Note: The blood of the mother never passes to the embryo because
1. It would damage the embryonic capillaries since the mother’s blood pressure is greater.
2. Waste substances, antibodies and hormones of the mother may damage the embryo.
3. The disease in the mother’s blood would pass to the embryo’s blood and cause damage.

Extraembryonic membrane:
A. Amnion: This is a thin innermost membrane that covers the embryo. The space between the amnion and the
embryo is called amniotic cavity and it is filled with amniotic fluids.
Function of amnion
1. The amniotic fluid protects the embryo from shock and mechanical injury.
2. Amniotic fluid provide an even temperature for the embryo and allow the embryo to move freely.
3. The amniotic fluid keep the embryo moist.
4. The amniotic fluid is slippery and so enable an easy passage of the foetus during child birth.

B. Chorion: This is the outermost membrane that surround the amnion.

Functions:
1. It protects the embryo outside
2. It helps in the formation of placenta.
Note: After the full formation of placenta, chorion and amnion, the embryo is now called foetus. This
happens after about eight (8) weeks

C. Allantois: Allantois grows out from embryionic gut and fuses with the chorionic villi in the uterine wall.
Functions:
It is part of umbilical cord that carries foetal blood vessel to and fro the chorionic villi, thus serving for
respiration, nutrition and excretion of the foetus.
D. Yolk Sac: it has no function in mammals. It is hidden in placenta.

Human foetus
Gestation Period:
This the period of development of foetus. It starts from the time of conception (fertilization) to the time of birth.

Multiple Pregnancies
A pregnancy with one baby growing in the womb (uterus) on its own is said to be singleton pregnancy while a
pregnancy with two or more fetuses is said to be a multiple pregnancy. Multiple pregnancy leads to multiple births.
Some names for multiple pregnancies include:
 Twins for 2 fetuses
 Triplets for 3 fetuses
 Quadruplet for 4 fetuses
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 Quintuplets for 5 fetuses
 Sextuplets from 6 fetuses
 Septuplets for 7 fetuses
Twins can be of two types:
1. Fraternal (Dizygotic) Twins: Fratenal twins are non identical. They result when two ova are released and
each is fertilized by separate sperm. Two babies result which might be either of same/separate sex. They are
genetically different and during pregnancy each foetus has its own placenta amnion and chorion.
2. Identical (monozygotic) Twins: Mono means one and zygote means a fertilized egg so monozygote means
“one fertilized egg”. Identical twins are monozygotic. They are produced when a fertilized egg splits into two
equal halves before developing. Monozygotic babies are genetically identical to one another, they are of the
same sex, have identical genes and look similar as they grow up.
Note: Occasionally a fertilized egg might fail to split completely. In this case a conjoined (siamese) twins
might result.

TEST TUBE BABIES: A test tube baby is a child that is conceived outside the body of the mother. Test tube babies
are conceived in the laboratory through the scientific process of in-vitro fertilization (IVF). In-vitro fertilization is a
process of fertilization in which the fusion of the eggs and sperm happens outside the body (i.e there is no sexual
intercourse). Although fusion of the egg and sperm cells happens outside the body, development of the fetus happens
in the uterus of the mother. The steps involved in in-vitro fertilization (IVF) includes:
1. Stimulation of egg production by hormone therapy.
2. Retrieval of eggs from the ovary.
3. Collection of sperm sample.
4. Fusion of Eggs and sperm to allow fertilization.
5. Introduction of fertilized eggs into the uterus.

Example
The structure of the embryo which develops and makes contact with the uterine wall is known as the
A. umbilical cord B. placenta C. allantois D. amnion E. chorion (1990/34)
Answer: B – The placenta is the structure of the embryo which develops and makes contact with the uterine wall.

4(a) What is sexual reproduction

(b) State five functions of the placenta and four functions of the umbilical cord of a mammal. (2002/4a, b)
Answer: 4a.Sexual reproduction is the fusion of male and female gametes or nuclei to form a zygote which later
develops into an organism.
b. Function of the placenta:
- It prevents the mixing of foetal and mother’s blood.
- It exchanges carbon(iv)oxide form the foetus blood for oxygen from the mothers blood.
- It attaches the foetus to the uterine wall of the mother.
- It absorbs digested food from the mother’s blood and passes it to the foetus by diffusion.
- It prevents the passage of some pathogens from the mother to the foetus.
Function of the umbilical cord:
-It connects the foetus to the placenta.
-It suspends the foetus in the amniotic cavity.
-It serves as passage for the artery which transports waste metabolic products and deoxygenated blood from the foetus to the
placenta.
-It serves as a passage for the vein which transports digested food and oxygenated blood from the placenta to the foetus.
Example
The function of the amniotic fluid in human is to
A. protects the foetus against shocks B. remove waste products from the foetus
C. supply food and water to foetus D. carry oxygen to the foetus (2003/26)
Answer: A – The amniotic fluid functions to protect the embryo against shocks.
Example
(b) Explain the importance of the amniotic sac to the mammalian embryo (2003/2b)
Answer: - It products the embryo from shock and mechanical injury. - It provides an even temperature for the embryo.
- It allows the embryo to move freely. - It keeps the embryo moist.

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Example
The developing embryo is attached to the mother’s uterus by
A. amnion B. blood vessels C. placenta D. umbilical cord E. uterine cavity (2008/18 Neco)
Answer: C – The placenta attaches the developing embryo to the uterine wall of the mother.
Example
In man, the period of gestation for the embryo occurs in the
A. abdomen B. uterus C. cervix D. ovary E. fallopian tube (1990/45 Health Science Nov)
Answer: B – The period of gestation for embryo in man occurs in the uterus.
Example
The foetus in man receives oxygen and nourishment through the
A. wall of the uterus B. chorion membrane C. amniotic membrane
D. amniotic fluid E. villi of the placenta (1990/46 Health Science Nov)
Answer: E – The foetus in man receives oxygen and nourishment through the villi of the placenta.

EXERCISE 18.7
1. Sate five functions of the placenta and four function of the umbilical cord of a mammal. (2002/4b)
2. Explain the importance of the amniotic sac to the mammalian embryo. (2003/2b)
3. The development of a human zygote in a female is determined by the
A. course taken by the ovum in reaching the uterus B. chromosomes of the sperm
C. chromosomes of the ovum D. time at which copulation takes place (2004/21 Nov)
4. A woman giving birth to twins, a boy and a girl. Which of the following statements correctly interprets this
information?
A. her uterus was large enough for two embryo to develop B. she had her ovaries which were functional
C. her ovaries produced one egg which was fertilized
D. her ovaries produced two eggs which were both fertilized (2013/23 Nov)
5. Which of the following does not pass across the placenta of a mother to the foetus?
A. red blood cells B. Glucose C. water D. Oxygen (2002/26 Nov)

Reproduction in Bryophyte and Pteridophyte

The Bryophytes
The reproduction process of bryophytes and pteridophytes shows a clear phenomenon of alternation of generation.

Alternation of generation is a type of life cycle in which subsequent generations of individuals alternate between
haploid and diploid organism. This is seen in terrestrial plants and algae. The haploid organism is known as the
gametophyte generation because of the production of gametes. The diploid organism is known as the sporophyte
generation as it produces spores. In bryophytes, the gametophyte generation is dominant while in pteridophytes the
sporophyte generation is dominant.

Life cycle of a bryophyte

The life cycle of bryophyte consists of alternation of generation between a haploid gametophyte and the diploid
sporophyte. In the gametophyte stage, haploid gametes (male and female) are formed in the specialized sex organs.
These are the male sex organ (antheridia) and the female sex organ (archegonium). The antheridia produces
(spermatozoa) while the archegonia produces a large ovum (egg). The gametophyte reproduces sexually and water is
needed for this reproduction as the antherozoid needs to swim to the archegonium of the female, where it fuses with
the egg. The fusion of one antherozoid with the egg in the archegonium, gives rise to a diploid zygote which develops
into the diploid sporophyte

The sporophyte generation consists of sporangium which bears spores. On maturity, the spores are released and
dispersed by wind onto a suitable substratum where it germinates into a gametophyte.
The sporophyte generation depends upon gametophyte generation for most of it nutrients. Example of a bryophyte
include the Funaria hygrometrica (moss).

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 Life cycle of the moss Bryophyte
Life cycle of Pteridophyte
In the life cycle of pteridophyte, alternation of generation involving a diploid sporophyte stage and a haploid
gametophyte also takes place but one of the difference it has with that of bryophyte is that the sporophyte generation
is dominant over the gametophyte generation.
On the underside (abaxial surface) of the leaves, sporangia which produce spores are organized into a sorus. When
spores mature, they are released from the sporangia and dispersed by wind. The released spores locate suitable
substratum and grows into a small heart shaped prothallus plant which represent the gametophyte generation. The
prothallus bears both male and female reproductive organs (antheridia and archegonium). The reproductive organs
produce gametes which fuse to form the zygote. The male gamete is known as the antherozoids. It swims in water to
meet the female gametes (ova) located in the archegonium. The zygote grows using mitosis into the sporophyte and
the cycle continues again. Example of pteridophyte includes ferns (e.g. dryopteris) and club mosses.

Life cycle of pteridophyte

Reproductive System in Flowering Plant

The part of the shoot modified for sexual reproduction is known as the flower. The flower is a cluster of modified
leaves consisting of four whorls (floral leaves). The floral leaves are borne on a shortened stem called the flower stalk
or pedicel. Some flowers however lack the pedicel and are said to the “sessile”. The four flower whorls are
1. Sepals/calyx
2. Petals/corolla
3. Stamens/androecium
4. Carpels/gynoecium/pistil

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Functions of the reproductive part of flower
PART OF A FLOWER FUNCTIONS
1. Pedicle (flower stalks) Attaches the flower to the shoot.
2. Receptacle Carries and hold together the other parts of the flower.
3. Sepals (calyx) Encloses the other parts of the flower when the flower is in the bud stage. If
brightly coloured, it also attracts insects, if green, it makes plant food
4. Petals Attract insects which pollinate the flower
5. Filament Holds up the anthers
6. Anther Contains pollen grains
7. Pollens Gives rise to male gamete that fertilize the ovules
8. Stigma Receives pollen grains at pollination
9. Style Connects the stigma to the ovary, pollen tube grows through it to reach the ovule
10. Ovary Contains ovules, develops into the fruit
11. Ovules Contain the female gametes. It develops into seeds.

Essential and Non Essential Parts of a Flower

Androecium (Stamen) and Gynoecium (pistils) are considered the essential organs of a flower. This is because they
produce the gametes which will ensure fertilization.

Non essential parts of a flower: The petals and the sepals are regarded as the non essential parts of a flower because
they are not required for gamete production in flowers. Others are pedicel and recepetacle e.t.c.

Perianth and Perianth Segment

Perianth is a word commonly used to describe the unidentified calyx and corolla of a flower together. In many
monocot flowers, the petals and sepals are so alike in number, size and colour that it is often not easy to distinguish
between them. In such flowers, the calyx (sepals) and corolla (petals) are referred together as the perianth segments.
The individuals parts are called tepals.

Androecium
This is a collection of stamens that form the male reproductive organs of a flowering plant. A stamen consist of an
anther and a filament which is attached to either to the receptacle or petals.
Different shapes of anther can be seen in flowering plants but irrespective of the shape, an anther consists of two lobes
and each lobes consists of pollen sacs. Pollen grains from which the male gametes are produced, are located in the
pollen sac. On maturity, the anther dehisces and releases the pollen grains which are seen as yellowish powdery
substances at the surfaces.

Stamen Transverse section through an anther showing the

pollen sacs in the anther lobes.

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The Gymnoecium (Pistil, Carpel)
The female reproductive organs of a flower are known as the gymnoecium. It forms the innermost whorl of flower
and can also be referred to as the pistil or carpel. The gymnoecium consist of the ovary, the style and the stigma.
The stigma receives the pollen grains and it is connected to the ovary by a narrow tube known as the style. After
pollination, the male gamete is carried to the ovary by a pollen tube which grows from the style.

Female reproductive organ of a flower

An ovary may be monocarpous, apocarpous or syncarpous.

An ovary is monocarpous if it consists of only one chamber as in Cassia, Crotalaria, pride of Barbados.

Monocarpous ovary of cassia

In an apocarpous ovary there are two or more carpels which are free from each other.

An apocarpous ovary of bryophyllum

An ovary is syncarpous if it consists of two or more united carpels as in hibiscus and orange

A syncarpous ovary of hibiscus

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Types of Ovary
Superior Ovary
An ovary is described as superior when it is placed above the other floral parts e.g. Hibiscus. This type of flower with
superior ovary is known as hypogynous flower.

Superior ovary

Half Inferior Ovary

An ovary is described as half inferior when the ovary lies inside a cup – shaped receptacle and other floral parts
attached slightly above it or almost the same level e.g. rose flower. The flower having this type of half inferior ovary
is described as perigynous flower.

Inferior ovary
An ovary is described as inferior when it is placed below the other floral plants. i.e. other floral parts are above it on
the receptacle e.g. Cana lily, sunflower, quava e.t.c. The flower having this type of inferior ovary is described as
epigynous flower.

Inferior ovary
Some other important facts to note about flowers
1. Different symmetries are present in flowers. Flowers that have multiple line of symmetry are radially symmetrical.
Such flowers are called Regular or actinomorphic flowers.While flowers with only a single line of symmetry are
said to be bilaterally symmetrical and are referred to as Irregular or Zygomorphic flowers.

2. Flowers pollinated by wind are said to be anemophilous e.g grass, maize, wheat, oat e.t.c while those pollinated by
insects are said to be entomophilous e.g Rose, Bougainvillea, lotus, Jasmine e.t.c.

Example
The female part of a flower consists of the
A. stigma, style and ovary B. petals, sepals and pollen grains C. terrestrial habitat
D. marine habitat E. aquatic habitat (1991/36)
Answer: A – The female part of a flower consist of the: stigma, style and ovary.
Example
Which of the following is the function of bright coloration of petals in flowers?
A. Beautifying the environment B. Providing warning coloration for insects
C. Attracting pollinating insects D. Production of chloroplasts for photosynthesis
E. Synthesizing dyes for textile industries (1992/32)
Answer: C – The bright coloration of petals in a flower attracts pollinating insects.
Example
(c). Describe the structure and function of the male reproduction organ of a flowering plant. (1992/2c)
Answer: The male reproductive organ of a flowering plant is called the androecium. This is made up of the stamens
which are made up of filaments and anthers. The filaments suspend the anthers which contain pollen sacs. The pollen
sacs contain pollen grains (male gametes).

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Example
The essential parts of a flower are
A. petals and sepals B. anther and filament C. stigma and style
D. androecium and gynoecium E. petals and gynoecium (1997/32)
Answer: D – The essential parts of a flower consist of the androecium and the gymnoecium.
Example
The collective name for the female parts of the flower is
A. gymnoecium B. androecium C. ovary D. stigma E. style (1998/26)
Answer: A – The collective name for the female part of a flower is gymnoecium.
Example
If the petals of a flowering plant are removed, which of the flowering processes is likely to be affected?
A. Transpiration B. Pollination C. Germination D. Photosynthesis E. Dispersal (1998/27)
Answer: B – Pollination is likely to be affected when the petal of a flower plant is removed. This is because the
bright coloration of the petals attracts pollinators.
Example
Which of the following is not an example of entomophilous flower?
A. Hibiscus B. Flamboyant C. Guinea grass D. Allamanda (2002/24)
Answer: C – Guinea grass.
NB: Entomophilous flowers are those that are polilanted by insect. This is due to them having a bright coloured
petals and the presence of nectar.
Example
An inferior ovary of a flower is situated
A. below the floral parts B. above the floral parts
C. at the same level with all the floral parts D. at the centre of the floral parts (2014/19)
Answer: A – An inferior ovary of a flower is situated below other floral parts.

Example
The androecium is composed of filament
A. pollen grains and ovules B. Anther and pollen sac
C. style and pollen sac D. stigma and pollen sac (2019/34 NABTEB)
Answer: B – The androecium is composed of filament, anther and pollen sac.

Example
A flower with two or more fused carpels is called
A. apocarpous B. monocarpous C. polycarpous D. postillate E. synocarpous (2014/49 Neco)
Answer: E – Syncarpous.
Example
The diagram below is an illustration of the longitudinal section of a flower.
Study it and Answer: questions 20 and 21.

Which part of the flower is responsible for the protection of young flower buds?
A. I B. II C. III D. IV (2019/20) Answer: B – II (receptacle)
Example
The essential parts of the flower are labeled
A. I, II and III B. II, III and IV C. III, V and VI D. IV, V and VI (2019/21)
Answer: D – IV: Ovary, V: Style and VI: Anther

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Example
Use the diagram below to Answer: questions 29 and 30.

In the diagram above, identify the essential parts of a typical flower in the following lists
A. pedicel, calyx, ovary and corolla B. stigma, ovary, anther and filament
C. filament, style ovary and peduncle D. style, anther petal and sepal (2001/29 NABTEB)
Answer: B – Stigma, ovary, anther and filament are the essential part of a flower.
Example
Which part(s) of the diagram is the ovary
A. III and IV B. V and VI C. VI only D. IV only (2001/30 NABTEB) Answer: C – VI only.

Example
Use the diagram below to Answer: questions 56 and 57

The part labeled I is the

A. anther B. ovary C. petal D. stamen E. stigma Answer: E – Stigma.
The part that receives pollen grains during pollination is
A. I B. II C. III D. IV E. V (2014/56-57 Neco) Answer: A – I (Stigma)
Example
Petals join together to form a tube known as
A. epigynous B. gamopetalous C. hypogynous D. polypetalpus E. polysepalous (2008/19 Neco)
Answer: B – A Gamopetalous flower has it Petals totally or partially fused in such a way that the corolla takes the
form of a tube.

Example
A flower made up of one carpel is referred to as
A. apocarpous B. monocarpous C. monogamous D. pericarpous E. syncarpous (2007/11 Neco)
Answer: B – A flower made up of one carpel is referred to as monocarpous flower.
Example
The male and female gametes of a flower are
A. stigma and anthers B. style and stigma C. pollen grains and ovules
D. ovary and anthers E. anthers and filaments (2007/18 Neco)
Answer: C – The male and female gametes are pollen grains and ovules respectively.
Example
When both petals and sepals of flower are of the same colour, they are referred to as
A. corolla B. inflorescence C. perianth D. petaloid E. sepaloid (2005/53 Neco Nov)
Answer: C – Perianth is the collection of the sepal and petal. When the perianth are of the same colour, it is called
tepal.
NB: Sepaloid – When a part of the flower looks like the sepal.
Petaloid – When a part of the flower looks like the petal.
Example
Which part of the flower contains the male gametes?
A. anther B. filament C. ovary D. petal E. style (2005/57 Neco Nov)
Answer: A – The anther contains the male gamete.

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Example
In flowers, stigma style and ovary are collectively called
A. Androecium B. gynoecium C. inflorescence D. pedicel E. phosphorus (2005/49 Neco)
Answer: B – In flower, stigma, style and ovary are collectively called gymnoecium.
Example
A flower with two or more fused carpels is called
A. apocarpous B. monocarpous C. polycarpous D. pilstillate E. syncarpous (2018/8 Neco)
Answer: E – A flower with two or more fused carpels is called syncarpous flower.
Example
Which of the following structures produces the male gametes in flowering plants?
A. generative nucleus B. Tube nucleus C. pollen tube
D. endosperm nucleus E. antipodal cell (1992/31 Nov)
Answer: A – The generative nucleus is also known as the male nucleus. It divides into two nuclei which are used for
fertilization when they get to the ovary.
EXERCISE 18.8
1. The androecium is composed of filament
A. pollen grains and ovules B. anther and pollen sac
C. style and pollen sac D. stigma and pollen sac (1999/35 Nov)
2. A flower is described as apocarpous when its
A. carpels are separated from one another B. floral parts are below the ovary
C. floral parts are above the ovary D. carpels are found below the receptacle (1999/39 Nov)
3. A collection of petals is called
A. Perianth B. inflorescence C. episepal D. stamen E. corolla (1996/24 Nov)
4. If sepals are joined in a flower, such a flower is said to be
A. polysepalous B. gamopetalous C. gamosepalous D. polypetalous E.syncarpous (1997/29 Nov)

5. Which of the following flowers has bilateral symmetry?

A. morning glory B. Hibiscus C. Crotalaria D. Allamanda E. pawpaw flower (1998/29 Nov)
6. (d) (i) Describe the female reproductive structure of a flowering plant (2013/2di Nov)
7. A flowering plant is monoecious if
A. the androecium is found on one plant B. the gynoecium is monocarpous essential organs
C. it produces essential organs D. the gynoecium and androecium are on the same plant
E. the flowers are unisexual (1984/28 JAMB)

Use the figure below to Answer: questions 34 to 36

8. The flower shown beside is

A. complete, regular hermaphroditic with superior ovary B. incomplete, regular, staminate with inferior ovary
C. complete, regular, hermaphroditic with inferior ovary
D. incomplete, irregular pistillate with superior ovary (1987/29 JAMB)
9. A flower showing radial symmetry is said to be
A. pentamerous B. prontandous C. protygynous D. actinomorphic (1987/30 JAMB)
10. The fleshy base of a flower to which the different floral parts are attached is known as
A. calyx B. sepals C. receptacle D. hypothalamus (1994/26 JAMB)

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 Use the diagram below to Answer: questions 22 and 23

11. The ovary represented is

A. half-superior B. inferior C. superior D. half-inferior (1997/22 JAMB)
12. The corolla is partly represented by
A. I B. II C. III D. IV (1997/23 JAMB)
Use the diagram below to Answer: questions 33 and 34

13. The part labelled II is the

A. stigma B. Anther C. filament D. style (2004/34 JAMB)

14. The male reproductive organ of a flower is the

A. carpel B. stamen C. petal D. sepal (2013/33 JAMB)
15. The main functions of the petal of a flower is to
A. attract pollination agents B. protect the flower while still in the bud
C. serve as landing stage for insects D. protect the inner parts of desiccation (2019/8 JAMB)

Placentation
This is the arrangement of the ovules within the ovary. The ovules are attached to the ovary by fleshy structure called
placenta through short stalk called funicles.

Types of Placentation
1. Marginal: In this type, the ovules are attached to the placenta along one margin of the ovary (monocarpous).
Examples include Delonix regia, crotalaria, cassia, flamboyant, pride of Barbados e.t.c.

Marginal placentation

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2. Parietal: In the parietal plancentation, the ovules are attached to the edges of the fusion points of a syncarporus
ovary e.g. paw-paw.

Parietal placentation

3. Axile placentation: In this type, the carpels of a syncarpous ovary meet in the centre to form the placenta to
which the ovules are attached e.g. tomato, orange e.t.c.

Axile placentation

4. Free Central: In this type of arrangement, the ovules are borne on a knob which projects from the base of the
ovary e.g. Cana lily, coconut, water leaf.

free central placentation

5. Basal placentation: In this type, the ovules are attached the base of a syncarpous ovary e.g sunflower, mango
e.t.c.

basal placentation
Example
(c) List four types of placentation in flowering plants. (2002/4c)
Answer: i. Marginal placentation ii. Parietal placentation iii. Axile placentation iv.Free central placentation
Example
Placentation of plants is best described as the
A. arrangement of ovules on the ovary B. arrangement of fruits on fruits on the branches
C. development of ovules in the ovary D. formation of pericarp from the ovary wall. (2003/24)
Answer: A – Placentation is the arrangement of ovules within the ovary.

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Example
Use the diagram below to Answer: questions 36-38

The type of placentation shown above is found in

A. cana lily B. orange C. pawpaw D. pride of Barbados E. sunflower
Answer: B – Orange has axile placentation.
The part labeled X is the
A. ovule B. petal C. placenta D. sepal E. stamen
Answer: C – “X” points to the placenta.
The type of placentation represented in the diagram is
A. axile B. basal C. free central D. marginal E. parietal (2018/36-38 Neco)
Answer: A – Axile placentation.
EXERCISE 18.9
1. When the ovules are arranged along one edge of an ovary, the placentation is said to be
A. parietal B. marginal C. free-central D. axile (2000/29 Nov)
2. The term placentation in fruits describes the
A. Arrangement of inflorescence on the periant B. development of the ovary wall to form pericarp
C. arrangement of ovules in the ovary D. arrangement of petals in the reptacle
E. development of ovules in the ovary (1996/25 Nov)

3. The type of placentation shown in the figure beside is

A. parietal B. marginal C. axile D. free-central (1990/30 JAMB)
Use the diagram below to Answer: questions 21 and 22.

4. The type of placentation shown is

A. axial B. marginal C. parietal D. central (1995/21 JAMB)
5. An example of a plant having the placentation shown is
A. allamander B. hibiscus C. water lily D. pride of Barbados (1995/22 JAMB)

Pollination in Plant
Pollination is the transfer of mature pollen grains from the anther to the mature stigma of flowers.

Types of Pollination
There are two types of pollination
1. Self pollination
2. Cross pollination

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Self pollination: is the transfer of mature pollen grains from the anther of a flower to the stigma of the same flower
or to the stigma of another flower of the same plant e.g. pea, cotton, tomato. For self pollination, only one parent is
involved.
Features that aid Self Pollination
1. HOMOGAMY: A bisexual flower is one that posses both stamens and carpel on it. The maturation of the
anthers and stigmas of a bisexual flower at the same time is known as homogamy. Under this condition, self
pollination may occur in the following ways:
i. A gentle breeze may blow the mature pollen grains which may be shed on mature stigma that are
situated below
ii. A visiting insect may transfer the mature pollen grains to the stigma of the same flower.
iii. Self pollination may also occur when mature stigma push their way out of the corolla during which they
are brushed against the anthers and in the process pollen grains are collected
iv. In a situation where the filaments are longer than the stigma, the filament may recoil to touch the mature
stigma e.g. four o clock plant.
v. In like manner, self pollination may occur where the style are longer than the filaments. The style may
also bend or recoil to make the stigma touch the anther.

2. CLEISTOGAMY: This is the phenomenon in which flowers never open and in such flowers, only self
pollination occurs. Some bisexual flowers never open and in these “closed” flowers, the pollen grains are
discharged directly on the receptive stigma.
Advantages of Self Pollination
1. It reduces wastage of pollen grains.
2. Since transfer of pollen grains is on same plant, pollination is certain as little or no distance is involved.
Disadvantages of Self Pollination
1. Variation is minimal amongst species and the rate of evolution is slow.
2. Adaptation to environmental changes is low, leading to lack of survival.
3. Weak offspring usually results due to repeated self pollination.
Cross pollination: This is the transfer of mature pollen grains from the anther of a flower to the stigma of a flower
of another plant of the same or closely related species. e.g. morning glory, hibiscus, pride of Barbados. For cross
pollination to occur, two parent plants are involved.
Features that aid Cross Pollination
1. Dichogamy: The maturation of the anther and stigma of a bisexual flower at different times is known as Dichogamy. It
occurs in two ways:
i. Protandry: This is when the anthers of a flower mature before the stigma does. The pollen grains are usually
liberated before the stigma matures and are useful only to the flower of other plants that have mature stigma to
receive them e.g. sun flower, okro and corn. Flower of this nature are said to be protandrous.
ii. Protogyny: In this condition, the stigma of a flower matures before the anther does. The pollen grains of such
flowers cannot be useful for pollination in the flower. Flower of these nature are said to be protogynous e.g.
dutchmars pipe
2. Unisexuality: Unisexuality is the condition in which an organism produces only male/female gamete but never both. A
unisexual flower is one that has either stamen/carpels as its sexual part. If the flower has only stamens, it is described as
staminate. If on the anther only carpels are present, it is referred to as pistillate. Examples of unisexual plants include
the maize and paw-paw. In dioecious plants like pawpaw, only cross pollination can occur as the male and female flower
are borne on separate plants while in monoecious plants like oil palm and maize. Self pollination is possible but
likelihood is reduced by having:
i. Female flowers above and male flowers below.
ii. Male flowers and female flowers ripening different times.
In the latter case, the plant function as a male plant when only the male flowers are mature, and as a female plant when
the female flowers are mature
3. Self – sterility (self incompatibility): The inability of a flower or plant to fertilize itself is known as self
sterility. The bisexual flowers of some species may bear mature stamen and carpel at the same time. However, if pollen grains fall
on the stigma of the same flower or of flowers on the same plant, they fail to germinate. This is called self incompatibility and is
an inherited condition. Examples of such plants are passion flower.

ADVANTAGES OF CROSS POLLINATION

1. Cross pollination leads to the production of more viable seeds
2. It leads to production of seeds that are resistant to disease and unfavourable environmental conditions.
3. Undesirable characters of plants can be eliminated through cross pollination.
4. It helps in evolution.
5. It leads to the production of more seeds.

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DISADVANTAGES OF CROSS POLLINATION
1. It leads to wastage of pollen grains.
2. Pollination may fail due to distance barrier.
3. Flowers have to rely on external agencies for pollination. These external agencies are unreliable as their
presence cannot be guaranteed at the right time. They include bird and insects.

CHARACTERISTICS OF INSECT POLLINATED FLOWER

Insects–pollinated flowers are also called entomophilous flowers. Examples are Hibiscus, Delonix (Flamboyant)
cowpea, Crotalaria, pride of barbados e.t.c.
They have the following characteristics
1. They have large conspicuous petal/sepals
2. The petals of the flowers are usually brightly coloured.
3. Other parts of the flower may be brightly coloured in some other plants e.g Bract in Bougainvillea and
Pornsetta, or sepals in Caesalpinia pulcherima
4. Many have sweet smell/scents. Those that are pollinated at night tend to be more strongly scented to attract
the nocturnal insects e.g. moths
5. Insects pollinated flowers e.g. Hibiscus and flamboyant, have nectars – a sweet juice, which is the liquid food
for many of the insect pollinators e.g. honey bee, moth and butterfly
6. The stamens are conspicuous. They occur in definite numbers
7. Pollen grains are rough, sticky and relatively few
8. Petals are arranged to enable visiting insects become dusted with pollen grains

CHARACTERISTICS OF WIND POLLINATED FLOWERS

Wind pollinated flowers are also called anemophilous flowers. Examples are maize, rice, millet, grasses, wheat and
sugarcane.
They have the following features
1. They have small inconspicuous petal/sepal.
2. Flowers are usually dull coloured. The perianth (i.e calyx and corolla) is usually tiny, pale green and
inconspicuous.
3. The sizes of the flowers are usually inconspicuous but they are often borne in large inflorescences e.g. cereals,
sugar cane and coconut.
4. They have neither scent nor nectar.
5. They are not bilaterally symmetrical but are radially symmetrical.
6. Large quantities of pollen grains are produced.
7. Pollen grains are smooth, light and not sticky.
8. Anthers are attached to the flowers in such a way that they readily swing in the air and release the pollen
grains.
9. The stigmas are usually large, branched and feathery. This feature provides a wide surface on which floating
pollen grains may be caught. Styles are long and they project out of the flower.

AGENTS OF POLLINATION (POLLINATORS)

Pollination is mediated commonly by living and non – living agents called pollinators

BIOTIC–POLLINATORS: Examples include insects (entomorphily) such as bees, moth, butterfly, wasp and ant,
and vertebrates (zoophily) such as bats and birds especially sunbirds, humming bird and honey eaters.

ABIOTIC POLLINATORS: Examples include wind (anemophyl) and water (hydrophily). Only 10% of flowering
plants are pollinated without animal assistance. Many plants show various structural adaptation which relate them to
each agent of pollination

POLLINATION BY WATER: This occurs in aquatic habitats. The flower releases their pollen directly into
surrounding water. A very small percentage roughly 2% of pollination occurs by water.

DEVELOPMENT OF NEW SEED

The flower is the reproductive structure in flowering plants. The flower is attached to the stem by the flower stalk or
pedicel. The flower consists of four whorls which are:
i. Sepals
ii. Petals
iii. Stamen (androecium)
iv. Carpel (gymnoecium or pistil)

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Only the stamen and carpels are involved in the development of zygote. Fertilization occurs after pollination has
taken place in the flowers. Pollination as earlier treated is the transfer of pollen grains from the anther to the mature
stigma of the same flower or of another flower of the same species. After pollination, the pollen grains absorb a
sugary liquid on the stigma, swell and germinate. The pollen grain and the ovule are the main sex cells (male and
female) respectively, involved in the formation of zygote in flowering plants.

The pollen grain is a haploid cell consisting of:

i. Exine which is the outer thick wall.
ii. Intine which is the inner thick wall
iii. A centrally placed nucleus.
The exine covers the intine while the nucleus is embedded in the intine.

Development of Ovule:
It has earlier been stated that the carpel consists of a stigma, style and ovary. Within the ovary, the ovules develop.
Each ovary is attached to the ovary wall at a point called the placenta by a short stalk or funicle through which food
and water passes to the developing ovule.

An immature ovule consists of nucleus, and cytoplasm protected by two sheaths of integuments. A tiny hole known
as micropyle is left in the integuments at one end of the ovule. It is through this hole that pollen tube enters the
ovule. At maturity the ovules undergoes repeated mitosis until eight nuclei are produce in an embryo sac. Four nuclei
can be seen at each end of the embryo sac. The two ends of the embryo sac are known as the micropylar end and
chalaza end respectively. One nucleus from each end moves to the centre and they both fuse to become the
secondary nucleus. The remaining three nuclei at the chalaza end forms the antipodal cells while amongst those at
the micropylar end, one functions as the female gamete/ovum while the remaining two nuclei serves as guard synergid
cells below it. At this stage, the ovule is ready for fertilization.

Stages in the development of an ovule

Development of the pollen grain and fertilization in flowering plants:

In flowering plants, the zygote is formed through the following processes:
1. After pollination the pollen grain absorb a sugary liquid secreted by the stigma. It then swells and germinates.
2. The outer thick wall of the pollen grain, the exine split. The pollen tube grows out and down inside the style.
At this stage the pollen grain has only one nucleus which later divides into two (a larger tube nucleus and a
smaller generative nucleus).
3. The generative nucleus divides into two male nuclei, which functions as the male gamete.
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4. The pollen tube grows into the ovule through the micropyle, and the end of the pollen tube degenerates
releasing the two male nuclei into the embryo sac.
5. One of the male nucleus fuses with the ovum to form a zygote. The zygote develops into the embryo.
6. The second male nucleus fuses with the secondary nucleus to form a triploid cell that produces the
endosperm. This is called the second fertilization (double fertilization) and it occurs only in flowering
plants.

Generative nucleus

The stages in the development of a pollen grain and the process of fertilization

Example
A flowering plant having both the male and female flowers on the same plant, is said to be
A. regular B. monoecious C. irregular D. dioecious (2003/25)
Answer: B – Flowering plant having both the male and female flowers on the same plant is said to be monoecious.
NB: Dioecious is the opposite of monoecious.

Example
Double fertilization is said to occur in flowering plants because
A. two embryos are formed B. one egg is fertilized twice C. two sperms fertilize each egg
D. one embryo and an endosperm nucleus are formed E. two sperms and two pollen grains are involved. (1988/9)
Answer: D – Double fertilization is said to occur in flowering plants because one embryo and an endosperm
nucleus are formed.
Example
A monoecious plant bears
A. perfect staminate flowers on the same plant B. staminate and pistillate flowers on the same plant
C. perfect and pistillate flowers on different plants D. pistillate and staminate flowers on different plants. (2011/19 Nov)
Answer: B – A monoecious plant bears staminate and pistillate flowers on the same plant.
Example
Which of the following is not correct about a fruit? It
A. may contain many seeds B. is a mature ovary C. is covered by the pericarp
D. may develop from the receptacle E. possesses only one scar. (1988/24)
Answer: C – The pericarp is the walls of a ripened ovary.
NB: The pericarp covers the seed and not the fruit. Hence option “C” is not correct about fruit.
Example
3(a) Describe how the floral parts of a named flower are adapted to wind-pollination. (1989/3a)
Answer:
- The flowers produce a large number of light smooth and powdery pollen grains. These pollen grains are borne
in large inflorescence but are small and inconspicuous.
- The stigma are large and feathery and are hanged outside the flower. This provides a large surface area for
pollination and increases the chance of trapping pollen grains in the air.
- They possess long style which makes the stigma prominent.
- They possess long filaments that bear loosely attached anthers which are exposed to the wind. This facilitates
the dispersal of pollen grain by wind.
- They have dull coloured flowers.
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Example
The ovary of a flower after fertilization will
A. become the seed B. wither away C. become the fruit D. develop into sepals (2019/36 NABTEB)
Answer: C – The ovary of a flower after fertilization will become the fruit.
NB: The ovule will become the seed.
Example
Which of the following is the effect of using artificial pollination in plant breeding?
A. Production of healthy crops B. Improvement of the variety of crops
C. Making crops susceptible to diseases D. Lengthening the maturity time of crops
E. Encouraging competition amongst crops (1990/36)
Answer: B – Artificial pollination in plant breeding improves the variety of crops.
Example
Which of the following is not a feature of a seed or fruit dispersed by the wind?
A. Light weight B. Parachute C. Pappus D. Wings E. Hooks (1992/34)
Answer: E – Possession of hooks is not a feature of a seed or fruit dispersed by wind.
Example
Which of the following structures are characteristics of insect pollinated flowers?
A. dull colored flowers with no nectar B. Very light, numerous, and pendulous stamen
C. Brightly colored petals, scent and nectar D. flowers are usually small and inconspicuous
E. stigma are large, feathery and hang outside the flower (1995/24)
Answer: C – Brightly coloured petals, scent and nectar are characteristics of insect pollinated flowers.

Example
Which of the following is a feature of wind pollinated flowers?
A. Large and brightly coloured petals B. Possession of sweet scent C. Presence of nectar
D. Presence of pollen guides E. Smooth, light and numerous pollen grains (1998/31)
Answer: E – Wind pollinated flowers possess smooth, light and numerous pollen grains.
Example
(b) (i) in a tabular form, state five differences between wind and insect pollinated flowers
(ii) give one example of each
(c) (i) State three agents of fruit and seed dispersal
(ii) Give an example of fruits or seeds dispersed by each agent (1998/2b-c)
Answer:
2bi. Wind pollinated flowers Insect pollinated flowers
- Flowers are not brightly coloured. - Flowers are brightly coloured.
- They have no odour or smell. - They possess odour or scent.
- No nectar is present. - Present of nectar.
- Flowers are small or inconspicuous. - Flowers are large and conspicuous.
- Pollen grains are not sticky. - Pollen grains are sticky.

bii. Examples of wind pollinated flower are: Rice, maize, grass etc.
Examples of insect pollinated flower are: Mango, Hibiscus, orange, sunflower, Pride of Barbados etc.

ci. Agents of fruit and seed dispersal are wind, animals and man.
ii. Examples of fruits or seeds dispersed by each agent:
Wind: Cotton, tridax etc.
Animals: Pawpaw, guava, etc.
Man: Cocoa, coconut etc.

Example
Which of the following is not a characteristics feature of a wind dispersed fruit?
A. Light weight B. Winged apparatus C. Flossy structure D. Buoyancy (1999/28)
Answer: D – Buoyancy is not a characteristic feature of a wind dispersed fruit.
Example
Which of the following is an agent of pollination of grasses?
A. Insects B. Water C. Wind D. Mammals (2001/29)
Answer: C – Wind is an agent of pollination of grasses.
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Example
When the zygote of an organism continues to grow, it produces new cells by
A. meiosis B. crossing-over C. gestation D. mitosis (2003/9)
Answer: D – The zyote of an organism produces new cells by mitotic division.
Example
(a) Describe the process that occur from the time a pollen grain is deposited on the stigma of a flower to the formation
of a zygote. (2003/2a)
Answer: When the pollen grain falls on the stigma, it absorbs water and nutrients from the stigma after which it starts
to grow towards the ovule by swelling and germinating to form the pollen tube which carries a tube nucleus and a
generative nucleus. It finally enters the ovule through the micropyle to enter the embryonic sac. In this sac, the
pollen tube releases the male nuclei as the tube nucleus degenerates. Then one of the male nuclei fuses with the egg
cell to form a zygote.

Example
(b)(i) State five features which ensure cross pollination in plants. (ii) Name one plant example for each feature.
(c) (i) Name three agents of pollination (ii) State three features of wind-dispersed fruits/seeds. (2004/3bi-ii, ci &ii)
Answer:
3bi-ii. Features which ensures cross pollination in plants and one plant example each:
- Possession of male and female flowers on different plant. E.g. Pawpaw.
- Maturation of male and female flowers at different time. E.g. Mistletoe.
- Possession of longer style and shorter stamen. E.g. Morinda.
- Possession of male and female flowers on the same plant but in different position. E.g. Maize.
- Maturation of stamen before carpel. E.g. sunflower.

ci. Three agents of pollination: Wind, animals and man.

ii. Three features of wind-dispersed fruits/seeds:
- Possession of light-weight.
- Possession of winged structures.
- Possession of hair-like structures.
Example
Which of the following adaptation is not found in fruits and seeds dispersed by the wind?
A. Small and light body B. Spongy coats C. Turfs of hairs D. Wings on pericarp (2005/5)
Answer: B – Spongy coats are not features found in fruits and seeds dispersed by wind.
Example
Which of the following statements best describes pollination? The transfer of pollen grain from
A. anther to stigmas B. stigmas to stamens
C. the anther of a flower to the stigma of another flower of a different species D. anther to the ovary. (2006/24)
Answer: A – Pollination is the transfer of pollen grains from the anther to the stigma.
Example
The transfer of ripe pollen grains from the anther to the stigma of thesame flower is termed
A. fertilization. B. self pollination C. reproduction. D. conjugation (2007/3)
Answer: B – Self pollination is the transfer of ripe pollen grain from the anther to the stigma of the same flower.
Example
The brightly coloured petals in some plants is an adaptive colouration for
A. feeding B. pollination C. dispersal D. shedding. (2012/24)
Answer: B – Brightly coloured petals in some plants is an adaptive coloration for pollination.
Example
Which of the following structures is not essential in a wind pollinated flower?
A. Anther B. Ovary C. Stigma D. Petal (2013/21)
Answer: D – Petal is not an essential floral part of a wind pollinated flower.
Example
A flower has its stigma above the anther and the anther always ripens before the stigma. What type of pollination will
be possible in this type of floral arrangement?
A. Self pollination B. Cross pollination C. Wind pollination D. Water pollination (2011/18 Nov)
Answer: B – A flower that has it’s stigma above the anther and in which the anther ripens before the stigma will
undergo cross pollination.

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Example
Study the diagram below and use it Answer: questions 22 and 24

Which part of the flowers produces the structure labeled III?

A. Carpel B. Pollen C. Stigma D. Anther
Answer: B – Pollen grain produces the pollen tube III.
The parts labeled III and IV respectively are called
A. Pollen tube and style B. Pollen grains and pollen tube C. Anther and filament D. Stigma and style
Answer: A – III: Pollen tube and IV: Style
Which of the labeled parts would become a component of the seed after fertilization?
A. I B. II C. IV D. V (2013/22-24)
Answer: A – I: Embryo sac forms part of the seed.
Example
Which of the following condition in flowering plants enhance self-pollination?
A. Cleistogany B. Heterostyly C. Protandry D. Protogyny (2014/14)
Answer: A – Cleistogamy is the production of flowers which do not open and are self-fertilized in the bud.
NB:
Protandry: This is a condition where the male reproductive part of a flower matures before the female reproductive part.
Protogyny: This is a condition where the female reproductive part of a flower matures before the male reproductive part.
Heterostyly: This is a condition where a flower has unequal styles.
Protandry, protogyny and heterostyly encourange cross-pollination
Example
(c) State three reasons why the dispersal of fruits and seeds are important. (2014/3c)
Answer:
- Prevents overcrowding of plant.
- Prevents diseases from spreading among the plant easily.
- Results in the colonization of new areas with new plant.
Example
3(a) State FOUR agents of fruits and seeds dispersal, giving one example in each case. (2001/3a NABTEB)
Answer: Wind e.g. Tridax ; Water e.g. Coconut ; Animals e.g. Hibiscus ; Man e.g. mango
Example
Which of these is dispersed by wind?
A. tridax B. coconut C. mango D. tomato (2017/38 NABTEB)
Answer: A – Tridax is an example of plant that is dispersed by wind.
Example
Which of the following structures are characteristics of insect pollinated flowers?
A. dull colored flowers with no nectar B. Very light, numerous, and pendulous stamen
C. Brightly colored petals, scent and nectar D. flowers are usually small and inconspicuous
E. stigma are large, feathery and hang outside the flower. (1995/24)
Answer: C – Flowers with brightly coloured petals, nectar and scent are mostly pollinated by insects.

EXERCISE 18.10
1. 2(a) (i) Define the term pollination. (ii) List two agents of pollination. (2018/2ai-ii NABTEB)
2. (c) Write TWO features each for:
(i) Self pollinated flowers (ii) Cross pollinated flowers. (2005/2ci, ii Neco Nov)
3. The transfer of rice pollen grains from the anther to the stigma of the same flower is termed
A. fertilization B. self-pollination C. reproduction D. Cross pollination (2002/27 Nov)

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4. (d) Explain the terms: (i) Self-pollination ii. Cross-pollination
(e) In a tabular form, state six differences between wind-pollinated flowers. (2002/2di & ii, e Nov)
5. Which of the following insects is not an agent of pollination?
A. Bees B. Butterflies C. Termites D. Moths (2011/20 Nov)
6. 3ai. Define the term pollination
ii. List four characteristics of insect-pollinated flowers (1992/3a, Nov)
7. Wind pollinated flowers usually have
A. loosely hanging anthers B. large conspicuous flowers
C. compact and stich stigma D. highly scented flowers (2006/24 Nov)
8. Seeds obtained from cross-pollinated flowers give rise to plants which show much variation because
A. the zygote undergoes repeated mitotic divisions
B. there is recombination of genes from different sources
C. there may be many seeds in each fruit formed D. each plant arises from a separate seed (2006/25 Nov)
9. (b) State three differences between pollination (i) Self and cross pollination. (1996/2bi Nov)
10. Which of this is not a characteristic of wind pollinated seed?
A. Small light seed B. Sharp spines or hooks on fruit
C. Wing on seed in addition to light weight D. Parachute-like tuft of hairs on fruit (2004/22 Nov)
11. Which of these is NOT a characteristic of wind pollinated flowers?
A. Smaller quantities of sticky pollen produced B. Feathery styles of stigmas pendulously hang outside the flower
C. Small, inconspicuous scentless flowers D. large anthers which are loosely attached to filaments
E. Light pollen grains produced in large quantities from anthers (1978/45 JAMB)
12. Which of the statements below is not characteristic of wind pollinated flowers?
A. Stigma are usually large and feathery B. Nectary is usually absent
C. The pollen grains have rough spiny surfaces D. The flowers are not scented
E. The pollen is light and smooth (1979/15 JAMB)
13. For pollination and fruit formation, the essential part(s) of the flower should be the
A. corolla B. ovary C. pistil (gynoecium) D. ovules E. receptacle (1980/21 JAMB)
14. Which of the following is NOT true of wind-pollinated flowers?
A. Large amount of pollen produced B. Light smooth pollen grains
C. small inconspicuous flowers D. scented petals E. large pendulous anters (1981/3 JAMB)
15. Airspaces are characteristics of seeds or fruits dispersed by
A. birds B. water C. wind D. explosive mechanism (1988/29 JAMB)
16. A flowering plant is monoecius if
A. the androecium is found on one plant B. the gynoecium is monocarpous essential organs
C. it produces essential organs D. the gynoecium and androecium are on the same plant
E. the flowers are unisexual (1984/28 JAMB)
Use the diagram below to Answer: questions 26 and 27

17. The function of the part labeled V is for the passage of

A. pollen tube and pollen nucleus B. air, water and pollen nucleus
C. air, antipodal cells and ovum D. synergies and egg cell
18. The female gamete is represented by
A. I B. II C. III D. IV (1997/26-27 JAMB)

19. Insect visit flowers in order to

A. feed on the nectar B. deposit pollen on the stigma
C. pollinate the flowers D. transfer pollen from anthers (1999/25 JAMB)

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Use the diagram below to Answer: question 23 and 24

20. The male sex cells are contained in the part labelled
A. I B. II C. III D. IV (2009/23 JAMB)
21. The likely pollinating agent of the flower is
A. wind B. water C. insect D. man (2009/24 JAMB)
22. Which of the following is a characteristic of wind pollinated flower?
A. Flowers lack nectar B. Flowers are conspicuous
C. Flowers have pariants D. Flowers are bisexual (2017/18 JAMB)
23. If a flower is protandrous then it
A. must be unisexual B. has an underdeveloped androecium C. has no androecium
D. must be insect pollinated E. can prevent self pollination (1985/31 JAMB)
24. Double fertilization in higher plants is significant because it ensures the
A. formation of a fertile embryo B. formation of a fertile embryo and the endosperm
C. development of the seed D. development of the fruit (1992/25 JAMB

Development of plant embryo:

As soon as fertilization is completed, the zygote grows by repeated cell division, cell enlargement and differentiation
to form embryo. The embryo becomes differentiated into the plumule, radicles, one or two cotyledons and
sometimes an endosperm or food reserve.

As the embryo develops, the nucleus degenerates, the endosperm may be used up or may persist. The ovules develops
into seed while the outer and inner integuments of the ovules develop into the outer and inner seed coat (testa and
tegument) respectively.

The ovary develops into a fruit, the ovary wall develops into the fruit wall. The sepals, petals, style and stigma
withers away.

In tridax and related family, the calyx becomes modified into hairy pappus for dispersal by wind.

Structure and Germination of seed:

Seed germination, is in no doubts the most important stage in the life cycle of a plant. Before we talk about
germination it is important to first look at the structure of the seed.

Structure of a seed
A seed is a ripened ovule which has the ability to germinate into a new plant. A seed generally consists of:
1. Seed coat/testa: Which is its protective/hard covering.
2. Hilium: Which is the point of attachment of seed to seed stalk.
3. Micropyle: Through which water and air enters the embryo of the seed.
4. Embryo: Which develops into a plant. The embryo comprises a plumule or embryonic shoot, radicle or
embryonic root and cotyledon which stores food for the nourishment of the embryo. The radicle is protected
by a sheath known as “coleorhiza” while the plumule is protected by a sheath known as “coleoptile”.

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Classification of seeds:
Seeds have different basis of classification:
On the basis of the presence or not of cotyledon seeds are classified into:
a. Monocotyledon seeds: These are seeds that possesses only on cotyledon e.g. rice, maize wheat and sorghum.
b. Dicotyledonous seed: These are seed having two cotyledons e.g. mango, beans, cowpea.
On the basis of presence of persistent endosperm, seeds are classified as:
a. Albuminous seeds: Which are seeds with persistent endosperm. Their cotyledons are thin and membranous
e.g. corn, millets, custard, apple seeds, custard oil seed.
b. Exalbuminous seed: These are seeds that do not have persistent endosperm. They posses thick and fleshy
cotyledons e.g. mango seed, orchid seed.
Note: An albuminous seed can be either a monocot or dicot and an exalbuminous seed can either be a monocot or
dicot also. Based on this, seeds can then be grouped as:
a. Monocot albuminous seed e.g .maize.
b. Dicot albuminous seed e.g. custard, apple seed.
c. Monocot exalbuminous seed e.g. mango seed.
d. Dicot exalbuminous seed e.g .orchid seed.

Cotyledon

Structure of a monocot (maize) seed Structure of a dicot (bean seed)

Structure and Germination of Seed

Germination is a process by which the embryo of a seed grows out of its testa and develops into a seedling.
Sequence of seed germination:
1. Seed absorb water and swell.
2. Testa splits.
3. Radicles appears and grow downward.
4. Plumule appears and grow upward

Types of germination:
There are two types of germination. These are epigeal germination and hypogeal germination.

1. Epigeal germination: This is the type of germination in which the cotyledons appear above the soil surface.
The cotyledons are carried above the soil surface by the elongating hypocotyl. e.g. germination of cowpea,
groundnut, melon, etc. it is usually associated with dicotyledonous plants.

Epigeal germination

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2. Hypogeal germination: This is the type of germination is which the cotyledons remain under the soil surface
e.g. maize, oil palm, guinea corn, yam bean seed (mucuna bean). Most monocotyledonous seed exhibit
hypogeal germination. Mucuna bean (the yam bean) and rubber are some of the dicotyledonous seed with
hypogeal germination.

Hypogeal germination

Differences between Epigeal and Hypogeal germination

Epigeal germination Hypogeal germination
1. Seed leaves or cotyledons are brought above the soil Seed leaves or cotyledon remain below the soil surface
surface during germination. during germination.
2. The plumule comes out of the seed coat by the elongation The plumule comes out of the seed coat by the elongation
of the hypocotyl. of the epicotyl.
3. It is found mostly in dicot seeds. It is found mostly in monocot seeds.
4. The energy for growth is derived from cotyledon. The energy for growth is derived from endosperm.
5. It occurs in beans, onion, pawpaw and castor seeds. It is found in coconut, maize and oil palm.

Condition necessary for germination of seed:

1. Water/moisture
2. Oxygen/air
3. Warmth/suitable temperature
4. Viability of seed (viable seed)
5. Enzymes
6. Energy

Example
Which of the following is not a condition necessary for germination to occur in most seeds?
A. Water B. Air C. activation of enzymes D. Temperature E. soil fertility (1994/53)
Answer: E – Soil fertility is not a condition necessary for germination.
Example
Use the diagram below to Answer: questions 28-30

The part labeled IV in the diagram is the

A. plumule B. endosperm C. radical D. coleorhiza E. pericarp (1998/29)
Answer: C – Label IV is the radical.

Example
During the germination of seeds water is taken in by the process of
A. diffusion B. hydrolysis C. imbibition D. translocation (1999/27)
Answer: C – During the process of germination, water is taken in by imbibitions.

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Example
(e) Name the type of germination which takes place in:
(i) Monocotyledonous plants; (ii) Dicotyledonous plants.
(f) In a tabular form state four differences between the forms of germination named in 8(e) above. (2009/8e & f)
Answer:
8ei. Hypogeal germination.
ii. Epigeal germination.

f. Epigeal Germination Hypogeal Germination

- It is found mostly in dicot seeds. - It is found mostly in monocot seeds.
- The energy for growth is - The energy for growth is derived from endosperm.
derived from the cotyledon.
- Seed leaves or cotyledons are - The seed leaves or cotyledon remain below the soil
brought above the soil surface surface during germination.
during germination.
- The plumule comes out of the seed - The plumule comes out of the seed coat by the
coat by the elongation of the elongatation of the epicotyl.
hypocotyl.

Example
Which of the following does not take place during germination of a seed?
A. New products are synthesized using water, carbondioxide and radiant energy B. water is absorbed and seed swells
C. the seed coat becomes soft and permeable to gases D. carbohydrates are used in respiration (1996/30 Nov)
Answer: A – New products are not synthesized during germination.

EXERCISE 18.11
1. (c) Describe an experiment to show that oxygen is necessary for germination. (1996/2c Nov)
2. (ii) List two factors necessary for germination of seeds. (2013/2dii Nov)
3. A germinating seed requires oxygen which is essential for
A. Converting carbohydrate into glucose B. Transporting energy from one part of the plant to another
C. The production of energy by oxidizing essential carbohydrates D. Hydrolysis of proteins
E. The formation of water molecules within the germinating seed (1978/46 JAMB)
4. Water is required for speed germination to take place because it
A. activates the enzymes B. softens the testa C. liberates energy for growth
D. permits, radicle growth E. allows oxygen to diffuse into the seed (1980/12 JAMB)
5. Hypogeal germination is characterized by the
A. emergence of the plumule out of the ground B. provision of nourishment by the endosperm
C. elongation of the hypocotyls D. elongation of the epicotyls. (1992/27 JAMB)
6. In epigeal germination, the cotyledons are
A. carried above the ground by the elongating hypocotyls B. pulled underground by elongating hypocotly
C. pulled underground by elongating epicotly
D. carried above the ground by the elongating epicotly (1999/26 JAMB)
7. Epigeal germination of a seed is characterized by
A. equal growth rate of both the hypocotyls and epicotyls
B. more rapid elongation of the hypocotyls than the epicotyls
C. lack of growth of the hypocotyls than the epicotyls
D. more rapid elongation of the epicotyls (2004/36 JAMB)

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Use the diagram below to Answer: questions 17 and 18

8. The main function of the structure labelled I is to

A. store water for the seedling B. protect the young plumule
C. pull the young shoot above the ground D. store food for the young plant
9. The type of germination illustrated is termed
A. hypocotyls B. epigeal C. hypogeal D. epicotyls (2005/17-18 JAMB) Example

Study the diagrams below and use them to Answer: questions 23-25

10. The part labelled I in A represents the

A. root B. radicle C. hypocotyl D. shoot E. stem
11. The part labeled II represents the
A. root B. epicotyl C. hypocotyl D. cotyledon E. hilum
12. What is the importance of the part labeled II to the seedling? It
A. protects the foliage leaves B. grows into the first foliage leaves C. later develops into the fruit
D. provides the seedling with food E. serves as the water reservoir for the seedling (1996/23-25)

FRUIT
A fruit is the structure containing one or more seed that result after the fertilization of an ovary. In some plants,
however, fruits can develop without fertilization. The development of a fruit without fertilization is known as
pathenorcarpy and such fruits are called parthenacarpic fruits example includes the pineapple and banana fruits.

Although Pathenocarpic fruits show some resemblance to those fruits produced by fertilization, they however do not
possess seeds.

Structure of a fruit:
A fruit consists of a fruit wall/pericarp enclosing one or more seeds. It is attached to the plant by a fruit stalk that
develops from the flower stalk. The pericarp is made up of three (3) layers.
1. Epicarp, the outer layer
2. Mesocarp, the middle layer
3. Endocarp, the inner layer

The layers may be hard, soft, dry, fleshy or fibrous. In ripe fruits, the pericarp may contain food substances such as
sugar, fat and oils. It may also become attractively coloured due to the presence of pigments like carotenes and
anthocyanins.

Differences between a fruit and a seed

Fruit Seed
1. Fruit is developed from an ovary after fertilization. Seed is developed from the ovule.
2. The outer layer of fruit is the epicarp. The outer layer of seed is the testa.
3. Has two scar Has one scar.
4. It has no micropyle. It has micropyle.
5. Possesses line of suture. Has no line of suture.
6. Bears remain of style left by it. Remain of style is absent.

Note: The two scars present in a fruit can be seen at both ends. These are the remains of style and the point it attaches
to the receptacle. While the only scar which is present in a seed shows the point of attachment of the seed to the
placenta of the ovary and this is known as the hilium.
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Types of Fruit
Fruits are classified in different ways depending on which aspect of their origin or structure is being considered. The
following is common ways of classifying fruit.
1. True and False Fruits
2. Simple aggregate and composite (multiple)
3. Fleshy and dry fruits
4. Dehiscent and indehiscent fruits

True and False Fruits:

A true fruit is the type of fruit that develops from a fertilized ovary alone. It consists of a pericarp and seed or seeds.
Examples are mango, orange and cowpea. A true fruit is also known as a eucarp.

On the other hand, a false fruit is the type of fruit that is formed from ovary and other floral parts as well. Examples
are apple, pineapple and cashew etc. A false fruit is also known as a pseudo-carp.

Simple, aggregate and composite fruits:

Simple fruit: A simple fruit develops from a flower with a single ovary. The ovary may be monocarpous as in
cowpea and maize or syncarpous as in okro, tomato and pawpaw.

Aggregate Fruit: An aggregate fruit is one which develops from a single flower with several ovaries. The pistil of
such flowers are apocarpous i.e. pistil in which the carpels are separate and so have several ovaries. Example is cola.
Examples of false aggregate fruits are strawberry, raspberry and bustard apple in which the fruitlets are embedded in
a fleshy receptacle. Soursop and custard apple are false fruit in which the receptacles ripen with the free carpels,
where a seed or many seed occur.

Composite Fruit: A composite or multiple fruit develops from an inflorescence (several flowers) or flower
positioned very close to one another. In this type, all the fruitlet and floral parts fuse together to form a single large
false fruit as in fig, pineapple and breadfruit as well as whistling pine.

Fleshy Fruits: Fleshy fruits are fruits whose pericarp or at least one of its layer is thick, soft and fleshy (succulent)
especially when ripe.
There are 6 main types of fleshy fruits.

1. Drupe 2. Berry 3. Hesperidium 4. Pome 5. Sorosis 6. Syconium

1. Drupe: The drupes are true simple fruit with a well developed pericarp in which the epicarp is thin and form
the skin. The mesocarp is fleshy/fibrous and the endocarp is hard and woody and encloses the seed to form the
stone/shell. Examples are mango with a fleshy edible mesocarp, oil palm fruit and coconut fruit with a fibrous
inedible mesocarp. In raspberries (aggregate fruit) the fruitlets are drupe.

The longitudinal section of a coconut fruit (drupe)

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2. Berry: This is a true simple fruit in which, the epicarp forms a thin membranous skin while the meso and
endocarp form a fleshy edible mass within which lie one or more seeds. Examples are tomato, guava, garden
egg and banana.

Longitudinal section of tomato Transverse section of tomato.

3. Hesparidium (Pepo): This is a special type of berry in which the epicarp and mesocarp fuse to form the
skin/rind. The endocarp is sheet-like projecting inwards to form distinct chambers filled with succulent hairs.
Examples are orange, lemon, line etc.

Transverse section of an orange longitudinal section of an orange

4. Pome: This is a simple false fruit in which the skin and the fleshy edible parts are derived from the receptacle,
with only the core enclosing the seeds arising from the ovary. Examples are apple and pear.

Transverse section of an apple

5. Sorosis: This is a composite false fruit formed from a dense inflorescence. Examples are pineapple and bread
fruit.

Longitudinal section of bread fruit

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6. Syconuim: This is a composite false fruit that develops from a cup-like inflorescence axis enclosing
numerous tiny male and female flowers. The inflorescence axis becomes a fleshy edible part while the female
flowers develop into tiny fruit. Example is fig in which the female flowers ripen into drupes.

Longitudinal section of a fig

Differences between a Berry and a Drupe

Berry (Tomato) Drupe (Mango)
1. Mesocarp and endocarp are fused Mesocarp and endocarp are not fused
2. Mesocarp is edible Mesocarp may or not be edible
3. Contains many seeds Has only one seed
4. Has an edible Endocarp Endocarp is not edible

Dry Fruit: In dry fruit, the pericarp become dry, hard and woody or fibrous when the fruits ripens. There are two
types of dry fruits.
1. Dry dehiscent fruits
2. Dry indehiscent fruits

1. Dry Dehiscent Fruit: This fruit splits to release the seeds when ripe leaving the fruit wall on the plant. There
are four (4) main types of dry dehiscent fruits namely:

A. Legume B. Follicle C. Capsule D. Siliqua.

a. Legume: Legumes/Pod is a simple fruit formed from a superior monocarpous pistil. When ripe, the
pericarp dehisces longitudinally along both sides to release the seeds inside it. The seed are arranged
along one of the margin of the fruit (marginal placentation). Example are bean, flamboyant,
Caesalpinia, oil, bean tree, pride of Barbados, Crotalaria etc.
b. Follicle: This is formed, from a superior monocarpous pistil. The ripe fruit dehisce longitudinally
on one side only: Examples are cola, rose periwinkle etc.
c. Capsule: This is formed from a superior syncarpous pistil. The pericarp may dehisce
longitudinally at more than two places as in Dutchman’s pipe and okro. Transversely, as in Cock’s
comb or by a vine of pores at the top as in poppy. Other examples are Castor Oil and water leaf.
d. Siliqua: This is a long narrow capsule formed from an ovary with two carpels (bicarpellary ovary).
It has two chambers separated by a false septum or replum. It dehisces in both sutures. Examples are
Tecoma and the African tulip
e. Schizocarp: This is a many-seeded fruit that develops from a syncarpous ovary. It breaks up into
one-seeded part at maturity. The one-seeded part is called a mericarp. Examples are Urena lobata,
Sida species, Cassia and Desmodium.

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 Different dehiscent fruit

2. Dry indehiscent Fruit: These fruits possess hard and dry fruit wall that do not split open when mature but
usually fall to the ground. The pericarp (fruit wall) eventually decays to release the seed. They include:
a. Achenes: This develops from an apocarpous pistil and contains only one seed. Examples are the fruit of
sunflowers and four O clock plant. Other examples are Clematis fruit and rose which are aggregate of
achene, strawberry.
b. Cypsela: This is formed from a bicarpellary (double ovary) in which only one ovule develops into a
seed. Examples include Tridax, Emilia, Eupatorium and goat weed. These fruits also possess a hairy
pappus which aid in seed disposal.
c. Nuts: This is a simple true fruit with a tough woody pericarp. It develops from a superior bicarpous or
polycarpous ovary and contains one seed chamber with only one seed. Example is the cashew nut. It is
important to note that many seeds such as colanut, coconut, palmnut, groundnut, which are often referred
to as nuts, are actually not nuts. This is because they lack the characteristic of true nuts. They are however
placed in categories that befits their characteristics e.g. coconut which is a drupe.
d. Caryopsis: This is a small, simple fruit. It develops from a single pistil consisting of single ovary. The
pericarp and the seed coat are fused to form a covering over the centre seed. Examples are maize grain,
rice, millet, guinea corn etc.
e. Samara: This is an achene in which the pericarp become extended into a flat membranous wing for
dispersal by wind. Examples are the fruit of Combretum and obeche tree.

Various dry indehiscent fruits.

Dispersal of seed and fruits:

Dispersal is the transfer of a seed or fruit from the parent plant to other places where the seed may germinate.

Importance of dispersal of fruits and seed:

1. It prevents overcrowding of plants.
2. It reduces the degree of undesirable competition for space, light, water and nutrients.
3. It prevents diseases from spreading among plant species.
4. It results in colonization of new areas with new plants

Agents for Dispersal of seed and fruits:

The agent of dispersal of seed and fruits include: wind, animal, water, human, explosive mechanisms.
1. Wind: Features that enables fruit or seed dispersal by wind are:
a. The fruit/seeds are light so they are easily carried by the wind from the parent plants to other plants.
b. Fruits/seed may have wings e.g. Combretum
c. Fruits/seeds may have floss which makes them to be easily carried by the wings e.g. cotton.
d. Fruits/seed e.g. Tridax and Emilia may have long hairy or thread-like structure (hairy pappus) acting like
parachute

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2. Animals: Features of fruits and seed dispersed by animals:
a. The fruits/seed e.g. Desmodium and Boerhavia difussa may have hooks/hair by means of which they
adhere to the furs of animals or clothes of man.
b. The fruits are edible and seed pass through the alimentary canal undigested e.g. pepper, guava seeds eaten
by birds.
c. The fruits are edible with sticky juice. The fruits/seeds stick to the beak of a bird or hip of an animal.
When rubbed off somewhere, the seed germinates e.g. mistletoe.
d. Fruits and seed transported by man: Man distributes farm products to different part of the world market.
This is a kind of dispersal.

3. Water: Features that enables fruits and seeds dispersed by water are:
a. The fruits and seeds are light and can float on water.
b. The fruits have waterproof epicarp which prevents it from imbibing water so that they can remain afloat
e.g. coconut fruit.
c. The fruits have fibrous mesocarp that traps air, thus enabling it to remain afloat e.g. coconut
d. Fruits or seed can remain afloat for a long time until they are washed ashore where they germinate e.g.
coconut.

4. Human: Features that enables fruit/seeds dispersal by human are:

a. The fruits are eaten by man and the seeds are dropped/thrown elsewhere to germinate e.g. apple, orange,
palmnut and mango etc.
b. The fruit or seed may be collected and planted deliberately either for commercial or private purpose.

5. Explosive mechanism: Features that enables fruits or seed dispersal by explosive mechanism are:
a. There is presence of one or more lines of weakness or fusion of carpels (presence of suture lines of
splitting)
b. When the pericarp dries up, it contracts. Pressure and tension build up within the fruit as a result of
uneven drying up of the pericarp, causing the pericarp to split along the lives of fusion or carpels. The
splitting and thrusting of the pericarp disperse the seeds from the parent plant. Examples are oil bean, para
rubber, pride of Barbados, flamboyant, balsam, mahogany and Crotalaria
Example
Which of the following is an advantage of dispersal of fruits and seeds? It allows
A. fair distribution of source of food for animals B. growth in close association with parent plant
C. even distribution of plants and reduction of intraspecific competition D. keen competition for food
E. the seeds to evolve new species (1995/26)
Answer: C – Even distribution of plants and reduction of intraspecific competition is an advantage of fruits and seed
dispersal.
Example
Which of the following is not a feature of a seed or fruit dispersed by the wind?
A. light weight B. parachute C. pappus D. wings E. hooks (1992/34)
Answer: E – Hooks
Example
What is the fate of the ovary of a flower after fertilization? It
A. becomes the seed B. withers away C. becomes the fruit
D. develops more nuclei E. develops into sepals (1994/27)
Answer: C – The ovary becomes the fruit after fertilization.
Example
(b) Describe the process of fertilization in flowering plants. (1994/4b)
Answer: Just after pollination, the pollen grains on the stigma absorb water and nutrient and swells until the exine
bursts and the intine grows into a pollen tube along the style. The nucleus of the pollen grain divides into tube nucleus
and generative nucleus. The generative nucleus divides into two (2) male nuclei (gametes). One of the male nuclei
fuses with the ovum to form zygote while the other fuses with the pollar nuclei to form the endosperm nucleus which
matures to become the nutritive endosperm. The zygote undergoes several mitotic division to become the embryo. At
the end of fertilization, the ovum becomes the seed while the ovary becomes the fruit.

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Example
Use the diagram below Answer: questions 21 and 22

The diagram above represents a

A. germinating seed B. radicle C. shoot showing negative phototropism D. germinating pollen grain
Answer: D – The diagram represents a germinating pollen grain.
The part labeled I in the diagram is the
A. cytoplasm B. pollen nucleus C. pollen tube D. endosperm E. intine (1997/21-22)
Answer: E – Intine.
Example
A dry indehiscent fruit containing one seed and possessing a hairy pappus is described as
A. a nut B. a drupe C. a cypsela D. a follicle E. an achene (1990/37)
Answer: C – Cypsela is a dry indehiscent fruit which contain one seed and possess a hairy pappus which aid it
dispersal.
NB: Drupe – Fleshy fruit, follicle → Drydehiscent fruits, nut and achenes → Dry indehiscent fruits.
Example
In flowering plants, fertilization would occur when
A. the pollen grows downwards penetrating the style B. a pollen grain is transferred to the stigma
C. one of the nuclei inside the pollen tube fuses with the ovum D. the nucleus of the pollen tube divides (2002/25)
Answer: C – Fertilization would occur in flowering plant when one of the nuclei inside the pollen tube fuses with the
ovum.
Example
After fertilization in the flowering plants, the zygote develops into the
A. plumule B. radicle C. cotyledon D. embryo (2002/26)
Answer: D – After fertilization the zygote develops into the embryo.
Example
The immediate product of meiosis in flowering plants is the
A. sporophyte B. gametophyte C. zygote D. pollen grain (2009/54)
Answer: D – The immediate product of meiosis in flowering plant is pollen grain.
Example
Which of the following structures in a flower develops into the seed?
A. Testa B. Integument C. Ovule D. Ovary (2012/22)
Answer: C – The ovule develops into seed. NB: The ovary develops into fruit.
Example
The main difference between a seed and a fruit is that a fruit
A. is large while a seed is small B. has two scar while a seed has one
C. is pigmented while a seed is not D. can be dispersed by animals while a seed cannot (2015/20)
Answer: B – A fruit has two scar while a seed has one.
Example
Which of the following fruits is schizocarp?
A. Groundnut B. Desmodium C. Cashew D. Pride of Barbados (2019/35 NABTEB)
Answer: B – Desmodium.
Example
Pineapple is an example of a/an
A. dishiscent fruit B. aggregate fruit C. composite fruit D. simple fruit (2019/37 NABTEB)
Answer: C – Pineapple is an example of a composite fruit.
Example
After fertilization, the ovary of a flower
A. develops into seed B. withered away C. develops into calyx D. develop into fruit (2001/24 NABTEB)
Answer: D – After fertilization, the ovary develops into fruit.

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Example
The process by which a fruit develops without fertilization is called
A. parthenocarpy B. parthology C. hermaphroditism D. layering (2018/17 NABTEB)
Answer: A – Parthenocarpy. This is a process where fruit develops without fertilization.
Example
(b)(i) What is a fruit? (ii) Give two differences between a fruit and a seed.
(c)(i) List two importance of fruit/seed dispersal.
(ii) Name three agents of dispersal other than wind. (iii) State two features of wind-dispersal.(2018/2b, c NABTEB)
Answer:
2bi. A fruit is the structure containing one or more seeds that results after the fertilization of an ovary.

ii. Fruit Seed

- Develops from ovary after fertilization. - Develops from ovule after fertilization.
- Has two scar. - Has one scar.

ci. Importance of fruit/seed dispersal: Prevents over crowding; Prevents intraspecific competition.
ii. Three agents of dispersal: Wind; Water and Animals
iii. Features of wind dispersal: Possession of wing-like structure; Possession of hair-like structure.
Example
A dehiscent fruit formed from several fused carpels with many seeds is classified as a/an
A. achene B. capsule C. caryopisis D. follicle E. legume (2008/20 Neco)
Answer: B – Capsule.
Example
1a (i) State TWO agents of seed dispersal and give TWO examples of seed and fruits dispersed by each. (2007/1ai Neco)
Answer: Wind e.g. cotton, tridax etc.; Animal e.g. orange.
Example
The following are characteristics of wind dispersed fruits and seeds EXCEPT
A. light weight B. winged body C. presence of floss
D. presence of hooks E. parachute-like hairs (2005/17 Neco Nov)
Answer: D – Presence of Hooks is not a characteristic of wind dispersed fruits and seeds.
Example
In epigeal germination, the part of the seed that comes about the soil surface is the
A. coloeptile B. cotyledon C. hypocotyl D. plumule E. radical (2005/18 Neco Nov)
Answer: B – The cotyledon is carried above the soil by the hypocotyl.
Example
Which of the following fruits is a berry?
A. apple B. mango C. tomato D. pear E. pineapple (2005/19 Neco Nov)
Answer: C – Tomato is an example of a berry.
Example
Which type of fruit is pineapple?
A. Aggregate B. capsule C. complex D. multiple E. simple (2005/34 Neco)
Answer: D – Pineapple is an example of a multiple (composite) fruit.
Example
Which of the following fruits is an example of caryopsis?
A. Cashew nut B. combreteum C. maize D. orange E. tridax (2005/47 Neco)
Answer: C – Maize is an example of caryopsis.
Example
The difference between a fruit and a seed is that a fruit
A. mature before a seed B. has two scars while a seed has one scar
C. has one scar while a seed has none D. has a covering while a seed has none (1999/36 Nov)
Answer: B – The difference between a fruit and a seed is that a fruit has two scars while a seed has one scar.
Example
Which of the following is not true about the development of fruits?
A. the wall of the ovary becomes the pericarp B. a fruit which develops solely from the ovary is known as a true fruit
C. a fruit which develops without fertilization is parthenocarpic
D. a fruit which develops from whole inflorescence is a true fruit (1999/37 Nov)
Answer: D – A fruit which develops from a whole inflorescence is not a true fruit but a false fruit.

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Example
A simple, dry, many-seed fruit which splits into many one-seeded units at maturity is a
A. schizocarp B. samara C. capsule D. drupe (1999/41 Nov)
Answer: A – Schizocarp is a simple, dry, many-seed fruit which splits into many one-seeded units at maturity.
Example
Fruits formed from the ovary wall are described as
A. complex fruits B. false fruits C. simple fruits D. multiple fruits E. true fruits (1992/30 Nov)
Answer: E – True fruits are fruits that develop solely from the ovary.
Example
Which of the following structures produces the male gametes in flowering plants?
A. generative nucleus B. Tube nucleus C. pollen tube D. endosperm nucleus E. antipodal cell (1992/31 Nov)
Answer: A – The generative nucleus divides into two male gametes.
Example
Seeds obtained from cross-pollinated flowers give rise to plants which show much variation because
A. the zygote undergoes repeated mitotic divisions B. there is recombination of genes from different sources
C. there may be many seeds in each fruit formed D. each plant arises from a separate seed (2006/25 Nov)
Answer: B – Seeds obtained from cross-pollinated flowers gives rise to plants which show much variation because
there is a recombination of genes from different sources.
Example
A fruit with a thin epicarp, fleshy or fibrous mesocarp and a hard endocarp enclosing the seed is a
A. Nut B. berry C. drupe D. cypsela E. legume (1996/29 Nov)
Answer: C – Drupe is a fruit with a thin epicarp, fleshy or fibrous mesocarp and a hard endocarp enclosing the seed.

Example
Which of these is not a common feature for seed or fruit dispersed by wind?
A. Wings B. Floss C. Hooks D. Pappus E. Lightness (1998/31 Nov)
Answer: C – Hooks.

EXERCISE 18.12
1. A dry, winged fruit formed from one carpel is known as a
A. schizocarp B. caryopsis C. samara D. nut (1979/25 JAMB)
2. The maize grain is regarded as a fruit and not a seed because
A. It is covered by a sheath of leaves B. the testa and fruit wall fuse after fertilization
C. It has both endosperm and cotyledon D. it has coleaorhiza and coleoptile (1979/38 JAMB)

Fig2
3. Figure 2 is a section of a drupe. The part numbered 2 is
A. epicarp B. endocarp C. mesocarp D. seed E. pericarp (1979/40 JAMB)
4. The one-seeded fruit in which the pericarp and seed coat have become fused together is known as
A. achene B. samara C. caryopsis D. legume E. drupe (1979/41 JAMB)
5. A true fruit is formed from
A. a fertilized ovary and other floral parts B. a fertilized ovary
C. a fertilized ovary and calyx D. a fertilized ovary and fleshy receptacle (1980/11 JAMB)

6. Water is required for speed germination to take place because it

A. activates the enzymes B. softens the testa C. liberates energy for growth
D. permits, radicle growth E. allows oxygen to diffuse into the seed (1980/12 JAMB)
7. The maize grain is a fruit and not a seed because it
A. has a large endosperm B. is formed from an ovary C. has no plumule and radicle
E. has a hypogela germination (1985/30 JAMB)
8. The pineapple fruit is best described as
A. aggregate, succulent and indehiscent B. aggregate, succulent and dehiscent
C. multiple, succulent and indehiscent D. multiple, succulent and dehiscent (1987/28 JAMB)

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 Use fig. 3 to Answer: questions 23 and 24.

9. The testa option

A. is normally absent B. is included in the part numbered (1)
C. is fused with the part numbered (3) D. is the part numbered (1)
E. surrounds the parts numbered (4) and (5) (1980/23 JAMB)
10. Reserved food material is
A. stored in the parts numbered (2) and (3) B. stored in the part numbered (3) only
C. stored in the parts numbered (4) and (5) D. not concentrated in any particular part
E. Found in all the parts except (1) (1980/24 JAMB)
Use Fig. 1 to Answer: questions 1 and 2

11. The correct figured sequence for the following labelled parts (stigma, ovary wall, embryo sac, integument
and micropyle) is
A. 12453 B. 24135 C. 21435 D. 14325 E. 31425 (1981/1 JAMB)
12. Which structure becomes the seed coat after fertilization?
A. 1 B. 2 C. 3 D. 4 E. 5 (1981/2 JAMB)
13. A fruit formed from a single flower having several free carpels, is
A. a multiple fruit B. a dry dehiscent fruit C. a dry indehiscent fruit
D. a simple fruit E. an aggregate fruit (1981/35 JAMB)
14. If the anthers of a flower mature before the stigma, the condition is termed
A. epigyny B. hypogyny C. protogyny D. protandry E. perigyny (1981/36 JAMB)
15. A flower showing radial symmetry is said to be
A. pentamerous B. prontandous C. protygynous D. actinomorrphic (1987/30 JAMB)

16. A samara differs from a cypsela by having

A. extended pericarp B. a hard pericarp
C. a pericarp fused with the seed coat D. some hairy outgrowth on the pericarp (1987/31 JAMB)
17. A dry dehiscent fruit which breaks up into one-seeded parts is a
A. schizoarp B. capsule C. follicle D. legume (1988/29 JAMB)
18. Fruit which develop without fertilization is described as
A. simple B. pathenocarpic C. aggregate D. compound (1990/31 JAMB)
19. A collection of achenes formed from several carpels of a flower is
A. a complex fruit B. an aggregate fruit C. schizocarp D. a simple fruit (1991/33 JAMB)
20. Double fertilization in higher plants is significant because it ensures the
A. formation of a fertile embryo B. formation of a fertile embryo and the endosperm
C. development of the seed D. development of the fruit (1992/25 JAMB)
21. The sex of a foetus is determined during
A. meiosis B. copulation C. fertilization D. placentation (1995/24 JAMB)
22. The term caryopsis is used to describe a fruit in which the
A. testa and pericarp are separate B. seed and endocarp are fused
C. testa and pericarp are fused D. seed coat and fruit wall are impermeable (1995/23 JAMB)
23. Coconut and oil palm fruits can be grouped as
A. berry B. legumes C. capsule D. drupe (1997/29 JAMB)

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24. A dry fruit formed from two or more carpels containing several seeds is a
A. follicle B. legume C. capsule D. schizocarp (1998/25 JAMB)

Use the diagram below to Answer: questions 20 and 21

25. The fruit represented is mainly dispersed by

A. animals B. wind C. water D. birds (2000/20 JAMB)
26. The part labeled II is the
A. endocarp B. pericarp C. mesocarp D. epicarp (2000/21 JAMB)
27. Pineapple is an example of
A. dehiscent fruit B. an aggregate fruit C. a composite fruit D. a simple fruit (2007/27 JAMB)
28. An example of an endospermous seed is
A. cashew nut B. cotton seed C. bean seed D. maize grain (2011/17 JAMB)
29. A water medium is necessary for fertilization in
A. conifers B. angiosperms C. ferns D. fungi (2015/9 JAMB)
30. A seed of a flowering plant can best be described as
A. radical and plumule B. the developed ovule C. the embryo and endosperm D. developed ovary (2018/20 JAMB)

31. Which of the following is not a characteristics feature of wind dispersed fruit?
A. light weight B. winged apparatus C. flossy structure D. buoyancy (1999/28)
32. The following are characteristics of wind dispersed fruits and seeds except
A. light weight B. winged body C. presence of floss
D. presence of hooks E. parachute like hairs (2005/17 Nov)
33. State three (3) agent of fruit and seed dispersal. Give an example of fruits or seeds dispersal by each agent.
(1998/2ci)
34. List two importance of fruit/seed dispersal.
i. Name three agents of dispersal other than wind.
ii. State two features of wind-dispersed fruit/seed. (2018/1c NABTEB)

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REPRODUCTIVE BEHAVIOUR
Courtship is a complex behavior pattern designed to stimulate organisms for sexual activity. It is the series of activities
that precedes mating.

Courtship display in male duck Courtship display in fishes

In vertebrate mating is dependent on courtship. Courtship may be defined as a reproductive communication between
males and females of a species that end in sexual union.

Importance of courtship behaviour

Various signals are uses by different organisms to attract members of opposite sex. This includes sight, sound, smell
etc. courtship might be accompanied by conflict behavior in some animal species. Some importance of courtship are
listed below:
1. Courtship brings the male and female animals together.
2. It prepares male and female for possible mating.
3. Courtship stimulates egg laying and sperm release in the partners.
4. It enables mature males and females of a species to recognize one another.
5. In external fertilization, it synchronizes the release of gametes by both partners.
6. Courtship enhances fertilization and reproduction.

Example
The series of activities preceding mating of the male and female animals is generally known as
A. conjugation B. paining C. courtship D. nuptial flight E. territoriality (1992/33)
Answer: C – Courtship is the series of activities preceding mating of a male and female animals.
Example
Explain the term Courtship behaviour in animals. (1994/4ai)
Answer:
Courtship is the reproductive communication between males and females of the same species that ends in sexual
union.

Types of courtship behaviour in animal

The types/forms of courtship beahaviour found in animal includes:

1. Pairing: This involves two animals (male and female) which separate themselves from others in a group to
form a mating pair.
This type of courtship often leads to a compatiable male and female pairing up, to mate. This pairing may be
very brief i.e. just for mating act only, or it may last for a lifetime, examples of animals that exhibit pairing
includes:
a. Pairing in winged termites: Which eventually becomes a king and queen in a new colony. The
offspring form other caste.

373
 b. Pairing in fish: During the breeding season, the male fish picks a female as a partner. They swim
together to a quiet portion of the river. The male stimulates the female to lay eggs. The male releases
sperm on the egg for external fertilization to take place.
c. Pairing in toad: During breeding season, the male goes to a pond, it croaks; the croaking attracts and
excites the female. When the female come closer, the male mounts on the back of the female. The
female carries the male on the back for 2-3 days. During this period, the female lays her eggs in
shallow water and the male pours sperms over the eggs for external fertilization to take place.
d. Pairing in human: Male and female after they have attained sexual maturity come together as
husband and wife. They form sexual partners. They live together, mate and reproduce. They perform
most of their duties within and outside their home as pairs or partner throughout their lifetime.
Pairing is also found in birds and lizard.

2. Display: Display involves a series of fixed pattern of movement or attractive exhibition between mating
partners.
Types of display:
1. Dancing e.g. human beings
2. Singing e.g. human beings, birds
3. Croaking e.g. toad
4. Nest making e.g. birds
5. Production of odour by female to attract the male e.g. dog
6. Symbolic feeding of the female to attract the male.
Examples of courtship display by some animals
1. Display in Agama lizard: The male Agama lizard displays its bright colours and approaches the
female. The female lizard curves her back and lifts her tail vertically. The male then wags his tail,
nods his head and grips her by the neck and push his tail under her body so that their cloacas come
into contact for copulation to take place.
2. Display in birds: In domestic fowl, the cock dances towards the female (hen); the hen runs away if it
is not ready for courtship. If ready for courtship, the cock chases the hen, overtakes her, mounts on
her back and pecks on her head while it stoops down and raises her tail feathers, exposing the cloaca.
Mating then takes place. In peacock the male and the female also carryout display as a form of
courtship. The male bird uses his long, large and beautifully coloured tail feathers which it opens to
display to the female. This display may attract the female for mating.
3. Display in human beings: This includes:
Reproductive Behaviour:
a. Dancing to musical instruments.
b. Singing with melodious voices.
c. Facial expression.
d. Beautiful and attractive dressing.
e. Make up and use of highly perfumed cream including use of lip stick.
f. Use of powerful body perfumes and sprays.
g. Walking gracefully and majestically.
h. Wearing of tight fitting dresses to display the body curves (i.e. to show the figure 8) or
generally wearing of brightly coloured dresses.
i. Display of thighs by wearing short dresses.
j. Wearing of transparent or perforated dresses to show the attractive parts of the body.
k. Walking with the shaking of buttocks.
l. Wearing of artificial eye lashes, finger nails, breasts and buttocks.
m. Wearing of large and brightly coloured bangle and dangling ear-rings.
n. Weaving, plaiting, curling of hair, wearing wigs of different colours.
o. Attractive smile with dazzling eyes and genuflecting to senior males.
p. Showing kindness, favour and generosity with good manners.

3. Territoriality: Territoriality is a form of behaviour in which a member of a species marks out a fixed area and
defends it against intruders of the same species. Territorial behaviour ensures that breeding pairs or groups
obtain adequate food and space. Examples include male fishes, reptiles e.g. agama lizards, birds and
mammals

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4. Seasonal Migration: This is the movement of animals from one place to another with the eventual return to
the original place. Many species of animals migrates with seasons, in connection with breeding and escaping
unfavourable conditions. Examples of organisms which exhibit seasonal migration include.
a. Fish e.g. mud fish migrate from deep to shallow water before laying their eggs.
b. Birds e.g. cattle egrets, during the dry season migrate from the northern parts of Nigeria to the
southern states as a result of lack of water, food and to escape the unfavourable weather of the north.
During rainy season they migrate back from the south to the northern parts of the country where
conditions for feeding and breeding have again become favourable.
c. Insects: Some insects e.g. desert locust migrate from dry areas in North Africa in June towards the
South across the Sahara to Niger and Mali where it s already rainy season and the green grass for food
is already available and there is suitable conditions for reproduction. Later in the year, around October
to November, swarms of desert locust migrate to North Africa where conditions for feeding and
breading have again become favourable.
Example
Which of the following is an example of reproductive adaptation?
A. Succulent stems of cactus plant B. Changing colour of chameleon
C. Possession of spines by desert plants D. Neck colouration in Agama lizard E. Leaf-shedding in trees (1989/58)
Answer: D – Neck colouration in agama lizard is a example of reproductive adaptation.
Example
(b) Explain how each of the following behaviours in animals affect the reproduction process
(i) territoriality (ii) display (iii) seasonal migration. (1989/3b)
Answer:
i. Territoriality: This is a form of behavior in which a member of a species marks out a fixed area and defend it
against intruders of the same species.
ii. Display: This is a series of fixed pattern of movement or attractive exhibition between mating partners.
iii. Seasonal migration: This is the movement of animals from one place to another with the eventual return to the
original place.
Example
Which of the following is not a courtship behaviour exhibited by animals?
A. Pairing B. Display C. Seasonal migration D. Hibernation E. Territorialism (1993/21)
Answer: D – Hibernation is not a courtship between exhibited by animals.
Example
The swarming especially at the beginning of the rainy season is a courtship behaviour shown by
A. migratory birds B. pigeons C. crickets D. winged termites E. bees (1993/58)
Answer: D – Winged termites.
Example
Display is a phenomenon which occurs when an animal is
A. ready for mating B. fighting to defend C. approaching puberty D. chasing away an intruder (2001/12)
Answer: A – Display is a phenomenon which occurs when an animal is ready for mating.
Example
Which of the following animals exhibit territoriality?
A. Bees B. Bats C. Lizards D. Rabbits (2001/60)
Answer: C – Lizards.
Example
Courtship behaviour in animals may include all of the following except
A. howling of a dog B. dancing of the worker bee C. croaking of a toad D. basking in the sun by a lizard (2006/58)
Answer: D – Basking in the sun by a lizard is not courtship behavior.
Example
Which of these is a courtship behavior in toad?
A. display of bird parts B. display of colours C. pairing D. production of scent E. territoriality (2008/44 Neco)
Answer: C – Pairing is a courtship behavior in toad.

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EXERCISE 18.13
1. The exclusion of other adult male agama lizards from an area by a single male lizard is referred to as
A. aggression B. dominance C. monopoly D. territorialism (2006/60 Nov)
2. 1(a) State four modes of dispersal of fruits and seeds, giving one example of each case
(b) State one feature each that adapts fruits and seeds to the differential modes of dispersal
(c) Give four reasons why dispersal of fruits and seeds is important (2006/1a – c)
3. Courtship behaviour in animals is not exhibited as
A. pairing B. metamorphosis C. display D. territoriality E. nuptial flight (1994/24 Nov)
4. (a) (i) What is courtship behavior?
(ii) Outline five benefits derived by the exhibition of courtship behavior (2013/7ai, ii Nov)

5. In a group of male Agama lizards, the one with the brightest head colour is the
A. largest B. youngest C. oldest D. dominant (2000/47 JAMB)
6. In which of the following groups of fruits is the pericarp inseparable from the seed coat?
A. Follicle B. Cypsela C. Caryopsis D. Nut (2002/16 JAMB)
7. When a peacock displays its colourful feathers it is
A. courting a female B. ready for a fight
C. protecting itself from predators D. protecting its mate from predators (2005/19 JAMB)
8. The bright colours of the comb and feathers in the peacock are for
A. sex differentiation B. beauty C. courtship D. defense (2019/7 JAMB)

9. Which of the following animals exhibits territoriality?

A. bat B. cow C. lizard D. rabbit E. toad (2017/28 Neco)
10. The following are examples of visual signals displayed by animals during courtship except
A. dancing performed by a male jumping soldier B. raising and tapping of the claw of a male fiddler crab
C. pheronomas released by a male dear D. display of tail feather by a peacock (2018/34 NABTEB)
11. What is courtship behaviour in animals? ii. List three courtship behaviours in animal. (2016/6e iii)
12. List five importance of courtship behaviour in reproduction. (2007/4c i Neco)

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Growth
Growth is a characteristic of every living organism. It is defined as the irreversible increase in volume or size, mass or
weight, and length of an organism due to formation of new protoplasm.
It can also be defined as the permanent and irreversible increase in size that occurs as an organism mature. Growth
also includes increase in the number of cells.
Aspect of growth: Essential aspects of growth are:
1. Irreversible increase in size and length.
2. Increase in dry weight.
3. Increase in the number of cells as a result of mitosis.
4. Synthesis of new body material
5. Cell differentiation.
Basis of Growth
The major basis of growth are:
i. Cell division (also called mitosis)
ii. Cell enlargement
iii. Cell differentiation
Plants have growth pattern called open growth. Throughout life, the plant adds new organs such as branches, leaves
and roots, enlarging from the tips of roots and shoot. In vascular plants, growth occurs through the activity of
meristems. Meristems are young tissues or group of cells that retain the potential to divide.
In lower plants the entire plant body is capable of growing. In higher plants, the entire plant body is not capable of
growing but growth is limited to certain regions known as growing points. These growing points are also called
meristems and consist of groups of cells which are capable of division.
Types of meristems:
i. Apical Meristem: These are found at the tips of roots and shoot and are primarily concerned with the
extension of plant body. They are found at the apices of roots and stem. They are responsible for increase in
the number of cells at the tips of roots and stem, therefore they play important role in primary growth.
ii. Intercalary Meristem: These are the parts of the apical meristem which get separated from the apex by
permanent tissues. They are situated at the bases of internodes in many plants.
They play important role in the formation of leaves and flowers.
iii. Lateral Meristems: These are cylinders of dividing cells. They are present in dicots gymnosperms. Examples
are vascular and cork cambium. They play an important role in the increase in diameter of stem and root. They
are responsible for secondary growth.
Example
Which of the following tissues does not offer support in plants
A. Meristem B. Sclerenchyma C. Collenchyma D. Xylem (2003/11)
Answer: A – Meristematic tissues are tissues that contain cells that are actively dividing. Hence, they do not offer
support in plant.
Example
The basis of growth involves the following processes except
A. cell reduction B. cell division C. cell differentiation D. cell enlargement (2005/18)
Answer: A – Cell reduction is not a basis of growth.
Example
Which of the following processes does not contribute towards growth?
A. Cell division B. Cell enlargement C. cell differentiation D. Cell plasmolysis (2006/11)
Answer: C – Cell plasmolysis is the shrinkage of cell when placed in a hypertonic solution. Hence it does not
contribute towards growth.
Example
The aspects off growth in living organisms include all the following processes except
A. increase in dry weight B. reversible increase in size
C. irreversible increase in length D. increase in number of cells (2006/12)
Answer: B – Growth is an irreversible process, hence “reversible increase” in size is not an aspect of growth.
Example
Primary growth in plants is brought about by the activity of the
A. meristem B. endodermis C. epidermis D. mesophyll (2008/6)
Answer: A – The primary growth in plant is brought about by the activity of the meristem.
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EXERCISE 19.1
1. (a)What is growth? (2009/8a)
2. Which of the following is described as an increase in dry weight?
A. Reproduction B. Absorption C. Ingestion D. Growth (2003/8)
3. Biological growth refers strictly to an increase in the
A. protoplasm of an organism B. number of organisms
C. size of an organisms D. development of form (1995/25 JAMB)
4. 1.(a)(i) What is primary growth in flowering plants? (2011/1a Nov)

Cell Division (Mitosis): Mitosis is the cell division which occurs in somatic cells (ordinary body cells), in which a
parent cell divides to produce two daughter cells with the same number of chromosome as itself. Mitosis takes place
during growth, development and asexual reproduction. Mitosis occurs in five stages namely:
1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase
(Note: The interphase in real sense is not part of mitosis as the nucleus is still controlling the activities of the cell. It is
a preparatory stage).

Mitosis occurs in somatic cells such as skin, bone marrow, lymph nodes, and meristematic tissues in plant.

Interphase: At this stage, chromosomes become elongated and form a network of fine threads called chromatids. The
nuclear membrane becomes clearly visible. DNA duplicates (doubles) itself and chromosomes becomes a double
thread. Two centrioles are formed just outside the nuclear membrane.

Interphase

Prophase: Prophase is divided into two stages these are the early prophase and late prophase.
Features of early prophase
1. Chromosomes becomes visible as chromatin thread condense.
2. Chromosomes are long and thin.
3. Nucleolus starts shrinking.
4. Centrioles start moving apart from each other forming asters.
5. Formation of spindle fibres starts.

Late Prophase Features

1. Chromosome become shorter, thicker and very visible.
2. Each chromosome now forms two distinct chromatids joined by centromere.
3. Nucleolus disappears entirely.
4. Nuclear membrane disappears allowing the mixing up of cytoplasmic and nuclear materials freely.

Prophase stage

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Metaphase (features)
Chromatids are now attached to the spindle fibres by their centromere.
They position themselves at the equator of the cells.

Metaphase
Anaphase (Features)
The chromatids of each chromosome separate.
The chromatids start migrating to the poles by the elongation of the spindle axis.
The chromatids eventually reach the poles.

Anaphase
Telophase (Features)
1. The cells starts dividing into two by constricting at the equator.
2. The chromosomes now loses their thick appearance.
3. The nuclear material and nucleolus reform, bounded by nuclear membrane.
4. The spindle fibres disappear.
5. Constriction is completed and two daughter cells are formed at the interphase condition is restored.

Telophase

Importance of Mitosis
(i) It ensures that the diploid nature of the cell is retained from generation to generation.
(ii) Growth: it enable growth to take place in multicellular organisms through cell division.
(iii) It makes asexual reproduction possible e.g. binary or multiple fission in protozoa, budding in hydra and
formation of vegetative organs from parent plant such as corm and bulb is by mitosis.
Differences and similarities between mitosis and meiosis (refer to page 311 under Reproduction)
Cell enlargement and differentiation
After mitosis in animals, the daughter cells absorb nutrient from their surroundings. A part of the nutrient is used for
respiration to generate energy while the remaining part is assimilated resulting in enlargement of the cells. As the cells
enlarges, differentiation results leading to development of specialized cells. In plants the cell walls at this young stage
are flexible, therefore tugor pressure from inside the cell presses them outwards, leading to the expansion of their
walls and consequently vacuole are formed.

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Example
Study the diagram below and use it to Answer: Questions 6 and 7.

What stage of mitotic division is represented in the diagram of the cell illustrated above?
A. Prophase B. Telophase C. Anaphse D. Metaphase E. Interphase (1988/6)
Answer: A – Prophase
Example
This stage of mitosis is characterized by the
A. movement of the chromosomes to the poles B. arrangement of chromosomes on the equatorial plate
C. centromeres moving apart along the spindle D. interaction of the spindles with the chromosomes
E. condensation of chromosomes and formation of spindles (1988/7)
Answer: E – Condensation of chromosomes and formation of spindles.
Example
At which of the following stages of cell division can the cell be said to be resting
A. Anaphase B. Telophase C. prophase D. Interphase E. Metaphase (1989/37)
Answer: D – Interphase is also known as resting stage.
Example
At the end of mitosis the number of cells produced from a parent cell is
A. four B. six C. eight D. three E. two (1990/6)
Answer: E – At the end of mitosis, only two daughter cells are produced from a parent cel.

Example
At which of the following stages of mitosis do the two daughter chromosomes separate completely?
A. Early prophase B. Telophase C. Anaphase D. Late Prophase E. Metaphase (1990/8)
Answer: C– Anaphase
Example
(c) Describe the process of mitosis (d) what is the importance of mitosis to living organisms? (1995/3c, d)
Answer:
c. The process of mitosis is divided into four different stages which are:
- Prophase: In this stage, chromosome appears as two threads called chromatids. The chromosomes
become shorter and thicker, nuclear membrane and nucleolus disappear, each centrioles moves to the
opposite sides of the cytoplasm; spindle fibre are formed.
- Metaphase: Spindle formation is completed; chromosomes are arranged at the equator of the spindle and
are attached by their centromeres.
- Anaphase: The paired chromatids are pulled apart and start to migrate towards the opposite poles of the
cell; spindle fibres shorten.
- Telophase: Chromatids reach the poles, spindle fibres disappear; nuclear membrane and nucleolus are
formed; the cell constricts and two daughter cells are produced.
d. - Promote cell growth.
- Promote repair of damaged tissues.
- Forms the Basis of vegetative reproduction.
- Helps to Maintain the diploid number of the chromosome in cells.

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Example
4(a) Describe an experiment to show that green plants require sunlight for photosynthesis. (Details of test for
starch not required)
(b) What other conditions are necessary for photosynthesis? (2008/4a, b)
Answer:
Aim: To show that green plants require sunlight for photosynthesis.
Apparatus: Healthy potted plants, petri dish, beaker containing water, forceps, water bath a piece of wire gauze,
tripod, burner, iodine solution and clip.
Procedure: - Take two potted plants and water them very well.
- De-starch the leaves by keeping the potted plants in a dark cupboard for at least 24 hours.
- Then test the leaf samples of both plants for starch.
- The result is negative i.e. the leaves appear yellowish-brown which signifies the absence of starch.
- Then, leave one potted plant in a dark cupboard as a control and put the other plant in sunlight for
about 4 – 6 hours.
- Re-test leaves from both plants for starch.
Observation: The leaves from the potted plant exposed to sunlight tested positive (contained starch) while those
from the potted plant placed in a dark cupboard (i.e. the control) tested negative (contains no starch).
Conclusion: This reveals that sunlight is necessary for photosynthesis to take place in green plants.
(b) - Carbon(iv)oxide
- Chlorophyll
- Presence of water
- Temperature
Example
Two organelles directly involved in mitotic cell division are
A. nucleus and mitochondrion B. ribosome and nucleus
C. centriole and golgi apparatus D. nucleus and centriole (2009/11)
Answer: D – The nucleus which contains the chromosome and the centriole which are responsible for organizing
microtubules (spindle fibre) are directly involved in mitotic cell division.
Example
Cytokinesis of mitosis is a process that ensures that
A. each daughter cell gets the necessary organelles
B. there is distribution of a complete set of genes into each daughter cell
C. daughter cells inherit new genetic combinations
D. worn out organelles are excluded from daughter cells (2009/58)
Answer: B – Cytokinesis ensures that there is distribution of complete set of genes into each daughter cell.
Example
When the zygote of an organism continues to grow, it produces new cells by
A. meiosis B. crossing-over C. gestation D. mitosis (2003/9)
Answer: D – The production of new cells in a zygote is by mitosis.
NB: Meiosis only occurs during gamete production.
Example
Use the figure below to Answer: questions 38

What stage during cell division is represented in the figure beside?

A. Prophase B. Metaphase C. Anaphase D. Telophase (1990/38 JAMB)
Answer: C – Anaphase

EXERCISE 19.2
1. Cytokinesis of mitosis is a process that ensures that
A. each daughter cell gets the necessary organelles
B. there is distribution of a complete set of genes into each daughter cell
C. daughter cells inherit new genetic combinations
D. worn out organelles are excluded from daughter cells (2018/33 JAMB)

381
2. Which of the following CANNOT be used to describe mitotic division?
A. daughter cells possess one – half chromosome number as in parent cells
B. daughter cells possess diploid number of chromosome number as in parent cell
C. it occurs during growth of body cells
D. homologous chromosomes do not associate with each other (1999/1 NABTEB)
3. The total diploid number of chromosome in man is
A. 45 B. 23 C. 46 D. 24 (1999/9 NABTEB)
4. The first stage in the process of mitosis is
A. prophase B. diplotene C. anaphase D. telophase (1999/10 NABTEB)
5. At which of these stages in mitosis are the chromosomes arranged at the equatorial region of the cell?
A. anaphase B. telophase C. metaphase D. prophase (1999/11 NABTEB)
6. At which stage of mitosis does each sister chromatid moves to the opposite pole?
A. anaphase B. prophase C. metaphase D. telophase (2001/20 NABTEB)
7. During prophase in mitosis
A. chromatin thread condense to become chromosomes
B. chromosomes line up along the equator of the spindle
C. spindle fibres break down D. division of the cytoplasm occur (2018/9 NABTEB)
8. Which of these statements best describes metaphase of mitosis
A. The daughter chromatids separate and become mature chromatids
B. the spindle forms and chromosomes become attached at the centre
C. The nuclear membranes disappear and chromosomes thicken D. Two daughter cells are formed
E. The chromosomes thicken and can be seen as two daughter chromatids (1997/4 Nov)
9. (b) Briefly describe what happens in a cell undergoing mitosis during:
(i) Prophase; (ii) Metaphase; (iii) Anaphase (c) State two important functions of mitosis (2005/8b, c Nov)

Patterns of growth:
1. Isometric and Allometric growth: Isometric growth occurs when an organ grows at the same mean rate as
the rest of the body. This type of growth pattern is seen in leaves of plants. Allometric growth occurs when
an organ grows at a different rate from the rest of the body. This type of growth pattern is seen in mammals
(particularly in their reproductive structures).
2. Limited and Unlimited growth: The two basic type of growth patterns in plants and animals are the limited
and unlimited growth patterns.
Growth is limited in animals, that is to say it is definite or determinate but plants show
unlimited/indeterminate growth. The unlimited nature of plants growth, enables some of them to attain very
great heights.

Region of fastest growth in plants: In plants, the shoot apex and root apex consist of cells which divide
continuously (i.e. meristematic cells). The cells in this region have dense protoplasm, no vacuoles and thin cell walls.

Behind the zone of cell division is the zone of cell enlargement or elongation. This is the region where the cells
become enlarged to their maximum size by the stretching of their walls. This is the region where vacuole begins to
form in the protoplasm. Behind the zone of enlargement is the zone of cell differentiation or maturation. The zone
of cell enlargement is the zone of fastest growth in stems and roots. It occurs a few millimeters behind the shoot or
root apex.

Longitudinal section of the Shoot tip Longitidunal section of the Root tip

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Primary and Secondary Growth in plants:
Unlike animals that have limited growth, growth in plant is unlimited and involves both a primary and secondary
stage.

Meristems contribute to both primary (taller/longer) and secondary (wider) growth. Primary growth in plants forms
the main ground tissue in the plant body and results in the elongation of the roots and stem while secondary growth is
responsible for the increase in the width or girth of plants. The vascular cambium produces new xylem and phloem
cells called secondary xylem and secondary phloem.

Primary growth is controlled by root apical meristems or shoots apical meristems while secondary growth is
controlled by the two lateral meristems called the vascular cambium and the cork cambium. Not all plants
however exhibit secondary growth. Herbaceous plants are example of such plant that undergoes only primary growth.

Factors affecting growth in plants

The rate of growth of a plant is affected by the following factors:
1. Availability of water and nutrient. 2. Humidity 3. Light 4. Temperature
5. Hormones 6. PH 7. Genetic constitution
Genetic constitution and hormones are internal factors while the rest are external factors.

Factors affecting growth in animals

The factors that affect the growth in animals include:
1. Food: Availability of food greatly influences the growth of an animal since animals cannot manufacture their
own food.
2. Hormones: In animals hormones are secreted by ductless glands. The hormones associated with growth are
secreted by the anterior pituitary gland, the thyroid gland and the gonads. An error in the secretion of
hormones by any of these glands can have a great effect in the animals growth pattern.
3. Genetic constitution.

Difference between growth in plants and animals

Plants Animals
1. Growths in plants takes place in some special parts Growth in animals does not occur only in some
such as the meristemic tissues at the root tip and parts as it occurs in all parts of the body.
shoot apices.
2. Growth in plants is dependent on external factors i.e. Growth in animal is not dependent on external
temperature, humidity, gravity, sunlight etc. factors.
3. Growth in plant is unlimited. Growth in animals is limited.

Regulation of growth by hormones

Hormones and enzymes are internal factors controlling growth. Both plants and animal hormones are known to effect
growth in one way or the other. A hormone is a chemical substance produced in one part of the plant or animal body
and transported from there to another part where it produces a particular physiological effect.

In animals, hormones influence growth and sexual maturity. Some hormones of importance that regulate growth in
animals include:
i. Growth hormone (somatotropin): This is produced by the pituitary gland. It is concerned with normal
growth in an animal. Over-secretion in human cause gigantism, a condition in which the long bones of the
body lengthen abnormally. Undersecretion of the growth hormones results in the formation of dwarfs.

ii. Thyroxine: This is produced by the thyroid gland. Thyroxine, apart from speeding up body metabolism
especially respiration, stimulates growth and development in young animals. For example, for metarmorphosis
to occurs in frogs or toad, thyroxine is needed. In man, severe undersecretion of thyroxine leads to cretinism
(which is a kind of defective development in which the person is dwarfed).

iii. Sex hormone: These are produced by the gonads i.e. the testis and ovary. The testes produce the male
hormone testosterone while the ovaries produce the female hormone called oestrogen and progesterone. Sex
hormones stimulate the growth of sex organs from the time of puberty.

383
Hormones of importance in plant growth:
Auxins: Auxins are secreted by the apical meristem cell. They perform the following functions:
1. Bring about enlargement in the growth region.
2. Causes the formation of root in stem cutting and grafting.
3. Responsible for fruit development, seed germination, seedling growth and growth of plant organs.
4. Stimulate cell division and cell elongation.

Gibberellins: Cytokinin:
1. It controls flowering in some plants. 1. Stimulates cell division in plant cell.
2. It stimulates leaf expansion. 2. Promotes the growth of lateral buds
3. It controls fruit growth and development. 3. It can slow ageing of plant organs
4. Stimulate growth (stem elongation).
Ethyne (ethylene) gas:
1. Hasten ripening of fruits.
2. Inhibit stem elongation.
3. Accelerates abscission of leaves, flowers and fruit.
4. Accelerates ageing of plant organs.

Growth curve (growth curvature)

A growth curve is a graph which shows the pattern of increase in size of breath or length, or dry weight, or any other
aspect of growth with time. For example, if the height of a sunflower seedling is measured each day for thirty days,
the data can be used to plot a growth curve. The growth curves of many organisms show that growth may be first slow
in a very young organism, fast in a middle life and slow again in old age. The period of fastest growth in a human
being is in early childhood.

Example of growth curve An arc auxanometer

N/B: Auxanometer can be used to determine the rate of growth of a shoot.

Example
The endocrine gland secreting hormone that induces the thyroid gland to produce more thyroxine is
A. islets of Langerhans B. adrenal gland C. pituitary gland D. parathyroid gland (2003/21)
Answer: C – The pituitary gland secretes hormone that stimulates (induces) the thyroid gland to produce more
thyroxin.
Example
(b) State two differences each between:
(i) Growth in plants and animals; (ii) Metamorphosis in housefly and toad.
(c) Name two hormones each involved in:
(i) Plant growth; (ii) animal growth.
(d) State the effects of the hormones named in 8(c)above. (2009/8b, c, d)
Answer:
bi. - Plant growth is unlimited while animal growth is limited.
- In plant, growth is mainly restricted to growing regions (apical meristem) whereas in animals, growth occur
in all parts of the body .
ii. - Metamorphosis in housefly takes place on land while in toad it takes place in water.
- Metamorphosis in housefly takes a shorter time while in toad it takes a longer time.
ci. Auxin and Cytokinins
ii. Thyroxin and Sex hormones (testosterone/oestrogen)

384
d. Effects of the Hormones:
 Auxin – Causes rapid growth of root and shoot.
 Cytokinins – Causes growth of lateral buds.
 Thyroxin – Stimulates the growth of long bones.
 Sex hormones – Stimulates the growth of sex organs.
Example
Secondary growth is brought about by the activities of the
A. phellogen and phelloderm B. phellogen and procambium
C. vascular cambium and pheloderm D. vascular cambium and phellogen (2011/11)
Answer: D – Secondary growth is brought about by the activities of the vascular cambium and phellogen.
NOTE: phellogen is also known as the cork cambium
Example
Use the figure below to Answer: questions 29 – 30

Which part of the curve represents the fastest rate of growth?

A. K B. L C. M D. N
Answer: C – M
The grand period of growth is represented by
A. N B. M C. L D. K (1992/29-30 JAMB)
Answer: B – M; The grand period is the period where there is rapid growth.
Example
The hormones that regulate plant growth are
A. ethylene and auxins B. auxin and gibberellins C. cytokinins and abscisic acid D. ethylene and gibberellins (2017/2 JAMB)
Answer: B – Auxin and gibberellins regulate plant growth.
Example
Unlike auxins, gibberllins
A. induce the formation of adventious roots B. do not affect leaf and fruit abscission
C. cannot stimulate stem elongation D. are quite effective as herbicides (2019/4 JAMB)
Answer: B – Unlike auxins, gibberellins do not affect leaf and fruit abscission.
Example
(c) (i) Name two plant hormones other than auxins. (2019/3ci NABTEB)
Answer: Gibberellins and cytokinins
Example
Under secretion of thyroxine before maturity causes an abnormality known as
A. cretinism B. gigantism C. dwarfism D. myxedema E. obesity (2001/27 Neco)
Answer: A – Cretinism is the retarded mental and physical development in children due to under secretation of
thyroid hormone (thyroxine).
Example
Excessive thyroxine secretion causes
A. hyperactivity B. hypoactivity C. isoactivity D. metamorphosis E. sensitivity (2007/17 Neco)
Answer: A – Excess thyroxine secretion causes hyperactivity.
Example
Auxins are more concentrated at the
A. shoot apex B. midrib C. petiole D. flower (2004/16 Nov)
Answer: A – Auxins are more concentrated at the shoot apex
Example
Over secrection of thyroxin is likely to lead to
A. thinness of body B. sluggishness C. cretinism in infants
D. reduced metabolism E. dwarfism (1991/18 Nov)
Answer: A – Over secretion of thyroxin is likely to lead to thinness of the body.

385
Example
Cretinism results from a deficiency of
A. calcium B. haemoglobin C. thyroxin D. vitamin E. adrenalin (1995/22 Nov)
Answer: C – Cretinism results from the deficiency of thyroxin.

EXERCISE 19.3
The graph below shows the normal growth rate of Guinea pigs in an experiment. It Also shows the growth rate of 25 Guinea pigs
which were fed on a normal diet from birth to point X, when they were deprived of two nutrients, a and b. At point Y nutrient a
was added to the diet. At point Z nutrient b was also added.
Study the graph carefully and use it to Answer: Questions 31 to 33.

1. From the graph, at what age does normally fed Guinea pig reach a full weight?
A. 5 months B. 6 months C. 7 months D. 5 months E. 10 months (1995/31 Nov)
2. It is reasonable to conclude from evidence in the graph that at birth the weight gained by the 25 Guinea pigs in the
experiment as compared to Guinea pigs in general
A. is not related to the average B. is higher than average
C. is representative of Guinea pigs D. shows sign of susceptibility to diseases
E. is an indication of superior qualities (1995/32 Nov)
3. If the experiment had continued as described except that at point Z, nutrient b was not included in the diet of the 25
Guinea pigs, it can be concluded that the Guinea pigs would probably have
A. continued to gain weight but more slowly than normal Guinea pigs
B. remained at about half the size of normally fed Guinea pigs
C. lived for about four months and died D. become sexually immature
E. continued to gain weight much faster than normal Guinea pigs (1995/33 Nov)
4. Auxins are produced in
A. shoot apices B. branches C. cotyledons D. bark of trees E. coloured petals (1997/17 Nov)
5. Which of the following factors accounts for the upward growth of plant shoot?
A. pH B. Light C. Temperature D. Gravity E. Water (1997/3 Nov)
6. (b) Mention two effects of auxins on plants. (1997/2b Nov)
7. The hormone responsible for the development of secondary sexual characteristics in females is
A. follicle stimulating hormone B. oestrogen C. oxytocin D. luteinizing hormone (2019/16 PC2)
8. A hormone mainly concerned with the development of secondary sexual characters, in males is
A. thyroxine B. adrenalin C. insulin D. progesterone E. testosterone (1994/16 Nov)
9. Which of the following does not apply to auxins?
A. Growth in plant is mainly by auxins B. Auxins are produced at the tips of the roots and shoots
C. Initial effectof auxins is to stimulate the growth rate of stems and roots
D. Concentration above optimum auxin level will cause inhibition in growth rate (1994/22 Nov)
10. Which of the following is not involved in the process of growth or specialization in living cells?
A. mitosis B. meiosis C. cyclosis D. Auxins E. cell enlargement (1996/5 Nov)
11. In which of the following parts of plants are auxins produced?
A. In the petals of flowers B. At the petals of leaves
C. In the epidermis of roots arid stems D. In the sclerenchyma tissues of roots and stems
E. At the apical regions of roots and shoots (1992/23 Nov)
12. Which of the following hormones will increase the growth rate of tadpole?
A. insulin B. adrenalin C. thyroxin D. oxytocin (1999/19 Nov)
13. (b) Describe growth in a named insect.
(c) Make a drawing of a growth curve of an: (i) insect; (ii) annual herbaceous plant. (2011/1b, c Nov)
14. Which of the following hormones is responsible for plant growth?
A. prolactin B. Auxin C. Insulin D. Ethene (2002/21 Nov)
15. (e) State two differences between growth in plants and growth in animals. (2007/1e)
16. Which of the following features could be used to determine the growth of a seedling?
A. Number of flowers B. Number of leaves C. Length of flowers D. Length of radicle (2015/10)
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Biology of Heredity (Genetics) & Variation
Genetic is a branch of biology that deals with the scientific study of heredity and variation. Heredity includes those
traits or characteristics that are transmitted from parents to offspring and from one generation to the other. Variation
on the other hand is the visible difference between individuals of the same species. Variation is of two types viz: (i)
Heredity variation and (ii) Environmental variation.

Heredity variation refers to difference in inherited traits. All offspring, inherit different traits from their parents.
Identical twins however are an exception to this heredity variation.

Environmental variations are those that arise due to the environment. The major difference between heredity and
environmental variation is that while hereditary variations are transmitted from one generation to the other,
environmental variation are temporary and are not passed to the next generation.

Characteristics that can be transmitted in man:

1. Body stature/shape 6. Height of human 11. Haemophilia
2. Shape of head, nose and ear 7. Blood group 12. Colour blindness
3. Colour of skin, hair and eye 8. Baldness 13. Fingerprint etc
4. Characteristic of voice/speech 9. Tongue rolling
5. Intelligence 10. Sickle cell anaemia
Not all characteristics are inheritable. Characteristics which are developed by an organism as a result of practice or
exposure to a particular environment are not inheritable. These are called acquired characteristics.

How characteristics are transmitted

The link between the parents and the offspring are the gametes. Therefore, the characteristics of parents are
transmitted to the offspring through the gamete.

Meaning of some basic terms in genetic

1. Gene: Gene is any segment of DNA which by itself or in association with other genes expresses a trait in an
organism. They are located in chromosomes and are responsible for the transmission of characters from
parents to offspring.
2. Hybrid: Hybrid is an offspring from a cross between parents that are genetically different but of the same
species e.g. tall and dwarf parents.
3. Characters/Traits: Traits are the features possessed by an organism e.g. seed colour, seed size, plant height
etc.
4. Alleles: These are pair of contrasting genes on the chromosome for expressing a pair of contrasting character
e.g. for height (T = tall; t = short)
5. Phenotype: This refers to the physical appearance of an individual it also includes the physiological and
behavioural characters e.g. height, weight, skin colour etc.
6. Genotype: This is the sum total of all the genes that the individual inherits from his parents. Genotype
includes both dominant and the recessive characters that form the genetic makeup of an individual.
7. Homozygous: An individual is said to be homozygous if it has two similar gene for same character e.g. (TT)
for tallness or (tt) for shortness.
8. Heterozygous: An individual is said to be heterozygous if the two members of a pair of genes controlling a
pair of contrasting characters are different, e.g. pair of contrasting characters are different. E.g. (Tt) for
tallness.
9. Recessive: A character is said to be recessive when it is not expressed in the presence of another contrasting
character.
10. Test Cross: Test cross is the crossing of an organism with homozygous recessive organisms.
11. Dominant: A trait is said to be dominant when it is expressed in the presence of another character that is
suppressed.
12. Monohybrid cross: This is the cross which relates to only one pair of contrasting character.
13. Mutation: Mutation is a change in the genetic make-up of an organism resulting in a new characteristic that is
inheritable.
14. Chromosomes: This is a dark staining structure found in the nucleus of a cell on which the genes of an
organism are arranged.
15. Locus: The location of a gene on a chromosome.
16. Diploid: Having two sets of chromosome known as homologous e.g. Animals and higher plants.
17. Haploid: Having one set of chromosome e.g. gametes.
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Example
When the two alleles present in an organism are of the same type, the genotype is described as
A. heterozygous B. heterogamous C. homozygous D. homologous (1989/37 JAMB)
Answer: C – When the two alleles present in an organism are of the same type, the genotype is described as
homozygous.
Example
A pair of genes that control a trait is referred to as
A. an allele B. recessive C. dominant D. a hybrid (2010/45 JAMB)
Answer: A – A pair of genes that control a trait is called an allelic pair.
Example
The genetic make-up of an organism is described as
A. phenotype B. genotype C. allele D. chromosome (2014/28 JAMB)
Answer: B – The genetic makeup of an organism is known as the genotype
Example
The transmission of characters from parents to offspring is termed
A. cloning B. evolution C. heredity D. resemblance E. variation (2014/11 Neco)
Answer: C – Heredity is the transmission of characters from parents to offspring.
Example
A pair of genes that controls a trait is described as a/an
A. allele B. dominant C. hybrid D. recessive E. variant (2014/19 Neco)
Answer:
A – A pair of genes that controls a triat is described as an allele.
Example
The gene responsible for the character not expressed physically in an individual is described as
A. recessive B. dominant C. variation D. genotype E. mutant (1996/24 Health Science)
Answer: A – Recessive gene is that responsible for the character not expressed physically in an individual.
Example
In an individual who is heterozygous for a particular character, the hereditary factor that is always expressed is
described as
A. allele B. sickle cell gene C. dominant gene D. recessive gene E. homozygous gene (1995/55 Nov)
Answer: C – Dominant gene is that which is always expressed.
Example
Which of the following statements best explains the meaning of homologous chromosomes?
A. Extra chromosome in a cell B. Two identical chromosomes from each parent
C. Chromosomes arranged on spindle fibre during cell division D. Chromosomes arranged on the middle of the cell
E. Daughter chromatid in the first meiotic division (1995/56 Nov)
Answer: B – Homologous chromosomes are two identical chromosomes from each parent.
Example
Which of the following statements about alleles is correct? It is the
A. genetic complement of an organism B. single unit of heredity
C. product from a cross between parents D. different forms of a gene that occupies the same locus (2013/52 Nov)
Answer:
D – Alleles are different forms of a gene that occupies the same locus.
Example
The recessive genes refers to a gene
A. that suppressed the effect of its alternate form B. which is prevalent in all populations
C. which does not manifest in the presence of the other allele D. that is resistant to mutation (2013/53 Nov)
Answer: C – A recessive gene is that which does not manifest in the presence of the other allele.
Example
Two alternate forms of the same gene are known as
A. alleles B. genotypes C. heterozygotes D. phenotypes (2013/59 Nov)
Answer: A – Two alternate forms of the same gene are called Alleles.

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Example
The major difference between genotype and phenotype is that phenotype
A. is an observable trait while genotype is a dominant character
B. is an observable trait while genotype is-a recessive character
C. is the sum total of observable traits while genotype is the sum total of dominant and recessive genes
D. is an observed feature in female offspring while genotype is the sum total of genes inherited in male offspring (2011/53 Nov)
Answer: C – The phenotype is the sum total of observable trait while genotype is the sum total of dominant and
recessive genes.
Example
3.(a) Explain the following terms: (i) test cross; (ii) recessive allele; (iii) homozygote. (2011/3a i-iii Nov)
Answer:
i. Test cross – This is the cross between an organism with unknown genotype and a homozygous recessive
organism.
ii. Recessive allele – This is an allele which is not expressed in the presence of another contrasting allele.
iii. Homozygote – This is an individual having two identical alleles of a particular gene.
Example
What is the name given to the genes affecting a trait of character and located on the same position of the homologous
chromosomes?
A. Alleles B. Loci C. Chromatids D. Chromomeres (2002/56 Nov)
Answer: A – Alleles
Example
Genotype can be defined as
A. a genetic makeup of an organism B. an outward character of an organism
C. a unit responsible for the formation of offspring D. a basic structural and functional unit of life (2019/44 PC2)
Answer: A – Genotype is the genetic make-up of an organism.

EXERCISE 20.1
1. A pair of genes which controls a trait is described as
A. dominant B. recess C. allele D. variant E. hybrid (1990/53)
2. The genetic make-up of an organism is described as its
A. phenotype B. genotype C. character D. chromosome E. allele (1990/54)
3. Which of the following is the unit of transmission of hereditary traits in living organisms
A. Nucleus B. Nucleolus C. Gametes D. Genes E. Chromosomes (1991/42)
4. Which of the following statements best explains the meaning of homologous chromosomes?
A. Product of division of chromosomes B. Two identical chromosomes from each parent
C. Chromosomes arranged on spindle fibre during cell division
D. Chromosomes arranged on the equatorial plate of the cell
E. Daughter chromatids in the first meiotic division (1991/60)
5. In an individual who is heterozygous for a particular character, the hereditary factor that is always expressed
is described as
A. allele B. sickle-cell gene C. dominant gene D. chromosome E. sex-linked character (1991/59)
6. The offspring produced when pure strains interbreed is described as
A. dominance B. phenotype C. allele D. genotype E. hybrid (1993/51)
7. Which of the following is the carrier of hereditary materials?
A. Centriole B. Cytoplasm C. Nucleolus D. Chromosome E. Lysosome (1994/57)
8. Hereditary variation is best described as
A. characters transmitted from generation to generation B. traits acquired from diseases
C. characters that show up due to social conditions
D. traits acquired from habits and environmental conditions
E. characters that result in physical injuries (1995/51)
9. Which of the following is a definition for hereditary? It is the
A. non-resemblance of closely related organisms B. total absence of parental traits in offspring
C. absence of variation in organisms D. transfer of characteristics from parents to offspring
E. cause of infant mortality (1995/54)
10. The pair of gene expressed in a heterozygous individual is described as
A. allele B. chromatid C. dominant gene D. centrosome E. chromomere (1995/56)

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11. Character which fails to express itself in the first filial generation but emerges in the second is
A. heterozygote B. homozygote C. dominant D. recessive (2000/56)
12. 7(a) Explain the following terms:
(i) trait, (ii) recessive gene; (iii) test cross; (iv) heterozygous (2005/7a)
13. The observable characteristics of an individual usually resulting· from the interaction between the gene
composition and the environment is referred to as
A. allele B. genotype C. phenotype D. chromosome (2008/49)
14. The sudden change is a gene structure or chromosome number in an organism likely to cause an inheritable
change in the phenotype is known as
A. migration B. mutation C. mitosis D. meiosis. (2008/50)
15. The outward appearance of an organism is referred to as
A. phenotype B. genotype C. dominance D. recessiveness (2009/51)

The diagram below are illustrations of the inheritance of coat colour in J, K, L, M and N are parents. The cross
between two parents mice gave rise to P, Q, R and S. Study the diagrams and Answer: questions 42 and 43.

16. Which parent mouse is heterozygous for coat colour?

A. M B. J C. K D. L (2018/42)
17. Which of the offsprings are all homozygous?
A. P B. Q C. S D. R (2018/43)
Mendel’s work in genetics
Gregor Mendel (1822-1884) was a monk in an Augustinian monastery at Brunn, Austria. Mendel’s work was
published in 1865 and formed the basis of modern genetics. All the work that has been done in genetics has made use
of Mendel’s basic discoveries and so, today, he is known as the father of modern genetics.

Mendel’s aim was to find out the pattern of inheritance of different characteristics of the pea plant, pisum sativum. He
chose the pea plant for his experiment because the pea was an annual crop which result of breeding experiment could
be obtained in a short period of time.

The seed was found to have seven distinct characteristics which existed in contrasting pairs. Some of these characters
and their pair includes that some were round while others were yellow, some flowers were axial while some were
terminal, some were smooth while some were constricted, some flowers were white while some were red.

Mendel artificially crossed two types of plants at a time which differed in one pair of contrasting characters (e.g. tall
and short plant). This is called monohybrid inheritance, Mendel collected the seeds formed after the cross. When he
sowed these seeds, the plants produced were all tall plant. These he called the first filial or F1 generation.

The genotype of all the F1 plant is Tt. The phenotype is “all tall” plants, but they are heterozygous i.e. they are not
pure breeding. He crossed the F1 plants, collected their seeds and sowed them. The phenotype of plants which resulted
from these were tall and short plants in the ratio of 3:1 respectively. He called these the second filial or F2
generation.
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The genotype of the F2 plant are 1 TT : 2 Tt : 1 tt
The genotypic ratio is 1 : 2 : 1
Their phenotypes are 3 tall plants, 1 dwarf plant. Their phenotypic ratio is 3:1.

The outcome of this experiment led to Mendel first law of inheritance called the law of segregation of gene. The law
states that the characteristic of an organism are controlled by genes which occur in pairs, of such a pair of gene, only
one can be earned in a single gamete.

The law can also be stated thus: Gene are responsible for the development of the individual and that they are
independently transmitted from one generation to another without undergoing any alteration. Mendel deduced this law
from the idea that the disappearance of the recessive characteristics in F1 and its reappearance in F2 would occur only
if one gamete contained only one factor.

Dihybrid inheritance:
Mendel also carried out experiment in which he crossed plants which differed in two pairs of contrasting
characteristics such as seed shape (round and wrinkled seeds) and seed colour (yellow and green seeds). This is called
dihybrid inheritance.
When Mendel crossed plants which had round and yellow seed with those which had wrinkled and green seeds, all
the F1 generation plants produced round and yellow seed. However when the F1 generation was crossed, the F2 plants
were of four kinds namely:
Plants that produce round and yellow seeds, wrinkled and yellow seeds, round and green seeds and wrinkled and
green seed in the ratio of 9:3:3:1.
Mendel referred that this could result if the contrasting characteristic of round and wrinkled seeds were inherited
independently of each other.
This led to the statement of Mendel’s second law also called the law of independent Assortment of gene. The law
states that each character behaves as separate unit and is inherited independently of any other character.

Male RY Ry rY ry
Female
RY RYRYo1 RYRyo2 RYry3o RYry4o
Ry RYRyo5 RyRyo6 RyrY7o Ryry8o
rY rYRY o9 rYRyo16 rYrYo11 rYryo12
ry ryRYo13 ryRyo14 ryrYo15 ryryo16

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Punnet square
R and Y – round and yellow = 9
R and y – round and green = 3
r and Y – wrinkled and yellow = 3
r and y – wrinkled and green = 1
The four phenotypes which appear in the ratio 9:3:3:1 are as follows:
1. 9 round yellow = 1, 2, 3, 4, 5, 7, 9, 10, 13
2. 3 round and green = 6, 8, 14
3. 3 wrinkled and yellow = 11, 12, 15
4. 1 wrinkled and green = 16

Back cross
The crossing of a hybrid organism with either of its parents is known as a back cross. Back crossing is useful in
genetics study for separating out certain characteristics in a related group of animals or plant.

It is important to note that test cross is a type of back crossing in which the parent with the “homozygous recessive”
trait is crossed with the hybrid offspring.

Let’s consider a cross between a pure homozygous round seed parent and a pure homozygous wrinkled seed parent

We can observe that the first cross was a cross between a pure round seed and a pure wrinkled seed, that is they are
both homozygous for the respective character. The offspring produced however is heterozygous and therefore
referred to as a hybrid. In such hybrid offspring, the dominant character is expressed which in this case, is the round
nature of the seed as manifested in the phenotype.

The second cross is an example of a back cross involving the homozygous dominant parent (pure round seed i.e. RR)
with the hybrid. This type of back crossing is usually used to preserve some characters from the parent.

The third cross is also a back cross but this type of back cross is known as a test cross. It involves crossing the
homozygous recessive parent which in this case is the pure wrinkled seed rr with the hybrid offspring.

N.B: Test cross is usually used to find out which offspring is homozygous dominant or not.

Incomplete dominance and co-dominance

Gregor Mendel in his laws of genetics explained the law of dominance to indicate that in a heterozygous individual
one of the two alleles is dominant, as it is always expressed in the phenotype in the presence of a recessive character.
Mendel was unable to study the principle of incomplete dominance as the pea plant he used for his experiment didn’t
show incomplete dominance.

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Incomplete dominance which is also known as partial dominance results when phenotype is a blend of the
recessive and dominant allele. In this type of dominance, the dominant allele cannot completely dominate the
recessive allele, as a result of which, the phenotype becomes a mix of both. For example in a flower in which the
dominant allele for colour is red (R) and recessive allele is white (r) but a heterozygous flower appears pink. In this
situation the dominant red couldn’t dominate fully but shows incomplete dominance.
Another phenomenon in which Mendel’s laws failed to explain is the principle of co-dominance. Co-dominance is
the expression of the two alleles in a heterozygous individual. That is to say the presence of one doesn’t affect the
effect of the other. An example of co-dominance can be observed in plants where the dominant phenotype is red and
the recessive phenotype is white but the heterozygous plant will have flowers with pink and white spots. An example
of co-dominance that occurs in human is that of blood types (an individual who inherits an A allele from one parent
and a B allele from the other will express both in a co-dominant fashion).
Co-dominance is different from incomplete dominance in that as can be seen in co-dominance both the alleles
co exist but separately but in incomplete dominance, the phenotype is a blend of the two alleles.
Example
If a tall man (TT) marries a dwarf woman (tt)) and they have male children, the offspring will be
A. all short B. three short and one tall C. two short and two tall
D. one short and three tall E. all tall (1982/9 JAMB)
Answer: E – All tall

NB: The genotype of all offspring = Tt. The phenotype of all offspring will be All tall (Tt). This is because “T” is the
dominant gene for height and it represents tallness while “t” is the recessive gene for height and it represents shortness
Example
The greatest contribution to genetic studies was made by
A. Thomas Morgan B. Gregor Mendel C. Charles Darwin D. Robert Hooke (1991/37 JAMB)
Answer: B – The greatest contribution to genetics studies was made by Gregor Mendel.
Example
When two heterozygotes mate, the dominant trait will appear in
A. F1 generation only B. F2 generation only
C. both the F1 and F2 generations D. neither the F1 nor F2 generation (1991/39 JAMB)
Answer: C – When two heterozygotes mate, the dominant trait will appear in both the F1 and F2 generations.
Example
If a woman’s genotype is Tt Qp, Rr. What would be the gene content of her eggs?
A. TQr, tqr B. TQR, tqr C. Tqr, tQr D. tQr, TQR (1994/44 JAMB)
Answer: B – TQR, tqr
Example
The F1 of a cross between a tall and a dwarf plant was tall. The F1 was advanced to F2 how many of 120 F2 plants will
be dwarf?
A. 30 B 60 C. 90 D. 120 (1995/44 JAMB)
Answer: If the F1 of a cross between a tall and a dwarf plant was all tall, it means that the genotypes for both parents
were TT and tt respectively.
Diagrammatically: When F1 was advanced to F2 will get:

Phenotypic ratio: All tall Phenotypic ratio: 3 Tall: 1 Dwarf

In 4 F2 plants,only one dwarf plant can be seen from the cross
1
Therefore Number of dwarf in 120 F2 is 4 × 120 = 30 𝑑𝑤𝑎𝑟𝑓𝑠 𝑝𝑙𝑎𝑛𝑡𝑠
393
Example
A cross between an albino female and genetically normal male will result in offspring that are
A. all albino B. half albino and half normal
C. all genetically normal D. all phenotypically normal (2000/42 JAMB)
Answer: D – The cross between an albino female and a genetically normal male will result in offsprings that are all
phenotypically normal.
Example
The surest way to combine the best qualities of both parents in the offspring is by
A. selective breeding B. inbreeding C. cross-breeding D. pure breeding (2000/43 JAMB)
Answer:
C – The surest way to combine the best qualities of both parents in the offspring is by cross-breeding.
Example
Mendel’s second law of inheritance states that
A. alleles combine randomly B. alleles segregate independently
C. alleles separate predictably D. chromosomes segregate independently (2006/23 JAMB)
Answer: B – Mendels second law of inheritance states that alleles segregate independently. The law is also
known as the law of independent assortment.
Example
A farmer’s assumption that the seed from a good harvest will produce a good yield is explained by the theory of
A. evolution B. adaptation C. variation D. heredity (2009/41 JAMB)
Answer: D – Heredity
Example
In Mendelian inheritance, discontinuous characters are controlled by the
A. centromeres B. alleles C. chromosomes D. chromatids (2009/42 JAMB)
Answer: B – Alleles control discontinuous characters
Example
A yellow maize is planted and all the fruits obtained are yellow seeds. When they are cross-bred, yellow seed and
white seeds are obtained in a ration 3:1. The yellow seed is said to be
A. non-heritable B. sex-linked C. a recessive trait D. a dominant trait (2012/41 JAMB)
Answer: D – The yellow seed is said to be the dominant trait.
Example
Which of the following results from the cross between Yy and Yy?
A.2Yy-2yy B.2Y:yy:YY C.YY:2Yy:yy D.YY:Yy:2yy (2016/6 JAMB)
Answer: C – YY:2Yy:yy
Example
Mendel’s first law is known as law of
A. use and disuse B. segregation of genes
C. evolution D. independent assortment of genes (2019/47 NABTEB)
Answer: B – Mendel’s first law is also known as the law of segregation of gene.
Example
6a. State the TWO Mendelian laws of inheritance.
b. Name THREE diseases in man that are sex-linked. (1999/6a-b NABTEB)
Answer:
6a. Medelian laws of inheritance:
- Mendel’s first law states that during gamete formation, the two alleles at a gene locus segregate from each
other and that each gamete has an equal probability of containing either allele.
- Mendel second law states that during gamete formation, the way one pair of alleles of a given character
distributes itself in the gametes does not affect the way other allelic pairs distribute themselves.
b. Hemophilia, red-green colour blindness and congenital night blindness.
Example
What will be the phenotypic ratio when a tall pea plant (TT) is crossed with a short pea plant (Tt)?
A. 0:4 B. 1:3 C. 2:2 D. 3:1 E. 4:0 (2008/57 Neco)
Answer: C - Phenotypic ratio: 2TT: 2Tt i.e. 2:2

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Example
A Homozygous normal skin father (AA) got married to a homozygous albino fathered (aa). All the offsprings were
heterozygous normal skin (Aa)
From the crossing above:
i. What would be the genotypic and phenotypic ratio if two of the offspring (F1) were married?
ii. What percentage of the offsprings in (i) are albino (2008/4ai-ii Neco)
Answer:
1
ii. Percentage of offsprings in (i) that are albino: 4 × 100 = 25%

i.
Genotypic ratio = 1:2:1
Phenotypic ratio: 3:1
Example
A geneticist conducted series of crosses between male rats with genotype bb and female rats with genotype Bb for a
certain character, at the end of the experiment he has a total number of 200 rats. What is the likely distribution of
genotypes
A. 152 bb 48Bb B. 75bb 125Bb C. 102Bb 98bb E. 175Bb 25b (2006/52 Nov)
Answer: Genotypic ratio: 2Bb:2bb
2
∴ Number of offspring with Bb genotype: 4 × 200 = 100 offspring with Bb genotype.
Same will apply for number of offsprings with bb genotype.
∴ We will have 100Bb and 100bb. The options closest to our Answer: are C which is 102Bb and 98bb
Example
If the cross of a red-flowered plant with a white flowered plant produces a pink-flowered plant, it is an example
A. incomplete dominance B. mutation C. linkage D. codominance (2012/43 JAMB)
Answer: A – Incomplete dominance
Example
A test cross is carried out to determine an organisms
A. phenotype B. genotype C. dominant gene D. blood group E. sex (1997/53 Nov)
Answer: B – A test cross is carried out to determine the genotype of an organism.
Example
If a red gene is represented by (R) and a white gene by (r), a cross between a heterozygous red flowered plant (Rr) and
a white flowered plant (rr) will produce offspring in the ratio of
A. 1 red: 3 white B. 3 white: 1 red C. 4 red: 0 white
D. 2 red: 2 white E. 4 white: 0 red (1994/54 Nov)
Answer:

D – 2 red:2white
Example
In a monohybrid cross when two heterozygous individual are crossed, what will be the expected inheritance of the
offspring in F1 generation?
A. All offspring will be homozygous B. All offspring will be phenotypically the same.
C. Genotypic ratio will be 2:2 D. Genotypic ratio will be 1:2:1
E. Phenotypic ratio will be 2:1 (1994/55 Nov)
Answer: D – Genotypic ratio will be 1:2:1
Example
Traits which can be used for selective breeding for production of stable strains of crops may involve the following
except
A. ease of harvesting B. high yield C. adaptation to local conditions D. reduced resistance to diseases(2005/55 Nov)
Answer: A – Ease of harvesting
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Example
Which of the following pairs of characters was not observed by Mendel in his experiments with pea plants? Some
A. plants were tall, while some were short B. seeds were round, while others were wrinkled
C. seeds were yellow, while some were green D. leaves were white, while some were red (2000/55 Nov)
Answer: D – Leave colour was not observed by Mendel in his experiment with pea plants.
Example
How many pairs of contrasting characters is/are involved in Mendel’s second law of inheritance?
A. four B. three C. two D. one (2000/56 Nov)
Answer: D – One pair of contrasting character is involved in Mendel second law of inheritance.
Example
Mendel’s first law is known as law of
A. use and disuse B. segregation of genes C. evolution D. independent assortment of genes (2000/57 Nov)
Answer: B – Segregation of gene.

EXERCISE 20.2
1. In Mendel’s experiment on monohybrid crossing the result of the F2 generation was that
1 3
A. 2 of the offspring showed the dominant trait B. 4 of the offspring showed the dominant trait
1
C. all the offspring showed the dominant trait D. 4 of the offspring showed the dominant trait (2019/45 PC2)
2. When homozygous dominant and heterozygous organisms are crossed over two generations, the dominant
trait will appear in
A. the F1 generation only B. the F2 generation only
C. both the F1 and F2 generations D. one offspring of the F2 generation only (2019/46 PC2)
3. The F generation of a cross between a red flower and a white flower of the same species were all red because
the gene for the
A. white colour did hot segregate B. red colour was dominant
C. white colour was dominant D. red colour was recessive (2020/44 PC1)
4. When gametes from pure breeding parents with contrasting features such as tallness and shortness are
involved in monohybrid cross, the offspring in the first filial generation are usually.
A. pure breed B. heterozygous dominant C. homozygous recessive
D. mutants E. co-dominant (1990/52)
5. One of the major criticisms against Mendelian laws is that they do not recognise that
A. One trait is often controlled by many pairs of genes
B. singe factor inheritance is never a reality C. complete dominance is always possible
D. incomplete dominance is not possible E. hybrids exist in living organisms (1993/49)
Study the genetic cross below showing the inheritance of blood groups.

6. From the cross above which of the following F1 offspring does not belong to the father?
A. AA B. AO C. OB D. OO E. AB (1993/53)
7. (d) In a monohybrid cross between a pure breeding plant that produces blue flowers and a pure breeding plant
that produces white flowers, the F1 generation produces only blue flowers. By means of labelled cross
diagrams, state the type of flowers you would expect if the F1 generation is (i) self-pollinated (ii) cross-
pollinated with a pure breeding plant that produces white flowers. Give reasons for your Answer: s in (d)(i)
and (ii). (1993/4d)
8. One of Mendel’s experiments was repeated by crossing a red variety of pepper with that of a yellow variety
which produced all red offspring. The red offspring were then self-pollinated and these produced both red and
yellow pepper. The yellow pepper can be said to be
A. dominant to red B. recessive to red C. homozygous to red
D. heterozygous to red E. linked to red (1996/52)
9. The genotypic ratio of 1:2:1 in the offspring of a hybrid cross illustrates
A. use and disuse B. dominance C. segregation D. linkage (1999/55)
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10. 4(a)(i) Definee the law of independent assortment (ii) State the findings from Mendel’s experiment involving
white flowered and red-flowered pea plants (iii) Illustrate these findings by means of simple diagrams (b)
Explain why blood groups A and B in man can exist both in heterozygous and homozygous conditions while
blood group O can only exist in homozygous state. (1999/4a, b)
11. When Mendel crossed round seeds with wrinkled seeds of Pea Plant, what was the ratio of wrinkled seeds to
round seeds in the F2 plants
A. 3:1 B. 2:1 C. 1:3 D. 1:2 (2002/52)
Use the following information to Answer: questions 54 and 55
In an experiment, a red-flower plant was crossed with another red-flowered plant and the following
results were obtained:
448 red flowers and 154 white flowers in the F1 generation
12. Which of the following represents the genotypes of the parents if R is for red gene and r for white gene?
A. RR × Rr B. RR × rr C. rr × rr D. Rr × Rr (2003/54)
13. Which of the following represents the phenotypic ratio of the above genetic cross?
A. 1:2:1 B. 4:1 C. 3:1 D. 2:2 (2003/55)
14. What will be the genotypic ratio when two heterozygous red pea plants are crossed?
A. 1:0 B. 1:2:1 C. 2:1 D. 3:1 (2004/53)
15. If two parents are sickle cell carriers then their genotypes would be
A. HbA HbA and HbS HbS B. HbS HbS and HbS HbS
A S A S
C. Hb Hb and Hb Hb D. HbA HbA and HbA HbA (2005/53)
16. Heterozygous tall plants were crossed with pure-breeding dwarf plants of the same species. What were the
approximate percentages of the offspring?
A. 100% tall 0% dwarf B. 75% tall 25% dwarf C. 50% tall 50% dwarf D. 25% tall 75% dwarf (2004/55)
17. In the F1 generation of Mendel’s experiment obtained by crossing pea plants of long stems with those of short
stems, what was his observation?
A. Some were short while others were long B. all were long
C. half of them were long while half were short
D. three-quarters were long while one-quarter were short (2004/56)
18. (c) Mention two ways in which the application of genetics is beneficial to agriculture. (2005/7ci)
19. If a heterozygous red flowered plant, (Rr) was self fertilized, the offspring would be expected to be
A. all red flowered plants B. all white flowered plants
C. ¾ white flowered, ¼ red white flowered plants D. ¾ red flowered, ¼ white flowered plants (2006/54)
20. If a pure breeding white cat (homozygous dominant) mates with a pure breeding black cat (recessive), what
would be the fur colour of the F1 generation?
A. Homozygous white B. Homozygous black C. Heterozygous white D. Heterozygous black (2006/57)
21. What would be the phenotypic ratio of the offspring of a cross between a heterozygous dominant parent and a
double recessive parent?
A. 1:2:1 B. 1:1 C. 3:1 D. 2:1 (2010/55)
22. Two plants with red flowers were back crossed, which of the following results indicates that the plants are
heterozygous red flowers, where red flowers are dominant?
A. 75% red and 25%white B. 50% red and 50% white C. 100% white D. 100% red (2012/54)
23. In case of complete dominance, what is the phenotypic ratio of the cross Bb X Bb; where B= black and b =
white?
A. 1 black :1 grey: 2 whites B. 1 black:3 whites C. 1 black:2 blues: 1 white D. 3 blacks: 1 white (2012/56)

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 Use the diagram below to Answer: question 44 and 45

24. Which of the following statements about the cross is correct?

A. The gene for the spotted coat is recessive to the gene for the black coat
B. Black coat and spotted coat are co-dominant
C. The gene for the spotted coat is dominant over the gene for the black coat
D. The genotype for the F1 are homozygous dominant (2015/44)
25. What are the genotypes of the parents if the gene for skin colour is H?
Spoted leopard Black panther
a. HH hh
b. HH Hh
c. Hh Hh
d. Hh hh (2015/45)
26. According to Mendel’s first law of inheritance, segregation of genes occur when
A. tall plants are crossbred B. short plants are crossbred
C. tall plants and short plants are crossbred D. plants are crossbred (2015/46)
27. (a) Explain the following terms: (i) test cross (ii) monohybrid cross (b) in a mango plant, the allele for bean
shaped seed is r and is recessive to round shaped seed R. with the aid of a genetic diagram, determine
genotypes of the offspring if: (i) a homozygous bean-shaped parent is crossed with a homozygous round
parent; (ii) a heterozygous bean-shaped parent is crossed with a heterozygous round shaped parent (2015/4a, b)
28. The greatest contribution to genetic studies was made by
A. Gregor Mendel B. Thomas Morgan C. Charles Darwin D. Robert Hooke (2018/40)
29. In a complete dominance monohybrid cross between a pure breeding yellow flowered plant Y and a pure
breeding White flowered plant y, the result of the first filial generation is
A. 50% yellow flowers B. 75% yellow flowers C. all yellow flowers D. all white flowers (2019/46)
30. The cross between RrTt and rrtt where R is a gene for red colour and T for tallness will result in
A. all the offspring being tall with red fruits B. 25% tall with red fruits
C. 50% tall with red fruits D. 75% tall with red fruits (2019/48)
The diagram below is an illustration of a cross between plants A and B of the same species. Study it and
Answer: questions 46 and 47

31. If the F1 generation are plants with high yield and resistance, the genotype of the F1 generation plants would
be
A. YYRR B. YyRr C. yyRr D. yyrr (2020/46)
32. The process that gave rise to the F1 generation is
A. self fertilization B. cross fertilization C. out-breeding D. test cross (2020/47)

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Chromosomes: Basis of Heredity
Chromosomes are string-like structure within the nucleus of the cell. It contains genes which carries the genetic
information that are transmitted from parents to offspring.

Chromosomes are nuclear component having a special organization, individuality and function. It is capable of self
reproduction (duplication) during cell division and maintains its morphological and physiological properties through
successive cell division.
Genes: Genes are factors that determine both the mental, physical and physiological attitude of the individual.
Therefore a gene is a unit of heredity. The genes are made up of a long chain of Deoxyribonucleic Acid molecule
(DNA).
Structure of chromosomes
The structure of chromosomes are seen with the microscope only during cell division (mitosis and meiosis). At the
beginning of cell division, they appear as long slender thread. As the division progresses, they shorten and thicken.
After sometimes, each chromosome is observed to be made up of two threads called chromatid held together at the
centromere.
The chromosome is made up of dexoxyribonucleic acid (DNA) and protein.
Deoxyribonuclei acid (DNA) and Ribonucleic acid (RNA)
The DNA is made up of repeating unit called nucleotide. Each nucleotide is made up of a sugar called deoxyribose (5
– carbon sugar), a phosphate group and a nitrogenous compound (a base). The nitrogenous base can be one of the
following: Adenine (A), guanine (G), cytosine (C), thymine (T). The nucleotide are arranged in a ladder – like
structures to form double helix. The sides of the helix are formed by sugar and phosphate while the steps are formed
by the nitrogenous base (purine and pyrimidine) which are joined by hydrogen bond.
The purine consist of adenine and guanine while the pyrimidine consists of cytosine and thymine. A purine base
usually links up with the compactable pyrimidine base to form a bond.
During the formation of bond, adenine pair only with thymine and guanine with cytosine. These bonds formed are
hydrogen bond resulting from the pairing of adenine with thymine (A = T) and cytosine with guanine (C ≡ G).

Helix structure of DNA

A=T
G≡C
P = phosphate group
S = sugar

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Roles of DNA
1. The DNA transcribe the hereditary characteristics of the parent into the offspring.
2. It keeps the number of chromosomes peculiar to organism constant from generation to generation. This is
achieved during mitosis and meiosis.
3. It regulates the synthesis of protein and enzymes in the cytoplasm, thereby controlling growth and
development in living things.
The DNA uses three types of ribonucleic acid (RNA) for the synthesis of protein and enzyme in the cytoplasm of the
cell.
The three RNA are:
1. Messenger RNA (MRNA).
2. Transfer RNA (tRNA)
3. Ribosomal RNA (rRNA)

The messenger RNA carries the information from the DNA regarding the synthesis of certain kind of protein.

The process involved in the formation of the messenger RNA is called transcription. The MRNA has code for the
synthesis of protein cytoplasm.

The tRNA recognizes special amino acid floating in the cytoplasm and carry them to the site of the synthesis of
protein.

The ribosomal RNA is the site where protein synthesis take place.
Structure of RNA
The RNA is similar to DNA. Both are formed in the nucleus and are acidic in nature. There are two important
difference between DNA and RNA.
Differences between DNA and RNA
1. In place of the sugar Deoxyribose, RNA contains ribose which has additional oxygen atom.
2. RNA contains the pyrimidine uracil instead of thymine.
Another difference is that RNA does not have a regular helical structure and is usually single stranded.

Similarities between DNA and RNA

The DNA and RNA are both genetic code. This is why viruses that lack DNA have RNA to carry out their function.

Structure of RNA
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Number of chromosomes
Every organisms of the same species have the same number of chromosomes in each body cell also known as somatic
cell.
Such cells contain the full chromosome number and is called the diploid number (2n).
The second group of cells are called germ cells. These cells are found in gonads (testes and ovaries), plant structures
such as anthers and ovaries for the formation of gametes.
The somatic cell divide to produce daughter cells having the same number of chromosomes as the parent cells,
division of germ cell gives rise to daughter cells in which the number of chromosomes is reduced to half (haploid)
number (n). This type of division is called meiosis (reduction) division. It takes place only during the formation of sex
cells such as the sperms and eggs.

The somatic cells of man contain 46 chromosomes where each egg contains 23 chromosomes. The number of
chromosomes in each organism is constant from generation to generation.

Each gamete has the haploid number of chromosomes. During fertilization, there is a fusion of the nucleus of the
sperm with the nucleus of the egg therefore restoring the diploid number of chromosomes (2n) characteristic of the
organism.

These 46 chromosomes in human occur as 23 pairs (23 × 2 = 46). Each pair occupies the same position and is similar
in shape and size to the other. Each pair is therefore called homologous chromosomes and is separated during meiosis
only.

Diploid and haploid number of chromosomes in some organisms

Organism Diploid number Haploid number
Man 46 23
Dog 52 26
Monkey 48 24
Cat 38 19
Horse 66 33
Domestic fowl 18 9
Rabbit 44 22
Fruit fly (drosophile) 8 4
Garden pea 14 7
Honey bee 6 3
Housefly 12 6
Crayfish 196 98
Pig 40 2
Example
The carrier of the hereditary character in plants and animals is the
A. cell B. nucleus C. chromosome D. chloroplast E. gene (1979/11 JAMB)
Answer: C – The chromosome carries the hereditary materials in plants and animals.
Example
The hereditary material in a cell is known as
A. ADP B. CNS C. RNA D. ATP E. DNA (1985/35 JAMB)
Answer: E – The DNA is the hereditary material in a cell.
Example
The DNA molecule is a chain of repeating
A. nucleosides B. nitrogenous bases C. sugar phosphates D. nucleotides (1995/41 JAMB)
Answer: D – The DNA chain is made up of repeating unit of nucleotides.
NB: Nucleotides are different from nucleosides in that; nucleotides contain phosphate group, pentose sugar and
nitrogenous bases while nucleoside consist of just pentose sugar and nitrogenous bases

401
Example
The specific number of chromosomes in each somatic cell is represented by
A. 2N B. 23 C. 2N D. N (1995/42 JAMB)
Answer: C – The specific number of chromosomes in each somatic cell is represented by 2n.
NB: “n” stands for haploid number of chromosomes. “2n” stands for diploid number of chromosomes.
Example
The correct increasing order of size for the cell components rensponsible for heredity is
A. chromosome→DNA→nucleus→gene B. DNA→gene→chromosome→nucleus
C. chromosome→nucleus→DNA→gene D. DNA→gene→nucleus→chromosome (1998/41 JAMB)
Answer: B – DNA→Gene→Chromosome→Nucleus
Example
The biological factor that is unique to each individual is the
A. DNA B. eye colour C. blood group D. RNA (1999/44 JAMB)
Answer: A – DNA is the biological factor that is unique to each individual.
Example
An organism that has been extensively used to test the chromosome theory of heredity is
A. Homo sapiens B. Drosphila melanogaster C. Zea mays D. Musca domestica (2003/39 JAMB)
Answer: B – Drosophila melanogaster
Example
A feature associated with the Y-chromosome in humans is
A. facial hairs B. Prominent finger nails C. long eyelashes D. enlarged breat (2003/40 JAMB)
Answer: A – facial hairs
Example
The two normal types of sex chromosomes are
A. XXY and XYY B. XX and SYY C. XY and XXY D. XX and XY (2006/19 JAMB)
Answer: D – XX and XY are the two normal types of sex chromosomes.
Example
Use the diagram below to Answer: questions 20 and 21.

The diagram represents the structure of

A. proteins B. chromosones C. RNA D. DNA (2006/20 JAMB)
Answer: D – DNA
Example
The part labelled I represents the
A. base pairs B. ribose sugar C. phosphate linkage D. deoxyri-bose sugar (2006/21 JAMB)
Answer: A – I represents base pairs
Example
The chromosome number of a cell before and after the process of meiosis is conventionally represented as
A. 2n  2n B. n  n C. n  2n D. 2n  n (2010/46 JAMB)
Answer: D – 2n (before meiosis) and n (after meiosis) i.e. 2n → n.
Example
DNA in eukaryotic cells is contained in the
A. central vacuole B. nucleus C. lysosome D. golgi body (2018/31 JAMB)
Answer: B – DNA in eukaryotic cell is contained in the nucleus
Example
The unit of transmission of hereditary traits in a living organism is the
A. nucleoplasm B. gene C. nucleolus D. nuclear membrane (2001/39 NABTEB)
Answer: B – Gene is the unit of transmission of hereditary trait in a living organism.

402
Example
In which of the following parts of a cell is the chromosome found?
A. Nucleus B. Cytoplasm C. Cell membrane D. Golgi body (2019/9 NABTEB)
Answer: A – Nucleus.
Example
An organism where the 2n number of chromosome is 16, the number of chromosomes in each gamete will be
A. 32 B. 16 C. 8 D. 4 (2019/44 NABTEB)
2𝑛 16
Answer: C – 8. When 2n = 16, the gamete which are haploid (n) will be 2
= 2
= n = 8.
Example
Which of the following bases is not present in deoxyribonucleic acid (DNA)?
A. Adenine B. Thymine C. Uracil D. Guanine (2018/26 NABTEB)
Answer: C – Uracil is not present in DNA.
NB: It is present in RNA
Example
The hereditary material controlling a particular trait in organisms is called
A. centrosome B. chromatid C. chromosome D. gene E. lysosome (2007/44 Neco)
Answer: D – Gene
Example
The diagrarm below represents a chromososme yet to divide. Use it to answer question 58-59

The part labelled I represents

A. Chromatid B. chramomere C. gene locus D. centromere E. chiasma (1992/58 Nov)
Answer: D – The part labeled I represents centromere which is the point of attachment of non-sister chromatids
Example
What does the shaded part represent?
A. Allele B. Chiasma C. Chromatid D. Gene E. Centriole (1992/59 Nov)
Answer: C – The shaded part represents a chromatid.
Note: A chromatid is one half of a duplicated chromosome
Example
Which of the following organic molecules constitute the nucleus of a living organism
A. RNA and ATP B. DNA and ATP C. ATP and AMP D. RNA and DNA (2004/4 Nov)
Answer: D – RNA and DNA
Example
On which structures are genes located in the nucleus?
A. Nuclear membrane B. Nucleolus C. Chromosome D. Nucleoplasm (2004/52 Nov)
Answer: C – Chromosomes houses the genes.
Example
Which of the following is the unit of transmission of hereditary traits in living organisms?
A. Nucleus B. Nucleolus C. Gametes D. Genes E. Chromosomes (1991/42 Nov)
Answer: D – Gene.
Example
The process of transmission of hereditary characters from parents to offspring does not involve
A. reduction in chromosome number of sex cell at the end of second meiotic division
B. each gamete cell containing arandom mixture of paternal line and maternal line of chromosomes
C. exchange of chromosome segments between homologous chromosomeswhich encourage variation
D. homologous chromosomes exchanging genetic material within the interphase nucleus
E. recombination of genes during fertilization (1994/57 Nov)
Answer: D – The process of transmission of hereditary characteristic from parent to offsprings does not involve
homologous chromosome exchanging genetic material within the interphase nucleus. This is because exchange of
genetic material only occur at prophase 1 of meiosis.

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EXERCISE 20.3
1. The simplest unit for transfer of character from parents to offspring is the
A. chromosome B. gene C. DNA D. ribosome (2011/49 Nov)
2. Which of the following statements about chromosomes is correct?
A. In kidney cells of diploid organisms, chromosomes occur singly
B. In gametes, chromosomes occur in pairs
C. A given species always has a varying number of homologous chromosomes
D. In gonads, chromosomes occur in pairs (2011/50 Nov)
3. Deoxyribonucleic acid is most suitable for the transmission of information from generation to generation
through chromosomes because it
A is made up of anti-parallel chains B. is made up of nucleotides
C. has the ability to replicate D. is made up of a sugar, an acid and a base (2011/51 Nov)
4. Which of the following statements is correct about genes? They
A. diminish with ageing B. are usually affected by the environment
C. remain constant throughout life D. grow with ageing (2011/52 Nov)
5. In crossing over, chromosomes break and rejoin at points along their lengths called
A. chromatids B. centromeres C. chiasmata D. locus (2005/54 Nov)
6. (b) What are chromosomes? (2000/4b Nov)
7. DNA molecules always have equal numbers of
A. phosphate groups, purines and pyrimidines B. ribose, purines and pyrimidines
C. purines and pyrimidines D. nucleotides and adenine (2019/48 PC2)
8. The part of the cell that stores acid is
A. nucleolus B. nuclear membrane C. chromosome D. nuclear pore (2020/43 PC1)
9. An abnormal number of chromosomes could result during meiosis because of
A. non-disjunction B. recombination C. inversion D. translocation (2020/45 PC1)
10. How many chromosomes are found in the human ovum?
A. 46 B. 23 C. 33 D. 13 E. 43 (1992/56)
11. In which of the following parts of a cell is the chromosome found?
A. Nucleus B. Golgi body C. Cytoplasm D. Cell membrane E. Cell wall (1993/4)
12. Which of the following is a function of the chromosome?
A. Transmission of hereditary traits B. Protein synthesis C. Excretion
D. Energy production E. Manufacture of enzyme (1993/54)
13. (b) Describe briefly the structure of DNA. (1995/3b)

14. Which of the following statements is not true about chromosomes?

A. Each chromosomes is made up of two chromatids B. Body cells have lipoid numbers of chromosomes
C. Homologous chromosomes do not occur in pairs naturally
D. The sex cells have haploid number of chromosomes
E. Chromosomes have many transverse bands (1996/53)
15. How many chromosomes will be present in a gamete if the somatic cell has eight(8) chromosomes?
A. 4 B. 6 C. 8 D. 10 E. 16 (1998/55)
16. Which of the following statements is correct about the chromosomes in the gametes? At the end of the second
meiotic division
A. each gamete contains only paternal hereditary information
B. chromosomes contain a random mixture of paternal and maternal chromosomes
C. chromosomes in the four gamete cells are diploid in number
D. chromosomes contain only maternal hereditary information (2004/57)
17. (c) (ii) What is the difference between the chromosome number of a gamete and that of the body cell of the
same organism? (2005/7cii)
18. The haploid number of chromosomes in humans is
A. 48 B. 46 C. 24 D. 23 (2006/56)

19. What does the chemical composition of the genetic material of all living organisms consist of?
A. Deoxyribonucleic acid B. Adenosine diphosphate
C. Adenosine triphosphate D. Follicle stimulating hormone (2008/52)

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20. If red is dominant to white and homozygous red pea-plants are crossed with homozygous white pea-plants,
the first filial generation will have
A. 2 red flowers, 2 white flowers B. 4 red flowers C. 4 white flowers D. 4 pink flowers (2008/55)
21. Which of the following statements is correct about the structure of a chromosome? A chromosomes consist of
A. two chromatids joined at the centromere B. two chromatids joined at the spindle
C. two chromatin joined at the centrioles D. thread-like structures not joined together (2010/53)
22. Which of the following statements best describes protein synthesis?
A. DNA is directly involved in translation
B. Translocation of the ribosomes exposes a new codon for base pairing with an amino acid
C. Each RNA with particular anticondon always carries a different protein in the protein in the process
D. One amino acid is always carried by more than one RNA (2011/53)
23. In the structure of DNA, which of the following statement is true?
A. The double helix are held by together by covalent bonds
B. Nucleotide is made up of ribose, phosphate and an organic nitrogen compound
C. Guanine is the opposite of cytosine D. Adenine is the opposite of cytosine (2012/55)
24. Which of the following statements about chromosomes is correct?
A. All the chromosomes of a species are the same in shape B. The number present in a species is constant
C. They are neatly arranged in the cytoplasm D. They bear ribosomes (2014/43)
25. How many chromosomes will be in a gamete if the normal cell has four chromosomes?
A. 2 B. 4 C. 6 D.8 (2015/43)
26. The chemical bond that hold the bases of the two strands of DNA together is
A. oxygen bond B hydrogen bond C. electrovalent bond D. covalent bond (2018/46)
The diagram below is an illustration of a process occurring in a living animal cell. Study it and Answer:
questions 43 and 44.

27. The process occurs in the

A. nucleus B. mitochondrion C. Golgi body D. cytoplasm (2019/43)
28. The process is called
A. replication B. cell maturation C. crossing over D. mutation (2019/44)
29. Which of the following nucleotides is not found in the DNA molecule?
A. Adehine B. Cytosine C. Guanine D. Uracil (2019/45)
30. Which of the following statements about chromosomes is correct?
A. all the chromosomes of a species are the same in shape B. the number represent in a species is constant
C. they are neatly arranged in the cytoplasm D. they bear ribosomes or their outer members (2020/44)
31. Replication of DNA molecules is catalyzed by the enzyme called
A. polymerase B. ptyalin C. pepsin D. amylase (2020/48)

Probability of genetics
Probability is a branch of mathematics that deals with the analysis of how likely it is that an event will happen. It is
concerned with the prediction of the likelihood of an occurrence

Principles of probability which are relevant to genetics include the following:

1. The result of one trial of a chance event does not affect the result of later trait of the same event.
2. The probability of two independents events occurring together can be calculated by multiplying the individual
probabilities of each event occurring alone. This is the product rule and it is applied to the phenomenon of
independent transmission of characteristics.
3. If a particular event can occur in several ways the probability of the event occurring is the sum of the
probabilities of the different ways.

405
Application of probability in genetics
1 1
If a pea plant has a genotype TT, the probability that a gamete will contain gene T is 2
+ 2
= 1.
But if a pea plant has genotype Tt, the plant can form two types of gametes. One type of gamete will contain gene T,
1 1
while the other contain gene t is 2 and the probability that a gamete will contain gene T is also 2.
If a pea plant of genotype Aa is crossed with a pea plant of genotype aa, the probability of producing different
genotypes in offspring are:
1 1
Probability of Aa = probability of A (from Aa)  Probability of a (from aa) = 2  1 = 2
1 1
Probability of aa = probability of a (from Aa) Probability of a (from aa) = 2  1 = 2
Note: The mendelian cross can also be used to predict occurrence of a trait in genetics. For example in humans the
albino trait is recessive (aa) and the normal skin colour is dominant (AA) if two parents that are heterozygous for the
albino trait (Aa) are crossed, the probability of getting a normal child, a carrier and an albino child is as follow:

From the above cross the possible outcomes are: AA, Aa, Aa and aa i.e. total outcome is four.
The probability of having an albino child (aa) is one in a total of four outcome. i.e. ¼ =0.25 or 25%
2
The probability of having a carrier child is two in a total of four outcome. i.e. 4 = 0.50 or 50%.
The probability of having a normal child (AA) is 1 in a total of 4 outcome i.e. ¼ = 0.25 or 25%
1
AA = 4 normal skin
1
Aa = 2 carrier
1
aa = 4 recessive (albino)

Example
A married couple have 10 children, and they are all girls. Which of the following is the CORRECT explanation?
A. The woman is incapable of producing male children B. The man’s sperms are very weak
C. The man is not athletic enough D. The Y component of the man’s sex chromosomes was always involved
E. The X components of the man’s sex chromosomes was always involved (1982/10 JAMB)
Answer: E – The reason for the couple having all 10 children to be girls is that the x- component of the man’s sex
chromosomes was always involved in fertilizing the woman’s egg.
Example
The homozygous condition Hbs Hbs results in sickle cell anaemia whereas Hba Hbs has the sickling trait. What is the
probability that a couple with sickling trait will give birth to a normal child
A. ½ B. ¼ C. 1/8 D. 0 (1997/44 JAMB)
Answer: B – ¼ Couple with sickling trait

1 HbaHba – Normal Child

2 HbaHbs – Carrier of sickling trait
1 HbsHbs – Sickle cell anaemia
Probability of a normal child = ¼

406
Example
The probability of a baby being a boy or a girl depends on the contribution of the
A. fathers sex cell B. fathers somatic chromosome
C. mothers sex cell D. mothers X-chromosome (2001/39 JAMB)
Answer: A – The probability of a baby being a boy or girl depends on the contribution of the father sex cell.
Example
The first four children of a couple were all girls. The probability that the fifth will also be a girl is
A. ½ B. 1/3 C. ¼ D. 1/5 (2002/13 JAMB)
Answer: A – ½. The probability of a baby being a boy or girl depends on the contribution of the father sex cell and
this is a 50% or ½ probability.
Example
A woman with the ability to roll her tongue (Tt) marries a man who cannot roll his tongue (tt). What is the probability
of each of their children being a tongue roller?
A. 100% B. 75% C. 50% D. 25% (2009/43 JAMB)
Answer: C – 50%

2 Tt – Tongue rollers
2 tt – Can’t roll tongue.
2
Probability of children who are tongue rollers = × 100 = 50%
4
Example
Which of these pair of sex phenotype is normal among the following allele? (i) XXY (ii) XY (iii) XX (iv) XO
A. XXY, XY B. XO, XX C. XO, XXY D. XY, XX (1999/41 NABTEB)
Answer: D – XY, XX
Example
The structure in the gamete of a male mammal that determines the sex of a child is the
A. gene B. chiasma C. X chromosome D. Y chromosome (1999/43 NABTEB)
Answer: D – Y – Chromosome
Example
What is the probability of a man of blood group AB married to woman of blood group O producing a child of blood
group O?
A. 0% B. 25% C. 50% D. 75% (201749 NABTEB)
Answer: A – 0% This is because the blood group O wont be expressed as it is recessive to both blood group A and B
Example
Normal skin pigmentation is caused by a dominant gene A. Albinism is caused by double recessive aa. What the
chances of getting an albino from the cross between two individuals with Aa and Aa?
A. 100% B. 50% C. 305 D. 25% (2018/36 NABTEB)
Answer: D – 25%

1 Aa
2 Aa
1 aa
1
∴ Chance of getting an albino = 4 × 100 = 25%
Example
Which of the following chromosome combinations will produce a baby girl?
A. XY B. XX C. YY D. YX (2003/4 Health Science)
Answer: B – XX.
NB: XY – Boy

407
Example
If the normal skin colour is dominant over the albino trait in humans, what is the probability of having an albino child
if the parents are heterozygous for albinism?
𝟑
A. 1 B.𝟒 C. ½ D. ¼ (2006/50 Nov)
Answer: D – ¼
Example
Probability in genetic inheritance means
A. first, second and thud filial generations B. dominant and recessive characters and genes +
C. sex determination in mammals D. inheritance of recessive characters
E. the random nature of segregation and recombination of genes (1994/52 Nov)
Answer: E – Probability in genetic inheritance means the random nature of segregation and recombination of genes.
Example
The probability of a woman with blood group AB married to a man of group O, producing children with blood group
O is
𝟏
A. 0% B. 33 𝟑% D. 50% E. 75% (2000/54 Nov)
Answer: A – 0%
NB: Blood group O = OO
Blood group A = AO
O

OO OO
NB: Blood group AO and BO are blood group A and blood group B respectively.
∴ The chance of producing children with blood group O is 0%
1
Probability of producing a child of blood group O is 2 × 100 = 50%
Example
If the normal skin colour is dominant over the albino trait in humans, what is the probability of having an albino child
if the parents are heterozygous for albinism?
𝟑
A. 1 B.𝟒 C. ½ D. ¼ (2006/50 Nov)
Answer: D – ¼
Example
Probability in genetic inheritance means
A. first, second and thud filial generations B. dominant and recessive characters and genes +
C. sex determination in mammals D. inheritance of recessive characters
E. the random nature of segregation and recombination of genes (1994/52 Nov)
Answer: E – Probability in genetic inheritance means the random nature of segregation and recombination of genes.
Example
The probability of a woman with blood group AB married to a man of group O, producing children with blood group
O is
𝟏
A. 0% B. 33 % D. 50% E. 75% (2000/54 Nov)
𝟑
Answer: A – 0%
NB: Blood group O = OO
Blood group A = AO

NB: Blood group AO and BO are blood group A and blood group B respectively.
∴ The change of producing children with blood group O is 0%

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Example
What is the probability of producing a child of blood group O by a woman of blood group O and a man of blood group A?
A. 25% B. 50% C. 75% D.100% (2002/57 Nov)
Answer: B – 50%
NB: Blood group O = OO
Blood group A = AO

2AO: 2OO = 1:1

1
Probability of producing a child of blood group O is 2 × 100 = 50%
Example
The probability of a carrier mother and a normal father having a haemophiliac male is
A. 25% B.50% C. 75% D. l00% (2020/46 PC1)
Answer: A – 25%

1 XX – Normal Female
1 XXh – Carrier Female
1 XY – Normal Male
1 XhY – Haemophiliac Male
1
∴ Probability of having a haemophiliac male = 4 × 100 = 25%
Example
Assuming that ‘A’ is gene for normal skin and it is dominant, while ‘a’ is gene for albinism and it is recessive, what is
the likely genotype of a couple which had 50% normal and 50% albinos?
A. AA, Aa B. AA, aa C. Aa, Aa D. Aa, aa E. AA, AA (1988/46)
Answer: D – Aa, aa
Example
If a cross is made between a pure-breeding red flowered plant and a pure-breeding white flowered plant where R is
dominant for red flower and r is recessive for white, the most likely result of F1 generation will be
A. 75% red flowers and 25% white flowers B. all red flowers
C. 75% white flowers and 25% red flowers D. 50% red flowers and 50% white flowers
E. all white flowers (1988/50)
Answer: B – All red flowers

∴ Phenotypic ratio: 4:0 (All red)

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Example
If a black guinea pig of genotype BB, is crossed with a white guinea pig of genotype bb, what will be the phenotype
of the F1 generation?
A. Half of the offspring would be black while the other half would be white B. All the offsprings would be black
C. All the offsprins would be grey D. One-third of the offspring would be black while two-third would be white
E. Two-thirds of the offspring would be black while one-third would be white (1992/57)
Answer: B – All the offsprings will be black

Phenotypic Ratio: 4:0 (All Black)

EXERCISE 20.4
The table below is a Punnett square for sex determination in man. Use it to Answer: questions 30 and 31
1.5

1. Which of the following determines a normal male offspring?

A. X B. Y C. XX D. XY E. YY (1994/30)
2. What is the theoretical probability that a normal male child will be born?
A. ½ B. ¼ C. 1/3 D. 1 E. 2/3 (1994/31)
3. In human beings the albino trait it recessive and the normal skin colour is dominant. Therefore the probability
of parents that are heterozygous for albinism, having an albino child is
A. ¼ B. ½ C. 1/3 D. 2/3 E. 1 (1994/56)
4. In a plant of genotype Tt, what is the probability that a gamete will contain gene t?
A.1⁄2 B. 3⁄4 C. 1⁄8 D. 1⁄6 E. 1⁄4 (1998/56)

5. In a cross-involving heterozygous red flowered plant (Rr) and a white flowered plant (rr). What is the
probability that the off spring will be Rr?
A.1 B. 1⁄2 C. 1⁄4 D. 3⁄4 E. 2 (1998/57)

6. A man with heterozygous genotype for blood group B marries a woman with heterozygous A, what
percentage (%) of their children would be universal donor?
A. 50% B. 25% C. 15% D. 10 (2002/56)
7. In man, sex is determined by the inheritance of
A. a pair of homologus chromosomes
B. an extra chromosome in the cells of a female
C. a dominant gene for maleness present in man
D. two similar X chromosomes in the female and X and Y chromosomes in the male (2004/52)
8. A man heterozygous for albino gene marries a woman who is also heterozygous for the gene. Both have
normal skin colour. The probability that they will have an albino child is
1 𝟏 4 2
A. B. C. D. (2010/48)
3 𝟒 4 4
9. In a family of eight (8) all the children are girls. Which of the following reasons correctly explains this?
A. The woman cannot produce male children B. The man has a low sperm count
C. The Y component of the man’s sex chromosome was always involved
D. The X component of the man’s chromosomes was always involved (2010/52)

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Sex determination in humans
In humans, there are two types of sex chromosomes represented as X and Y chromosomes. The female carries the pair
XX while the male carries the pair XY. Both female and male paired chromosomes are reduced to half by a process
known as reduction division (meiosis).

The female produces only one type of gamete (X) while the male produces the two different types of gamete (X) and
(Y).

After mating, numerous male gametes surround the female gametes. Some of these male gametes carry Y and others
carry X chromosomes.

If the male gamete carrying (Y) fuses with the female gamete (X), the zygote is XY which is male embryo.

If the male gamete carrying (X) fuses with the female gamete (X), then the zygote is XX which is a female embryo.
The male embryo develops into a male child while the female embryo develops into a female child.

From the cross above, there is an equal chance that an ovum will be fertilized by a sperm with Y – chromosomes to
form a zygote (XY) or by an X chromosome to form a female zygote (XX).

Since the sex is naturally determined by chance, then mothers who consistently have female children one after the
other should not be blamed from genetical stand point. As can be seen from above, it is infact the male that is
responsible for sex determination in man and this determination is usually by chance.

Sex – linked characteristics

Characteristics whose genes are carried on the x chromosomes of the sex chromosomes are said to be sex – linked.
Genes on the same chromosome are said to be linked because they are inherited together.

Examples of sex – linked characteristics are

(i) Colour blindness (ii) Haemophilia (iii) Baldness (iv) Sickle cell anaemia (v) albinism

1. Colour blindness: The retina of the eye consists of light sensitive cells (photo-receptors) called rods and
cones. The rods are sensitive to dim light and colourless vision while the cones are sensitive to bright light
and colour vision. When the cones have all the photo pigments, the eyes sees all possible colours but when
there is a problem with the pigments, difficulty in seeing colours arises. This is called colour deficiency or
colour blindness. It arises usually when offspring inherits genes causing faulty photo-pigments from parent.
Note: If just one pigment is missing, one might have trouble in seeing certain colours but if there is no
pigments in the cones, one won’t see colour at all. A condition known as achromatopsia.

2. Haemophilia: This is the inability of blood to cloth easily in some persons. It is a hereditary disease and it is
sex-linked. Individuals with this condition lack the enzyme thrombokinase which is responsible for blood
clotting.

3. Baldness: Baldness is simply hair loss or absence of hair. It is also called alopecia. Several reasons can be
responsible for baldness but one of the most common is if there is a family history of baldness (sex linked
character). In humans baldness is more common in the male.

4. Sickle cell anaemia: Sickle cell anaemia is a blood disorder caused by a inherited abnormal haemoglobin
gene (HbS). The abnormal haemoglobin causes distorted red blood cells which are sickle shaped in
appearance when viewed under a microscope. It is important to note that this gene is recessive and a person
can only suffer this condition if he has two copy of the genes i.e. HbS HbS . Such a person is referred to as a
sickler.

411
 The normal haemoglobin gene is represented by the symbol HbA HbA. When a person has one normal
haemoglobin gene and an abnormal haemoglobin gene (HbA HbS), such a person is said to be a carrier of the
sickle cell trait as the normal trait (HbA) will be dominant over the recessive abnormal trait (HbS). This disease
shortens the lifespan of children as they are easily susceptible to infection and tissue damage.

5. Albinism: This is a genetic condition which results from a reduction or absence of the melanin pigment. This
condition often affects the hair, skin, eyes and vision. The cause of this condition is as a result of the
interruption in function of a particular enzyme known as tyrosinase.

BLOOD TYPES
There are four blood types namely A, B, AB and O. They are controlled by three allele which are denoted by A, B and
O but only two can be represented in an individual. The ability of the two allele in a heterozygous individual to
express themselves fully is called co – dominance. Antigen A and B are co – dominant i.e non is dominant over the
other.

Blood group Genotype

A AA, AO
B BB, BO
AB AB
O OO

Suppose a man’s genotype is AO and the woman genotype is BB. The offspring will be as follow from the cross.

Genotype = 2AB, 2BO

Phenotype = 2 blood group AB, 2 blood group B

Uses of the knowledge of genetics

The knowledge of the principles of heredity is used in agriculture and medicine.

A. Application of genetics in agriculture

1. To develop early maturing varieties – the knowledge of genetics has led to the development of crop
varieties and animal breeds which mature early.

2. Development of disease resistant crops and animals– The knowledge of the principles of genetics has led to
the development of crop varieties and animal breeds which are resistant to certain diseases within the locality.

3. To improve quality of product – The quality of farm produce enhances its usefulness and value. Breeders
can improve on the taste, colour, size and nutritive value of crops and animal products.

4. To increase yield: The varieties of crops and breed of animals create room for high yield in crops and animal
products.

5. To produce crops and animals that can adapt to climatic conditions.

412
B. Application of genetics in medicine
Genetics has contributed in various field of medicine.
1. Determination of paternity of a child.
2. Blood transfusion: Genetics is useful in the determining compatible blood groups (A, B, AB and O ) before
blood transfusion inorder to prevent agglutination and death of the recipient.

Blood transfusion
Recipients
A B AB O
A √ X √ X
B X √ √ X
Donor

AB X X √ X
O √ √ √ √
Table of blood transfusion
√ = correct transfusion
X = incorrect transfusion

3. Marriage counseling: Couples yet to get married are advised on certain hereditary diseases such as
haemophilia and sickle cell anaemia so that carriers do not go into marriage.
4. Crime detection: The use of blood group and fingerprints enable law enforcement agents to detect criminals.
5. Genetic enables the development of test tube babies, choosing the sex of a child and even knowing the sex of
a baby before they are born.
Example
If a 26 year old blind man married a young one-eye woman and they had four children, how many of them would be
like their father?
A. all B. 3 C. 2 D. 1 E. none (1982/11 JAMB)
Answer:
E – None. Blindness is not a character that can be transfer from parent to offspring.
Example
If parents with blood groups AB and OO produce six children
A. three of them will have group B B. two of them will have blood group A
C. all the offspring will have O D. none of them will have group A (1989/39 JAMB)
Answer:
A – Three of them will have group B

Probability of getting an individual of blood group A = ½

Probability of getting an individual of blood group B = ½
∴ It is logically possible for half or 3 of the children to have blood group B while the other half or 3 have blood group A.
Example
An individual in the AB blood group is a universal recipient for blood donation because
A. all the red blood cells do not carry antigen B. all the red blood cells carry antigen A
C. all the red blood cells carry antigen B D. there are no anti-A and anti-B antibodies in the serum (1990/39 JAMB)
Answer: D – An individual in the AB blood group is a universal recipient for blood donation because there are no
anti-A and anti-B antibodies in the serum.
Example
Haemophilia results from the mutuation of the genes
A. in the sex chromosomes B. which control skin colour
C. which controls the mechanism for blood clotting D. which control the formation of haemoglobin (1990/40 JAMB)
Answer: C – Haemophilia results from the mutation of the genes which control the mechanism for blood
clotting.

413
Example
Which of the following characters is NOT sex-linked?
A. River blindness B. Baldness C. Haemophilia D. Colour blindness (1991/40 JAMB)
Answer: A – River blindness is not a sex-linked character
Example
Which of the following is true of the children of a haemophilic man who marries a woman that is not haemophilic
and does not carry the trait?
A. all their sons will be haemophilic B. all their daughters will be haemophilic
C. all their daughters will be carriers D. all their sons will be carriers (1992/40 JAMB)
Answer: C – All their daughters will be carriers.
NB: A man can only pass is x-chromosome to his daughters.
Example
A child with blood group genotype different from those of both parents and with a mother of genotype, OO can only
have a father of genotype.
A. A B. B C. AB D. OO (1992/41 JAMB)
Answer: C – The child can only have a father of genotype AB.
Example
People with sickle-cell anaemia have heamoglobin
A. S and are homozygous recessive B. A and are heterozygous recessive
C. S and are heterozygous recessive D. A and are homozygous recessive (1994/42 JAMB)
Answer: A – People with sickle-cell anaemia have haemoglobin S and are heterozygous recessive.
Example
One reason for the success of Mendel’s work is that he
A. was the first to carry out research work on modern genetics
B. introduced quantitative and qualitative elements into his work
C. selected two characteristics only at a time into his work
D. drew up his laws of inheritance based on his knowledge of chromosomes (1997/43 JAMB)
Answer: D – One reason for the success of Mendel’s work is that he drew up his laws for inheritance based on his
knowledge of chromosome.

Example
Blood grouping in human in beings is derived from combinations of
A. two different alleles B. three different alleles
C. four different alleles D. two different genes (2000/41 JAMB)
Answer: B – Blood grouping in human beings is derived from combination of three (3) different alleles
Example
Which of the following statement is true of blood groups and blood transfusion?
A. Group O is the universe recipient B. Group A can donate to group A only
C. Group AB is the universal recipient D. Group B can donate to group B only (2001/40 JAMB)
Answer: C – Group AB is the universal recipient.
Example
If XN is the dominant allele for normal vision and Xn the recessive allele for colour – blindness, a boy with the
genotype YXn will
A. be totally blind B. have normal vision C. be a carrier of colour-blindness D. be colour-blind (2002/10 JAMB)
Answer: D – A boy who has a genotype YXn will be colour blind.
Example
What proportion of the offspring of a cross between two heterozygous parents will exhibit the recessive condition
phenotypically?
A. ¾ B. ¼ C. 4/4 D. ½ (2002/11 JAMB)
Answer: B – ¼
Example
If the pair of alleles for baldness is given as Bb, a female carrier will be denoted by
A. XBXb B. XBXB C. Xby D. XBY (2003/38 JAMB)
Answer: A – XBXb

414
Example
A man and his wife are both heterozygous for the sickle-cell trait. The likely percentage of their offspring that will be
either carriers or ‘sicklers’ is
A. 50% B. 25% C. 75% D. 100% (2003/41 JAMB)
Answer: C – 75%

1 AA – Normal
2 AS – Carriers
1 SS – Sickler
3
∴ Percentage of offspring that will be either carrier of sicklers = 4 × 100 = 75%
Example
An example of a sex-linked trait is the
A. ability to grow long hair in females B. colour of the skin in humans
C. ability to roll the tongue D. possession of facial hair in adult humans (2007/50 JAMB)
Answer: D – Possession of facial hair in adult humans
Example
A health condition that is known to have resulted from gene mutation is
A. haemophilia B. colour blindness C. sickle-cell anaemia D. anaemia (2009/44 JAMB)
Answer: A – Haemophilia.
Note: Haemophilia is caused by a mutation or change in one of the genes that provides instructions for making the
clotting factor proteins needed to form blood clot.
Example
When a colour-blind man marries a carrier woman, what is the probability of their offspring being colour blind
A. 25% B. 50% C. 75% D. 100% (2012/42 JAMB)
Answer: B – 50%

1 XBY – Normal child (1)

1 XBXb – Carrier Child (1)
1 XbXb, 1 XbY – Colour blind children (2)
2
Probability of their offspring being colour blind = 4 × 100 = 50%
Example
A man who is heterozygous for the disease haemophilia marries a woman who is double recessive for haemophilia.
What percentage of their offspring would have the disease?
A. 0% B. 25% C. 50% D. 75% (2018/32 JAMB)
Answer: C – 50%

2 Hh – Carrier
2 hh – Haemophiac
2
∴ Percentage of their offspring with the disease = 4 × 100 = 50%

415
Example
The following characteristics are inherited EXCEPT
A. haemophilia B. night blindness C. albinism D. sickle cell anaemia (2001/41 NABTEB)
Answer: B – Night blindness is not inheritable.
Example
A child with genotype AO with a mother of genotype OO, can only have a father of genotype
A. AA B. BB C. AB D. OO (2019/45 NABTEB)
Answer: A – AA
NB: The father can still be AB but AA is more appropriate.
Example
Which of the following blood groups is a universal donor?
A. O blood group B. A blood group C. B blood group D. AB blood group (2001/40 NABTEB)
Answer: A – O blood group is a universal donor.
Example
If a person has two alleles of the sickle cell anaemia gene, the person
A. is a heterozygous carrier of the disease B. is immune to the disease and cannot pass it onto his offspring
C. has the disease D. is probably of Asian ancestry (2017/48 NABTEB)
Answer: C – If a person has two alleles of the sickle cell anaemia gene, the person has the disease.
Example
Sex-linked characters include the following except
A. albinism B. asthma C. baldness D. haemophilia E. sickle cell anaemia (2014/60 Neco)
Answer: B – Asthma is not sex-linked trait (character).

Example
4(a) A woman with blood group A and genotype AO has a child with blood group AB and genotype AB. TWO men
(X and Y) with blood groups O and B, genotype OO and BO respectively are claiming the paternity of the child.
(i) By means of crosses, determine the real father of the child (2005/4a Neco Nov)
Answer: To know the true father of the child whose genotype is AB and blood group is AB, we must cross the
genotype of the woman with the genotype of each of the men.
Genotype of the woman = AO, blood group = A
Genotype of Man X = OO, blood group = O
Genotype of Man Y = BO, blood group = B

A cross of Man X and the woman: A cross of Man Y and the woman:

Genotype of possible offspring = AO and OO Genotype of possible offspring = AB, BO, AO and OO
∴ It is clear now that Man Y whose genotype is BO and
blood group is B can produce a child of genotype AB
and blood group AB when he marries a woman of
genotype AO and blood group A.
In conclusion, Man Y is the true father of the child.

Example
Sex- linked traits are
A. carried by genes on sex chromosomes B. carried by genes on autosomes
C. most often x- linked D. mostly transferred from mother to offspring E. often recessive in nature (2007/48 Neco)
Answer: A – Sex-linked traits are carried by genes on sex chromosomes.

416
Example
X NY X X NX n Parents.
Above is a representation of a father with normal colour vision married to a woman who is a carrier for colour
blindness. (Hint n = colour blindness)
(a) By means of crosses, show the offspring of the 1st filial generation (F1)
(b) How many of the male offspring
i. Are colour blind?
ii. Have normal colour-visions
(c) How many of the female offspring:
i. Have normal colour-vision?
ii. Are carriers? (2005/3a-c Neco)
Answer:

Parents 

F1 Generation 
∴ ½ of the Male offsprings are colour blind.
½ of the Male offsprings have normal colour-vision.
½ of the Female offsprings have normal colour-vision.
½ of the female offsprings are carriers.
Example
Two individuals with heterozygous gene for albinism married. Which of the following statements about their children
is correct?
A. all the children of the couple would be albinos
B. all the children of the couple would have the heterozygous gene for albinism
C. 50% of their children would have normal skin colour D. 25% of their children would be albinos (2013/54 Nov)
Answer: D – 25% of their children would be albinos.

NB: Where AA and Aa are Normal skin colour and aa is albino

Phenotypic ratio: 3:1
3
Percentage of normal skin colour = 4 × 100 = 75%
1
Percentage of albino = 4 × 100 = 25%

EXERCISE 20.5
1. One apparent advantage of the possession of sickle trait As is that
A. It gives good appetite to carriers B. the offspring that have the trait recover fast from anaemia
C. it gives resistance against malarial attack D. it cannot be transferred to a new generation
E. carries have better physique than non-carriers (1996/58 Nov)
2. Which of the following statements is true about carriers of sickle cell trait?
A. They are often short of blood B. They have joint pains
C. They are resistant to malaria D. All their blood cells are sickle-shaped (2011/54 Nov)
3. (b) (1) Why is sickle-cell anaemia considered a deadly disease?
(ii) Explain briefly how sickle-cell anaemia can be reduced in a population.
(iii) State one advantage which a carrier of the sickle-cell anaemia trait has. (2011/3bi-iii Nov)
4. Which of the following diseases is most likely to be passed on from a carrier mother to a son?
A. night blindness B. Haemophilia C. Beriberi D. kwashiorkor (2005/53 Nov)
5. What is the percentage of having an albino offspring if two parents who are carriers of albino genes
reproduce?
A. 100% B. 75% C. 50% D. 25% (2019/47 PC2)
417
6. The gene for sex-linked characters is carried by
A. X chromosome B. Y chromosome C. X and Y chromosomes D. autosomes (2020/47 PC1)
7. Which disease is sex-linked and mainly afflicts male offspring?
A. Sickle cell anaemia B. Haemophilia C. Diabetes D. Malaria (2005/54)
8. The defective cells involved in sickle-cell anaemia disease are
A. phagocytes B. lymphocytes C. erythrocytes D. thrombocytes (2008/51)
9. The allele responsible for sickle-cell anaemia first appeared in the tropical and subtropical regions of Asia, the
Middle East and Africa. It entered the United States of America when individuals were forcibly brought over
from Africa. In micro-evolutionary terms this is an example of
A. mutation B. gene flow C. genetic drift D. natural selection (2009/52)
10. Which of the following diseases is not hereditary?
A. Albinism B. Scabies C. Haemophilia D. Colour blindness (2009/53)
11. Mr. Andrew, his wife and child belong to blood groups A, B and O respectively. The genotype of both parents
are
A. |A|O| and |B|B B. |A|A| and |B|B C.|A|B| and |A|O D. |A|O and |B|O (2010/54)
12. If a person has two alleles of the sickle cell anaemia gene, the person
A. is a heterozygous carrier of the disease B. is immune to the disease and cannot pass it on to an offspring
C. has the disease D. is probably of Asian ancestry (2011/54)
13. What is the probability of a man of blood group AB married to a woman of blood group O producing a child
of blood group O?
A. 0% B. 25% C. 50% D. 75% (2011/55)
14. A man with blood group |A|A is married to a woman with blood group |A|O. The blood group of their son is
likely to be
A. A B. O C. B D. AB (2011/56)
15. Which of the following diseases is transmitted through genes?
A. HIV/AIDS B. Sickle cell anaemia C. Diabetes D. Presbyopia (2012/53)
16. In genetics, linkages refer to linking of genes of the
A. same chromosomes B. different chromosomes C. same nucleus D. different nuclei (2013/48)
17. A man’s blood group is AB. What is the probability of the man giving birth to a child with blood group O?
A. 0% B. 25% C. 50% D. 100% (2013/49)
18. A gene that is only located on X-chromosome is said to be
A. expressed in females only B. defective C. sex-linked D. expressed in males only (2013/52)
19. If a boy has blood type O and his mother has blood type A, what is the genotype of his father?
A. BB B. AA C. AO D. AB (2013/53)
20. Which of the following statements about human blood groups is not true?
A. A is dominant over B B. O is recessive
C. B is dominant over O D. A and B are co-dominant (2015/40)
21. A woman with blood group A gives birth to a child with blood group O. Which of the following blood group
cannot belong to the father?
A. A B. B C. AB D. O (2015/42)
22. Which of the following scientists did not contribute to the development of genetics?
A. Wilhem Johansen B. Thomas Morgan C. Gregor Mendel D. Felix Durjadin (2015/47)

23. A cross between two parents produced four offsprings with blood groups AB, BB, BO and AO. What is the
blood group of their parents?
A. AA and BO B. BB and AO C. AB and BO D. AB and AO (2016/42)
24. A sick baby was successfully transfused with blood from the father who has blood group AB. What is group
of the sick baby?
A. A B. B C. AB D. O (2016/43)

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 The illustration below represents a cross between a colour – blind male and a normal female.
Study it carefully and Answer: questions 44 and 45.

25. What is the genotypic ratio of carrier females to normal males in the cross?
A. 1:1 B. 2:3 C. 3:4 D. 4:1 (2016/44)
26. Scientists who study genetics are known as
A. genealogists B. geneticists C. mendelists D. genescientists (2016/46)
Two unconscious patients X and Y whose blood group genotypes: are AO and AB respectively were
transfused with blood from the same donor. Patient X immediately showed signs of difficulty in breathing
while patient Y showed no negative reaction.
27. Patient X and Y were likely transfused with blood of genotype
A. OO B. AO C. BO D. AA (2018/38)
28. What should the hospital have done to prevent patient x from showing the symptoms described above? Patient
X should have
A. undergo agglutination test B. been asked for the blood group
C. been screened for HIV D. undergo malaria test (2018/39)
29. Genes that remains linked are those
A. close to each other on the chromosomes B. on the same locus on the chromosomes
C. on the homologous chromosome D. which are allelic pair (2018/44)
30. Individuals with blood group AB can donate blood to individuals with blood group(s)
A. A and B B. A and O C. AB only D. O only (2019/42)
31. A man whose blood group is heterozygous B is married to a woman whose blood group is also heterozygous
B which of the following statements is correct about the blood group of their four offspring?
A. Three of them belong to blood group B B. Three of them belong to blood group O
C. None of them belongs to blood group O D. Two of them belong to blood group B (2019/47)
32. A child that can receive blood donation from anybody belongs to the blood group.
A. O B. A C. B D. AB (2020/41)
33. Which of the following diseases can be inherited?
A. pneumonia B. whooping cough C. sickle cell anaemia D. malaria (2020/45)

34. 6(a) List three transmittable characters in: ( i ) Human beings ( ii ) Plants
(b) State four ways in which genetics has contributed to the improvement of agriculture.
(c) A homozygous tall parent was crossed with a homozygous short parents. The offspring in F1
generation were all tall. An offspring of F1 generation was then crossed with another homozygous
short individual.
(i) illustrate the crosses with suitable diagrams
(ii) What is the phenotype ratio of offspring in the F2 generation?
(iii) What is the genotype ratio of offspring in the F2 generation?
(d) What is the probability that an individual that has genotype Tt will produce a gamete with T gene?
(2019/6a-d NABTEB)
35. 6a. In a monohybrid cross between a pure line plant that produces white flower and a pure line that
produces red flowers, the F1 generation produces only red flowers by means of diagrams, state the type of
flowers you would expect if the F1 generation is:
( i ) Self-pollinated ( ii ) Cross pollinated with a pure line that produce red flowers
( iii ) Give reasons for your Answer: in (i) and (ii) (2017/6a NABTEB)
36. (b)(i) State four desirable characteristics a genetic breeder may use to improve agriculture
(ii) For two parents with sickle trait, work out the chances of producing a sickle cell anaemic child and a
normal child (2004/1bi & ii Nov)

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37. Individuals with undesirable traits may be prevented from mating by the following except
A. eliminating such individuals
B. preventing such individuals from mating with those with undesirable traits
C. surgical removal of important parts of the reproductive system
D. crossing two genetically dissimilar varieties to produce hybrid vigour (2002/58 Nov)
38. (a) List three transmittable characters in (i) human beings (ii) plants (b) State three ways in which genetics
has contributed to improvement of agriculture (c) A homozygous tall parent was crossed with a homozygous
short parent. The offspring in F1 generation were all tall. An offspring of F1 generation was then crossed with
another homozygous short individual (i) illustrate the crosses with suitable diagrams (ii) What is the
phenotypic ratio of offspring in the F2 generation? (iii) What is the genotypic ratio of offspring in the F2
generation? (d) What is the probability that an individual that has genotype Tt will produce a gamete withT1
gene? Briefly explain your Answer: . (1996/4a-d)
39. (a) Define the following terms: (i) gene; (ii) gene mutation. (b) Name two structures each of plants and
animals where the following processes take place: (i) mitosis; (ii) meiosis. (c) State four advantages a farmer
may hope to derive in cross breeding two different breeds of cows. (d) State three applications of the
knowledge of genetics in medicine. (2007/3a-d)
40. Which of the following statements about heredity is not true? In hereditary the traits are
A. carried by genes B. contained in the ovum and sperm
C. always transmitted by one parent D. transmitted from parents to offspring (2010/49)
41. 4(a) List four characteristics which can be genetically transmitted in humans
(b) (i) Name two sites each in plants and animals where meiosis occurs.
(ii) State two differences between meiosis and mitosis
(c) A woman with blood group ‘A’ (heterozygous) claimed that her son who has group ‘O’ was fathered
by Mr. James who has blood group ‘A’ (homozygous). With the aid of suitable diagrams (i) prove or
disprove the woman’s claim (ii) give reasons to support your Answer: . (2010/4a-c)

A survey to determine blood groups was carried out on 250 people living in a community. The results are
represented in the table below.
Blood Group Percentage
A 8.0
B 14.0
AB 32.8
O 45.2

4. (a)(i) Explain the term co-dominance (ii) calculate the number of individuals with co-dominant blood group
(iii)What is the total number of individuals in the table that are able to donate blood to an accident victim with
blood group B (b) A man whose blood group is heterozygous A is married to a woman whose blood group is
AB. With the aid of a genetic diagram, suggest the possible blood groups of their children. (2014/4a, b)
42. Scientists who study genetics are known as
A. genealogists B. geneticists C. mendelists D. genescientists (2016/46)
43. Which of the following scientists did not contribute to the development of genetics?
A. Wilhem Johansen B. Thomas Morgan C. Gregor Mendel D. Felix Durjadin (2016/47)
44. 4(a) Explain briefly the following terms: (i) gene (ii) hybrid (iii) trait (b) Two heterozygous yellow flowers
are crossed. (c) Using a genetic diagram; state the phenotypic and genotypic ratios of the first filial generation.
(2018/4a-c)
45. Scientist who study genetics are known as
A. genealogists B. geneticists C. mendelists D. gene scientists (2016/46)
46. The outward appearance of an organism is referred to as
A. phenotype B. genotype C. dominance D. recessiveness (2017/44 NABTEB)
47. Which of the following is not a hereditary disease?
A. albinism B. haemophilia C. colour blindness D. scabies (2017/45 NABTEB)
48. The sudden change in the structure of the gene or chromosome is known as
A. conjugation B. duplication C. fertilization D. mutation E. replication (2008/54 Neco)
49. The simplest unit for transfer of character from parents to offspring is the
A. chromosome B. gene C. DNA D. Ribosome (2017/49 Nov)

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50. The major difference between genotype and phenotype is that phenotype
A. is an observable trait while genotype is a dominant trait
B. is an observable trait while genotype is a recessive character
C. is the sum total of observation traits while genotype is the sum total of dominant and recessive gene
D. is an observable feature in female offspring while genotype is the sum total of genes inherited in the male
offspring (1990/54)
51. Which of the following is the precise location of the gene?
A. chromosome B. centrosome C. centriole D. ribosome E. endoplasmic reticulum (1992/55)

52. Which of the following is a function of the chromosome?

A. transmission of hereditary traits B. protein synthesis C. excretion
D. energy production E. manufacture of enzymes (1993/54)
53. The pair of gene expressed in a heterozygous individual is described as
A. allele B. chromatid C. dominant genes D. centrosome E. centromere (1995/56)
54. In which of the following is the knowledge of genetics not applicable?
A. development of high yielding varieties B. preservation of seeds
C. development of early maturing varieties D. improvement in quality of yield
E. development of disease – resistant varieties (1997/56)
55. How many chromosomes will be present in a gamete of the somatic cell of eight (8) chromosomes?
A. 4 B. 6 C. 8 D. 10 E. 16 (1998/55)
56. Which of the following statements about sex determination is correct? At fertility
1
A. the probability of male to female offspring is 2
3
B. the y chromosomes of the father decreases the probability of having a male child to 4
3
C. the XX chromosomes of the mother decreases the probability of having a female child to 4
D. the vigour of either parents determines the sex of the offspring. (1999/54)
57. Which of the following may not be important in marriage counseling?
A. sex determination B. sickle cell anaemia C. rhesus factor D. colour of skin (1999/57)
58. Characters which fails to express itself in the first filial generation but emerges in the second is?
A. heterozygous B. homozygote C. dominant D. recessive (2000/56)
59. Which of these statements is correct?
A. recombination at fertilization does not occur between two homologous chromosomes
B. in homologous chromosomes, two genes very close to each other are more likely to form recombination at
meiotic prophase
C. a dominant gene masks the presence of a recessive gene
D. meiosis leads to the formation of a daughter cell with diploid chromosomes number
E. mitosis increases variation within a population (1996/5)
60. Which of the following represents Mendel’s second law of inheritance? The factor for two pairs of controlling
characters are
A. dependent on each other B. on homologous chromosomes
C. allelomorphic D. inherited independently of each other (2000/58)
61. When Mendel crossed round seeds with wrinkled seeds of pea plant, what was the ratio of wrinkled seed to
round seeds in the f2 plants?
A. 3:1 B. 2:1 C. 1:3 D. 1:2 (2002/52)
62. In Mendel’s experiment, it was discovered that the f1 generation of a cross between a brown cock and a white
hen were all brown because the gene for the
A. brown colour was recessive B. white colour was dominant
C. brown colour was dominant D. white colour did not combine (2003/57)
63. Which of the following nucleotides is not found in the DNA molecules?
A. adenine B. cytosine C. guanine D. uracil (2019/45 Nov; 1994/56)
64. In a complete dominance monohybrid cross between a pure breeding yellow flowered plant y and a pure breed
of white flowered plant y, the result of the first filial generation is
A. 50% yellow flower B. 75% yellow flower C. all yellow flowers D. all white flowers (2019/46)
65. The cross between Rr Tt and rr where R is a gene for red colour and T for tallness will result in
A. all the offspring being tall with red fruits B. 25% tall with red fruits
C. 50% tall with red fruits D. 75% tall with red fruits (2019/48)

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66. The structure in the gamete of a male mammal that determines the sex of a child is the
A. gene B. chiasma C. x chromosome D. y chromosome (1999/43 NABTEB)
67. Which of the following terms describes the sudden changes that may occur in a gene or chromosome?
A. duplication B. inversion C. fertilization D. mutation (2004/53 Nov)
68. List three transmittable characters in: i. human beings ii. plants (1996/4a)
69. Define the law of independent assortment. State the findings from Mendel’s experiment involving white –
flowered and red – flowered pea plants.
ii. Illustrate these findings by means of a simple diagram. (1999/4a)
70. Explain the following terms: i. trait ii. recessive gene iii. test cross iv. heterozygous (2005/7a)
71. List four characteristics which can be genetically transmitted in humans (2010/4a)
72. State four transmittable characters in plants (2018/4c)
73. State the two Mendelian laws of inheritance (1999/6a NABTEB)
74. A homozygous normal skin father (AA) get married to a homozygous albino mother (aa). All the offspring
were heterozygous normal skin (Aa)
(a) From the cross above,
(i) What would be the genotypic and phenotypic ratios if two of the offspring f1 were married.
(ii) What percentage of the offspring in (i) are albino (2008/4a Neco)

VARIATIONS IN POPULATION
Variation can be defined as the differences in characteristics that exist between individuals within a specie. This can
arise as a result of inherited or environmental factors. Variation can be continous or discontinuous.
All human beings in one geographical area constitute a population of human beings. Likewise the population of a
particular plant e.g. cowpea. Observations made from nature and of the results from carefully controlled experiments
in both plants and animal breeding have shown that no two individual are exactly alike. Even identical twins show
clear differences when closely looked at. In short, variation exists in nature, and it simply means the differences
between individuals of the same species. All members of a population have some characteristics in common, by which
they can be recognized as members of the species.

At the same time, members of the same species have individual differences. For example, in a classroom, each student
differs from the other though they belong to the same human population.

Types of variation
There are two types of variation
1. Morphological variation/continuous variation
Morphological variation is the noticeable physical appearance of individuals of the same species. This
physical appearance enables us to identify individual of a population.

Examples of morphological variation include,

(1) Size of various parts of the body such as head, eyes, hands, neck.
(2) Height of the body.
(3) Colour of parts of the body such as skin, eyes and hair.
(4) Shape of different parts of the body such as head, mouth, nose, jaw, eyes, ears, hands and legs.
(5) Weight of the body.
(6) Fingerprints: Fingerprints are impressions of the ridges on the ends of our fingers and thumbs. These ridges
form patterns that can be sorted into several distinctive groups. There are many subclasses of fingerprint
patterns, however these subclasses are grouped into three main classes these are: whorls, arch and loops.
Other examples of fingerprint patterns include compound/double loop, tented arch, central pocket loop,
accidental etc.

No two individual have the same fingerprint pattern. This makes it a very useful tool in crime detection.

Different fingerprints

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In plants, morphological variation include
(1) Size of various parts of the plants such as stem, roots, leaves, fruits, flower.
(2) Colour of parts of the plant such as green, white and brown of leaves, stem and roots.
(3) Height of plants.
(4) Shape of various parts of the plant such as stem, root, leaves, flower e.t.c.

Continuous variations are variation that changes gradually, within a population. They show gradual transition
between two extreme forms. For example, height, weight and intelligence are continuous variation in human beings.

Also, some people are fat, some are very thin while others are of intermediate sizes. Many known examples of
continuous variation are morphological in nature.

2. Physiological/discontinuous variation
Physiological variation is a type of variation, in which characteristics are expressed in a limited number of
ways without intermediate groups. In other words, physiological variation is the differences in the ways
individuals of the same species responds to various environmental condition. It relates to the functioning of
the body. This is also referred to as discontinuous variation.

Examples of physiological/discontinuous variation in human beings include

(1) Behaviour e.g. (1) Aggressive or non aggressive (2) excitable or calm (3) Timid or brave
(4) Caring or uncaring
(2) Ability to roll tongue: Some people can roll their tongue when it is pushed out of the mouth while others
cannot.
(3) Ability to move the ears without moving the head.
(4) Ability to close one eye and keep the other open.
(5) Ability to taste a chemical substance called phenylthiocarbamide (PTC): Some people have the ability to
taste this chemical in its dilute form in which it is bitter while to others it may be tasteless.
(6) Difference in blood group: Every human being can be grouped into one of the four blood groups known as
A, B, AB and O. there are no intermediate between any two blood groups, this is also a type of discontinuous
variation.

Examples of discontinuous variation in plant includes:

1. Colour of leaves. 3. Colour of fruits. 5. Shape of seeds and fruits.
2. Colour of flowers. 4. Colour of seeds.

Differences between continuous and discontinuous variation

Continuous Discontinuous
1. Gradual change in a trait from one extreme to the other. Differences in a trait with no intermediate state
2. Characteristics are usually measured. Characteristics can not be measured.
3. Affected by the environment. Not affected by the environment.
4. Caused by co-dominance. Caused by complete dominance.
5. They are controlled by genes. They are not controlled by genes.
Causes of variation
There are two major factors which may cause variation in living organisms.
1. Genetic difference.
2. Influence of the environment.

Genetic differences
Offspring usually inherit different trait from their parent and sometimes other traits not synonymous to that of the
parent might be seen. The reason for the above is that new genetic combinations can occur during sexual reproduction
and mutation might also occur. Mutation is the spontaneous change in a gene or chromosome. If a mutated gene is
inherited, variation will definitely result e.g. a gene responsible for green fruit may be altered to produce a yellow fruit
from the same plant. Genetic differences are concerned with those traits that are inherited from parents. When parents
bear children, each child inherits some traits of the father and some of the mother.
Environment influence: The environment plays an important role in the variation that occurs in human beings. These
include housing, food, health care, education facilities, parental care e.t.c.
Example
Which of the following characteristics is an example of continuous variation?
A. blood type B. ability to taste phenylthiocarbamide (PTC)
C. Ability to roll the tongue D. Height (2018/37 NABTEB)
Answer: D – Height is an example of continuous variation.
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Example
6(a) Define the terms: (i) Variation
(b) Give three examples each of:
(i) continuous variation (ii) discontinuous variation (2018/6ai & b NABTEB)
Answer:
6ai. Variation can be defined as the differences in characteristics that exist between individual of the same species.
bi. Examples of Continuous variation: ii. Examples of Discontinuous variation
- Height of the body - Behaviour
- Size of the head - Ability to roll tongue
- Colour of the skin - Difference in blood group
Example
Blood group and tongue rolling are examples of
A. adaptive variation B. continuous variation C. discontinuous variation
D. environmental variation E. sex-linked variation (2014/16 Neco)
Answer: C – Blood group and tongue rolling are examples of discontinuous variation.
Example
Which of the following is an example of discontinuous variation?
A. body weight B. height C. left-handedness D. size E. skin colouration (2014/17 Neco)
Answer: C – Left handedness
Example
(ii)List four types of finger print in man. (2014/5bii Neco)
Answer: Whorls; Archs; Loop; Compound
Example
Variation can best be defined as
A. ability of an organisms to adapt to changes in its environment
B. change in an organism that makes it to survive in its environment
C. differences which exist in individuals of the same species
D. study of how traits are transmitted from one generation to another
E. study of how organisms react to factors in their environment (2005/51 Neco Nov)
Answer: C – Variation is the differences which exist in individuals of the same species.
Example
The following are types of finger prints except
A. arch B. compound C. loop D. simple E. whorl (2008/56 Neco)
Answer: D – Simple is not an example of types of finger prints
Example
4a (iii) Give two examples each of morphological and physiological traits in man
(b) State two main causes of variation (2008/4aiii, b Neco)
Answer:
4aiii. Examples of morphological trait and physiological trait in man:
Finger prints Ability to roll the tongue
Size of the eye Ability to move the ear without moving the head
b. Causes of variation are : Genetic difference, Environmental influence.
Example
Which is a morphological variation?
A. Ability to taste PTC B. ability to roll the tongue C. behavior D. blood group E. Finger print (2001/60 Neco)
Answer: E – Finger print is a morphological variation.
Example
Which of these is a morphological variation?
A. blood groups B. colour blindness C. height D. Tasting PTC E. Tongue rolling (2007/34 Neco)
Answer: C – Height is a morphological variation.
Example
4(a) i. Define the term “variation”. (2007/4ai Neco)
Answer: Variation can be defined as the differences in characteristics that exist between individuals
of the same species.

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Example
Which of the following is not a factor encouraging variation?
A. Multiple alleles B. Mutation C Crossing over
D. Random assortment of chromosomes E. Mitosis (1995/54 Nov)
Answer: E – Mitosis is not a factor that encourages variation.
Example
The inability of some individuals to roll the tongue is an example of
A. personal adaptation B. psychological adaptation
C. behavioral variation D. morphological variation (2006/49 Nov)
Answer: B – The ability for an individual to roll the tongue is an example of physiological variation.
Example
Which of the following characteristics does not show any variation from generation to generation in humans?
A. muscle development B. blood group C. ability to roll the tongue D. height (2004/55 Nov)
Answer: A – Muscle development does not show variation from generation to generation as it is an acquired
character.
Example
The term variation is used to describe organisms
A. feeding on different type of food B. showing different traits from each other
C. which resemble their parents D. living in different habitats (2013/50 Nov)
Answer: B – Variation is used to describe organism showing different trait from each other.
Example
The following may be classified as continuous variation except
A. skin colouration B. blood group C. weight D. height E. size of finger nails (1997/52 Nov)
Answer: B – Blood group is a discontinuous variation.
Example
A mother is likely to be able to distinguish between her identical twin daughters because of
A. physiological variations B. morphological variations
C. character variations D. genetic variations (2011/45 Nov)
Answer: A – A mother is likely to be to distinguish between her identical twin daughters because of physiological
variation.
Example
Which of the following factors does not contribute to variations in living organisms?
A. Mitosis B. Meiosis C. Mutation D. Environment (2011/46 Nov)
Answer: A – Mitosis does not contribute to variation in living things.
Example
Which of the following traits shows clear-cut differences with no intermediate forms?
A. Intelligence B. Sex C. Skin colour D. Comb shape (2011/47 Nov)
Answer: B – Sex does not show an intermediate form; it is either an individual is a male or a female.
Example
Which of the following characteristics in humans is an example of continuous variation?
A. height B. blood group C. tongue rolling D. Rhesus factor (2005/51 Nov)
Answer: A – Height is an example of continuous variation.
Example
Which of the following is an application of knowledge of variation?
A. Crime direction B. choosing for recording
C. choosing athletes for races D. classification of human race (2002/50 Nov)
Answer: A – Crime detection is an application of the knowledge of variation.
Example
The term variation is used to describe organisms that
A. feed on different type of food B. show different traits from one another
C. shoe resemblance to parents D. live in difference habitats (2019/42 PC2)
Answer: B – The term variation is used to describe organism that show different trait from one another.
Example
Which of the following forms of variation will give a normal distribution?
A. Blood group B. Tongue rolling C. Body weights D. Fingerprints (2020/42 PC1)
Answer: C – Body weight

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Example
The inability of some individuals to perceive the taste of some substances is an example of
A. individual adaptation B. physiological variation C. morphological variation
D. morphological adaptation E. physical variation (1989/50)
Answer: B – The inability for some individuals to perceive the taste of some substances is an example of
physiological variation.

Example
Which of the following is correct about variation?
A. Offsprings are different from their parents only B. Offsprings from the same parents look alike
C. Offsprings differ from their ancestors and but look like their immediate parents
D. Offspring differ from their ancestors and each other (1999/53)
Answer: D – Offsprings differ from their ancestors and from each other
Example
Which of the following terms is not associated with fingerprint and classification?
A. Whorl B. Contour C. Arch D. Loop (2000/59)
Answer: B – Contour is not associated with finger print and classification.
Example
Which of these statements is true about fingerprint patterns?
A. consistent for a lifetime B. may be exactly the same for two individuals
C. prominent only at puberty D. correlate with the individual blood group (2002/48)
Answer: A – Finger print patterns are consistent for a lifetime.
Example
Which of the following is a continuous variation, in human population?
A. Sex B. Rh factor C Height D. Down syndrome (2002/50)
Answer: C – Height is a continous/morphological variation in human population.

EXERCISE 20.6
1. The ability of some individuals to taste phenylthiocarbamide (PTC) is a
A. morphological adaption B. morphological variation
C. physiological adaptation D. physiological variation (2004/51)
2. Which of the following traits in humans can be affected by environmental factors?
A. skin colour B. eye colour C. baldness D. tongue-rolling (2004/54)
3. Variation is a factor which
A. differentiates between individuals of the same species B. qualifies an organism to live with others
C. enables organisms to adapt to the environment D. state the external features of an organism (2006/51)
4. Which of the following traits in humans is not a morphological variation?
A. Height B. Shape of head C. Colour of skin D. Ability to roll the tongue (2006/52)
5. Which of the following statements about phenylthiocarbamide (PTC) is not correct?
A. Some people find the taste of PTC to be bitter B. Others find this substance to be tasteless
C. Ability to taste this chemical is heritable D. Ability to taste the chemical is not heritable (2008/46)
6. Which of the following characters is not an example of discontinuous variation?
A. Skin colour B. Finger print C. Ability to roll tongue D. Sex type (2008/47)
7. An example of continuous variation is
A. fingerprint B. tongue rolling C. blood grouping D. body size (2009/50)
8. Which of the following is an example of variation?
A. Blood B. Tongue rolling C. Reproduction D. Growth (2010/44)
9. The parameters of size, height, weight and colour in a population of living things are examples of
A. environmental variation B. non – heritable variations
C. continuous variation D. discontinuous variations (2010/45)
10. Fingerprints are useful in crime detection because
A. the police have sophisticated fingerprint machines B. thieves may leave their prints in the scene of a crime
C. no two people have the same fingerprints D. fingerprints are easy to make (2010/46)
11. The following pairs of traits are examples of continuous and discontinuous variations respectively except
A. eye colour and body weight B. height and blood group
C. skin colour and fingerprints D. body weight and tongue rolling (2012/50)
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12. The classes of fingerprints in man are
A. whorl, alternate, opposite and compound B. compound, loop, whorl and alternate
C. whorl, arch, compound and loop D. arch, simple, compound and opposite (2012/52)
13. Characteristic that exhibit continuous variation are generally controlled by
A. a single gene B. recessive genes C. epistatic interaction D. multiple genes (2014/40)
14. Differences in characteristics that exist among individual of the same species is referred to as
A. genetics B. dominance C. hybrid D. variation (2014/41)
15. Which of the following traits is not a morphological variation in humans?
A. Ability to taste PTC B. Colour C. Fingerprints D. Size (2014/42)
16. Which of the following characters is not a morphological variation?
A. Shape of the nose B. Colour of skin C. Colour of hair D. Tongue rolling (2017/44)
17. Which of the following factors is not a source of variation in living organisms?
A. Environment B. Inheritance C. Mitosis D. Meiosis (2019/41)
18. Variation which exhibits a wide range from one extreme to the other is
A. phenotypic variation B. discontinuous variation C. continuous variation D. genotypic variation (2020/42)
19. Measurement of height and weight of students in a class show
A. discontinuous variation B. continuous variation
C. shortness is more prevalent D. fatness is less prevalent (2020/43)
20. Human height is an example of a feature which depends on both.
A. genotype and phenotype B. genetic and environmental factors
C. mother’s genotype and environmental factors D. phenotypic and environmental factors (1995/39 JAMB)
21. Hassan and Hussain are identical twins but Hassan grows taller and fatter than Hussain. This is probably because
A. Hassan inherits genes for tallness and fatness from the father B. they have dissimilar genotypes
C. Hussain is endowed with genes for shortness and thinness
D. they are raised in different environments (2006/18 JAMB)
22. A phenotypic character with intermediate forms that can be graded from one extreme to the other is referred to as
A. discontinuous variation B. continuous variation C. a mutant D. a genome (2009/40 JAMB)
23. Variation can occur among offspring of living organism because
A. seeds are produced by self pollination B. zygotes are produced by cross fertilization
C. they are produced by binary fission D. they are produced without fertilization (2016/27 JAMB)

APPLICATION OF VARIATION
The applications of variation includes:
1. Determination of paternity: In cases where the paternity of a child is in dispute, knowledge of a blood group
is usually applied to resolve the dispute.
2. Crime detection: Morphological features which are peculiar to individuals can be used by police and other
detectives to trace criminals. Examples of such features include height, colour of skin, colour of hair, colour of
eyes and fingerprint. . The use of fingerprint in crime detection is based on the fact that no two individuals
have exactly the same fingerprints and human fingerprints remain unchanged throughout life. Physiological
features such as rolling of tongue and difference in blood group are also used
3. Blood transfusion: There are four main blood groups. These are A, B, AB and O. Blood groups are
characterized by specific proteins in the blood and these are antigens in the red blood cells and antibodies in
the blood plasma.
Antigens are substances that will stimulate an animal to form protein compounds called antibodies. A victim
receiving the blood is called recipient and the person giving out the blood is called a donor. The process of
transferring blood from one person to another is called blood transfusion. If wrong blood groups are mixed,
the red blood agglutinates because of the antibodies in the plasma of the recipient. This will result in blocking
of the blood vessels and may finally lead to death.
Blood group of donor Blood group of recipient
A B AB O
A + – + –
B – + + –
AB – – + –
O + + + +
+ positive ; – negative
People in blood group O can donate blood to people in all other groups therefore they are called universal donor.
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4. In medicine: The knowledge of variation is used widely in various field of medicine. Because of the
differences in skin colour, certain body cream are recommended for use differently between the black and
white human races.

5. In agriculture: Animal and plant breeders make use of variations to develop better breeds of animals and
varieties of crops that have high yield, taste, disease resistance, adaptation to local environment e.t.c.

Example
The following are applications of variation, except
A. blood transfusion B crime detection C. determination of paternity D. medicine E. mutation (2014/13 Neco)
Answer: E – Mutation is not an application of variation.
Example
Crime detection in a forensic laboratory involves the use of
A. blood transfusion B. blood analysis C. finger prints D. genetic combination E. tongue rolling ability (2008/55 Neco)
Answer: C - Finger prints
Example
The knowledge of heredity and variation are not required in
A. blood transfusion B. crime detection C. determination of paternity D. longevity E. marriage (2018/56 Neco)
Answer: D – The knowledge of heredity and variation is not required in longevity.
Example
Which of the following statements is correct about blood transfusion?
A patient with blood group
A. B can receive blood from groups B, AB and O B. A can receive blood from groups A, AB and O
C. AB can receive blood from groups AB, A, B and O D. O can receive blood from groups O, A, B and AB
E. A can receive blood from groups B, AB and O (1998/10 Health Science)
Answer: C – A patient with blood group AB can receive blood from groups AB, A, B and O. Blood group AB is also
known as universal recipient.
Example
Which of the following is considered during blood transfusion? The donor and the recipient must have
A. equal haemoglobin count B. matching blood groups
C. no blood relation D. the same type (2000/14 Health Science)
Answer: B – The donor and the recipient must have matching blood groups.
NB: The donor and the recipient must not necessary have the same blood groups except in the case where the recipient
is blood group O.
Example
Finger prints are used in detecting crime because
A. it is a continuous variation B. it is a discontinuous variation
C. no two individuals have the same finger prints D. it is passed on from mothers to their daughters only
E. it is passed on from fathers to their sons only (1992/56 Nov)
Answer: C – Finger prints are used in detecting crime because no two individuals have the same finger prints.
Example
In the knowledge of variations, heredity has been applied in the following ways except
A. detection of crime B. blood transfusion C. management of malaria fever
D. paternity determination E. sex determination (1998/53 Nov)
Answer: C – Management of malaria.
Example
During blood transfusion, agglutination may occur as a result of the reaction between
A. similar antigens and antibodies B. contrasting antigens and antibodies C. two different antigens
D. two different antibodies E. white blood cells from the two individuals (1988/44)
Answer: A – During blood transfusion, agglutination may occur as a result of the reaction between similar antigens
and antibodies.
Example
One of the factors that must be considered for safe blood transfusion is
A. social class of the donor B. age of the recipient C. rhesus factors of the donor and the recipient
D. nationality of the donor E. weight of the recipient (1993/48)
Answer: C – One of the factors that must be considered for safe blood transfusion is the rhesus factors of the donor
and the recipient.

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Example
One of the applications of variation is in
A. determining the size and weight of individuals B. determining paternity C. conservation of wild life
D. controlling of diseases vectors E. sex determination (1997/51)
Answer: B – One of the application of variation is in determination of paternity.
Example
DONOR RECIPIENT
I toto TATA
II TBto TBTB
III TATA TATB
IV TATB toto
V toto TBTB
In which of the under listed blood groupings is agglutination likely occur during transfusion?
A. I B. II C. III D. IV E. V (1997/52)
Answer: D – IV individuals of blood group O can only receive blood transfusion from individual of blood group O. if
any other blood group individuals donate blood to an individual of blood group O, agglutination will occur.

EXERCISE 20.7
1. Which of the following traits may not be important in marriage counseling?
A. Sex-determination B. Sickle-cell anaemia C. Rhesus factor D. Colour of skin (1999/57)
2. During blood transfusion, agglutination could be prevented if a patient having blood group O is given blood
from group.
A. AB B. A C. O D. B (2000/60)
3. A person with blood group B can only donate blood to individuals with blood groups
A. A and B B. B and AB C. O only D. B only (2005/51)
4. The blood group in humans referred to as a universal recipient is
A. O B. A C. B D. AB (2006/53)
5. Variation is important in human life and can be used for the following activities except
A. crime detection B. population distribution C. blood transfusion D. determination of paternity (2009/49)
6. 4 (a) What is variation? (b) State five advantages of variation within a species. (c) In a tabular form, outline
four differences between continuous and discontinuous variations. (d) Explain the following terms: (i) Sex
linked characters; (ii) Co-dominance; (iii) Hybrid vigour (2009/4a-d)
7. A person with blood group O can be given blood from persons who have blood belonging to
A. group O only B. group A only C. groups A and O D. groups A, B and O (2010/47)
8. When a man is Rh-positive marries a woman who is Rh-negative, there will be incidence of
A. still births B. sicklers C. albinos D. living children (2013/50)
9. Which of the following traits may be considered in marriage counseling?
A. Height B. Fingerprints C. Rhesus factor D. Colour of skin (2013/55)
10. During blood transfusion agglutination may occur when
A. contrasting antigens react with contrasting antibodies B. similar antigens react with similar antibodies
C. two different antigens react with each other
D. two different antibodies react with each other (1993/47 JAMB)
11. Which of the following is a major cause of variation among organisms?
A. Inbreeding B. Backcrossing C. Sexual reproduction D. Gene dominance (2008/40 JAMB)
12. The Rhesus factor of blood was first identified in a category of
A. monkeys B. human females C. human males D. chimpanzees (2008/41 JAMB)
13. An accurate identification of a rapist can be carried out by conducting a
A. RNA analysis B. blood group test
C. behavioural trait test D. DNA analysis (2019/40 JAMB)

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 REVISION EXERCISE
1. Hereditary variation is best described as
A. characters transmitted from generation to generation B. traits acquired from diseases
C. characters that show up due to social conditions D. traits acquired from habits and environmental conditions
E. characters that result from physical injuries (1995/51)
2. A blend of inherited and acquired characteristics shows
A. variation B. inheritance C. evolution D. hereditary (2016/41)
3. Which of these is not a hereditary variation
A. infant penalysis B. blood group C. sickle cell D. shape of face and nose E. colour of hair (1996/50)
4. A noticeable physical appearance of individuals of the same species is called
A. physical variation B. physiological variation C. morphological variation D. discontinuous variations (2016/40)
5. Which of the following is not a morphological variation in human beings?
A. size B. blood groups C. colour D. fingerprints (2002/53)
6. Which of the following terms is not associated with fingerprints and classifications?
A. whorl B. contour C. arch D. loop (2000/59)
7. Which of the following is an example of variation
A. blood B. tongue rolling C. reproduction D. growth (2010/44)
8. Which of the following variation is applicable to a weight lifter?
A. continuous variation B. discontinuous variation
C. hereditary variation D. acquired variation (2001/58)
9. The parameters of size, height, weight and colour in a population of living things are examples of
A. environmental variation B. non – heritable variation
C. continuous variation D. discontinuous variation (2010/45)
10. Which of the following statement is not true of continuous variation? It
A. is usually controlled by several genes B. can be influenced by environment factors
C. follows a normal distribution curve D. is usually controlled by one or two pair(s) of gene (2011/50)
11. The following pairs of traits are examples of continuous and discontinuous variations respectively except
A. eye colour and body weight B. height and blood group
C. skin colour and fingerprints D. body weight and tongue rolling (2012/50)
12. Which of these statements is true about fingerprint pattern?
A. consistent for a lifetime B. may be exactly the same for two individuals
C. prominent only at puberty D. correlate with the individual blood group (2002/48)
13. Fingerprints are useful in crime detection because
A. the police have sophisticated fingerprint machines
B. thieves may leave their fingerprints at the scene of a crime
C. no two people have the same finger prints D. fingerprints are easy to make (2010/46)
14. The classes of fingerprints in man are
A. whorl, alternate, opposite and compound B. compound, loop, whorl and alternate
C. whorl, arch, compound and loop D. arch, simple, compound and opposite (2012/52)
15. Crime detection in a forensic laboratory involves the use of
A. blood analysis B. fingerprints C. genetic combination D. tongue rolling ability (2008/55 Neco)
16. Which of the following statements is true about blood groupings?
A. group AB can donate blood to all other groups B. group O are universal recipients
C. group A has A antigen in its plasma D. group O has no antigens (2001/15)
17. Define the term variation
Give three examples each of : i. Continuous variation. ii. Discontinuous variation (2018/6a NABTEB)
18. Give two examples each of morphological and physiological traits in man (2008/4a(iii) Neco)
19. Copy and complete the table below to indicate the corresponding antigen in the red blood cell (RBC) and
antibody in plasma of each blood group.
Blood group Antigen (RBC) Antigen in plasma
A
B
AB
O
i. What is the importance of blood group in humans.
ii. Why is it dangerous, to transfer blood from one person to another without a preliminary test. (2014/8b Nov)
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Relevance of Biology to Agriculture
Classification of plants: Plants can be classified based on the following:
(1) Botanical classification
(2) Nature and uses of products (i.e. economic uses)
(3) Life cycle.

Botanical Classification: This is the classification system of flora and fauna using the binomial system of
nomenclature, in which every plant is given two names (generic and specific names). In zoology, names of families
are formed by adding “idae” to the generic name e.g. Ranidae from Rana (the frog); subfamily names usually end in
“inae”.
In botany, family names usually end in “aceae”, e.g Rosaceae (the rose family) orders end in “ales” e.g. “Rasales”
(the rose plant), division end in “phyta” e.g. Spermatophyta (seed bearing plants).

Rules in binomial system of naming

(1) The generic and specific names are written separately.
(2) They are either italicized or underlined separately.
(3) The first letter of the generic name is written in capital letter, whereas the rest and the specific names are
written in small letter.
(4) The generic names are always written first followed by the specific name.
(5) When there are more than one species under the same genus, the first letter of the generic name can be
abbreviated followed by the specific names e.g. Citrus spp; C. Sinensis, C. paradis, C. lima and C. reticulata.

Kingdom Plantae
There are four divisions (phyla) in this kingdom namely:
(1) Thallophyta
(2) Bryophyta
(3) Pteridophyta
(4) Spermatophyta
The pteridophyta and spermatophyte are commonly referred to as tracheophytes because they possess vascular
tissues for conducting water and foods. Spermatophyte is divided into gymnosperms and the angiosperms.
Angiosperms are the largest groups of plants.

The angiosperms are divided into two sub classes namely:

(1) Monocotyledon (one – seed plant)
(2) Dicotyledon (two - seed plant)

Differences between monocotyledon and dicotyledon

Monotocyledon Dicotyledon
(1) Seed has only one cotyledon Seed has two cotyledon
(2) Leaves have parallel venation Leaves have net venation.
(3) Mostly herbaceous plants except palm and bamboos. They are herbs, shrubs and trees
(4) Vascular bundles are arranged irregularly in the stem Vascular bundles are arranged in rings in the stem.
(5) Secondary growth rarely occurs Secondary growth usually occurs
(6) Have fibrous root system. Have tap root system.
(7) Floral parts occur in threes and multiples of three Floral parts occurs in fours, fives or multiple of such.
(8) Absence of cambium Presence of cambium.
(9) Examples of monocotyledon are banana, palm tree, Examples of dicotyledonous are hibiscus, mango,
maize e.t.c orange e.t.c.
Agricultural classification of plants
1) Legumes: The seeds of legumes are rich in proteins. They also replenish the soil because they contain
nitrogen fixing bacteria on their root nodules, examples are cowpea, lima bean, pigeon peas, soya bean,
groundnut and beans.
2) Cereals: These plants belongs to the grass family graminaea or poceae. Their seeds are rich in carbohydrates
(i.e. starch). Examples are maize, barley, millet, oath, rice, sorghum and wheat.
3) Stem tubers: These plants store food in underground stem that are swollen with food reserves. Examples are
yam, irish potatoe e.t.c. They are rich in carbohydrates.

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4) Root tubers: These crops store food in their swollen roots which contain carbohydrates. Examples are
cassava, carrot, sweet potato.
5) Vegetables: This contains vitamins and sugar. Examples are pawpaw, avocado pear, mango, banana, orange,
pineapple e.t.c.
6) Oil crops: Contains oil extracted from seeds and fruits. Examples are oil palm, coconut, groundnut, shear
butter and sunflower.
7) Spices: These are grown for special flavor which they add to foods. Examples are green or red pepper, black
pepper, ginger, cinnamon cloves and garlic.
8) Forage crops: These are mainly legumes and grasses for feeding farm animals. Examples are Tridax, goat
weed, guinea grass, elephant grass e.t.c.
9) Beverages and drug plant: These are grown for making beverages (food drinks) and drugs. Examples
include cocoa, coffee, kolanut, tea, tobacco (used as stimulant) neem, lemon grass and quinine.
10) Rubber or latex crops: The latex of these crops are used to produce rubber. Examples are para rubber (Hevea
brasiliensis), Ficus elastica, Funtamia elastica (Lagos rubber) and Landolphia owariensis.
11) Fibre crops: This crop contains fibre used for cloths, rope, sack and paper. Examples are cotton, pineapple,
sisal hemp, sorrel plant, jute, guinea hemp and baobab.
12) Wood crop: These are trees grown to provide hard wood (timbers) used for building construction and
furniture. Examples are ebony, mahogany, iroko et.c.
Classification based on life cycle
1) Ephemerals: These plants complete their life cycle and die within three or four months. They can undergo
two to three life cycles within a growing season. Examples are tomatoes and water leaf.
2) Annual: They complete their life cycle in a year. Examples are rice, maize, millet, sorghum and beans. They
are mostly herbaceous.
3) Biennials: These complete their life cycle within two years. Examples are carrot, onions, cabbage, turnip,
cocoyam.
4) Perennials: These plants live for several years. Examples are rubber, oil palm, cocoa, mango, coconut,
orange, hibiscus, ailamanda, flamboyant e.t.c.
Example
In the binomial system of naming organisms, the second name is called the
A. scientific name B. common name C. generic name D. specific name (2008/1)
Answer: D – In the binomial system of naming organism, the second name is called the specific name
Example
Crops grown mainly to feed animals are called
A. forage crops B. fiber crops C. wood crops D. oil crops E. spices (1997/47)
Answer: A – Forage crops are crops grown mainly to feed animals.
Example
Legumes incorporate nitrogen gas into their protein because
A. of the presence of azotobacter in the root B. they possess root nodules containing rhizobium
C. they are autotrophic (2003/48)
Answer: B – Legumes incorporate nitrogen gas into their protein because they possess root nodules containing
rhizobium.
Example
A monocot root is different from dicot root by having
A. endodermis B. cambium C wide pith D. root hair (2011/12)
Answer: C – Monocot root is different from a dicot not by having a wide pith.
NB: A monocot stem does not have a pith while a dicot stem has a pith.
Example
1(a) (i) What is classification of living things? (2017/1a)
Answer: Classification of living things is the science of arranging living things into groups based on structural,
genetic or cellular organization. NB: This is also called taxonomy.
Example
Which of the following is an example of a biennial crop?
A. cabbage B. maize C. mango D. spinach E. yam (2005/31 Neco Nov)
Answer: A – Cabbage is a biennial crop. NB: Maize, spinach and yam are annual crops while mango is a perennial crop.
Example
Which of the following crops is a beverage crop?
A. cocoa B. cotton C. kolanut D. rubber E. tobacco (2005/34 Neco Nov)
Answer: A – Cocoa
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EXERCISE 21.1
1. Angiosperms and gymnosperms belong to the plant group known as
A. schizophyta B. bryophita C. pteridophyta D. spermatophyte (1991/3 JAMB)
2. Which of the following features are all associated with monocots?
A. fibrous root system, branched network of veins and one seed leaf
B. one seed leaf, petals in threes or groups of threes and parallel venation of leaves
C. fibrous root system, two seed leaves and floral parts in trees
D. one seed leaf, net-veined leaves and petals in trees multiples of tree (2000/5 JAMB)
3. Most monocots are easily recognized by their
A. short leaves with petioles B. long and sword-like leaves
C. long and palm-like leaves D. short leaves with many veinlets (2001/6 JAMB)
4. Angiosperms and gymnosperms belong to the class
A. spermatophyte B. bryophyte C. schizophyta D. pteridophyta (2005/43 JAMB)
5. Mycorhizae promote plant growth by
A. absorbing inorganic ions from the soil B. protecting it from infection
C. helping it to utilize atmospheric nitrogen D. serving as a growth regulator (2010/29 JAMB)

Effect of agricultural activities on Ecological activities

1) Bush burning: Bush burning is practiced by the African peasant farmers on the tropical rain forest and the
savanna. Bush burning exposes the soil surface to erosion by wind and rain, reduces organic (humus) content
of the soil, destroy microorganisms of the soil, kill animals in the soil such as termite and earthworms and
destroy other important plants and animals. Bush burning therefore, disturb the balance of the ecosystem.

2) Tillage: Tillage is a practice of preparing the land for cropping by tiling it manually with farm tools such as
hoes, spades, cutlass etc. It is necessary for the cultivation of crops and helps to mix top soil with sub – soil. It
encourages soil aeration and permeability of water. It removes weed and stumps, root, stolon and rhizomes.
Tillage also encourages erosion, exposes the soil microbes and destroys the humus on the top soil.
Differences between tillage and bush burning
Tillage Bush burning
1. Tillage helps to loosen the soil. Bush burning does not lose the soil.
2. It changes the structure and texture of soil. It does not affect the structure and texture of the
soil.
3. It exposes soil organisms. Does not expose soil organisms.
4. Does not consume or burn humus. It consumes or burns humus, causing loss of soil
fertility.
5. Does not destroy useful organisms in the soil. Destroy useful organisms in the soil.

3) Fertilizer/herbicide and their effects: A fertilizer is any material of natural or synthetic origin that is applied
to soils or to plant tissues (usually leaves) to supply one or more plant nutrient essential to the growth of plant.
While herbicides are substances used to control unwanted plants. The use of chemical fertilizer causes loss of
organic humus, destroys the soil crumb structure and its permeability to air. Chemical fertilizers are washed
off by rain and drained into rivers and lake where they cause eutrophication. Eutrophication is the over-
growth of microscopic aquatic plants resulting from excess nitrogenous and sulphate fertilizers reaching rivers
and lake. These provide nutrient for microscopic green algae. The algae overgrow and then die and
decompose. The decomposition exhaust the oxygen thus causing suffocation to aquatic animals.

Use of chemical fertilizer destroys crumb structure of soil. This makes it dry and powdery and therefore open
to wind erosion. Some herbicides are ineffective against weeds but are highly toxic to young seedlings.

4) Effect of pesticides: A pesticide is defined as a chemical agent used to destroy or control pest. Sometimes
pesticides disturb the dynamic balance of the ecosystem. For example, insecticides affect both beneficial and
harmful insects. The accumulation of insecticides such as DDT in the body of animals has adverse effects on
their breeding e.g. birds.

5) Effects of different types of farming on ecological system

(a) Shifting cultivation: This involves cultivating a piece of land and planting crops for one or two years
on it before moving to an uncultivated piece of land. Due to population increase, this method is now
on the decline.

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 (b) Bush fallow: This method is used in West Africa. It involves allowing a used land to fallow for some
years e.g. 8 – 10 years to regain its original structure and fertility. During this period the farmer moves
to another land.
(c) Crop rotation: This is common in temperate countries and some part of Africa. It involves
cultivating a piece of land with different plant at every growing season. Usually, legumes are included
in a crop rotation to restore the nitrogen content of the soil.
Examples of crop rotation

Yam Groundnut

Maize Cassava

(d) Monoculture: This involves planting only one type of crop on a piece of farm land or rearing one
type of animal. Monoculture can lead to efficiency and increase size of the growing field. The
major disadvantage is that it increases the spread and population of parasites.
(e) Mixed cropping: This involves planting two or more species of plant on the same piece of land.
E.g. surface feeder and deep feeder are planted to extract the maximum quantity of water and
mineral salt from the soil. For example, cocoa and banana can be planted on the same land. One
advantage of this method is that insect pests and fungal diseases do not easily spread.

Example
Which of the following statements is not correct about the ecological effects of agricultural activities?
A. The use of herbicides and pesticides in farms can cause pollution B. Bush-burning encourages desertification
C. Excessive use of fertilizers in farms may have harmful effects
D. Tillage of tropical soils with ploughs and harrows may encourage erosion
E. Monocropping is one of the cultural methods of controlling pests (1989/28)
Answer: E – Monocropping is one of the cultural methods of controlling pest.
Example
Which of the following can cause desert encroachment?
A. Afforestation B. Irrigation C. Planting of trees D. Establishment of game reserve E. Overgrazing (1994/18)
Answer: E – Overgrazing can cause desert encroachment.
Example
The farming practices by which an exhausted farm land is left for a number of years before cultivation is known as
A. crop rotation B. continuous cropping C. monocropping D. bush fallowing E. mixed cropping (1997/48)
Answer: D – Bush fallowing is a kind of farm practices in which land is cultivated for a period of time and then left
uncultivated for several years so that its fertility will be restored.
Example
Which of the following farm practices can cause loss of soil fertility?
A. Mulching B. Compost application C. Use of fertilizers
D. Terracing E. Intensive cropping (1997/50)
Answer: E – Intensive cropping can cause loss of soil fertility
EXERCISE 21.2
1. To avoid over-fishing in a lake, the following measures may be helpful except
A. limiting fishing periods B. regulating the size of nets
C. fishing throughout the year D. fish breeding exercise (2008/43)
2. Leguminous crops are incorporated into crop rotation in order to
A. improve aeration of the soil B. promote nitrogen fixation
C. increase the rate of soil formation D. improve upon the water holding capacity of the soil (2011/47)
3. Which of the following practices improve crop yield in a clayey soil? Addition of
A. more water and humus B. lime and humus C. fertilizers D weedicides and fertilizers (2011/48)
4. The planting of cover crops does the following except
A. preventing soil erosion B adding nutrients to the soil C. holding the soil particles together
D. reducing excessive transpiration from the soil E. reducing the amount of nitrogen in the soil (1997/48 Nov)
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Pest and diseases of agricultural importance
Pest are insects or animals which causes damage to farm animals, crops, plants and food. A disease is a departure from
normal state of health, expressing remarkable symptoms of outward visible signs.
Pest of crops: These attack crops and reduce their yield. They may be plants or animals. Plant pest which attack crops
are mostly weeds. The most dangerous pests of crops are animal pests, especially insects such as grasshopper, locust
and caterpillars. Other animals pest include nematodes (such as Ascaris, hookworm and guinea worm), rodents (e.g.
rats), birds (e.g. pigeon, fowl, parrot and weaver bird), mollusces (e.g. snail) and mite. Insects and rodents easily
destroys stored crops like cocoa, coffee, groundnut, yam and beans.
Plant pests
(1) Capside bug of cocoa: This pest feed on the leaves, stem and pods. They cause secondary infection by a
fungus, e.g. Calonectria. Symptoms include die back of the young branches. Capsid are controlled by
spraying aldrex 40, BHC, Dieldrin and Gammalin 20.
(2) Cotton stainer (Dysdercus spp): Cotton stainer bugs, attacks cotton plant. They pierce the young bolls and
seeds in the open bolls and suck the sap. They transmit viral, fungal and bacterial diseases from one plant to
another. The fungus causes the boll to rot internally.
(3) Yam beetle: These destroy yam farm. They are controlled by treating yam setts and seeds with Aldrin just
before planting. Eel worm also feed on the yam tuber. Rodents also destroys tubers.
(4) Pest of cassava: Grasshopper is the main pest of cassava. Zonocerus variegates can eat up the leaves and
young shot of cassava. Some rodent also feed on the tubers.

Control of plant pest

(1) Physical method: This involves hand picking of the pest or the use of trap to destroy them. Deterrents such as
bird scares can be used to keep away birds from the farm or store.
(2) Cultural method: This involves modifying the usual farming practices to discourage the development of
pests.
(3) Biological method: This involves use of natural enemies such as predators and parasites to destroy the pests
and reduce its population.
(4) Sterile male technique: This involves sterilizing the male insect pests with chemical or radiation and then
releasing them into pest population.
The general control measures for plants disease include:
(1) Destroying all diseased plant materials in the farm.
(2) Planting of healthy plants.
(3) Growing of disease resistant varieties of plant.
(4) Legislating against the movement of crops between countries.
Pest and parasite of farm animals
A pest is an organism which carries pathogens or cause damage to other organisms. Livestock pest and parasites make
farm animals unhealthy and even cause death that decreases their productivity. Animal pest include ectoparasite such
as tick, lice, fleas, bugs, tse-tse flies, mite e.t.c. They have biting or piercing and sucking mouth part. They cause loss
of blood and make farm animal unhealthy. Some pests are vectors and transmit disease to farm animals. Some pests
are endoparasite e.g. liverfluke, roundworm, trypanosome and tapeworm.
Trypanosome: This is transmitted by tse-tseflies to humans and farm animals. It causes Trypanosomiasis (sleeping
sickness). It causes anaemia, weight loss, fever e.t.c.
The young stage of the trypanosome lives in tsetse fly. The adult stage is found in human and farm animals. It is
transmitted to humans by the bite of an infected tsetse fly. In humans, the parasite feed and live in the blood and then
multiply and eventually migrate to other organs in the body until they get to the lymphatic glands and cerebrospinal
fluid where they cause serious damage or effects. The economic importance of Trypanosomiasis is that it causes low
livestock production in tropical Africa.

Trypanosome
Economic importance of tse – tse fly
(1) It transmits the protozoan called trypanosome to cattle.
(2) The trypanosome causes sleeping sickness, anaemia, loss of weight and releasing fever.
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Control
(1) By clearing the bushes around the breeding ground.
(2) Spray the resting places of tse – tsefly with DDT or other insecticides.
(3) Rear resistant cattle in an infected area.

Ticks: The ticks are ectoparasites that live on domestic and farm animals. The tick may have one or more host. They
suck blood of their host and transmit viruses and protozoa that causesdiseases.

Life history of a tick: The mature female attaches itself to the skin of its host such as cattle, horse, goat or sheep and
sucks blood. The mature male crawls about until it finds a female. The male dies after mating and after fertilization,
the female tick drops to the ground. The eggs are laid on the ground or crevices of stones. The eggs then hatch into
larvae with six legs. The larvae are very active and they climb to the apex or top of blades of grasses to enable them
attach themselves to the host when the host passes by. Once the larvae attach themselves to their host, they pierce the
skin of the host animal to suck blood. Once the larvae have sucked enough blood they drop to the ground and develop
into nymphs with eight legs. The nymphs crawl to the blades of the grasses again waiting for another host to cling to.
Then once they are able to cling to the host, they then suck blood and then drop to the ground where they moult into
adults.

Life cycle of a Tick

Economic importance of tick:
(1) The tick sucks blood which causes irritation and this result into restlessness and lost of weight in farm animals
and poultry.
(2) Sucking spots in the host develop sores on the skin and this provides surfaces for diseases infection.
(3) Sucking of blood causes loss of blood and this leads to anaemia and weakness.
(4) The skin of the animals is destroyed leading to poor hides.
(5) Tick transmits diseases such as red water fever, relapsing fever, east coast fever e.t.c.
(6) Infestation of young animals results in retarded growth.
Control
(1) Keep environment clean and tidy.
(2) Any tick seen should be removed from the body of the animal physically.
(3) Spray animal houses with insecticides such as BHC or melathion
(4) Dip infected animals into a solution of arsenic.
(5) There should be rotation of pasture and livestock. This will make the larvae and nymphs to die of starvation
due to lack of hosts.

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Liver fluke (Fasciola hepatica): This attack sheep or cattle. The sheep and the cattle are the primary host. The
secondary host is the water snail. The eggs of the fluke are passed out in the faeces of the farm animals. As soon as the
eggs get into water bodies, they develop into motile larvae or miracidia which swim about until they find a water
snail. They enter the body of the snail and develop into tiny worms called cercaria. The cercaria leaves the snail and
may enter the drinking water of farm animals and get to the animal through drinking of water. Cercaria may also get
to vegetation and form cysts which may then be eaten with grasses by grazing farm animals (NB: The cercaria comes
out of the cysts in the body of the farm animals).
In the body of the farm animals, the cercaria makes their way to the liver, and then to the bile ducts where they grow
into adult flukes. During their movement to the bile duct, the flukes damages the liver and affect its function. The
adult fluke may block the bile duct and impair digestion of the farm animal.

Control of liver fluke

(1) By killing the intermediate host by spraying water bodies in infected areas with chemicals like copper
sulphate.
(2) Deprivation of the miracidia of its intermediate host. An effective way to do this is to introduce ducks into
pools and streams. The ducks helps to eat the intermediate host.
(3) Snail habitat management: Wet areas should be drained completely and water snails on grazing ground should
be physically picked and destroyed completely.
(4) Drinking water supplied to animals should be clean.
(5) Veterinary doctor should be consulted to treat infected animals.

Life cycle of a liver fluke

Example
Which of the following organisms is an endo-parasite?
A. Tapeworm B. Flea C. Tick D. Aphid (2015/35) Answer: A – Tapeworm is an endo-parasite.
Example
The following organisms are ectoparasites except
A. mite B. louse C. ascaris D. tick (2017/2a NABTEB) Answer: C – Ascaris is an endoparasite
Example
Which of the following animals is NEVER a secondary host of tapeworms?
A. Cow B. Fish C. Pig D. Man E. bat (1980/5 JAMB)
Answer: D – Man is never a secondary host of tapeworm, but a primary host.
Example
The vector f trypanosome is the
A. black fly B. cockroach C. housefly D. mosquito E. tsetse fly (2001/47 Neco)
Answer: E – The vector of trypanosome is the tse-tse fly

437
EXERCISE 21.3
1. A tropical disease caused by trapanosoma is
A. sleeping sickness B. river blindness C. yellow fever D. malaria (2013/41)

Use the diagram below to Answer: Questions 56 and 57

2. Which of the following diseases will the organisms above cause?

A. Filariasis B. Trypanosomiasis C. Cholera D. Malaria E. Bilharzia (1990/56 Health Science Nov)
3. These organisms are usually transmitted through
A. eating poorly cooked meat B. drinking contaminated water
C. droplets D. insect bite E. skin contact (1990/57 Health Science Nov)

Diseases of farm animals

Diseases of farm animals: A disease refers to a situation where there is an abnormality in health condition. It refers to
abnormality or deviation in health conditions.
Some common livestock pest and disease of farm animals
Name of diseases Causative agent Animal Symptoms Mode of Control
affected transmission
Rinder pest Virus Cattle, High fever, blood stained Through contact (i) Vaccination
disease. Very sheep and diarhoea, difficulty in with infected (ii) Isolate infected
contagious and fatal goat breathing, death rate is animals and by animals from
very high and this reduces eating healthy ones.
animal population. contaminated food. (iii) Slaughtering of
infected animals.
Food and mouth Virus Cattle Sore on feet, lips, tongues, Transmitted by (i) Vaccination
diseases cheek salivation, inability contact with (ii) Isolation of
to eat, loss of animal infected animals or infected animals
through death. by contact with from healthy ones.
infected feed (iii) Bury dead
materials animals.
Newcastle disease Virus Poultry i. Drop in feed Through contact (i) Vaccination
consumption. with substances (ii) Destroying
ii. Difficulty in contaminated by affected fowls.
breathing. the virus such as (iii) Good sanitation.
iii. Neck twisting. nasal discharges
iv. Paralysis of legs and and feeds.
wings.
v. Greenish-watery
diarrhea.
vi. There is high
mortality rate leading
to loss of birds.
Coccidiosis Protozoan Poultry, Affect intestine and caeca; Contact with Keep healthy fowl
pigs, causes death eventually. infected faeces or away from the
cattle, Diarrhea which may ingestion of droppings of affected
sheep, become bloody. infected tissue. i.e ones; give coccidiostat
goat, Weakness; pale comb or it spreads from one to the farm animals for
rabbit skin, ruffled feathers, animal to another treatment.
weight loss etc. by contact with
infected feaces.
Trypanosomiasis Protozoa Mainly i. Intermittent fever. Transmitted by tse- (i) Use of drugs
(sleeping sickness) (trypanosome) cattle and ii. General weakness tse fly through (trypanosomide)
sheep iii. Hairs on the tail of biting and sucking (ii) Roar resistant
animals pull out and habits. breed.
the animal finally (iii) Spray tse-tse flies
dies. with insecticides.
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 Name of diseases Causative agent Animal Symptoms Mode of Control
affected transmission
Brucellosis Bacteria Cattle Irritation and catarrhal Contacted through (i) Vaccination.
condition in the womb of feeding on (ii) Report any
the pregnant cow. contaminated occurrence to the
This results in the pasture or other nearest veterinary
expulsion of the foetus. food. officer.
Also servicing bull
and flies can
transmit it.
Anthrax Bacterium Cattle, i. Blood stained Through contact (i) Vaccination.
(Baccilus sheep and discharged from with infected (ii) Burn and bury
anthracis) goat nostrils and mouth. animals or the deeply any
ii. Swelling in the neck, products from diseased animal.
genital and lower them.
abdomen.
iii. In acute cases, the
only symptom is
death of the animal.
Ringworm Fungus All i. Lesions or scars It is spread by (i) Good hygiene.
animals develop on the contact. (ii) Affected areas
animal skin. should be treated
ii. This causes irritation. with iodine.
iii. Hair falls off.
iv. Gray patches on the
comb and wattle of
birds.
Hog cholera Virus Pig i. High fever. Through (i) Vaccination.
ii. Loss of appetite. contaminated (ii) Kill and bury
iii. Sticky discharges substances e.g. infected animals.
from the eye. faeces, urine and
secretions from
nostrils, eyes and
mouth.
Tuberculosis Bacteria Cattle, Persistent cough, loss of Droplet infection Kill and bury deeply
(mycobacterium poultry, weight. through air, close infected animals.
tuberculosis) pigs contact with
sufferer or
contaminated
materials.
Scabies Fungus Cattle, Loss of skin and By touching Maintain high level of
goat, destruction of skin. affected parts of cleanliness in the
sheep Reduced productivity animals or houses. Dip animals in
bedding. lindane solution.

Example
A pandemic is an outbreak of diseases that
A. is confined to a town B. is widespread C. will not spread D. has limited spread (2016/36)
Answer: B – Pandemic is an outbreak of a disease that is wide spread.
Example
Which of the following diseases is caused by a fungus?
A. Cholera B. malaria C. measles D. ringworm (2002/47 Nov)
Answer: D – Ringworm is a disease caused by fungus.
Example
The vector f trypanosome is the
A. black fly B. cockroach C. housefly D. mosquito E. tsetse fly (2001/47 Neco)
Answer: E – The vector of trypanosome is the tse-tse fly
Example
Rinderpest is a disease of farm animals caused by
A. bacteria B. fungi C. nematodes D. protozoans E. viruses (2005/30 Neco Nov)
Answer: E– viruses

439
EXERCISE 21.4
1. The causative organism of sleeping sickness is the
A. Trypanosome B. Vibro bacterium C. pennicilium D. tsetse fly (2019/43 NABTEB)
2. In the life history of Schistosoma (Bilharzia) one of the following is the intermediate host
A. man B. snail C. mosquito larva D. crayfish E. fish (1978/15)
3. Which of the following diseases is NOT caused by a virus?
A. Rinderpest B. Maize rust C. Newcastle diseases
D. Swine fever E. Cassava mosaic disease (1983/22)
4. 1(a)(i) List two diseases each of plants and animals caused by bacteria (ii) State three ways in which
bacteria are useful (1993/1ai, ii)

PEST AND DISEASE OF CROPS

Pests are organism which causes harm or damage to plants and animals and also destroy crops as well as lower the
quality of their products.
Some pests carry pathogens (disease organism) that tend to harm or damage plants and animals.
TYPES OF CROP PEST
Crop pests are grouped into the following;
i. Insects iii. Rodents v. Man
ii. Birds iv. Monkeys vi. Nematodes

Pest could be plants or animals. Pests in form of plants are called weeds where as animal pests could be vertebrates or
invertebrates. Vertebrate pests include animals such as birds, rats and other small rodents. Invertebrate pests included
aphid, beetle, mollusc, grasshopper e.t.c

Classification of pest, crop attacked, nature of damages, Prevention and control

INSECT CROPS NATURE OF DAMAGE, PREVENTION AND
PESTS AFFECTED ECONOMIC IMPORTANCE CONTROL
1. Stem borer Cereals e.g rice, Larvae bore holes into stem i. Uproot infected crops
maize e.t.c Reduce growth and yield ii. Spray with insecticides
2. Pod borer Legumes e.g cowpea, Larvae bore into pod i. Crop rotation
soyabeans Reduce yield ii Early harvesting
ii. Spray with insecticides
3. Leaf beetle Legumes They eat up leaves, i. spray with insecticides
Reduces yield ii. Use resistant varieties
4. Yam beetle Tubers e.g yam Bore holes into yam tubers Crop rotation
Reduces market value
5. Cassava mealy Tubers e.g cassava Twisting of stem and swelling i. Early planting
bugs of shoots ii. Use resistant varieties
Reduced yield iii. Spray with insecticides
6. cotton Cotton stainer Leaf distortion Hand picking
Reduced quality of boll Spray with insecticides
Pierce and suck sap from plant
7. Leaf beetle Vegetables They eat up leaves and stems Spray with insecticides
Reduced yield
8. Bean beetle, Stored produce e.g Bore holes into grains i. Early harvesting
grain weevils rice, beans, maize Reduce the quality ii. proper storage of produce
e.t.c Reduced market value iii. fumigation of store
9. Birds Rice, maize, millets, Feed on grains in the field Early harvesting
sorghum, banga Reduce income Scare them away
Rodents Rice, yam, cassava, They feed on crops Use of traps
fruits, maize. Reduce yield Use of poison baits
10. Monkeys Cocoa, mango, They eat up fruits Use of traps
banana, orange They cause loses to farm Shoot with gun

Example
Which of the following are not causative organisms of plant diseases?
A. fungi B. viruses C. bacteria D. nematodes E. cercariae (1988/39)
Answer: E – Carcariae is not a causative organism of plant disease. Carcariae is a larva of parasitic flukes. It is a parasite of
animals.
440
Example
(c) Name two viral diseases each of (i) plants; (ii) animals (2017/1ci)
Answer:
i. Viral diseases of plant ii. Viral disease of animal
Cassava mosaic Small pox
Rosette diseases Common cold
Example
Which of the following group of crop disease is caused by bacteria?
A. Rust, smut, and aspergillosis B. Mosaic, mildew and leaf curl C. Blight, rust, mosaic
D. leafspots, blight and soft root E. black pod, rust and mosaic (1998/51 Nov)
Answer: D – leaf spots, blight and soft rots are diseases in plant caused by bacteria
Example
Which of the following groups of organisms causes blackpod disease?
A. Bacteria B. Bryophytes C. Protozoans D. Fungi E. Viruses (2007/6 Neco)
Answer: D – Fungi

EXERCISE 21.5
1. Which of the following crop diseases is caused by a fungus?
A. cassava blight B. cocoa black pod C. groundnut rosette D. potato wilt E. yam mosaic (2008/8 Neco)
2. Swollen shoot is a disease of
A. cassava B. cocoa C. groundnut D. maize E. rice (2005/54 Neco Nov)
3. In which of the following plants is swollen shoot disease common?
A. Groundnut B. Cocoa C. Corn D. Cotton E. Rubber (1981/38 JAMB)
DISEASE
A disease refers to a situation where there is an abnormality in health condition. Diseases causes damage to parts of
plants and animals and this may result to death in some cases

CAUSES OF CROP DISEASE

Diseases of crops are caused by the following agents:
i. Viruses iii. Fungi v. Nutrient deficiency
ii. Bacteria iv. Nematodes
Some disease of crops
NAME OF DISEASE CASUAL METHOD OF SYMPTOMS AND ECONOMIC PREVENTION AND CONTROL
ORGANISM TRANSMISSION IMPORTANCE
1. Maize smut, maize Fungus Air borne Spores Reduction in yield Use of resistant varieties
rust deposited on fruits Spots on leaves Crop rotation
Death of the crop Early planting
2. Rice blight Fungus Air borne Spores on Small longitudinal red spots Use clean seed
leaves on leaves Use resistant varieties
Reduced yield
3. Onion twister Fungus Infected soil, Twisting of leaves Crop rotation
disease infected bulb Reduction in yield Spray with fungicides
Death of plant
4. Cassava mosaic Virus Infected plant Molting of leaves Use resistant varieties
cuttings Stunted plants Use disease free stem
Reduction on yield cutting
5. Black arm (bacteria Bacterium Through leaves Spots on leaves Crop rotation
blight of cotton) Stems near the Retarded growth Use resistant varieties
ground Reduction in yield Destroy infected plants
6. Rosette disease of Virus Aphid Shortening of internodes Early planting
groundnut Wilting and death of plants Crop planting
Use of insecticides
7. Cocoa black pod Fungus Rain splash Brown spots on pods Destroy infected pods
disease Insects Pod turn black Spray with fungicides
Low yield
8. Root knot of Nematode Infected soil Knotting of roots Use resistant varieties
tomato and okro Reduced yield Uproot and burn infected
plants
9. Stored produce fungus High humidity Black mould on seeds and Remove contaminated seeds
mould Infected soil fruits before storage.
Sour taste Proper drying before storage
Decay of stored products Spray with fungicides

441
Control of pests
Pest control refers to management and prevention of spread of pest, thus minimizing their effects and maximizing
food production. This could be achieved by taking measures to reduce the pest population through the use of
pesticides and farm practices that would not favor multiplication of the pests. Farm practices such as crop rotation,
use of resistant varieties, mixed cropping and use of biological agents could be adopted for controlling pest.

Apart from these, a number of pest control methods are available. This includes;
1. Physical method 3. Biological methods 5. Integrated pest management
2. Cultural methods 4. Chemical methods
1. Physical method: This method involves hand picking the pests and killing them physically. This method is
applicable to large sized pests such as snails and beetles. It could be carried out on small plots but it is a
tedious and strenuous process.

2. Cultural method: This involves farm practices such as bush fallowing, crop rotation and mixed
cropping. This method is effective because most pests are specific to crops. By this method, infected crops
are removed and burned and the cultivation of resistant varieties is encouraged.

3. Chemical method: This involves the use of pesticides such as insecticides, fungicides, herbicides and
rodenticides. This method is effective but is now being discouraged as a result to the fact that the pests
become resistant to the pesticides with time. Important and useful soil organism may also be affected.

4. Biological control: This involves the use of predators or parasites on the pests. Extract from plants sources
are also used in pest control. In biological pest control, the pest population is reduced using natural enemies.
Biological control is long lasting and is not expensive.

5. Integrated pest management (IPM): This is an effective and environmentally sensitive method of pest
control. It relies on the combination of control practices and knowledge of the life cycle of the pest.

Example
The control method of pests using predators is called
A. biological B. chemical C. cultural D. mechanical E. physical (2018/52 Neco)
Answer: A – Control method of pest using predators is called biological method.
Example
Which is the most ecologically viable method of insect pest control?
A. draining all stagnant pools of water B. eliminating one of the development stages of the insect
C. employing a lot of labourers to physically handpick the insects pests
D. erecting physical barriers against insect pests
E. using stronger insecticides which can kill a greater number of insects (2001/50 Neco)
Answer: B – Eliminating one of the development stages of the insect

EXERCISE 21.6
1. The use of predators to control the population of pests is best described as control
A. biological B. chemical C. mechanical D. physical E. systematic (2001/51 Neco)
2. Which of the following is NOT a method of pest control?
A. Biological B. breeding of resistant varieties C. crop rotation
D. monocropping E. use of pesticides (2005/33 Neco Nov)
3. c. i. State six pests of crops.
ii. Name three diseases of plant caused by bacteria and virus. (2017/3c NABTEB)
4. The use of predators in a farmland is known as
A. biological control B. parasitic control C. physical control D. physiological control (2001/21 NABTEB)
5. Biological control of pest depends on
A. the predator – prey relationship in the ecological community B. how much biology the farmer knows
C. the plant and animal relationship in biology
D. the presence of poisonous organisms and animals on farms (1999/50 NABTEB)

442
LIFE CYCLE OF PEST
Most insects have the following stages in their life cycle, namely; adult, egg and larvae. The adults feed mostly on
leaves of crops and fruits. The adult female lay eggs, which are either attached under the leaf surfaces, bark, stem or
branches. The eggs hatch into larvae which are without legs and segmented.

The larvae chew through the bark and feed on the phloem thus causing damage to plants. The larvae often pupate
when fully developed and further develops into adult which emerges by chewing their way out through the bark
leaving holes which could serve as avenues for entry of disease causing agents. Some crop pest show complete
metamorphosis while other show incomplete metamorphosis
Metamorphosis is defined as the series of gradual changes of forms and shape of an insect from fertilized egg
(immature stage) to adult (mature stage/adulthood).

TYPES OF METHAMORPHOSIS
1. Complete metamorphosis: This is the series of gradual changes which takes place in insect from fertilized
eggs to larva, then to pupa and finally to the adult stage.
Complete metamorphosis involves four stages which are: Eggs → Larva → Pupa → Adult
Examples of insect pests which exhibit complete metamorphosis include butterfly, bees and beetles note:
others are housefly, mosquito wasp etc.

Incomplete metamorphosis is the series of changes in insects that takes place from fertilized eggs to nymph and
finally to the adult stage.
Incomplete metamorphosis involves only three stages they are: Eggs → Nymph → Adult. Examples of insects
which exhibits incomplete metamorphosis include grasshopper, locust, aphid, termites which are pest of crops.
Others are cockroach, dragon fly, praying mantis, locust etc.

Differences between complete and incomplete metamorphosis

COMPLETE METAMORPHOSIS INCOMPLETE METAMORPHOSIS
1. Four stages of development are involved Three stages of development are involved
2. There is presence of pupa (resting stage) There is absence of pupa (no resting stage)
3. There is no resemblance between pupa and adult There is resemblance between nymph and adult
4. There is absence of nymph e.g. beetle, moth, Nymph is present e.g. grasshopper, termite, aphid etc.
butterfly e.t.c.

Example
Pests can be controlled without the subsequent danger of polluting the ecosystem by
A. introducing a population of species similar to that of the pest
B. increasing the population of the natural enemies of the pest C. eliminating the natural enemies of the best
D. keeping the population of natural enemies of the pest constant E. spraying the ecosystem with pesticide (1989/29)
Answer: B – Increasing the population of the natural enemies of the pest.

Example
The use of predators or parasites to control pests in the farm is known as
A. predator control B. chemical control C. biological control D. animal control E. parasitic control (1993/42)
Answer: C – The use of predator or parasite to control pest in the farm is known as biological control.
Example
The process is which insects undergo conspicuous changes in form and appearance during development is known as
A. ecdysis B. metamorphosis C. aestivation D. migration E. hibernation (1994/5)
Answer: B – The process in which insects undergo conspicuous changes in form and appearance during development
is known as Metamorphosis.
NB: Ecdysis is the shedding of the outer covering of the skin or exoskeleton in some animals. it is also called
moulting.
Example
2(a) (i) Define the term metamorphosis
(ii) Name the two types of metamorphosis that organisms undergo and mention two organisms that undergo each type
(b)(i) State four economic importance of insects and name an example of each of the insects involved.
(ii) List four peculiar features of social insects. (1999/2a, b)

443
Answer:
2ai. Metamorphosis is defined as the series of gradual changes of forms and shape of an insect from fertilized egg
(immature stage) to adult (mature stage or adulthood).
ii. - Complete metamorphosis e.g. housefly and mosquitoes.
- Incomplete metamorphosis e.g. grasshopper and termites.
b. Economic Importance of Insects
- They serve as pollinating agents of flowering plants (e.g. bee, ant, butterfly, beetle etc).
- They act as pest and are destructive to plant or stored food (e.g. locust, weevil etc).
- They acts as carrier, vectors or transmitters of diseases (tsetsefly, anopheles mosquito etc.)
- Serve as food or source of protein (e.g. termites, honey, cricket, grasshopper etc).
ii. Peculiar features of social insects
- They show distinct castes. , -They live in nest. - They show or display division labuor
- They live together or form colonies

EXERCISE 21.7
1. Trypanosomiasis is associated with
A. cockroach B. mosquito C. housefly D. tse tse fly (2000/52)
2. The following insects undergo incomplete metamorphosis except
A. termite B. cockroach C. butterfly D. locust (2004/23)
3. Which of these insects undergoes incomplete metamorphosis?
A. Beetle B. Butterfly C. Cockroach D. Housefly E. Mosquito (2007/40 Neco)
4. Which of the following insects undergoes incomplete metamorphosis?
A. Mosquito B. Termite C. Housefly D. Moth (1992/9 JAMB)
5. Which of the following are not causative organisms of plants diseases?
A. fungi B. viruses C. bacteria D. nematodes E. cercaride (1988/39)
6. Maize is best stored against insect attack
A. on raised platforms B. in fumigated soils C. in a sunny area
D. warming the food daily E. salting and drying the food (1989/33)
7. Predators are beneficial in pest control because they
A. are natural enemies of small mammals B. devour farm animals C. feed on pests of crop
D. prey on game animals E. compete for food with the pest (1991/47)
8. Which of the following is the underlining principle in the adaptation of biological control of pests?
A. Knowledge of agricultural practices by the farmer B. Relationship between plants and animals
C. The presence of poisonous chemicals in the farm
D. The relative population of plants and animals in the farm
E. The predator – prey relationship in the ecological community (1993/44)
9. Which of the following plant disease is indicated when grains of cereals are covered with a mass of spores?
A. smut B. mosaic C. maize streak D. fungal blast E. rust (1994/50)
10. When a farmer sprays crop with a pesticide, the pesticides becomes
A. poisonous to all plants B. is broken down by soil algae
C. easily washed down into lakes and rivers D. absorbed by bodies of mammals (2004/42)
11. The following organisms are pests of plants except
A. birds B. nematodes C. bacteria D. rodents (2013/44)
12. Which of the following groups of crop disease is caused by bacteria?
A. Rust, smut and aspergillosis B. Mosaic, mildew and leaf curl Blight, rust and mosaic
C. Leaf spots, blight and soft rot D. Black pod, rust and mosaic (1998/51 Nov)
13. The use of predators, to control the population of pests is best described as ____ control
A. biological B. chemical C. mechanical D. physical E. systematic (2001/52 Neco)
14. The control method of pests using predators is called
A. biological B. chemical C. cultural D. mechanical E. physical (2018/52 Neco)
15. Which of the following groups of organisms causes black pod disease?
A. bacteria B. bryophytes C. protozoans D. fungi E. viruses (Neco 2007/6)
16. List two diseases each of plants and animals caused by bacteria. (1993/19)
17. Define the term metamophorsis. (2019/6e)
18. 2(ii) Name the two types of metamorphosis that organisms undergo and mention two organism that
undergo each type. (1998/2aii)
444
Food Production and Storage
Food production involves the cultivation of crops and rearing of animals or livestock to meet human nutritional
requirements. Food production requires arable land – which is a land that is suitable for agricultural operations.
Ways of improving crop yield
1. Development and use of high-yielding varieties of crops.
2. Use of fertilizers such as N.P.K, farm yard manure and green manure. These raise the nutrient status of the
soil for crop use thus leading to increase in the yield of crops harvested per unit area.
3. Adequate tillage practices: Soil tillage is necessary because:
i. It increases the ability of the soil to absorb water.
ii. Prepare a seed bed for crops.
iii. Admit air to the soil.
iv. Remove weed.
v. Enhances proper root development.
Tillage must be done in such a way as to avoid damage to soil structure. Over tilled soil can lead to land
erosion.
4. Proper time should be set for farming operation so as to ensure improved yield.
5. Adequate water supply: Water should be supplied through irrigation system to supplement insufficient
rainfall.
6. There should be pest and disease control to ensure good crop yield.
7. There should be proper weed control measures to ensure good growth and good yield of food materials. Weed
control through chemical, physical and biological method are necessary to ensure good crop yield.
Causes of food wastage
1. Inadequate storage: Food storage can result if there are no modern storage facilities such as silos for grains
and cold store for animal products and vegetables.
2. Inadequate and untimely harvesting of agricultural products.
3. Poor preservation of agricultural products. i.e. lack of proper drying of crops such as grain before storage.
4. Pest infestation: This affects both stored grains or crops and those in the field before harvesting.
5. Processing of agricultural product also causes wastage since most of the crops are lost and wasted during the
processing operation.
6. Separation of edible from non edible parts of crops also causes wastage e.g. peeling of yam tuber, cassava
tuber and fruits such as mango and pineapple etc.
7. Inadequate transportation resulting from bad road and dilapidated motor vehicles. This can make the crops to
go bad before getting to their destination.
Methods of preserving and storing food
1. Use of silos
2. Use of cribs
3. Use of refrigerators and cold room
4. Use of barn
5. Use of boxes and underground pits or trenches
6. Use of basket, bins and roof of building
7. Use of bags and sacks
8. Freeze-drying: In this method, the food is first frozen rapidly under vacuum pressure. Then it is heated
carefully. The ice crystals in the food sublime to form vapour which is then removed. The dried food is then
packed in an inert gas like nitrogen in moisture proof container.
9. Canning: The food is first prepared after cleaning. Air is then removed from it before it is sealed in air-tight
containers. Then the containers are heated to a high temperature for a given period of time before they are
cooled. Food such as meat, fish, milk and vegetables are heated to about 116oC, while fruits are heated to
about 100oC. This process kills all spoilage microorganisms and keeps air away from the food, preventing any
chemical changes.
10. Pasteurization: This method is mainly used in the preservation and processing of milk. Pasteurization
involves the heating of milk to a temperature of 72oC for 15 seconds and cooling rapidly. This destroys most
of the microorganism, thereby allowing the milk to be kept for a longer time.
11. Chemical preservation such as use of salt, sugar and vinegar: Salt is used for salting and this method is
used to preserve beef, pork and fish. Vinegar is used to pickle vegetables, meat and fish. As it is an acid, it
gives a sour taste to the preserved food and growth of microorganism is slowed down by the acid medium of
the food. Fish and meat can be preserved by smoking in most cases. If this process is combined with salting
and drying, it is known as curing. Ham and bacon are prepared by curing.
12. Fermentation: Fermentation is carried out by microorganisms under special conditions. This process is often
combined with salting. Fruits and vegetables are preserved by this process.
13. Irradiation: This kills microorganisms and parasites hence it is used to sterilize food and prolong its keeping
quality.
445
Example
Which of the following is a traditional method of food preservation?
A. Heating B. Freezing C. Smoking
D. Adding chemicals E. Keeping in silos (1996/34 Health Science)
Answer: C – Smoking is a traditional method of food preservation.

Example
Which of the following methods is used in food preservation for a long period?
A. Adding oil to food B. Exposing food to fresh air C. keeping the food in a store
D. Warming the food daily E. Salting and drying the food (1989/32)
Answer: E – Salting and drying food is used for food preservation for a long period
Example
All these methods can be used to completely eradicate microbes EXCEPT
A. freezing B. sterilization C. drug D. ultraviolet radiation (1999/49 NABTEB)
Answer: A – Freezing cannot be used to completely eradicate microbes.
Example
In which of the following are food grains best preserved?
A. Silos B. Sacks C. Refrigerators D. Ovens E. Baskets (1992/46)
Answer: A – Silos are structures used in storing food grains.
Example
Which of these methods is a modern way of food preservation?
A. drying B. frying C. refrigeration D. salting E. smoking (2007/46 Neco)
Answer: C – Refrigeration is a modern way of food preservation
Example
Pathogenic micro-organisms in milk can be killed through
A. antiseptics B. dehydration C. high salinity D. pasteurization (2019/41 NABTEB)
Answer: D – Pathogenic organisms in milk can be killed through the process of pasteurization
Example
Method of food preservation involves the following except
A. soaking B. salting C. smoking D. refrigerator (2001/49)
Answer: A – Soaking is not a method of preservation.
Example
(d)(i) List four bacteria diseases associated with poor food hygiene. (2018/6d)
Answer:
Food poisoning, Hepatitis, Typhoid, Tuberculosis, Cholera and Dysentry

EXERCISE 21.8
1. In food preservation, methods used are intended to inhibit bacterial growth to prevent spoilage. Which of the
following is not applicable?
A. Salting B. Hydrating C. Smoking D. Freezing (2004/46 Nov)
2. Pasteurization is concerned with the
A. growing of microbial culture B. killing of micro-organisms in milk
C. breeding of cattle in pasture D. extraction of milk from cows
E. stimulation of vital growth in cells (1997/49 Nov)
3. Which of these methods is a modern way of food preservations?
A. Drying B. frying C. refrigerating D. salting E. smoking (2007/46 Neco)
4. The following are ways of preserving food except
A. Boiling B. canning C. drying D. freezing E. salting (2005/60 Neco)
5. Dehydration as a method of food preservation
A. prevents the activity of micro-organisms in food B. increases the nutrient value of food
C. improves the taste of food D. makes food more attractive (2003/28 Health Science Nov)

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Population growth and food supply:
Population is the total number of people living in a place or an environment at a particular time. Food supply does not increase at
the same rate as population growth. Many factors are responsible for population increase. This includes:
1. Improvement in medical care: There is low death rate while birth rate is increasing because of medical improvement.
Medical programmes e.g. Expanded Programme on Immunization (EPI) and Oral Rehydration Therapy (ORT) has
reduced death of children.
2. Improved feeding habit: This has lead to increased fertility among the population.
3. Early marriage and lack of birth control measure.
Relationship between availability of food and human population: Adequate food supply leads to increase in population growth
because it will promote good health and proper growth and development. Limited food supply can lead to deficiency and
infectious diseases and this can reduce energy for hard work. Inadequate food supply can also lead to high mortality rate in the
population and as a result, population growth will be reduced.
Effects of food storage
1. It ensures even and regular supply of food throughout the year.
2. There is reduction in quality in stored food because of pest attack.
3. Viability of products e.g. seeds is reduced due to storage. Most pest and disease destroy viable seeds in the store.
4. Sometimes the taste and quality are improved due to storage, e.g. yam tubers taste better when stored in the barn.
5. Storage sometimes after texture of some food. For example meat stored for a very long time in cold storage.

Government efforts to increase food production

The government has set up some special programme to ensure that there is an increase in the productivity of food for the nation,
some of these programmes include:
1. The operation feed the nation programme.
2. The green revolution programme.
3. Agricultural development project.
Ways of maintaining food hygiene
1. Proper harvesting or storage methods must be ensured to prevent damage of food item.
2. Food items must be properly washed/clean to prevent contamination.
3. Food items must be properly cooked at appropriate temperatures.
4. Kitchen or cooking areas must be kept clean always.
5. Perishable food items must be properly preserved or refrigerated.
6. Proper personal hygiene must be observed by those handling food.
7. Cooking utensils must be properly washed or cleaned before and after use.
8. Cooked or prepared food must be covered at all time.
9. Proper disposal of unused or leftover food.
Example
Which of the following ecological factors causes food shortage?
A. low rate of reproduction B. emigration C. drought D. topography E. wind direction (1995/58)
Answer: C – Drought is a prolonged shortage of water supply. Water is an important factor for seed germination and plant
growth; hence when water is not available, crops cannot grow neither can they produce food.
Example
What has NO effect on the food shortage of a population?
A. Cannibalism B. competition C. increase in mortality D. increase in natality E. Migration (2001/44 Neco)
Answer: A – Cannibalism – This is the act of consuming another individual of the same species as food. Cannibalism is a
consequence of food shortage and not a cause of it.
Example
A major effect of food shortage on the population is
A. increased mortality rates B. co-operation among siblings
C. high productivity D. effective mobilization towards growth (2004/42 Nov)
Answer: A – A major effect of food shortage on the population is an increase in mortality rate.
Example
Which of the following conditions would lead to an increase in the size of an animal population?
Food supply Predation Disease
A. Decreased Decreased Increased
B. Decreased Increased Increased
C. Increased Decreased Decreased
D. Increased Increased decreased (2004/43 Nov)

Answer: C – Animal population will increase in size when there is an increase in food supply and a decrease in predation and disease.
EXERCISE 21.9
1. Food shortage leads to reduction in population size due to the following except
A. competition B. disease C. emigration D. immigration E. mortality (2014/24 Neco)
2. The scarcity of food causes a sudden decrease in population size by
A. raising the mortality rate B. minimizing the rate of competition
C. decreasing the reproductive rate D. bringing about immigration (2004/6 JAMB)
3. (c) Explain three ways by which the government may increase food production. (1999/5c)
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Microorganisms around us and towards better health
Microorganisms or microbes are minute organisms that are visible only with the aid of a microscope. The study of
microorganisms is a branch of biology known as microbiology.
Microorganism are found everywhere, in the air, soil, water, on our bodies, clothes e.t.c. some are beneficial while
others are harmful

GROUPS OF MICROORGANISMS
1. Viruses 3. Some Algae 5. Some Fungi.
2. Bacteria 4. Protozoa
Viruses:
Viruses are non-cellular microscopic organisms which can only be seen with the aid of an electron microscope. A
virus cell is made up of a coiled strand of nuclei acid enclosed within a protein coat, this infectious particle is called
Virion
Viruses may be classified as either DNA or RNA virus depending on whether they possess a DNA or an RNA. An
example of a DNA virus is the herpes virus while an RNA virus is the polio virus.
Virus is a small parasite that cannot reproduce by itself but once it infects a susceptible cell, the virus can redirect the
cell process to produce more viruses. Outside a living host, they are non-living and appears as crystals other examples
of viruses are adenovirus, picornavirus, togavirus and coronavirus. Example of diseases caused by viruses are
influenza, poliomyelitis, measles, COVID-19, AIDS, tobacco mosaic diseases etc.
Viral diseases of humans include poliomyelitis/polio, chicken pox, mumps, measles, influenza/flu, AIDS, Ebola,
infective hepatitis, lassa fever, Avian influenza or Bird flu, COVID-19. Viral disease of animals include Rinder
pest of cattle, Newcastle of chicken and rabies in dogs and cats.

Viral disease of plants is as follows cassava mosaic, bean mosaic, cocoa swollen shoot, groundnut rosette, maize
streak, cucumber mosaic.

Human Immunodefiency Virus

Example
Which of the following is a microorganism?
A. Ant B. maggot C. mosquito D. pinworm E. virus (2014/3 Neco)
Answer: E – Virus is a microorganism.
Example
Which disease is caused by a virus?
A. cholera B. measles C. tetanus D. typhoid E. tuberculosis (2001/52 Neco)
Answer: B – Measles is a disease caused by a type of virus called a Paramyxovirus.
NB: Cholera, tetanus, typhoid and tuberculosis are diseases caused by bacteria.
Example
Viruses are pathogens of the following diseases except
A. measles B. small pox C. poliomyelitis D. tuberculosis (2003/45)
Answer: D – Tuberculosis is caused by a bacteria.
Example
Viruses are economically important because they
A. do not have cell structures B. can only reproduce inside living cells
C. cause disease in plants and animals D. exits as crystals outside the living cell (2009/2)
Answer: C – Viruses are economically important because they cause diseases in plant and animals.
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Example
State two features each which viruses have in common with (i) living things (ii) non – living things. (2017/1b).
Answer:
1bi. Features that viruses have in common with living things:
- Reproduce when inside a living cell.
- Respire when inside a living cell.

ii. Features that viruses have in common with non-living things:

- Appear as crystal.
- Have no cytoplasm or cellular organelles.

Example
A virus can sometimes be regarded as a living organism because it
A. causes disease in plants and animals B. exists in a variety of shapes
C. reproduces in living cells D. is easily visible with the aid of an electron microscope. (2005/3)
Answer: C – A virus can sometimes be regarded as a living organism because it reproduce in living cells.
Example
List five groups into which microorganisms can be classified. (1992/29 Nov)
Answer: 1. Viruses , 2. Bacteria , 3. Algae, 4. Protozoa, 5. Fungi.
EXERCISE 22.1
1. (c) Why is virus classified as a living thing? (2001/1c NABTEB)
2. Which of these diseases is caused by a virus?
A. cholera B. measles C. tetanus D. tuberculosis (2019/42 NABTEB)
3. One basic characteristic feature of viruses is that they grow
A. As colonies B. as jelly-like material C. in culture media
D. inside living cells E. on dead cells (2005/6 Neco)

4. Name two viral diseases each of (i) plants (ii) humans. (2017/1c)

Bacteria
These are unicellular organisms that cannot be seen with the unaided eye. They can be seen with the light microscope.
Bacteria was first discovered by Van Leeuwenhoek in 1683.

A typical bacterium consists of a cell that might be covered with a slimy capsule, a cell wall, a cell membrane, dense
cytoplasmic granules and a nuclear material (deoxyribonucleic acid DNA) that spreads through the cell.

Bacteria
TYPES OF BACTERIA
Bacteria are grouped on the basis of two major factors:
1. Bacteria based on the use of oxygen
2. Bacteria based on their shape

Bacteria based on the basis of the use of oxygen are:

1. Aerobic bacteria: These are bacteria that require oxygen for their respiration.
2. Anaerobic bacteria: These are bacteria which do not require oxygen for their respiration.
3. Facultative bacteria: These are bacteria that can live under aerobic and anaerobic condition.

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Bacteria based on their shape:
1. Cocci: These are bacteria that are spherical or rounded in shape. Some may stick together to form a chain,
hence they are referred to as streptococci e.g. sore throat bacteria. Some occur in cluster form and are called
staphylococci e.g. boil bacteria. Others stick together in pairs and they are called Diplococci e.g. bacteria that
can cause pneumonia. Where bacteria occur in group of four, they are called tetrads.
2. Bacilli: These are bacteria cells that appear rod like in shape. Some may possess flagella which they use for
movement e.g. bacteria that cause typhoid fever.
3. Vibrio: Vibrio are curved in shape, just like comma e.g. cholera bacteria
4. Spirillae: Spirillae are twisted bacteria. Some are mobile e.g. syphilis bacteria.

Different shapes of bacteria

Some diseases caused by bacteria
Disease Causative organs Mode of infection
Gonorrhea Neisseria gonorrhea (gonococcus) 1. By sexual intercourse
2. Transmission from mother to child (congenital).
Syphilis Treponema pallidim 1. Sexual intercourse.
Cholera Vibrio cholera 1. Drinking of infected water.
2. Eating of infected food.
3. Through houseflies that carry germs to food.
Tuberculosis Mycobacteria tuberculosis 1. Personal contact with an infected person.
2. Consumption of infected water and food such as
meat or milk of an infected cow.
3. Inhalation of contaminated air or dust.
4. Flies also carry the germs to our food.
Dysentery Dysentery bacillus 1. Drinking infected water or eating an infected food.
2. Through flies that spread the germs by conveying
them from infected faeces to our food.

Example
Which of the following organisms causes syphilis?
A. Mycobacterium tuberculosis B. Bordetella pertusis C. Treponema Pallidium D. Clostridium tetani (2005/21)
Answer: C– Treponema Pallidium

Example
Bacteria, which derive energy by oxidizing certain inorganic compounds, are said to be
A. chemosynthetic B. holozoic C. parasitic D. photosynthetic E. saprophytic (2001/20 Neco)
Answer: A – Bacteria which derive energy by oxidizing certain inorganic compound are said to be chemiosynthetic.
Example
Which of the following diseases is not caused by bacteria?
A. tuberculosis B. cholera C. leprosy D. measles (2004/44 Nov)
Answer: D – Measles is caused by a virus.

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Example
The diagrams below represent the shape of the major groups of bacteria. Use the to Answer: question 45

The groups staphylococci and streptobacilli are represented by

A. I and II B. II and IV C. III and VII D. IV and VII E. IV and VIII (1995/45)
Answer: D – IV = Staphylococci; VII – Streptobacilli
NB: To Answer: this question correctly, you must be familiar with the various shapes of bacteria.
 Coccus (plural cocci) – arc round shaped bacteria.
 Bacillus (plural bacilli) – are rod-shaped bacteria.
 Spirilla/spirochete – are spiral in shape
 When cocci are attached ends to ends to form a straight chain they are known as streptococci.
 When cocci are clustered together, they are known as staphylococci.
 When bacilli are attached ends to ends to form a straight claim, they are known as streptobacilli.
 When two cocci are attached to each other, they are known as diplococci.
 When two bacilli are attached to each other, they are known as diplobacilli.
Example
The strand of nucleic acid structure B is A. injected into a host cell during feeding. B. Either DNA or Which of the
following statements is not correct about bacteria?
A. Bacteria in the intestine of man digest cellulose B. They are used in the process of n cheese, vinegar and silage
C. Bacteria are used in tanning, curing of tobacco and tea
D. They aid the process of fermentation in the baking industry
E. They are used in the treatment plants for water purification. (2020/3 PC3)
Answer: E – Bacteria are not used in the treatment plant for water purification.

EXERCISE 22.2
1. Which of the following statements is not correct about bacteria?
A. Bacteria in the intestine of man digest cellulose B. They are used in the process of n cheese, vinegar and silage
C. Bacteria are used in tanning, curing of tobacco and tea D. They aid the process of fermentation in the baking industry
E. They are used in the treatment plants for water purification (1992/55 Nov)
2. Which of the following diseases is caused by bacteria?
A. Athlete’s foot B. Measles C. malaria D. common cold E. cholera (1998/50 Nov)
3. Which of the following diseases is not caused by bacteria?
A. Tuberculosis B. Cholera C. Leprosy D. Measles (2004/44 Nov)
4. One disease NOT caused directly by bacteria is
A. malaria B. tuberculosis C. pneumonia D. tetanus E. cholera (1955/44 JAMB)
5. Bacteria multiply rapidly by means of
A. budding B. fragmentation C. binary fission D. spore formation (1999/27 JAMB)
6. The bacteria type that are arranged in chains are the
A. Staphylococci B. Clostridia C. Streptococci D. Bacilli (2008/7 JAMB)

ALGAE: Algae are microscopic green plants with the majority mainly found in aquatic environment e.g. Diatom,
spirogyra, volvox, chlamydomonas, oscillatoria, and Nostoc.

PROTOZOA: These microorganisms are microscopic, free living, unicellular animals e.g. amoeba and paramecium.
Some are parasites e.g. trypanosome which causes trypanosomiasis and plasmodium, malaria fever.

FUNGI: Fungi are saprophytic or parasitic non – green plants. The saprophytic fungi are beneficial while the parasitic
fungi cause different types of disease.

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Concept of Culturing
A culture is a collection of microbial cells growing on or in a medium. A medium (plural: media) is a solid or liquid
preparation containing nutrients for the culture (growth) of micro organisms. A culture media enables biologists to
study the features of micro organisms. The process of culturing involves making of sterile medium, inoculating,
incubating and examination.

A micro-organism culture can be grown from water, air, animals, plants and various parts of human body. Apart from
micro-organisms, living tissues and cells of multicellular organisms. The process of culturing involves making a
sterile medium, inoculating, incubating and examination. A micro-organism culture can be grown from water, air,
animals, plants and various parts of human body. Apart from micro-organisms, living tissues and cells of multicellular
organisms can also be cultured in a suitable media. This technique is however referred to as tissue culturing.

Preparation of Culture Solution

The culture medium for growing micro organisms consists of:
A. Agar (an extract from red algae)
B. Various nutrient usually in the form of yeast extract, beef extract or vegetable juice.

There are many types of culture media. This is due to the fact that micro organisms have different nutritional
requirements and their survival is restricted to certain environmental conditions.

Instruments required for the preparation of culture:

1. Microscope 4. Slide 7. Inoculating needles or loop
2. Sterile petri-dish 5. Cover slips 8. Inoculating chamber
3. Test-tube 6. Hand lends

Procedures in preparing culture solution

1. Agar is produced under sterile condition.
2. Boil the agar and pour it into a sterile petri-dish
3. Allow it to cool and set in the petri-dish
4. A heat sterilizer may be used to kill microorganisms in petri-dish
5. The materials is then introduced into the agar medium and covered immediately.
6. Place petri-dish in a warm but dark compartment or an incubator.
7. Observe and record what you have seen for 2 – 3 days.

Precautions to be taken during preparation of culture solution

In culturing micro organisms, certain precautions/procedures are needed in order to prevent the introduction of
microbial contaminants from the surrounding such as air, water, apparatus, hands or clothes. These procedures are
known as aseptic techniques.

Aseptic technique involves using sterilized equipment and solutions and preventing their contamination while in use.
The following precaution should be strictly adhered to while culturing.

1. Wash hands with soap before and after preparation of agar solution.
2. Open Petri – dish slightly and cover at once
3. Close Petri – dish firmly with adhesive tape
4. Sick persons should not take part in culturing equipment
5. Avoiding talking, coughing, sneezing and touching of infested jelly
6. Unused agar should be sterilized by washing with antiseptic soap and disinfectant e.g. 40% of formaldehyde.
Heat can also be used to sterilize.
7. All instruments should be sterilized before the beginning of culturing solution preparation.

Identification of microorganisms
Microorganisms can be identified in the air, pond water, river and stream by preparing a culture medium.
The following procedure should be followed.
1. Five Petri – dishes with culture medium are labeled A, B, C, D and E respectively.
2. Expose Petri – dish A to air for about 10 – 15 minutes and then cover it.
3. Put in Petri – dish B a few drops of pond water and cover it
4. Put in Petri – dish C a few drops of river water and cover it
5. Put in Petri – dish D a few drops of stream water and cover it
6. Allow Petri – dish E to serve as control, that is do not introduce anything into it
7. Leave all Petri – dishes in the laboratory for 3 – 4 days
8. Observe all the Petri – dishes for any development and note any difference in each of the Petri – dishes.
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9. Record the characteristics (colour, pattern of growth, appearance) of colonies of microorganisms in each Petri
– dishes.
10. The recorded observation is then followed by class discussion.
Example
Which of the following diseases is NOT caused by micro organisms?
A. cholera B. gonorrhea C. anaemia D. tuberculosis E. syphilis (2005/36 Neco)
Answer: C – Anaemia is a condition in which the number of red blood cells or the haemoglobin concentration within
them is lower than normal.
Example
Many disease caused by bacteria can be treated and cured by using
A. antiseptics B. antibiotics C. antigens D. antibodies (2008/42)
Answer: B – Antibiotics are medicines that help to stop infections caused by bacteria.
Example
The detection of vibro cholera in public drinking water is a sign of
A. clean water B. outbreak of disease C. water pollution D. decayed organisms in the water (2012/47)
Answer: C– Detection of vibro cholera in public drinking water is a sign of water pollution.
Example
Only specially adapted micro-organisms are found in
A. salty water B. humid air C. moist soil D. mouth cavities (2005/20)
Answer: A – Only specially adopted micro-organism are found in salty water.

EXERCISE 22.3
1. Which of the following groups of organisms causes blackpod disease?
A. Bacteria B. Bryophytes C. Protozoans D. Fungi E. Viruses (2007/6 Neco)
2. Which of the following diseases is caused by a fungus?
A. Cholera B. malaria C. measles D. ringworm (2002/47 Nov)
3. An example of a parasitic protozoan is
A. Paramecium B. Plasmodium C. Euglena D. Chlamydomonas (2013/22 JAMB)

Micro organisms in our bodies and food:

Micro organisms are also found in or on our bodies such as mouth, in expired air, in the dirt under the nails as well as
in our food.

Experiment to show the presence of microorganisms in the dirt under the finger nail
1. Prepare sterile medium
2. Then use a sterile inoculating wire to pick some dirt under the nails.
3. Draw lightly in streaks on a sterile agar (culture medium) in the Petri – dish labeled A
4. Take every precaution to avoid contamination of the agar.
5. Cover the Petri – dishes immediately after streaking
6. Heat the inoculating wire to redness over a bursen flame and allow to cool
7. Then streak another sterile agar with the sterile inoculating wire, cover it and label it B to serves as control.
8. Place Petri – dish A and B in an inoculating incubator and examine them daily
9. It will be observed that clusters of bacteria will appear on the line of the streak in the Petri – dish A and
increase gradually in size.
10. There will be no growth on streaks in Petri – dish B which shows that growth in Petri dish A is from bacteria
introduced under the dirt in the finger nails.

Experiment to show the presence of microorganisms in the teeth or mouth

1. Prepare a sterile medium.
2. Use sterile cotton wool to clean the teeth very early in the morning i.e before brushing with toothpaste.
3. Then use platinum/inoculating wire to collect the extracts from cotton wool or chewing stick.
4. Draw lightly in streaks on a sterile agar in a Petri – dish labeled C.
5. Take every precaution to avoid contamination of the agar or culture medium.
6. Cover the Petri – dish immediately after streaking.
7. Heat the platinum wire to redness and allow to cool.
Follow the rest procedures as was done in the experiment above. The control should be labelled D

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Experiment to demonstrate the presence of microorganisms in expired or exhaled air
1. Prepare a sterile medium.
2. Then blow air from the mouth into the medium and then cover it immediately and label it Petri dish E.
3. Take every precaution to avoid contamination of the agar.
4. In another sterile medium, do not blow air into it and it will serve as control. This is labeled Petri – dish F.
5. Place Petri – dish E and F in a warm dark cupboard or incubator and examine them daily.
6. It will be observed that clusters of microorganisms culture (colonies) will appear on Petri – dish E and
gradually increase in size.
7. There will be no growth of micro organisms in Petri – dish F which shows that the growth formed in Petri –
dish E is from bacteria introduced through exhaled air from the mouth.
Experiment to show presence of microorganisms in food
1. Prepare a sterile medium
2. Scoop some portion of the food (e.g. yam, cassava or eba, fufu, rice, beans etc) with inoculating wire.
3. Draw lightly in streaks on a sterile agar in a Petri – dish labeled G.
4. Take every precaution to avoid contamination of the agar.
5. Cover the Petri – dishes immediately after streaking
6. Heat the inoculating wire to redness over a bursen flame and allow to cool
7. Then streak another sterile agar with the sterile inoculating wire, cover it and label it H to serves as control.
8. Place Petri – dish G and H in an inoculating incubator and examine them daily
9. It will be observed that clusters of bacteria will appear on the line of the streak in the Petri – dish G and
increase gradually in size.
10. There will be no growth on streaks in Petri – dish H which shows that growth in G is from microorganisms
introduced in the food.
Ways and places through which microorganisms enter the body
1. The mouth: Micro organisms will pass through the mouth when we eat contaminated food or drink
contaminated water.
2. The nose: Micro organisms will pass through the nose when we breathe in contaminated air.
3. The skin due to the presence of wounds.
4. Through the anus because it is an opening.
5. Through vectors such as mosquito and tsetse-fly.
6. Through blood contact i.e. sharp object and blood transfusion.
7. During child birth.
8. Through sexual intercourse.
Carrier of microorganisms
Carriers are agents which are capable of transferring or carrying micro organisms from one place to another. Non
living agents that carry micro organisms from place to place are air, water and food.
Animals are the living agents which transfer microorganisms from one place to another. They are known as vector.
Important living carriers of microorganisms, the microorganism they carry and the disease they cause;
Vectors/carriers Micro-organism Disease caused
1. Female anopheles mosquito Plasmodium Malaria fever
2. Tsetse fly Trypanosome Sleeping sickness
3. House fly Vibrio cholera Cholera and typhoid fever
4. Rat flea/body louse Rickettsia Typhus
5. Aedes mosquito Virus Yellow fever and dengue fever
6. Rat flea Bacterium Plague

Carrier’s use various parts of their bodies e.g. legs, wings, mouth parts, hairy bodies etc. to carry micro organisms.
Therefore microorganisms can be located in the mouth parts, legs, abdomen, wings and hairy bodies of insect.
Example
(a) (i) State six ways the body adopts as defense against diseases.
(ii) Name three parts through which disease-causing organisms enter into the body. (1998/4ai & iii Health Science)
Answer:
4ai. Ways the body adopts as defense against diseases: 4aii. Parts through which disease-causing
- Production of sweat. organisms enter into the body:
- Production of tears. - Broken/injured skin.
- Secretion of mucus. - The eye.
- Production of antibodies. - The mouth.
- Inflammatory response.
- Increase of body temperature (fever).
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Example
Which of the following organism causes syphilis?
A. mycobacterium tuberculosis B. Bordetella pertusis
C. Treponema pallidum D. clostrum tetani (2005/21)
Answer: C – Treponema pallidum is the organism that causes syphilis.
-

Example
Below is a list of microorganisms which are of economic importance to man. Use it to Answer: the questions.
I. Plasmodium II. Vibrio choleroe III. Gonococcus sp IV. Poliomyelitis virus V. Syphilis bacteria
Which of the following organisms are transmitted by houseflies?
A. I and II only B. II and V only C. III and IV only D. II and IV only E. III and V only. (1991/48)
Answer: D – II (Vibro choleroe) and IV (Poliomyelitis virus)
Example
(c) Describe an experiment to demonstrate the presence of bacteria under the finger nails. (1993/1c)
Answer:
Title : Experiment to demonstrste the presence of bacteria under the finger nails
Aim: To show the presence of bacteria under the finger nails.
Apparatus: Petri dish, blood agar, incubator, finger nails.
Procedures: Cut the finger nails and placed them in a petridish which have the blood agar. Then incubate at 37oCfor
two days.
Observation: It was discovered that colonies of bacteria were growing on the blood agar. On the application of
gram staining, clusters of cocci bacteria were visible.
Conclusion: The growth of coci bacteria indicate that bacteria are present under the finger nails.

Example
In a water culture experiment, the culture solution in a transparent beaker turned green. What precaution should have
been taken to prevent the culture solution from turning green?
A. Changing the culture solution regularly B. Increasing the number of times the culture is aerated
C. Covering the transparent beaker with black cloth D. Adding warm alcohol to bleach the green color
E. Sterilizing the beaker in a hot oven before use (1996/27)
Answer: C – Covering the transparent beaker with black cloth

Micro organisms in action

Growth of micro organisms
Microorganisms increases in size and multiply in number of cells using either culture medium provided or any suitable
surface such as moist bread as source of food. It can also increase in mass. Such increase in size and number of cells is
known as growth in microorganisms.
Ways of measuring growth in micro-organisms
When measuring the growth of population of bacteria or yeast, we can do it directing by counting the number of cells
or indirectly by measuring some indication of the number of cells such as cloudiness of a solution or production of a
gas.
1. In-direct method: This involves inoculating a bacteria sample into a nutrient agar. As the bacterial
population increases, the clear liquid medium becomes cloudy or turbid. Progressive increase in turbidity
indicates a relative increase in the number of bacteria cells. The turbidity is measured using a
spectrophotometer.
2. Direct method: In this method, small sample of bacteria are taken from nutrient agar at regular intervals.
Each sample is diluted several times. Each diluted samples is inoculated into a nutrient agar medium in a Petri
– dish and incubated. The number of colonies formed in each petri-dish is counted.
Beneficial effects of microorganisms
1. In Nature:
a. Microorganisms especially bacteria aid compost formation through the decay of dead organisms and
humus.
b. Certain bacteria aid nitrogen fixation into plant through the root nodules of leguminous plants.
c. Most saprophytic bacteria, due to their decomposition activities release nutrients through nitrogen
cycle.
d. Some bacteria living in the rumen of ruminant animals like cattle, sheep and goat help such animals to
digest cellulose in the rumen.
e. Some bacteria are also useful in silage making which involves the preservation of pasture crops for
future use.
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2. In Medicine:
a. Manufacture of drugs and vaccines: Micro organisms are used in medicine for the manufacturing of
drug, vaccines and antibiotics which help in curing many human diseases e.g. penicillin (an
antibiotic) is obtained from Penicillin notatum (a fungus), and streptomycin which is obtained form a
bacterium called Streptomyces griseus.
b. Sources of enzymes: Certain yeast and bacteria are rich sources of enzymes like amylase and
invertase.
c. Sources of vitamin B: Yeast and certain bacteria are rich sources of vitamin B complex.
3. In industries:
a. The action of bacteria is useful in the conversion of hides and skin to leather during the taning
process.
b. Bacteria are useful in the curing or ripening of tobacco leaves.
c. Yeast (fungus) is useful in baking industries as it causes dough to rise in bread and other allied food
processing.
d. Yeast is also used in brewing industries for the fermentation of sugar to produce alcohol.
e. Certain bacteria are used in food processing such as cheese, vinegar and yoghurt. Certain bacteria
action are used in the rotting of jute to obtain sack fibres from flax plants.

Harmful effects of some micro organisms

1. Micro organisms are responsible for various diseases in plants and animals.
2. They are the cause of food spoilage.
3. They are responsible for the deterioration of materials like wood, cotton, paper, leather etc.
4. Microorganisms can cause the death of plants and animals.

Diseases caused by microorganisms

Viruses: Animal diseases caused by viruses include poliomyelitis, infective hepatitis, measles, small pox, chicken
pox, yellow fever, common cold, rabies, influenza, Acquired Immune Deficiency Syndrome (AIDS), Coronavirus
disease (COVID-19) etc. Other viral diseases are foot and mouth disease, rinder pest disease and new castle disease.
Plant diseases caused by viruses are rosette disease, cassava mosaic disease, maize streak, yam mosaic disease etc.

BACTERIA
Animal diseases caused by bacteria include leprosy, tuberculosis, tetani, typhoid, dysentery, cholera, pneumonia,
gonorrhea, syphilis, meningitis, whooping cough, contagious abortion e.t.c.
Plant disease caused by bacteria include leaf blight of cassava, tomato rot, onion rot, bacterial fire blight, black arm
cassava wilt, yam rot e.t.c.

FUNGI
Animal diseases caused by fungi include ringworm, aspergilosis, athletic foot thrush etc.
Plant disease caused by fungi are maize smut, rice blight, coffee leaf rust, okro damping of onion twister disease, rice
smut, gummosis, citrus scab, sigatoka disease, black spot disease.

Disease caused by protozoa

This includes malaria, trypanasomisis, coccidiosis, trichomoniasis, red water disease.

Spread of diseases
Micro organisms are spread or transmitted through the following;
1. Air borne pathogen i.e. air
2. Water borne pathogen i.e. water
3. Food borne pathogens i.e through food
4. Animal vectors or carriers
5. Direct skin contact i.e contagious disease e.g. S.T.D, leprosy, measles, tuberculosis.

Example
Which of the following substances cannot control the growth of harmful microorganisms?
A. Antibiotics B. Hypertonic salt solution C. Disinfectants D. Isotonic sugar solution E. Antiseptics (1993/43)
Answer: D – Isotonic sugar solution cannot control the growth of harmful microorganism.

Example
(ii) State three ways in which bacteria are useful. (1993/1aii)
Answer: 1. Ferment food. 2. Clean up oil spills and toxic waste. 3. Kill plant pest. Make biogas such as methane.

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Example
The following are the names of some common diseases: malaria, typhoid, amoeboid dysentery, tetanus, tuberculosis,
leprosy, cholera, yellow fever, pollomyelitis, measles, common cold, small pox, influenza, chicken pox whooping pox,
and trypanaosmasis. Use the format below to classify the diseases according to their causative organisms. (2003/2c)
Answer:
Viral Diseases Bacteria Diseases Protozoan Diseases
Yellow fever Typhoid Malaria
Poliomyelitis Tetanus Amoeboid dysentery
Measles Tuberculosis Trypanosomiasis
Common cold Leprosy
Small pox Cholera
Influenza Whooping cough
Chicken pox
Example
The following are useful effect of micro-organisms except
A. production of vaccines B. curring of tobacco C. tanning of leather D. decay of meat (2000/14)
Answer: D – Decaying of meat is not a useful effect of microorganism.
Example
The major reason why foods should be properly covered is that
A. micro-organisms in air would contaminate the food B. hot foods cool off easily when properly covered
C. the taste of the food is maintained when covered D. all water easily evaporates from uncovered food (2000/53)
Answer: A – The major reason for the proper covering of food is to prevent micro-organisms in the air from
contaminating food.
Example
Which of the following statement about poliomyelitis is not correct. It
A. is a bacteria disease B. is capable of paralyzing the limbs C. can be prevented by immunization
D. is an infant disease E. may cause wasting of the limb muscles (1998/52)
Answer: A – Poliomyelitis is a disease caused by a virus, not by a bacteria.
Example
Fresh milk is often kept in refrigerated vehicles, for distribution to customers in order to
A. ensure proper share of fresh milk to all customers B. ensure delivery of milk to consumers in good time
C. improve in quality of the milk D. ensure that the milk is preserved for a longer period (2001/54)
Answer: D – Fresh milk is often kept in refrigerated vehicle, for distribution to customers in order to ensure that the
milk is preserved for a longer period.
Example
In medicine, bacteria have proved very useful due to the production of
A. nitrate B. antibiotics C. cure tobacco D. tanned leather (2001/55)
Answer: B – In medicine, bacteria have proved very useful due to the production of antibiotics.
Example
Micro-organisms are important in recycling nutrients because
A. they are capable of multiplying quickly B. they are eaten by large organisms
C. they break down dead organic materials D. many of them are parasites (2002/45)
Answer: C – Micro-organisms are important in recycling nutrient because they break down dead organic materials.
Example
(c) (i) State three harmful effects of microorganisms to plants.
(ii) State six beneficial effects of microorganisms to humans. (2016/3c)
Answer:
i. Harmful effects of microorganisms to plants: 1. Reduction in plant yield, 3.They cause spoilage.
2.They cause diseases.
ii. Beneficial effects of microorganisms to humans: 1. Bacteria are used to clean up oil spillage.
2. Used for fermentation of food. 3. Used in making some antibiotics. 4. Used for tanning of leather.
5. Used in making alcoholic beverages. 6.Used for sewage treatment.

Example
Microbes CANNOT be controlled by
A. antibiotics B. antiseptics C. high salinity D. high temperatures E. isotonic solutions (2001/49 Neco)
Answer: E – Microbes cannot be controlled by isotonic solutions.
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Example
Which of the following diseases is NOT caused by micro organisms?
A. cholera B. gonorrhoea C. anaemia D. tuberculosis E. syphilis (2005/36 Neco (Nov)
Answer: C – Anaemia.

Example
(b) State one beneficial effect each, of the following micro-organisms
(i) Rhizobium sp; (ii) Penicilliumsp; (iii) Yeast; (iv) Saprophytic bacteria. (1997/3b Nov)
Answer:
i. Rhizobium: Fix atmospheric nitrogen into the root nodule of plant.
ii. Penicilium: Used for the production of antibiotic.
iii. Yeast: Used as leavening agent for baking.
iv. Saprophytic bacteria: Help in the breakdown/decomposition of dead organic matter.
Example
Which of the following scientists discovered penicillin?
A. Alexander Fleming B. Ronald Ross C. Louis Pasteur D. Gowland Hopkins E. Edward Jenner (1996/47 Health Science)
Answer: A – Alexander Fleming discovered penicillin.
Example
List two diseases each of plants and animals caused by bacteria. (1993/1a)
Answer:
Plant Animal
o Tomato rot Tetanus
o Leaf blight of cassava Leprosy
Example
The following are useful effect of micro organisms except?
A. production of vaccine B. curing of tobacco C. tanning of leather D. decay (2000/14)
Answer: D – Decay
Example
The substances recycled in the soil by the activities of micro organisms during the decay of dead organisms are first
utilized by the
A. carnivore B. herbivores C. scavengers D. autotrophs (2001/48)
Answer: D – Substances recycled in the soil by the activities of microorganisms during the decay of dead organism
are first utilized by the autotrophs (green plant).
Example
Which of the following health conditions cannot be treated with antibiotics?
A. tetanus B. kwashiorkor C. cholera D. typhoid fever (2019/39 PC2)
Answer: B – Kwashiokor is caused as a result of the deficiency of protein. NB: Antibiotic are used to treat infection
caused by bacteria.

Example
Which of the following is not correct of fungi?
A. fungi cause decay of organic matter B. fungi are used to produce antibiotics
C. fungi can be used in breweries for production D. some fungi are edible
E. fungi can be used to produce starch (1991/44)
Answer: E – Fungi cannot be used to produce starch because they do not have chlorophyll to carry out
photosynthesis.
Example
Which of the following is not true about a bacterial colony grown on an algae plate?
A. they are visible without the aid of the microscope B. bacterial cells found in one colony often belong to one specie
C. different colonies have different colours D. only one species of bacterial colony can grow on a culture at any time
E. colonies grow on an algae plate under the same conditions must belong to one species (1989/56)
Answer: C – In algae plate, different bacteria colonies do not have different colours.

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EXERCISE 22.4
1. The process whereby microorganisms can convert atmospheric nitrogen into nitrogenous comounds is known
as
A. nitrogen cycle B. nitrogen fixation C. denitrification D. putrefaction E. decomposition (1993/24)

2. Describe an experiment to demonstrate the presence of bacteria under the finger nails. (1993/1c)

3. Microorganisms which breakdown dead organisms and absorb their contents are called
A. decomposer B. consumers C. parasites D. commensals (2001/47)
4. Only specialy adapted micro-organisms are found in
A. salty water B. humid air C. moist soil D. mouth cavity (2005/20)

5. Which of the following statements is true of microorganisms?

A. they are useful to human beings B. the are harmful to human beings
C. they do not cause world-wide epidemic D. some are used in the manufacture of drugs (2002/46 Nov)

6. Which of the following methods does not inhibit the growth of harmful organisms?
A. Exposure of high temperature B. application of antiseptics
C. application of salt D. immersion in water (2005/47 Nov)

7. List five economic importance of microorganisms. (1992/2b)

8. The following can be used to control the growth of microorganisms except

A. antiseptics B. antibiotics C. isotonic solution D. high temperature (2018/47 NABTEB)
9. Explain briefly five ways by which disease causing organisms can be controlled in order to maintain good
health. (1992/2c Nov)
10. Which of the following statement is not correct about bacteria?
A. bacteria in the intestine of man digest of man digest cellulose B. they are used in the process of making cheese
C. bacteria are used in tanning, curving of tobacco and tea D. they aid the process of fermentation in the baking industry
E. they are used in the treatment plants for water purification (1992/55 Nov)

11. State one beneficial effect each of the following micro-organims:

I. Rhizobium spp. II. Penicullium spp. III. Yeast IV. Saprophytic bacteria (1997/3b)

12. For each of the following diseases: measles, cholera and tuberculosis, state the
I. causative organisms II. host III. symptoms IV. mode of transmission (1997/3a)
13. Mention three beneficial use of bacteria. (2004/5c Nov)

14. List five human disease caused by:

I. bacteria II. viruses and III. four human diseases caused by fungi (2004/5a Nov)

15. The drugs which inhibit growth of disease – causing organisms and thus used in the treatment of infection are
referred to as
A. antibodies B. antibiotics C. antiobiotic D. septic (2004/45)
16. Mention one bacterial parasite of humans. (2002/1bii)

17. List for symptoms of malaria. (2002/1ci)

18. List five economic importances of microorganisms. (2006/5b Nov)

Towards better health

Health and diseases
According to the world health organization (W.H.O), Health is not merely the absence of disease or infirmity, but it is
“a state of complete physical, mental and social well being”. Based on the above, a disease will not necessarily
therefore be a state of ill health.

The term disease is not so easy to define. One of the definition states that “a disease is a state of disorder”. This
definition might have some limitations. Take for example a dislocated arm which is in a state of disorder. Such a state
of disorder cannot be referred to as disease.

For better comprehension of what we mean by the term “disease”, it will be of necessity to do a suitable classification.

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Classification of diseases
1. Infectious disease: These are disease that are transmitted from one organism to the other. Disease causing
organisms include viruses, bacteria, fungi , protozoans, flatworms and tape worms.

2. Non-infectious disease: These are diseases that are non-infectious or non-transmittable. They include Deficiency
diseases (resulting from lack of certain nutrient in diets), ageing and degenerative diseases, mental illness e.t.c

Infectious diseases contribute greatly towards the poor health of people. To move towards better health, we have to
control disease-causing microorganism and their animal vectors, and improve public health facilities.

To prevent infectious diseases from spreading, we have to kill or inhibit the growth of disease causing microorganism.
This can be done through the following ways:
1. Sterilization. 4. High temperature 7. Dehydration 10. Personal hygiene
2. Antibiotics 5. High salinity 8. Quarantine services
3. Use of antiseptics 6. Immunization or vaccination 9. Health education

1. Sterilization: Sterilization method kills all microorganisms from the objects that are being treated. High
temperature and chemicals are effective sterilizing agents.

2. Antibiotic: These are chemicals which in low concentrations, can selectively kill or inhibit the growth of most
pathogenic microorganisms. Antibiotics are produced by microorganisms like bacteria and fungi and are not
harmful to humans.

Antibiotics like chloramphenicol and tetracycline are effective against both gram – positive and gram –
negative bacteria. However, they are not effective in controlling pathogenic viruses and protozoa.

3. Use of antiseptic: These are chemicals that can kill or inhibit the growth of pathogenic microorganisms.
Antiseptic are used on cuts, abrasion and wounds on the skin to prevent infection by microorganisms.
Examples of antiseptics are dettol, hydrogen peroxide, tincture of iodine, Milton, chlorine water, KMnO4,
alcohol (70%) e.t.c.

4. Disinfectant: These are stronger antiseptic used to disinfect hospital, warehouse and public buildings. They
can also be used for bathing, cleaning woods, and treating clothes. Examples are izal, sanitas, Lysol, carbonic
acid. These are used regularly to prevent infection caused by microorganisms.

5. High temperature: This involves sterilization by boiling, autoclaving or heating of food and other products
to kill disease causing micro-organisms. Micro organisms are killed or destroyed at very high temperature.

6. High salinity: This is the application of salt on food to kill micro-organisms or render them inactive, thereby
preserving the food.

7. Dehydration: Water is essential for the growth of microorganisms. When we remove water, growth of
microorganisms is inhibited. Many food are preserved by such method as drying.

8. Immunization or vaccination: This is a process by which a healthy person is inoculated with a preparation of
a mild form of the pathogen. This preparation is called vaccine. The vaccine is given to protect against deadly
diseases especially those caused by virus like measles, tuberculosis, cholera, rabbies and tetanus.

N.B: Vaccination results in the production of antibodies which destroy toxins of germ

9. Quarantine services: This is when isolation of infected person or animal is done to observe such a person or
animal for evidence of a disease before he is mixed with general population.

10. Health education: This is the process of making people aware of ways in which microorganisms are
transmitted and how to prevent them.

11. Personal hygiene: Personal hygiene such as washing of hands before and after meals, before preparation of
food, after every defecation e.t.c. should be practiced regularly to prevent or check the spread of pathogenic
microorganisms.

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Example
Vaccination results in
A. aiding red blood cells to carry more oxygen B. production of antibodies which destroy toxins of germ
C. arresting excessive bleeding D. production of white blood cells which engulf and digest bacteria (2011/46)
Answer: B – Vaccination results in the production of antibodies which destroy toxins of germ.
Example
Which of the following infections is unlikely to respond to antibiotic treatment?
A. Typhoid fever B. Ring worm C. Measles D. Tetanus (2005/44)
Answer: C – Measles is a disease caused by a virus. Antibiotic are mostly used to treat diseases/infections that are
caused by bacteria.
Example
Which of the following infections would not respond to an antibiotic treatment?
A. Gonorrhoea B. Measles C. Diarrhoea D. Tuberculosis (2007/46)
Answer: B – Measles
Example
A vaccine is introduced into a person's body to
A. destroy all disease-causing organisms in the body B. stimulate the body to produce antibodies
C. enhance the production of red blood cells D. isolate disease-causing pathogens from the blood (2008/40)
Answer: B – Vaccine is introduced into a person’s body to stimulate the body to produce antibodies.
Example
Measles in infants can be prevented by
A. sleeping under mosquito nets B. providing clean water supply
C. taking anti-malaria tablets D. vaccinating young children (2002/44)
Answer: D – Measles in infants can be prevented by vaccinating young children.
Example
The drugs which inhibit the growth of disease-causing organisms and thus used in the treatment of infections are
referred to as
A. antibodies B. antibiotics C. antitoxics D. septics (2004/45)
Answer: B – Antibiotics.
Example
Which of these diseases CANNOT be prevented by immunization?
A. poliomyelitis B. tuberculosis C. cholera D. Onchocerciasis (1986/44 JAMB)
Answer: D – Onchocerciasis cannot be prevented by immunization.
Example
Vaccination is carried out in order to
A. check the production of poison B. increase the activity of white blood cells
C. increase the number of red blood cells D. stimulate the production of antibodies (1999/37 JAMB)
Answer: D – Vaccination is carried out in order to stimulate the production of antibodies.
Example
The following diseases are airborne except
A. cholera B. measles C. meningitis D. pneumonia E. small pox (2018/21 Neco)
Answer: A – Cholera is not an airborne disease.

Example
The production of antibodies in the body occurs when
A. the body temperature rises sharply B. foreign organisms enter the body
C. there are few red blood cells D. the body is malnourished (2000/48 Neco)
Answer: B – The production of antibodies in the body occurs when foreign organisms enter the body.

EXERCISE 22.5
1. Which of the following disease is not sexually transmitted?
A. AIDS B. Hepatitis C. herpes D. influenza E. syphilis (2018/28 Neco)
2. Which of the following health conditions cannot be treated with antibiotics?
A. tetanus B. kwashiorkor C. cholera D. typhoid fever (2019/39 PCII)
3. Which of the following types of immunity is an individual likely to develop after an attack of malaria?
A. Artificial acquired immunity B. Natural acquired immunity
C. Active artificial immunity D. Passive artificial immunity (2003/43 Health Science Nov)
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4. Which of the following ailments is not infectious?
A. Tuberculosis B. Measles C. Asthma D. Ringworm (2003/44 Health Science Nov)

5. Malaria is contacted when an infected

A. male anopheles mosquito bites a victim B. female aedes mosquito bites a victim
C. female culex mosquito D. male culex mosquito bites a victim
E. female anopheles mosquito bites a victim (1998/43 Health Science)
6. Immunity can be defined as the
A. ability of the body tissues to resist pathogenic organisms
B. introduction of disease-causing organisms into the body
C. production of poisons by micro-organisms in the blood
D. production of toxins in the body E. method of preventing the spread of diseases (1998/44 Health Science)
7. The production of antibodies in the blood against disease-causing organisms is described as
A. active immunity B. passive immunity C. artificial immunity D. acquired immunity (2000/33 Health Science Nov)
Study the list below and use it to Answer: questions 34-36
I Shistosoma II. Plasmodium III. Mosquito IV. Ascaris
8. Which of the organisms lives in the small intestine of man?
A. I B. II C. III D. IV (2000/34 Health Science)
9. Which of the organisms is a pathogen?
A. I B. II C. III D. IV (2000/35 Health Science Nov)
10. Which of the organisms uses the water snail as an intermediate host?
A. IV B. III C. II D. I (2000/36 Health Science Nov)
11. Which of the following infestations could be prevented when meat is properly cooked?
A. Filariasis B. Hookworm C. Bilarzia D. Tapeworm (2000/39 Health Science Nov)
12. Which of the following is associated with female anopheles mosquito?
A. Yellow fever B. Dengue fever C. Malaria fever D. Typhoid fever (2000/42 Health Science Nov)
13. Which of the following practices should be encouraged in a hookworm infested area
A. Boiling of drinking water B. Washing of fruits before eating
C. Wearing of shoes always D. Covering mouth while sneezing and coughing (2000/43 Health Science Nov)
14. Rabies can be prevented by
A. isolating victims of dog bite B. vaccinating dogs regularly
C. legislating on the possession of dogs D. breeding only male dogs (2003/39 Health Science Nov)

VECTORS AND THEIR CONTROL

Vectors are animals that transmit disease-causing organisms. The most important vectors are insects and rodents.
Insect vectors include mosquitoes, houseflies, tse-tse flies, lice and fleas. Common rodent vectors include rats and
mice. To control, we have to know their habit and lifecycles, then we can use biological, environmental or chemical
method to control the given vector.
Mosquitoes
There are three groups of mosquitoes that spread diseases.
1. Anopheles
2. Culex
3. Aedes
They spread serious disease like: malaria (female Anopheles mosquito),
yellow fever, dengue (Aedes mosquito),
elephantiasis or lymphatic filariasis. (Culex mosquito),
Life cycle and habit
Mosquito undergo complete metamorphosis. The first three stages are in water. The anopheles breeds in clear moving
water. The culex and aedes breed in stagnant water bodies like containers found around our houses. The adult
mosquito is an active flying insect which lives for about two weeks. The female feeds on blood while the male feed on
plant juice. Most mosquitoes are active between sunset and sunrise.
Control of mosquitoes
This employs environmental, chemical, biological and genetic method

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Environmental method: This includes
1. Draining swamps, ditches, pools, clogged drains, unwanted tin cans, coconut shells which collect water and
provide breeding places for mosquitoes.
2. Spraying stagnant water bodies which cannot be drained with oil such as kerosene. The oil forms a film which
prevents larvae from breathing in air.
3. Clearing bushes around houses to reduce the hiding places for adult mosquitoes.
Chemical method includes the use of insecticides which kill the various stages of mosquitoes. Certain drugs are also
taken to control or cure malaria fever.

Biological method involves the use of predators, parasite and pathogen to reduce the mosquito population. Mosquito
– eating fishes like the guppies are introduced into ponds and ditches to feed on the larvae and pupae of mosquitoes.
Genetic control: This includes the release of sterile male mosquitoes into the environment which mate with female
mosquitoes without producing eggs. To make a male mosquitoes sterile, you expose it to certain chemical and
radiation in the laboratory.
Other methods include fitting the doors and windows of houses with wire netting, applying physical attack and killing
of mosquitoes.

Houseflies: They act as mechanical carriers of disease causing agent. They spread the microorganism that cause
disease like typhoid, cholera, dysentery and poliomyelitis.
Life cycle and habit
Houseflies undergo complete metamorphosis. The female lays eggs in any decaying organic matter such as garbage,
rotting fruit and human excreta. The eggs hatch into larva within a day and the larvae feed on decaying material and
moult about three times and after about 3 – 6 days the larvae enter the pupa stage. The pupa stage lasts for about 5
days. The adult fly that emerges from the pupa has a life span of about 2 to 3 weeks.
Houseflies move around mostly during the day and they like warm places. At night they rest usually on twigs, fences,
wires and ropes. They have the habit of flying almost everywhere and feeding on almost anything. They are very
effective in collecting and spreading pathogenic microorganisms.
Control of houseflies
This is usually done by burning and burying of all garbage.Storing household refuse in cover bins for collection and
disposal by public health services. Covering of food especially already prepared ones to prevent houseflies from
feeding or defecating on them.The use of insecticides to kill maggot and the adult flies. Other measures include fitting
the doors and windows of houses with wire netting and applying physical attack to kill houseflies directly.
Rodent vectors
Common rodent vectors include rats and mice. Rat spreads disease like plague and typhus to human. They
contaminate food and drinking water with their faeces and urine. Rats are omnivores, eating many types of food. They
are nocturnal animals.

Control of rats
Environmental control aims at destroying them from getting food. This is done by
1. Keeping refuse in cover waste bin for subsequent disposal.
2. Storing all food properly.
3. Keeping the house clean and unclustered.
4. Clearing all rubbish dumps and bush area around the house.

Chemicals control involves the use of rat poisons. The poison is mixed with the food that is used as bait. Food is also
used as bait in rat traps. Cat is the natural predator of rats.

Blackfly
Blackflies are the vector of onchocerciasis (river blindness). The blackflies that transmit the parasite bites during the
day. Female blackflies need to ingest blood for ovulation, so they feed on humans. Some species of blackflies may
also feed on certain animals as well.

Lifecycle of Blackfly
If a black fly bites an infected person, the onchocerciasis larvae (microfilariae) can be ingested by the blackfly after
which, they migrate to the flight muscles of the insects. The larvae develop inside the black fly and become infective
for humans in about one week. They migrate to the biting part of the fly where they can be transmitted back when it
bites again.

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Humans become infected when blackflies deposit onchocerca infective larvae into the skin when biting to extract
blood. Once inside the human body, the larvae matures into adult in approximately 12 – 18 months. Most adult female
worms live in fibrous nodules under the skin and sometimes near muscles and joints. Adult male worms are usually
found near the female worms. Nodules form around the worms as part of the interaction between the parasite and its
human host. Inside the nodules the worms are relatively safe from the human immune response. As adult female
worms produce thousands of new larvae daily, the larvae becomes detectable in the skin about 12 – 18 months after
the initial infection. The adult worms can live approximately 10 – 15 years inside the human body and their larvae
have a life span of approximately 12 – 15 months.

Symptoms:
Some of the symptoms associated with river blindness include, itchy skin rashes, development of fibrous nodules
under the skin particularly around the waist, head and shoulder and vision changes which eventually leads to
blindness.

Flukes
Bilharziasis (schistosomiasis), blood fluke of man
Bilharziasis is a disease caused by some species of blood trematodes (flukes) in the genus schistosoma. The three main
species infecting humans are Schistosoma haematobium, S. japonicum and S. mansoni.The disease is characterized by
the presence of blood in the faeces and urine of the sufferer.

Causative agent: Bilharzia (schistosoma)

Location in man: Veins close to small intestine (mesenteric vein) or veins of the bladder.

Life cycle:
Schistosoma eggs are eliminated with faeces or urine, depending on species. Under appropriate conditions, the eggs
hatch and releases miracidia which swims and penetrate specific snail intermediate hosts. The stages in the snail
include two generations of sporocysts and the production of cercariae. Upon release from the snail, the infective
cercariae swim, penetrate the skin of the human host, and shed their forked tails, becoming schistosomulae. The
schistosomulae migrate via venous circulation to lungs, then to the heart, and then develops in the liver, exiting the
liver via the portal vein system when mature. Male and female adult worms copoluate and reside in the mesenteric
venules, the location of which varies by species (with some exceptions).

Symptoms
Skin irritation at the point of entry after few hours. Fever, headache, sweating and backache occur. Blood is found in
urine or in faeces. Enlargement of liver and spleen. Anaemia results.

Control and prevention

1. Avoid swimming or wading in freshwater infected with the fluke’s larvae.
2. Faeces and urine should not be passed into water bodies.
3. Water used for bathing should be boiled in order to kill any cercariae.
4. The body should be cleaned with towel immediately after bathing.
5. Reduction of the population of snails by clearing the vegetation around standing water.

Example
Which of the following is not true of the housefly.
A. it is a vector of cholera B. it is immuned to the effect of its disease agent
C. it is associated with the transfer of trypanosomiasis D. its hairy body harbours microorganisms (2000/16)
Answer: C – Housefly is not associated with the transfer of trypanosomiasis.
Example
The protozoa that causes malaria fever is
A. plasmodium B. trypanosome C. culex D. flarial worm (2001/21)
Answer: A – The protozoan that causes malaria fever is plasmodium.
Example
The vector of the malaria/parasite is the
A. male anopheles B. female culex C. male culex D. female anopheles E. female aedes (1988/40)

Answer: D – The Vector of the malaria parasite is the female anopheles mosquito.

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Example
The causative organism of sleeping sickness is the
A. trypanosome B. plasmodium C. vibro bacterium D. penicillin E. tse-tse fly (1988/38)
Answer: A – The causative organism of sleeping sickness is trypanosome.
NB: Tse-tse fly is the vector that carry the trypanosome.

Example
Transmission of the malaria parasite is affected through the bite of the
A. male anopheles mosquito B. female anopheles mosquito C. infected male anopheles mosquito
D. infected aedes mosquito E. infected female anopheles mosquito (1992/49)
Answer: B – Female anopheles mosquito.
Example
Which of these is not correct about the tsetse fly and mosquito? They
A. harbour protozoa as disease agent B. possess piercing and sucking mouth part
C. have intermediate hosts D. inject diseases causing organisms into the blood stream (2001/52)
Answer: C – They do not have intermediate host. Tsetse fly and mosquito are vectors (carriers of disease causing
organisms). They do not need intermediate hosts because they are not pathogens
Example
State three methods by which mosquitoes can be controlled and state the reason for each method. (1993/1b).
Answer:
- Application of insecticides: This will kill the mosquito.
- Pouring of oil or kerosene on stagnant water: This will prevent the growth of mosquito eggs and larvae.
- Use of mosquito net: This will prevent mosquito from gaining access into the room/house.
Example
One of the ecological conditions which favour the spread of malaria is
A. improper disposal of decaying organic matter B. clearing bushes around dwelling houses
C. presence of water weeds D. presence of stagnant water in ponds
E. improper disposal of sewage into the sea (1996/45)
Answer: D – One of the ecological conditions which favours the spread of malaria is the presence of stagnant water
in ponds.
Example
The causative agent of sleeping sickness is called
A. entamoeba histolytica B. plasmodium falciparum C. plasmodium villax
D. teponema palidun E. trypanosome gambiense (2014/21 NABTEB)
Answer: E – The causative agent of sleeping sickness is called trypanosome gambiense.
Example
Which of the following is a vector of river blindness?
A. Blackfly B female aedes C. female anopheles D. housefly E. tse-tse fly (2014/55 NABTEB)
Answer: A – The vector that carries onchocerca volvulus which causes onchocerciasis (Sleeping sickness) is called
blackfly (simulium).

Example
The vector of the malaria parasite is the
A. female anopheles mosquito B. female culex mosquito C. female aedes
D. male anopheles mosquito E. male culex mosquito (2001/48)
Answer: A – Female anopheles mosquito.
Example
Oil is sprayed over stagnant water in which mosquitoes breed in order to
A. provide landing surface for the adult B. prevent larva or pupa from attaching itself to the surface
C. prevent the water from overheating D. lubricate the larva for easy movement
E. provide surface for laying their eggs (1998/53)
Answer: B – Oil is sprayed over stagnant water in which mosquitoes breed in order to prevent larva or pupa from
attaching itself to the surface.
Example
The vector of the sleeping sickness disease parasite is the
A. cockroach B. mosquito C. black fly D. tse-tse fly (2007/47)
Answer: C – Blackfly.

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Example
Trypanosomiasis is associated with
A. cockroach B. mosquito C. housefly D. tse tse fly (2000/52)
Answer: D – Trypanosomiasis is associated with tse-tse fly

Example
Which of the following structures in a housefly aids the transmission of diseases in man?
A. Hairs B. Spiracles C. Antennae D. Wings (2001/51)
Answer: A – Hairs are structures in housefly that aid the transmission of diseases in man.
Example
Which of these is not correct about the tsetse fly and mosquito? They
A. harbor protozoa as disease agents B. possesses piercing and sucking mouth parts
C. have intermediate hosts D. inject disease-causing organisms into the blood stream (2001/52)
Answer: C – Tsetsefly and mosquito are vectors (carriers of disease causing organisms). They do not need
intermediate hosts because they are not pathogens.
Example
Which of these is a vector of malaria fever?
A. Female anopheles mosquito B. Male anopheles mosquito
C. Female culex mosquito D. Male culex mosquito (2001/53)
Answer: A – Female anopheles to a vector of malaria fever.
Example
Which of these diseases cannot be controlled by killing the vectors?
A. River blindness B. Malaria C. Polio D. Cholera E. Billharzia (Schistosomiasis) (1979/18 JAMB)
Answer: C – Polio cannot be controlled by killing the vectors.
Example
A mosquito which produces eggs with float, and whose larvae lie horizontal to the water surface, also rests at angle on
a vertical surface. This type of mosquito is
A. Aedes B. Anospheles C. Culex D. Tiger mosquito E. none of the above (1980/48 JAMB)
Answer: B – Anopheles.
Example
Which of the following diseases could be exclusively associated with a river basin?
A. Malaria B. Syphilis C. Onchocerciases D. Cholera E. Poliomyelitis (1983/33 JAMB)
Answer: C – Onchocerciasis. This is also known as river blindness.
Example
Which of the following lists if disease, their causes and transmission is CORRECT?
A. Cholera, virus, severe diarrhea, infected water B. Malaria, protozoan, high fever, contact with infected person
C. Syphilis, venereal disease, sexual intercourse
D. Small pox, virus, skin with blister, close contact with infected person
E. Sleeping sickness, bacteria, tiredness, headache and dozing, tsetse fly bite (1984/45 JAMB)
Answer: D – Small pox, virus, skin blister, close contact with infected person

Example
The primary and secondary hosts respectively of bilharzia are
A. fish and man B. man and dog C. snail and man
D. man and snail E. fish and snail (1985/43 JAMB)
Answer: D – Primary host (man) and secondary host (snail).
Example
Tsetse fly is harmful to man because it is associated with the spread of
A. river blindness B. malaria C. sleeping sickness D. leprosy E. dysentery (1985/45 JAMB)
Answer: C – Tsetse fly is harmful to man because it is associated with the spread of sleeping sickness
(trypanosomiasis)
Example
The vector for yellow fever is
A. Aedes mosquito B. Anopheles mosquito C. Tsetse fly D. Blackfly (2010/39 JAMB)
Answer: A – Yellow fever is caused by a virus that is spread by Aedes mosquito.

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Example
The protozoan plasmodium falciparum is transmitted by
A. female Anopheles mosquitoes B. female Aedes mosquito
C. female Culex mosquitoes D. female blackfly (2010/40 JAMB)
Answer: A – Plasmodium falciparum is transmitted by female anopheles mosquito.

Example
Drancunculiasis can be contacted through
A. drinking contaminated water B. bathing in contaminated water
C. bites of black fly D. eating contaminated food (2011/37 JAMB)
Answer: D – Dracunculiasis can be contracted through drinking contaminated water.
Example
The diseases caused by water-borne pathogens include
A. gonorrhea and poliomyelitis B. typhoid and syphilis
C. tuberculosis and cholera D. typhoid and cholera (2012/37 JAMB)
Answer: D – Typhoid and cholera are diseases caused by water borne pathogen.
Example
The causative agent of bird flu is a
A. protozoan B. Virus C. bacterium D. fungus (2015/8 JAMB)
Answer: B – The causative agent of bird flu is a virus.
Example
Which of the following is common to the mosquito, housefly and blackfly
A. They are parasites of man B. Their immature stages are aquatic
C. They undergo complete metamorphosis D. Their adults have two pairs of wings (2015/19 JAMB)
Answer: C – Mosquito, hosuefly and blackfly all undergo complete metamorphoses
Example
Which of the following is not a vector?
A. ant B. mosquito C. house fly D. rat E. tse-tse fly (2014/18 Neco) Answer: A – Ant is not a vector.

EXERCISE 22.6
1. The causative agent of sleeping sickness is called
A. entamoebahistolytica B. plasmodium falciparum C. plasmodium vivax
D. treponema pallidum E. trypanosome gambiense (2014/21 Neco)
2. Which of the following is a vector of river blindness
A. Black fly B. female aedes C. female anopheles D. house fly E. tse-tse fly (2014/55 Neco)
3. Sleeping sickness is a disease transmitted through the bite of
A. blackfly B. housefly C. fruit fly D. tsetsefly (2001/50 NABTEB)
4. The causative organism of sleeping sickness is the
A. Trypanosome B. Vibro bacterium C. pennicilium D. tsetse fly (2019/43 NABTEB)
5. The following are vectors except
A. black fly B. butterfly C. housefly D. mosquito E. tsetse fly (2018/53 Neco)
6. The vector of trypanosome is the
A. black fly B. cockroach C. housefly D. mosquito E. tsetse fly (2001/47 Neco)
7. The vector of the malarial parasite is the
A. Female anopheles mosquito B. female culex mosquito C. male aedes mosquito
D. Male anopheles mosquito E. male culex mosquito (2001/48 Neco)
8. Which of these organisms is a protozoan?
A. hydra B. mucor C. paramecium D. spirogyra E. volvox (2005/3 Neco)
9. All these are examples of vectors EXCEPT
A. beetles B. black flies C. mosquitoes D. ticks E. tse-tse flies (2005/37 Neco Nov)
10. (b) State four methods of controlling the vector of malaria parasite. (2002/7b Nov)
11. Which of the following is not true of the housefly?
A. it is a vector of cholera B. it is immune to the effect of its disease agent
C. it is associated with the transfer of trypanosomiasis D. its hairy body harboursmicro-organisms (2000/16 Nov)
12. The protozoan that causes malaria fever is
A. plasmodium B. trypanosome C. culex D. filarial worm (2000/51 Nov)

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13. 6. (a) Name the pathogens for the following diseases: I. Cholera II. Measles III. Malaria
(b) State (i) their mode of transmission and (ii) two symptoms each for each of the diseases. (2000/6a, b Nov)
14. (c) (i) Describe the life history of the housefly
(ii) State two economic importance of the housefly
(iii) State three methods of control of the housefly
(iv) In a tabular form list two differences between a fruit and a seed. (2005/2c Nov)
15. (a) For each of the following diseases: measles, cholera and tuberculosis, state the
(i) causative. organisms; (ii) host; (iii) symptoms; (iv) mode of transmission.
(b) State one beneficial effect each, of the following micro-organisms
(i) Rhizobium sp; (ii) Penicilliumsp; (iii) Yeast; (iv) Saprophytic bacteria.
(c) State four methods of controlling the’ vector of malaria. (1997/3a, c Nov)
16. Which of the following should be examined in order to confirm the presence of plasmodium in the body?
A. Sputum B. Urine C. Lymph D. Blood (2003/37 Health Science Nov)
17. Disease-causing organism is carried by a
A. Pathogen B. Pest C. Parasite D. vector (2003/38 Health Science Nov)
18. Which of the following diseases is transmitted through a vector?
A. Athlete’s foot B. Ringworm C. Cholera D. Tetanus E. Leprosy (1990/55 Health Science Nov)
19. Which of the following pairs of causative organisms and site of infection do not match?
A. Roundworm-Intestine B. Guineaworm-Intestine C. Tapeworm-Intestine
D. Filariaworms-Lymph vessels E. Hookworm-Intestine (1990/58 Health Science Nov)
20. The following are symptoms of infestation of Taenia Solium except
A. paleness B. rashes on the skin C. anemia
D. abdominal skin E. inability to swallow (1990/62 Health Science Nov)
21. The vector of the causative organism for dysentery is
A. mosquito B. houseflies C. water snail D. sand-fly E. rat (1990/65 Health Science Nov)

Public Health
A healthy nation contributes greatly to the economic progress of a country. Maintaining the health of the people in a
country is the responsibility of the individual, the community, the government and health organizations.
Ways of maintaining good health in a community
Effective public health administration in a community can be achieved through the following ways:
1. Refuse disposal: Refuse are solid waste materials discharged through human activities from homes and
industries into the environment. Reckless refuse dump around dwelling places creates bad odour, provide
breeding grounds for insects and rodents that spread diseases.

Refuse disposal can be done through the following ways:

i. Provision of dust bins in strategic locations.
ii. Burning refuse in incinerators.
iii. Dumping them in isolated areas far from human habitation.
iv. Burying refuse in a sanitary landfill.
2. Sewage disposal: Sewage are waste water materials discharged from laundries, kitchens, toilets, bathrooms
e.g. urine and faeces. Sewage disposal can be done through:
1. The use of pit toilets where faeces and urine are passed into dip pits.
2. The use of septic tanks where water is used to flush faeces and urine into a big tank dug in the ground.
3. Community treatment process where sewage from various homes are collected and treated before
being discharged into oceans or rivers.
3. Protection of water: Water should be protected through the following ways:
i. Addition of alum to water.
ii. Boiling of water before drinking it.
iii. Filtration of water on cooling.
iv. Addition of chlorine to kill miscroscopic germs.
v. Storage of water in clean containers.
All these should be done before water is passed through pipes into houses and other places where it is
required.
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4. Protection of food: It is true that diseases can be contracted through food. Therefore, both raw and cooked
food should be properly protected. The following methods of food protection are recommended.
1. Keep food in refrigerators or deep freezers.
2. Boil food properly before eating.
3. There should be inspection of food meant for public consumption.
4. Washing of hands before and after eating of food.
5. Food can also be preserved through canning.
6. Keep the environment where the food is prepared clean.
7. Avoid exposure of food to flies and other microorganisms.
5. Control of diseases: Individuals can control diseases by living in clean environment. They can prevent
diseases through the following ways:
1. Daily sweeping of the surroundings.
2. Eating of good food and balanced diet.
3. Taking of bath regularly.
4. Wearing of clean and neat dresses.
5. Living in well ventilated houses.
6. Cleaning of teeth regularly with toothbrush and paste.
7. Doing exercises regularly.
8. Cleaning of latrines and urinal with disinfectants regularly.
9. Taking children through the various immunizations as prescribed by doctors.
10. Taking no drugs except those prescribed by doctors.
Example
Conventional method of sewage disposal involves all the following except defecating
A. into pit latrines B. in open fields C. into cesspit D. into bucket latrines E. into water borne sewage system (1994/9)
Answer: B – Defecating in open fields is not a conventional method of sewage disposal.
Example
The major reason why food should be properly covered is that
A. microorganisms in air would contaminate the food B. hot food cool off easily when properly covered
C. the taste of the food is maintained when covered D. all water easily evaporates from uncovered food (2000/53)
Answer: A – The major reason why food should be properly covered is that microorganisms in air would contaminate
the food if it is not properly covered.
Example
The following diseases are airborne except
A. cholera B. measles C. meaningitis D. pneumonia E. small pox (2018/21 Neco)
Answer: A – Cholera is not air borne.
Example
Improper sewage disposal could be dangerous for the following reasons except
A. the smell of carelessly disposed sewage water is most undesirable
B. the spread of gastro-intestinal diseases are enhanced
C. resultant outbreak of water borne diseases D. there would be little space for disposal of wastes (2003/49)
Answer: D – There would be little space for disposal of waste if not danger imposed by improper sewage disposal.
Example
Name the causative agent of each of the following diseases and state how the diseases can be spread.
(I) cholera (II) Acquired Immune Deficiency Syndrome (AIDS) (III) Athlete’s foot (IV) measles (2005/5a)
Answer:
i. Cholera: Vibro cholera (bacteria)
ii. Acquired Immune Deficiency Syndrome (AIDS): Human Immuno-deficiency Virus (HIV)
iii. Athlete’s foot: Tinia Pedis (Fungus)
iv. Measles: Rubeola Virus
Example
All these are examples of vectors except
A. beetle B. black flies C. mosquito D. tick E. tse-tsefly (2005/37 Neco)
Answer: A – Beetle is not a vector i.e. is not a carrier of pathogens (disease causing organisms).
Example
Which of the following water pollutants may contain organisms that cause dysentery?
A. fertilizers B. sewage C. pesticides D. crude oil (1999/47 NABTEB)
Answer: B – Sewage.

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Example
The use of water closet and septic tanks is preferred to the use of bucket and pit latrines because
A. it is cost effective B. contaminated faeces are completely kept away from files
C. the water for flushing contains chlorine which kills germs D. it prevents files from breeding (2012/46)
Answer: B – Contaminated faeces are completely kept away from flies.
Example
(a)(i) What is sewage? (ii) State five effects of releasing untreated sewage into a stagnant water body. (2015/3ai, ii)
Answer:
3ai. Sewage is the wet waste resulting from faeces, urine, bath water, domestic, industrial and agricultural waste.
ii. Effects of releasing untreated sewages into stagnant water:
1. Poisoning of aquatic life. 4. Generation of offensive odour.
2. Death of aquatic animals. 5. Makes water unfit for consumption.
3. Leads to the rapid growth of algae (eutrophication)
Example
Cholera is mostly spread by
A. air B. soil C. water D. noise (2019/38) Answer: C – Cholera is mostly spread by water.
Example
(a) State eight human activities that may pollute water bodies
(b) Explain the measures that may be used to prevent pollution of water bodies
(c) Mention four methods of purifying water. (2001/3a, b, c)
Answer:
3a. Human activities that may produce water bodies:
- Oil spillage from drilling or tanker.
- Dumping of agro chemicals e.g. fertilizer, fungicides, pesticides etc.
- Pouring of detergents from home and factories into water bodies.
- Dumping of dye from textile factories into water bodies.
- Use of chemical (e.g. gamalin) in fishing.
- Use of explosive for fishing.
- Dumping of household refuse or organic waste into water bodies.
b. Measures that may be used to prevent pollution of water bodies:
- Treatment of raw sewage before disposing into bodies.
- Refuse must be burnt or buried and must not be disposed into water bodies.
- Cooling of water from industrial plants before disclosing into water bodies.
- Limiting the use of pesticides and fertilizers.
- Proper education of farmers on correct usage of fertilizers to limit run-off into water bodies.
- Enacting or enforcement of laws to prevent the use of explosive and chemicals in fishing activities.
- Waste should be discharged in controlled amount.
c. Methods of purifying water: Boiling, Chlorination, Sedimentation, Distillation.
Example
The construction of dams may lead to an increase in the prevalence of
A. typhoid fever, measles, and yellow fever B. tuberculosis, leprosy and trypanosomiasis
C. guinea worm, malaria and tuberculosis D. malaria, biharziasis and onchocerciasis (1999/35 JAMB)
Answer: D – Malaria, biharziasis and onchocerciasis.
Example
Which pollutant is likely to cause cholera?
A. agricultural wastes B. Industrial wastes C. nuclear fallouts D. oil spillages E. Untreated sewage (2001/37 Neco)
Answer: E – Untreated sewage is likely to cause cholera
Example
The incidence of diseases is reduced when the environment is clean because
A. houseflies are destroyed B. disease causing organisms can easily be destroyed
C. pathogens will be eliminated from the environment
D. breeding grounds of vectors and pathogens will be destroyed (2013/45 Nov)
Answer: D – The incidence of diseases is reduced when the environment is clean because the breeding grounds of
vectors and pathogens will be destroyed.
Example
The objective of food hygiene is to
A. eat several times a day B. prevent food contamination C. stimulate appetite
D. impress the public E prevent constipation (1996/32 Health Science)
Answer: B – The objective of food hygiene is to prevent food contamination.
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Example
If all pork were thoroughly cooked before being eaten, there would be very few cases of infection of
A. tapeworm B. hook worm C. roundworm D. bilharzia E. filarial (1996/33 Health Science)
Answer: A – Tapeworm is found in pork meats that are not thoroughly would be very few cases of infection of
tapeworm. NB: The species of tapeworm found in pork is taenia soluim while that found in beef is taenia saginata.

Example
List four symptoms and four prenventive protocols of coronavirus disease (COVID-19) as prescribed by Nigeria
Centre for Disease Control (NCDC). (2020/2bi Neco)
Answer:
Four symptoms coronavirus disease (COVID-19) : i. sudden loss of taste iii. sudden loss of smell
ii. cough and fever iv. Difficulty in breathing

Four prenventive protocols of coronavirus disease (COVID-19): i. avoid public gathering ii. Use of Nose-mask
iii. Wash of hands with soap under running water
iv. Self isolation (by staying at home)
EXERCISE 22.7
1. The practice of warming soup regularly as it concerns food preservation is essentially to
A. retain the taste B. help to break down the cellulose C. remove the excess water
D. kill the bacteria in it E. raise the temperature (1991/49 Nov)
2. The following are principles of safety except
A. inspecting equipment before use B. working in a well lighted environment
C. removing objects that can cause accidents D. making new materials available at all times (2003/35 Health Science Nov)
3. The intestines are suitable habitat for worms because
A. the female worms lay several eggs B. digested foods are readily available
C. the male and female worms can mate easily in the intestines
D. there is enough room to accommodate the worms (2003/46 Health Science Nov)
4. Ventilation is defined as the
A. type of windows and doors in a house B. removal of carbon dioxide from a medium
C. amount of oxygen in the lungs at a time D. flow of fresh air into a house (2003/49 Health Science Nov)
5. Which of the following poses the greatest danger to well water?
A. Pit latrine B. Bucket latrine C. Septic tank D. Sewage works (2003/50 Health Science Nov)
6. The prevention and control of diseases means
A. dealing with diseases in the event of an outbreak B. keeping off and checking the spread of diseases
C. identifying the causes of diseases
D. identifying the methods of transmission of diseases (2003/42 Health Science Nov)
7. Resistance to disease may be influenced by
A. adequate rest B. inheritance C. environment D. medication (2003/41 Health Science Nov)
8. The period between infection and the manifestation of symptoms of a disease is known as
A. resting period B. incubation period C. convalescence period D. latent period (2003/40 Health Science Nov)
9. Sudden onset of diarrhea accompanied by vomiting and cramps in the stomach are symptoms of
A. diabetes B. cholera C. measles D. appendicitis (2003/45 Health Science Nov)
10. 3(a) State six ways by which skin diseases can be prevented. (2003/3a Nov)
11. Which of the following will enhance the spread of diseases and disorders of the digestive system?
A. Giving up dirty personal habits B. Drinking purified water
C. Keeping away rats and flies from the house D. Improper handling of food substances
E. Irregular feeding (1990/61 Health Science)
12. Through which of the following ways can diseases not be spread?
A. Air B. Underfeeding C. Water D. Droplets E. Contact (1990/63 Health Science)
13. When fresh foods are stored in refrigerators
A. the vitamin content of the food is increased B. the quality of the food is improved
C. bacterial growth is reduced D. the taste of the food is improved (2000/27 Health Science Nov)
14. Hands should be washed before eating in order to
A. prevent food from being dirty B. heat the real taste of food
C. prevent the transfer of germs into food D. improve the quality of food (2000/28 Health Science Nov)

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15. (b) State two ways in which each of the following conditions of poor housing can constitute health hazards:
(i) poor toilet facilities (ii) poor ventilation; (iii) inadequate water supply; (iv) poor refuse disposal
(v) poor physical state of the house (1996/2b Health Science Nov)
16. 4.(a) (i) State four advantages of cooking food. (ii) Mention three uses of water in the home.
(d) State: (i) Four ways of maintaining the sanitation of market;
(ii) Three roles of school health services. (1996/4a, di Health Science Nov)

Health Organisations
Health organizations are corporate (local and international) bodies concerned with the maintenance of good health of
the people.

International Organizations include:

1. World Health Organisation (W.H.O)
2. United Nations International Children’s Emergency Fund (UNICEF).
3. International Red Cross and Red Crescent Society
4. Food and Agricultural Organization (FAO)
The major local health organizations in Nigeria is the Nigerian Medical Association (NMA)

Roles of health organizations

World Health Organisation (WHO): This is a specialized division of the United Nations Organisation (UNO)
established in 1948 with headquarters in Geneva, Switzerland. Its major aim is to improve the health of the people in
all the countries of the world. The main functions of the organization are:
1. It promote measures for the control of the world major diseases through vaccination.
2. It assist in the training of medical personnel and in the publishing of medical journals.
3. It helps to set up international quarantine regulations.
4. It provides warning signals in the event of an outbreak of epidemic or pandemic diseases as in the case of
Covid–19.
5. It assists national health organizations in the control of diseases and vectors of diseases.
6. It helps in maternal and child health care.
7. It helps to set and recommend safe standard for drugs e.t.c.
8. It helps in promoting nutritional and sanitary products.

UNITED NATION INTERNATIONAL CHILDREN’S EMERGENCY FUND (UNICEF)

Specific function of UNICEF are
1. To provide for the emergency need of children in devastated area.
2. To provide food for destitute children.
3. To assist in the improvement of the mothers and their children by providing training programmes and
necessary equipment e.g. Provision of Oral Rehydration Therapy (ORT) to control diarrhea in children.
4. To improve the nutrition of undernourished children.
5. To provide children’s clothing and other needs e.t.c.
6. It helps to train doctors, nurses, midwives, nutritionist and sanitary officers in order to improve health
services.
INTERNATIONAL RED CROSS AND RED CRESCENT SOCIETY:
The international red cross and red crescent society plays important roles in two major ways.
1. In time of war
(a) They take proper care of the injured.
(b) Provides emergency aid to those in distress.
(c) They are involved in negotiation of exchange of prisoners of war between countries. They provide
transport for the evacuation of refugees e.t.c.

2. In time of peace
(a) They provide the general first aid to patient.
(b) They assist in preventing accident.
(c) They assist in the training of nursing aides.
(d) They provide help to victims of natural disaster such as earthquakes, flood, fire e.t.c.

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FOOD AND AGRICULTURAL ORGANIZATION (FAO)
F.A.O was created on 16th October, 1945 with headquarters in Rome.

Specific function includes:

(1) To promote the common welfare through separate and collective action aimed at raising the level of nutrition
and standards of living.
(2) They help to spread to the public the knowledge of nutritional and agricultural science and practice.
(3) To improve the efficiency of production and distribution of all food and agricultural products.
(4) To better the conditions of rural population by ensuring human freedom from hunger.
(5) They help in the improvement of education and administration relating to nutrition, food and agriculture.
(6) They help to promote scientific, technological, social and economic research, relating to nutrition, food and
agriculture.

NIGERIA MEDICAL ASSOCIATION (N.M.A)

Their main functions are:
(1) Advising the government on how to improve the health status of people.
(2) Alerting the nation when there is an outbreak of a disease.
(3) Assisting in the training of medical and paramedical staff needed in health care delivery.
(4) Monitoring the recruitment of well trained doctors in hospital.
(5) Carrying out research on the ways to prevent and control disease.
Example
The control and prevention of diseases on a worldwide scale is the function of
A. Nigeria Medical Association B. Red Cross Society C. UNESCO D. UNICEF E. WHO (2005/31)
Answer: E – The control and prevention of diseases on a worldwide scale is the function of World Health
Organization (WHO).
Example
State four functions of World Health Organisation (W.H.O). (2014/1b NABTEB)
Answer:
- Improving the knowledge and standard of health all over the world.
- Assist in training medical personnel.
- Assist in prenatal and postnatal health care.
- Controls the distributions of dangerous drugs.
- Helps in standardizing the quality and dosages of drugs.

Example
Which of the following roles is not performed by a government agency responsible for forest maintenance?
A. Regulating the harvest of timber and poaching B. Creating, protecting and managing the forest reserves
C. Tracking the movement of timber, wood and wildlife D. Regulating mining activities in the forest (2019/40)
Answer: D – Regulating mining activities in the forest is not a role performed by a government agency responsible for
forest maintenance

Example
Which of the following organizations is mainly involved in improving the standards of living with children?
A. UNICEF B. WHO C. NACA D. FAO (2018/48 NABTEB)
Answer: A – United Nation International Children Emergency Fund (UNICEF) is mainly involved in improving the
standards of living of children.
Example
(d) Name: (i) Two international and (ii) Four national health organizations. (2008/3di & ii Neco)
Answer:
di. International Health Organizations: ii. National Health Organization
- Red Cross Society Nigerian Medical Association (NMA)
- World Health Organization (WHO) Nigeria Institute of Medical Research
National Agency for Food and Drug Administrative and Control
National Institute of Health (NIA)
Example
Which of the following is a role of the public Health Authorities?
A. controlling the spread of disease B. providing shelter for the people C. distributing relief fund
D. Manufacturing drugs E. distribution of improved planting materials (1998/49 Nov)
Answer: A – Control of the spread of disease is a role of the public health authority.

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EXERCISE 22.8
1. Which of the following international organizations is responsible for standardizing drugs?
A. Food and Agricultural Organization B. Red Cross Society
C. United Nations Children’s Emergency Fund D. World Health Organization (2003/52 Health Science Nov)
2. Medical quackery is the
A. same as orthodox medicine B. practice of deceit in medical services
D. cheapest imitation of the original E. use of expired drugs. (2003/60 Health Science Nov)
3. Which of the following behavior of a school child may be due to drug abuse?
A. Regular attendance at the school clinic B. Neglect of self appearance
C. Failure to do assignment D. Eating in the classroom (2003/59 Health Science Nov)
4. 5(a) State six benefits that member countries derive from the World Health Organization. (1996/5a Health
Science)
5. The following are functions of the UNICEF except
A. supplying medical equipment to rural health centers B. collecting and disposing refuse in urban cities
C. providing equipment for school children D. funding training of midwives
E. providing milk for children (1996/51 Health Science)
6. Which of the following is not under the control of the WHO
A. Disease prevention B. Red Cross activities C. Health education
D. Dissemination of information on diseases E. Anti-tuberculosis campaign (1990/67 Health Science)
7. Which of these organization is mainly concerned with the health of the people throughout the world?
A. Red Cross Society B. United Nations Children’s Emergency Fund
C. World Health Organization D. Food and Agricultural Organization
E. United Nations Educational, Scientific and Cultural Organization (1998/51 Health Science)
8. (b)(ii) State four health services that should be provided for factory workers
(c)(i) State three functions of the Red Cross Society. (1998/4b ii, ci Health Science)

REVISION EXERCISE
1. Which of these is a vector of malaria fever
A. female anopheles mosquito B. male anopheles mosquito
C. female culex mosquito D. male culex mosquito (2001/53)
2. The drugs which inhibit the growth of disease causing organisms and thus used in the treatment of infection
are referred to as
A. antibodies B. antibiotics C. antitoxic D. septics (2004/45)
3. Which of the following infection is unlikely to respond to antibiotic treatment?
A. typhoid fever B. ringworm C. measles D. tetanus (2005/44)
4. Which of the following infection would not respond to an antibiotic treatment
A. gonorrhea B. measles C. diarrhea D. tuberculosis (2007/46)
5. The vector of the sleeping sickness diseases parasite is the
A. cockroach B. mosquito C. backfly D. tsetse fly (2007/47)
6. Many diseases caused by bacteria can be treated and cured by using
A. antiseptic B. antibiotics C. antigens D. antibodies (2008/42)
7. Vaccination results in
A. aiding red blood cells to carry more oxygen B. production of antibodies which destroy toxins of germs
C. arresting excessive bleeding
D. production of white blood cells which engulf and digest bacteria (2011/46)
8. The use of water to the closet and septic tanks is preferred to the use of bucket and pit latrines because
A. it is cost effective B. contaminated faeces are completely kept away from flies
C. the water for flushing contains chlorine which will kill germs D. it prevents flies from breeding (2012/46)
9. The detection of vibrio cholera in public drinking water is a sign of
A. clean water B. outbreak of disease
C. water pollution D. decayed organisms in the water (2012/47)
10. Explain the following terms: (i) disease (ii) symptoms of diseases (2012/7a)
11. (b) Explain how vaccination protects the body from contracting infectious diseases. (2012/7b)
12. Distinguish between antibody and antigen. (2012/7c)
13. Name the causative agents of (i) Malaria (ii) Cholera (iii) AIDS (2012/7d)

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14. The main reason for immunizing children is to
A. destroy pathogens in their bodies B. increase the production of white blood cells
C. stimulate the production of antibodies D. stimulate the production of antibodies
D. stimulate the production of antigens (2013/41)
15. Oil applied to the surface of water kills the larvae of mosquitoes through
A. dehydration B. poisoning C. starvation D. suffocation (2015/36)
16. (i) What is sewage?
(ii) State five effects of releasing untreated sewage into a stagnant water body. (2015/3a)
17. State five functions of the World Health Organisation. (2017/6d)
18. Cholera is mostly spread by
A. air B. soil C. water D. noise (2019/38)
19. Which of the following methods does not make water fit for drinking
A. addition of chlorine B. boiling C. distillation D. addition of alum (2011/45)

20. The causative organism of sleeping sickness is the

A. trypanosome B. vibrio bacterium C. penicillum D. tsetse fly (2019/43 NABTEB)
21. List four (i) methods of controlling harmful microorganisms
(ii) roles of World Health Organization in maintaining good public health. (2000/6c Nov)
22. State briefly three methods that can be adopted in the prevention of viral diseases in humans. (2004/5b Nov)
23. State four methods of controlling the vector of malaria parasite. (2002/7b)
24. Name (i) Two international and
(ii) Four national Health Organisation (1999/49 NABTEB)
25. The following can be used to control the growth of micro-organisms except
A. antiseptics B. antibiotics C. isotonic solution D. high temperature (2018/47 NABTEB)
26. State four methods of controlling the vector of malaria. (1997/3c)
27. Factories where food is processed should be kept very cool and dry in order to
A. keep the building neat B. prevent the workers from perspiring excessively
C. prevent dust from setting in the raw materials D. allow the air to circulate
E. prevent bacteria from multiplying (1992/53 Nov)

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ECOLOGY
Basic Ecological Concept
Ecology is the study of the relationship between organisms and their environment. It also reveals how organisms
interact with each other and their physical environment i.e the influence of the organism on the environment and the
influence of the environment on the organisms.
1. Environment: This is the total surrounding of an organisms. The environment is made up of two components
a. Biotic (living) components: plants, animals
b. Abiotic (non-living) components: e.g. soil, water, atmosphere, temperature e.t.c

2. Biosphere: This is the part of the earth in which life exist. Earth is composed of the atmosphere which
envelopes a layer of air; hydrosphere which is composed of water and lithosphere which is the solid part.
The biosphere is the largest level of biological organization. It includes the part of the atmosphere,
hydrosphere and lithosphere where life can exists.

a. Atmosphere: The atmosphere surrounds the earth. It is the air layer surrounding the earth. It consists of
three main gases: nitrogen (78%), oxygen (21%) and carbon IV oxide (0.03%) and some other gases
(0.97%). The atmosphere consists of four main divisions. These are the troposphere (first layer),
stratosphere (second layer) mesosphere (third layer) and thermosphere (fourth layer)

b. Hydrosphere: This is the aquatic part of the biosphere e.g. rivers, lake, sea, ocean e.t.c.

c. Lithosphere: This is the solid part of the earth crust where plants and animals live

3. Habitat: A habitat is a place where an organism lives. It has all the necessary conditions that is needed to
support the life of the organisms examples of habitat includes aquatic habitat which include pond, stream,
river, lake e.t.c Terrestrial habitat are on land e.g. field, farmland, forests, grassland, desert and arboreal
habitats which is on trees.

4. Niche: A niche is a special place within a habitat where organism lives or the special function OF an organism
with respect to other organism’s e.g. the niche of a monkey may be describe as follows;
1. The monkey dwell on tree branches in a forest (arboreal habitat)
2. The monkey is a primary consumer.
The ecological niche is a sum total of all the roles played by any given organisms within a given
habitat
5. Population: This is defined as the total number of a particular species of animal or plant living in a given
area. It is made up of all the individual belonging to one species which occupy a particular area or space
within a period of time
6. Community: A community consists of all the organisms which occupy a particular area or space. E.g. the
organism in a pond within a period of time i.e. plants, animals and micro organisms
It is important to note that the organisms living in a particular community are interdependent i.e. they depend
on one another
7. Biomes: A biome is a large natural terrestrial ecosystem which has a characteristic appearance e.g. savannah,
forest
8. Ecosystem: An ecosystem or ecological system consists of living organisms and their non living environment
with which they interact and exchange materials e.g. a pond. An ecosystem is also described a natural unit in
which there is an interaction between all the living organism (biotic factors) and non – living (abiotic factors)
within an environment or habitat.
Example
All the available places on earth which supports life constitute the
A. lithosphere B. atmosphere C. biosphere D. hydrosphere (2000/43)
Answer: C – Biosphere is the part of the earth which life exist.
Example
Which of the following make up an eco system?
A. decomposers, animals and non living factors B. living and non living factors
C. plant and non living factors D. plants, decomposers and non living factors (2015/28)
Answer: B – The ecosystem is made up of living (biotic) and non-living (abiotic) factors.
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Example
The difference between a community and population is
A. a community is made up of organisms of the same species while a population is made up of organisms of different species
B. a community is made up of population of living organisms while a population is made up of organisms of the same species
C. an ecological niche does not exist but it does in a population
D. a community attracts competition but a population does not (2014/29)
Answer: B – The difference between a community and a population is that a community is made up of population of
living organisms while a population is made up of organisms of the same species.
Example
The area around the earth where life Activities go on is referred to as
A. biosphere B. lithosphere C. habitat D. ecosystem (2012/38)
Answer: A – The area around the earth where life activities go on is referred to as biosphere.
Example
A space containing a group of interactive organisms is called
A. community B. habitat C. ecosystem D. population (2012/37)
Answer: A – A space containing a group of interactive organism is called a community.
Example
A stable self sustaining environment produced by an interaction between the biotic and abiotic components is best
described as
A. a niche B. a community C. an ecosystem D. a habitat (2005/37)
Answer: A – An ecosystem is a stable self sustaining environment produced by an interaction between the biotic and
abiotic component.
Example
The activities of an organism which affect the survival of another organism in a habitat can be described as
A. biotic factors B. climatic factors C. physiographic factors D. edaphic factors E. abiotic factors (1989/30)
Answer: A – Biotic factor
Example
The entire habits and habitat of an organism can be described as its
A. ecological community B. ecological niche C. habitat factor D. biotic factor E. abiotic factor (1996/31)
Answer: B – The entire habits and habitat of an organism is described as its ecological niche.
Example
In ecology, a community refers to
A. a number of individuals of a given specie B. groups of different organisms living in a habitat
C. existing species in an abandoned farmland D. the dominant species in a habitat (2016/30)
Answer:
B – In ecology, a community refers to groups of different organism living in a habitat.
Example
6(a)(i) Define the term hydrosphere (ii) Give three examples of hydrosphere. (1999/6a (i), (ii)
Answer: 6ai. Hydrosphere is the aquatic portion of the biosphere or earth. ii. Lake, streams, rivers.
Example
The term ecosystem refers to
A. different groups of green plants in a habitat B. living members of a habitat
C. living organisms interacting with the physical environment
D. members of physical plants living in a habitat (2003/35)
Answer: C – Ecosystem refers to living organisms interacting with the physical environment.
Example
The group of several populations that interact and share a habitat form
A. a species B. a community C. an ecotype D. a tribe (2006/41) Answer: B – A community.

Example
3(a) Write short notes on each of the following:
(i) ecosystem; (ii) population; (iii) ecological succession in plants. (2006/3a)
Answer:
i. Ecosystem: This is an ecological community consisting of different populations of organisms that live
together in a particular environment/habitat.
ii. Population: This is the sum total of the number of a particular species of plant or animals living in a given
area.
iii. Ecological succession in plant: This is the process of change in the species structure of plant in an ecological
community over time.
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Example
The term community is defined as
A. the different groups of plants and animals in the same area and interacting with each other
B. the consumers and producers living in a habitat
C. living organisms interacting with physical factors of an environment
D. animals which mutually derive benefit from their association (2007/37)
Answer: A – Community is defined as the different groups of plant and animals in the same area and interacting with
each other.
Example
In a particular habitat the role of an organism is referred to as its
A. level B. biomass C. niche D. space (2010/32)
Answer: C – The role of an organism in a particular habitat is referred to as niche.
NB: A niche is also the special place in a habitat whwere an organsism lives.
Example
Ecology simply means the study of
A. particular species of plants and animals B. the interrelationship between plants and animals
C. carrying capacity D. the properties of a habitat (2013/35)
Answer: B – Ecology simply refers to the study of the interrelationship between plant and animals and the
environment.
EXERCISE 23.1
1. (b) Explain the following terms: (i) biosphere (ii) population (iii) community (iv) ecosystem (2013/3b)
2. Which of the following components makes up an ecosystem?
A. Decomposers, animals and non-living factors B. Living and non-living factors
C. Plants and non-living factors D. Plants, decomposers and non-living factors (2015/28)
3. What is the term used to describe the sum total of biotic and abiotic factors in the environment of the
organisms?
A. Habitat B. Biome C. Ecosystem D. Ecological niche (1993/35 JAMB)
4. A caterpillar and an aphid living in different parts of the same plant can be said to
A. be in similar micro habitats B. Occupy the same ecological niche
C. be in different habitats D. occupy different ecological niches (2004/8 JAMB)
5. The highest level of ecological organization is the
A. ecosystem B. niche C. biosphere D. population (2015/26 JAMB)

6. A group of organisms of different species living in a particular area is described as a

A. colony B. community C. population D. niche (1998/28 JAMB)
7. The physical space occupied by an organism together with its functional role in the community can be
described as
A. environment B. biome C. niche D. habitat (2001/34 JAMB)
8. Which of the following statements best describes an ecosystem?
A. a place where living organisms can live successfully
B. the interaction between living organisms in a habitat and he non-living part of the environment
C. a biological association between a plant and an animal
D. a system of grouping organisms in a habitat (2006/37 Nov)
9. Community can be defined as a
A. population of plants and terrestrial animals living in any habitat
B. group of plants h in a particular habitat with some degree of interdependence
C. collection of different plant populations in a habitat
D. collection of plants and animals living in a particular habitat with full interdependence (2004/50 Nov)
10. d. Define the ecosystem. (2018/1d Neco)

Components of an Ecosystem
The components of the ecosystem are the non-living environment and the living community.
The living part of an ecosystem is known as biotic component. It is composed of all the biotic community.
The biotic community includes population of
1. Food producers (autotrophs) e.g. green plants.
2. Food consumers (heterotrophs) e.g. animals and protozoans.
3. Decomposers (Saprophytes) e.g. Fungi.
The non living part of an ecosystem is its abiotic component. It consists of abiotic resources and abiotic conditions.
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The abiotic resources are what organisms need in order to stay alive e.g. source of energy i.e sunlight and inorganic
nutrients like CO2, H2O, nitrogen e.t.c.
Abiotic conditions affect the behavior, growth and breeding pattern of organisms e.g. habitat and other factors such as
temperature, light intensity, rainfall, humidity, turbidity e.t.c.
Example
3(a)(i) List three components of an ecosystem
(ii) Describe briefly the interaction among the components named in (a) (i). (1991/3a i, ii)
Answer:
3ai. Three components of an ecosystem are: Producers, Consumers, Decomposers
ii. The producers (green plants) manufacture food by making use of sunlight water, chlorophyll and carbon(iv)oxide
through the process of photosynthesis. The consumers (animals) feed on the plant and release carbon(iv)oxide
which the consumers (green plants) take in to manufacture their food. Decomposers (microorganisms) break down
dead and decaying plant and animals to release nutrients into the soil for plant use.
Example
Which of the following processes is not due to interaction between the biotic and abiotic components of an
ecosystem?
A. Soil nutrient depletion B. Condensation C. Decomposition
D. Osmosis E. Photosynthesis (1996/30)
Answer: D – Osmosis is not due to interaction between the biotic and abiotic components of an ecosystem.
Example
Which of the following is an abiotic factor?
A. Predation B. Rainfall C. Cropping D. Grazing E. Migration (1997/40)
Answer: B – Rainfall is an abiotic factor.
Example
Which of the following is not a biotic factor?
A. Parasites B. Predators C. Grazers D. Pressure (1999/37) Answer: D – Pressure is not a biotic factor.
Example
5(a) What is an ecosystem? (2001/5a)
Answer: An ecosystem is an ecological community of interacting organisms and their physical environment.
Example
Which of the following components of an ecosystem does not contribute to the biomass of the system?
A. Producers B. Consumers C. Micro-organisms D. Habitat (2006/39)
Answer: D – habitat does not contribute to the biomass of the ecosystem.
Example
The following are abiotic components of the ecosystem except
A. bacteria B. topography C. water D. wind (2012/39) Answer: A – Bacteria are biotic factors.

EXERCISE 23.2
1. In an agricultural ecosystem, the biotic component consists of
A. crops, pest and beneficial insects B. crops, temperature and humidity
C. pests, beneficial insects and water D. crops, water and soil (1986/43 JAMB)
2. The activity of an organism which affects the survival of another organism in the same habitat constitutes
A. an edaphic factor B. an abiotic factor C. a biotic factor D. a physiographic factor (2010/37 JAMB)
3. The solid part of the ecosystem is referred to as the
A. atmosphere B. hydrosphere C. biosphere D. lithosphere (2013/42 JAMB)
4. In an agricultural ecosystem, the biotic component consists of
A. crops, pests and beneficial insects B. crops, temperature and humidity
C. pests, beneficial insects and water D. crops, water and soil (2019/3 JAMB)
5. Which of the following is not a biotic factor of an ecosystem?
A. Predation B. parasitism C. Commensalism D. Radiation (2001/42 NABTEB)
6. In an ecosystem green plants are referred to as
A. primary consumers B. decomposers C. primary producers D. secondary consumers (2001/44 NABTEB)
7. Which of the following is not an ecosystem?
A. Poddle of water in rock crevices B. An aquarium C. Savanna D. Lake E. Quadrat (1995/37 Nov)

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8. 4.(a) Name the four major components of an ecosystem
(b) Describe briefly the interaction among the major components of an ecosystem. (2006/4a, b Nov)

LOCAL BIOTIC COMMUNITY OR BIOMES IN NIGERIA

A biome is a large biotic (biological) community which corresponds to vegetation belt or zone. Each biome has its
characteristics climate and the living organisms that are found there and are adapted to that particular climatic
condition.
The local biotic communities in Nigeria can be grouped into two major zones
1. Forest zone
2. Savanna zone
The forest zone is made up of vegetation having mainly trees and it comprises of the following local biotic
communities.
a. Mangrove swamp forest (salts and fresh water swamp)
b. Tropical rain forest

The savanna zone is made up of mainly grasses and it is further sub divided into three savanna belt or biotic
communities
a. Southern guinea savanna
b. Northern guinea savanna
c. Sahelian savanna

MANGROVE SWAMP FOREST

The mangrove swamp forest is found in areas along the coast especially in states like Delta, Cross-river, Akwa Ibom,
Bayelsa, Ogun and Lagos.

Characteristics of the Swamp Forest

1. It has tall woody trees
2. Plants mainly have prop root and breathing roots (aerial roots)
3. Its water is a combination of fresh and salt water
4. The total annual rainfall is usually above 2500mm throughout the year which results in water logging
5. It has ever green trees with broad leaves
6. Some common plant species found includes white mangrove, red mangrove, raffia palm, coconut e.t.c.
7. Animals found in the biotic community include tilapia, fish, oyster, crabs, snakes, birds and king fishers

Tropical Rain Forest: This biotic community can be found in states like Edo, delta, Ondo, Imo, Abia, Lagos, Ogun,
Rivers, Oyo and Bayelsa.

Characteristics of Tropical Rain Forest

1. The vegetation consists mainly of woody plants like trees, shrubs and herbs. Grasses are almost absent.
2. Trees form three layers of strata i.e. bottom, middle and upper layers
3. It has numerous climbers, creepers, epiphytes and parasitic plants
4. It has little undergrowth due to canopy formed by the tall trees
5. Plant species includes iroko, obeche, mahogany, African walnut, opepe, ebony e.t.c.
6. Animals found include monkeys, birds, snakes, chameleon, squirrel e.t.c

Savanna Zones
a. Southern Guinea Savanna: This biotic communities are found in states like Enugu, Kogi, Benue, Kwara,
Uyo, Ebonyi, Osun and Ekiti states.

Characteristics of Southern Guinea Grass

1. It is the largest of all the biotic community in Nigeria
2. It has moderate rainfall of between 100-150cm
3. It has tall grasses
4. It has tall trees with broad leaves
5. The trees are scattered and deciduous i.e. they shed their leaves during the dry season
6. Important trees include locust bean trees, shea-butter and isoberlinia. (Isoberlinia doka)
7. Important animals commonly found in this biome includes antelopes, lion, leopards, zebra e.t.c
b. Northern guinea savanna: This biome is found in states like plateau, Kaduna. Bauchi, Niger, Taraba,
Adamawa and Kano states

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Characteristics of Northern Guinea Savanna
1. It has low rainfall of about 500-1000mm per annum
2. It has short but numerous grasses
3. It has scattered and short deciduous trees
4. Some of the trees have thorns while others have thick barks
5. Some of the trees wither in dry season and sprout at the beginning of the rainy season
6. Common plant species found include acacia, date palm, silk cotton plants and baobab
7. Common animals include snakes, lizard, deer, lion, leopards, antelope e.t.c.
c. Sahel Savanna: This local biotic community is found only in the extreme northern part of Nigeria such as
Bornu, Katsina, Sokoto, Yobe, Kebbi, Zamfara, Kano and Jigawa.
Characteristics of Sahel Savanna
1. It has high temperature and very low rainfall (below 500mm per annum)
2. Presence of short and scanty grasses
3. Presence of short and tough shrubs or trees.
4. Presence of short, thorny and sparsely distributed grasses
5. Important plant species includes gum Arabic and date palm (Phoenix dactylifera) .
d. Desert: These are areas with maximum rainfall of about 250mm per year. This biome is located at the northern
borders of Sokoto, Katsina, Jigawa, Yobe and Bornu states.
Characteristics of Desert
1. A desert has little or no rainfall in most of the year (less than 250mm annually).
2. It has high temperature at day and very low humidity at night.
3. It has fewer grasses and shrubs.
4. The plants have special adaptive features like absence of leaves, swollen and succulent stems, and long root
e.t.c.
5. Common examples of trees found in this biome are baobab and cacti trees.
Example
Very low annual rainfall, sparse vegetation, high day temperature and biome known as
A. swamp B. tropical C. southern guinea savanna D. afro alphine E. desert (1995/35)
Answer: E – Desert. It is chracterstized by very low annual rain fall, sparse vegetation, high day temperature.
Example
Which of the following is a characteristic of a swamp?
A. vegetation with stratified arrangement B. mesophytes with broad leaves
C. the ground is flooded most of the time D. predominance of climbing plants
E. many plant with five resistant structure (1995/34)
Answer: C – The ground is flood most of the time.
Example
State three characters each of the plant community in the tropical rain forest and savanna. (1994/1d)
Answer:
Three characteristics of plant community in the rain forest: Three characteristics of plant community in Savana:
The plants have regularly stratified canopies. The plants have no stratified canopies.
The plants have broad leaves and buttress root. The area of predominantly grassland.
The ground is generally littered with a lot of leaves. The trees are drought resistant.
Example
Which of the following is not an adaption of plants or animals to desert environment?
A. a well developed tap root system B. small leaves with thick epidermis
C. stems with spike like leaves D. metabolic waste in the form of uric acid in some animals
E. broad leaves per storage (1993/39)
Answer: E – Broad leaves per storage is not an adaptation of plants or animal to desert environment.
Example
Which of the following world biomes is found in Nigeria?
A. sahel savanna B. tundra C. desert D. afro alpine vegetation E. temperature deciduous forest (1992/40)
Answer: A – Sahel Savannah
Example
Fewer number of trees is characteristic of the Savanna zones of Nigeria because
A. there is too much sunlight B. there is limited amount of rainfall
C. they are usually exposed to grazing animals D. they are covered by high mountains
E. the farmers always engage in bush-burning (1991/39)
Answer: B – Savana zones in Nigeria have fewer number of trees because there is limited rainfall.
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Example
8(a). Describe the characteristic features of the vegetation of the tropical rain forest. (2007/8a, b)
(b) Name two types of savanna found in Nigeria giving one example in each case of a town where they occur.
Answer:
a. Characteristics of Tropical Rain Forest
- The vegetation consists mainly of woody plants like trees, shrubs and herbs. Grasses are almost absent.
- Trees form three layers of strata i.e. bottom, middle and upper layers
- It has numerous climbers, creepers, epiphytes and parasitic plants
- It has little undergrowth due to canopy formed by the tall trees
- Plant species includes iroko, obeche, mahogany, African walnut, opepe, ebony e.t.c.
- Animals found include monkeys, birds, snakes, chameleon, squirrel e.t.c
b. Types of Savanna found in Nigeria
- Guinea Savanna: Bida, Kaduna, ilorin - Sahel Savanna: Maiduguri
Example
Northern Guinea savanna is associated with
A. abundant rainfall B. abundant trees and shrubs C. soil with very little plant cover
D. abundant grasses E. high humidity (1997/38)
Answer: D – Northern Guinea Savanna is associated with abundant grasses.
Example
The Southern Guinea Savanna differs from the Northern Guinea Savanna in that it has
A. lower rainfall and shorter grass B. less grasses and scattered grasses
C. more rainfall and taller grasses D. less arboreal and burrowing animals (1997/37 JAMB)
Answer: C – The southern Guinea Savannah differ from the northern guinea savannah in that it has more rainfall and taller grass.
Example
The most important environmental factor which epiphytes in the rain forest compete for is
A. water B. nutrient C. light D. space (2000/30 JAMB)
Answer: C – Epiphytes in the rain forest compete for light.
Example
The physical and climatic factors of a region primarily determine the
A. types of plants found in the area B. Kinds of animal inhabiting the area
C. community of organisms in the region D. Nature of the soil in that region (2002/38 JAMB)
Answer: C – Community of organisms in the region.
Example
The correct sequence of biomes from Northern to Southern Nigeria is
A. estuarine → tropical rain forest → guinea savanna →sahel savanna
B. Sahel savanna →sudan savanna → guinea savanna → tropical rainforest → estuarine
C. sahel savanna → tropical rain forest → estuarine → guinea savanna
D. guinea savanna →sudan savanna → tropical rain forest → sahel savanna → estuarine (2003/36 JAMB)
Answer: B – Sahel savanna →sudan savanna → guinea savanna → tropical rainforest → estuarine
Example
The Membilla plateau is a unique Nigerian biome located in
A. Taraba State B. Plateau State C. Benue State D. Borno State (2005/28 JAMB)
Answer: A – The mambilla plateau is located in Taraba State of Nigeria.
Example
In Nigeria, the Guinea savanna belt borders the
A. rainforests and the desert B. mangrove swamps and the Sahel savanna
C. rainforests and the Sudan savanna D. deserts and the Sudan savanna (2005/33 JAMB)
Answer: C – Guinea Savanna belt borders the rainforest and the Sudan Savannah
EXERCISE 23.3
1. A biotic factor which affects the distribution and abundance of organisms in a terrestrial habitat is
A. temperature B. competition C. pH D. light (2007/9 JAMB)
2. In which of the following Nigerian states can mountain vegetation be found?
A. Taraba B. Enugu C. Bauchi D. Plateau (2007/10 JAMB)
3. Millet, sorghum, maize and onions are common crops, grown in Nigeria in the
A. Sahel savanna B. montane forests C. Sahel savanna D. tropical rainforests (2011/39 JAMB)
4. In which of the following biomes is the South Western part of Nigeria located?
A. Tropical rain forest B. Tropical woodland C. Desert D. Temperate forest (2011/40 JAMB)
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5. The mangrove swamp in Nigeria is restricted to the
A. Sahel savanna B. Guinea savanna C. Tropical rainforest D. Sudan savanna (2015/6 JAMB)
6. In which of the following Nigerian states can montane vegetation be found
A. Bauchi B. Plateau C. Taraba D. Enugu (2015/11 JAMB)
7. (b) Describe the vegetation of the tropical rain forest.
(c) List five animals that inhabit the Tropical Rain Forest. (2013/8b, c Nov)
8. Which of the following biomes is not found in Nigeria?
A. Tundra B. tropical rain forest C. savanna D. fresh water swamp E. salt water swamp (1999/51 Nov)
9. Which world biomes can be found in Nigeria?
A. afro-alpine B. coniferous forest C. desert D. savanna E. tundra (2001/38 Neco)

Major Biomes of the World

The major biomes of the world are:
1. Tropical rain forest 3. Desert 5. Afro-alpine
2. Savanna 4. Shrubs 6. Swamp

Tropical Rain Forest: The tropical rain forest is the richest of all the biomes. It is located around the equator (i.e.
within 5°N and S of the equator). The forest is found in the Amazon basin of South America, Zaire Basin of central
Africa, the coast of West Africa and interior of Malaysia.

Characteristics of Tropical Rain Forest

1. It has a high temperature of about 25°C – 27°C with a small annual range of 2-3°C.
2. Rain fall is throughout the year with two peaks (double maxima).
3. It has an annual rainfall range of about 1500mm-2000mm.
4. It has abundant sunshine.
5. Relative humidity is very high.
6. Forest trees have broad ever green leaves.
7. There is abundance of hardwoods. Iroko, obeche, mahogany, African walnut, ebony e.t.c.
8. The forest has little undergrowth.
9. The trees are of great varieties.
10. It consists of five layers. The first three comprises of trees, the fourth layer consists mainly of shrubs and the
fifth layer comprises of the forest floor.
11. Creepers, climbers, epiphyte and parasitic plant are commonly found in the tropical rain forest.

Grassland
Grassland biomes consists of large open area of grass with little or no trees. Grassland covers very extensive area of
the world i.e. about 20% of the earths total land mass. Grassland can be differentiated from forest by the relatively
absence of trees and the abundance of grasses. The grassland occupies areas lying between the tropical rain forest and
the semi desert vegetation.
Grass land is grouped into: 1.Tropical grassland /savanna 2. Temperate grassland

Tropical grassland: The tropical grass land also called savanna is located between 5° and 20°N S of the equator.
The grassland is found in Central America, North West part of South America, interior of Brazil, West Africa, part of
the East Africa, South East Asia and Northern Australia.

Characteristics of Tropical Grass Land

1. Temperature ranges from 21°C – 30°C at extremes.
2. It has an annual temperature range of 11°C.
3. The annual rainfall is about 600 – 1500mm.
4. It has seasonal conventional rainfall with single maximum.
5. There is presence of short and scattered trees. Popular trees in the community include acacia, baobab and shea=butter
6. The grasses are called savanna in Africa and Australia, campos in Brazil and Ilanos in Orinoco (South America).

Temperate Grassland: Temperate grassland are areas with low annual rainfall, fluctuating seasonal temperature and
few trees. They are found throughout central North America, where they are also known as prairies. They are also
found in Asia where they are known as Steppes and also in South America and Australia.

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 Characteristics of temperate grassland
ii. Temperate grasslands have hot summers and cold winters; the growing season occurs during the spring summer and fall.
iii. Annual rainfall is about 250mm – 750mm.
iv. Rainfall is usually conventional and light.
v. Dominant vegetation consists of grasses.
vi. Few trees are present.
vii. Example of animals found in this biome includes reptile, birds, insects, giant ant eaters, American Bison, Blue
Wild Beast e.t.c.

Deserts: Deserts are dry (arid) places where the availability of water is the major factor that determines the type of
organisms that can live there. Typically a desert is characterized by having less than an average of 250mm of Annual
rainfall, but a more important factor is that deserts have a strong tendency to lose water by evaporation and this
potential for water loss exceeds the annual rainfall.

So deserts are characterized by having sparse vegetation and the organisms that live in deserts are adapted to
withstand or avoid water stress. Deserts soils tend to be poorly developed, with a high content of mineral particles but
little organic matter.

Plants that grow in deserts environment must have special adaptations to conserve water. Such plants are referred to as
xerophytes e.g. cactus. Xerophytes usually have needle like or spring leaves to reduce the rate of transpiration.
There are two types of deserts, these are the hot and the cold deserts. Examples of hot deserts include Sahara Desert
(North Africa), Arabian Desert (Arabia), Kalahari Desert, Great Australia desert while example of cold deserts include
the Atacama desert (Peru and Chile), Namib desert (South Western Africa).

Characteristics of Hot Deserts

1. Hot desert has high temperature between 30°C and 60°C.
2. Annual rainfall is about 250mm.
3. Evaporation is high while the relative humidity is very low.
4. The desert is associated with cold current.
5. Vegetation is sparse or scanty.
6. Common vegetation includes grasses, shrubs and herbs.
7. Most plant are xerophytes (drought resistant plants) like thorny bushes, the bulbous cacti, wiring grasses, date
palm and acacia.

Cold Desert
Cold desert are located in the interior of the continents around 45° – 60° North and South of the equator. Cold
deserts are found in the interior of Eurasia, North America and in Patagonia (South America).

Characteristics of Cold Deserts

1. It has hot summers and cold winters
2. Rainfall is about 250mm (low and unreliable due to long distance from the sea)
3. Diurnal temperature range is about 35°c while annual range is 40°c
4. Cold deserts have short and scanty grasses
5. It has drought resistance plants with woody stems and needle like or spiny leaves to reduce the rate of
transpiration
Shrubs
The shrub vegetation is found on the equatorial margins of the sub tropical and tropical deserts with a short rainy
season in summer and a long winter dry season. It is found in west Africa close to the Sahara Desert, North Eastern
Brazil and Australia.

Characteristics OF SHRUBS
1. These vegetations have a very high temperature of over 30°C.
2. Mean annual rainfall is about 250mm – 475mm which is very low.
3. Summers are hot and dry while winter is mild and rainy.
4. The vegetation of this biome is dominated by thorny trees or shrubs.

Afro – Alpine
Afro – alpine is a kind of vegetation associated with high mountains or highlands. The afro – alpine vegetation as it
relates to Africa is found in highlands such as Cameroon Mountain, Kenya highland, Kilimanjaro Mountain (East
Africa).

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Characteristics of Afro – Alpine
1. Temperature and pressure of afro – alpine decreases with altitude
2. Heavy rainfall is experienced on the wind ward side of the mountain while lesser rainfall is experienced on
the leeward side
3. The windward side of the mountain may have a luxuriant forest type of vegetation
4. The leeward side may experience savanna type of vegetation
5. Vegetation decreases with height of the mountain
6. The peak of the mountain may experience ice – cap or permanent snows
Swamp
The swamp forests are usually found in the tropic along coastal regions and river mouths in west Africa, east Africa
and South Africa. Swamps are generally found along the coast all over the world.
Characteristics of Swamp
1. Swamp has high temperature of about 27°C throughout the year
2. It has high rainfall of over 2500mm with no distinct season.
3. Relative humidity in swamps is very high. It is close to 90%.
4. The dominant plants are the white mangrove, red mangroves and raffia palm
5. The white mangrove has roots which enables it to carry out gaseous exchange
6. Animals commonly found include mud skipper, crabs, tilapia fish, e.t.c.

Example
The following habitats can be found in West Africa except
A. mangrove swamp B. Sahel savanna C. savanna grassland D. temperate grassland (2014/28)
Answer: D – Temperate grassland cannot be found in West Africa.
Example
The rate of decomposition of organism is faster in the tropical rain forest than in other biomes because
A. of the relatively constant daylight B. there are more plants per square feet
C. of abundance of water D. of constant cool temperature (2011/40)
Answer: C – The rate of decomposition of organism is faster in the tropical rainforest than in other biomes because of
abundance of water.
Example
Which world biomes can be found in Nigeria?
A. afro – alpine B. coniferous forest C. desert D. savanna E. tundra (2001/38 Neco)
Answer: D – Savannah
Example
A water logged habitat with low light penetration and very low quantity of dissolved oxygen best describes a/an
______ habitat
A. estuarine B. marine C. Sahel savanna D. swampy E. tropical rain forest (2005/54)
Answer: D – A water logged habitat with low light penetration and very low quality of dissolved oxygen best
describes a swampy habit.
Example
The following are features of northern guinea savanna except
A. presence of tall trees with thick bark B. bare soils with very few trees
C. presence of fire resistant trees D. abundant herbivores E. predominance of woody tree (1993/34)
Answer: A – Presence of tall trees with thick bark is not a feature of savanna .
Example
The following are features of the tropical rain forest except
A. abundant water supply B. loose and moist soil C. short trees growing beneath tall trees
D. scanty trees with small leaves E. presence of many animals (1993/33)
Answer: D – Scanty trees with small leaves is not a feature of the tropical rain forest.
Example
Which of these is not a true characteristic of the tropical rain forest?
A. Vegetation consists predominantly of tall trees, with thick canopy B. Forest is rich in epiphysis and climber’s
C. Annual rainfall is less than 100cm D. Interior has low light intensity; high humidity and damp floor
E. Fruits of trees are often large-sized and are generally without adaptation to wind dispersal (1996/32)
Answer: C – Annual rainfall is less than 100cm is not true of the tropical rainforest.

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Example
One of the characteristics of plant in the savanna is the
A. possession of thin, smooth barks B. possession of large tap roots
C. production of seedlings on mother plant D. possession of thick, flasky barks (1988/44 JAMB)
Answer: D – Possession of thick, flaky bark is a characteristic of plants in the savannah.
Example
In a savanna ecosystem the abiotic factors include
A. legumes, temperature and sandy soil B. water, temperature and soil
C. minerals, oxygen and reptiles C. water, soil and grasses (1990/41 JAMB)
Answer: B – Water, temperature and soil are abiotic factors in a savannah ecosystem
EXERCISE 23.4
1. Which of the following biomass could be characterized by very low rainfall, cold nights, hot days and fast
blooming plants
A. Northern Guinea savannah B. Southern Guinea savanna
C. Tropic desert D. Montane forest (2009/33 JAMB)
2. Low annual rainfall, sparse vegetation high diurnal temperature and cold nights are characteristics features of
the
A. tropical forest B. desert C. montane forest D. guinea savanna (2010/35 JAMB)
Use the list of biomes below to Answer: questions 35 and 36.
1. Desert 2. Rain 3. Southern Guinea Savannah 4. Northern Guinea Savannah forest
3. A biome with a low annual rainfall, few scattered trees within, dense layer of grasses and found in Kano and
Katsina states is
A. 1 B. 2 C. 3 D. 4 E. 5 (1994/35 JAMB)
4. A biome where there are many cacti and the small mammals undergo aestivation for long periods is
A. 1 B. 2 C. 3 D. 4 (1994/36 JAMB)
5. Which of the following biomes is not found in Africa?
A. mangrove swamp B. Desert C. savannah D. tropical rain forest E. tundra (2014/27 Neco)
6. In ecology a community refers to
A. a number of individuals of a given species B. groups of different organism living in a habitat
C. existing species in an abandon farmland D. the dominant species in habitat (2016/30)
7. The following biotic communities are found in Nigeria except
A. afro – alpine B. derived savanna C. Sahel savanna
D. swamp E. tropical rain forest (2000/35 Neco)
8. Name the two types of savanna found in Nigeria giving an example in each case of a town where they occur.
(2007/8b)
9. Describe the characteristic features of the vegetation of the tropical rain forest. (2007/8a)
10. Trees in savanna habitat usually have heavy bark which mainly
A. reduces the rate of transpiration B. protect them from the scorching sun
C. protect them from heavy winds D. resist bush fire (2005/33)
11. State five important uses of water to organism in the tropical rainforest. (2003/8b)
12. The term ecosystem refers to
A. different groups of green plant in a habitat B. living members of a habitat
C. living organisms interacting with the physical environment
D. members of a particular plants and animals living in habitat (2003/35)
13. List four characteristics each of (i) trees of the tropical rain forest (ii) tree/shrubs of the savanna. (2002/8b)
14. Desert plant are usually called
A. hydrophytes B. mesophytes C. xerophytes D. sporophyte (1999/38)
15. Northern guinea savanna is associated with
A. abundant rainfall B. abundant trees and shrubs C. soil very little plant cover
D. abundant grasses E. high humidity (1998/38)
16. Which of these is not a true characteristic of the tropical rain forest?
A. vegetation consists of predominantly of tall trees, with thick canopy
B. forest is rich epiphytes and climbers C. annual rainfall is less than 100cm
D. interior has low light intensity, high humidity and damp floor
E. fruits of trees are often large seeded and are generally without adaptation to wind dispersal (1996/32)
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17. Fewer numbers of trees is a characteristics of the savanna zone in Nigeria because
A. there is too much sunlight B. there is limited amount of rainfall
C. they are usually exposed to grazing animals D. they are covered by high mountains
E. the farmers always engage in bush burning (1991/39)
18. List three component of an ecosystem. (1989/3ai)
19. The populations of different organisms living and interacting in a given habitat is
A. a biome B. a community C. an ecosystem D. a niche (2019/31)

Aquatic Habitat (Marine and Estuarine Habitat)

An aquatic habitat is a body of water in which organisms live. Such organisms are called aquatic organisms e.g. fish,
algae, crabs, e.t.c.

Types of aquatic habitat

There are three types of aquatic habitats namely:
(1) Marine/salt water habitats.
(2) Estuarine/brackish water habitats.
(3) The fresh water habitats.

Marine habitats
A Marine habitat can be defined as an aquatic habitat in which the water is salty (salt water). Example of marine
habitat includes the seas and oceans. It is worthy to note that over 70% of the earth’s surface is covered by water and
most of that includes marine habitat.

Characteristics of marine habitat

(1) High salinity/salt concentration: The water present in marine habitat is known as salt water. Salt water is
water that has 35g of salt for every kg (1000g) of water. It is not something that can be consumed by humans.
(2) Pressure increases with depth.
(3) High density of about 1.028; thus enables organisms to float on it.
(4) The oxygen concentration of the ocean is not uniform. It is highest at the surface, and decreases with depth.
(5) The pH (hydrogen ion concentration) at the surface water of marine habitat ranges from 8.0 to 8.5 i.e.
alkalinic nature.
(6) Tides: This is the rise and fall of the ocean water. It happens usually two times a day. Tides are caused by the
gravitational pull on the earth. Water level increases in marine habitat during high tide but reduces in low tide
and this affects the organisms living in it.
(7) Turbidity and light penetration: The ocean water has a high turbidity and this reduces the intensity of light
penetration. The turbidity is as a result of suspended particles washed into it from land rivers.
(8) Size: Marine habitat represents the largest of the water body. Majority of the earth surface is water and the
marine habitat accounts for about 97% of that water.
(9) Currents: Currents are always produced at the surface of the ocean. The cause of this current could be wind,
rotation of the earth or difference in water density between one part of the ocean and another.
(10) Waves: Ocean are usually subjected to wave action. Waves are non – directional movement of water caused
by the blowing of winds against the water surface.

Major Zones of the Marine Habitats

The major zones of marine habitat includes.
(1) Splash (supratidal) zone.
(2) Intertidal (euphotic/neritic) zone.
(3) Littoral (euphotic/subtidal) zone.
(4) Benthic (diphotic/bathyal) zone.
(5) Abyssal (aphotic) zone and
(6) Hadal (aphotic) zone.

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 Zone of marine habitat

Supratidal or splash zone: This is the exposed zone of the marine habitat. This zone can be argued to be part of the
terrestrial habitat and not a marine habitat as it is not submerged by ocean but only sprayed by splashes of water from
breaking waves.

Intertidal or neritic zone: This zone is also called planktonic or euphotic zone. It is exposed to air during low tide
but covered by water at high tide. This zone is also exposed to wave action. It has high photosynthetic activities
because of the abundant sunlight. The water temperature in this zone also fluctuates.

Subtidal zone is also the disphotic zone

This area of the ocean covers the continental shelf. It is also known as the euphotic zone. It is about 200m deep. It is
constantly under water and has abundant light and nutrient. Consumers and decomposers are also found here.

Benthic zone: This is also known as the disphotic zone. It starts from the continental shelf to about 2000m. It has low
light penetration and low nutrient.

Pelagic or abyssal zone: This zone has low temperature, low light penetration, high pressure, low photosynthetic
activities and the primary production of food is by chemosynthesis.

Hadal or aphotic zone: This is the deepest zone of the marine habitat. It is over 7000m deep. It forms the floor or bed
of the ocean. There is no light present and no photosynthetic activities.

Distribution of organisms in marine habitat and their adaptive features

The organisms in marine habitats include plants and animals.
Plants in marine habitats:
1. Algae: e.g. sargassum: Possesses chlorophyll for photosynthetic activities, small size or large surface area for
drifting or floating.
2. Sea weeds: They possess hold fast for anchorage into the soil. They have divided leaves, floating devices or
air bladder for buoyancy. Their body is protected with mucilaginous cover to reduce dessication . They also
possess chloroplasts for photosynthesis
3. Sesuvium: Possess thick leaves or reduced leaves which aid in water conservation.
4. Plankton e.g. diatoms: They possess air spaces in their tissues, rhizoid (false feet) for attachment to rocks
and air bladder for buoyancy.

Animals in marine habitats and their adaptive features

Barnacles: They have basal disc for strong attachment to rock shore, cilila for feeding, shell which prevents
dessication during low tide and mantle which retains water.
Periwinkle: They possess lungs for breathing and foot for attachment to substratum and shell which prevent
dessication.
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Star fish: They possess tube feet which aid in the attachment to substratum and hard shell which prevent dessication
or drying up.
Crabs: They are capable of burrowing fast into the mud to protect them against predators, strong waves or tides.
Possession of exoskeleton aids in preventing dessication on land. Their body fluid is isotonic to sea water
Shrimps: They possess powerful claws for seizing food.
Bony fish: Fishes like tilapia and herring drink salt water to cope with high salt content of ocean. They also possess
salt secreting glands in their gills to enable them maintain osmo-regulation.
Cartilagenous fishes: Cartilagenous fishes like shark and dogfish have the ability to retain urea in their body to cope
with high salinity.

Food chain in marine habitat

A typical food chain in marine habitat could be up to three or four trophic levels. The planktons e.g. diatoms serve as
the major producers which support the food chain. Examples of food chains include
1. Diatoms   zooplanktons   tilapia   shark
2. Diatoms 
 crabs 
 tilapia e.t.c

Factors affecting marine habitat: Temperature, wind, density, pH, sunlight and salinity.

Example
Puddles, ponds, rivers, lake, sea and oceans are group together as
A. ecosystem B. biosphere C. terrestrial habitat D. marine habitat E. aquatic habitat (1991/37)
Answer: E – Puddles, ponds, river, lake, sea and ocean are grouped together as aquatic habit.
Example
Which of the following describes a marine habitat? A large body of water
A. which has no distinctive colour or taste B. with high concentration of salt
C. with little suspended materials D. with no water weeds
E. which sustains no animal life (1993/32)
Answer: B – Marine habitat is a large body of water with high concentration of salt.
Example
Which of the following is not an aquatic habitat?
A. estuarines B. pond C. rainforest D. swamp E. salt lake (1996/40)
Answer: C – Rainforest is not an aquatic habitat.
Example
The following factors affect organisms in aquatic habitat except
A. humidity B. light C. temperature D. turbidity (2017/15)
Answer: A – Humidity does not affects organism in aquatic habitat.
Example
Aquatic plants are referred to as
A. epiphyte B. mesophytes C. xerophytes D. hydrophytes (2016/16 NABTEB)
Answer: D – Hydrophytes are another name for aquatic plants.
Example
The following characteristics are associated with marine habitats except
A. high salinity B. wave action C. increased pressure with depth
D. fewer species of organisms than on land E. rise and fall of water level (1996/47 Nov)
Answer: E – Rise and fall of water level is not associated with marine habitats.
Example
Plants that survive in marine habitats are called
A. halophytes B. hydrophytes C. mesophyte D. saprophytes E. xerophytes (2018/59 Neco)
Answer: A – halophytes are plants that survive in marine habitat

Example
List three major zones in the marine habitat, stating one characteristics features of each zone. (1994/1a)
Answer:
- Splash zone (supratidal) zone; - it is exposed and usually moistened by the splashed water.
- Littoral zone: It is always covered with water and also receive sufficient light.
- Intertidal zone: It is exposed at lowtide and covered with water at high tide.
- Hadal/Aphotic zone: It receives no light

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Example
(i) Give one example each of plants and animals in the marine habitats
(ii) Explain how each of the plants and animal is adapted to the habitat. (1994/1b)
Answer:
1bi. Examples of plants in marine habitat: Sea weed (diatom), sesevium, algae.
Examples of animals in marine habitat: Periwinkle, shrimps, barnacle, star fish etc.
ii. Adaptation of algae in marine habitat:
- Possession of hold fast for anchorage into the soil.
- The thallus contains bladder filled with air that functions as floats and gives it buoyancy.
- Possession of chlorophyll for photosynthesis.
Adaptation of barnacle in marine habitat
- Possession of basal disc for strong attachment of substratum
- Possession of shell to prevent dessication during low tide.
- During low tide, the mantle clamps down tightly to a substratum in such a way that water is retained in the
mantle for respiratory activity.
Example
Which of the following is the correct food chain for the organism found in an aquatic community?
A. paramecium, phytoplankton, prawn, water flea, tilapia, shark
B. water flea, paramecium, phytoplankton, prawn, tilapia, shark
C. phytoplankton, water flea, paramecium, prawn, shark, tilapia
D. phytoplankton, paramecium, water flea, prawn, tilapia, shark
E. paramecium, phytoplankton, waterflea, prawn, shark, tilapia (1995/38)
Answer: D – Phytoplankton, paramecium, water flea, prawn, tilapia, shark.
Example
Rabbits cannot survive in an aquatic habitat because they have
A. fore and hind limbs B. no gills C. no fins D. no scales (2003/44)
Answer: B – Rabbits cannot survive in aquatic habitat because they have no gill for breathing under water.
NB. Gills are used by aquatic animals for breathing
Example
Which of the following features is not an adaptation of plants to aquatic habitats
A. breaking roots for entry of air B. flowers raised above water for the purpose of pollination
C. spongy tissues containing gases for buoyancy D. hairy structures on the leaves to reduce water loss (2009/42)
Answer: D – Hairy structures on the leaves to reduce water loss is not an adaption of plants to aquatic habitat.
Example
Study the diagram of the zones of a marine habitat above and use it to Answer: question 19 and 20

In which of these zones can very few organisms be found?

A. I B. II C. III D. IV Answer: D – IV (Abyssal zone)
Which of the following factors exerts a major effect on the distribution of living organisms in the habitat?
A. salt B. pH C. light D. rainfall (2012/44-45) Answer: C – Light
Example
7b. Name three types of aquatic habitats and give one example in each case.
ii. Mention six ecological factors that are common to them (2005/7b Nov)
Answer:
7bi. 1. Fresh water habitat e.g. river 2. Marine habitat e.g. ocean 3. Estuary (brackish water)
ii. Six ecological factors that is common to them:
1. Light 2. Temperature 3. PH 4. Depth 5. Dissolve oxygen 6. Wind

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Example
(ii) List three factors that affect organisms in the marine habitat
(iii) State three adaptive features of sea weeds. (1999/6cii-iii)
Answer:
ii. Factors that affect organisms in the marine habitat: Light, PH, Temperature
iii. Adaptive features of sea weeds
- Possession of mucilaginous cover to prevent desiccation.
- Divided leaves, floating devices and air bladder for buoyancy.
- Possession of structure of attachment that makes it hold fast to water.
Example
Plants found in the aquatic habitat are generally referred to as
A. epiphytes B. halophytes C. xerophytes D. hydrophytes (2004/41)
Answer: D – Plant found in aquatic habitat are generally referred to as hydrophyte.
Example
Which of the following factors is not associated with aquatic habitats?
A. Salinity B. Turbidity C. Temperature D. Edaphic (2005/38)
Answer: D – Edaphic factors are factors relating to the soil. It is not associated with aquatic habitats.
EXERCISE 23.5
1. Which of the following factors is not associated with aquatic habitat?
A. Temperature B. Light Intensity C. Turbidity D. Wave action E. Humidity (1990/43)
2. Plants that survive in marine habitats are called
A. halophytes B. Hydrophytes C. mesophytes D. saprophytes E. xerophytes (2018/59 Neco)
3. A marine protozoan is likely to have no contractile vacuole mainly because the cytoplasm is
A. isotonic to sea water B. hypotonic to sea water
C. hypertonic to sea water D. impervious to sea water (2009/31 JAMB)
ESTUARINE HABITAT
An estuary is an area in which fresh water from a river mixes with salt from the ocean. An estuarine habitat occurs
where salt water from ocean, mixes with fresh water from land (river). This results to what is called brackish water.
Brackish water has a salinity which fluctuates with the tides and the wet and dry seasons.
TYPES OF ESTUARIES
(1) Delta: A delta is where a river divides into many channels before entry into the ocean or sea. A Delta is
formed at the mouth of a river as it enters the sea.
(2) Lagoon: Lagoon is a body of ocean water that enters into the land through a canal and therefore has the
opportunity of mixing with fresh water from rivers and streams. In lagoons, the salinity of water is high during
dry season but becomes low in rainy season.
(3) Bay: Bay is a little or small portion of the sea water which enters the land and mixes up with fresh water from
rivers and streams.
CHARACTERISTICS OF ESTUARINE HABITATS
(1) High sediment output resulting in soft, muddy substrates.
(2) Estuarines are among the most productive natural systems on earth due to the making of nutrients from land
and sea.
(3) It forms the border between fresh water biome and marine biome (brackish water).
(4) It is not very deep so sunlight gets to all the water.
(5) There is usually no wave action.
(6) Estuaries are influenced by tide; volume of water rise with high tide and falls with low tide.
(7) High variable salinity gradient i.e. fluctuation in salinity/salt concentration.
ADAPTATION OF PLANTS AND ANIMALS TO ESTUARINE HABITAT
Plants species and their adaptive features:
(1) Planktons (diatoms): They possess air spaces in their tissues, rhizoid or false foot for attachment to rock
shores and air bladder for buoyancy.
(2) Algae: They have chlorophyll which aid photosynthetic activities. Their small size or large surface area
enables them to float on water.
(3) White mangrove (Avicennia nitida): It has pnuematophores i.e. breathing root for exchange of gases.
(4) Red mangrove (Rhizophora racemosa): It possesses stilt root that grows down into soft mud from the stem
and develops numerous rootlets that possesses air spaces. The air space conducts air to the tissues of the roots.
The root also provides anchorage thus, preventing plant from being washed away by the tides. The seeds of
the red mangrove germinate while they are still on the parent plant thereby preventing the seedling from being
washed away by water current.
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Animal species and their adaptive features
(1) Mosquito larvae and pupae: The possession of breathing trumpets enables them to exchange gases.
(2) Crabs: They burrow fast into the mud against predators, strong wave and tides.
(3) Worms: They are able to withstand high salinity because they possess impermeable and strong outer
covering.
(4) Water snails and shrimps: They burrow into the mud when the tide is going out therefore escaping the
periodic dilution of its external medium.
(5) Mud skippers: This is a fish with modified pectoral fin adapted for walking and climbing trees on land as
well as for swimming when in the water.
(6) Fishes: Fishes like tilapia possesses fins that enable them to move in water and swim bladder that aid
buoyancy.
Food chain in estuarine habitat
1. Detritus   worms   mollusks   birds
2. Diatoms   shrimps   fishes  birds

Factors affecting estuarine habitat

Temperature, wind, relative humidity, light, pH e.t.c.

Example
Which of these features enables a bony fish to remain afloat in water?
A. air bladder B. counter shading C. fins D. lateral line E. scales (2005/58 Neco)
Answer: A– The swim bladder is also known as the air bladder.It aids buoyuancy in fishes thus keeping them afloat
Example
Which organism is an aquatic producer?
A. copepus B. diatom C. elephant grass D. paramecium E. water flea (2001/33 Neco)
Answer: B– Diatom is an aquatic algae and thus an example of an aquatic producer.
N.B– Algae possesses chlorophyll with which they used to produce (manufacture) food through photosynthesis
Example
The salinity of a brackish habitat
A. increases immediately after rainfall B. increases at the end of the rainy season
C. decreases with an increase in the number of organisms D. increases during the dry season (2019/29)
Answer: D– increases during the dry season

EXERCISE 23.6
1. The following characteristics are associated with marine habitats except
A. High salinity B. wave action C. increased pressure with depth
D. fewer species of organisms than on land E. rise and fall of water level (1996/47 Nov)
2. The salinity of a brackish environment
A. increases immediately after rain B. increases at the end of rainy season
C. decreases with increase in micro-organism D. increases during the dry season (1990/44 JAMB)
3. The major limiting factor of productivity in the aquatic habitat is
A. water B. sunlight C. food D. temperature (2014/29 JAMB)
4. What is the critical limiting factor for plants below the photic zone in an aquatic ecosystem?
A. availability of nutrients B. availability of water
C. intensity of light D. carbon dioxide concentration (2018/23 JAMB)

FRESH WATER HABITAT

Fresh water habitat includes water bodies with little salt concentration. Examples are the river, lakes, ponds, streams,
springs. They are formed mainly from inland water.

The main difference existing between fresh water and sea water is the concentration of mineral salts in them. The salt
concentration of fresh water compared to that of marine habitat is very low. As a result of high salt concentration in
marine environment, marine organisms have developed special osmoregulatory adaptations to prevent water loss.
Fresh water organisms have also developed their own adaptations to cope with the entry of excess water into their
body.

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Types of fresh water
1. Lotic fresh water: This includes all fresh water bodies that flows continuously in a particular direction e.g.
river, streams and springs.
2. Lenthic fresh waters: This includes standing or stagnant bodies of fresh water e.g. lake, pond, swamp and
dams.

Characteristics of fresh water habitats

1. Low salinity: Fresh water habitats contain very low salt concentration. The salt concentration of fresh water is
about 0.5% compared to 3.5% for sea water.
2. Small in size: Fresh water habitat is a small water body compared to the marine water like sea and oceans.
3. Currents: Fresh water habitats have feeble/no currents. Current can affect the distribution of gases, salts and
small organisms in fresh water habitats.
4. High oxygen concentration: Oxygen is usually available in all parts of the fresh water especially in the
surface of the water.
5. Seasonal variation: Some fresh water habitat like streams and rivers normally dry up during the dry season
while others have volume reduced. The volume of water in the river also increases during the rainy season.
Turbidity and fast flow of rivers are also high during rainy season than in dry season.
6. Shallowness of water: Most fresh water habitats have very shallow depths. This enables sunlight pass easily
through the water to the bottom.
7. Variation in temperature: The temperature of fresh water habitat usually depends on the season and depth.
Temperature at the surface of the water varies slightly with that of the bottom of the water.
Major ecological zones of fresh water habitat
A lentic fresh water habitat has two zones namely:
1. Littoral zone: Littoral zone is the shallow part of a lentic fresh water habitat. It contains several plants and
animals. The littoral zone has rooted vegetation at its base. Primary production is highest in this zone because
sunlight can penetrate easily in this zone. Plants found within this zone include spirogyra, chlamydomonas,
water lettuce, water fern, duck weed, diatoms and sedges.

Animals associated with the zone include water fleas, water snail, flatworms, frogs, toads ,water skaters, duck,
snakes, crocodiles, tadpoles, hydra and hippopotamus.

2. Benthic zone: Benthic zone is the deepest part of the lentic fresh water habitat. The benthic zone does not
have rooted vegetation like the littoral zone, although flowering plants may occur at its surface.
Plants associated wtih the benthic zone have well developed root system in the mud. These plants include
water lily, water arum, ferns, crinum, lily, commelina and grasses. Animals associated with the benthic zone
include protozoa rotifers, hydra, tilapia fish, mud fish, cat fish, leeches, caddish fly larvae, larvae and pupae
of mosquito, water snail, water spider, crayfish, water scorpion, water boatman and water bugs

Lotic fresh water habitat

There are two zones in lotic fresh water habitat
(1) Pool Zone: The water in this zone is calm and its speed is relatively slow.
(2) Rapid zone: The speed of water in this zone is relatively fast.

Adaptation of some plants and animals to fresh water habitat

Some plants and their adaptive features

Spirogyra: The plant has mucilaginous cover which protects them in water.

Water lettuce (Pistia): Water lettuce has hairs on their leaves which help them to trap air and enable them to float.

Water lily (Nymphaea): The plant has air bladders. Its expanded shape and light weight helps to keep it afloat. It has
long petioles attached at the centre of the leaf blade which prevents them from being drawn under water by the
current.

Water Hyacinth (Ipomea grassipis): They have cavities and intercellular air spaces which give them the ability to
float or maintain buoyancy on water.

Water weed (Elodea): The plant has a long and flexible submerged petiole which enables it to swing with water
current.

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Hornwort (Cerataphyllum): The plants have submerged leaves which increase their surface area to sunlight and
gaseous exchange.

Some animals and their adaptive features in fresh water habitats

Protozoa: They have special cell organelle known as the contractile vacuole which is used for osmoregulation.

Tilapia fish: The major adaptive features of the tilapia fish in fresh water habitat is the presence of swim bladder for
buoyancy in water and the presence of gills for respiration.

Tadpoles: The adaptation shown by tadpole to fresh water habitat includes possession of broad muscular tail for
swimming and steering, possession of external or internal gills (depending on the developmental stage) for respiration
and possession of streamlined body for easy swimming.

Pond skater: The pond skater adapts to the fresh water habitats by having a slender and light body which makes it
possible for it to stay on the thin water surface without breaking it and also by possessing thin and long legs for
skating (sliding movements) in water surface.

Duck: It has webbed digit on its feet for easy locomotion and serrated beak for sieving food in water into its mouth.

Water boatman: This animal can carry bubbles of air with it as it goes below the water surface to the bottom and use
these as their air supply (respiration) under water.

Food chain in fresh water habitat

Diatom   fish fly  tilapia  human
Detritus 
 worm   shrimps   birds
Spirogyra  tadpoles   carps 
 king fisher

Factors affecting fresh water habitat:

1. Degree of water movement. 3. Temperature. 5.Rainfall.
2. Degree of turbidity which affects light penetration. 4. PH of water body.
Example
The distribution of organisms in a fresh-water habitat like a stream of pond is determined by the following except
A. rainfall B. temperature C. pH of soil D. light penetration E. tidal movements (1995/35)
Answer: C – PH of the soil does not affects the distribution of organisms in fresh-water habitat like stream.
Example
Which of the following organisms can be found in fresh water habitat?
A. sargassum and dog fish B. Red mangrove and pond skater
C. sargassum and red mangrove D. spirogyra and pond skater (1999/36)
Answer: D – Spirogyra and pond skaters are found in fresh water habitat.

Example
Which of the following factors may not affect living organisms in an aquatic habitat?
A. Turbidity B. Temperature C. Humidity D. Light (1999/45) Answer: C – Humidity

Example
(c) List (i) three biotic factors; (ii) five abiotic factors which affect plants in freshwater habitat. (2004/1c)
Answer:
C. i. Biotic Factors which affect plants in freshwater habitat: ii.Abiotic factors which affect plants in freshwater habitat:
- Producers (green plants) Temperature, Sunlight, Wind, pH, Turbidity
- Consumers (animals)
- Decomposers (microorganism)
Example
Which of the following organisms are the producers in an aquatic habitat?
A. Benthons B. Phytoplankton C. Zooplanktons D. Nektons (2007/38)
Answer: B – Phytoplankton are primary producers in an aquatic environment.

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Example
What is the critical limiting factor for plants below the photic zone in an aquatic ecosystem?
A. Availability of nutrients B. Availability of water C. Intensity of light D. Carbon dioxide concentration (2009/33)
Answer: C – Intensity of light.
Example
Which of the following features is not an adaptation of plants to aquatic habitat?
A. Breathing roots for entry of air B. Flowers raised above water for the purpose of pollination
C. Spongy tissues containing gases for buoyance D. Hairy structures on the leaves to reduce water loss (2009/42)
Answer: D–Hairy structures on the leaves to reduce water loss is not an adaptation of plants in the aquatic habitat.
Example
Pond weeds normally lack thick layers of cuticle because
A. their system of photosynthesis is not efficient B. there is no danger of becoming desiccated
C. their leaves are either dissected or ribbon-shaped D. there are numerous stomata on their upper epidermis. (2008/35)
Answer: B - Pond weeds normally lack thick layers of cuticle because there is no danger of becoming desiccated.
Example
Which of these is NOT a fresh water habitat?
A. lake B. pond C. river D. stream E. swamp (2005/42 Neco Nov)
Answer: E – Swamp is not a fresh water habitat.
Example
Which organism is an aquatic producer?
A. copepod B. diatom C. elephant grass D. paramecium E. water flea (2001/33 Neco)
Answer: B – Diatom is a producer in aquatic habitat.

EXERCISE 23.7
1. Which is NOT an adaptive feature of hydrophytes?
A. Air spaces in tissues for buoyancy B. broadleaves to enhance transpiration
C. Extensive root system for absorption of water D. fibrous roots for absorption of water
E. waxy cuticle on leaves to prevent wetting (2001/41 Neco)
2. An example of a fresh water habitat is
A. estuarine B. lagoon C. ocean D. pond E. sea (2014/30 Neco)
3. A natural fresh water pond is richer in dissolved oxygen during the day time than at night. Which of these best
explains this observation?
A. Fermentation occurs more rapidly in day time B. Oxygen is liberated by waterweeds during respiration
C. Photosynthesis occurs in the water weeds during the day
D. Excretory product of fresh water animal is oxygen
E. During respiration in day time, plants take in carbondioxide and liberate oxygen (1995/40 Nov)
4. Which of the following is the correct sequence in the food relationship in a pond?
A. Duckling  Turtles Duckweeds Man B. Duckweeds Ducking  Man Turtle
C. Duckweeds Duckling TurtlesMan D. Turtles  Duckweeds  Duckling Man
E. Duckweeds  Man  Duckling Turtle (1997/43 Nov)
5. Which of the following factors is least likely to affect the organisms in the pond?
A. Acidity of the water B. high temperature C. age of the pond
D. amount of rainfall E. amount of sunlight (1998/40 Nov)
6. The turbidity of a pond can be measured using the
A. anemometer B. secchi disc C. theodolite D. hydrometer (1988/38 JAMB)
7. Which of the following has the greatest influence on the distribution of animals in marine and fresh water
habitats?
A. pH B. Salinity C. Water current D. Turbidity (1988/42 JAMB)
8. Which of these groups of animals is likely to be found in fresh water?
A. Blood worm, pond skater and scorpion B. Blood worm, pond skater and dragonfly larva
C. Pond skater, scorpion and dragonfly larva D. Pond skater, blood worm and ant-lion (1988/43 JAMB)
9. A freshwater plant such as water lily can solve the problem of buoyancy by the possession of
A. aerenchytamatous tissues B. dissected leaves
C. thin cell walls of the epidermis D. water-repelling epidermis (1998/31 JAMB)
10. Floating microscopic heterotrophs are mostly grouped as
A. phytoplankton B. zooplankton C. microbes D. nekton (1999/36 JAMB)

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11. The major characteristic of a fresh water habitat is the possession of
A. high turbidity B. high density C. low salinity D. high current (2017/12 JAMB)
12. Which of the following factors may not affect living organisms in an aquatic habitat?
A. turbidity B. temperature C. humidity D. turbidity (1999/45)
13. Explain two ways each by which the following organisms adapt to their habitats
(I) hydrophytes (II) xerophytes (2015/3d)
14. Which of the following factors is not associated with aquatic habitat?
A. turbidity B. wave action C. light intensity D. humidity (2001/43 NABTEB)
15. In which of the following order do marine zones occur?
A. abyssal, splash, intertidal, subtidal and bathyal B. splash, intertidal, subtidal, bathyal and abyssal
C. intertidal, bathyal, subtidal, abyssal and splash D. subtidal, bathyal, abyssal, splash and intertidal (1999/50 Nov)
16. Plants that survives in marine habitats are called
A. halophytes B. hydrophytes C. mesophytes D. saprophytes E. xerophytes (2018/5a)

TERRESTRIAL HABITATS (MARSH, FOREST)

Terrestrial Habitat: Terrestrial habitat refers to those habitats that are found predominantly on land. They include
habitat in caves, deserts, grasslands, wetlands e.t.c.
Terrestrial habitats also include some man made habitats/semi natural habitats such as national parks and biosphere
reserves.
Types of terrestrial habitat
Terrestrial habitats are classified into the following major groups.
Wetlands, Forest, Grassland, Deserts (arid land) and Mountains

Wetlands
These include the marsh and swamp habitats. They form transition zone (ecotones) between terrestrial and deep
water aquatic systems. Wetlands form the most productive ecosystem on earth. They are common in areas where
land and water meet.
Marsh Habitat: Marsh habitat is a type of wetland ecosystem characterized by poorly drained mineral soil and by
plant life dominated mainly of grasses unlike swamps where plant life is dominated by trees.
Types of Marsh
Marshes differ depending mainly on their location which determines their life span and their salinity (salt content).
The classification of marshes is therefore based on two factors. These are:
(1) Life span
(2) Salinity

(1) Based on life span: Based on life span, marshes are classified as
A. Temporary marshes: These marshes are affected by the season. They appear during rainy season and
dry up during the dry season.

B. Permanent marshes: These are mashes that are located near water bodies and have them as permanent
source. Thus, they contain water throughout the year. They are not affected by seasons.

(2) Based on salinity

These include:
A. Fresh water marshes: These are formed in areas where freshwater from rivers overflows into the river
banks to flood the adjoining lowlands.

B. Salt water marshes: They can be found along the coastal plains i.e. between land and open salt
(brackish) water. Salt water marshes are coastal wetlands that are flooded and drained by salt water
brought in by tides.
Formation of marshes
Marshes are produced by flooding, and as a consequence, they have distinctive soils, microorganisms, plants and
animals. Marshes can also be formed as a result of debris uniformly filling the bottom of ponds or lakes. This
introduces grasses and lilies into them. Other organisms like birds, aquatic insects and water snakes might also migrate
into them later.

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Characteristics of marsh
1. Soil is always water logged, poorly aerated and soft. This characteristic makes it difficult for big animals to
move on them.
2. The depth of the water present in marshes is very low i.e. shallow (about 0.6m – 0.7m).
3. The vegetation in this region is dominated mainly by grasses.
4. The water is quite turbid as a result of decaying organic matter in suspension. This makes light penetration to
be very low.
5. The relative humidity around marshy region is quite high.

Living organisms found in marshes

Plant: The plants found in marshes include: algae, water lettuce (Pistia), sword grasses, duckweeds, water lilies
(Nymphaea), hornwort, sedges, white mangrove, red mangrove and raffia palm.

Animal: Animals found in marshes include: mangrove crab, lagoon crab, hermit crab, mud skipper, fishes, bloody
clam oysters, barnacles, frogs, toads, lizards, snakes, turtles, birds, crocodiles and mammals.

Food chain in marshes

The plants and decaying matter form the basis of food chain in marshes. Examples of food chain in marshes include:
1. Flowering plants → insects → frog → crocodile
2. Detritus → worms → fishes
3. Humus → earthworm → frogs → snakes
Example
Which of the following is not classified as a terrestrial habitat?
A. forest B. guinea savannah C. apro alpine D. littoral zone E. desert (1998/32)
Answer: D – Littoral zone is a well lit zone in the marine habitat hence, it is not classified as a terrestrial habitat.
Example
Which of the following is a characteristic of a swamp?
A. Vegetation with stratified arrangement B. Mesophytes with broad leaves
C. The ground is flooded most of the time D. Predominance of climbing plants
E. Many plants with fire resistant structures (1995/34)
Answer: C – In a swamp, the ground is flooded most of the times.

Example
Breathing roots are characteristics of plants growing in a
A. desert B. savannah C. tropical rain forest D. mangrove swamp (2018/24 NABTEB)
Answer: D – Breathing roots are characteristics of plant growing in a mangrove swamp.
Example
Plants with breathing roots are characteristic feature of vegetation in
A. tropical grassland B. temperature grassland C. salt water swamp D. tropical rain forest (2012/43)
Answer: C – Plant with breathing roots are characteristic feature of vegetation in salt water swamp.
Example
(c)(i) State four characteristics of a salt marsh habitat. (ii) Explain briefly how plants are modified for
anchorage in a salt marsh habitat. (2018/6ci & ii)
Answer:
6ci. Four characteristics of Salt Marsh Habitat are: Presence of low oxygen level , High salnity,
Safe muddy environment, Low light penetration
ii. Plants are modified for anchorage in a salt marsh habitat by growing long, and possessing numerous root to
hold to the substration; they also possess stilt root for anchorage.
Example
Breathing roots are characteristic structures of plants growing in
A. afro-alpine B. desert C. rainforest D. savanna E. swamp (2005/38 Neco Nov)
Answer: E – Breathing roots are characteristic structure of plants growing in swamp.
Example
Which of these is the function of pneumatophores in white mangrove plants?
A. Anchorage B. breathing C. clasping D. excretion E. storage (2005/17 Neco)
Answer: B – Pneumetrophore in white mangrove plant is used for breathing.

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Example
Pneumatophores are very essential for
A. feeding B. movement C. breathing D. growth (2006/36 Nov)
Answer: C – Pneumatophores are very essential for breathing.

EXERCISE 23.8
1. (c) Describe the characteristics features of vegetation of a mangrove swamp forest. (2006/8c Nov)
2. Mangrove swamp can be found
A. on a sea shore with flat terrain B. where a river meets the sea
C. on a mud flat near the sea D. where two rivers meet (1992/37 JAMB)
3. Breathing root is an adaptation for survival in the
A. mangrove swamp B. desert C. arboreal habitat D. savannah (1994/47 JAMB)
4. Which of the following characterizes the white mangrove?
A. prop roots b. buttress roots C. breathing roots D. stilt roots (1999/42 JAMB)
5. The mangrove swamp in Nigeria is restricted to the
A. Sahel savanna B. Sudan savanna C. Guinea savanna D. Tropical rainforest (2007/8 JAMB)
6. In freshwater marshes and swamps, the most important abiotic factor that organisms have to adapt to is
A. nature of substratum B. high salinity C. high temperature D. low pH (2009/32 JAMB)
Forest: This is a terrestrial habitat in which the dominant plant community are trees. Some climatic factors are a
major determinant on the distribution of forest. These include temperature, rainfall and humidity. The main forest
biomes include the tropical rain forest, the temperate deciduous forests, coniferous forest. The rain forest is the
dominant forest biome in Nigeria.

Strata in Forest: Stratification refers to the vertical layering of a habitat i.e. the arrangement of vegetation in layers.
It is the classification of the layers (strata) of vegetation according to the different heights to which plants grow. The
rain forest has five strata or layers. These are:

Underground layer

The strata of a forest

1. Emergent layer: This layer is very sunny because it is the very top and only the tallest trees reach this level.
It is also known as the over story. Animals found in this layer include birds, butterfly, small monkeys, bats,
snakes and bugs.

2. Upper/canopy layer: This is the thickest layer. It is made up of tall trees whose crowns form a continuous
canopy. Much of the rain that fall is stopped by the thick foliage present in this layer. Majority of the forest
trees, grow to this height. There are plants that grow in the canopy layer whose roots don’t reach the ground.
These are called air plants (epiphytes). Animals found in this layer include birds, monkeys, frogs, lizards,
snakes and many insects.
3. Middle layer: This is the third layer and it is made up of smaller trees with elongated narrow crowns.
4. Lower layer/under story: This is the layer of shade – loving dwarf trees, palms and shrubs. It is made up of
dense vegetation because they do not receive much sunlight as the light is been blocked by the canopy.
5. Ground layer/forest floor: This layer is dark, damp and full of many dead leaves, twigs and dead plants. It is
usually clear of vegetation with little or no winds reaching there. It is estimated that only 2% of the sunlight
actually reaches the floor. Due to little penetration of sunlight, the forest floor appears dark. Animals found in
this layer include jaguar, gorilla, leopards, tigers and elephants.
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Adaptation of living organism to forest habitat
A. Plants:
As a result of the vegetation of rainforest, very little light is able to penetrate through the forest floor. Based
on this fact, very few plants are able to survive on the rainforest floor. Some plants have however developed
some adaptive features to enable them thrive in this environment.

Adaptive features of plants in tropical rain forest

(1) Plants of forest floor have large leaves to soak up the very little sunlight that gets to them.
(2) Most plants found in the tropical rain forest possess well developed buttress, prop roots to support their large
and tall trunk e.g. iroko (chlorophora excelsa), mahogany (khaya ivorensis). To ensure that their leaves get
enough sunlight.
(3) Some terrestrial trees possesses slender straight trunk that do not branch till near the top.
(4) Plants found below the canopy tree of the forest strata tend to be shade – loving plants e.g. fern, raphia, shrubs
and herbaceous plants like ginger. This is because the humidity in this region in this region is high with little
sun penetration.
(5) Some forest plants like the epiphytes, climbers and parasitic plants are able to survive in the tropical forest by
forming close association with the dominant plants. For example, the mistletoe which is a parasitic plant
develops root system (haustoria) that can penetrate the stem of dominant plants from where it gets its nutritive
requirement.
Epiphytes on the other hand are capable of lodging on the trunks of branches of trees without causing harm to
them. They have special mechanism for storing water and absorbing moisture from the air e.g. orchid.
Animals
Monkeys: Monkeys have prehensile tails and long limbs for climbing trees and jumping from one tree branch to
another.
Bats: They have a way in which the limbs are joined on each side of the body by a fold of skin to form wings used for
flight.
Green snake: They have protective colouration on their skin which makes it difficult to be detected by their enemies.
They also have slim elongated body with grasping scales for winding around tree branches.
Apes: They move in group to protect themselves from predators. They also have high sense of sight to detect enemies.
Earthworms and snail: They have water permeable cuticle which reduces water loss and prevent drying up.
Bird: They have powerful wings used for flying.

Food Chain in forest habitat:

Green plants → grasshopper → toad → hawk
Green plants → monkeys → lion etc
Factors affecting the forest
Climatic factors which affect the rain forest include rainfall, temperature, wind, relative humidity, sunlight etc.
Rainfall and temperature are the dominant factors affecting the rain forest.
Example
Which of the following is not a characteristic feature of tropical rainforest habitat?
A. trees with longer bole than these in savannah B. fewer canopy strata than the savannah
C. many more trees and climbers than savannah D. plenty of leaf litter on the ground
E. more diverse communities than the savannah (1998/33)
Answer: B – Fewer canopy than savannah is not a characteristic feature of tropical rainforest habitat.
Example
The following are features of tropical rain forest except
A. abundant water supply B. loose and moist soil C. short trees growing beneath tall trees
D. scanty trees with small leaves E. presence of many animal (1993/33)
Answer: B – Scanty trees with small leaves is not a feature of tropical rain forest.
Example
State three behavioural adaptations of animals to seasonal changes in terrestrial habitat. (1994/1c)
Answer:
- Basking in the sun to raise body temperature. - Aestivation in unfavourable weather condition.
- Hibernation in cold weather condition. - Covering body with warm clothings.

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Example
State three characters each of the plant community in the tropical rainforest and savannah. (1994/1d)
Answer:
Rainforest: Savannah:
- The ground is generally littered with leaves. - The plant has no stratified canopies.
- The tree of the forest grow very tall. - Possession of underground stem.
- Possession of broad leaves and buttress root. - Presence of fewer trees that are scattered.
Example
In a tropical rain forest, non – epiphytic ferns and fern allies occurs as
A. middle storey species B. upper storey species C. shade – loving species D. emergent species (1995/34 JAMB)
Answer: C - In a tropical rain forest, non – epiphytic ferns and fern allies occurs as shade – loving species
Example
Which of these is not a tree characteristics of the tropical rain forest?
A. vegetable consists predominantly of tall trees with thick canopy B. forest is rich in epiphysis and climbers
C. annual rainfall is less than 100cm D. interior has low light intensity, high humidity and damp floor
E. fruits of trees are often large-sized and are generally without adaptation to wind dispersal (1996/32)
Answer: C – Annual rainfall is less than 100cm is not a true characteristic of the tropical rainforest.
Example
The presence of stilt and breathing roots are features of plants found in the
A. tropical rainforest B. fresh water swamp forests
C. mangrove forests D. southern guinea savannah E. northern guinea savanna (1998/47)
Answer: B – Possession of stilt and breathy roots are features of plants found in the fresh water swamp forest.
Example
List four adaptive features of animals that climb rain forest trees. (2003/8a)
Answer:
- Possession of grapsing pads e.g. tree frog. - Possession of opposable digits e.g. monkey.
- Possession of grasping scales e.g. snakes. - Possession of prehensile tails e.g. monkey
Example
Describe the characteristics features of the vegetation of the tropical rainforest. (2007/8a)
Answer:
- The vegetation is divided into 5 strata. - Presence of ever green trees.
- Presence of shade-loving plants. = Possession of broad leaves and buttress root.
- Presence of abundant species of plant and animals. - Fallen leaves generally litter the ground.
Example
Most Tropical plants shed their leaves during dry weather condition in order to
A. reduce their growth rate B. conserve water C. reduce competition D. minimize the rate of photosynthesis (2009/41)
Answer: B – Most tropical plants shed their leaves in dry weather condition in order to conserve water.
Example
The rate of decomposition of organisms is faster in tropical rainforest than the other biomes because
A. of relatively constant day light B. there are more plants per square feet
C. of abundance of water D. of constant cool temperature (2001/40)
Answer: C – The rate of decomposition of organisms is faster in tropical rainforest than the other biomes because of
abundance of water.
Example
Which of these groups of abiotic factors is common to terrestrial ecosystem?
A. rainfall, wind, sunlight and humidity B. waves, humidity, salinity and rainfall
C. turbidity, wind, rainfall and tide D. humidity wind, rainfall and tide (2000/41 Nov)
Answer: A – Rainfall, wind, sunlight and humidity is common to terrestrial ecosystem.
Example
In the tropical rainforest there is little or no litter on the forest floor because of high.
A. rainfall B. temperature C. light intensity D. rate of decomposition (1999/51 Nov)
Answer: D – In tropical forest, there is little or no litter on the forest floor because of high rate of decomposition.
Example
The following habitat are classified as terrestrial habitat except
A. littoral zone B. afro-alpine C. desert zone D. guinea savannah (2018/30 NABTEB)
Answer: A– Littoral zone.

500
Example
Which of the following plants is not found in the tropical forest floor layer?
A. epiphytes B. fungi C. mosses D. algae E. lichen (1992/40 Nov)
Answer: A – Epiphytes are not found in the tropical forest floor layer.
Example
Terrestrial organisms which are capable of maintaining their body temperature constant within fairly close limits are
referred to as
A. thermoclines B. hometherms C. poikilotherms D. eurytherms E. stenotherms (1998/36)
Answer: B – Homotherms are organism that are capable of maintain their body temperature within fairly close limits.
Example
1.(a) List five morphological features that are characteristic of plants found in each of the following habitats:
(i) tropical rainforest. (1989/1ai)
Answer:
- Leaves are large, leathery and dark green.
- The tree often have thin, smooth bark without conspicuous lenticels.
- The trees have straight, slender trunks with branches mostly near the top.
- The trunks of some of the trees have buttresses.
- The flowers are often small, inconspicuous and of greenish or whitish in colour.
Example
Which of the following structures is a protective adaptive feature of the Agama lizard to terrestrial habitat?
A. Claws B. Gular fold C. Scaly skin D. Nuchal crest E. Tail (1991/54)
Answer: C – The scaly skin in agama lizard is used to protect against water loss through evaporation from the skin.

EXERCISE 23.9
1. Which of the following processes can be affected by wind in a terrestrial ecosystem?
A. Translocation B. Germination C. transpiration D. fertilization (2004/34 Nov)
2. Which of these groups of abiotic factors is common to terrestrial ecosystems?
A. rainfall, wind, sunlight and humidity B. waves, humidity, salinity and rainfall
C. turbidity, wind, rainfall and tide D. Humidity, wind, rainfall and tide (2000/41 Nov)
3. Which of the following plants is not found in the tropical forest floor layer?
A. Epiphytes B. Fungi C. Mosses D. Algae E. Lichens (1992/40 Nov)
4. In the tropical rainforest there is little or no litter on the forest floor because of high
A. rainfall B. temperature C. light intensity D. rate of decomposition (1999/51 Nov)
5. Which of the following ecological factors are common to both terrestrial and aquatic habitats?
A. Rainfall, temperature, light and wind B Salinity, rainfall, temperature and light
C. Tides, wind, rainfall and altitude D. pH, salinity, rainfall and humidity (1986/45 JAMB)
6. In a tropical rain forest, non – epiphytic ferns and fern allies occurs as
A. middle storey species B. upper storey species C. shade – loving species D. emergent species (1995/34 JAMB)
7. A characteristic feature of tropical rainforest is that it
A. contains fewer number of plant species B. has total annual rainfall of less than 50cm
C. contains trees with narrow leaves D. contains large numbers of plant species (2014/31 JAMB)
8. The most important characteristic that makes reptiles to conquer terrestrial habitats is the possession of
A. long tail B. scaly skin C. sharp claw D. aminiotic egg (2008/12 JAMB)
9. The most important ecological factor in a terrestrial environment is
A. rainfall B. humidity C. wind D. soil (2009/29 JAMB)
10. Which of the following is characteristics of a swamp?
A. vegetation with stratified arrangement B. mesophyte with broad leaves
C. the ground is flooded most of the time D. predominance of climbing plants
E. many plants with fire resistant structures (1995/34)
11. The possession of breathing roots is a characteristics of plants growing in
A. mangrove swamp B. coastal savanna C. guinea savanna D. shrub biome (2002/42)
12. State five important uses of water organism in the tropical rain forest. (2003/8b)
13. A waterlogged habitat with low light penetration and very low quantity of dissolved oxygen best describes
a/an _____ habitat
A. estuarine B. marine C. sahel savanna D. swamping E. tropical rainforest (2005/54 Nov)

501
14. Which of the following processes can be affected by wind in a terrestrial habitat?
A. translocation B. germination C. transpiration D. fertilization (2004/43)
15. Pneumatophores are very essential for
A. feeding B. movement C. breathing D. growth (2006/36 Nov)
16. Which of the following plant is not found in the tropical forest floor layer?
A. epiphyte B. fungi C. mosses D. algae E. lichen (1992/40 Nov)

GRASS AND ARID HABITAT

Grassland is an area in which the vegetation is dominated by nearly continuous cover of grasses. They lie between
forests and deserts. Two major types of grassland exists. There are the tropical grassland and temperate grassland.
1. Tropical grassland: Tropical grassland are also known as savannahs. They are warmer than temperate
grassland. They stay pretty hot all year long. In Nigeria, savanna has three major belts these are Guinea
savanna, Sudan savanna and Sahel savanna
2. Temperate grassland: The main temperate grasslands are the steppes of Eurasia, the Prairies of North
America, the downs of Australia and New Zealand, and the pampa of Argentina. These regions experience
low rainfall, a hot wet summer and a cold dry winter.

Characteristic of grassland:
1. Unlike forest land, grassland lacks stratified canopies as few trees are present.
2. The vegetation of grassland is dominated by grass.
3. The rainfall and soils are insufficient to support significant tree growth.
4. Plants found in savanna usually shed their leaves during the dry season in order to prevent excessive water
loss. This is a characteristic of deciduous plants.
5. Trees present in savanna have adaptations to reduce drought.

Adaptation of some living organisms to grassland habitats

Plants
i. Spear Grass: It possesses a rhizome that helps it to withstand intense heat, fire and dry season.
ii. Baobab: These trees has broad and succulent trunks used for storing excess water.
iii. Acacia: It possess long root that enables it to search for ground water.
iv. Elephant grass: It has succulent stem to store excess water against dry season and strong fibrous root system
for absorbing water from the soil.
v. Palm: This plant has thick bark which protects it from being severely burnt by bush fires.

Animals:
i. Termite: They live in ant hills which protect them from danger and unfavourable climatic condition.
ii. Zebras and Giraffes: They have body colours that camouflage among grasses and trees which make them
undectable.
iii. Lion, Tiger and Leopard: These animals have powerful jaws and teeth for attacking other animals. They
also have high sense of smell to enable them detect their prey.
iv. Elephant and Lions: These animals move in group or herd thus enabling them to achieve strength in
numbers.
v. Rats: Burrow into the soil to avoid heat and fire.

Other animal species include antelopes, snakes, squirrels, deer, porcupines, grass cutter etc.
Food chain in a grassland Habitat:
Grass → grasshopper → lizard → snake
Grass → zebras → lions
Grass → grasshopper → toad → birds

Climate factors affecting Grassland habitat:

a. High temperature: This habitat is affected by extremes of temperatures which range from 21o – 30oC.
b. Moderate rainfall: The grassland has an annual rainfall of about 600 – 1,500mm. It has seasonal
convectional rainfall with single maximum.
c. Light intensity: Light intensity is very high since there is little vegetation to shield its rays. Also
photosynthetic activities are high in this habitat.
d. Fertile soil: Soil here are very fertile as most of the nutrients are not leached because of low rainfall.
e. Relative humidity: Relative humidity is low.

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Example
How are Savannah plants protected from bush fires? They
A. have sunken stomata B. roll their leaves during hot days C. have thick barks
D. ways produce flowers E. shed their leaves gradually (1992/58)
Answer: C – The presence of thick barks protects savannah plants from bush fires.
Example
Northern Guinea savanna is associated with
A. abundant rainfall B. abundant trees and shrubs C. soil with very little plant cover
D. abundant grasses E. high humidity (1997/38)
Answer: D – Northern Savanna is associated with abundant grasses.
Example
Trees in Savannah habitats usually have heavy thick bark which mainly
A. reduces the rate of transpiration B. protect them from the scorching sun
C. protect them from heavy winds D. resist bush fires (2005/33)
Answer: D – Trees in Savannah habitats usually have heavy thick bark which mainly resist fire.
Example
The falling of leaves of deciduous trees is helpful to the plant because it
A. reduces the rate of transpiration B. enables the plant to conveniently eliminate its excretory products
C. enables the plant to bear more fruits D. ensures that the limited mineral salts get to only growing regions (2011/42)
Answer: A – The falling of leaves of deciduous trees is helpful to the plant because it reduces the rate of transpiration.

EXERCISE 23.10
1. An adaptation of savanna plants for resistance against bush fires is the possession of
A. extensive root system B. sunken stomata C. broad leaves D. thick bark (2006/43 Nov)
2. Fewer number of tees is characteristic of the Savanna zones of Nigeria because
A. there is too much sunlight B. there is limited amount of rainfall
C. they are usually exposed to gazing animals D they are covered by high mountains
E. the farmers always engage in bush-burning (1991/39 Nov)
3. In a savanna ecosystem the abiotic factors include
A. legumes, temperature and sandy soil B. water, temperature and soil
C. minerals, oxygen and reptiles D. water, soil and grasses (1990/41 JAMB)
4. In Nigeria, the Guinea savanna belt borders the
A. rainforests and the desert B. mangrove swamps and the Sahel savanna
C. rainforests and the Sudan savanna D. deserts and the Sudan savanna (2005/33 JAMB)
Arid land or desert Habitat:
Deserts are dry (arid) places where the availability of water is the major factor that determines the type of organisms
that can live there. Typically a desert is characterized by having less than an average of 250mm of Annual rainfall. But
a more important factor is that deserts have a strong tendency to lose water by evaporation and this potential for water
loss exceeds the annual rainfall.
So deserts are characterized by having sparse vegetation and the organisms that live in deserts are adapted to
withstand or avoid water stress. Deserts soils tend to be poorly developed, with a high content of mineral particles but
little organic matter.
Plants that grow in deserts environment must have special adaptations to conserve water. Such plants are referred to as
xerophytes e.g. cactus. Xerophytes usually have needle like or spring leaves to reduce the rate of transpiration.
There are two types of deserts, these are the hot and the cold deserts.

Hot Desert: They are located on the western coast of the continents with latitude 15o – 30o North and South of the
equator. Examples of hot deserts are Sahara desert (North Africa), Arabian desert and Kalahari deserts (South Africa),
Great Australia desert and Atacama desert of South America.

Cold Desert: Cold deserts are located in the interiors of the continent around 45° – 60° North and South of the
equator. The deserts are found in interior of Eurasia, North America and in Patagonia (South America)

Characteristic of Arid Land (Hot Desert)

1. Scarcity of water 4. High sunshine 7. Low relative humidity
2. Hot temperatures 5. Predominance of strong winds 8. Poor vegetation
3. Presence of sandy soil 6. Presence of drought resistant plants.
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Example
Which of the following limit resources is competed for by organisms in the desert?
A. light B. temperature C. oxygen D. water E. carbondioxide (1991/52)
Answer: D – Water is a limited resources in the desert, organisms compete for it.
Example
Study the diagrams below carefully. Use them to Answer: question 3 and 4.

The plant best adapted for life in the desert are

A. I and IV B. II and IV C. III and IV D. IV and V only E. I, II, III and V. (1988/58)
Answer: E – I, II, III and V
The rate of transportation will be highest in
A. I B. II C. III D. IV E. V (1988/58-59) Answer: D – IV
Example
The adaptation for water conservation in organisms include the following except?
A. scales in fishes B. scales on leaves C. think leaves D. spine in plants E. succulent stem (1991/53)
Answer: A – Scales in fishes are not used for water conservation.
Example
Desert plants are usually
A. hydrophytes B. mesophytes C. xerophytes D. sporophyte (1999/35)
Answer: C – Xerophytes are desert plants.
Example
A habitat with low rainfall, very low humidity, exposed soil with little plant cover, few trees and shrubs is likely to be
A. a rain forest B. a mangrove forest C. a desert D. a swamp E. an estuarine (1997/45)
Answer: C – A desert
Example
Which of the following characteristics is not found in arid land animals?
A. Nocturnal habits B. Hard impermeable body covering
C. Production of dry waste materials D. Broad flattened body (2011/35 Nov)
Answer: D – Broad flattened body is not a characteristics found in arid land animals.
Example
Use the information in the graph below to Answer: questions 25 and 26

Which of the plants is likely to have broadleaves with thin cuticle?

A. R B. S C. T D. U Answer: A – “R” is likely to have broad leaves with thin cuticle.
Which of the plants is likely to be a desert species
A. U B. T C. S D. R (1987/25-26 JAMB)
Answer: A. “U” is likely to be a desert plant because of the low rate of transpiration.

504
EXERCISE 23.11
Use the list of biomes below to Answer: questions 35 and 36.
1. Desert 3. Southern Guinea Savannah
2. Rain forest 4. Northern Guinea Savannah
1. A biome with a low annual rainfall, few scattered trees within, dense layer of grasses and found in Kano and
Katsina states is
A. 1 B. 2 C. 3 D. 4 E. 5 (1994/35 JAMB)
2. A biome where there are many cacti and the small mammals undergo aestivation for long periods is
A. 1 B. 2 C. 3 D. 4 (1994/36 JAMB)
3. The plant that grow in deserts or very dry areas are referred to as
A. mesophytes B. hydrophytes C. epiphytes D. xerophytes (2013/11 JAMB)

Adaptive features of plants in arid lands:

Cactus: Cactus is a leafless plant with prickles or thorns to reduce transpiration. It also has thick succulent stem and
side branches to store water for long drought.
Acacia: This is a drought resistant plant. It has deep roots which absorb underground water deep down in the soil.
Oleander: This plant has extremely deep root which is able to absorb underground water deep down the soil.
Baobab Tree: The leaves are waxy, hairy or needle shaped like and helps to reduce the rate of transpiration.
Wiring grass: It has narrow and slender leaves which enables them to reduce the rate of transpiration.

Adaptive features of animals in Arid land:

i. Locust: It has waterproof bodies and impervious cuticles. It also produces dry waste product e.g. uric acid and
guanine to enable them conserve water.
ii. Lizard and Snakes: These animals have scales which limit the rate of water loss from their body.
iii. Kangaroo rats: They burrow during the day to avoid excessive heat thereby cutting down evaporation from
its body.
iv. Camel: A camel can drink a lot of water to sustain itself for several days and hence withstand a wide range of
body temperature up to 40oC during the day. It can also walk for several days without drinking water.

Factors affecting arid land: They are temperature, rainfall, sunlight, wind and low relative humidity.

Food chain in Arid land Habitat:

1. Plants → desert rats → snakes
2. Plants → locust → wasps → lizards
3. Plants → ants → scorpion → snakes

Example
Xerophytes possess the following structural characteristics except
A. reduction of leaves into spines B. green succulent stems
C. broad thin green leaves D. hardened waxy cuticle on leaves (2002/37 Nov)
Answer: C – Broad this green leaves is not a structural characteristic in xerophytes.
Example
A xerophytes conserves water by possession of the following features except
A. thick cuticle B. sunken stomata C. broad leaves D. fleshy stem (2011/41)
Answer: C – Xerophytes do not conserve water by possessing broad leaves.

Example
Plants adapted to live in an arid land environment are called
A. epiphytes B. halophytes C. hydrophytes D. mesophytes E. xerophytes (2014/15 Neco)
Answer: E – Xerophytes are plants adapted to live in and land environment.
Example
Which of these is not a structural adaptation of desert plants for water conservation?
A. Broad leaves with many stomata B. leaves reduced into spines C. scale leaves
D. stems and leaves with thick cuticle E. sunken stomata (2005/19 Neco)
Answer: A – Broad leaves with many stomata is not a structural adaptation of desert plants for water conservation.
505
Example
Which of the following animals is best adapted to desert life?
A. camel B. horse C. leopard D. rat E. tiger (2005/39 Neco Nov)
Answer: A – Camels are best adapted to desert life.

Example
Which of the following features is not an adaptation for water conservation in plants?
A. leaves reduced to spines B. tiny hairs covering leaf surfaces
C. fleshy stems D. leave with thin cuticle (2006/44 Nov)
Answer: D – Leaves with thin cuticle is not an adaptation for water conservation in plants.

EXERCISE 23.12
1. Which of the following is not an adaptive feature of plants found in arid lands?
A. Long roots for absorbing water from deep soil level B. Succulent stems which store water
C. Leaves reduced to spines D. Stems containing chlorophyll
E. Presence of thick bark (1992/52 Nov)
2. An examination adaptation to a xerophytes environment is represented by the development of
A. fleshy tissues and reduced leaves B. broad canopy and extensive surface root system
C. thick barks and broad leaves D. rough leaves and shallow root system (1992/47 JAMB)
3. In a drought situation, plants suffer from water stress which could result in
A. reduced biochemical activities B. enhanced chemical activities
C. enhanced microbial activities D. reduced photropical activities (1994/38 JAMB)
4. Which of the following structural features are adapted for uses other than water conservation?
A. feathers in birds B. scales in animals C. spines in plants D. succulent stems (2000/45 JAMB)
5. The most important adaption of xerophytes is the ability of the protoplasm to
A. resist being damaged by the loss water B. store sugar and mineral in the vacuoles
C. absorb water and swell D. shrink from the cell wall (2004/15 JAMB)
6. Low annual rainfall, sparse vegetation high diurnal temperature and cold nights are characteristics features of
the
A. tropical forest B. desert C. montane forest D. guinea savanna (2010/35 JAMB)
7. The structural adaptation of desert plants for water conservation is
A. broad leaves with numerous stomata B. spongy mesophyll
C. spiny leaves D. prominent stomata in leaves (2013/14 JAMB)

8. Physiological adaptation to very dry conditions in animals demonstrates

A. rejuvenation B. xerromorphism C. hibernation D. aestivation (2013/46 JAMB)

9. One adaptation of Cactus opuntia to conserve water is the reduction of

A. intermodes B. stem to leaves C. leaves to spine D. flower size (2013/47 JAMB)

I. Strong winds II. High temperature III. Dry and porous soils.
10. Which group of plants is specially adapted to grow under environmental conditions stated above?
A. Thallophytic B. Mesophytes C. Xerophytes D. Hydrophytes (2016/39 JAMB)
11. Which of the following characteristics is not found in arid land animals?
A. nocturnal habits B. hard impermeable body cover
C. production of dry waste materials D. broad flattened body (2011/35)
12. Explain two ways each by which the following organisms adapt to their habitats
(i) Hydrophytes (ii) Xerophytes. (2011/35)
13. Xerophytes conserves water by possession of the following features except
A. thick cuticle B. sunken stomata C. broad leaves D. fleshy stem (2011/41)
14. Xerophytes have the following characteristics aimed at conserving water except
A. thick cuticle B. broad leaf surface C. sunken stomata D. waxy cuticle (2018/33)

506
Population studies by sampling method
Population is defined as the total number of organisms of the same species living together in a particular area at a
particular time

Population Size: This refers to the total number of the species of the same kind in a given area or habitat.
Density × area of habitat = population size
A large population is capable of surviving dangerous and unfavorable condition such as fire, disease e.t.c. while a
small population can easily be wipe out.

Population Density: This is the average number of individuals of a species per unit area of a habitat. It can be used to
estimate the total number of individuals of a population,
i.e. population size = population density × area of habitat or
total population size
Population density =
area of habitat

Dominance: The dominant species in a community are those organisms that exert a greater influence or a major
controlling influence on the nature, or other members of the community. The relative importance of a species in a
community is expressed by dominance.
Dominance could be expressed in terms of their number, occupation of largest portion of space and possession of the
highest biomass and the largest contribution of energy flow in the habitat

Population Frequency: This refers to the number of times an organism occurs within a given area of a habitat

Percentage Cover: This refers to the area or space covered or occupied by a given species in it’s habitat. It is
expressed in percentage.
Population Distribution: This refers to the way in which individuals of a particular population are arranged in a
given habitat. The individual may be clumped, evenly spaced, or randomly spaced.
Example
The number of individuals in a habitat in relation to the unit space available to each organism is referred to as the
A. birthrate B. density C. mortality D. frequency E. dispersion (1991/40 Nov)
Answer: B – Density
Example
The populations of different organisms living and interacting in a given habitat is
A. a biome B. a community C. an ecosystem D. a niche (2019/31 PC2)
Answer: B – A community is the collection of different organisms living and interacting in a given habitat.
Example
Which of the following statements is not true of population?
A. members of a population may be of the same species
B. members of a population may be of the same species but do not interbreed
C. size of population may be limited by space
D. some species can form another population elsewhere E. members of a population must co-exist (1996/43)
Answer: B – “Members of a population may be of the same species but do not interbreed” is not true of a population

Example
Population is defined as
A. the number of individual organisms per unit area
B. a progressive series of changes over a period of time in a human community
C. the total number of organisms of the same species living together in a given period of time
D. the total number of different species of communities living in an environment in a given per of time (2011/38 Nov)
Answer: C – Population is the total number of organisms of the same species living together in a given period of time.
Example
In population studies samplings dominance is best described as
A. those species’ that consume most of the herbivores present
B. those specie operate at the highest level of the food chain
C. those carnivores that control the population of herbivores
D. those species that exercise major controlling effect on the nature of the community
E. the most numerous species found at the lowest level of the food chain (1994/40 Nov)
Answer: D– In population studies samplings dominance is best described as those species that exercise major
controlling effect on the nature of the community

507
Example
Which of these is the correct definition of a population? Population is a
A. group of lower animals living together in a habitat B. group of plants and animals a community
C. group of higher plantain a p interacting with each other
D. group of organisms of the d species in a community interacting with each other
E. term used only for a group people living together in a community (1994/41 Nov)
Answer: D – A population is a group of organisms of the same species in a community interacting with each other.
Example
The number of individuals of a species per unit area of the habitat can best be described as
A. distribution B. frequency C. percentage cover D. population size E. population density (2001/39 Neco)
Answer: E – Population density is the number of individuals of a species per unit area of the habitat.
Example
In an ecological study, the total number of individuals of the same species in a given area at the same time can be
described as
A. a population B. a community C. an ecosystem D. a niche (2005/41 Nov)
Answer: A – A population is the total number of individual of the same species in a given area at the same time.
Example
A population is defined as the collection of
A. similar organisms that are found in the same habitat B. similar organisms that breed in the same habitat
C. similar organisms that interbreed freely in the same habitat D. similar organisms that eat the same food
E. different organisms in the same habitat (1982/1 JAMB)
Answer: C – Population is defined as the collection of similar organisms that interbreed freely in the same habitat.
Example
The population density of Tridax in an abandoned square farmland of size 200m was found to be 5 plants per m2. The
population size of the plant one the farm is
A. 1000 B. 4000 C. 200000 D. 40 (2019/37 JAMB)
Solution
𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑖𝑧𝑒
𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =
𝑓𝑎𝑟𝑚𝑙𝑎𝑛𝑑 𝑎𝑟𝑒𝑎
Population density = 5 plant/m2 , Population size = ? Farm land area (square) = L2, (where L = 200m )
∴ Farm land area = 2002 = 40000m2
Substituting for the given values
𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑖𝑧𝑒
𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =
𝑓𝑎𝑟𝑚𝑙𝑎𝑛𝑑 𝑎𝑟𝑒𝑎
5 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑖𝑧𝑒
=
1 40000

∴ Population size = 5 × 4000

= 200,000 plants Answer C
Example
A population that doubles in size at constant interview is an indication of
A. sigmoid growth B. exponential growth C. population explosive D. rapid growth (2006/49 JAMB)
Answer: B – Exponential growth
Example
The study of how and why population size change over time is
A. population ecology B. population cycles C. population estimation D. population dynamics (2014/32 JAMB)
Answer: D – Population dynamics in the study of how and why population size changes over time.

508
EXERCISE 23.13
Use the diagram below to Answer: questions 35 and 36.

1. If species I, II and III interact in a community, which of the following statements is true?
A. The population of species II is growing at a slow rate
B. The population of species III has reached its carrying capacity
C. The population of species I has become extinct
D. The population of species I is always higher than species II (2008/35 JAMB)
2. The population size of species II on the 20th day is
A. 100 B. 200 C. 300 D. 400 (2008/36 JAMB)
3. Which of the following statements is not true of population
A. Members of a population may be of the same species
B. Members of a population may be of the same species but do not interbreed
C. Size of a population may be limited by space D. Some species can form another population elsewhere
E. Members of a population must co-exist (1996/43)
4. 3(a) Write short note on each of the following:
(i) ecological niche (ii) population density (iii) climax community (2010/3aii)
5. Fewer number of trees is characteristic of the Savanna zones of Nigeria because
A. there is too much sunlight B. there is limited amount of rainfall
C. they are usually exposed to grazing animals D. they are covered by high mountains
E. the farmers always engage in bush-burning (1991/39)
6. The number of individuals in a habitat in relation to the unit space available to each organism is referred to as
the
A. birth rate B. density C. mortality D. frequency E. dispersion (1991/40)
7. The maximum size of a population that is given area can support is known as
A. population density B. carrying capacity C. population growth D. maximum population (2013/36)

Factors that Affect Population

1. Natality: This is also known as birth rate. It is the ratio of the number of births to the size of the population.
Increase in birth rate leads to increase in population size and vice versa.
2. Mortality: This is the number of death within a population at a given time. It is also known as death rate.
Increase in death rate leads to a decrease in population size and vice versa.
3. Immigration: This is simply the movement of individuals into a population.
4. Emigration” This is the movement of organism out of a particular population.
5. Changes in food availability: This can lead to emigration, immigration depending on the location in which
food is available or scarce.
6. Seasonal climatic changes: This can affect population size depending on whether the climatic conditions are
favourable or not to the survival of the organism.
7. Breeding Period: Some organisms move out of a habitat during their breeding period or season. This reduces
the population of that habitat.
8. Unfavourable natural events: Natural disasters such as fire, flood, earthquakes e.t.c. may reduce population
size as a result of death or emigration.

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Methods of Population Studies
1. Complete census (direct counting)
This method is applied when
a. The individual is large
b. The individuals are comparatively few.
c. The area of habitat is small
2. Sampling method: This is when the individuals are small in size or very many in numbers. In this method,
samples are taken, counted and used to obtain an estimate of the total population. There are different sampling
methods used
1. Quadrant method and volume sampling
2. Transect method
3. Capture – recapture method
1. Quadrant method: A quadrant is a square or rectangular frame made of metal or wood. In quadrant
sampling, the quadrant is thrown in a random manner on a plot. After each throw, the presence or absence of a
species is observed and recorded. After about 10 or more throws, the average number of individuals of a
species per area (i.e. /m2) as calculated from this number of individuals, in the population, in a known area can
be estimated.
In quadrant sampling,
Total count of individual
Average No of organisms = No of throws of the quadrant

average number of organisms

Population density = area of quadrant (m2 )

Exaample
In a quadrant sampling experiment using a quadrant of 1m2, the following were recorded.
Sampling 1 2 3 4 5 6 7 8 9 10 Total
Number of carpet grass per quadrant area 10 12 14 6 4 18 20 11 13 9 117
If the area of field studied is 200m2. Calculate the population density of the carpet grass
Solution
Area of field studied = 200m2
Area of quadrant = 1m2
Number of unit area tossed = 10
Total unit area tossed = 10 × 1m2 = 10m2
Number of carpet grass in 10m2 = 117
117
Average number of carpet grass per unit area (per 1m2) = = 11.7
10
2
Area of habitat studied = 200m
Estimated population of carpet grass is as follows : 1m2 = 11.7
∴ 200m2 = 11.7 ×200 = 2340
Total population
population density = Area of habitat
2340
=
200𝑚2
= 11.7per m2 = 11.7/m2

2. Transect Method: In this method, a tape marked at convenient intervals is stretched across the area. The plants
encountered at the interval marks are recorded. This is repeated a few times. A fairly accurate estimate of the
number and types of plants in the area can be made or obtained. The instrument used in this method is called
line transect.

3. Capture – Recapture Method: This method can be used to estimate the population of aquatic animals e.g.
Tilapia fish in a pond. In this method, the animal of one type in a particular area are caught, counted, marked
with ink (assume A) and released. After a day or two days, the process is repeated and the number of animals
caught is also counted, marked (assume B) and also recorded. At the same time the number of marked animals
from the previous day or two that were found in the second catch are also counted and marked (this time with C)
and recorded. The population of animals present in the area can the be calculated by using the formula below
A ×B
Population in area =
C

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 For example, in a pond, 200 tilapia are captured and then marked or tagged and then released. After a day,
another 200 tilapia are captured. If 20 were found to be already marked in the second catch, then the total
population can be estimated as follows

Total in 1st catch × total in second catch 200 ×200

Total population = = = 2000
Total number of marked ones in second 𝐜𝐚𝐭𝐜𝐡 20

Estimated population of tilapia in the pond = 2000

4. Volume sampling: In this method, a volume sample is taken in an aquatic habitat. For example, to find the
number of mosquito larvae in stagnant water in a pot, Stir the water and take a known volume sample e.g. 5cm3.
Count all the larvae in the sample, return the sample; stir the water and repeat the exercise several times. Find the
average number of larvae per 5cm3 sample. Calculate the total number in the whole body of water.
population size
Population density = area or volume
Example
A 500cm3 pot containing mosquito larvae was analysed to know the population of the larvae using 5cm3
container. The result obtained from each sample is as shown below.
Sampling 1 2 3 4 5 6 TOTAL
Number of Mosquito larvae 15 20 22 16 18 24 115
Calculate the population density
Solution
Total number of mosquito larvae = 115
Total number of sampling = 6
115
Average number of larvae per 5cm3 sample = 19.5
6
∴ 5cm3 of sample = 19.5
19.5
1cm3 =
5
19.5
∴ 500cm3 pot = × 500 = 1950
5
Total Population 1950
Population density = Total Volume
= 500𝑐𝑚3
= 3.9/cm3

Example
Which of the following methods can be used in studying the population of lizard?
A. use of sweep net B. killing and counting the number caught in a sky
C. capture – recapture method D. using chloroform on abandoned farmland (1999/45 Nov)
Answer: C – Capture and recapture method can be used to study the population of lizard. This method involves the
capturing of as many lizard as possible in a given area and after which the lizards are counted, marked/tagged and then
released. This connotes the capture stage. At a later time, this is repeated, representing the recapturing stage.
Example
The use of transect method in ecological studies is to identify the
A. population of organisms in a habitat B. height of trees in a section of the forest
C. distribution of plant species D. number of young plants in a forest (2013/44 Nov)
Answer: C – Transect method in ecological studies is to identify the distribution of organisms (e.g. plant species) in
relation to a certain area.
Example
A population with a relatively large population of reproductive adults will be
A. increasing B. less crowded C. decreasing rapidly B. unchanged (2020/28 PC1)
Answer: A – When the reproduction adults are relatively large in number, there is every tendency that a population
will increase in size.
Example
The transect method can be used in ecology to show the
A. number of plants and animals in a habitat B. population of a particular plant species
C. distribution of organisms along line D. heights of trees in a section of a forest
E. number of young plants across a forest (1984/33 JAMB)
Answer: C – The transect method can be used in ecology to show the distribution of organisms along line.

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Example
In a population study using the transect method, a student is likely to record the highest number of species in
A. a sahel savanna B. An estuarine swamp C. a tropical rain forest D. A guinea savanna (2002/41 JAMB)
Answer: C – A student is likely to record the highest number of species in a tropical rainforest when using a transect
method to carry out population study.
Example
The effects of overcrowding on populations are
A. cannibalism and competition only B. competition and death only
C. cannibalism, competition and death only D. cannibalism, competition, death and aggression (2000/50 Nov)
Answer: D – Overcrowding can lead to cannibalism, competition, death and aggression.
Example
Natality is a factor affecting population density because it involves
A. Increase in population due to immigration B. increases in population due to emigration
C. the number of mature females in the population D. the number of females in the population
E. the number of all the young ones produced (1996/49 Nov)
Answer: E – Natality is a factor affecting population density because it involves the number of all the young ones
produced.
Example
All of the following factors contribute to overcrowding of organisms in a habitat except
A. natality B. immigration C. emigration D. survival (2005/46 Nov)
Answer: C – Emigration involves the outward movement of organisms from one place to another in search for food,
space and safety. This will invariably lead to decrease in the population of habitat and hence does not contribute to
overcrowding.

EXERCISE 23.14
1. The numbers in a population would rise, if there was an increase in the
A. spread of disease B. number of deaths C. number of predators D. amount of food available (2002/43)
2. (b) Explain four factors which affect population size. (2002/7b)
3. Which of the following will have the least effect on the rate of change of the numbers in a population?
A. Food supply B. Mutation C. Predation D. Disease (2003/42)
4. Competition among individuals of a population increases the
A. number of organisms B. survival of the fittest
C. availability of nutrient supplied D. enlargement of the territory (2003/43)
5. Which of the following factors will_ most likely lead to overcrowding within a population?
A. Absence of predators B. Emigration C. Food shortage D. Absence of territorial behaviour (2009/46)

6. Which of the following ecological factors will result in food shortage?

A. Drought B. Low rate of reproduction C. Emigration D. Topography (2017/33)
7. The maximum size of a population that is given area can support is known as
A. population density B. carrying capacity C. population growth D. maximum population (2013/36)
8. b) Explain the following terms: (i) biosphere (ii) population (iii) community (iv) ecosystem. (2013/3b)
9. Overcrowding in a population does not result in
A. death B. commensalism C. competition D. migration (2016/35)

10. (b) (i) State three factors that can likely limit the size of human populations
(ii) Outline two ways each by which humans can overcome the factors named in 3(b)(i) (2011/36b(i) (ii)
11. Density, mortality rate, birth rate are the factors that affect
A. population B. dominance C. cover D. habitat E. abiotic community (1995/59)
12. Which of the following is an abiotic factor which affects a population
A. Predator B. Parasite C. Consumer D. Producer E. Temperature (1996/44)
13. Which of the following activities is not necessary in population sampling?
A. Selecting the habitat B. Dividing the selected habitat into portions C. Throwing the quadrat randomly
D. Counting the number of organisms E. Feeding the organisms (1997/39)
14. Which of the following methods is best for the determination of population density of Tridax in an open field?
A. transect B. quadrat C. sweep-net D. pit-fall (2004/43)

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Ecological Factors Common to all Habitat
The ecological factors that affect both aquatic and terrestrial habitats include:
(i) Temperature (ii) Rainfall (iii) Light (iv) Wind (v) Pressure (vi) Hydrogen ion concentrations (PH). Of these
factors, temperature and rainfall determines the major biomes of the world
1. Temperature
This is the measurement of the degree of hotness or coldness of a particular habitat or body. The temperature
of a particular habitat, vary from time and it is mainly influenced by sunlight. The variation in temperature
affects the distribution of organisms, regulates their physiological activities and their mode of life.

2. Rainfall:
Rainfall is an important ecological factor as it determines seasons in some places. It also determines the
pattern and distribution of vegetation. With rainfall, seeds germination is made possible, plant growth is
enhanced to form vegetation. Vegetation in turn forms protective habitats for animals and food for them.

3. Wind
This can be described as air in motion. As an important ecological factor, it aid in the pollination of flowers,
the distribution of rainfall, spreading of bush fires at a fast rate across the forest and grassland biomes. High
velocity wind may cause soil erosion. Wind is responsible for water current and wave.

4. Light
Light is another essential ecological factor. All habitats (aquatic and terrestrial) are constantly exposed to
sunlight from morning till evening everyday. Variation in light intensity influences the behavior of organisms.
Light is the ultimate sources of energy and is essential for photosynthesis to take place in green plants.

5. Pressure
Atmospheric pressure is defined as the force of the weight of the air. Its value is 76mm of mercury (Hg) at
sea level, but as one goes up from the sea level, the atmospheric pressure decreases. Conversely, in aquatic
environment, pressure increases as one move down the water. Movement of winds is pressure dependant and
pressure affects the lives and activities of living organism.

6. Hydrogen ion Concentration (pH)

The PH scale is used to express the degree of acidity or alkalinity of a medium. It has a range from 1-14. PH
1-6 represents acidic PH, 7 is netural while from 8-14 represents alkaline PH .Variation in pH value, affects
the life of living organisms in the particular habitat to a great extent.
Example
Which of these is not an abiotic factor?
A. Light B. pressure C. protists D. rainfall E. wind (2005/40 Neco)
Answer: C – Protists are biotic factors.
Example
Which of the following factors is not biotic?
A. pressure B. competition C. predation D. grazing (2019/32 PC2)
Answer: A – Pressure is an abiotic factor
Example
Important abiotic factors which affect all plants and animals in the habitat are
A. temperature and turbidity B. rainfall and relative humidity
C. salinity and wind direction D. temperature and rainfall (1993/36 JAMB)
Answer: D–Temperature and rainfall
Example
Which of the following factors mostly determine the major biomes of the world?
A. pressure and wind speed B. Temperature and wind speed
C. Pressure and rainfall D. temperature and rainfall (2016/28 JAMB)
Answer: D – Temperature and rainfall are factors that mostly determine the major biomes of the world.

EXERCISE 23.15
1. (c) Describe how temperature as an ecological factor can be measured. (2003/8c)
2. Which of these factors are common to both aquatic and terrestrial habitats?
A. Light, rainfall and turbidity B. Light, temperature and tide
C. Light, rainfall and temperature D. Rainfall, turbidity and salinity (2006/42)

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3. Ecological investigation in a habitat includes the following procedures except
A. choosing a habitat B. identification of specimens
C. determining the genetic makeup of specimens D. measuring abiotic and biotic factor (2011/38)
4. Which of the following factors exerts a major effect on the distribution of living organisms in the habitat?
A. Salt B. PH C. Light D. Rainfall (2012/45)
5. Which of the following physical factors is likely to affect the distribution of plants in a pond?
A. Light B. Humidity C. Wind D. Temperature (2008/30)
Ecological Factors Common to Aquatic Habitat are :
i. Temperature ii. Rain fall iii. Wind iv. Light v. Salinity
vi. Dissolved gases vii. Density viii. Currents ix. Turbidity/transparency
x. Pressure Hydrogen ion concentration (pH) xi. Tidal movements and waves
Example
Which of the following is not associated with aquatic habitat?
A. salinity B. turbidity C. temperature D. edaphic (2005/38)
Answer: D – Edapic factors are not associated with aquatic habitat
Example
Which of the following factors is least likely to affect the organisms in the pond?
A. Acidity of the water B. high temperature C. age of the pond
D. amount of rainfall E. amount of sunlight (1998/40 Nov)
Answer: C – Age of the pond is least likely to affect organisms in the pond.
Example
The most important physical factor which affects an organism living in the intertidal zone of the seashore is
A. pH B. salinity C. wave action D. temperature (1993/37 JAMB)
Answer: C – Wave action is the most important physical factor that affects organisms living in the intertidal zone of the
seashore.
Example
Which of the following factors is not associated with aquatic habitat?
A. Temperature B. Light Intensity C. Turbidity D. Wave action E. Humidity (1990/43)
Answer: E – Humidity is not associated with aquatic habitat.
Example
Which of the following ecological factors are common to both terrestrial and aquatic habitats?
A. Rainfall, temperature, light and wind B Salinity, rainfall, temperature and light
C. Tides, wind, rainfall and altitude D. pH, salinity, rainfall and humidity (1986/45 JAMB)
Answer: A – Rainfall, temperature, light and wind are ecological factors that are common to terrestrial and aquatic habitats.

Example
The abiotic factor which determine the depth to which light penetrate in a pond is
A. current B. turbidity C. wind D. salinity (1999/40)
Answer: B– Turbidity
N.B–Turbidity is the measurement of how cloudy the water in a lake or river is and it determines the penetrating power of
light in a water body.

EXERCISE 23.16

1. Which of the following factors does not affect the distribution of organisms in an aquatic habitat?
A. Turbidity B. Depth of water C. Humidity D. Temperature E. Availability of nutrient (1997/44)

2. (c) List: (i) three biotic factors; (ii) five abiotic factors which affect plants in freshwater habitat. (2004/1c)

3. Which of the following factors is not associated with aquatic habitats?

A. Salinity B. Turbidity C. Temperature D. Edaphic (2005/38)

4. The speed of the flow of water in a river is faster in the middle than along the banks due to
A. differences in turbidity at different parts of the river
B. the abundance of fishes and other organisms along the bank
C. reduced force of gravity in the middle portion of the river
D. resistance offered by the walls of the banks (2008/37)

5. The distribution of organism in a fresh water habitats like a stream or pond is determined by the following factors
except
A. light penetration B. pH of the soil C. rainfall D. temperature (2010/33)

514
Ecological Factors Common to Terrestrial Habitat
These are: 1. Temperature 2. Rainfall 3. Wind 4. Light 5. Pressure 6. PH
Other factors are: - Relative humidity;
- Edaphic or soil factor: This includes soil type, soil texture, soil structure, moisture content.
Example
Which of the following groups of factors is completely abiotic?
A. salinity, tide, plankton, turbidity B. temperature, pH, soil, insect C. wind, altitude, humidity, light
D. conifers, wind pH, rainfall E. soil, water, bacteria, salinity (1984/44 JAMB)
Answer: C – wind, attitude, humidity and light are all abiotic factor
Example
Which of these groups of abiotic factors is common to terrestrial ecosystems?
A. rainfall, wind, sunlight and humidity B. waves, humidity, salinity and rainfall
C. turbidity, wind, rainfall and tide D. Humidity, wind, rainfall and tide (2000/41 Nov)
Answer: A – Rainfall, wind, sunlight and humidity is common to terrestrial ecosystem.
Example
The most important ecological factor in a terrestrial environment is
A. rainfall B. humidity C. wind D. soil (2009/29 JAMB)
Answer: D – Soil is the most important ecological factor in a terrestrial habitat.

Example
The addition of lime to clayed soil serves to
A. prevent water – logging B. aid water retention C. improve capillary action D. close up the texture (2002/42 JAMB)
Answer: C – The addition of lime to clayed soil serves to improve capillary action of the soil.
Example
A biotic factor which affects the distribution and abundance of organisms in a terrestrial habitat is
A. temperature B. competition C. pH D. light (2007/9 JAMB)
Answer: B – Competition is the biotic factor that affects the distribution and abundance of organisms in a terrestrial
habitat.
EXERCISE 23.17
1. A limiting factor in a plant population near a chemical factory is likely to be
A. humidity B. pH C. wind D. light (2003/30 JAMB)
2. Which ecological factor exerts the greatest influence on the structure of the profiles?
A. Topographic B. Edaphic C. Biotic D. Climatic (1989/50 JAMB)
3. Which of the following environmental factors is not considered in a terrestrial habitat?
A. Temperature B. Sunlight C. Humidity D. Turbidity (2003/37)
4. Which of the following limiting resources is competed for by organisms in the desert?
A. Light B. Temperature C. Oxygen D. Water E. Carbondioxide (1991/52)

Topographical Factor or Land Surface

These are;
a. Elevation
b. Type of drainage
c. Degree of exposure: The degree of exposure of a land is affected by rainfall and vegetation cover
At high elevation, plants become stunted, a few species of plants and animals occur. This is so because the
higher one goes above sea level, the lower the temperature and the greater the wind action.
Gradient or slope of the ground affects living things or organisms. For example, when the slope is steep, rain
water runs off fast on the earth and as a result of that, little water soaks into the soil. Fast flow of water on the
earth’s surface causes erosion so that the soil becomes shallow and infertile. As a result, a few plants and
animals occur in such a place.
Exposed habitats receive much sunshine and strong winds and only adapted plants and animals can live in
such places.

515
Edaphic Factor or Soil Factors
Soil or edaphic factor are related to
1. Type of soil particles
2. The humus, mineral, water and air content
3. The pH
4. The depth of the water table.

Types and Characteristics of Soil

1. Sandy Soil: Sandy soil retains little water, and is easily drain. It is well aerated and easily become infertile
due to leaching. It favours the growth of grasses.
2. Loamy soil:
This is a balanced mixture of sand, silt and clay. It is well drain and has sufficient air. It is fertile and favour
the growth of most plants.

3. Clay soil:
This retains much water. It is neither well drained nor well aerated. It is heavy and sticky when wet and hard
when dry; it favours the growth of certain species of plant.
4. pH:
Some plant (e.g. tea) prefers acidic soils, while most plants prefer almost neutral soils.
Other soil factor e.g. soil water, soil organic matter, soil air, soil fertility, affect the growth of plants and
animals and their population.
Importance of Ecological Factors to Population of Plants and Animals
1. It controls the occurrence of organism in a particular place.
2. It controls the abundance of organism in a particular habitat.
3. It determines the distribution of organism over the habitat.
For example, in a stream, some organisms are found near the edge of the water where speed of flow of water
is gentle. Some other organisms are found only at the surface of water (where light is available).

Examples of ecological factors that can control the distribution of organisms in a particular situation include
fire (in savanna), salinity (in estuary) and ocean currents which may influence climate of adjacent masses.

Instruments for Measuring Ecological Factors

Ecological Factors Instruments
Rainfall Rain – gauge
Temperature Thermometer
Relative humidity Hygrometer
Wind Wind vane (for direction of wind)
Anemometer (for wind speed)
Light Photometer
Pressure Barometer
Elevation Barometer
Slope Meter rule method, slope guage
PH Soil kit or PH meter
Turbidity Secchi disc
Gradient or land Slope guage

516
 Photo Meter Aneroid barometer

SECCHI DISK WET AND DRY BULB HYGROMETER

Example
When large numbers of organisms share limited space and resources the result is
A. immigration B. commensalism C. symbiosis D. extinction E. competition (1988/53)
Answer: E – Competition will result when large numbers of organisms share limited space and resources.
Example
Which of the following statements is not correct about the ecological effects of agricultural activities?
A. the use of herbicides and pesticides can cause pollution B. bush burning encourages desertification
C. excessive effects D. tillage of tropical soil with plough and harrow may encourage erosion
E. mono cropping of the cultural method of controlling pests (1989/28)
Answer: E – “monocropping is one of the cultural methods of controlling pest” is not correct about the ecological
effects of agricultural activities.
Example
The activities of an organism which in a habitat can be described as
A. biotic factors B. climatic factors C. physiographic factors D. edaphic factor E. abiotic factors (1989/30)
Answer: A – Biotic factors
Example
Secchi disc is used to measure
A. Light intensity B. turbidity C. water current D. salinity (2020/27 PC1)
Answer: B – Secchi disc is used to measure the turbidity of water.
Example
The number of individuals in a habitat in relation to the unit space available to each organism is referred to as the
A. birth rate B. density C. mortality D. frequency E. dispersion (1991/40)
Answer: B – Density
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Example
The abiotic factor which determines the depth to which light penetrates in a pond is
A. current B. turbidity C. wind D. salinity (1999/44)
Answer: B – Turbidity is the measure of relative clarity of a liquid. It is also the cloudiness or haziness of a fluid
caused by large number of particles in a fluid. Hence the abiotic factor which determines the depth to which light
penetrates in a pond is called turbidity.
Example
An ecological instrument used for the collection of small insects from the soil, leaf litter and crevices is
A. pooter B. quadrat C. sweep net D. drag net (2020/29 PC1)
Answer: A – Pooter is an ecological instrument used for the collection of small insects from the soil, leaf, litter and
crevices.
Example
Predation is an example of a factor in an ecological system referred to as
A. edaphic B. topographic C. abiotic D. biome E. biotic (1992/39)
Answer: E – Predator is a biotic factor.

Example
Which of the following ecological factor causes food shortage?
A. low rate of reproduction B. emigration C. drought D. topography E. wind direction (1995/58)
Answer: C – Drought is an ecological factor that cause food shortage.
Example
Which of the following instruments is used to measure the speed of a stream?
A. Simple float B. Secchi disc C. Quadrat frame D. Rain gauge (2005/39)
Answer: A – A simple float is used to measure the speed of a stream.
Example
The gradient of land can be measured with an instrument called a/an
A. aneroid barometer B. hygrometer C. meter rule D. secchi disc E. slope gauge (2001/32 Neco)
Answer: E – The gradient of land can be measured with an instrument called slope guage.
Example
Relative humidity can be measured with a/an
A. anemometer B. barometer C. hydrometer D. hygrometer E. photometer (2001/29 Neco)
Answer: D – Hygrometer is used to measure relative humidity. N.B– Hydrometer is used to measure density
Example
Which instrument is used to measure wind speed in a terrestrial habitat?
A. barometer B. Anemometer C. photometer D. Thermometer (2002/38 Nov)
Answer: B – An anemometer is used to measure wind speed.
NB: Wind direction is measured by an instrument called wind vane.

Example
The unit of measurement for the amount of rainfall by a rain gauge is
A. cubic centimetres B. cubic metres C. cubic kilometers D. cubic decimeters (2004/35 Nov)
Answer: A – Cubic centimeters.
Example
Which of the following is not a procedure in the use of Secchi disc for determining the turbidity of water?
A. Indicating the depth at which the white colour disappears B. Lowering the disc into water gradually
C. Attaching a string to the centre of the disc D. Diving into the stream to take readings
E. Attaching a weight to the centre of the disc to sink it (1995/46 Nov)
Answer: D – Diving into the stream to take readings is not a procedure in the use of secchi disc for determining the
turbidity of water.

EXERCISE 23.18
1. (c) (i) List three instruments used in the measurement of ecological factors.
(ii) Briefly state how one instrument listed in c(i) above is used. (2018/6c (i) & (ii) NABTEB)
2. An instrument used in measuring the speed of wind is
A. a barometer B. a wind gauge C. a wind vane D. an anemometer (1981/37 JAMB)
3. Which of the following instruments is used for determining turbidity of water?
A. thermometer B. secchi disc C. rain gauge D. hygrometer E. wind (1983/40 JAMB)
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4. Which of the following instruments is used to measure relative humidity?
A. Thermometer B. Hygrometer C. Anemometer D. Hydrometer (2011/34 JAMB)
5. Which of the following instrument is used for measuring atmospheric pressure?
A. Thermometer B. Barometer C. Hydrometer D. Hygrometer (2014/26 JAMB)
6. (c) Describe how temperature as an ecological factor can be measured. (2003/8c)
7. Wind speed is measured with
A. a maximum-minimum thermometer B. a hygrometer
C. a wet and dry bulb hygrometer D. an anemometer (2007/39)
8. Which of the following instruments is used to measure wind speed?
A. Thermometer B. Barometer C. Hygrometer D. Anemometer (2008/31)
9. The speed of wind is measured using the
A. wind vane B. anemometer C. photometer D. barometer (2010/34)

10. Which of the following instruments is used to determine the turbidity of water?
A. Hygrometer B. Hydrometer C. Secchi disc D. Rain gauge (2018/31)
11. Which of the following instruments is used to measure the speed of a stream?
A. Simple float B. Secchi disc C. Quadrat frame D. Rain gauge (2005/39)
12. A population is best described as
A. a group of the same species of organisms living together B. a group of animal and plant living together
C. a group of insects and grasses D. different species of wild animals (2005/35)
13. List (i) three biotic factors (ii) five abiotic factors which affects plants in fresh water habitat. (2004/1c)
14. Which of the following is not essential in the studying of the ecological factors that directly affects plants
A. wind B. temperature C. herbivores D. carnivores (2004/34)
15. Describe how temperature as an ecological factor can be measured. (2003/8c)
16. Which of the following environmental factors is not considered as terrestrial habitat?
A. temperature B. sunlight C. turbidity (2003/37)
17. Explain four factors which affects population size. (2002/7b)
18. The numbers in a population would rise if there was an increase in the
A. spread of disease B. number of death
C. number of predators D. amount of food available (2002/43)
19. Name four abiotic factors each which affect plants and animals in terrestrial habitat. (2001/5b)
20. Describe the effect of three abiotic factors on a named plant and an animal in the habitat mentioned (in
question 12) above. (2001/5c)
21. Soil factors in an ecosystem are referred to as
A. topographic B. climate C. biotic D. edaphic (1994/40)
22. Which of these is not a biotic factor
A. parasite B. predator C. grazers D. pressure (1999/37)
23. In an inter species competition, the less successful species usually
A. reproduce faster B. become more active C. become dormant
D. occupy more space E. become eliminated (1997/57)
24. Describe how you can estimate the density of a plant species using a quadrant. (1993/3b)

ECOLOGICAL SUCCESSION
Ecological succession is defined as a long term series of changes occurring in the structure, composition, diversity and
numbers of species in an area till a stable/climax community is established. A climax community is established when
a stable/unchanging community is attained/established i.e a community capable of maintaining its structure and
composition

GENERAL CHARACTERISTICS OF SUCCESSION

1. Succession occurs in newly formed natural habitats e.g. sea shores and abandoned farm lands.
2. Increase in number of organisms: In a succession, there is always a progressive increase in the number of
organisms from time to time until a stable community is attained.
3. Succession is orderly and progressive: Succession is usually an orderly and progressive process as
microscopic green plants usually start it and bigger trees eventually result.

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4. Competition among organisms: There is usually competition among the organisms for available food, light,
space, nutrients and other resources within a habitat as stronger ones survive while weaker ones die.
5. Changes in habitat: Each generation of species changes the habitat by adding more soil and making it more
fertile as well as shading other plants.
6. Changes in species composition: Due to strong competition among the organisms, the fittest survive while
the weak die away and this results in succession of species in a community.
7. Diversity of organisms: There is always diversity of organisms in succession as the species and number of
organisms changes from time to time until a climax community is attained.
OUTCOME OF SUCCESSION:
1. Changes in the physical environment: During the process of succession, there is gradual change in the
specie composition of the community. This leads to changes in the activities of the community and eventually
a change in the physical environment results.
2. Fast Replacement: The rate of replacement process is fast as some species which make conditions favourable
for others do so at their own expense.
3. Replacement by complex organisms: There is an evolutionary and sequential replacement of simpler
organisms by more complex ones in the succession process.
4. Attainment of equilibrium point: It brings about the attainment of an equilibrium point due to the fact that
bare or abandoned habitats are colonized by a variety of organisms similar to those in nearby habitats.
5. Establishment of a climax community: The establishment of a climax community is the final outcome of
succession.
Example
(b) Explain the term: ecological succession. (1989/1b)
Answer:
b. Ecological succession is the gradual and orderly changes that occur in plant and animal community of a given
area over a period of time until a climax community is established.
Example
Succession is best described as
A. a process whereby different organisms systematically colonize a barren habitat until a stable community is formed
B. a process whereby plants occupy a barren habitat until a suitable habitat is formed
C. a process whereby animals occupy a barren habitat until a suitable habitat is formed
D. the subsequent taking over of the land through emigration or dispersal of seeds
E. the replacement of weaker plants and animals by the stronger ones (1991/46)
Answer: A – Succession is best described as a process whereby different organisms systematically colonize a barren
habitat until a stable community is formed.
Example
Which of the following habitats cannot be used for the study of succession?
A. Savannah grassland B. Abandoned farmland C. A pond D. Well cultivated land (1999/60)
Answer: D – A well cultivated land cannot be used for the study of succession.

Example
The following observations concerning succession are true except that the
A. pioneer community has fewer species B. middle stages communities are most diverse
C. climax community has the greatest number of species
D. total biomass of the community increases as succession progresses (2008/39)
Answer: C – Climax community has the greatest number of species.
Example
The following habitats can be used in the study of succession except
A. savanna grassland B. abandoned farmland C. a pond D. a well cultivated land (2009/43)
Answer: D – A well cultivated land.
N.B – Succession occurs in newly formed natural habitats e.g. sea shores and abandoned farm lands. A well cultivated
land is not a newly formed habitat

EXERCISE 23.19
1. The following habitats can be used in the study of succession except
A. burnt savanna grassland B. abandoned farmed
C. a well cultivated land D. dried up pond (2017/32 NABTEB)
2. The following are associated with succession except
A. change in species composition B. competition among organisms
C. decrease in the number of organisms D. diversity of organisms
E. habitat change (2008/38 Neco)
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3. 4(a) Define ecological succession. (1997/4a Nov)
4. The following statements are characteristic of succession except that it
A. takes place in newly formed habitats
B. involves gradual progressive increase of species over a period of time
C. always involves competition among organisms
D. can start with complex communities (2011/39 Nov)
5. The biological association that contributes directly to succession in a community is
A. competition B. predation C. parasitism D. commensialism (1998/43 JAMB)
6. The order of primary succession by plants in a very dry habitat is
A. xerophytes →mesophytes→ shrub B. mesophytes→ xerophytes→ shrub
C. mesophytes→ shrub → xerophytes D. xerophytes → shrub →mesophytes (2007/44)

TYPES OF SUCCESSION:
There are two main types of succession;
1. Primary succession
2. Secondary succession

PRIMARY SUCCESSION:
This succession starts on barren, lifeless habitat. It usually starts with lower organisms and takes a longer time to reach
a climax community. Examples of primary succession can be found in ponds, vegetation on rocks, mangrove forest,
estuary etc. it involves the formation of new soil.

Primary succession in aquatic habitat e.g. pond

A plant succession which occurs in an area of fresh water such as a lake or pond is known as a hydrosere. Succession
in a new and virgin pond hydrosere starts with the colonization of phytoplankton and finally terminates into a forest
(the climax community). The stages in a pond succession are as follows:

1. Phytoplankton/bare bottom stage:

In the initial stage of succession, algal spores are brought into the body of water. The simple forms of life like
bacteria, algae and many other aquatic plants (phytoplankton) and animals (zooplankton) floating in water are
the pioneer colonizers. All these organisms add large amount of organic matter and nutrients into the
community as a result of their various life activities and after their death, they settle at bottom of pond to form
a layer of mulk.

2. Submerged vegetation stage:

This stage follows the phytoplankton stage. It develops in the region of the pond where the water depth is
about 10 feet or more. The plants found in this stage include Elodia, Utricularia and Ceratophyllum. When
these plants die, their remains are deposited at the bottom of ponds or lakes. Eroded soil particles and other
materials are deposited as well at the bottom. This gradually raises the ponds and lakes up.
As this process of stratification progresses, the body of water becomes more and more shallow. Consequently
the habitat becomes less suited for the submerged vegetation but more favourable for other plants.

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3. Floating stage:
As the water depth becomes more shallow (about 4 to 8 feet), the submerged vegetation starts disappearing
from its original place and then the floating plants make their appearance gradually in the area. Important
floating plants that may replace submerged vegetation includes Pistia, Nymphaea and Trapa.

4. Temporary pond stage:

At this stage, the depth of the pond is so shallow that it becomes less suited to floating plants and some other
plants (mainly terrestrial plants) which can thrive in this new environment begin to grow. Various mammals
and birds also visit the edges of the pond at this stage.

5. Climax forest:
As the level of soil is raised much above the water level by progressive accumulation of humus and soil
particles, the habitat becomes more dry and well aerated. This leads to the development of climax vegetation.
In the climax forest all types of plants can be found e.g. herbs, shrubs, mosses but the trees are dominant and
they have control over the entire vegetation.

Factors which can give rise to primary bare surface includes Erosion, Volcanic Ash, Land Slides, Earthquake,
Thunderstorms, Hurricanes, Tornadoes, Extreme Drought, Mining Activities Etc.

SECONDARY SUCCESSION
Secondary succession starts on already colonized surface. It may start with fairly complex organisms and it takes a
shorter time to reach a climax community.
Examples of secondary succession are found in abandoned farmlands and grasslands.

Differences between primary and secondary succession

Primary succession Secondary succession
It starts on a barren area or surface It starts on already colonized surface
It takes longer time to complete i.e. to reach a It takes a shorter time to complete
climax community
It starts with lower organisms It starts with fairly complex organisms.
No previous community is present in the Previous communities are present in the
environment prior to primary succession. environment prior to secondary succession.
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Major communities in a plant succession
There are three major communities in a plant succession. These include
1. Pioneers communities: This is the first group of plants in a succession. They are small, lower plants and
drought resistant organisms. They require minimum space and nutrients. They are adapted on bare surfaces.
e.g. algae, lichens, mosses and liverworts.

2. Development/intermediate/transitory communities: These are series of communities which follow the

pioneers with each succeeding communities more complex than the one it replaced. Examples are herbivores
plants such as Talinum, Ageratum, Cyanotus and Sida acuta.

3. Climax communities: This is the stable community in a succession. It has the greatest specie diversity and
greater population diversity. E.g. trees and shrubs.

Process of succession in abandoned farmland (example of secondary succession)

The initial pioneers of an abandoned farmland include the insects, eggs, larva, worms, plants seeds and underground
stems etc. they derive their nutrient from the left over of the abandoned farmland. They form the first stage of
succession.
The second stage involves the germination and growth of more grasses, the hatching of eggs of insects and some
other species.
In the third stage, herbs are displaced by shrubs and there is an increase in the diversity of the species.

The fourth stage involves the growth of more trees and increased species diversity. These include bird, snakes,
monkeys etc. living in different strata of the habitat. The population and activities of detritus feeders now increase and
climax vegetation is reached. The animal community will include herbivores, carnivores and detritus feeders which
are involved in a complex food web.
Example
Which of the following statements is not true of a climax vegetation? It
A. is an ecological phenomenon B. is a stable community C. eliminates competition
D. results from succession E. involves the colonization of a habitat (1988/37)
Answer: C – A climax vegetation does not eliminates competition.
Example
3(a) Describe the process of succession in an abandoned farm land. (1990/3a)
Answer: The process of succession in an abandoned farm land starts by the decay of dead plants and animals of the
old farm, and this enhances nutrients of the soil. Then, pioneers such insects’ eggs, larva, worms, seeds of plants that
are carried by animals or wind and underground stems (e.g. rhizomes and stem tubers) colonizes the farmland. After
this, germination and growth of herbaceous plants (e.g. grasses and lilies), hatching of eggs and development of insect
occur. The growth of herbaceous plant and development of insects attract rodents and reptiles respectively. Then, the
herbs are replaced by shrubs and the shrubs are subsequently replaced by trees. The tree attracts birds, monkeys, and
tree reptiles. The presence of herbivores, carnivores and omnivores (animal community) makes the community to
reach a climax.
Example
A climax community is characterized by
A. a stable composition of plant and animal species B. rapid changes in the composition of species
C. constant changes in appearance of the habitat D. different species occurring at different times
E. gradual change in animal population (1993/40)
Answer: A – A climax community is characterized by a stable composition of plant and animal species.
Example
Which of the following is not an outcome of ecological succession
A. There is a progressive change of species structure, organic matter and energy flow
B. The climax stage consists of a comparatively long lasting species composition
C. There is no dynamic equilibrium between the community and habitat in the climax stage
D. Communities occurring later in the sequence of succession are more complex
E. There are fewer dominant species in the late stages of succession (1995/43)
Answer: A – There is a progressive change in species structure, organic matter and energy flow is not an outcome of
ecological succession.

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Example
A good site for secondary succession would be
A. a sand dune B. a bare rock C. a land that has just had forest fire D. a stretch of barren land (2017/30)
Answer: C – A good site for secondary succession would be a land that has just had forest fire. This is because
before the forest fire, such land area already had nutrient rich soil and therefore can be easily recolonized much more
quickly than the bare rock for primary succession.
Example
(b) State two differences between primary and secondary successions. (1997/4b Nov)
Answer:
- Primary succession arises in a virtually lifeless area with no soil while secondary succession arises after a
disturbance that destroys a community without destroying the soil.
- Primary succession takes longer time to complete while secondary succession takes shorter time to complete.
Example
During succession on a bare rock surface the pioneer community consists of
A. mosses B. lichens C. ferns D. grasses (2002/44 Nov)
Answer: B – Lichens are the pioneer community during succession on a bare rock surface.
Example
The following statements are true about climax communities except that
A. the community is at its equilibrium B. the community is stable
C. species of plants and animals can change from year to year
D. the vegetation reaches the highest development (2011/40 Nov)
Answer: C – In climax communities, species of plants and animals do not change from year to year.

EXERCISE 23.20
1. Which of the following is true of a climax community?
A. It persists until the environment or climate changes B. It changes drastically from one year to the next
C. It is the first stage in succession D. It is made up of the tallest trees and the smallest animals (1992/32 JAMB)
2. Ecological succession ends with the formation of a stable
A. Niche B. population C. pionner community D. climax community (1994/37 JAMB)
3. Colonization of a bare rock surface is termed
A. evolution B. speciation C. primary succession D. secondary succession (1995/35 JAMB)
4. An ecological succession often leads to
A. an unstable community B. a decrease in species diversity
C. an increase in species diversity D. the dispersal of species (2000/34 JAMB)
5. The pioneer organisms in ecological succession are usually the
A. lichens B. algae C. ferns D. mosses (2003/31 JAMB)
6. Climax communities in a biotic succession are usually characterized by
A. a constant change in the appearance of the communities B. different species that are constantly changing
C. a stable composition of plant and animal species D. rapid changes in the plant and animal species (2006/43 JAMB)
7. The most likely first colonizers of bare rock are
A. mosses B. ferns C. lichen D. fungi (2012/33 JAMB)

8. After a heavy rainfall and the formation of a large pond the most likely sequence of changes in the vegetation
of the pond is
A. Euglena→water lily→ spirogyra→grass B. Water lily→spirogyra→grass→Euglena
C. Spirogyra→euglena→grass→water lily D. Euglena→spirogyra→water lily→grass (1997/38 JAMB)
9. In ecological succession, since lichens grow on bare rock, they are considered to be
A. primary consumers B. pioneer organisms C. climax organisms D. producers (2009/45)

OVER CROWDING
Overcrowding is a situation that occurs when a population in a given habitat increases beyond a point where resources
in the habitat become limited. i.e. it is not enough to support all the individuals in the population. It simply means too
many organisms.

POPULATION AND POPULATION DENSITY

Population is defined as the total number of organisms of the same species living together in a given area at a
particular time. In an ecosystem, the community is made up of many populations of different species.

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POPULATION DENSITY
Population density is the average number of individuals of species per unit area of the habitat.
Factors that may cause overcrowding
1. Limited space 6. Decrease in mortality rate
area of habitat
Space = number of individual 7. Increase in survival rate

2. Increase in birth rate (Natality) 8. Barriers

3. Limited food supply 9. Lack of dispersal
4. Flux of immigrant 10. Absence of predators
5. Less emigration

Effects of Overcrowding
1. Shortage of food: Overcrowding speeds up the depletion of available resources (food, water, health facilities
etc.) This may then lead to scarcity of food or malnutrition or high cost of living.
2. Spread of disease: Overcrowding leads to the spread of some infectious diseases at fast rate, leading to
epidemics and pandemic in some cases.
3. In lower animals, it may lead to fighting and cannibalism as well as a reduction in birth rate.
4. In human beings, overcrowding may lead to promiscuity as well as various anti–social behaviors or serious
criminal tendencies such as robberies, begging, prostitution and rape.
5. Competition for limited resources like food and living space, as well as for mate (within members of the
same species).
6. It leads to build up of toxic wastes in the environment from the organisms themselves
7. It increases death and immigration.
8. It decreases reproductive rate until the size of the population reaches the carrying capacity of its habitat.
Note: Carrying capacity is the maximum number, density or biomass of a population that a specific area can support
sustainably.
Adaptation/measure to avoid overcrowding:
Plants and animals have devised various means of spreading their offspring and preventing overcrowding. They
include:
1. Dispersal of seeds and fruits: Many plants ensure that their seeds and fruits are dispersed far and wide by
agent like animal, wind and water. For example, many plants have edible fruits which birds eat. The seeds of
these fruits passes through the digestive tract of the birds unharmed and are egested in their droppings, usually
far away from the parent plants. Sticky or hooked seeds of some plants cling to the fur of animals moving
through them. Such seeds may be carried to long distances before they are brushed off. The wind carries very
light or winged seeds and fruits far away from the parent plants. These various adaptations of fruits and seeds
for dispersal prevent overcrowding within members of the same species.
2. Migration of animals: In many habitats, food supply is affected by seasonal changes. E.g. in the savanna,
food is abundant during the rainy season but scarce during dry season. Many animals overcome such seasonal
food shortage by moving to other habitats during the unfavourable season and returning at the onset of the
favourable season.
Another limiting factor that causes migration is the cold winter temperatures. Most migration are also linked
with breeding.
Migrating behavior is common among birds. Birds have adaptations that enable them travel great distance
without wasting energy.
3. Life cycle and lifespan: Overcrowding within a species is avoided in some by having life cycles where the
young and adults occupy different ecological niches. For example, adult toad lives mainly on land, feeding on
insect while tadpoles live in water, feeding on aquatic plants and animals. Overcrowding within a species is
also prevented by having life spans, where the adults usually die shortly after the young are produced.
4. Territorial behavior: Territory refers to an area that an organism defends against intruders. Some animals,
especially birds and mammals establish territories. Territories are resting areas or a certain portion of the land,
wood, or tree which the animals carve out for themselves. They are usually possessive of the areas. They fight
for and defend them against intruders or other members of the same species.
Claiming the territory successfully ensures that they have sufficient space, foods, mating partners and parental
care. The establishment of territories ensures that there is no overcrowding and even under crowding.
Territorial behavior is shown by the rainbow lizard (Agama agama).
Other examples of animals with territorial behavior are male fiddler crab, Siamese fighting fish, some species
of tilapia, male antelope etc.

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5. Alleopathy by some plants: The roots and leaves of many plants release to the environment some chemicals
which are toxic to the germination and growth of other plants. This phenomenon is called allelopathy.
Examples are Salivanemorosa which secretes terpene. This plant does not allow the growth of any plant in a
radius of one meter.
Other measures of avoiding overcrowding are swarming of certain social animals such as termites and bees
and production of canopies by tall plants to trap sunlight while the one below eventually die off due to lack of
sunlight.
Example
When large numbers of organisms share limited space and resources the result is
A. immigration B. commensalism C. symbiosis D. extinction E. competition (1988/53)
Answer: E – Competition will result, when large numbers of organs share a limited space and resources.
Example
Over-crowding in seedlings of different species is less serious than over-crowding involving one species because
different species may
A. have different nutritional needs B. lack the same nutrient C. be active at the same time
D. have similar tolerance E. need equal spacing (1989/52)
Answer: A – Overcrowding in seedlings of different species is less serious than overcrowding involving one species
because different species may have different nutritional needs.
Example
Which of the following is not a characteristic of overcrowding in plant and animal community?
A. Population outstripping available space B. Population exceeding available food
C. Competition within the population D. Increase in primary production
E. Population increasing at the same rate as the birth rate (1993/41)
Answer: D – Increase in primary production is not a characteristic of over crowding in plant and animal community.

Example
Which of the following is an advantage of dispersal of fruits and seeds? It allows
A. fair distribution of source of food for animals B. growth in close association with parent plant
C. even distribution of plants and reduction of intraspecific competition D. keen competition for food
E. the seeds to evolve new species (1995/26)
Answer: C – An advantage of dispersal of fruit and seed is that it allows for the even distribution of plants and
reduction of intra specific competition.
Example
Which of the following animals exhibit territoriality?
A. Bees B. Bats C. Lizards D. Rabbits (2001/60)
Answer: C – Lizards exhibit territoriality.
Example
Competition among individuals of a population increases the
A. number of organisms B. survival of the fittest
C. availability of nutrient supplied D. enlargement of the territory (2003/43)
Answer: B – Competition among individual of a population increase the survival of the fittest.
Example
Overcrowding in a population does not result in
A. death B. commensalism C. competition D. migration (2016/35)
Answer: B – Commensalism is an example of a biological association and not an effect of overcrowding. All other
options are effects of overcrowding
Example
Which of the following factors may not cause overcrowding?
A. limited space B. scarcity of food C. reduced birth rate D. lose immigration conditions E. increased birth rate (1997/46)
Answer: C – Reduce birth rate will not cause over crowding.

Example
(ii) List twos causes of over-crowding. (2014/5cii Neco)
Answer: 1. Immigration 2. Reduce mortality (death) rate - Increase in Natality (birth) rate
EXERCISE 23.21
1. (b) List four causes of overcrowding. (2008/3b Neco)
2. 3(a) Define competition. (2008/3a Neco)
3. 4b. State four effects of overcrowding. (2018/4b Neco)
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4. Which of the following animals exhibits territoriality?
A. bat B. cow C. Lizard D. rabbit E. toad (2007/28 Neco)
5. All of the following factors contribute to overcrowding of organisms in a habitat except
A. natality B. immigration C. emigration D. survival (2005/46 Nov)
6. Which combination of the above can cause rapid overcrowding in climax biotic communities and human
settlement?
A. II and III B. I and IV C. I and III D. I and II (2000/35 JAMB)
7. Plants tend to prevent overcrowding by means of efficient
A. seed germination B. pollination C. seed dispersal D. water uptake (2002/44 JAMB)
8. Lack of space in a population could lead to an increase in
A. birthrate B. disease rate C. drought D. water scarcity (2011/41 JAMB)

Food Shortage
In all habitats, producers are responsible for providing the food that supports all consumers either directly or
indirectly. Certain factors can however decrease the food supply to the habitat and thereby causing food shortage.

Causes of food shortage:

1. Drought: Drought causes water scarcity and without water most plants die. Primary consumers face food
shortage when this happens, if the drought last for a long period, the primary consumers starts to die or
emigrate to other areas causing food shortage for secondary consumers. In time, consumers at various tropic
levels face food shortage.
2. Disease: A highly contagious viral disease like rinder pest can kill off large numbers of herbivores. This
causes a shortage of food for the consumers that prey on the herbivores. Plant disease can also bring about
shortage of food.
3. Overpopulation
4. Soil erosion
5. Floods
6. Lack of interest in farming by young generation
7. Poor methods of preserving and storing food
8. Poor transport of agricultural produce
9. Lack of crop insurance and credit facilities
10. Lack of irrigation facilities
11. Use of low yield seedling materials
12. Infertility of soil
13. Non availability of good fertilizers
14. Inconsistency of government agricultural policies in many under developed countries
15. Subsistence farming.

Effects of Food Shortage

1. Food shortage causes population size to decrease. The decrease is brought about by
a. Competition
b. Emigration
c. Rate of reproduction
d. Mortality (death)

a. Competition: During food shortage, members of a population will compete with one another for the limited
food supply. Only the most vigorous individuals succeed in getting food, the rest starve.
Competition between organisms also occurs when other resources in the habitat are limited.
Competition between different species results in the elimination of the less vigorous species from the habitat.
b. Emigration: This is the movement of members of a population away from its habitat to various other areas as
a direct response to lack of food or living space. It occurs at irregular intervals and there is no return
movement as in migration. Individuals only emigrate if their chances of survival are better by doing so than by
staying in the habitat. These individuals join an existing population or establish new population.
Locust swarms are example of emigration.

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c. Rate of reproduction: The reproductive rate is the rate at which new individuals are produced. Food shortage
lowers the rate of reproduction and delays sexual maturity. Growth is retarded during food shortage. This
often delays sexual maturity which seems to be more related to size than to age in some species. Under
starvation conditions, many female humans stop ovulating and so would not be able to conceive. Many plants
and lower animals reproduce vegetatively when food is plentiful, and produce seeds and spores only when
food is scarce. Seed and spores only germinate under favourable conditions. So reproduction rate is reduced in
this manner.

d. Mortality (death rate): This is the number of individuals of a species which die from whatever cause, in a
given period of time. Food shortage increases the death rate especially among the young and old (the
vulnerable age group).
Scarcity of available food to organisms leads to malnutrition among organisms.

Differences between Competition and Succession

Competition Succession
1. starts when resources are in short supply in a habitat. Usually starts with new habitat.
2. Occur in all places inhabited by organisms. Occurs only in a particular area.
3. Competition has no end, it continues even in a stable Succession ends at the establishment of a stable or
or climax community. climax community.
4. The basis for competition is provided by succession. Succession is speed up by competition i.e. without
competition there is no succession.
5. The replacement of one population by another in a In succession, the replacement of one population by
given environment in competition is due to survival of another in a particular area is transitory and it leads
the fittest. to climax or stable community.
6. In competition replacement of old population by new In succession replacement of old population by new
population is as a result of inter-specific competition. population is by a gradual process.

Example
What is the significance of the bee dance to other bees?
A. Warning signal B. Presence of food C. Mating signal by the male
D. Scaring the enemies away E. Time for nuptial flight (1990/59)
Answer: B – Presence of food
Example
Which of the following statements is not correct?
A. Shortage of food nay be caused by pestilence, rinderpest and neglect of farming
B. Shortage of food may lead to competition, emigration, death and decline in the rate of reproduction
C. Overcrowding may lead to scarcity of food
D. Dispersal of seeds and fruits prevents overcrowding
E. Territorial defense encourages food scarcity in a habitat (1995/25)
Answer: E – Territorial defense does not encourage food scarcity in a habitat.
Example
(c) Explain three ways by which the government may increase food production. (1999/5c)
Answer:
- Granting of interest free loans to farmers as a way of encouragement.
- Providing land for agricultural practices.
- Provision of fertilizers herbicides, pesticides, fungicides and drugs to farmers at a subsidized rate.
Example
Which of the following ecological factors will result in food shortage?
A. Drought B. Low rate of reproduction C. Emigration D. Topography (2017/33)
Answer: A – Drought will result in food shortage.
Example
Food shortage leads to reduction in population size due to the following except
A. competition B. disease C. emigration D. immigration E. mortality (2014/24 Neco)
Answer: D – Food shortage does not lead to reduction in population size due to immigration.

EXERCISE 23.22
1. What has NO effect on the food shortage of a population?
A. Cannibalism B. competition C. increase in mortality
D. increase in natality E. Migration (2001/44 Neco)

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2. An abandoned farmland which went through a series of changes in flora before attaining final stable
vegetation could be said to have undergone
A. evolution B. succession C. adaptation D. progression (2005/44 Nov)
3. Which of the following is not associated with food shortage?
A. Increase in death rate B. Rapid rate of reproduction C. Fall in natality rate
D. Competition E. Emigration (1995/49 Nov)
4. The effect of food shortage is an area includes
A. Increase in population size B. decrease in secretion of enzyme C. immigration
D. competition E. high rate of reproduction (1996/50 Nov)
5. Food shortage may be caused by the following factors except
A. storage in air-tight silos B. infertility of the soil C. poor storage facilities
D. pest and diseases E. flooding of farmlands (1994/42 Nov)
6. The factor that least affects food shortages in sub-Saharan Africa is
A. flooding B. pests C. mixed-cropping D. drought (2001/30 JAMB)
7. The scarcity of food causes a sudden decrease in population size by
A. raising the mortality rate B. minimizing the rate of competition
C. decreasing the reproductive rate D. bringing about immigration (2004/6 JAMB)
8. (a) (i) What is competition?
(ii) In a tabular form, state four differences between competition and succession. (2013/4ai, ii Nov)

Factors affecting a Population

A number of factors collectively known as environmental resistance are responsible for controlling the population of
organisms in a particular habitat. These factors are classified as abiotic and biotic factors.

Abiotic factors affecting a population

1. Light: The importance of light as an abiotic factor cannot be overemphasized. It plays a vital role in the
manufacturing of food needed in a habitat. In fact without light it would be impossible for green plants to
manufacture food. The growth and development of plants can also be hampered if light intensity is low.

2. Space: Space is very important to all organisms for normal growth and development. Lack of space leads to
overcrowding and competition among organisms.

3. Heat: The degree of hotness of a place can determine the size of population. Hot environment generally is not
conducive for habitation as organisms tend to run away from such areas. Heat can cause stress and death of
organisms.

4. Water: Availability of water in a habitat determines the rate of survival of population. Lack of water can
cause decrease in population.

5. Nutrients: Plants require nutrients in the soil to synthesize their various food substances. Lack of nutrients
can result to stunted growth and poor yield of crops.

Biotic factors affecting a population

1. Mortality: Mortality is the rate at which organisms die in a habitat, while low death rate increases population,
high death rate reduces it. Low death rate also causes food shortage and overcrowding.

2. Parasites: Parasites are organisms which feed on another organism called the host. In the process, the host is
harmed, even killed thereby reducing the population of such organisms.

3. Predators: These are organisms which prey on weaker ones. High level of predation in a habitat can reduce
the population of prey.

4. Food: Lack of food in a habitat can adversely affect the population of organisms. Food is the basic material
required for the survival of the organisms as it is needed for growth, development and reproduction.

5. Natality: Natality refers to the rate at which organisms give birth to young ones. High birth rate increases
population and can result in overcrowding.

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6. Pathogens: Pathogens are disease causing organisms such as viruses and bacteria which affect the well being
of other organisms. High level of pathogenic attack reduces the population of the host organisms.

7. Competition: Competition will arise among organisms when there is lack of space, food and other resources
within the environment. High level of competition leads to fighting and cannibalism among organisms.

8. Dispersal: This is a natural means of avoiding overcrowding especially in plants. The dispersal of seeds and
fruits either by water, wind, animals, insects reduces the chances of overcrowding and so overpopulation is
avoided.

Density dependent and density independent factors

Some of the factors mentioned above that affect population are density dependent while others are density
independent.

The Density of a population is number of individuals in a given unit of an area of a particular time. Some factors affect
the growth of a population irrespective of its population density. Example of these factors includes temperature, forest
fire, floods, drought and storms. These factors do not depend on the size of the population in the area and are referred
to as density independent factors. For example a sudden flood which may kill a large number of individuals in a
population regardless of whether the population density is small or large.

The density dependent factors includes all those factors that increases or decreases in intensity alongside the
population density of a particular habitat. In other words they are influenced by population size e.g. food supply.

Both of these factors (density dependent and density independent) combines to control the size of a population.
Example
3(a) (i) Define the term population
(ii) List two biotic and abiotic factors each that affect population growth. (1988/3ai, ii)
Answer:
i. Population is defined as the total number of organisms of the same species living together in a given area at a
particular time
ii. Abiotic factors affecting a population : Light and space
Biotic factors affecting a population : Competition and natality
Example
The activities of an organism which affect the survival of another organism in a habitat can be described as
A. biotic factors B. climatic factors C. physiographic factors D. edaphic factors E. abiotic factors (1989/30)
Answer: A – Biotic factor
Example
Predation is an example of a factor in an ecological system referred to as
A. edaphic B. topographic C. abiotic D. biome E. biotic (1992/39)
Answer: E– Predation is an example of a biotic factor
Example
Density, mortality rate, birth rate are the factors that affect
A. population B. dominance C. cover D. habitat E. abiotic community (1995/59)
Answer: A – Density, mortality rate, birth rate are the factor that affect a population
Example
Which of the following is an abiotic factor which affects a population
A. Predator B. Parasite C. Consumer D. Producer E. Temperature (1996/44)
Answer: E – Temperature is a abiotic factor that affects a population.
Example
(b) State four problems that may be caused by human overpopulation. (1999/5b)
Answer:
1.High rate of crime 2. Competition 3. Rapid spread of disease 4. Depletion of natural resources
Example
The numbers in a population would rise, if there was an increase in the
A. spread of disease B. number of deaths C. number of predators D. amount of food available (2002/43)
Answer: D – The number of a population would rise, if there was an increase in the amount of food available.
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Example
A population which exceeds its carrying capacity and then collapses is represented graphically as a
A. bell shaped curve B. skewed curve C. s-shaped curve D. linear curve (2007/45)
Answer: D – A population which exceed it carrying capacity and then collapses will be represented graphically as a
linear curve.
Example
Population growth rate may be defined as the
A. mortality rate per unit area over a period B. number of times an organism occurs within a given period
C. number of a particular species per unit area D. net rate of natality and mortality in the habitat over a period (2009/44)
Answer: D – Net rate of natality and mortality in the habitat over a period
Example
(c) Discuss how the following factors affect the population
i. Food ii. Light iii. Temperature iv. War (2007/3c Neco)
Answer:
i. Food: Increase in food supply leads to the increase in population and when there is shortage of food supply
population size decreases.
ii. Light: When there is sufficient amount of light, green plants can manufacture enough food which will lead to
an increase in population. The reverse is true if the amount of light decrease.
iii. Temperature: Moderate temperature leads to the increase in population. Extreme high or low temperature
leads to decrease in population.
iv. War: War leads to the killing of people, destruction of resources and properties. This will invariably lead to
decrease in population.
Example
The density-dependent factors that operate to regulate a population size may include the following except
A. shortage of food supply B. fire outbreak C. spread of diseases D. increased competition (2005/43)
Answer: B– Fire outbreak is not an example of a density dependent factor. All other options are examples of density
dependent factors
Example
Which of the following organisms may bring about reduction inhuman population?
A. Trees B. Butterflies C. Houseflies D. Shrubs (2011/37 Nov)
Answer: C – House flies may bring about the reduction in human population because they serve as vectors which
transmit vibro cholerae; the causative agent of cholera. This disease can lead to the death of human being and
therefore cause reduction in population.

EXERCISE 23.23
1. A population which exceed its carrying capacity and then collapses is represented graphically by a
A. bell-shaped curve B. linear curve C. sigmoid curve D. skewed curve (2017/31)
2. Population growth rate may be defined as the
A. mortality rate per unit area over a period B. number of times an organisms occurs within a given period
C. number of a particular species per unit area
D. net rate of natality and mortality in the habitat over a period (2017/33 NABTEB)
3. Which of the following is a biotic factor that affects population?
A. predator B. salinity C. space D. temperature E. water (2008/37 Neco)
4. Population may be affected by the following factors except
A. disease outbreaks B. food C. immigration D. census figures E. pathogens (1995/39 Nov)
5. A major effect of food shortage on the population is
A. increased mortality rates B. co-operation among siblings
C. high productivity D. effective mobilization towards growth (2004/42 Nov)
6. Natality is a factor affecting population density because it involves
A. Increase in population due to immigration B. increases in population due to emigration
C. the number of mature females in the population D. the number of females in the population
E. the number of all the young ones produced (1996/49 Nov)
7. Which of the following organisms may bring about reduction inhuman population?
A. Trees B. Butterflies C. Houseflies D. Shrubs (2011/37 Nov)

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8. Population is defined as
A. the number of individual organisms per unit area
B. a progressive series of changes over a period of time in a human community
C. the total number of organisms of the same species living together in a given period of time
D. the total number of different species of communities living in an environment in a given per of time (2011/38 Nov)
9. Which of these is the correct definition of a population? Population is a
A. group of lower animals living together in a habitat B. group of plants and animals a community
C. group of higher plantain a p interacting with each other
D. group of organisms of the d species in a community interacting with each
E. term used only for a group people living together in a community (1994/41 Nov)

10. A population with a relatively large population of reproductive adults will be

A. increasing B. less crowded C. decreasing rapidly B. unchanged (2020/28 PC 1)

11. A population is defined as a collection of similar organisms that

A. behave in the same way B. interbreed freely
C. are found in the same habitat D. eat the same food (1992/33 JAMB)
12. The carrying capacity of a habitat is reached when the population growth begins to
A. increase slowly B. increase exponentially C. slow down D. remain steady (2012/34 JAMB)
13. The abiotic factors that control human population include
A. disease and famine B. space and rainfall
C. flooding and earthquake D. temperature and diseases (2012/35 JAMB)
14. Which of the following factors can bring about competition in population?
A. emigration B. drought C. mortality D. dispersion (2015/31 JAMB)
15. (c) State the importance of each of the following in a population and explain how each affects the growth of a
population. (i) competition; (ii) pathogens; (iii) water (1991/3c)

BALANCE IN NATURE
The net effect of these abiotic and biotic factors is that at a point, the population size of living organisms tends
towards a dynamic equilibrium known as balance in nature. When both abiotic and biotic factors are favourable
growth is promoted but when they are scarce, growth is retarded. A factor which limits a population growth is called a
limiting factor and the sum of limiting factors is known as environmental resistance.
When population increases, the available food tends to decrease. This leads to death of the weaker organisms, thereby
keeping the population relatively constant. Human beings are able to control their population by family planning and
birth control where as in nature; biological equilibrium is attained by predator prey relationship.

FAMILY PLANNING AND BIRTH CONTROL:

Family planning: This is the method adopted by a couple to control the number of children they can adequately cater
for and the right time to have them.

IMPORTANCE OF FAMILY PLANNING:

1. It prevents unwanted pregnancies that could lead to illegal abortion.
2. It eliminates child dumping which is the main cause of motherless babies.
3. It prevent population explosion in the country
4. Adequate nutritional care of the children is ensured
5. It reduces maternal death rate usually caused by frequency of pregnancy
6. The children has access to good health care and quality education

Birth control is the method used to prevent a woman from becoming pregnant, for as long as she wishes. The method
could be grouped into two, the natural and the modern method.

NATURAL METHOD:
1. Breast feeding: During breast feeding, there is delay in fertility of woman as some women does not
menstruate. This method is not effective in all women and so not reliable.

2. Withdrawal method: This involves the withdrawing of penis from the vagina when the man is about to
ejaculate so that the sperm are released outside. This is also unreliable because some sperm may escape into
the vagina before withdrawal.

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3. Rhythm/safe period: This involves the calculation of safe periods for each woman. A woman should not
have sex with a man during the fertile days.16  2 day of her menstruation. This is not all that reliable as
sometimes miscalculation of ovulation period may occur.

4. Cervical mucus billing ovulation: When ovulation is about to occur, there is the slippery mucus that looks
like an eggs albumen. This mucus stretches out without breaking when placed between two fingers. This helps
to note the ovulation period and sex must be avoided if pregnancy is unwanted.

MODERN METHOD
5. Contraceptive pill (family planning pills): This is a tablet that a woman takes to prevent ovulation. The pill
is effective and must be used according to prescription to obtain good result.
6. Injection: This involves injecting a hormone called progesterone into the woman’s body to prevent ovulation
for about two to three month interval.
7. Condom (sheath): This is a rubber sheath which the man wears over the penis before sexual intercourse.
When he ejaculates sperm they are collected within the condom thereby preventing them from entering into
the vagina. There is also a female condom.
8. Intra uterine device (IUD): This may be a metal or plastic coil that is inserted into the uterus of the woman
to prevent fertilization. When properly inserted, it is reliable and more economical.
9. Spermicidal cream/ foaming tablet: A spermicidal cream is a substance that kills sperm cells. A woman
applies such cream inside the vagina 5 – 10 minutes before sexual intercourse. The spermatozoa discharged
after ejaculation are killed by the spermaticide.
10. Sterilization: This involves the cutting of the sperm ducts in case of a man and oviduct (fallopian tube) in
case of a woman. Once it is done, it is not reversible. This is done by a qualified doctor. In male it is called
vasectomy. In female it is called tubal ligation.
Example
7(a) (i) List five birth control methods.
(ii) State five reasons why family planning is important to a nation. (2007/7ai, ii)
Answer:
7ai. Birth control methods: 7a ii. Reasons why family planning is important to a nation:
- Use of contraceptive pills. - Prevents indiscriminate abortion.
- Withdrawal method. - Reduces maternal/infant mortality.
- Safe period/calendar method. - It prevents population explosion in the country.
- Use of condom (sheath). - It make child spacing possible.
- Intrauterine device (IUD). - Eliminates child dumping which is the main cause of
motherless babies.
Example
(d) State two methods of birth control in humans. (2018/1d)
Answer: Use of contraceptive pills and Intrauterine device (IUD)

Example
Which of the following is not a natural method of birth control?
A. abstaining for sex B. prolonged breast feeding C. rhythm method
D. use of condom E. withdrawal method (2008/27 Neco)
Answer: D – Use of condom is not a natural birth control in human.
Example
Which of the following is not recommended method of birth control?
A. Using spermicidal sperms B. contraceptive pills C. use of condom
D. abortion E. intra uterine device (1996/48 Nov)
Answer: D – Abortion is not a recommended method of birth control.
Example
(b) Name two abiotic factors each which affect plants and animals terrestrial habitat. (2001/5b)
Answer: Plants: Light, Rainfall Animal: Temperature, Rainfall
EXERCISE 23.24
1. Which of the following statements is not true of population?
A. members of a population may be of the same species
B. members of a population may be of the same species but does not interbreed
C. size of population may be limited by space D. some species can form another population elsewhere
E. members of a population must co-exist (1996/43)

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2. A population is best described as
A. a group of the same species of organisms living together B. a group of animals and plants living together
C. a group of insects and grasses D. different species of wild animals (2005/35)

3. Overcrowding in seedling of different species is less serious than overcrowding involving one species because
different species may
A. have different nutritional needs B. lack the same nutrient
C. be active at the same time D. have similar tolerance E. need equal spacing (1989/52)

4. Which of the following is not an effect of overcrowding in plant and animal community?
A. population outstripping available space B. population exceeding available food
C. competition with the population D. increase in primary production
E. population increasing at the same rate as the birth rate (1993/41)

5. All of the following factors contribute to overcrowding of organisms in a habitat except?

A natality B. immigration C. emigration D. survival (2005/46 Nov)

6. The effect of overcrowding on population are

A. cannibalism and competition only B. competition and death only
C. cannibalism, competition and death only D. cannibalism, competition, death and aggression (Nov. 2000/50)

7. Which of the following is not a recommended method of birth control?

A. using spermicidal creams B. contraceptive pills C. use of condom
D. abortion E. intra – uterine device (1996/48 Nov)

8. Explain the following terms: ii. Population iii. Competition iv.Succession. (2008/3a).

9. Explain the following terms:

Discuss how the following factors affect population
i. Food ii. Light iii. Temperature iv. War. (2007/3c Neco)

FUNCTIONING ECOSYSTEM
Autotrophy and heterotrophy: In a community, different organisms are found which constitute the biotic
components of an ecosystem. This community of organism usually includes:
1. Green plants (producers)
2. Animals (producers)
3. Fungi and bacteria (decomposers)

The producers in the community are called autotrophs. They can manufacture their own food using the solar energy
in the process called photosynthesis or through chemical energy in the process called chemosynthesis. It is also
important to note that only a fraction (about 1%) of sunlight energy that actually strikes the earth surface is absorbed
by green plants and used for photosynthesis the rest are converted into heat energy.
Consumers are heterotrophic animals that feed on other organisms (plants and animals). Their food consists of
complex organic molecules that require digestion before absorption. They include all
1. Holozoic organism such as herbivores, carnivores, omnivores, scavengers.
2. Parasites e.g water fleas, tadpoles, fishes, insects.
Consumers can be classified as either being primary, secondary or tertiary:
1. Primary consumers which are herbivores which feed directly on plants e.g. sheep, cattle, grasshopper,
butterflies, birds that eats seeds only and suck nectars
2. Secondary consumers which are animals that feed on herbivores e.g. toad, cats.
3. Tertiary consumers which are animals that feed on secondary consumers e.g. lion, leopard, hawk e.t.c.
Decomposers are organisms that feed on dead organic matter which they digest using extracellular means and
as a result brings about the decay of the organic matter. Examples are bacteria and fungi.

N.B: In terrestrial habitats, the main food producers are green plants such as maize, rice, yam, pawpaw e.t.c. In aquatic
habitat, the main food producers are protists like diatoms and algae like spirogyra, which are referred to a
phytoplankton. Some examples of consumers in a terrestrial habitat or ecosystem are caterpillars, cows, dogs, lions,
toad, hawk and vipers. The consumers in an aquatic habitat include copepods, water fleas, tadpoles, larvae of insects
and fishes.

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Example
The examples of autotrophic organisms include the following except
A. Euglena B. Chlamydomonas C. Hydra D. Spirogyra (2006/35)
Answer: C – Hydra is a hetrotrophic organism.
Example
Organisms that feed essentially on plants within any ecosystem may be referred to as
A. carnivores B. herbivores C. saprophytes D. omnivores (2006/43)
Answer: B – Herbivores feed essentially on plant.
Example
Which of the following organisms is a primary consumer?
A. Dog B. Sheep C. Grass D. Fungus (2009/36)
Answer: B – Primary consumers are herbivores and feed directly on plants. Sheep therefore is a primary consumer as
it is herbivorous and it feeds directly on plants. Other examples of primary consumers include cattles, goats and Grass
hoppers.

Example
The producers in a food chain in an aquatic environment are
A. birds B. phytoplankton C. zooplankton D. fishes (2013/37)
Answer: B – Phytoplankton is a producer in an aquatic environment. He possess chlorophyll and carryout
photosynthesis.
Example
Which of the following would be the primary producer in a food chain?
A. Saprophytes B. Herbivores C. Carnivores D. Green plants E. Parasites (1991/38 Nov)
Answer:
D – Green plants are primary produces in a food chain.
EXERCISE 23.25
1. (b) Explain the role of the following in a food chain:
(i) green plants; (ii) herbivores; (iii) carnivores; (iv) decomposers. (1995/4b Nov)
2. In an ecosystem green plants are referred to as
A. primary consumers B. decomposers C. primary producers D. secondary consumers (2001/44 NABTEB)

3. Which of the following is a primary consumer?

A. dog B. cow C. man D. grass (2017/30 NABTEB)
4. Which of the following organisms is a primary consumer?
A. dog B. sheep C. grass D. fungus (2018/26)
Trophic level:
Trophic level refers to each step along a feeding pathway. In any food chain or web, the total number of individuals
fed upon at each level is usually greater in number than the number of the individual that feed on them e.g. the number
of grasses is more than the number of grasshoppers and this in turn is more than the number of lizard. This is
relationship is normally represented in a diagram.
Food chain: A food chain is a linear feeding and energy relationship among organisms in the same community in
which each organism feeds on the one before it in a sequence.
It is important to note that as the organisms are feeding on each other, there is a transfer of energy from one organism
to the other. This transfer of energy from one organism to another in a series of tropic levels of eating and getting
eaten is called food chain.

A food chain is normally written with arrow inserted between the organisms. For example;
Guinea grass → grasshopper → lizard → snake
In a food chain, each successive level or step is called a tropic level.

The food chain that has been analyzed above can be collectively grouped as the predator (grazing) food chain as it is
made up of the predator species and their corresponding prey specie
There is however another classification of food chain known as detritus (decomposer) food chain. In this food chain,
the starting material is dead and unused organic material e.g.
Humus →earthworm →domestic fowl →man →decomposer

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FOOD CHAIN FROM AQUATIC COMMUNITY e.g FOOD
a. Plankton → tadpole → tilapia → water snake
b. Algae → zooplankton → fish → king fisher
c. Diatom → tadpole → crayfish, → fish

FOOD CHAIN FROM FOREST COMMUNITY

a. Fruits → bat → snake → hawk
b. Nectar → butterfly → small bird → hawk
c. Leaves → caterpillar → praying mantis → bird

FOOD CHAIN FROM SAVANNA COMMUNITY

a. Grass → grasshopper → toad → snake
b. Grass → grasshopper → lizard → hawk
c. Millet → locust → bird → snake

Example
Which of the following statements is not correct about the ecological effects of agricultural activities?
A. The use of herbicides and pesticides in farms can cause pollution
B. Food chains involve feeding relationships among organisms
C. Shorter food chains indicate more effective utilization of energy than longer ones
D. There is no energy loss in a food chain E. All food chains have primary consumers (1989/26)
Answer: D – As we move from one trophic level to the next in a food chain, energy is usually lost. So saying “there is
no energy loss in a food chain” is a wrong statement
Example
In a food chain, each stage in the chain is a
A. chain level B. web level C. consumption level D. trophic level E. product level. (1998/43)
Answer: D – In a food chain, each stage is a trophic level.
Example
The amount of energy passed from one trophic level to the next decreases because
A. many organisms are present at the first trophic level B. many organisms occur at the higher trophic level
C. more energy is conserved at lower trophic levels
D. parts of the organisms remain unutilized at each trophic level. (2007/40)
Answer: D – The amount of energy passed from one trophic level to the next decreases because parts of the
organisms remain unutilized at each trophic level.

Example
Food chains are relatively short because
A. of energy recycling in the ecosystem B. energy gain at each trophic level is high
C. of energy loss at each trophic level D. energy flow in an ecosystem is uni-directional (2009/39)
Answer: C – Food chain are relatively short because of energy loss at each trophic level.
Example
Which of the following statements about feeding relationships is correct?
A. In a food web on land, grasshopper feeds on praying mantis and on predator bugs
B. In a food chain on land, green plant is the producer
C. In an aquatic food chain, mollusc larvae are the producers
D. In aquatic food web, various copepods feed on mollusc larvae and on sand eel (2006/45)
Answer: B – In a food chain on land, green plant is the producer.
Example
(c) What is trophic level? (2002/5c Nov)
Answer: Trophic level refers to each step along a feeding pathway. It is the group of organism within an ecosystem
which occupies the same level in a food chain.

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Example
(ii) Classify the following organisms into their trophic levels: Bacterium, earthworm, frog, grass, grasshoppers,
groundnut plant, hawk, rhizopus. (2006/4cii Nov)
Answer:
Producers: Grass, groundnut part
Primary consumers: Grasshoppers
Secondary consumers: Frog
Tertiary consumers: Hawk
Decomposers: Bacteria, earthworm, rhizopus
Example
Organisms that occupy the second trophic level are called
A. herbivores B. carnivores C. decomposers D. scavengers (2011/33 Nov)
Answer: A – Herbivores occupy the second trophic level. This is because the feed on plants which occupies the first
trophic level.

Example
Organisms in an ecosystem are usually groped according to their tropic level as
A. carnivores and epiphytes B. consumers and parasites
C. producers and consumers D. producers and saprophytes (1991/42)
Answer: C – Organisms in an ecosystem are usually grouped according to their trophic level as producers and consumers.
Example
At which trophic level would be highest accumulation of a non-biodegradable substance occur?
A. Primary producers B. Tertiary consumers C. Primary consumers D. Secondary consumers (1993/38)
Answer: B – Tertiary consumers would have the highest accumulation of a non-biodegradable substance.
Example
A step in the movement of energy through an ecosystem is a description that best fits the term
A. pyramid of numbers B. food web C. trophic level D. food chain (2002/43)
Answer: C – Trophic level can be described as the step in the movement of energy through an ecosystem.
Example
Which of these is the correct chain for the organism found in an aquatic community?
A. Paramecium, Phytoplankton, Prawn, water flea, Tilapia, shark
B. Water flea, paramecium, phytoplankton, prawn, tilapia, shark
C. Phytoplankton, water flea, paramecium, prawn, shark, tilapia
D. Phytoplankton, paramecium, water flea, prawn, tilapia, shark
E. Paramecium, phytoplankton, water flea, prawn, shark, tilapia (1995/38)
Answer: D – Phytoplankton, paramecium, water flea, prawn, tilapia, shark.
Example
In a food chain the position occupied by an organism is called
A. the trophic level B. energy level C. the feeding level D. the habitat level E. niche (1995/39)
Answer: A – The position occupied by an organism in a food chain is called the trophic level.
Example
Which of these statements about food chain is not correct?
A. Animals in the chain-are consumers B. A food chain usually begins with a green plant
C. All organisms in a food chain are animals D. Living things are dependent on one another
E. The food chain involves energy transfer in an ecosystem (1995/40)
Answer: C – “All organisms in a food chain are animals” is not a correct statement because green plants are also part
of and are usually the primary producers in a food chain.
Example
In any food chain, the first member must be a
A. carnivore B. herbivore C. zooplankton D. autotroph (2002/37)
Answer: D – In any food chain, the first member must be a producer i.e an autotroph

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Example
Study the diagram below showing three food chains. Use it to Answer: question 36.

Which of the following are consumers in these food chains?

A. maize and rabbits B. chicken, rats and maize C. eagle, maize and snakes D. humans, eagle and snakes (2004/36)
Answer: D – Humans, eagle and snakes are consumers in the various food chains.
Example
The continuity of an ecosystem depends on constant flow of energy and circulation of matter. However, the amount of
energy passed on from decomposers to producers should be
A. great B. small C. reversible D. zero (2004/38)
Answer: D – The energy passed from decomposers to producers is zero. This is because producers derive their
energy from the sun and not from drcomposers.

Example
If a pond contains waterweed, tadpoles, Tap-minnows (fish) and is visited after by Herons (bird) what would be the
possible food chain?
A. Water weed→ Tap-minnow → Heron →Tadpole B. Water weed → Tadpole → Tap-minnow → Heron
C. Water weed → Heron → Tap-minnow → Tadpole D. Water weed → Tadpole → Heron → Tap-minnow (2006/44)
Answer: B – Water weed → Tadpole → Tap-minnow(fish) → Heron
Example
3(a) What is meant by the term Food chain? (2009/3a)
Answer: A food chain is a linear network of feeding relationship which usually starts with a producer (green plants)
and end with a decomposer (e.g. bacteria, fungi).

EXERCISE 23.26
1. An organism at the start of a food chain which provides the total input of energy into an ecosystem is the
A. sun B. producer C. consumer D. decomposer (2015/31)
2. (d) (i) State the role of each organism in food chain given below:
Algae→ Periwinkles → crabs → seagull
(ii) What do arrows in the food chain represent?
(iii) What is the ultimate source of energy in a food chain? (2002/5d Nov)
3. Which of the following is the correct sequence in the food relationship in a pond?
A. Duckling  Turtles Duckweeds Man B. DuckweedsDuckingMan Turtle
C. Duckweeds Duckling TurtlesMan D. TurtlesDuckweedsDucklingMan
E. DuckweedsManDuckling Turtle (1997/43 Nov)
4. (c) (i) What is a food chain? (2006/4c Nov)
5. Which of the following is the correct sequence of a food chain?
A. Grass→Grasshopper→Toad→snake →Hawk B. Grasshopper→Toad→Hawk→Grass→snake
C. Snake→Grass→Hawk→Grasshopper→Toad D. Hawk→Grass→Snake→Grasshopper→Toad
E. Grass→Grasshopper→Toad→Hawk→Snake (2007/80 Neco)
6. c. Explain the role of the following in a food chain:
(i) Carnivores (ii) decomposers (iii) herbivores (iv) Producers (2007/1c Neco)
7. Which of the following is a correct food chain in a school garden?
A. Grass →grasshopper → kingfisher → man B. grass → kingfisher → mice→ hawk
C. maize → mice → snake → hawk D. maize → kingfisher → hawk (2001/46 NABTEB)
8. Which of the following statements is not correct about food chain?
A. Food chains involve feeding relationships among organisms B. All food chains start with a green plant
C. shorter food chains indicate more effect utilization of energy than longer ones
D. There is no energy loss in a food chain (2018/27 NABTEB)

538
9. Which sequence represents the correct order of organisms in a food chain? 1. Toad 2. Mucuna 3. Grass
hopper 4. Snake 5. Hawk
A. 5→4→1→3→2 B. 1→2→3→4→4 C. 2→1→3→4→5
D. 2→3→1→5→4 E. 2→3→1→4→5 (1983/42 JAMB)
10. In a typical predator food chain involving secondary and tertiary consumers, the organisms become
progressively
A. smaller and more numerous along the four chain B. equal in number and size along the food chain
C. larger and fewer along the food chain D. parasitized along the food chain as consumers get bigger (1992/34 JAMB)
11. The correct order in a food chain involving the organisms
(1) Grasses (2) Hawks (3) snakes (4) grasshopper (5) lizard is
A. 1, 2, 3, 4, 5 B. 5, 4, 3, 2, 1 C. 1, 4, 5, 3, 2 D. 3, 2, 4, 5, 1 (1994/33 JAMB)
12. In a food chain involving a primary producer, a primary consumer as well as secondary consumer, the sharing
of trophic energy is in the form that the
A. primary consumer has more energy than the primary producer
B. secondary consumer takes all the energy contents of the primary consumer
C. energy is shared equally between three groups of organisms
D. secondary consumers get only a small portion of the energy contained in the primary producer. (1995/32 JAMB)

13. In a food chain, each succeeding level in a forward direction represents

A. an increase in the number of individuals B. an increase in the biomass of individuals
C. a decrease in the number of individuals D. a gain in the total energy being transferred (2000/31 JAMB)
Study the diagram of a food chain shown below and use it to Answer: questions 27 and 28
P→Q→R→S→T
14. The organism designated P in the food chain above is normally sustained by energy from
A. sunlight B. carbohydrates C. green plants D. mineral salts (2018/27 JAMB)

FOOD WEB:
A food web is a complex feeding relationship which consists of inter-related food chain. The food web shows all the
possible pathways through which energy (food) can flow. A typical food web can be constructed as shown below:

Food web
Example
A food web can be described a
A. complex feeding relationship in a community B. transfer of food energy from one community to another
C. complex pattern of food production in a community D. group of many populations competing for the same type of food
E. group of organisms belonging to the same trophic level (1992/43)
Answer: A – Food web is a complex feeding relationship in a community which consist of inter-related food chain.
Example
In the marine food web, the source of energy to the producer comes from
A. sea waves B. sea water C. Sun D. air (2005/34)
Answer: C – In the marine food web, the source of energy to the producers comes from the sun.

539
Example
An importance of food web is that living organisms
A. use web to collect food B. can live on their own
C. have to form a web D. depend on one another for their existence (2004/37)
Answer: D – An importance of food web is that living organism depend on one another for their coexistence.

Example
Study the food web below carefully and use it Answer: questions 32 and 33.

Tertiary consumers within the web are

A. cat and lion only B. man and lion only C. man and cat only D. man cat and lion
Answer: D – Tertiary consumers within the web are man, Cat and lion.

Example
What would be the effect of taking the lion out of the web?
A. The number of organism at each trophic of the web
B. Man would occupy the apex of the web
C. There would be more rabbits in the web
D. the energy reaching the remaining trophic levels would increase (2008/32-33)
Answer: B – Man would occupy the apex of the web if the lion is taken out of the web.

EXERCISE 23.27
1. Food webs are complex because
A. the number of producers are large B. many animals feed directly on producers
C. they include primary, secondary and tertiary consumers
D. some animals form part of several food chain. (2016/32)
2. Which of the organisms will have the lowest in an ecosystem
A. Hawk B. Cowpea C. Praying mantis D. Mouse (1990/43 JAMB)

3. Which organism in the food web illustrated below above is an omnivore?

A. weevils B. rat C. hawk D. praying mantis (1997/34 JAMB)
Use the diagram below to Answer: questions 40 and 41

4. Primary consumers are found in

A. 1, 2 and 3 B. 1, 3 and 7 C. 2, 3 and 7 D. 2, 4 and 5 (1999/40 JAMB)
5. The biomas is likely to increase in the sequence
A. 1→2→4→5 B. 1→3→4→5 C. 3→5→6→7 D. 5→4→3→1 (1999/41 JAMB)

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PYRAMID OF NUMBER:
A diagram which represents the reducing number of individuals from one trophic level to the other in a food chain is
called a pyramid of numbers.
Most food chains or food webs begin with producers. However, there are some food chains which begin with dead
organic matter. e.g. humus → earthworm → domestic chicken → man
This type of food chain is called detritus (decomposer). The type of food chain which is made up of predator species
which are usually alive or freshly killed is called grazing food chain. In the predator (grazing) food chain, the energy
source is the sun and green plants uses the solar energy to make food for the ecosystem. The pyramid of number
represents the number of individuals at each tropic level of a food chain at a particular time.
3 Carnivores II
354,904 Carnivores I
t
708,904 Herbivores
5,842,424 Producers
Pyramid of numbers

N.B: In tropical forest ecosystem, a few trees provide sufficient food to support numerous small insects and insect
eating birds. This gives odd-shaped pyramid as shown above.

Example
Which of the following explains the pyramid of numbers?
A. the number of organisms in a trophic level B. the relationship between plants in different tropic level
C. the number of saprophytes and parasites in a habitat D. the number of predators in a habitat
E. progressive decrease in the number of individuals from lower to higher tropic level (1993/35)
Answer: E – Pyramid of number is the progressive decrease in the number of individual from lower to higher trophic
level.
Example
Which of these groups of organisms is responsible for capturing energy for the biotic community?
A decomposers B omnivore C consumer D producers E detritus feeders (1996/35)
Answer: D – The producers (green plant) captures energy for the biotic community.
Example
Which of the following organisms are the producers in an aquatic habitat?
A. benthons B. phytoplanktons C. zooplanktons D. nektons (2007/38)
Answer: B – Phytoplankton are producers in aquatic habitat.
Example
Which of the following statements is not correct about food chain?
A. a food chain start with a green plant B. food chain involves feeding relationship among organisms
C. shorter food chain indicates more effective utilization of energy than longer ones
D. there is no energy loss in a food chain E. all food chains have primary consumer (1989/26)
Answer: D – “This is no energy loss in a food chain” is not a correct statement. This is because, as energy passes from
one trophic level to the next, some of it is lost to the surrounding as heat.
Example
A pyramid of numbers is constructed by
A. comparing living and non-living organisms B. measuring productivity
C. conducting census D. labeling the living organisms (2013/40)
Answer: C – A pyramid of number is constructed by conducting a census.
Example
The following statements are true about pyramid numbers except that
A. energy is lost from the food chain at each transfer B. energy content of each successive trophic level decreases
C. it always has a pyramidal shape D. organisms at successive trophic levels increase rapidly in number (2013/40 Nov)
Answer: D – “Organisms at successive trophic levels increase rapidly in number” is not true about pyramid of
number”.

541
EXERCISE 23.28

Pyramid of numbers
1. Which of the following shows the number of producers in the diagram?
A. I B. II C. III D. IV E. V (1996/42 Nov)
2. If there is a long drought in the habitat, which of the following animal groups will be the last to die off?
A. I B. II C. III D. IV E. V (1996/43 Nov)

3. Which of the following represents the correct order in a possible food chain?
A. crustacean → diatom → fish → man B. fish → crustacean → man → diatom
C. man → fish → crustacean → diatom D. diatom → crustaceans →fish → man
E. man → diatom → fish → crustaceans (1994/21)
4. A food web can be described as a
A. complex feeding relationship in a community B. transfer of food energy from one community to another
C. complex pattern of food production competing for the same type of food
D. group of organisms belonging to the same tropic level (1992/43)
5. The organisms with the least number of individuals in a pyramid of numbers are the
A. secondary consumers B. tertiary consumers C. primary consumers D. primary producers (1994/34 JAMB)

PYRAMID OF BIOMASS:
This represents the total wet or dry mass of the organisms in each trophic level. To obtain biomass pyramid, we count
and weigh the organisms in a given area of habitat. Then the total wet biomass of the organisms in each tropic level is
obtained from these data. The dry biomass may be estimated from the wet biomass.

Biomass takes into account both the size of the individual organisms and their numbers.
Some pyramids of biomass also have odd-shape

Pyramid of Biomass for a lake food

Example
Which of the following values showing the total biomass of organisms in a food chain represents the secondary
consumer?
A. 40,000 B. 3000 C. 20 D. 1 (2003/38)
Answer: C – 20.
NB: As we move from producers to tertiary consumers in a food chain, number of organisms decreases.
Example
The group of organisms at the base of the pyramid of numbers are
A. decomposers B. primary consumers C. producers D. secondary consumers E. tertiary consumers (2008/42 Neco)
Answer: C – The producers are the group of organisms which located at the base of the pyramid of numbers.
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Example
Which of the following components of an ecosystem does not contribute to the biomass of the system?
A. producers B. consumers C. micro organisms D. habitat (2006/39)
Answer: D – The habitat does not contribute to the biomass of the system.

EXERCISE 23.29
Use the diagram below to Answer: questions 40 and 41

1. The biomas is likely to increase in the sequence

A. 1→2→4→5 B. 1→3→4→5 C. 3→5→6→7 D. 5→4→3→1 (1999/41 JAMB)
2. In which of the following species is the biomass of an individual the smallest?
A. Agama sp B. Bufo sp C. Spirogyra sp D. Tilapia sp (2011/3 JAMB)

PYRAMID OF ENERGY
Pyramid of energy is defined as the amount of energy present in the living organisms at the different trophic levels of
a food chain.
Just like we have in the pyramid of number, there is a decrease in energy from one trophic level to another along the
food chain. The primary consumers are seen to have lesser energy in comparison to the producers while the secondary
and tertiary consumers have the lesser and least energy respectively. The producers (green plants e.g. grasses) form
the base of the pyramid while the tertiary consumers e.g hawks form the apex. Energy therefore decreases form the
base of the pyramid to the apex. The rate of flow of energy is measured in KJ/m2/yr.

Pyramid of Energy
Example
Which of the following organism is the highest biomass?
A. small fish B. tadpole C. hawk D. phytoplankton E. big fish (1997/42)
Answer: D – Phytoplankton.
NB: Biomass decreases as we move from produces to final consumers.

543
Example
Use the diagram to Answer: questions 44 and 45.

What phenomenon in ecosystem does the diagram illustrate?

A. Pyramid of numbers B. Food web among organisms C. Pyramid of energy
D. Pyramid of biomass E. evolutionary trend in organisms (1989/44)
Answer: C – The diagram above illustrates pyramid of energy. This is so because, the value of energy at each trophic
level is written at the side of the pyramid.
Example
Changes in Energy flow between organisms in habitat can be represented by a
A. pyramid of biomass B. pyramid of numbers C. pyramid of energy D. food chain E. food web (1990/45)
Answer: C – Changes in energy flow between organisms in a habitat can be represented by a pyramid of energy.

Example
Use the diagram below to Answer: questions 44-46

The diagram above illustrates

A. the size of various organisms B. types of organisms in a habitat C. the flow of energy in a habitat
D. the hierarchy of organisms in a habitat E. the food chain (1998/44)
Answer: C – The flow of energy in a habitat.
Example
Which of these organisms occupies the 3rd trophic level?
A. King fisher B. Small fish C. Phytoplankton D. Big fish E. Tadpole (1998/45)
Answer: B – Small fish occupies the 3 trophic level.
rd

N.B– The numbering of the trophic levels start from the base.

EXERCISE 23.30
1. Which of these organisms is a herbivore?
A. Tadpole B. Phytoplankton C. King fisher D. Small fish E. Big fish (1998/46)

2. Which of the following pyramids gives the most accurate picture of the relationships between the organisms
at the various trophic levels in a food chain? A pyramid of
A. numbers B. energy C. biomass D size (2019/36)
3. Which of the following helps to measure the amount of energy passed from one trophic level to another in an
Ecosystem?
A. food chain B. pyramid of biomass C. pyramid of energy D. food web (2005/43 Nov)
4. Which of these statements best defines pyramid of energy?
A. Energy flow from one trophic level to another B. energy flow from one habitat to another
C. the amount of energy in a given area D. the loss of energy from one organism to another
E. the rate of energy flow in an area (2005/10 Neco)
5. What does a pyramid of energy reveal?
A. Energy flow from one habitat to another B. Energy from one trophic level to another
C. Total amount of energy in an ecosystem D. Rate of conversion of light energy to chemical energy (2018/49 NABTEB)

544
6. A pyramid of numbers is constructed by
A. comparing living and non living things B. measuring productivity
C. conducting census D. labeling the living organisms (2013/40)
7. Which of the following pyramids gives the most accurate picture of the relationships between the organisms at
the various trophic level in a food chain? Pyramids of
A. numbers B. energy C. biomass D. size (2017/36)
8. Which of the following statements is not associated with pyramid of energy?
A. efficiency of energy transfer between tropic levels can be studied
B. comparisons of pyramids for different ecosystem can be made
C. more accurate comparisons of tropic levels
D. representation of numbers of organisms at different trophic levels (2017/37)
9. In an ecosystem, the least efficient energy transfer link is from the
A. secondary consumers to decomposers B. sun to producers
C. primary consumers to secondary consumers D. producers to primary consumers (2018/32)
10. An organisms at the start of a food chain which provides the total input of energy into an ecosystem is
A. the sun B. producers C. consumers D. decomposers (2015/31)
11. The producers in a food chain in an aquatic environment are
A. birds B. plytoplanktons C. zooplankton D. fishes (2013/37)
12. Food chain are relatively short because
A. of energy recycling in the ecosystem B. energy gain at each tropic level is high
C. of energy loss at each tropic D. energy flow in an ecosystem is unidirectional (2009/39)
Study the diagram below and use it to Answer: question 11 and 12

13. The best title for the for the above diagram is
A. terrestrial food web B. terrestrial food chain C. aquatic food web D. aquatic food chain (2012/41)
14. How many food chains are in the diagram?
A. three B. four C. five D. six (2012/42)
15. Which of the following statements about the transfer of energy in an ecosystem is correct?
A. energy increases at higher tropic levels B. more organisms can be supported at higher levels
C. there are fewer organisms at lower tropic level E. energy is lost at each tropic level (2008/34)

16. In the food chain shown in Fig 5, above, the secondary consumer is
A. 6 B. 2 C. 3 D. 5 E. 4 (1978/48 JAMB)
17. Explain briefly energy flow in a fresh water habitat. (2016/3b)

545
ENERGY TRANSFORMATION IN NATURE
All living things require energy to do the work necessary for survival and reproduction. Energy is defined as the
ability to do work and work is done when a force moves an object. Let’s consider your own needs for a moment. You
need energy to get out of the bed in the morning, you need energy to walk down to school and you need energy to
listen to your teacher during classes. So the question is from where does energy come, how does it get to us and how
do we use it?

On earth, energy ultimately comes from the sun. Plants use the sun’s energy to make sugar, organisms, in turn, use
sugar as a source of energy to do work; it is also of essence to understand that energy can exist in various forms which
are interconvertible. The conversion of one form of energy to another is known as energy transformation and it is
governed by the law of thermodynamics.

Energy flow in ecosystem: The sun generates a lot of energy which reaches the earth 148.8 million km away. The
part of the energy (solar radiation) that reaches the earth comes in form of electromagnetic waves and only about
1% of the solar energy that reaches the earth surface is available for use by plant (primary producer in the ecosystem)
During photosynthesis, energy (solar radiation) received by green plants from the sun are converted into potential
energy in the bond of carbohydrates. This shows energy is flowing from the sun to the plants through photosynthesis.
The primary consumers such as cattle, goat (herbivores) feed on the plant to transform the energy in the plant into
their own energy in their bodies. They use some of the energy for their physiological activities such as movement,
synthesis and growth. Part of the energy in the plant materials eaten by herbivores is lost in the form of heat. The
secondary consumers obtain energy by feeding on primary consumers. Some of the energy in the food is stored in
their own molecules as bond energy and some part is used for life activities while some is lost as heat.

As a result of feeding processes, energy is transferred as it passes from one trophic level to another. Some energy is
lost at each trophic level. Thus, energy flow is unidirectional or monocyclic.

As energy is transferred from one trophic level to another, some of it is lost as heat. As a result, the total quantity of
energy decreases from the first trophic level to the last. The reason why there are decreases in the energy includes the
following:
1. Not all the grass is eaten by grasshopper
2. Not all the grass eaten by grasshopper is digested
3. Not all the grass digested by grasshoppers are absorbed
4. Not all the grass absorbed by grasshoppers is assimilated
5. Not all the energy transformed by the grass hopper is effectively stored or used
6. Some energy is used by grasshopper
7. Some energy is lost as heat
The total energy available at each trophic level in a food chain can be represented in a pyramid of energy.
Example
Which of the following groups of organisms feeds directly on green plants?
A. Producer B. Decomposer C. Primary consumer D. Secondary consumer E. Tertiary consumer (1989/31)
Answer: C – Primary consumer (herbivores) feeds directly on producers (green plants).
Example
Which of the following is the correct sequence for energy transfer and nutrient cycling among living things in an
ecosystem?
A. Consumers → producers → decomposers B. Producers → consumers → decomposers
C. Decomposers → producers → consumer D. Producers → consumers → decomposers
E. Consumers → decomposer → producer (1997/43)
Answer: B - Producers→consumers→decomposers
Example
The total amount of energy entering a food chain is that which is present in the
A. consumer B. ecosystem C. producer D. decomposer (2002/39)
Answer: C – The total amount of energy entering a food chain is that which is present in the producer.
Example
In an ecosystem the organism which changes light energy into stored chemical energy is the
A. consumer B. decomposer C. producer D. carnivore (2005/40)
Answer: C – Producers change light energy into stored chemical energy in a ecosystem.

546
Example
Which of the following statements about the transfer of energy in an ecosystem is correct?
A. Energy increases at higher trophic levels B. More organisms can be supported at higher levels
C. There are fewer organisms at lower trophic levels D. Energy is lost at each trophic level (2008/34)
Answer: D – Energy is lost at each trophic level is correct about the transfer of energy.

EXERCISE 23.31
1. In a food chain, how much energy in one trophic level is actually transferred into the next trophic level?
A. 5% B. 10% C. 80% D. 100% (2013/39 Nov)

2. What does the part labeled I represent

A. soil and minerals B. carbon dioxide and water C. sunlight D. oxygen and water (2002/40 Nov)

3. Through which of these sources will energy reach producers in the ecosystem?
A. VII B. VI C. III D. II E. I (1995/44 Nov)
4. Which of the following is the direct consequence of transferring energy from one tropic level to another?
A. An increase in biomass B. A decrease in the efficiency of energy conversion
C. An increase in the tortal numbers of resulting individuals D. A decrease in the resulting biomass (1998/29 JAMB)
5. The highest percentage of energy in a ecosystem occurs at the level of the
A. secondary consumers B. decomposers C. producers D. primary consumers (2019/36 JAMB)

Study the diagram below and use it to answer thequestion

6. Which of the following phenomena cannot be illustrated by the use of the diagram above?
A. Pyramid of numbers B. Pyramid of biomass C. Pyramid of energy
D. Energy cycle in the ecosystem E. Nutrient cycle in an ecosystem (1995/43 Nov)

ENERGY LOSS IN THE ECOSYSTEM AND BIOSPHERE

The energy released by the sun to the earth is lost in so many ways. Only a small fraction of solar energy reaches the
earth’s surface as sunlight. The fraction is called solar flux. About half of the solar flux is absorbed by the upper
atmosphere or reflected back to space. Some part of the sunlight is also converted into heat energy at the earth’s
surface. It is only a fraction or 1 percent (1%) that is absorbed by green plants and used in photosynthesis. The flow of
energy and loss of energy in an ecosystem follows the laws of thermodynamics.

547
FIRST LAW OF THERMODYNAMICS
This states that energy can neither be created nor destroyed, although it can be changed from one form to another.

SECOND LAW OF THERMODYNAMICS

The second law states that in any conversion of energy from one form to another, there is always a decrease in the
amount of useful energy. i.e. no transformation of energy from one state to another is ever 100 percent efficient.

The implication of this is that when energy is transformed from one kind to another, some of it is not successfully
transformed, while some inevitably lost as heat
The energy which is received primarily from the sun is lost in the biosphere in different ways;
1. In the atmosphere, part of the sun radiant energy is reflected or scattered or absorbed by the ozone layer. This
reduces the amount of energy radiating to the earth. Thus, only a small part of the energy passes through the
atmosphere.
2. At the earth surface, a part of the radiant energy is reflected and a part is absorbed by the earth
3. At the surfaces of green leaves, a part of the sun’s radiant energy is reflected away by the cuticle, only a small
part penetrates the leaf. Also, not all part that penetrates are absorbed by the chloroplast and used for
photosynthesis
4. Some percentage of energy is lost through energy transformation at trophic level. At each trophic level,
organisms use some, while some energy is inevitably lost as heat.

Most of the energy from the sun is also lost in ecosystem in so many ways.
1. Some of the energy is lost to the water bodies in the form of heat which is absorbed by the water
2. Rock surfaces also reflects and absorb some energy thus reducing the energy available in the ecosystem

Application of both Laws to Ecological Phenomena or Event

Ecological events that can be explained by the laws of thermodynamics are food-chain, pyramid of energy and
energy flow.

FOOD CHAIN:
a. Using the first law: Energy is generated through the sun and is transferred from the producer to the final
consumers. The green plant transfers the energy to the primary consumers which again transfer the energy to
the secondary consumers. In all, the sum total of the energy remains constant.

b. Using the second law: While the energy is transferred to the next trophic level, part of it is lost as heat
energy. In that manner, it is clear that there is no transfer that is 100% efficient. This means that energy is lost
to the environment in form of heat.
PYRAMID OF ENERGY
a. Using the first law: It is discovered that energy is transferred from one trophic level to another. The energy of
the producer at the base of the pyramid is higher and it is transformed gradually form one stage of the trophic
level to another. Even as energy is transformed into various forms in the successive trophic levels, the sum
total of energy is constant
b. Using the second law: As energy is transformed form one trophic level to another, part of it is converted into
heat which is lost, causing a progressive drop in energy in successive trophic levels.

ENERGY FLOW
a. Using the first law: As the producers convert the solar energy to useful energy, the energy is progressively
transformed from one trophic level to the next and so on. So the flow of energy on a food chain is in one direction
only.
b. Using the second law: The transfer of energy between trophic levels is not 100%. Successive levels have less of
useful energy and support fewer organisms. Primary producers have the highest amount of energy. When
herbivores feed on plants, the energy level is reduced. When carnivores consumes the herbivores the energy level
is further reduced.
Example
In an ecosystem, the least efficient energy transfer link is from the
A. secondary consumers to decomposers B. sun to producers
C. primary consumers to secondary consumers D. producer to primary consumers (2018/32)
Answer: A – Secondary consumer to decomposer is the least efficient energy transfer in an ecosystem.
Example
An organisms at the start of a food chain which provides the total input of energy into an ecosystem is the
A. sun B. producers C. consumers D. decomposers. (2015/31).
Answer: B – Producers (green plant) are usually at the start of any food chain and provide the total
548
Example
ai. State the second law of thermodynamics
ii. Use the second law of thermodynamics to explain the flow of energy across different trophic levels in a food
chain. (2011/3ai, ii)
Answer:
i. The second law of thermodynamics states that when there is conversion of energy from one form to another,
there is always a decrease in the amount of useful energy.
ii. As energy is being transferred from one trophic level to another, there is always a decrease in the amount of
useful energy i.e. energy is not 100% transferred to the next trophic level which normally contains fewer
organism. The primary producers (green plants) have the highest energy. When the herbivores (primary
consumers) feed on the primary producers, energy is reduced and when the carnivores (secondary consumers)
feed on the herbivores, the energy is further reduced. This reduction in energy goes on and on until the final
consumers are reached. Part of the energy is lost as heat at each trophic level and not all parts of the preceding
organisms are eaten by the predator organisms at the next trophic level. Energy is also lost in the process of
feeding, movement and metabolic activities.
Example
The amount of energy passed from one trophic level to the next decreases because
A. many organisms are present at the first trophic level B. many organisms occur at the higher trophic level
C. more energy is conserved at lower trophic levels
D. parts of the organisms remain unutilized at each trophic level (2007/40)
Answer: D – The amount of energy passed from one trophic level to the next decreases because parts of the organism
remain unutilized at each trophic level.

EXERCISE 23.32
1. In a food chain involving lettuce, rabbit and eagle, energy is lost at each trophic level by
A. transpiration B. translocation C. evaporation D. respiration (2004/36 Nov)
2. Energy is never lost, destroyed nor created, rather only converted from one form into another. This refers to
A. 1st Law of Thermodynamics B. 2nd Law of Thermodynamics C. 3rd Law of Thermodynamics
th
D. 4 Law of Thermodynamics E. 5th Law of Thermodynamics (1996/45 Nov)
3. The first law of thermodynamics states that energy
A. can be equated to power B. can neither be created nor destroyed
C. is the ability to do work D. transformation can never be completely efficient (2017/18 NABTEB)
4. The progressive loss of energy at each level in a food chain leads to
A. an increase in the number of organisms at each successive level
B. an increase in the total weight of living mater at each successive level
C. a decreasing in biomass at each successive level
D. an increase in biomass at each successive level (2004/7 JAMB)

5. Draw a food chain involving four trophic levels which can be found in a terrestrial habitat.
b. Explain (i) the flow of energy through the food chain drawn 1ai above.
ii. How energy in the chain is lost to the environment. (2009/3b, c)
6. Which of the following statements about the transfer of energy in an ecosystem is correct?
A. energy increases at higher trophic levels B. More organisms can be supported at higher level
C. there are fewer organisms to lower trophic level D. energy is lost at each trophic level (2008/34)
7. The total amount of energy entering a food chain is that which is present in the
A. consumer B. ecosystem C. producer D. decomposer (2002/39)
8. (i) State the two laws of thermodynamics
(ii) Use the second law of thermodynamics to explain the energy flow across trophic levels. (1999/6bi, ii)

Nutrient Cycling in Nature

Nutrient cycling is the movement of certain nutrients such as nitrogen, carbon, water and other element from the
environment into various organisms and back to the environment. The path along which the element pass is called a
cycle. A number of cycles exists, some of which includes the nitrogen, carbon, oxygen, an water cycle. These various
cycles, shows the dynamic nature of the ecosystem

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Example
The pathway through which nutrient elements are replenished and circulated in an ecosystem is called a
A. cycle B. food chain C. food web D. kreb cycle E. pyramid of numbers (1992/44)
Answer: A – The pathway through which nutrient element are replenished and circulated in an ecosystem is called a
cycle.
Example
All the following can illustrate the dynamic nature of the ecosystem except
A. nitrogen cycle B. carbon cycle C. water cycle
D. nutrient cycle E. locomotion in organisms (1994/13)
Answer: E – Locomotion in organism can not illustrate the dynamic in nature of the ecosystem.

EXERCISE 23.33
1. Which of the following substances is not recycled in an ecosystem?
A. Carbon B. Energy C. Water D. Nitrogen (2008/45)
2. Recycling of materials in an ecosystem is largely due to the activities of
A. decomposers B. primary consumers C. producers D. secondary consumers (2020/32 PC1)
Use the graph below to Answer: questions 37 and 38

3. The unrestricted pattern is represented by

A. I B. II C. III D. IV (1998/37 JAMB)
4. The line that represents efficient cycling combined with stringent conservation is
A. IV B. III C. II D. I (1998/38 JAMB)

The carbon cycle

The carbon cycle involves the processes which bring about the circulation of carbon compounds in nature. Carbon
exists in different forms. As a solid, it can be found in charcoal, coke, soot and diamond. It occurs as the common gas
carbondioxide which make up 0.03% of air. It occurs in inorganic salt such as the carbonate and bicarbonates of
metals and in organic compounds such as carbohydrates and fats. The important processes which bring about the
recycling of carbondioxide between the biotic and abiotic compounds of ecosystem are photosynthesis, respiration
and decay. All processes are carried out by living organisms.

The carbon cycle

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Major steps involved in the process of the carbon cycle
1. Carbon present in the atmosphere is absorbed by plants for photosynthesis.
2. The plants are then consumed by animals and carbon gets accumulated in their body in the form of
biomolecules.
3. Carbon is released back into the atmosphere upon death and decomposition of these plants and animals.
Respiration in plants and animals also releases carbondioxide into the atmosphere.
4. Some of the carbon that is not released back into the atmosphere eventually become fossil fuels.
5. These fossil fuels are then used for man-made activities, which pumps more carbon back into the atmosphere
and the cycle continues again.

Importance of carbon cycle

1. Through photosynthesis and respiration, it forms the means through which the trapped solar energy passes
from one organisms to enter organisms in the food chain ecosystem.
2. Organic matter which is made from carbon helps to replenish the soil.
3. It provides carbon which is an essential element for all life.
4. It helps to purify the atmosphere and checkmate atmospheric level of carbondioxide.
Example
Which of the following processes is not involved in the carbon cycle?
A. Burning B. Decay C. Transpiration D. Respiration E. Photosynthesis (1990/46)
Answer: C – Transpiration is the exhalation of water vapour through the stomata
Example
In which of the following processes is carbondioxide not given out?
A. Respiration in plants B. Decay of organism C. Burning of organic matter
D. Burning of fuels E. During photosynthesis (1993/36)
Answer: E – During photosynthesis, carbondioxide is taken from the atmosphere and used to synthesize carbohydrate.
Example
Which of these following processes removes carbon from the atmosphere
A. Purification of animals B. Burning of fuels C. Photosynthesis
D. Volcanic eruption E. Respiration in plants (1995/31)
Answer: C – Photosynthesis helps to remove carbon from the atmosphere.
Example
Which of the following processes removes CO2 from the atmosphere?
A. Respiration B. Photosynthesis C. Transpiration D. Excretion E. Combustion (1998/33)
Answer: B – Photosynthesis.
EXERCISE 23.34
1. Which of the following processes removes carbon from the atmosphere?
A. Putrefaction B. Photosynthesis C. Volcanic eruption D. Burning of fuels (2009/25)
2. Which of the following processes removes carbon(iv) oxide from the atmosphere?
A. Burning fuels B. Putrefaction C. Photosynthesis D. Respiration in plants (2015/21)
3. Which of the following conditions would not increase atmospheric carbon concentration?
A. forest fire B. a forest at midday C. A forest at night D. Rottening of fruits by day (2002/43 Nov)
Use the diagram below to answer question 46 and 47

4. At what point does radiant energy enter the cycle? Between

A. I and II B. II and III C. III and IV D. IV and V E. V and I (1992/46 Nov)
5. Which of the following contain(s) stored energy?
A. 1or only B. I and V C. III only D. II and IV E. III and V (1992/47 Nov)
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6. Which of the following is not a process in the carbon cycle?
A. respiration B. burning C. transpiration D. coal formation (1999/48 Nov)

7. By means of a diagram only, outline the carbon cycle to show the relative importance of the cycle to life in
general. (1989/1c)

Oxygen cycle
This is the process whereby atmospheric oxygen is converted to carbondioxide in animal respiration and regenerated
by a green plant in photosynthesis. The oxygen of the atmosphere is in dynamic equilibrium. The air contains about
21% of oxygen. This is maintained by the photosynthetic and respiratory activities of living things (plants and
animals.)

Oxygen cycle
As seen in the diagram above, respiration, decay or decomposition and combustion are the processes that
remove oxygen from the atmosphere while photosynthesis is the process that releases atmospheric oxygen.

Carbon – oxygen balance

Oxygen constitute 21% of atmospheric gases while carbondioxide is about 0.03%. The processes involved in removal
of oxygen from the atmosphere includes respiration, decay and combustion while photosynthesis is the process that
releases oxygen into the atmosphere.

Deforestation and combustion of fuel are two human activities which affect the carbon and oxygen cycle.

A decrease in the atmospheric oxygen level by about 2 to 8% has little or no effect. However, a slight increase in
atmospheric carbon – dioxide may result to a green house effect (i.e. lead to an increase in the retention of sun’s
radiant or heat energy). This could lead to warming of earth’s atmosphere with disastrous effects such as melting of
the polar ice – caps with a related rise in sea level. Climatic changes could also result, affecting the important food
growing areas of the world. Human activities also affect the oxygen and carbondioxide content of aquatic bodies.
Pollution of such bodies has increased the activities of decomposers. This has resulted in a significant drop of oxygen
level, threatening the survival of many aquatic organism especially fish. Therefore, to prevent the effect, there is need
to always balance the carbon – oxygen level in the atmosphere. The oxygen and carbon cycle ensure that this is
possible.

Water cycle
The water cycle refers to the continous movement of water from the atmosphere to the earth and from the earth to the
atmosphere. All living organisms contain a high percentage of water. Plants takes up water from the soil in large
amount and lose most of it by transpiration. Only small amount is used during photosynthesis and metabolic reactions.
Animals take in water from food and drink and lose most of it in the air they breathe out and urine e.t.c.

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The water cycle is maintained mainly by evaporation and condensation of the water in the abiotic environment.

The water cycle

Importance of water to living organism

1. Water provides the medium for absorption of dissolved mineral salts by plants.
2. Water is an essential raw material in the process of photosynthesis.
3. Water is the solvent for chemical reaction in the human body.
4. It acts as a medium of transport for plant nutrients.
5. A large portion of the blood is made up of water.
6. It aids excretion of waste products by plants and animals.
7. It helps to regulate the body temperature.
8. It maintains osmotic content of body tissues.
9. Water forms the main component of plant and animal protoplasm.
10. Water is an important requirement for seed germination.
11. Water provides a natural habitat for aquatic organisms.
12. Water helps to hydrate the skin.
13. By moving toxins through the body system faster, water aid in detoxification.
Example
Which of the following processes are involved in a water cycle?
A. Evaporation, condensation and precipitation B. Evaporation, percolation and transpiration
C. Evaporation and precipitation D. Evaporation and transpiration
E. Precipitation and condensation (1993/37)
Answer: A – Evaporation, condensation and precipitation are involved in water cycle.
Example
Which of these is not applicable to the circulation of water in nature?
A. Water removed from oceans are permanently lost
B. Water constantly evaporates from the seas, rivers, lakes and soil
C. Water vapour rises, cools, condenses and precipitates as rain and dew
D. Water is absorbed by plants and animals from their external environment
E. Plant lose water by transpiration and decay (1995/41)
Answer: A – “Water removed from the oceans are permanently lost” is not applicable to the circulation of water in
nature. N.B– The circulation of water in nature is a dynamic process
Example
Which of the following cycles involves the process of precipitation and transpiration?
A. Water cycle B. Carbon cycle C. Nitrogen cycle D. Oxygen cycle (2009/26)
Answer: A – Water cycle involves both precipitation and transpiration.
Example
Which of the following statements about the circulation of water in nature is not correct?
A. constantly evaporates from seas, rivers, lakes and soil B. vapour rises cools, condenses and dew
C. removed from oceans is permanently lost D. is lost in plants by transpiration and decay (2014/30)
Answer: C – “Water removed from the oceans is permanently lost” is not correct about the circulation of water in
nature.

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EXERCISE 23.35
1. Which of the following substances is not recycled in an ecosystem?
A. carbon B. energy C. water D. nitrogen (2008/45)
2. Which of the following processes removes carbon from the atmosphere?
A. putrefaction B. photosynthesis C. volcanic eruption D. burning of fuels (2009/25)
3. Which of the following is not released during decay of living matter?
A. ammonia B. oxygen C. carbondioxide D. heat energy (2000/48)
4. Which of the following cycles involes the process of precipitation and transpiration?
A. water cycle B. carbon cycle C. nitrogen cycle D. oxygen cycle (2009/26)
5. Make a labeled diagram of the carbon cycle. (2015/6b)
6. Describe the water cycle using an annotated diagram(s) only. (2002/5a)
7. State five important uses of water to organisms in the tropic rain forest. (2003/8)
8. 5(a) Describe the water cycle using an annotated diagram(s) only
(b) What is the importance of water to living organisms? (2000/5a, b)
Nitrogen cycle
Nitrogen gas is abundantly present in the atmosphere or air but it cannot be used directly by green plants. It is used by them
in the form of nitrates and ammonium salts. Nitrogen which constitutes about 78% of air is utilized for making proteins and
chlorophyll in plants. When these plants are eaten by animals, the proteins are transferred along the food chain to animals.
Plants are continually absorbing salts from the soil and if these salts are not replenished, they will eventually become
exhausted.

The nitrogen cycle is a natural cycle of series of reactions which ensure that as nitrogen of the soil is being used up, it is
added to it at the same time so that the percentage of nitrogen remains fairly constant. The diagram below summarizes and
explain what happen in the nitrogen cycle.

Nitrogen cycle
Processes of nitrogen cycling:
There is a pool of nitrogen in the atmosphere and this can be made available in the soil through the following ways.
1. During lightening/thunderstorm:
Nitrogen in the air can combine with oxygen to form nitrous oxide, nitric oxide and nitrogen peroxide (which
are gaseous oxide of nitrogen).
N2 + O2 → 2NO (nitrous oxide)
This forms nitrous acid and nitric acid in contact with rain water.
2NO2 + O2 → 2NO2 (nitrogen(iv)oxide)
2NO2 + H2O → HNO3 + HNO2
Nitrates are then formed when these weak solution of dioxonitrate III acid combines with mineral salts in the
soil. The nitrates are then absorbed by the root of plants with soil water to make their proteins.
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2. Denitrification:
This is the process by which nitrates in the soil can be reduced to gaseous nitrogen which escapes into the
atmosphere. This reduction is done by certain soil bacteria called denitrifying bacteria.
It should be noted that apart from denitrification which results to loss of nitrogen from the soil, nitrogen is
also lost from the soil through the process of leaching. Leaching is the process by which nitrogenous
compounds are washed out from the soil by rain water.
3. Non-symbiotic nitrogen fixation:
Atmospheric nitrogen can be added to the soil and this process is called nitrogen fixation. This is done by
certain soil bacteria such as Azotobacter clostridium. They are free-living i.e. they live on their own.
4. Symbiotic nitrogen fixation (Rhizobium i.e root nodule bacteria):
Atmospheric nitrogen can be added to the soil by this bacteria which lives in the small root nodules of
leguminous plants e.g. beans, groundnut, crotalaria e.t.c. The energy heeded by these bacteria to make their
proteins is derived from carbohydrate and gaseous nitrogen from the air.
The free living bacteria obtain their carbohydrates from humus while root nodules bacteria obtain theirs
directly from the plants. Leguminous plants obtain compounds of nitrogen from the action of nitrogen fixing
bacteria like Rhizobium leguminosarium which live on their nodules. Hence, soil with leguminous plants
growing on them generally become richer in nitrogen compounds.
Other nitrogen fixing organisms can be blue-green algae e.g. nostoc which live freely in the soil.
5. Nitrification:
This is the process by which nitrite is converted to nitrate by nitrifying bacteria called Nitrosomonas. These
nitrifying bacteria converts ammonium compounds first to nitrite. These nitrites are converted by oxidation to
nitrates by another bacteria called Nitrobacter. Plants can only absorb nitrates from the soil. The process
whereby ammonium compounds from dead decaying plants and animals are formed is called
Ammonification at nitrification.
Example
List five ways by which nitrogen can be made available to the soil for plant growth. (2006/3b)
Answer: By nitrification, By nitrogen fixation, By putrefaction (decay of organic matter).
Through thunder storms and lightning, By application of artificial fertilizers.
Example
What is the importance of decomposers in the ecosystem? (2012/3ci)
Answer: They help in the recycling of nutrients in the ecosystem.
Example
Which of the following fixes atmospheric nitrogen?
A. Rhizobium B. Nitrosomonas C. Nitrobacter D. Putrefying bacteria E. Denitrifying bacteria (1989/48)
Answer: A – Rhizobium fixes atmosphere nitrogen into the root nodes of leguminous plant.
Example
Which of the following organisms reduces nitrates in the soil to gaseous nitrogen?
A. Euglena B. Protozoan C. Denitrifying bacterium
D. Parasitic mould E. Nitrifying bacterium (1993/23)
Answer: C – Denitrifying between reduces nitrates in the soil to gaseous nitrogen.
Example
The role of bacteria in the nitrogen cycle includes the following except
A. fixing atmospheric nitrogen B. converting ammonia to nitrites
C. converting nitrites to nitrates D. converting carbohydrates to carbon dioxide
E. causing the decay of dead organisms (1998/34)
Answer: D – Converting of carbohydrates to carbondioxide is not a role of bacteria in the nitrogen cycle.
Example
The process whereby microorganisms can convert atmospheric nitrogen into nitrogenous compound is known as
A. nitrogen cycle B. nitrogen fixation C. denitrification
D. putrefaction E. decomposition (1993/24)
Answer: B – Nitrogen fixation is the process whereby microorganisms covert atmosphere nitrogen into nitrogenous
compound.

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Example
Which of the following processes removes water from the water cycle?
A. Condensation B. Perspiration C. Photosynthesis D. Transpiration (2002/35)
Answer: D – Transpiration
Example
Which of the following processes does not contribute to the maintenance of the nitrogen content of the soil?
A. Decomposition B. Dentrification C. Nitrification D. Nitrogen fixation (2005/41)
Answer: D – Denitrification removes nitrogen from the soil, hence it does not contribute to the maintenance of the
nitrogen content of the soil.
Example
(d) Describe what happens during the denitrification stage of the nitrogen cycle. (2006/4d)
EXERCISE 23.36
1. (c) (i) Describe three ways by which nitrogen is added to the soil for plant use.
(ii) State two ways by which nitrogen is lost from the soil. (2008/8c)
2. The phenomenon in the diagram is termed
A. denitrification B. conservation C. eutrophication D. global warming (2016/28)
3. Another cause that could lead to the phenomenon in the diagram is
A. exhaust from cars B. oil spillage C. dumping of sewage D. excess rainfall (2016/29)

4. Nitrogen-fixing microorganisms in leguminous plants live symbiotically in the

A. root nodules B. taproots C. adventitious roots D. root hairs (2019/30 PC2)
The diagram below shows the effect of nitrites water bodies.
Study it carefully and Answer: questions 27 to 29.

5. The source of the nitrates in the part labeled I is the

A. root nodules of legumes B. cloud C. fertilizers D. organic matter (2016/27)

6. c. Describe the nitrogen cycle. (1999/5c Nov)

7. The process which reduces the nitrogen content of the soil is
A. Ammonification B. denitrification C. nitrogen fixation
D. nitrification E. putrefaction (2005/7 Neco)
8. Denitrifying bacteria in nature liberate gaseous nitrogen directly from
A. ammonium salts B. soil nitrates C. thunderstorms D. soil nitrites (2019/49 NABTEB)

Decomposition in nature:
Decomposition is the breakdown of organic matter into its component through chemical and biological process.

Decomposition could occur in the absence of oxygen. This is known as anaerobic decomposition or fermentation.
When it occurs in the presence of oxygen, it is known as aerobic decomposition. Organisms that obtain their energy
through breaking down of dead organisms are called decomposers. Examples are bacteria, fungi , moulds, protozoa,
mite millipedes, centipede, beetles and earthworms.
Decomposers are important in the ecosystem, because they help in recycling of the materials in the ecosystem. Micro-
decomposers include bacteria, protozoa and moulds where as macro-decomposers include multi-cellular organisms
such as fungi, millipede, centipedes earthworm, beetles, mite etc.

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Role of decomposers
Decomposers breakdown and recycle dead remain of plants and animals in the environment. They return nutrients to
the ecosystem. They make use of little quanitity of the materials they breakdown and the bulk of the materials are
recycled.
Example
(c) (i) What is the importance of decomposers in the ecosystem?
(ii) Name one plant and one animal decomposer. (2012/3c)
Answer:
i. They break down organic materials that are difficult for organism to digest. They also return organic matter to
the environment in an inorganic form, so that they can be re-assimilated by plant.
ii. Plant decomposer: Bacteria
Animal decomposer: Earthworm.
Example
Which of the following factors of an ecosystem is a decomposer?
A. Green plants B. sun C. bacteria D. herbivores (2013/35 Nov)
Answer: C – Bacteria serve as decomposers in an ecosystem.
Example
The following processes are benefits of decomposer in the ecosystem except
A. recycling of nutrients B. formation of humus
C. release of carbon dioxide and hydrogen sulphide D. metabolism of free nitrogen to nitrate (2019/36 PC1)
Answer: D – Metabolism of free nitrogen to nitrate is not a benefit of decomposers in the ecosystem.

EXERCISE 23.37
1. Which of the following processes does not contribute to the maintenance of the nitrogen content of the soil?
A. decomposition B. denitrification C. nitrification D. nitrogen fixation (2005/14)
2. Which of the following organisms reduces nitrates in the soil to gaseous nitrogen
A. euglena B. protozoan C. denitfiying bacterium
D. parasitic mould E. nitrifying bacterium (1993/23)
3. Which of the following is a nitrifying bacterium?
A. azotobacter B. clostridium C. nitrobacter D. rhizobium E. staphylococcus (2005/44 Neco)
4. Thunderstorm can be beneficial to plants because it
A. kills the pest that attacks crops B. destroys some of the major crops C. adds nitrates to the soil
D. adds lime to the soil E. makes rain water available to plants (2000/33)
5. State the functions of: i. Nitrogen fixing bacteria ii. Nitrifying bacteria
iii. Denitfifying bacteria in natural. (2013/76)
6. State three difference between nitrogen fixation and denitrification. (2011/7b)
7. Explain how nitrogen from urine gets to the roots of plants. (2011/7c)
8. Describe what happens during the denitrificiation stage of the nitrogen cycle. (2006/4d)
9. Explain briefly the importance of the following factor and organism in the nitrogen cycle.
(i) lightening (ii) Nitrosomonas (iii) Azotobacter. (2019/6a)
10. Explain briefly three roles of a decomposer in an ecosystem. (2016/3a(ii)
11. Name one plant and one animal decomposer. (2012/3cii)

ECOLOGICAL MANAGEMENT
Ecological management deals with methods and ways or how organisms adjust themselves so as to cope with
problems of survival in their environments. Ecological management is aimed at maintaining the equilibrium in the
ecosystem.
Ecological management can be in the form of association, adaptation, tolerance e.t.c.
Association
Association in ecosystem refers to the interaction of organism with one another and with the physical factors of the
environment. There are different types of association among organisms in an ecosystem and different signs have been
attached to them to describe their effect. The signs include positive (+) which means benefits, neutral (0) which means
that there is no harm or benefit and negative (-) which means that there is harm.

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1. Neutralism (0/0): This type of association is neither beneficial nor harmful to either population i.e. they do
not affect each other. For example, the direct interaction between squirrel and a bird appear to be of this type.
Neither serves as a food for the other nor do they compete for the same food supply, yet they are part of the
same forest community.

2. Symbiosis or mutualism (+/+)

Mutualism is a close association (relationship) between two organisms in which both of them benefit from
each other. Example of symbiotic relationship include:
I. Leguminous plant and nitrogen fixing bacteria: The bacteria (Rhizobium) derive shelter and food
from the leguminous plant while the leguminous plants benefit the supply of nitrogenous compound
from the bacteria.
II. The association between fungi and algae in lichens: The algae derives protection, shelter, water and
mineral salt from the fungus while the fungus benefits from the manufactured food produced by the
algae through photosynthesis.
III. Termite and protozoa in their alimentary canals: The protozoa help the termite to digest the
cellulose in the food while protozoa are protected by the termites.
IV. Grass-eating animals and bacteria in their alimentary canal (caecum and colon of herbivores):
The protozoa and the bacteria in the alimentary canal help to digest cellulose. The bacteria gain
shelter and abundant nutrient in caecum and colon.
V. Pollination: Pollination of flowers by insects such as butterflies is also symbiotic.
VI. The association between humans and the bacteria in their intestine is also mutualistic: The
bacteria make vitamin B12 and carry out some microbial digestion for human beings. The bacteria
benefit by having nutrients and shelter from human beings.
3. Parasitism (+/-)
This is a close association between two organisms in which one called the parasite lives in or on the other
known as the host and causes harm to the host. Parasites which lives inside the body of their hosts are called
endoparasites e.g. Plasmodium which causes malaria fever. The Plasmodium lives inside the red blood
corpuscles. Other examples of endoparasites are Ascaris lubricoides (roundworm and tapeworm which live in
the small intestine of man).

On the other hand, parasite which live on the surface of their hosts aer known as ectoparasites e.g. head lice,
ticks, fleas, lampreys (a fish parasite) dodder and mistletoe (plants).

Mistletoe is a semi parasite on the stem of many trees in the forest. It grows in the stem of its host and absorb
the nutrients from the host using their special developed roots called haustoria.

4. Commensalism (+/O)
This is a close association between two living organisms in which one of them derives benefit while the other
(host) is neither benefited nor harmed. Example of commensal relationship is found between a small fish
called remora and shark. Another example is the hermit crab and bristle worm. The bristle worm live in the
shell of the hermit crab and also feed on the scraps of the crab’s food. The hermit crab neither gains nor
experience harm. Some bacteria in the large intestine of man are also commensals.

Another example is found between a small tropical fish known as pearlfish or cucumberfish (fierasfer) which
is about 11cm long andlives in the rectum of a particular species of sea cucumber. The sea cucumber breathes
by taking water through its anus, a pearlfish can wait for the cucumber to open for a breath and swim in, the
relationship between the pearlfish and the sea cucumber is beneficial to the pearlfish providing shelter for it.
The sea cucumber suffers no harm neither does it benefit from the relationship.

5. Saprophytism
This is an association in which an organism called a saprophyte derives their food from dead decaying
organisms by secreting enzymes on the dead matter and absorbing the nutrient by diffusion. They digest their
food extracellular or externally. Examples are fungi (mucor and yeast) and bacteria. Saprophytes play an
important role in the detritus food chain. The mucor is a saprophyte that grows on organic matter like bread,
cheese, leather, or deadwood. It provides a hyphae which penetrates the host or substratum and absorb
already digested food from the substratum. Bacteria are either parasitic or saprophytic.

The saprophytic bacteria lack chlorophyll. They are found in water and soil containing organic compound.

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6. Predation
This is an association involving two free-living organisms in which one known as the predator kills the other
organism known as the prey and use it for food e.g. domestic cat kills rat for food. The rat is the prey while
the cat is the predator.

The effects of a predatory organism on its prey:

a. Predator sometimes reduces the number and distributions of its preys population often below what the
environmental resources can support.
b. Extinction of the prey might occur if there is excess predation.

7. Interspecific competition (-/-) and (- /0)

This is a type of competition in which the individuals of different species compete for the same resources in
an ecosystem. Some of these resources include food, water, sunlight etc. e.g. The competitive interaction
between rice plants and weeds (broad-leaved).
Example
The relationship between a herbivore and the bacteria which live in its caecum is known as
A. parasitism B. symbiosis C. commensalism D. saprophytism E. predation (1988/30)
Answer: B – The relationship between a herbivore and the bacteria which lives in its caecum is known as symbiosis.
Symbiosis is an association between two dissimilar organism.
Example
When large numbers of organisms share limited space and resources the result is
A. immigration B. commensalism C. symbiosis D. extinction E. competition (1988/53)
Answer: E – Competition will result when large numbers of organism share limited space and resources.

Example
Which of the following characteristics is associated with commensalism?
A. Both organisms are harmful to each other B. The association involves many organisms
C. The association is beneficial to one of the organisms D. Both species are beneficial to each other
E. This relationship is found only among higher plants (1991/52)
Answer: C – In commensalism, only one organism benefits while the other neither derives benefit nor harm.
Example
What type of relationship exists between a tapeworm and an infected mammal?
A. Symbiosis B. Commensalism C. Predation D. Parasitism E. Saprophytism (1993/28)
Answer: D – The relationship between a tapeworm and an infested mammal is parasitism.
Example
Which of the following relationships illustrates competition?
A. Cattle egret moving along with cattle B. Goats and cows grazing on a small grass lawn
C. Mosses succeeding lichens in a rocky terrain D. Red mangrove swamp dying and replaced by white mangrove
E. Forest trees, shrubs and grasses replaced white mangrove in a swamp (1994/22)
Answer: B – Goats and cows. Grazing on a small grass lawn is a good illustration of competition because both
animals will struggle to get the limit grass in the small grass lawn.
Example
An association between two organisms in which both benefit is called
A. parasitism B. commensalism C. symbiosis D. predation E. competition (1995/42)
Answer: C – Symbiosis (mutualism) is an association between two organism in which both benefit.
Example
(a) What is meant by competition
(b) Explain briefly the terms (i) inter-species competition (ii) intra - species competition. (1996/3a, b)
Answer:
a. Competition is the process by which living organisms in a particular habitat struggle with one another for
limited resources such as shelter, food, nutrient mate etc.
b. Terms:
i. Inter-species competition: This is the competition that exist between individuals of different species.
e.g. Goats and cows grazing on a small grass lawn.
ii. Intra-species competition: This is the competition that exist between individuals of the same species
e.g. maize seedlings in a nursery.

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Example
The association between protozoa and termites is an example of
A. symbiosis B. parasitism C. predation D. saprophytism E. epiphytism (1997/30)
Answer: A – Symbiosis. In this association, the protozoan helps the termite to digest cellulose while the termite
provides food and shelter for the protozoan.
Example
In commensalism
A. one of the organisms gains and the other loses B. both organisms benefit from the association
C. one of the organisms gains while the other neither gains nor loses
D. one off the organisms produces extra cellular digestive juices (2000/49)
Answer: C – In commensalism, one of the organisms gains while the other neither gains nor loses.
Example
Paratism can best be defined as an association between two organisms in which
A. both organisms B. one organism gains and the other neither gains nor losees
C. both organisms suffer some disadvantages D. one organism gains and the other looses (2000/50)
Answer: D – Parasitism is an association in which one organism gains and the other losses.

Example
(a)Explain the terms (i) Parasitism (ii) Commensalism. (2002/1ai, ii)
Answer:
i. Parasitism: This is an association that involves two organisms where one organism called the parasite lives on
or inside another organism called the host, causing harm to it.
ii. Commensalism: This is an association between two organisms where one organism benefit and the other
derives neither benefit nor harm.
Example
Competition among individuals of a population increases the
A. number of organisms B. survival of the fittest
C. availability of nutrient supplied D. enlargement of the territory (2003/43)
Answer: B – Competition among individuals of a population increases the survival of the fittest.
Example
An example of a saprophytic relationship is a/an
A. vulture feeding on decaying meat B. mushroom growing on decaying vegetation
C. boy eating stale food D. earthworm feeding on decaying vegetation (2010/50)
Answer: B - Mushroom growing on decaying vegetation is an example of a saprophytic relationship.
Example
Which of the following associations is an example of epiphytism?
A. Lice in the human hair B. Mistletoe or citrus fruit C. Egret on cow D. Fern on palm tree (2013/32)
Answer: D – Fern on a palm tree is an example of epiphytism.
NB: Epiphytes are different from parasite in that they grow on another plant and depends on it for support and not for
food. Mistletoe is a parasitic plant.
Example
Which of the following relationships does not involve two organisms?
A. commensalism B. saprophytism C. symbiosis D. parasitism (2016/34)
Answer: B – Saprophytism does not involve two organisms. It only involves an organism and a decaying organic
matter.

Example
In which of these associations is much harm done to one of the partners?
A. symbiosis B. Epiphytism C. commensalism D. parasitism E. mutualism (1979/19 JAMB)
Answer: D – Parasitism. In this association, the host suffers while the parasite benefits.
Example
An organism X lives entirely on the waste products in another organism Y. In this association X is a
A. symbiont B. commensal C. saprophyte D. parasite E. epiphyte (1980/39 JAMB)
Answer: C – X is a saprophyte.
Example
Lichen is an example of
A. a saprophytic organism B. a symbiotic organism C. an epiphytic plant D. a carnivorous plant (1989/41 JAMB)
Answer: B – Lichen is an example of a symbiotic organism. A lichen is composed of a fungi and an algal.

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Example
Toads and lizards in an ecosystem depend on a limited quantity of food. This is an example of
A. parasitism B. intraspecific competition C. predation D. interspecific competition (1997/35 JAMB)
Answer: D – Since toad and lizards are different species of animals, competition between them will be interspecific
competition.
Example
The biological association that contributes directly to succession in a community is
A. competition B. predation C. parasitism D. commensialism (1998/43 JAMB)
Answer: A – Competition is the biological association in a community.
Example
The sign + is used to indicate an association where an organisms gains, while 0 is used where an organisms is
unaffected. An association indicated as + 0 is known as
A. predation B. commensalism C. parasitism D. competition (1999/39 JAMB)
Answer: B – Commensalism. This is because one organism gains (+) whiel the other was unaffected (0)

EXERCISE 23.38
1. For heterotrophic organisms, competition is least caused by the inadequacy of
A. mates B. space C. light D. nutrients (2001/50 JAMB)

2. The most important environmental factor which epiphytes in the rain forest compete for is
A. water B. nutrient C. light D. space (1999/50 JAMB)

3. Which of the following is an example of intraspecific competition?

A. Yam and potato shoots growing out through the same window
B. A hawk and an eagle targeting the same chicken
C. A lizard and an ant-eater chasing an insect
D. A worker termite and a soldier in a limited space (2004/13 JAMB)

Use the diagram below to Answer: questions 47 and 48.

4. The importance of the association to the fungus that it obtains

A. a partner for reproduction B. anchorage from the algae
C. oxygen a carbohydrates from the algae D. water and mine salts from the algae (2006/47 JAMB)
5. The association illustrated demonstrated
A. parasitism B. commensalism C. saprophytic D. mutualism (2006/48 JAMB)
6. Which of the following is an example of parasitism?
A. Fungi growing on a dead tree branch B. A squirrel living in abandoned nest of a bird
C. Mistletoe growing on an orange tree D. Cattle regrets taking ticks from the body cattle (2007/4 JAMB)
7. Which of the following factors can bring about competition in a population?
A. Dispersion B. Emigration C. Drought D. Mortality (2007/13 JAMB)
8. Which of the following associations is an example of mutualism?
A. Hydra viridis and zoochlorellae B. Human and lice
C. shark and Remora fish D. Bread and Rhizopus stolonifer (2008/30 JAMB)
9. The association between bacteria residing in the caccum and the ruminant is
A. parasitism B. predation C. saprophytism D. mutualism (2009/30 JAMB)

10. Which of the following pair of organisms exhibit parasitic association?

A. Insect and plant B. Cattle and egret C. Shark and remora D. Tsetse-fly and cattle (2017/3 JAMB)
11. The relationship between remora and shark can best be described as
A. parasitism B. amensalism C. mutualism D. commensalism (2017/11 JAMB)
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12. The difference between symbiosis and commensalism is that in commensalism
A. both organisms gain front the association B. neither of the organisms gains
C. one organism gains and the other suffers no harm D. both organisms suffer from the association
E. one organism harms the other (1992/39 Nov)

13. Which of the following limiting resources is competed for by organisms in the desert?
A. Light B. Temperature C. Oxygen D. Water E. Carbon dioxide (1991/52 Nov)
14. The relationship between a herbivore and the bacteria which leaves in its caecum is an example of
A. saprophytism B. predation C. commensalism D. mutualism (2006/32 Nov)
15. Which of the following features is not associated with epiphytes? They
A. live high on trees B. have to compete for light C. cannot produce their own food
D. have root systems which are on the outside of the tree (2013/42 Nov)
16. A relationship that is beneficial to two organisms is best described as
A. symbiosis B. commensalism C. predation D. saprophytism E. parasitism (1997/44 Nov)

17. Which of these best defines an association in which the host is harmed?
A. commensalism B. mutualism C. parasitism D. saprophytism E. symbiosis (2007/20 Neco)

18. An epiphyte growing on a tree trunk illustrates

A. commensalism B. mycorrhiza C. parasitism D. saprophytism E. symbiosis (2005/60 Neco Nov)

19. Which of these statements is NOT true about parasitism?

A. parasitism, one parasite derives all its benefits from the host
B. parasites can live either on or in the host C. most parasites die along with the host
D. in parasitism the host also derives some benefits from the parasite (1999/30 NABTEB)

TOLERANCE
Tolerance is the ability of an organism to withstand or tolerate unfavourable ecological factors in their habitats at a
given period of time. In other words, tolerance is a structural development in an organism to withstand a certain
condition of an environment at a given period of time. It is the ability of a living thing to successfully cope with the
extreme variations (upper and lower) limits of an environment.
Abiotic factors that may impose tolerance on organisms include: Temperature, rainfall (availability of moisture),
light intensity, salinity and edaphic factors. Each of these factors occurs over a range in the various habitats. For
example, temperature can range from – 250° to 0°C in the polar ice caps and from 15°C to 50°C in the hot deserts.
Living organisms can only live in a particular habitat if they can tolerate the range of the abiotic factors that operate
in it.
Tolerance range
The tolerance range is that limit of environmental conditions within which a species can survive, grow and reproduce.
Each species has a minimum and maximum limit of tolerance for each environmental factors such as heat, moisture,
salinity, pH e.t.c.
The lower limit of tolerance to any of the environmental factors is known as the minimum range or minimum
tolerance while the upper limit is known as the maximum range or maximum tolerance.
Between the minimum and maximum limit of tolerance is the optimum range where conditions are mostly favourable
for optimum growth or activity. For example, for most animals, the minimum temperature limit is 0°C while the
maximum limit is 42°C. Their tolerance range is 0 – 42°C. Below 0°C or above 42°C the organisms may die.
The diagram of tolerance range is shown below:

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Tolerance range, optimum range and population size: The above graph is a geographical graph illustrating
maximum and minimum range of tolerance.

Geographical range is the area where a species of organism can only be found within the minimum and maximum
limit of its tolerance.

Plants and animals can only be found in habitats with the minimum and maximum limits of tolerance to the
environmental factors. This limit constitutes the geographic or distributional range of the species.

This branch of biology that deals with the geographical distribution of animals and plants is known as biogeography.

Variations in abiotic factors are responsible for the major biomes such as tropical rain forest, grassland (savannah)
desert), freshwater and marine biomes.

Ecological niche
Ecological niche of an organism is the total sum of an organisms actual dwelling place in the habitat. It is also
organism’s role in the ecosystem. It may be a producer, consumer (predator, parasite, carnivores e.t.c.) or decomposer.
It could also be the organisms requirement for abiotic resources and organisms tolerance range for each abiotic
condition in the ecosystem.

Therefore, an organism’s ecological niche is its dwelling place as well as its activities, requirement and effects on the
environment.

ADAPTATION
Adaptation are modification of structure or function or behaviour which enable organisms to adjust to or fit into the
condition in their environment. It is any characteristic that enhances the fitness of a living organism to survive and
successfully reproduce its kind in its living environment.

Different organisms show different adaptation in different habitat. Below, gives the adaptation of different organisms
to their respective environment.

A. HYDROPYTES: Hydrophytes are plants that have adapted to living in the aquatic environment. Their
adaptive feature include:
1. Possession of spongy tissue, large intercellular spaces and cavities which contains gases used for
buoyancy e.g. water hyacinth, pistia.
2. Submerged plants lack cuticles.
3. Mechanical and water conducting tissues are considerably reduced.
4. Roots are shorter and less branched. Rootlets are without root hairs.
5. Some plants like red mangrove, white mangrove and raphia palm, possess breathing roots or
pneumatophores (stilt root).
6. Flowers are raised above water for the purpose of pollination.
7. Presence of waxy cuticles to prevent wetting of leaves e.g. leaves of Pistia lotus (water lettuce).
8. Presence of chloroplasts even in the epidermal cells of leaves and stem of submerged plants is meant
to meet the reduced light conditions.

B. XEROPHYTES: These are plants that live in dry areas or habitat (Terrestrial habitat). Their adaptation
includes.
1. Possession of deep and extensive root system.
2. Possession of water storage tissues e.g. Cactus, Baobab.
3. Possession of protoplasm (cells) which can recover after considerable drying e.g. moss plant.
4. Presence of thick cuticles or wax on the leaves surface to reduce transpiration.
5. Modification of leaves into thorns to reduce water loss e.g. Acacia.
6. Reduction of leaves to scales to reduce water loss e.g. Casuarina.
7. Possession of sunken stomata to reduce transpiration.
8. Presence of thick back e.g. Daniellia Oliveri to cover the buds during bush fires.

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C. MESOPHYTE: These are plants which live in area that are neither too wet nor too dry. Their adaptations
include:
1. Possession of well developed root system.
2. Presence of broad thin leaves.
3. Absence of sunken stomata, thick cuticles or bark and hairy leaves. Examples of mesophyte are Iroko,
Mahogany e.t.c.

Adaptation of animals to terrestrial habitat

Animals that live on land have the following adaption for water conservation.
1. They possess cuticles covering their body surface e.g. insects.
2. They possess shell covering the body e.g. land snail.
3. Possession of scales on the skin e.g. agama lizard.
4. Possession of hair and sweat glands that regulate water loss e.g. man.
5. Efficient kidney that regulates water loss e.g. man.
6. Excretion of uric acid e.g. insects and birds.

Adaptation of animals to aquatic habitats

1. Possessions of structures that aid buoyancy e.g. many zooplanktons have a small size and expanded shape to
make them float. Fish also have swim bladder for moving up and down in water.
2. They have streamlined shape to reduce water resistance e.g. fish. They also have organs for swimming e.g.
Tail in fish, webbed digits in frogs, tails in tadpole, fins in fish, e.t.c.
3. Possess gills for breathing e.g. tadpoles, crustaceans, fishes. Aquatic micro-organisms exchange gases through
their body surfaces.
4. They possess structural organs for osmo-regulation. For example, kidney regulates water content of the body.
In fish, scales prevent uncontrolled entry of water into the body; Protozoa have contractile vacuoles which
removes excess water.

Adaptation for avoiding enemies

1. Counter-shading in fish, i.e. dorsal surface is dark-grey while the ventral surface is silvery white. This
camouflages it against predator above and below.
2. Withdrawing into burrow e.g. earthworm.
3. Lateral lines for detecting changes in water vibrations.
4. Concealing colouration i.e. a close matching in appearance of the animal to its background e.g. chameleon.
5. Secretion of poisonous skin glands e.g. toad.
6. Hard outer covering/shell e.g. Giant snail, tortoise, oysters e.t.c.
7. Injection of painful chemicals e.g. bees, wasps, scorpions, electric fish e.t.c.
8. Movement in groups to frighten predators e.g. Monkeys, baboons e.t.c.
9. Inflation of the body to frighten predators e.g. Chameleon, Octopus, Cats.

Adaptation of animal parasite

1. They possess structures for attachment e.g. Tapeworm has suckers and hooks, while liver fluke has suckers.
Ectoparasites possess flattened body to retain their position without falling off the host e.g. lice. Some use
their mouth parts and limbs to hold onto the host.
2. They possess mouth part for feeding while others use their body surfaces.
3. Some endoparasites are hermaphrodites e.g. tapeworm – some female parasites carry the male groove or
pouches on their bodies e.g. roundworm

Example
Terrestrial organisms which are capable of maintaining their body temperature constant within fairly close limits are
referred to as
A. thermoclines B. homotherms C. poikilotherms D. eurytherms E. stenotherms (1988/36)
Answer: B – Homeotherms are terrestrial organisms that maintain their body temperature within a narrow range

Example
The change in colour of the chameleon serves as a means of
A. attraction to the opposite sex B. repulsion of the enemy
C. a camouflage from a predator D. regulation of body temperature
E. production of a variety of skin pigments (1988/54)
Answer: C – The change in colour of the chameleon serves as a means of camouflaging from predators.

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Example
Which of the following is an example of reproductive adaptation?
A. Succulent stems of cactus plant B. Changing colour of chameleon C. Possession of spines by desert plant
D. Neck colouration in Agama lizard E. Leaf-shedding in trees (1989/58)
Answer: D – Neck colouration in agama lizard is an example of reproductive adaptation.

Example
The large intercellular air spaces which penetrate the tissues of most hyrophytes provide a pathway through which
A. carbondioxide absorbed by leaves can diffuse to the roots
B. oxygen produced in the leaves can diffuse to the submerged parts
C. salts absorbed by roots can reach other parts of the plant
D. plant hormones are transported to various parts E. manufactured food is translocated (1989/59)
Answer: B – Oxygen produced in the leaves can diffuse to the submerged parts.
Example
(b) Describe five behavioural adaptations of termites which enable them to survive in their environment. (1990/2b)
Answer:
- They move in group in order to ward off enemies.
- They feed on their dead members and this helps them to keep a healthy and a clean colony.
- The presence of inter-connectivity tunnels enhance aeration within the termite nest.
- Laying many eggs which hatch into nymphs ensures the survival of many.
- They build tunnels and burrow into the heart of woods. This enables them to evade their enemies and harsh
weather conditions.
Example
Which of the following organs is specially adapted for gas exchange in aquatic organs?
A. Lung B. Trachea C. Gills D. Tracheoles E. Alveoli (1992/22)
Answer: C – The gill is specially adapted for gaseous exchange in aquatic organisms.

Example
Which of the following is not a structural adaptation of desert plants for water conservation?
A. Tiny leaves B. Sunken stomata in leaves C. Stems and leaves with heavy cuticle
D. Broad leaves with numerous stomata E. Scale leaves (1992/47)
Answer: D – Broad leaves with numerous stomata.
Example
How are Savannah plants protected from bush fires? They
A. have sunken stomata B. roll their leaves during hot days C. have thick barks
D. ways produce flowers E. shed their leaves gradually (1992/58)
Answer: C – Savanna plants are protected from bush fire by having thick barks.
Example
Which of the following does not illustrate adaptation to the environment?
A. Colour changes by chameleon B. Streamline shape of fishes C. Light bones in birds
D. Development of big muscles by a weight lifter E. Possession of fins by fishes (1993/55)
Answer: D – Development of big muscles by a weight lifter does not illustrate adaptation to the environment.
Example
The changing of colour by a chameleon to that of the environment is an example of
A. Adaptive radiation B. Protective colouration C. courtship display
D. Display of body colour E. territorial behavior (1993/56)
Answer: B – The changing of colour by a chameleon to that of the environment is an example of Protective
colouration.
Example
The morphological, physiological and behavioural characteristics which enable an organism to survive in its
environment is called
A. heredity B. ecology C. competition D. adaptation E. variation (1994/19)
Answer: D – Adaptation
Example
Which of the following performs the same function as the contractile vacuoles of a unicellular organism?
A. Kidney B. Alimentary canal C. Liver D. Pancreas E. Bladder (1994/20)
Answer: A – The kidney helps in osmoregulation in animals just like the contractile vacuole in unicellular organism.
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Example
Describe briefly three ways each by which animals in arid habitats are adapted to
(i) drought (ii) high temperature. (2007/8c)
Answer:
i. Drought: ii. High temperature:
- Production of concentrated urine. - Living in borrows where temperature is low.
- Thick scales/skin to prevent water loss by evapouration. - Restriction of activities to cooler periods.
- Lives in borrows. - Seeking shades to keep body cool.
- Use of metabolic water.
Example
The following structures are adaptation for water conservation except
A. sunken stomata B. scales in animals C. lenticels in stems D. spines in plants E. thick leaves (1995/57)
Answer: C – Lenticels in stem are not adaptation for water conservation.
Example
(b) Explain how each of the following structures adapt the organisms that possess them to the mode of life:
(i) Succulent leaves in Aloe sp;
(ii) succulent stems and reduced leaves in cactus plants.
(iii) Short, strong beaks in fowls
(iv) counter shading in fish (v) tiny scales leaves on needle-like braches of pine trees. (2010/8b)
Answer:
i. Succulent leaves in aloe sp: These are adaptations for water storage.
ii. Succulent stem in cactus is for water storage while reduced leaves are for water conservation by the reduction
of transpiration rate.
iii. Short, strong beaks in fowls are adapted for picking food (insect, seeds, earthworm etc) and picking of feathers.
iv. Counter shading in fish is adapted for protection from predators.
v. Tiny scale leaves on needle-line branches of pine tree are adapted to reduced water loss by transpiration.

Example
The structure used by fishes to detect the presence and movement of other animals by the vibration they produce is the
A. eye B. nostril C. lateral line D. scales E. fins (1994/24)
Answer: C – The structure used by fishes to detect the presence and movement of other animals by the vibration they
produce is the Lateral line.
Example
The following structures are adaptation for water conservation except
A. sunken stomata B. scales in animals C. lenticels in stems
D. spines in plants E. thick leaves (1995/57)
Answer: C – Lenticels in stem aid transpiration through the stem. It is not an adaptation for water conservation.
Example
(c) Explain two ways each by which the toad/frog is structurally adapted to the following:
(i) obtaining food; (ii) protection (iii) movement. (1996/3c)
Answer:
i. Obtaining Food:
- Possession of a long and sticky tongue for capturing prey.
- Possessing the ability to draw eyes in so that they make bulges in the roof of their mouth which help to
prevent their prey from escaping and also aid in swallowing.
ii. Protection:
- Possession of poison glands on the skin which makes them dangerous to predators.
- Having skin colour that makes them blend with their environment makes them unnoticed by their enemies
or predators.
iii. Movement:
- Possession of long hind limbs with powerful muscles which enables them to jump efficiently away from
predators.
- Possession of webbed digits in the hind limbs enable them to swimming efficiently in water.
Example
Desert plants are usually called
A. hydrophytes B. mesophytes C. xerophytes D. sporophytes (1999/38)
Answer: C – Xerophytes

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Example
A xerophytes conserves water by possession of the following features except
A. thick cubicle B. sunken stomata C. broad leaves D. fleshy stem (2011/41)
Answer: C – Xerophytes do not conserve water by possessing broad leaves.
Example
The cactus plan is modified to perform the following functions except
A. Maximum absorption of water from the atmosphere B. green stem for photosynthesis
C. Prevention of excessive transpiration through thick cuticle on stem
D. conservation of water in the succulent thick stems E. protection against herbivores by spinny leaves (1998/42 Nov)
Answer: A – Cactus plant is not modified to carry out maximum absorption of water from the atmosphere.
Example
Which of the following resources is competed for by organisms in the desert?
A. Light B. Temperature C. Oxygen D. Water (1999/50)
Answer: D – Water
Example
Which of the following best describes the adaptation of the earthworm to its habitat?
A. Living in borrow during the day to prevent desiccation B. Burrowing into soft soil to store food
C. Possession of segmented body to reduce movement D. Possession of a few bristles for defence (2000/51)
Answer: A – Living in borrow during the day to prevent desiccation is an adaptation of earthworm to it habitat.
Example
Special modifications which enable an organism to survive in its habitat is known as
A. adaptation B. tolerance C. mimicry D. colouration (2016/33)
Answer: A – Adaptations are special modifications which enable an organism to survive in its habitat.
Example
Pneumatophores are essential for
A. nutrition B. movement C. breathing D. growth (2003/41)
Answer: C – Pneumatophores are essential for breathing.
Example
Rabbits cannot survive in an aquatic habitat because they have
A. for and hind limbs B. no gills C. no fins D. no scales (2003/44)
Answer: B – Rabbits do not have gills which are essential in breathing under water hence, they cannot survive in aquatic
habitat.
Example
Most tropical plants shed their leaves during dry weather conditions in order to
A. reduce their growth rate B. conserve water
C. reduce competition D. minimize the rate of photosynthesis (2009/41)
Answer: B – The shedding of the leaves by most tropical plants is to enable them Conserve water.
Example
Which of the following features is not an adaptation of plants to aquatic habitat?
A. Breathing roots for entry of air B. Flowers raised above water for the purpose of pollination
C. Spongy tissues containing gases for buoyancy D. Hairy structures on the leaves to reduce water loss (2009/42)
Answer: D – Hairy structures on the leaves to reduce water loss is not an adaptation of plants in the aquatic environment.
Example
Xerophytes have the following characteristics aimed at conserving water except
A. thick cuticle B. broad leaf surfaces C. sunken stomata D. waxy cuticle (2018/33)
Answer: B – Broad leaf surface.
Example
Which of the following factors is the main problem facing xerophytic plants?
A. Competition for sunlight B. Conservation of excess water
C. Inadequate root for water absorption D. Lack of adequate water (2010/37)
Answer: D – Lack of adequate water is a major problem that xerophytes encounter because of their environment.
Example
The organelle which eliminates water from the body of a protozoan is the
A. plasma membrane B. contractile vacuole C. nucleus D. cell wall (2010/3)
Answer: B – Contractile vacuole

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Example
The following adaptations are associated with the flight of birds except
A. reduced body weight B. streamlined shape C. presence of powerful muscles D. clawed digits (2014/27)
Answer: D – Clawed digits are not adaptation associated with the flight of birds, instead they are adaptation for food/prey
catching in birds.
Example
(c) Explain the term adaptation
(d) Explain two ways each by which the following organisms adapt to their habitats:
(i) hydrophytes (ii) xerophytes. (2015/3c, d)
Answer:
c. Adaptation are the special features or characteristics that an organism possess which enables it to live successfully
in an environment.
d. Ways by which the following organisms adapt to their habitats:
i. Hydrophytes:
- Possession of air spaces to enable them float in water.
- Possession of breathing roots.
ii. Xerophytes:
- Possession of scaly leaves to prevent excession water loss.
- Possession of succulent stem to conserve water.
Example
Insects show considerable powers of water conservation. This is due to the fact that
A. the chitinous cuticle is impregnated with tanned proteins B. nitrogenous waste is eliminated as urea
C. chitin is impermeable to water D. the Malpighian tubules are impermeable to water
E. the cuticle is covered with wax (1979/45 JAMB)
Answer: C – Chitin is impermeable to water. (N.B– Chitin is the major constituent of insects exoskeleton)
Example
Which of these is NOT an adaptive feature for arboreal life?
A. Possession of a long tail B. Possession of claw
C. Possession of teeth D. Counter shading in coat colour (1991/46 JAMB)
Answer: C – Possession of teeth.
Example
An examination adaptation to a xerophytes environment is represented by the development of
A. fleshy tissues and reduced leaves B. broad canopy and extensive surface root system
C. thick barks and broad leaves D. rough leaves and shallow root system (1992/47 JAMB)
Answer: A – Fleshy tissues and reduced leaves.
Example
Plants adapted for life in salty marsh are called
A. hydrophytes B. xerophytes C. halophytes D. epiphytes (1993/41 JAMB)
Answer: C – Halophytes
Example
In a drought situation, plants suffer from water stress which could result in
A. reduced biochemical activities B. enhanced chemical activities
C. enhanced microbial activities D. reduced photropical activities (1994/38 JAMB)
Answer: A – Reduced biochemical activities.
Example
Scales on reptiles are a feature for
A. Conserving water B. conserving food C. protecting the skin D. locomotion (1995/47 JAMB)
Answer: A – Conserving water
Example
Birds maintain their body temperature with the help of their
A. blood which maintains constant temperature B. feathers which cover the body
C. skin which conserves moisture
D. veins which transport fluid of constant temperature to all body tissues (1995/9 JAMB)
Answer: B – Feathers which covers the body
Example
In the whistling pine, leaves are reduced to brown scales and young stems are green this is an adaptation for
A. obtaining food B. conserving nutrients C. storing water D. reducing transpiration (1998/48 JAMB)
Answer: D – Reducing transpiration

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Example
Which of the following are adaptations of animals to aquatic habitats?
A. gills, scaly sin and lungs B. lateral line, streamlined bodies and lungs
C. gills, streamlined bodies and lateral line D. gills, streamlined bodies and spiracle (2000/29 JAMB)
Answer: C – Gills, streamlined bodies and lateral line are adaptations of animals to aquatic habitats
Example
Which of the following structural features are adapted for uses other than water conservation?
A. feathers in birds B. scales in animals C. spines in plants D. succulent stems (2000/45 JAMB)
Answer: A – Feathers in birds have functions other than water conservation.An example of such function is for flight.

EXERCISE 23.39
1. The stem of a typical aquatic plant usually has many
A. air cavities B. intercellular spaces C. water cavities D. water-conducting cells (2001/45 JAMB)
2. A noticeable adaptation of the animal to its aquatic habitat is the possession of
A. webbed digits B. four limbs C. a wide mouth D. large eyes (2003/3 JAMB)
3. One adaptation of reptiles to water loss is the presence of
A. claws on limbs B. keratinous scales C. long sticky tongues D. long tails (2004/10 JAMB)

4. Plants survive hot dry conditions by

A. producing numerous leaves B. Having evergreen leaves
C. storing water in large parenchyma cells D. Having numerous stomata (2004/15 JAMB)
5. The most important characteristic that makes reptiles to conquer terrestrial habitats is the possession of
A. long tail B. scaly skin C. sharp claw D. aminiotic egg (2008/12 JAMB)
6. One adaptation shown by hydrophytes in fresh water habitats is the
A. waxy cuticle on shoot surface B. poor development and roots xylem tissues
C. well-developed roots and supporting system D. leaves reduced to spine (2015/2 JAMB)
7. Stomata of some plants are sunken and protected by hairs. These are features of
A. mesophytes B. epiphytes C. hydrophytes D. xerophytes (2008/33 JAMB)
8. Chewing the cud is an adaption peculiar to
A. herbivores B. omnivores C. rodents D. ruminants (2009/12 JAMB)
9. Plants that grow in an area that is neither too wet nor too dry are
A. xerophytes B. mesophytes C. epiphytes D. hydrophytes (2009/45 JAMB)
10. I. Adoption of appropriate nocturnal habits III. Adjusting their internal body temperature
II. Burrowing IV. Possession of many sweat pores
Which of the above are ways in which desert animals adapt to extreme heat of the environment?
A. I and IV only B. II and III only C. I and II only D. I, II and III only (2010/34 JAMB)

11. The plant that grow in deserts or very dry areas are referred to as
A. mesophytes B. hydrophytes C. epiphytes D. xerophytes (2013/11 JAMB)

12. One adaptation of Cactus opuntia to conserve water is the reduction of

A. intermodes B. stem to leaves C. leaves to spine D. flower size (2013/47 JAMB)

13. The behavioral adaptation in social insects could best be described as

A. symbiosis B. saphytism C. parasitism D. commensialism (2013/50 JAMB)
14. The stream-lined shape of fishes is an adaptation for
A. obtaining food B. defence and attack C. securing mates D. easy movement (2014/47 JAMB)
15. An example of poikilothermic organisms is a
A. rabbit B. bird C. lizard D. cockroach (2014/48 JAMB)
16. I. Strong winds II. High temperature III. Dry and porous soils.
Which groups of plants are specially adapted to grow under environmental conditions stated above?
A. Thallophytic B. Mesophytes C. Xerophytes D. Hydrophytes (2016/39 JAMB)
17. Which of the following animals is best adapted to desert life?
A. camel B. horse C. leopard D. rat E. tiger (2005/39 Neco Nov)

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18. Which of these is not a structural adaptation of desert plants for water conservation?
A. Broad leaves with many stomata B. leaves reduced into spines
C. scale leaves D. stems and leaves with thick cuticle
E. sunken stomata (2005/19 Neco)
19. Dry, horny scales in reptiles help them to
A. Carryout gaseous exchange B. escape from predator C. facilitate movement
D. look for mating partners E. prevent water loss (2005/43 Neco)
20. Plants with succulent stems and leaves, sunken stomata and deep root systems are
A. epiphytes B. hydrophytes C. mesophytes
D. Pteridophytes E. Xerophytes (2007/3 Neco)
21. Which is NOT an adaptive feature of hydrophytes?
A. Air spaces in tissues for buoyancy B. broadleaves to enhance transpiration
C. Extensive root system for absorption of water D. fibrous roots for absorption of water
E. waxy cuticle on leaves to prevent wetting (2001/41 Neco)
22. Which of the following animals exhibit basking?
A. cat B. cow C. duck D. eagle E. lizard (2018/47 Neco)
23. Plants adapted to live in an arid land environment are called
A. epiphytes B. halophytes C. hydrophytes
D. mesophytes E. xerophytes (2014/15 Neco)
24. A major reason why tilapia fish survives well in fresh water habitat than in a bowl filled with tap water is that
A. it cannot move around in the bowl
B. dissolved oxygen in the fresh water will diffuse into the gills
C. it will starve inside the bowl
D. its gills will be affected by chemicals in the tap water (2000/9 Nov)
25. 6ai. What is ecological tolerance of organisms? (1999/6ai Nov)
26. The adaptations for water conservation in organisms include the following except
A. scales in fishes B. scales on leaves C. thick leaves
D. spine in plants E. succulent stems (1991/53 Nov)
27. Which of the following is an adaptation for flight by birds?
A. long tail feathers B. long legs and neck C. well developed wing feathers and chest muscles
D. well developed toes that end in claws (2004/39 Nov)
28. The Agama lizard excretes uric acid as an adaptation to
A. Feeding B. Egestion C. Conservation D. Egg production (2004/40 Nov)
29. An adaptation of savanna plants for resistance against bush fires is the possession of
A. extensive root system B. sunken stomata C. broad leaves D. thick bark (2006/43 Nov)
30. Which of the following features is not an adaptation for water conservation in plants?
A. leaves reduced to spines B. tiny hairs covering leaf surfaces
C. fleshy stems D. leave with thin cuticle (2006/44 Nov)
31. 4.(a) What is structural adaptation?
(b) Discuss the structural adaptations that enable the following organisms survive in their environment.
(1996/4a, b Nov)

32. Xerophytes possess the following structural characteristics except

A. reduction of leaves into spines B. green succulent stem
C. broad thin green leaves D. hardened, waxy cuticle on leaves (2002/37 Nov)

33. One adaptive feature of plants to both terrestrial and aquatic habitat is the possession of
A. reduced leaves B. extensive root system C. waxy cuticle on leaf surfaces
D. sunken stomata E. Well-developed vascular system (1998/47 Nov)
34. Which of the following is not true about the nature of adaptation in fish?
A. Fishes are coloured to blend with their habitat
B. In general, fishes have light dorsal surfaces
C. Fishes flora weedy waters are striped and usually greenish
D. The bodies of many bottom-dwelling fishes are usually flat
E. Fishes living near the surface of the water are silvery on the ventral surface and dark on the dorsal surface
(1995/58 Nov)

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35. Which of the following are adaptations of animals to aquatic habitats?
A. gills, scaly sin and lungs B. lateral line, streamlined bodies and lungs
C. gills, streamlined bodies and lateral line D. gills, streamlined bodies and spiracle (2000/29 JAMB)
36. Which of the following structural features are adapted for uses other than water conservation?
A. feathers in birds B. scales in animals C. spines in plants D. succulent stems (2000/45 JAMB)

POLLUTION
Pollution is the unfavourable change that occurs in the environment due to the addition of impurities by man, thus
causing danger to either his health or natural resources. Pollution also mean any process or activity that leads to
harmful increase in the quantity of a substance in the environment.

Pollutant
A pollutant is any substance which when introduced into the environment by man may cause the destruction or distort
of the environmental purity thus resulting to harm of living organisms including man.

The parts of the environments which are polluted include the atmosphere (air), the water, and the land.

Major types of pollution

1. Air pollution 2. Water pollution 3. Land (soil) pollution

Air pollution
Air pollution is the release of pollutant such as gases, particles, biological molecules etc. that are harmful to human
health and the environment into the air.

Air pollutant, sources and effects

Sources Pollutant Harmful effect
Motor vehicle Carbon monoxide, carbon (1) Poisonous to man because it combines with
dioxide, nitrogen oxide, sulphur haemoglobin and reduces the ability of the
VI oxide. blood to carry oxygen.
Smoke/soot Burning of substance from (1) Smoke reduces visibility.
industries, machines and coal into (2) If CO2 rises above normally it may cause a global
the air. increase in temperature and affect crops
adversely.
(3) It blackens paint on building.
Industries Dust particles, lead compounds (1) Causes irritation of the respiratory system in
sulphur IV oxide man and animals
(2) Reduces efficiency of photosynthesis by covering
plant leaves.
Mine, city traffic and Dust particles (1) Blackens paint on buildings, cut down sunlight
construction sites reaching green plants.
Agricultural waste Spraying of crops with herbicides (1) Harm the respiratory system of animals, damage
and pesticides some plants.
Air conditioners, Chlorofluorocarbon (CFC) (1) Destroy the ozone layer, the stratosphere.
refrigerators, aerosol N.BThe ozone layer prevents much of the
spray cans ultraviolet rays from reaching the earth’s surface.

Control of air pollution

1. Poisonous gas resulting from industrial emission should be treated or controlled at the source to reduce the
effects.
2. Use of clean energy resources. The use of solar, wind and geothermal energies should be encouraged as they
reduce air pollution at a large level.
3. Avoid using vehicles: People should avoid using vehicles for short distances, rather they should prefer public
modes of transport to travel from one place to another. This not only prevents pollution, but also conserves
energy.
4. The ozone layer must be preserved. This can be done by banning all those harmful substances that react with
the ozone layer and thereby causing its depletion.
5. Trees should be planted and we must take care of the existing trees. Trees absorb CO2 from the atmosphere.
6. All laws regulating air pollution must be obeyed by all companies and citizens.

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Water pollution
Water pollution is the discharge into water body of any substance (usually by man) which may become harmful to
plants and animals in the water and make them unfit for human consumption.

Water in estuaries, lake, rivers and sea may be, polluted by detergents, insecticides, artificial fertilizer, herbicides,
domestic and industrial wastes, crude oil, cleared vegetation and heat (thermal).

S/N Water Pollutant Sources Effects

1. Fertilizers, insecticides, Agricultural waste Encourages undergrowth of water plants which may
herbicides e.t.c block water and decrease water oxygen content,
making water unfit for drinking.
2. Detergents chemical Industrial waste (i) causes death of aquatic organism
waste (ii) It makes water unfit for drinking
(iii) Some chemical pass along food chain and
accumulate in man causing ill – health or death
e.g mercury.
3. Untreated sewage City sewage system (i) It results in offensive odour
channeled into rivers, (ii) It may contain bacteria that cause diseases such
lagoons, e.t.c without as cholera
treatment (iii) It makes water unfit for drinking
(iv) It may stimulate excess growth of water plant.

4. Crude oil (oil spillage) Oil drilling, loading and (i) It destroys aquatic plants and animals
unloading of tankers (ii) It makes water unfit for consumption
(iii) It affects food chain
(iv) It leads to migration of animals
5. Faeces Humans and animals (i) It produces unpleasant odour
(ii) It serves as a medium for the breeding of
pathogens
Control of Water Pollution
1. Government should strictly monitor all industrial waste
2. Effective and proper sewage disposal system should be made available
3. Siting of industries in places far from residential areas
4. Recycling of industrial effluents
5. Adoption of effective techniques to treat the problem of oil spillage
6. Strict measures should be put in place to check the dumping of refuse.
Methods of Purifying Water
The following are methods involved in purifying water:
(i) Boiling
(ii) Filtration
(iii) Distillation
(iv) Addition of chlorine
(v) Sterilization
(vi) Sedimentation

Land Pollution
Land pollution is the dumping of rubbish and chemicals on land by man which makes the land infertile and causing
harm to both plants and animals.

The land is polluted primarily by dumping of refuse. This includes discarded household materials like bottles, plastics,
cans, papers food remnants and in some cases human and animal feaces.

Refuse dumps are sources of unpleasant odour and breeding for many disease vectors and disease causing micro –
organisms. The soil might be polluted by some air pollutant e.g compounds of lead, industrial and agricultural waste
such as herbicides, fungicides, insecticides and pesticides.

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Sometimes, these substances contaminate the soil and may harm the plants grown on such soil.

Refuse is ugly in sight and causes discomfort due to its offensive odour. It also occupies a space which would have
been used for farming.

Indiscriminate dumping of refuse should therefore be discouraged. Refuse must be burnt or buried in proper places.
All refuse should be deposited in a refuse bin.

Noise pollution
Noise pollution is from factory noise, aeroplane, railway engine, car horn and sirens, heavy gun cannon shot, thunder
noise, generator noise, high pitched musical sound from loud speakers e.t.c

Effects of Noise Pollution

1. Loss of hearing
2. Causes emotional disorder and lack of concentration
3. Can cause high blood pressure
4. It causes general irritation
5. It can cause change in behaviours

Control
1. There should be reduction of noise from loud speakers
2. Railways and airports should be sited far away from residential areas
3. There should be installation of sound proof generators
4. Ban on the use of heavy guns must be placed
5. Laws should be made against the use of loud speakers in public places
Example
A constituent of the exhaust gases of motor vehicles which causes serious air pollution is
A. water vapour B. carbondioxide C. carbon monoxide D. oxygen E. ozone (1988/41)
Answer: C – Carbon Monoxide
Example
Which of the following is not a way of reducing air pollution?
A. Sitting factories and from residential areas B. Building tall factory chimneys
C. Passing waste gases absorbers D. Using lead-free petrol in cars E. Recycling tins, cans and bottles (1990/42)
Answer: E – Recycling tins cans and bottles is not a way of reducing air pollution
Example
Which of the following may not contribute to environmental pollution?
A. Solar energy radiation B. Industrial wastes C. Waste disposal
D. Smoke E. Nuclear power plant (1991/45)
Answer: A – Solar energy radiation does not contribute to environment pollution.
Example
Which of the following is a pollutant of air?
A. Oxygen B. Water vapour C. Carbon monoxide D. Nitrogen E. Hydrogen (1992/48)
Answer: C – Carbon monoxide
Example
Which of the following water pollutants may contain organisms that cause dysentery?
A. Pesticides B. Sewage C. Industrial wastes D. Fertilizers E. Crude Oil (1993/38)
Answer: B – Sewage
Example
Which of the following is not a pollution control measure?
A. Penalizing those who dump refuse on water or land
B. Controlling the emission of smoke from automobiles and industries C. Ensuring that there is no spillage of oil
D. Establishing government agencies like Federal Environmental Protection Agency (FEPA)
E. Channeling sewage into streams (1994/45)
Answer: E – Channeling sewage into streams is not a pollution control measure

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Example
3(a) (i) What is Pollution? (ii) Name two pollutants each of air and water
(b) (i) State four effects of water pollution on organisms
(ii) Mention four ways of preventing water pollution in an environment
(c) (i) Name three sources of noise pollution (ii) State three effects of noise pollution on man. (1999/3a, b, c)
Answer:
3ai. Pollution is the release of harmful or toxic substances into the environment either by natural forces, man or
other animals to an extent that causes damage to man and his resources.
ii. Air: Smoke , Dust
Water: Sewage, Chemicals from factories
bi. Effects of water pollution on organisms:
- Aquatic food chain is disrupted.
- Causes death of aquatic animals and plants.
- Encourages bacterial growth which leads to the reduction of the amount of dissolved oxygen in the water.
- It renders water unsafe for domestic use.
ii. Ways of preventing water pollution in an environment:
- Proper sewage disposal.
- Dumping of refuse or petro-chemical by-product into water bodies should be prohibited.
- Establishment of agencies that monitors the disposal of sewage and industrial waste.
- Public enlightenment about the negative effects of water pollution should be done.
ci. Sources of Noise pollution:
- Factory or industrial noise.
- Rail way engine/Locomotion noise.
- Automobile or car horns/sirens.
ii. Effects of Noise pollution to man:
- Loss of hearing.
- High blood pressure.
- Emotional disorder.
Example
Which of the following associations can upset the balance of nature?
A. Epiphitism B. Parasitism C. Symbiosis D. Saprophytism (2001/49) Answer: B – Parasitism
Example
The major pollutant around airport residential areas is
A. oil spillage B. soot C. noise D. dust (2007/42) Answer: C – Noise
Example
The effect of chlorofluorocarbon is
A. reduction of oxygen concentration in the atmosphere B. depletion of the ozone layer
C. screening of ultra violet rays D. increase in carbon dioxide concentration (2007/43)
Answer: B – Depletion of the ozone layer.
Example
The following are greenhouse effect except
A. carbon dioxide B. chlorofluorocarbon C. methane D. oxygen (2010/38) Answer: D – Oxygen
Example
Use the substances listed below to Answer: question 34 and 35
I. Fertilizer II. Insecticides III. Sewage IV. Crude oil V. Sulphur dioxide
The atmosphere can be polluted by
A. I only B. III only C. IV only D. II and V only (2014/34) Answer: C – IV = Sulphur dioxide only
Example
Which of the substance constitute domestic waste?
A. I only B. III only C. IV only D. II and V only (2014/35) Answer: B – III = Sewage only
Example
(b) (i) State three sources of noise pollution.
(ii) List two ways by which noise pollution can be reduced. (2008/3bi, ii)
Answer:
3bi. Sources of Noise Pollution: 3bii. Ways by which noise pollution can be reduced:
- Automobile or car sirens and horns. - Citing of factory and industries far from residential areas.
- Factories or industrial noise. - Regulating the use of horns and sirens.
- Railway engine or locomotion noise.

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Example
Which of the following causes pollution
A. Consumption of canned foods B. The addition of fertilizer to farm land
C. Respiration of living organisms D. Burning of refuse (1988/46 JAMB)
Answer: D – Burning of refuse.
Example
Which of the ways of controlling bilharzia can result in pollution?
A. Clearing water weeds on which the snails feed B. Treating infected people with drugs
C. Preventing contamination of water by infected urine and faeces
D. Applying chemical to kill the snails (1989/43 JAMB)
Answer: D – Applying chemical to kill the snails can cause pollutions.
Example
Which of the following constitutes pollution?
A. Droppings from birds B. Loud disco music C. A pack of cigarettes D. Refuse in an incinerator (1990/47 JAMB)
Answer: B – Loud disco music is a type of noise pollution.
Example
Sources of air pollutants are
A. Industrial chimneys, burning fossil oils and river dams B. Sulphurdioxide, acid rain and pesticides
C. Sulphurmines, vehicle exhausts and aerosols D. sewage, smoke and old vehicles (1991/48 JAMB)
Answer: C – Sulphurmines, vehicle exhausts and aerosols.
Example
Environmental pollutants which can work through the media of water, soil and air include.
A. Carbon monoxide B. noise C. sulphur (IV) oxide D. smoke (1995/38 JAMB)
Answer: C – Sulphur(iv)oxide
Example
Which is the most important pollutant of the marine environment in Nigeria?
A. insecticides B. sewage C. oil D. inorganic fertilizers (1997/40 JAMB)
Answer: C – Oil is the most important pollutant in the marine environment because of its numerous economical
benefits.
EXERCISE 23.40
1. The pollutants that contribute to the depletion of the ozone layer in the atmosphere are
A. chlorofluoro carbons B. oxides of sulphur C. oxides of carbon D. radioactive materials (2000/40 JAMB)
2. Which of the following is NOT regarded as a pollutant on land or in the air?
A. Smoke B. Noise C. Sulphur dioxide D. Carbon monoxide E. Nitrogen (1984/43 JAMB)
3. The most effective method of dealing with non-biodegradable pollutants, is by
A. burying B. dumping C. inceneration D. recycling (2003/34 JAMB)
4. The major cause of global warming is the
A. burning of fossil fuels B. construction of dams C. use of electricity D. exploration of space (2009/38 JAMB)
5. One of the ways of controlling noise pollution in urban areas is
A. by planting trees on both sides of the road B. by wearing ear devices
C. by sitting industries away from residential area
D. that fuel should be completely combusted by engines (2014/37 JAMB)
6. A constituent of the exhaust fumes from electricity generating sets which causes serious air pollution is
A. Ozone B. Carbon(IV)oxide C. Carbon (II)oxide D. Water vapour (2014/38 JAMB)
7. A pollutant that is mostly associated with acid rain is
A. fluorine B. carbon (IV)oxide C. nitrogen(IV)oxide D. Ozone (2014/40 JAMB)
8. All these are methods of controlling pollution EXCEPT
A. continuous felling of trees B. legislation by government
C. recycling of waste materials D. sitting of industries away from residential areas
E. treatment of sewage (2005/41 Neco Nov)
9. Which of these pollutants can cause mutation?
A. agricultural wastes B. industrial wastes C. nuclear fallouts
D. chlorofluorocarbons E. untreated sewage (2005/47 Neco Nov)
10. Which agricultural activity could give rise to a greenhouse effect?
A. bush burning B. bush clearing C. deforestation D. over-cropping E. over grazing (2001/36 Neco)

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11. Which pollutant is likely to cause cholera?
A. agricultural wastes B. Industrial wastes C. nuclear fallouts
D. oil spillages E. Untreated sewage (2001/37 Neco)
12. The following are air pollutants except
A. dust B. smoke C. noise D. sulphur dioxide (2000/49 Nov)

13. Which of the following statements about water pollution is not correct? It
A. May be caused by oil spillage B. may be caused by untreated sewage
C. is dangerous to fishes D. may be caused by fertilizers
E. increases the amount of oxygen in the water (1996/46 Nov)
14. The major pollutant of residential areas close to the airport is
A. dust B. noise C. oil spillage D. smoke (2019/37 PC II)
15. 4.(a) Explain the following terms: (i) Pollution;
(b) List three pollutants each of (i) Water; (ii) Air.
(c) State five ways each of preventing: (i) water pollution; (ii) air pollution (2011/4a, b, c Nov)

16. An air pollution that damage plants is

A. insecticide B. fertilizer C. sulphur dioxide D. sewage (2013/43 Nov)
17. Which of the following is a characteristic of sewage pollution along a river? Increase in bacterial population
and
A. increase in concentration of dissolved oxygen B. unaltered concentration of dissolved carbon dioxide
C. decrease in concentration of dissolved oxygen
D. decrease in concentration of dissolved carbon dioxide (2002/42 Nov)

18. The term pollutant means a substance that

A. can be used to send man to sleep during surgical operations B. can purify the surrounding air
C. Upsets the balance of the environment and can be harmful to organism D. is produce only in industries
E. is useless to plants and animals in their environment (1998/45 Nov)
19. Pollution of the environment can be controlled by the following except
A. treatment of industrial waste before release B. proper disposal of domestic wastes
C. encouraging population increase D. educational programme on the bad effects of pollution
E. citing industries away from residential areas (1995/45 Nov)
20. (a) (i) What is pollution
(ii) Complete the table below in your Answer: booklet:
Pollutant Two sources Three sffects on man Two ways of controlling
Carbon dioxide

Sulphur dioxide

(b) State four ways in which oil pollution can be avoided. (2005/3a-b Nov)
21. (a) (i) What is pollution? (ii) State four pollutants of water
(b) Describe the effects of each of the pollutants named on aquatic organisms. (2007/4a, b)

22. (c) State three effects each of the following-pollutants on humans: (i) smoke (ii) sewage. (2008/3c)

Conservation of Natural Resources

Earth’s natural resources include air, minerals, plants, soil, water and wild life. Conservation of these natural resources
is the care and protection of these resources so that they can persists for future generation.

Natural resources can be renewable and non – renewable.

1. Renewable natural resources are resources that are recoverable. Examples are rain, animals, plants, water,
food and soil.
2. Non – renewable natural resources are resources which cannot be replaced when the original stock is
exhausted. Examples are mainly mineral resources like petroleum, coal, tin, copper e.t.c.

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Needs for Conservation of Natural Resources
1. Prevention of wanton destruction of natural environment.
2. Promoting sensible use of natural resources
3. Preservation of rare and valuable species of animals and plants for future generation or to save them from
extinction or permanent destruction
4. Preservation of naturally beautiful sceneries and landscapes for their aesthetic value
5. Promotion of the recycling of some scarce mineral resources e.g water
6. To prevent the destruction of natural ecosystem; This will allow the organisms in the ecosystem to survive
7. Forest which provides medicinal material must be conserved to ensure easy availability and continued
existence
8. Natural resources e.g wild life, forest, minerals e.t.c provides basis for research purposes
Natural Resources to be conserved
1. Forest: These include important species of trees, shrubs, herbs, grasses and other related forest products.
2. Wild life: These are mostly the wild animals found in the forest.
3. Soil: These include the soil texture and soil microbes (Soil flora and fauna).
4. Water: These include the water bodies, aquatic plants and animals (mainly fishes).
5. Minerals: These are important elements found in water, atmosphere and on the earth crust.
Methods of Conserving Wild life
1. Establishing of zoological gardens.
2. Establishment of game or Natural (forest) reserves.
3. Control of hunting to prevent extinction of some animal species.
4. Poaching or killing of animals should be checked.
5. Prohibition of bush burning as this might result in the migration or displacement of wildlife.
6. Afforestation should be encouraged while deforestation should be prohibited.
7. Education: This involves making people aware of the need to protect and preserve the environment. through
schools, youth organization and the media.
8. Preventing pollution of aquatic bodies so as to limit the destruction of aquatic life.
Methods of Conserving Water
1. Trapping or storage of water in tanks or wells.
2. Damming of rivers to allow for more management of water.
3. Treatment and recycling of used water.
4. Economical use of water E.g turning off of tap water after use in-order to prevent unnecessary wastage.
5. Encouragement of tree planting as it provides vegetation cover, reduces evaporation and promotes water
retention.
6. The existence of vegetation also bring about formation of rain fall.
7. Reduction or prevention of water pollution by ensuring effective waste disposal.
Method of Conserving Forest
1. Cutting of trees without destroying the under growth
2. Encouragement of Afforestation by planting of new trees
3. Discouragement of deforestation by preventing bush burning and uncontrolled felling of forest trees
4. Prevention of plant pest and disease
5. Establishment of forest reserves
6. Establishment of public awareness programs that will educate the public on the value of forest and the
importance of conservation.
Method of Conserving Soil
10. Overgrazing should be prevented as it may lead to soil erosion.
11. Prevention of indiscriminate felling of trees or deforestation which exposes the soil to erosion.
12. Better farming systems like crop rotation should be adopted in order to prevent erosion, leaching and water
logging or acidity.
13. Land pollution should be discouraged for effective functioning of soil organisms.
14. Avoidance of clean clearing which may expose the soil to erosion.
15. Prevention of bush burning which may expose the soil to erosion.
Method of Conserving Mineral Resources
1. There should legislation against indiscriminate mining of mineral resources.
2. Effective and efficient extraction method of mining should be adopted to prevent wastage.
3. There should be effective and efficient utilization of available mineral resources for man’s use.
4. Over – dependence on particular mineral resources should be discouraged as this can lead to the depletion of
such mineral resources.
5. There should be proper pricing of mineral resources and their by-products to ensure maximum value for the
mineral products.
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Importance/benefits of Conservation of Natural Resources
A. Benefit of Wildlife Resources
1. It provides food for human consumption e.g meat, fish, and eggs e.t.c.
2. It helps in the generation of revenue for government.
3. it can serve as tourist centers for pleasure and relaxation.
4. It provides research work for scientists.
5. It can generate employment for some people.
B. Benefits of Water Resources Conservation
1. It serves as a source of food supply e.g fish, prawn, and crayfish e.t.c.
2. It is used for Hydro Electric Power (H.E.P) generation which provides electricity e.g kainji dam.
3. Water is useful for agricultural purposes i.e. irrigation.
4. Water serves as a medium of transportation in rivers, lakes and oceans.
5. Water is important for domestic and industrial uses e.g drinking, washing, cooking e.t.c.
6. Water can be used for recreational and tourist purpose.
7. Water provides employment for people e.g. fisher men, canoe or ship builders e.t.c.
C. Benefits of Forest Resources Conversation
1. Forests are resources of food supply e.g. fruits, vegetable, meat e.t.c.
2. Forests are sources of timbers for construction purposes.
3. Forest provides medicinal herbs.
4. They are sources of (fuel) firewood used for cooking.
5. Forests are the home or habitat of wild animals which can serve as game reserves.
6. Forest provides employment for some people e.g. forest guards, timber men, and hunters.
7. Forests provide raw materials for industries e.g. cotton, rubber, ropes and twine, latex, timber, e.t.c.
8. Forest can serve as centre of tourism.
9. Forest can also serve as wind break.
D. Benefits of Soil Resources Conservation
1. Soil supports agricultural or farming activities.
2. Soil also supports forest and its resources.
3. Soil supports wildlife resources.
4. It is the home of some organisms.
5. It supports the growth of valuable wood for building and furniture making.
6. Building are erected on the soil.
7. Mineral resources are obtained from the soil.
E. Benefits of Mineral Resources Conservation
1. Mineral resources provide fuel e.g. coal, petroleum and natural gas for use.
2. They are used for construction purposes e.g. iron, zinc, aluminum e.t.c.
3. Some are used for industrial development e.g. diamond, iron, copper, silver e.t.c.
4. Some are sources of ornamentals e.g. gold, silver, bronze e.t.c.
5. Minerals are sources of foreign exchange.
6. They also provide employment e.g. miners, drillers, marketers e.t.c.
Problems and Difficulties of Natural Resources Conservation
1. Bush burning: This destroys timbers, young trees, seeds and the humus rich soil. The natural habitats of
animals are destroyed: This may lead to death of some animals.
2. Limited land area for development leads to destruction of forest for the establishment of industries, road e.t.c.
3. Limited source of energy: The poor people in the society destroy forests for firewood.
4. Over fishing.
5. Over grazing leads to the destruction of soil structure.
6. Over hunting of animals can also lead to the extinction of animals.
7. Inadequate guards to protect the resources.
8. Insufficient money and equipment.
9. Poaching: This is a practice of illegal killing of animals for commercial purposes.
Ways of ensuring the conservation of Natural Resources
1. Establishment of agencies for conservation: Agencies are established to ensure that these natural resources are
conserved e.g. preservation of wild life, forest resources, water resources, soil and mineral resources.
The agencies are;
A. Nigerian conservation foundation
B. Federal Environmental Protection agency (F.E.PA)
C. River Basin Development Authorities (R.B.D.A)
D. Ministries of agriculture
E. Department of wildlife conservation
F. Forest department
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2. Establishment of game reserves or national parks: The game reserves serve for the protection of wild life,
rare or endangered species and for recreational purposes and scientific purposes.
Some game reserve in Nigeria includes;
1. Yankari game reserve in Bauchi state
2. Olumu forest reserve in kwara state
3. Zamfara forest reserve in Zamfara state
4. Mamu river forest in Anambra state
5. Shasha river forest in Ogun state
6. Borgu game reserve in Niger state

3. Conservation Education: This serves to inform the public about the need to conserve natural resources.
4. Setting standard for pollution control
5. Making of conversation laws and decree: These laws are made by the government to regulate the felling of
trees and hunting of endangered species.
Examples:
Which of the following steps would not be taken to protect or conserve fishing grounds from over-exploitation?
A. Use of nets with all sizes of mesh B. Use of nets with a particular mesh size
C. Ban on harvesting of some species D. Regulating the size of ships allowed into fishing grounds
E. Limiting the period of fishing in the waters (1988/42)
Answer: A – Use of nets with all sizes of mash would not be taken to protect or conserve fishing ground from over
exploitation.
Example
Which of the following is not part of the objectives of conservation of natural resources?
A. To eliminate wild animals in order to enable other plants and animals survive
B. To use our resources on sustained yield basis C. To guard against indiscriminate killing of plants and animals
D. To guard against the extinction and exhaustion of natural resources E. To protect the environment (1988/43)
Answer: A – To eliminate wild animals in order to enable other plant and animal survive is not part of the objectives
of conservation of natural resources.
Example
(a) Define the term “Conservation”
(b) State three reasons for conservation
(c) List four methods of conserving each of the following: (i) water (ii) wildlife (iii) forest
(d) Mention three forest or game reserves in Nigeria. (1997/4a, b, c, d)
Answer:
a. Conservation can be defined as the preservation of natural resources from loss or waste, through wise or sensible
use to ensure their continuous availability and to preserve their original nature.
b. Reasons for conservation:
- It allows for the continued use of natural resource for man’s benefit.
- It preserve rare and valuable species of plants and animals for future generation.
- Promote sensible use of natural resources.
c. Methods of conserving the following:
i. Water:
- Trapping or storing of water in tanks and wells.
- Treatment and recycling of used water.
- Encouragement of Tree planting as it provides vegetation cover, reduces evaporation and promotes water retention.
- Damaging of rivers to allow more effective management of water.
ii. Wild life: Forest:
- Prohibition of bush burning. - Prohibiting bush-burning.
- Establishment of zoological gardens. - Establishment of forest reserves.
- Establishment of game/forest reserves. - Encourage afforestation.
- Prohibiting killing or poaching of animals - Prohibition of indiscriminate felling of trees.
in game reserves.

d. Forest/Game reserves in Nigeria: Olomu Forest Reserve in Kwara State,

Yankari Game Reserve in Bauchi State, Sakpoba Forest Reserve in Edo State.
Example
Which of the following is not a way of conserving natural resources?
A. Controlling farming practices B. Establishing forest reserves
C. Establishing of parks and gardens D. Encouraging poaching in game reserves
E. Protecting the endangered species (1991/51)
Answer: D – Encouraging poaching in game reserves is not a way of conserving natural resources.
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Example
The adaptations for water conservation in organisms include the following except
A. scales in fishes B. scales on leaves C. thick leaves D. spine in plants E. succulent stems (1991/53)
Answer: A – Scales in fishes
Example
The rational and prudent use of natural resources is known as
A. preservation B. conservation C. utilization D. management (2016/37)
Answer: B – Conservation is the rational and prudent use of natural resources.
Example
Which of the following natural resources cannot be conserved?
A. Soil B. Water C. Wildlife D. Air (2016/38) Answer: D – Air
Example
Which of the following actions supports conservation? To
A. protect endangered species B. preserve trees for timber
C. permit hunting activities D. provide income for the governments (2016/39)
Answer: A – Protection of endangered species is a way of supporting conservation.
Example
The following agencies are responsible for conservation in Nigeria except
A. Forestry Department B. Nigerian Conservation Society
C. Games Reserve Authority D. Nigerian Red Cross Society
E. Ministry of Agriculture and Natural Resources (1993/45)
Answer: D – Nigeria Red Cross Society is not an agency involved in conservation
Example
The largest game reserve in Nigeria is the
A. Kainji Game Reserve in Niger State B. Zamfara Forest Reserve in Sokoto State
C. Yankari Game Reserve in Bauchi State D. Borgu Game Reserve in Niger State
E. Oban Hills Game Reserve in Cross River State (1993/46)
Answer: C – The Yankari Game Reserve situated in Bauchi state, is the largest game reserve in Nigeria
Example
Which of the following measures does not ensure conservation?
A. Establishing forest and game reserves B. Encouraging people to plant trees
C. Founding societies that promote conservation D. Enacting conservation laws and bye-laws
E. Enclosing fishes in ponds where they will not be stolen (1994/14)
Answer: E – Enclosing fishes in ponds where they will not be stolen is not a method of ensuring conservation.
Example
Which of the following can cause desert encroachment?
A. Afforestation B. Irrigation C. Planting of trees
D. Establishment of game reserve E. Overgrazing (1994/18) Answer: E – Overgrazing
Example
Which of the following is not a way of conserving natural resources?
A. Adopting good farming practices B. Establishing of forest reserves
C. Establishing game reserves D. Encouraging poaching
E. Protecting the endangered species (1996/48)
Answer: D – Encouraging poaching is not a way of conserving natural resources.
Example
The following are useful measures for conserving forest except
A. preventing and controlling accidental forest fire
B. encouraging the use of charcoal for industrial and domestic purposes
C. combating and preventing plant diseases
D. reafforestation of depleted forest
E. protection of young growing trees (1995/47)
Answer: D – Encouraging the use of chemical for industrial and domestic purpose
Example
The following practices are aimed at soil conservation except
A. contour ridging B. application of manures C. strip cropping D. bush clearing E. crop rotation (1995/48)
Answer: D – Bush clearing.

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Example
Conservation may be promoted by
A. encouraging tree planting B. systematic deforestation
C. overgrazing of pastures D. unabated bush burning (2008/44)
Answer: A – Encouraging tree planting.
Example
Which of the following is not a means of conserving natural resources?
A. Establishment of national parks B. Selective logging C. Building of dams D. Bush burning (2000//54)
Answer: D – Bush burning is not a means of cvonserving natural resources
Example
Which of the following resources is non-renewable?
A. forest B. wildlife C. mineral deposits D. water (2000/55)
Answer: C – Mineral deposits
Example
Forest conservation includes the following except
A. prevention of bush fires B. extensive felling of forest trees
C. replacing the harvested trees by planting seedlings D. selective exploitation of forest trees (2003/47)
Answer: B – Extensive felling of forest trees is not a way of conserving forest.
Example
Which of the following natural resources is most readily available to all organisms?
A. Oil B. Water C. Air D. Food (2015/37)
Answer: C – Air
Example
Soil erosion could be prevented by
A. flooding a farmland B. cover cropping C. deforestation D. leaving the soil bare (2015/39)
Answer: B – Cover cropping is a me
Example
The following are natural resources except
A. rubber A. soil C. water C. cellophane (2004/47)
Answer: C – Cellophane is not a natural resources

Example
Which of the following practices does not contribute to intensive depletion of forest resources in West Africa?
A. use of powerful tools for felling trees B. regrowing of forest trees
C. clearance of forests for cash crops D. use of fire for hunting in forests (2004/48)
Answer: B – Regrowing of forest trees is one of the ways of promoting forest conservation. It does not contribute to
the intensive depletion of forest resources.
Example
Tropical rain forests can be conserved by the following practices except
A. agroforestry B. deforestation C. shifting cultivation D. crop rotation (2004/49)
Answer: B – Deforestation
Example
Which of the following is not a means of conservation?
A. Controlling excessive deforestation B. Prevention of poaching
C. Replacing harvested mature trees with seedlings D. Burning of vegetation before cropping (2005/47)
Answer: D – Burning of vegetation before cropping
Example
An effective management of natural resources to ensure their continued yield from generation to generation may
involve all the following except
A. protection of wildlife B. prevention of habitat destruction
C. biological control of pests D. disposal of raw sewage into the sea (2006/49)
Answer: D – Disposal of raw sewage into the sea

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Example
3(a) Explain briefly the following terms:
(i) renewable natural resources (ii) non-renewable natural resources.
(b) Give two examples each of: (i) renewable natural resources; (ii) non-renewable natural resources.
(c) State five ways of conserving forests.
(d) State four effects of adding animal manure to garden soil. (2018/3a-d)
Answer:
3ai. Renewable natural resources: These are materials that can be regenerated, recycled or reused after they have been used.
ii. Non-renewable natural resources: These are materials that are impossible to be regenerated or recycled after they have
been depleted.
bi. Water, air
ii. Gold, petroleum
c. Ways of conserving forest: d. Effects of adding animal manure to garden soil
- Prevention of forest fire. - It improves soil fertility.
- Prevention of indiscriminate felling of trees. - Prevents soil erosion.
- Use of pesticide to kill pest and control plant disease. - It provides nitrates for plants.
- Enacting of laws that control excessive clearing of forest. - It improves the water holding capacity of
- Enlightening the public on the dangers of deforestation. the soil by binding the soil particles together.
Example
4.(a) Explain the term, conservation of natural resources.
(b) (i) List seven methods of soil conservation.
(ii) Name four other natural resources that may be conserved.
(c) State three factors, which negatively affect conservation of forest in West Africa. (2006/4a, b, c)
Answer:
4a. Conservation of natural resources is the prevention of natural resources from loss or waste through wise or sensible uses
to ensure the continuous availability and to preserve their original nature.
bi. Methods of soil conservation: bii. Natural resources that may be conserved:
- Plant grass/legumes - Wild life
- Avoiding bush burning - Water
- Planting trees (afforestation) - Forest
- Preventing over grazing - Minerals
- Planting of cover crops
- Practicing shifting cultivation or crop rotation
- Planting crops on ridges across slopes.
c. Factors which negatively affect conservation of forest in west Africa :
- Indiscriminate felling of trees.
- Lack of afforestation
- Non-enforcement of conservation laws.
Example
Which of the following actions do not reflect the objectives of conservation of natural resources?
A. Protection of the ecosystem B. Saving some species from extinction
C. Elimination of some wild animals to enable others survive D. Prevention of indiscriminate killing of organism (2007/51)
Answer: C – Eliminating of some wild animals to enable others survive.
Example
The following effects are associated with deforestation except
A. gully erosion B. extinction of plants species C. migration of wildlife D. increase in rainfall (2010/42)
Answer: D – Increase in rain fall.
Example
The main reason for the conservation of wildlife is to
A. create national parks for recreation B. maintain ecological balance in communities
C. prevent hunters from being cruel to animals D. save some species from extinction (2010/43)
Answer: D – Save some species from extinction.
Example
Which of the following activities promotes forest conservation? It
A. Lumbering B. Use of firewood for cooking C. Afforestation D. Production of paper (2011/49)
Answer: C – Afforestation is one of the ways of promoting forest conservstion
EXERCISE 23.41
1. The primary cause of species endangerment is
A. disappearing habitats B. increase in temperature C. acid rain D. exposure to hazardous wastes (2012/49)
2. 3(a) Explain briefly the following terms; (i) conservation (ii) endangered species
(b) State (i) five reasons why conservation of forest is important;
(ii) Four ways by which forest reserves can be conserved. (2012/3a, b)
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3. (c)(i) What is Eutrophication? (ii) State two causes of eutrophication. (2013/4ci, ii)
4. Which of the following practices is not used in conserving water?
A. afforestation B. damming C. deforestation D. reforestation (2017/41)
5. Which of the following resources cannot be renewed?
A. Air B. Petroleum C. Food crop D. Soil (2017/42)
6. The following are methods of soil conservation EXCEPT
A. contour terracing B. strip cropping C. contour ploughing D. mixed grazing (1986/49 JAMB)
7. Farmers practice crop rotation because it
A. helps to prevent soil erosion B. allows two crops to be planted at the same time
C. helps to conserve soil fertility D. is an alternative to shifting cultivation (1989/48 JAMB)
8. Soil fertility can be conserved and renewed by
A. yearly monocropping B. crop rotation and cover crops
C. bush burning to remove unwanted debris D. avoiding artificial manures (1993/43 JAMB)
9. Water loss is regulated in plants and animals by both the
A. scales and skin B. scales and the hair
C. thick leaves and the feathers D. leathery cuticle and the feathers (1997/46 JAMB)
10. Soil fertility can best be conserved and renewed by the activities of
A. microbes B. earthworms C. man D. rodents (2003/35 JAMB)
11. Which of the following animals is most adapted for water conservation?
A. Earthworms B. Mammals C. Flatworms D. Insects (2009/47 JAMB)
12. The loss of soil through erosion can be reduced by
A. watering B. crop rotation C. manuring D. irrigation (2010/38 JAMB)
13. The structural adaptation of desert plants for water conservation is
A. broad leaves with numerous stomata B. spongy mesophyll
C. spiny leaves D. prominent stomata in leaves (2013/14 JAMB)

14. The best way of protecting natural resources is by

A. creating game and forest reserve B. enforcing conversion laws
C. embarking on tree planning D. prohibiting lumbering in plant reserves (2000/53 Nov)
15. Endangered species, are organisms that ought to be
A. hunted B. killed C. poached D. protected (2020/37 PCI)
16. 4a. List four:
i. Natural resources that should be conserved apart from forests,
ii. Conservation agencies or societies.
b i. State five benefits derived from forests and name two forest game reserves in Nigeria.
ii. Mention five factors affecting conservation of natural reserves. (1999/4a & b Nov)
17. Which of the following natural resources is non-renewable?
A. Soil B. Water C. Solid mineral D. Wildlife (2011/42 Nov)
18. Which of the following occurrences is not an advantage of forest conservation?
A. Increased rainfall B. Purification of the atmosphere
C. Production of timber D. Preservation of natural habitats (2011/43 Nov)
19. Importance of conservation of wildlife includes the following except
A. generation of income through tourism B. preservation of natural habitats.
C. generation of income the through sale of ivory D. maintaining the balance of the ecosystem(2011/44 Nov)
20. Which of the following is not a way of conserving natural resources?
A. Controlling farming Practices B. Establishing forest reserves
C. Establishment of parks and gardens D. Encouraging poaching in game reserves
E. Protecting the endangered species (1991/51 Nov)
21. Conservation of forest in West Africa is a major problem. Which of the following statements best explains this?
A. construction of roads B. dependency on forest trees for fuel
C. use of trees for furniture D. lack of education for all (2006/45 Nov)
22. Which of the following resources is renewable?
A. petroleum B. coal C. iron D. trees (2006/46 Nov)
23. Which of the following farming practices would prevent soil erosion?
A. rotation of crops B. application of artificial fertilizers
C. cover cropping D. burning vegetation before cropping (2013/47 Nov)
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24. A biodegradable substance is one that is
A. easily decomposed by microorganism B. easily decomposed in the stomach
C. of no biological importance D. capable of duplication (2002/39 Nov)
25. With conservation and proper management of natural resources, the following can be achieved except
A. prevention of pollution B. prevention of habitat destruction C. depletion of natural resources
D. both renewable and non- renewable resources can be used Again and again (2002/49 Nov)
26. Conservation of natural resources may not include
A. recycling of empty cans or bottles B. setting up a game reserve
C. finding new energy sources D. over-fishing the seas and lakes (2004/47 Nov)
27. Which of these measures cannot be used to achieve conservation of natural resources?
A. Using all resources properly B. Using substitutes for non-renewable resources
C. Recycling used materials or wastes D. Avoiding recycling material because it is expensive
E. Discovering other acceptable energy sources (1995/53 Nov)
28. Which of these is not an adaptation for conservation of water in plants?
A. Possession of thick cuticle by the leaves B. Presence of broad leaves
C. Shedding of leaves D. Presence of thick bark E. Reduction in size of leaves (1997/45 Nov)
29. What is NOT a benefit of conservation of natural resources?
A. permits nature studies B. preserves the beauty of nature C. prosecutes poachers
D. Protect endangered species E. sources of revenue earning (2001/59 Neco)
30. The following practices are adopted in the conservation of tropical rain forest except
A. afforestation B. creation of game reserve C. creation of forest reserve
D. re-afforestation E. deforestation (2008/59 Neco)
31. b. (i) List five methods of soil conservation. (2014/3bi Neco)
32. Mention two ways of conserving wildlife. (2018/4bii Neco)
REVISION EXERCISE
1. Which of the following measure does not ensure conservation?
A. establishing forest and game reserves B. encouraging people to plant trees
C. founding societies that promotes conservation D. enacting conservation laws and bye – laws
E. enclosing fishes in ponds where they will not be stolen (1994/14)
2. Which of the following is not a conservable natural resources
A. water B. sunlight C. forest D. soil E. minerals (1994/49)
3. Wild life conservation is enhanced by
A. enacting laws to encourage poaching B. discouraging elimination of endangered species
C. encouraging creation of satellite hunting unit
D. suppressing the activities of wild life conservation agencies (2002/47)
4. Which of the following actions do not reflect the objectives of conservation of natural resources?
A. protection of the ecosystem B. saving from species from extinction
C. elimination of some wild animals to enable others survive
D. prevention of indiscriminate killing of organisms (2007/51)
5. Conservation may be promoted by
A. encouraging tree planting B. systematic deforestation
C. overgrazing of pastures D. unabated bush burning (2008/44)
6. The main reason of the conservation of wild life is to
A. create national parks for recreation B. maintain ecological balance in communities
C. prevents hunters from being cruel to animals D. save some species from extinction. (2011/43)
7. Which of the following promotes forest conservation
A. lumbering B. use of fire wood for cooking C. afforestation D. production of paper (2011/49)
8. Which of the following actions supports conservation?
A. protect endangered species B. preserve trees for timber
C. permit hunting activities D. provide income for the government (2016/39)
9. The establishment of game reserve and parks is a method of
A. conserving natural resources B. cultivating game
C. controlling pollution D. cultural awareness (2017/40)
10. Which of the following practices is not used in conserving water
A. afforestation B. damming C. deforestation D. reforestation (2017/41)
11. Which of the following resources cannot be renewed
A. air B. petroleum C. food crop D. soil (2017/42)

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Evolution (History of Life)
Evolution is a process of gradual development of characteristics of plants and animals over many generations.
The history of life has been explained by diverse theories. The major theories accounting for the origin of life on earth
are:
i. Life was created by a supernatural being at a particular time (special creation);
ii. Life arose from non-living matter on numerous occasions by a process of spontaneous generation.
iii. Life has no origin (steady-state).
iv. Life arrived on this planet from elsewhere (cosmozoan);
v. Life arose according to chemical and physical laws (biochemical/organic evolution).

The theory of organic evolution states that:

1. The first living organisms is believed to have come from certain molecules that combined together to form the
first living things about billions of years ago.
2. Various organisms evolved from the first living organism.
3. The complex organisms evolved from the simple organisms.
4. All organisms change from generation to generation, producing descendants with new modifications.
5. These living organisms are related to each other in one way or the other.

From the above theory, Organic evolution can be described as the series of gradual and adaptive changes which living
organisms had undergone in response to changes in environment.

EVIDENCE OF EVOLUTION
1. Evidence from fossils: Fossils are the preserved remains or traces of animals, plants and other organisms
from the past. Fossils are important evidence of evolution. The age of a fossil can be determined by scientific
technique such as radio – isotope dating. The study of fossil is called palaeontology. The study of fossils has
shown that.
(a) Fossils are not found in rocks more than 600 million years old. This implies that there were not living
organisms then or such organisms did not form fossils.
(b) Fossils appear in other rocks of different ages. This gives an idea of the order in which living thing appeared
on earth. Fossils are normally preserved in sedimentary rocks. Fossil records can also be referred to as
geological, paleontological, archeological or historical record.

2. Evidence from comparative anatomy: Comparative anatomy is the study of similarities and difference in
the anatomy of different species. It provides evidence for organic evolution in the sense that:
(a) There are structural similarities between all organisms e.g. all organisms have cellular structure. This
similarities show that the organisms evolved from the same ancestor.
(b) Presence of vestigial organs: Certain homologous structures in some species have no apparent function and
are described as vestigial organs. Examples includes the appendix in man, the vertebrae of the human coccyx.
Posterior auricular muscle of the human ear. These vestigial organs such as appendix in man show that organs
were present and useful in ancestors from which the organisms evolved. Infact, it would be very difficult to
explain the occurrence of vestigial organs, without reference to some process of evolution.

3. Embryological evidence: The development of vertebrates embryos are similar e.g. the embryo of man in the
womb at different stages of development resembles embryos of fish, amphibians and reptiles. The presence of
gill slits like those of fish, two chambered heart like that of reptiles are obvious facts to show that human
being evolved through the fish, amphibians, reptile and mammal lineage. Another example is the birds which
have no teeth yet their embryo have tooth buds. The presence of tooth buds proves that they have descended
from ancestors that had teeth. The above examples explains the biogenetic law which states that the stages an
animal embryo undergoes during development are a chronological replay of that specie’s past evolutionary
forms in other words, “ontogeny (the development of an organism) recapitulates phylogeny (evolution of
that organism)”
4. Physiological evidence and comparative physiology
Enzyme and hormones are similar in many groups of an animal e.g. trypsin is found in protozoa and mammals
(man).

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 Amylase is also found in majority of animals. The actions of these two enzymes are similar in all animals.
Thyroid hormone is present in all vertebrate and studies have shown that the thyroid hormone of vertebrate is
exchangeable among them. E.g. the thyroid hormone from beef has been used successfully to treat human
thyroid deficiencies. This proves that all vertebrates descended from a common ancestor.
Other physiological evidence is the presence of ATP in all organisms. DNA is universal in all organisms.
Respiration is also the same in all organisms.
5. Evidence from cytology: Electron microscope has shown that the cell structures (including all organelles) are
similar in all living organisms. This is a proof that all living organisms evolved from a common ancestor with
similar structures.
6. Evidence from plant and animal breeding.

7. Evidence from geographical distribution.

ADAPTIVE RADIATION, CONVERGENT & DIVERGENT EVOLUTION
Adaptive radiation: This is the process by which a particular specie evolves and gives rise to many descendant
species that occupy different ecological niches.
Consider for example a family consisting of four children, having the same parents and origin, grew under the same
circumstances and moved to different regions for a better opportunity. Now each of them has their individual
adaptation according to their lifestyle and place they stay cuurently. It is seen here that the lineage splits and radiate
different characteristics.
The phenomenon of adaptive radiation was first observed by Darwin when he travelled to a place called Galapagos
Island. There he observed that there were finches with different types of beaks. So, he concluded that all of these
finches radiated on the same island from a single ancestor Finch. All of these finches developed beaks according to the
kind of food available to them. Hence, they evolved from the conventional seed-eating finches to vegetarian and
insectivorous finches. They later came to be known as Darwin’s finches.

Note: The significance of adaptive radiation is that it suggests the existence of divergent evolution based on
modification of homologous structure.

Evolution of Darwin’s finches

Convergent evolution: This is the evolution toward similar characteristics in unrelated species, resulting from
adaptations to similar environmental conditions. These unrelated species posses similar structures, physiological
processes or mode of life that do not have any close phylogenetic links but yet shows adaptation in performing
similar functions. Such structures are described as analogous.

The existence of analogous structures suggests the occurrence of convergent evolution. Examples of analogous
structures include the eye of vertebrate & cephalopod mollusks (squids and octopuses), the jointed legs of insects
and vertebrates, the wings of insects and bats etc.

Divergent evolution: This is the evolution of one or more closely related species into different species; resulting from
adaptations to different environmental conditions. The existence of divergent evolution is suggested by the principle
of adaptive radiation. A typical example of divergent evolution is seen in the fore limbs of frog, bird, horse, whale &
man. It is observed that the fore limb of the organisms mentioned above have the same plan but they actually perform
different function (homologous structure) this is as a result of adaptation to different environmental conditions.

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Lamarck Theory of Organic Evolution
Jean Lamarck, a French zoologist was the first to suggest that organisms undergo evolution in 1801. His idea of
organic evolution is based on three theories these are: the theory of need, the theory of use and disuse and the
theory of acquired inheritance.
Lamarck postulates of these theories are as follows.
1. There are environmental changes which make an organism less suited to its environment and as such it needs
better adaptations to enable it survive in its environment (theory of need).
2. As a reaction to these changes an organism behaves in such a way as to suit it better to its new environment in
doing so, it may either increase or decrease the use of a particular part of its body (this is a response to need).
3. The body part or organs used frequently develop while underutilized parts or organs become underdeveloped
(theory of use and disuse).
4. The physical changes to body parts created in this way may be inherited by the offspring of the individual
(theory of acquired inheritance).
Lamarck explained his theory using the giraffe as an example. He explained how a giraffe developed a long neck.
According to him, there were other animals feeding on the available grasses leading to a competition among the
animals. As a result of that the giraffe began to feed on leaves of shrubs and young trees. By constantly stretching its
neck to reach the leaves of trees the giraffe developed a long neck. This quality was inherited by offspring from
generation to generation.
Example
The long necks and legs of the present day giraffes were some of the basis of
A. Darwin’s theory of evolution B. Mendel’s theory of inheritance C. Lamarcks theory of evolution
D. Devris theory of evolution (2006/60)
Answer: C – Larmarcks theory of evolution
This theory is not accepted now because modern scientific finding shows that physical features of a parent, acquired
through use or disuse are not inherited by offspring (e.g. a boxer may develop thick muscles but the offspring do not
inherit that character) only features represented in the genes are inherited.

Darwin’s Theory of Evolution

This is also known as Darwin theory of natural selection.
Charles Darwin, a British naturalist in 1859 propounded this theory of evolution.
Darwin postulates are as follows:
(1) Organisms bear more offspring than can survive and the size of population tend to increase (over population).
(2) That this process then leads to competition by these offspring i.e. there is a struggle for survival among
members of a population.
(3) All members of a species vary and some variations are inheritable.
(4) There is survival of the fittest and the elimination of the unfit.
(5) The well adapted ones will transmit such variation to their offspring. Those with poor adaptation will die off.
(6) An accumulation of favourable variation will in a long time lead to divergence (spread).
(7) That the population gradually becomes better adapted to the environment leading to the origin of new
offsprings.

Modern Evolutionary Theory

The modern evolutionary theory combines the theory of natural selection and genetic origin of variations.
The modern evolutionary theory postulates as follows:
1. There are variations in species population.
2. Some variations have a survival advantage.
3. Individuals with favourable variations are more adapted to the environment than others.
4. There is a struggle for existence.
5. There is a survival of the fittest.
6. The fittest contributes more offspring, to the next generation than the unfit. This brings about a gradual shift in
the features of the population.
The main causes of variations are
(a) Mutation and
(b) Recombination of genes
Mutation is a random change in DNA structure which causes a change in the protein formed and hence a change in the
phenotype of species involved.
Mutation occurs during meiosis when sperm and egg are being formed.
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Causes of mutation
1. Exposure to x – ray frequently.
2. Frequent exposure to ultra – violet light.
3. Frequent exposure to cosmic radiation

Formation of a new specie by isolation

When numbers of a species are separated into two or more population by natural barriers like desert, mountains, drift,
rivers e.t.c. for a long period, their genes may change to the extent that they cannot interbreed again to produce viable
offspring and the population may have produced new species.

Evolutionary trends in organisms

Evolutionary trend is from
1. Simple to complex organisms: In both plant and animals, simple organisms appear before the multicellular
ones. In plants, evolutionary trends from the unicellular to multicellular organisms are in this order:
algae, liver worts, moses, fern, gymnosperms and angiosperms.
2. Aquatic to terrestrial life: In both plants and animals, life started in water and then moved on to the land.

Example
Which of the following pairs of scientists are associated with the development of the theory of evolution?
A. Mendel and Morgan B. Lemarck and Darwin C. Schleiden and Schwann
D. Hooke and Schwann E. Darwin and Mendel (1995/60 Nov)
Answer: B – Lamarck and Darwin
Example
In evolution, analogous structures are significant because they show
A. physiological diversity B. functional diversity C. genetic diversity D. structural diversity (2010/58)
Answer: A – Physiological diversity
Example
The man who postulated that new feature develops in an organism when there is need for them the environment is
A. hooke B. Koch C. Mendel D. Lamarck E. Wallace (1997/57 Nov)
Answer: D – Lamarck
Example
The evidence that evolution has occurred in living organisms comes mostly from fossil records from fossil records
found in
A. sedimentary rocks B. igneous rocks C. metamorphic rocks D. molten lava in the earth’s crust (2013/60 Nov)
Answer: A – Sedimentary rocks
Example
Who is the proponent of the theory of use and disuse of parts of an organism?
A. Charles Darwin B. Jean-Baptiste Lamarck C. Thomas Morgan D. Gregor Mendel (1996/59 Nov)
Answer: B – Jean Baptiste Lamarck
Example
Which of the following is not an evidence of evolution?
A. Fossil records B. Comparative embryology C. Polymorphism D. Comparative anatomy (2020/50 Nov)
Answer: C – Polymorphism
N.B Polymorphism is a discontinuous genetic variation that results in the occurence of different forms of members of
a single species. It is not an evidence of evolution.
Example
Which of the following is non an evidence of evolution?
A. geology B. pollination C. embryology D. anatomy (1999/59 Nov)
Answer: B – Pollination is not an evidence of evolution.
Example
The theory of Acquired characters put forward by Lamarck attempted to explain evolution in the following except
A. The strong influence of the environment
B. that the use and exercise of certain parts of the body result in the modification and better adaptation of those parts
C. the mechanism for inheritance of acquired characters from parents
D. parts of the body not used or exercised might degenerate and disappear or persists as vestigial (2002/59 Nov)
Answer: A – The strong influence of the environment

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Example
Lamarck’s theory of evolution emphasized the concept of
A. Organisms inheriting genotypes B. Use and disuse of organs
C. Creation by a designer D. Geographical distribution of organisms (2011/57 Nov)
Answer: B – Use and disuse of organ
Example
Larmack’s theory of evolution consists of the following except
A. influence of the environment B. use and disuse of body parts
C. survival of the fittest D. inheritance of acquired characters (2011/58 Nov)
Answer: B – Survival of the fittest
N.B The phenomenon of survival of the fittest was clearly expressed by Charles Darwin in his theory of Natural
selection.
Example
Which of the following is not associated with the Theory of Natural Selection?
A. Offspring produced in excess of available food B. There is competition among the offspring
C. The weaker off-spring are eliminated D. Food and other needs are abundant in a habitat
E. Nature selects survivors to reproduce their kinds (1994/60 Nov)
Answer: Food and other needs are abundant.
N.B In Darwins theory of natural selection, food and other resources were never abundant. It was the limited
availability of food and other essential resources that lead to competition amongst individual and gradually into
survival of fittest and elimination of the weak.
Example
Which of the following does not apply to Lamarck’s theory of organic evolution?
A. Need B. Use C. Segregation D. acquired characteristics by inheritance (2004/60 Nov)
Answer: C – Segregation
N.B The law of segregation is one of mendel’s law of Hereditary. It has nothing to do with Lamarck’s theory of
organic Evolution
Example
The following studies support the theory of evolution except
A. trophic structure B. comparative anatomy C. embryology of vertebrates D. fossil records (2004/59 Nov)
Answer: A – Trophic structure
Example
(c) List SIX evidences of evolution. (2007/2c Neco)
Answer: Comparative anatomy , Comparative embryology, Vestigial organs, Comparative physiology, Fossil
Records, Cytology
Example
Natural selection is a consequence of
A. distribution of organisms B. adverse conditions C. variation in organisms D. inbreeding (2017/46 NABTEB)
Answer: B – Adverse condition
Example
Which of the following is not an evidence of evolution?
A. Fossil B. Anatomy C. Embryology C. Genetics E. Behavior (1988/56)
Answer: E – Behaviour. All other options are evidence of organic evolution
Example
The theory that new organs or characteristics develop in organisms when there is a need for them was postulated by
A. Charles Darwin B. Jean Lamarck C. Gregor Mendel C. Wallace E. Louis Pasteur (1989/57)
Answer: B – Jean Lamark’s idea of organic evolution is based on three theories these are: the theory of need, the
theory of use and disuse and the theory of acquired inheritance.

Example
The wing of a bat and that of a bird, the flippers of a whale and the fins of a fish are examples of
A. adaptive radiation B. vestigial structures C. continuous variation
D. convergent evolution E. divergent evolution (1991/57) Answer: E –Divergent Evolution
Example
A phenomenon in which two organisms that are not closely related develop similar adaptive structure for a particular
mode of life is called
A. Convergence B. divergence C. vestigial organ (1995/59 Nov) Answer: A – Convergence

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Example
The theory of use and disuse of organs was propounded by
A. Gregor Mendel B. Charles Darwin C. Jean Lamarck D. Louis Pasteur E. Robert Hooke (1992/60)
Answer: C – Jean Lamarck
N.B; Jean Lamark’s idea of organic evolution is based on three theories these are: the theory of need, the theory of
use and disuse and the theory of acquired inheritance.
Example
Larmarck’s evolution theory could be summarised by the statement that
A. only the fittest can survive in a challenging environment B. species that are unable to adapt become extinct
C. new characteristics do not arise in organisms in time of need
D. the changing environment imposes structural physiological and behavioural changes in organisms
E. in a changing and unstable environment nature rejects the weak (1993/59)
Answer: D – The changing environment imposes structural, physiological and behavioural changes in organisms.
Example
Mutation leads to evolution in that it
A. give rise to offspring which have the same characteristics as the parents B. kills all organisms where it has occurred
C. gives rise to new individuals which differ considerably from their parents
D. always confers adaptability to the offspring E. does not confer adaptability to the offspring (1994/36)
Answer: C – Give rise to new individuals which differ considerably from their parent.
Example
The gradual, cumulative, adaptive and heritable changes in an organism over a long period of time resulting in
emergence of new species is known a
A. adaption B. survival C. regeneration D. variation E. organic evolution (1994/41)
Answer: E – Organic evolution
Example
The statement that the environment determines which organisms survives to reproduce
A. explains the theory of acquired characters B. supports Jean Lamarck’s theory to use and disuse
C. supports the idea of survival of the fittest D. is refuted by fossil records
E. implies that organisms modify their environment in order to survive (1995/53)
Answer: C – Supports the idea of survival of the fittest.
Example
Adaptive radiation as illustrated by the variety of forms in insects can be regarded as
A. a behavioural modification B. a case of rapid population growth
C. a physiological process D. an evidence of evolution E. a population control mechanism (1990/56)
Answer: D – An evidence of evolution.
Example
Which of the following fields of study may not yield strong evidence of evolution?
A. Fossil B. Histology C. Ecology D. Genetics E. Cytology (1996/59) Answer: C – Ecology
Example
According to Charles Darwin’s Theory of Evolution, natural selection involves the survival of the
A. weakest B. most populous C. youngest D. fittest (1999/59)
Answer: D–According to Charles Darwin’s Theory of Evolution, natural selection involves the survival of the Fittest.

Example
Which of the following can be considered as a direct evidence of evolution?
A. Classification B. Comparative C. Comparative embryology D. Fossil record (2002/60)
Answer: C – Comparative embryology
Example
(d) (i) Name two scientists who have contributed to the study of evolution.
(ii) List five evidences to support the occurrence of evolution (2003/8di-ii)
Answer:
i. Jean B. Larmarck, Charles Darwin
ii. Evidences to support the occurrence of evolution: - Comparative anatomy, - Comparative embryology
- Vestigial organ, -Fossil records , -Geographical distribution
Example
The theory of survival of the fittest was propounded by
A. Darwin B. Lamarck C. Linnaeus D. Mendel (2007/59)
Answer: A – The theory of survival of the fittest was propounded by Darwin
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Example
4(a) Define the term “Organic Evolution”
(b) Outline the contributions of (i) Larmak; (ii) Darwin to organic evolution
(c) List three evidences of organic evolution
(d) Explain the role of (i) Mutation; (ii) Isolation in the formation of new species. (1998/4a-d)
Answer:
4a. Organic evolution is the sum total of adaptive changes from pre-existing or old forms which have taken place
over a long time and which result in diversity of form, structure and function among organism.
bi. Larmarck Contribution:
- There are environmental changes which make an organism less suited to its environment and as such it
needs better adaptations to enable it survive in its environment (Theory of need).
- As a reaction to these changes an organism behaves in such a way as to suit it better to its new
environment in doing so, it may either increase or decrease the use of a particular part of its body (this is a
response to need).
- The body part or organs used frequently develop while underutilized parts or organs become
underdeveloped (theory of use and disuse).
- The physical changes to body parts created in the way may be inherited by the offspring of the individual
(theory of acquired inheritance).
ii. Darwin contribution
- Organisms bear more offspring than can survive and the size of population tend to increase (over
population).
- That this process then leads to competition by these offspring i.e. there is a struggle for survival among
member of a population.
- All members of a species vary and some variations are inheritable.
- There is survival of the fittest and the eliminated of the unfit.
- The well adapted ones will transmit such variation to their offspring. Those with poor adaptation will die
off.
- An accumulation of favourable variation will in a long time lead to divergence (spread).
- That the population gradually becomes better adapted to that environment leading to the origin of new
species.
c. Evidence of organic evolution: - Fossil records - Geographical distribution - Comparative anatomy
- Comparative embryology - Vestigial organ
di. Mutation brings about sudden appearance of distinct trait or character in large population of organisms due to
minor changes or alteration in the gene of chromosome. Mutation can only be inherited when it occurs in the
gene of gametes leading to production and perpetuation of new species. mutation elsewhere in the body
cannot be passed on or inherited.
ii. The role of isolation in the formation fo new species is that if members of a species are separated into two or
more populations by natural barriers like desert, mountains, oceans, rivers, continental drift, etc for a long
period, their genes may change to the extent that they cannot interbreed again to produce viable offspring, the
population thereby may have produced new species.

Example
The accepted concepts for the theory of Natural Selection does not include
A. tendency for organisms to overproduce B. struggle for existence
C. survival of the fittest D. use and disuse of body parts (2008/59)
Answer: D – The accepted concepts for the theory of Natural Selection does not include Use and disuse of body parts.

Example
Which of the following statements reflect the mechanism of natural selection?
A. There are variations within every species B. Individuals of every species are genetically identical
C. No organism in a species dies before sexual maturity
D. Organisms with selective advantages are less likely to survive (2010/59)
Answer: A – There are variations within every species.
EXERCISE 24.1
1. Natural selection is a consequence of
A. distribution of organisms B. adverse conditions C. variation in organism D. inbreeding (2011/57)
2. Which of the following components of Larmark’s theory of evolution is considered faulty?
A. Individuals of the same species growing under different environmental conditions differ from each other
B. Use of certain organs results development of those parts C. Used organs degenerate
D. Changes that result in individuals of the same species are transmitted to offspring (2011/58)

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3. A vestigial structure in human is
A. earlobe B. toe bone C. tail bone D. spleen (2011/59)
4. Which of the following sequences is the correct evolutionary trend in plants?
A. Algae → liverworts → mosses → ferns B. Liverworts → mosses → ferns → algae
C. Mosses → algae → ferns → liverworts D. Fern → liverworts → mosses → algae (2012/60)
5. Lamarck’s theory of evolution is based on the fact that
A. organisms required genes from their parents
B. organisms pass on acquired characters to their offspring
C. characteristics of organisms are determined by the creator
D. characteristics of organisms are the sum of their parent’s characters (2014/50)

6. Which of the following terms is associated with natural selection?

A. Adaptive radiation B. Differential reproduction C. Population variability D. Survival of the fittest (2016/48)

7. Which of the following statements is true about mutation?

A. Phenotype is not involved B. Genotype is not involved
C. Artificial induction is not possible D. Genotype is involved (2017/47)
8. The gradual cumulative, adaptive and heritable change in an organism over a long period of time resulting in
new species is called
A. adaptation B. survival C. organic evolution D. interspecific competition (2017/50)
The diagram below is an illustration of one of the theories of evolution. Study it and Answer: questions 47 and 48.

9. Who proposed the theory in the illustration?

A. Louis Pasteur B. Gregor Mendel C. Robert Hooke D. Jean Lamarck (2018/47)
10. The theory supports
A. struggle for survival B. natural selection
C. independent assortment D. the use and disuse of body parts (2018/49)
11. Who proposed the theory of evolution by natural selection?
A. Darwin B. Lamarck C. Aristotle D. Linnaeus (2020/49)
12. The theory of natural selection was developed by
A. Lamarck and Darwin B. Darwin and Wallace C. Wallace a Mendel D. Mendel and Lamarck (1992/49 JAMB)

13. Fossil records found in sedimentary rocks offer some explanation for the theory of evolution because
A. the deposits have remains of organisms characteristic of when they were formed
B. different strata have remains of organisms of the same kind
C. only organisms with strong parts are fossilized
D. most animal and plant fossils bear little resemblance to present day living specimens (1992/50 JAMB)
14. Which of the following organisms has lost the pentadactyl limb structure
A. Bat B. Fish C. Frog D. Pigeon (1993/50 JAMB)
15. The anatomical evidence usually used in support of the evolutionary relationship among whales, humans birds
and dogs, is the possession of
A. thick skin B. pentadactyl limb C. tail D. epidermal structures (1994/50 JAMB)
16. The least evidence in support of the theory of evolution is provided by the study of
A. anatomy B. ecology C. geology D. embryology (1995/49 JAMB)
17. From which group of animals are the mammals generally believed to have most recently evolved?
A. reptiles B. fishes C. amphibians D. birds (1995/50 JAMB)
18. The mutation theory of organic evolution was propounded by
A. Gregor Mendel B. Jean Lamark C. Hugo de Vries D. Charles Darwin (2000/49 JAMB)

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19. The older fossil-bearing rocks, in contrast to the more recent ones, are more likely to contain
A. animal rather than plant remains B. flowering plants rather than mosses
C. invertebrates rather than birds D. reptiles rather than fishes (2000/50 JAMB)
20. An evidence of a common ancestry for-fishes, amphibians, reptiles, birds and mammals is the
A. cold-bloodedness of fishes, amphibians and reptiles B. possession of wings by birds and bats
C. possession of scales by fishes and reptiles D. presence of gill clefts in vertebrate (2005/20 JAMB)
I. Rattus rattus
II. Agama agama
III. Bufo regularis
IV. Tilapia Zilli.
21. The order of evolutionary advancement of the above vertebrates is
A. IV, III, II, I B. II, III, IV, I C. I, IV, III, II D. I, II, III, IV (2005/39 JAMB)
22. The transition from amphibians to mammals involves the limbs becoming arrange to support the weight more
effectively requiring modifications in the
A. scapulae and clavicles B. vertebrae and sternum
C. collar bones and coccyx D. pectoral and pelvic girdles (2005/40 JAMB)
Use the diagram below to Answer: questions 31 and 32.

23. The change in the length of the neck of the giraffes shown was brought about by
A. geographical isolation B. predation C. symbiosis D. natural selection (2006/24 JAMB)
24. Which of the following has the most primitive respiratory system?
A. Snail B. Fish C. Insect D. Mouse (2007/35 JAMB)
25. According to Darwin, the driving force behind evolutionary change is
A. natural selection B. genetic drift C. mutation D. gene flow (2009/50 JAMB)
26. Which of the following theories was NOT considered by Darwin in his evolutionary theory?
A. Survival of the fittest B. Use and disuse C. Competition D. Variation (2011/44 JAMB)
27. The fallacy in Lamarck’s evolutionary theory was the assumption that
A. acquired traits are heritable B. acquired traits are seldom found
C. traits are acquired through the use of body parts D. traits are acquired through disuse of body parts (2011/48 JAMB)
28. The use and disuse of body parts and the inheritance of acquired traits were used to explain
A. Darwin’s theory B. Lamarck’s theory C. genetic drift D. gene flow (2012/49 JAMB)
29. From his study of Galapagos finches, Darwin derived from his theory of evolution from
A. comparative anatomy B. comparative physiology
C. fossil remains D. comparative embryology (2012/50 JAMB)
30. All living organisms are constantly involved in a struggle for existence. This was proposed by
A. Lamarck B. Wallace C. Morgan D. Darwin (2014/49 JAMB)
31. The theory of evolution which postulates that all living organisms have a common ancestors was proposed by
A. Linnaeus B. Darwin C. Lamarck D. Mendel (2016/25 JAMB)
32. The flippers of a whale and the fins of a fish are examples of
A. divergent evolution B. coevolution C. continuous variation D. convergent evolution (2018/40 JAMB)
33. Fossil records found in sedimentary rocks offer some explanation for the theory of evolution because
A. the deposits have remains of organisms characteristic of when they were formed
B. different strata have remains of organisms of the same kind
C. only organisms with strong parts are fossilized
D. most animal and plant fossils bear little resemblance to present day living specimens (1997/49 JAMB)
34. Long neck in giraffe is used to illustrate the theory of
A. use and disuse B. origin of species C. origin of life D. natural selection (1997/50 JAMB)

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35. The wings of a bat and that of a bird are examples of
A. co-evolution B. continuous variation C. divergent evolution D. convergent evolution (2011/50 JAMB)

36. Adaptive radiation is illustrated in

A. wings in birds and rats B. appendages in insects
C. modified insect mouthparts D. dentition in mammals (2014/50 JAMB)

The Outcome of Organic Evolution (Adaptation)

The outcome of organic evolution is the adaptation of living organisms to their various environments. Living things
use their structures and behaviours to carry out a lot of activities, to obtain food of their choice and to avoid being
eaten by other organisms. This enables survival for the individual organisms and the species as a whole.
Adaptation is the process which enables organisms to adjust to their environment in order to ensure survival. It is any
genetically controlled characteristic that enhances the fitness of a living organism, to survive and successfully replace
its kind in its living environment.
An organism must be adapted in such a way so as to obtain food, compete favourably for space and mates. It must also
be able to respond efficiently to the ever changing conditions in its environment.
Types of adaptation
Adaptation may be
(1) Structural (morphological) or
(2) Behavioural (physiological)

Structural adaptation
Structural adaptation are special modification in physical features which enables organisms to survive better in their
various environments.

Examples of structural adaptation in organism are as follows.

Structural adaptation for obtaining food

(a) By toad
1. The presence of a special olfactory organ in the toad enables it to perceive the odour of its food.
2. It uses the tongue which is attached to the front of the mouth to trap its prey.
3. By drawing its bulgy eyes to the roof of its mouth, the toad prevents its prey from escaping.
4. Its long and sticky tongue enables it to catch and hold its prey.

(b) In birds
1. Birds of prey or Carnivores birds like eagles and owls have powerful, sharp, curved beaks for killing and
tearing the flesh of their prey.
2. Grain eating birds like domestic chicken have short horny beak for pecking at grains.
3. Filter feeding birds such as water duck have flattened and broad beak for sieving out food from the water.
They also have webbed feet for swimming in water.
4. Insectivorous birds, such as warblers have long, thin, pointed bill/beak while wood peckers have bills that are
long and chisel like
5. Nectar eating bird e.g. humming bird, sun bird e.t.c. have long hollow and slender bill for sucking nectar from
flowers.
6. Birds like herons and kingfisher have spear like beaks for fishing. They are referred to as fish eaters. They
also have long feet for wading in the water.

Different beak types in birds

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(c) In insects
1. Presence of biting and chewing mouth part in insects such as cockroach, grasshopper and caterpillars enables
them to feed on plant materials.
2. Piercing and sucking mouthpart are found in mosquitoes for feeding on human blood, and in aphids for
feeding on plant juice. These mouth parts are known as proboscics
3. Sucking mouthpart are found in butterflies and bees for feeding on nectars and houseflies for sucking various
kinds of food in liquid form.
4. Boring mouthpart are found in weevils for feeding on stored dry grains.

Different insects mouth parts

Some plants also show structural adaptation for feeding. For example bladderwort which live in slow flowing streams
catch insects and other small organisms by means of their bladders. Other example is sundew which bear tentacles that
secrets a clear shiny and sticky liquid. This liquid attracts insects.

Venus fly trap also has a structural adaptation that enables it to capture insects. Parasitic plant such as mistletoe,
Cassytha, pitcher have sucker called haustoria for absorbing water, sap and minerals from their host.

Structural adaptation for protection and defense

1. Praying mantis: The praying mantis has sharp spines on the first pair of legs which is use to attack and kill
insects on which it feeds. It also uses these insects legs to defend itself.
2. Bees and wasp have stings for attacking their enemies or persons which intrude their nests.
3. Scorpions use stings to attack their prey or defend themselves.
4. Snake attack their enemies or defend themselves by biting and injecting their venom into the victim.
5. Presence of wings, hollow bones and powerful wing muscles in birds enables them to fly away from
predators.
6. Bony plate in tortoise and turtle protect the animals from being eaten by predators. The bony plate also
protect them from harsh environmental factors such as severe cold and heat.
7. Presence of spines and scale in porcupine and
8. Presence of exoskeleton.

Structural adaptation to attract mate

1. Bright colouration of flowers attract insects which pollinate the flowers.
2. The adult male rainbow lizard (Agama agama) is brightly coloured. The bright colour helps to attract the
female. It also display itself under the sun, to attract female lizard for mating.
3. Male domestic fowl, crown bird and peacocks are brightly coloured with beautiful feathers. The male display
their feathers to attract the female for mating.
4. In some butterflies and beetles, the males are beautifully coloured and this enables them to be attracted to
their partners.
5. Some female fishes have coloured belly such as bright red which attracts the male for mating.
6. Male toad and frog develop nuptial pads on the first digits of their forelimbs for gripping the female firmly
during breeding.

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Structural adaptation to regulate body temperature
Mammals and birds normally regulate their body temperature so that their body temperature will remain constant. The
human body temperature is approximately 37°C and that is the temperature at which enzymes in the body work best.
Animals such as birds and mammals which regulate their body temperature are described as homoiothermic (constant
body temperature) while those which do not such as fishes, amphibians and reptiles are said to be poikilothermic
(cold blooded) since their body temperature changes with external temperature.

Structural adaptation in mammals to regulate body temperature

(ai) The hair which encloses a layer of air around the body act as an insulator which reduces heat loss from the
body.
(ii) The layer of air also reduces the rate at which sweat evaporates from the body.
(iii) When it is cold, the hairs stand almost erect and enclose a thicker layer of air. The hair regulates the thickness
of the layer of air above the skin and hence the rate of heat loss from the body.
(b) Presence of fat layers under the skin. The fat layer is a poor conductor of heat and this reduces heat loss from
the body.
(c) Presence of sweat glands in the skin. The sweat glands in the skin make it possible for sweat to be produced.
Evaporation of the sweat from the skin brings heat loss.

Structural adaptation in birds to regulate body temperature

1. Presence of feathers on the skin encloses air which forms an insulator around the bird. This insulator heat –
loss from the body.
2. Subcutaneous fat in the bird form a layer of insulation which reduces heat loss from the body.
3. Regular flight by birds enables them to generate heat which keeps the body temperature fairly constant.
4. Basking: This is the practice of warming the body in sunlight to gain heat and be able to move about. It is
common with poikilothermic animals e.g. lizard, snake, crocodiles e.t.c.

Plants do not have external covering of cuticle for shielding their body from excessive heat of sunlight in their habitat.

Structural adaptation for conserving water in plants

(a) Xerophytes adapt various method of conserving water. These are
1. Presence of thick cuticles over the leaves to reduce transpiration e.g. cactus plant.
2. Presence of thick bark reduces water loss from the stem e.g. silk cotton tree.
3. Presence of thick succulent stem for storing water e.g. cactus plant. They have wide stem where water is
stored.
4. Presence of succulent leaves for water storage e.g. Byrophyllum and Aloe.
5. Reduction in the size of leaves to reduce the rate of transpiration e.g. Acacia.
6. Presence of deep tap root system enables the plant to obtain water from greater depth of the soil.

Structural adaptation for conserving water in animals

1. In animals presence of exoskeleton which is made up of chitin in insects reduces water loss from the body of
insects e.g. cockroach.
2. Presence of scales on the skin reduces water loss from the body e.g. Agama lizard, snake e.t.c.
3. Possession of shell reduces evaporation of water from the body e.g. land snail.
4. Presence of hairs on the skin reduces water loss from the skin e.g. dog, goat, e.t.c.
5. Possession of feathers on the skin reduces water evaporation from the skin e.g. pigeon.

Adaptive Colouration
Some plant and animals possesses specific colour or pattern of colours that plays a vital role in their adaptation. These
colour factors enables them to catch their prey, prepare for mating activities, and to avoid predators thus ensuring their
survival. The possession of this colour or colour patterns is known as adaptive colouration. Three types of colour
adaptations are recognized by biologists these are cryptic (concealing or camouflage) colouration, warning
(aposematic) colouration and mimicry.

6. Cryptic (concealing/camouflage) colouration: This involves the process whereby plants and animals use
biological colouration to mask (hide) their location, identity and movement. It is a means of camouflage that
prevents prey & predators from been noticed. Some types of conceeling colouration are given below:

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 1. Counter shading: This is a form of concealing colouration in which the upper surface of the body are
more darkly pigmented than the unilluminated lower areas, thus giving the body a uniform darkness.
A typical example is the dark colour on the dorsal surface and the silvery colour found on the ventral
surface of most fishes.

Counter shading in fishes

2. Disruptive colouration: This involves concealing the location & identity of an animal through a
colouration pattern that causes visual disruption. This is so because the pattern does not coincide with
the shape and outline of the animal’s body. An example is the zebra (Equus zebra) having alternating
parallel bands of black and white colours arranged vertically on the trunk and horizontal on the limbs.
3. Colour change: Some animals posses special pigment cells (chromatophores) on their body that are
involved in colouration and colour change. This change of colour in these animals, enables them to
match their environment, thus serving as a camouflage and resulting to their escape from detection.
Examples of colour changes in some animals include the change in colour of the body of grasshopper
from green in the rainy season when the grasses are green to brown in the dry season when the grasses
are brown. The chameleon also is known for its rapid colour changes as it moves from a background
of one colour to another.
Note:
i. Colouration that animals undergo in order to prevent them from been detected by predators is known
as protective colouration.
ii. Green snakes in green grasses is another type of camouflage in which snake blends with its
environment making it difficult for the prey to be detected by predators and preys.
7. Warning Coloration: Some animals posses bright attractive and conspicuous coloration that advertises then
as been poisonous and non palatable to predators. This type of coloration is known as warning colouration
and it helps to protect the animals from attacks. Examples of such coloration includes the bright and yellow
colour of variegated grasshopper (zonocerrus variegatus) which is avoided because of its smell and the bright
and yellow bands of wasps which is avoided by predators because of its painful sting.
3. Mimicry: This is a condition in which a harmless organism resembles a distasteful/harmful one so that its
enemies would avoid it.
Mimics obtain protection by looking like dangerous or distasteful organism whereby they are naturally
unrelated, e.g. the shallow tail butterfly has red colouration on the wings like distasteful one.
Adaptive colouration in plants
1. Pollination: Many insect pollinated flowers are brightly coloured so as to attract insects that pollinate them.
2. Some insectivorous plants have bright colour that attract insect that may fall into the pitchers, drown in the
liquid and get digested.

Behavioural adaption
Behaviour is everything an organism does in response to change in its environment. It aims at the overall survival and
reproduction of the organism.

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Behavioural adaptations of predators
1. A spider makes a web for trapping insects and other small animals.
2. The praying mantis remains in hiding and in waiting until the prey is within a striking distance.
3. A leopard chases its prey, over takes its by greater speed and catches it.
4. Snakes may wait in hiding or chase their prey.
Behavioural adaptations for protection from predators
(1) Remaining motionless: When a moving snail is touched, coils into its shell and remain motionless.
(2) Swaying in the air: Bats hold onto branches of trees with the head upside down and sway in the air like
leaves. By so doing, they escape being noticed by predators.
(3) Secretion of offensive odour: Some beetles and buds secret offensive odour when attacked. This smell scares
away their predators.
(4) Feigning death: A moving millipede hit with a stick, rolls up and feigns death. After a while the millipede
resumes its movement.
(5) Secretion of irritating liquids: Toads secretes a liquid that irritates the skin of the predator and repel it when
attacked.
(6) Swelling up: Snakes prey on toads. Toads may swell up and become difficult to be swallowed by the
predators.
(7) Retraction into a burrow: The earthworm leaves the hind part of its body in the burrow. Its quickly retreats
into its burrow whenever threatened by an enemy.
(8) Running/flying away: Many animals depend on speed to escape from their predators while birds simply fly
away. Examples of animals that depend on speed for escape are mainly gazelles and antelopes.

Behavioural adaptation for avoiding adverse weather conditions.

1. Hibernation
Hibernation is a behavioural adaptation in which some small mammals such as shrews and bats spend cold
season (winter) in an inactive state in a warm and safe place. During hibernation, the rate of metabolism of the
body drops greatly. No food is eaten, instead the animal uses up its stored body fats.
The hibernating animal wake up as the temperature of the environment rises and the metabolic activities speed
up.
2. Aestivation
Aestivation is a behavioural adaptation in which some animals such as African lungfish, snails and frogs
spend hot weather (drought) in inactive condition. For example, living fish, crocodiles e.t.c. bury themselves
in the mud during dry season re – emerge at the beginning of the rainy season.
3. Migration: Migration is the movement of certain animals from one place to new habitats where conditions
are more favourable than in their original habitats. This method also prevents overcrowding and also to
establish new habitats for the purpose of reproduction e.g. the cattle egrets migrate between the north and
south of Nigeria during the dry and rainy season.
Behavioural adaptation in plants
(1) Shedding of leaves: Some plants shed their leaves during the dry season in order to reduce water loss.
Examples of such plants are iroko and silk cotton tree.
(2) Dormancy: Dormancy is the period of minimal metabolic activities of an organism in order to survive
adverse conditions of cold and drought. Example seeds of plants.
(3) Death of vegetable parts: some plants die down and survive the dry season as underground stem, e.g. yam
tuber, sweet potato e.t.c.
(4) Phototropic movements of plants shoot: Plant shoot moves in response to light which is needed for the
manufacture of its food.
Social animals
Animals that live in groups are called social animals. These include mammals like apes, elephants and human beings
and insects like ants, bees, termites and wasps.

Social insects lives in highly organized societies/colonies in which each member serves the whole group instead of its
own needs. As in human societies, social insects have division of labour. Therefore each individual has a special task
to perform.

Termites
Termites are found in all tropical countries worldwide. They live in nests, underground tunnels and above the ground
in mounds called termitaria that can be about 8m high. They feed on cellulose and so damage wooden household
materials and plants.

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Castes
The individuals/castes in a colony consist of a queen, a king, soldiers, workers and nymphs.

Termite castes

1. Reproductive caste: There are three (3) types of reproductives. These are (i) king (ii) queen and winged
reproductive.
The king fertilizes the queen who produces the eggs. The royal pair (i.e. king and queen) and their young
males and females with wings are called reproductive.

2. Workers caste: These are the wingless sterile females. Their mouthparts are well developed. They build the
nest, gather food, take care of the eggs and nymphs, and feed the young soldiers and reproductive.

3. Soldier caste: These are the wingless, blind sterile males with big heads bearing strong mandibles with which
they bite. Soldiers defend the nest against any invaders/intruders.

Behavioural adaptation of termite for survival

(1) The move in a group or cluster which enable them to ward off their enemies.
(2) Their ability to build tunnels offer them protection against enemies and adverse weather conditions.
(3) The ability to feed on plants and dead wood provides them a wide variety of diet.
(4) Tunneling provides aeration within the anthill.
(5) Nuptial/wedding flights lead to the formation of new colonies.
(6) Production of many young ones ensures survival

Economic importance of termites

1. Termites destroy wood and furniture by feeding on them.
2. Termites loosen and aerates the soil through the tunnels they build.
3. They add humus to the soil by breaking down of wood.
4. The clay obtained from anthill is used to build the surface of tennis court.

Honey bees
Honey bees are social insects that live in large communities in hives that is made up of chambers. Each chamber is
called a cell.
There are three (3) castes in a bee colony. These are (i) drone (ii) queen and (iii) workers

Bee castes

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Drone of the honey bee
These are the winged male with abdomen shorter than that of the queen and bigger than the workers. The function of
the drone is to mate with the queen during nuptial flight in order to fertilize the queen after which the drone dies.

Queen of the honey bee

The queen is the fertile winged female that is being attended to by the workers. It is fed with royal jelly.

The function of the queen is to lay eggs.

Workers of the honey bee

It is a sterile female that is smaller than the queen or drone. It possesses eyes and sting, it mouthparts are modified for
collecting nectar and for building hive. The legs are modified for collecting pollen grains for flowers.

Functions of the worker bee

The function of the worker changes with age. The young worker bee performs household chores like clearing the
cells, feeding the older larvae with honey, clearing the nest and ventilating the hive. The adult worker bee forages for
food outside by collecting pollen and nectar and guard the hive e.t.c.

As soon as a worker bee locates a food source, it performs a special dance called “tail waggling” dance, which
indicates to other workers the direction and distance of the food source.

Economic importance of honey bees

Honey bees perform two beneficial roles to man
(i) They pollinate flowers.
(ii) They are sources of honey.
Example
Which of the following is not true about the nature of adaptation in fish?
A. Fishes are coloured to blend with their habitat B. In general, fishes have light dorsal surfaces
C. Fishes flora weedy waters are striped and usually greenish
D. The bodies of many bottom-dwelling fishes are usually flat
E. Fishes living near the surface of the water are silvery on the ventral surface and dark on the dorsal surface (1995/58 Nov)
Answer:
B – In general, fishes have light dorsal surfaces is not true about the nature of adaptation in fish.
N.B ; A dark colour is found on the dorsal surface and a silvery colour found on the ventral surface of most fishes
Example
Termites are classified as social insects because they
A. have division of labour B. are destructive C. feed on nectars
D. consist of both males and females E. have incomplete metamorphosis (1997/56 Nov)
Answer: A – Termites are classified as social insects because they Have division of labour
Example
Termites are called social insects because
A. the nests are built by the nasute soldiers B. they live together in common communities
C. the queen allocates duties to the workers D. the king and queen do mate
E. the function of the workers and soldiers are very important (1998/58)
Answer: B – Termites are called social insects because they live together in communities.
Example
Which of the following makes up the bee caste?
A. soldiers and queen B. drones, soldiers and workers C. queen, workers and soldiers
D. queen, drones and workers E. soldiers, queens and drones (1998/59)
Answer: D – A bee caste is made up of Queen, drones, and workers.

Example
The slender, long and slightly curved beak of the sun-bird is an adaptation for feeding on
A. nectar B. small seeds C. big seeds D. insects (1995/46 JAMB)
Answer: A – Nectar
Example
Which of the following is not an example of behavioural adaptation for protection?
A. Ministry B. Feigning death C. Croaking D. Offensive smell E. Camouflage (1997/59 Nov)
Answer: C – Croaking is not an example of behavioural adaptation for protection

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Example
A certain savanna grasshopper changes colour from green during the rainy season to black during the dry season and
black after the dry season bush fires. The reason for these colour changes is that the
A. grasshopper is getting older B. grasshopper is avoiding predation
C. environmental temperature is changing D. grasshopper is frequently moutling (2000/46 JAMB)
Answer: B – The type of colouration done by the grasshopper is known as protective colouration. By doing this, it is
seen that the grasshopper is avoiding predators.
Example
A green snake in green grass is able to escape notice from predators because of it’s
A. disruptive colouration B. counter shading C. warning colouration D. cryptic colouration (2001/49 JAMB)
Answer: D – Cryptic colouration
Example
Use the diagram below to Answer: questions 45 and 46

The birds bill adapted for fishing is labeled

A. I B. II C. III D. IV (1998/46 JAMB) Answer: D – IV
Toes of the feet ending in a sharp, curved hook suitable for holding and tearing are most likely to belong to the bird
with the bill in
A. I B. II C. III D. IV (1998/46 JAMB) Answer: C – III
Example
The loud cry made by a brooding hen when a predator is around is meant to
A. alert the poultry attendants B. attract cocks to come and fight the predator
C. advertise the boundaries of its territory to intruders D. warn its chicks and other chickens of impending danger (1999/49 JAMB)
Answer: D – Warn its chicks and other chickens of impending danger.
Example
A honeybee communicates with others after locating a source of food by
A. Dancing B. stinging C. instinct D. flare (2020/49 PC1) Answer: A – Dancing
N.B- As soon as a worker bee locates a food source, it performs a special dance called “tail waggling” dance, which
indicates to other workers the direction and distance of the food source
Example
Which of the following animals exhibits territorially?
A. rabbit B. earthworm C. lizard D. toad (1999/60 Nov) Answer: C – Lizard
Example
Bees and termites are noted for their
A. warning signals B. territorial behavior C. caste system D. honey production (1999/58 Nov)
Answer: C – Caste System
Example
The ability of a chameleon to change its colour and blend with its environment is a form of
A. defense B. protection C. attack D. invitation (2019/49 PC2)
Answer: B – The ability of a chameleon to change its colour and blend with its environment is a form of Protection
Example
The presence of pigments in plant and animal cells which enable them adapt to their environment is called
A. adaptation B. adaptive colouration C. mimicry D. environmental colouration (2019/50 PC2)
Answer: B – Adaptive colouration
Example
All the following are social insects except
A. grasshoppers B. termites C. honey bees D. ants (2005/57 Nov)
Answer: A – Grasshoppers are not example of social insects

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Example
In explaining the term camouflage, to a class, the diagram below showing four varieties P, Q, R, and S of the same
species of fish living amongst water plants in a river were used.
Use the diagram to Answer: question 48 to 50

Which of the varieties is likely to decrease most in number if a predatory fish is introduced into river?
A. P B. Q C. R D. S
Answer: C – “R” is likely to decrease in number if a predator fish is introduced into the river because it body colour
does not blend with that of it environment. This will allow it to be easily noticed by a predator.
Which of the varieties is most likely to outlive the others?
A. P B. Q C. R D. S
Answer: D – “S” is most likely to outlive the others because it body colour blends very well with it environment. This
will enable it to become unnoticed by a predator.
Example
The chameleon avoids predators in its habitat by
A. releasing undigested wastes through its mouth B. moving its tail to hold tree branch
C. changing its colour to blend with the surrounding D. hiding in holes (2005/56 Nov)
Answer: C – The chameleon avoids predators in its habitat by Changing its colour to blend with the surrounding.
Example
In the colony of bees the only role of the drone is to
A. lay eggs B. fertilize the queen
C. feed the queen and workers D. pollinate the flowers (2005/58 Nov)
Answer: B – Fertilize the queen.
N.B: The function of the drone is to mate with the queen during nuptial flight in order to fertilize the queen after
which the drone dies
Example
The caste that carries out tail-waggling dance in bees is the
A. drone B. queen C. worker D. soldier termite (2011/56 Nov)
Answer: C – Worker
N.B: As soon as a worker bee locates a food source, it performs a special dance called “tail waggling” dance, which
indicates to other workers the direction and distance of the food source.
Example
Structural adaptations found in organism such a thick skin, thick leaves, and long beaks are used for which of the
following functions respectively?
A. Regulating body temperature, conserving water and obtaining food
B. Conserving water, regulating body temperature and obtaining food
C. Securing mate, escaping from enemies and conserving water
D. Obtaining food, escaping from enemies and securing mate
E. Obtaining food, conserving g water and regulating body temperature (1994/58 Nov)
Answer: A – Following a chronological order, the functions of the aforementioned structures in the questions
are for Regulating body temperature, conserving water and obtaining food respectively.
Example
Which of the following is not a feature of a worker in the termite colony
A. large head B. wingless C. well-developed mouth parts
D. Under developed reproductive system E. Absence of eyes (1998/58 Nov)
Answer: A – Large head
N.B: The characteristic of having a Large head does not belong to the worker caste in the termite colony. It is a
feature of the soldier caste

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Example
The process by which plants and animals are modified in structure, physiology arid behaviour in order to
survive is known as
A. evolution B. adaption C. succession D. aggregation E. hibernation (1990/58)
Answer: B – Adaptation
Example
The adaptations for water conservation in organisms include the following except
A. scales in fishes B. scales on leaves C. thick leaves D. spine in plants E. succulent stems (1991/53)
Answer: A – Presence of scales in fishes is not an adaptation of water conservation.
Example
Which of the following structures is a protective adaptive feature of the Agama lizard to terrestrial habitat?
A. Claws B. Gular fold C. Scaly skin D. Nuchal crest E. Tail (1991/54)
Answer: C – Presence of Scaly skin is a protective adaptive feature of the Agama lizard to terrestrial habitat
Example
Which of the following is not a structural adaptation of desert plants for water conservation?
A. Tiny leaves B. Sunken stomata in leaves C. Stems and leaves with heavy cuticle
D. Broad leaves with numerous stomata E. Scale leaves (1992/47)
Answer: D – Broad leaves with numerous stomata is not a structural adaptation of desert plants for water conservation.
Example
The failure of a species to adapt to any environment leads to
A. domination B. competition C. stunted growth D. extinction E. adaptation (1992/59)
Answer: D – The failure of a species to adapt to any environment leads to Extinction
Example
How are Savannah plants protected from bush fires? They
A. have sunken stomata B. roll their leaves during hot days C. have thick barks
D. ways produce flowers E. shed their leaves gradually (1992/58)
Answer: C – By having thick barks, savannah plants are protected from bush fires
Example
Which of the following does not illustrate adaptation to the environment?
A. Colour changes by chameleon B. Streamline shape of fishes
C. Light bones in birds D. Development of big muscles by a weight lifter
E. Possession of fins by fishes (1993/55)
Answer: D – Development of big muscles by a weight lifter.
Example
The changing of colour by a chameleon to that of the environment is an example of
A. Adaptive radiation B. Protective colouration C. courtship display
D. Display of body colour E. territorial behaviour (1993/56)
Answer: B – Protective colouration
Example
The division of labour in social insects is an example of
A. structural adaptation B. physiological adaptation C. commensalism
D. behavioural adaptation E. hormonal influence (1993/57)
Answer: D – The division of labour in social insects is an example of Behavioural adaptation
Example
Which of the following behavioral patterns describes adaptive coloration?
A. Counter shading B. Hibernation C. Aestivation D. Aggregation E. Migration (1997/60)
Answer: A – Counter shading is a behavioural pattern that describes the phenomena of adaptive coloration
Example
Which of the following best describes the adaptation of the earthworm to its habitat?
A. Living in borrow during the day to prevent desiccation B. Burrowing into soft soil to store food
C. Possession of segmented body to reduce movement D. Possession of a few bristles for defence (2000/51)
Answer: A – Living in borrow during the day to prevent desiccation.
Example
Which of the following statements best explains the reason why termites swarm at night?
A. light is not necessary for swarming B. they avoid day-flying birds
C. light destroys their wings D. they can only see in the dark (2020/50)
Answer: B– They avoid day-flying birds.
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Example
Which of the following organisms is a social insect?
A. Grasshopper B. Honey bee C. Butterfly D. Housefly (2005/57)
Answer: B – Honey bee
Example
Territoriality is a phenomenon among
A. lower organisms B. plants of different species
C. male animals with a group of females D. animals and plants (2005/58)
Answer: C – Territoriality is a phenomenon among Male animals with group of females.
Example
A honey bee worker communicates with others on locating a source of food by
A. dancing B. stinging C. instinct D. flares (2005/59)
Answer: A – Dancing
Example
Diagrams I, II and III below illustrate the feet of birds adapted to various modes of feeding and movement, use
them to Answer: questions 6 to 8.

What is the foot labelled I adapted to?

A. Feeding on flesh B. Eating grains C. Swimming in water
D. Perching on trees E. catching insects in flight (1994/6)
Answer: C – I is adapted for swimming in water.
Example
The foot labelled III is strong and has blunt claws on its digits. This implies that the bird
A. is a scavenger B. is a bird of prey C. is a marine bird
D. uses the foot to scratch the soil E. uses the foot to supplement wing action in flight (1994/7)
Answer: D – III the bird uses the foot to scratch the soil.

EXERCISE 24.2
1. Courtship behaviour in animals may include all of the following except
A. howling of a dog B. dancing of the worker bee
C. croaking of a toad D. basking in the sun by a lizard (2006/58)
2. Honey-bee workers carry out the following functions except
A. laying eggs B. building nests C. cleaning the nest D. gathering food (2006/59)
3. The long necks and legs of the present day giraffes were some of the basis of
A. Darwins’ theory of evolution B. Mendel's theory of inheritance
C. Lamarck's theory-of evolution D. De Vries theory of evolution (2006/60)
4. A termite with a relatively large head and powerful jaws is likely to be a
A. king B. queen C. soldier D. reproductive (2007/60)
5. Which of the following statements is not true of the worker termites? They
A. build and repair the nest B. produce enzymes to digest cellulose
C. search for food to feed the colony D. look after the nymph (2008/57)
6. Evidence for evolution includes the following except
A. fossil records B. comparative anatomy
C. mutation of genes D. geographical distribution of organisms (2009/60)
7. Which of the following animals exhibits territoriality?
A. Rabbit B. Earthworm C. Lizard D. Toad (2010/60)
8. 8 (a) Explain the term adaptation in relation to the mode of life of an organism
(b) Explain how each of the following structures adapt the organisms that possess them to the mode of life:
(i) Succulent leaves in Aloe sp; (ii) succulent stems and reduced leaves in cactus plants
(iii) Short, strong beaks in fowls (iv) counter shading in fish (v) tiny scales leaves on needle-like braches
of pine trees
(c) (i) What is population? (ii) State fives effects of overpopulation on a community. (2010/8a-c)
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9. Which of the following organisms is not a social insects?
A. Termites B. Ants C. Grasshoppers D. Bees (2014/49)
10. The inability of an organism to adapt to its habitat can lead to
A. dormancy B. adaptation C. extinction D. survival (2016/50)
11. In which of the following insects is group instinct not displayed?
A. Soldier ants B. Cockroaches C. Honeybees D. Termites (2016/49)
12. One of the structural adaptations of mammals for movement on land is the development of the
A. hollow bones B. pentadactyl limb C. fused thoracic bones D. streamlined body (2017/48)
13. Which of the following traits is not characteristic of social insects?
A. All members are identical B. There is division of labour
C. The members dwell in the same habitat D. Some members protect the queen (2017/49)
14. Which of the following insects is not a social insect?
A. Termite B. Housefly C. Honeybee D. Ant (2018/50)
15. The yellow and black stripes on the body of wasps is an example of
A. mimicry B. courtship behavior C. camouflage D. warning colouration (2019/49)
16. The biological importance of the dance by the worker honeybee is that it
A. acts as a signal for mating B. serves as a warning signal
C. signals the availability of food D. serves as a means of identifying members on the caste (2019/50)
17. The slender, long and slightly curved beak of the sun-bird is an adaptation for feeding on
A. nectar B. small seeds C. big seeds D. insects (1995/46 JAMB)
18. Scales on reptiles are a feature for
A. Conserving water B. conserving food C. protecting the skin D. locomotion (1995/47 JAMB)
19. The colour of the ventral surface of a fish is lighter than that of the dorsal. This is mainly
A. an adaptation for movement B. an adaptation for camourflage
C. for attracting mates D. for regulating body temperature (1995/48 JAMB)
20. Water loss is regulated in plants and animals by both the
A. scales and skin B. scales and the hair
C. thick leaves and the feathers D. leathery cuticle and the feathers (1997/46 JAMB)

21. What combination of characters should a prey develop to survive in the environment of its predator?
A. camouflage, well developed limbs and effective vision
B. showy colour, big body and well developed limbs
C. camouflage, big body and effective vision
D. showy colour, well developed muscles and an acute sense of smell (1997/47 JAMB)
22. The three classes in a termitarium are
A. soldiers, queen and workers B. workers, soldiers and reproductive
C. soldiers, workers and king D. kings, queen and soldiers (1997/48 JAMB)
23. A certain savanna grasshopper changes colour from green during the rainy season to black during the dry
season and black after the dry season bush fires. The reason for these colour changes is that the
A. grasshopper is getting older B. grasshopper is avoiding predation
C. environmental temperature is changing D. grasshopper is frequently moutling (2000/46 JAMB)
24. Complex social behavour and organization are found mostly in
A. birds B. insects C. reptiles D. mammals (2000/48 JAMB)
25. One of the adaptations to life on trees by a monkey is its possession of digits which are
A. big B. long C. extensible D. opposable (2002/46 JAMB)
26. An example of cryptic colouration is the
A. bright marks on a poisonous tropical frog on variegated leaves
B. bright colour of an insect-pollinated flower C. mottled colours on moths that rest on lichens
D. green colour of a plant (2003/49 JAMB)
27. The function of the long-winged reproductive in a termite colony is to
A. feed the young B. disperse the population C. protect the young D. participate in swarming (2004/42 JAMB)
28. The only caste in the termite colony whose members can feed themselves are the
A. workers B. reproductives C. soldiers D. nymphs (2005/23 JAMB)

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29. The brightly coloured eye spots on the hind wings of a moth are an example of
A. disruptive colouration B. crypsis C. mimicry D. warning colouration (2011/49 JAMB)
30. The significance of a very large number of termites involved in nuptial swarming is to
A. provide birds with plenty of food B. ensure their perpetuation despite predatory pressure
C. search for a favorable place to breed D. ensure that every individual gets a mate (2012/48 JAMB)
31. The behavioral adaptation in social insects could best be described as
A. symbiosis B. saphytism C. parasitism D. commensialism (2013/50 JAMB)
32. The stream-lined shape of fishes is an adaptation for
A. obtaining food B. defence and attack C. securing mates D. easy movement (2014/47 JAMB)

33. Which of the following practices is an adaptation for regulation of body temperature?
A. Hibernation B. Tree climbing C. Encystment D. Shedding skin E. Croaking at night (1997/58 Nov)

Use the diagram below to Answer: question49 and 50

34. The type of protective adaptation exhibited by the animal is

A. flash coloration B. countershading coloration C. warning colouration D. disruptive colouration (2015/48 JAMB)
35. The structure labelled I is
A. tactile B. radiosensitive C. photosensitive D. chemoreceptive (2015/49 JAMB)

Use the diagram below to Answer: questions 27 and 28.

36. The economic importance of the larva is that it

A. is eaten by birds B. develops into a moth
C. resembles the plant on which it lives D. fees on the leaves of crops (2006/27 JAMB)
37. The type of adaptation shown by the larva is
A. mimicry B. countershading
C. flash coloration D. cisruptive coloration (2006/28 JAMB)
38. Countershading is an adaptive feature that enables animals to
A. fight enemies B. remain undetected C. warn enemies D. attract mates (2012/12 JAMB)
39. The short thick beak in birds is an adaptation for
A. crushing seeds B. sucking nectar C. tearing flesh D. straining mud (2012/46 JAMB)
40. The basking of Agama lizards in the sun is to
A. change the colour of their body B. raise their body temperature to become active
C. fight to defend their territories D. attract the female for courtship (2012/47 JAMB)
41. Which of the following structure is adapted for feeding in a bird for a prey?
A. Hooked beak and sharp claws B. Smooth beak and strong claws
C. Big beaks and strong feet D. Pointed beak and strong claws (2013/48 JAMB)
42. The special pigment for colour change in chameleon is
A. melanin B. carotenoid C. chromatin D. chromatophore (2013/49 JAMB)

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 43. Which of the following statements best explains the term aestivation?
A. A device for survival during the period of extreme food and water shortage
B. A method of survival adopted by plants during the dry season
C. Movement of animals over long distances
D. A method of survival adopted by animals under favourable condition
E. A device for rapid multiplication during abundance of food (1991/55 Nov)
44. An animal which is active during the day is known as a
A. nocturnal animal B. diurnal animal C. terrestrial animal D. homortacmic animal (2018/34 JAMB)
45. Animals aestivate when the environment in which they live becomes
A. warm and humid B. windy and snowy C. hot and dry D. cold and wet (2019/31 JAMB)

46. Which of the following pairs of features adapt the hawk for feeding?
A. sharp, hooked beak and long claws B. Flat, sharp beak and long claws
C. pointed, sharp beak and adhesive claws D. Hard, sharp beak and long talons (2002/41 Nov)
47. A situation in which the African lung fish encases itself in a cocoon, mud and mucus until the next rainy
season is called
A. adaptation B. aestivation C. diapause D. dormancy E. hibernation (2008/43 Neco)

REVISION EXERCISE
1. The process by which plants and animals are modified in structure, physiology and behaviour in order to
survive is known as
A. evolution B. adaptation C. succession D. aggregation E. hibernation (2018/38)
2. The failure of a species to adapt to any environment leads to
A. domination B. competition C. stunted growth D. extinction E. adaptation (2016/50)
3. For an organism to survive changes in its environment it must
A. absorb more water B. adapt to new conditions C. find shelter
D. obtain more food E. obtain no light (2001/58 Neco)
4. Which of the following structure is a protective adaptive features of the Agama lizard to terrestrial habitat?
A. claws B. gular fold C. scaly skin D. nuchal crest E. tail (1991/54)
5. Which of the behavioural pattern describes adaptive colouration?
A. counter shading B. hibernation C. aestivation D. aggregation E. migration (1997/60)
6. Which of the following features is used by chameleons to escape predation?
A. fearsome appearance B. coiling tail C. offensive smell D. adaptive colouration (2013/58)
7. The change in colour of a chameleon is an adaptation for
A. feeding B. growth C. movement D. protection E. reproduction (2007/10 Neco)
8. Which of the following is not an example of behavioural adaptation for protection?
A. mimicry B. feigning death C. croaking D. offensive smell E. camouflage (1997/59 Nov)
9. The division of labour in social insects is an example of
A. structural adaptation B. physiological adaptation C. commensalism
D. behavioural adaptation E. hormonal (1993/57)
10. Which of the following organisms exhibit division of labour?
A. houseflies B. butterflies C. cockroaches D. termites (2004/58)
11. Termites are called social insects because
A. the nests are built by nasute soldiers B. they live together in communities
C. the queen allocates duties to the workers D. the king and queen do mate
E. the function of the workers and soldiers are very important (2004/58 Nov)
12. Which of the following organisms is not a social insects?
A. termites B. ants C. grasshoppers D. bees (2018/50)
13. Termites are classified as social insects because they
A. have division of labour B. are destructive C. feed on nectars
D. consist of both males and females D. have incomplete metamorphosis (1992/56)
14. Which of the following is not a caste in a termitarium?
A. drones B. king C. queen D. soldiers E. workers (2018/29 Neco)
15. A termite with a relatively large head and powerful jaws is likely to be a
A. king B. queen C. soldier D. reproductive (2007/66)

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16. Bees communicate with one another to obtain information about the direction of food source through
A. complicated set of dances B. smell C. contract notes D. observation E. sounds (2020/49)
17. Honey bee workers carry out the following functions except
A. laying eggs B. building nests C. clearing the nest D. gathering food (2006/59)
18. In the bee hive, the location of nectar is the responsibility of a
A. king B. queen C. winged reproductive D. worker (2010/60)
19. Bees are of great importance to the farmer because they
A. provide him with honey B. pollinate flowers C. sting crop pest to death
D. destroy flowers by sucking nectar from them (2012/59)
20. Bees and termites are noted for their
A. warning signals B. territorial behaviour C. caste system D. honey production (1999/58 Nov)
21. Explain the term adaptation in relation to the mode of life of an organism. (2010/8a)
22. Give two examples of social animals. (2007/4b(iii) Neco)
23. Mention three functions of a worker caste in a termitarium. (20007/1c Neco)
24. 4a. Give two reasons why termites are described as social insects.
b. Name four castes found in the termites nest stating one role of each caste. (1990/2a)
25. 5a. Mention four castes found among the termite nests. (1998/3a)

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First Aid
First aid is defined as the provision of immediate care to a victim with an injury or illness before medical services
arrive or can be reached.

First Aider: The person that provides this immediate care to the victim is known as a First Aider.

First Aid Kit: A first aid kit is a box, bag or pack that holds supplies used to treat minor injuries, including cuts,
burns, bruises sprains etc.

Component of a first aid kit/box

1. Different sizes and shapes of plaster.
2. Safety pin
3. Scissors
4. Sticky tape
5. Tweezers
6. Alcohol-free cleansing wipes
7. Thermometer
8. Pain killers like paracetamol/aspirin
9. Distilled water for cleaning wounds
10. Disposable sterile gloves
11. Triangular bandages
12. Antiseptic cream
13. First aid manual/instructor booklet.

Importance of a first aid:

The importance of first aid is hard to overestimate. Among the major benefits of first aid are the following:
1. Providing quick medical treatment until professional assistance arrives.
2. It affords people with the ability to provide help during various emergency situations.
3. Sustainance of life.
4. Knowledge in first aid also benefits the individuals themselves.
5. Helps to prevent the wounds of the victim from disease infection.

Burns and scalds first aid

Burns and scalds are injuries that result from the effect of heat on the skin. While a burn results from the action of dry
heat like fire, hot metal or hot charcoal, a scald result from injury caused from moist heat like boiling water or steam.
Treating burns and scalds
To treat burns and scalds, follow the first aid advice below:
1. Immediately get the person away from the heat source to stop the burning.
2. Cool the burn with cool or lukewarm running water for 20 minutes. Iced water or any creams or greasy
substance such as butter should not be used.
3. Remove any clothing or jewelry that’s near the burnt area of skin. Don’t move anything that’s stuck to the
skin.
4. Make sure the person keeps warm by using a blanket. Care should be taken so that the blanket doesn’t rub
against the burnt area.
5. Painkillers like paracetamol or ibuprofen should be used to treat pain.
6. If the person’s face or eyes are burnt, sit him/her up as much as possible, rather than lying him/her down. This
helps to reduce swelling.
Haemorrhage and bleeding
Bleeding also called haemorrhage, is the name used to describe blood loss. It can be referred to as blood loss inside the
body, called internal bleeding or to blood loss outside the body called external bleeding. It is not advisable to render
first aid to a patient of internal bleeding. The best thing you can do for a person with an internal bleeding is to rush
that person to a nearby hospital. But if the person has an external bleeding, some first aid can be given.

First aid for bleeding

Mouth bleeding:
1. The mouth should be rinsed with cold water many times.
2. Put ice block if available into the mouth and let it remain there for some time to reduce bleeding.

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Bleeding limbs:
1. Let the patient lie down or sit and raise the bleeding limb above the heart so that less blood flows to the
wounded area thereby reducing loss of blood and promoting clotting except in case of fractured limb.
2. Direct pressure:
a. If the wound is small, use finger to apply direct pressure on the surface of the wound area.
b. If the wound is large and bleeding is serious, you may have to use your bare hand to apply pressure
evenly on the wound area for someone to bring dressing material. Pressure squeezes the dmaged
blood vessels closer together and promotes clotting of blood to prevent more loss of blood. If the
pressure is not evenly applied, the unpressed area may continue to bleed.
3. Clean the surrounding skin (not the wound itself) with iodine or methylated spirit or hydrogen peroxide.
4. Cover the bleeding spot with clean soft material (e.g. handkerchief, shirt, sanitary napkin) or wool and apply
pressure until the bleeding has stopped or slowed to the point that a bandage can be applied. (Don’t be in
hurry to stop the pressure).
5. Apply the bandage firmly over the pad and continue the pressure. (Note: The bandage must be checked after
the knot has been tied to be sure that it is not too tight to stop blood circulation to the area).
6. Pressure point: A pressure point is a point where an artery is pressed against a bone externally to stop
bleeding. For example, to stop bleeding from the elbow or fore-arm, the brachial artery is pressed against the
humerus. To stop bleeding from the thigh, knee or foot, press femoral artery against the femur (hip bone).
7. Application of tourniquet: This is tying of a narrow bandage or strap tightly above the wound so that the
blood vessels especially arteries are pressed against a bone or near a pressure point. At interval of about 20
minutes, the tourniquet must be relaxed and tied again. In carrying out tourniquet, the position of the arteries
must be known.
Nose bleeding:
When there is bleeding from the nose (nostrils) the following steps are to be followed:
1. Let the victim sit on a comfortable place such as chair.
2. Let him receive fresh air.
3. The victim’s head should be bent backwards slightly so as to reduce or prevent further loss of blood.
4. The victim should be encouraged to breathe through the mouth and not through nose to reduce or prevent loss
of blood and also to promote clotting. The nose is pinched for 10 minutes.
5. Use cotton wool or tissue paper to remove blood from the nostrils and push in some of the cotton wool or
tissue paper into the nostrils to absorb blood. The blood soaked cotton wool is removed at interval and new
cotton wool is pushed in until bleeding stops.
6. The nose must not be blown, as doing so will promote bleeding.
7. Apply pressure point. Press the carotid artery against the jaw bone to reduce bleeding.
8. Send the victim to hospital for medical treatment.
Fainting:
Fainting happens when someone loses consciousness for a short amount of time becausethe brain is not getting enough
oxygen.
Symptoms of fainting
1. Sweating
2. Pale face
3. Weakness
4. Weak pulse
5. Irregular breathing
6. Dizziness and unconsciousness

First aid for fainting

If you feel faint, it is advisable to do the following:
1. Lie down or sit down to reduce the chance of fainting again, don’t get up too quickly
2. Place your head between your knees if you sit-down.
If someone else faints
 Position the person on his or her back.
 If there are no injuries and the person is breathing, raise the person’s legs above heart level about 12 inches/30cm
if possible.
 Loosen belts, collars or other constrictive clothing.
 To reduce the chance of fainting again, don’t get the person up too quickly.
 If the person doesn’t regain consciousness within one minute, find a possible means to take the person to the
hospital quickly.
 But when signs of recovery appear, give the person some fluid in order to replenish the lost fluid as a result of
sweating.
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Bruise:
This is also called ecchymosis. It is blood or bleeding under the skin due to trauma of any kind. It is typically black
and blue at first, with colour changes as healing progresses.
First aid for bruises
 Rest the bruised area, if possible.
 Ice the bruise with an ice pack wrapped in a towel. Leave it in place for 10 to 20 minutes. Repeat several times a
day for a day or two as needed.
 Compress the bruised area if it is swelling using an elastic bandage. Don’t make it too tight.
 Elevate the injured area.
 If your skin isn’t broken, you don’t need a bandage.

Drowning:
Drowning is death caused by suffocation when water or other liquid fills the lungs. Someone who is drowning and
struggling to breathe is usually unable to call for help. The skin may appear blue from lack of oxygen in the blood. A
drowned person can be revived if the water can be removed from lungs and his natural breathing restored by artificial
respiration.
Artificial respiration:
This is breathing induced by some manipulation techniques when natural respiration has stopped or is faltering.
Resuscitation by inducing artificial respiration consists chiefly of two actions :
a. Establishing and maintaining an open air passage from the upper respiratory tract (mouth, throat and pharynx)
to the lungs and
b. Exchanging air and carbondioxide in the terminal sacs of the lungs while the heart is still functioning.

In performing mouth to mouth artificial respiration for a drown person, the following steps should be employed:
1. Lay the victim on his side with his head lower than his rest body as in diagram. With the heel of your hand on
his belly between the ribs and navel, make a quick upward push to force water from his lungs and stomach.

2. Then turn the victim to lie on his back. All tight clothing must be loosened to allow free passage of fresh air to
the lungs.
3. Pull his lower jaw forward to open the mouth and remove any obstacle such as mucus, weeds or mud that may
likely block his air passage (throat) to the lungs.
4. Close his nostrils with your fingers and open his mouth wide and cover his mouth with your mouth tightly.
Take a deep breath and gently blow in air into his lungs.
5. Remove your mouth so that the person breathes out while you wait to take another deep breath. Repeat this
procedure for about 15 times per minute.
6. Repeat mouth-to-mouth respiration until the person is able to breathe by himself or until there is no hope of
his living. Sometimes, it may take you up to one hour.
Dislocation:
The place where two or more bones in the body come together is called a joint. A dislocation occurs when the bones
in a joint becomes separated or knocked out of their usual positions. Any joint in the body can become dislocated. If
the joint is partially dislocated it is called “subluxation”.
Signs and symptoms of dislocation
Symptoms of a dislocation vary depending on the severity and location of the injury. The symptoms of a dislocated
joint include:
1. Severe pains at the affect joint.
2. Instability of the joint.
3. Swelling around the affected joint.
4. Loss of ability to move the joint.
5. Visibly deformed joint (bone looks out of place)
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First aid for dislocation
1. Bind the affected joint with a bandage or handkerchief or piece of cloth so as to give support to the limb. The
bandage should not be too tight so that it may not interfere with blood circulation.
2. Apply cold water or ice water to the bandage frequently to reduce pains.
3. Rest the patient in bed.
4. Apply embrocation gently to the affected joint to reduce pains.

Drug Abuse and Its Effect

What are drugs?
A drug is a substance taken into the body that modifies or affects chemical reaction in the body. Some drugs are
beneficial, while others are harmful.
S/N Type of drug Effect on body Example
1. Depressant Slows down nerve and brain activity. Alcohol, solvents, temazepam.
2. Hallucinogen Alters what we see and hear. LSD
3. Painkiller Blocks nerve impulses. Aspirin, paracetamol.
4. Performance enhancer Improves muscle development. Anabolic steroids.
5. Stimulant Increase nerve and brain activity. Nicotine, caffeine, estasy

Drug abuse:
Drug abuse is the use of illegal drugs or the use of prescription or over the counter drugs for purposes other than those
for which they are meant to be used. Drug abuse may lead to social, physical, emotional and job-related problems.

Effect of drug abuse:

1. It might result to having a weakened immune system, thus increasing the risk of illness and infection.
2. It causes seizures, stroke, mental confusion and brain damage.
3. Heart conditions ranging from abnormal heart rates to heart attacks and collapsed vein and blood vessel
infections from infected drugs might arise.
4. Signs of nausea and abdominal pain.
5. Change in appetite and weight loss.
6. Problems with memory, attention and decision making which make daily living more difficult.
7. Increased strain on the liver, which puts the person at risk of significant liver damage or liver failure.
Example
6a. (i) What is first aid?
(ii) List six items you would include in a first aid box for your school.
b. Describe the first aid which would be administered to a person who has fainted.
c. (i) What is drug abuse?
(ii) State five effects of drug abuse. (2006/6a-c Nov)
Answer:
6ai. First aid is the immediate and temporary treatment given to a victim of accident or an injured person until the
victim receives medical attention.
ii. Items you would include in first aid box: - Adhesive tape - Elastic bandage - Antiseptic wipes
- Hydrogen peroxide - A first aid manual
b. First aid for fainting
If someone else faints:
 I will Position the person on his or her back.
 If there are no injuries and the person is breathing,I will raise the person’s legs above heart level about 12
inches/30cm if possible.
 I will Loosen belts, collars or other constrictive clothing on the person.
 To reduce the chance of fainting again,I would not get the person up too quickly.
 If the person doesn’t regain consciousness within one minute,I will find a possible means to take the person to the
hospital quickly.
 But when signs of recovery appear, I will give the person some fluid in order to replenish the lost fluid as a result
of sweating.

ci. Drug abuse is the use of illegal drugs or the use of prescription or over the counter drug for the purposes other
than those for which they are meant to be used.
ii. Effects of drug abuse: - Mental illness - Depression - Loss of weight
- Severe headache - Withdrawal from school - Abnormal behaviour

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Example
5(a)(i) What is First Aid?
(ii) Give two reasons why First Aid should be administered. (2003/5a Health Science)
Answer:
i. First aid is the immediate and temporary treatment given to a victim of accident or an injured person until the
victim receives medical attention.
ii. Reasons why first aid should be administered:
- To prevent the excessive loss of blood.
- To save life.
Example
One of the basic aims of first aid is to
A. impress spectators B. exhibit skills C. promote recovery
D. avoid injury E. prevent diseases (1996/40 Health Science)
Answer: C – Promote recovery
Example
Scalds are caused by
A. pouring hot water on the skin B. exposing the skin to direct heat of the sun C. touching a hot iron
D. pouring alkali on the body E. stepping on a hot knife (1990/73 Health Science)
Answer: A – Pouring hot water on the skin.

EXERCISE 25.1
1. What first aid should be given to a person who has just fainted?
A. Carrying him to the doctor B. Covering him with blanket C. Loosening all tight clothing
D. Giving him a drink E. Pulling the person up (1990/71 Health Science)
2. Fatigue can be cured by
A. adequate intake of roughage B. adequate fluid intakes C. having enough rest
D. taking a walk E. taking salt solution (1990/43 Health Science)
3. Which of the following is not a procedure for administering first aid to person rescued from drowning?
A. Placing the victim on his back B. Loosening clothing around the neck and waist
C. Removing debris from the mouth D. Tying a tourniquet on a pressure point to increase pulse rate
E. Placing the head of the victim sideways (1996/42 Health Science)

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 EXERCISE ANSWERS 29. Calcium compounds 30.Amphibians Exercise 5.4
CHAPTER ONE 31. Two pairs of antennae. 32. Protists 1. Water will enter the cell and it will swell and burst
Exercise 1.1 33. Schistosomia 34. Annelid 35. 36. Millipede because it lacks a cell wall 2.
1. Biology 3. Its content exert pressure on the cell wall
Revision Exercise
CHAPTER TWO 4. Hypertonic solution 5.
1. Reproduces in living cells
Exercise 2.1 2. There is free movement in animals while this is limited
6. Solution X was stronger than Y
1. Becomes crystallized 2. Virus in plants 3. A high demand for food and energy 7. Loses water and shrivels
3. Can neither respire nor excrete 4. Photosynthesis 5. Presence of micro and meganuclei Exercise 5.5
5. Reproduction and respiration 6. 7. Porifera 8. Carrying out tissue respiration 1. Water moves into the cell and the cell becomes turgid
9. Reproduction and respiration 2. Turgidity and flaccidity
6. Air 7. Feed
10. Repair damaged tissues 11. Euglena 3. Substance across a living cell membrane using
8. Store metabolic waste the contractile vacuole of cells
12. Presence of chlorophyll 13. 14. energy from the cell 4. Radiation
9. Locomotion 10. Virus
15. Rhizopus, Ascaris and Amoeba
Exercise 2.2 16. Require moisture for fertilization 17. Rattus CHAPTER SIX
1. Have a similar structure and function Exercise 6.1
2. They perform a certain overall function CHAPTER FOUR 1. 2. Sundew 3. 4. Fungi 5. Photosynthesis
3. organelles Exercise 4.1 6. Holophytic 7. Saprophytic
4. sclerenchyma, cartilage and chitin 1. The cylindrical cells are linked end to end 8. Feeds on decaying organic matter 9. Algae
5. System → organ → tissue → cell 2. Spirogyra 3. There is division of labour 10. Club-shaped glandular hairs on leaves
6. Hair 7. A tissue 4. Contractile vacuole 5. Volvox 11. Rhizopus 12. 13. Photosynthesis and carnivorous
8. Mass of different cells, assembled to perform more functions 6. Euglena can photosynthesize 7. Protozoa 14. A pitcher 15. Nitrogen deficient 16.
11. Multicellular 8. Plasmodium 9. Euglena 10. 11. Amoeba 17. cassytha 18. 19. Parasitic
12. An aggregate of similar cells performing the same function 12. Spirogyra 13. 14. 15. III 16. 20. Rostellum, hooks and suckers
13. A tissue 14. Hydra osmoregulation 21. Holding fast to the hosts 22. Nitrogen
16. Meristem 17. Liver 18. Single cells 17. Contractile vacuole 18. III 23. Bladderwort 24. Holozoic 25. I and III 26. IV
19. Organ 20. Virus 21. Cell 22. Heart Exercise 4.2 27. Oxidation 28. Carnivorous 29. Dodder plant
1. Mitochondria 2. Organelles 3. Protein
Exercise 2.3 Exercise 6.2
synthesis
2. It allows for division of labour among the cells 1. Activation of chlorophyll 2. Sunlight 3.
4. Mitochondrion 5. Chromosome 6. Ribosome
3. Cellular differentiation leads to internal structural 4. Plants can photosynthesize without an increase in
7. Plastid 8. Mitochondrion
specialization 4. 9. Regulate the movement of substances to and from the cell
dry weight 5. Enables the leaf to store the starch
10. RNA and DNA 11. Chromosome 12. 13. 6. 7. 8. I, III and IV 9.
Exercises 3.1
1. Taxonomy 2. Kingdom 3. Class 4.Species 14. Cell membrane 15. Cellulose 16. 10. It represent; the photolysis of water
Chloroplast 11. Green parts only 12.
5. 6. Taxonomy 7. Kingdom
17. Mitochondrion 18. Red blood cell 19. DNA 13. It is an exothermic reaction
Exercise 3.2 20. It controls all chemical activities within the cell 14. Splitting of water molecules
1. Monera 21. Nucleus 22. Nucleus 23. Mitochondria 15. Chemical energy 16. H2O
2. They are used in the treatment plants for water 24. Mitochondria 25. Intracellular transport of material 17. Split water molecules 18. Photolysis of water
purification. 26. Cell membrane 27. Mitochondrion 19. Energy is released during the formation of glucose in
3. Binary fission 4. Streptococci 28. Mitocondria and chloroplasts 29. A large empty space plant cells 20. Nutrition 21. 22. Chlorophyll
Exercise 3.3 30. Nucleus 31. Ribosome 23. 24. Lightrays 25. 1, 2, 3 and 4
1. Pellicle 2. Mobility 3. Large vacuole 32. It is a reservoir of energy for the cell. 26. Sunlight is necessary for photosynthesis
4. Its cells are prokaryotic 5. Possession of chloroplast 33. Endoplasmic reticulum 27. Inorganic substances 28. Oxygen concentration
34. Mitochondria and chloroplast 29. 30. 31. Chloroplast 32. Oxygen 33.
Exercise 3.4 35. Mitochondrion 36. III 37. 38. Mitochondria 34. Photolysis 35. 36.
1. Fungi 2. Lack chlorophyll 37. Food for plants and animals
3. Cell-like compartments with one nucleus each Exercise 4.3
4. Chitin 5. oxygen a carbohydrates from the algae 1. Ribosome 2. Cheek cells are irregular in shape Exercise 6.3
6. No chlorophyll 7. lack chlorophyll 3. 4. Cellulose 5. Large vacuoles 6. 1. Molybdenum 2. Copper 3. Manganese
7. Plasma membranes, chromosomes, mitochondria, lysosomes 8. 4. Magnesium 5. Phosphorus
Exercise 3.5 Tonoplast 9. A. cell wall and chloroplast 6. Plants in small quantity 7.
1. The male gametes must swim to fertilize the ovum 10. Plasmalemma 11. Cell wall 8. Calcium, magnesium and potassium
2. Algae and fungi 3. Bears sexual organs 4. Fungi 9. Complete culture solution
5. require moisture for fertilization 6. Wind Revision Exercise 10. The cells of the plant will be turgid
7. Gametophyte 8. Spermatophyte 9. Fungi 1. Somatic cells 2. Spermatozoan and ovum
3. Mitochondria Exercise 6.4
10. Pteridophyta 11. Spore dispersal 1. All digestive enzymes pass through a precursor stage.
12. Spore → thallus → spermatozoa + ovum → sporangium 4. Distinguish clearly between two objects
5. Respiratory system 6. Erythrocyte 2. Glucose 3. Proteins 4. Margarine and butter 5.
13. Conifers 14. Presence of a vascular system.
7. Cytoplasm 6. Carbohydrates 7. Reducing sugar 8. Vitamin B
15. Chloroplasts
9. Benedict’s solution 10. 11. B1 12. Blue to pink
16. Bacteria → algae → moses → fern → seed plants
CHAPTER FIVE 13. Water 14. Protein 15. Ileum and pancreas
17. Manufacture their own food
Exercise 5.1 16. Scurvy 17. Rice 18. A balanced diet
18. Sorus and indusium
1. Diffusion 19. Fertility 20. Kilojoules 21. Egg yolk 22. Goiter
19. Schizophyta, thalophyta, bryophyta, pteridophyta 2. Passage of digested food from the villi into the blood 23. Protein 24. Remove the chlorophyll 25. K
and spermatophyta 3. Molecules move from a region of higher 26. Bleeding 27. Fish liver oil, milk and palm oil
20. Gymnosperms 21. Long and sword-like leaves concentration to a region of lower concentration
22. Alternation of generation 23.Algae, liverworts and mosses 28. Vitamin C 29. Amino acids
24. Spermatophyte 25. Gametophyte 4. There is uniformity in the concentration gradient 30. Water-constipation 31. Roughage
5. Exchange of nutrients between a mother and the foetus 32. Iodine solution 33. Kwashiorkor 34.
26. Comparative anatomy 27. Sporophyte
6. Light 35. Protein 36. Lipids 37. Kwashiorkor
28. Angiosperms and gymnosperms 29. Dicotyledons 7. Differences in concentration of soil water and cell sap
30. Angiosperms 31. Maize 38. Night blindness 39. 40.
8. Earthworm
Exercise 3.6 Exercise 6.5
1. Are metametrically segmented 2. Mantle Exercise 5.2 1. Steapsin and trypsinogen 2. Pancreas
3. Dorso-ventrally flattened body 4. Arachnida 1. The presence of a membrane is essential for 3. Amylase, lipase and trypsin 4. Lipases
5. Reptiles and fishes 6. The possession of scrotum osmosis to occur 2. 5. Fats, proteins and carbohydrates
7. Hair 8. In water and on moist land 9. Antenna 3. Movement of water molecules from a region of 6. Can withstand high temperatures
10. Crustacean 11. Annelids and molluscs lower concentration solution to a region of higher 7. II and III only 8. Lung fish 9. Enzyme
12. Have sebaceous glands concentration solution through a semi permeable 10. Work both in acid and alkaline medium
13. Survive in various environmental conditions membrane. 4. Osmosis and diffusion 11. Bile 12. Acid 13. Glucose and fructose
14. IV, III, II, I 15. Annelids 16. Fish 5. Rise in Y only 6. Osmosis 14. 37oC 15. 20cm3
17. A covering of feathers 18. I and II 7. Decrease in the volume of water inside the yam 16. In this experiment 25oC is the best observed
19. Radial symmetry 8. Acts as a semi permeable membrane temperature for ptyalin activity
20. Viviparous mode of reproduction 21. Insecta Exercise 5.3 17. Ptyalin 18. Trypsin 19. Pancreas
22. Birds 23. Mammalia 24. Cockroach 1. Put in hypotonic solution 2. 3. Remains unchanged 20. Enzymes 21. Lysosome 22. Co-enzymes
25. Butterfly 26. Bilaterally symmetrical 4. Haemolysis 5. Be formed less frequently 6. 23. Proteins 24. Pepsin and renin 25.
27. Whale
28. The organism has a pair of jointed appendages

702
CHAPTER SEVEN 18. The movement of the air bubble in the poto-meter CHAPTER ELEVEN
Exercise 7.1 cannot be timed accurately Exercise 11.1
1. Mouth, intestine and tail 2. Herbivorous 19. Transpiration occurs through the leaves 1. Homeostasis 2. Homeostasis
3. Internal gill stage 4. 5. Holozoic 20. Evaporation 21. Translocation
6. Feeds on decaying organic matter 22. Transpiration 23. C. 2→1→3→4 Exercise 11.2
7. Mosquito larva 8. Holophytically Exercise 8.6 1. Glomerulus
9. Its body absorbs digested food 1. William Harvey 2. Liver 2. Blockage of the tubules by solid particles
10. Glycogen11. Lapping and sponging 3. It passes twice through the heart in a complete circuit 3. Production of bile 4. Urea
12. Suitable mouth parts 13. Heterotrophic 4. Closed 5. A large surface area to volume ratio 5. Blood corpuscles
6. Subclavian vein 6. Glomerulus and Bowman's capsule
Exercise 7.2 7. Osmosis through the xylem tissues 7. Osmoregulation 8. Bowman’s capsule 9.
1. 1 2.Seizure and tearing of prey 3. 8. Pulmonary vein 10. The glomerulus is a part of urinferous tubules
4. Enamel 5. Man 6. Tearing and grasping 9. Heart → artery → arteriole → tissue 11. Keep the composition of the plasma constant 12. 2
7. Z 8. Dog 9. The diastema 10. Tearing 10. Systemic circulation 13. Concentrate sodium chloride in the medulla of the
11. Pulp cavity 12. Canines 13. Lizard kidney 14. Ultrafiltration and selective reabsorption
14. Enamel 15. Dog 16. A herbivore CHAPTER NINE 15. Cortex 16. Kidney 17.
17. 18. 19. 20. Fat 21. Proteins Exercise 9.1
22. Repairs damaged tissues 1. 2. 3. Energy Exercise 11.3
23. Benedict’s solution 24.Lipids 25. 26.27. Glucose 4. Buccal cavity, skin and lungs 1. Maintenance of osmotic balance 2. Liver 3. Liver
5. Newts 6. Kidney 7. 4. Detoxification 5. Liver 6. Filtration
Exercise 7.3 7. Stomach and gall bladder
1. Pharynx 2. Crop Exercise 9.2 8. Production of vitamin D 9.
3. Mechanical grinding of food 1. Spiracle 2. Mouth 3. 4. Gills 10. Excretion of urea from the blood 11. Liver
5. Tracheal tubes 12. Formation of urea 13. Liver
Exercise 7.4
6. Mouth and passes it through the operculum
1. Gizzard 2. Long, slender and slightly curved 3. Exercise 11.4
7. Frog 8. Mouth → gills → operculum
Exercise 7.5 9. Snail 10. Earthworm 1. Using skin toning creams 2. Melanin
1. Breakdown of fat into small globules 3. The subcutaneous fatty layer
Exercise 9.3 4. Dilation of the capillaries supplying blood to the skin
2. Glycogen 3. Capillaries of the villi
1. tarynx 2. Inspiration 5. 6. Relaxation of the erector muscles
4. Digestion 5. I → II → V → VI → IV → III
3. The taking of air into the lungs and expelling it 7. Production of pigments to reduce temperature
6. IV 7. V and VI 8. Liver 9. Proteins
4. Mammals 5. 8. Produce an oily substance 9. Malpighian layer
10. Starch, protein and fats 11. Chyme
6. Contraction of its own fibres 7. Larynx 10. An excretory organ 11. Growth 12. Nerve ending
12. Gall bladder, pancreas and spleen
8. Sternum moves forward 13. Sweat gland
13. Digestion of fats and oils 14. Cooked rice
9. size of thoracic cavity increases
15. Increases the surface area for absorption Revision Exercise
10. The diaphragm and intercostal muscles relax
16. Rattus 17. Pancreas 18. Stomach 1. 2. 3. 4. Homeostatsis 5. Scales 6.
11. Intercostal muscles contract, ribs move forwards
19. Liver 20. Gizzard 21. 22.
12. Nose→trachea→bronchus→lungs 7. Relaxation of the erector muscles
CHAPTER EIGHT 8. Metabolic activities function best at certain
Exercise 9.4
Exercise 8.1 temperature (2004/16) 9. A mammal
1. Guard cell 2. 3. For gaseous exchange
1. Light 2. 3.Water moves through the cell membrane 10. The body temperature of the bird remained
4. From a submerged plant 5. Intercellular spaces
4. There is uniformity in the concentration gradient constant despite changes in environmental temperature
5. A large surface area to volume ratio Exercise 9.5 11.Liver 12. Poikilothermic
1. Aerobic respiration 2. Oxidation of glucose 13. Feathers which cover the body
Exercise 8.2 3. Mitochondria 4. Mitochondrion 14. Leathery cuticle and the feathers
1. Cell sap 2. Synovial fluid 3. Bones 5. Acetyl coenzyme 15. Shivering in a cold environment
6. Energy, carbon dioxide and water are given off. 16. Sebaceous gland
Exercise 8.3
7. Splitting of glucose in the absence of oxygen 17. Lizard 18. Reproduction 19.Homeostasis
1. Carbon dioxide and metabolic waste
8. Lactic acid 9. V 10. Carbon dioxide is used up 20. Homeostasis
2. Fibrinogen is converted to fibrin which traps blood
11. Pyruvic acid 21. Cooling effect resulting from evaporation of
cells and prevent loss of blood
Exercise 9.6 water from the body surface
3. Bone marrow 4. Erythrocyte
1. 2. Accumulation of lactic acid 22. Constancy of the internal environment despite
5. Lymphatic system 6. Haemophilia
3. Lactic acid 4. Absence of oxygen 5. 6. changes in the external environment
7. Lymph 8. 9. 10.
6. Fermentation 7. Cytoplasm 8. Mitochondria 23. Production of bile 24. Bowman’s capsule
11. Phenylthiocarbamide (PTC) 12.
9. Carbon dioxide and ethanol 25. Kidney 26. Eating a meal rich in protein
13. AB only 14. Production of hormones
10. C6H12O6 → 2C2H5OH + 2CO2 + energy 27. Glucose 28. Detoxification
15. They have nuclei at maturity
29. Deamination of amino acids 30. 31. 32. 33.34. 35
16. Release thrombin for blood clotting
CHAPTER TEN
17. Leucocytes 18. Liver 19. Clotting of blood CHAPTER TWELVE
Exercise 10.1
20. Leucocytes 21. Erythrocytes Exercise 12.1
1. 2. Ammonia 3. 4. Malpighian tubule
22. Lacks blood protein and fibrinogen 1. Brain and spinal cord 2.
5. Contractile vacuole 6. 7. Flame cell
23. Hepatic portal vein 24. Erythrocytes
8. Gets rid of excess water 9. Excretory system Exercise 12.2
25. They are large and nucleated 26. Lymphocytes
10. Excretory system of flatworms 11. Nephridium 1. General memory 2. Cerebrum
Exercise 8.4 12. Uric acid 13. Crickets, houseflies and grasshoppers 3. Many involuntary actions 4. Hypothalamus 5.
1. 2. Oxygenated blood from the lungs to the left auricle 6. Cerebellum 7. Medulla oblongata 8. Spinal cord
Exercise 10.2
3. Thick elastic walls 4. Pulmonary vein 9. Walking 10. Brain and spinal cord 11. Cerebellum
1. A lot of liquid is required for the process
5. Pulmonary vein 12. Hypothalamus 13. 14.
2. Maintain water balance in the tissues
6. Ventricles are responsible for pumping blood into 15. Controlling respiratory action 16. Cerebrum
3. Flagellum 4. Absorption of water vapour
the main artery 7. Shortness of breath
5. Broken down in the liver 6. Ammonia
8. Swelling of veins along lower limbs Exercise 12.3
7. Excretory structures of organisms vary in complexity
9. Superior vena cava 10. Bicuspid valve 1. Grey matter 2. I only 3. Pineal body
8. Removal of urea by the kidney
11. Hepatic portal vein 4. Medulla oblongata 5.
9. Manufacture of blood plasma 10. Hepatisis
12. One ventricle and two auricles13. Left ventricle
11. Glomerulus 12. Faeces 13. Cirrhosis Exercise 12.4
14. Capillaries 15. Heart 16. IV 17. Aorta
18. Left ventricle 19. Heart, arteries, capillaries and veins
14. Tannins 15. Dust 16. Large intestine 1. Receptors
20. Platelets 21. Plasma 22.Hepatic portal vein 17. Malpighian capsule 2. Sympathetic and parasympathetic systems
18. keep the composition of the plasma constant 3. Reduction of blood pressure
Exercise 8.5 19. III 20. Malphighian body
1. 2. 3. Xylem 21. Ultrafiltration and selective reabsorption Exercise 12.5
4. Osmosis→root pressure→transpiration 22. Transpiration and guttation 23. 1. Dendrites 2. An afferent neurone
5. 3 6. Xylem fibres Exercise 10.3 3. Effector cells 4. 5. Muscle
7. Food manufactured in the leaves will accumulate 1. Blue cobalt chloride paper 2. 2→1→3→4 6. Dendron → cell body → axon → terminal branch
8. Phloem 9. Xylem 10. IV 3. cytokinin 4. Osmosis 5. Anthocyanins 7. 8. Brain 9.
11. Movement of nutrients 12. Xylem 10. The cell body is always found at the end of the neurone
6. Carbon dioxide 7. Tannin 8. Transpiration
13. Xylem and phloem 14. 15. 11. Afferent nerves 12. Dendrite
9. 10.
16. Cobalt chloride paper
17. Dry, warm, moving air

703
Exercise 12.6 4. Semicircular canals 5. 6. Stapes Exercise 16.6
1. 2. 3. 4. Chemical 7. Damaged cochlea 8. Suspensory ligament 1. Chitin 2. Millipede 3. Spider
5. Involves both electrical impulses and chemical transmissions 9. Cochlea 10. 11. 12. Pinna 4. Skull and vertebral column 5. Vertebra Column
13. Hearing and balance 14. Noise pollution 15. 6. Limbs 7. Sternum 8. Limbs
Exercise 12.7 16. Outer ear→semi-circular canals→cochlea→brain 9. Girdles and limbs
1. Involve chemical transmission 17.
2. Produces short-term changes Exercise 16.7
3. Central nervous system 4. Cerebrum 1. Chest 2. Thoracic vertebra 3. Odontoid process
5. Walking 6. Hind brain 7. Spinal cord 4. Rotary and nodding movements 5. 4 and 5
8. Spinal cord 9.Sneezing 10. Laughing Exercise 14.5 6. Cervical 7. Short neural spine and vertebral
11. Receptor→sensoryneurone→synapse→intermediate 1. Astigmatism 2. B 3. In front of B canal
neurone→synapse→motor neurone→ effector 4. Retina 5. Hypermetropia 8. Atlas 9. Atlas
12. Dendrites 13. Effector cells 6. Altering the focal length of the eye lens 10. Atlas → cervical → thoracic → lumbar
14. Impulses from the brain cannot travel to the legs 7. Hypermetropia 8. Ampulla 9. Hypermetropia 11. Lumbar vertebrae 12. Sliding joint
15. Brain cells 10. Blind spot 11. Cylindrical lens 12. Stapes 13. Vertebraterial canal 14. Lumbar
16. Dendron → cell body → axon → terminal branch 13. See only distant objects clearly 15. Neural canal 16. Axis and atlas
17. 18. 19. 14. Narrower and adapted for bright-light vision Exercise 16.8
15. Behind the retina 16. Short sightedness 1. Passage of blood vessels 2. Femur 3. Waist
CHAPTER THIRTEEN
17. Smaller 18. Pupil 19. 20. Accommodation 4. 5. Scapula 6. Shoulder 7. Hinge joint 8. IV
Exercise 13.1
1. Chemical co-ordination 21. Refraction 22. Superior vena cava 23. II 24.
Exercise 16.9
2. Secreted directly into the blood stream 3. Blood 25. Hypermetropia 26. Pupils 27. 28. Choroids 1. Olecranon process
4. 5. Hormonal responses are usually swift, instant 29. Cataract 30. Wearing concave lens 2. Prevent the wearing of body surfaces
and electrical 31. Long sight 32. Concave lens 33. Short sight
3. Synovial fluid 4. Knee
Exercise 13.2 Revision Exercise 5. Pubic symphysis 6. Femur
1. Prolactin 2. Pituitary 3. Increasing 1. Mouth 2. Taste buds Exercise 16.10
dehydration 3. Dead taste buds on the tongue
1. Forearm bends 2. Tendons 3. Origin
4. Ceasation of growth 5. 4. Has nerve endings 5. Stress
4. Cardiac muscle 5. Tendons
6. Abnormally high blood sugar level 6. Semi-circular canals 7. Suspensing ligament
8. Inner ear 9. Utriculus & sacculus Revision Exercise
Exercise 13.3 10. Eustachian tube 11. Cochlea 1. Scales in birds 2. Cartilage, bone and pseudopodia
1. Hyperactivity 2. Cretinism 12. Semi-circular canals 13. Retina 3. Femur 4. Carpals 5. Lower arm 6. II
3. Increased rate of metabolism 14. Stapes 15. Accommodation 16. Blind spot 7. III 8. Chitin, cartilage, bone 9. Prevent friction
4. Thyroid gland 5. Neck 6. 17. Ampulla 18. Smaller 19. Pupils 10. First class order 11. Scoliosis 12. Carpals
Exercise 13.4 20. Converging the light rays before they enter the
eye CHAPTER SEVENTEEN
1. Prepares the body for action 2. Adrenal glands Exercise 17.1
3. 4. Muscular power and resistance to fatigue 21. Eye lens becomes fat
22. Relaxes and the eye lens get thinner 1. Cyclosis 2. Locomotion 3. Cilia
5. Heart 6. 4. Protists 5. Pseudopodia
23. Cochlea and brain 24. Respond to external
Exercise 13.5 stimuli Exercise 17.2
1. Pancreas 1. Light bones 2. Pectoral and pelvic
2. Accelerates the absorption of glucose of the glomerulus CHAPTER FIFTEEN 3. Streamlined body 4. Anvil 5. Muscle cell 6.
3. Diabetes 4. Insulin 5. Low production of insulin Exercise 15.1
6. Pancreas 7. Pancreas 8. Diabetes 1. Thigmotropism 2. Geotropism 3. Auxins 4. 5. Revision Exercise
9. Aids the rate at which glucose is converted to glycogen 6. Grow towards source of water 1. Cytoplasmic membrane
7. Increase in auxin on the side away from the source 2. Mammalian alimentary canal
Exercise 13.6 of light
1. Adrenal gland 2. 3. 4. Antidiuretic 8. Concentration of auxin on the shaded side CHAPTER EIGHTEEN
5. Facilitate the development of facial hairs stimulates cell elongation Exercise 18.1
6. Pituitary 7. Produces short-term changes 9. Klinostat 10. 11. 12. 13. Hydrotropism 1. Fission 2. Binary fission 3. Scion
8. Involve the use of chemical substances 9. III 14. Roots of plants are positively hydrotropic 15. 4. Stolons 5. Reproductive organs are not involved
10. Regulate the activities of other endocrine glands 6. Adventitious bud 7. Rhizome
11. Behavioural patterns 12. Nerves and hormones CHAPTER SIXTEEN
13. Thyroid gland 14. Pancreas Exercise 16.1 Exercise 18.2
15. Their responses are voluntary 16. 17. 1. Secretory 2. Xylem vessels 1. Anaphase 2. Pollen grain
18. Secreted directly into the blood stream 3. Submerged water plants 4. Xylema 3. Chromatin thread condense to become chromosomes
19. Pituitary gland 20. Insulin 4. Prophase 5. Metaphase 6. Centromere
Exercise 16.2 7. Production of cells with diploid number of chromosomes
21. Abnormally high sugar level
1. Food manufactured in the leaves will accumulate 8. Metaphase 9. Spindle
Exercise 13.7 2. Food storage 10. Production of gametes
1. Auxins 2. Thyroxin 3. Auxin and gibberellins Exercise 16.3 11. The spindle forms and chromosomes become
4. Apical regions of roots and shoots attached at the centre 12. 13. Before fertilization
1. 2. Cambium 3. Cambium 14. Sexual reproduction 15. 2n → n
5. Stimulate growth 6. Insulin 7. Grow rapidly 4. Branch roots originate in the pericyle while branch 16. There is distribution of a complete set of genes
Revision Exercise stems do not into each daughter cell 17. Pollen grains
1. 2. 3. 4. Auxin, cytokinin and gibberellin 5. 3 6. Epidermis of roots 18. Homologous chromosomes separate
5. Thyroid gland 6. Auxin 7. 8. 9. 10. 7. The xylem is more interiorly located than the phloem
11. Insulin 12. Thyroxine 13. Stimulate growth 8. Position of 7 9. Produce more of 5 and 7 Exercise 18.3
10. Surround the inner tissues11. Has a very thin cuticle 1. 2. Consists of branched filaments
14. Stimulating growth of lateral branches
12. Central pith 13. Sieve tube 14. II
15. Shoot apex 16. 17. 18. Exercise 18.4
15. Pericycle 16. Dicot stems and monocot roots
CHAPTER FOURTEEN 17. Pericycle 1. Cockroach 2. Toad 3. Grasshopper
Exercise 14.1 4. Termite 5. They undergo complete metamorphosis
Exercise 16.4
1. Impure air would be breathed into their lungs 1. Dermis 2. Turgidity 3. Cross section of a root Exercise 18.5
2. Olfactory lobes of the brain 3. Smell 4. Cortex 5. Xylem 6. Malleability 1. 2. III 3. IV 4. 5. Halters 6. Mosquito
Exercise 14.2 7. Sclerenchyma, cartilage and chitin
8. Collenchyma and sclerenchyma Exercise 18.6
1. Taste buds 2. 3. Taste buds 1. Lack of ovulation 2. Viteline membrane
9. Dermis 10. Epidermis, Sclerenchyma and xylem
Exercise 14.3 11. Meristem 12. 13. Fehling’s solution 14. 3. Oviduct 4. Epididymis 5. Toad
1. Sweat gland 2. Renal tube 15. Turgidity 16. Parenchyma 17. Cambium 6. Nucleus 7. Fallopian tube 8. Fish, bird, mammal
3. Insulation 4. 18. Cork 9. 10. Testis 11. Store mature sperms
5. The secretion from sebaceous gland keeps the skin cool 12. Prostrate gland 13. Nuchal chest
6. Below the malphigian layer 7. Exercise 16.5 14. 2 15. 3 and 4 16. Upper part of the oviduct
1. Muscle 17. III 18. Protection 19. II
Exercise 14.4 2. Protective cover for delicate organs 20. Testis, prostrate gland, sperm duct and vas deferens
1. Semicircular canals 3. Destruction of old blood cells 21. Epididymis 22. Whale 23. 24.
2. Equalize the pressure of the middle ear with the atmosphere 4. Connective tissue 5. 25. Tilapia 26. Mammals 27. IV
3. Cochlea and its associated nerve endings

704
Exercise 18.7 Exercise 19.3 30. AB only 31. Three of them belong to blood group
1. 2. 3. Chromosomes of the sperm 1. 10 months 2. Is representative of Guinea pigs 32. AB 33. Sickle cell anaemia 34. 35. 36.
4. Her ovaries produced two eggs which were both fertilized
3. Remained at about half the size of normally fed 37. Crossing two genetically dissimilar varieties to
5. Red blood cells Guinea pigs 4. Shoot apices 5. Light 6. produce hybrid vigour 38. 39.
Exercise 18.8 7. Oestrogen 8. Testosterone 40. Transmitted by the parents 41.
1. Anther and pollen sac 9. Growth in plant is mainly by auxins 42. Geneticists 43. Felix Durjadin 44.
2. Carpels are separated from one another 10. Cyclosis 11. At the apical regions of roots and shoots 45. Geneticists 46. Phenotype 47. Scabies
3. Corolla 4. Gamosepalous 5. Crotalaria 6. 12. Thyroxin 13. 14. Auxin 15. 48. Mutation 49. Gene
7. The gynoecium and androecium are on the same plant 16. Length of radicle 50. Is the sum total of observation traits while genotype is
8. Complete, regular, hermaphroditic with inferior ovary the sum total of dominant and recessive gene
CHAPTER TWENTY 51. Chromosome 52. Transmission of hereditary traits
9. Actinomorphic 10. Receptacle 11. Inferior
Exercise 20.1 53. Allele 54. Preservation of seeds 55. 4
12. I 13. Anther 14. Stamen
1. Allele 2. Genotype 3. Chromosomes 1
15. Attract pollination agents 56. The probability of male to female offspring is
4. Two identical chromosomes from each parent 2
5. Dominant gene 6. Hybrid 7. Chromosome 57. Colour of skin 58. Recessive
Exercise 18.9 8. Characters transmitted from generation to generation 59. A dominant gene masks the presence of a recessive gene
1. Marginal 2. Arrangement of ovules in the ovary 9.Transfer of characteristics from parents to offspring 60. Inherited independently of each other 61. 1:3
3. Parietal 4. Marginal 5. Pride of Barbados 10. Dominant gene 11. Recessive 12. 62. Brown colour was dominant 63. Uracil
Exercise 18.10 13. Phenotype 14. Mutation 15. Phenotype 64. All yellow flowers 65. 25% tall with red fruits
1. 2. 3. Self-pollination 4. 5. Termites 6. 16. L 17. S 66. Y chromosome 67. Mutation 68. 69. 70.
7. Loosely hanging anthers 71. 72. 73. 74.
Exercise 20.2
8. There is recombination of genes from different sources 3 Exercise 20.6
9. 10. Sharp spines or hooks on fruit 1. of the offspring showed the dominant trait 1. Physiological variation 2. Skin colour
4
11. Smaller quantities of sticky pollen produced 2. Both the F1 and F2 generations 3. Differentiates between individuals of the same species
12. The pollen grains have rough spiny surfaces 3. Red colour was dominant 4. Ability to roll the tongue
13. Pistil (gynoecium) 14. Scented petals 4. Heterozygous dominant 5. Ability to taste the chemical is not heritable
15. Water 5. One trait is often controlled by many pairs of 6. Skin colour 7. Body size 8. Tongue rolling
16. The gynoecium and androecium are on the same plant genes 9. Continuous variation
17. Pollen tube and pollen nucleus 18. III 6. OO 7. 8. Recessive to red 9. Segregation 10. No two people have the same fingerprints
19. Feed on the nectar 20. III 21. Insect 10. 11. 1:3 12. Rr × Rr 13. 3:1 14. 1:2:1 11. Body weight and tongue rolling
22. Flowers lack nectar 15. HbA HbS and HbA HbS 16. 50% tall 50% dwarf 12. Whorl, arch, compound and loop
23. Can prevent self pollination 17. All were long 18. 13. Multiple genes 14. Variation
24. Formation of a fertile embryo and the endosperm 19. ¾ red flowered, ¼ white flowered plants 15. Ability to taste PTC 16. Tongue rolling
20. Heterozygous white 21. 1:1 17. Mitosis 18. Continuous variation
Exercise 18.11 22. 75% red and 25% white 23. 3 blacks: 1 white 19. Continuous variation
1. 2. 24. The gene for the spotted coat is dominant over 20. Genetic and environmental factors
3. The production of energy by oxidizing essential the gene for the black coat 21. They are raised in different environments
carbohydrates 25. HH hh 22. Continuous variation
4. Activates the enzymes 5. Elongation of the epicotyls 26. Tall plants and short plants are crossbred 27. 23. Zygotes are produced by cross fertilization
6. Carried above the ground by the elongating hypocotyls
28. Gregor Mendel 29. All yellow flowers
7. More rapid elongation of the hypocotyls than the epicotyls Exercise 20.7
8. Store food for the young plant 9. Epigeal 30. 25% tall with red fruits 31. YyRr
32. Cross fertilization 1. Colour of skin 2. O 3. B and AB 4. AB
10. Hypocotyl 11. Epicotyl 5. Population distribution 6. 7. Group O only
12. Protects the foliage leaves Exercise 20.3 8. Still births 9. Rhesus factor
Exercise 18.12 1. Gene 2. In gonads, chromosomes occur in pairs 10. Similar antigens react with similar antibodies
1. Samara 3. Has the ability to replicate 11. Sexual reproduction 12. Monkeys
2. The testa and fruit wall fuse after fertilization 4. Are usually affected by the environment 13. DNA analysis
3. Mesocarp 4. Caryopsis 5. Chiasmata 6. 7. Purines and pyrimidines Revision Exercise
8. Chromosome 9. Non-disjunction 10. 46 1. Characters transmitted from generation to generation
5. A fertilized ovary 6. Activates the enzymes
11. Nucleus 12. Transmission of hereditary traits 2. Variation 3. Infant penalysis
7. Is formed from an ovary
13. 4. Morphological variation 5. Blood groups
8. Multiple, succulent and indehiscent
14. Homologous chromosomes do not occur in pairs naturally 6. Contour 7. Tongue rolling
9. Is fused with the part numbered (3)
15. 4 16. Chromosomes contain a random mixture of 8. Continuous variation 9. Continuous variation
10. Stored in the part numbered (3) only
paternal and maternal chromosomes 17. 10. Is usually controlled by one or two pair(s) of gene
11. 21435 12. 3 13. An aggregate fruit
18. 23 19. Deoxyribonucleic acid 11. Eye colour and body weight
14. Protandry 15. Actinomorphic
20. 4 red flowers 12. Consistent for a lifetime
16. Extended pericarp 17. Schizoarp
21. Two chromatids joined at the centromere 13. No two people have the same finger prints
18. Pathenocarpic 19. Schizocarp
22. DNA is directly involved in translation 14. Whorl, arch, compound and loop
20. Formation of a fertile embryo and the endosperm
23. Nucleotide is made up of ribose, phosphate and 15. Fingerprints 16. Group O has no antigens
21. Fertilization 22. Testa and pericarp are fused
an organic nitrogen compound 17. 18. 19.
23. Drupe 24. Capsule 25. Water
24. The number present in a species is constant 25. 2
26. Mesocarp 27. A composite fruit
26. Hydrogen bond 27. Nucleus 28. Replication CHAPTER TWENTY ONE
28. Maize grain 29. Ferns Exercise 21.1
29. Uracil
30. The developed ovule 31. Buoyancy 1. Spermatophyte
30. The number represent in a species is constant
32. Presence of hooks 33. 34. 2. One seed leaf, petals in threes or groups of threes
31. Polymerase
and parallel venation of leaves
Exercise 18.13
Exercise 20.4 3. Long and sword-like leaves 4. Spermatophyte
1. Territorialism 2. 3. Metamorphosis
4. 5. Dominant 6. Caryopsis 1. XY 2. ½ 3. ¼ 4. 1⁄2 5. 1⁄2 6. 25% 5. Absorbing inorganic ions from the soil
7. Courting a female 8. Courtship 7. Two similar X chromosomes in the female and X Exercise 21.2
1
9. Lizard 10. Pheronomas released by a male dear and Y chromosomes in the male 8. 1. Fishing throughout the year
4
11. 12. 9. The X component of the man’s chromosomes was 2. Promote nitrogen fixation 3. Lime and humus
always involved 4. Reducing the amount of nitrogen in the soil
CHAPTER NINETEEN
Exercise 19.1 Exercise 20.5 Exercise 21.3
1. 2. Growth 3. Protoplasm of an organism 4. 1. It gives resistance against malarial attack 1. Sleeping sickness 2.Trypanosomiasis
2. They are resistant to malaria 3. 3. Insect bite
Exercise 19.2
4. Haemophilia 5. 25% 6. X chromosome
1. There is distribution of a complete set of genes Exercise 21.4
7. Haemophilia 8. Erythrocytes 9. Gene flow
into each daughter cell 1. Trypanosome 2. Snail 3. Maize rust 4.
10. Scabies 11. |A|O and |B|O 12. Has the disease
2. Daughter cells possess one – half chromosome
13. 0% 14. A 15. Sickle cell anaemia Exercise 21.5
number as in parent cells
16. Same chromosomes 17. 0% 18. Sex-linked 1. Cocoa black pod 2. Cocoa 3. Cocoa
3. 46 4. Prophase 5. Metaphase 6. Anaphase
7. Chromatin thread condense to become chromosomes
19. AO 20. A is dominant over B 21. AB
Exercise 21.6
8. The spindle forms and chromosomes become 22. Felix Durjadin 23. AB and BO 24. AB
1. Biological 2. Monocropping 3.
attached at the centre 9. 25. 1:1 26. Geneticists 27. BO
28. Undergo agglutination test 4. Biological control
5. The predator – prey relationship in the ecological
29. Close to each other on the chromosomes
community
705
Exercise 21.7 Exercise 23.13
1. Tse tse fly 2. Butterfly 3. Cockroach CHAPTER TWENTY THREE 1. The population of species I has become extinct
4. Termite 5. Cercaride 6. In fumigated soils Exercise 23.1 2. 200
7. Feed on pests of crop 1. 2. Living and non-living factors 3. Members of a population may be of the same
8. The predator–prey relationship in the ecological community 3. Ecosystem 4. Occupy different ecological niches species but do not interbreed 4.
9. Smut 10. Easily washed down into lakes and rivers 5. Biosphere 6. Community 7. Niche 5. There is limited amount of rainfall 6. Density
11. Bacteria 12. Leaf spots, blight and soft rot 8. The interaction between living organisms in a 7. Carrying capacity
13. Biological 14. Biological 15. Fungi habitat and he non-living part of the environment
16. 17. 18. 9. Collection of plants and animals living in a Exercise 23.14
particular habitat with full interdependence 10. 1. Amount of food available 2. 3. Mutation
Exercise 21.8 Exercise 23.2 4. Survival of the fittest 5. Absence of predators
1. Hydrating 2. Killing of micro-organisms in milk 1. Crops, pest and beneficial insects 6. Drought 7. Carrying capacity 8.
3. Refrigerating 4. Boiling 2. A biotic factor 3. Lithosphere 9. Commensalism 10. 11. Population
5. Prevents the activity of micro-organisms in food 4. Crops, pests and beneficial insects 12. Temperature 13. Feeding the organisms
5. Radiation 6. Primary producers 7. Quadrat 8. 14. Qudrat
Exercise 21.9
1. Immigration 2. Raising the mortality rate 3. Exercise 23.3 Exercise 23.15
1. Competition 2. Plateau 3. Sahel savanna 1. 2. Light, rainfall and temperature
CHAPTER TWENTY TWO 4. Tropical rain forest 5. Tropical rainforest 3. Determining the genetic makeup of specimens
Exercise 22.1 6. Plateaeu 7. 8. Tundra 9. Savanna 4. Light 5. Light
1. 2. Measles 3. Inside living cells 4.
Exercise 23.4 Exercise 23.16
Exercise 22.2 1. Tropic desert 2. Desert 3. 4 4. 1 5. Tundra 1. Humidity 2. 3. Edaphic
1. They are used in the treatment plants for water purification 6. Groups of different organism living in a habitat 4. Resistance offered by the walls of the banks
2. Cholera 3. Measles 4. Malaria 5. Binary fission 7. Afro – alpine 8. 9. 5. pH of the soil
6. Streptococci 10. Reduces the rate of transpiration 11. Exercise 23.17
12. Living organisms interacting with the physical 1. pH 2. Climatic 3. Turbidity 4. Water
Exercise 22.3 environment 13. 14. Xerophytes
1. Fungi 2. Ringworm 3. Plasmodium 15. Abundant grasses Exercise 23.18
Exercise 22.4 16. Annual rainfall is less than 100cm 1. 2. An anemometer 3. Secchi disc 4. Hygrometer
1. Nitrogen fixation 2. 3. Decomposer 17. There is limited amount of rainfall 18. 5. Barometer 6. 7. An anemometer
4. Salty water 19. A community 8. Anemometer 9. Wind vane 10. Secchi disc
5. They do not cause world-wide epidemic 11. Simple float
Exercise 23.5 12. A group of the same species of organisms living together
6. Immersion in water 7. 8. Isotonic solution 9. 1. Humidity 2. Halophytes
10. They are used in the treatment plants for water 13. 14. Carnivores 15. 16. Turbidity
purification
3. isotonic to sea water 17. 18. Amount of food available 19. 20.
11. 12. 13. 14. 15. Antibiotics 16. 17. 18. Exercise 23.6 21. Edaphic 22. Pressure 23. Become eliminated 24.

Exercise 22.5 1. Rise and fall of water level Exercise 23.19

1. Influenza 2. Kwashiorkor 2. Increases during the dry season 3. Sunlight 1. A well cultivated land
3. Natural acquired immunity 4. Asthma 4. Intensity of light 2. Decrease in the number of organisms 3.
5. Female anopheles mosquito bites a victim 4. Can start with complex communities
Exercise 23.7
6. Ability of the body tissues to resist pathogenic 5. Competition 6. Mesophytes→ shrub → xerophytes
organisms
1. Waxy cuticle on leaves to prevent wetting
7. Active immunity 8. IV 9. II 10. I 2. Pond Exercise 23.20
3. Photosynthesis occurs in the water weeds during the day 1. It persists until the environment or climate changes
11. Tapeworm 12. Malaria fever
13. Wearing of shoes always 4. DuckweedsDucklingTurtlesMan 2. Climax community 3. Primary succession
14. Vaccinating dogs regularly 4. An increase in species diversity 5. Lichens
5. Age of the pond 6. Secchi disc 7. pH
6. A stable composition of plant and animal species
8. Blood worm, pond skater and dragonfly larva
Exercise 22.6 7. Lichen 8. Spirogyra→euglena→grass→water lily
1. Trypanosome gambiense 2. Black fly 9. Aerenchytamatous tissues 10. Zooplankton
9. Pioneer organisms
3. Tsetsefly 4. Trypanosome 5. Butterfly 11. Low salinity 12. Humidity 13.
14. Humidity Exercise 23.21
6. Blackfly 7. Female anopheles mosquito
15. Splash, intertidal, subtidal, bathyal and abyssal 1. 2. 3. 4. Lizard 5. Emigration 6. I and III
8. Paramecium 9. Beetles 10.
16. Halophytes 7. Seed dispersal 8. Disease rate
11. It is associated with the transfer of trypanosomiasis
12. Plasmodium 13. 14. 15. 16. Blood Exercise 23.8 Exercise 23.22
17. Pathogen 18. Cholera 19. Guineaworm-Intestine 1. 2. On a mud flat near the sea 3. Mangrove swamp 1. Increase in natality 2. Succession
20. Inability to swallow 21. Houseflies 4. Prop roots 5. Tropical rainforest 3. Rapid rate of reproduction 4. Competition
6. Nature of substratum 5. Storage in air-tight silos 6. Mixed-cropping
Exercise 22.7
7. Raising the mortality rate 8.
1. Kill the bacteria in it Exercise 23.9
2. Making new materials available at all times 1. Transpiration Exercise 23.23
3. Digested foods are readily available 2. Rainfall, wind, sunlight and humidity 3. Epiphytes 1. Linear curve
4. Flow of fresh air into a house 5. Sewage works 4. Rate of decomposition 2. Net rate of natality and mortality in the habitat
6. Keeping off and checking the spread of diseases 5. Rainfall, temperature, light and wind over a period 3.Predator 4. Census figures
7. Environment 8. Incubation period 9. Cholera 10. 6. Shade – loving species 5. Increased mortality rates
11. Improper handling of food substances 7. Contains large numbers of plant species 6. The number of all the young ones produced
12. Underfeeding 13. Bacterial growth is reduced 8. Aminiotic egg 9. Soil 7. Houseflies
14. Prevent the transfer of germs into food 15. 16. 10. The ground is flooded most of the time 8. The total number of organisms of the same species
11. Mangrove swamp 12. 13. Swamping living together in a given period of time
Exercise 22.8
14. Transpiration 15. Breathing 16. Epiphyte 9. Group of organisms of the d species in a
1. World Health Organization
community interacting with each
2. Practice of deceit in medical services
Exercise 23.10 10. Increasing 11. Interbreed freely
3. Neglect of self appearance 4.
1. Thick bark 2. There is limited amount of rainfall 12. Remain steady 13. Flooding and earthquake
5. Collecting and disposing refuse in urban cities
3. Water, temperature and soil 14. Drought 15.
6. Red Cross activities 7. World Health Organization
8. 4. Rainforest and the Sudan savanna Exercise 23.24
1. Members of a population may be of the same
Revision Exercise Exercise 23.11 species but does not interbreed
1. Female anopheles mosquito 2. Antibiotics 1. 4 2. 1 3. Xerophytes 2. A group of the same species of organisms living
3. Measles 4. Measles 5. Tsetse fly
Exercise 23.12 together
6. Antibiotics
1. Presence of thick bark 3. Have different nutritional needs
7. Production of antibodies which destroy toxins of germs
8. Contaminated faeces are completely kept away from flies 2. Fleshy tissues and reduced leaves 4. Increase in primary production 5. Emigration
9. Outbreak of disease 10. 11. 12. 13. 3. Reduced biochemical activities 4. Feathers in birds 6. Cannibalism, competition, death and aggression
14. Stimulate the production of antibodies 5. Resist being damaged by the loss water 7. Abortion 8. 9.
15. Suffocation 16. 17. 18. Water 6. Desert 7. Spiny leaves 8. Aestivation
19. Distillation 20. Trypanosome 9. Leaves to spine 10. Xerophytes
21. 22. 23. 24. 25. Isotonic solution 26. 11. Broad flattened body 12. 13. Broad leaves
27. Prevent bacteria from multiplying 14. Broad leaf surface

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Exercise 23.25 Exercise 23.39 20. Presence of gill clefts in vertebrate
1. 2. Primary producers 3. Cow 4. Sheep 1. Air cavities 2. Webbed digits 21. IV, III, II, I 22. Pectoral and pelvic girdles
Exercise 23.26 3. Keratinous scales 23. Natural selection 24. Snail
1. Producer 2. 4. Storing water in large parenchyma cells 25. Natural selection 26. Use and disuse
5. Aminiotic egg 27. Acquired traits are heritable
3. DuckweedsDucklingTurtlesMan 6. Poor development and roots xylem tissues 28. Lamarck’s theory 29. Comparative anatomy
4. 5. Grass→Grasshopper→Toad→snake→Hawk 7. Xerophytes 8. Ruminants 9. Mesophytes 30. Darwin 31. Darwin 32. Convergent evolution
6. 7. Maize → mice → snake → hawk 10. I and II only 11. Xerophytes 12. Leaves to spine 33. The deposits have remains of organisms
8. There is no energy loss in a food chain 13. Symbiosis 14. Easy movement 15. Lizard characteristic of when they were formed
9. 2→3→1→4→5 16. Xerophytes 17. Camel 34. Use and disuse 35. Convergent evolution
10. Larger and fewer along the food chain 18. Broad leaves with many stomata 36. Modified insect mouthparts
11. 1, 4, 5, 3, 2 19. Prevent water loss 20. Xerophytes
12. Secondary consumers get only a small portion of 21. Waxy cuticle on leaves to prevent wetting Exercise 24.2
the energy contained in the primary producer. 22. Lizard 23. Xerophytes 1. Dancing of the worker bee 2. Laying eggs
13. A decrease in the number of individuals 24. Dissolved oxygen in the fresh water will diffuse 3. Lamarck's theory-of evolution 4. Soldier
14. Sunlight into the gills 25. 26. Scales in fishes 5. Produce enzymes to digest cellulose
Exercise 23.27 27. Well developed 28. Conservation 29. Thick bark 6. Geographical distribution of organisms
1. Some animals form part of several food chain. 30. Leave with thin cuticle 31. 7. Lizard 8. 9. Grasshoppers
2. Hawk 3. Rat 4. 2, 3 and 7 5. 5→4→3→1 32. Broad thin green leaves 33. Extensive root system 10. Extinction 11. Cockroaches 12. Pentadactyl limb
34. In general, fishes have light dorsal surfaces 13. All members are identical 14. Housefly
Exercise 23.28 35. Gills, streamlined bodies and lateral line 15. Warning colouration
1. I 2. V 3. Diatom → crustaceans →fish → man 36. Feathers in birds 16. Signals the availability of food 17. Nectar
4. Complex feeding relationship in a community 18. Conserving water
5. Tertiary consumers Exercise 23.40 19. An adaptation for camourflage
Exercise 23.29 1. Chlorofluoro carbons 2. Nitrogen 3. Recycling 20. Leathery cuticle and the feathers
1. 5→4→3→1 2. Spirogyra 4. Burning of fossil fuels 21. Camouflage, well developed limbs and effective vision
5. By sitting industries away from residential area 22. Workers, soldiers and reproductive
Exercise 23.30 6. Carbon (II)oxide 7. Nitrogen(IV)oxide 23. Grasshopper is avoiding predation
1. Tadpole 2. Energy 3. Pyramid of energy 8. Continuous felling of trees 9. Nuclear fallouts 24. Mammals 25. Opposable
4. Energy flow from one trophic level to another 10. Bush burning 11. Untreated sewage 26. Mottled colours on moths that rest on lichens
5. Energy from one trophic level to another 12. Noise 27. Disperse the population 28. Workers
6. Conducting census 7. Energy 13. Increases the amount of oxygen in the water 29. Mimicry
8. Representation of numbers of organisms at 14. Noise 15. 16. Sulphur dioxide 30. Ensure their perpetuation despite predatory pressure
different trophic levels 17. Decrease in concentration of dissolved oxygen 31. Symbiosis 32. Easy movement
9. Secondary consumers to decomposers 18. Upsets the balance of the environment and can be 33. Hibernation 34. Countershading coloration
10. Producers 11. Plytoplanktons harmful to organism 35. Tactile 36. Fees on the leaves of crops
12. Of energy loss at each tropic 19. Encouraging population increase 20. 21. 22. 37. Mimicry 38. Remain undetected
13. Terrestrial food web 14. Five 39. Crushing seeds
15. Energy is lost at each tropic level 16. 4 15. Exercise 23.41 40. Raise their body temperature to become active
1. Disappearing habitats 2. 3. 4. 41. Hooked beak and sharp claws 42. Chromatophore
Exercise 23.31 Deforestation 43. A method of survival adopted by plants during
1. 10% 2. Sunlight 3. I 5. Petroleum 6. Mixed grazing the dry season 44. Diurnal animal 45. Hot and dry
4. A decrease in the efficiency of energy conversion 7. Helps to conserve soil fertility 46. Sharp, hooked beak and long claws 47. Aestivation
5. Producers 6. Pyramid of energy 8. Crop rotation and cover crops
9. Leathery cuticle and the feathers 10. Microbes Revision Exercise
Exercise 23.32 11. Insects 12. Crop rotation 13. Spiny leaves 1. Adaptation 2. Extinction
1. Respiration 2. 1st Law of Thermodynamics 14. Creating game and forest reserve 15. Protected 3. Adapt to new conditions 4. Scaly skin
3. Can neither be created nor destroyed 16. 17. Solid mineral 18. Increased rainfall 5. Counter shading 6. Adaptive colouration
4. A decreasing in biomass at each successive level 19. Generation of income the through sale of ivory 7. Protection 8. Croaking 9. Behavioural adaptation
5. 6. Energy is lost at each trophic level 20. Encouraging poaching in game reserves 10. Termites 11. They live together in communities
7. Producer 8. 21. Dependency on forest trees for fuel 22. Trees 12. Grasshoppers 13. Have division of labour
23. Cover cropping 14. Drones 15. Soldier
Exercise 23.33 24. Easily decomposed by microorganism 16. Complicated set of dances 17. Laying eggs
1. Energy 2. Decomposers 3. II 4. I 25. Depletion of natural resources 18. Worker 19. Pollinate flowers 20. Caste system.
26. Over-fishing the seas and lakes
Exercise 23.34 27. Avoiding recycling material because it is expensive
1. Photosynthesis 2. Photosynthesis 28. Presence of broad leaves 29. Prosecutes poachers CHAPTER TWENTY FIVE
3. A forest at midday 4. I and II 30. Deforestation 31. 32. Exercise 25.1
5. II and IV 6. Transpiration 7. 1. Loosening all tight clothing
Revision Exercise 2. Having enough rest
1. Enclosing fishes in ponds where they will not be stolen 3. Tying a tourniquet on a pressure point to increase pulse rate
Exercise 23.35
1. Energy 2. Photosynthesis 3. Oxygen 2. Sunlight
4. Water cycle 5. 6. 7. 8. 3. Discouraging elimination of endangered species
4. Elimination of some wild animals to enable others survive
Exercise 23.36 5. Encouraging tree planting
1. 2. Eutrophication 6. Save some species from extinction.
3. Dumping of sewage 4. Root nodules 7. Afforestation 8. Protect endangered species
9. Conserving natural resources 10. Deforestation
Exercise 23.37 11. Petroleum
1. Denitrification 2. Denitfiying bacterium
3. Nitrobacter 4. Adds nitrates to the soil CHAPTER TWENTY FOUR
5. 6. 7. 8. 9. 10. 11. Exercise 24.1
Exercise 23.38 1. Adverse conditions
1. Light 2. Light 2. Changes that result in individuals of the same
3. A worker termite and a soldier in a limited space species are transmitted to offspring
4. Oxygen a carbohydrates from the algae 3. Tail bone 4. Algae→liverworts→ mosses→ferns
5. Mutualism 6. Mistletoe growing on an orange tree 5. Organisms pass on acquired characters to their offspring
7. Drought 8. Hydra viridis and zoochlorellae 6. Survival of the fittest 7. Genotype is involved
9. Mutualism 10. Tsetse-fly and cattle 8.Organic evolution 9. Jean Lamarck
11. Commensalism 10. The use and disuse of body parts 11. Darwin
12. One organism gains and the other suffers no harm 12. Darwin and Wallace
13. Water 14. Mutualism 13. The deposits have remains of organisms
15. Cannot produce their own food 16. Symbiosis characteristic of when they were formed
17. Parasitism 18. Commensalism 14. Fish 15. Pentadactyl limb 16. Ecology
19. In parasitism the host also derives some benefits 17. Birds 18. Hugo de Vries
from the parasite 19. Animal rather than plant remains

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