CELL
OBJECTIVE: Identify different parts of plant and animal cells
CELL is a basic unit of life.
a) Animal cell
1
b) Plant cell
2
SOME PARTS REVEALED UNDER AN ELECTRON MICROSCOPE
CELL SURFACE MEMBRANE

Partially permeable membrane which controls movement substances in and out of the cell.
CYTOPLASM


Made out of water, other dissolved substances like amino acids and sugars.
Metabolic reactions occur in the cytoplasm and organelles.
NUCLEUS



Control all chemical reaction in a cell,
it stores genetic information of the organism;
cell division start in the nucleus.
MITOCHONDRION
 Site for liberation of energy during aerobic respiration
RIBOSOME
 for assembling of amino acids to form proteins of the organism
PARTS FOUND IN PALNT CELLS ONLY
CELL WALL



Freely permeable and made up of
cellulose. Cell wall gives plant cell its rigid shape ( provide structural support.)
Protect against damage or bursting
caused by osmotic intake of water.
Being freely permeable allows
water and dissolved substances to pass through it.
VACUOLE
Large and central in a plant cell.
Animal may have tiny or temporary


vacuoles.



Its contents are called cell sap.
Accumulation of water in a vacuole
provides the cell with turgor pressure, making the cell to be firm.
Cell sap is made up of water and
dissolved substances.
3
CHLOROPLASTS
Plastids containing chloroplasts

trap light energy used in photosynthesis.
QUESTIONS

LIST FIVE SIMILARITIES AND FIVE
DIFFERENCES BETWEEN A PLANT CELL AND AN ANIMAL CELL.
4
SPECIALISED CELLS
OBJECTIVE: Describe the relationship between cell structure and function using an animal cell and a
plant cell as examples
This means cells:
Do one particular job
Developed a distinctive shape
Special kinds of chemical changes take place in their cytoplasm
NB: This enables the cell to carry out its special function




EXAMPLES OF SPECIALISED CELLS:
1. ROOT HAIR CELL
FUNTION OF A ROOT HAIR CELL IN PLANTS
Its function is to absorb water and mineral ions from the cell.

ADAPTATIONS
Has an extension which increases surface area, making absorption/diffusion rapid.
Cell wall of the elongation is very thin making it more permeable to water and mineral


ions.
5
Vacuole is relatively large for accumulation of water and mineral ions.

2. PALASADE CELLS
FUNTION OF A PALISADE CELL
These are the most photosynthesizing cells in a leaf.

ADAPTATIONS


Numerous chloroplasts with highest concentration of chlorophyll for maximum
absorption of light.
Large vacuole for accumulation of more water needed in photosynthesis.
6
EXAMPLES OF SPECIALISED CELLS IN ANIMALS:
1. RED BLOOD CELL
FUNTION OF A RED BLOOD CELL

The function is to carry oxygen from the lungs to the different cells of the body.
ADAPTATIONS




Shape : Flat biconcave disc; this shape creates a larger surface area for rapid
absorption of oxygen.
Have no nucleus, this increases the oxygen carrying capacity of the cell.
Have a pliable surface membrane to squeeze through narrow blood capillaries.
Have haemoglobin, which has affinity to oxygen, forming oxy-haemoglobin
7
2. NERVE CELL
FUNTION OF A NERVE CELL
Conducts electrical impulses in the body

ADAPTATIONS



Has a long cytoplasm /nerve fibre stretching through length of the body to carry the
electrical impulses.
Has myelin (fatty) sheath which insulates the nerve fibre preventing loss of impulses
and making transmission faster.
Has many branches to link the neurone to other neurones.
8
3. SPERM CELL
FUNTION OF A SPERM CELL
Its function is to fertilise an ovum (its nucleus fuses with that of an ovum.

ADAPTATIONS



Has a tail which allows it to swim or be highly mobile to reach an ovum.
Has a middle piece with numerous mitochondria to generate energy for the cell in
order for it to move.
Acrosome has enzymes that just digest the wall of the ovum.
CELL ORGANISTION
OBJECTIVE: Define tissue, organ, system, and organism
1. TISSUE

A group of similar cells with the same functions.
EXAMPLES OF ANIMAL TISSUES



MUSCLE TISSUE- Contracts to support and move the body.
EPITHELUM – Lines tubes such as the gut and covers surfaces such as the skin.
NERVOUS TISSUE- Sets up nerve impulses and transmits them around.
9
EXAMPLES OF PLANT TISSUES
EPIDERMIS-Protecting against water loss and may be involved in absorption of water

and ions.



VASCULAR TISSUE-Transports materials through the plant.
XYLEM- Transports water and mineral ions up the plant
PHLOEM-Molecules conducts soluble food molecules from the leaves to different parts
of the plant.
XYLEM TISSUE


Walls have lignin deposits to make water-proof and strong enough to prevent them
from collapsing inwards.
No cytoplasm or organelles, cells dead. The hollowed structure is for flow of water
minerals ion.
PHLOEM TISSUE


Phloem tissue contains sieve tubes and companion cell. It is adapted for the transport
of the organic products of photosynthesis.
Mesophlly – Photosynthesising cell.
2. ORGAN
ORGAN is a group of different tissues working together.
Examples of plant organs: leaves, flowers, roots, stems and fruits
Examples of animal organs: mouth, stomach, liver, heart, penis, eye, ear, etc
3. ORGAN SYSTEM
ORGAN SYSTEM is different organs working together.
This is found in complex organisms such as animals.
Examples of organs are: Digestive system, circulatory system, nervous system, endocrine system,
reproductive system, etc.
4. ORGANISM
ORGANISM is all organ system working together.
Examples : mophane plant, human being etc
10
DIFFUSION
OBJECTIVE: Definition of diffusion
DIFFUSION: The movement of molecules or ions from a region where they are at a higher concentration
to a region where they are at a lower concentration (i.e. down a concentration gradient).
OBJECTIVE: * Describe how concentration gradient, particle size, thickness of membrane and
temperature affect diffusion rate.
FACTORS AFFECTING RATE OF DIFFUSION
1.

2.

3.


4.


CONCENTRATION GRADIENT( concentration difference)
The steeper the concentration gradient the higher the rate of diffusion.
SIZE OF MOLECULES
The smaller the size of the molecules the higher the rate of diffusion. Smaller
molecules use less kinetic energy to move, whilst larger ones need more energy.
THICKNES OF MOLECULES/WALL
The thicker thermometer wall or wall the lower the rate of diffusion.
The thinner the membrane/wall the higher the rate of diffusion. However generally
cell membranes generally have the same thickness, but thickness of cell walls may differ
from cell to cell.
TEMPERATURE:
Increase of temperature increases kinetic energy of particles, and the rate of diffusion
of particles will increase.
Decrease of temperature decreases kinetic energy of particles, and the rate of
diffusion of particles will decrease.
SOME EXAMPLES OF DIFFUSION IN LIVING ORGANISMS
ANIMAL



Gaseous exchange in lungs
Movement of food molecules/mineral ions into cells or from alimentary canal into
bloodstream.
Movement of water molecule from tissue fluid into blood stream or vice.
PLANTS
Movement of oxygen and carbon dioxide molecules into or out the of the plant via

stomata.


Movement of water molecules in cells of the plant or out of the cells ( special diffusion
– osmosis)
Movement of mineral ions into or out of the cell.
11
OBJECTIVE: Definition of osmosis
OSMOSIS
OSMOSIS is the movement of water molecules from an area of where they are highly concentrated to an
area where they are less concentrated through a selective or partially permeable membrane.
12



Water molecules are highly concentrated outside the visking tubing compared to the
inside of the visking tubing.
Therefore water molecules moved into the visking tubing
Volume of the solution in the visking tubing increased and solutions level in the
capillary tube rose.
OBJECTIVE: Describe the effect of concentration gradient in the uptake of water by plants

Higher concentration gradient of water particles make absorption of water rapid

Lower concentration gradient of water particles make absorption of water slow
OBJECTIVE: State how osmosis is a special form of diffusion

Osmosis is specifically movement of water molecules from area of higher
concentration to area of lower concentration

The water molecules pass through a partially/selectively permeable membrane
OBJECTIVE: Describe the effect of osmosis on plant cells, in terms of flaccid cells, turgid cells, wilting
and plasmolysis.
diagrams
OBJECTIVE: Describe the effect of osmosis on animal cells,B [refer to bursting and shrinking].
diagrams
OBJECTIVE: Experiment, observation, on how solutions of varying concentration affect plant tissue
EFFECT OF OSMOSIS ON PLANT TISSUE
INVESTIGATION
TOPIC: OSMOSIS
13
AIM
To find out how different concentration of sugar solutions affect plant tissues.

APPARATUS USED
Potato cylinder ( diameter 5mm, length 40mm)
Solutions 0.55%,55%,10%, sugar
Distilled water
Forceps
4 Beakers





PROCEDURES





Distilled water, 0.5% sugar solutions,5% sugar solution, 10% of sugar solution were
each poured into a beaker up to the 100ml mark of the beaker.
Potato cylinder (of known size) was weighed, mass recorded then placed in the beaker
of distilled water.
This was repeated using sugar of the following concentrations : 0.55,5%10%
Each cylinder was left in its medium for 60 minutes
Mass of each cylinder was measured and recorded.
ACTIVE TRANSPORT
OBJECTIVE: Define active transport
Active Transport is movement of molecules or ions from the region of lower concentration to the region
of higher concentration using energy generated by the cell.
Movement from lower concentration to higher concentration is movement against concentration
gradient.
OBJECTIVE: Define passive transport
Passive transport is a non- energy consuming process in which substances are transferred down their
concentration gradient.
OBJECTIVE: Distinguish active transport from osmosis and diffusion, which are passive processes
DIFFERENCES BETWEEN ACTIVE TRANSPORT AND PASSIVE TRANSPORT
ACTIVE TRANSPORT

Molecules move from region of
PASSIVE TRANSPORT

Molecules move from region of
14



lower
Concentration to region of higher
concentration/molecules more against
concentration gradient
Energy from used /ATP from cell
used
Living cell membrane
needed/occurs only in living cells


Direction of movement of
molecules /ions not reversible

higher
Concentration to region of lower
concentration/molecules move down the
concentration gradient
No energy from cell used /no
ATP used from cell
No living cell membrane
needed/occurs both living and non living
cells
Direction of movement of
molecules/ions reversible
DIVERSITY OF ORGANISMS:
Objective: Discusss the concept of diversity of organisms with examples in Botswana








There are millions of organisms on earth.
classified according to the important features they have
The Whittaker 5-kingdom scheme has five kingdoms, namely: Monera, Protoctista, Fungi, Plants
and Animals
Kingdom Monera: Chromosomes are not organized into nucleus e.g. bacteria
Kingdom Protoctista: Chromosomes are enclosed in a nucleus e.g. protozoa
Kingdom Fungi: Are made up of threads like hyphae rather than cells e.g. Mushrooms
Kingdom Plants: Multicellular photosynthetic organisms whose cell walls are made from
cellulose e.g. Zea may plant
Kingdom Animals: e.g. Multicellular organisms whose cells have no cell wall. Most ingest solid
food and digest it externally e.g. insect
Objective: * List at least 3 main characteristics of protozoa, viruses, Bacteria, Fungi, Green algae,
athropoda and vertebrates.
copy notes from the other hand out
15
Objective: Discuss the role of protozoa and mosquitoes in causing malaria
Objective: Describe control of malaria
copy notes from the other hand out
NUTRITION
TYPES OF NUTRITION
OBJECTIVE: Describe autotrophic and heterotrophic modes of nutrition
16
1.
AUTOTROPHIC NUTRITION- When an organism makes organic food molecules from
simple inorganic molecules such as water and carbon dioxide.
TWO FORMS OF AUTOTROPHIC NUTRITION


2.
PHOTO – Autotrophic nutrition whereby an organism uses light energy to make
organic food molecules- Plants are examples of photo – autotrophs.
CHEMO – Autotrophic nutrition: Whereby an organism uses chemical energy to make
food molecules. Some bacteria are chemo – autotrophs
HETEROTROPHIC NUTRION: Whereby an organism feed on ready made food
molecules. Below are examples of heterotrophs.

HOLOZOIC: Feed on materials of other organisms and digest the material internally
 Herbivores
 Omnivores
 Carnivores.
PARASITES: Completely dependent on other organisms ( host organism) to obtain food e.g. tick and
some fungi.
SAPROPHITES: Digest food externally and absorb simple food molecules e.g bacteria and fungi.
LEAF STRUCTURE
OBJECTIVE: Identify and label the cellular and tissue structure of a dicotyledonous leaf, as seen in cross
section under the microscope
drawing
17
OBJECTIVE: Describe the significance of the cellular and tissue structure of a dicotyledon leaf in terms
of:



Destribution of chloroplasts - photosynthesis
Stomata and mesophyll cells - gaseous exchange
Vascular bundles - transport
Cuticle: Reduces water loss from the plant.
Epidermis: Closely fitting cells reducing evaporation and prevent bacteria and fungi from entering the
leaf.
Mesophyll: Found between the upper and lower epidermis. It consists of the palisade mesophyll and
the lower spongy mesophyll.


Palisade mesophyll - Have the highest concentration of Chloroplasts, for maximal
absorption of light. This is the most photosynthetic tissue in the leaf.
Spongy mesophyll – Cells vary in shape and fit loosely together, leaving many air
spaces between them. The inter-cellular spaces allow air to circulate in the leaf.
Vein: Water is supplied through the vascular bundles present in the leaf as vein. Ample water must be
conducted to photosynthesizing cells. Sugars formed from photosynthesis are conducted out of the leaf
to other parts of the plant by the phloems in the vascular bundles.
Stoma: Consists of a pair of guard cells facing each other. Turgidity of the pair of guard cells results in
the stoma opening and flaccidity results in closing of the stoma.
Adaptation of leaves for photosynthesis






Their broad, flat shape offers a large surface area for absorption of sunlight and carbon dioxide.
Most leaves are thin and the carbon dioxide has to diffuse across short distance to reach inner
cells.
The large spaces between cells inside the leaf provide an easy passage through which carbon
dioxide can diffuse.
There are many stomata (pore) in the lower surface of the leaf. These allow the exchange off
carbon dioxide and oxygen
There are more chloroplast in the upper cells than in the lower cells. The palisade cells, being on
the upper surface, will receive most sunlight and this will reach the chloroplast without being
absorbed by too many cell walls.
The branching network of veins provide a good supply of water to the photosynthesing cells.
PHOTOSYNTHESIS
OBJECTIVE: Describe trapping of light by chlorophyll , conversion of light energy into chemical energy,
the formation of carbohydrates, their subsequent storage, and the release of oxygen.
18
PHOTOSYNTHESIS:- Process by which light energy is transformed into chemical energy in the form of
carbohydrates molecules. Carbon dioxide and water react together using energy absorbed by
chlorophyll to produce glucose and oxygen.
The photosynthesis process occurs in chloroplast in two stages:
a) LIGHT REACTION:- A light – dependent stage which requires light energy. During the light
reaction, photosynthesis of water occurs i.e photochemical splitting of water molecules into
hydrogen and oxygen. Using light energy trapped by chlorophyll present in chloroplasts The light
energy is also converted to chemical energy in the form of ATP(Adenosive triphosphate.)
b) DARK REACTION:- Carbondioxide is reduced by hydrogen(produced in the light stage) to form
glucose using ATP produced in the light stage. This is a temperature dependent stage as
enzymes are involved.
c) Glucose made during photosynthesis is stored in photosynthesizing leave cells as starch
EQUATIONS:
OBJECTIVE: State both word and symbol equation
WORD EQUATION:
Light
Carbondioxide +Water
glucose + Oxygen
Chloropyll
SYMBOL EQUATION:
Light
6CO2 + 6H2O
C 6H12 O6 + 6O2
Chloropyll
INTAKE OF CARBON DIOXIDE BY A PLANT
OBJECTIVE: Describe intake of carbon dioxide



Carbondioxide from the atmosphere diffuse into the leaf through the stomatas.
In the leaf, carbon dioxide dissolves in the thin film of water surrounding the mesophyll cells;
Carbon dioxide diffuse into the chloroplasts within the cells, where its used for photosynthesis.
19
FACTORS AFFECTING RATE OF PHOTOSYNTHESIS
OBJECTIVE: *Discuss the effect of varying light intensity, carbon dioxide concentration and
temperature on the rate of photosynthesis (e.g. in submerged aquatic plants)
The chief factors are: Light intensity
Temperature
Carbon dioxide concentration
a) LIGHT INTENSITY
 The rate of photosynthesis increased by increasing the light intensity up to the light
saturation point where further increase in light intensity has no effect on the rate of
photosynthesis.
 In the absence of light, photosynthesis does not occur only respiration continues. As
light intensity increases, the rate of photosynthesis increases until the amount of carbon
dioxide released from respiration is equal to the amount of carbon dioxide absorbed for
photosynthesis. At higher light intensities, a net uptake of carbon dioxide and release of
oxygen is reached and the amount of carbohydrates in the plant will increase.
 Very high light intensity will slow down photosynthesis, excessive amounts of ultra
violet rays damage chlorophyll molecule.
b) TEMPERATURE
 The reactions in the dark stage of the photosynthetic process are enzyme controlled;
therefore temperature has an effect on the rate of photosynthesis.
 Increasing temperature up to 40c will increase the rate of photosynthesis due to the
increased enzyme activity. At temperature above 40c, the rate of photosynthesis
decreases as the enzyme gradually becomes denatured.
c) CARBON DIOXIDE
 The normal percentage of carbon dioxide in the atmospheric air is 0.03%. Increasing
carbon dioxide level increases the rate of photosynthesis up to the carbon dioxide
saturation point where further increase in carbon dioxide level; has no effect. A carbon
dioxide level above 0.1% has no effect on the rate of photosynthesis.

THE GRAPH WAS PRODUCED USING CO2 CONCENTRATIOPN OF0.05%
THE GRAPHS SHOW RATES OF PHOTOSYNTHESIS WHEN CO2 CONCENTRATION WAS AT 0.05%




Suggest how the rate of photosynthesis can be further increased beyond when
temperature is at 40oC Increase CO2 concentration
3 limiting factors of rate of photosynthesis when temperature at 25oC
carbon dioxide concentration
low temperature
20

surface area of leaves
INVESTIGATING NECESSITY OF CHLOROPHYLL, LIGHT AND CARBON DIOXIDE IN PHOTOSYNTHESIS
OBJECTIVE: Discuss the necessity for chlorophyll, light and carbon dioxide in photosynthesis
ELEMEMTS NEEDED BY PLANTS
OBJECTIVE: explain importance of nitrogen containing ions for protein synthesis
1. NITROGEN
 Nitrogen is absorbed by plants as nitrates
 Nitrogen is used to form protein or Amino acids molecules.
 Lack f nitrates in the soil results in the stunted growth of plant and yellowing of leaves.
 Addition of magnesium to the soil is by any compound containing magnesium such as:
potassium nitrate, ammonium nitrate.
OBJECTIVE: explain importance of magnesium containing ions for chlorophyll synthesis
2. MAGNESIUM
 Magnesium is absorbed by plants as magnesium ions.
 Magnesium is to form chlorophyll molecules.
 Lack of magnesium in the soil results in the following: yellow leaves.
 Addition of magnesium to the soil is by any compound containing magnesium such as:
magnesium sulphate.
EXPLAIN HOW LACK OF MAGNESIUM IONS AND NITROGENS IN THE SOIL MAY LEAD TO STUNTED
GROWTH


NITRATE IONS
Needed for synthesizing proteins which are needed by plant to grow since they are used for the
formation of new cells.
Lack of nitrate ions in the soil will cause stunted growth since proteins are not synthesised.
MAGNESIUM IONS


The chlorophyll molecules need magnesium to be present. The absence of this metallic element
can lead to leaves have less chlorophyll which leads to less carbohydrates being formed.
There will not be enough energy generated by cells and cell division will be less leading to the
slow growing of a plant.
21
OBJECTIVE: Investigate the effect of nitrogen deprivation on plant
copy from the back part of the note book
ENZYMES
OBJECTIVE: Define term enzyme
An enzyme is a protein which functions as biological catalysts to speed up chemical reaction in living
organisms.
PROPERTIES OF ENZYMES




Enzymes are produced in minute quantities by cells. A minute amount of enzymes is required to
produce a rapid change in their rate of chemical reaction. Enzymes remain unchanged at the
end of the reaction and can be used over and over again.
Enzymes work on specific types of substrates molecules. Each enzymes has a specific shape and
its active site will bind to a substrate that has a complementary shape.
Enzymes are easily destroyed by heat, sensitive to Ph and inactivated by poisons. The active site
of an enzyme altered by heat and Ph.
Enzyme activity is inhibited as the substrate molecules will no longer fit into the active site of
the enzyme.
GROUPING OF ENZYMES
1. CATABOLIC AND ANABOLIC ENZYMES
OBJECTIVE: Discuss the importance of enzyme in anabolic and catabolic reactions.


Enzymes act on catabolic reactions (reactions which involve break down of larger
molecules to smaller molecules.
Enzymes act on anabolic reactions( reactions which involve building of larger molecules
by use of smaller molecules.
2. INTRACELLULAR AND EXTRACELLULAR ENZYMES:
OBJECTIVE: Describe intra-cellular and extra-cellular enzymes.

INTRACELLULAR ENZYMES are enzymes functioning inside the cell where they are made.
The enzymes speed up the chemical reactions inside the cells.
22

EXTRACELLULAR ENZYMES are enzymes functioning outside the cells that made them.
e.g digestive enzymes.
CLASSIFICATION ACCORDING TO SUBSTRATE
Enzymes can be classified according to the type of substrate they act on. Digestive enzymes are
classified according to the food they digest.
a. AMYLASE are a group of enzymes which breakdown starch to glucose.
b. LIPASE are a group of enzymes which breakdown fats and oils to the component fatty acids and
glycerol
c. PROTEASE are a group of enzymes which breakdown proteins to their component amino acids.
EFFECTS OF TEMPERATURE ON ENZYME ACTIVITY
OBJECTIVE: Investigate and describe effect of temperature on enzyme activity
1. In general, increase in temperature, from 5oC to around 40oC increases enzyme activity.
At temperature below 5oC, enzymes are inactivated. At temperature above 50oC,
enzymes become progressively denatured.
2. Rise in temperature increases the rate of metabolic reactions as the frequency of
collisions between substrate and enzyme molecules increases but at temperatures
above 50oC enzymes become chemically altered, denatured.
3. Enzyme function best at a temperature known as optimum temperature. For every
enzyme there is an optimum temperature at which the enzyme works fastest.
4. Human enzymes have an optimum temperature of 37oC.
Graphs on back part of the note book
EFFECT OF pH ON ENZYME ACTIVITY
OBJECTIVE: Investigate and describe effect of pH on enzyme activity

Enzymes are influenced by the acidity and alkalinity of the medium in which they function.
23


Each enzyme requires a specific pH level for optimum efficiently. This is the optimum pH of the
enzyme.
Optimum pH of pepsin in the stomach is pH 2 and that of trypsin in the duodenum is pH 8.
Graphs on back part of the note book
FOOD
Food is required




as a source of energy
For formation of new protoplasm during growth
repair of body tissues
for metabolic reactions to keep organism healthy and warm
OBJECTIVE: Define a balanced diet
Balanced diet is a meal with all the nutrients needed by the body in right quantities and correct
proportions.
OBJECTIVE: List the chemical elements which make up: carbohydrates, proteins and fats
Classes of energy providing foods: carbohydrates, proteins, fats/oils
A SUMMARY OF CARBOHYDRATES, PROTEINS AND FATS /OILS IS SHOWN BELOW.
ELEMENTS
CARBOHYDRATES
 Carbon, Hydrogen,
Oxygen
MAIN
SOURCES

BASIC UNIT



TYPE

Proteins, fruits,
cereals, grains,
rice, bread, sugar
cane and other
plant storage
organs
Monosaccharide
Single sugar unit
Monosaccharide
e.g. glucose,
fructose
Disaccharide e.g.
maltose, sucrose,
PROTEINS
 Carbon,
Hydrogen,
Oxygen, nitrogen
and sometimes
sulphur
 Lean meat, fish,
liver, milk, cheese
,egg white,
legumes, soya
beans and cereal
grains
 Amino acids


Animal and plant
proteins
In which humans,
non essential
amino acids are
24
FATS/OILS
 Carbon, Hydrogen, Oxygen with
different proportions to
carbohydrates

Egg yolk, butter, cream, fatty
meat, cheese, vegetables

One molecule of glycerol and
fatty acid molecules
Fats from animals are solid at
room temperature and certain a
high proportion of saturated fatty
acids.
Oils from plant sources are liquid



lactose
Polysaccharide e.g.
starch cellulose.
CARBOHYDRATES
 Main source of
energy in the
diet.
 Glucose is the
main
respiratory
substrate
carbohydrate
 Cellulose
cannot be
digest
Provide bulk to
food assist in
peristaltic
movement
along the
alimentary
canal.
FUNCTIONS
ENERGY SUPPLY
joined together in
any number or
order to form
different proteins
(may be folded,
twisted or
straight).
at room temperature and have a
high proportion of unsaturated
fatty acids
PROTEINS
FATS/OILS
 A source of
 Component of
amino acids for
cell
growth of new
membranes,
tissues and
hormones,
replacement of
mylin sheath
cell
surrounding
components
nerve fibres.
 To build up
 Stored in a
body structures
adipose tissue
e.g hair, cell
beneath skin
membranes and
and around
red blood cells.
body organs as
insulator.
 Formation of
muscles,
 Fats around
tendons and
delicate organs
ligaments
protect them
from physical
 Formation of
damage.
enzymes and
antibodies.
 As an energy
reserve
CARBOHYDRATES
 1g of
carbohydrates
respires to give
17kJ of energy
 Immediate
source of
energy
PROTEINS
1g of protein respires to
give 17kJ of energy
Only oxidized when
carbohydrates,
glycogen and fats have
been used up.
FATS/OILS
1g of fat
respires to
give 37kJ of
energy
OBJECTIVE: Explain why diet, especially energy intake, should be related to age, sex and physical
activity of an individual
Food Intake in human depends on the following factors: sex, age, occupation and lifestyle.
1. SEX
25
 Males need more carbohydrates and proteins than female.
 Carbohydrates provide energy for the formation of new cells.
 Proteins from many compacted cells of the muscles.
2. OCCUPATION
 Labourer needs more proteins and carbohydrates than someone doing a white collar job.
 Carbohydrates provide energy for the formation of new cells.
 Proteins from many muscles cells wearing off during physical work.
3. AGE
 Younger people need more carbohydrates and proteins than older people.
 Carbohydrates provide energy for formation of new cells, new cells are needed for
growth of younger person
 Proteins from many cells needed in growth
 Younger people are more active, carbohydrate generate energy for contraction and
relaxation of muscles; movements.
4. Someone who exercises regularly needs more carbohydrates and proteins than someone who
never exercises.
 Carbohydrates provide energy for formation of new cells
 Proteins form many muscle cells wearing off during physical work.
OBJECTIVE: Describe tests for starch (iodine solution), reducing sugars (Benedict’s solution), protein
(biuret test) and fats (ethanol).
FOOD TESTS
TEST
1)CARBOHYDRATES:
CHEMICAL TEST
BENEDICT TEST
PROCEDURE
 To about 5ml of a food
26
OBSERVATION
 If reducing
REDUCING
a)SUGARS(e.g
glucose)

b)STARCH
IODINE TEST

sample in a solution form,
add about 4 drops of
Benedict’s solution.
Gently shake to mix.
Place the test tube with
the mixture in a hot water
bath
Place a drop or two drops
of iodine solution into a
test tube containing a
food sample in solution
form



2.PROTEINS
BIURET TEST

3.FATS/OILS
ETHANOL
EMULSION TEST


To about 2ml of a solution
of a food sample in a test
tube, add about 2ml of
1% sodium hydroxide,
gently shake then add
about 2ml of 1% of
copper (II) Sulphate,
gently shake and observe
after adding each drop.
To a test tube with 2ml of
a food sample in add
about 5ml of ethanol.
Shake thoroughly then
transfer the liquid part of
the mixture into an empty
test tube.
To the liquid mixture add
distilled water drop by
drop. Observe after
adding each drop.
27



sugar is absent,
mixture
remains blue.
If present the
mixture turns
from blue to
green, then to
yellow then to
orange and
finally brick red
If starch is
absent the
mixture
remains brown
with iodine
solution.
If starch is
present the
mixture turns
blue-black
If proteins are
absent the
mixture
remains blue, if
present the
mixture turns
purple or violet
If fats /oils are
absent the
mixture
remains clear.
If fats /oils are
present a
cloudy white
emulsion is
formed.
THE DIGESTIVE SYSTEM
FEEDING
HOLOZOIC NUTRITION in human consists of five main stages.
1. INGESTION: Where food is taken into the alimentary canal via the mouth
2. DIGESTION: Which a process whereby large molecules of food is broken-down into smaller
molecules which can be absorbed into the blood system. It is also known as extracellular
digestion because it takes place outside the cells of the body.


DIGESTION is achieved by both physical and chemical means. The physical action is achieved
by the teeth (mastication) stomach contracts and bile (emulsification).
Chemical breakdown is achieved by digestive enzymes contained in saliva, gastric juices,
pancreatic juices and intestinal juices. The chemical bonds in the complex food substances
are broken-down by specific enzymes in the presence of water –a process called hydrolysis.
3. ABSORPTION: Where by food molecules pass through the gut wall into the blood stream.
4. ASSIMILATION: This is the distribution and use of some of these small molecules as an energy
source and conversion of other substances required for growth.
5. EGESTION: where undigested food and other gut contents are removed as feces, via the anus
(also called defecation).
28
THE HUMAN DIGESTIVE SYSTEM
OBJECTIVE: Using diagrams and models identify the main regions of the alimentary canal and the
associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder,
liver, ileum, colon, rectum and anus

The human alimentary canal is differential into a series of specialized regions.
29

Below is a summary of functions of parts of the digestive system.
OBJECTIVE: Describe the main functions of the identified parts of the alimentary canal in relation to
ingestion, digestion, absorption, assimilation and egestion of food, as appropriate
PARTS OF THE
DIGESTIVE SYSTEM
MOUTH {ingestion,
digestion [physical
and chemical means]}
a) Teeth
b) Savary glands
SECRETIONS AND ENZYMES

Salivary secreted by
salivary glands
contains:
i) water
ii) Mucus
iii) amylase
c) Tongue
OESOPHAGUS(Peristal
sis)
MUCUS
FUNCTIONS
OBJECTIVE:
OBJECTIVE:describe
describechewing
chewing
 Cut and grind large pieces of food to smaller
– mastication/chewing.
This increases
 pieces
Cut and
grind large pieces of food
to
surface
area
of
food
for
enzymatic
action.
smaller pieces – mastication/chewing.
This increases surface area of food for
 Used as a solvent and in the hydrolysis of
enzymatic action.
food.
 Binds food particles and lubricates the food
to help in swallowing process.
amylase
Starch
maltose

Mixes food with saliva and rolls food into a
ball of bolus from which is easy to be
swallowed

Has muscular walls made up of circular and
longitudinal muscles under involuntary
control. Transports food to stomach by
peristalsis
Aids in the passage of food into the stomach
by reducing friction between food bolus and
walls of oesophagus

30
STOMACH Ph 1(acidic)
digestion [physical
and chemical means]
Gastric glands secrete
gastric juice which contains:
i.) WATER
DUODENUM p H 7-8
(Slightly alkaline)
PANCREASE
{digestion [physical
and chemical means]}
Bile from the gall
bladder produced by
the liver

Has muscular walls made up of circular and
longitudinal muscles which are under
involuntary control.
i.)
Churns food and mixes it with gastric
juice to food chime
ii.)
Absorbs alcohol and glucose
iii.)
Stores food temporarily(chime is held
by sphincter muscles in the stomach
for about four hours.

Used as a solvent and in the hydrolysis of
food
Protects stomach wall from the action of
acidic gastric juice. Acts as a lubricant for
movement of food within stomach.
ii.) MUCUS

iii.) HYDROCHLORIC
ACID

iv.) ENZYME PEPSIN

a) Secrets pancreatic
juice which contains
i)trypsin


ii)Amylase

iii)Lipase
iv) Water


b)Hormone insulin

c) Hormone glucagon

Produce bile using pigments
from old red blood cells
broken down in the liver.
Bile is an alkaline solution of

31
Provides the acidic medium (optimum pH)
for enzymatic action. Kills bacteria brought in
with the food. Activates enzymes in gastric
juice.
pepsin
Protein
polypeptides
Hydrolysis of food in duodenum
trypsin
polypeptides
peptides
amylase
Starch
maltose
lipase
Fats
Fatty acids + Glycerol
Used as a solvent and in the hydrolysis
makes liver cells to converts excess glucose to
glycogen
makes liver cells to converts excess glucose to
glycogen
increase of pH of acidic chime from the
stomach by sodium hydrogen carbonate and
provides alkaline pH for enzyme action in
small intestines
bile salts
ILEUM
{digestion [chemical
means] and
absorption }

Bile salts breakdown large globule of fats and
oils into smaller droplets – a process called
emulsification.

This increases the surface area for digestion
of fats.
Walls of secrete intestinal
juices with enzymes:
i). maltase
maltose
ii). sucrase
sucrose
iii).lactase
lactose
iv). erepsin/peptidase
peptides


COLON (absorption)

RECTUM


OBJECTIVE: describe peristalsis
PERISTALSIS
32
maltase
sucrase
lactase
glucose
glucose + fructose
glucose + galactose
erepsin/peptidase
amino acids
The main function is absorption of soluble
digested food
To aid in absorption, the surface area of the
small intestine is increased by villi in
epithelial and microvilli in the epithelial cells
Absorbs almost all the water from undigested
residues
Absorbs mineral ions
Stores feces prior to removal via anus
(egestion)
Peristalsis is the contraction of circular and longitudinal muscles along the length of the alimentary canal
resulting in the movement of food.
OBJECTIVE: describe the absorption and the significance of villi in increasing the intestinal surface area
ABSORPTION OF DIGESTED FOOD
33
Digested food is absorbed in the ileum. The ileum is adapted to facilitate rapid absorption of digested
food substances in the following ways:
a) The folded internal surface of the ileum is covered with numerous finger like projections called
villi(singular:villus) to increase the surface area for absorption.
b) The surface area of each villus is further increased by microvilli which are tiny microscopic
projections from the epithelial cells of the villus.
c) The long length of the ileum also helps to increase surface area for absorption.
34
d) Each villus contains a dense capillary network close to the epithelium to carry away the
absorbed food substances as quickly as possible. This helps to maintain the concentration
gradient between the solution of nutrients in the ileum and the blood cell plasma in the blood
capillaries for rapid diffusion.
e) The epithelium of the villus is one – cell thick allowing digested food substances to diffuse
rapidly over a short distance into the blood capillaries of the villus.
2. End product of digestion are soluble in water (e.g glucose amino acids) enter the blood system
by diffusing into the capillary network of the villi.
FATE OF THE PRODUCTS OF DIGESTION
OBJECTIVE: describe assimilation and how large molecules are synthesised from smaller basic units:
I.
starch from simple sugars
II.
proteins from amino acids
III.
lipids from glycerol and fatty acids

The end-products of digestion are assimilated (utilized in the body in various ways) according to
the needs as shown in the table below
END PRODUCT
OF DIGESTION
GLUCOSE
PATH TAKEN TO EACH BODY CELLS

AMINO ACIDS

FATTY ACIDS

Ileum
hepatic portal vein
liver
hepatic vein
venacava
right heart lungs
left heart all
parts of the body
FATE OF THE END PRODUCTS
1. Utilsed by all cells in
respiration
2. Excess glucose is
converted to glycogen by
insulin and stored in
liver.
3. Makes starch and
glycogen
1. Used to make new
protoplasm hormones
and enzymes
2. Used in repair of worn
out tissues
3. Utility by the cells in
respiration only when
glucose and glycogen are
used up.
4. Make proteins.
1.Fatty acids and glycerol
recombine in lacteal to form fat
globules.
35
2. Fats stored under skin and
around organs as an energy
store and for heat insulation.
3. Utilsed by the cells in
respiration only when glucose
and glycogen are used up.
OBJECTIVE: State the function of the hepatic portal vein as the route taken by most of the food
absorbed from the small intestines
drawing from a chart
1. LIVER is a large, reddish brown organ concerned with maintaining the concentration and
composition of blood (homeostasis) and excretion. It lies just below the diaphragm and
partly overlaps the stomach. The blood vessels serving the liver are:a) HEPATIC PORTAL VEIN:- Carries blood containing digested food substances absorbed
in ileum to the liver. Blood capillaries in the villi of ileum join to form the hepatic
portal vein.
b) HEPATIC ARTERY:- Carries containing oxygen to liver
c) HEPATIC VEIN: - Carries blood containing waste products and substances produced
by liver cells away from the liver.
OBJECTIVE: Describe the role of the liver in the metabolism of glucose, as a storage organ,
deamination and detoxification
2.)
THE MAIN FUNCTIONS OF THE LIVER ARE:
a) FORMATION OF BILE
 Contains bile salts produced by the liver cells and bile pigments from the breakdown of old red
blood cells in the liver.
 Bile is stored in gall bladder and used to emulsify fats before digestion by lipase in duodenum.
b.)STORAGE OF GLUCOSE

c.)
Helps maintain concentration of glucose in blood by converting glucose which is excess of
the body’s needs to glycogen by hormone insulin. Insulin is secreted by the pancrease and
carried to the liver by blood.
DEAMATION

Formation of urea. Amino acids that are excess of the body’s needs cannot be stored. The
amino group (-NH2 part) of the amino acids is removed and converted to urea. The residue is
converted to glucose for metabolism or storage.
36
d.)
DETOXIFICATION

e.)
Poisonous substances , used hormones and alcohol are converted to harmless substances by
liver cells.
PRODUCTION OF PLASMA PROTEINS

Blood clotting proteins such as fibrinogen and plasma proteins phothrombin are made by
liver cells.
F.) STORAGE OF IRON

Old red blood cells are destroyed in the liver and the iron and vitamins from haemoglobin is
stored for the manufacture of new red blood cells in the bone marrow. Fat soluble vitamins
(A, B, D) taken in the diet are stored in liver. Vitamin B12 is used in the manufacture of red
blood cells.
g.) PRODUCTION


The many chemical reactions taking place in the liver result in the formation of heat.
The heat produced is distributed throughout the body by the circulatory system and helps to
maintain a constant body temperature.
OBJECTIVE: Investgate action of amylase on starch
Inv estigation : Action of amylase on starch
RESPIRATION
OBJECTIVE: Define respiration
RESPIRATION is the release of energy from food substances in all living cells.
OBJECTIVE: Describe uses of energy in living organisms
37
Most of the energy is lost as heat energy and remaining energy is used up for the vital activities of the
cells such as:
a)
b)
c)
d)
e)
f)
Cell division for growth and repair of tissues
Metabolic reactions e.g. synthesis of proteins, hormones, enzymes e.tc
Contraction of skeletal muscles, heart muscles e.tc
Transport of materials in and out of cells e.g. active transport
Conduction of nerve impulses
Maintenance of a constant body temperature
OBJECTIVE: Describe respiration
ATP AND ENERGY TRANSFER



The energy release when glucose is broken down is not used directly in the cell instead it is
transferred to the chemicals which act as a store of readily available.
One of these chemicals is adenosine triphosphate (ATP).Adenosine combines with one,two or
three phosphate groups. Energy released when the glucose molecule breaks down is used to
combine a phosphate ion ( PO2 2- ) with a molecule of adenosine triphosphate.
When there is need of energy in a cell, in the presence of an appropriate enzyme, ATP readily
breaks down to ADP, releasing energy and phosphate ion. The energy can be used to drive other
chemical reactions such as those producing muscle contraction.
ATP
ADP +PO3
muscle contraction
AEROBIC AND ANAEROBIC RESPIRATION
OBJECTIVE: Define aerobic respiration

AEROBIC RESPIRATION is release of relatively large amount of energy by break down of food in
the presence of oxygen
38
A chain of enzyme controlled chemical reactions are involved and the total effect is
OBJECTIVE: State the equations of aerobic respiration
Word equation:
Glucose + Oxygen
Carbon dioxide + Water + energy
Symbol equation:
C6 H12O6 + 6O2
respiratory enzymes
6CO2+6H2O+Energy
OBJECTIVE: Define anaerobic respiration

ANAEROBIC RESPIRATION is release of relatively small amount of energy by the break down of
food in the absence of oxygen
OBJECTIVE: Describe fermentation

Fermentation is a form of anaerobic respiraton. Fermentation is also used more broadly to refer
to the bulk growth of microorganisms on a growth medium
OBJECTIVE: State the equations of anaerobic respiration
1. Alcoholic (yeast) fermentation:
 Word equation:
Glucose
Alcohol + Carbon dioxide + energy

Symbol equation:
C6 H12O12
2. Lactate fermentation:
 Word equation:
Glucose

2C2H5OH+2CO2+2ATP (
lactic acid + energy
Symbol equation:
39
G=-210kJ/mol)
C6 H12O12
2C3H6O3+2ATP (
G=-150kJ/mol)
3. Differences between aerobic and anaerobic respiration
CONDITION
RESPIRATORY
PRODUCTS
AEROBIC RESPIRATION
 Presence of oxygen
 Carbon dioxide, water and a
relatively large amount of energy
for both plants and animals
ENERGY
LILBERATED

Release all the available energy
within each glucose molecule
ORGANIC

All organisms breathe in air
(oxygen)
yeast can also respire aerobically

ANAEROBIC RESPIRATION
 Absence of oxygen
 Ethanol carbon dioxide and
a little energy for plants
 A process called Alcoholic
fermentation
 Lactic acid and a little energy
for animals
 Lactic acid is toxic in large
amount
 Release for less energy
because glucose is not
completely broken down
 Yeasts, bacteria, organisms
living in stagnant water or
mud e.g. worms
 Muscles of human and other
mammals during strenuous
exercise
 Mammals which dive for a
long period of time in the
ocean e.g. seals and whales.
OBJECTIVE: Describe the production of lactic acid in muscles during exercising
4. ANAEROBIC RESPIRATION IN HUMAN SKELTAL MUSCLES

Anaerobic respiration occurs during strenuous exercise or vigorous activity over
a period of time.

Despite the increased heart rate, the oxygen cannot be transported to the
muscles fast enough for tissue respiration

Insufficient oxygen causes the muscles to respire anaerobically to release
energy.

Glucose is broken down to lactic acid instead of carbon dioxide

Lactic acid accumulates in the muscles and mucus and causes muscle cramps

Oxygen debt incurred during the period of anaerobic respiration

The oxygen debt is paid off by rapid breathing in the recovery period after the
exercise to break down the lactic acid built up.

OBJECTIVE: Demonstrate release of energy through anaerobic respiration using yeast
40
Experiment (d) To Demonstrate Anaerobic Respiration by Living Organisms







Boil water for 15 minutes to remove all the dissolved oxygen.
Almost fill two flasks with the water, allow them to cool to 25°C in the sealed flasks - sealed to
prevent re-oxygenation.
Dissolve glucose in each flask.
Add live yeast to one - the experiment. No yeast in the other - the control.
Place a thin layer of oil on the top of the water in each - the water remains deoxygenated by
preventing contact with air.
Insert a thin glass tube from each stoppered flask into a test tube of limewater.
Maintain the temperature at 25°C in a water bath or heating tray.
OBJECTIVE: Describe the role of the exchange surface of the alveoli in gaseouse exchange
GASEOUS EXCHANGE IN MAN



Gaseous exchange takes place in the lungs where oxygen from atmospheric air is absorbed by
blood and carbondioxide carried by blood is released in to the environment
Breathing is the process by which external air is brought into contact with the respiratory
surface of the lungs for gaseous exchange
The complete gas exchange systems consists of the nasal passages,
pharynx,larynx,trachea,broncholi,lungs and the muscles involved in the breathing movements.
OBJECTIVE: Identify on diagram and name the larynx, trachea, bronchi, bronchioles, alveoli and
associated capillaries
41
The main respiratory organs and their role in the gas exchange system are summarized below.
STRUCTURE
Nasal passages and phalynx
Lined with ciliated cells and goblet
cells
LARYNX
TRACHEA
THE WINDPIPE LINED WITH ALLIATED
MUCOUS MEMBRANE AND
SUPPORTED BY C-SHAPED CARTILAGE
BRONCHI AND BRONCHILES
FUNCTIONS
 Air passing through is warmed to body temperature
and moistened.
 goblet cells produce mucus which traps dust a
 ciliated cells have cilia which flicks in a certain
direction causing mucus to move (flow or stream) in
that direction
 Dust and bacteria in air removed by hair and mucous
 The pharynx is a common passage for air and food
 The voice box for sound production
 Air passage
 Air passage to the lungs via the bronchi
 Dust and bacteria in air removed
LUNGS
- SPONGY,LOBED ORGANS
MADE UP OF NUMEROUS AIR
SACS CALLED ALVEOLI -: HAVE
RICH BLOOD SUPPLY
DIAPHRAGM
- A sheet of muscular tissue
with air cumference attached
to thoracic cavity



Air passage
Bronchioles terminate in air sacs or aveoli
Site of gaseous exchange of gases between blood
system and atmospheric air.


Separates thoracic cavity from abdominal cavity
Changes the volume of the thoracic cavity for
breathing
STRUCTURE AND FUNCTION AF ALVEOLUS:
42
1. Alveoli are efficient gas exchange surfaces because of :
a)
The very large surface area provided by the numerous alveoli
b)
The one cell thick walls of alveoli which allow rapid diffusion of gases.
c)
The presence of a thin film of moisture on the internal surface of alveoli which oxygen
can dissolve.
d)
The dense network of capillary around the alveoli which allows rapid efficient gas
exchange.
2. Oxygen from the air in the lungs dissolves in thin film of moisture on the cells lining the alveolus.
The oxygen then diffuses across the alveolus wall and through the wall of the capillary into the
blood plasma. The oxygen in the plasma then diffuses into the red blood cells and combines
with haemoglobin to from oxy-haemoglobin.
43
3. The carbon dioxide carried as bicarbonate ions in deoxygenated blood breaks down to liberate
carbon dioxide which diffuses out of the capillary wall and across the alveolus wall into the
alveolus. The carbon dioxide is expelled out of the lungs together with water vapour from the
water film on the alveolus during expiration.
4. The concentration gradient required for rapid diffusion of gases in and out of the alveolus is
maintained by:
a) Keeping the oxygen concentration high in the alveolus by replenishing air in alveolus.
b) the rapid absorption of oxygen across the thin alveolus and capillary wall and the
formation of oxy-haemoglobin.
c) the constant replacement of oxygenated blood by deoxygenated blood by blood flow.
GAS
Oxygen
Carbondioxide
Nitrogen
Water Vapour
INSPIRED AIR(15 VOLUME)
21
0.04
79
Varies
EXPIRED AIR (5 VOLUME)
16
4
79
Saturated
OBJECTIVE: Describe the role of the diaphragm, ribs and intercostals muscles in breathing.
44
BREATHING MOVEMENTS IN MAN
 Breathing is the physical process resulting in the exchange of gases at a gas exchange surface.
INSPIRATION
 Diaphragm contracts and flattens
 External intercostals muscles between
ribs contract, internal intercostals
muscles relax
 Ribcage moves upwards and outwards
EXPIRATION
 Diaphragm relaxes and becomes dome shape
 External intercostals muscles between ribs
relax internal intercostals muscles contract

Ribcage moves down wards and inwards

Volume of chest cavity increases

Volume of chest cavity decreases

Air pressure inside chest cavity and
lungs decreases

Air pressure inside chest cavity and lungs
increases

Atmospheric pressure drives air into
lungs

Air is forced out of lungs
NB: EXPIRATION is the opposite of Inspiration






Rib cage
Diaphragm
Volume
Pressure
Intercostals and External muscles
Air pressure pushes air inwards
45
Control of breathing rate:
a) The rate of breathing is influenced by the carbon dioxide content in the blood
An increase in carbon dioxide level in the blood during exercise stimulates the respiratory
centre in the brain to send more nerve impulses to the intercostals muscles between the
ribs and the diaphragm to contract and relax faster resulting in faster breathing rate.
b) Breathing rate is increased during anxiety, anger and fight due to the action of the hormone
adrenaline.
c) Breathing rate is faster when the metabolic rate of the body is higher. Thus, children and
infants have faster breathing rates than adults
d) Breathing rate is slowed down or even stopped by metabolic poisons which inhibit enzyme
controlled reactions in tissue respiration and paralyse breathing movements.
RESPIRATORY DISEASES
OBJECTIVE: Describe the effect of tobacco smoke and its major toxic components (nicotine, tar and
carbon monoxide) on health: strong association with bronchitis, emphysema, lung cancer and heart
disease, and the association between smoking during pregnancy and reduced birth weight.
There is a strong link between smoking and respiratory diseases (cigarette/tobacco smoke) has a
complex composition of many harmful chemical substances.
The constituents of smoke drawn into lungs with each inhabitation can be classified into irritant
substances.
MAIN
EFFECTS ON HUMAN BODY
CONSTITUENT
NICOTINE
 A stimulant in small amounts,
causes body to release hormone
adrenaline, thus increasing heart
rate and blood pressure
 Causes blood vessels to constrict
 makes blood clots more easily,
thus increasing the risk of
developing coronary heart
disease
 Causes addiction. Smokers who
stop smoking experience
withdrawal symptoms such as
irritation and tension.
CARBON
 Colourless, odourless poisonous
MONOXIDE
gas
 Causes a reduction of oxygen
supply to heart as carbon
46
ASSOCIATED RESPIRATOTY DISEASE

Thrombosis formed as the
increased blood pressure irritates
the lining of the arteries

Chronic bronchitis, Emphysema


TAR




IRRITANT
SUBSTANCES






monoxide combines 200 times
more readily with haemoglobin
than oxygen to form
carboxyhaemoglobin than
oxygen to form
carboxyhaemoglobin
This reaction is irreversible
Damages lining of blood vessels
and increases fatty deposition on
the walls of bold vessels.
Dark brown, sticky substance
containing cancer causing
chemicals.
forms yellowish brown stains on
smokers teeth and fingers
causes the persistent smokers
cough and shortens of breath
deposits in the lungs and may
cause cell changes leading to
uncontrolled abnormal growth
and spread of cancerous cells in
lungs and to other parts of the
body.
Carbon particles oxides of
nitrogen, etc
irritate the nose, eyes and throat
cause narrowing of air passages
Paralyse cilia and affect the
cleaning action of the cilia in the
air passages which removes dust
and bacteria from the air
entering the lungs
Stimulate excessive secretion of
mucous



Lung cancer
Throat cancer
Mouth cancer


Chronic bronchitis
Emphysema
1. In pregnant women who smoke, nicotine also constricts blood vessels in the placenta, therefore
reducing the blood supply to the foetus. Carbon dioxide combines irreversibly with haemoglobin
to form carboxyhaemoglobin, thus decreasing oxygen supplied to the foetus.
When a pregnant women smoke, their babies are smaller at birth and there is a higher risk of
miscarriage, stillbirth and infant death. There is also a tendency for slower physical and
intellectual development among the babies of women who smoke.
2. Passive smoker (non – smoker exposed to cigarette smoke continuously) has a higher risk of
developing lung cancer. They may inhale in as much of the harmful constituents of cigarette
smoke as a smoker because side – stream smoke is unfiltered and contains higher concentration
of harmful than main streams smoke inhaled through the cigarette.
47
3. The main signs and symptoms of the main respiratory diseases associated with smoking are:
RESPIRATORY DISEASE
CHRONIC BRONCHITIS
EMPHYSEMA
CAUSES
SIGNS AND SYMPTOMS
 Smoking: continual
 Inflammation of the membrane
exposure and inhalation of
of the trachea and the bronchi
polluted air
 excessive production of phlegm
 chronic cough
 difficulty in breathing
 lungs become susceptible to
infection
 may result in emphysema and
lung failure

Smoking, continual
exposure and inhalation of
polluted air: developed
from chronic bronchitis





LUNG CANCER

Smoking, continual
exposure and inhalation of
smoke; polluted air and
vehicle exhaust fumes






Chronic coughing from chronic,
bronchitis causes destruction of
thin alveolous walls.
Alveoli enlarged and surface
area is reduced
Lungs expand and lose elasticity
great difficulty in breathing
leading to strain on the heat
lung tissue is damaged beyond
repair
Uncontrolled growth of cells in a
small area of lungs may spread
throughout lungs and block
bronchioles
The cancerous growth may
eventually spread throughout
the body
difficulty in breathing
blood in spitum
weight loss
NOTE: These signs and
symptoms are not noticeable in
the early stages of lung cancer
OBJECTIVE: Investigate the effect of physical activity on the rate and depth of breathing
Effect of exercise on breathing
During exercise, the muscle cells respire more than they do at rest. This means:
Oxygen and glucose must be delivered to them more quickly
Waste carbon dioxide must be removed more quickly
48
This is achieved by increasing the breathing rate and heart rate. The increase in heart rate
can be detected by measuring the pulse rate. The stroke volume also increases – this is the
volume of blood pumped each beat. The total cardiac output can be calculated using the
equation:
Cardiac output = stroke volume x heart rate
During hard exercise, the oxygen supply may not be enough for the needs of the muscle
cells. When this happens, anaerobic respiration takes place, as well as aerobic respiration.
TRANSPORT IN PLASMA
TYPICAL STRUCTURE OF STEM
TYPICAL STRUCTURES OF A ROOT
FUNCTIONS OF THE MAIN TISSUES IN THE STEM AND ROOT
TYPES OF TISSUE
EPIDERMIS
PACKING TISSUE
SUPPORTING TISSUE
VASCULAR TISSUE
COMBIUM
FUCTION
 A thin layer of living cells of root and stem
 Epidermis maintain the shape and protects against bacterial or
fungal infection.
 The epidermis of roots develop projections called root hairs which
absorb water from soil
 Several layers of relatively large, thin walled living cells found in
the cortex i.e. between the epidermis and pith.
 The cells are highly permeable to water and dissolved solutes
 Intercellular air spaces in the cortex allows oxygen to diffuse into
the stem or root for cell respiration
 Starch granules may be present.
 Beneath epidermis – living cells with cellulose thickening in cell
corners
 In vascular bundle – no-living xylem vessels with cellulose and
lignin thickening
 Provide mechanical support.
 Found in the central part of the root: arranged in a ring in a
dicotyledons stems and scattered irregularly in a monocotyledons
plant
 Contains conducting tissues: xylem and phloem
 Actively dividing cells found between xylem and phloem. Cells
undergo mitotic divisions to produce new cells from growth found
in (meristems) region of active growth and cell multiplications)
Form xylem and phloem for secondary growth in older stems and
roots
49
TRANSPORT IN PLANTS
Objective: identify vascular tissues in cross sections of stem roots and leaves of dicotyledons and
monocotyledons .
1.1 Typical structures of stem
A cross section of a monocotelydonous stem

A cross section of a dicotelydonous stem
List two differences between a monocotelydonous stem and a dicotelydonous stem
1.2 Typical structures of root
A cross section of a monocotelydonous root

A cross section of a dicotelydonous root
List two differences between a monocotelydonous root and a dicotelydonous root
Transverse section of leave:
Drawing from text book
1.3 Functions of the main tissues in the stem and root:
50
Objective: Describe the structure and function of root hairs in relation to their surface area, and to
water and ions uptake.
see notes for root hair cell
51
Objective:Describe absorption of water in terms of osmosis
Water: Absorption of water:
 root hair cells absorb water
 absorption of water occurs b y process osmosis
 water molecules are highly concentrated in the soil than in root hair cell
 water molecule diffuse in root hair cells; from root hair cells molecules will diffuse into
other into other root cells;
*Objective: Describe absorption of mineral ions in terms of active transport

Mineral ions: absorption of mineral ions can occur by active transport
 If mineral ions are less concentrated in the soil than in root hair cell
 mineral ions move by active transport from the area of lower concentration
outside the root hair cell to the area of higher concentration inside the root hair
cell
 from root hair cells the mineral ions will be actively transported to other root
cells;
Objective: Describe the structure and functions of vascular tissues (xylem vessels and phloem tissues)
2.2 Xylem and Phloem
Xylem tissue is for transport of water and mineral salts from the root, through the stem and to the
leaves.
Phloem tissue are responsible for translocation of products of photosynthesis from leaves to the rest of
the plants.
52
Structure
Xylem
 Xylem consists of non-living, long, hollow
fine tube-like vessels with thick lignified
cellulose walls
 The strong lignified walls provide
mechanical support as they resist pressure
changes and prevents the vessels from
collapsing
53
Phloem
 Phloem consists of thin and
elongated living cells joined
end to end to form living long
tubes.
 The cells contain very fine
strands of cytoplasm and have
perforated end walls called
sieve plates to allow
substances to pass from cell
to cell
Objective: Define translocation as movement of substances (water; mineral ions, and organic
materials) through vascular tissue
TRANSLOCATION:

Translocation is the movement of organic soluble materials; water and mineral ions through the
phloem and the xylem.
54
3.1 Transpiration
Objective: Define transpiration as loss of water vapour from the stomata

Transpiration is the process by which water vapour is lost from the aerial part of the plant via
the stomata
*Objective: Discuss how transpiration is related to cell surfaces, stomata and intercellular air spaces.

Water is evaporated from the surface of the spongy mesophyll cells into the air spaces in the
leaf and finally diffuse through the stomata into the surrounding atmosphere
Objective: Describe transpiration stream as a process of water movement throough xylem vessels.


Transpiration pull is a suction force generated by transpiration which draws water from the soil
up the xylem vessels in the stem to the leaves of a plant.
The thin, continous column of water which flows up the plant from roots through the stem to
the leaves in the xylem vessels is called the transpiration stream
55
56
Objective: Discuss factors that affect transpiration
Objective: Discuss effect of temperature, humidity and wind on the rate of transpiration
Objective: Discuss adaptations for controlling transpiration
57
Objective: Investigate effect of temperature, humidity and wind on the rate of transpiration
Potometer:
A potometer is used to measure the rate of water uptake which can be an indirect measure of
the rate of transpiration.
A shoot inserted in a photometer can be subjected to different conditions such as:
1. lower speed of air and higher speed of air
2. lower temperature and higher temperature
3. lower humidity and higher humidity
Objective: Demonstrate wilting, a result of excessive transpiration
Wilting:
58
CIRCULATORY SYSTEM
1. The Human Transport System
OBJECTIVE: describe the circulatory system as consisting of tubes(blood vessels) with a pump
(heart) and valves to ensure one-way flow of blood
 The transport system in the human body consists of the blood, the blood vessels and
the heart.
 It is made up of a continuous sytem of blood vessels with a muscular pump (the heart)
and valves which ensures that the blood flow is always in one direction.
 The transport medium of the body is blood tissue which distributed essential
substances to body cells and collect their metabolic waste.
 The blood is circulated by the muscular contraction of the heart.
OBJECTIVE: Explain why multicellullar animals need a circulatory system
 A circulation system is required because:
 The body is multi-cellular and small surface area to volume ratio.
 Diffusion alone is far too slow a process for adequate distribution of oxygen and
dissolved food substance to substance to cells and the removal of waste from
cells.
2. The Double (Dual) Circulation System.
OBJECTIVE :Describe circulation as consisting of pulmonary and systemic circuits.




The human transport system is an efficient and complete double circulatory system.
It is made up of two main system which are connected of the heart.
 Pulmonary circulation – blood circulation from the heart to the lungs and back
to the heart.
 System circulation - blood circulation from the heart to the body parts and back
to the heart.
Therefore, in one complete circulation blood passes twice through the heart.
The heart has two halves that are completely separated by a septum.
 Therefore, there is no mixing of deoxygenated blood from the body and
oxygenated blood from the lungs.
59
OBJECTIVE: Discuss the difference between the two circuits (pulmonary and systemic) in terms of
pressure, direction of blood flow and quality of blood:
Systemic Circuit
Pulmonary Circuit
Blood is from the heart to the body parts the back
to the heart.
Blood is from the heart then to the lungs
then back to the heart
Oxygenated blood flows away from the heart
/deoxygenated blood flows towards the heart.
Oxygenated blood flows towards the heart
/deoxygenated blood flows away from the
heart.
Oxygenated blood flows along arteries and
deoxygenated blood flows along veins
Oxygenated blood flows along veins and
deoxygenated blood flows along arteries
Blood covers a longer distance
Blood covers a shorter distance
Blood is at relatively high pressure
Blood at relatively low pressure
60
3. The Structure, Function, And Action Of The Heart
OBJECTIVE: Describe the structure and function of the heart
61
Structure
Position in the heart
Function
Superior vena
cava
Main vein which comes from the
upper part of the body
Returns deoxygenated blood from the head and
upper limbs to the heart
Inferior vena
cava
Main vein which comes from the
lower part of the body
Returns deoxygenated blood from the organs
and lower limbs to the heart
Right atrium
Upper cambers from the heart
Receives deoxygenated blood from the vena
cava
Semi-lunar
valves
Found at the opening of the
pulmonary artery
Prevents back flow of blood from the pulmonary
artery into the right ventricle when the right
atrium relaxes.
Tricuspid
valve
Between right atrium and right
ventricle consists of flaps
Prevents backflow of blood to the right atrium
when the right ventricle contracts
Right ventricle
Lower chamber of the heart (right)
Pumps blood the lungs via pulmonary artery
Septum
Muscular wall separating the left
and right chambers.
Prevents mixing of deoxygenated blood in the
right side of the heart with the oxygenated
blood from the left side of the heart
Bicuspid valve
Between left atrium and left
ventricle. Consists of two flaps.
Prevents back flow of blood to the left atrium
when the left ventricle contracts.
Chordae
tendineae
Elastic tendons which attach valve
flaps to the capillary muscles.
Tendons become taut and prevent the valve
from flapping back into the atrium under the
blood pressure generated during the contraction
of the ventricles
Left ventricle
Lower chambers of the heart, the
most muscular part
Pumps blood to all parts of the body (except the
lungs) via the aorta
Left atrium
Upper chamber of the heart
Receives oxygenated blood from the lungs via
pulmonary vein
Pulmonary
artery
Arises from the top of the right
atrium , forms two branches one
each lungs
Carries deoxygenated blood from the right
ventricle to the lungs.
Pulmonary
vein
Empties into the left atrium
Carries oxygenated blood from the lungs to the
left atrium of the heart.
Aorta
Largest artery of the body
Carries oxygenated blood to all parts of the body
except the lungs.
62
Semilunar
valves
Prevents backflow of oxygenated blood from the
aorta into the left ventricle when the left
ventricle relaxes
Found at the opening of the aorta


The walls of the ventricles of the heart are more muscular than those of the atria
because the ventricles have to pump blood over a greater distance : to the lung the rest
of the body whereas the atria only pump blood into the ventricles.
The left ventricle has a much thick wall than the right ventricle because a higher
pressure is required to pump the blood to the rest of the body.
4. The Heart Beat






The heart contracts rhythmically with a period of relaxation and rest between each
contraction.
The contraction period is called systole and the relaxation period is called diastole.
During rest, a healthy adult has a heart beat rate of about 72 beats per minute.
The direction of blood flow in the major arteries and veins of the circulatory system is
shown below
The walls of the ventricles of the heart are more muscular than those of the atria because the
ventricles have to pump blood over a greater distance – to the lungs and the rest of the body
whereas the atria only pump blood into the ventricles.
The left ventricle has a much thicker wall than the right ventricles because a higher pressure is
required to pump the blood to the rest of the body.
63
ATRIAL DIASTOLE
 Both left and right atria contract and
force blood into the ventricles



Bicuspid valve of the left side of the
heart and tricuspid valve of the right
side of the heart
Semi – lunar valves of the pulmonary
artery close to prevent backflow of
blood
Left and right ventricles relax
VENTRICULAR SYSTOLE
Both left and right ventricles contract and
force blood under pressure, into the
pulmonary vein and artery respectively
Bicuspid valve and tricuspid valve close to prevent
backflow of blood into the left and right atria
respectively
Semi-lunar valves of the pulmonary artery open
Left and right ventricles
5. BLOOD PRESSURE AND PULSE RATE
OBJECTIVE: Locate pulse points and count the pulse rate
 The high blood pressure exerted on the elastic and muscular walls of the aorta during
ventricular contraction causes a wave of contraction to pass along the main arteries of the
body.
 This succession of waves can be felt as a pulse in many places where the arteries are sufficiently
superficial such as the wrist and the neck







The blood pressure is the force exerted by the blood on the walls of the blood vessels as a result
of the contraction and relaxation of the heart.
Blood pressure varies with the distance of the blood vessels from the heart, the phase of the
heartbeat, the activity and physiological state of the body and age.
Blood pressure is highest in the aorta and lowest in the veins.
Blood pressure is higher during ventricular contraction and lower during relaxation
During vigorous physical activities e.g. exercise; hormone adrenaline secreted causes an
increase in the rate of heartbeat and a rise in blood pressure.
Blood pressure increases with age.
Heart beats can be measured by counting the pulse rate.
OBJECTIVE: Investigate the effect of physical activity on pulse rate
insert tables from back part of the note book including explanation
64
 BLOOD FLOW IN VEINS IS MAINTAINED BY:
 Flow of blood from the capillaries
 Pressure from the surrounding organs, especially from the contraction and relaxation of
skeletal muscle
 Pairs of valves along the length of the veins which prevent backflow.
6. Coronary Heart Disease
OBJECTIVE: Describe coronary heart disease in terms of occlusion of coronary arteries


A heart attack or heart failure is the sudden slowing or stoppage of the heartbeat
due to severe damage or death of the heart (cardiac) muscles.
A heart attack is caused by a blockage in either of the two coronary arteries which
branch out of the aorta to supply oxygen and soluble substances to the heart
muscles.
 The blockage stops the flow of blood and deprives that part of the heart
muscles of oxygen and food.
 Less respiration will occur at the heart muscles and less energy will be
liberated.
 This will cause severe damage to the heart and failure of contraction of
the heart muscles at the affected part
 Resulting in death.
Two main conditions which cause a blockage in the coronary artery:
Atherosclerosis – The narrowing and Hardening of artery due to fatty deposits (cholesterol) on
the walls of artery.
65
Coronary thrombosis - The formation of a blood clot inside the artery. Thrombosis is more
likely to occur in narrow arteries with fatty
Occurance of both atherosclerosis and coronary thrombosis in the human body.
66
OBJECTIVE: Discuss possible causes of coronary heart diseases (diet, stress, smoking)
 The main factors which contribute to increase risk of coronary heart disease are:
Smoking - Nicotine




Increase heart rate by increasing secretion of hormone adrenalin
Constricts blood vessels increasing blood pressure
Causes blood to clot more easily
Carbon monoxide increases the rate of deposition of cholesterol and
decreases oxygen supply to heat.
67
Diet
 A diet rich in cholesterol and saturated fats results in high blood
cholesterol level.
 This increases deposition of fat on inner surface of the artery.
Stress
 Hormone adrenaline secreted under stress conditions increases heart
rate and blood pressure.
 Forceful thrust of blood makes fats to be deposited on the inner
surface of the arteries, causing narrowing of the artery.
Preventative Measures of Coronary Heart Disease
OBJECTIVE: Discuss preventative measures of coronary heart diseases
Avoid smoking :
 no nicotine in the body which and less narrowing of blood vessels
 no carbon monoxide and less atherosclerosis
Diet with less fat:
 less cholesterol and saturated fats results in high blood
 less deposition of fat on inner surface of the artery
Avoid Stress:




less adrenaline secreted
normal heart rate and normal blood pressure
less fats deposited on the inner surface of the arteries
less narrowing of the arteries.
68
THE GENERAL CIRCLATORY SYSTEM
OBJECTIVE: Name and identify the main blood vessels to and from the heart, lungs , liver and kidneys
Fig. A
69
Fig. B
****TASK****
Label fig. A above using information in Fig. B
70
THE STRUCTURE AND FUNCTIONS OF ARTERIES, VEINS AND CAPILLARIES
OBJECTIVE: compare the structure and functions of arteries, veins and capillaries
 A comparison of the structure and functions of arteries, veins and capillaries
FUNCTIONAL DIFFERENCES:
ARTERIES
VEINS
CAPILLARIES

All arteries transport
blood away from the
heart

All veins transport blood
towards the heart

Capillaries transport
blood from artery to vein

All arteries carry
oxygenated blood except
the pulmonary artery

All veins carry
deoxygenated blood
except the pulmonary
vein

They carry blood at
intermediate pressure.
The repeatedly branched
fine capillaries provide a
large surface area for
exchange of substances
between the blood and
tissue cells.
The rate of blood flow is
slow allowing maximum
time for diffusion of
substances
No pulse


Pulse is strong

No pulse

STRUCTURAL DIFFERENCES:
ARTERIES
VEINS
CAPILLARIES

Thick muscular, elastic walls

Thinner, inelastic and
less muscular walls


Walls are not permeable

Walls are not permeable


Relatively small lumens

Relatively large lumens


Circular cross-section

Oval cross - section

71
Thin, one cell thick
walls, no muscle and
elastic tissue
Walls are permeable
to tissue fluid and
phagocytes
Very small lumens
(smallest blood
vessels)
Circular cross -section
Exchange of Materials Between Capillaries and Tissue fluid
OBJECTIVE: describe the transfer of materials between capillaries and tissue fluid
 blood entering the capillary from the arteriole is at higher pressure
 fluids exude out through the capillary walls to bath cells, forming tissue fluid
 water, oxygen, glucose, phagocytes and other smaller molecules pass through the capillary
walls into tissue fluid
 carbon dioxide, urea and other wastes diffuse from the tissue fluid into the capillary
 water re-enters the capillary by osmosis
72
BLOOD
OBJECTIVE: list components of blood as red blood cells, white blood cells, platelets, and plasma
Blood consists of red blood cells, white blood cells, platelets, and plasma
OBJECTIVE: Identify red and white blood cells as seen in diagrams and/ photomicrographs.
OBJECTIVE:Describe the function of:
I.red blood cells – haemoglobin and oxygen transport
II.white blood cells – phagocytosis, antibody formation and
tissue rejection
III.platelets – fibrinogen to fibrin causing clotting
IV.plasma – transport of blood cells, ions, end products of
digestion, hormones, carbon dioxide, urea, vitamins,
plasma proteins
BLOOD CELLS:



red blood cells
white blood cells
platelets
CELL STRUCTURE
VOL/mm3
1.Red blood cell
5
SITE OF
FORMATION
Red bone marrow
BLOOD CELLS AND THEIR FUNCTIONS
million


(particularly the
ribs)
FUNCTION OF CELL
Lungs
Haemoglobin
Oxyhaemoglobin
(purplish red) (bright red) + Oxygen
a) Haemoglobin is a pigment
which contains iron. It is
capable of combining
reversibly with oxygen
b) Red blood cell has a short life
span of about 120 days. The
dead cells are broken down in
the spleen and liver. Iron is
stored in the liver and the rest
of the haemoglobin molecule
forms bile pigments
Biconcave disc without
nucleus
Has elastic cell
membrane
73
White blood cell
 large than red blood cell
 contains nucleus
1 Phagocytes
7000
million
2. Lymphocyte
PLATELET

0.25
Lymph
Engulf, ingest and digest foreign
particles.
Lymph
Produces antibodies which destroy
invading bacteria/foreign particles and
neutralize toxins produced by bacteria
Red bone marrow
Forms a temporary plug at wound or
cut. Damaged tissues and platelets
form enzyme
Throbokinase +
Calcium ions
a)
Prothrombin
thrombin
A tiny fragment of cell
without nucleus
b)
c)
thrombin
Fibrinogen
Fibrin
Fibrin mesh traps blood
cells and forms blood clot to
seal up wound
PLASMA
(Straw-colored liquid)
CONSISTS OF








water (90%)
Soluble food substances e.g glucose, amino acids,oil
droplets
mineral salts e.g sodium,calcium, chloride ions and
bicarbonate ions (HCO-3)
plasma proteins e.g fibrinogen and antibodies
waste e.g carbondioxide and urea
hormones in minute quantities e.g adrenalin and insulin
enzymes
gases in mall quantities e.g oxygen and nitrogen
74
IMMUNITY
ANTIBODY


Antibody is a protein molecule produced by the body in response to an antigen. Each different
antigen stimulates the production of the particular type of antibody that will destroy that
antigen.
Once the lymphocytes have learnt to make a particular type of antibody in response to the
antigen on an infective organism, the body begins to recover as the organisms or pathogens are
destroyed. It takes a few days to produce antibodies, so the infected individual will show some
symptoms of the disease.
LYMPHOCYTES
The types are:
B – LYMPHOCYTES – Produce antibodies
T – LYMPHOCYTES – either attack pathogens directly, or produce chemicals which coordinate
the activity of all cells in the immune system.
OBJECTIVE: explain why immunity often results after an infection or vaccination
IMMUNITY


After an infection, some lymphocytes are kept as a memory which helps the body to quickly
form antibodies that defend the body against further attacks by the same antigen/pathogen
. The memory cells may last for years, and the body is said to be immune to the disease.
VACCINES



Vaccine is an example of active artificial immunity
Vaccines are produced in several ways:
 Dead pathogens, e.g. whooping rough vaccine
 Weakened pathogens e.g. oral polio vaccine
 Genetically engineered fragments – Protein from the
pathogens surface which are recognized by lymphocytes, e.g.
hepatitis B viral coat protein
a vaccine causes formation of memory cells against a specific pathogen which will help the
body to quickly form antibodies when there is a real attack by the same pathogen
75
IMMUNITY MAY BE:
1.ACTIVE
Individual makes his or her own antibodies
NATURAL (Pathogen infects individual)

ARTIFICIAL (Weakened pathogen (vaccine)
Individual contracts disease
Vaccine does not cause disease but lymphocyte
but survives, makes
do produce antibodies.
antibodies and is now immune
Individual is now immune to this pathogen.e.g
to further infection by the same
vaccination against rubella virus ( which causes
pathogen, e.g. immunity develops
German measles) in teenage girls.
to different strains of the common cold.
76
2.PASSIVE
Individual is given ready –made antibodies
NATURAL

ARTIFICIAL
Mother antibodies cross the placenta
and are in breast milk – new born for
which mother produced antibodies e.g
gust infections.
Adult is now immune to disease used if
disease is too fast – acting for the
immune system to deal with, e.g
injection of anti tetanus antibodies
following a deep, dirty cut or wound
This offers only a temporary immunity,
since the body is not producing
antibodies.
OBJECTIVE: explain why people do not become immune to some diseases
 Some diseases have pathogens than mutate easely
 the memory cells formed in the body will form antibodies that are unable to attack the mutant
pathogen
BLOOD GROUPS AND BLOOD TRANSFUSSION
OBJECTIVE: describe the four blood group (A, B, AB, O) in terms of antigen present in the blood and
antibody production
THE ABO BLOOD GROUPING IS BASED ON:

Two antigens called agglutinogens, symbolized as A and B, are genetically determined
carbohydrate molecules carried on the surface membrane of the red blood cells.
Red blood cell
shows agglutinogen A
A
Red blood cell shows
agglutinogen B
77
Red blood cell shows
both A nor B
agglutinogen
Red blood cell
shows neither
A or B agglutinogen

Two antibodies called agglutinins, anti-A and anti – B, carried in the blood plasma.
OBJECTIVE: Discuss blood transfusion in terms of donors and recipient and precautions to be taken




A blood transfusion may be necessary to make up blood volume following hemorrhage
or during surgery.
Only compatible blood should be transfused, or agglutination and haemolysis may
occur.
Agglutinated (clumped) cells may block capillaries and cause kidney or brain damage, or
even death.
Haemolysed cells ‘leak’ haemoglobin so oxygen transport is affected.
Transfusion of Blood:
Donor
RECIPIENT
A
(anti – B)
B
(anti – A)
AB
( no anti-A and
no anti –B)
O
(anti –A and anti- B)



A
antigen A
B
antigen B
AB
antigen A and
antigen B
compatible
clumping
clumping
or
or
agglutination agglutination
O
no antigen
compatible
clumping
or
compatible
agglutination
clumping
or
agglutination
compatible
compatible
compatible
compatible
compatible
clumping
clumping
clumping
or
or
or
agglutination agglutination agglutination
compatible
An incomplete transfussion: blood group B red blood cells are clumped by anti – B
agglutinins/antibody in plasma of blood group A
The agglutinins/antibodies in the donor blood are ignored – they are in too low a concentration
to cause major damage.
AB is the universal recipient since its plasma contains no agglutinins antibodies to clump donor’s
red blood cells.
78
BLOOD RELATED DISEASES:
OBJECTIVE: discuss common blood diseases e.g. HIV/AIDS, malaria, leukemia, and anemia
OBJECTIVE: discuss how blood related diseases can be prevented
These are diseases that are related to blood. They include the following; Leukaemia, Anaemia,
haemophilia, malaria, HIV/AIDS e.t.c.
1.Leukaemia/cancer of the blood
This is overproduction of white blood cells
Many of the white blood cells fail to mature and the overproduction leads to overcrowding
of the cells out of the bone marrow cells which produce the red blood cells and the
platelets.
 This leads to bleeding (bleeding can occur in the gums, nose, and rectum.
 Other symptoms include, infection of the mouth, throat and fever, anaemia, extreme
weakness and headache, excessive bleeding in children, enlargement of lymph nodes
 The disease can be hereditary.
 Can be treated by transplanting healthy bone marrow from a close relative, after their own
bone marrow has been destroyed using radiation.
An individual who has Leukaemia has a high chance of getting HIV/AIDS why?





Weakened immune system.
Infections with HIV is not resisted
Easy for leukemia patient with HIV to develop AIDS because of few normal
lymphocytes.
2. Haemophilia
o It is a sex linked diseases linked to the males because it is carried in the X chromosome.
o A condition where the blood cannot clot and once the individual starts bleeding, without
any help he/she can die.
o Haemophiliacs may require blood transfusion for fairly minor injuries to replace lost blood
and may need to inject themselves with the missing blood clot factor.
79
3. Anaemia
All other blood related diseases show anaemia as a symptom and there are many forms of
anaemia.



This results when there are a few red blood cells in the bloodstream or if the concentration
of haemoglobin is low.
This can be due to a diet lacking iron or the inability to absorb vitamin B12 from the
alimentary canal. Pregnant women. Therefore one has to take a diet rich in iron and taking
iron supplements (in tablets).
Sickle cell anaemia: a hereditary form of anaemia where the red blood cells become
deformed and form a sickle shape. This anaemia reduces the large surface area of the red
blood cell and therefore hinders/reduces the diffusion of O2 into the red blood cell. This
usually results in extreme fatigue, pale skin, low red blood cell count and general body
weakness. The condition however is important in reducing excessive blood loss in case of
accident/injuries, lack of iron e.g. during pregnancy, and helps control plasmodium.
4.HIV/AIDS







AIDS stands for acquired immune deficiency syndrome. The disease is caused by a virus,
human immuno-deficiency virus.
The HI virus attacks the T-lymphocytes and reduces their count to very low levels.
When T-lymphocytes are too few, the body fails to fight opportunistic infections,
eventually AIDS develops.
Transmitted through exchange of body fluids such as blood and sexual fluids
Sign/symptoms: loss of weight, TB, skin cancer, prolonged diarrhea.
Treatment: ARVs to reduce viral load in blood.
Prevention: avoid exchange of body fluids with infected person, and use condoms and
gloves when handling blood.
*****For malaria check your previous notes*****
80
HOMEOSTASIS
OBJECTIVE: Define homeostasis.
1. HOMEOSTASIS is the control and maintenance of a constant internal environment around the cells
in the body despite unfavorable fluctuations in the external environment.
OBJECTIVE: locate and name the main organs which maintain a constant internal environment,
namely pancreas and liver ( blood glocuse), kidneys (water content) and skin (temperature).
2. The composition of the tissue fluid that surrounds the cells kept constant by the action of a number
of different organs which constantly regulates particular factors in the blood.
ORGANS
LUNGS
BLOOD FACTORS REGULATED
Carbon dioxide and Oxygen
KIDNEYS
Water, Urea and Excess
mineral salts
LIVER and PANCREASE
Blood glucose
SKIN AND LIVER
Temperature
MECHANISM OF CONTROL
 Breathing rate and carbon dioxide
level in blood are regulated via the
respiratory canters in the brain
 Amount of water reabsorbed by
kidney tubules is regulated in the
action of anti-diuretic hormone. Urea
and excess mineral salts are removed
from the blood and are excreted in
urine.
 Glucose level is regulated by
hormones insulin and glucagon
 A combination of involuntary actions
are controlled and coordinated by the
hypothalamus of the brain.
SKIN AND TEMPERATURE REGULATIONS
1. The functions of the skin
a) A continuous covering to protect body tissues from ultra violet radiation as well as
mechanical damage, entry of bacteria and excessive loss of water by evaporation.
b) A sense organ to detect pain, pressure changes and temperature
c) For temperature regulation to maintain a constant body temperature
d) Removes excess salts, water and urea from the body in the form of sweat as a homeostatic
organ and not an excretory one.
81
2. The structure of skin and its functions are summarized below:
OBJECTIVE: Identify and label on the diagram of the skin: hairs, sweat, sweat glands receptors
and blood vessels
PARTS OF SKIN
FUNCTIONS
EPIDERMIS
1. Cornified layer

Protect layer
Top most layer which consists of flat, dead cells that continually
wear off.
2. Granular layer

Contains living cells which is gradually pushed up to replace the
worn – out cells in the cornified layer.

DERMIS

SEBACIOUS GLANDS

Contains actively dividing cells to produce new epidermis. Has
pigment melanin that gives skin its colour and absorbs ultra
violet radiation
A layer of connective tissue with many collagen fibres and some
elastic fibres. It contains most of the important structures found
in skin.
Secrete oily sebum to lubricate skin
HAIR FOLLICLE AND HAIR

A deep pit of granular and malpighian layer where cells multiply
3. Malpighian layer
82
ERECTOR MUSCLE
SWEAT GLANDS
SENSORY NERVE ENDINGS
BLOOD CAPILLARIES




to form a hair inside the follicle
Controls the erection of hair- contracts to raise the hair and
relaxes to make the hair lie down.
Absorbs salts and water from blood capillaries to produce sweat
for temperature regulation and excretion
Detect pain, changes in temperature and pressure on skin
Regulate temperature by vascular constriction or dilation.
3. A negative feed back mechanism is used in homeostasis. A summary of this mechanism used is
illustrated by the diagram below.
Hypothalamus:
OBJECTIVE: Discuss the coordinating role of the brain in maintaining a constant body temperature




In the hypothalamus there is a thermoregulatory center
The thermoregulatory center monitors the temperature of the blood passing through it and also
receives sensory nerve impulses from temperature receptors in the skin.
A rise in body temperature is detected by the thermoregulatory center of hypothalamus:
 It then sends nerve impulses to the skin which results in vasodilation and sweating
A fall in body temperature is detected by the thermoregulatory center of hypothalamus:
 It then sends nerve impulses to the skin which results in vasoconstriction, minimal
sweating and decrease of exothermic reactions of the liver.
83
4. THE ROLE OF THE SKIN IN TEMPERATURE REGULATION
Temperature of blood
decreases
1. Increase production of sweat, evaporation of liquid in sweat,
latent heat energy lost from the body, the body cools
2. Hair erector muscles relax, hair lie close to skin surface
(for furry mammals only).
3. Blood arterioles near surface of skin dilate (vasodilation)
more blood flows closer to skin , more heat lost from the
body by radiation.
4. Metabolic rate decreases
stimulates
Normal blood
Rise in temperature of blood stimulates
Hypothalamus
(brain)
stimulates
temperature
Drop in temperature of blood
Temperature of blood
increases
1. Shivering occurs, contraction of muscle fibres , friction
between muscle fibres, heat released
2. Hair erector muscles contract, hairs stand on ends forming
an insulating layer of air between hairs (for furry mammals
only).
3.Blood arterioles near surface of skin constrict
(vasoconstriction),less blood flows closer to skin surface of
skin. Less heat lost by the radiation.
4. Metabolic rate reaction in the liver (exothermic reactions)
84
Hypothalamus
(brain)
85
EXCRETION
OBJECTIVE: Define excrtion as given below
1. Excretion is the removal of metabolic waste products and toxic materials from organisms, to
maintain constant internal environment.
2. The accumulation of these substances can interfere with the proper functioning of cells and
change the concentration of tissue fluid around.
3. A variety of excretory products are removed from the body by the excretory organs.
EXCRETORY ORGANS
Lungs
Kidneys
Liver
TYPES OF WASTE EXCRETED
Carbon dioxide
Urea, excess water, and mineral salts
Urea ( from the breakdown of amino acids),
pigment
Heat, excess water, mineral salts and urea
Skin
4. Used hormones, drugs and toxic substances such as alcohol are also excreted.
THE HUMAN URINARY SYSTEM
OBJECTIVE: Identify parts of the urinary system: kidneys, ureter,bladder; urethra.
86
OBJECTIVE: Describe the functions of : kidneys, ureter, bladder; urethra.
STRUCTURE
KIDNEY
RENAL ARTERY
RENAL VEIN
URETER
BLADDER
SPINCHER MUSCLE
URETHRA
FUNCTIONS
 Filters blood and excretes nitrogenous wastes, excess salts and
water as urine
 Branching from the aorta, the renal artery carries oxygenated
blood to the kidney
 Carries deoxygenated blood away from the kidney to the vena
cava
 Peristallic waves of contraction in the thin tube carries urine
produced by the kidneys to the urinary bladder
 A distensible sac in which urine is temporarily stored
 Voluntarily relaxes to release urine from the bladder
 Passage of urine out of the body is through the urethra
STRUCTURE AND FUNCTIONS OF THE MAMMALIAN KIDNEY
1. The kidney contains about one million microscopic urine formation units called kidney tubules
or nephrons.
STRUCTURE OF KIDNEY
OBJECTIVE: Draw and label a cross section of a mammalian kidney
87
2. The various regions in the internal structure of the mammalian kidney and their functions are
summarized in Table 2
REGION IN THE KIDNEY
Outer Cortex ( dark colour)
FUNCTION
 Contains the Brownman’s capsules and
glomeruliol.
 The nephrons. The dark colour is due to
the millions of coiled capillaries of the
glomeruli.
 Contains U – Shaped top of hale and the
collecting dusts
 Cone shaped areas in medulla where
urine produced by the kidney tubules
drain into the pelvis of the ureter.
 Funnel – Shaped spaces formed by the
top of the ureter collects urine.
 Peristaltic waves of contraction in the
thin tube carries urine produced by the
kidneys to the bladder.
INNER MEDULLA( light clour)
PYRAMIDS
PELVIS
URETER
STRUCTURE OF A KIDNEY NEPHRON
OBJECTIVE: Discuss the structure and function of the nephron
88
FORMATION OF URINE
OBJECTIVE: Describe the removal of water and urea through the kidneys.
1. Urine is formed in two stages
a) HIGH BLOOD FILTRATION (ULTRAFILTRATION)
 The blood in the glomerulus of Browman’s capsule is under high pressure. This causes the
plasma of the blood to filter through thin capillary walls and to collect in the Browman’s capsule.
The filtrate contains glucose, amino acids, salts and nitrogenous products dissolved in water.
Blood cells and blood proteins remain in the capillaries
2. SELECTIVE REABSORPTION
 As the filtrate flows down the nephron, all useful substances such as glucose, amino acids, salts
and water required by the body are reabsorbed back into the network capillaries surrounding
the coiled parts of the tubules.
 This reabsorption process is against the concentration gradient (active transport) and therefore,
requires energy from respiration within the cells of the nephron.
 The remaining liquid, which is urine, passes down the collecting duct to the renal pelvis.
3. The composition of liquids at different regions of the nephron
89
SUBSTANCE
Water
Glucose
Mineral Salts
Urea
Proteins
% IN PLASMA
90 – 93
0.1
0.35
0.03
7-9
% IN BROWMAN’S CAPSULE
99
0.1
0.35
0.03
0
% IN URINE
95
0
2
2
0
4. The actual composition of urine fluctuates depending on the changes in the amount of water
and concentration of substances dissolved in the blood entering the kidney. If there is excess
water in the blood, less water is reabsorbed by the kidney tubules and urine becomes more
dilute. If blood is more concentrated, more water is reabsorbed by the kidney tubules and urine
becomes more concentrated and smaller in volume.
5. The hormone ADH (anti – diuretic hormone) controls the re-absorption of water by altering the
permeability of the cell membranes of the kidney tubules.
 More solute concentrated blood results in pituitary gland secreting more ADH. Increase
of levels of ADH in blood make the walls of the nephrons more permeable to water
molecules , therefore more re-absorption of water into the blood stream. Urine
becomes more concentrated and smaller in volume.
 More dilute blood results in pituitary gland secreting less ADH. Decrease of levels of
ADH in blood make the walls of the nephrons less permeable to water molecules,
therefore less re-absorption of water into the blood stream. Urine becomes more
dilute and large in volume.
KIDNEY FAILURE AND THE DIALYSIS MACHINE
*OBJECTIVE: Describe dialysis in kidney machines as the diffusion of waste products and salts
(small molecules) through a partially or selectively permeable membrane.
1. Kidney diseases can reduce the efficiency of the kidney and can cause kidney failure. One or
both kidneys may cease to function properly. A person with one functional kidney can survive
and leave a more or less normal life but failure of both kidneys results in the accumulation of
nitrogenous waste and toxins leading to death.
2. The condition can be alleviated by the use of a dialysis machine or an artificial kidney which
eliminates the excess salts and nitrogenous waste from the patient’s blood.
90
a.
The patient’s blood is led from the radial artery in his arm through the coiled
cellophane tube in the dialysis machine and then returned to a vein in the same arm. The
cellophane tubule is a partially permeable membrane which allows small molecules of dissolved
substances to diffuse through and prevents the passage of blood cells and large proteins.
b.
The coiled cellophane tube is bathed in a sterile dialysis fluid which contains a
carefully regulated amount of dissolved salts and sugars with a composition similar to the blood
plasma ( without nitrogenous waste.)
A diffusion gradient is set up and nitrogenous waste, excess mineral salts and other toxins
diffuse from patient’s blood across the cellophane into the dialysis fluid.
91
The dialysis fluid is changed regularly to remove the waste substances and to maintain the
diffusion gradient between the patient’s blood and the dialysis fluid. The temperature of the
dialysis fluid is maintained at body temperature.
3.
Patients with permanent kidney failure become totally dependent on the kidney
machine. They have to keep a strict diet (restricted salt, water and protein) and usually undergo
3 sessions of dialysis per week for 4 – 5 hours per session.
Patients suffer from tiredness, anemia, develop bone problems and risk being infected by diseases
transmitted by blood such as AIDS. The stress and difficulty in accepting and adjusting to a rigid a
restricted lifestyle and poor employment opportunities can cause psychological problems.
4.
An alternative treatment is a KIDNEY TRANSPLANT
92
THE NERVOUS SYSTEM
1.
The main function of the nervous system is to transmit messages. ( Carried via
nerves) rapidly from one part of the body to another and to coordinate the organism’s actions.
OBJECTIVE: Discuss the relationship of sensory (receptor) cells, sense organs and the effector
organs.
The human body has sensory organs with receptor cells that generate electrical /nerve impulses
when stimulated by specific stimuli. The nerve impulses are sent to the effectors that change to
make a response.
The table below shows the relationship between sensory organs and the stimulus
Sensory Organ
Receptor cell
Stimulus
Eye
photo receptors
light
ear
sound receptors
sound
nose
chemo receptors
chemicals
Skin
pressure receptors
pressure
pain receptors
pain
thermo receptors
temperature
chemo receptors
chemicals
tongue
2.
Composition of the nervous system: Comprises of the Central nervous system and
the peripheral nervous system. Central nervous system comprises of the brain and the spinal
cord. The peripheral nervous system comprises of the cranial nerves and the spinal nerves.
93
NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
PEREPHERAL NERVOUS SYSTEM
(CNS)
Brain is protected by
Spinal cord is protected
Cranial nerves
Spinal nerve
cranium
by vertebral column
that arise from the brain
that arise from
the surface
cord.
OBJECTIVE: Discuss the principle of detecting change in the environment and responding to it.
3. Changes in the environment are called stimuli ( singular stimulus) and they are detected by
receptors with special types of nerves ends. Receptors transmit a message via a nerve to the
central nervous system (CNS). The CNS which consists of the brain and the spinal cord causes a
response brought about by the effectors. An effector may be a gland or a muscle which
responds to the stimulus. The whole process is represented in the fig. below.
CNS
sensory nerve
stimulus
motor nerve
Effector (muscles or glands)
receptor cells
94
4. The CNS interacts with the peripheral nervous system, both receiving and sending messages.
The pheripheral nervous system is made up of all the nerves which connect the body to the CNS.
The cranial nerves supply areas in the head such as the eyes and ears, and the spinal nerves
supply areas in the rest of the body such as the arms and legs.
5. The brain and the spinal cord are surrounded by cerebrospinal fluid which acts as a shock
absorber and a source of nutrients for the nerve cells.
NEURONES AND NERVOUS IMPULSES
 A nerve is made up of hundreds of microscopic nerve cells bundled together called neurons.
 A neurone is the basic unit of the nervous system. Neurones link the receptors, the CNS and the
effectors together. A neurone consists of 3 main parts;
a. CELL BODY –Contains the cell membrane, cytoplasm and the nucleus. They are grey in colour
and make up the grey matter of the brain and spinal cord.
b. AXON – A long fibre that extends from the cell body to the effector and carries impulses away
from the cell body. The impulses are carried over long or short distances depending on its
length. The axon is surrounded by a fatty structure called a myelin sheath and has small
constrictions along its length called Nodes of Ranvier.
The myelin sheath acts as an electrical insulator and helps to speed up the transmission of
impulses.
At the end of an axon are terminals that release neurotransmitters which are chemicals that
cause the effectors to act. They are white in colour and make up the white matter of the brain
and spinal cord.
c. DENDRONS – Dendrons arise from the cell body and branch to small, fine fibres called the
dendrites. They receive messages from axons of other neurones and carry these impulses
towards the cell body.
THERE ARE THREE TYPES OF NEURONES IN THE HUMAN NERVOUS SYSTEM:
1. SENSORY NEURONES
OBJECTIVE: Describe the function of a sensory neurone.


Transmit messages from the sensory receptors to the CNS. Receptors are the ends of
terminals of sensory.
They have a long Dendron and short axon. Their cell body’s are found outside the CNS in the
dorsal root ganglion of the spinal cord.
95
OBJECTIVE: Draw a labelled diagram of a sensory neurone.
2. MOTOR NEURONES:
OBJECTIVE: Describe the function of a motor neurone


Transmit messages from the CNS to effector ( muscles and glands). They link intermediate
(relay) neurones in the CNS to effectors.
They have long axons and short dendrons. Their axons branch repeatedly in the muscle it is
supplying, with each branch terminating in a motor end place on a single muscle fibre.
OBJECTIVE: Draw a labelled diagram of a motor neurone.
96
3. INTERMEDIATE ( RELAY) NEURONES
OBJECTIVE: Describe the function of a relay neurone

They are found in the brain and spinalcord where they link the
sensory neurons with the motor neurones. They transmit messages directly from sensory to
motor neurones in the CNS.
OBJECTIVE: Draw a labelled diagram of a relay neurone.


Nervous impulses are generated by direct electrical stimulation
or by a variety of different stimuli such as pressure, temperature, chemicals, pain, light
e.t.c. These stimuli will initiate nervous impulses to occur in the appropriate receptors.
Neurones transmit messages in the form of electrical impulses.
An electrical impulse is a wave of electrical charge (caused by chemical changes in and
around the neurone). It is known as a nervous impulses. Transmission of nervous
impulse requires energy from aerobic respiration.
Nervous impulses travel rapidly in one direction starting at the dendrites and finishing at
the axon of each neurone.
97
THE SPINAL CORD
The spinal cord is the continuation of the brain. It is dorsal in
position and occupies the neural canal of the vertebral column, protected by the
vertebrae. It is surrounded by protective membranes and cerebrospinal fluid.

Between the vertebrae, spinal nerves arising from the spinal
cord merge and run to all parts of the body concerned with spinal reflexes. All the
sensory fibres enter through the dorsal root of the spinal cord. The motor fibres
enter through the ventral root of the spinal cord. The cell bodies of all the sensory
fibres are situated in the dorsal root forming dorsal root ganglion.

It is composed of white matter ( composed of nerve fibres)
enclosing the central portion of grey matter ( composed of nerve cells of motor and
intermediate neurones). A central canal which is continuous with the cavities in the
brain runs through the centre of the spinal cord and contains cerebrospinal fluid.

The spinal cord receives and transmits messages to and the
brain. It coordinates body reflex arcs which occur via the spinal cord. The spinal
nerves carry snsory impulses to the brain or motor impulses from the brain to the
effector organs of the body.

98
THE SYNAPE




A synape is a tiny space at the junction between the axon terminal of one
neurone and the dendrites of the next neurone or effector cell.
When a nervous impulse reaches the terminals of an axon, it stimulates the
secretion of minute amounts of chemicals called neurotransmitters such as
acetylcholine. The neurotransmitters are contained in small vesicles within the
terminal of the axon.
The chemical quickly diffuses across the synapse and activates a new impulse in
the next neurone. The neurone transmitters are then broken down by enzymes.
The higher the frequency of the nervous impulse, the greater the amount of
neurotransmitters formed.
99
TYPES OF REACTIONS
THERE ARE THREE MAIN TYPES OF REACTIONS IN THE HUMAN NEVOUS SYSTEM
1.
VOLUNTARY ACTIONS
These are under the conscious control of the cerebral cortex of the brain. They are
intelligent responses which require conscious effort and involve processing of
information and conscious decision.
2.
THE INVOLUNTARY
These are rapid actions not under conscious control of the brain. They are automatic,
inborn, instinctive and learned responses to external stimulus which have a high survival
value e.g immediate and rapid response to danger.
Examples of reflex actions: blinking, yawning, knee jerk, sneezing, coughing, secretion,
breathing, withdrawing hands from a hot object pupils responding to light intensity
changes.
OBJECTIVE: Demonstrate and describe a reflex action
3.
REFLECTION ACTION – involuntary, Rapid action that often lack thinking, does
not involve the brain, uncontrolled, protects the body from danger.
There are two types of reflex action:
Spinal reflex – Nervous impulses in these automatic responses pass through the spinal
cord and do not involve the brain ( below the neck
Stimulus
receptors
sensory
neurones
relay neurones
in spinal cord
motor
neurones
effector
Cranial reflex – Nervous impulses in these automatic responses pass through the brain
and the brain can control and coordinate reflex
100
Stimulus
receptors
sensory
relay neurone
neurones in brain
motor
neurone
effector
Examples of cranial reflexes are blinking, yawnings, secretion of saliva.
An external stimulus such as the sight of a sharp object approaching the eye is detected
by the photoreceptors in the retina of the eye and initiates nerve impulses in the
sensory neurones. The nerve impulses travel along sensory neurones, which join to form
the optic nerve, to the visual region in the cerebral cortex of the brain. The processed
information is sent out of the brain and is carried by motor neurones to the eyelid
muscles which contract to close the eyelids to protect eyes.
A reflex arc is the route or pathway along which nervous impulses travel, bringing about a
reflex action (pathway of impulses during a reflex action).
OBJECTIVE: Describe, with the aid of a labelled diagram, a reflex arc.
1.
A typical knee jerk reflex arc is shown below
101
2.
Touching a hot object reflex arc
OBJECTIVE: Measure and explain reaction time.
Reaction time: Time taken for a stimulus to cause a response. It is not very easy to measure the time.
Experiment 1. Reaction time
It is necessary to work in pairs for this experiment.
(a) Copy Table 1 into your notebook
(b) The subject marks a pencil line down the centre of his thumb-nail and sits sideways at a bench or
table with the forearm resting flat on the bench and the hand over the edge (Fig. 1).
(c) The experimenter holds a ruler vertically between the subject's first finger and thumb with the zero
opposite the line on the thumb but not quite touching either the thumb or fingers.
(d) The subject watches the zero mark and, as soon as the experimenter releases the ruler, the subject
grips it between finger and thumb to stop it falling any further. The distance on the ruler opposite the
mark on the thumb is recorded in column 2 of Table 1.
(e) This is repeated 4 times and the average distance calculated. This distance can be converted to a
time by consulting Table 3.
(f) The ruler is now used to measure the distance from the subject's eye to the base of the neck
and along the arm to the middle of the forearm. This distance is recorded in the table.
(g) The experiment is now repeated with the same subject but this time the subject lets the ruler rest
lightly against the thumb or fingers, with closed eyes, and grips the ruler as quickly as possible after he
or she feels it begin to fall. The experiment is repeated 4 times and the results recorded in column 4 of
Table 1.
(h) The total distance is measured from the finger-tips to the head, and the head to forearm, and
recorded in the table.
102
(i) Copy Table 2 into your notebook and collect the reaction times for your class and calculate the
average in both cases.
Table 1
Speed of response
Speed of response
to sight
to touch
1
1
2
2
3
3
4
4
Total
Total
Average
Average
Time
Time
Distance
(nerve
pathway)
Distance
(nerve
pathway)
THE STRUCTURE AND FUNCTIONS OF THE HUMAN BRAIN
1.
The brain is a direct continuation of the spinal cord and consists of three main
parts.
OBJECTIVE: Identify and label on diagram of the human central nervous system the cerebrum,
cerebellum, pituitary gland, hypothalamus, medulla and spinal cord.
*OBJECTIVE: Describe the function of the cerebrum, cerebellum, pituitary gland, hypothalamus,
medulla and spinal cord.
103
The main parts of the human brain and their function are summarized in that follows:
PARTS OF THE BRAIN
CEREBRUM
(FORE – BRAIN)
CEREBELLUM
MEDULLA OBLONGATA
HYPOTHALAMUS
PITUARY GLAND
( the master gland)
STRUCTURE AND FUNCTIONS

Consists of 2 cerebral hemispheres that make up 70%
of brain. The cerebral cortex (outer surface) of the
hemispheres is covered by grey matter and has many
folding which dramatically increase the amount of
surface area for grey matter.

Controls all voluntary actions. Cerebral cortex is
divided into regions containing specialized groups of
neurones responsible for generating and coordinating
sensations such as touch, vision, hearing, taste and
smell.

Responsible for human intelligence, reasoning,
speech, processing and storage of information.

The left cerebral hemisphere is responsible for
coordinating actions on the right side of the body and
the right cerebral hemisphere controls the left side of
the body.

Controls and coordinates muscles to maintain
balance and make precise movements.

Part of the brain stem. Controls involuntary (
automatic) functions such as heartbeat, breathing
movements blood circulation etc.

Controls blood pressure, heart rate and peristaltic
movements in the alimentary canal.

Contains osmoreceptors and thermal receptors to
detect changes in the concentration and temperature of
blood to help regulate water balance and temperature to
maintain a constant environment in the body.

Also responsible for feelings of pleasure and pain.

An endocrine gland which secrets a number of
hormones directly into the bloodstream to control and
regulate various body’s activities:
1.
Growth hormone which controls the rate of bone
growth
2.
Thyroid – stimulating hormone which stimulates the
thyroid gland to secrete hormone. Thyroxine influence
growth (especially in childhood) by controlling respiration
and the rate of metabolic process.
3.
Gonad - stimulating hormone which stimulates the
gonads (ovaries and testes) to secrete sex hormones.
4.
Anti – diuretic hormone which promotes
reabsorption of water in kidney nephrons and reduces
urine volume
104
THE HUMAN EYE
STRUCTURE AND FUNCTION OF THE HUMAN EYE
OBJECTIVE: Describe the gross structure of the eyes as seen in front view
OBJECTIVE: Draw and label the longitudinal section of the eye
a.)
Each eye is set in a deep cavity called the orbit in the skull that encloses and protects
all except the front of the eyeball. The main parts of the human eye and their functions
are summarized in Table 1.
PART OF THE EYE
EYELID AND EYELASH
DESCRIPTIONS AND FUNCTIONS

Eyelid opens under voluntary or reflex action to
protect the eye. Blinking (rapid reflex) serves to
distribute tears over the surface of the eye to keep
conjunctiva clean and moist. It also protects the eye
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CONJUCTIVA


SCEROTIC LAYER ( Sclera)

CORNEA

CHOROID LAYER
( CHOROID)

RETINA

YELLOW SPOT

( FORVEA CENTRALIS)
BLIND SPOT


OPTIC NERVE


LENS

CILIARY BODY
(muscle)
SUSPENSORY LIGAMNETS


from injury.
Eyelash traps large air –borne particles.
A thin transparent epithelium covering exposed
parts of the eye including the front of the sclera. It is
a self – repairing skin kept moist and clean by tears
and reflex blinking movements
A tough, non elastic fibrous coat on the outside of
eyeball. It is opaque and helps to maintain the shape
of the eyeball by exerting an opposing force against
the outward pressure exerted by aqueous and
vitreous humor
A transparent region in the front part of the
sclerotic coat. The curved surface of the cornea
refracts light passing through and causes light rays to
converge at the lens.
A layer of tissue lining the inside of the sclerotic
coat. It contains black pigment which prevents
internal reflection of light in the eye and carries a
network of blood vessels which supply oxygen and
nutrients to the eye.
A light – sensitive layer of the eye made of
specialized nerve cells ( photoreceptors): rods ( for
black and white vision) and the cones ( for bright
light and colour vision)
The region of the retina where most cones are
located.
Most light sensitive region for sharp colour vision
A non – photosensitive disc that is devoid of light
sensitive cells. It is the region where nerve fibres
connecting the rods and cones leave the eye as the
optic nerve.
Made up of sensory nerve fibres from rods and
cones in the retina.
It transmits impulses initiated by different
wavelengths of light to the visual region of the brain
where the information is processed to form an
image.
Made up of soft transparent and elastic material
which refracts light entering the eye onto the
retina. It can become more or less biconvex to focus
light from near or fat objects on retina.
A ring of muscle fibres which alter the shape of
the lens for focusing.
They hold lens in place and connect the lens to
the cilliary body.
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IRIS

PUPIL

AQUEOUS HUMOUR


VITREOUS HUMOUR

TEAR GLAND




EYE MUSCLES
The coloured part of the eye which regulates the
amount of light entering the eye. It consists of radial
and circular involuntary muscles which act
antagonistically to change the size of pupil.
The round hole at the centre of the iris through
which light passes from the front to the back of
eyes.
A transport watery liquid in the front cavity of
eye. It acts as a medium for the diffusion of oxygen
and nutrients from the network of blood vessels in
the chroid layer to the cornea and the lens.
Also helps to refract light which enters eye and
maintains the shape of the eyeball.
A transparent jelly (mainly protein) in the rear
cavity of eye exerts an outward pressure on the
eyeball to maintain the shape of the eye.
Also helps to refract light which enters eye
Exocrine gland which secretes tears - a protective
anti- bacterial fluid to lubricate the conjunctiva and
cornea of the eye.
Hold eyes in place in their orbits
Allow coordinated movements on both eyes in
their sockets.
b). PHOTORECEPTIVE NERVE CELLS
The table below summarises the differences in the action of two kinds of light sensitive
nerve cells in the retina of the human eye.
CHARACTERISTIC
SHAPE
NUMBERS
TYPE OF VISION
CONES




Cone shaped
About 7 million
Highly
concentrated and
closely packed at the
centre of the retina,
particularly in the
yellow spot
Respond to high light
intensity and sharp
colour vision,
effectiveness decreases
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RODS





Rod - shaped
About 12 million
Less closely packed
than cones in the
more peripheral parts
of the retina
Insensitive to
colour, Produces
black and white and
less distinct vision.
Responsible for
night/dim light vision.
Contain a pigment
called visual purple (


as light intensity
decreases
Three kinds of cone
present, each is
particularly sensitive to
blue, green or yellow
light.
The different degree
and proportion of
stimulation of these
cones by different
wave length of light is
interpreted and
distinguished by the
brain as different
colours.
requires Vit A for
formation) which
bleaches (breaks
down) in bright light
and reforms in the
dark.
The difference in action of two kinds of light sensitive nerve cells in the retina of the human
eye.
c). IMAGE FORMATION
1. Light rays from objects enter the eye are refracted by the cornea, the lens, the
aqueous and vitreous humours and becomes, focused on to the retina.
2. The image formed on the retina is real, upside – down and diminished. The light
falling on the retina stimulates the photoreceptors in the retina and initiates nerve
impulses. These nerve impulses carry information about the object focused. The
nerve impulses are interpreted and translated into a three dimensional, upright and
coloured image in action. The image is, however, temporary unlike that of the image
in a camera which can be recorded permanently on a film.
3. Each eye sees a slightly different view and sends a set of impulses to the brain. The
brain puts the two views together from each eye into one three dimensional
impression or stereoscopic view. Stereoscopic or three dimensional vision makes it
possible for humans to judge distances up to about 50 metres.
ACCOMODATION
OBJECTIVE: Discuss how the eye produces a focused image of near and distant objects
(accommodation)
1.
Accommodation is the adjustments made in the eye to focus on near or distinct
objects sharply on the retina.
2.
In the eye, focusing is accomplished by the refraction of the light by the cornea and
most importantly, the lens of the eye. The curvature of the lens can be altered by the
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action of the cilliary muscles in the cilliary body so that light is always focused onto the
retina.
Distant objects
Near objects
a.)
b.)
c.)
Cilliary muscles relax
Suspensory ligaments become taut
Lens stretches to a longer and flatter
shape i.e less convex and refracts
light less
d.) Circular muscles fibres in the iris
contract, the size of the pupil is
reduced and less light is admitted.
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a.) Cilliary muscles contract
b.) Suspensory ligaments slacken
c.) lens shortens and become
thicker i.e more convex and
refracts light more
d.) Circular muscles fibres in the iris
relax, the size of the pupil is
increased and more is admitted.
CONTROL OF LIGHT INTENSITY
OBJECTIVE: Describe the pupil reflex in response to bright and dim light
1. The size of the pupil changes with changing light conditions. The pupil dilates in the
dark and constricts in bright light to protect the retina from damage by high light
intensity.
2. The regulations of the size of the pupil by the circular and radial muscles in the iris is a
reflex action with light acting as a stimulus. Each eye makes the same adjustment
depending on the intensity of the light stimulus.
Dim
light
Bright light
drawing
a.)Circular muscles relax, radial
muscles contract
b.) Pupil dilates (widens)
c.) More light is admitted into the eye,
brightness of image
drawing
a.) Circular muscles contract, radial muscles
relax
b.) Pupil constricts (narrows)
c.) Less light is admitted into the eye, increases
110
HORMONES
OBJECTIVE: Define a hormone
1. A hormone is a chemical substance, produced directly into the blood stream by
a ductless gland, carried by blood, which alters the activity of one of more target
organs..
2. Hormones are secreted by the endocrine system which consists of ductless
glands called endocrine glands. Each endocrine gland produces a particular
hormone or hormones and each hormone affects the body in a different way.
3. Hormones are produced in minute concentrations and their effect lasts longer
than nerve impulses.
4. Spent hormones are destroyed by the liver.
5. Both the endocrine and nervous system coordinate the body’s activities in
different ways.
*OBJECTIVE: Compare the nervous system and the endocrine system
A comparison of nervous control and hormonal control in the body is shown below:
NERVOUS CONTROL
HORMONAL CONTROL
Message
Electrical impulses
Chemical messenger Hormone
Rate of conduction
Rapid
Usually slower
Conductor
Neurones
Blood plasma (blood stream)
Effectors
Specific effectors, mainly
muscles or glands
specific target organ(s) or
whole body
Type of response
Responses are localised
Responses may be widespread
e.g. effect of adrenaline
Duration of reponse
Rapid and Short term
Often slow long lasting e.g
growth, sexual development
Type of control
Both voluntary and
involuntary
Involuntary control
OBJECTIVE: Identify and label on diagram the endocrine glands of the human body
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MAIN ENDOCRINE GLANDS AND THEIR FUNCTIONS
OBJECTIVE: Name the hormone produced by the endocrine glands in the human body .
ENDOCRINE GLAND
PITUATARY GLAND
HORMONE
FUNCTION

Growth hormone

Controls the rate of bone
growth

Thyroid –
stimulating
hormone
Ganad stimulating
hormone
Anti - diuretic
hormone

Stimulates the thyroid gland to
secrete thyroxine

Thyroxine

Stimulates the gonads (ovaries
and testes) to secrete sex
hormones.
Promotes reabsorption of
water in kidney nephrons and
reduces urine volume
Influences growth (especially in
childhood) by controlling
respiration and rate of
metabolic process.
( MASTER GLAND)


THYROID GLAND

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
PANCREAS
1. insulin
3. Glucagon
ADRENALINE GLANDS

Adrenaline
OVARIES

Oestrogen

Progesterone

Testosterone
TESTES
2. Regulates the amount of blood
glucose. Promoting the storage
of excess glucose as glycogen in
liver and muscles
4. Regulates the amount of blood
glucose by promoting
conversion of glycogen in liver
and muscles to glucose when
concentration of blood glucose
is low
 Prepares the body for action
and emergency
 Controls ovulation and
secondary sexual characteristics
 Responsible for thickening of
uterus lining after ovulation
 Controls sperm production and
secondary sexual characteristics
ACTION OF ADRENALINE
OBJECTIVE: Discuss the functions of adrenaline
1) Adrenaline is secreted by the adrenal medulla (inner region) of the two glands, each of
which is located just above each of the kidneys.
2) Adrenaline is secreted during
a.) emotional excitement, anger, stress or fear
b.) situations that require sudden bursts of physical activity.
The sensory receptors detect the stimuli and initiates nerve impulses that are sent to
the hypothalamus of the brain which sends nerve impulses to stimulate the adrenaline
gland to produce adrenaline.
3) THE EFFECTS OF ADRENALINE ON THE BODY ARE:
a.) Increased heart rate and breathing rate so that oxygen and glucose are carried faster to
the muscles.
b.) Dilation of the pupils of eyes
c.) Constriction of blood vessels to the skin and digestive system and dilation of blood
vessels to the muscles and brain results in more blood directed to the muscles and
brain.
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d.) Increasing blood glucose level due to conversion of glycogen stored in liver to glucose.
e.) Increased metabolic rate to release more energy to cope with the situation.
f.) Contraction of hair erector muscle producing ( goose pimples) on skin
The overall effect is to prepare the body for fight or flight.
CONTROL OF BLOOD GLUCOSE LEVEL BY INSULIN AND GLUCAGON
OBJECTIVE: Discuss the functions of insulin
1.) Insulin is secreted by the islets of Langerhans in the pancrease
2.) Insulin controls blood sugar level by increasing the rate at which liver converts glucose to
glycogen and the utilization of glucose by cells. Insulin also increases the rate of uptake
and metabolisation of glucose by the muscles.
3.) Diabetis (Diabetis mellitus) is a disease caused by the failure of pancrease to secrete sufficient
insulin to regulate the blood glucose level. The signs and symptoms of the disease are:
a.) High blood glucose levels
b.) Glucose excreted in urine
c.) Persistent redness
d.) Loss of weight
e.) Increased thirst
OTHER COMPLICATIONS INCLUDE:
a.) Premature thickening and narrowing of arteries causing poor blood to vital organs resulting in
high blood pressure, heart attack, blindness and poor healing of wounds which may develop in
to gangrene which requires amputation of limb.
b.) Diabetes can be treated by regular injection of insulin and controlling the intake of
carbohydrates in the diet.
4.) Summary of the homeostatic regulations of blood glucose level:
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increases
Pancrease secretes more insulin
which causes liver to convert excess
glucoses to glycogen. Insulin also
increases the metabolism of glucose
in cells:
increases uptake of glucose
of in cells
It promotes the convertion of glu
-cose to fats; slows down the conv
-ersion of protein to glucose
Returns to normal
Normal glucose
normal glucose
Concentration in blood
Concentration in blood
decreases
Pancrease secretes more glucagon which
Retuns to normal
causes liver cells to convert glycogen to
glucose.
It stimulates the breakdown of proteins fats to carbohydrates.
 Both glucagon and adrenalin activi
-vates enzyme which stimulate brea
-kdown of glycogen to glucose

OBJECTIVE: Discuss the functions of glucagon
1).Glucagon is release in response to a fall of blood glucose level in.
2). Glucagon makes liver cells to convert glycogen to glucose.
3). It stimulates conversion of proteins and fats carbohydrates/glucose.
4). The hormone adrenaline accelerates the conversion of glycogen in liver to glucose
during emotional excitement and dangerous situations.
5). Action of glucagon is similar to that of adrenaline.
115
OBJECTIVE: Discuss the functions of testosterone and oestrogen
Secondary sexual characteristics of male and female developed by sex hormones:
HORMONE
Testosterone
(Male 12 – 16
years puberty)
Oestrogen
(Female 10 – 14
years puberty)
above 42
Years
SEXUAL DEVELOPMENTS
Pituitary gland secretes gonad – stimulating hormone which
stimulates testes to produce testosterone
SECONDARY SEXUAL CHARACTERISTICS

a.)
b.)
c.)
d.)
e.)

testis starts to produce sperm
enlargement of the prostate gland and penis
voice ( breaks) and becomes deeper
growth of hair on face, body and pubic region
Increase in growth rate
Pituitary gland secretes ganad – stimulating hormone which
stimulates ovaries to produce oestrogen
SECONDARY SEXUAL CHARACTERISTICS







menstruation begins i.e start of ovulation
enlargement of breasts
growth of hair in armpit and pubic region
widening of the pelvic girdle ( hip)
increase in the size of the uterus and vagina
Increase growth rate.
Production of oestrogen stops. Ovaries stop producing ovum,
ovulation and menstrual cycle cease.
MENOPAUSE
Endocrine glands and Exocrine glands:
*OBJECTIVE: Distinguish between exocrine and endocrine system
Endocrine glands
Exocrine glands
Ductless glands
glands with ducts
Contents carried by blood
contents carried by ducts
produce hormones smaller quantities
produce fluids in larger quantities
e.g. thyroid gland; pancreas, adrenal
glands
e.g. salivary glands; pancreas
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NEGATIVE FEEDBACK
*OBJECTIVE: Explain the concept of negative feedback




When a change sets off a response that cancels out the change.
A constant internal environment in the human body is maintained by negative feedback
The diagram explains how negative feedback keeps variable factors within the narrow suitable
for life.
Negative feedback mechanism regulate hormone level in blood, the diagram below
explains that.
117
Any change from the
set point is a deviation.
This deviation acts as a
signal to the control
center
Level
Defention outside the normal range may
of
not be controlled by homeostasis and can
Factor in
lead to disease .
Blood
This is the range of
this factor that can
be controlled by
homeostasis. Cells
work well within
this range
Time
This is the norm or set point for the
homeostatic control system . This would
be the ideal level of this factor for cells to
work
118
Control centre sets
off the correct
responses.
Response cancels
out the deviation
and returns the
factor towards its
set point
TROPISMS
OBJECTIVE: Geotropism as the growth response of a plant to gravity
1. Although plants do not have a nervous system and muscle system to control and coordinate
their activities, they do have ability to detect and respond to external stimuli.
2. A tropic response is a growth movement in response to an external stimulus. It is a directional
movement either growing towards or away from the source of the stimulus.
3. The main external stimuli to which plants respond are light, gravity and water. The parts and
structure of plants respond to external stimuli in different ways. The main tropic responses in
plant are summarized in Table 1.
4. Changes in the growth of any part of the plant are under the influence of plant hormone auxin.
OBJECTIVE: Define geotropism as the growth response of a plant to gravity
OBJECTIVE: Define phototropism as the growth response of a plant to gravity
TROPIC RESPONSE
STIMULUS
Phototropism
Light
RESPONSE OF PLANT



Geotropism
Gravity


Hydrotropism
Water


Shoots grow towards light source to absorb maximum light for
photosynthesis,( positive phototropism)
Roots grow away from light source, ( negative phototropism)
Leaves orientate in such a away to receive maximum sunlight for
photosynthesis.
Roots grow downwards into the soil in the direction of the
gravitational pull.( positive geotropism)
This ensures that the roots are in contact with soil water and
nutrients and they grow deep into the soil to anchor plant firmly
on the ground.
Shoots grow upwards away from gravity. ( negative geotropism)
The roots grow towards moisture and soil water
*OBJECTIVE: Describe geotropism and phototropism in term of auxin regulating growth
CONTROL OF GROWTH AND TROPIC MOVEMENTS BY PLANT HORMONES
1. The growth and tropic movements of plants are controlled by a combination of external
stimuli and plant hormones. One of the most important plant hormone is auxin which is
produced at the tips of shoots and roots. Auxin promotes growth by elongation of cells.
2. The distribution of auxin affects the growth of shoots and roots. There is a strong indication
that the growth curvatures formed in tropism are due to the redistribution of auxin in the
shoot and root tips under the influence of the external stimulus. The unequal distribution of
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auxin concentration results in different rates of growth and elongation of cells in the shoot
and root tips resulting in growth curvatures.
3. The possible explanations for the various tropisms are summarized in Table 2.
*OBJECTIVE: Describe the control of plant growth by auxins
4. Growth of plants is restricted to the meristems of the plant. Meristems occur at the tips
of the root and shoot of a plant. Rapid cell division occurs at the meristems (zone of cell
120
division). Now cells produced grow to maximum size and differentiate into the various plant
tissues. The main regions of growth in the tip of a shoot and root are shown in Fig. 1
SHOOT TIP (DRAWING)
ROOT TIP (DRAWING)
a) A range of synthetic plant hormones have been manufactured commercially for
control of plant growth in agriculture.
b) AUXIN – Like growth substances are used in the artificial propagation of plants to
stimulate and promote the growth of roots in stem cuttings.
c) Synthetic plant hormones are also used to encourage fruiting and cause fruits to
develop even without fertilization.
d) Herbicides are used as hormone weed killers. Most herbicides are selective and
accelerate the growth of weed plants so rapidly that the weeds exhaust themselves
and die.
121
OBJECTIVE: Investigate the effects of removing the apical bud fromplant seedlings
Some experiments to test the auxin theory:
1
2
122
3
4
5
123
6
124
USE AND ABUSE OF DRUGS
OBJECTIVE: Define a drug
DEFINITION OF DRUGS

An externally administered substance which modifies or affects chemical reactions in the body.
ADMINISTRATION OF DRUGS

Drugs are administered orally, by injection, application on the skin or inhalation.
Objective: Describe medicinal use of drugs including antibiotics, painkillers, antacids
CLASSIFICATION
ANTACIDS
EFFECTS
Neutralises acids in the stomach
PAIN KILLERS
Block transmission of pain
signals or suppress the part of
the brain responsible for the
sense of pain
Cure bacterial diseases – by
destroying bacteria
ANTIBIOTICS
EXAMPLES
Sodium bicarbonate, Milk of
magnesia
Aspirin, ibuprofen, paracetamol,
morphinel
Penicilin, Tetracyline
COMMON MEDICINAL DRUGS AND THEIR USES
COMMON NAME
DRUG TYPE
USE
SIDE EFFECTS
Aspirin
Painkiller
Relieve pain and fever, reduce
inflammation
Prevents blood clotting,
ran cause irritations to
the stomach bleeding;
not recommended for
children under 12 years
old as it causes fatal
liver and brain damage
Ibruprofen
Pain killer
Relieve severe pain
Paracetamol
Mild pain killer
Relieve mild pain and fever
Milk of magnesia
Antacid
Neutralised in the stomach
Sodium
bicarbonate
Antacid
Relieve indigestion and discomfort
125
Overdose can damage
liver and kidney
Penicilin
Antibiotic
Treats common bacterial infection (
stops bacterial infection ( stops
bacteria from multiplying)
Can cause allergic
reactions
Tetracyline
Antibiotic
Treats pneumonia, bronchitis and
chest pains
Nausea and vomiting
CLASIFICATION OF DRUGS (ON THE BASIS OF THEIR EFFECTS ON THE CENTRAL NERVOUS SYSYTEM
OBJECTIVE: Describe non-medicinal (abusive) drugs according to their effect on the central nervous
system: depressant, stimulant, hallucinogen
CLASSIFICATION
STIMULANTS
DEPRESANTS
NARCOTICS
HALLUCINOGENS
EFFECTS
Speed up transmission of nerve
impulses
Slow down transmission of nerve
impulses
Produce a sense of euphoria or
well being (sense of enhanced
energy, excitement and
alertness.
Causes a pronounced alteration
of perception
EXAMPLES
Caffeine, nicotine, cocaine,
amphetamines
Alcohol, barbiturates,
tranquilizers opiates
Heroin, morphine, codeine
LSD, PCP, Marijuana, Harshis,
peyote, ganja
OBJECTIVE: Distinguish between medicinal drugs and non-medicinal drugs
Medicinal drugs
Non-medicinal drugs
alleviate diseases, relieve symptoms, ease pain
and provide other benefits to the body
taken for habitual satisfaction
prescribed by doctors
not prescribed by doctors
administered at prescribed doses
administered at any dose to the satisfaction of
user
legal drugs
mostly illegal drugs
126
*OBJECTIVE :Discuss dependence (emotional/psychological and physical) and tolerance of medicinal
drugs
Objective: Discuss the dangers of drug abuse such as dependence and body tissues damage
DEFINITIONS









Drug abuse; the means international improper use of drugs
Drug addiction; this means intense habitual craving for drugs or physical and psychological
dependence on drugs.
Drug dependence : compulsive use of drugs resulting in physical or psychological dependence (
condition where user cannot do without do the substance)
Physical dependence; occurs when the body adapts to a drug and increases its tolerance, this
leads to larger and uncontrolled doses of the drug to achieve the original effect; physical
dependence produces severe physical withdrawal symptoms if the drug is not taken.
Psychological dependence; intense mental craving for a drug if the drug is unavailable or
withdrawn
Drug tolerance; this occurs as a result of regular use of a drug. Eventually the body requires
higher doses of the drug to achieve the same effect.
Withdrawal symptoms; illness - like symptoms / signs which occurs when one stops taking a
drug.
Physical symptoms which shown when the substance is withheld i.e. nausea, vomiting, diarrhea,
muscular pain, uncontrollable shaking
Overall effect of drugs on the body is damage to tissues of organs such as the liver, lungs, brain,
and alimentary canal.
OBJECTIVE: Discuss allergic reactions to drugs and other substances.
Allergy simply defined as hypersensitivity to various substances which would normally be harmless to
the average person. It is a result of the immune system not being able to distinguish between a
pathogen and a relatively harmful substance. An allergen is a substance that triggers an allergic reaction.
ALLERGEN
FOOD ALLERGENS: Dairy
products(eggs and cows’ milk)
nuts, shell, fish, strawberries,
beef, fish, food additives etc.
RESPIRATORY ALLERGENS;
Pollen, dust mites, pet fur,
inhalants etc
CONTACT ALLERGENS;
Rubber, chemicals ( irritants)
nickel, copper, certain plants,
certain animals, lanolin e.t.c
SYMPTOMS
 Swelling of lips or
mouth, Stomach
upsets, itchy rash
TREATMENT
 Antihistamines cromoglycate for
some allergies

Sneezing, running
nose, asthma


Eczema, rash,
itchiness

127
Adrenaline, or corticosteroid drugs
to relieve acute symptoms
cromoglycate, etc
Antihistamines( adrenaline or
corticosteroid drugs to relieve
acute symptoms)
COMMONLY ABUSED DRUGS
Objective: Find out which drugs are commonly abused in the community e.g. dagga/marijuana,
solvents, glue, alcohol
Objective: Classify a named drug of abuse e.g. dagga/marijuana: uses, dangers of taking the drug,
signs of dependence, withdrawal symptoms and popular names
DRUG ( STREET NAME) CLASSIFICATION
IN BRACKETS
IMMEDIATE EFFECTS
EFFECTS ON HEALTH
WITHDRAWAL
SYMPTOMS
Mrijuana(ganja, weed,
herb,dagga etc &
harshish from
cannabis sativa
HALLUCINOGEN
Enhanced vitality, energy
and enthusiasm, euphoria,
relaxation, hallucinations,
loss of self control, intense
yearning for food, dryness
of mouth, perspiration,
brightness and ruddiness
of eyes, intellectual
difficulties, decrease in
short term memory and
speech impediments),
poor motor coordination
Damage to brain,
heart, damage to the
respiratory system,
increases appetite,
poor absorption in the
alimentary canal,
depressed immune
system, lowers sperm
count and diminishes
sexual drive
Irritability, insomnia,
restlessness,
hallucinations may
occur ( flash backs)
Heroin
Narcotic and
Pain killer
Euphoria, insensitivity to
pain, loss of appetite
Tooth decay,
gingivitis, poor sight,
facial boils weight
loss, anaemia,
digestive difficulties
and constipation,
sexual dysfunction,
menstrual disorder
Restlessness, fever,
diarrhea nausea,
vomiting, cramps,
watery eyes, running
nose etc
Increase in body
temperature dilation
of pupils, injury
Depression,
sleepiness, hunger,
disorientation to
nostrils and nasal
septum, respiratory
infections, impotence,
cardio vascular
problems etc
Cocaine (crack)
Stimulant
Euphoria, mental
alertness, reduced
tiredness, reduced
appetite
128
Risk of hepatitis and
HIV infection Sexual
Nicotine( in tobacco)
Stimulant
Relaxation, tension
reduction
Cardiovascular
diseases
Irritability, hostility,
anger, excessive
drowsiness
Caffeine ( in tea,
coffee, cocoa and
coke
Stimulant
Wakefulness, increased
heartbeat, nervousness
Insomnia, gastritis,
more uric acid in
body, arrhythmia,
osteoporosis,
miscarriage mammary
cysts, hypertension
and risk of heart
attack
Tiredness, irritability,
inability to
concentrate
headache, dizziness,
trembling
EFFECTS OF EXCESSIVE CONSUMPTION OF ALCOHOL
OBJECTIVE: Describe the effects of excessive consumption of alcohol:reduced self-control, depressant,
effects of effect on reaction time, damage to liver, social implication
Alcohol (ethanol) is a CNS depressant. It reduces anxiety, tensions and inhibitions. It dilates small blood
vessels, particularly those in skin, leading to flushing.
IMMEDIATE EFFECTS
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
Speech is slurred
Double vision
Loss of balance
Poor coordination of muscles ( causing staggering and unsteadiness)
Nausea and vomiting
Impaired concentration and judgment
It slows down the speed of transmission of nerve impulses involved reacting to an emergency
situation) increases reaction time.
Violent or aggressive behavior
Loss of consciousness
SOCIAL EFFECTS
i.
ii.
iii.
iv.
v.
vi.
Fatal road accidents
Lack of productivity leading to jobs loss
Accidents in the work place
Abuse, vandalism and delinquency
Suicides
Sexual assaults
129
vii.
Huge economic impact on public health ( due to medical bills in treating diseases caused
directly or indirectly related to alcohol consumption e.g AIDS, Cancers)
LONG TERM EFFECTS AND HEALTH HAZARDS
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
xi.
xii.
Malnutrition and nutritional deficiency diseases
Liver diseases: hepatitis, fatty liver and liver cirihosis
Blood diseases; enlarged RBC’s, reduction in clotting factors, low WBC ‘s count ( weak immune
system)
Diseases on the nervous system : damage to the CNS (brain atrophy), paralysis of the extremities
Cardiovascular disease: Fatty heart, hypertension
Pancreatitis and sugar diabetes
Cancers: Cancer of esophagus, pharynx, liver and larynx
Babies born to abnormalities of the heart, face and the skull structure (foetal alcohol syndrome )
Ulcers and infernal bleeding
Testicular atrophy and impotence
Enlargement of mammary glands in men
Amenorrhea ( absence of menstruation
WITHDRAWAL SYMPTOMS
i.
ii.
iii.
iv.
v.
vi.
Nausea and vomiting
Trembling ( shaking)
Abdominal pains and cramps
Restlessness
Sweating
Severe craving for alcohol
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SUPPORT, MOVEMENT AND LOCOMOTION
The vertebrate skeleton
1. The human skeleton is an endoskeleton (internal skeleton) composed of bone
and cartilage which are formed by living cells.
2. Bone and cartilage contain non – living mineral substances such as calcium
phosphates and calcium carbonates.
3. Bones are hard, rigid and non – elastic tissues. Cartilage is softer than bone, less
rigid and slightly elastic.
4. A summary of the main parts of a vertebrate:
THE VERTEBRATE SKELETON
AXIAL SKELETON
Skull (cranium)
APPENDICULAR SKELETON
a) Vertebral column
Pectoral girdle
b) Ribs Sternum
a) Shoulder
a) Hip
b) Arms
b) Legs
131
Pelvic girdle
OBJECTIVE: Identify from diagrams, photographs and real specimens, the main bones of the forelimb
(scapula, humerus, radius,ulna) of a mammal.
SKELETON
132
FUNCTIONS OF THE HUMAN VERTEBRATE SKELETON
SUPPORT



A rigid skeleton to support soft parts of the body
To raise body from the ground and maintain shape of the body during movement and
muscular activity
The arrangement of the bones gives shape to the body as a whole.
MOVEMENT

The skeleton is joined to allow movement. Movement is achieved by muscles which are
attached to the bones. The bones act as leavers and the muscles contract to pull them in
different positions.
PROTECTION

To protect the more delicate parts of the body e.g the cranium protects the brain, the
rib cage protects the heart and the lungs, and the vertebral column surrounds the spinal
cord.
PRODUCTION

Production of red and white blood cells in the bone marrow.
THE DIFFERENT TYPE OF JOINTS
OBJECTIVE: Describe the type of movement permitted by the ball and socket joint and the hinge
joint of the fore-limb
Where two bones meet a joint is formed. Bones can move in relation to one another at
joints. Joints are classified according to the degree of movement possible between the
articulating surfaces.
TYPE OF JOINT
MOVEMENT
LOCATION IN SKELETAL
SYSTEM
FIXED JOINT
No movement permitted


133
Structures between
the bones of the skull
Pelvic girdle
GLIDING JOINT
Limitted sliding movement
PIVOT JOINT
Allow nodding and limited rotation
of head
HINGE JOINT
Allows movement in one plane
BALL AND SOCKET
JOINT
Allows movement in 3 planes


The vertebrae of the
vertebral column
Wrist
Neck




Elbow
Knee
Shoulder
Hip

The largest movement occurs at the synovial joints such as the ball and socket joint and the
hinge joint.
STRUCTURE OF A SYMBOL JOINT
The structure and functions of the various parts of the synovial joint are shown below.
PARTS OF THE SYNOVIAL JOINT
FUNCTIONS
1. Synovial capsule
A tough , fibrous capsule which holds the joint
together.
It surrounds the joint, synovial membrane and
contains the synovial fluid
2. Synovial membrane
Secrets the synovial fluid and seals in the
synovial fluid
3. Synovial Fluid
Acts as a lubricant between bones and also
provides nutrients to the bone surfaces.
4. Cartilage
Soft, slippery, slightly elastic tissue covering
the heads of the bones allow friction free
movement, acts as a shock absorber and
prevents wearing of the bones at the joint
5. Ligament
Elastic connective tissue which connects bones
to bone.
134
Provides external support and strengthens the
joint
135
THE STRUCTURE OF THE FOREARM
OBJECTIVE: Describe the component bones of the fore-limb of a mammal
1. The forearm is made up of the humerus ( upper arm) the ulna and the radius.
2. The wrist and the hand are made up of small carpal bones metacarpal and phalanges
3. The humerus forms a ball and socket joint with the scapula at the shoulder and a hinge
joint is formed between the humerus and the ulna at the elbow.
ACTION OF ANTAGONISTIC MUSCLES OF THE FOREARM
OBJECTIVE: Describe the action of antagonistic muscles at the hinge joint
1. The skeletal muscles are attached to the projections or ridges in the bones of the
fore arm by tendons which are non – elastic fibrous tissues connecting muscles
to bones. One end of the muscle must be attached to the bone that is to be
moved while the other end is anchored to a part of the skeleton to be held
stationery with respect to the moving part.
2. Movement in the forearm is brought about by the alternate contraction and
relaxation of a pair of antagonistic muscles in the forearm.
136
3. In the forearm, the antagonistic pair of flexor and extensor muscles are arranged
in such a way that when they contract, they pull in opposite directions
4. A summary of the action of the antagonistic muscles in the forearm.
BENDING FOREARM (FLEXIN)
STRAIGHTENING OF FOREARM( EXTENSION)
1. Biceps (flexor) contract and
1. Triceps contract and become shorter and
thicker
become shorter and thicker
2. Triceps ( extensor) relax
Ulna and radius pull closer to the
humerus
2. Biceps relax
3. Ulna and radius pull away from the
humerus
137
REPRODUCTION IN PLANTS
OBJECTIVE: Describe asexual reproduction as the process resulting in the production of genetically
identically offspring from one parent
ASEXUAL REPRODUCTION
It is the process resulting in the production of genetically identical offspring(s) from one parent.
PLANTS
OBJECTIVE: Give examples of asexual reproduction in plants and animals
There are two main methods of asexual reproduction in flowering plants:
a) Vegetative propagation
b) Artificial propagation
VEGETATATIVE PROPAGATION
Plants which reproduce this way have special food storage organs which enable them to grow
year after year. Examples of this plant are: tubers, corns and rhizomes.
Perennating Food storage
organ
Tubers
(Underground
stem)
Features
Young shoot from terminal bud
Mainly starch, vitamin C
and water in swollen stem.
Scale leaf Lateral bud at the node
138
‘eye’
Rhizomes
(Underground
stem)
Mainly starch.
Adventitious roots
Vegetative reproduction takes place when the lateral
bud on the node develops into a new shoot
Bulbs
(Underground
shoot)
Mainly water and sugar
(glucose) stored in
fleshy leaves
White, fleshy storage scale leaves
Thin, dry. brown scale leaves
Young shoot
Condensed stem
Lateral bud which
will grow into a
new bulb
Terminal bud which will
grow into new shoot
139
Corm
(Underground
shoot)
Mainly water and sugar
stored in the short and
swollen stem.
flower bud
Aerial shoot
Node
Internode
Adventitious roots
OBJECTIVE: Discuss the advantages and disadvantages of reproducing asexually
ADVANTAGES OF VEGETATIVE PROPAGATION ARE:
a) It reproduces daughter plants identical to parent within a short period of time. This
ensures that desirable characteristics of the parent plant such as hardness and high fruit
yield will persist
b) Parent plant supplies food to offspring until they are independent
c) Stored food from parent organ can be used for rapid growth of aerial shoots and so
avoids competition with other species
d) Plants are independent of pollinating agents and formation of gametes is not necessary.
e) There are no hazards of seed dispersal and germination ( in sexual reproduction as
vegetative propagation only occurs under favourable conditions.
DISADVANTAGES OF VEGETATIVE REPRODUCTION ARE:
a) Overcrowding which rise from the dense growth of daughter plants near to the
parent plant. This results in competition between plants for mineral salts, water
and sunlight
140
b) Since daughter plants are identical to parent, there is no genetic variation for
natural selection. Species are unlikely to colonise new habitats and may die out if
environmental conditions change.
OBJECTIVE: Describe one commercially important application of asexual reproduction in plants and
animals
ARTIFICIAL PROPAGATION
a) Artificial Propagation is a form of vegetative propagation used by man to propagate and
to preserve useful in bred characteristics of plant such as good fruits or flowers.
b) By using artificial propagation, gardeners can produce any number of plants with
identical genetic composition and characteristics. Two important methods of artificial
propagation include cutting and grafting.
CUTTINGS




A cutting is any portion of a root or shoot removed from the parent plant.
The cutting is usually treated with plant hormone to promote root growth.
It is placed in most soil or dipped in water until adventitious roots appear to support
plant and absorb water
. The cutting may also be covered with a transparent plastic to reduce water loss by
transpiration.
GRAFTING
 Grafting is a popular method used to maintain or build up certain desirable
characteristics in plants.
 It is used to propagate fruits (e.g. apple, pear) which are difficult to grow from seed.
 The bud /shoot /scion of the desired variety is inserted into a T-shaped cut made on the
stem of another closely related plant ( the stock).
 The scion is tied into position on to the stock with its cambium layer in contact with the
vascular will soon produce vascular tissue which unite the scion and the stock.
 The stock is obtained by growing a plant from a seed and then cutting away the shoot.
The type of stock usually affects the ultimate size of the plant and the time it takes to
mature. The scion is a branch of a bud cut from a cultivated variety with the desired fruit
or flower characteristics.
141
A bud graft

A bud graft with desired characteristics is cut

A T-shaped slit is made in the bark of the stock to expose cambium tissue.
"Stock of a closely related variety”.

The bud graft (scion) is slipped inside the T-shaped slit of the stock. The cambium
of the scion is in contact with the cambium of the stock.

The scion is held in place with tape and wax to exclude fungi and reduce evaporation
Asexual Reproduction in Animals

Few animals reproduce asexually. Aphids( belonging to class insect) reproduce asexually
by parthenogensis.
Asexual Reproduction in micro-orgainsms

Some common examples of asexual reproduction in micro – organisms are:
Binary Fission;
Budding
142
SEXUAL REPRODUCTION IN PLANTS
OBJECTIVE: Describe sexual reproduction as the process involving the fusion of nuclei from two
different gametes to form a zygote
OBJECTIVE: Identify the sepals, petals, stamens and carpels of one locally available insect pollinated
flower
OBJECTIVE: Observe using a hand lens the sepals, petals, stamens and carpels of one locally available
insect pollinated flower and draw the parts
OBJECTIVE: Use a hand lens to identify stamens and carpels of one locally available wind pollinated
flowee.
Flowers are reproductive structures which contain the reproductive organs of the plant.
OBJECTIVE: describe the functions of the sepals, petals, stamens and carpels.
FUNCTIONS OF PARTS OF A FLOWER
1. CALYX
 A ring of sepals (small, green leaf – like) outside petals.
 Protects the petals of the flower when it is in the bud stage.
2. COROLLA
 Consists of 4 – 10 petals, may be separated or joined together.
143


Encloses reproductive organs. Usually large, brightly coloured and scented to attract
insects to pollinate flower.
Small and leaf – like structures in wind pollinated flowers.
3. ANDROECIUM
 Consists of stamens, each of which has an anther borne on a stalk called the
filament .
 Male consists of four pollen sacks in which the pollen grains are produced by cell
division
 Meosis occurs in the anthers to form haploid male gametes in pollen grains.
 When the pollen is fully formed, the anthers split and release the matured pollen
grains.
4.





5.



GYNOECIUM (PISTIL)
Female reproductive organs.
Consists of carpels.
Each carpel has an ovary containing one or more ovules and bears a style which
terminates in a sticky surface, the stigma.
Development of egg cells proceeds in the ovary, ovules containing the female gamete
arise from the inner wall of the carpel.
The style holds up the stigma on which pollen lands during pollination.
RECEPTACLE
Expanded end of a flower stalk
For attachment of all other flower parts.
In some cases, after fertilization it becomes, fleshy and edible such as apple, pear,
strawberry.
POLLINATION
OBJECTIVE: Discuss pollination in terms of types, agents and methods

Pollination is the transfer of pollen grains from the anthers to the stigma of a flower.
The two types of pollination are:
o Cross pollination
o Self pollination
144


Cross pollination is transfer of pollen grains from the anthers of one flower to the
stigma of another flower on another plant of the same species.
o There is cross fertilization therefore out breeding.
o Anther of flowers which cross pollinate mature before the ovary and may be self
incompatible i.e. pollen grains from the same flower will not germinate on the
stigma of the same flower.
Self pollination is transfer of pollen grains from the anthers of one flower to the stigma
of the same flower or another flower on the same plant.
o This leads to self – fertilization therefore inbreeding.
Agents of Pollination
 Insects and wind are the main two agents of natural pollination.
 The general modifications which adapt flower to their methods of pollination are
summarised below.
145
OBJECTIVE: Compare wind pollinated and insect pollinated flower using fresh specimens
OBJECTIVE: Prepare a slide of the pollen grains from the stamens of a wind and insect pollinated
flower and examine them under a microscope
PARTS OF
FLOWER
Size of a flower
INSECT POLLINATION

Large flowers

Corolla

Coloured and scented to attract a
variety of insects
Has honey guides( dark lines) on
petals that help to direct the
insects to the nectaries
With nectarines at the base of the
outer stamens.
Has short filaments and stamens
are arranged within the flower

Small, inconspicuous
flower
Without scent or sepals
usually small, green
petals.

Without nectaries

Heavy, sticky and rough surfaced,
adhere easily to insects body
Produced in smaller quantities

Stigma is small and sticky and is
found inside the flower

Large, pendulous
stamens which projects
outside the flower
Produced in larger
quantities
Stigma is large and
feathery
Projecting outside the
flower to act as a net (
large surface area) to
trap passing pollen
grains.

Nectary

Stamens

Pollen grains


Stigma

WIND POLLINATION

Pollination By An Insect




When an insect visits a mature flower to collect nectar, pollen grains released by the ripe
mature anthers are likely to adhere to its long tube - like mouth [ parts (e.g. butterfly)] or hairy
body (e.g. bee)
These pollen grains are transferred to the stigma of another flower when the insect visits it for
nectar.
As the insect pushes its way into to reach the nectarines at the base of the filaments, its body
brushes onto the sticky surface of the stigma which pick up the pollen grains on its body.
Pollination is complete when the pollen grain has landed on a stigma.
146
FERTILISATION
OBJECTIVE: Describe the growth of the pollen tube and its entry into the ovule followed by
fertilization.





When a pollen grain lands on the stigma, it absorbs liquid from the stigma and germinates to
from a pollen tube.
The pollen tube grows through the tissues of the style towards the ovary. As the pollen tube
grows, its nucleus divides to form two male gametes.
The pollen tube enters the ovule at the micropyle and releases two male garmetes.
One of male gametes fuses with the ovum to form the zygote ( fertilization) and the other fuses
with the secondary nucleus in the embryo sac to form the endosperm nucleus.
The zygote now has the normal diploid of chromosomes for the plant cell.
Dispersal of Fruits

Fruits and seeds may be dispersed by external agents such as humans, animals, wind or
by self-dispersal explosion mechanism.
Advantages of fruit and seed dispersal
OBJECTIVE: State the advantages of seed dispersal

Dispersal of fruits and seeds some distance away from the parent plant reduces
overcrowding and reduces the competition for light, mineral salts and water between
plants.

It also enhances the survival of that species of plant by distributing the plants to new habitats.
147
The main adaptations of fruits and seeds to the various dispersal methods are summarised
below
OBJECTIVE: Describe modes of seed dispersal
Dispersal method
Wind dispersal
Main adaptation features
Examples
• Small size.
1
Parachute or tuft of
hairs projecting from
fruit or seed. Examples:
Tridex and dandelion.
•Wing-like outgrowths
extension from ovary wall
of fruit. Example: winged
fruits of shorea and
angsana.
Dandelion
Open seed case shaken
by wind. Example: small,
light seeds of poppy.
Angsana
Animal dispersal
1. 'Hooked and hairy
fruits -hooks caught in
the fur of passing
animals and the seeds
fall out as the
mammals move about.
Examples: Urena fruit
and spear grass.
2. Succulent, brightly
coloured and scented
fruits - when eaten by
animals and birds,
undigested seeds pass
out
with
faeces.
Examples:
Papaya,
mango and berries.
148
Shorea
Dispersal method
Explosive mechanism
Main adaptation features
Examples
Pericarp dries in the
sun and shrink. The
tension
generated
splits
fruit
longitudinally into two
halves suddenly and
ejects seeds. Example:
pods of leguminous
plants.
Fruit pod
Garden pea pod
149
GERMINATION OF DICOTYLEDONOUS SEED
OBJECTIVE: Examine the structure of a seed (both endospermicand non-endospermic)
Non-endospermic seed
OBJECTIVE: Describe the structure and function of parts of a seed in terms of embryo, (radical and
plumule) cotyledons and testa






Parts of the seed:
Embryo: grows to form a root and a shoot. The plumule forms the shoot and the radicle forms
the root.
Cotyledon: stores food to be used by the embryo to grow.
Testa: a tough coat which protects the seed from mechanical damage; reduces loss of water
from the seed and reduces entry of micro-organisms.
Micropyle : a small hole in the testa and an important route for entry of water in some seeds
Germination
Germination is when the embryo part of seed begins to grow.
Conditions for germination are:
o A supply of water.
o Temperature suitable for enzymes involved in germination.
o Oxygen for aerobic respiration.
The requirements are explained more fully in the diagram below:
150
OBJECTIVE: Investigate the environmental conditions which affect germination of seeds
OBJECTIVE: Describe the role of enzymes in seed germination
151
Germination of Dicotyledonous Seed

The graph below shows the changes in the dry mass and fresh mass of the seed
during germination. The dry mass of the seed is the mass of the actual amount of
organic matter present in the seed whereas the fresh mass includes the amount of water
absorbed by the seed.

As the seed germinates, its dry mass decreases gradually as the stored food in its
cotyledons is oxidised during respiration to produce energy needed for germination and
growth of new tissues. The dry weight continues to decrease until the first foliage leaf are
matured enough to carry out photosynthesis at a rate faster than respiration of the plant
cells.

The fresh mass increases continuously as the seed absorbs water, grows roots and
begins making food by photosynthesis.
152
SEXUAL REPRODUCTION IN MAN
Objective: describe the functions of the testes, scrotum, sperm ducts,
prostate gland, seminal vesicle, urethra and penis.
Male Reproductive System:

The main parts of the human male reproductive system and their
functions are summarized below
153
Objective: Use a diagram of the male reproductive system to identify
testes, scrotum, sperm ducts, prostate gland, seminal vesicle, urethra
and penis.
154
Female Reproductive System:

The main parts of the human female reproductive system and their
functions are summarized below
Objective: Use a diagram of the female reproductive system to
identify ovaries, oviducts, uterus, cervix, bladder and vagina.
155
Objective: describe the function of the ovaries, oviducts, uterus, cervix,
bladder and vagina.
156
Objective: compare the male and female gametes in term of size,
number, mobility and life span.
Difference between a sperm and an ovum
Sperm
Ovum

It is very small
in size (in fact it is the smallest cell in the
body).

Is larger than
the sperm (in fact it is the largest cell in
the body).

It is mobile/can
move by swimming with the help of the
tail.

The ova cannot
swim because it does not have a tail, but
the peristaltic movements and the tiny
cilia hairs in the oviducts help move it.

It is produced
in large numbers (millions) per day.

for 2 to 3 days

survives
is produced per month.

for 24 hours
Only one ovum
survives
Objective: Discuss the menstrual cycle
The Menstrual Cycle:
For a girl, the first sign of puberty is the monthly discharge of blood from the uterus via the vagina.
This is called menstruation and it occurs in a cycle called the menstrual cycle. The menstrual cycle is
sometimes referred to as the oestrous cycle. It is controlled by some hormones such as,
157
progesterone and Oestrogen hormones working hand in hand with FSH (Follicle Stimulating
Hormone) and LH (Lutenising hormone). The menstrual cycle, on average takes about 28 days. It is a
long term process controlled by a number of hormones, which;


Prepare the uterus to receive any fertilized egg
Control the development of mature ova.
The menstrual cycle occurs in four stages/phases:
1. Menstruation: The uterus lining is shed, and blood and fragments of tissue leave the body
through the vagina. Menstruation triggers a decrease in the progesterone levels. Blood is lost
and at this stage and it needs to be replaced during a repair phase. Menstruation takes about 46 days depending on the amount of blood lost. About 60-75cm3 of blood is lost along with the
mucus and uterus cells.
2. Repair phase/safe period phase: More blood vessels grow in the lining of the uterus, and the
lining thickens and becomes more stable. These changes are triggered by Oestrogen hormone.
At this point, the FSH stimulates primary follicles to mature and become Graafian follicle. The
Graafian follicle contains an egg surrounded by follicle cells and a fluid filled space. The Graafian
follicle ruptures and releases an egg into the oviduct and this marks Ovulation which occurs
when the Oestrogen levels are high. Ovulation is triggered by the release of a hormone secreted
by from the anterior pituitary gland the LH (Lutenising Hormone) this hormone also helps in the
development of corpus luteum from the remains of the follicle.
3. Receptive Phase: The lining of the uterus and its blood vessels are now well developed, if
fertilization occurred, the embryo can be implanted in its lining. At this point any unprotected
sexual activity will lead to pregnancy.
4. Premenstrual phase: The lining of the uterus degenerates as the progesterone levels drop
unless implantation has occurred. After ovulation, the follicle develops into Corpus luteum,
which secretes the female hormone Progesterone. The progesterone keeps the walls to remain
thick in order to receive a fertilized egg for implantation. This phase is usually characterized with
some contraction of the uterus leading to period pains.
158
159
Objective: Describe the effects of diet and emotional state on the
menstrual cycle
Factors affecting the menstrual Cycle:
1
Stress over excitement mental fatigue and illness may alter or stop
the menstrual
2
Diet - An unbalanced diet or malnutrition may also cause the period
to be very irregular or stop completely.

A girl who has reached puberty has to eat food rich in iron, why?
Change of environment
3
Objective: Discuss the functions of the placenta and umbilical cord in
relation to exchange of dissolved nutrients, gases and wastes.
FERTILISATION AND DEVELOPMENT OF ZYGOTE:







ovum to form a zygote
form a ball of cells.
Fertilisation is the fusion of nucleus of the sperm and nucleus of the
Fertilisation occurs in the oviduct in human
After fertilisation the zygote under goes several mitotic divisions to
The ball of cells is moved along the oviduct by the sweeping action
of cilia and peristaltic contractions of the walls of the oviduct until it reaches the uterus.
The journey of the ball of cells to reach the uterus may take 4 to 7
days,
By the time the ball of cells reaches the uterus it has developed
finger like projections, villi, for implantation in the uterus wall.
THE PLACENTA AND THE UMBILICAL CORD:






The implanted embryo undergoes mitosis and forms embryonic
tissues, extra-embryonic membranes and the placenta.
The placenta develops partly from the embryo’s tissues and partly
from the uterus wall. It is a large, thick mass of uterus lining containing blood spaces filled
with the mother’s blood and numerous finger-like projections called villi which grow into
the uterus wall.
The foetus is attached to the placenta by the umbilical cord, which
carries 2 umbilical arteries and an umbilical vein from embryo’s circulatory system
The main blood vessels of the placenta lead to an immense network
of capillaries in the villi.
The embryo’s blood system and the maternal blood system are
separated by the capillary walls and the membrane covering each villus.
Substances which diffuse from mother’s blood system to embryo’s
blood system are:
1.
Dissolved food molecules such as glucose and amino acids
160





2.
3.
4.
blood system are:
1.
2.
3.
Oxygen
Mineral ions such as iron, calcium, phosphates
Antibodies
Substances which diffuse from embryo’s blood system to mother’s
Urea
Carbon dioxide
Other nitrogenous wastes
The placenta functions like the digestive system, respiratory system
and the excretory system of the embryo
The rate of diffusion at the placenta is increased by:
1.
The close proximity between mothers blood system and the
embryo’s blood system
2.
The large surface area provided by the numerous villi and the
network of capillaries in the villi
The embryo and maternal bloodstreams are not mixed. The reasons
are:
1.
The delicate embryo’s blood vessels could be easily damaged by the
high blood pressure of the mother’ s blood system.
2.
Agglutination could occur due to the mixing of different blood
groups from mother and embryo
3.
To reduces chances of transmission of diseases from mother to
embryo
Umbilical cord: transports substance to and from the baby from
the placenta in an artery and vein.

The umbilical artery takes deoxygenated blood with waste
substances from the foetus to the mother.

The umbilical vein carries oxygenated blood with the nutrients and
antibodies to the foetus’ heart.
161
162
Objective: Discuss the functions of the amniotic sac and amniotic fluid
During the whole gestation/pregnancy period (9 months), the foetus is enclosed in a fluid filled sac
called the Amniotic sac which surrounded by a tough fibrous material called the chorion.
The fluid (amniotic fluid) provides a watery medium

in which the foetus can move freely in it,

which protects it against external shocks and dehydration,

which protects against change in temperature and malformation of
the foetus due to gravity.
During pregnancy the amniotic fluid lubricates and reduces friction in

the birth canal (vagina).
163
Objective: Distinguish between identical and fraternal twins
Differences Between fraternal and identical twins:
Fraternal Twins
Identical Twins
Develop from:
Two different eggs fertilized by two
different sperm cells
The splitting of the same fertilized
egg into two
Genetic code:
Like any other sibling; not identical
identical
Gender:
Usually different
Always the same
In utero:
Develop separate sacs in utero
(amniotic sac and chorion).
May be contained in one sac in utero
(amniotic sac and chorion).
Objective: Describe the special dietary needs of a pregnant woman
Dietary Requirements of a Pregnant Woman:





Carbohydrates: To provide energy to the life processes of the baby and an extra energy for
carrying the extra mass of the baby around.
Iron: for the formation of haemoglobin in the red blood cells.
Proteins: making and repairing worn out tissues. Replacing old tissues.
Vitamin D, Calcium and Phosphorus: formation of the foetus’ bones.
Iodine to prevent slow mental development.
Objective: Discuss the advantages of breast milk compared to bottle milk
Advantages of Bottle Feeding:

Readily available, cheap

more hygienic than bottle, clean

nutrients in correct proportion

ready made anti-bodies obtained by the baby from the milk

improve mother to baby bond
164
Objective: Discuss the following methods of birth control: Natural
Hormonal/chemical, Physical/mechanical and Surgical methods
METHODS OF BIRTH CONTROL/CONTRACEPTIVES
Contraceptives: An agent or device intended to prevent conception. Contraception is the birth
control by the use of devices (diaphragm or intrauterine device or condom) or drugs or surgery.
Contraceptives are used for family planning as they prevent pregnancy. They help couples decide
whether or not to have children and some of them are used to prevent STDs even though their
main job is to prevent conception. Contraceptives can be divided into four groups;
1.
2.
3.
4.
Natural
Hormonal/chemical
Physical/mechanical
Surgical methods
1. Natural methods
Method
Abstinence: no sexual
intercourse at all.
advantages
Disadvantages
 100% effective against
pregnancy and STDs
Withdraw (Coitus interruptus);  Purely natural and does
not depend on artificial
penis withdrawn from the
devices.
vagina before ejaculation
o No disadvantage
o Highly unreliable as there is a preejaculation fluid which can be
secreted and contains sperms and
it is not easy for the man to
withdraw his penis as he will be at
the peak of pleasure.
o There is high pregnancy risk.
o STDs are spread with this method.
Rhythm (safe period): sexual
intercourse done only during
the safe periods and avoided
during fertile periods (when
fertilization is likely to lead to
pregnancy). Uses the mucus,
calendar and temperature
method.
 Acceptable in most
religions.
 Can be effective against
pregnancy if the dates
are noted well.
165
o It is unreliable because keeping
track of ovulation can be difficult
as it can change any time and it is
difficult t be certain about the safe
period length.
o Encourages the spread of STDs
Prolonged breastfeeding
(cultural method)
o Not effective against STDs
 Very effective against
pregnancy.
2. Hormonal/chemical methods
Method
Pill e.g. RU486: two kinds minipill (contains progesterone
which causes changes in the
uterus lining preventing
implantation) and combined
pill (contains Oestrogen and
progesterone and this prevents
ovulation)
advantages
Disadvantages
 Easy to use.
o Does to prevent STDs.
 Reversible
o Must be taken daily.
o Have side effects to women’s health;
 Does not interfere
breast swelling, cervical cancer, nausea,
with sexual activity.
diarrhoea and weight gain.
 99% safe at
preventing ovulation
and pregnancy.
 Can be administered
by individuals
Implant contraceptives:
Needs
 Long term protection o
trained personnel to insert and remove
against pregnancy
chemicals that contain
it.
99%
effective
(just
synthetic Oestrogen and
like the pill)
progesterone and placed under
o
Encourages
the skin to prevent ovulation. It  No need to visit
the spread of STDs.
lasts for 5 years.
health centres.
o
Has some
side
effects
e.g.
prolonged
periods
and
 Reversible.
irregular menstrual bleeding during the
first month of use.
Spermicides: kills sperms, must  Kill sperms.
be applied inside the vagina as
far up as possible ten minutes  Effective when used
with the diaphragm
before sexual intercourse.
o
o
It is messy.
 Serves as a lubricant
for the vagina.
o
Unreliable
 Easy to be
used/applied.
o
o
166
Must be
applied before every sexual activity.
when used alone.
prevent STDs.
used with the diaphragm.
Does not
Has to be
Injection (Depo-Provera):
injected into the body every 3
months. Stops ovulation by
preventing formation of ova in
the ovaries.
o Can lead to sterility.
 Reversible.
 99% effective against o Administered by a doctor.
pregnancy.
o Causes abnormalities in the period.
o Can lead to heavy menstrual bleeding.
o Have side effects like; dizziness, weight
gain.
o Does not protect against STDs.
Morning-after pill: Used after  Effective against
pregnancy if taken
intercourse has taken place.
before 3 days of
Contains hormones which
sexual act.
cause lining of the uterus to be
shed. It is to be taken 48-72
hours after sexual intercourse
especially if pregnancy poses a
risk.
o Only prescribed by a doctor in case of risk
it is not for regular use.
o Therefore not easily accessible.
3. Physical/mechanical/barrier Methods
Method
advantages
Disadvantages
Condom sheath (male: thin
o Allergy of the lubricant or latex.
 99 % effective in
preventing
pregnancy
rubber covering fitted on an
o Improper use can result leading to the
and STDs
erect penis. Has a bulb to
spread of STDs.
collect sperms after
 Easily available,
ejaculation. Femidom/female
o There is a possibility of bursting in case
accessible
of too mush friction during sexual act
condom: thin sheath which
 No need for medical
lines the vagina prevents
assistance needed.
entry of sperms.
 Can be used with
Spermicides
167
Diaphragm/cap: it is a dome  Fairly effective (98%) o High risk of infections.
in blocking the sperms.
shaped piece of rubber with a
o Has to be used with other methods e.g.
piece of metal worn by
 Does not have any side Spermicides.
women fitted on the cervix
effects.
opening to prevent sperms
o Possibility of discomfort if not inserted
properly.
from reaching the uterus.
o In rare cases may lead to irritation to
the penis or vagina.
o Has to inserted by a physician
o Correct size must be fitted
Intra-Uterine Device
(IUD)/Loop: small objects
(spiral, loop, ring) made of
steel or plastic which is
inserted by a physician into
the uterus. Fitted by
straightening in a tube like
instrument, pushing this
through the cervix then
pushing the IUD out at the
tube’s end. The IUD interferes
with implantation of the
embryo)
 Reliable for women
who already has
children and those
who do not live far
from the health
facilities
o Has to be inserted by a qualified doctor.
 Stops implantation.
o Do not protect against STDs.
o There is need for pelvic examination to
determine the size of the cervix.
o Can cause excessive bleeding.
 Reversible.
 Long term
contraception
4. Surgical methods
Method
advantages
Disadvantages
Vasectomy and Laparatomy
(tubal ligation):
Vasectomy in men sperm
duct is cut and tied to
prevent sperms from passing  Permanent and 100 %
to the urethra.
effective.
168
o Does not prevent STDs
o Irreversible
In women (Laparatomy)
oviduct cut and tied to
prevent the sperms from
reaching the egg in the
oviduct.
 Safe and simple out patient o Has to be done at a hospital.
operation.
o Pains can be experienced
after surgery.
 Sexual characteristics are
not affected as the
individual can still ejaculate o Not suitable for young
people but for people who
(men)
already have children
Objective: Describe the causes, transmission, symptoms/signs, effects and
treatment of gonorrhea, syphilis and AIDS.
Objective: Discuss the control of the spread of sexually transmitted diseases.
Objective: Interpret data to establish prevalence rate of sexually transmitted
diseases.
SEXUALLY TRANSMITTED DISEASAES
169
170
171
172
MITOSIS
Objective: Describe stages in mitosis and meiosis
Mitosis is cell division which results in formation two identical daughter cells with diploid number of
chromosomes(2n). Mitosis occurs in somatic cells (these are cells which are not involved in the
production of gametes).
Below are changes occurring in a cell during mitosis
1.PROPHASE
Organelles are synthesized and cell increases in size. Each chromosome replicates to form chromatids
joined together by a centromeres.
Chromosomes shorten an become thicker, two chromatids become visible in each chromosome.
Centrioles migrate to the opposite poles of the cell.
173
2. METAPHSE
The pairs of chromatids become attached to the spindle by spindle fibres at the centromeres. The
chromatids move along the spindle until their centromeres line up across the “ equator” of the spindled
and at right angles to the spindle axis.
3. ANAPHASE
The centromeres split into two and the spindle fibres pull the daughter centromeres to opposite. The
separated chromatids, now called chromosomes, are pulled along behind the centromeres.
174
The chromosomes reach the poles of the cell, uncoil, lengthen and lose the ability to be seen clearly.
175
4. TELOPHASE
The spindle fibres disintegrate and the centrioles replicate. A nuclear envelope re-forms around the
chromosomes at each pole and the nucleoli reappear. Division of cytoplasm and cell membrane will
result in two daughter cells.
176
MEIOSIS
Meiosis is division of cells which results in formation of gametes or cells with haploid number of
chromosomes(n)
1. PROPHASE I
Organelles are synthesized and cell increases in size. Each chromosome replicates to form chromatids
joined together by a centromeres. Homologous chromosomes come together to form bivalents. Cross
over of genes occur between chromatids of homologous chromosomes. Centrioles migrate to opposite
poles, spindle fibres form and homologous chromosomes lineup along the ‘equator’ of the cell.
177
2. METAPHASE I
Bevalent become arranged across the equatorial plate of the spindle
The spindle fibres of pull the bivalents with crossed genes apart. Starting at the centromeres
The homologous chromosomes, each made up of two chromatids, separate to occupy the opposite ends
of the cell. The chromatids making the chromosomes are now not genetically identical due to crossover.
178
3. ANAPHASE I
Spindles form again at right angle to the spindle axis of the first cell division.
4. TELOPHASE I
The arrival of chromosomes, in the form of chromatids at opposite poles, marks the end of the first
meiotic division. Reduction of chromosome number has occurred but each pole possesses chromosomes
composed of two chromatids.
As a result of crossing over, or chiasma formation, these chromosomes are not genetically identical and
must be separated in the second meiotic division
179
5. PROPHASE II
Centrioles, if present, move to opposite poles of the cells and spindle fibre appear. The spindle fibres are
arranged at right-angles to the spindle axis of the first meiotic division.
6. METAPHASE II
At this division the centromeres now behave as structurally double. They organize spindle fibres on each
side to both poles and hence become aligned on the equator of the spindle.
7. ANAPHASE II
The spindles separate the chromatids, now called chromosomes, to the new opposite poles.
8. ANAPHASE II
Four new nuclear envelope form around the four sets of chromosomes. The cytoplasm and the cell
membrane divide to form 4 new cells with haploid number of chromosomes.
180
181
INHERITANCE
Objective: define gene, allele and chromosome
Objective: Discuss the relationship between gene and chromosome
Chromosomes and Genes
Genetics is the study of inheritance of characters by transmission of gene from one generation to
another.
In the nuclei of cells are thread-like structure called chromosomes. Chromosomes are made up of many
genes along their length and the genes determine the characteristics that are inherited. Chromosomes
in normal cells exist in homologous pairs with both members having identical shape, size and length.
One chromosome of the pair comes from the male parent, the other from the female parent when their
gametes fuse together during fertilization to form a zygote.
Genes are basic units of inheritance. Genes are made of DNA (deoxyribonucleic acid) which codes for
the synthesis of functional proteins (enzymes) and structural proteins which determine the
characteristics.
The gene controlling a particular characteristic can exist in two in forms called alleles.The gene
controlling a particular characteristic can exist in two forms called alleles. Each gene will have two
alleles, one at a particular position (locus) on one chromosome.
Objective: Distinguish between phenotype and genotype, recessive and
dominant.
Alleles can exist in dominant or recessive forms. The dominant form is expressed in capital letter and
the recessive form is represented by the corresponding small letter.
The genotype of an organism is its genetic make-up which is inherited from the individual parents. The
two alleles for a particular characteristic can exist in three different combinations resulting in a
homozygous dominant, homozygous recessive or heterozygous genotype as shown in below.
The phenotype of an organism is its observable characteristics. The phenotype of an organism is
influenced by both its genotype and the environment.
When a dominant allele and recessive alleles are present together, only the dominant allele expresses
itself in the phenotype. A recessive allele will only express itself in a homozygous recessive genotype (i.e.
in the absence of a dominant allele).
The transmission of chromosomes from generation to generation in sexually reproducing organisms is
through the process of meiosis and subsequent fertilization. Fertilization involves a process of pairing
182
homologous chromosomes provided by haploid gametes to restore the species chromosome number in
the zygote.
The transmission of chromosome from cell to cell during growth or replacement is through the process
of mitosis.
Female
Male
Diploid cell in ovary
Diploid (2n) cell in testis
(46 Chromosomes)
(46 Chromosomes)
meiosis
meiosis
Haploid
Haploid
Female gametes
Female gametes
(23 chnromosomes)
(23 chnromosomes)
Fertilisation
Diploid zygote (46 chromosome)
Adult (46 chromosomes)
183
Objective :Describe monohybrid inheritance
Monohybrid Inheritance
Monohybrid in heritance refers to the inheritance of one characteristic that has two contrasting forms
e.g. tall/dwarf for plant height, red/white for colour of flowers and normal pigmentation /albinism in
human and animals.
Each characteristic is controlled by one gene which consists of one pair of alleles which can exist as
dominant or recessive alleles. The dominant allele controls the dominant character such tallness, red
coloured flower and normal pigmentation.
The recessive allele controls the recessive character which is only expressed in the homozygous state,
white coloured flowers and absence of pigment (albinism).
Objective: Discuss Mendelian Experiments in peas and maize
Gregor Mendel’s investigations on monohybrid inheritance
1. Mendel’s First Law: The Principle of Segregation
Alleles of genes exist in pairs, each on separate members of a homologous pair of
chromosomes. The homologous chromosomes separate during meiosis resulting in the alleles
separating into different gametes. The fusion of the male and female gametes during
fertilization allows the alleles recombine again
2. Mendel’s Second Law: The Principle of independent assortment
The segregation of a pair of alleles of a gene for a particular characteristic is independent of the
segregation of the pair of alleles of another gene controlling a different characteristic.
Therefore, the inheritance of one gene is not affected by another gene.
Mendel observed discontinuous variation in some characteristics of pea plants. That is,
characteristics exhibited only two alternative forms, e.g. tall/dwarf, round/wrinkled seeds. He
started his experiment by pure breeding plants or pure lines.
He later did hybridization which is the cross fertilization cross fertilization between pure line
parents with strongly contrasting characteristics.
184
Diagram 1 below summarizes Mendel’s first experiment on inheritance of crossing pure lines
in height of pea plants.
Further investigations on monohybrid inheritance were carried out by self –pollination of
offspring in F1 to form F2, the second filial generation.
Diagram 2 summarises Mendel’s second experiment of crossing offsprings of parents in
Diagram 1.
185
Objective : Predict results of simple crosses with ratio of 3:1 and 1:1 using
terms homozygous, heterogygous, F1 and F2 generations
Objective :Explain why observed ratio differ from expected ratios
especially when there are small number of progeny
From ratio of phenotypes in the offspring, the possible genotypes of the parents can be
deduced.
Ratio of phenotype in offspring
Possible genotype of parents
1. Both homozygous dominat TT x TT
2. One homozygous dominant and one
heterozygous TT x Tt
All tall
All short
Both homozygous recessive tt x tt
1 tall:1 short
One heterozygous and one homozygous
recessive TT x tt
3 tall:1 short
Both heterozygous Tt x Tt
Some of the other characteristics studied in Mendel’s monohybrid crosses and results are
summarized in below:
P1 crosses
F1 phenotype
F2 phenotypic ratio
Homozygous x Homozygous
Dominant
recessive
(pure breed) (pure breed)
Round x wrinkled seeds
All round seeds
3 round : 1 wrinkled
seeds
seed
Yellow x green cotyledons
All yellow cotyledons
Green x yellow pods
All green pods
3 yellow : 1 green
seeds
seed
3 green pods:1 yellow pod
Smooth x constricted pods
All smooth pods
186
3 smooth pods: 1constricted
pod
Objective: Describe a back cross to determine the genotype of a dominant
phenotype
Back – Cross test
A back-cross test distinguishes between organisms of the same dominant phenotype but
different genotype for example, a heterozygous dominant genotype have the same phenotype.
It is use in animal and plant breeding to detect and eliminate undesirable recessive conditions
which are not observed in the phenotype of heterozygous individuals in the breeding stock. A
back-cross involves crossing the offspring to be identified genetically with the recessive
homozygous parent.
If the suspected heterozygous individual is crossed with a homozygous recessive individual, the
expected ratio to confirm the heterozygous state is 1:1 i.e. half of the offspring has the
dominant phenotype and half with the recessive phenotype.
If the suspected individual is homozygous dominant, all offspring will have the dominant
phenotype.
Objective :Discuss complete, *incomplete and *co-dominance
Co-dominance
Co-dominance is a situation in which both alleles are equally strong and both alleles are visible in a
heterozygous genotype. An example of co-dominance is found in chickens. When white chickens are
crossed with black chickens, the result is not a grey chicken, but a chicken with both black and white
feathers. When expressing incomplete alleles, both alleles are written as superscript capital letters
placed above the letter "i".

The formation of roan coat colour in cattle by cross breeding cattle with red and white coat.
187


The formation of pink flower by crossing red-flowered snapdragon with white flowered
snapdragon plants.
The inheritance of ABO blood group in man IA and IB alleles are co dominant, resulting in the AB
blood group.
188
Incomplete dominance
This is where by both allele of the gene are expressed in a heterozygous genotype, however the a
dominant allele does not mask completely the phenotypic expression of the recessive allele
in a heterozygote, then a blending of both dominant and recessive traits takes place in the
F1 and F2 heterozygotes.


In northeast Kansas there is a creature know as a wildcat. It comes in three colors, blue, red, and
purple. This trait is controlled by a single locus gene with incomplete dominance. A homozygous
(BB) individual is blue, a homozygous (bb) individual is red, and a heterozygous (Bb) individual is
purple.
An excellent example of incomplete dominance is snapdragon flowers. When one crosses a red
flowered snapdragon with a white flowered, all of the F1 generation have pink heterozygous
flowers. It appears that the red and white colors were mixed together two create a pink pigment,
but this proves to be untrue when you cross two plants from the F1 generation. The F2
generation has all three colors; red, pink and white, with a ratio of 1:2:1.
*Objective : Explain co-dominance by referring to inheritance of the ABO blood
group phenotypes (A, B, AB & O).
Multiple Alleles
Certain characteristics are controlled by more than two alleles. The gene that control the ABO
bood group in man has three different alleles IA , IB and IO , however, there can be only two
alleles in any one genotype.
IA and IB are co dominant and IO is recessive to both IA and IB alleles.
Genotypes of the three types of blood groups
Blood group (Phenotype)
Genotype
A
IAIA or IAIO
B
IBIB or IBIO
AB
IAIB
O
IOIO
189
Objective :Discuss the determination of sex in humans
Sex Inheritance:
The sex of an individual is determined by a pair of sex chromosomes. In humans, the 23 rd pair of
chromosome is known as the sex chromosomes. In diploid female cells, the sex chromosomes exist as a
homologous pair of two X chromosomes which are identical in length. In the diploid male cells, the sex
chromosome is made up of a single long X and a single short Y chromosome.
The female gametes produced by the ovaries by meiosis will contain one X chromosome. Half the
sperms produced by the testes will contain an X chromosome and the other half a Y chromosome.
Whether an X-carrying sperm or a Y-carrying sperm fertilizes the ovum determines the sex of the zygote
and hence of the child as shown below.
Since there is an equal chance of either an X or a Y sperm fertilizing the ovum, there are approximately
equal numbers of males and females born.
*Objective :Discuss sex linkage
Sex-linked Inheritance:
Certain characteristics are linked with the sex chromosomes. Some examples of sex-linked
characteristics are red-green blindness, muscular dystrophy and haemophilia. In humans, the
chromosomes may contain a recessive allele for colour blindness, muscular dystrophy or haemophilia.
These inherited sex-linked characteristics frequently affected man but occur very rarely in women. They
are expressed in males because of the lack of dominant counterpart on the Y chromosome. Only female
who are homozygous recessive for the trait are affected. Female with heterozygous genotype are carries
who do not show the conditions but carry a recessive allele which they may pass to their offspring.
190
In red-green colour-blindness, the dominant allele for normal vision is XC and the recessive allele for
colour-blindness is XC. The possible genotype and phenotypes in female and males are:
Genotype
Female
Male
Phenotype
X CX C
normal colour vision
X CX c
normal colour vision carrier
Xc Xc
red-green colour-blindness
X CY
normal colour vision
X CY
red-green colour-blindness
Haemophilia is a disease in which a person’s blood will not clot( (lack of clotting factor). The dominant
allele XH produces blood clotting factor for clotting of blood. The recessive allele X h causes haemophilia.
The possible genotype and phenotypes in female and males are:
Genotype
Female
Male
Phenotype
X HXH
normal
XHXh
normal carrier
XhXh
haemophiliac
X HY
normal
XhY
haemophiliac
Objective : Construct pedigrees for monohybrid crosses
191
VARIATION AND SELECTION
Variation
Variation is the differences in characteristics which exist between individuals belonging
to the same population or species.
The variation between individuals in a population can be continuous and discontinuous
variation.
Objective: describe differences between continuous and discontinuous variation and give
examples of each.
A comparison of continuous and discontinuous variation is shown in below.
Continuous variation
1.Continuous variation exhibits many
intermediate charateristics
In a population, this variation involves
a wide range of individual, whose statistics
wjll produce a nonnal distribution curve
when plotted as a histogram.
2. The characteristic. are not easily
Discontinuous variation
1.Has sharply contrasting
characteristics with no
intermediate forms between
2. The characteristics can be
distinguished easily.
distinguishable.
3. Environmental factors affect the way the 3. The environment has little or
no effect
onway the
genes express themselves. Environmental or no effect
on the
changes prevent the genes from expressing
its full effects.
4. It ls brought about by the combined
effects of many Ilenes.
S. Examples: intelligence. height. weight,
colour of skin.
genes
genesexpress
expressthemseives.
themselves
4. It is brought about by one or
only a
only a few genes.
5. Examples: ABO blood group,
ability to roll tongue,
to taste phenylthiourea.
192
no.of
no. of
people
people
Height
Continuous variation of height in
In a population group
AB A
O
B
Discontinuous variation of ABO blood
in a population
2.Variation is caused by new combinations of genes through sexual reproduction, mutation and
immigration of individuals with new gene combination.
(a) Continuous variation is caused by :
(i) Random assortment of genes during gamete formation by meiosis.
(ii) Random pairing of individual gametes during fertilisation gives rise to new sets of
gene combinations in the offspring.
(b) Discontinuous variation is caused by:
(i) Mutations or sudden changes in chromosomes and genes in normal cells or
gametes. Mutations occur spontaneously or due to the effects of certain drugs and
radiation.
(ii) Immigration of new individual which may bring new genes into the population.
When new individuals reproduce with existing members of the population, new gene
combinations can occur.
The gene pool is the sum of all the genes for a population of a species. Mutation and
immigration can introduce new genes into a gene pool whereas sexual reproduction
can only produce new combinations of existing genes. Many farmers introduce
new stock or crops to bring new and possibly better characteristics into their
population.
3. Variation is an advantage because it increases the chances of survival for breeding and
produces offspring that survive under new conditions.
4. Variation is an important source of differences within a species, These differences may be
selected (by natural selection) for evolution.
193
Mutation
1. A mutation is a spontaneous change to a chromosome or a gene that causes it to code a
different characteristic. Mutation can occur in ordinary cells or in gametes.
2. Since chromosomes and genes control the making of proteins, a change in the number,
size of chromosomes and the chemical structure of a gene can result in a different protein or
enzyme causing a different characteristic to arise.
Factors Leading to Mutation:
Objective: discuss factors which may lead to mutation
Spontaneous mutation is very rare. However, the rate of mutation is greatly increased by
the presence of mutagens.
 Environmental mutagens include ultraviolet light and high energy
radiations.
 Chemicals such as artificial sweetener, cyclamates (now banned) and
formaldehyde in certain concentrations are mutagenic to certain organisms.
Two main Types of Mutation:
1. Gene Mutation
Objective: describe gene mutation and discuss causes of gene mutation
i.
ii.
iii.
In gene mutation, the gene may mutate to become dominant or recessive
The mutation can be inherited and may persist within a species. The gene may mutate again or
revert back to the original state
Examples of gene mutation in organisms:

Gene mutation in bacteria and insects is generally beneficial and increases their chance
of survival. Mutant forms of bacteria are usually resistant to antibiotics and mutant
forms of flies and mosquitoes are resistant to the pesticide DDT.

Gene mutation in humans leads to severe genetic disorder such as sickle-cell anaemia
and haemophilia. Sickle-cell blood contains sickle-shaped (distorted) red blood cells
which reduces the oxygen carrying capacity of blood causing anaemia. Haemophiliac
blood lacks blood clotting factors.

Most gene mutations are recessive and are masked by dominant normal genes. In the
case of sickle-cell anaemia, the individual with a heterozygous incomplete dominance
sickle- cell trait (Ss) is not anaemic but resistant to malaria. This gives a selective
advantage to people living in areas where malaria is endemic. Persons with two
recessive mutant genes (i,e. homozygous genotype, ss) usually die of fatal anaemia.
194

In the case of haemophilia, the gene on the X chromosome of the ovum mutates and
becomes recessive, Females with genotype XHXh are carriers and do not suffer from
haernophiha, Since there is no allele for normal blood in the Y chromosome, males with
genotype XhY are haemophiliac.
2. Chromosome mutation
Objective: describe chromosomal mutation and discuss causes of chromosomal
mutation
i.
Chromosome mutation involves the change in number (lack of a chromosome or have
an extra chromosome) and size of chromosomes resulting in a different phenotype.
ii.
It is caused by abnormal behaviour of chromosomes during meiosis.
iii.
Chromosome mutation in human beings leads to abnormal characteristics which are
harmful. The genetic disorder Down's Syndrome is the effect of one extra chromosome
in zygote i.e. individuals have 47 chromosomes in their cells instead of 46.The extra
chromosome comes from the mother or the father. During meiosis an extra chromosome
may result when one of the duplicate chromosomes does not separate. Individuals with
Down's syndrome are born with characteristic facial features, physical defects and
mental disability.
iv.
Mutation causes variations in the population wh.ich 8Ie the basis upon which natural
selection operates. Individuals with advantageous variations resulting from mutations
are selected for and they are more likely to mature and reproduce and thus passing on
these variations to their offspring.
Natural Selection
Objective: Discuss effect of variation and competition to the survival of organisms in the
environment.
1. Natural selection is the competition for existence between individuals in a population.
It is a process whereby individuals which are better adapted to their environment tend to
have an increased chance of survival and have a greater opportunity to reproduce
themselves whereas poorly adapted individuals dies off even before they can reproduce.
2. Natural selection involves a struggle for survival and the fittest of all survives.
Competition among members of the same species for the same requirements (e.g. food,
water, spaces etc.) and the pressure of the environment force the weaker members of the
population to die off or become limited in members.
3. Natural selection depends on variation within every species. Some of these variations
help an organism to survive in the struggle of survival. Organisms with these
advantageous variations tend to survive and reproduce and therefore pass onto their
offspring favourable characteristics. Mutations can give rise to beneficial variations
allowing a species to adapt to changes in the environment and even prevent their
extinction.
195
How Natural Selection can Lead to Evolution:
Objective: Assess the importance of natural selection as a possible mechanism for evolution
Natural selection is an on-going process which promotes long term changes in a species
over many generations. It is, therefore, a possible mechanism for evolution. Charles
Darwin's theory of evolution proposes that existing species colonising different and
isolated habitats could develop certain characteristics adapted to these environments as a
result of natural selection over millions of years; this would eventually lead to the
formation of a new species.
Struggle for Survival
Variation
Organisms reproduce at a faster rate than
food production rate leading to
competition among members of the same
species for resources like food, shelter
and mates
Particularly, discontinuous variation caused
by mutation. Also caused by the
inheritances of new gene combinations in
continuous variation.
Natural Selection
Advantageous characteristics or variations are selected for
Survival of the fittest
Organism with best suited characteristics predominate in the population
Inheritance of beneficial variations
Favourable characteristics pass onto offspring over a period of many generations
New Species
Formation of genetically distinct species
196
Examples of natural selection:
o The dark peppered moth
Before the industrial revolution in England, light coloured peppered
moth which rests on trunk of trees during the day are camouflaged by the
light coloured lichen on the bark making it difficult for birds to prey on
them. A sooty environment after the industrial revolution allowed the dark
variation of the peppered moth to increase in number as they can survive
predation from birds against soot blackened tree trunks. Hence, dark
moths were selected for and the light coloured moths were selected against
as they are better adapted than the light coloured moths to the new sooty
environment.
o Sickle-cell anaemia
The mutant gene for sickle-cell anaemia is common in areas where malaria
is endemic because it gives a selective advantage to individuals with the
sickle-cell trait (Ss). These individuals have a slight immunity to malaria.
o Penicillin-resistant bacteria
Disease causing bacterium becomes resistant to penicillin because of a
mutant allele which could prevent the cell from being destroyed by
penicillin. This allele provides a selective advantage to the bacteria and is
passed onto the offspring by natural selection.
Therefore, the bacteria continue to multiply in the diseased organism
despite treatment with penicillin.
o Insecticide resistant Insects
Some mutant forms of insects are resistant to the pesticide DDT. If the use
of DDT is continued, the mutant species of insects will multiply and soon
replace the entire species of insects which can be destroyed by DDT.
197
Artificial Selection
Objective: Describe the role of artificial selection in the production of economically important
and animals.
1. In artificial selection, man deliberately selects and interbreeds individual plants or
animals to produce completely new varieties of animals and plants with desirable
characteristics.
2. Artificial selection allows farmers and breeders to select the best and fittest offspring to
improve agricultural livestock and crop plants. Plants and animals are selectively bred for
specific characteristics. For example:
(a) New varieties of crop plants such as wheat, barley and potatoes are bred for higher crop
yield, better nutritional value and greater resistance to disease and a greater tolerance to
extremes of environmental conditions.
(b) Selective breeding of fruit trees results in larger and better quality fruits with improved
taste.
(c) Selective breeding of animals such as cattle could lead to higher meat and milk
production. Similarly, sheep are selected for their wool quality, thickest and length of coat
to improve the quality and yield of wool.
(d) Horses and dogs are bred for hunting, racing and appearance.
3. There are two main types of artificial selection:
(a) In-breeding which involves the crossing of closely related individuals in a species.
In crop plants, self-pollination and self-fertilisation are carried out to maintain desirable
characteristics of parent. In animals, related offspring from the same parents are mated e.g.
highly bred pedigree dogs. This can also lead to the accumulation of harmful genes in the
offspring resulting in physical and/or mental defects which reduce their chances of survival
when they to return to the wild.
(b) Out-breeding which involve the crossing of unrelated species. For example, crossing a
wild species of grass with a strain of wheat produces a hybrid variety with increased
resistance to diseases and adverse environmental conditions.
198
ENERGY FLOW, FOOD CHAINS AND FOOD WEB
1. Ecosystem: is the living and non-living components of a region which interact to produce a
stable system.
Components of the ecosystem are:
 Biotic component: living organisms such as the producers, preys, predators and parasites.
 Abiotic component: Non-living components of the environment which influence the living
organisms such as climate, soil conditions, water, temperature, etc.
Examples of ecosystem are a pond, seashore.
Abiotic factors influence the distribution of organisms within an ecosystem while biotic factors affect
the population of organisms within an ecosystem.
An ecosystem consists of a network of a number of different habitats with their communities of
organisms interlinked by the flow of energy and nutrients.
Habitat : is a place where an organism lives.
Population: is a group of individuals of one species found in the same habitat.
Community: refers to all organisms that interact in an ecosystem.
Objective: Describe energy transfer through an ecosystem
2. Food Chains and Energy Flow along Food chains:
The living organisms in the ecosystem interact with each other via a chain of energy transfers called
food chains.
A food chain is a group of organisms linked or related by their feeding habitats
Producer
Green plants which
Absorbs the sun’s energy
And produce food by photosynthesis.
Primary consumer
Secondary Consumer
Herbivores Feed on green
plants as their sources of energy
for growth, metabolic activities
and reproduction.
Carnivores(predators) prey
upon herbivores as their
source of energy for growth,
metabolic activities and
reproduction.
Food chains end with decomposers: bacteria and fungi which promote the breakdown and decay of
dead plants and animals and thus help return vital mineral salts to the soil. This improves soil fertility
which in turn promotes healthy growth of more producers.
Some examples of food chains:
 Wheat
grasshopper
sparrow
 Grass
rabbit
fox
 algae
water fleas
stickleback fish
199
hawk
perch fish
pike fish
3. Food Webs:
Food webs are made up of several interconnected food chains. Ecosystems with complex food webs are
more stable than those with simple ones. Within food webs, organisms obtain their food in different
ways as shown below:
Tree(wood, leaves, fruits)
Woodlouse
slug
Caterpillar
worm
Blackbird
Ground beetle
Spider
Bluetit
Frog
Shrew
Grass snake
Hawk
Fox
4. Pyramids of Numbers, Biomass and Energy:
Food chains can also be presented as a pyramid of numbers which shows the number of each organism
at each trophic level. The position of an organism in a food chain is called its trophic level.
In an ecosystem, there are usually far more organisms at lower trophic levels than at higher trohpic
levels.
Number of
organisms
at each
level
decreases
Hawk
Sparrow
Grasshopper
Wheat plant
Tertiary consumer
Secondary consumer
Primary consumer
Producer
Number of organisms
A pyramid ofbiomass shows the mass of material at each trophic level. The biomass of the successive
trophic levels decreases progressively due to the loss of energy in respiration at each level.
200
Bird
Biomass
at each
level
decreases
Tertiary consumer
Secondary consumer
Beetle
Aphid
Primary consumer
Grass
Producer
Biomass
There are situations where pyramids of numbers and biomasss can be inverted or shaped differently.
These are situations which involve parasites in a food chain.
Aphids
Greenfly
Plasmodium in mosquito
Plasmodium in red
blood cells
Ticks
Sheep
Man
Rose bush
Objective: Describe the importance of the sun as the principal source
of energy for biological systems.
Objective: Describe the non cyclic nature of energy flow
5. Non-cyclical Nature of Energy Flow in Biological System:

Energy from the sun enters the ecosystem through organic compounds (carbohydrates)
produced by photosynthesis in green plants. However, only about 1% of sunlight striking a leaf
is absorbed by chlorophyll and used in photosynthesis. Most of the light striking a leaf is
reflected, or transmitted or converted to heat energy and lost by radiation.

Energy from the sun passes along a food chain. The energy is progressively lost at each trophic
level as heat energy in respiration. Successive members of a food chain incorporate into their
biomass (as a new tissue) only about 10% of the energy available in the organism they consume.
201
The remainder 90% is lost as heat energy in respiration and a small amount lost through
excretion.
When a herbivore consumes a plant, only a small fraction of the sun’s energy (about 10%)
stored in the plant is used by the herbivore for growth and formation of new tissues. The bulk of
the energy is lost as heat in respiration to the surroundings, in urine and faeces.

The energy flow in the food chain is non-cyclical. Energy flows in one direction and it is either
utilized or lost into the surrounding but cannot be recycled.
See diagram below:
Producer
sun
100%
Pasture area(1m2)
20 000kJ
1% of energy
incorporated
in
photosynthe
sis
2
Primary consumer
Secondary consumer
2 000kJ
200 kJ
Tertiary consumer
20kJ
10% of
10% of
energy
energy
incorporated
incorporated
in new
in new tissues
tissues of
of herbivore
new tissues
herbivore
90% lost
of herbivore
.some material may not be eaten
is
.some material not digestible
.some used in excretion & a lot used in respiration
10% of
energy
incorporated
in new tissues
of herbivore
99% lost by
. being transmitted through
. being reflected back
90% lost
. not being correct
.much of plant body e.g
wavelength.
lignin and cellulose may be undigestible,
consumers rarely eat the whole plant
.a lot of energy used in
90% lost
respiration.
.some material may not be eaten
.some material not digestible
. some used in excretion
. a lot used in respiration.

Energy loss at each trophic level results in insufficient energy to support higher trophic levels.
Thus, the length of the food chain is limited. The longer the food chain the more energy will be
lost, the shorter the chain, the more energy will be available for higher consumers.
202

Worldwide people feed mainly on plant foods. There is greater efficiency in supplying green
plants as food because plant crops produced on a given area of land will provide more energy
than the number of animals that could be raised on that area.
6. Accumulation of Substances along a Food Chain:
 Non-biodegradable substances, poisons and toxic substances can accumulate along a food
chain reaching significant amounts in the bodies of consumers in the higher trophic levels.
This is because small amount of such substances persist in the tissue of organisms, builds up in
their bodies and passes onto the organism that feeds on it.

DDT is an insecticide used to control mosquitoes, it is non-biodegradable.
7. Relationship Between Prey and Predator:
Predator starve and
die as population of
prey decreases
population
Prey number decreases due to
Increased predator population

fewer predators; allow prey
to increase in number
Time(yrs)
The population size of prey and predator fluctuates together with the fluctuation in the
predator population, which usually lag behind those of the prey. This is because the predator
depends on the prey for food.
203
NUTRIENTS CYCLE IN NATURE
Objective: Describe the use and retention of nutrients in the ecosystem
Nutrient Cycling and Retention
The elements organisms require for development, maintenance, and reproduction are called nutrients.
Ecologists refer to the use, transformation, movement, and reuse of nutrients in ecosystems as nutrient cycling.
Examples of nutrient cycling are: the carbon and nitrogen cycles.
Element carbon is used in the ecosystem to form food molecules such as carbohydrates, proteins and fats/oils in
living organisms.
Element nitrogen is used to form proteins in plants.
Objective: Describe the carbon cycle including the role of photosynthesis,
respiration, animal nutrition, decomposers, fossil fuels and combustion.
Carbon Cycle
204
Photosynthesis:

Plants use atmospheric carbon dioxide to make carbohydrate,sugar, by the process of
photosynthesis. The animals the eat plant material obtaining the carbon in the form of
carbohydrates, proteins and other carbon compounds made by the plant.
Respiration:

Animals, plant and micro-organisms such as bacteria and fungi break down carbohydrates in
their cells to produce carbon dioxide and water
Decay and Decomposition:

Saprotrophs break down organic matter of dead plants and animals, especial bacteria and fungi.
Then organic compounds such as carbohydrates are decompose be the micro-organisms to
produce carbon dioxide.
Fossil Fuels:

These are formed from sedimentation of partly decomposed plant remains over millions
of years. The fossil fuels are oil, coal and natural gases.
Combustion:

This is burning of the fossil fuels, oxidizing the carbon to carbon dioxide
205
Nitrogen Cycle
Objective: Describe the nitrogen cycle in terms of decomposition, nitrogen
fixation and absorption.
leguminuous
plants
Decomposition:
 Saprophytic bacteria and fungi decompose plant and animal remains. One of
the products of this decomposition is ammonia, which is washed into the soil.
 Excretory products from animals contain nitrogenous waste products such as
ammonia, urea and uric acid.
206
 The organic matter in animal droppings is also decomposed by soil bacteria.
Nitrifying bacteria (nitrification):
 Bacteria living in the soil use ammonia from excretory products and
decomposed organic material as a source of energy, in the process converting
ammonia to nitrates.


Nitrosomonas bacteria oxidizes ammonium compounds to nitrite
(NH4- NH2-).
Nitrobacter bacteria oxidizes nitrites to nitrates (NH 2- NH3-).
207
Nitrogen fixation (by nitrogen fixing bacteria):
 This is the process of converting the gas nitrogen to ammonium
compounds by some special bacteria found in the soil and in root
nodules of leguminous plants.
Nitrogen fixation (by lightening):
 The high temperature of lightning discharge causes some of the
nitrogen and oxygen in the air to combine and form oxides of nitrogen.
These dissolve in the rain and are washed into the soil as weak acids,
where they form nitrates
208
Poor Agricultural Practices Resulting in Destruction of the Ecosystem.
Objective: discuss how poor agricultural practices result in destruction of the ecosystem e.g.
monoculture, excessive use of fertilizers and pesticides, overstocking, deforestation .
Impact of Agriculture on the Ecosystem:
1. Deforestation – removal of natural vegetation such as forest from the land.
One reason for deforestation is provide more land for agriculture.
The harmful effects of deforestation are:
(a) Destruction of natural habitats for plants and animals
Food chains and food webs are affected causing an imbalance in ecosystem. With the
removal of producers from ecosystem, herbivores may not be able to find alternative
sources of food. Eventually they die and carnivores which feed on herbivores will also die
out
(b) Extinction of many plants and animal
Plants and animals die out more rapidly than the can reproduce. Their population decrease
to such a point that they become endangered species and may die out completely.
(c) Soil erosion
The roots of plant and trees, hold and bind soil particles together. Then there are removed
the soil is exposed to direct rainfall and wind that gradually remove the fertile top soil,
leaving the land infertile and uncultivable.
(d) Reduction of rainfall
With the removal of plants and trees, the amount of transpiration decreases drastically.
This decreases water vapour content in the water cycle leading to reduction in rainfall.
(e) Loss of robust species that can be used in artificial breeding to improve crops
Wild species of plant are able to withstand changes in the environment. It is possible to
develop stronger crop varieties with increased resistance to diseases and adverse conditions
by cross-breeding with related species.
(f) Increase in carbon dioxide level and temperature
The carbon dioxide level in the atmosphere increases due to the drastic decreases in
photosynthesis. Carbon dioxide, being a greenhouse gas, will trap sunlight and heat in the
atmosphere causing a rise in temperature. Increase in temperature is also due to removal of
shade provided by the leaves of the trees.
(g) Decrease in gene pool
The gene refers to the total variety of genes present in a population of plant and animals
species in the ecosystem. With deforestation the gene pool decreases due to:
- Loss/destruction of natural habitats of plants and animals resulting in reduction in the
number and variety of species leading to endangered species and extinction of species.
- Destruction of organisms by pesticides such as insecticides, fungicides which are used in
agriculture to kill crop pests. These toxic chemicals kill organisms directly or through the
food chains.
209
2. Eutrophication
- Excessive use of fertlisers in agriculture results in nitrates and phosphates being carried
away by water into ponds, lakes and rivers. The water become enrinched with nutrients
and this causes rapid and excessive growth of algae on the water surface
eutrophication.
- This results in overcrowding and prevents penetration of light into water. The weds and
the aquatic plants die and aerobic bacteria that decompose them increase in number
and deplete oxygen in water. Since there is a reduction of photosynthesis and a
decrease in dissolve oxygen available for consumers, both the producer and consumer
populations in the aquatic ecosystem fall greatly.
- Eutrophication can also be caused by the discharge of untreaded sewage, detergents
(containing a lot phosphates) and animal waste into waterways. The organic waste
pollutants are also decomposed by aerobic bacteria that deplete oxygen dissolve in
water.
- One method used to reduce the use of excessive artificial fertilizers is crop rotation.
Different crop are grown on the same land in successive years. The two harvested
crops, have different mineral requirements and often obtain them from different soil
depths. Planting legumes and ploughing the leguminous plants back into the soil after
harversting restore nitrogen compounds to the soil.
3. Pest Control
- Agriculture promotes monoculture in crop production and in animal production.
Because of these pests usually spread rapidly were there are agricultural practices.
Therefore, use of insecticides and pesticides is in agriculture.to
- Insectcides used in concentrations which seem harmless to man can be poisonous for
other organisms like fish and birds.
- DDT is a stable, non-biodegradable insecticides that is effective in killing pests and
mosquitoes. However, DDT accumulates in the fat deposits of the bodies of consumers
in higher trophic levels causing death
(a) Birds consuming worms and insects contaminated with DDT from sprayed leave can
accumulate lethal doses of DDT.
(b) Insecticide may also destroy insect organisms in soil.
(c) Insecticides washed off into the rivers and lakes can accumulate to significant
amounts to poison fish and other aquatic l life.
- Non-biodegradable pesticide are discouraged in many countries. Alternative less
harmful but just effective methods used in pesticides are:
(a) The use biodegradable organophosphates pesticides which are less harmful to the
environment but toxic to man.
(b) Biological control which uses a natural predator of the pest to control its numbers.
4. Monoculture: growing of a single species of crop on the same piece of land, year after year
- Involves destruction organisms which feed on, compete with or infect the crop plant.
This might result in extinction of other animal and plant species.
210
-
The balanced life of a natural plant and animal community displaced from farmland and
left to survive only in small areas of woodland, heath or hedgerow.
5. Overstocking: keeping of livestock whose number exceeds the carrying capacity of a piece of a
piece of land.
- Overstocking leads to over grazing which makes grass not to have time to complete its
reproductive cycle. Therefore, resulting in some grass species becoming extinct.
- Trampling of soil by some hoofed animals result in the soil forming a hard layer and the
soil losing its properties.
FAMINE
Objective: Discuss the problem which contribute to famine such as unequal distribution of food,
natural disasters (such as floods and droughts) and increase in population
Famine: Lack of food over large geographical areas sufficiently long and severe to cause widespread
disease and death from starvation.
Problems Which Contribute To Famine:
1. Unequal distribution of food
 Some geographic feature of areas make food production difficult, therefore such area may remain
with minimal chances of food production.
 Wars have also led to minimal food production in some regions of the continent
2. Increase in population
 Increase in population lead to increase in demand for food, and usage of land for food
production. The rate of population growth often exceeds the rate of food production
3. Natural disasters
 Droughts – persistent shortage of rainfall over years leads to minimal food production
and insufficient foods.
 Flooding – frequent floods can disturb food production in fields/farms, leading to minimal
food production and starvation.
211
Pollution
Objective: Describe a cause, effect and control of each of the following types of pollution: air, water
and land.
Pollution is contamination of air, water, or soil by substances that are harmful to living organisms.
A pollutant is a harmful substance which contaminates the environment and causes harm to living
organisms in the environment.
The consequences of pollution are observed in the effects on living organisms and in possible long term
effects on climate.
1. Air Pollution:
Type of pollutants
a) Sulphur dioxide
Source of pollution
Burning of fossil
fuel.
Car exhausts.
Natural
disasters such
as volcano
eruptions



Effects of pollution
Causes acid rain
(sulphuric acid formed).
Changes pH of soil and
water ways.
Damages plants leaves
Irritates eyes and lungs
when breathed in.
Aggravates diseases such
as asthma and
bronchitis.
Corrodes metal
structures and erodes
limestone in buildings
and sculptures
Causes acid rain (nitric
acid formed).
Irritates eyes and lungs
when breathed in.
Nitrogen dioxide
combines with smoke in
the presence of sunlight
to produce destructive
photochemical smog.






b) Nitrogen Oxide

Car exhausts.



c) Carbon monoxide


Burning of
fossil fuels.
Car exhaust.


212
Competes with oxygen
for haemoglobin and
therefore reduces the
capacity of blood to
carry oxygen.
Colourless and
Control

Coal and
Petroleum are
treated to
remove
sulphur.

Catalyctic
convertors
change
nitrogen gas
before it is
released into
atmosphere.

Catalyctic
convertors
change
carbon
monoxide to
carbon
d) Lead

e) Chlorofluorocarbon


e) Smoke and dust


Anti-knock in
petrol
Aerosol
propellants.
Cooling agents
in
refrigerators
and air
conditioning.

Soot –unburnt
carbon
particles due
to incomplete
burning of
fossil fuels.
From quarries
saw mills and
asbestos
factories.





odourless gas –an
increase of carbon
monoxide level in
blood causes death.
Causes brain damage in
children
Breaks down ozone
layer and allow more
UV radiation to
penetrate earth, may
increase skin cancer
incidence.
Absorbs infrared
radiation. Cause global
warming
Blacken buildings,
covers plant leaves and
reduces rate of
photosynthesis.
Irritates eyes and lungs
when breathed in.
Causes lung diseases.



dioxide
before it is
released into
atmosphere.
Use unleaded
petrol
Reduce usage
in industry
Increase
efficiency of
combustion
engines.
2. Water Pollution:
Type of
pollution
Raw sewage
Sources of Pollution




Artificial
Fertilisers

Effect of Pollution
Human and
domestic waste.
Detergents rich in
phosphates.
Farmyard waste.
Industrial waste
from food
processing
industries.

Excessive use of
fertilizer in
farming.



Encourages
eutrophication.
Increases population of
bacteria and decreases
oxygen content in water.
Kills fish and aquatic
organisms.
Bacteria present in
sewage can cause
disease such as cholera
and typhoid in man when
the polluted water is
consumed.
Encourage
eutrophication.
Increases population of
213
Control



Proper sewage
disposal and
sewage
treatment
systems.
Use
bioldegradable
washing
detergents
Use of natural
fertilizers.
bacteria and decreases
oxygen content in water.

Soil erosion
causes mineral
salts to leach
away into
waterways.



Inorganic
waste
(Toxic
Chemical)
Mercury

Pesticides
containing
chlorine used in
crop protection
and control of
disease vector
such as mosquito
Industrial wastes
Lead
cyanide

Industrial waste

Minute concentrations
may be paralysis.

Petroleum

Tanker accidents
and oil spillage.

Clogs respiratiory
systems of animals. Kills
marine creatures and sea
birds.
Ruins beaches and
destroy marine life.

DDT


Non-biodegradable.
Accumulates in fat
tissues of animals along
food chains, reaching
toxic levels in the
consumers of higher
trophic levels.
Affects nervous system,
causes paralysis.



214



Banned
Use
biodegrable
pesticides.
Use biological
control of
pesticides.
Proper disposal
of waste
containing
mercury.
Proper disposal
of waste
containing lead
cyanide and
other toxic
chemicals.
Effective
accident
prevention and
legislation.
Efficient
removal of oil
slicks by
special
detergents.
3. Land Pollution:
Type of Pollution
Refuse/litter e.g.
plastic, used
paper,
Source of Pollution



Used plastic
bags.
Used papers
Used cans and
bottles
Effect of pollution



215
Plastic is not digestible in
alimentary canal of
animals; blocks the
alimentary canal of
animals; causes death of
animals
Litter makes environment
to be unattractive.
Creates breeding place for
disease vectors.
Control


Proper
disposal of
litter.
Recycling
of uses
plastic,
paper,
bottle, can
and metal
scraps.
Conservation
Conservation is protection and preservation of natural resources and the environment.
Conservation is adynamic process requiring active intervention and management on a global scale.
Objective: Discuss reasons for conservation of species with reference to local plants and species
Reasons for conservation of wild life species and forests:
(a) Economic reasons: Many species of plants are useful sources of oil, fibre, rubber, food(Mowana
and Mosukujane),chemicals(pyrethrum) and medicinal drugs(Sengaparile). Pyrethrum is a
natural insecticide obtained from the flower of the pyrethrum plant.
(b) Ecological reasons: (i) Forests provide many different habitats for living organisms and support
a large number and variety of living organisms.
(ii) A large gene pool is important in the process of artificial selection of
new crops and cattle e.g. crossing a wild grass with a strain of wheat
produced an improved variety.
(iii) Conserve species for scientific studies and prevent extinction of
species.
(c) Climatic reasons: Prevent global warming, disruption of water cycle, reduction of rainfall etc.
Objective: Find out from the local community which plant and animal have become scarce and why?
Use the table below to identify scarce plants in your community and give a reason why they are scarce
Plant identified as
scarce
Reason(s) for being scarce
1.
2.
3.
4.
5.
6.
7.
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Use the table below to identify scarce animals in your community and give a reason why they are scarce
Animal identified as
scarce
Reason(s) for being scarce
1.
2.
3.
4.
5.
6.
7.
Objective: Investigate threatened species (plants and animals) and the need to conserve them
(emphasise examples from Botswana).
The table below identifies some of the threatened plants species. Give a reason why they have to be conserved.
Plant threatened
Reason(s) for being conserved
1. Mosukujane
2. Sengaparile
3. Monepenepe
The table below identifies some of the threatened animals species. Give a reason why they have to be
conserved.
Animal threatened
Reason(s) for being conserved
1. Rhino
2. Wild dog
3. Cheetah
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Some common conservation measures are:
(a)
(b)
(c)
(d)
(e)
(f)
Restriction on the destruction of natural habitats.
Replanting of trees(reforestation).
Impose and enforce limits on the release of pollutants
Preservation of sites of special scientific interest.
Educate and raise public awareness of the importance of conservation.
Setup organisations to legislate and enforce laws to safeguard environment and prevent
deforestation and pollution.
(g) Recycling of materials such as cloth, glass, metal, paper.
Recycling
Objective: discuss reasons for recycling of materials including sewage water, paper, bottles and tins.
Reasons for recycling materials:
(a) Reduce the usage of the natural resources which can be conserved.
For example: recycling paper (which is made from wood pulp) will reduce the amount of timber
used, therefore slows down the rate of deforestation.
Water from treated sewage can be used as industrial water and for watering plants.
The solid waste from treated sewage can be used as a fertilizer for plants.
(b) Reduce the amount of waste materials(paper,plastic metals etc) disposed.
(c) Conserve fossil fuels.
Recycling of materials uses less energy and lower production cost than making new products. It
takes far less energy to melt down scrap metal(iron, aluminium) and use it again than to
produce it from its metal ore.
Project:
Objective: Carryout a project to identify natural resources conserved in Botswana
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BIOTECHNOLOGY
Objective:Difine biotechnology as the application of biological organisms, systems or processes to
manufacturing and service industries
BIOTECHNOLOGY can be defined as the application of biological organisms, systems or processes to
manufacturing and service industries.
USE OF MICRO-ORGANISMS IN BIOTECHNOLOGY
Objective: Explain why micro-organisms are used in biotechnology
MICRO – ORGANISMS ARE USED IN BIOTECHNOLOGY
Because:






They can be grown in large quantities in small vessels
Reproduce very fast and products are obtained faster
Micro-organism and their production can be produced in small scale trials in laboratories
Micro-organisms can be easily genetically manipulated to achieve the desired products
Pure products can be cheaply and safely produced by use of simple inorganic products
Most bacteria produce extra cellular enzymes and other chemicals, making it easy to extract the
products.
ROLE OF MICRO-ORGANISMS IN FOOD PRODUCTION
*Objective: Investigate the role of micro-organisms in food production e.g. bread, madila , chibuku,
single cell protein
1. BREAD (yeast used)
 Wheat flour, a little sugar and salt, and yeast are mixed with water to form dough.
 Addition of water and suitable temperature activate amylase present in flour to digest
starch into simple sugars, glucose
 Within the dough the yeast respires the simple sugars ana-erobically for hour at 350C;
 Alcohol and carbon dioxide are produced.
 The carbon dioxide makes the dough to rise or expand with bubbles.
 The risen dough is kneaded and cooked.
 carbon dioxide is trapped in the dough forming bubbles, this makes the dough to rise.
 During baking (200oC), yeast is killed, the small amount of ethanol produced evaporates
 Bubbles of carbon dioxide expand and trap heat in the bread improving its cooking.
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2. MADILA(bacteria used)
 At commercial level, a specific species of bacteria is used and the conditions are carefully
controlled to assure the quality of the product.
 First, milk is pasteurized (heated at 72oC for 15 minutes). This process kills most potential
pathogenic micro-organisms and those that may interfere with the product quality
 A starter culture of bacteria (Streptococcus thermophilus and Lactobacillus bulgarius) is used
in fermentation of milk.
 The bacteria use the milk as a food source
 Bacteria turn lactose in milk to lactic acid, lowering pH of milk
 The milk proteins coagulates at pH 4.4 forming a thick cream of sour milk
 Fermantation is stopped by reducing temperature of sour milk from 46 OC to 5OC
 Amount of whey in sour milk can be reduced
 The product is then sealed in sterilized containers
Raw
Milk
pasteurised
Bacteria
+
milk
Milk Proteins
Coagulates due
due to lactic acid
Madila
+
Whey
Madila
Whey
Removed
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3. Beer Making (chibuku):
 Yeast fermentation is used to produce alcohol.
 A number of cereals are used to provide the sugars needed by yeast in fermentation.
 During the germination of barley/sorghum grains, enzymes are activated and start the
digestion of starch to maltose and glucose.
Barley grains germinate for 4 days. Enzymes
in the barley digest starch to maltose. The
barley is now called malt.
Grains are dried at a temperature which kills
seeds but do not denature enzymes.
The dried grains are crushed (milled)
Water is added to the milled malt to form
marsh; digestion of starch continues and
sugars dissolve in the water.
Mash is boiled for 2½ hours to kill bacteria
and wild yeast.
Mixture is cooled and there is straining of some
solids. The liquid filtrate is called wort.
Yeast is added to the wort and left to ferment for 24days. Glucose is converted to ethanol, carbon
dioxide and energy is released for the yeast
Mature Chibuku is put in containers
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4. SINGLE CELL PROTEIN – (myco protein):
 Mycoprotein is an example of a ‘single cell’ protein food
 Whole dried filaments of fungus Fusarium graminearum, produced in a continuous process
fermenter. ( it is marked as Quorn, suitable as a meat substitute for humans.
 The hyphae have the same texture as meat fibres and are tasteless
FUSARIUM
GRAMINEARUM
Cut and coloured
to resemble
meat
GLUCOSE
Add meat or
Fish flavouring
NUTRIENTS
(high in nitrogen)
Fusarium
Graminearum

ADVANTAGES OF MYCOPROTEINS
 Grow fast (doubles its mass every few hours)
 High in first class proteins and fibre
 Low in fat, with no cholesterol
 Rich protein source for vegetarians and vegans.
DISADVANTAGES OF MYCOPROTEINS



Can be indigestible and taste different
May cause gout due to high RNA content.
Costly at present.
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Quorn
ROLE OF MICRO – ORGANISM IN FUELS AND CHEMICALS
Objective: Investigate the role of micro-organisms in fuels and chemicals e.g. biogas, alcohol,
biological enzyme washing powder.
1. BIOGAS (METHANE)
 Methane is produced by use of anaerobic and methanogenic bacteria.
 Cow dung, human waete and vegetables waste are fed into an underground
fermenter or biodigester.
 The bacteria digest the proteins, carbohydrate and fats.
 The anaerobic respiration will lead to production of methane and carbon dioxide.
 The gas piped to burners for cooking, heating or generating electricity.
Gas supply
to home
gas
Inlet
Organic waste
Enters here
0utlet
Ground
Discharged slurry used as manure
Digestion vessel
Organic waste
Anaerobic bacteria
Methanogenic bacteria
Carbohydrates
glucose
ethanoic acid
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methane + carbon dioxide
2. ENZYMES
 Can be produced commercially by fermentation using feedstock such as molasses..
 Fungus(e.g. Aspergillus) or bacteria(e.g. Bacillus) are used to produce enzymes.
 The micro-organisms produce the enzyme in a fermenter.
 Air and the food to be digested are fed into the fermenter.
 Mixture coming from fermenter is filtered.
 Enzymes are then extracted from filtrate collected.
 They can be used either in solution or trapped in polymer beads (where they are
less easily destroyed).
USES OF ENZYMES
PROCESS
WASHING CLOTHES
WASHING DISHES
ENZYME FROM
MICRO-ORGANISM USED
 Proteases
 Lipases
 Amylase
CHEESE MAKING


Rennin
Lipase
MEAT TENDERING

Proteases
PURPOSE
Biological washing powders
remove stains e.g. blood and fat
Dishwasher powder remove
starch smears on plates
 Curdles milk
 Speed up ripening of
Danish blue cheese
Begin break of protein fibres.
3. ALCOHOL:
 As a fuel: The country Brazil, in Southern America, uses ethanol produced by
biotechnology from sugar cane as a fuel for their cars.
 This idea came around in the 1970's when the price of petrol rose to a very high
level. Sugar cane, usually used to make sugar for human consumption, was grown.
 The juices containing sugar are extracted and yeasts are used to ferment the juice
to make alcohol (ethanol).
 The resulting mixture is then distilled to concentrate the percentage of alcohol in
the liquid.
 The waste material left over from the juices are extracted is burnt to supply the
heat energy for the distillation process.
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ROLE OF MICRO-ORGANISMS IN THE PRODUCTION OF MEDICINE SUCH AS
Objective: Discuss the role of micro-organisms in the production of medicine such as antibiotics and
vaccines
1. ANTI-BIOTICS
Penicillin is produced by fungus PENICILLIUM notatum. Penicillin destroys cell walls of a wide
range of pathogenic bacteria.
As the fungus (Penicillium sp) grows aerobically in the fermenter . It uses up nutrients. Only
when the nutrient level falls greatly does the fungus produce penicillin. Production of the
antibiotic begins after about 40 hours in the fermenter and reaches its maximum after about 7
days.
PENICILLIUM
SP
GLUCOSE
NITRATES AND SULPHATES
AIR
FILTERING
Dry fungus
And cell as
Animal feed
Purify and
Modify
Penicillin
2. Vaccine:


Vaccines have been made for many viral diseases.
Vaccines can be made in several ways:
Dead pathogens – e.g. whooping cough vaccine
Weakened pathogens – oral polio vaccine
Genetically engineered fragments – proteins from the pathogen’s surface which are recognized
by lymphocytes, e.g. hepatitis B viral coat protein.

The products are then made in solution form and are injected into bodies of animals
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ROLE OF MICRO-ORGANISMS IN GENETIC ENGINEERING
*Objective: Discuss the role of micro-organisms in genetic engineering e.g. insulin production, crop
plant resistance, gene therapy
GENETIC ENGINEERING
This is the insertion genes from one species into another in order to produce desirable traits such as
production of important substances, to develop resistances to diseases, pests, spoilage, and herbicides
etc.
General Procedure:




Identification and isolation of the gene
Insertion of the gene into bacterial plasmid (circular DNA molecules)
The bacterium now has acquired the ability to produce the desired product
Culture, extraction and purification of the product.
E.g. 1. Production of insulin:






Restriction enzymes in the bacteria are use to cut the plasmid open to allow the insertion of the
insulin gene isolated from human pancreatic cells.
The donor DNA is also cut by the restriction enzymes
The enzyme ligase splices the human insulin gene into the plasmid to form recombinant plasmid
The plasmid is then reintroduced into the bacteria
The bacteria acquires the ability to produce insulin
Bacteria can then be cultured in large fermenters and the insulin extracted and purified.
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2. Crop plant resistance

Bacillus thuringiensis produces toxin that kills insects by affecting their guts. Several different
kinds of crop plants have been genetically engineered to produce this toxin.

Some plants have genes that make them resistant to herbicides
Agro bacterium tumefacien is an ideal cell for introducing desirable genes for crop resistance into
host cell:
 Restriction enzymes cut desirable gene from the chromosome of a cell of plant
that is resistant to herbicides
 Restriction enzymes in the bacteria are used to cut open the Ti plasmid found in
the Agro bacterium so as to allow the insertion of the desirable gene.
 The enzyme ligase splices the desirable gene into the Ti plasmid to form
recombinant plasmid
 A plant is then infected with the engineered Agro bacterium
 The Ti plasmid in the Agro bacterium causes formation of cancerous growth
(tumour), called a crown gall, on the plant.
 Each cell in the gall contain the Ti plasmid with the desirable gene in place.
 Plantlets can then be cultured from small pieces of tissue cut out of the gall.
 The plantlets carrying the Ti plasmid are transferred to the soil.
 With the help of the desirable characteristic from the gene, the plantlets grow
to form genetically identical mature plants.
3. Gene therapy
Gene therapy is an attempt to correct a hereditary disease caused by an inheritance of a defective gene
A normal gene is inserted into the defective cells.





Identification and isolation of the gene
Insertion of the gene into vector (disabled virus or liposome)
the virus is introduced into the defective cell
virus infects the defective cell
the healthy gene repairs the diseased cell
Cystic fibrosis is condition caused by lack of cell membrane protein leading to production of a thick,
sticky mucus in the air passages
The condition is a good candidate for gene therapy:

the coat of an influenza virus is uses

The disabled virus is sprayed into the passages.
How Industries in Botswana can Benefit from Biotechnology
227
*Objective: Discuss how industries in Botswana can benefit from Biotechnology
Benefit from Biotechnology:

It creates employment

Foreign exchange where money is generated by selling the products.

Improved general health by drugs (vaccines and antibodies)

Conservation of certain resources (using proteins produced from micro-organisms spares grass
thus preventing overgrazing.
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