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Section A - Living Organisms and the Environment.
1.
The characteristics of living things, cell structure, function and specialization
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All living things exhibit seven characteristics – Nutrition, respiration, excretion, movement,
growth, sensitivity, reproduction
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Animal and plant cells have a nucleus, cytoplasm and an outer c ell membrane.
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Animal cells also have cell wall, a large vacuole and many have chloroplasts.
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Animal and plant cells contain ribosomes, mitochondria and endoplasmic reticulum in the
cytoplasm.
Microbes or microorganisms include bacteria, fungi and virus, many of which cause, disease in
humans.
Bacteria and fungi lack some features of animal and plant cells. Eg bacteria have no nucleus,
mitochondria, ribosomes or endoplasmic reticulum and fungi never have chloroplasts and often
have cells with many nuclei.
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Viruses do not have any cellular structures.
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Multicellular organisms such as humans have many different types of cells.
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Each type of cell has features t hat allow it to perform different functions.
2.
Diffusion, Osmosis and Active Transport
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Movement of substances in and out of cells involves diffusion, osmosis or active transport.
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Diffusion is the movement of ions and molecules in gases or liquids.
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Diffusion always occurs from a higher to a lower concentration
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Osmosis is a special type of diffusion and only involves water molecules.
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Osmosis only occurs through a partially permeable membrane
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The cell membrane of all cells is partially permeable
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Active transport involves the movement of ions and molecules against the concentration
gradient.
Active transport involves the movement of ions and molecules against the concentrat ion
gradient.
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Active transport needs a supply of energy
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Diffusion and osmosis do not need a supply of energy to occur.
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Active transport only occurs through a ce ll membrane.
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3.
Photosynthesis and food chains
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Photosynthesis only occurs in cells with chloroplasts.
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Photosynthesis needs carbon dioxide, water and light
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Photosynthesis changes light energy to chemical energy with the chloroplasts.
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Photosynthesis produce sugars and oxygen which is a waste product.
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Only green plants are producers in a food chain
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The other organisms in a food chain are consumers and decomposers
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All organisms in a food chain belong to a trophic level.
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Chemical energy is transferred betwee n tropic levels in a food chain.
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Energy is lost from the food chain at e ach trophic level
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Food webs are composed of interlinked food chains
4.
Carbon and Nitrogen Cycles
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Recycling returns some materials to the environment so that they can be reused.
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The carbon and nitrogen cycles recycle material between the environment and living organisms.
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Carbon dioxide is used in photosynthesis to form sugars and many other compounds.
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Carbon dioxide is released from these compounds by respiration, combustion and
decomposition.
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Nitrogen is an essential element in all proteins.
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Produces use nitrates to form proteins.
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Decomposers return nitrates to the environment.
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Bacteria and fungi are the main decomposers in the carbon and nitrogen cycles
Section B - Life Processes.
5.
Major nutrients, minerals and vitamins
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Humans need a supply of nutrients to provide the materials for growth and for energy
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Carbohydrates, fats and proteins are needed in the diet.
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Carbohydrates and fats are the main source or energy
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Cells are made of cytoplasm which is prote in based.
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Proteins are needed for growth and enzyme formation.
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Vitamins are mineral salts are needed in small quantities for healthy development.
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The absence of a vitamin or mineral salt leads to deficiency disease
6.
Water and fibre, human diet.
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A balanced diet contains all the main nutrients in the quantities needed by the body.
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Malnutrition occurs if too much or too little of a nutrient is present in the diet.
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Diseases of malnutrition include anorexia, bulimia, obesity, kwashiorkor and marasmus.
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Dietary fibre is needed to ensure movement of food through he alimentary canal
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Fibre is made of cellulose, found in plant material, and is indigestible
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7.
Water is needed in the daily diet to replace water lost from t he body
Water is the main component of cytoplasm, solvent for all chemical reactions of the body ,the
basis of the body’s transport system, and is needed for excretion and for the control of body
temperature.
Tooth structure, function and care
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8.
Teeth carry out the first stage of egestion and humans have two sets of te eth – milk and
permanent.
The types of teeth are incisors, canines, premolars and molars
A tooth is made of dentine covered by enamel, both made of hard calcium salts on a ske leton of
protein fibres.
Tooth decay, dental caries occurs when bacteria gain access to living cells in the tooth. When
bacteria respire using sugars, they form an acid that erodes enamel
Plaque is a mixture of saliva, food remain and bacter ia collects on teeth.
Enzymes
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Catalysts are chemicals that alter the spee d of a chemical reaction.
Enzymes are biological catalysts, they are formed by living cells, t hey control the metabolic
reactions of the body.
Enzymes are made of protein, are temperature and pH sensitive , are denatured or destroyed by
high temperatures.
Each enzyme acts as a catalyst on o nly one type of reactions and normally only waroks with oe
substrate.
Digestion
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Digestion is the process that converts food material into simple, soluble molecules.
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The digestive system is composed of the alimentary canal and some other organs.
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The alimentary canal is a long tube, with muscular walls, linking the mouth and the anus.
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Digestion occurs in the mouth, stomach, duodenum and ileum
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There are two types of digestion in humans – physical and chemical. Physical digestion involves
emulsification of fats by bile and the mechanical action of teeth and muscles of the alimentary
canal.
Chemical digestion involves the action of digestive enzymes.
Digestive enzymes are produced by parts o f the alimentary canal and by organs linked to it, such
as the salivary glands and the pancreas.
The liver produces bile, which is alkaline but no digestive enzymes.
Respiratory Organs
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Breathing is the physical pumping of air in and out of the lungs. It is a series of chemical
reactions in cells that releases energy.
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The breathing system in humans is contained within the head and the thorax.
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Air travels between the throat and the lungs throught the trachea, bronchi and bronchioles.
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Gaseous exchange is the movement of g ases between air in the alveoli ( fine branches of
bronchioles) inside the lungs.
Gaseous exchanges is the movement of gases between air in the alveoli and blood in the
capillaries.
Oxygen diffuses down a concentration gradient from alveolar air to the blood and Co2 diffuses
down a concertation gradient from blood to the alveolar air.
11. Breathing
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Breathing depends on differences in air pressure between the atmosphere and air in the lugns.
Air pressure in the lungs can be altered to be lower than atmospheric pressure (breathing in)
and higher than atmospheric pressure ( breathing out).
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Air pressure in the lugs is altered by increasing or decreasing the volume of t he lungs
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Rib cage is moved by sets of inter costal muscles and the diaphragm is moved by other muscles.
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The ribcage is moved upwards and outwards by one set o f intercostal muscles, increasing the
volume of the thorax.
The diaphragm is pulled flat by its own muscles, increasing the volume of the thorax.
These actions lower the air pressure in the lugs and air is forced by atmospheric pre ssure – this
is breathing in. The reverse actions occur causing a rise in pressure in the lungs and air is forced
out. – this is breathing out.
Vital capacity is the maximum volume of air that c an be breathed out after breathing in as fully
as possible.
12. Circulatory system
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The main transport system in the human body is blood.
The heart pumps the blood through a series o f closed vessels called arteries, capillaries and
veins.
There are two circuits in all mammals a pulmonary circuit serving the lungs and a systemic
circuit serving the rest of the of body.
The heart is made up of two pumps – the right hand pump forces deoxygenated blood to the
lungs and the left hand pump forces oxygenated blood to all other organs of the body. The heart
prevents oxygenated and deoxygenated blood mixing.
The heart muscle or cardiac muscle has its own blood system, the coronary artery ( a branch of
aorta) and a coronary vein ( lined to the vena cava).
Each pump is made up of two chances an atrium and a ventricle separated by cuspid valves.
The atria receives blood from veins and ventricles pump blood into arteries through semilunar
valves.
The muscular valve of the left ventricle is much thicker than that of the right ventricle.
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13. Blood, tissue fluid and lymph
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Blood is composed of a liquid with living cells and protein materials floating in it 
Blood cells are formed in the bone marrow and lymph glands.
Red blood cells have no nucleus, are full of haemoglobin and they tr ansport oxygen
as oxyheamoglobin.
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There are several types of white blood cells – phagocytes have a lobed nucleus and
engulf bacteria. Lymphocytes have a large nucleus and produce antibodies.
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Platelets and blood protein fibrinogen are involved in blood clotting.
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Tissue fluid is the liquid surrounding the living cells in tissues. Tissue fluid and plasma are
in contract through he walls of the capillaries.
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Lymph vessels have special nodes that produce the lymphocytes and help trap bacteria. 
Special lymph vessels called lacteal are found in the intestinal villi and absorb fatty acids,
glycerol and some vitamins.
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Serum is blood without any blood cells, platelets and fibrinogen.
Skeletal system
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The skeleton is formed of bone and cartilage, both of which contain living cells.
Bone is made from protein fibres embedded in a mass of calcium phosphate and
calcium carbonate salts.
Cartilage is mainly made of protein and is flexible and rubbery w hile bone is very had and
not flexible.
The functions of the parts of the skeleton are support, protection, allowing movement and
the production of blood cells.
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The axial skeleton is the skill and vertebral column
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The appendicular skeleton is the limbs, their supporting girdles and rib cage
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Bones are joined to bones by tough, elastic ligaments.
Muscles are joined to bones by tough, non-elastic tendons.
Joints and Movements
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Movement is brought about by the contraction of muscles.
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Locomotion can happen when skeletal muscles move the limb bones of the body
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Bones meet at joints that can be moveable or fixed.
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The most important moveable joints are ball and socket and hinge joints.
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In moveable joints the bones move against each other and friction must be kept to a minimum
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The lower arm is moved at the elbow by the biceps and triceps muscles.
Skeletal muscles act in antagonistic pairs, and the members of a pair cause opposite
effects when they contract.
Locomotion in a human involves the coordination of several sets of antagonistic muscles.
Regular exercise improves muscle tone. Poor posture and unsuitable footwear can damage
the skeletal system.
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16.
Excretion
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Excretion is the process of getting rid of metabolic waste. It also ge ts rid of products in excess of
the body’s needs.
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The waste could be toxic if allowed to accumulate in the body.
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The main excretory organs are the lungs, kidneys and skin
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The lungs get rid of carbon dioxide and water, the products of cell respiration.
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The skin gets rid of water and salts when sweat is released.
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The kidneys remove urea from the blood and also excrete excess water and mineral salts.
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The kidneys filter the blood plasma under pressure.
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Substances in the kidney filtrate which are ne ed by the body are reabsorbed.
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The remaining materials in the filtrate become the unite that flows to the bladder.
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The composition of urine varies depending on the diet and activity.
17.
Homeostasis
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Homeostasis is the process that keeps internal body conditions within narrow limits.
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Substances kept within these narrow limits include carbon dioxide, water, glucose and salts.
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The concentration of carbon dioxide is controlled by hypothalamus.
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The concentration of glucose in the blood is co ntrolled by the hormones insulin and glucagon.
These hormones are produced by the pancreas and are active in the liver and m uscles.
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Homeostatic mechanisms are controlled by feedback mechanisms,
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The process of osmoregulation controls the water c ontent of the blood.
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Water content is controlled by ADH< a hormone produced by the pituitary gland.
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ADH is secreted in varying amounts and controls water reabsorption by the kidney.
18.
Kidney and temperature regulation
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19.
Body temperature must remain between narr ow limits and this is controlled by the
hypothalamus of the brain.
Body temperatures above 400C can cause enzyme damage and denaturing and below 340C can
result in hypothermia when enzyme activity slows and too little energy is released.
The outer layer of the skin is a barrier between the living cells and the environment.
The skin is covered by a layer o f dead cells and this prevents the e ntry of many microorganisms
and chemicals.
The skin is waterproof. Most body heat is lost to the environment through the skin. Body
temperature can be adjusted by hanging the flow of blood through the skin.
When body temperature rises above normal, heat is removed by the evaporation of sweat by
conduction, convection and radiation
Damage to large areas of the skin can lead to dehydration and death.
Nervous system brain and reflex actions
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The nervous system is formed from the brain and spinal cord and peripheral nerves.
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The brain has regions such as the cer ebrum, cerebellum, medulla oblongata and the
hypothalamus that coordinate different functions.
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The spinal cord links the brain and the peripheral nerves below the skull.
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Peripheral nerves carry impulses into and from the brain and spinal cord.
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Electrical nerve impulses travel along neurones and neurones are bound together in bundles –
these are called nerves.
Sensory neurones carry impulses to the Ce ntral Nervous System and motor neurones carry
impulses from the Central Nervous System.
Connector(relay) neurones exist with in the brain and spinal cord and link sensory and motor
neurones.
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Nerve impulses pass between neurones at synapses by means of chemical tr ansmitters.
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Impulses reaching an effector at the end of a motor neurones cause a response.
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Some stimuli produce very rapid, automatic responses – reflex actions – that are involuntary.
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Voluntary responses involve conscious decisions made in the brain
20.
The Eye
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Sense organs contain receptors that detect external stimuli and produce nerve impulses.
These organs and their stimuli are the e ye- light, nose- smell, tongue – taste, ear- sound,
movement and gravity. Skin – touch and temperature change.
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All receptions in the eye detect light and some detect color.
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The retina contains these receptions rod and co ne cells.
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The retina sends nerve impulses to the brain through the optic nerve.
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The eye focuses light rays on the retina.
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The eye changes the shape of t he lens to focus near and distant objects.
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The eye changes the shape of t he iris and pupil to control the amount of light reaching the
retina.
The eye sometimes falls to focus light rays on the retina – this results in long and short sight.
Endocrine System
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The endocrine systems, like the nervous system helps to coordinate and control process in the
body.
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This system consists of glands that produce hormones when they are stimulated.
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These include the pituitary, thyroid and adrenal glands, the pancreas, ovaries and testes.
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Hormones are chemical that are released directly into the blood.
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Hormones rely on the circulatory system to re ach their target organs.
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When hormones reach their target organ hey trigger it to respond.
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Some hormones such as adrenalin and insult produce rapid but short lived effects.
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Some hormones such as grown hormone, oestrogen and testosterone, produce slower but more
long-lived effects.
Nerve impulses travel very rapidly along neurones but hormones travel at the slower speed of
the movement of the blood.
A hormone may affect a number of tar get organs but nerve impulses are directed t o a particular
localized effector.
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22.
Reproductive System
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23.
Reproduction is the formation o f new individuals.
In asexual reproduction individuals do not produce gametes but part of a single parent become
detached and grows into a new individual.
Asexual reproduction can be very rapid, producing large number of individuals all with identical
hereditary information to the parent.
In sexual reproduction male and female individuals produce gametes ( sex cells) called
spermatozoa (sperm) and ova (egg cells).
Sperm and ova fuse together (fertilization) and form zygote. The zygote has a mix of hereditary
information from the two parents.
The male reproductive system is destined tor produce sperm and release them within the
female system.
The female system is designed to produce ova, receive sperm, enable fertilization and assist the
development of the zygote up to birth.
In the menstrual cycle, the uterus forms a new lining ready for implantation and further
development each time ovulation occurs.
This lining is broken down if fertilization and implantation does not happen.
Pregnancy, Birth and planning a family
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Ovulation, fertilization and implantation must happen before a fetus can develop into an
embryo.
An embryo is attached to the uterus lining by the placenta and umbilical cord.
The mother’s blood supply is separate from but very close to the fetal blood supply in the
placenta.
The maternal blood supply is rich in oxygen and nutrients that diffuse into the fetal blood
supply. Carbon dioxide and urea diffuse in the opposite direction.
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The fetal blood flows to and from the placenta along the umbilical cord.
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The placenta protects the embryo from mo st pathogens and toxic substances.
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The amnion and amniotic fluid around the fetus act as a shock absorber.
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The birth process involves waves of muscle contractions, widening of the cervix, release of
amniotic fluid, expulsion of the baby and then the placenta.
Both ante-natal and post –natal care of mother and baby are essential.
Family planning involves preventing live sperm and ova meeting within the reproductive system
and can involve natural or artificial methods.
Section C - Heredity and Variation.
24.
Chromosomes, Mitosis and Meosis
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The nucleus of a cell controls the cell’s structure and activity.
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When a cell divides its nuclear mater ial divides before the cytoplasm.
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The nucleus contains chromosomes made of genes – these are the units of inheritance
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The genes control the production of proteins, including enzymes by ce lls.
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The nucleus of each body cell contains 23 pairs of chromosomes and two copies of each gene.
This is the diploid state.
When a diploid nucleus divides by mitosis, each daughter nucleus has 23 pairs of c hromosomes.
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25.
Nuclei produced by mitosis are identical to one another and to their parent cell nucleus. They
are clones.
Gametes have the haploid number of 23 single c hromosomes in each nucleus and they are
formed by meiosis.
In meiosis, homologous pairs of chromosomes split into chromatids and these separate to from
groups that become the chromosomes of four g ametes.
Meiosis is important because it allows new combinations of genes to be formed.
Variation, Genes, monohybrid inheritance and genetic engineering
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Inheritance is controlled by genes present in the chromosomes of cells
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Genes are made of deoxyribose Nucleic Ac id (DNA)
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DNA acts as a code controlling the fe atures of an organism. The code is passed to ribose nucleic
acid (RNA) that then oversees the formation of all proteins that from the structure of cells,
enzymes and even some hormones.
Alleles are alternative forms of a gene.
An alleles that always has an effect is said to be dominant while an allele that only has an effect
when the dominant allele is absent is said to be recessive.
A homozygous individual has a pair of identical alleles of a gene but an individual that has the
two alternative alleles of a gene is heterozygous.
The genotype is the actual combination of an individual alleles, while the phenotype is the
detectable effects shown by these alleles.
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Variation is the difference that show in the phenotypes of individuals.
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Cation can be continuous, like body height or discontinuous like human blood groups.
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A mutation is a change in the DNA found in genes or even a change in the chromosome number.
It may show itself as a difference or abnormality in the phenotype.
The sex of an individual is determined by the se x chromosomes (23rd pair). Females have two X
chromosomes, while males have one X and one Y chromosome. Gametes only have a single sex
chromosome.
Section D - Diseases and their Impact on Humans.
26.
Disease and its impact on humans
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A disease is something that reduces the physical, mental or social well-being of a human.
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Diseases may be caused by organisms or by harmful material entering the body/
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Some diseases are caused by failure or degeneration of part of the body or by the lifestyle of a
human.
A disease is sometimes preceded by a period while it is developing in the body but when it
shows no effects.
Infections (communicable) diseases can be transferred directly between humans or can be
passed by an agent such as a vector , or by air, water or food.
The signs of a disease are visible effects detectable by another person such as a rash, vomiting,
or high temperature.
The symptoms of a disease are the effect that are only detectable by the patient such as pain,
nausea or numbness.
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27.
Some diseases are incurable and will remain with patients for t he rest of their lives.
Asthma and lifestyle diseases
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A diet that contains too much or too little of one of the main components may cause a disease.
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Too much or too little food can lead to obesity or anorexia.
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Too little of one component can lead to a deficiency disease such as kwashiorkor, rickets o r
scurvy.
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Obesity can lead to cardiovascular disease, hypertension or lead to diabetes.
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Lack of exercise can increase the risk of obesity.
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Asthma restricts the entry of air into the lungs because the airways become constricted by a
muscular spasm.
Smoking and exposure to airborne particles and chemicals, c alled allergens increase the risk of
asthma.
Cardiovascular disease causes damage to the heart and blood vessels. It can increase the risk of
heart attacks and strokes.
Hypertension causes a rise in blood pressure, and may lead to strokes and brain damage.
Infectious diseases
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Infectious diseases can be passed from one organism to another.
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They are caused by pathogens such as bacter ia, fungi, parasitic worms, protozoa and viruses.
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The skin normally protects living tissues from pathogens. Infections may occur when there are
cuts or punctures to the skin.
Some diseases are transmitted directly from person to person, others need living vectors, air,
water or food for their transmission.
Respiratory infections are often transmitted by air and include bronchitis, influenza, the
common cold and pneumonia.
Digestive system diseases are often transmitted by food or water and include cholera,
dysentery, gastroenteritis and typhoid.
Tuberculosis can be transmitted by food and by bacteria in the air. It may affect the lungs and
bones.
STDs are infections only spread through sexual intercourse and include gonorrhea, syphilis and
genital herpes.
HIV is a virus that infects white blood cells. It can be spread by contact between living cells,
infected blood or other body fluids.
STDs and some viruses can affect a developing fetus o r be contracted by a baby at birth.
Vectors and vector transmitted diseases
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A Vector is an organism that transmits a pathogen but is not affected by it. The pathogen must
be smaller than the vector.
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Common vectors include mosquitoes, house flies, rats and snails.
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A vector and the organisms that receives the pathogen are often mem bers of a food chain.
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The pathogens transmitted by vectors may be very c omplex life cycles.
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The spread of some diseases is often most easily controlled by elimination of the vector.
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The vector has a relationship with humans when transmitting pathogens that affect them.
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Mosquitoes are vectors of the pathogens causing malaria, dengue and yellow fever.
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Mosquitoes spend the first stages of their life cycle in water.
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The house fly can be the vecto r of the pathogens causing typhoid, cholera and dysentery.
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Rats and rat fleas are vectors of leptospirosis.
30.
Immunity and Control of microorganisms
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Microorganisms can be destroyed by very high temperatures, ster ilization or by chemicals,
disinfectants and antiseptics.
High temperatures are used to sterilize medical equipment preserve food and keep milk fresh.
Disinfectants include chlorine, carbolic acid and phenol. They are used to kill pathogens or nonliving surfaces as they damage human cells.
Antiseptics prevent the growth and re production of bacteria. They can be used to clean sin and
some wounds.
Antibodies are produced by white blood cells. They attach to antigens on t he surface of
pathogens and destroy them.
Antibodies can be injected into the body to give immunity to a disease – this called passive
immunity.
An injection of dead or weakened pathogens triggers the production of antibodies, this is called
active immunity.
Vaccination is the injector of material( the vaccine) and this triggers the formation of antibodies.
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Section E - The Impact of Health Practices on the Environment.
31.
Pollution and Water
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Pollution harms the environment and is caused by human activities.
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Pollutions are substances that cause harm and are released by human actions.
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The air and water are polluted by c hemicals such as gases, liquids and solids from homes,
industrial processes and agriculture.
Living organism and soil can also be affected by pollutants.
The water cycle circulates water between liquid water and water vapor and this depends on
heat or evaporation to occur.
Evaporation occurs from fresh and sea water, t he soli, animals and plants (transpiration).
Cooling condenses the water that then falls as rain.
Water from underground can contain pathogens and water from lakes and rivers can also
contain silt and rubbish.
Small amounts of water for personal use can be purified by boiling and by using chemicals such
as sterilizing tablets.
Purifying large quantities of water involves screening, sedimentation, filtration and chlorination.
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32.
Sewage
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Sewage is liquid waste that flows through pipes called sewers.
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Domestic sewage includes urine, faeces and domestic water waste from sinks and baths.
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Sewage can carry pathogens for cholera, dysentery, typhoid and some parasitic worm infections
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Sewage must not have contact with drinking water supplies.
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Sewage is a feeding and breeding material for some disease vectors such as flies.
The treatment of sewage to make it harmless depends on the activity of both aerobic
and anaerobic bacteria.
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Small scale sewage treatment is in pit latrines and septic tanks.
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Large scale treatment is by screening, sedimentation, digestion of sludge and effluent
treatment in biological filters or activated sludge methods.
Refuse and recycling
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Refuse is solid waste from homes and businesses.
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It includes metal, glass, plastic, food waste, paper, china and textiles.

Biodegradable refuse such as paper, food waste, natural textiles and even some plastic can
be decomposed by microorganisms.

Non-biodegradable refuse includes metals, glass, artificial textiles, chia and most plastics
.
Some of these material can be separated from refuse and can be reused or recycled. 
The food waster is a breeding area and feeing material for vectors such as rats and flies. 
Contains such as tins, bottles and jars can be a breeding area for mosquitoes.

Refuse should be disposed of well away from homes to reduce the risk of pests causing
problem 
Some refuse is disposed by incineration. Some reuse is deposited in landfill sites
where it must
be compacted and buried to avoid access by vectors.
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12 | P a g e
Wondershare
PDFelement