Biology MSC
Biology MSC
Biology MSC
a) Animal cell
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b) Plant cell
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SOME PARTS REVEALED UNDER AN ELECTRON MICROSCOPE
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
MITOCHONDRION
Site for liberation of energy during aerobic respiration
RIBOSOME
for assembling of amino acids to form proteins of the organism
CELL WALL
VACUOLE
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CHLOROPLASTS
QUESTIONS
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SPECIALISED CELLS
OBJECTIVE: Describe the relationship between cell structure and function using an animal cell and a
plant cell as examples
Its function is to absorb water and mineral ions from the cell.
ADAPTATIONS
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Vacuole is relatively large for accumulation of water and mineral ions.
2. PALASADE CELLS
ADAPTATIONS
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EXAMPLES OF SPECIALISED CELLS IN ANIMALS:
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
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2. NERVE CELL
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.
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3. SPERM CELL
Its function is to fertilise an ovum (its nucleus fuses with that of an ovum.
ADAPTATIONS
CELL ORGANISTION
OBJECTIVE: Define tissue, organ, system, and organism
1. TISSUE
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EXAMPLES OF PLANT TISSUES
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
Examples of animal organs: mouth, stomach, liver, heart, penis, eye, ear, etc
3. ORGAN SYSTEM
Examples of organs are: Digestive system, circulatory system, nervous system, endocrine system,
reproductive system, etc.
4. ORGANISM
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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.
ANIMAL
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.
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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.
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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
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
INVESTIGATION
TOPIC: OSMOSIS
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AIM
To find out how different concentration of sugar solutions affect plant tissues.
APPARATUS USED
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
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.
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
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lower higher
Concentration to region of higher Concentration to region of lower
concentration/molecules more against concentration/molecules move down the
concentration gradient concentration gradient
Energy from used /ATP from cell No energy from cell used /no
used ATP used from cell
Living cell membrane No living cell membrane
needed/occurs only in living cells needed/occurs both living and non living
cells
Direction of movement of Direction of movement of
molecules /ions not reversible molecules/ions reversible
DIVERSITY OF ORGANISMS:
Objective: * List at least 3 main characteristics of protozoa, viruses, Bacteria, Fungi, Green algae,
athropoda and vertebrates.
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Objective: Discuss the role of protozoa and mosquitoes in causing malaria
Objective: Describe control of malaria
NUTRITION
TYPES OF NUTRITION
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1. AUTOTROPHIC NUTRITION- When an organism makes organic food molecules from
simple inorganic molecules such as water and carbon dioxide.
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
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OBJECTIVE: Describe the significance of the cellular and tissue structure of a dicotyledon leaf in terms
of:
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.
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.
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.
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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.
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:
WORD EQUATION:
Light
Carbondioxide +Water glucose + Oxygen
Chloropyll
SYMBOL EQUATION:
Light
6CO2 + 6H2O C 6H12 O6 + 6O2
Chloropyll
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.
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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)
Temperature
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 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
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surface area of leaves
OBJECTIVE: Discuss the necessity for chlorophyll, light and carbon dioxide in photosynthesis
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.
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.
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OBJECTIVE: Investigate the effect of nitrogen deprivation on plant
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
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.
INTRACELLULAR ENZYMES are enzymes functioning inside the cell where they are made.
The enzymes speed up the chemical reactions inside the cells.
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EXTRACELLULAR ENZYMES are enzymes functioning outside the cells that made them.
e.g digestive enzymes.
Enzymes can be classified according to the type of substrate they act on. Digestive enzymes are
classified according to the food they digest.
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.
Enzymes are influenced by the acidity and alkalinity of the medium in which they function.
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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.
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
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
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lactose joined together in at room temperature and have a
Polysaccharide e.g. any number or high proportion of unsaturated
starch cellulose. order to form fatty acids
different proteins
(may be folded,
twisted or
straight).
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
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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
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REDUCING sample in a solution form, sugar is absent,
a)SUGARS(e.g add about 4 drops of mixture
glucose) Benedict’s solution. remains blue.
Gently shake to mix. If present the
Place the test tube with mixture turns
the mixture in a hot water from blue to
bath green, then to
yellow then to
orange and
finally brick red
b)STARCH IODINE TEST Place a drop or two drops If starch is
of iodine solution into a absent the
test tube containing a mixture
food sample in solution remains brown
form with iodine
solution.
If starch is
present the
mixture turns
blue-black
2.PROTEINS BIURET TEST To about 2ml of a solution If proteins are
of a food sample in a test absent the
tube, add about 2ml of mixture
1% sodium hydroxide, remains blue, if
gently shake then add present the
about 2ml of 1% of mixture turns
copper (II) Sulphate, purple or violet
gently shake and observe
after adding each drop.
3.FATS/OILS ETHANOL To a test tube with 2ml of If fats /oils are
EMULSION TEST a food sample in add absent the
about 5ml of ethanol. mixture
Shake thoroughly then remains clear.
transfer the liquid part of If fats /oils are
the mixture into an empty present a
test tube. cloudy white
To the liquid mixture add emulsion is
distilled water drop by formed.
drop. Observe after
adding each drop.
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THE DIGESTIVE SYSTEM
FEEDING
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).
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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
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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
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STOMACH Ph 1(acidic) Has muscular walls made up of circular and
digestion [physical longitudinal muscles which are under
and chemical means] 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.
Gastric glands secrete
gastric juice which contains:
i.) WATER Used as a solvent and in the hydrolysis of
food
ii.) MUCUS Protects stomach wall from the action of
acidic gastric juice. Acts as a lubricant for
movement of food within stomach.
DUODENUM p H 7-8
(Slightly alkaline)
PANCREASE a) Secrets pancreatic Hydrolysis of food in duodenum
{digestion [physical juice which contains trypsin
and chemical means]} i)trypsin polypeptides peptides
amylase
ii)Amylase Starch maltose
lipase
iii)Lipase Fats Fatty acids + Glycerol
iv) Water Used as a solvent and in the hydrolysis
Bile from the gall Produce bile using pigments increase of pH of acidic chime from the
bladder produced by from old red blood cells stomach by sodium hydrogen carbonate and
the liver broken down in the liver. provides alkaline pH for enzyme action in
Bile is an alkaline solution of small intestines
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bile salts Bile salts breakdown large globule of fats and
oils into smaller droplets – a process called
emulsification.
lactase
iii).lactase lactose glucose + galactose
erepsin/peptidase
iv). erepsin/peptidase peptides amino acids
PERISTALSIS
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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
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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.
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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.
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 PATH TAKEN TO EACH BODY CELLS FATE OF THE END PRODUCTS
OF DIGESTION
GLUCOSE Ileum hepatic portal vein 1. Utilsed by all cells in
liver hepatic vein venacava respiration
right heart lungs left heart all 2. Excess glucose is
parts of the body converted to glycogen by
insulin and stored in
liver.
3. Makes starch and
glycogen
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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
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
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.) 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.
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d.) DETOXIFICATION
Poisonous substances , used hormones and alcohol are converted to harmless substances by
liver cells.
Blood clotting proteins such as fibrinogen and plasma proteins phothrombin are made by
liver cells.
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.
RESPIRATION
OBJECTIVE: Define respiration
RESPIRATION is the release of energy from food substances in all living cells.
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Most of the energy is lost as heat energy and remaining energy is used up for the vital activities of the
cells such as:
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.
muscle contraction
AEROBIC RESPIRATION is release of relatively large amount of energy by break down of food in
the presence of oxygen
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A chain of enzyme controlled chemical reactions are involved and the total effect is
Word equation:
Symbol equation:
respiratory enzymes
C6 H12O6 + 6O2 6CO2+6H2O+Energy
ANAEROBIC RESPIRATION is release of relatively small amount of energy by the break down of
food in the absence of oxygen
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
Symbol equation:
2. Lactate fermentation:
Word equation:
Glucose lactic acid + energy
Symbol equation:
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C6 H12O12 2C3H6O3+2ATP ( G=-150kJ/mol)
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Experiment (d) To Demonstrate Anaerobic Respiration by Living Organisms
OBJECTIVE: Describe the role of the exchange surface of the alveoli in gaseouse exchange
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
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The main respiratory organs and their role in the gas exchange system are summarized below.
STRUCTURE FUNCTIONS
Nasal passages and phalynx Air passing through is warmed to body temperature
Lined with ciliated cells and goblet and moistened.
cells 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
LARYNX The voice box for sound production
Air passage
TRACHEA Air passage to the lungs via the bronchi
THE WINDPIPE LINED WITH ALLIATED Dust and bacteria in air removed
MUCOUS MEMBRANE AND
SUPPORTED BY C-SHAPED CARTILAGE
BRONCHI AND BRONCHILES Air passage
Bronchioles terminate in air sacs or aveoli
LUNGS Site of gaseous exchange of gases between blood
- SPONGY,LOBED ORGANS system and atmospheric air.
MADE UP OF NUMEROUS AIR
SACS CALLED ALVEOLI -: HAVE
RICH BLOOD SUPPLY
DIAPHRAGM Separates thoracic cavity from abdominal cavity
- A sheet of muscular tissue Changes the volume of the thoracic cavity for
with air cumference attached breathing
to thoracic cavity
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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.
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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.
OBJECTIVE: Describe the role of the diaphragm, ribs and intercostals muscles in breathing.
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BREATHING MOVEMENTS IN MAN
Breathing is the physical process resulting in the exchange of gases at a gas exchange surface.
INSPIRATION EXPIRATION
Diaphragm contracts and flattens Diaphragm relaxes and becomes dome shape
External intercostals muscles between External intercostals muscles between ribs
ribs contract, internal intercostals relax internal intercostals muscles contract
muscles relax
Ribcage moves upwards and outwards Ribcage moves down wards and inwards
Air pressure inside chest cavity and Air pressure inside chest cavity and lungs
lungs decreases increases
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.
46
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.
TAR Dark brown, sticky substance Lung cancer
containing cancer causing Throat cancer
chemicals. Mouth cancer
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.
IRRITANT Carbon particles oxides of Chronic bronchitis
SUBSTANCES nitrogen, etc Emphysema
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
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.
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3. The main signs and symptoms of the main respiratory diseases associated with smoking are:
OBJECTIVE: Investigate the effect of physical activity on the rate and depth of breathing
During exercise, the muscle cells respire more than they do at rest. This means:
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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:
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
49
TRANSPORT IN PLANTS
Objective: identify vascular tissues in cross sections of stem roots and leaves of dicotyledons and
monocotyledons .
50
Objective: Describe the structure and function of root hairs in relation to their surface area, and to
water and ions uptake.
51
Objective:Describe absorption of water in terms of osmosis
Objective: Describe the structure and functions of vascular tissues (xylem vessels and phloem tissues)
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.
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Xylem Phloem
Structure Xylem consists of non-living, long, hollow Phloem consists of thin and
fine tube-like vessels with thick lignified elongated living cells joined
cellulose walls end to end to form living long
The strong lignified walls provide tubes.
mechanical support as they resist pressure The cells contain very fine
changes and prevents the vessels from strands of cytoplasm and have
collapsing perforated end walls called
sieve plates to allow
substances to pass from cell
to cell
53
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.
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3.1 Transpiration
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
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.
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.
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.
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OBJECTIVE: Discuss the difference between the two circuits (pulmonary and systemic) in terms of
pressure, direction of blood flow and quality of blood:
Blood is from the heart to the body parts the back Blood is from the heart then to the lungs
to the heart. then back to the heart
Oxygenated blood flows away from the heart Oxygenated blood flows towards the heart
/deoxygenated blood flows towards the heart. /deoxygenated blood flows away from the
heart.
Oxygenated blood flows along arteries and Oxygenated blood flows along veins and
deoxygenated blood flows along veins deoxygenated blood flows along arteries
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3. The Structure, Function, And Action Of The Heart
61
Structure Position in the heart Function
Superior vena Main vein which comes from the Returns deoxygenated blood from the head and
cava upper part of the body upper limbs to the heart
Inferior vena Main vein which comes from the Returns deoxygenated blood from the organs
cava lower part of the body and lower limbs to the heart
Right atrium Upper cambers from the heart Receives deoxygenated blood from the vena
cava
Semi-lunar Found at the opening of the Prevents back flow of blood from the pulmonary
valves pulmonary artery artery into the right ventricle when the right
atrium relaxes.
Tricuspid Between right atrium and right Prevents backflow of blood to the right atrium
valve ventricle consists of flaps 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 Prevents mixing of deoxygenated blood in the
and right chambers. right side of the heart with the oxygenated
blood from the left side of the heart
Bicuspid valve Between left atrium and left Prevents back flow of blood to the left atrium
ventricle. Consists of two flaps. when the left ventricle contracts.
Chordae Elastic tendons which attach valve Tendons become taut and prevent the valve
tendineae flaps to the capillary muscles. 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 Pumps blood to all parts of the body (except the
most muscular part lungs) via the aorta
Left atrium Upper chamber of the heart Receives oxygenated blood from the lungs via
pulmonary vein
Pulmonary Arises from the top of the right Carries deoxygenated blood from the right
artery atrium , forms two branches one ventricle to the lungs.
each lungs
Pulmonary Empties into the left atrium Carries oxygenated blood from the lungs to the
vein left atrium of the heart.
Aorta Largest artery of the body Carries oxygenated blood to all parts of the body
except the lungs.
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Semilunar Found at the opening of the aorta Prevents backflow of oxygenated blood from the
valves aorta into the left ventricle when the left
ventricle relaxes
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.
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.
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ATRIAL DIASTOLE VENTRICULAR SYSTOLE
Both left and right atria contract and
force blood into the ventricles Both left and right ventricles contract and
force blood under pressure, into the
pulmonary vein and artery respectively
Bicuspid valve of the left side of the Bicuspid valve and tricuspid valve close to prevent
heart and tricuspid valve of the right backflow of blood into the left and right atria
side of the heart respectively
Semi – lunar valves of the pulmonary Semi-lunar valves of the pulmonary artery open
artery close to prevent backflow of
blood
Left and right ventricles relax Left and right ventricles
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.
insert tables from back part of the note book including explanation
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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.
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.
Atherosclerosis – The narrowing and Hardening of artery due to fatty deposits (cholesterol) on
the walls of artery.
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Coronary thrombosis - The formation of a blood clot inside the artery. Thrombosis is more
likely to occur in narrow arteries with fatty
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
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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.
Avoid smoking :
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.
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THE GENERAL CIRCLATORY SYSTEM
OBJECTIVE: Name and identify the main blood vessels to and from the heart, lungs , liver and kidneys
Fig. A
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Fig. B
****TASK****
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THE STRUCTURE AND FUNCTIONS OF ARTERIES, VEINS AND CAPILLARIES
OBJECTIVE: compare the structure and functions of arteries, veins and capillaries
FUNCTIONAL DIFFERENCES:
STRUCTURAL DIFFERENCES:
Thick muscular, elastic walls Thinner, inelastic and Thin, one cell thick
less muscular walls walls, no muscle and
elastic tissue
Walls are not permeable Walls are not permeable Walls are permeable
to tissue fluid and
phagocytes
Relatively small lumens Relatively large lumens Very small lumens
(smallest blood
vessels)
Circular cross-section Oval cross - section Circular cross -section
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Exchange of Materials Between Capillaries and Tissue fluid
OBJECTIVE: describe the transfer of materials between capillaries and tissue fluid
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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.
BLOOD CELLS:
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
Biconcave disc without the spleen and liver. Iron is
nucleus stored in the liver and the rest
Has elastic cell of the haemoglobin molecule
membrane forms bile pigments
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White blood cell 7000 Lymph Engulf, ingest and digest foreign
million particles.
large than red blood cell
contains nucleus
1 Phagocytes
thrombin
b) Fibrinogen
Fibrin
PLASMA
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
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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
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
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IMMUNITY MAY BE:
1.ACTIVE
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.
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2.PASSIVE
Individual is given ready –made antibodies
NATURAL ARTIFICIAL
Mother antibodies cross the placenta Adult is now immune to disease used if
and are in breast milk – new born for disease is too fast – acting for the
which mother produced antibodies e.g immune system to deal with, e.g
gust infections. injection of anti tetanus antibodies
Red blood cell Red blood cell shows Red blood cell shows Red blood cell
shows agglutinogen A agglutinogen B both A nor B shows neither
A agglutinogen A or B agglutinogen
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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
Transfusion of Blood:
Donor A B AB O
antigen A antigen B antigen A and no antigen
RECIPIENT antigen B
A clumping clumping
(anti – B) compatible or or compatible
agglutination agglutination
B clumping clumping
(anti – A) or compatible or compatible
agglutination agglutination
AB
( no anti-A and compatible compatible compatible compatible
no anti –B)
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.
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BLOOD RELATED DISEASES:
OBJECTIVE: discuss common blood diseases e.g. HIV/AIDS, malaria, leukemia, and anemia
These are diseases that are related to blood. They include the following; Leukaemia, Anaemia,
haemophilia, malaria, HIV/AIDS e.t.c.
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.
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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.
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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.
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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
2. Granular layer Contains living cells which is gradually pushed up to replace the
worn – out cells in the cornified layer.
HAIR FOLLICLE AND HAIR A deep pit of granular and malpighian layer where cells multiply
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to form a hair inside the follicle
ERECTOR MUSCLE Controls the erection of hair- contracts to raise the hair and
relaxes to make the hair lie down.
SWEAT GLANDS
Absorbs salts and water from blood capillaries to produce sweat
for temperature regulation and excretion
SENSORY NERVE ENDINGS Detect pain, changes in temperature and pressure on skin
BLOOD CAPILLARIES 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
83
4. THE ROLE OF THE SKIN IN TEMPERATURE REGULATION
stimulates
84
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.
4. Used hormones, drugs and toxic substances such as alcohol are also excreted.
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OBJECTIVE: Describe the functions of : kidneys, ureter, bladder; urethra.
STRUCTURE FUNCTIONS
KIDNEY Filters blood and excretes nitrogenous wastes, excess salts and
water as urine
RENAL ARTERY Branching from the aorta, the renal artery carries oxygenated
blood to the kidney
RENAL VEIN Carries deoxygenated blood away from the kidney to the vena
cava
URETER Peristallic waves of contraction in the thin tube carries urine
produced by the kidneys to the urinary bladder
BLADDER A distensible sac in which urine is temporarily stored
SPINCHER MUSCLE Voluntarily relaxes to release urine from the bladder
URETHRA Passage of urine out of the body is through the urethra
1. The kidney contains about one million microscopic urine formation units called kidney tubules
or nephrons.
STRUCTURE OF KIDNEY
87
2. The various regions in the internal structure of the mammalian kidney and their functions are
summarized in Table 2
88
FORMATION OF URINE
OBJECTIVE: Describe the removal of water and urea through the kidneys.
89
SUBSTANCE % IN PLASMA % IN BROWMAN’S CAPSULE % IN URINE
Water 90 – 93 99 95
Glucose 0.1 0.1 0
Mineral Salts 0.35 0.35 2
Urea 0.03 0.03 2
Proteins 7-9 0 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.
*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.
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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.
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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.
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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
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.
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NERVOUS SYSTEM
(CNS)
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
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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.
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.
1. SENSORY NEURONES
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.
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OBJECTIVE: Draw a labelled diagram of a sensory neurone.
2. MOTOR NEURONES:
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.
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3. INTERMEDIATE ( RELAY) NEURONES
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.
Nervous impulses travel rapidly in one direction starting at the dendrites and finishing at
the axon of each neurone.
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THE SPINAL CORD
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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.
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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.
3. REFLECTION ACTION – involuntary, Rapid action that often lack thinking, does
not involve the brain, uncontrolled, protects the body from danger.
Cranial reflex – Nervous impulses in these automatic responses pass through the brain
and the brain can control and coordinate reflex
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Stimulus receptors sensory relay neurone motor effector
neurones in brain neurone
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).
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2. Touching a hot object reflex arc
Reaction time: Time taken for a stimulus to cause a response. It is not very easy to measure the time.
(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.
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(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 Distance
(nerve (nerve
pathway) pathway)
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.
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The main parts of the human brain and their function are summarized in that follows:
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THE HUMAN EYE
STRUCTURE AND FUNCTION OF THE HUMAN EYE
OBJECTIVE: Describe the gross structure of the eyes as seen in front view
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.
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from injury.
Eyelash traps large air –borne particles.
CONJUCTIVA 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
SCEROTIC LAYER ( Sclera) 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
CORNEA 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.
CHOROID LAYER A layer of tissue lining the inside of the sclerotic
( CHOROID) 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.
RETINA 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)
YELLOW SPOT The region of the retina where most cones are
located.
( FORVEA CENTRALIS) Most light sensitive region for sharp colour vision
BLIND SPOT 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.
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.
LENS 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.
CILIARY BODY A ring of muscle fibres which alter the shape of
(muscle) the lens for focusing.
SUSPENSORY LIGAMNETS They hold lens in place and connect the lens to
the cilliary body.
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IRIS 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.
PUPIL The round hole at the centre of the iris through
which light passes from the front to the back of
eyes.
AQUEOUS HUMOUR 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.
VITREOUS HUMOUR 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
TEAR GLAND Exocrine gland which secretes tears - a protective
anti- bacterial fluid to lubricate the conjunctiva and
cornea of the eye.
EYE MUSCLES Hold eyes in place in their orbits
Allow coordinated movements on both eyes in
their sockets.
The table below summarises the differences in the action of two kinds of light sensitive
nerve cells in the retina of the human eye.
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as light intensity requires Vit A for
decreases formation) which
Three kinds of cone bleaches (breaks
present, each is down) in bright light
particularly sensitive to and reforms in the
blue, green or yellow
dark.
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.
The difference in action of two kinds of light sensitive nerve cells in the retina of the human
eye.
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)
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action of the cilliary muscles in the cilliary body so that light is always focused onto the
retina.
109
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.
drawing drawing
a.)Circular muscles relax, radial a.) Circular muscles contract, radial muscles
muscles contract relax
b.) Pupil dilates (widens) b.) Pupil constricts (narrows)
c.) More light is admitted into the eye, c.) Less light is admitted into the eye, increases
brightness of image
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HORMONES
OBJECTIVE: Define a hormone
A comparison of nervous control and hormonal control in the body is shown below:
Duration of reponse Rapid and Short term Often slow long lasting e.g
growth, sexual development
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 .
112
PANCREAS 1. insulin 2. Regulates the amount of blood
glucose. Promoting the storage
of excess glucose as glycogen in
liver and muscles
3. Glucagon 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
ADRENALINE GLANDS Adrenaline Prepares the body for action
and emergency
OVARIES Oestrogen Controls ovulation and
secondary sexual characteristics
Progesterone Responsible for thickening of
uterus lining after ovulation
TESTES Testosterone Controls sperm production and
secondary sexual characteristics
ACTION 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.
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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
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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Pancrease secretes more insulin
which causes liver to convert excess
glucoses to glycogen. Insulin also
increases the metabolism of glucose
in cells:
increases increases uptake of glucose
of in cells
It promotes the convertion of glu Returns to normal
-cose to fats; slows down the conv
-ersion of protein to glucose
glucose.
115
OBJECTIVE: Discuss the functions of testosterone and oestrogen
MENOPAUSE
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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.
Blood
118
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.
Phototropism Light 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.
Geotropism Gravity 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)
Hydrotropism Water The roots grow towards moisture and soil water
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.
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
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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
121
OBJECTIVE: Investigate the effects of removing the apical bud fromplant seedlings
122
3
123
6
124
USE AND ABUSE OF DRUGS
DEFINITION OF DRUGS
An externally administered substance which modifies or affects chemical reactions in the body.
ADMINISTRATION OF DRUGS
Aspirin Painkiller Relieve pain and fever, reduce Prevents blood clotting,
inflammation ran cause irritations to
the stomach bleeding;
not recommended for
children under 12 years
old as it causes fatal
liver and brain damage
Paracetamol Mild pain killer Relieve mild pain and fever Overdose can damage
liver and kidney
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Penicilin Antibiotic Treats common bacterial infection ( Can cause allergic
stops bacterial infection ( stops reactions
bacteria from multiplying)
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
alleviate diseases, relieve symptoms, ease pain taken for habitual satisfaction
and provide other benefits to the body
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
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.
127
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
Mrijuana(ganja, weed, HALLUCINOGEN Enhanced vitality, energy Damage to brain, Irritability, insomnia,
herb,dagga etc & and enthusiasm, euphoria, heart, damage to the restlessness,
harshish from relaxation, hallucinations, respiratory system, hallucinations may
cannabis sativa loss of self control, intense increases appetite, occur ( flash backs)
yearning for food, dryness poor absorption in the
of mouth, perspiration, alimentary canal,
brightness and ruddiness depressed immune
of eyes, intellectual system, lowers sperm
difficulties, decrease in count and diminishes
short term memory and sexual drive
speech impediments),
poor motor coordination
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Nicotine( in tobacco) Stimulant Relaxation, tension Cardiovascular Irritability, hostility,
reduction diseases anger, excessive
drowsiness
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. Speech is slurred
ii. Double vision
iii. Loss of balance
iv. Poor coordination of muscles ( causing staggering and unsteadiness)
v. Nausea and vomiting
vi. Impaired concentration and judgment
vii. It slows down the speed of transmission of nerve impulses involved reacting to an emergency
situation) increases reaction time.
viii. Violent or aggressive behavior
ix. Loss of consciousness
SOCIAL EFFECTS
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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)
WITHDRAWAL SYMPTOMS
130
SUPPORT, MOVEMENT AND LOCOMOTION
The vertebrate skeleton
b) Arms b) Legs
131
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
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
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.
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GLIDING JOINT Limitted sliding movement The vertebrae of the
vertebral column
Wrist
PIVOT JOINT Allow nodding and limited rotation Neck
of head
The largest movement occurs at the synovial joints such as the ball and socket joint and the
hinge joint.
The structure and functions of the various parts of the synovial joint are shown below.
134
Provides external support and strengthens the
joint
135
THE STRUCTURE OF THE FOREARM
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.
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.
1. Biceps (flexor) contract and 1. Triceps contract and become shorter and
thicker
become shorter and thicker
2. Biceps relax
2. Triceps ( extensor) relax
3. Ulna and radius pull away from the
Ulna and radius pull closer to the
humerus
humerus
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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
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.
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‘eye’
Adventitious roots
Bulbs White, fleshy storage scale leaves Thin, dry. brown scale leaves
(Underground Mainly water and sugar Young shoot
shoot) (glucose) stored in
fleshy leaves
Condensed stem
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Corm Mainly water and sugar flower bud Aerial shoot
(Underground stored in the short and
shoot) swollen stem.
Node
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.
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
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 T-shaped slit is made in the bark of the stock to expose cambium tissue.
The bud graft (scion) is slipped inside the T-shaped slit of the stock. The cambium
The scion is held in place with tape and wax to exclude fungi and reduce evaporation
Few animals reproduce asexually. Aphids( belonging to class insect) reproduce asexually
by parthenogensis.
Binary Fission;
Budding
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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.
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. 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.
5. 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
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
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.
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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.
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
•Wing-like outgrowths
extension from ovary wall
of fruit. Example: winged
fruits of shorea and Dandelion Shorea
angsana.
Angsana
148
Dispersal method Main adaptation features Examples
Explosive mechanism
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
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GERMINATION OF DICOTYLEDONOUS SEED
Non-endospermic seed
OBJECTIVE: Describe the structure and function of parts of a seed in terms of embryo, (radical and
plumule) cotyledons and testa
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OBJECTIVE: Investigate the environmental conditions which affect germination of seeds
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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.
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SEXUAL REPRODUCTION IN MAN
153
Objective: Use a diagram of the male reproductive system to identify
testes, scrotum, sperm ducts, prostate gland, seminal vesicle, urethra
and penis.
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Female Reproductive System:
The main parts of the human female reproductive system and their
functions are summarized below
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Objective: describe the function of the ovaries, oviducts, uterus, cervix,
bladder and vagina.
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Objective: compare the male and female gametes in term of size,
number, mobility and life span.
Sperm Ovum
survives survives
for 2 to 3 days for 24 hours
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,
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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;
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 4-
6 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.
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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
A girl who has reached puberty has to eat food rich in iron, why?
3 Change of environment
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2. Oxygen
3. Mineral ions such as iron, calcium, phosphates
4. Antibodies
Substances which diffuse from embryo’s blood system to mother’s
blood system are:
1. Urea
2. Carbon dioxide
3. 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.
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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.
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Objective: Distinguish between identical and fraternal twins
Differences Between fraternal and identical twins:
In utero: Develop separate sacs in utero May be contained in one sac in utero
(amniotic sac and chorion). (amniotic sac and chorion).
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.
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Objective: Discuss the following methods of birth control: Natural
Hormonal/chemical, Physical/mechanical and Surgical methods
1. Natural
2. Hormonal/chemical
3. Physical/mechanical
4. Surgical methods
1. Natural methods
Withdraw (Coitus interruptus); Purely natural and does o Highly unreliable as there is a pre-
penis withdrawn from the not depend on artificial ejaculation fluid which can be
vagina before ejaculation devices. 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.
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Prolonged breastfeeding Very effective against o Not effective against STDs
(cultural method) pregnancy.
2. Hormonal/chemical methods
Pill e.g. RU486: two kinds mini- Easy to use. o Does to prevent STDs.
pill (contains progesterone
Reversible o Must be taken daily.
which causes changes in the
uterus lining preventing Does not interfere o Have side effects to women’s health;
implantation) and combined with sexual activity. breast swelling, cervical cancer, nausea,
pill (contains Oestrogen and diarrhoea and weight gain.
progesterone and this prevents 99% safe at
ovulation) preventing ovulation
and pregnancy.
Can be administered
by individuals
o Has to be
used with the diaphragm.
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Injection (Depo-Provera): Reversible. o Can lead to sterility.
injected into the body every 3
months. Stops ovulation by 99% effective against o Administered by a doctor.
pregnancy.
preventing formation of ova in o Causes abnormalities in the period.
the ovaries.
o Can lead to heavy menstrual bleeding.
Morning-after pill: Used after Effective against o Only prescribed by a doctor in case of risk
intercourse has taken place. pregnancy if taken it is not for regular use.
Contains hormones which before 3 days of
sexual act. o Therefore not easily accessible.
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.
3. Physical/mechanical/barrier Methods
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Diaphragm/cap: it is a dome Fairly effective (98%) o High risk of infections.
shaped piece of rubber with a in blocking the sperms.
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
from reaching the uterus. properly.
4. Surgical methods
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In women (Laparatomy) Safe and simple out patient o Has to be done at a hospital.
oviduct cut and tied to operation.
o Pains can be experienced
prevent the sperms from
Sexual characteristics are after surgery.
reaching the egg in the
not affected as the
oviduct. individual can still ejaculate o Not suitable for young
(men) people but for people who
already have children
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170
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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).
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.
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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.
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The chromosomes reach the poles of the cell, uncoil, lengthen and lose the ability to be seen clearly.
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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.
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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.
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2. METAPHASE I
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.
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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
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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.
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INHERITANCE
Objective: define gene, allele and chromosome
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.
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.
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).
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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
meiosis meiosis
Haploid Haploid
Fertilisation
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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).
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.
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Diagram 1 below summarizes Mendel’s first experiment on inheritance of crossing pure lines
in height of pea plants.
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Objective : Predict results of simple crosses with ratio of 3:1 and 1:1 using
terms homozygous, heterogygous, F1 and F2 generations
From ratio of phenotypes in the offspring, the possible genotypes of the parents can be
deduced.
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 3 yellow : 1 green
seeds seed
Green x yellow pods All green pods 3 green pods:1 yellow pod
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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.
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.
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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.
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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.
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.
A IAIA or IAIO
B IBIB or IBIO
AB IAIB
O IOIO
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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.
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.
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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 Phenotype
Xc Xc red-green colour-blindness
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.
Genotype Phenotype
XhXh haemophiliac
Male X HY normal
XhY haemophiliac
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VARIATION AND SELECTION
Variation
Objective: describe differences between continuous and discontinuous variation and give
examples of each.
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no.of no. of
people people
Height AB A O B
2.Variation is caused by new combinations of genes through sexual reproduction, mutation and
immigration of individuals with new gene combination.
3. Variation is an advantage because it increases the chances of survival for breeding and
produces offspring that survive under new conditions.
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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.
1. Gene Mutation
Objective: describe gene mutation and discuss causes of gene mutation
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.
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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
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.
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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.
Natural Selection
Advantageous characteristics or variations are selected for
New Species
Formation of genetically distinct species
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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.
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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.
(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.
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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.
The living organisms in the ecosystem interact with each other via a chain of energy transfers called
food chains.
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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:
Ground beetle
Spider Bluetit
Frog
Fox
In an ecosystem, there are usually far more organisms at lower trophic levels than at higher trohpic
levels.
Hawk
Number of Tertiary consumer
organisms Sparrow Secondary consumer
at each
level Grasshopper Primary consumer
decreases
Wheat plant 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.
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Bird
Tertiary consumer
Biomass Beetle Secondary consumer
at each
level Aphid Primary consumer
decreases
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.
Man
Rose bush
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.
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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.
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.
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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.
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.
population
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NUTRIENTS CYCLE IN NATURE
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.
Element carbon is used in the ecosystem to form food molecules such as carbohydrates, proteins and fats/oils in
living organisms.
Carbon Cycle
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Photosynthesis:
Respiration:
Animals, plant and micro-organisms such as bacteria and fungi break down carbohydrates in
their cells to produce carbon dioxide and water
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
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Nitrogen Cycle
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.
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The organic matter in animal droppings is also decomposed by soil bacteria.
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-).
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Nitrogen fixation (by nitrogen fixing bacteria):
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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 .
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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.
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- 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.
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.
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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:
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odourless gas –an dioxide
increase of carbon before it is
monoxide level in released into
blood causes death. atmosphere.
d) Lead Anti-knock in Causes brain damage in Use unleaded
petrol children petrol
e) Chlorofluoro- Aerosol Breaks down ozone Reduce usage
carbon propellants. layer and allow more in industry
Cooling agents UV radiation to
in penetrate earth, may
refrigerators increase skin cancer
and air incidence.
conditioning. Absorbs infrared
radiation. Cause global
warming
e) Smoke and dust Soot –unburnt Blacken buildings, Increase
carbon covers plant leaves and efficiency of
particles due reduces rate of combustion
to incomplete photosynthesis. engines.
burning of Irritates eyes and lungs
fossil fuels. when breathed in.
From quarries Causes lung diseases.
saw mills and
asbestos
factories.
2. Water Pollution:
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Soil erosion bacteria and decreases
causes mineral oxygen content in water.
salts to leach
away into
waterways.
Inorganic
waste
(Toxic
Chemical)
Pesticides Non-biodegradable. Banned
containing Accumulates in fat Use
DDT chlorine used in tissues of animals along biodegrable
crop protection food chains, reaching pesticides.
and control of toxic levels in the Use biological
disease vector consumers of higher control of
such as mosquito trophic levels. pesticides.
Mercury Industrial wastes Affects nervous system, Proper disposal
causes paralysis. of waste
containing
mercury.
Lead Industrial waste Minute concentrations Proper disposal
cyanide may be paralysis. of waste
containing lead
cyanide and
other toxic
chemicals.
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3. Land Pollution:
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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
(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
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
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.
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.
1. Rhino
2. Wild dog
3. Cheetah
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Some common conservation measures are:
Recycling
Objective: discuss reasons for recycling of materials including sewage water, paper, bottles and tins.
(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
Because:
*Objective: Investigate the role of micro-organisms in food production e.g. bread, madila , chibuku,
single cell protein
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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
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.
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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
GLUCOSE
Add meat or
Fish flavouring
NUTRIENTS
(high in nitrogen)
Fusarium Quorn
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
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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 0utlet
Enters here
Ground
Digestion vessel
Organic waste
Anaerobic bacteria
Methanogenic bacteria
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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
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
Dry fungus
And cell as
Animal feed
AIR FILTERING
Purify and
Modify
Penicillin
2. Vaccine:
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:
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.
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
Cystic fibrosis is condition caused by lack of cell membrane protein leading to production of a thick,
sticky mucus in the air passages
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*Objective: Discuss how industries in Botswana can benefit from Biotechnology
It creates employment
Conservation of certain resources (using proteins produced from micro-organisms spares grass
thus preventing overgrazing.
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