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Biology Notes

(page 244)
1. Puberty is the start of the time when a girl I capable of becoming a mother and a boy a father.
2. Puberty begins at the age of 11-13 for girls and 12-14 for boys.
3. Changes that males go through during puberty include: enlargement of sexual organs,
ejaculation is possible, muscle development, pubic and underarm hair, deepening of voice etc.
Changes that females go through during puberty include: enlargement of reproductive organs
and breast, menstruation starts, broadening of hips for childbearing etc.
4. The hormone testosterone I made in the testis. (male)
5. Sperm is stored in the epididymis for some time. (male)
6. The hormone released by the ovary is oestrogen. (female)
7. The function of the fallopian tube is to transport the egg from the ovary to
the uterus. Fertilisation also occurs in it.
8. The egg last for 3-4 days before it can’t be fertilised, one is produced monthly
until menopause and the egg can’t move on its own but relies on the cilia to
transport it.
The sperm lasts for 2-3 days in the female, millions of sperm is produced during each ejaculation
and sperms do have tails and can swim on their own to the egg.
9. Fertilisation is the fusion of male and female gametes to form a zygote.
Zygote is the result of the fusion of the gametes.
Embryo is a ball of cells form when the zygote divides multiple times.
Implantation is when the embryo puts itself into the thickened lining of the
Foetus is when the embryo develops tissues and organs.
Ovulation is when a matured egg is released into the oviduct.
Menstruation is when the dead egg and the uterus lining breaks down and is
lost through the vagina.
The Menstrual Cycle is the journey of the egg if it isn’t fertilized from the ovary until it is lost
through the vagina which normally lasts 28 days.
 Reproduction is a characteristic of life. There are two types: asexual and sexual reproduction.
 Asexual reproduction happens when one individual produces offspring without fertilization.
 Advantages may include large numbers of offspring can be produced, they can be produced
continuously etc.
 Disadvantages may include overcrowding and competition may occur, environment change can
make it difficult to survive etc.
 Sexual reproduction involves two parents producing special reproductive cells or
 A developing embryo is protected by amniotic fluids and is nourished by the
developing placenta.
 Advantages may include: genetic variability, may be able to colonise new areas
successfully, more likely to adapt to changing environment etc.
 Disadvantages may include: waste of time spent seeking a mate, offspring produced
less frequently etc.
The ovum travels along the oviduct with aid of cilia (hair-like vibrating structure) and
contractions of the oviduct walls.
Oestrogen is the hormone responsible for ovulation.
Parturition is the act of giving birth.
(page 253)
1. Vasectomy (male) is when the vas deferens are cut and tied off.
2. Tubal Ligation (female) is when the oviducts are cut and tied off.
3. Disadvantages of the pill may include: nausea, breast tenderness, increase
risk of cervical cancer etc.
4. A condom is a latex unrolled onto the penis that prevents the sperm from
entering the vagina.
5. A temporary contraceptive method is the pill and a permanent
contraceptive method id sterilization (vasectomy or tubal ligation).
 Contraception is also known as birth control and persons may want to practice this in order to
limit the number of children they have.
 Some methods of birth control are: abstinence, sterilisation, contraceptive pill, condoms,
diaphragm etc.
(page 254)
HIV is the disease that caused AIDS.
HIV is passed from a positive person through semen or blood.
Symptoms of HIV/AIDS are: persistent cough, fever, skin rashes, diarrhoea, weakness etc.
Gonorrhoea, chlamydia and syphilis are all caused by bacteria.
HPV means human papilloma virus and some symptoms of it are: skin growth and warts.
AIDS caused by HIV attacks and weakens the immune system, making it easy for other diseases
to infect and kill the person. (opportunistic infections)
7. To prevent the spread of HIV/AIDS, don’t share needles, get tested regularly etc.
 A communicable disease is a disease that can easily spread from person to person.
 An STD is a sexually transmitted disease meaning that it can be passed during sexual
1. Metabolism is all the chemical reactions happening inside the cell. It is
important because it provides energy for vital processes and for
synthesising new organic material.
2. Excretion is the elimination of metabolic waste or excretory products
from organisms.
3. Egestion is the act of removing undigested or waste material from a cell or organism specifically.
4. All living organisms carry out excretion.
5. Some waste products in plants are: tannins, nicotine, resin,
morphine, gum etc. The waste is stored in leaves and the bark and
when they are to be removed, the leaves and bark shed.
6. There are two bean-shaped kidneys in the human body.
7. The function of the kidney is to filter waste from the body which is
then removed as urine.
8. Urine is made up of salt, water and urea.
9. Nephrons, found in the kidney, is the structure that actually produces
urine in the process of removing waste and excess substances from
the blood.
10. Your kidney can be damaged when your glomerulus burst caused by high blood pressure.
11. A kidney transplant is the movement of the kidney from the doner to the recipient.
12. A dialysis is a method of removing any substances in excess in the blood such as urea and salts.
It must be done for many hours every few days.
 The needle will slowly remove blood and transfer it to the machine where the waste products
are filtered out and the clean blood is returned to the body.
 Defecation is the removal of faeces during egestion.
 A red blood cell has a life span of about three months and after that, it is destroyed by the liver
or spleen. The excess protein is broken down to amino acids and reused by the body.
 Secretion is the release of substances like hormones from cells.
 Osmoregulation is the control of the amount of water in the blood.
 The bladder stores urine temporarily until it is released through the urethra.
 Sphincter muscles control the release of urine from the bladder.
 The cortex is made up of Bowman’s capsules and convoluted tubules of all nephrons.
 The medulla contains loops of Henle and collecting ducts which open into the pelvis.
 The pelvis collects urine from all the collecting ducts.
 Selective reabsorption is the reabsorption of a substance in preference to others that are
 Homeostasis is used to describe all the mechanisms by which a constant internal environment is
 While the external temp. may change, the internal temp. within the body must remain fairly
constant otherwise all the reactions need may be disrupted.
 Feedback mechanisms are used to control blood glucose levels, water, body temperature and
the amount of carbon dioxide in the blood.
(chpt 7)
1. There is approximately 7.7 billion people on Earth right now.
2. To create more space and more food, humans have cleared forests,
back-filled coastal areas, skyscrapers were constructed, mass farming,
genetic engineering etc.
3. To reduce diseases, humans have invented immunisation, vaccines and
education about vaccines. To reduce predators, the use of gunpower
was introduces along with weapons.
4. Definitions:
 Renewable resources are one that doesn’t pollute and can be reused or quickly replaced.
 Non-Renewable resources are one which is in limited supply and once used up, is gone forever.
 Biodegradable waste is those that can be decomposed by living organisms like fungi.
 Non-Biodegradable waste is waste that will not breakdown and that will
take many years to breakdown or decompose.
5. Endemic species are species of plants or animals that can be found in one
particular area or region and can’t be found anywhere else.
6. Deforestation refers to the microorganisms, plants and animals that
inhabit the Earth.
7. Humans practice deforestation because the land is needed for other things
like factories, housing, to provide hardwood timber etc.
8. The negative effects of deforestation include: increased amount of carbon dioxide emissions,
soil erosion, habitat loss etc.
9. Biodiversity refers to the millions of plants, animals and microorganisms that inhabit the Earth.
10. Extinct species are no longer known to exist.
11. Reasons for increased extinction rate are habitat destruction, pollution, introduction of more
competitive species, hunting etc.
12. Sewage contains liquid and solid waste from urine and faeces, water from domestic use and
industrial waste.
13. Eutrophication is the process whereby large amounts of nutrients is added to a water system
which leads to the death of many of the organisms living in it.
 Due to the run-off from land.
 Prevent it by treating sewage properly and using limited fertilizer.
14. The greenhouse effect is the trapping of the Sun’s warmth in a planet’s lower atmosphere.
 Greenhouse gases is gases like carbon dioxide and methane that absorbs some of the
escaping heat and sends it back to the Earth’s surface.
15. Global warming is a gradual increase in the overall temperature of the Earth’s
 Generally caused by the increased level of carbon dioxide, CFC etc.
 Some effects are melted icecaps, temperature and rainfall pattern change,
increased number of tornadoes and hurricanes etc.
16. The use of CFC has resulted in the thinning of the ozone layer in several areas.
 The ozone layer protects us from harmful UV rays (the sun).
17. Effects of UV radiation include: the increased chance of skin cancer and cataracts,
premature aging to the skin (wrinkles, liver spots etc.), damaging of crops etc.
18. You can help conserve the environment by:
 Reuse things if possible. Example: tins, jars etc.
 Reduce- only buy things that is necessary. Example: avoid one use razors etc.
 Recycle things into new products. Example: paper, glass etc.
 Repair, fix things instead of throwing them out. Example: replanting trees etc.
 Refusing to be a part of. Example: littering, bush fires etc.
 Compost is used as a natural fertilizer and soil conditioner.
 Although humans don’t live in water, their activities have polluted it:
 Over-fishing marine life, caused oil spills etc.
 Biogeochemical cycle is the cycling process by which these essential atoms are released and
reused in nature. Examples: carbon and nitrogen cycles.
 The carbon cycle shows how carbon atoms are passed from one organism to another and to
their environment as they live, breathe, eat, die and decay.
 The nitrogen cycle shows how nitrogen passes between air, soil, plants and animals and back
again. Bacteria is really important in this cycle.
 The Industrial Revolution refers to the time when people started making machines to do a lot of
their work.
 Acid rain is when rainfall is made so acidic by atmospheric pollution that it causes
environmental harm.
 Mainly caused by industrial burning of coals, waste gases from which contain sulphur
and nitrogen oxides which combine with atmospheric water to form acids etc.
 The greenhouse effect is an important natural process, caused by greenhouse gases in the
atmosphere that absorb heat energy from the Sun and keep the surface of Earth warm enough.
 Though humans subject to the same constraints as other organisms, they
have advised many ways to overcome them, thus the population still
 Endangered species are those which numbers have been reduced to the
point that survival of that species is unlikely.
 Vulnerable species are those that be become endangered soon because
their population is decreasing at alarming rates.
 Desalination plants converts salt water from the ocean into drinkable water.
 Pollution is the contamination of land, water and air by the discharge of harmful substances.
 Land- non-biodegradable waste, insecticides, herbicides etc.
 Water- oil, hot water, organic waste, mineral salts, toxic chemicals etc.
 Air- carbon dioxide, lead, smoke sulfuric acid, carbon monoxide etc.
Biological control is the use of living organisms to control pests, often in agriculture.
 Much care must be taken to insure those introduced predators or parasites don’t
become pests themselves.
Biochemical oxygen demand is the amount of dissolved oxygen needed to break down organic
matter present in a given body of water.
Industrialization, though signs of human success, has serious consequences to the environment:
 Pollution, water shortages, deforestation, increased flooding etc.
With the constant increase of humans on Earth, more carbon dioxide is being released and the
ozone layer is beginning to for holes.
(page 78)
The seven characteristics of life:
 Growth- living things start of small and gets bigger.
 Reproduction- all living things can make more of themselves.
 Irritability- plants are sensible to light while animals are sensible to light, sound, smell.
 Movement- animals can be fast or slow. Plants do this by moving their petals.
 Nutrition- all living things need to obtain substances from their environment to obtain
energy, grow and remain healthy.
 Excretion- all living things get rid of metabolic waste.
 Respiration- living things need to get energy from oxygen and food.
 Magnification= Length of drawing/ length of specimen.
 When observing materials under the microscope, it is necessary to cut a very thin
section to allow light to pass through it.
Uni-cellular organisms are made up of one cell.
Multi-cellular organisms are made up of multiple cells.
The cell membrane has a selectively permeable membrane barrier which controls exchange
between cells.
Chloroplasts are found in plants and algae and is responsible for capturing light energy.
Mitochondria are the ‘powerhouse’ of the cell, breaking down fuel molecules.
Plant and animal cells both contain cell membrane and nucleus.
Differences in plants and animal cells: chloroplast is present in plant cells but absent in animals
and in plants, carbohydrates are stored as starch but stored as glycogen in animals.
Cell specialization is the process in which a cell changes from one cell type to another. This
happens numerous times during the development of a multicellular organism.
Multicellular Organisms
 Cells are the basic building blocks of all living things. Example: red blood cells etc.
 Tissue is made up of many similar of identical cells. Example: connective tissue etc.
 Organs are the body recognizable structure. Example: heart, lungs, stomach etc.
 Systems are a set of organs working together. Example: circulatory system etc.
Diffusion is the movement of molecules from a region of high concentration to a region of low
concentration. It can happen in gases and liquids.
For diffusion to occur rapidly, you need to keep the differences between the concentrations as
high as possible, have a large surface area to volume ratio, so it has a large surface to diffuse
through etc.
Osmosis is the diffusion of water molecules across a selectively permeable membrane or semipermeable membrane.
Cell wall is critical to maintain the cell shape to transport water from one region to another.
Chloroplasts take care of the oxygen production by absorbing large amounts of CO2.
Cell organelles are the structures found within a cell.
Nucleus controls the activities of the cell and contains chromosomes.
Chromosome carries genetic information in the form of DNA.
Permanent vacuole is important during the exchange of water and minerals.
Ribosomes is where proteins are made (protein synthesis).
Endoplasmic Reticulum is where lipids are made (lipid synthesis).
Microbes are microscopic organisms that can’t be seen by a naked eye.
 Viruses aren’t made of cells and referred to as virus particles. They can’t be killed by
antibiotics such as penicillin.
 Bacteria are single-celled organisms referred to as ‘germs’ that decompose dead
organisms and digest cellulose.
 Protozoa are generally single-celled organisms.
Amoeba is very common and can be found in backyard ponds and drains.
Glycogen granule stores food in animal cells.
The cells of unicellular organisms are independent but are still capable to carry out all
characteristics of life.
In multicellular organisms, the cells work together and are often dependent on one another.
Secretion is the removal of substances from the cell.
 It may be waste products like carbon dioxide and urea or substances needed by other
cells like enzymes.
Water enters and leaves cells by osmosis.
Concentration gradient or diffusion gradient occurs when there is a difference in the number of
molecules, or the concentration of molecules between two regions
Diffusion in the Human body.
 In the lungs, carbon dioxide diffuses from the blood and oxygen diffuses the other way.
 Carbon dioxide diffuses out of the cells and into the blood since it is of higher
concentration in the blood.
 The oxygen in the blood diffuses into the cell because the oxygen concentration in the
cell is low because of respiration.
Exocytosis is the process by which the contents of a cell vacuole are released to the exterior.
Isotonic is a solution with the same concentration as the cell contents.
 No concentration gradient so the movement each way is balanced.
Hypotonic is a solution that is less concentrated than the cell contents.
 More water molecule moves into the cell. (net flow is out)
 The cell becomes full of water and is described as turgid.
Hypertonic is a solution that is more concentrated than the cell contents.
 Most water molecule move out. (net flow is in)
 The cell loses water and becomes flaccid.
Flaccid cells are easy to distinguish under the microscope because the cell membrane and
contents pull away from the cell wall.
If an animal cell is placed in a hypotonic solution, it will swell and eventually burst due to the
absence of a cell wall.
If an animal cell is placed in a hypertonic solution, it will lose water and shrink.
If a plant cell is placed in a hypotonic solution, it will become turgid but not burst due to the
presence of a cell wall.
If a plant cell is placed in a hypertonic solution, the cell membrane pulls away from the cell wall
and it becomes flaccid.
(page 91)
1. Autotrophic nutrition is carried out by ‘self-feeders.’ (plants)-create their own food.
 The intake of simple, inorganic substances by plants during photosynthesis.
 Plants don’t eat yet they are full of food. They are rich in carbohydrates, fats and
proteins because they are able to manufacture their own food.
2. Heterotrophic nutrition are organisms that are dependent on other organisms to survive.
(humans, chicken, tigers etc.)
 The intake of complex, organic substances when animals feed.
3. Saprophytic nutrition is the mode where organisms feed on dead or decaying matter.
(decomposers)-bacteria, fungi.
 They are very important to enable the cycling back of these materials to Earth so they
are available to plants again.
4. The organ that photosynthesis takes place in is the leaves.
 The transverse section (cross section at or around the lamina) reveals many cells.
5. The organelle that photosynthesis takes place in is the chloroplasts.
6. Sunlight, carbon dioxide and water are the raw material needed for photosynthesis.
7. Glucose is the carbohydrate made at the end of photosynthesis.
8. Oxygen is the by-product/waste product made at the end of photosynthesis.
 The cell will use some oxygen for respiration but the majority diffuses out through the
9. Light dependent stage is when sunlight is absorbed and converted into chemical energy.
 The energy is used to split water:
Oxygen is the waste product.
The hydrogen combines with
carbon dioxide to make
10. Light independent stage is when the energized electrons provide the energy to form
carbohydrates from carbon dioxide molecules.
 It is converted to starch and stored in the leaf to be used in the night when the plant
isn’t photosynthesising.
 It I broken down during respiration to release energy so the plant can carry out the
processes of life.
 Converted to sucrose, transported to other parts of the plant then converted to other
carbohydrates, lipids and protein and used for growth or converted to starch and stored
like a potato.
 They are generally broad and flat with a large surface area to absorb a lot of carbon
dioxide and light.
 They lie at 90° to the sunlight to catch as much light as possible.
 They are thin to allow light and carbon dioxide to reach all cells rapidly.
 A waxy cuticle prevents water loss.
 Xylem vessels transport water to the leaf cells.
 The guard cells vary the size of the opening of the stomata by changing
their shape.
Limiting factors are factors that limit the reaction rate in any process.
 Temperature- the rate of reaction increases as the temperature does.
 Water- the availability varies on the environment.
 Light- the amount varies between night and day
 Carbon dioxide- the concentration is relatively low in the atmosphere.
(this is usually the limiting factor)
Variegation is the appearance of different coloured zones in the leaves and
sometimes the stem of plants.
 Variegated leaves occur rarely in nature.
Etiolation is a process in flowering plants grown in partial or complete absence of light.
 When a plant is out of light, all of the energy is used to make thin long cells so the
stem becomes elongated and thin.
The chemical reaction for photosynthesis:
Water+ Carbon Dioxide
Glucose+ Oxygen
Oxygen is the gas released during photosynthesis.
Glucose is the reactant used to produce oxygen.
From glucose, the plant makes all the other protein, carbohydrates and fats it needs.
Chlorophyll is a complex green pigment.
 At the centre, there is a single atom of magnesium chemically
bonded to four atoms of nitrogen.
 Without nitrogen, a plant can’t make chlorophyll this not being
able to photosynthesise.
The stoma is the route by which water is lost from the plant during
transpiration and also by which gaseous exchange necessary for photosynthesis occurs.
 Stomatal openings vary as a result of changes in the turgidity (the state of being
swollen especially due to high fluid content) of the guard cells.
 Most stomata open during the day and close at night.
 Carbon dioxide move into the cells themselves. As it is used up during photosynthesis,
the concentration inside the cell is less than the concentration outside so diffusion
occurs and the process repeats itself.
 Water moves in by osmosis from the soil into the roots of the plant. It travels up the
xylem vessels to the leaves and moves by osmosis to the palisade cells where it is used
during photosynthesis.
 Light rays pass into the leaves from all around. Chloroplasts are found mainly in the
palisade layer where the chlorophyll can easily intercept and trap the light energy.
Photosynthesis is a chemical reaction, and the rate at which reactions can occur depend on
how rapidly the chemicals that are reacting can get together.
 A plant requires water, carbon dioxide and light to photosynthesise.
 If one of these are in short supply, the rate of reaction will slow down.
Living cells need a constant supply of oxygen, and need to get rid of carbon dioxide as
respiration takes place.
Gaseous Exchange is the diffusion of oxygen in and caron dioxide out of the body.
In human, the respiratory surface is the lungs.
1. The nose filters the air and also warms and moistens it.
2. The pharynx is the back of the throat.
3. The larynx is the voice box.
4. The trachea, also known as the windpipe has rings of cartilage to help
keep it open. A small flap known as the epiglottis which prevents
food from going into the lungs.
5. The trachea into two bronchi (singular-bronchus), one for each lung.
6. Each bronchus further divides into smaller tubes called bronchioles.
7. The alveoli are a cluster of tiny air sacs at the end of each bronchiole. It has
tiny blood vessels called capillaries surrounding them and it is where gas
exchange occurs.
 Oxygen passes out the lungs into the blood capillaries to be
transported around the body.
8. There are two lungs inside of us (right and left).
9. The diaphragm is the largest muscle in the body. It contracts and relaxes
allowing the lungs to move.
The walls of the alveoli are the gaseous exchange surface or the respiratory surface.
Oxygen diffuses into the capillary and the blood in the capillary becomes oxygenated.
The trachea is lined with mucus and cilia.
 Mucus is a slimy substance that traps and holds dust and microorganisms.
 Cilia are microscopic hair-like extensions that beat in a wave like manner, moving the
mucus containing dust and microorganisms upwards and out of the lungs.
 The mucus and cilia afford some protection against pathogens.
 Pathogens are organisms that cause diseases.
Breathing is the movement of air into and out of the lungs.
Inspiration or inhalation is breathing in of air.
Expiration or exhalation is the breathing out or air.
Some of the oxygen is used by the cells of the
body during respiration.
Carbon Dioxide
Carbon Dioxide is made by the cells and is
transported by the blood to the lungs.
Not Used.
During inspiration, the diaphragm contracts and moves downwards, the
rib raises and the intercostal muscle contracts.
 The volume of the thorax(chest) increases and air rushes into the
lungs through the nose, mouth and trachea.
During expiration, the diaphragm relaxes and moves upwards, the rib is
lowered and the internal intercoastal muscles contrasts.
 The volume of the thorax(chest) decreases and air is pushed out
of the lungs through trachea and the moth or nose.
In humans, the lungs are adapted for gas exchange, in fishes, the gills are adapted for gas
exchange and in plants, the leaves are adapted for gas exchange.
 The leaf is the gaseous exchange surface or respiratory surface in plants.
 There are tiny pores called stomata on the underside of the leaf through
which gases pass. The gas diffuses into and out of the plant cells.
 Plants also photosynthesise and thus, during the day, require carbon
dioxide and must get rid of oxygen because it is a waste product.
Gas exchange surfaces is where the exchange of carbon dioxide and oxygen occurs.
 Large surface area- many alveoli are present in the lungs with shapes hat further
increase the surface area.
 Thin surface- the walls of the alveoli and capillaries are just one cell across, providing
gases with a short diffusion distance.
 Moist surface- gases dissolve in the moisture helping them to pass across the gas
exchange surface.
 Rich blood supply- this ensures oxygen rich blood is taken away from the lungs and
carbon dioxide rich blood is taken to the lungs.
 Tobacco may be the cause of 3 million deaths worldwide each year. They come mainly
from lung cancer but heart disease is also associated with smoking.
 Cigarette smoke includes nicotine, tar and carbon monoxide.
 A large percentage of smokers are young people who become addicted
very quickly.
 25% of smokers die of lung cancer.
Nicotine makes cigarettes highly addictive, reduces air flow into and out of the lungs, paralyses
the cilia lining the trachea so it is unable to remove dirt and bacteria, raises blood pressure,
raises heart rate and increases the risk of osteoporosis.
Osteoporosis is the loss of calcium carbonate from the bones thus making them brittle, so the
break easier and are more difficult to heal.
Tar sticks to cells in the lungs, causes the development of cancer, damages lung tissue, breaks
down the alveoli thus decreasing the surface area for gas exchange and causes bronchitis.
Carbon Monoxide causes less oxygen to be transported by blood, combines irreversibility with
haemoglobin the blood, causes breathlessness, reduces the smoker ability to take strenuous
exercise and can cause problems to babies if it gets into a pregnant lady’s blood.
Marijuana is a green or grey mix of dried shredded flowers and leaves of hemp plant Cannabis
Savita also called ganga, weed, pot etc.
 Short term effects can include problems with memory and learning,
distorted perception, difficulty in thinking, anxiety, increased heart rate etc.
 The effects on the lungs are greater than those of tobacco smoke because
users inhale more deeply and hold the smoke in their lungs.
Respiration is the process by which energy is released from food in all living
cells to do the work necessary to keep it alive.
 It is the process of producing cellular energy involving oxygen.
 In animals, food eaten id digested and absorbed into the bloodstream
and the end product eventually reach all the body cells.
 Oxygen comes from the air we breathe and it diffuses into the
bloodstream and is transported to all the body cells.
 In both plants and animals, energy is usually released from glucose. It is released when
glucose combines with oxygen.
 Equation for aerobic respiration:
Glucose + Oxygen
C6H1206 + 6O2
(page 122)
Energy + Carbon Dioxide + Water
Energy + 6C02 + 6H2O
 At each step in the breakdown of glucose, energy is released.
 It is used to convert a chemical called adenosine diphosphate (ADP) into adenosine
triphosphate (ATP). The energy is then stored in little packets.
 The energy can be released wherever and whenever from ATP.
 A cell may not require much energy at once so by storing it in
smaller packets, wastage is prevented.
 The energy can be used to drive many different chemical
reactions rapidly.
 It can be transported and used elsewhere without reactions in
 Energy production and utilisation are very efficiently and carefully controlled by the
 It occurs in an organelle called the mitochondrion.
 Mitochondria are present in all cells, animal and plant, and are sometimes referred to as
‘power house’ of the cell.
 The energy in ATP is released when it is converted back to ADP.
 It is respiration that can occur without oxygen.
 In anaerobic respiration, the glucose isn’t completely broken
 Stagnant ponds and deep underground have no oxygen thus
requiring organisms living there to adapt for their own survival.
Examples: tapeworm, some worms, some bacteria and fungi etc.
 Many living cells that respire aerobically, can also respire anaerobically if oxygen is
Uses oxygen.
In plants and animals:
Water and carbon dioxide are the waste
Large amounts of energy produced (2800 kJ
per mole for the breakdown of glucose).
Glucose is broken down completely to
inorganic molecules.
Occurs in the mitochondria of the cell.
 During strenuous exercise, muscle cells need more energy thus increasing the breathing
and heart rate in attempt to get more oxygen to those cells.
 Sweating occurs to help lose some of the extra energy as heat.
 When the oxygen supply becomes inadequate, the muscle cells respire anaerobically.
 Energy is still produced just in smaller amounts.
Doesn’t use oxygen.
In animal cells:
Lactic acid is the waste product.
In plant cells:
Ethanol and carbon dioxide are the waste products.
Small amounts of energy are produced (150 kJ per mole for
breakdown of glucose in animals and 210kJ per mole in plants).
Glucose is not broken down completely. Ethanol and lactic acid
are organic molecules that still contains useful energy.
Occurs in the cytoplasm of the cell.
lactic acid + a little energy
2C3H6O3 + a little energy
 Lactic acid is a waste product of this reaction. It builds up in the muscles and causes
them to ache (fatigue). It also creates an oxygen debt which has to be repaired.
 After exercising, oxygen is used to change the lactic acid back to a chemical like glucose
so that it can be broken down completely in aerobic respiration.
 Ethanol and carbon dioxide are produced as waste products. Ethanol is
an alcohol and the process is known as alcoholic fermentation.
 Ethanol can be produced in many ways to make a wide range of
alcoholic drinks.
 The production of carbon dioxide is used to make the dough rise in
bread-making. It gets bigger as the gas expands with warmth.
 Only a little ethanol is made but it evaporates while the bread is baking.
 Like animal cells, bacteria make lactic acid as a waste product and we make use of this in
the manufacturing or yoghurt and cheese.
The circulatory system is the system that transports blood through the body.
The circulatory system is made up of three parts:
 The heart- a pump to push the blood through the tubes.
 The blood- the fluid being pumped which contains all the materials to
be transported around the body.
 The blood vessels- tubes through which blood flows to get to and from the cells.
Cardiac muscles contracts and relaxes constantly throughout life and never grows tired.
The heart is divided into a left side and a right side, each side is divided into two chambers:
 The atrium which receives blood.
 The ventricle which pumps blood away.
Deoxygenated blood is blood coming from the body cells where some of the oxygen
has been used during respiration, it flows into the right atrium through the vena cava.
Vena cava
right atrium
tricuspid valve
right ventricle
At the lungs, carbon dioxide leaved the blood and diffuses into the lungs, and oxygen moves into
the blood from the alveoli. Oxygen-rich blood return from the lungs.
pulmonary vein
left atrium
bicuspid valve
left ventricle
Valves prevent the backflow of blood in the heart.
Atrioventricular valves (bicuspid and tricuspid) ensures that blood flows in one direction.
Semi-lunar valves are found at the start of the pulmonary artery and aorta and
they prevent the backflow of blood into the ventricles when they relax.
The heart beats when the muscles of the heart contracts and relaxes.
The rate of the heartbeat is controlled by the pacemaker which is found in the
muscles between the ventricles.
There are about 70-80 beats per minute but it may speed up due to hormones
such as adrenalin.
Blood flow through blood vessels to get to the heart. There are three types of blood vessels:
 Arteries- carries blood away from the heart.
 Capillaries- tiny vessels that pass close to all body cells.
 Veins (and venules)- carries blood back to the heart.
An artery branches into smaller and smaller vessels called arterioles
which brank into even smaller vessels called capillaries (one cell thick).
Capillaries then join up to form larger vessels called venules which then
join to form veins which carries blood back to the heart.
From heart to rest of body.
Connects arteries and veins. From rest of body to heart.
Thick elastic walls.
Walls one cell across.
Thin elastic walls.
Carries mostly oxygenated
Carries both oxygenated
Carries mostly deoxygenated
and deoxygenated blood.
Blood pressure is high.
Blood pressure decreases.
Blood at low pressure.
No valves.
No valves.
Has valves.
High blood speed
Low blood speed.
When the capillaries reach the body cells, the blood gives up food and oxygen and picks up
wastes such as carbon dioxide or urea.
Deoxygenated blood from
the rest of the body.
Oxygenated blood flow
from the pulmonary vein
to the left atrium.
Left atrium contracts and blood
flows through the bicuspid valve
to the left ventricle.
This enters the right
atrium via the vena cava.
Right atrium contracts and
blood passes through the
tricuspid valve to the right
Blood goes to the lungs
where it gets oxygenated.
Right ventricle contracts
and blood is pushed to
the pulmonary artery.
The coronary artery supplies oxygen to the tissues of the heart.
The aorta has the thickest walls because it receives blood at the highest pressure.
Your pulse is the rate at which your heart beats. It is usually called your heartrate
and is the number of times your heart beats per minute.
Blood passes through the heart twice for each time it circulates the body.
Blood is the medium by which substances and materials are transported. It is
made up of about:
 55% blood plasma.
 45% blood cells.
PLASMA- the liquid
part of blood.
CELLS- red blood cells, white
blood cells and platelets.
The blood plasma is about 90% water and most of the substances which must be transported
are dissolved in it. That includes dissolved food, carbon dioxide, nitrogenous waste, hormones
and mineral salts.
 The blood cells are made up of two main types, red and white. There are also fragments of cells
called platelets.
Red blood cells or erythrocytes.
Transport oxygen combined with
haemoglobin, from the lungs to
 Has no nucleus so it only lives for 3-4 months.
tissues where the oxygen is given
 Made in the bone marrow of bones.
up readily.
 Transport oxygen.
 Contains the red pigment haemoglobin which combines with
and released oxygen readily.
White blood cells or leucocytes.
 Fight diseases.
 Two types: phagocytes and lymphocytes.
 Can move through the capillary walls to sites of infections.
 Formed in bone marrow.
 Eat germs.
 Produce antibodies.
 Remembers bacteria.
Lymphocytes- engulf diseases
causing organisms at sites of
 Helps blood clot.
 Cell fragments.
 No nucleus.
 Formed in bone marrow of lone bone.
Platelets help blood to clot to
prevent loss.
Phagocytes- produce antibodies
that kill pathogens by causing them
to clump together.
Most of the carbon dioxide is transported in solution in blood plasma as hydrogen carbonate
Oxygen is carried by the molecule haemoglobin, which is found inside red blood cells.
When a small blood vessel is broken, a blood clot forms to prevent further blood loss.
The clot also prevents the entry of disease-causing organisms.
There are four blood groups, known as A, B, AB and O. They are based on proteins,
called antigens, that are present on the surface of red blood cells.
During transfusion, it is important to note:
 The protein (antigen) on the red blood cell of the donor.
 The type of antibody present in the plasma of the recipient.
If the antibody and the antigen react together, the red blood cells stick
together and transfusion will not be successful.
High blood pressure is when the pressure caused by the blood pushing against the inside walls
of the main arteries is high. Persistent high blood pressure is called hypertension.
A stroke happens when a blood vessel in the brain bursts, causing a portion of
the brain to be damaged from a lack of oxygen.
Hypertension is linked with a number of factors such as: high levels or emotional
stress, lack of exercise, tobacco smoking, obesity, high alcohol intake etc.
A healthy lifestyle can prevent the development of hypertension.
Viruses and bacteria are in the air we breathe, the food we eat, on everything we
touch and all over our bodies.
The body has three lines of defence to protect against infections, these include: the
skin, phagocytes and the immune system.
The skin is the body’s first line of defence and acts as a physical barrier. When there
are cuts or sores, the body reacts to produce blood clot and a fibrous scar tissue. That blocks the
opening, preventing pathogens from entering the body.
Our second line of defence is phagocytes. They move to the infected areas, engulfing
the invading microorganisms, killing and removing them from the body before they
can cause diseases.
If more dangerous, specific pathogens enter, then an immune response is activated,
this is the third line of defence.
Lymphocytes recognise the specific pathogen and mobilise other lymphocytes to make
antibodies to attack, disarm, destroy and remove these pathogens.
An antigen is a foreign substance that induces an immune response in the body.
To defend the body against diseases, antibodies act in a number of ways:
 They cause the antigens to clump together, resulting in their death and easy removal by
the phagocytes.
 They neutralize toxins produced by the antigens.
 They prevent the antigen from entering body cells.
Memory lymphocytes can immediately recognize an antigen introduced to the body during a
previous infection and rapidly make large amounts of the needed antigen.
A person is immune to a disease if upon infection, no symptoms develop.
Natural immunity is when a person becomes immune to a disease naturally.
There are two types of natural immunity:
Actively acquired immunity- when the body has already experienced an
infection by a pathogen or antigen and the lymphocytes produce large
quantities of antibodies to fight the disease.
Passively acquired immunity- antibodies can pass across the placenta
providing a new born baby with immunity against diseases that the mother is immune to.
Immunisation provides immunity to communicable diseases.
Vaccination is injecting or administering orally, small amounts of dead or weakened antigens
into the body. This then stimulates the body to produce antibodies.
 Example- MRR vaccine is given to protect children against measles, mumps etc.
Artificial immunity is when the body is given immunity from a disease by intentional exposure
to small quantities of it.
Actively acquired- this vaccine contains treated antigens that cannot cause the disease, but
which can stimulate the body to make antibodies. When the real antigen enters the body, the
antibodies are rapidly produced to destroy it.
Passively acquired- this vaccine contains ready-made antibodies which provide immediate relief
by destroying the antigen. This is given when the person has been infected with the antigen and
has no previous immunity.
(page 100)
We eat food to get the nutrients needed by the body in order to be healthy.
 Carbohydrates
 Proteins
Needed in large amounts daily.
 Fats
 Vitamins
Needed in small amounts daily.
 Minerals
 Water
These aren’t nutrients but are also needed by the body.
 Fibre/ Roughage
Water is essential because about 70% of our body mass is water.
Fibre is essential to the healthy working of the gut. Without it, we will suffer from constipation.
Carbohydrates Energy
Potatoes, pasta, bread, rice, sugar etc.
Growth and repair, making new cells Meat, fish, nuts, eggs, beans, milk etc.
Store of energy. Used to keep us
Butter, nuts, cheese, red meat, salmon, oil etc.
warm and make cell membrane.
Vitamin A
Vision and healthy skin
Night blindness
Carrots, spinach etc.
Vitamin C
Healthy immune system
Scurvy (bleeding gums,
Oranges, lemons etc.
bad breath)
Vitamin D
Helps absorb calcium
Rickets (bones are soft
Sunshine, milk, eggs etc.
and bend)
To build strong bones and teeth
Rickets and bowlegs
Cheese, spinach, milk
Needed to make red blood cells
Anaemia (red blood cells
Liver, spinach, meat etc.
are smaller)
Helps in chemical reactions in the Goitre (swelling of gland
Seafood (tuna, shrimp),
in neck)
table salt etc.
Organic nutrients are needed in relatively large amounts in the diet.
 Examples: carbohydrates, lipid, proteins and vitamins.
Inorganic nutrients or trace elements is required in small amounts for good health.
 Examples: iron, zinc, water etc.
A deficiency disease develops when there is a shortage of a specific nutrient in the body.
 Examples: night blindness, scurvy, rickets, anaemia etc.
You can prevent a deficiency disease by eating a balanced diet.
Diet is the quantity and quality of food eaten everyday by an individual.
A balanced diet has the correct type of nutrients in the right amounts. It is very important to eat
a variety of food daily since there is no one food that contains all the nutrients the body needs.
There are five food groups you should eat from daily.
 Fruit and vegetables.
 Bread, potatoes and other cereals.
 Meat, fish and alternatives.
 Milk and dairy foods.
 Foods containing fats, food and drinks
containing sugar.
Malnutrition means bad nutrition, and can be applied to under-eating, overeating and bad eating habits. This may be the cause of many diseases.
Under-eating means not eating enough food to supply the energy requirements for daily
 Starvation is one kind of under-eating and is often associated with developing countries.
 Anorexia is another kind of under-eating but is associated with developed countries. It is
the voluntary refusal to eat and it most common in teenagers.
Obesity results from over-eating, especially fatty foods, and a lack of exercise. Obese people are
pre-disposed to many diseases like:
 Diabetes is a group of metabolic diseases in which a person has high blood sugar.
The eat well plate shows how much of what you eat should come from each food group.
Nutritional requirements are the amount of nutrients a person needs. This may vary with age,
gender, level of activity etc.
Men require more protein than women from the age of 11 but extra protein is needed during
pregnancy and breastfeeding.
Mineral intake is especially important during pregnancy and lactation.
Food additives may be natural or artificial.
 Common natural additives- sugar, corn syrup and pepper.
 Common artificial additives- flavours and sweeteners.
Dyes and colouring are purely cosmetic and rarely add nutritional value.
Side effects may include: hyperactivity in children, allergic reactions,
adverse effects on asthmatics etc.
Preservatives make food less subjective to bacterial infections or bacterial poisoning so food can
be kept for longer periods of time without spoiling.
Synthetic flavouring is added to improve or change the flavour of foods during preparation.
Acids are added to give a sour taste to prepared food.
Firming agents are used to retain crispness.
(page 108)
Digestion is the process in which food is broken down into nutrients which can be used by the
body cells.
There are four stages to food processing:
 Ingestion- taking in of food.
 Digestion- breaking down food into nutrients.
 Absorption- taking in of nutrients by cells.
 Egestion- removing of undigested food.
There are two types of digestion:
 Mechanical digestion: physically breaking down food into smaller pieces using teeth
and tongue.
 Chemical digestion: the use of enzymes and chemicals to breakdown or chemically
change food into smaller substances.
Teeth help with the physical or mechanical breakdown of food.
There are four types of teeth:
 Incisors (biting and cutting), chisel shaped.
 Canines (grasping and tearing), pointed or dagger shaped.
 Pre-molars (grinding and crushing), flat with cusps or bumps on the
fairly broad surface.
 Molars (grinding and crushing), flat with cusps on the broad surface.
Milk teeth are the first set of teeth in humans. They appear singly or in pairs from the time a
child is approximately 3 months old. It begins falling out at about 7 years.
Permanent teeth are the teeth that replace the ones that have fallen out.
Most adult have 8 incisors, 4 canines, 8 premolars and 12 molars.
Enzyme’s catalysts, which mean they speed up chemical reactions. They are
made from proteins and work best at 37°C.
The alimentary canal (gut) is a long muscular tube, which extends from the
mouth to the anus and consists of the major parts of the digestive system
where digestion and absorption of food takes place.
Food is moistened and lubricated. Physical digestion takes place here.
Acid contents kill bacteria in foods and then food is turned into
chyme. In adults, protein digestion begins.
Duodenum Chemical digestion takes place here. Enzymes break down starch,
polypeptides and lipids.
The tongue moves the food around until it forms a ball called a bolus.
The teeth break the food down into smaller pieces with the help of saliva.
Saliva is secreted from the salivary glands and is a mixture of water, mucus and salivary
amylase. It has an enzyme that starts breaking down starch.
When we swallow, the food is passed to the pharynx (back of throat) and the epiglottis makes
sure it passes into the oesophagus and not into the windpipe.
 The food moves down the oesophagus by peristalsis.
 Peristalsis is a wave of muscular contractions that push the food towards the stomach.
 The stomach is a big muscular pouch which churns the food and mixes it with gastric juices.
 Gastric juices are a mixture of stomach acid, mucus and enzymes
 Acid kills off any germs.
 Enzymes help break down protein.
 Mucus protects the lining of the stomach from being eaten away by the acid.
 The digested bolus is now called chyme and it leaves the stomach and enters the small intestine.
 The majority of absorption takes place the small intestine and it is broken up into
three parts:
 Bile which is produced by liver cells and stored in the gall bladder, enters
through the bile duct and breaks down large lumps of fats into tiny droplets.
 The pancreas secretes pancreatic juice which has enzymes that break down
carbohydrates, proteins and fats.
 This is where the majority of absorption takes place. It has tiny finger-like
projections called villi lining it, which increase the surface area for absorbing
 By the time the food reaches the ileum, it has been broken down into glucose,
fatty acids, glycerol, amino acids, vitamins, minerals and water.
 The ileum basically compacts the leftovers to pass through to the large intestine.
 The main function of the large intestine (colon) is to reabsorb water from the faeces
into the bloodstream so that water loss from the body is minimized.
 Faeces consist of undigested cellulose and plant fibre, dead bacteria and intestinal cells
scraped off the gut walls. It is stored temporarily in the rectum.
 When the rectum is full, the waste passes out of the body through the anus.
Small Intestine
Large Intestine
Constipation results from poor eating habits. A diet lacking fibre can lead to a blockage of the
alimentary canal. Egestion of undigested waste material cannot them occur normally.
Assimilation is the process of incorporating and making use of the digested food into the body.
 These absorbed food molecules may be stored in the body for future use, broken down
to produce energy or used for growth, repair and to maintain good health.
Glucose is taken to the liver, then to the rest of the body where it is used in respiration and
excess amounts are converted and stored as fats or glycogen.
Amino acids are taken to the liver and then to the rest of the body where they are used by body
cells for growth and repair, to make hormones and enzymes and the excess amounts are
converted to glycogen and fats.
Fat molecules are carried by the lymph to the blood and are stored under the skin are around
the organs, used to form new membranes in cells and organelles and used for respiration in
some circumstances.
ECOLOGY* (page15)
Ecology is the study of the relationships of organisms with each other and their environment.
Environmental factors may be of two kinds: abiotic or physical factors or biotic (living).
Abiotic factors are the non-living components of the environment.
 Climatic factors such as light, temperature, rainfall, wind and water availability.
 Edaphic factors (associated with soil) such as Ph, texture, temperature, organic and
mineral content.
 Aquatic factors such as salinity, wave action and dissolved oxygen.
 Topographic factors (associated with physical features on the Earth’s
surface) such as the angle of the slope.
Biotic factors result from the activities of living organisms in the environment.
 Factors like: predation, symbiosis, competition and disease all involve the living
elements of the environment.
 Relationships between living organisms: feeding relationship (food webs and food
chains), camouflage, pollination and dispersal.
Ecosystem is made up of a community and its environment. E.g., ocean, forest etc.
 Self-sustaining system of organisms interacting with each other and their environment.
Habitat is the area in which an organism lives. E.g., pond, swamp.
Microhabitat is a very small habitat. E.g., crevice of a rock, roots of mangrove trees etc.
Niche is the role of an organism within the ecosystem. E.g., fish would eat algae etc.
Population is a group of organisms of the same species which live in a particular
habitat. E.g., a population of fishes in a pond.
Community is all the different organisms or populations which live in the same habitat
and interact with each other. E.g., fishes, snails and tadpoles living together in a pond.
 They all feed on each other, compete with each other, hiding and protecting each other
and also communicating with each other.
Species is a group of individuals of common ancestry that closely resemble each
other, that can be interbreed to produce fertile off springs. E.g., human species.
The distribution of species is related to the physical or abiotic factors of the
environment as well as the availability of food and prey.
 A species is adapted to live in its environment.
 Example: only animals that can tolerate dehydration and survive extreme temperatures
would be found living in the desert.
The abiotic factors of an environment affect the distribution of the species found there.
 Xerophytes are plants that live in areas where water is in short supply. They have special
features which helps reduce water loss. These include:
 Reduction of leaves to fine spikes
 The stomata are sunken in grooves and reduce in number
 The leaves roll into a cylindrical shape
 Water is an abiotic factor that affects the distribution of species.
 Organisms that live in water must be able to use oxygen dissolved in water or take their
oxygen from the air above the water.
 If they don’t attach themselves to rocks or bury themselves in the seabed, they must
also adapt to moving in water.
There are two main kinds of water found on Earth:
 Freshwater found in lakes, rivers and ponds.
 Saltwater found in the oceans and seas.
Freshwater is low in salt and mineral content, but saltwater can be very concentrated. Most
animal species are adapted to live in either freshwater or saltwater.
Freshwater animals have mechanisms to get rid of excess water that enter their body through
Xerophytes are plants that live in areas with short supplies of water.
 Light also affects the distribution of pants and animals throughout the Earth.
 Animals use light to see their prey and some animals use light to escape predators.
 The duration of light and its intensity are important for the distribution of species,
particularly plants.
 Temperature also affects the distribution of species.
 Poikilothermic animals are particularly affected because their body temperature
reflects the temperature of their surroundings.
 Homeothermic animals (mammals and birds) may be able to live in a greater range of
temperatures but they show adaptions to cope with extreme temperatures.
 Thick layer of fat (blubber) just beneath the skin insulates them from the cold.
 Mercury and lead are particularly dangerous to humans.
 Mercury can cause various nervous and mental disorders.
 Lead compounds damage the brains in young children and lead poisoning can cause
serious mental disorders.
 Soil supports terrestrial life and provides and anchor and medium of nutrition for plants.
 Humans need soil to build homes on and depend on agriculture for food.
 Soil provides homes for thousands of microbes and shelter for subterranean animals.
 Soil type is very important for the distribution of species.
Plants are autotrophs because they can photosynthesize.
Animals are heterotrophs because they depend on plants for food.
The sun is the ultimate source of energy for almost all life on earth.
Producers are organisms that produces or makes organic food.
Consumers are organisms that eat or consume organic food.
Decomposers are organisms that feed on dead organic food.
Herbivores are organisms that feed only on plants. E.g., bees, cows, elephants etc.
Carnivores are organisms that feed only on animals. E.g., hawks, lions, dolphins etc.
Omnivores feed on both plants and animals. E.g., pigs, humans, dogs etc.
A food chain is a simple diagram that shows how the food or nutrients (the energy
source) pass from on organism to another.
The arrows in a food chain shows the movement of energy along the food chain.
Each organism in the food chain represents a trophic level.
 The number of trophic levels in a food chain is normally limited to four or
five since the amount of energy being passed on decreases at each level.
 Arboreal (animals spend most of their lives in trees) [leavescricketgeckosnake]
 Edaphic (soil) [decaying leaves earthworms ground beetle lizard]
 Freshwater [phytoplanktonfreshwater mullock small fish salmon]
 Marine [phytoplankton zooplankton small fish mackerel]
First trophic level
Primary consumer
Second trophic level
Secondary consumer
Third trophic level
Tertiary consumer
Forth trophic level
 A food web is the interlinking of a number of food chains.
 The trophic level of an organism is the position it occupies in a food web.
 A food web start at trophic level 1 with primary producers like plants, level 2 is
herbivores, carnivores are level 3 or higher and apex predators are lever 4 or 5.
 As you go up the trophic levels, energy decreases, causing as little as 10% of the
energy at any trophic level to be transferred to the next.
 Decomposers and detritivores obtain their food or energy from the remains of dead organisms.
 They help in the recycling of nutrients since they return the nutrients trapped in dead
organisms back to the environment, making it available once again.
 Decomposers, including bacteria and fungi, secrete enzymes which breaks down dead
plants and animals into a substance called humus.
 Humus enriches and improves the structure of soils in which plants grow.
 Detritivores, including woodlice and earthworms, also help in the removal and recycling
of dead organisms by feeding on small fragments of the dead material which are called detritus.
 Saprophyte is any organism that feed on dead organic material.
 Symbiosis describes a relationship that exists when different species of organisms live together.
 Predators are carnivores that hunt, capture, kill and eat other animals that are called their prey.
 Food chains therefore include predators, they are the higher order consumer.
1) Mutualism is when organisms of different species live closely together and both benefits.
 Example: ‘egret and cow’- the egret is obtaining food and the cow benefits
by having blood-sucking insects removed from its body.
2) Commensalism is a relationship between two species in which one clearly benefits
and the other one is not harmed.
 Example: ‘orchids on trees’- the orchid uses the tree for support but not as
a food source, the tree is not harmed, nor does it benefit.
3) Parasitism is a relationship between species where one organism lives on or in
another organism. One species benefits at the expense of the other.
 A parasite is an organism which lives and feeds on or inside another organism.
 Ectoparasites are parasites that live on the outer surface of their hosts. E.g., ticks, fleas, lice etc.
 Endoparasites are parasites that live within a host.
 Energy is lost at each step of a food chain, there is less energy at each level for an animal in that
level than in the level below.
 A food chain is limited by the amount of energy lost at each level.
 A pyramid of energy is a good way of showing the energy relationships between
organisms in different trophic levels.
 Each block shows the amount of energy available to the next trophic level.
 Less and less energy is available to higher trophic level in a food chain.
 A pyramid of numbers is like a pyramid of energy but shows the numbers of all
the organisms at each trophic level of a food chain within a given area.
 Ecosystems usually contain a large number of small organisms and a
smaller number of larger animals.
 A pyramid of biomass is a diagram that compares the biomass of different trophic levels
within an ecosystem.
 The width of the boxes shows the relative amount of biomass present at each level.
 Bioaccumulation or biological magnification is the gradual accumulation of substances such as
pesticides or other chemicals in an organism.
 Pesticides can spread through the environment in food chains.
 Biological control is the control of a pest by the introduction of a natural enemy of predator.