SSI FIRST TERM BIOLOGY

RECOGNIZING LIVING THINGS

INTRODUCTION TO BIOLOGY
The term biology was coined from two Greek words; Bios meaning life and
logos meaning study. Hence, biology can be defined as the study of life.

BRANCHES OF BIOLOGY
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The branches of biology include;
(1)Botany: Study of plants.
(2)Zoology: Study of animals.
(3)Ecology: Study of plants and animals in relation to their environments.
(4)Morphology: Study of external features of plants and animals.
(5)Anatomy: Study of internal structures of plants and animals.
(6)Genetics: Study of heredity and variation.
(7)Physiology: Study of how plants and animals function etc.

LIVING AND NON LIVING THINGS

Everything on earth can be classified as either living or non living things.
- Living things are those things that have life. They include: plants and
animals.
- Non-living things are those things that do not have life e.g air, rock,
water, book, etc.
CHARACTERISTICS OF LIVING THINGS
The characteristics of living things are;
(1)Movement: This is the ability of an organism to move its own whole
body or part of its body from one place to another. Living organisms
move in order to look for food, for reproduction and to run away from
danger or respond to the environment.
(2)Nutrition: This is the ability of living organisms to feed. The reason for
feeding is to enable living things live and carry out life processes like
growth, respiration and reproduction.
(3)Respiration: This is the oxidation of food substances in order to
release energy.
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 (4)Excretion: This is the removal of metabolic waste products from the
body.
(5)Irritability (sensitivity): This is the ability of organisms to respond to
stimuli. Stimuli include heat, light, pain, water and chemical
substances to which living things respond.
(6)Growth: This is the irreversible increase in size and complexity of an
organism. The purpose of growth is to enable organisms to repair or
replace damaged or old tissues in their bodies.
(7)Reproduction: This is the ability of living things to give birth to young
ones. The purpose of reproduction is to ensure continuity of life.
(8)Death: This is the end of life of all living things. All living things must
die because they have a definite and limited period of existence.

ORGANIZATION OF LIFE
All living things are highly organized and this organization occurs in levels.
The simplest structures are found at the lowest levels and they interact to
build up more complex structures at the next level.

LEVELS OF ORGANIZATION OF LIFE

There are four levels in the organization of life in organisms. The levels are;
(1)CELL
A cell is the basic structural and functional unit of life. It is the first level
in the organization of life. The cell is made up of organelles and these
organelles carry out all functions to sustain the life of the cell. e.g. red
blood cell, white blood cell, rods, cones, nerve cells, phloem cells, etc.
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(2)TISSUE
A tissue is a group of cells that are similar in shape and size and work
together to carry out a specific function in the body. Some animals exist
in the tissue level e.g. Hydra. Examples of tissues in organisms are:
blood, epithelial tissue, skeletal tissue, vascular tissue, etc.
(3)ORGAN
An organ is a collection of different tissues that carry out a specific
function in the body. Some organs perform only one function e.g heart
while others perform many functions e.g Kidney and liver. Examples of
organs in plants are leaves, flowers, roots, stems, etc.
(4)SYSTEM:
A system consists of two or more organs that work together to perform
specific functions. Systems are peculiar to higher organisms. Examples
of systems include; digestive system, respiratory system, shoots system
etc.

COMPLEXITY OF ORGANIZATION IN HIGHER ORGANISMS

There is an increase in complexity from unicellular organisms to
multicellular organisms. This complexity in higher organisms has some
advantages and disadvantages.
ADVANTAGES OF COMPLEXITY IN HIGHER ORGANISMS
(i) It leads to specialization
(ii) Specialization leads to division of labour.
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 (iii) Division of labour leads to efficiency.
(iv) Onebody function does not adversely affect other body functions.
(v) Reproduction does not lead to the breaking down of the parent
body.
(vi) Complexity leads to increase in size.
(vii) Complexity leads to increase in adaptation to environment.
DISADVANTAGES OF COMPLEXITY
(i) Inability of individual cells to exist on their own.
(ii) Difficulty in acquisition of oxygen and food materials.
(iii) It leads to slower rate of diffusion.
(iv) Internal organs breakdown easily due to wear and tear
(v) It leads to slower rate of expelling waste products.
(vi) It leads to difficulty in reproduction.
(vii) It leads to inability to regenerate body parts.

CLASSIFICATION OF LIVING THINGS

Classification of living things involves placing livingthings in groups that
have certain features in common which distinguish them from other groups.
The system of classification currently in use was introduced by a Swiss
scientist called Carolus Linnaeus (1707-1778). He published the
classification of plants in 1753 and that of animals in 1758.

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 HIERARCHY OF CLASSIFYING LIVING THINGS
There are seven major groups used in classification of living things. They
are;
Kingdom
Phylum/division
Class
Order
Family
Genus
Species

Examples are:

Man Lion Maize

Kingdom Animalia Animalia Plantae
Phylum Chordate Chordata Spermatopyta
Class Mammalia Mammalia Monocotyledonae
Order Primate Carnivora Cyperales
Family Hominidae Felidae Poaceae
Genus Homo Panthera Zea
species Sapiens Leo Mays

BINOMIAL SYSTEM OF NOMENCLATURE

This system of naming living things was introduced by Carolus Linnaeus.

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In this system, each organism is given two names.
-The first name is the generic name and it always begins with a capital
letter.

- The second name is the specific name and it always begins with a
small letter.
- The scientific names are written in italics when typed or underlined
when hand written.
Examples include;
Man : Homo sapiens
Tiger : Felis tigris
Maize : Panthera leo
Rat : Ratusratus
Rice : Oryza sativa
Housefly : Musca domestica
Orange : Citrus sinensis
Cocoa : Theobroma cacao
Dog : Canisdomesticae.t.c

KINGDOMS OF LIVING THINGS

Living things can be classified into five kingdoms namely;
1) Monera
2) Protista
3) Fungi
4) Plantae
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 5) Animalia

(1)Kingdom Monera:
They have the following characteristics:
- They are unicellular
- The cells are prokaryotic
- The cells have no organized nucleus, with nuclear membrane.
- They do not have complex chromosomes.
- They have no mitochrondria, endoplasmic reticulum and
chloroplasts.
- Their cell walls do not contain cellulose
- There is no sexual reproduction
- They may possessheterotrophic and autotrophic mode of
nutrition.
Kingdom monera is divided into two phyla namely:
(a)Schizophytae.g. Bacteria
(b)Cyanophyta e.g. Blue green algae.
(2)Kingdom Protista:
They have the following characteristics:
- They are unicellular organisms.
- They are all eukaryotic
- They move either by cilia, flagella or may be amoeboid in nature.
- Some are heterotrophic while others are both heterotrophic and
photosynthetic.
- They reproduce asexually by mitosis while some reproduce sexually
by fusion of gametes.
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- There are four phyla in this kingdom namely:
(a)Euglenophyta:
- Possess flagellum for movement
- Possess contractile vacuole for osmoregulation.
- Possess eye spot
- Have ability to carry out holozoic nutrition.
- Possess pellicle that makes its body flexible. e.g. Euglena.
(b)Protozoa
- They are microscopic
- They have eukaryotic cells
- They reproduce asexually by binary fission.
- They are mainly aquatic organisms while some are parasitic.
- They are unicellular. e.g. amoeba, paramecium.
Other phyla are;
(c) Chrysophyta
(d)Pyrrophyta
(3)Kingdom Fungi
Fungi were formally classified as plants. But they differ from plants in
the composition of their cell walls. They have the following
characteristics:
- They are eucaryotes
- Some are unicellular e.g. yeast while others are multicellular e.g.
mushroom.
- They have no true roots, stems and leaves.
- They lack chlorophyII.
- They are mainly saprophytes while others are parasites.
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- Their cell walls are made up of chitin instead of cellulose.
- The vegetative body parts are made up of fine and delicate threads
called hyphae.
- They reproduce asexually by formation of spores and some sexually
by conjugation.
- They are mainly found in moist environment.
- They are mainly non-motile organisms. e.g. rhizopus, mushroom,
mucor, yeast, toad stools, etc.
(4)Kingdom Plantae
The plant kingdom consists of three main divisions namely:
Thallophyta, Bryophyta and Tracheophyta.
(a)THALLOPHYTA:
They have the following characteristics:
- They are simple microscopic plants.
- Some are unicellular while others are multicellular
- They are simple aquatic plants.
- They do not have true roots, stems and leaves
- They have cellulose cell walls.
- They are mainly autotrophic plants.
- They exhibit both sexual and asexual means of reproduction.
- Examples include; Chlamydomonas, Spirogyra, Volvox.
This division has 3 sub-divisions namely;
i. Rhodophyta (Red Algae)
ii. Chlorophyta (Green Algae)
iii. Phaeophyta (Brown Algae).
(b)BRYOPHYTA:
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 They have the following characteristics:
- They are complex multi-cellular green plants.
- Their cells are differentiated into tissues.
- They lack true roots, stems and leaves.
- They are non-vascular plants.
- They are usually found growing in moist places.
- Some are terrestrial while others are aquatic.
- They exhibit alternation of generation. i.e. can reproduce both
asexually and sexually.
Examples are mosses, liverworts, bladderworts, etc.

(c)TRACHEOPHYTA
- This division is made up of vascular plants.
- This division is divided into two sub-divisions namely; Pteridophyta
and Spermatophyta
(i)Pteridophyta: (ferns)
They have the following characteristics;
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 - They are multi-cellular plants
- They are vascular green plants.
- They are non flowering plants.
- They have true roots, stems and leaves.
- They are mainly terrestrial plants but few are aquatic.
- They are non-seed producing plants
- They reproduce asexually by spores.
Examples include; dryopteris, ferns etc.

(ii)Spermatophyta:
They have the following characteristics:
- They are multicellular seed producing plants
- They have well developed vascular tissues.
- They have true roots, stems and leaves
- They reproduce sexually.
- They do not need water for reproduction.
- They are mainly terrestrial green plants.
Spermatophytes can be divided into two main classes namely;
gymnospermae and angiospermae.

Gymnospermae:
They have the following characteristics:
- They are plants with naked seeds
- They do not bear flowers
- They have true roots, stems and leaves
- Their seeds are borne on cones.
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 - They are vascular green plants.
Examples include; Pinus, Cycads, Ginkgos, Conifers, etc.
Angiospermae:
They have the following characteristics:
- They are the most complex green plants.
- They are vascular plants
- They are flowering plants
- Their seeds are enclosed in fruits.
- They are mainly terrestrial plants.
- They show more specialized reproductive mechanism.
Angiosperms can be subdivided into two sub-classes namely; dicotyledons
and monocotyledons.
(a)Dicotyledons:
They have the following characteristics:
- They bear seeds with two seed leaves or cotyledons
- Their vascular bundles are arranged in a regular pattern.
- Their floral parts exist in groups of four or five.
- They have net venation.
- They have tap root system.
- They usually undergo secondary growth.
Examples include; mango, cowpea, cashew, groundnut, etc.
(b)Mono cotyledons:
They have the following characteristics:
- They bear seeds with only one seed leaf (cotyledon)
- Their vascular bundles are scattered.
- Their floral parts exist in group of three of multiples of three.
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 - They have parallel venation.
- They have fibrous root system.
- They do not undergo secondary growth.
Examples include; maize, rice, palm trees, guinea grass etc.
(5)KINGDOM ANIMALIA
The kingdom animalia consist of the following phyla: Porifera,
Coelenterata, Platyhelminthes, Nematoda, Annelida, Mollusca,
Arthropoda, Echinodermata and Chordata.

(1)PHYLUM PORIFERA
They have the following characteristics:
- They are simple aquatic invertebrates.
- They do not move about but are attached to rocks or shells.
- They live in colonies
- Their larval stage is usually motile
- They are primitive multi-cellular animals.
- They lack tissues.
Example includes the sponges.
(2)PHYLUM COELENTERATA (CNIDARIA)
They have the following characteristics;
- They are multi-cellular organisms.
- Their body is made up of two layers (ectoderm and endoderm).
- They are mainly aquatic organisms.
- Their bodies possess radial symmetry
- They have soft jelly-like bodies.
- They have tentacles and stinging cells for capturing their preys.
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 - They reproduce asexually by budding.
Examples include; jelly fish, hydra, sea anemones and coral.

(3)PLATYHELMINTHES (Flat worms)

They have the following characteristics;
- They are multi-cellular flatworms.
- They are bilaterally symmetrical
- They do not have body cavity (Acoelomate)
- Their body is made up of three layers; ectoderm, mesoderm and
endoderm.
- They are mainly parasites in man and other animals.
- They are mostly hermaphrodites and reproduce sexually.
Examples include; Tapeworm, planaria, liver fluke, blood fluke. etc.

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(4)PHYLUM NEMATODA (round worms)
They have the following characteristics.
- They have round and cylindrical bodies.
- They are pointed at both ends.
- Their bodies are not segmented
- They have partial body cavity (pseudo-coelomate)
- They are bilaterally symmetrical.
- Some are parasites while others are free living.
- Their body is made up of three layers.
Examples include; roundworms (ascaris), hookworms, guinea worms,
thread worms and filarial worms.

(5)PHYLUM ANNELIDA (segmented worms)

They have the following characteristics:
- Their bodies are segmented.
- They are coelomates i.e. they have true body cavity.
- Some are aquatic while others are terrestrial.
- Their body is long and cylindrical.
- They have both mouth and anus.
- They are hermaphrodites and reproduce sexually.
- Their bodies are made up of three layers.
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Examples include; earthworms, leeches, and tube worms.
(6)PHYLUM MOLLUSCA
They have the following characteristics:
- They have soft, unsegmented bodies.
- They have tentacles on their heads.
- They have muscular foots adapted for crawling or burrowing.
- Their body is covered by a soft tissue called mantle.
- Some have shells while others do not have.
- Some are aquatic while others are terrestrial.
Examples include; snails, octopus, oysters, periwinkles, mussel, etc.

(7)PHYLUM ARTHROPODA
- This is the largest phylum in the animal kingdom.
- They have segmented bodies,
- They have hard, rigid exoskeleton made of chitin.
- They have jointed appendages.
- They exhibit moulting or ecdysis.
- Some are aquatic while others are terrestrial.
- They are bilaterally symmetrical
- They have three body layers. (triploblastic)
They have the following classes:
(a)Insecta:
- Their body is divided into three parts/ segments namely head
thorax and abdomen.
- They have three pairs of jointed legs.
- They have two pairs of membranous wings.
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 - They have a pair of antennae.
- They have a pair of compound eyes.
Examples include; grasshoppers, cockroach, housefly, butterfly,
housefly, etc.
(b)Arachnida
- They are mainly terrestrial but a few are aquatic
- They have two body parts namely cephalothorax and abdomen.
- They have no antenna.
- They have four pairs of walking legs.
- They have simple eyes.
Examples include: spiders, scorpion, ticks and mites.
(c)Crustaceans:
- They are mainly aquatic.
- They have two body parts cephalothorax and abdomen.
- Their body is protected by a carapace.
- They have two pairs of antennae.
- They have simple eyes
Examples are: crab, crayfish, prawns, shrimps, barnacles, lobsters, etc.
(d)Myriapoda:
- They have long bodies with many segments.
- They have many legs.
- They have two sub classes namely;
(i) Chilopoda e.g. Centipedes.
(ii) Diplopoda e.g. Millipedes.
(8)PHYLUM ECHINODERMATA
They have the following characteristics;
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- Their bodies are radially symmetrical.
- They have spiny skin.
- They are mainly marine animals.
- They have three body layers.
- Their body is not segmented.
- They do not have a head nor a brain.
- They have tube feet used for movement.
Examples are; starfish, sea urchins, sea cucumber, and bristle star.
(9)PHYLUM CHORDATA
They have the following characteristics:
- They have a backbone or vertebral column
- They possess endoskeleton.
- They are bilaterally symmetrical
- They have three body divisions namely head, trunk and tail.
- They have a well developed central nervous system
- They have well developed sense organs.
- They have three body layers.
- They have skins which may be covered by scales, feathers or hairs.
They are divided into five classes namely;

(a)Pisces (Fishes);
- They are aquatic animals
- Their skins are covered with scales in most cases.
- They have fins for swimming
- They have gills for gaseous exchange
- They have lateral lines for detecting vibrations.
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- They have swim bladder for buoyancy.
- They undergo external fertilization
- They have two chambered heart.
- Their bodies are streamlined for easy navigation.
- They show parental care for their young.
They are divided into two sub-groups namely;
(i) Bony fish: These are fish with bony skeleton e.g. Tilapia, Carp,
Salmon, Mackerel, etc.
(ii) Cartilaginous fish: These are fish with cartilaginous skeletons e.g.
Shark, Skates, Rays, Dog fish, etc.
(b)Amphibia
- They are cold-blooded animals (poikilothermic)
- They have two pairs of limbs
- They have naked or moist skin.
- They respire through skin, lungs or mouth.
- Reproduction is sexual while fertilization is external.
- The young’s (tadpoles) are herbivorous while the adults are
carnivorous.
- They have poison glands for defense
- They have 3 chambered heart
- They have sticky tongue which can be protruded and retracted
quickly.
- They can live successfully both in water and on land.
- They do not show parental care.
Examples include; frogs, toads, salamander, newts.
(c) Reptilia:
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- They are cold-blooded animals (poikilothermic)
- They have dry skins covered with scales
- They have two pairs of limbs except snakes.
- They have lungs for gaseous exchange.
- Reproduction is asexual and fertilization is internal.
- They have an incompletely developed four chambered heart.
- They have homodont dentition.
- They do not show parental care for their young.
Examples include; snakes, lizard, geckos, tortoise, chameleon, turtle,
crocodile, etc.
(d)Aves:
- They are warm-blooded (homoiothermic)
- They have feathers.
- They have two pairs of limbs with the forelimbs modified to wings for
flight.
- They have beak
- They have rigid and hollow bones with air sacs.
- They have four chambered heart.
- Reproduction is sexual and fertilization is internal
- They are oviparous.
- They have lungs for gaseous exchange.
- They show parental care for their young.
Examples include; pigeons, hen, duck, ostrich, eagle, hawks, geese, etc.
(e)Mammalia:
- They are warm blooded (homoiothermic)
- Their bodies are covered with hair.
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- They have heterodont dentition
- They have lungs for gaseous exchange.
- They have two pairs of limbs
- Reproduction is sexual and fertilization is internal.
- They are viviparous.
- They have a well developed brain
- They have four-chambered heart.
- They have external ears (pinna).
- They show parental care for their young.
Examples include; man, cat, dog, rat, rabbit, lion, giraffe, goat, cow,
elephant, etc.

VIRUS
- A virus is a microscopic organism that can only be seen with the aid
of an electron microscope.
- Viruses cannot fit into any of the kingdom of living things.
- Virus does not have a cell structure.
- Viruses have either DNA or RNA enclosed within a protein coat.
- A virus behaves as a living thing when it is in a living cell by
replicating (reproduction).
- When a virus is outside a living cell, it forms crystals and becomes
non living.
- Virus does not respire, feed, excrete, etc.
- Virus does not have structures for synthesis of protein.
LIVING CHARACTERISTICS OF VIRUS
- Can reproduce when placed in a living cell.
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 - Possess characters that can be transmitted from generation to
generation.
NON-LIVING CHARACTERISTICS OF VIRUS
- Forms crystals when outside a living cell and becomes non living.
- Cannot respond to stimuli
- Cannot respire, excrete, feed, etc.

THE CELL
The cell can be defined as the basic structural and functional unit of life. All
living things are made up of cells.
CLASSIFICATION OF LIVING THINGS BASED ON NUMBER OF CELLS
Based on number of cells, living things can be classified into:

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 (a)Unicellular organisms: These are organisms which consist of only
one cell e.g. Euglena, Amoeba, Paramecium, etc.
(b)Multi-cellular organisms: These are organisms which consist of two
or more cells. e.g. volvox, hydra, spirogyra, plants, fish, man, etc.

HISTORY OF THE CELL

The following scientists contributed to the history of the cell:
(1)Robert Hooke (1665): He was an English scientist who is seen as the
father of cells. He discovered the cell from thin slices of cork made
from an oak tree.
(2)Felix Dujardin (1835): He was a French biologist who discovered that
the cell was made up of living substance called protoplasm.
(3)Matthias Schleiden (1838): He was a German botanist who revealed
that the bodies of plants are made up of cells.
(4)Theodor Schwann (1839): He was a German zoologist who
discovered that the bodies of animals are composed of cells.
(5)Rudolf Von Virchow (1855): He was a German biologist who
discovered that all cells come from previously existing cells.
CELL THEORY
The cell theory states that:
(1)The cell is the structural and functional unit of life.
(2)All living things are made up of cells.
(3)There is no life apart from the life of cells
(4)All cells come from previously existing cells.
(5)All living things are either unicellular or multi-cellular.
FORMS IN WHICH LIVING CELLS EXIST
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There are four forms in which living cells exist. They are:
(1)Single and freeliving or independent: These are organisms which
possess only one cell and are capable of living freely on their own.
E.g. Amoeba, Paramecium, Euglena, etc.
(2)As a colony: These are organisms made up of similar cells which
are joined together but cannot be differentiated from each other. E.g
Volvox, Sponges, Pandorina, Eudorina, etc.
(3)As a filament: These are similar or identical cells which are joined
end to end to form unbranched filaments e.g. Spirogyra, Oscillatoria,
Oedogonium, Zygnema, etc.
(4)As part of a living organism: In multi-cellular organisms, cells form
the unit of their life. All parts of the body of a multicellular organism
are made up of cells.

STRUCTURE OF PLANT AND ANIMAL CELLS

The structure of plant and animal cell can fully be understood through the
use of a microscope. Plant and animal cells consist of the following
components/organelles:

CELL ORGANELLES FUNCTIONS

1. Nucleus - Controls life activities of the cell.
- Stores hereditaryinformation.
2. Chromosomes - Contain DNA which stores hereditary
information.
3. Mitochondria - Power house of the cell.
- Site for cellular respiration.

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4. Vacuole - Contains cell sap.
- Acts as osmoregulator to remove excess
water from cells.
5. Nucleolus - Produce ribosomes for protein synthesis.
6. Endoplasmic - Aid in the transport of materials within
reticulum the cell.
7. Golgi bodies - They function in synthesis, packaging
and distribution of materials.
8. Chloroplasts - ContainchlorophyII which aids in
photosynthesis by green plants.
9. Lysosomes - Site for respiratory enzymes.
- Contain lytic enzymes which help to
destroy foreign bodies.
10. Ribosomes - Responsible for protein synthesis.
11. Cell wall - Gives protection, shape, and support to
the cell.
- Allows free passages of materials in and
out of the cell.
12. Cell membrane - Helps in selective absorption of
materials.
- Protects the cell.

13. Centrioles - They are important in cell division.

14. Starch granules - Store starch for the cell.
15. Cytoplasm - Contains all cell organelles.
- Helps in cell division.

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 SIMILARITIES BETWEEN PLANT AND ANIMAL CELLS
Both cells have the following organelles in common:
- Nucleus
- Mitochondria
- Cell membrane
- Chromosomes
- Lysosomes
- Golgi bodies
- Endoplasmic reticulum
- Cytoplasm.

DIFFERENCES BETWEEN PLANT AND ANIMAL CELLS

Plant cell Animal cell
- Has chloroplasts - No chloroplasts
- Has definite shape - No definite shape
- Has cellulose cell wall - No cellulose cell wall
- Has a large central - Has small vacuole
vacuole
- Store lipids as oils - Store lipids as fats
- Nucleus placed at the - Nucleus centrally
edge of cytoplasm placed
- Centrioles absent - Centrioles present

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 THE CELL AND ITS ENVIRONMENT
The cell is defined as the structural unit of life. For a cell to survive and
function properly, it must exchange materials with its environment in the
following ways:
(1)DIFFUSION:
Diffusion can be defined as the process by which molecules of solid
liquid or gases move from a region of higher concentration to a region
of lower concentration until they are evenly distributed.
FACTORS AFFECTING THE RATE OF DIFFUSION

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 (i) State of the matter: The rate of diffusion is faster in gases than in
liquid or solid molecules.
(ii) Size of molecules: The rate of diffusion is faster in smaller molecules
than in larger molecules.
(iii) Differences in concentration: The rate of diffusion is faster if the
difference in concentration of the molecules is greater.
(iv) Temperature: The rate of diffusion is faster with higher temperatures.
IMPORTANCE OF DIFFUSION TO ANIMALS
Diffusion is important to animals in the following ways:
(i) The passage of oxygen from the mother to thefoetus through the
placenta is by diffusion.
(ii) The passage of nutrients from the mother to thefoetus through the
placenta is by diffusion.
(iii) Gaseous exchange in the lungs of mammals during breathing is by
diffusion.
(iv) Gaseous exchange in unicellular organisms is by diffusion.

IMPORTANCE OF DIFFUSION TO FLOWERING PLANTS

(i) Movement of CO2 and O2 through the stomata of leaves during
respiration.
(ii) Movement of CO2 through the stomata during photosynthesis.
(iii) Water vapor leaving the leaves during transpiration.
(2)OSMOSIS:
Osmosis can be defined as the movement of water or solvent
molecules from a region of dilute or weaker solution to a region of

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 concentrated or stronger solution through a semi-permeable
membrane.
CONDITIONS NECESSARY FOR OSMOSIS TO OCCUR
The conditions are:
(i) There must be a weak or dilute solution.
(ii) There must be a concentrated or strong solution.
(iii) There must be a semi-permeable membrane.
LIVING CELLS AS OSMOMETERS
In osmosis, there are usually three types of solutions namely:
(a)Hypotonic solution: This is a weak or dilute solution.
(b)Hypertonic solution: This is a concentrated or strong solution.
(c) This is a situation where both solutions have the same or equal
concentration.

OSMOTIC PRESSURE:
This is the pressure created when water moves across the membrane into
a solution of higher concentration. In other words, it is the force that draws
water into the cell.
OSMOTIC POTENTIAL:
This is the pressure which a solution can potentially exert.
PLASMOLYSIS:
This is the outward flow of water from a living cell when it is placed in a
hypertonic solution until the cell becomes plasmolysed.
HAEMOLYSIS:
This is the process by which red blood cells burst as a result of too much
water passing into it when it is placed in a hypotonic solution.
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TURGIDITY:
This is the condition in which cells absorb plenty of water when placed in a
hypotonic solution until the cell is fully stretched.
FLACCIDITY:
This is a condition in which plants loose water to their surroundings faster
than they absorb.
ACTIVE TRANSPORT:
This is the movement of substances through the membranes of living cells
against concentration gradient.

SOME PROPERTIES AND FUNCTIONS OF THE CELL

All living cells require nutrients to enable them function properly. The
various metabolic reactions which take place in a living cell arise from this
need. Metabolic processes are very important for life, if they stop, the cell
will die. Some of the properties and functions of the cell include;

NUTRITION (FEEDING)

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Nutrition can be defined as the process by which food is taken in by living
organisms in order to supply nutrients required for metabolic activities in
the body.
TYPES OF NUTRITION
There are two major types of nutrition namely; autotrophic & heterotrophic
nutrition.
(1)AUTOTROPHIC NUTRITION
- This is the type of nutrition in which organisms are able to
manufacture their own food.
- Organisms which can manufacture their own foods are called
autotrophs.
- Autotrophic nutrition can either be photosynthetic or chemosynthetic.
(2)HETEROTROPHIC NUTRITION
This is the type of nutrition in which organisms cannot manufacture
their own food but depend directly or indirectly on plants (autotrophs)
for their own food.
- Organisms that cannot manufacture their own food are called
heterotrophs.
- Heterotrophic nutrition can either be holozoic, parasitic, saprophytic
or symbiotic.

MACRO NUTRIENTS
Macro nutrients are nutrients that are required in relatively large amounts
by organisms for healthy growth & development. Examples are; nitrogen,
phosphorus, potassium, magnesium, calcium, oxygen, hydrogen, carbon,
sulphur, iron.
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 MICRO NUTRIENTS
Micronutrients are nutrients that are required by organisms in small
quantities for healthy growth and development. Examples are; zinc, copper,
boron, molybdenum, cobalt, chlorine, manganese.

METABOLISM
Metabolism can be defined as the sum of all chemical reactions that occur
within a living organism. Metabolism is grouped into two namely; Anabolism
and Catabolism.
(i) ANABOLISM
Anabolism is defined as the building up of complex organic molecules
from simple ones in a biological system. Examples of anabolic
reactions include; formation of glycogen from glucose,photosynthesis,
formation of proteins from amino acids, etc. It is usually energy
consuming.
(ii) CATABOLISM
Catabolism is defined as the breaking down of complex organic
molecules into simple substances. Examples include; respiration,
fermentation and digestion. Catabolism produces or releases
energy.

CELLULAR RESPIRATION
Cellular respiration can be defined as the breaking down of food
substances (glucose) in the cell to release energy.
TYPES OF CELLULAR RESPIRATION

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There are two main types of cellular respiration namely; Aerobic and
Anaerobic respiration.
(1)AEROBIC RESPIRATION
This is the type of respiration which requires oxygen to breakdown
glucose to release water, CO2 and energy (ATP). It can be
represented by the chemical equation below:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

(glucose) (oxygen) (carbondioxide) (water) (ATP)

PATHWAYS OF AEROBICRESPIRATION
The pathways involved in the complete breakdown of glucose in the cell
are glycolysis and kreb’s cycle.
(a)GLYCOLYSIS: Glycolysis is a series of chemical reactions which
involves the breaking down of glucose into a three carbon
molecule called pyruvic acid.
- Oxygen is not required during glycolysis.
- Glycolysis takes place in the cytoplasm.
- Very little energy (2ATP) is produced during glycolysis.
- In the absence of oxygen in the cell, pyruvic acid is converted
to alcohol in plant cells and lactic acid in animal cells.
- In the presence of oxygen, the pyruvic acid will enter the
mitochondria where it is converted into a 2-carbon compound
called acetyI co-enzyme A. Acetyl Co-A links glycolysis to
kreb’s cycle.
(b)Kreb’s cycle (citric acid cycle or tricarboxylic acid cycle):kreb’s
cycle involves a series of cyclic reactions which begin with the
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 pyruvic acid formed from glycolysis combined with AcetyI Co-A to
form citric acid.
- Kreb’s cycle takes place in the presence of oxygen.
- It takes place in the mitochondria.
- A large amount of energy is produced during kreb’s cycle (36
ATP)

(2)ANAEROBIC RESPIRATION
This is the type of respiration that does not require oxygen to
breakdown glucose to provide energy. It can be represented by the
chemical equation below:
C6H12O6 2C2H5OH + 2CO2 + Energy
(glucose) (Alcohol (carbondioxide) (ATP)

- The process of breaking down glucose in the absence of oxygen is

called fermentation.

SIMILARITIES BETWEEN AEROBIC AND ANAEROBIC RESPIRATION

- Both lead to the release of energy
- Both occur in plant and animal cells
- Both require enzymes to speed up reactions.
- Both lead to generation of heat.
- Both release CO2 as by-product

Aerobic Anaerobic
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 - Oxygen is required - Oxygen is not
required
- Water is given off as - Alcohol is given off
by-product. as by-product.
- More energy is - Less energy is
released released.
- Takes place in - Takes place in
mitochondria cytoplasm.

EXCRETION
Excretion can be defined as the removal of metabolic waste products which
may be toxic or harmful from the bodies of organisms. Different organisms
use different means to remove waste products from their bodies. The table
below summaries different organisms, their excretory organs and their
waste products

Organisms Excretory organs Waste products

1) Protozoa e.g Body surface and CO2 , water, excess
Amoeba contractile vacuole mineral salts.
2) Flatworms e.g Flame cells Water, urea, carbon
tapeworm dioxide, nitrogenous
waste
3) Round worm Nephridia CO2, urea, nitrogenous
e.g earthworm waste

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4) Insects Malpighian tubules CO2, water, uric acid.
5) Vertebrates Lungs, skins, liver, Water, CO2, mineral
and kidney salts, sweat,
nitrogenous waste.
6) Flowering Stomata & lenticels Water, oxygen, CO2,
plants alkaloids, Tannins,
gums, etc.

GROWTH
Growth can be defined as the permanent or irreversible increase in size
and complexity of organisms.
Basis of growth
The basis of growth includes:
(a)Cell division: This is the multiplication of cells through certain
divisions.
(b)Cell enlargement: This is the process which follows cell division in
which daughter cells increase in mass and size.
(c) Cell differentiation: This is the phase in which each cell develops into
a special type of cell by changing its shape and structure in order to
carry out a specialized or particular function.

ASPECTS OF GROWTH
These are the parameters used to measure growth. They include;
(a)Mass: This is the total matter that makes up the body of an organism.
Mass may be measured as wet mass or dry mass.

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 (b)Size: Size includes length, height, width, area, volume, etc. which can
be measured at successive intervals on the same organism.
(c) Increase in number of cells: This involves counting the number of
cells in the body of an organism at intervals.

REGIONS OF FASTEST GROWTH IN PLANTS

The regions of fastest growth in plants are the root and stem apices. The
root and stem apices are divided into the following:
(a)Region of cell division (Apical meristem): It consists of meristematic
cells.i. e., cells capable of active division.
(b)Region of cell elongation: Here, the cells become enlarge to their
maximum size.
(c) Region of maturation: This is the region where the cells attain their
permanent maturation and become specialized to carry out certain
functions.
FACTORS AFFECTING GROWTH
Factors affecting growth can either be external or internal.
External factors include;
(a)Availability of nutrient
(b)Humidity
(c) Light
(d)Temperature.
(e)PH
(f) Accumulation of metabolic products.
Internal factors include:
(a)Hormones e.g auxins, cytokinins
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 (b)Biochemicalse.g Amino acids
(c) Enzymes

CELL REACTION TO ITS ENVIRONMENT

All living things are capable of responding to external and internal stimuli.
The ability to do this is called irritability or sensitivity.
TYPES OF RESPONSES
There are three types of responses namely;
(1)Taxis or tactic movement: This is a directional type of response or
movement in which a whole organism moves from one place to
another in response to external stimuli. Tactic responses could either
be positive or negative. They include:
- Thermotaxis: response to temperature
- Phototaxis: response to light.
- Hydrotaxis: response to water.
- Chemotaxis: response to chemicals

(2)Nastic movement (Nastism): This is the type of response in which a

part of a plant moves in response to a non-directional stimulus. The
responses are also non directional. Examples include;
- Closing off morning glory flower under low light intensity.
- Opening of petals of sunflower in the day light and closing in the dark.
- Folding of leaflets of mimosa plants when it is touched.

(3)Tropic movements (Tropism): This is the type of response in which a

part of a plant moves in response to a directional stimulus. Tropisms
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 are very slow growth movements and can either be negative or
positive. Tropic responses include;
- Phototropism: response to light
- Geotropism: response to gravity
- Hydrotropism: response to water
- Thigmotropism: response to touch

MOVEMENT
This is the ability of living organisms to change position from one place to
another in search of food, mates, shelter, and to escape from danger.
ORGANELLES FOR MOVEMENT
Organelles for movement include cilia, flagella and pseudopodia in lower
organisms while higher organisms move by muscular coordination.
(a)Flagella: These are long whip-like projections on the cell surface.
They are usually one or two on a cell e.g Euglena, Chlamydomonas,
etc.
(b)Cilia: These are short, hair-like structures that project out of the cell
surface. They are usually numerous and packed closely together e.g
Paramecium.
(c)Pseudopodia: These are false organelles of locomotion used by
Amoeba.

CYCLOSIS (CYTOPLASMIC STREAMING)

This is the movement of the cytoplasm within individual cells. This
movement of cytoplasm is brought about by special protein molecules

40
which can be used to move organelles round the cell. Cyclosis is very
important in plant cell.

REPRODUCTION
Reproduction can be defined as the ability of living organisms to give rise to
new individuals of the same species for the purpose of continuity of life.

TYPES OF REPRODUCTION
There are two types of reproduction namely; Asexual and Sexual
reproduction.
1) ASEXUAL REPRODUCTION
This is the type of reproduction in which new organisms are produced from
a single parent without the production of gametes. The offspring produced
are the same in all respects to each other and to their parents.
TYPES OF ASEXUAL REPRODUCTION
There are four types of asexual reproduction. They are:
(a)FISSION: This is the type of asexual reproduction in unicellular
organisms in which a single cell (parent) splits/divides into two or
more equal parts by mitosis.
NOTE: If the cell divides into two equal parts, it is called binary fission, if
the cell divides into more than two equal parts, it is called multiple fission.
E.g Amoeba, Paramecium.

(b)BUDDING: This is a form of asexual reproduction in which the

parent organism forms an outgrowth (bud) which then grows into a
new organism after detaching from the parent. E.g yeast
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 (c) SPORE FORMATION: This is the type of asexual reproduction in
which lower organisms produce numerous spore in sporangia that
are borne at the end of sporangiophores. When the sporangia
become mature, they burst, and the spores are dispersed by wind.
If a spore falls on a suitable surface, it germinates and gives rise to
a new mycelium.
(d)Vegetative reproduction: This is the production of new individuals
from the vegetative parts of plants.
TYPES OF VEGETATIVE REPRODUCTION
There are two types of vegetative reproduction namely; natural and artificial
vegetative reproduction.
1. Natural vegetative reproduction: This involves the use of natural or
vegetative parts of plants to reproduce and get new individuals.
Natural vegetative reproduction includes;
(i) Rhizomes e.g ginger
(ii) Suckers e.g banana
(iii) Corm e.g cocoyam
(iv) Bulb e.g onions
(v) Fleshy leaves e.gbryophyllum

2. Artificial vegetation reproduction: This involves the use of intelligence

by man to grow new plants from the vegetative parts of an older
plant. Artificial propagation includes;
(i) Cutting: This involves cutting of a plant stem into portions and planting
them to produce new plants. The cuttings must have a node and an
internode e.g cassava, sugar cane etc.
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(ii) Layering: This method involves bending a branch or shoot growing near
the ground so that one or two nodes touch the ground. The bent branch
is pegged to the ground firmly and the node is covered with soil. After
sometime, adventitious roots grow out from the node after which the
bent stem is cut off from the parent plant to continue growing on its own
e.g tomato, cocoa, coffee.

(iii) Budding: This method involves cutting a bud from a matured

desirable plant and carefully inserting it into a seedling of the same
species. The bud is usually inserted into an inverted T-shaped cut and
then bound firmly with a budding tape. If the bud unites successfully, the
top shoot above the union is cut off so also all branches below it.
Examples of plants are orange, guava, mango, etc.

(iv) Grafting: This is closely related to budding. This method involves the
attachment of a whole shoot or stem (scion) onto another plant (stock).
Grafting brings into close contact the vascular cambium of both the
scion and the stock. Just as in budding, the stock and the scion must be
closely related to avoid incompatibility.

(v) Marcotting: This method involves cutting out a ring of tissue from a
mature branch. The cut portion is covered with a marcotting bag
containing soil and tied firmly. When root appear from the ringed area
the branch is cut off and then planted. Examples of plants include
mango, lemon, etc.
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 ADVANTAGES OF VEGETATIVE PROPAGATION
- Growth in young plant is rapid
- Only one parent is needed
- Desirable characters are retained
- Offspring mature more rapidly.
- Plants are less susceptible to adverse weather conditions.
- It can be used to propagate plants that do not produce seeds.
DISADVANTAGES OF VEGETATIVE PROPAGATION
- No new varieties of species are produced
- There is competition of resources between parent and offspring.
- It reduces resistance to diseases and changes in climate.
- Disease of parent can easily be transmitted to offspring
- Offspring can hardly colonize new areas since they are always close
to their parents.

2) SEXUAL REPRODUCTION
This is the type of reproduction which involves the fusion of gametes
from two different organisms to form a zygote.

FORMS OF SEXUAL REPRODUCTION

There are two major forms of sexual reproduction namely:
(1)CONJUGATION:
- This is a simple type of sexual reproduction in which nuclear material
is passed from one cell to another. It occurs in some lower organisms
such as Mucor, Rhizopus, Paramecium and Spirogyra.
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(2)FUSION OF MALE AND FEMALE GAMETES
- Sexual reproduction in animals and flowering plants involves the
formation of gametes.
- In higher animals, gametes are formed in special structure called
gonads.
- The male gamete is called spermatozoa and is produced in the testes
by the process of spermatogenesis.
- The female gamete is called ova or egg and is produced in the ovary
by the process of oogenesis.
- During mating, the male and female gametes are brought together.
The union of the male and female gametes is called fertilization.
- After fertilization, a zygote is formed and this zygote develops into a
new organism.
- In higher plants, flowers are their reproductive units. The male
gametes are called pollen grains and are produced by the anthers.
The female gametes are called ovules and are produced by the
ovary. Pollen grains and ovules fuse together during fertilization to
form a zygote.

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