REPRODUCTION & GROWTH IN PLANTS

Reproduction is the process whereby all living organisms produce new individuals of their own kind.

Types of reproduction

Sexual reproduction: Sexual reproduction is the type of reproduction where the male sex cell and the
female egg cells (gametes) fuse together to give rise to a new individual. Examples of organisms
which reproduce sexually are: humans, cats, birds, reptile, plants, etc.

Asexual reproduction: This type of reproduction involves the use of a part or whole of an organism
to reproduce a new one. Asexual reproduction is very prominent in plants.

FLOWER

A flower is the sexual reproductive part of a plant which may produce fruits and seeds.

STRUCTURE OF A FLOWER

Flowers typically are composed of four parts, or whorls, arranged in concentric rings attached to the
tip of the stem. these whorls are the:

Calyx: This is the outermost whorl which consists of a number of sepals. Sepals are small, green leaf
like structures that surround the carpel and stamen. They protect the flower at the bud stage.

Corolla: This lies within the calyx and consists of a number of petals. Petals are colourful parts of the
flower that attract pollinators. A slight swelling at the base of each petal is called nectary which
produces sugary liquid called nectar.

Androecium: This is the male reproductive parts of the flower and consists of a number of stamens.
Stamen, the male part of the flower consists of a stalk, called the filament and an anther in which
pollen grains are formed.

Gynaecium: This is the female reproductive parts of the flower and is composed of one or more
carpels (pistils). Pistil, the female part of the flower, consists of three main parts namely: stigma, style
and ovary.

The stigma: is the sticky part on which pollen grains will land and grow.

The style: is the slender stalk by which the pollen grains reach the ovary.

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The ovary: contains the ovule which is attached to the ovary wall by a short stalk. The ovule:
contains the embryo sac that holds the egg cell. A small hole in the wall of the ovule is called the
micropyle through which sperm nuclei enter. Types of
flowers

1. Bisexual /hermaphroditic flowers: These are the type of flowers which has both male and female
gamete –androecium (stamens) and gynaecium (carpels). In other words, they are complete flowers.
Examples of bisexual flowers are hibiscus, flamboyant, pride of Barbados, crotalaria.

2. Unisexual flowers: These flowers have only one of the reproductive parts. - they have either
androecium or gynaecium. They are therefore termed as incomplete. e.g. Pawpaw, Water melon etc.

Pollination and Fertilization

Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same flower
or another flower of the same species, which may or may not be on the same plant.

Types of pollination

There are two types of pollination. These are; self-pollination and cross pollination

1. Self Pollination: is the transfer of pollen grains from the anther of a flower to the stigma of
the same flower or another flower on the same plant.

Adaptations of Plants for Self Pollination

➢ Each flower is bisexual (has both male and female gametes)

➢ Flowers have the anther and stigma maturing at the same time.
➢ Flowers remain closed until self-pollination has occurred.

Advantages of self – pollination

➢ It does not require any agent of pollination.

➢ Pollen grains are transported over a short distance
➢ Less pollen grains are wasted or fall off

Disadvantages of self – pollination

➢ It does not yield new variety.

➢ Weaker or defective characters of the variety or breed cannot be eliminated.
➢ Continuous self-pollination, generation after generation may lead to weakening of the variety
or species.

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 ➢ Seeds produced through it are poor in quality and gives rise to less vigorous offspring.

2. stigma of a flower on another plant of the same species thus, involving two separate plants.

Adaptations of Plants for Cross Pollination

1. Flowers are unisexual.

2. Male and female flowers grow on different plants.

Advantages of cross – pollination

➢ Seeds produced in the case of cross-pollination are healthier than those formed from one single
parent.

➢ The pollen grains are brought from different flowers, which ensures variety. Varied seeds are often
resistant to diseases.

➢ Stigma and anthers ripe at different times but pollination is still possible.

Disadvantages of cross – pollination

• The pollination is not always certain because some pollinating agents are always needed which may
or may not be available at the appropriate time.

• Pollen has to be produced in large quantities.

Agents of pollination

The major agents are: Insect and Wind.

Other agents include:

➢ Animals (animals may include birds and bats).

➢ Gravity

➢ Man.

Characteristics of insect pollinated flowers and wind pollinated flowers

Insect pollinated flowers Wind pollinated flowers

Flowers are large and conspicuous. Flowers are small and inconspicuous.
The petals are brightly coloured. The petals are dull in colour.

Flowers are scented. Flowers are not scented.

The stigma is usually small, compact and stigma is usually large, feathery and hanging
enclosed in the flower. outside the flower.
Have relatively small anthers. Have relatively large anthers.
Pollen grains are large, rough and heavy. Pollen grains are small, smooth and light.
Produce small quantities of pollen grains. Produce large quantities of pollen grains.
Petals produce nectar. Petals do not produce nectar.

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 FERTILIZATION

Fertilization is the process whereby the male and the female gametes fuse together to form a zygote.
Fertilization occurs in the ovule, which contains the female gametes known as ovum.

Mechanism of Fertilization in Plants

1. When matured pollen grains lands on the stigma, it absorbs water and nutrients (sugar) from
the stigma causing it is to swell and germinate to form a pollen tube.
2. The pollen grain nucleus divides into two nuclei, the generative nucleus and vegetative
nucleus (tube nucleus).
3. The pollen tube grows through the style towards the ovary.
4. As the pollen tube gets closer to the ovary, the generative nucleus divides into two male
nuclei but the tube nucleus later disappears.
5. The pollen tube enters the embryo sac through a tiny hole called micropyle and releases the
two male nuclei.
6. One of the male nuclei fuses with the ovum (egg nucleus) to form a zygote. The other male
nucleus fuses with the polar nuclei to form the endosperm. This is known as double
fertilization.

FRUIT

Fruit is a fertilized and mature ovary containing one or more seeds. OR a fruit is a seed-bearing
structure in flowering plants formed from the ovary after fertilization.

Types of fruits

There are two types of fruits. There are:

➢ Dry fruits

➢ Succulent or fleshy fruits:

Succulent or fleshy fruits

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This are fruits with soft and fleshy pericarps. It can also be defined as fruits in which the pericarp
remains juicy and freshy when the fruit mature. E.g. mango, tomato, orange, palm fruit, etc.

Types of succulent fruits

➢ Drupes: A drupe has a thin epicarp, a thick, fleshy or fibrous mesocarp, and a hard endocarp. It
also contains one seed. Examples are mango, coconut and palm nut, etc.

➢ Berry: A berry has a thin epicarp, fleshy mesocarp and a thin fleshy endocarp. It also has many
seeds attached to the placenta at the centre of the fruit. Example are guava, tomato, pepper, banana,
orange, pawpaw.

Dry fruits

This are fruits with hard, dry and woody pericarps. Dry fruits can also be defined as fruits in which
the pericarp dries out when the fruit mature.

Types of dry fruits

1. Dry dehiscent fruit: these fruits are those whose pericarp splits open to release seeds. They are
classified as:
• Legume (pod), examples, cowpea, flamboyant, pride of Barbados.
• Capsule, examples, okro, cotton, poppy.
• Follicle, example, cola, cnestis.

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 • Schizocarp, example, Cassia, Desmodium.

2. Dry indehiscent: these fruits are those whose pericarp does not split open. They are classified as:
• Achene, an example is sunflower.
• Cypsela an example is tridax, dandelion
• Caryopsis an example is maize, rice.
• Samara examples are combretum, pteocarpus
• Nut an example is cashew nut, almond nut.

SEED

A seed is a fertilized ovule that contains an embryo, food and seed coat.

The structure of a seed

Seed is made up of a seed coat, an embryo, and an endosperm.

Seed coat: Protects the inner parts of the seed. It also allows water and oxygen to enter the seed

Embryo: The embryo consists of three parts – the plumule (embryonic shoot), radicle (embryonic
root) and cotyledons (seed leave).

Functions

➢ The plumule develops into the shoot system.

➢ The radicle develops into the root system of the plant.
➢ The cotyledon stores food for the use and growth of the embryo. It also encloses and protects
other parts of the embryo.

Endosperm: The endosperm is a large tissue found only in some seeds.

Function: Stores food. (In most seeds the cotyledon takes the place and function of the endosperm).

Cotyledon: Also called seed leaf, is the part of the seed which stores food for growth of the embryo.

Types of cotyledons

➢ Monocotyledonous seed (Endospermous): This is a seed which has one cotyledon. E.g. maize, rice,
wheat, onion and millet.

➢ Dicotyledonous seed (Non-Endospermous): This is a seed which has two cotyledons. E.g. tomato,
pepper, apple, beans, groundnut and castor oil seed.

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 Differences between monocotyledons and dicotyledons

Monocotyledons Dicotyledons
Has one cotyledon Has two cotyledons
Endosperm present Endosperm absent
Pericarp and testa fused together Pericarp and testa are separated
Leaf has parallel veins long and narrow leaf broad and branching network of veins

DISPERSAL OF FRUITS AND SEEDS

Dispersal is the scattering of fruits and seeds from the parent plants to new places by agents such as
wind, water and animals.

Agents of Dispersal

Agents of dispersal are the factors which bring about dispersal of fruits and seeds. They are wind,
water, and animals. Some fruits disperse the seeds themselves by a method known as explosive
mechanism or self-dispersal.

Adaptation for wind dispersal

For a fruit or seed to be dispersed by wind, it must have the following features:

• Dry and light in weight

• Small in size e.g. orchids
• Have floss (a mass of silk thread). e.g. cotton
• Have wings (flattened and extended pericarp). e.g. tecoma, dutchman‘s pipe, combretum
• Have pappus (parachute-like hair).e.g. tridax

Adaptation for animal dispersal

Features of fruits dispersed by animal are:

• Edible (eatable).

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 • Brightly coloured to attract animals. e.g. mango, guava, pawpaw and tomato.
• Fruits and seed with hooks to attach themselves to the fur of mammals and clothes of humans.
e.g. Desmodium, Pupalia seed and bidens.
• Fruits with sticky hairs to attach themselves to animals and people. e.g. boerhaavia and
plumbago

Adaptation for water dispersal

Features of fruits and seeds dispersed by water are:

• Thick and fibrous mesocarp with air spaces between the fibres. e.g. coconut.
• Spongy seed coat containing several air spaces. e.g. whit mangrove.
• Lower relative density than water therefore passively float in water

Dispersal by Explosive mechanism(self-dispersal)

Feature of fruits and seeds which undergo self-dispersal are:

1. Uneven drying of the seed coat. Some parts of the fruits dry faster than other parts creating tension
which causes the fruits to split open suddenly with an explosion. e.g. cowpea, flamboyant, pride of
Barbados, Crotalaria.

2. Turgidity of the seed coat. e.g. Balsam plants.

Advantages of Fruits and Seeds Dispersal

• Reduces overcrowding of plants.

• Reduces competition for light.
• Reduces competition for nutrients.
• Helps plants to move to new locations.
• Reduces epidemic diseases among plants.
• The rate of destruction of a species by fire, flood, etc. is reduced.

Disadvantages of Fruits and Seeds Dispersal

• Some of the fruits or seeds may land on an arid land (unproductive land) and die.
• Some of them may be in a colony of herbivores and therefore be eaten.
• Some could land in an overcrowded area and die from nutrients and sunlight starvation.
• Dispersal involves external agents which may not be available at the right time.

GERMINATION OF SEEDS

Germination is the process whereby the embryo emerges from the seed coat as a result of growth of
the seed into a seedling. It can also be defined as the process whereby the embryo of a seed grows into
a seedling.

Conditions necessary for germination

They include Adequate moisture, Suitable temperature, oxygen, viable seed.

The Germination Process

• The testa which is permeable to water and air absorbs water.

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 • Digestive enzymes in the seed become active and break down the food substances in the seed
to soluble forms.
• The soluble food substances are transported to the plumule and radicle.
• The radicle grows downwards into the soil to form the root system.
• The plumule grows upwards through the soil to become the shoot system.
• The young plant is called a seedling.

Types of germination

There are two types of germination: epigeal and hypogeal germination.

Epigeal germination: This is the type of germination which occurs when the cotyledon appears
above the ground. This is caused by the elongation of the radicle. Examples of plants which undergo
epigeal germination are mango, groundnut, cowpea, red beans, etc.

Hypogeal germination: This is the type of germination which occurs when the cotyledon remains
below the ground. This is caused by the elongation of the plumule. Examples of plants which undergo
hypogeal germination are maize grain, coconut, rice, wheat, oil palm, beans

Differences between epigeal and hypogeal germination

Epigeal germination Hypogeal germination

Cotyledons rise from the ground Cotyledons remain in the soil
Normally has small cotyledon Normally has larger cotyledons
Cotyledons turns green/photosynthetic Cotyledons play no role in photosynthesis
Cotyledons store less food Cotyledons store more food
Elongation of hypocotyl of radicle Elongation of epicotyl of plumule

VEGETATIVE (ASEXUAL) REPRODUCTION IN PLANTS

Vegetative propagation or asexual reproduction is the use of parts or the whole of an organism to give
rise to new organisms.

Methods of vegetative propagation

1. Natural propagation methods 2. Artificial propagation methods

Natural Propagation:

• propagation by bulbs
• propagation by rhizomes
• propagation by corms
• propagation by stolons or runners
• propagation by sucker
• propagation by stem tuber

Propagation by bulb: A bulb has a short, brown conical stem which grows vertically underground.
Adventitious roots arise directly from the base of the stem with very short internodes. The food is
stored in fleshy inner leaf bases (bulbs) which serve as storage organ for the plant e.g. onion, garlic,
spider lily etc. The whole bulb is planted and the terminal buds produce aerial shoots, while axillary
buds produce daughter bulbs.

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 Propagation by corms: A corm is a short, modified stem surrounded by brown scale leaves which
grows vertically underground with long internodes and adventitious roots arising from the nodes. The
stem is thick with stored food e.g. cocoyam. Caladium sp, Colocasia sp, Gladiolus etc.

Corms are propagated by planting the whole corm or sections of the corm singly in soil. The axillary
buds develop into daughter corms.

Propagation by rhizomes: A rhizome is a horizontal, underground stem, with terminal buds that
form aerial shoots, and buds that develop into lateral branches e.g. Canna lily, ginger, turmeric,
Zoysia grass.

The whole rhizome can be planted or cut into pieces, each piece having two or three buds and planted
in the soil and watered regularly. The buds sprout and grow into new aerial shoots after a few days

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Propagation by sucker: A sucker is a lateral outgrowth from the underground part of the stem of
certain plants. They grow obliquely to the soil level and produce new aerial shoots with adventitious
roots e.g. plantain and banana.

A sucker is propagated by cutting carefully, and uprooting the young sucker close to the parent stem
and transplanting in the soil.

Propagation by Stolons or runners: A runner is a thin, creeping stem which grows horizontally
along the surface of the ground. The stem has long internodes and produces adventitious roots at its
nodes. Aerial shoots develop from the nodes e.g. sweet potato, Desmodium, doob grass, moss
verbena.

The stem of runners is cut into pieces with each piece having at least two nodes. One end of the piece
of stem is pushed into the soil. The buds at the nodes sprout into new plants.

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Propagation by stem tuber: Stem tuber is swollen underground stem e.g. potato and yam. It is
propagated by cutting the big tuber into setts, each sett containing many eyes.

2. Artificial Propagation:

• Stem cutting
• Budding
• Grafting
• Layering

Propagation by stem cutting: this can be used for plants that produces flowers but do not form
seeds.

The stems are cut at an angle above the node. The lower end of the cutting is pushed in the soil with at
least one node in the soil. Adventitious roots develop from the node in the soil while aerial shoots
grow from the nodes above the soil surface. E.g. cassava, sugarcane, Croton, Hibiscus.

Propagation by budding: Budding is a form of grafting but the only difference is that, in grafting a
shoot is used for the scion, whereas a bud with part of the bark of the plant is used as the scion in

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budding. Both systems have the same advantages and are based on the same principle. However, with
budding many buds can be obtained from a single plant, while in grafting shoots have to be taken
from several plants if many operations are to be performed. The scion (a dormant bud on a silver of
stem) is carefully removed from one plant with a sharp knife and inserted into a T - shaped cut in the
bark of another plant called the stock. A polythene bag is used to bind firmly together the scion and
stock. The bud on the scion develops and bears fruits of the plant from which it was removed e.g.
citrus trees and roses.

Advantages of budding

o Changing undesirable variety to a desirable variety.

o Combination of good qualities of two different plants of the same species into one plant.
o Perpetuation of some varieties which cannot be propagated by any other means.
o Growing of two or more kinds of fruits/flowers on one plant/tree.
o Rapid method of developing new varieties of plants/crops.
o Hastens seed selection
o Hastens maturity or fruiting time/ develops faster

Propagation by grafting: grafting is the art of joining parts of plants together in such a way that
they will unite and continue to grow as one plant.

It is the process whereby a part of one plant (scion) may be pointed to fit a V – shaped of another
plant (stock). They are tied into place and sealed with grafting wax

The stock and scion continue to grow as one plant and bear the fruit of the plant from which the
scion was removed. E.g. grape fruit tree, lime tree to orange tree, white flowered bougainvillea to
pink or red – flowered one.

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Propagation by layering: Layering means bending a branch of the stem or shoots down to the
ground without breaking it. It should have a number of nodes. It is pushed into the soil and held in
place with two pegs. The two ends of the shoot are allowed to remain above ground level. It is then
watered regularly till adventitious roots develop, then the rooted twig is cut off and transplanted in a
fertile soil e.g. Roses, Bougainvillea, Petra volibilis, Cocoa, Coffee, Kola etc. Marcotting (air
layering) is another way of layering, but this time round the layering is done on the branch as it still
stands. A ball of soil is tied around the stem of a plant. Mangoes, Citrus and roses can easily be
propagated by air layering.

Differences between sexual and asexual reproduction

Sexual reproduction Asexual reproduction

Requires two parents unless a parent is requires only one parent
hermaphrodite
New varieties are produced due to mixing of no new varieties are produced as identical
characters of both parents characters are repeated over generations
Involves fusion of nuclei of gametes to form does not involve fusion of nuclei, zygotes are not
zygotes formed

Advantages of vegetative propagation

• Desirable characteristics are retained, as the offspring are identical to the parent plant.
• Plants that do not produce viable seeds can only be propagated through vegetative means e.g.
cassava, Irish potato etc.

Disadvantages of vegetative reproduction

o No new varieties are formed

o Less resistant offspring/progeny
o Lack of dispersal leading to competition
o Diseases are carried from parents to offspring
o Colonization of new areas unlikely
o Many individuals can be destroyed by natural disasters.

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 REVISION QUESTIONS

2000 Questions

1. Describe briefly the process of fertilization in flowering plants

2001 Questions
2. (i). Distinguish between epigeal and hypogeal germination, giving one example in each case.

(ii). State three factors necessary for germination.

2001 Nov Questions

2. (i) Distinguish between self pollination and cross pollination.
(ii) State five characteristics of insect pollinated flowers.
4. Describe briefly the characteristics of fruits dispersed by each of the following agents.
(a) water (b) Mammal (c) Wind
2002 July Questions
5. (i) What is a complete flower?
(ii) Name three parts of a flower and state one function of each part you have named.
2002 Nov Questions

(i) Distinguish between pollination and fertilization.

(ii) State four adaptations of wind dispersal fruits and seeds.

2004 Nov Questions

Briefly describe the events which occur in a flower from pollination to the formation of the
embryo.

2005 July Questions

8. (i) What is a flower?

(ii) Draw and label a fully complete flower.

FOOD AND NUTRITION

Food is anything that we eat and which nourishes our body. It is essential because it contains
substances which perform important functions in our body. Or Food is any substance that living
organisms consume to gain energy.

Nutrition is the process whereby living organisms get food. Or Nutrition is the intake of food by a
cell or an organism to support life or to stay alive for growth.

Types of food substances

The different classes of food are:

• Carbohydrates
• Proteins
• Fats and oils (lipid)
• Minerals
• Vitamins

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 Carbohydrates

Carbohydrates are group of food substances than contains hydrogen, carbon, and oxygen (C.H.O).
They are obtained from plants such as cereals (rice, maize, wheat, millet), potatoes, cassava, legumes
etc.

They are broken down in the body to form glucose and is stored in the liver as glycogen. There are
three types of carbohydrates:

Monosaccharides: they are known as simple sugars. This is because they have a reduction action on
Benedict‘s and Fehling‘s solution. They are therefore called reducing sugars, and their general
formula is C6H12O6. Monosaccharides are sweet and soluble in water. Examples of monosaccharides
are glucose in fruits, galactose in milk, fructose, flower nectar, fruits and honey.

Disaccharides: they are referred to as complex sugar. A disaccharide is made up of two

monosaccharides joined together in a chemical process known as condensation. The general formula
for disaccharides is C12H22O11. Disaccharides can be broken down into monosaccharides in a chemical
process known as hydrolysis. Disaccharides are sweet and soluble in water. Examples of
disaccharides are sucrose in sugar cane, lactose (milk sugar), maltose from germinating grains (e.g.
maize). All disaccharides except sucrose (non-reducing sugar) are reducing sugar.

Polysaccharides: they are made up of several monosaccharides chemically combined. The general
formula for polysaccharides is (C6H10O5)n where n represents the number repeating monosaccharides.
Polysaccharides are not sweet and usually insoluble in water. Examples are starch, cellulose,
glycogen, and chitin.

Test for starch

• Put a sample of the food into a test tube.

• Add some drops of iodine solution. It would be observed that the colour of the food sample
changes to blue-black, showing the presence of starch in the food.

Test for reducing sugar

• Put a food sample, e.g. glucose into a test tube.

• Add a few drops of Fehling’s solution (A and B mixed) or Benedict’s solution
• Heat the test tube gently for a few minutes.

It would be observed that the colour of the food sample changes to orange or brick-red indicating the
presence of reducing sugar.

Test for non-reducing sugar

• Put a piece of the food sample into a test tube

• Add a few drops of dilute hydrochloric acid (HCl)
• Heat gently for a few minutes in a water bath.
• Cool the mixture and add solid sodium hydrogen carbonate (NaHCO3) slowly until the fizzing
stops.
• Add a few drops of Benedict’s solution and heat for five minutes.

It would be observed that the colour of the food sample changes to orange or brick-red showing the
presence of non-reducing sugar.

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 Importance of carbohydrate

• It serves as a major source of energy.

• It forms the structural components of cells and other organisms. E.g. cellulose in plants cell
wall, chitin in fungi and exoskeleton.
• It serves as food storage compound. E.g. starch in plants and glycogen in animals.
• It serves as the basis of the synthesis of other organic food substances e.g. amino acids.

Proteins

Proteins are compounds which contain the elements carbon, hydrogen, oxygen and nitrogen. Some
proteins contain sulphur and phosphorus as well. The smallest unit of protein is called an amino acid.
One protein molecule contains thousands of amino acids, chemically combined by peptide bond and
peptide linkage. Proteins are destroyed by temperatures higher than 60⁰C. A destroyed protein loses it
chemical structure and physical texture, e.g boiled egg.

Classes of protein

Proteins are classed into two – first class proteins and second-class proteins.

First class proteins: These are usually found in animals and contains all the essential amino acids
needed by the body.

Second class proteins: These are plant proteins and lack some of the amino acids needed by the
body.

Sources of proteins are fish, meat, egg, beans etc.

Importance of protein

• For the repair of damaged and worn-out tissues

• For the formation of hormones
• For the formation of antibodies
• For the formation of pigments such as haemoglobin
• For the formation of skeletal muscles, cartilage and tendons etc.

Test for proteins

1. Millon’s Test
• Place small quantity of suspected food containing protein in a test tube
• Add few drops of millon’s reagent and boil the mixture for one minute.
• A deep red colour forms indicating protein is present.

2. Biuret’s test
• Place 2cm3 of a substance suspected to contain protein into a test tube.
• Add a few drops of 2% sodium hydroxide solution and mix.
• Add 1% copper (II) sulphate solution drop by drop, shake at each drop.
• A violet colour which appears is an indication of the presence of protein.

vitamins

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Vitamins are organic food substances needed by the human body in very small quantities for healthy
growth and development. The well-known vitamins are vitamins A, B, C, D, E and K. vitamins are
not to be digested, they are easily absorbed into the body

Vitamin Source from food Functions Symptom of deficiency

A Egg yolk, liver • Builds good • Night
(retinol) green vegetable, eyesight. blindness.
carrot, cocoa, red • Protects the
palm oil surface of the • Unhealthy
eye. skin.
• Maintains
membrane. • Retardation of
• Necessary for growth in children.
cell
respiration.
B1 Beans, egg yolk, • Necessary for • Retarded
(thiamine) cereal, bread, lean cell growth.
meat, unpolished respiration. • Beriberi.
cereal, palm wine • Stimulates • Nerve
appetite. inflammation.
• It maintains • loss of appetite.
muscles.
B2 (riboflavin) Yeast, fish, green • support • Skin disorders,
vegetables, meat healthy dermatitis
cereals, growth. disease.
• Maintains • Sores on mouth
healthy skin. and eye.
• Help in tissue • Stunted
metabolism. growth.
B12 Liver, kidney, • Helps in the • Anaemia
(cynobalamin) fish, beef and formation of red blood
milk cells
C Green leafy • Forms strong • scurvy disease,
(Ascorbic acid) vegetable, fresh skins e.g. swelling of
fruits, citrus fruits • Helps wounds tongue, gum
to heal bleeding and
• Good for poor healing of
some body wounds.
tissues • immune
disorders
D Fat, fish, liver, • Forms strong Rickets
(calciferol) egg yolk, bones and (Deformed bones)
sunlight, teeth.
margarine • Prevents
rickets.
• It is needed in
the absorption

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 of calcium or
phosphorus.
E Green vegetables, • Prevents • Anaemia
(tocopherol) liver, vegetable haemolysis of • Sterility in
oil red blood animals
cells in rats.
• Enhance
fertility and
prevent
sterility in
animals.
K (phylloquinone) Green vegetables, • Synthesizes proteins • Prolonged bleeding
liver, egg yolk, which help the blood
unpolished cereal to clot

Lipids (fats and oils)

Lipids are compounds containing carbon, hydrogen and oxygen.

The amount of oxygen atom in the structure of lipids is far lower than in carbohydrates. Lipids, which
are fat and oil, are formed from the chemical combination of glycerol and fatty acids. Fat is stored by
animals while oil is stored by plants.

Fats are solid at room temperature. They are obtained mainly from animals e.g. fatty meat from beef,
pork, and chicken. oils are liquid at room temperature. They are obtained mainly from plants

e.g. palm oil, vegetable oil palm kernel oil. Fats and oils are soluble in organic solvents, e.g. ethanol,
but insoluble in inorganic solvents e.g. water.

Importance of lipids

• Provide energy to the body in the absence of carbohydrates.

• Dissolve fat-soluble vitamins such as A, D, E, and K.
• Servers as food reserve stored in adipose cells under the skin of mammals.
• Helps in the lubrication of joints.
• Used in aquatic animals to enhance buoyancy (floating).
• Used in the formation of cell membrane.

Test for lipids

1. Emulsion test
• Put 2cm3 of ethanol in a test tube.
• Add 2cm3 of oil and shake vigorously.
• Pour the mixture into another test tube containing 2cm3 of water.
• A cloudy, white emulsion develops showing the presence of lipids.

2. Spot test or translucent test

• Dip a finger in oil and place it on a sheet of paper.
• Dip another finger in water and place it on the same paper.

19
 • Leave the paper for 10 minutes. Afterward, hold it up against light.
• It would be observed that the water has dried out whiles the oil stain remains visible on
the paper.

Mineral salts

Mineral salts are inorganic food substances needed for healthy growth and development of the body.
They are grouped into two, based on the quantity required by the body. They are :

- Major or macro elements: they are nutrients required by the body in large quantities. E.g.
nitrogen, calcium, potassium, phosphorus, hydrogen, oxygen, sodium, chlorine, fluorine,
magnesium, iron, and sulphur.

- Micro or minor or trace element: required by the body in small quantities. E.g. zinc,
copper, boron, manganese, iodine selenium and molybdenum.

Elements Source in food Importance Deficiency

Sodium Table salt, vegetables, Nerves transmission Hypertension
(Na) small amounts in milk Muscle contraction Muscle cramps
bread and unprocessed Maintenance of tissue
meat fluid
Chlorine Table salt, soy sauce, Maintenance of tissue Heat exhaustion and
(Cl) Small amounts in milk, fluid, stomach acid. muscle cramps
meat, bread and (Gastric acid)
vegetables
Potassium Meats, milk, fresh Proper fluid balance, Nervous dysfunction
(K) fruits and vegetables, nerve transmission and Week transmission of
whole grains, legumes muscle contraction, impulse across nerves
Lowers blood pressure
Calcium Milk and milk Formation of bones Rickets (poor
(Ca) products, canned fish and teeth development of bones
with bones, legumes, Muscle contraction and teeth)
green vegetables Blood clotting Haemophilia
Blood pressure
regulation

Phosphorus Meat, fish, poultry, For the synthesis of Absence causes rickets
(P) eggs, milk protein in children
Formation of ATP Low energy content in
cells
Iodine (I) Sea food, iodized salt, Formation of thyroxin Absence causes goiter
dairy products (thyroid hormone (swelling of the thyroid
which helps regulate gland)
growth)
Iron (Fe) Organ meat, egg York, Forms haemoglobin in Absence causes

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 legumes, dried fruits red blood cells Anaemia
Needed for energy
metabolism

BALANCED DIET

A balanced diet is the diet which contains all the necessary food nutrients in their right proportions
and quantity needed by the body for healthy growth and development.

Importance of Balanced Diet

1. A balanced diet helps in maintaining proper growth and development of the body.
2. It makes the body healthy.
3. It prevents deficiency diseases such as kwashiorkor, rickets etc.
4. It helps in weight control

MALNUTRITION

Malnutrition occurs when an organism has inadequate amounts of certain nutrients required by the
body.

Effects of Malnutrition

- It results in slow or stunted growth.

- Calcium deficiency causes rickets.
- Protein deficiency causes kwashiorkor.
- The deficiency of vitamin A causes night blindness.
- Malnutrition may eventually result in death.
- It causes emaciation (lean growth)
- Leads to fluid imbalance.

FOOD FORTIFICATION AND ENRICHMENT

Food fortification refers to the practice of deliberately increasing the content of an essential
micronutrient such as vitamins and mineral (including trace elements) in a food to improve the
nutrition quality and improve public health.

Food enrichment refers to the addition of micronutrients to a food which are lost during processing.

Examples of fortified food

The most common fortified foods include:

- Cereals and cereal based products

- Milk and milk products
- Fats and oils
- Tea and other beverages
- Infant formulas
- Iodized salt

Importance of food fortification and enrichment

- To replace nutrients which are lost during the manufacturing of the product.
- To act as public health intervention.

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 - To ensure the equivalence of substitute food (E.g. butter and margarine similar in quantity).
- To ensure the appropriate vitamin and mineral nutrient composition of food for special dietary
purposes.

Body mass index

The body mass index (BMI) is a measure of body fat based on height and weight.

BMI does not actually measure the percentage of body fat. Body mass index is expressed as the
individual's body mass divided by the square of his or her height. The formula universally used in
medicine produces a unit of measure of kg/m2.

Body weight (kg)

BMI = [Height (cm)] ²

• Individuals with BMI of less than 18.5 are classified as underweight.

• Children with BMI within 18.5 – 24.9 and adults with BMI of 25.0 – 29.9 are classified as
normal weight.
• Those with BMI of more than 30 are classified as obese (overweight).

Water

Water is essential for all living organisms. It makes up 70% of mammals’ body weight. It obtained
from food and by drinking.

Health benefits of water

• Water is used for transportation of substances e.g. food, hormones, oxygen, waste.
• Green plants use water for photosynthesis
• It is used for cooling the body (when it evaporates from the body surface)
• For the maintenance of osmotic balance
• For regulation of temperature the body

Roughage (dietary fibre)

Roughage is fibrous material that is indigestible and consists mostly of cellulose. Roughage can be
obtained from solid fibre parts of fruits such as oranges, pineapple, apples, vegetables and cereals.

Importance of Roughage

1. Facilitates free bowel movement and prevents constipation, thereby reducing the risk of bowel
cancer.

2. Helps in easy movement of food through the gut.

3. The cellulose in roughage is digested by some gut bacteria in humans to release important vitamins.

It helps to maintain healthy cholesterol and body sugar.

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 DENTITION, FEEDING & DIGESTION IN MAMMALS

DENTITION IN MAMMALS: Dentition is a description of the number, type and arrangement of

teeth in an organism. In human beings, children have milk or deciduous teeth. Milk teeth are fewer in
number (20), smaller and temporary. The milk teeth appear first and are progressively replaced by the
permanent teeth. Adults have permanent teeth. Permanent teeth are bigger, having full complement of
mammalian dentition. There are two types of dentitions:

homodont dentition: this is where the teeth of an organism are all of the same type i.e., shape, size
and function. E.g., Vertebrates such as fish, amphibians and reptiles

heterodont dentition: this is where the teeth of an organism are all of different size, shape and
function. E.g. mammals

STRUCTURE OF THE TOOTH

The teeth consist of three main parts: they are the crown, neck and root

• The Crown is the visible part of the tooth above the gum
• The neck is buried in the socket in the jawbone
• The root is the point where the crown and the root meet

Enamel: it is white and the hardest part of the teeth mainly composed of calcium phosphate. It
protects the tooth from mechanical damage and decay.

Dentine: The dentine is located beneath the enamel and extended into the root. It makes up the
greatest bulk of the tooth. Dentine is a very hard bone but is not as hard as the enamel. Fine channels,
containing living materials, pass through the dentine. The dentine encloses a central pulp cavity.

The pulp cavity: The pulp is made up of blood vessels, tooth-forming cells and nerve fibres with
sensory nerve endings, which penetrates the dentine, making it sensitive to pain and temperature
changes.

Cement: a hard body substance that covers the outside of the root. It fixes the teeth to the jawbone.

Periodontal membrane/ ligament: this consists of fibers that hold the tooth in its socket.

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 Types of teeth and their functions

Teeth in mammals come in four different types – incisors, canines, premolars and molars.

Incisors

1. They are chisel shaped.

2. They have broad, flat cutting edge for biting and cutting food.
3. There are eight (8) incisors in adult human beings
4. They have a single root

Canines

• They are conical and sharply pointed crown

• Canines have a single root
• They are used for tearing flesh from bone.
• They are four (4) canines in adult human beings

Premolars and Molars

They are collectively called cheek teeth.

The premolars have broad, flat tops with two small cusps (pointed ridges).

The premolars have a single root.

The molars have broad, flat tops but have four or five cusps.

The molars have three to four roots.

The premolars and molars are used for chewing, crushing and grinding solid foods

Dentition and Diet

The diet of an animal generally determines its dentition. For example, the dentition of a carnivore is
different from that of a herbivore or omnivore.

Carnivores: flesh eating mammals e.g. dog, cat, lion etc.

Characteristics of carnivore dentition

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 - The incisors are small, peg-like and closely packed. They are used for stripping flesh from
bones
- The canines are long, conical, pointed and curved slightly inwards (dagger-like). They are
used to hold and kill preys and tear flesh.
- The first and molar of the lower jaw and the last premolar of the upper jaw are modified to
form carnassial teeth which have sharp cutting edges to cut off flesh and crush bones.

Herbivores: plant eating mammals, e.g. rabbit, cow, sheep, cattle, goat, grass cutters etc.

Characteristics of carnivore dentition

- The incisors are long, curved and chisel shaped used for cutting and gnawing grass leaves or
food.
- They have a row of file-like premolars and molars with flat-ridged surfaces for grinding plant
materials.
- Absence of canine but instead, a large gap called a diastema between the incisors and
premolars for chewing plant material.
- The presence of horny pad in the upper jaw serves as support against which lower incisors
bite to cut off grass.

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 Care for the human teeth

- Cleaning or blushing teeth regularly at least twice a day.

- Feed on mineral rich food to form strong bones and teeth.
- Avoid eating too much sugary food.
- Vist the dentist regularly for at least twice a year.
- Avoid eating too cold or too hot food since it may cause cracking of the enamel.

Tooth decay

Conditions that encourage tooth decay include

- Intake of too much sugary foods

- Failure to brush teeth regularly.
- Misuse of the teeth which leads to injuries of the gum.
- Eating too hot or too cold food
- Bacteria action

Digestion in mammals

Digestion is the breakdown of complex food substances into simple, soluble and absorbable forms. Or
Digestion is the breakdown of food into smaller components, until they can be absorbed and
assimilated into the body.

Structure and functions of the digestive system of mammals

Mouth: Digestion starts in the mouth, where food is chewed with the teeth. Chewing (mastication)
breaks down solid food into smaller particles. Salivary glands produce saliva which:

- Contains an enzyme called salivary amylase or ptyalin that converts starch into maltose.
- is slightly alkaline and keeps the pH of the mouth approximately neutral which help in the
action of saliva amylase.
- mixes with the food during chewing, making it soft and easier to swallow.

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Oesophagus: A muscular tube that connects the mouth to the stomach. Food passes down the
oesophagus through contraction and relaxation of the circular muscles of the gut. This action is called
peristalsis.

The stomach: it allows temporary storage of food. It is the site where protein digestion starts. The
gastric gland in the stomach produces gastric juice which contains;

- hydrochloric acid which sterilizes food by killing microorganisms, ends action of salivary
amylase and provide acidic pH for action of the enzyme pepsin.
- pepsin which converts proteins to polypeptides,
- mucus: lubricates food masses in order to facilitate movement in the stomach and
- rennin which solidifies liquid proteins so that they will remain in the stomach for pepsin to
work on.

Small intestine: the small intestine is made up of two major parts: the duodenum and the ileum.

- Duodenum: the duodenum is the smallest and shortest segment of the small intestine. the
walls of the duodenum releases the hormone secretin into the blood stream which stimulates
the liver and gall bladder to release bile and the pancreas to release pancreatic juice.

Bile: it helps to emulsify (break down) the lipids (fat and oil) by changing large fats globules
in small fat droplets (emulsion).

Pancreatic juice: The pancreatic juice contains digestive enzymes that assist in digestion and
absorption of nutrients in the small intestine. It contains:

• amylase which converts starch to maltose,

• trypsin which converts protein to peptides and polypeptides and
• lipase which converts fat to fatty acids and glycerol.

All these enzymes digest food as is passes though the duodenum into the ileum.

- Ileum: The digestion process ends in the ileum. The walls of ileum secrets:
• lipase which converts all remaining fats into fatty acids and glycerol;
• maltase which converts maltose to glucose;
• lactase which converts lactose to glucose and galactose,
• sucrase which converts sucrose to glucose and fructose,
• erepsin which converts peptides to amino acids and
• enterokinase which converts trypsinogen to trypsin.

The small molecules of glucose, amino acids, fatty acids, and glycerol are the end products of
digestion in mammals and are absorbed into the bloodstream by a process known as diffusion.

The ileum contains microscopic finger-like projections called villi (singular, villus), which increases
the surface area of the ileum and facilitates the absorption process. Undigested food passes into the
colon.

Colon (large intestines)

The colon is responsible for the absorption of water from the undigested food. It contains some
bacteria which digest the cellulose and produce vitamin B and K which are absorbed into the body.
The remains of the undigested food pass on to become faeces.

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 Rectum and anus

The faeces move into the rectum, stored and periodically released through the anus. The removal of
faeces from the rectum is called egestion.

Organs and enzymes of digestion

Organ/ gland Secreted enzyme Enzyme action

Mouth (salivary glands) • Salivary amylase • Starch to maltose
Oesophagus • Passage of food to stomach
Stomach • Pepsin • Polypeptides
• Rennin • Solidifies protein
• Hydrochloric acid • sterilizes food; provide
acidic pH for action of the
enzyme
Duodenum • Secretin • Stimulates gall bladder to release
bile and pancreas to release
pancreatic juice
Liver • Bile • Emulsifies lipids
Pancreas (pancreatic juice) • Amylase • Starch to maltose
• Trypsin • Protein to peptides and
• Lipase polypeptides
• Fatty acids to glycerol
Ileum • Lipase • Fats into fatty acids and
• Maltase glycerol
• Lactase • Maltose to glucose
• Sucrase • Lactose to glucose
• Erepsin • Sucrose to glucose
• Peptides to amino acid
• Enterokinase • Trypsinogen to trypsin
Colon • Absorption of water from
undigested food
Rectum Temporary storage for faeces

Digestion of carbohydrates

1. Carbohydrate digestion starts in the mouth.

2. Saliva contains ptyalin (salivary amylase) which converts starch to maltose.
3. In the stomach, HCl in gastric juice sterilizes the food.
4. The food is churned into liquid paste called chyme.
5. In the duodenum, the bile secreted by the liver neutralizes the chime.
6. Pancreatic amylase secreted by the pancreas converts starch into maltose sugar.
7. In the ileum, the enzyme maltase converts maltose into glucose, which is the end-product of
starch digestion.

Digestion of proteins

1. Protein digestion starts in the stomach.

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 2. Pepsin converts proteins to peptones.
3. HCl sterilizes it; it is churned to chime and sent to duodenum where the bile neutralizes it.
4. In the duodenum, the trypsin which is secreted by the pancreas converts peptones into amino
acids.

Digestion of fats

1. The digestion of fat starts in the duodenum.

2. Gall bladder releases bile into the duodenum.
3. Bile neutralizes and emulsifies the fat.
4. The enzyme lipase secreted by the pancreas and the wall of the small intestines converts
emulsified fat into fatty acids and glycerol, which is the end-product of fat digestion.
End-products of digestion

Food End-product
Carbohydrates Glucose
Proteins Amino acids
Fats Fatty Acids and glycerol
Uses of Digested Food

The end-product of digestion is assimilated (taken up) by the cells in various parts of the body.
Glucose and others move into the blood by diffusion and enter the liver through the hepatic portal
vein. In the liver excess glucose is converted to glycogen and stored. Some of the monosaccharides
enter body cells where they are respired.

Amino acids are also assimilated into the liver though the hepatic portal vein. Some enter the body
cells where they are used to form protein for growth, repair of damaged and worn-out tissues and
formation of enzymes and hormones. Excess amino acids are excreted out of the body as urea.

Fatty acids and glycerol come together again to form fats, which enters the lymph system before
entering the bloodstream. They are stored as fat or respired to release energy.

Assimilation: is the process whereby digested food substances are absorbed into the bloodstream.

Enzymes: are protein substances produced by living cells to speed up the rate of chemical reactions in
the cells.

DISEASES AND DISORDERS ASSOCIATED WITH THE DIGESTIVE SYSTEM OF

HUMANS

Constipation: This is caused by not going to the toilet regularly. Faeces overstay in the rectum and
more water is absorbed from them. This hardens and dries it making it difficult to pass out.
Constipation is also caused by adequate chewing of food.

Prevention of constipation

Constipation can be prevented by including roughage in the diet, chewing food properly, eating more
fruits and visiting the toilet regularly.

Indigestion: Indigestion occurs when the complex food substances eaten or ingested fail to be
hydrolyzed or broken down into simpler substances. These food substances cannot be utilized by the
body cell.

Prevention of indigestion

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• Slowing down the rate and speed of eating can prevent indigestion
• Avoid oily and fatty foods.
• Avoid eating late at night.

Diarrhoea: This occurs when faeces move through the colon too quickly before water can be
absorbed from them. This causes the faeces to come out in a more liquid form. It is caused by
bacteria in the gut.

Prevention of diarrhoea

Staying away from food for a short period will cause the bacteria to be driven away with the
faeces. A lot of water should be drunk to prevent dehydration.

Stomach ulcer: This is caused by an attack on the stomach wall by excess hydrochloric acid in
the stomach; this makes is sore.

Prevention of stomach ulcer

Eating at normal intervals can prevent stomach ulcer.

DIGESTIVE SYSTEM OF RUMINANTS

Ruminants are mammals which have a stomach system consisting of four chambers. The stomach
system are rumen, reticulum, omasum and abomasums.

Rumen: This is the first and largest chamber. Swallowed food enters this chamber where it is
fermented by anaerobic bacteria which breakdown the cellulose.

Reticulum: When the food reaches the reticulum, it is regurgitated (brought back to the mouth)
and chewed again. Food in the reticulum is known as cud.

Omasum: Much of the water in the cud is reabsorbed in the omasum.

Abomasum: This is also known as the true stomach of a ruminant. Gastric secretion in the
abomasum digests the proteins in the food. Chyme is formed which moves on to the duodenum

Digestion in birds

The stomach of birds is divided into two – crop and gizzard. Food is stored in the crop and ground
up in the gizzard with the aid of small stones, before it is passed into the intestines.

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 FORMS OF ENERGY AND ENERGY TRANSFORMATION

Energy is defined as the ability to do work. The SI unit of energy is joules (J).

FORMS / TYPES OF ENERGY

Energy exists in many different forms. Some forms of energy are:

Light energy: This is the type of energy that makes vision possible. E.g. the Sun, fluorescent tube,
etc.

Chemical energy: This is the type of energy gained when atoms or molecules of a substance re-
arrange to form a new substance. e.g. battery, food, fossil fuel, etc.

Electrical energy This type of energy is acquired when electrical charges move through a conductor.
Electrical energy can be obtained from solar panel, dry cells, generators etc.

Solar energy This is the type of energy obtained from the sun. The sun is the major source of energy
needed for most life activities.

Heat energy This is the energy obtained as a result of the rise in temperature. E.g. sun, fire, electric
iron etc.

Nuclear energy This is the type of energy released during the splitting or fusing of atomic nuclei. E.g.
Hydrogen, Uranium, radium, etc.

Sound energy This is the energy produced when objects vibrate. E.g. bell, drums, etc.

Mechanical energy This is the energy possessed by a body due to its position, state or motion. There
are two types of mechanical energy:

• Potential energy
• Kinetic energy

Potential energy (P.E.): This is the energy a body has as a result of its position or state. Examples of
potential energy include:

A cat lying on a mat

A piece of cloth hanging on a line

A girl sitting on a chair

31
The formula for potential energy is given as P.E. = mgh. where m = mass, g = acceleration due to
gravity and h = height of the body

Example: A mango fruit of mass 0.06 kg hangs 4.0 m above the ground. Calculate its potential
energy. [g = 10 ms-2]

Solution

P.E. = mgh

m = 0.06 kg,

h = 4 m,

g = 10 ms-2

P.E. = 0.06 x 10 x 4

P.E. = 2.4 J

Kinetic energy (K.E.) This is the energy possessed by a body due to its motion. Examples of K.E.
include: A boy riding a bicycle, A fan whirling around, A car speeding

Kinetic energy is expressed as

1
K.E. = 2 mv2 where m = mass and v = velocity

Example: A particle of mass 20 g moves with a velocity of 3 ms-1. What is its kinetic energy?

Solution
1
K.E. = 2 mv2
20
m = 20 g = 1000
= 0.02 kg, v = 3 ms-1

1
K.E. = x 0.02 x 32 K.E. = 0.09J
2

ENERGY TRANSFORMATION

Energy transformation is the process of changing energy from one form to another. This process is
happening all the time, both in the world and within people. When people consume food, the body
utilizes the chemical energy in the bonds of the food and transforms it into mechanical energy, a new
form of chemical energy, or thermal energy. The following show various energy transformations.

1. Photosynthesis => SOLAR ENERGY CHEMICAL ENERGY

2. Voltaic cells => CHEMICAL ENERGY ELECTRICAL ENERGY MECHANICAL

ENERGY HEAT ENERGY

Solar cells => SOLAR ENERGY ELECTRICAL ENERGY MECHANICAL ENERGY

Electric bulb => CHEMICAL ENERGY ELECTRICAL ENERGY HEAT ENERGY

5. Fossil fuel => CHEMICAL ENERGY THERMAL ENERGY ELECTRICAL

ENERGY

32
6. Falling object => CHEMICAL ENERGY ELECTRICAL ENERGY POTENCILA
ENERGY

7. Cellular respiration => CHEMICAL ENERGY ELECTRICAL ENERGY

POTENCILA ENERGY

Energy transformation

The law of conservation of energy states that energy cannot be made or lost but can be changed from
one form to another.

How to conserve energy

1. Switch off all electrical appliances that are not in use.

2. Do not leave doors of fridges and freezers open.
3. Do not put hot food in fridges and freezers.
4. Turn off and remove mobile phone chargers from the power outlets after charging mobile
phones.
5. Iron clothes in bulk.
6. Close all doors and windows when using air-conditioners.
7. Use energy saving lamps.
8. Open doors and windows to allow in fresh air instead of electric fans and air-conditioners.
9. Turn off light during the (bright and sunny) day.
10. Have your electric metre earthed.

EFFICIENCY OF ENERGY

Efficiency of energy is the ratio of energy output to the energy input. Efficiency is expressed in
percentage. In other words, it is the ratio of energy put into a work to the energy obtained from it.
energy output
Mathematically, Efficiency = x 100%
energy input

Efficiency of energy is never 100%. This is because parts of the energy put into work are used to
overcome friction, inertia and gravity. This makes the energy output always less than the energy
input.

Sample question: A machine was supplied with 90 J of energy. It could do 75 J of work. Calculate its
efficiency.

Solution: Energy output = 75 J, energy input = 90 J

energy output
Efficiency = x 100% = 75 90 x 100 = 83%
energy input

33