BIOLOGY

PRACTICAL
FOR ORDINARY LEVEL STUDENT’S BOOK

(i)
 CHAPTER:1.

FOOD TEST PRACTICALS

Food tests are tests used to determine which nutrients are present in a
food substance

Procedure: This involves the steps to be followed when carrying out the
test for a particular food substance. Steps differ when testing for one food
type from another. Failure to follow these steps often results into a wrong
conclusion.

Observation: It refers to series of changes that occur when carrying Out

an experiment. Different changes are experienced as a person attempts one
Stage after another. These changes can be colour, smell, sound or heat
changes.
Inference:
It refers to the conclusion that is made following the observation. The
conclusion tells whether the type of food tested is present or absent,

Food substances tested at this level are;

 Carbohydrates (reducing sugar, non-reducing sugar and starch)
 Proteins and
 Lipids.
Carbohydrates

Carbohydrates are among of the fundamental classes of macromolecules found in

living organisms.

There are three types of carbohydrates that we can test for.

(a) Reducing sugar.
All monosaccharides and some disaccharides including maltose and
lactose are reducing sugars, meaning that they carry out a type of chemical
reaction known as reduction.
Chemical reagent used to test reducing sugar is called Benedict’s solution.
The function of Benedict’s solution.
To indicate the presence of reducing sugars by changing colour in
solution containing reducing sugar from blue, green, yellow and finally
orange colour which is observed when the mixture is heated. Heating
(boiling) is important since speed up the reduction of copper II (blue) to
copper I (orange)
Benedict’s solution contains copper sulphate. Reducing sugars reduce
soluble blue copper sulphate; containing copper (II) ions (Cu2+) to
insoluble red-brown copper oxide containing copper (I).
Cu2+ + e- →Cu +[Blue solution Brick red ppt]
Natural sources of reducing sugar are;
 Ripe bananas,
 Ripe oranges,
 Ripe pawpaw,
 Ripe mango and
 Onion bulb.
 Carrots
 Ginger
Functions of reducing sugars;
 They provide energy to the body
 They building blocks of molecules like cellulose.
Properties of reducing sugar
 They have sweet taste
 More soluble in water due to the presence of large number of
OH groups make reducing sugar much more water soluble than
most other molecules of similar molecular weight. They reduce
mild oxidizing agents, such as Benedict’s reagents.
 They are crystalline
(b)non-Reducing sugar (disaccharide and polysaccharide)
Disaccharides and polysaccharides are also called complex sugars. Other
disaccharides such as sucrose do not have the ability to reduce copper (II)
Ions to copper (I) ions. These are called non-reducing sugars. Therefore,
non-reducing sugars cannot be tested directly by Benedict's solution.
instead it is first convened to reducing sugar

Chemicals or reagents used to test non-reducing sugar are;

(i) Dilute hydrochloric acid: -
Function of dilute hydrochloric acid, is to break the bonds of
complex sugars to simple sugar (reducing sugar).
(ii) Sodium hydroxide solution: Its function is to neutralize dilute
hydrochloric acid solution added in the mixture solution.
(iii) Benedict’s solution which is blue in colour:-The function of
Benedict’s solution is to indicate the colour changes in solution
containing non-reducing sugars from blue, green, yellow, orange,
and finally brick red color solution observed when the mixture is
heated. Heating facilitates the breakdown (Hydrolysis) of complex
 sugar and reduction of copper II (blue) to copper I (orange)
Natural sources of non-reducing sugar are;
 Sugarcane,
 Honey Bee,
 Sprouted Cereals (Germinating Cereals Like Maize, Millet and
Wheat).
Functions of non-reducing sugar
 They are source of energy
 They are building blocks of molecules e.g. cellulose
Digestion of non-reducing sugar also ends in ileum and can be shown by
word equation; Sucrose+ Water Glucose + fructose
(c) Starch– This is a carbohydrate made by the condensation of many
glucose molecules. Starch occurs naturally in plant cells as small particles
called granules. It is found in abundance in plants.
Biochemical test for starch
The presence of starch in biological materials can be tested by using
Iodine solution. If is added to a sample that contains starch, the color
changes to a dark blue (or blue-black). In the absence of starch, theorange-
brown colour of the aqueous solution remains.
The function of Iodine solution
To indicate the presence of starch where blue-black colour will be
observed
Natural sources of starch are;
 Cassava Root,
 Maize Grain,
 Irish Potato,
 Millet Grain,
 Sorghum Grain.
 Rice grains
Digestion of starch starts in the mouth and ends in the small intestine
(ileum). In the mouth, the enzyme responsible for digestion of starch is
known as salivary amylase produced by salivary gland in form of saliva.
The word equation for hydrolysis of starch;
Starch + Water maltose
The second portion for the digestion of starch is in the duodenum. In the
duodenum the hydrolysis of starch is converted to maltose by the enzyme
pancreatic amylase produced by the pancreas.
The last portion for the digestion of starch is the ileum. In the ileum the
hydrolysis of maltose is converted to glucose by an enzyme called maltase
produced by the intestinal wall. The word equation for the hydrolysis of
maltose is;
Maltose + Water glucose
Excess glucose is stored in the liver muscles in the form of glycogen.
Glucose is converted to glycogen by insulin.
Glucose glycogen.
Functions of starch are;
 To provide energy to the body.
 It is important component of cell membrane.
Properties of starch
 Not sweet
 Insoluble in water
Proteins
Proteins are the compounds made up of the elements Carbon, Hydrogen,
Oxygen and Nitrogen or Sulphur depending on the type of amino acid.
Chemicals used to test proteins are;
(i)Sodium hydroxide solution and
(ii) 1% of copper (II) sulphate (1% CUSO4) solution.
Sodium hydroxide solution is added first, followed by drop by drop of 1%
of copper (II)sulphate (1% CUSO4) solution. If protein is present in the
sample solution (food components), the purple or violet colour will be
observed in the mixture solution.
Natural sources of proteins are;
 Beef (Meat)
 Fish
 Chicken
 Milk
 Egg Albumen
 Bean Seeds
 Pea Seeds
 Groundnuts
 Mushrooms.
 Castor seeds
Properties of proteins
 They have large molecules so they form colloids instead of true
solution.
 They are affected by pH
 Proteins are denatured by strong heat.
Functions of proteins are;
 To promote growth and repair of body tissues.
 It is the major component of the cell membrane.
 They play role in transportation of materials across cell
membrane.
 They form part of the cell structure like glycoproteins.
 They form antibodies that fight against pathogens in the body.
 They form enzymes.

Deficiency of protein in Children

It leads to disease called kwashiorkor.
NOTE
Protein is not stored in the body. The reason is that, the end product of
protein which is amino acid is broken down through the process called
Deamination in the liver to form ammonia (from amino group) which is
extremely toxic(poisonous) to the body tissues. Hence ammonia is made
less poisonous (less toxic) as it is converted to urea in the liver through the
processes called Detoxification. Urea is processed to the kidney and
removed from the human body in form of urine through the process
known as urination.
The remaining part of amino acid (with carboxyl group) is converted to
glucose and stored in the liver in form of glycogen.

Lipids
Lipids are the compounds made of the elements Carbon, Hydrogen and
Oxygen. A lipid is composed of glycerol molecule and fatty acids joined
through condensation.

Lipids can be tested in various ways;

1. Sudan III test.
2drops of Sudan III solution are added to 2ml of the sample
solution in a test tube. If lipid is present in the sample solution
(food component) droplets that turns red (red ring) will be
observed on the top of the mixture solution.
2. Grease spot test
(i) Rub a drop of the sample on to a piece of paper.
(ii) Allow time for any water to evaporate.
 (iii)Warm gently in order to speed up the process or reaction.
If A permanent translucent spot on the paper indicates the
presence of lipid on a food sample.
Natural sources of lipids are;
 Milk
 Avocado
 Sunflower Seeds
 Fish
 Groundnuts seeds
 Olives
 Coconuts.
 Castor seeds
Properties of lipids
 Lipids are insoluble in water.
 They dissolve in organic solvents
 When fat is rubbed against paper, the paper becomes
translucent.
 In a mixture of water and Oil, Oil takes up Sudan III dye to
form a red layer or ring on the top, leaving the water clear.
 Oils react with organic acid and stain black.
Functions of lipids are;

 Lipids are a source of energy.

 They provide more energy than all other food substances. Each
gram of lipid provides nine calories of energy.
 They are important components of cell membranes.
 Fat deposits surround and protect body Organs such as the heart
and kidneys.
 Storage of fat in the adipose tissue under the skin help to regulate
body temperature by insulating the body against loss of heat,
 Fat-soluble vitamins are also stored in fatly tissues.
 Essential fatty acids are important for the formation of substances
that help to control blood pressure and activate the body's immune
response.
Note:
There are two forms of lipid which are fats and oils.
 Fats are solid at room temperature and are usually extracted from
animals.
 Oils are liquid at room temperature and usually extracted from
plant seeds. fats are stored under skin
Note: Excess lipid in the human body leads to obesity
Obesity increases the likelihood of conditions such as;
 High blood pressure
 Heart diseases
 Diabetes
 Stroke
 Respiratory problems

Part of Medium Secretion Enzymes Substance Product of

alimentary secreted digested digestion
canal
Mouth Alkaline saliva Salivary amylase Carbohydrate Maltose
(starch)
Stomach Acidic Gastric Pepsin Protein Peptides
juice Renin Soluble milk Casein
protein
Duodenum Alkaline Pancreatic Trypsin Protein Peptides
juice Pancreatic Starch Maltose
amylase
Pancreatic lipase Lipid Fatty acids
and
glycerol
Ileum Alkaline Intestinal Maltase Maltose Glucose
juice Sucrase Sucrose Glucose
and
fructose
Lactase Lactose Glucose
and
galactose
Peptidase Peptides Amino
(erepsin) acids

Lipase lipid Fatty acids

and
glycerol

FOOD TEST REPORT

Food tested PROCEDURE OBSERVATION INFERENCE

STARCH To 2cm3of solution X in a test Blue-black colour was Starch was present
tube, 3drops of Iodine observed in the mixture
solution were added and then solution
shaken well.
REDUCING To 2cm3of solution X in a test Series of colour changes Reducing sugar
SUGAR tube,2ml of Benedict’s were observed from blue to was present
solution was added then green to yellow to orange to
heated. brick red precipitates
 NON- To 2cm3 of solution X in a test Series of colour changes Non-reducing
REDUCING tube,1ml of dilute were observed from blue to sugar was present
SUGAR hydrochloric acid was added green to yellow to orange to
followed by heating and then brick red precipitate
left to cool, 1ml of sodium
hydroxide solution followed
by addition of 2ml of
Benedict’s solution and then
heated again.
PROTEIN To 2cm3of solution X in a test Purple or violate colour Protein was
tube, 1cm3 of sodium observed. present
hydroxide solution was added
followed 2drops of 1% copper
II sulphate solution and the
mixture was shaken well then
allowed to settle.
FATS/OILS To 2cm3of solution X in a test A red- stained oil layer Fats/oils was
tube, 3drops of Sudan III separates on the surface of present
solution were added and the solution.
mixture was shaken well then
allowed to settle for 1miute.

Note: On the case of testing reducing sugar and non- reducing sugar, you
must start with reducing sugar. If reducing sugar present, there is no need
to test non- reducing sugar.
Report for some solution preparations
Preparation of Sample solution from Irish potato
(i) Irish potato was peeled and then sliced into small pieces.
(ii) Sliced pieces of Irish potato were put into mortar and then grinded
or crushed.
(iii)Little amount of water was added and then filtered to get potato
solution.
(iv)The solution was filtered in a beaker and labeled.

Preparation of sample solution from sugarcane

(i) A piece of fresh sugarcane was peeled and then sliced into small
pieces.
(ii) Sliced small pieces of sugarcane were put in the mortar and then
crushed.
(iii)Little amount of water was added in the mortar then fibers of
sugarcane was squeezed to get sugarcane juice(solution).
(iv)The solution was filtered in a beaker and labeled.

Preparation of sample solution from onion bulb

(i) Onion bulb was peeled and cut into two halves by using a knife.
 (ii) Halves of onion was sliced into small pieces.
(iii)Sliced of onions were put in the mortar and crushed using pestle
and mortar.
(iv)Little amount of water was added and then filtered to get solution.
(v) The solution was filtered in a beaker and labeled.
Preparation of sample solution from cassava root
(i) A piece of cassava was peeled and then sliced into small pieces.
(ii) Small pieces of cassava were put in the mortar and grinded or
crushed using pestle.
(iii) Little amount of water was added and then filtered to get solution.
(iv) The solution was filtered in a beaker and labeled.

ACTUAL PRACTICAL QUESTIONS AND THEIR ANSWERS

NECTA 2019
BIOLOGY 2B

1. You have been provided with four test tubes labeled 1,2,3 and 4; a
beaker, sieve measuring cylinder, test tube rack, specimen P and
table reagents. Use them to carry out the experiments instructed in
item (i)-(ix), then answer the questions that follow.
(i) Take specimen P, peel it to remove the outer cover and cut it
into four pieces.
(ii) Grind two pieces of specimen P by using a mortar and pestle
to obtain the paste
(iii)Put the paste in a beaker and the add 30ml of water and steer
the mixture
(iv)Filter by using a sieve to obtain solution P.
(v) Put 2ml of solution P into each of the test tube 1,2,3, and 4
(vi)Add 2 drops of iodine solution into the test tube 1
(vii) Add 2 ml of Benedict’s solution into test tube 2 and boil the
content.
(viii) Add 1 ml of dilute hydrochloric acid into the test tube 3 and
boil the mixture. After cooling, add 2 ml of sodium
hydroxide solution slowly until the fizzing stops followed
by 2 ml of Benedict’s solution and boil the mixture again
(ix)Add 1 ml of sodium hydroxide solution into the test tube 4,
followed by 2-3 drops of copper sulphate solution.
Questions
a) What is the aim of experiment?
b) Based on observations made in the test tubes 1, 2, 3 and 4, what
are the types of food substances contained in the specimen P? Give
reasons to justify your answers.
c) Why sodium hydroxide solution and dilute hydrochloric acid was
used in this experiment?
d) Why boiling and cooling is important in procedure (viii)?
e) What will be the end product of digestion of digestion of food
substances contained in specimen P to the human body?
f) What is the importance of the food substances identified in
specimen P food substances identified in specimen P to the human
body?
g) Why the skills used in this experiment useful for preparation of
balanced diet in your daily life?

ANSWERS
a) The aim of experiment was to determine which food nutrients were
present in food specimen P.
b) The food nutrients contained in specimen p was starch in a test
tube 1 since the colour of the mixture solution changed to blue-
black.
c) Sodium hydroxide solution: –Its function is to neutralize dilute
hydrochloric acid solution added in the mixture solution
Dilute hydrochloric acid: -
Function of dilute hydrochloric acid, is to break the bonds of
complex sugars to simple sugar (reducing sugar).
d) boiling is important in order to hydrolyse any polysaccharide and
disaccharide into monosaccharide.
e) The end product of digestion of food substance starch is glucose
f) Functions of starch are;
 To provide energy to the body.
 It is important component of cell membrane.
g) There are several reasons why food testing is important This
aspect is part of routine quality control, which in addition to
evaluating the food component, further helps determine the state of
the raw materials, which controls various stages of processing
a food from the moment it arrives, until it exits.
 PRACTICAL ACTIVITY
1. You have been provided with specimen P (Groundnuts seeds) and
a piece of white paper
Procedure
(i) Peel the specimen P.
(ii) Rub the peeled specimen P on a piece of white paper
(iii)Expose the paper to light,
(iv) Compare the part of the paper rubbed with seeds with the part
that was not rubbed.
(v) Record what you see.
Questions
a) What is the aim of experiment?
b) Based on observations made on a piece of white paper what
is the type of food substances contained in the specimen P?
Give reasons to justify your answers.
c) What will be the end product of digestion of digestion of
food substances contained in specimen P to the human body?
d) What is the importance of the food substances identified in
specimen P to the human body?
e) What other seeds can you use to perform the grease spot test
ANSWERS
a) The aim of experiment was to test for the presence of, lipids
in specimen P by the grease spot.
b) The food nutrients contained in specimen p was lipids on a
piece of white paper since the paper becomes translucent
c) the end product of digestion of digestion is fatty acids and
glycerol
d) Functions of lipids are;
 Used as energy source in the body
 Fat deposits protect organs such as heart and kidney
 Insulate the body against heat loss
 Activate the body’s immune response
e) Other seeds can you use to perform the grease spot test
 Avocado
 Sunflower Seeds
 Coconuts.
 Castor seeds
 NECTA 2018
BIOLOGY 2A
1. You are provided with specimen X
(a) write the procedures you will follow to prepare a solution X for
investigation
(b) Using chemical reagents provided, carry out experiments to
identify food substance(s) present in specimen x. Record your
experimental work as shown in table 1 below.
Table 1

Food tested Procedure Observations inference

(c) State two properties of the food substance(s) identified in specimen

X
(d) Name four other sources which contain the same food substance
as that identified in specimen X
(e) mention the parts of the human alimentally canal in which the
digestion of the food substance in specimen X takes place
(f) Explain how the body stores excess food substance(s) identified in
solution x
(g) Why the food substance(s) identified in solution X important in
human body?
ANSWERS
(a) Preparation of sample solution from orange fruit
(i) Orange fruit was peeled and then sliced into small pieces.
(ii) Small pieces of orange fruit were put into mortar and then grinded
or crushed.
(iii) Little amount of water was added and then filtered to get orange
fruit solution (juice).
(iv)The solution was filtered in a beaker and labeled X.

(b) Table 1

FOOD TESTED PROCEDURE OBSERVATION INFERENCE

STARCH To 2cm3of solution X The mixture solution Starch was not present
in a test tube,2drops retained reddish-brown
of iodine solution colour of iodine solution
were added and then
shaken well.
 REDUCING To 2cm3of solution X Series of colour changes Reducing sugar was
SUGAR in a test tube,2ml of were observed from blue to present
Benedict’s solution green to yellow to orange
was added then to brick red precipitates
heated.
Protein To 2cm3ofsolution X The mixture solution Protein was not
in a test tube, 1cm3 of retained the blue colour of present
sodium hydroxide 1% of copper II sulphate
solution was added solution

CHAPTER:2.
CLASSIFICATION OF LIVING THINGS.
Classification-Is the branch of science which deals with the process of
sorting, grouping and naming living organisms according to their
similarities and differences. The study of classification is known as
Taxonomy
Groups of organisms involved in biology practicals are:-
1. Kingdom fungi
2. Kingdom plantae
3. Kingdom animalia.

Kingdom Fungi
Organisms in this group include Mushrooms, yeast, mucor and bread mould
Characteristics of Kingdom Fungi
 They have chitin as a structural carbohydrate in the cell wall. This
is a feature typical of animals such as arthropods; example insects.
 They store carbohydrates in the form of glycogen.
 They are heterotrophs. Thus, they cannot manufacture their own
food since they are either saprophytes or parasites. The parasitic
fungi can be facultative or obligate.
Similarities between fungi and plants
 Their cells have cell wall.
 Some fungi have vegetative bodies that are superficially
differentiated into shoot-like and root-like systems.
 Most fungi’s growth is restricted to apical cells.
 They are non-motile.
 They reproduce sexually by formation of spores such as ascospore
in yeast and basidiospores in mushrooms. Some fungi reproduce
asexually by producing spores such as sporangiospore.
  They lack centrioles in their cells.
Phyla of kingdom fungi
a) Phylum Zygomycota
b) Phylum Ascomycota
c) Phylum Basidiomycota

Phylum Zygomycota
Phylum Ascomycota Members Of this phylum are commonly called
ascomycetes or sac fungi. This is because their spores are enclosed in sac
like structures known as asci (singular Ascomycetes can reproduce both
sexually through spores or asexually by budding. Some are single-celled
(unicellular) organisms such as yeast.
Representative organisms are mucor and black breadmould (Rhizopus).
Characteristics of Zygomycetes
 They are multicellular.
 They are saprophytic, growing on decaying organic materials.
 They reproduce sexually through zygospores or asexually through
sporangiosphores.
 Have hyphae without cross walls.
Distinctive features of phylum Zygomycota
Members of the phylum Zygomycota have the following features that
differentiate them from other phyla:
 They have aseptate hyphae which lack cross walls between
adjacent cells. They are therefore coenocytic in structure.
nuclei in their cell. The nuclei will fuse only after the
formation of ascus. The diploid nucleus will later undergo
meiotic and mitotic divisions to form ascospores.
 Some ascomycetes such as yeasts are unicellular and reproduce
asexually by budding (new cells form on the surface of the old
ones).
Distinctive features of phylum Ascomycota
The following are the distinctive features of the phylum Ascomycota:
 They have specialised spore producing structures called
ascocarps.
 They reproduce asexually using conidia formed on the tips of
conidiophores; in some members asexual reproduction is
through budding.
 Some are unicellular heterotrophs, and lack typical hyphae,
for example Saccharomyces.
 Figure;2.3: Yeast
Habitat of yeast
They grow on flowers, ripen fruits, juices and slim wax from the trees.

Economic importance of yeast to industries

 It is a reach source of vitamins B and proteins
 Used in fermentation of various carbohydrates
 Yeast cells are used in production of lactic acid and citric acids
 It is used in baking to make dough rise.

Adaptations of Saccharomyces(yeast) to its mode of life

Saccharomyces(yeast) species have the following adaptive features that
enable them suit to their mode of life:
 They store carbohydrates in the form of glycogen for use
during shortage of food supply.
 They have permeable cell walls to allow entry of nutrients that
are obtained from external digestion. Thus, they can absorb
simple monosaccharides and vitamins directly from their
environment.
 They secrete extracellular enzymes such as sucrase and
cellulase for digestion of carbohydrate, and protease for
digestion of protein.
 They have high reproductive rate through budding, to produce
new cells hence increase in number.
 Spores’ ability to remain dormant in unfavourable conditions
ensures their existence.
 Some Saccharomyces are facultative anaerobes. They have an
ability to respire anaerobically or aerobically, which ensures
survival in both aerobic and anaerobic conditions.
Economic importance of kingdom fungi
 They are source of food for example mushroom
 They are decomposers for example.
 Fermentation of carbohydrates
 Source of vitamin B
 Used in production of phytohormones.
 Used in food industry
 Increase soil fertility
 Used in making medicine for example peniciline from
penicilium
 Used in treatment of polluted water and soil.
 They are poisonous e.g. some of Mushroom (Amanita spp)
 They cause diseases to human e.g., Athletes foot disease
 They cause damage to crop plants during growth e.g. puccinia.
 They cause damage to woods on both living and stored timber
e.g. bracket fungi
 Cause food spoilage

Kingdom Plantae
Kingdom plantae- Is comprised of green plants that are able to make their
own food by the process known as photosynthesis. They include fern
plant, maize, pines, bean plants etc
General characteristics of kingdom plantae
 They possess chlorophyll
 Plants have cell wall made cellulose
 They are multi-cellular organism
 Their life cycle involves alteration of generation which is more
prominent in lower plants.
 They have well vegetative bodies and are sometime
differentiated into roots, stems and leaves.
 They have prominent large vacuoles in their cells and store
carbohydrate in form of starch.
Divisions of Kingdom Plantae
1. Division Bryophyta
2. Division Filicinophyta (Pteridophyta)
3. Division Coniferophyta
4. Division Angiospermophyta
Division Bryophyta
Members of the division Bryophyta are called bryophytes, which are the
most primitive plants. They are found in wet and shaded environments,
such as on forest floors, rock surfaces, bare soil, cracks of paved surfaces,
bricks, on trunks, and branches of trees. The reproduction process in
bryophytes depends on availability of water that is why their distribution
is restricted to shady and moist places. Examples of bryophytes are mosses
and hornworts.
The structure or mosses Mosses are primitive plants believed to be among
the plants to develop the ability to live on land.

Characteristics of bryophytes
 They show alternation of generations in which the haploid
gametophyte generation is dominant over the diploid sporophyte
generation.
 The sporophyte is attached on the gametophyte generation, and it
depends upon it for support and nutrition.
 The gametophyte generation is anchored by filamentous rhizoids
which provide support and used for absorption of water and
mineral salts.
 They lack vascular tissue, meaning that they have no xylem and
phloem.
 They have a thallus body which shows low level of differentiation;
hence, they lack true leaves, stems, and roots.

Figure;2. 5: Fern Plant

Advantages of fern plants
 They constitute ground-cover in moist areas; they are primary
producers, thus produce food for themselves and for heterotrophic
organisms in an ecosystem;
 They are used for decoration in homes and offices;
 They are the major components of coal, a fossil fuel which is made
up of the remains of primitive plants;
Adaptations of fern plants to its mode of life
Fern plant possess the following features which enable them to adapt to
their environment:
 They have chloroplasts containing chlorophyll for capturing light
energy needed for photosynthesis.
 They have roots for anchorage and absorption of water and mineral
salts.
 They have stomata which facilitate gaseous exchange.
 They have xylem responsible for transportation of water and
dissolved minerals and also, they have phloem for translocation of
manufactured food.
 Rhizomes play part in storing food and propagating new plants,
and can remain viable in the soil for a long time to ensure survival.
 They have a well-developed and independent sporophyte
generation, since the gametophyte withers and dies as the young
leaves of sporophyte grow.
 They have cuticle in their leaves to prevent excessive water loss.

 Archegonia secrete chemical which attracts antherozoids to swim

towards the egg during fertilization.

Division coniferophyta
Coniferophyta is a division of kingdom Plantae which belongs to a broad
group of non-flowering seed-bearing plants, referred to as gymnosperms.
The word gymnosperms originated from a combination of two Greek
words Gymno meaning ‘naked’ and sperma meaning ‘seed.’ Theophrastus
was the first person to use this term in his book “Enquiry into plants”
referring to plants producing naked seeds.
Characteristics of division Coniferophyta
 They are non-flowering, seed bearing plants, producing naked
seeds which are not enclosed in ovaries or fruit tissues.
 Sexual reproduction involves microspores (male gametophyte) and
megaspores (female gametophyte) which are found in male and
female cones or strobili respectively.
 Fertilisation does not require water; instead, they develop pollen
tubes which carry sperms to the ovule for fertilisation.
 They have poor xylem with only tracheids as conducting elements
but no vessel elements. This is the reason why most coniferophytes
produce soft wood.
  Leaves are reduced into spiny or needle-like leaves to minimize
water loss through transpiration.

Distinctive features of division Coniferophyta

Presence of the following features in members of division Coniferophyta
differentiate them from members of other divisions:
 The pollen grains are winged to provide buoyance; hence they are
wind pollinated.
 They have seeds which are not enclosed within the ovary; thus, no
ovaries, and no formation of fruits.
 Their phloem tissues are associated with albuminous cells instead
of companion cells.
 The majority produce resin in special ducts called resin canals.
Such resin is useful in wound healing and deterring browsers.
 Most are evergreen plants with needle-like shaped leaves.
 Fertilisation in conifers does not require water, instead male
gametes are carried by wind or insects to the female reproductive
organs
 They have simple xylem with only tracheids as conducting
elements but no vessel elements. This is the reason why most
coniferophytes produce soft wood.
 Their phloem tissues lack companion cells; instead, they are
associated with albuminous cells

Adaptations of Pinus to its mode of life

Pinus are able to adapt to their environment due to presence of the
following features:
 The root and shoot systems are well developed to provide the plant
with a good contact to the soil and atmosphere.
 They have roots for absorption of water and nutrients from the soil.
 The plant has mechanical tissues for support and vascular tissues
for transportation of water and food.
 They have an elaborate mechanism for reducing water loss through
transpiration. This becomes possible due to presence of thick
cuticle, needle-like leaves to reduce their surface area and a
reduced number of stomata pores.
 They produce lighter pollen grains, each with two wing-like
structures which make them to float in air, hence easily to be
carried by wind for pollination.
 They can reproduce sexually without necessity of using water,
because the transfer of male gametes to female gametes is through
 pollen tube, which ensures reproduction in terrestrial environment
where water is limited.
 The seeds are winged; hence, they can female cones. Normally,
male cones are borne in clusters at the axils of lower branches.
Take some pollen grains from the male cones and mount a few in a
drop of water on a slide for examination under the light
microscope to observe the wings on each.
Economic Importance of Conifers
 Provide soft woods for construction
 Used in making drugs
 Prevent soil erosion
 Production of turpentine and resin from pines
 They are ornamental plants

Figure; 2: Conifers
Adaptation of conifers(pine) to its habitats
 They have extensive roots for absorption of water
 They have needle-like to reduce transpiration
Disadvantages of the division Coniferophyta
 Coniferous forest completely shades the ground and prevents the
growth of other plants.
 Wood products from conifers are soft and can be easily attacked by
termites if not treated.
 They have needle like thorny leaves that can prick and cause
injury.
 Resins which are produced by pines catch fire easily. Thus, in case
of fire outbreak in a Pinus forest, fire is likely to spread rapidly
 because of the resins.

Division Angiospermophyta
Angiospermophyta is the division in Kingdom Plantae which comprises
plants commonly known as flowering plants or angiosperms. Angiosperms
are the most diverse and a successful group of all the plants.
Distinctive features of Angiospermophyta.
 They show alternation of generation
 Fertilization does not depend on water
 Have well developed vascular tissue
 They produce flowers
 They undergo double fertilization
 Their seeds are enclosed in an ovary
Classes of division Angiospermophyta
Old system of classification recognised two classes based on the number
of cotyledons; Monocotyledon and Dicotyledon.

Class Monocotyledoneae
This class contains plants with one cotyledon. Examples of monocots are
maize, sugarcane, wheat, millet, sisal, coconuts and banana plants.
Features possessed by members of the class Monocotyledoneae
 Monocots have parallel leaf venation.
 Flower parts normally occur in multiples of three.
 The embryo of monocot seeds bears one cotyledon.
 Monocot leaves are composed of an open or closed sheath which
encloses the stem.
 Their vascular bundles in stems are scattered.
 They have fibrous root system.
 They have long and thin leaves.
 Figure;2.7: Maize Plant

Class Dicotyledoneae
This class contains plants with two cotyledons. Examples of dicots arebeans,
mangoes, coffee, groundnuts and sunflower plants.
Distinctive features of class Dicotyledoneae
 Dicot leaves have net like venation.
 Their stems have vascular bundles which appear in a ring form.
 They have tap root system.
 Their seed embryo has two cotyledons.
 Floral parts are normally in multiples of four or five.
 Dicot plants have petioles that support the leaf.
 They have short and broader leaves
 Flower

Leaf
Bean pod

Stem

Tap root (Primary ro ot) Bean seed

Figure; 2.8: Bean Plant

Economic importance of angiosperms
 Are vital for the existence and economy of humans
 Source of medicines
 Fibres of plants are used in textile industries
 Rubber tyres are produced from sap of tropical rubber trees
 Prevent soil erosion
Adaptation of cactus plant to its habitat
 They have thorny for protection
 They have thick cuticle to reduce water loss
 They have long roots for absorption of water
 They have chlorophyll for photosynthesis

Kingdom Animalia
Animals are a diverse group of organisms that make up the kingdom
Animalia. This kingdom comprises of animals, which are multicellular
eukaryotic organisms.
It is the largest kingdom composed of variety of animals.
 Most animals have higher degree of differentiation
Phyla of the kingdom Animalia;
(a) Phylum Arthropoda
(b) Phylum Platyhelminthes
(c) Phylum Aschelminthes(Nematoda)
(d) Phylum Annelida
(e) Phylum Chordata
Phylum Arthropoda
This is the largest group in the Kingdom Animalia, with high species
diversity. Arthropods represent about three-quarters of all known living
organisms. Some of the well- known arthropods include insects,
crustaceans, and arachnids. Arthropoda comes from two Greek words
arthro that means ‘joint’ and podos that means ‘foot’. Therefore, all
arthropods have jointed appendages. Arthropods are found in almost every
known environment including marine, freshwater, and terrestrial
ecosystems. They vary extremely in their habitats, life histories, and
feeding habits

Characteristic features of Arthropods

 Have jointed appendages or legs
 Have exoskeleton made of chitin
 If wings present are in pairs
 Body division are in two (i.e. head and thorax) called cephalothorax
or in three (i.e. head, thorax and abdomen)
 Their hearts are dorsally located
 Some have antennae
 Have open circulatory system (i.e. blood not enclosed in blood
vessels)
Classes Phylum Arthropoda: -
(a) Class Insecta
(b) Class Arachnida
(c) Class Crustacea
(d) Class Diplopoda
(e) Class Chilopoda

1. Class Insecta
The members of class insecta are called insects.
Distinguishing characteristics of insects: -
Insects have the following features that differentiate them from other
arthropods:
 Their bodies are divided into three main regions or tagmata,
namely the head, thorax, and abdomen.
 They have three pairs of walking legs on the thorax (one pair per
thoracic segment).
 They usually have one or two pairs of wings on the thorax, some
members may lack wings.
 They use the tracheal system as their respiratory surface with
segmental spiracles.
 They undergo metamorphosis during their development through
the molting process.
 They have a pair of compound eyes and simple eyes.
  They usually have three pairs of mouthparts, which are maxillae,
mandible, and labrum
Grasshopper
Habitat: Grassland, plants
Economic importance of grasshopper
 Source of food to birds and other animals
 Used for biological studies
 Destroy crops e.g. locusts.
 Increase soil fertility

Figure;2.9: Grasshopper
Adaptation of grasshopper to its habitat.
 They have jointed legs for locomotion
 They have antenna for sensitivity
 They tracheal system for gaseous exchange
 They compound eyes for vision.
Housefly
Habitat: Decaying matter e.g. toilet
Economic importance of housefly.
 vector of disease e.g. cholera and sleeping sickness
 Used for biological studies
 Source of food to some organisms e.g. toad, chameleon
 Figure;2.10: Housefly
Beetle
Habitat: animal dung – on cow dungs.
Economic importance beetle:
 Contribute to soil fertility
 Used for biological studies/experiments
 Source of food to some animals e.g. birds
 Agents of pollination.

Figure;2.11: Beetle
Bee
Habitat; Found on beehives
Economic Importance Bee
 Source of food to some organism
 Agent of pollination
 Can sting and poison
 Increase soil fertility when die

Figure;2.12: Diagram of bee

Cockroach
Habitat: Found on toilets
Economic importance of cockroach
 Vector diseases such as cholera, plague and dysentery
 Source of food to some organism
 Used in biological studies

Fig: Structure of a cockroach

Mosquito
Habitat: on stagnant water
Economic importance of mosquito
 Vector of diseases. Example malaria, dengue, elephantiasis
 Used in biological studies

Figure;2.14: Mosquito
Butterfly
Habitat ;found on flowers

Figure ;2.14: Butterfly

Advantages of Class Insecta
 Are agents of pollination
 Are source of food for humans
 Insects are scanvegers
 Some commercial products are obtained from insects for example
honey
 Increase soil fertility
Disadvantages of Class Insecta
 Vector of diseases
 Can parasitize domestic animals for example lice
 Destroy crops for example locusts
2. Class Arachnida
The arachnids represent the second largest group of terrestrial arthropods
after the insects. The class includes the animals whose bodies are
organised into two tagmata called cephalothorax or prosoma (fused head
with thorax) and abdomen (opisthosoma). Most of them are carnivores,
except the mites, which are herbivores. Members of this class include
spiders, mites, ticks and scorpions.

Distinguishing characteristics of Arachnids,

Distinctive features of class Arachnida Arachnids can be distinguished
from other members of the phylum Arthropoda by the following features:
 Their bodies are divided into two regions; prosoma and
opisthosoma, separated by a narrow waist-like constriction.
 They lack antennae; alternatively, they use pedipalps to detect
external stimuli.
 They lack compound eyes; they only have simple eyes.
 They lack true mouthparts; instead, they have two pairs of
appendages born from prosoma. One pair, the chelicerae or
poisonous fangs, is used for killing preys or defending themselves;
the other pair called pedipalps holds the prey in place when the
 animal injects poison.
 Usually, they have four pairs of walking legs.
 Their respiratory structures are book lungs or book gills or trachea.

Tick
Habitat: on animal’s skin such as cow, goat

Figure;2. 15: tick

Scorpion
Habitat: at the corner of houses or caves.
Economic importance of scorpion:
 Used for biological study
 Can bite and poison other animals
 Source of food to some animals e.g. birds

Figure;2. 15: Scorpion

Spider
Habitat: Under the stones or tree logs
Economic importance of spider
 Used for biological study
 Can sting and poison other animals
 Source of food to some animals, e.g., birds, lizard

Figure; 2.16: Spider

Adaptations of spider to its mode of life
Spiders live in almost every habitat. They are adapted to different
environments because:
 They have pairs of chericerae which produce silk for capturing
preys.
 They have pedipalps for sensation.
 They have four pairs of legs for locomotion.
 The hairy spiders have stings used to paralyse prey and defend
themselves.
3. Class Crustacea
Crustaceans form a large group of arthropods that include familiar animals
such as crabs, lobsters, prawns, shrimps, barnacles, and crayfish. Most
crustaceans are marine aquatic animals, some are found in fresh water
habitats, and a few are terrestrial, for example woodlice (Isopota) found in
leaf litter.
Distinctive features of class Crustacea
Crustacea have distinctive features that make them unique among other
arthropods as highlighted below:
 They possess two body division, which are cephalothorax (the
head fused with thorax) and abdomen.
 They have carapace or an exoskeleton hardened with calcium salts
which acts as a protective shell.
 They have heads bearing two pairs of antennae.
  They have a pair of compound eyes at the ends of movable stalks.
 They have at least three pairs of mouthparts.
Crab
Habitat: Water bodies e.g. rivers, lake.
Economic importance of crab.
 Source of food to man
 Used for economic purpose when sold (source of income)
 Can bite other animals
 Used for biological studies

Figure;2.17: Crab
Adaptation of Crab to its habitat
 Have exoskeleton for protection against enemies
 They have pincer like claw at edges for catching prey
 Possess gills for respiration
 Their legs are modified for swimming
4. Class Diplopoda
The class Diplopoda consists of members with many legs; usually two
pairs of legs per body segment. An example of a member of class
Diplopoda is a millipede.

Diplopods have unique features, which differentiate them from other

Arthropods.
 They have two pairs of legs in each body segment
 Have cylindrical body (segmented)
 Have one pair of antennae
 They Curl up when disturbed or at rest
 Have two clusters of compound eyes example millipede.
 Mainly herbivores
 Gaseous exchange is by tracheal system.
 Mainly terrestrial
Millipede
Habitat: In cool dark places.
Economic importance of millipede.
 Used for biological studies
 Add soil fertility when die and decomposed
 Creates soil aeration i.e., pore spaces in the soil.
Adaptations of the millipede to its mode of life
Millipedes have the following features that make them adapt to their
environment:
 They have many, short and strong legs that enable them to burrow
into the soil.
 They produce special secretions, which help them to moisturize
dead organic matter on which they feed upon.
 A millipede tends to curl up into a tight flat coil for self-defense,
and protect their delicate legs inside an armoured exoskeleton.
 Millipedes produce an offensively odorous fluid (repugnatorial
fluid) when provoked, this acts as a defense against predators.

Figure;2.18: Millipede
Adaptation of millipede to its habitat
 They have many, short and strong legs that enable them to burrow
into the soil.
 They produce special secretions, which help them to moisturize
dead organic matter on which they feed upon.
 A millipede tends to curl up into a tight flat coil for self-defence,
and protect their delicate legs inside an armoured exoskeleton.
 Millipedes produce an offensively odorous fluid (repugnatorial
fluid) when provoked, this acts as a defence against predators.

5. Class Chilopoda
This class consists of organisms found in terrestrial environment. They
are terrestrial animals abundant in moist areas, such as leaf litters,
under logs or rocks. An example of chilopoda is centipedes.
The distinguishing characteristics of class chilopoda
 They have a flattened body with a distinct head. However, other
body segments are similar; the trunk is not obviously divided into
thorax and abdomen.
 They have one pair of legs per segment.
 They are carnivores, feeding mainly on insects and worms.
 Their first trunk segments have appendages, which are modified
into a pair of poisonous fangs.

Figure;2.19: CentipedeHabitat:
In cool dark places, under logs/stones. Adaptations of
the centipede to its mode of life
Centipedes are adapted to a wide range of habitats because:
 They are fast moving animals; this helps them to catch their prey.
 They feed on insects, spiders, and worms, which they hunt and
paralyse with a bite of their poisonous claws.
 They have antennae for sensation.
 They have poisonous claws for defence and hunting.
 They have legs for locomotion.
 The last pair of legs has hooks for defence.

Economic importance Centipede.

 Used for biological studies
 Add soil fertility when decomposed
 Can sting and bite leading to poisoning
Phylum Aschelminthes (Nematoda)
It includes the group of roundworms
The word ‘aschelminthes’ originates from two Greek words. ‘Aschel;
means round and ‘Minthos’ means worm.
Characteristic features of Aschelminthes
 Have round or cylindrical body
  Have pointed body ends
 Have un-segmented body
 Are parasite of vertebrates but some are free-living
 Have mouth and anus
 Body covered with thick elastic cuticle
 They have separate sex
 Examples of nematodes – Ascaris.
 Bilateral symmetry
 They are triploblastic
Ascaris
Habitat: small intestine of man, poultry guinea pig, pigs
Adaptations of Ascaris to its mode of life
 It has a tough cuticle, which protects it from being digested by the
enzymes of the alimentary canal of the host.
 It produces chemicals, which act as anti-enzymes to the digestive
enzymes of the host.
 It has an alimentary canal, which opens at the mouth and anus.
This enables the parasite to take food from the hosts’ digestive
system.
 It possesses digestive enzymes in its digestive system for the
completion of partially digested food from the hosts’ alimentary
canal.
 It has sensory papillae around its mouth for detecting food present
in the elementary canal of the host.
 It respires anaerobically, and have low metabolic rate; hence, they
are able to live inside the host’s intestine.
 It has high reproductive potential; thus, by producing large number
of eggs, it ensures its survival and existence.
Economic importance Ascaris
 It causes disease e.g. anaemiaie. ascariasis
 Used for biological study
 May lead to ulcers as they bore intestinal wall
 May lead to anemia
 May cause elephantiasis e.g. filarial worm
 Figure;2. 22: Ascaris
d.Phylum Annelida
 Members of this phylum are known as ringed or segmented worms.
This is a large phylum comprising of lugworms, earthworms, and
leeches. The species are adapted to various habitats; some members
are aquatic, living in marine and fresh water, and others live in moist
terrestrial environmentsCharacteristics of Annelids
 They are segmented worms
 They have cylindrical body made of series of similar segments
likerings.
 They use nephridia for excretion and osmoregulation
 Some are free-living and some are parasites
 They possess bristles called chaetae for locomotion
 They have bilateral symmetry
Classes of Phylum Annelida
(a) Class Oligochaeta
(b) Class Poligochaeta
(c) Class Hirudinea
a) Class Oligochaeta
General and distinctive features of class Oligochaeta
 Have fewer chaetae (bristles)
 They live in both fresh water or damp earth
 They are hermaphrodites (have both sexes male and female
parts)
 Have clitellum for secretion of mucus

Phylum Chordata
Phylum Chordata encompasses a diverse group of animals sharing key
characteristics including a notochord, dorsal nervecord, pharyngeal slits,
and post-anal tail at some point in their life cycle.

General features of chordates

Chordates possess the following features:
They are triploblastic animals.
They are coelomate animals.
Some are homotherms while some are piokiotherms
Most have endoskeletons made up of bones and cartilages
They occupy both terrestrial and aquatic habitats.
Distinctive features of chordates
Chordates have unique features that differentiate them from other
animals.
They have the following features at some stages of embryological
development:
A notochord.
Pharyngeal pouches or gill slits.
Post-anal tail.
A dorsal hollow tubular nerve cord.
Classes of phylum chordata
The classes of Phylum Chordata include:
1. Class Mammalia (Mammals)
2. Class Aves (Birds)
3. Class Reptilia (Reptiles)
4. Class Amphibia (Amphibians)
5. Class Chondrichthyes (Cartilaginous fishes)
6. Osteichthyes(bony fish)

Class Osteichthyes
This class comprises of the bony fish. Their skeleton is made upof hard bones
instead of cartilage.
Examples of bony fish include tuna, tilapia, Nile perch, herring,butterfly fish
and catfish
Distinctive features of bony fish
The following features differentiate bony fish from other chordates:
 They have four pairs of visceral clefts as their gill openings.
These are covered by an operculum.
 Most of bony fish have swim or air bladder which provides them
buoyancy during swimming.
 Most have a bony endoskeleton and their skin is covered by
glands producing mucus that make them slippery.
 Most have symmetrical or homocercal caudal fins. This means
that their caudal fins can be divided into equal parts.
 They have terminal mouth.
Structure of a Tilapia

Figure;2.24: Tilapia Fish

Adaptation of tilapia fish to its mode of life
 They have swim bladder for buoyancy maintenance
 They have gill for respiration and are protected by operculum from
mechanical damage
 They have fin for locomotion
 Has a streamlined shape to overcome water resistance during
swimming
 Its body surface is covered by cycloid scales, which point
backwards in order to reduce resistance during swimming.
 The fish has a lateral line that runs along the side of its body. The
lateral line is a series of sensory organs called neuromasts that
helps the fish to sense vibrations and water pressure for navigating
and locating prey
Economic importance of Tilapia fish
 Used in biological studies.
 Used as the source of food to human being.
 Source of income.
Class Reptilia
The word reptilian is a Latin word which means ‘crawl’
Some reptiles have limbs (e.g. lizards) while others are limbless (e.g.
snakes)
The reptiles occupy different habitats. Some are aquatic (e.g. Turtles)
while others are terrestrial (e.g. Lizards). Example of reptiles are Tortoise,
Turtles, Lizards, Snakes, Chameleons, crocodiles.
Characteristics of Reptiles
 Have dry skin covered with horny scales
 They are poikilothermic animals (cold blooded animals)
 They use lungs for gaseous exchange
 Their eggs are fertilized internally and laid on land. A membrane
known as amnion covers their eggs.
  With exception of crocodiles, they have heart which is divided into
two atria (singular atrium) and two partially divided ventricles. In
crocodiles the heart has four chambers.
 Some reptiles have shells e.g. Tortoise and turtles
 The limbs of reptiles arise from the lateral side of the body

Figure;2.25: Lizard
Adaptation of lizard to its mode of life
 Their dry skin is covered with horny scales to prevent dessication
 Produce uric acid as waste which require less amount of water
 Have nostrils for smell
 They protruding eyes for wider field of view.
Economic importance of lizard
 Used in biological studies.
 Source of food to some organisms
Class Mammalia
The class Mammalia consists of all animals with mammary glands. It is an
extremely diverse and very advanced group in the kingdom Animalia.
Members of the class Mammalia include: human, mouse, rabbit, cow, lion,
bat, whale, and donkey.

Characteristics of Mammals
 Are homoeothermic (warm blooded)
 Viviparous, give birth to young, not eggs (except platypus and
echdina)
 Have mammary glands
 Have external ear pinnae, (singular pinna) for collecting sound
waves.
 Have heterodont teeth-varied teeth for different functions.
 Have hairs or fur that covers the body for insulation
 Have sweat glands, for cooling the body
 Have diaphragm a muscular sheet separating the heart and the
 lungs from other organs.
 Have red blood cells (erythrocytes) that lack nuclei but having
hemoglobin for transportation of oxygen from the lungs to the
respiring cells.
 Possess pentadactyl limbs, limbs with five digits (phalanges) e.g.
man, chimpanzee
 Their heart has four chambers
 They have highly developed brains.

Figure; 2.26: Rat

Economic importance of rat
 Used for biological studies
 Reservoir of human disease e.g bubonic plague
 Consumers of grains that are basic food stuff to human being
 Produce fur that are useful to man
Adaptation of rat to its mode of life
 They have heterodont dentition for various purpose
 They have fur for insulation
 Has well developed blood circulatory system
 They have internal fertilization hence increase chances of survival

Class Amphibia
This class includes amphibians such as frogs, toads, caecilians as well as
salamanders. Amphibians are tetrapod with the exception of caecilians,
which are limbless
Characteristics of Amphibians
 They dwell both in water and on land, as they depend on water for
reproduction, hence the name amphibian, which means double life.
 Amphibians’ offspring begin their life cycle under water and
breath by means of gills. As they grow to adulthood they move to
terrestrial and breathe by means of either skin or lungs.
 They have soft moist skin without scale, used for gaseous
exchange to supplement lungs and buccal cavity.
 Amphibian eggs have a jelly structure, which is prone to
dehydration when exposed to air.
 Amphibian’s fertilization takes place outside the female body (with
the exception of some caecilians and some toads including the
Kihansi spray toad which give birth to live young). They have two
pairs of pentadactyl limbs for locomotion. The forelimbs have less
musculature, while the hind limbs are webbed and long with
powerful muscles for jumping.
 They have long and protruding eyes for viewing preys widely and
for avoiding enemies.
 They have sticky tongue, which helps them in capturing prey.
 They undergo metamorphosis for development from larval to adult
stage in their life cycle.

Figure; 2.27: Toad

Adaptation of frog to its mode of life
 Has long and muscular hind limbs for jumping
 Has webbed feet for swimming
 Has a long, sticky tongue for catching prey
 Has lungs for gaseous exchange on land and skin on water
Digestive system of a frog

The alimentary canal of a frog consists of the mouth, buccal cavity,

pharynx, oesophagus, duodenum, ileum, and the rectum, which open into
the cloaca at the anus.
 The mouth is wide for ingestion of large pieces of food material.
 These tubes are used for balancing pressure in the inner ear while
the frog is swimming. Ventrally in the midline there is a narrow
longitudinal slit (glottis) which leads into the larynx.
 They have a short oesophagus that bears longitudinal folds, which
close to prevent entry of air into the stomach and allow dilation
during swallowing of food. Buccal cavity, pharynx and oesophagus
have cilia, which constantly drive the mucus backward through the
pancreas. The pancreas lies and later discharge into the duodenum.
In between the stomach and the duodenum.
 The secretions are discharged into the bile spherical red structure
called spleen, which duct, which become hepato-pancreatic duct has
no digestive role

Oesophagus

Liver Stomach
Gall bladder Pancreas
Duodenum

Ileum

Rectum
Cloaca

Figure: digestive system of frog

Class Aves
The class Aves includes all birds. It is an extremely distinctive and
successful class. Aves are bipedal feathered and warm-blooded
(homoeothermous) animals, as they are able to maintain a constant body
temperature.

General Characteristics
 Their mouth is modified into horny beaks
 They have hollow bones filled with air
 They have scaly legs
  Body covered with feathers
 Fertilization is internal
 Use lungs for gaseous exchange
 They have amniotic eggs
 Fore limbs are modified into wings
 Their heart has four chambered hearts

Figure; 2.28: Pigeon

Adaptation of Birds to its mode of life
 Their body is covered with feathers for insulation and flight
 They have wing for flight
 They have streamed body to reduce air resistance
 They have simple eyes for vision
Economic importance of animals (kingdom Animalia)
 Used for biological studies
 Used as the source of food e.g cow, goat etc
 Used for biological control
 Used for security e.g. dogs
 Used as the source of income
 Some animals used for transport for example camels, donkeys
 Provide manure for example cow dung
Types of Feathers
 Flight Feathers. Flight feathers are found in two places on birds:
the wings and tail, They are used for flying
 Contour Feathers. Contour feathers give shape and color to the
bird. ...
 Down Feathers. Down feathers have little or no shaft, they are
used for insulation
 SAMPLE PRACTICAL QUESTIONS AND THEIR ANSWERS
NECTA 2021
BIOLOGY 2A
2. You are provided with specimens D, E and F. Study them carefully and
answer the questions that follow.
a) (i) What is the common name for each of the specimens D, E and F?
(ii) Why is it important to the scientists to classify specimens D, E and F
to their lowest taxonomic groups? Give two reasons.
b) Classify each of the specimens D, E and F to the phylum/Division level.
c) Why are specimens D and F placed to the Phylum/Division you named in
(b)? Give two reasons for each specimen.
d) What do the processing industries benefit from using the plants in which
specimen E was taken? Give three benefits.
e) (i) Draw a well labeled diagram of the specimen F.
(ii) State the habitat of the specimen F.
(iii) What are the two advantages of specimen F to the farmer?
ANSWERS

2(a)(i)

Specimen Common name

D Bread mould
E Pine branch (pine leaf)
F Earthworm
(i) Importance of classification

 It makes easy to classify all known organisms and predict the

placement of the yet to be discovered based on already known
features.
 Classification simplifies communication among taxonomists
worldwide.
 It helps to show evolutionary relationship between organisms.
 Organisms grouped in the same taxon, such as at genus level,
normally have many common features.
 It paves a way towards understanding other disciplines, such as
ecology, medicine and pharmacy

(b)
Specimen Kingdom Phylum Division
D Fungi Zygomycota -
E Plantae _ Coniferophyta
F Animalia Annelida -
(c) Features of Zygomycota (specimen D)

 They have aseptate hyphae which lack cross walls between

adjacent cells. They are therefore coenocytic in structure.
 Their cytoplasm is continuous and multinucleate.
 They undergo sexual reproduction involving two gametangia to
produce a resting spore known as zygospore
Features of Annelida (specimen F)

 They are segmented worms

 They have cylindrical body made of series of similar segments like
rings.
 They use nephridia for excretion and osmoregulation
 Some are free-living and some are parasites
 They possess bristles called chaetae for locomotion
 They have bilateral symmetry
(d) Advantages of division coniferophyte

 Provide soft woods for construction

 Used in making drugs
 Prevent soil erosion
 Production of turpentine and resin from pines
 They are ornamental plants
(e) (i)

Fig: diagram of specimen F

(ii) The specimen F is found in moist soil

(iv) State three distinctive features that made you and other scientist to
agree specimen C and F must dwell in the class(s) you mentioned in (b) iii
and not otherwise
(c) (i) In which ways are specimen C and F of advantage to man
(ii) Draw a diagram of specimen F and label the parts which are
involved in sensitivity and locomotion.
ANSWERS
2.(a)( i).
Specimen Common name
C Maize seedling
D Bread mould
F Grasshopper
(ii)
Specimen Kingdom
C Plantae
D Fungi
F Animalia

(b) (i)
Specimen Habitat
C Found terrestrial habitat
D Found on decayed bread
F Found on grassland

(ii) Adaptation of bread mould to its habitat

 Have rhizoids for absorption of nutrients
(iii)
Specimen Class
C Monocotyledonae
F Insecta

(iv) Distinctive Features of Monocotyledonous plants

 Vascular bundles are scattered in stem
 They have no vascular cambium except in palms
 They have no tap root
 They have one cotyledon
 They undergo hypogeal germination
 Usually wind-pollinated
Distinctive Features of Class Insecta
 The body is clearly divided into three regions i.e. head,
thorax and abdomen
 They have one pair of antennae for sensitivity
 They have three pairs of jointed walking legs
 Some have two pairs of wings (inner and outer wings)
e.g., grasshopper, beetle
(c)(i) Advantages of maize seedling
 Source of food to human being and other animals
 Used for biological studies
 Increase soil fertility

Advantages of maize seedling

 Source of food to human being
 Source of oxygen
 Used in biological studies
(i) Refer from notes

NECTA 2015
BIOLOGY 2C
(ACTUAL PRACTICAL)
2. You have been provided with specimens R,S and T
(a) Observe the specimens then:
(i) Identify the specimens R,S and T by their common name.
(ii) Classify specimen S and T to phylum level
(iii) Name the class and state two distinctive features for each class of
specimens R, S and T
(b) Study the specimens R, S and T carefully and then answer the
following questions:
(ii) State the habitat of specimen R and S.
(iii)State the adaptation features which indicates how specimen S is
adapted to its habitat.
(iv)In what ways are specimen S and T considered to be useful and
harmful to human being and his environment.

ANSWERS
2.(a)(i)
Specimen Common name
R Crab
S Grasshopper
T Rat
(ii)
Specimen Kingdom Phylum
S Animalia Arthropoda
T Animalia Chordata
(iii) Specimen R is placed class Crustacea
 Distinctive features of class Crustacea
 Have one pair of compound eyes raised in stalk
 Some have two pairs of antennae e.g. lobster, prawns,
crabs, examples of crustaceans are crabs, prawns, lobsters.
 Their gaseous exchange is by means of gills or through
body membrane
Specimen S is placed in Class Insecta

Distinctive features of class Insecta

 They have one pair of antennae for sensitivity
 They have three pairs of jointed walking legs
 Some have two pairs of wings (inner and outer wings) e.g.
grasshopper, beetle
 Some have one pair of wings e.g. housefly, bees
 They have well developed compound eyes (with
ommatidia)
Specimen R is placed in Class Mammalia

Distinctive features of class Mammalia

 Have heterodont teeth-varied teeth for different functions.
 Have hairs or fur that covers the body for insulation
 Have sweat glands, for cooling the body
 Have diaphragm a muscular sheet separating the heart and
the lungs from other organs.
 Have red blood cells (erythrocytes) that lack nuclei but
having hemoglobin for transportation of oxygen from the
lungs to the respiring cells.
(b) (i)Specimen R is found in Water bodies e.g. rivers, seas
Specimen S is found in grassland and trees
(ii) Adaptation of Grasshopper to its habitat (specimen S)
 It has one pair antenna for sensitivity
 It has exoskeleton for mechanical protection and support
 It has two pairs of wings for movement
 It has three pairs of jointed legs for locomotion
(iii) Advantages of grasshopper (specimen S)
 Source of food to human being
 Used for biological studies
Disadvantage of Grasshopper (specimen S)
 Destroy crops
Advantages of Rat (specimen T)
 Used for biological studies
  Produce fur that are useful to man
Disadvantage of Rat (specimen T)
 Reservoir of human disease e.g bubonic plague
 Consumers of grains that are basic food stuff to human.

CHAPTER:3.
REPRODUCTION IN FLOWERING PLANTS
Reproduction is the production of new generation of individuals of the
same species. It is one of the fundamental characteristics of living
organisms.

Structure of the flower

A flower is interpreted as a modified leaf of a plant which is highly
specialised for reproduction. It can be bisexual or unisexual, depending on
a plant species. Bisexual and unisexual flowers are called complete and
incomplete flowers respectively. Flowers are the main reproductive organs
of flowering plants.
There is great variation in morphology among flowers of different species,
but generally, a typical flower has the four main floral parts described
below.
1. Sepals form the outermost ring of floral leaves. They are
collectively termed as calyx. Sepals are small, green and
morphologically leaf-like in structure located at the base of the
flower.
The main function of sepals (Calyx) includes;
 Protecting the inner parts of a flower during the bud stage.
 They also carry out photosynthesis since they contain
chlorophyll.
 In some plants they are brightly coloured to attract insects
for pollination
2. Petals form a ring of floral parts next to the calyx. The collection
of petals is called corolla. In insect pollinated flowers, petals are
brightly coloured and have glandular swellings referred to as
nectaries at the base. Nectaries release a sugary substance known
as nectar which attracts insects. The sepals and petals are
collectively referred to as perianth.
The main function of petals
 Attract insects for pollination.
 They also offer protection to the inner parts of the flower
 and they are large to provide a broad landing area for
insects.
3. The stamen is the male reproductive organ of a flower. The male
reproductive structures are collectively referred to as the
androecium. Stamen consists of anthers and a stalk or filament.
The anther consists of four pollen sacs containing pollen grains
which are powdery substance. The filament is a thin long stalk that
supports the anthers on its top.
The main function of anthers is to produce pollen grains which
contain the male gametes.
4. Pistil is the female part of the flower. The female reproductive
structures are also called gynoecium. Pistil consists of three parts
namely stigma, style, and ovary.
 The style connects stigma to the ovary. The style is hollow
to allow growth of the pollen tube during fertilisation.
 Stigma is a glandular sticky structure found as the swelling
at the tip of the style. It receives the pollen grain during
pollination.
 The ovary is an expanded hollow base which contains
ovules. Ovules are unfertilised female gametes. They are
attached to the ridges of a soft fleshy tissue called the
placenta. After fertilisation, the ovary develops into a fruit
while ovules develop into seeds.

The other parts of the flower

5. Flower stalk or pedicel is the modified branch or stem on which
the flower develops. The branch of each flower is called a pedicel.
6. Receptacle is a swelling that develops at the tip of the flower stalk
into which the floral parts are attached in rings or whorls. Basing
on the position of ovary, there are two types of ovaries namely:
Inferior ovary and superior ovary.
 Inferior ovary is the ovary positioned below the attachment
of the petals, sepals and stamens. In this case, other floral
parts occur above the ovary. A flower with inferior ovary
is referred to as epigynous flower. Examples include
guava, rose and apple flowers.
 Superior ovary is the ovary positioned above the
attachment of the petals, sepals and stamens. The ovary
develops above the position of the other floral parts. A
flower with a superior ovary is referred to as hypogynous
flower. Examples include orange, Hibiscus sp and bean
 flowers.

Figure: 3.1 general structure of the Hibiscus flower

Figure;3.2:exteral structure of the Hibiscus flower

Types of Reproduction in plants

Sexual Reproduction; this is the type of reproduction which involves two
individuals. One parent is a male and the other is a female. Sexual
reproduction involves sperms and eggs which are specialised sex cells
called gametes. It occurs when the sperm from the male parent is fused
with the egg from the female parent to produce a new organism.
Asexual Reproduction
Asexual reproduction is the type of reproduction whereby only a single
individual give rise to new offspring. It does not involve the fusion of
gametes. As a result, the offspring reproduced asexually are genetically
identical to their parents.

There are different forms of asexual reproduction depending on the type of

organism. These forms include the following:
 Fission
In this form of asexual reproduction, a parent separates into two or
more individuals of equal size. Fission can be binary or multiple
fission
 Fragmentation
This is a form of asexual reproduction where by an organism
breaks down into fragments (pieces) and each fragment develops
into a mature organism containing features identical to those of the
parent
 Spore formation (sporulation) this is the type of asexual
reproduction whereby an organism reproduces new organisms by
reproductive cells called spores. Spores are small unicellular
structures which are capable of developing into new individuals
 Vegetative propagation; in plants asexual reproduction is called
vegetative propagation. This occurs when a new plant grows from
a fragment of a parent plant or through specialised reproductive
structures such as leaves, roots, stems or buds.

Figure; 3.3: Section through a dormant bulb

Advantages of asexual reproduction

 Only one parent is required
 Ensure genetic stability
 Rapid multiplication
Disadvantages of asexual reproduction
  No variation
 Most of spores are lost
 Increase competition of resources
Pollination
Pollination is the transfer of pollen grains from the anthers to the stigma
of a flower.
Types of pollination
 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 on the same plant. In self-pollination, the male
parts of the flower are located above the female parts, thus the
pollen grain fall easily onto the stigma. For self- pollination to take
place the plant must have both male and female flowers on the
same plant. Examples include peas, maize and Hibiscus sp.
 Cross-Pollination is the transfer of mature pollen grains from the
anther of one flower to the stigma of a flower of another plant of
the same species as shown. Examples include pawpaw, maize and
sorghum.
Agents of Pollination
In other plants there is a wide gap between the anther and stigma and since
the pollen grains are immobile, they must be carried from the anther to the
stigma. In such plants, wind, water, animals and insects act as the agents
of pollination. Each species of plant employs its own particular agent of
pollination and has features which enable them to carry out that kind of
pollination. These agents of pollination are also known as pollinators.

Wind-pollination
In wind pollinated flowers, wind transfers pollen grains from anthers to
the stigma. The anther and the stigma of wind pollinated flowers are
exposed. This makes it easy for the wind to blow the pollen that can easily
land on the stigma. Examples include flowers of most grasses such as rice,
maize and sorghum. Wind-pollinated flowers are also referred to as
anemophilous flowers

Features wind-pollinated flower

 Have small petals and not brightly coloured
 Nectaries are absent
 Produce large quantities of pollen grains
 Pollen grains are relatively light and small
 Not scented
 Figure; 3.4: Wind Pollinated Flower
Insect-Pollination
Insects visit a flower and are dusted with pollen grains from the ripe
stamens. When they visit another flower some of the pollen is transferred
to the stigma. Insects such as bees, butterflies and moths aid in pollination
of flowers. Insect-pollinated flowers are also known as entomophilous
flowers. The term entomophilous is derived from the word entomophily
which means to be carried by insects.
Features of Insect-Pollinated flowers
 Have large coloured petals
 Nectaries are present
 Less pollen grains are produced
 Scented
 Nectaries present
 Small stigma, sticky to hold pollen and enclosed within flower
 Pollen grains are relatively large and heavy.
THE CONCEPT OF GROWTH AND DEVELOPMENT.
Growth and development in plants usually begins with germination
Germination is the process whereby seeds develops into seedling.
Seed is a structure formed after fertilization of an ovule.
Parts of the seeds.
 An embryo: this part consists of radicle that develops into a root
and plumule develops into a shoot after germination.
 A seed coat: this part is also known as a testa. It is a protective
layer surrounding a seed.
 Cotyledons: This part grows to form embryonic first leaves after
germination
 Micropyle is the pore through which water enters the seed during
seed germination.
 Hilum: This is a scar that shows the seed's point of attachment to
the ovary wall.
 Figure4.1; structure of (a) dicot (b) monocot seed
Necessary conditions for germination
 Water,
A seed absorbs water through the micropyle. Water plays an important
role during seed germination. When a seed absorbs water, the embryo
cells enlarge due to pressure. Such action leads to the rapture of the seed
coat. Water softens the seed coat, hence Increases seed permeability.
Water also activates enzymes necessary for seed germination and growth
 Air(oxygen)
Oxygen gas is necessary for aerobic respiration to generate energy that is
required for the growth of the embryo of a seed.
 Optimum temperature
Seeds need the optimum temperature to germinate. The seed of each
plant species has its optimum temperature for germination. Temperature
is essential for the activation of enzymatic reactions during respiration.
Respiration is important as it provides the energy required for
germination.
 Light, required for photosynthesis

Internal factors that affect germination

 Enzymes. Break down food reserves in the cotyledons or
endosperm into soluble form
 Hormones such as auxins hormones acts as growth stimulators
 Viability. Refers to the ability of the seed to germinate. Only alive
and healthy seeds will germinate
Types of germination
There are two types of germination which are;
 Epigeal germination
 Hypogeal germination
Epigeal germination is the type of germination whereby cotyledons are brought
above the soil level. This type of germination occurs in dicotyledonous plants
such as;
 Beans
 Groundnuts
 Okra
 Amaranthus spp

Figure;4.2: stages of epigeal germination

Hypogeal germination is the type of germination in which the seed
cotyledons remain underground. It occurs in plants such as maize and
pigeon peas.

Figure; 4.3: stages of hypogeal germination of maize grain

Coleoptile is the sheath which protects plumule in maize (plumule

sheath).
Coleorhiza is the sheath which protects radicle as it emerges through the
maize grain.
 CHAPTER:5.
TRANSPORT IN LIVING ORGANISMS
In living organisms; Transport refers to the movement of materials within
the body of organisms. Transport is necessary for the movement of
substances within, into and out of cells so as to enable vital life process to
occur
Importance of transport in organisms
 It enables distribution of food materials in the body of an
organism.
 It enables distribution of respiratory gases (oxygen and carbon
dioxide) to the body.
 It enables removal of metabolic waste products from the body
 It enables absorption of food nutrients by organisms
 It enables cooling of the body of organisms.
Movement of materials occurs through: -
 Diffusion
 Osmosis
 Active transport
 Mass flow
Diffusion
Diffusion This is the passive movement of particles from an area of high
concentration to an area of low concentration. The difference in the
concentration of a substance between two areas is known as a
concentration gradient. When the difference in concentration between the
two areas is great, the concentration gradient becomes Steep and the rate
of diffusion increases.
As the difference in concentration between the two areas decreases the
rate of diffusion slows down. This process continues until the substances
are distributed evenly throughout the two areas. When the particles are
evenly distributed. They move at the same rate in either direction.

Concentration gradient is the difference in concentration of a substance

between two regions.
Example:
1. when tea bag is dissolved in hot water and cold water
2. when potassium permanganate crystals are dissolved in water
Note; for both particles the aim of experiment will be Demonstration of
diffusion in liquids
Roles of diffusion in living organisms.
 Movement of oxygen gas from the alveoli to the blood capillaries;
 Movement of oxygen gas from the blood capillaries to the tissue
fluid;
 Movement of oxygen gas from the tissue fluid to the cell;
movement of carbon dioxide gas from the cell to the tissue fluid;
 Movement of carbon dioxide gas from the tissue fluid to the blood
capillaries; movement of carbon dioxide gas from the blood
capillaries to the alveoli
 Movement of air from the atmosphere to the leaves;
 Movement of carbon dioxide gas from the intercellular space to the
palisade cells;
 Movement of oxygen gas from the palisade cells to the
intercellular spaces of spongy mesophyll;
 Movement of oxygen gas from the intercellular spaces to the
atmosphere;
 Movement of water vapour from the leaves to the atmosphere; and
 Movement of digested food substances from the ileum to the
circulatory system

Factors affecting the rate of diffusion

 Concentration gradient. When there is a big difference in
concentration of molecules between the two areas, high rate of
diffusion occurs.
 Surface area to volume ratio: The larger the surface area to
volume ratio, the larger the number of particles that will be able to
move in a given time hence, the higher the diffusion rate,
 Distance over which diffusion takes place: When the distance
over which the material is transported is long, the rate of diffusion
decreases. If the distance is short, diffusion occurs faster because
the materials do not have to travel far. For example, in a thin layer
of cells the rate of diffusion increases.
Osmosis
Osmosis is the passive diffusion of water through a semi-permeable
(partially permeable) membrane. It is regarded as a special form of
diffusion because it involves movement of water molecules through a
semi-permeable membrane. Osmosis is defined as the process by which
 PRACTICAL QUESTIONS AND THEIR ANSWERS

NECTA 2021
BIOLOGY 2A
1. You are provided with two Irish potatoes, water troughs, watch glasses with
sample A (table salt) and boiling water. carry out experiments as directed by
procedures (i) – (xi), and then answer the questions that follow:

(i) Peel off the two Irish potatoes provided to remove the outer cover.
(ii) Label one of the Irish potatoes as specimen U and the other as
specimen V.
(iii) Put specimen V into boiling water for 2 minutes, then take it out and
cool.
(iv) Using a knife/scalpel, cut the cross section of the specimen U to
obtain two halves.
(v) Scoop out the central portion of one half of the specimen U to make a
hole of about 2.5 cm deep from the cut surface. The walls of the hole
must be thin (5-8 mm) thick but take care not to damage it.
(vi) Place a scooped specimen U in the trough. (vii) Put 3 g of sample A in
the hole of the specimen U.
(vii) Using a pipette or dropper, add 1 drop of water to dissolve
sample A in a hole of specimen U.
(viii) Put water in the trough until specimen U is half immersed.
Carefully observe the experiment and note the set up and the level of
water in the beginning.
(ix) Repeat step (iv) and (ix) for specimen V that has been boiled and
cooled.
(x) Leave the experiment for 40 minutes, there after observe the
experiment again and note the changes.
Questions
(a) What is the aim of the experiment?
(b) Draw well labeled diagrams to indicate the setup of theexperiment;
(i) at the beginning
(ii) (ii) after 40 minutes
(c) Identify two changes observed after 40 minutes of the experiment.
(d) Give a reason for the observed changes in the holes and the troughs
after 40 minutes of the experiment.
(e) Identify the specimen which acts as a control experiment.
(f) Give the biological terminologies used to identify the
concentration of the solution in each of the following:
(i) Hole of the specimens
(iii)Water troughs
(g) Based on the observation made from the experiment, why is it not
 advised to urinate frequently nearby the plants in the dry season?
(h) What are the two benefits the plant gets by undergoing the process
you investigated in the experiment?
Answers
(a) The aim of the experiment was to investigate osmosis in living
organism using Irish potato
(b)

(c) (i)the volume of water in specimen U decreased

(ii) the volume of water in the trough of specimen V increased
(d) (i)The hole had high concentration of solute than water in the trough
therefore water moved from the trough to the potato hole through the
semipermiable membrane of raw potato.
(ii) The volume of water in the trough of specimen v remained the same
(e) The specimen wchich acted as the control experiment is specimen V
(f) (i) hypertonic solution in the potatoes
(ii) hypotonic solution in water trough
 CHAPTER:6
PHYSIOLOGY(COORDINATION)
Physiology Is the branch of biology which deals with normal functions of
living things and their parts. The normal functioning of the body is
controlled by sense organs. Coordination is accomplished through a set of
signals channeled into a series of nerve cells. Coordination in mammals
involves three main components which are receptors, coordinators and
effectors.
Stimulus: A change in the external or internal environment to which an
organism responds. Examples of stimuli are touch, pain, smell and sound.
Receptors: These are specialised cells that detect the changes in the
environment. Examples of receptors are sense organs, including the eye,
ear, nose, skin and tongue.
Coordinator: An organ that receives and interprets message from the
receptors. Coordinators include the brain and the spinal cord. A
coordinator uses messages to link activities in the body. The messages
received are called nerve impulses.
Effectors: These are the cells, organs or organelles which receive motor
impulses from the brain or spinal cord and bring about an appropriate
response. The effectors include: Muscles, cilia, flagella and glands.
Response: This is any change shown by the organism responding to
stimulus. Response may involve the movement of the whole or part of the
organism’s body. This movement can be either towards or away from the
stimulus. Examples include the quick removal of the leg if pricked by a
sharp object, or pulling the hand away if it accidentally touches a hot
object.
Feedback: The animal decides what to do after the response.
Sense organs are specialised organs composed of sensory receptors
responsible for receiving and responding to stimuli around us. These
stimuli include touch, heat, pressure, light, smell, taste and sound. In
mammals, there are five major sense organs namely; the ear, the eye, the
nose, the tongue, and the skin. Each sensory receptor responds to only one
specific stimulus.

Sensory receptors are the specialized region of the body detecting the
stimulus.
Types of receptors.
Classification of sensory receptors based on type of stimuli
Based on the type of stimulus they detect in the environment, there are
several types of sensory receptors, which include: mechanoreceptor,
photoreceptor, thermoreceptor, nociceptor, chemoreceptor, osmoreceptor
and electroreceptors.
Mechanoreceptors
 They detect mechanical stimuli which are caused by mechanical
forces such as sound or vibration, touch, pressure, and gravity.
Touch receptors are found all over the body. Other touch receptors
include Merkel’s discs and Meissner’s corpuscles which detect
light and pacinian corpuscles which sense deep pressure and
vibration. Mechanoreceptors are responsible for detecting changes
that are perceived such as sound or touch.
 They are also responsible for maintaining equilibrium balance and
proper tone in muscles and joints
Photoreceptors
These are receptors which detect electromagnetic stimuli such as light.
There are two types of photoreceptors namely; rods and cones. These
are found in the retina of an eye for detecting dim and bright light
respectively
Thermoreceptors
Thermoreceptors are specialised nerve cells or receptors that can
detect differences in temperature. They can detect hotness (heat) and
coldness (cold). They are thus of two types, heat and cold receptors.
They are found throughout the skin to allow sensory reception
throughout the body. The location and number of thermoreceptors
determine the sensitivity of the skin to temperature changes.
Examples of thermoreceptors are bulbs of Krauze which sense
coldness and organ of Ruffin which detects heat. These cells are
connected to heat gain and heat loss centres of the hypothalamus
Nociceptors (pain receptors)
These are receptors that can detect pain and they are found in the skin,
muscles, bones, blood vessels, and some organs
 Chemoreceptors
These are receptors which detect chemical stimuli such as smell, taste,
and humidity. They have the ability to respond to a diverse range of
chemical substances in food, nasal passage, and blood. For example,
olfactory receptors in the roof of the nasal cavity can be stimulated by
odours. Nerve impulses from these receptors travel to the olfactory
bulb. When odour molecules enter the nose, they stimulate the
olfactory cilia (tiny hairs) attached to receptor cells, causing nerve
impulses to pass to the olfactory bulb and then to the brain.
Osmoreceptor
They detect the changes in osmotic pressure. The osmoreceptors are
primarily found in the hypothalamus and kidney of most
homoeothermic organisms. They contribute to regulate fluid balance in
the body (osmoregulation) and modulate osmolarity in the kidney.
There are five sense organs
 An ear
 An Eye
 Tongue
 Nose
 Skin
The Ear
The Ear
The ear is the organ for hearing and maintenance of body balance. It
detects sound waves and vibration. It also provides information on the
position of the organism. The mammalian ear is composed of three parts;
the outer ear, the middle ear and the inner ear.

Function of the ear

 Hearing
 Body balance

Adaptation of the ear to its functions

The following are the adaptations of the ear to its functions:
 The presence of pinna which helps to collect the sound waves from
the external environment and directs them into the ear canal.
 The presence of the tube-like canal which directs the sound waves
to the ear drum.
 The existence of the ear ossicles which increase the force of the
 vibration and amplify the sound.
 Presence of fluid filled semicircular canals and utriculus which
help the body to maintain its balance.

Figure; 6.1: An Ear

The eye
The eye is an organ for vision which receives light from the environment
and converts it into electrical impulses. It is roughly spherical in shape and
located in a bony socket called orbit in the skull. The orbit protects the eye
against physical damage.
Function of the eye
 To enhance a person to determine distance.
 To bring sense of sight/vision
 Figure;6.2: External Appearance of an Eye
Functions of the parts of external parts of an eye
 Eyelid protects the cornea from mechanical and chemical damage.
 Iris
The contraction and relaxation of these muscles control the size of
the pupil and amount of light entering the eye
 Pupil allow light to enter the eye.
 Eye lashes, protects the eye from entering of small particles and
dusts
 Ciliary body When the eyes focus on an object they contract and
relax, and they change the shape of the lens.
 Eyelid is a thin fold of skin that covers and protects the eye
externally against entry of foreign particles. There are two eyelids
namely upper and lower eyelids. They are able to move and as the
result keep the surface of the eye moist. The movement of eyelids
is called blinking. The upper eyelid of the eye secretes a saline
fluid which contains enzymes that offer protection to the eye by
killing microorganisms that can attack the eye.
 Eye lashes are fine hairs that grow at the edge of eyelid. They
perform the function of protecting the eye from entry of small
foreign particles such as sand and dust.
 The eyebrow is an area of thick, short hairs above the eye that
follows the shape of the lower margin of the brow riges. Their
main function is to prevent sweat, water, and other debris from
falling down into the eye socket. They are also important in human
communication and facial expression
 Sclera This layer protects, supports, and maintains the shape of the
eyeball. The sclera is white in colour except the front part which is
transparent and it is called cornea. It also contains elastic
connective tissues.
 The cornea is the transparent part of the eyeball which is
continuous with the sclera and is covered with a thin membrane
called conjunctiva. Cornea is convex so that light rays can be
refracted, and since it is transparent, it allows light to pass through.
 The conjunctiva is a thin transparent membrane which is found
inside of the eyelids covering the front of the sclera. Conjunctiva
helps to cover and protect the cornea because it has tough and
 transparent membrane. Thus, it offers protections of the inner part
and also allows light to pass through.

Defects of the mammalian eyes

These are functional and structural deviations of the eye that alter the
focusing mechanism of an eye. The common defects of the eyes are
 Short sightedness (myopia)
 Long sightedness (hypermetropia).
 Astigmatism
 Presbyopia

(a) Short sightedness (Myopia)

This is a defect of vision in which far objects appear blurred but
near objects are seen clearly. The image of an object is focused in
front of the retina in vitreous humour rather than on the retina
This defect can be corrected by using suitable concave spectacle
lenses, which diverge the light rays entering the eyes to the correct
extent and bring them into focus on the retina.
(b) Long sightedness (hypermetropia)
This is a defect in which near object appears blurred but far objects
can be seen clearly. The image is focused behind the retina rather
than upon it.
This condition can be corrected by the use of a suitable convex
spectacle lens, which converges the light rays entering the eye to
the correct extent and brings them into focus on the retina
(c) Astigmatism
This defect occurs when the eye does not focus light evenly on the
retina, instead some light is focused on the retina while some is
focused behind or in front of the retina. This is usually caused by a
non-uniform curvature of the cornea.

PRACTICAL QUESTIONS

NECTA 2020
BIOLOGY 2A
1. you are provided with the following: tooth pick, piece of cotton wool,
methylated spirit and samples labelled A (sand) and B (wheat flour)
which are stimuli of receptors in the body. Carry out experiments in
item (i) – (iv) and then answer the questions that follow:
(i) Look at your body and observe the sense organ that covers the
 whole hands.
(ii) Take a tooth pick and prick slightly the upper part of your hand
and note the feeling.
(iii)Touch each of the samples A and B and feel their coarseness.
(iv)Take cotton wool and soak into methylated spirit. Rub it on your
hand and observe what is happening.
Questions
a) (i)Give the name of the sense organ that covers your hands.
(ii) Explain four functions of the sense organ mentioned in (a)(i).
b) (i)What did you feel when you pricked the upper part of your hand
with tooth pick?
(ii) What type of sensory receptor responsible for the feeling in
(b)(i)?
c) (i) identify the coarseness felt in each of the samples A and B.
(ii) What type of sensory receptor responsible for the feeling in
(c)(i)?
d) (i) What did you feel when you rubbed methylated spirit on your
skin?
(ii) Give the two types of sensory receptors responsible for the
feeling in (d)(i).
e) What was the aim of the experiment?
f) Explain the role of hairs and sweat pores on the sense organ
covering your hands.

PRACTICAL ACTIVITY
2. Open your mouth widely. Using the mirror provided observe what
you can see inside the mouth on the mirror.
(i) Name different sense organs which are visible.
(ii) What is the function(s) of each sense organ(s) observed?
(iii)Draw and label the sense organ you saw in the mouth. In your
diagram shows the location of the sensory structures associated
with the various named stimuli.
(iv) Name the fluid secreted in the mouth in response of food in the
mouth.
(v) State three functions of the liquid named in (iv) above in
digestion.
ANSWERS
2.
(i) The observed sense organs were: -
 Skin
 Tongue
 Eyes
 Nose
 Ears
(ii) The function(s) of each organ observed: -
Skin:
 To protect internal parts of the body.
 To bring sense to touch, pain, heat, cold and pressure.
Tongue:
 To enhance a person to speak.
 To bring sense of taste of food and other substances.
Eyes:
 To enhance a person to determine distance.
 To bring sense of sight/vision.
Ears:
 To enhance the body for posture and body balance.
 To bring a sense of sound.

Chapter 7

MOVEMENT AND LOCOMOTION

Movement is a process by which a part or parts of an organism move
without an organism changing its position. Movement includes change in
shape, size and direction of the body parts or part in relation to the body
axis

Locomotion is the movement of the whole body of an organism from one

location or place to another. This means that all forms of locomotion entail
movement, but not all movements are locomotion.

Skeleton is a structure in animals that provide mechanical support to the

body and protects the internal body organs.
Types of skeletons
There are three types of skeletons, namely;
  Exoskeleton is a hard covering on the outer side of the body of
arthropods such as insects, crustaceans and arachnids. It is made of
a tough polysaccharide called chitin and it is usually covered by a
water proof outer covering of wax.
 Hydrostatic skeleton is a type of skeleton which is provided by
fluid filled cavity under pressure. It acts as skeleton for muscle
movement and hence termed hydrostatic skeleton.
 Endoskeleton is the type of skeleton in vertebrates made of a very
hard tissue called bones. Bones are made up of widely spread
living cells into which mineral salts are deposited. The main
mineral salts are calcium phosphate, calcium carbonate and trace
amounts of magnesium phosphate.
Human skeleton
Human skeleton is a rigid frame work of cartilage and bones to which
softer tissues, organs and muscles are attached.
Components of human skeleton
 Tendons
These are tough connective tissues which attach muscles to bones.
The tendons are inelastic tissue that firmly holds the muscles to the
bones. Tendon may also attach muscles to body structures such as the
eye ball.
The function of the following component of human skeleton
(i) Skull is the bone frame work of the head. Skull consists of two
parts namely cranium and visceral skeleton. The cranium is made
up of flat bones joined tightly together to form immovable joints.
It has the following function;
 Protects the brain
 Protects the olfactory organs
 Protects the eyes, middle and inner ear
 The cranium possesses a special occipital bone with occipital
condyles which articulate with atlas vertebra to form a joint.
This joint permits the nodding and other movement of the
head
(ii) Ribs are thin, flat curved bones that form the protective cage
around the organs of the upper. It has the following functions;
 They give the chest its shape
 They protect the heart, lungs, spleen and kidneys against
injuries and shock.
 They help in breathing by expanding to let air in and
contracting to let air out.
(iii)Vertebral column is the series of 33 bones called vertebrae. It has
 the following functions;
 It allows human beings to stand upright and maintain
their balance
 It supports the head and arms
 Protects the spinal cord which mainly controls most
body functions
 It provides the site for attachment for the ribs and
many muscles.
Vertebral column has five types of vertebrae.
(i) The cervical vertebrae these are short bones that are found in
the neck region. There are seven vertebrae that make the
skeleton of the neck region. The first two cervical vertebrae
are called atlas and axis respectively
Adaptation of cervical vertebrae
 The cervical vertebrae are branched to increase surface
area for muscle attachment.
 They have spinal canal which houses and protects the
spinal cord and nerves.

Functions of cervical vertebrae

 Supports the skull or weight of the head
 They allow free rotation/nodding of the skull on vertebral
column
 They provide attachment for neck muscles

Figure; cervical vertebrae

(ii) The thoracic vertebrae the twelve thoracic vertebrae
together with the ribs and sternum form the thoracic cage
which protect the heart, lungs and some blood vessels against
injuries. In addition, the thoracic vertebrae play a major role in
breathing which is enhanced by movement of the intercostal
muscles.
 Figure; 7.1: the thoracic vertebrae

Adaptation of thoracic vertebrae

 They have long neural spine that increases surface area for
muscle attachment.
 They also have spinal canal for the passage of spinal cord
 They possess facets which facilitate articulation of bones.
Facets are small rounded surfaces on the thoracic vertebrae
on which the ribs are attached.
(iii) The lumbar vertebrae these are found in the lumbar or abdominal
region. Lumbar region is the lower back region of the vertebral
column. There are five bones in humans that make lumbar
vertebrae. They allow bending movements and rotation of the
trunk. In order to allow this movement large number of muscles
are attached in this region.
Adaptations of lumbar vertebrae
 They have long transverse processes that increase surface
area for abdominal muscles attachment
 They also have extra processes which increase surface area
for attachment of muscles, the neural spine bone which is
short and broader for muscle attachment and support. They
also have large and thick centrum for support.
 Figure; 7.2: the lumbar vertebrae

(iv)The sacral vertebrae. These are the vertebrae that are found
in the sacral region or pelvic region of the vertebral column.
They are fussed together to form a broader structure called
sacrum. Sacrum provides large surface area for muscle
attachment

Figure; sacral vertebrae

Adaptation of sacral vertebrae
 They have a sacrum which gives support and transmits the
weight of the stationary state to the rest of the body.
 They also have numerous posterior foramens or canals
which facilitate the passage of spine nerves.
 Their base is broader in order to provides large surface area
for muscle attachment.
(v) Caudal vertebrae, these are the vertebrae found in the tail
region. Depending on the length of the tail, the caudal
vertebrae bone varies greatly from one mammal to another.
(vi)Scapula is a flat triangular bone which covers a number of
anterior ribs. At one end, the scapula has concave depression
known as glenoid cavity which articulates with the head of
humerus to form a ball and socket joint
Adaptation of scapula to their function
 They have long spine projections called acromion and
metacromion. These projections are used in the
attachment of muscles
 Also it has a broad and a flattened surface. These two
surfaces provide large surface area for muscle
attachment and allow the upper limbs to move in many
planes and angles
 Figure; 7.3 Scapula
Function of Scapula
 Provide site for attachment of muscles that move the arms
Clavicles are collar bones.
Functions of Clavicles
 They provide sites for muscle attachment
 They aid in movement of the arm

The humerus is the skeleton in the upper arm. It’s rounded which
articulates with the glenoid cavity.

Figure; 7.4: the humerus

Function of humerus
 Attachments of biceps and triceps muscles
Adaptations of the humerus to its function include
 The presence of rounded head that fits into the glenoid cavity of
the scapula. This allows for greater flexibility of movement of the
arm. Humerus articulates with the fore arm at the elbow joint.
 It has trochlea at the lower ends which articulates with forearm(at
the ulna bone) that allows movement in one plane.
 Also, it has capitulum which articulates with the head of the
 radius.
 The humerus is long to provide large surface area for attachment of
biceps and triceps muscles.

Radius and ulna, these are bone found in the fore arm. Radius is on the
side of the thumb while ulna is on the side of small finger
Function of Radius and ulna
 Supports the carpals, metacarpals and phalanges
 They provide site for attachment of forearm
Pectoral girdle (shoulder girdle) this is a set of bones in the appendicular
skeleton that connect to the arm on each side. It consists of two dorsal
shoulder blades, the scapulae (singular: scapula) and a pair of ventral
collar bones called clavicles. They are not fussed to axial skeleton but are
flexible and attached to the vertebral column by ligaments and muscles.
This arrangement enables the girdle

Functions of Pectoral girdle

 It is strong enough to support the weight of quadruped animals
 Serves as shock absorber when an animal land to the end of a
jump
Femur is a long bone found in the thigh between the hip and the knee

Figure; 7.5: the femur

The adaption of femur to its role includes;
 Presence of the condyles which articulate to allow movement in
one plane.
 It has a strong shaft bone that offers support of the body weight.
 It has a large round head which articulates with the acetabulum of
the pelvic girdle to allow flexible movement of the leg.
 The long bone provides a large surface area for attachment of thigh
 muscles.
Functions of the femur
 Supports the upper part of the body
 Its shaft provides surface for attachment of thigh muscles
Tibia and fibula, these are skeleton of the lower hind limb. The tibia is
ventral while fibula is dorsal.
 Provides surface for attachment of leg muscles
 Supports the body weight

Figure; 7.6: (a) Tibia and fibula

(b) Femur and Tibia of grasshopper

Pelvic girdle is made up of two halves of bones known as pubic bones.
Each half comprises three bones namely pubis, ilium and ischium. The
pubic bones of each side join in the middle ventrally at the pubic
symphysis. The ilium is fused to the sacrum of the vertebral column on
each side. On the outer edge of each half, is a depression called
acetabulum which articulates with the head of the femur to form the ball
and socket hip joint.
Functions of the Pelvic girdle
  Supports the weight of the body from the vertebral column
 Protects and supports the organs in the lower body such as urinary
bladder and reproductive organs
 Protects the developing foetus in pregnant women.

Figure;7.7: The Pelvic girdle

The major functions of human skeleton
 Support
Skeletons provide a strong framework that maintains the shape of
the body. The skeleton supports the weight of the body against
gravitational force. It raises up the body above the ground for
efficient movement. Moreover, the skeleton provides attachment
for many organs
 Locomotion
The skeleton provides attachment for the muscles of the body. The
skeleton and the muscles operate as levers where the skeleton
provides an attachment base for the muscle and the muscle pulls
the skeleton to enhance locomotion.
 Protection
The skeleton protects delicate internal organs against mechanical
damage and injuries.
 Synthesis of red blood cell
 Storage of mineral salts
 Chapter 8

PHOTOSYNTHESIS
Photosynthesis is the process by which green plants, some bacteria and
some Protoctists their own food using water, carbon dioxide and energy
from the sun.
The process of photosynthesis mostly takes place in the green part of the
plants, mostly in the leaf
Photolysis is the process whereby water is broken down into hydrogen
and oxygen ions.
The Leaf’s Adaptation for Photosynthesis.
The external structure of a leaf can be viewed using either using hand lens
or unaided eyes.

 The petiole
The petiole or leaf stalk attaches the leaf to the branch or stem. It
keeps the lamina in a position that will enable it to get maximum
amount of sunlight.
 The lamina is the expanded portion or blade of a leaf. It has a
large surface area. This maximizes the absorption of sunlight
energy and carbon dioxide. The lamina is also thin so that carbon
dioxide gas can diffuse and sunlight energy can penetrate over a
short distance to reach cells.
 The mid-rib which gives rise to veins and veins contain xylem
and phloem. Xylem transports water and mineral salts and Phloem
transports manufactured food from the leaf to other parts of the
plant.

Figure; 8.1: External structure of leaf

 The cuticle: This is the outermost transparent and waxy layer of

 the leaf.
 It allows light to penetrate into the photosynthetic cells.
 It also protects the leaf from injury, pests, and excessive
loss of moisture. There is no cuticle on the stomata in
order to allow gaseous exchange
 The epidermis – allows sunlight to penetrate the leaf easily
 Stomata (singular is stoma) are small pores in the epidermis.
They allow oxygen and carbon dioxide to diffuse in and out of
the leaf. Stomata are surrounded by guard cells that close and
open the pores. The guard cells also have chloroplasts to allow
photosynthesis.
Note; Broad leaves, such as those of bean plants, have more
stomata on the lower epidermis than on the upper epidermis
 Vascular bundles. These are xylem and phloem tissues which
serve as conducting tissues. Xylem transports water and mineral
salts. Phloem transports manufactured food from the leaf to
other parts of the plant.
Importance of photosynthesis
 Photosynthesis produces food for the plants and animals that
feed on plants
 Photosynthesis produces oxygen that helps to replace the
oxygen that has been used up during burning, respiration and
other processes
 The process of photosynthesis uses carbon dioxide from the
atmosphere which is harmful to the environment
 Photosynthesis is the source of fuel. The remains of dead plants
and animals form fossil fuels such as coal, oil and natural gas.
 Photosynthesis is important for the lives of plants as well as
animal.
Conditions necessary for photosynthesis
 Chlorophyll that is responsible for trapping sunlight energy
that is used during photosynthesis.
 Sunlight(Light energy) causes photolysis, a chemical
process whereby water molecules (H2O) are split into
hydrogen ions (H+) and hydroxyl ions (OH-).
 NECTA 2003
BIOLOGY 2A
2. You are provided with specimen P.
Carry out an experiment as instructed below:
Make a drawing to show the colour pattern of specimen P.
Dip specimen P in hot water for about one minute.
Boil specimen P in alcohol using a hot water bath.
Dip the boiled specimen P in hot water.
Spread specimen P on a white tile and add 2 - 3 drops of iodine
solution on the specimen.
Questions
(a) (i) Identify specimen P
(ii) What observation did you make after applying iodine solution to
specimen P?
(b) Why was specimen P
(i) Dipped in hot water at the beginning of the experiment
(ii) Boiled in alcohol
(iii) Dipped in hot water after boiling in alcohol?
(c) Why was the alcohol boiled using a hot water bath?
(d) (i) What is the aim of the experiment?
(ii) Name the physiological process which was being investigated.
(iii) What conclusion can you make from this experiment?
Note
The specimen was variegated leaf

PRACTICAL ACTIVITY
1. You are provided with specimen M, hibiscus leaf, methylated spirit,
iodine solution, source of heat, test tube, 250 ml beaker, dropper,
forceps, water and white tile
Procedure
(i) Take a leaf from a plant that has been in the sunlight at least
6 hours.
(ii) Put the leaf in boiling water for 2-3 minutes
(iii)Remove the leaf rom the methylated spirit and rinse it in warm
water. The water softens the leaf.
(iv)Put the leaf on a White tile. Add 2-3 drops of iodine solution on
the leaf, what do you observe?
Questions
(a) (i) Identify specimen M by its common name
(ii)What observation did you make after applying iodine solution to
specimen M?
(b) Why was specimen M
(i) Dipped in hot water at the beginning of the experiment
(ii) Boiled in alcohol
(iii) Dipped in hot water after boiling in alcohol?
(c) Why was the alcohol boiled using a hot water bath?
(d) (i) What is the aim of the experiment?
(ii) Name the physiological process which was being investigated.
(iii) What conclus1on can you make from this experiment?
Answers
(a) (i) specimen M was hibiscus leaf
(ii)The blue-black colour was observed on the leaf
(b) (i) In order stops any chemical from taking place(photosynthesis)
(ii) This decolourise the leaf (removal of chlorophyll)
(iii) To soften the leaf
(c) Because it is highly flammable.
(d) (i) Testing a plant leaf for starch
(ii)Photosynthesis
(iii)The blue-black colour indicates the presence of starch

CHAPTER 9
GASEOUS EXCHANGE AND RESPIRATION
Gaseous exchange is the process which enables mammals to obtain
oxygen gas in their body for various uses such as energy production.
Gaseous exchange is possible through the respiratory system.

Characteristics of respiratory surfaces

 They are thin in Order to reduce the diffusion distance.
 They moist in order to dissolve gases that diffuse in a solution
form.
Note; this is confirmed when a person breathes onto the plain
mirror where by tiny liquid droplets formed the mirror
 They are highly branched, folded, or flattened in order to increase
the surface area for gaseous exchange.
 They are surrounded by blood capillaries so that gases can be taken
to and from the cells easily.
 They are well ventilated so that gases can pass through them
 easily.

The components of the respiratory system of mammals include

 The nostril, nasal cavity, pharynx, trachea, bronchi, lungs,
bronchioles, alveoli, intercostal muscles, diaphragm, and ribs,

Mechanism of gaseous exchange in mammals

Gaseous exchange in mammals occurs as a result of inhalation and
exhalation. Inhalation is the process of breathing in air into the lungs.
Exhalation is process of breathing out air from the lungs. The composition
of inhaled air is different from exhaled air,

Constituent In haled Exhaled air

Oxygen gas 20.95% 16.40%
0.03%
Carbon dioxide gas
Nitrogen gas 78.10% 78.100/0
Noble gases 0.94% 0.94%

Note; exhaled air(Carbon dioxide gas) can be confirmed by person

breathing onto lime water whereby colour change turn into milky; this
confirms the presence of carbon dioxide in the exhaled air.

Factors affecting the rate of gaseous exchange in mammals

Gaseous exchange is affected by many factors including the following:
 Carbon dioxide concentration
High concentration of carbon dioxide in the blood increases the
rate of gaseous exchange. The increase in the rate of gaseous
exchange provides the cells with adequate concentration of
oxygen and lager concentration of carbon dioxide in the blood.
 Haemoglobin concentration
Haemoglobin is a reddish protein molecule containing an Iron
atom, which is responsible for transporting oxygen and carbon
dioxide in the blood of vertebrates. Haemoglobin transports
oxygen gas from the lungs to the body cells and carbon dioxide
from the body cells to the lungs. Efficient transportation of gases
takes place When the body has adequate concentration of
haemoglobin. When a person is anemic, the body has a low
concentration of haemoglobin therefore, a low level of oxygen can
be transported at a time. This results into the increase of the rate of
 gaseous exchange so that the body cells can get enough oxygen.
 Physical activity
A more active body requires more oxygen than a active body.
During physical exercise the muscle cells respire more than when
the body is at rest. Therefore, the rate and depth of breathing
increases. This ensures that more oxygen is absorbed into the
blood and more carbon dioxide is removed, As a result, therefore
gaseous exchange increases when there is increased body activity.
 Health status
Generally, the rate of gaseous exchange increases when a person
is sick. This is due to increased metabolism by the liver during
removal of the toxins released by disease-causing micro-
organisms or break down of the drugs taken
 Altitude
Altitude is the height above sea level at high altitudes; the
concentration of oxygen is lower than at low altitudes. This is due
to reduced pressure at high altitudes compared to low altitudes.
 Age
Young people are generally more active than old people. Also,
many growth processes take place in the bodies of young people
compared to adults. This increases the demand for oxygen hence
increases the rate of gaseous exchange.

Gaseous exchange in plants

Gaseous exchange in plants is the process whereby oxygen gas leaves and
carbon dioxide gas enters the plant during the day. During the night
oxygen gas enters and carbon dioxide gas leaves the plant. Gaseous
exchange mostly takes place through the stomata on the leaves and
lenticels on the stem. In some plants such as mangrove, gaseous exchange
is carried through breathing roots, also called pneumatophores, which
usually project above the water surface,

During the day, green plants carry out photosynthesis to produce glucose.
This takes place also within the guard cells that surround the stomata. As a
result, the cell sap of guard cells becomes hypertonic and draws in water
from the neighbouring cells by osmosis.
The guard cells become turgid and the stomata open, Air from the
atmosphere enters into the air spaces in the spongy mesophyll. The cells
next to the air spaces have more oxygen that is produced by the cells
during photosynthesis and less carbon dioxide as it is used up during
photosynthesis.
Carbon dioxide and oxygen diffuse in opposite directions depending on
their concentration gradients. Carbon dioxide diffuses to neighbouring
cells until it reaches the site of photosynthesis. Oxygen moves out through
the open stomata to the atmosphere.
At night, there is no sunlight, therefore light reaction of photosynthesis
ceases. This means that little or no glucose is produced hence the guard
cells do not absorb water by osmosis. Therefore, the stomata remain
partially closed. On the other hand respiration continues during the night.
The partially open stomata allow in a small amount of air to accumulate in
the air spaces.
Oxygen diffuses into the plant cells while carbon dioxide diffuses out into
the intercellular spaces and eventually into the atmosphere through the
partially opened stomata.
Fermentation in the laboratory can be investigated by mixing glucose
solutions and 10% of yeast granules in a closed container and left for 15
minutes .bubbles will be observed on the surfaces of liquid with the smell
of alcohol. Bubbles are caused by rising up of carbon dioxide
C6H12O6 →2C2H5OH+2CO2+Energy

In animals, anaerobic respiration leads to the formation of lactic acid and

energy as shown in the following equation:

C6H12O6 →2C3H6O3+Energy

Anaerobic respiration occurs when the body's oxygen supply does not
meet the body's needs. For example, during vigorous activity such as
sports, lactic acid is accumulated in the muscles prevents from contracting
and relaxing due to its toxicity. and can also cause pain. When this occurs,
oxygen is required to oxidise lactic acid into water and carbon dioxide, the
oxygen required in such situation is known as oxygen debt. Accumulation
of lactic acid in the muscles prevent them from contracting and relaxation
due its toxicity and cause pain .
Oxygen debt causes the animal to breathe rapidly and deeply in Order to
get enough oxygen required to convert the lactic acid to carbon dioxide
and water. Some of the lactic acid is converted to glucose. Breathing goes
back to normal when the acid has been broken down.
Application of anaerobic respiration
 Bread making
 Beer brewing
 Distiller industries
 Production in citric acid.
 PRACTICAL ACTIVITY
1 You are provided with two beakers labeled with letter A and B
stirring rod rubber band plain paper and sample labeled C(glucose
crystals)),D(starch powder) and E(yeast). A beaker wit letter B
containing distilled water. Carry out experiment under the procedure
(i)-(v) and then answer the question that follow;

(i) Put a sample labeled C into beaker A followed by sample

labeled D
(ii) Add sample labeled E into a beaker A, then use stirring rod
to mix the contents
(iii)Add distilled water from beaker B into beaker A, then stir
the solution mixture
(iv)Use a rubber band and plain paper to cover on top of the
solution on a beaker A
(v) Leave the experiment for 15 minutes then remove cover
Questions
(a) (i) what did you observe
(ii) What brought about your observation in (a) (i) above?
(b) (i) Name the physiological process which takes place in
beaker. Give reasons for your answer
(ii) Define the physiological process you mentioned above
(c) (i)write a balanced chemical equation for the physiological
process
(ii) Write the main product and byproduct for the
physiological process
(d) (i)which byproduct is useful to the yeast in C(ii) and why
(ii) Where does the physiological process occur in the
human body?
(e) What was the aim of experiment
(f) Explain briefly four industrial application physiological
process you named in b(i)
Answer
(a) (i)Bubbles was observed on the surface of the liquid
(ii)Bubbles are caused by rising up of carbon dioxide
(b) (i)Anaerobic respiration (fermentation)
(ii)Anaerobic respiration (fermentation) takes place in the
absenceof oxygen.
(c) (i)C6H12O6 →2C2H5OH+2CO2+Energy
(ii)Mai product is 2C2H5OH and Energy, byproduct is 2CO2
 (d) (i) CO2 which makes dough rise
(ii) In the skeletal muscles
(e) The aim of the was to investigate anaerobic respiration in yeast
(f) Application of anaerobic respiration
 Bread making
 Beer brewing
 Distiller industries
 Production in citric acid.

Common Asked Specimens in Biology Practical Examinations

1. Tilapia fish 22. Butterfly
2. Yeast 23. Cockroach
3. Frog/toad 24. Cactus stem
4. Bread mould 25. Mites
5. Housefly 26. Bean seed
6. Spider 27. Termites
7. Bee 28. Maize grain
8. Sugarcane stem 29. Mushroom
9. Grasshopper 30. Maize seedling
10. Irish potato 31. Bean seedling
11. Liver fluke 32. Castor seeds
12. Centipede 33. Ticks
13. Fern plant 34. Rat
14. Ascaris 35. Lizard
15. Millipede 36. Onion bulb
16. Moss plant 37. Tea bag
17. Earthworm 38. Lime water
18. Crab 39. Potassium permanganates
19. Pine leaf 40. Plane mirror
20. Tapeworm 41. Variegated lea
21. Hibiscus leaf/flower