GCSE Biology
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Cells
Biology 1
Cells
Most animal cells have a nucleus, cytoplasm, membrane,
mitochondria and ribosomes.
Plant and algal cells also have a cell wall and often have
chloroplasts and a permanent vacuole.
Plant and animal cells are eukaryotic cells which have a
membrane, cytoplasm and a nucleus.
Bacterial cells are prokaryotic cells.
They are smaller than eukaryotic cells and have a cell wall,
membrane and cytoplasm, but do not have a nucleus.
Their genetic material is a single loop of DNA or several small
rings of DNA called plasmids in the cytoplasm.
7.
Specialised cell
Red blood cell
Function
Carries oxygen.
Adaptations
• Large surface area.
• Contains haemoglobin.
• No nucleus to create more space.
8.
White blood cell
Destroys microorganisms.
•
Irregular shape to get out of blood vessels.
9.
Egg cell (ovum)
Join with sperm cell and provide
food for new cell formed.
•
•
Large
Contains lots of cytoplasm
10.
Sperm cell
Reach and join with egg cell.
•
•
Long flagellum (tail) for swimming
Enzymes of head to break into egg.
11.
Nerve cell
Carry nerve impulses to different
parts of the body.
•
•
•
Long
Connections at each end.
Carry electrical signals.
12.
Muscle cell
Move the body.
•
•
Contain protein fibres that contract.
Large numbers of mitochondria.
13.
Ciliated cell
Move mucus.
•
Thin layer of tiny cilia (moving hairs).
14.
Palisade cell
Absorb sunlight for
photosynthesis.
•
•
Large surface area.
Lots of chloroplasts.
15.
Root hair cell
Absorb water and minerals
•
Large surface area.
16.
Xylem cell
Moves water through the plant.
17.
Phloem cell
Moves food through the plant.
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•
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Made of dead cells.
Thick, strengthened cellulose cell wall.
Hollow lumen.
Made of living cells.
Connected by sieve plates to form a tube.
Cell differentiation
18. Cells differentiate to form different types of cells. Animal cells differentiate at an early stage, whereas many plant cells can
differentiate throughout life.
19. Differentiation is the generation of specialised cells which acquire different organelles to enable them to carry out specific
functions.
20. Cells may be specialised to carry out a particular function.
21. Stem cells are unspecialised cells that can differentiate to form many different types of cells.
22. Stem cells from human embryos and adult bone marrow can be cloned and made to differentiate into different cells.
23. Stem cells may be used to treat paralysis and diabetes in the future.
24. In therapeutic cloning an embryo with the same genes as the patient is produced. Cells from this embryo will not be rejected
by the patient.
25. Risks e.g. transfer of viruses, associated with the use of stem cells in medicine.
26. Stem cells from meristems in plants are used to produce clones quickly and cheaply.
GCSE Biology
Cells
Culturing microorganisms
27. Bacteria multiply by simple cell
division (binary fission) as often as
once every 20 minutes if they have
enough nutrients and a suitable
temperature.
28. Bacteria can be grown in a nutrient
broth solution or as colonies on an
agar gel plate.
29. Uncontaminated cultures of
microorganisms are required for
investigating the action of
disinfectants and antibiotics.
Biology 1
Microscopes
30. An electron microscope has a much higher magnification and
resolution than a light microscope, so it can be used to study cells in
much finer detail and show organelles.
𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠
31. 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 =
32.
33.
34.
35.
36.
𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚
1m = 1000mm
1mm = 1000µm (micrometre)
1µm = 1000nm (nanometre)
To get smaller x 1000.
To get bigger ÷ 1000.
Mitosis
37. Chromosomes are found in the nucleus. They are made of DNA. Each chromosome carries a large number of genes.
38. In body cells chromosomes are found in pairs.
39. Mitosis occurs during growth or to produce replacement cells.
40. During mitosis:
• copies of the genetic material separate
• the cell then divides once to form two genetically identical cells.
41. Mitosis forms part of the cell cycle.
Diffusion
42. Substances can move into
and out of cells across
membranes by diffusion.
43. Diffusion is the net
movement of particles
from an area of high
concentration from an
area of low concentration
down a concentration
gradient.
44. Oxygen, carbon dioxide
and urea passes through
cell membranes by
diffusion.
45. Single celled organisms
have a bigger surface area
to volume ratio than
multicellular organisms, so
transfer sufficient
substances across their
surface.
46. Multicellular organisms
require specialised organ
systems to exchange
sufficient substances.
Osmosis
47. Water may move across cell membranes by osmosis.
48. Osmosis is the movement of water from a dilute solution (high concentration) to a
more concentrated solution (low concentration) through a partially permeable
membrane.
49. An isotonic solution is one that is the same concentration as the cell.
50. Water moves in and out at the same rate in an isotonic solution.
51. A hypotonic solution has a higher concentration of water (low concentration of
solutes) than the cell (low water and high solutes).
52. Water moves into the cell until it reaches equilibrium (equal concentrations).
53. A hypertonic solution has a lower concentration of water (high concentration of
solutes) than the cell (high water and low solutes).
54. Water moves out of the cell until it reaches equilibrium.
55. Lysis – bursting an animal cell by osmosis.
56. Crenation – shrinking an animal cell by osmosis.
57. Turgid – A plant cell fully inflated with water.
58. Flaccid – A plant cell that is limp through a reduction of pressure inside the cell (some
water lost).
59. Plasmolysed – a plant cell that has lost water causing the cell membrane to be pulled
away from inside the cell wall.
Active transport
60. Active transport involves the movement of ions or molecules from a low concentration
to a high concentration against a concentration gradient on a cell membrane.
61. Energy is required from respiration to move the substances.
62. Mineral ions can be absorbed by active transport into
plant root hairs from very dilute solutions in the soil.
63. Sugar can be absorbed by active transport from the
gut into the blood.
GCSE Biology
Organisation
Biology 2
Cell organisation
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Cells are the building blocks of living organisms.
A tissue is a group of cells with a similar structure and function.
Organs are groups of tissues working together.
Organs are organised into organ systems.
5. An organism is made up of several organ systems.
6.
Structure
Mouth
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Salivary glands
Oesophagus
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Stomach
Pancreas
Liver
Gall bladder
13.
Small intestine duodenum
Small intestine ileum
Large intestine colon
Large intestine rectum
Large intestine anus
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Function
Where food enters the alimentary canal
and digestion begins.
Produce saliva containing amylase.
Muscular tube which moves ingested food
to the stomach.
Muscular organ where digestion continues.
Produces digestive enzymes.
Produces bile.
Stores bile before releasing it into the
duodenum.
Where food is mixed with digestive
enzymes and bile.
Where digested food is absorbed into the
blood and lymph.
Where water is reabsorbed.
Where faeces are stored.
Where faeces leave the rectum.
Food tests
18. Foods can be tested to find out which food groups they contain.
19. Starch is identified by the iodine test. Food turns black or blue
if starch is present.
20. Sugars are identified by Benedict’s solution. If sugar is present,
the solution turns from blue to red / orange / yellow / green
when heated depending on the amount of sugar.
21. Protein is identified by Biuret reagent. Food becomes purple if
proteins are present.
22. Fat is identified using paper. The food is rubbed onto the paper.
If, when dry, the area becomes translucent, fats are present.
The digestive system
23. Enzymes are biological catalysts; they speed
up a reaction without being used up.
24. Food molecules must be small and soluble in
order to be absorbed into the blood.
25. Enzymes in the digestive system chemically
digest food into small, soluble molecules
that can be absorbed.
26. Carbohydrases break down carbohydrates
into simple sugars.
27. Amylase is a carbohydrase that breaks down
starch.
28. Amylase works in the mouth and small
intestine.
29. Protease breaks down protein into amino
acids.
30. Protease works in the stomach and small
intestine.
31. Lipase breaks down lipids (fats and oils) into
glycerol and fatty acids.
32. Lipase works in the small intestine.
33. The products of digestion are used to build
new carbohydrates, lipids and proteins.
Some glucose is used in respiration.
34. Bile is made by the liver and stored in the
gall bladder. It helps in the digestion of fats
by neutralising acid from the stomach and
emulsifying fats.
35. Different enzymes work best at different
temperatures and pH values.
The heart
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The heart is a double pump, blood passes through the heart twice on its journey around the body.
The right ventricle pumps blood to the lungs where gas exchange takes place.
The left ventricle pumps blood around the rest of the body.
The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker.
Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.
GCSE Biology
Organisation
Biology 2
Coronary heart disease
Blood
41. Fatty material builds up in coronary arteries reducing blood
flow to the heart muscle.
42. Stents can be used to keep the coronary arteries open.
43. Statins reduce cholesterol levels, so fatty material is
deposited more slowly.
44. Faulty heart valves can be replaced with biological or
mechanical ones.
45. Heart failure can be treated with a heart and lung transplant.
46. Artificial hearts can be used whilst waiting for a transplant, or
to allow the heart to rest and recover.
47. Blood is a tissue consisting of plasma, red
blood cells, white blood cells and platelets.
48. Plasma transports dissolved chemicals and
proteins around the body.
49. Red blood cells transport oxygen attached to
haemoglobin.
50. White blood cells help to protect the body
against infection.
51. Platelets are fragments of cells involved in
blood clotting.
Health issues
Lifestyle and health
52. Health is the state of physical and mental wellbeing.
53. Factors such as diet, stress and life situations can
have a serious effect on physical and mental
health.
54. Diseases are major causes of ill health.
55. Different diseases may interact:
• defects in the immune system increase the
chance of catching an infectious disease.
• Viral infections can trigger cancers.
• Immune reactions can trigger allergies.
• Physical ill-health can lead to depression and
mental illness.
56. Various risk factors are linked to some noncommunicable disease.
57. These can be aspects of a person’s lifestyle or substances
in the person’s body or environment.
58. A causal mechanism has been proven for some risk
factors but not in others:
• The effects of diet, smoking and exercise on
cardiovascular disease.
• Obesity as a risk factor for type 2 diabetes.
• The effect of alcohol on the liver and brain function.
• The effect of smoking on lung disease and lung cancer.
• The effects of smoking and alcohol on unborn babies.
• Carcinogens, including ionising radiation, as risk
factors in cancer.
59. Many diseases are caused by the interaction of a number
of factors.
Cancer
60. Cancers (malignant tumours) result from
uncontrolled cell division.
61. Cancer cells may invade neighbouring tissues, or
break off and spread to other parts of the body in
the blood, where they form secondary tumours.
Plant organ system
62. Plant organs include stems, roots and leaves.
63. Organs are made up of different tissues, eg meristem tissue at
growing tips.
64. The leaf is the organ of photosynthesis.
65. The roots, stem and leaves form a plant transport system.
66. Root hair cells absorb water by osmosis and mineral ions by
diffusion and active transport.
67. Xylem tissue transports water and dissolved ions. The flow of
water from the roots to leaves is called the transpiration
stream.
68. Xylem tissue is composed of hollow tubes strengthened with
lignin.
69. Phloem tissue transports dissolved sugars from the leaves to
other parts of the plant. The movement of food through
phloem is called translocation.
70. Phloem cells have pores in their end walls for moving of cell
sap.
Structure
71.
72.
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74.
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76.
Function
GCSE Biology
Infection and response
Communicable diseases
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Communicable diseases are infectious diseases
caused by pathogens.
Pathogens may be viruses, bacteria, protists or
fungi. They may infect plants or animals.
Pathogens can be spread by direct contact, by
water or by air.
The spread of diseases can be reduced or
prevented by:
• simple hygiene measures
• destroying vectors
• isolation of infected individuals
• vaccination
Bacterial disease
18. Bacterial diseases include salmonella food
poisoning and the sexually transmitted disease
gonorrhoea.
19. Salmonella food poisoning is spread by bacteria
ingested in food or on food prepared in
unhygienic conditions.
20. In the UK, poultry are vaccinated against
Salmonella to control the spread.
21. Fever, abdominal cramps, vomiting and
diarrhoea are caused by the bacteria and toxins
that they excrete.
22. Gonorrhoea is a sexually transmitted disease
with symptoms of a thick yellow or green
discharge from the vagina or penis and pain
when urinating.
23. It was easily treated with the antibiotic penicillin
until many resistant strains appeared.
24. The spread of gonorrhoea can be controlled by
antibiotic treatment and the use of a barrier
method of contraception such as a condom.
Biology 3
Viral disease
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Viral diseases include measles and AIDS, which is
caused by HIV.
Measles has symptoms of a fever and red skin
rash.
It is a serious illness that can be fatal if
complications arise.
Most young children are vaccinated against
measles.
The measles virus is spread by inhalation of
droplets from sneezes and coughs.
HIV initially causes a flu-like illness.
Unless successfully controlled with antiretroviral
drugs, the virus attacks the body’s immune cells.
Late stage HIV infection, or AIDS, occurs when
the body’s immune system becomes so badly
damaged it can no longer deal with other
infections or cancers.
HIV is spread by sexual contact of exchange of
bodily fluids such as blood, which occurs when
drug users share needles.
Tobacco mosaic virus (TMV) is a plant pathogen.
It has a distinct mosaic pattern of discolouration
on the leaves, which affects the growth of the
plant due to lack of photosynthesis.
Viruses enter cells and damage them to cause
symptoms.
Antibiotics don’t treat viruses as they cannot
enter cells.
Protist disease
30. Malaria is caused by a protist transmitted by
mosquitos.
31.
Fungal disease
25. Humans can also be infected with fungal
diseases.
26. Rose black spot is a fungal disease where purple
or black spots develop on leaves, which turn
them yellow and makes them drop off early.
27. It affects the growth of plants as photosynthesis
is reduced.
28. It is spread in the environment by wind or water.
29. It can be treated by using fungicides and /or
removing and destroying the affected leaves.
32. Malaria causes recurrent episodes of fever and
can be fatal.
33. Spread of malaria is controlled by preventing the
vectors (mosquitos) from breeding and by using
mosquito nets to avoid being bitten.
GCSE Biology
Infection and response
Biology 3
Vaccination
Human defence system
34. A vaccine contains a small amount of dead or
inactive pathogens. These stimulate white blood
cells to produce antibodies.
35. Edward Jenner made the first vaccination for
smallpox, which has now been wiped out.
36. Immunity allows a person to produce specific
antibodies quickly to prevent infection.
37. If a large proportion of the population is immune
to a pathogen, the spread of the pathogen is
very much reduced.
38. The body defends itself against the entry of
pathogens.
39. Non-specific defence systems of the body are
the: skin; nose; trachea and bronchi; stomach.
40. Bacteria may produce toxins that make us feel ill
and damage tissues.
41. Viruses live and reproduce inside cells, causing
damage.
42. The immune system tries to destroy pathogens
that enter the body.
43. White blood cells help to defend against
pathogens by:
• Phagocytosis
Antibiotics
53. Antibiotics, eg penicillin, are used to kill
infective bacteria inside the body.
54. Specific bacteria should be treated with specific
antibiotics.
55. The emergence of strains resistant to antibiotics
is of great concern.
56. Antibiotics cannot kill viral pathogens.
57. Painkillers and other medicines are used to treat
the symptoms of disease but do not kill
pathogens. It is difficult to kill viruses without
also damaging the body’s tissues.
58. Alexander Fleming discovered penicillin from the
Penicillium mould.
• antibody production
• antitoxin production.
Drug development
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Traditionally drugs were extracted from plants and microorganisms.
The heart drug digitalis originates from foxgloves.
The painkiller aspirin originates from the willow tree.
Most new drugs are synthesised by chemists; the starting point may still be a chemical extracted from a
plant.
New drugs are tested for toxicity, efficacy (the ability to produce a desired result) and dose.
Preclinical testing in the lab, then clinical trials involving healthy volunteers and then patients.
Very low doses of the drug are given at the start of the clinical trial (phase 1).
If the drug is found to be safe, further clinical trials (phase 2 /3) to find out the optimum dose for the drug.
In a double blind trial, some patients are given a placebo; neither the doctors nor the patients know who has
received a placebo and who has received the drug.
GCSE Biology
Infection and response
Biology 3
Monoclonal antibodies
59. Monoclonal antibodies (MAB) are produced from a single clone of cells. They are specific to one antigen, so
target a specific chemical or cell in the body.
60. A lymphocyte that makes a specific antibody is combined with a tumour cell to form a hybridoma cell. This is
cloned to produce many identical cells which all produce the specific antibody.
61. There are many uses for MABs:
• Diagnosis in pregnancy tests.
• In labs to measure the levels of hormones and other chemicals in the blood or to detect pathogens.
• In research to locate and identify specific molecules in a cell or tissue by binding them with a
fluorescent dye.
• To treat diseases: for cancer the monoclonal antibody can be bound to a radioactive substance, a
toxic drug or a chemical which stops cells growing and dividing. It delivers the substance to the
cancer cells without harming other ells.
62. MABs can have more serious side effects than expected.
63. They are not as widely used as everyone hoped when they were first developed.
Plant diseases
64. Plants can be infected by a range of viral,
bacterial and fungal pathogens as well as by
nematode worms and insects.
65. Tobacco mosaic virus affects many plants, eg
tomatoes.
66. Rose black spot is a fungal disease spread by
water or wind.
67. Aphids feed on the sap of plants and affect plant
growth.
68. Ion deficiencies can damage plants, eg stunted
growth by nitrate deficiency and chlorosis by
magnesium deficiency.
Detecting plant diseases
74. Plant diseases can be detected by:
• stunted growth
• spots on leaves
• areas of decay (rot)
• growths
• malformed stems or leaves
• discolouration
• presence of pests.
75. Identification can be made by:
• Using a gardening manual.
• Taking infected plants to a lab.
• testing kits that use monoclonal antibodies.
Ion deficiency
69. Plants can be damaged by a range of ion
deficiency conditions.
70. Nitrate deficiency causes stunted growth.
71. Nitrate is needed for protein synthesis and
therefore growth.
72. Magnesium deficiency causes chlorosis
(yellowing of the leaves).
73. Magnesium ions are needed to make
chlorophyll.
Plant defence responses
76. Plants have physical and chemical defence
responses to resist the invasion of
microorganisms.
77. Physical defences include: cellulose cell walls,
tough waxy cuticles on leaves; layers of dead
cells around stems (bark on trees) which fall off.
78. Chemical defence responses include:
antibacterial chemicals and poisons to deter
herbivores.
79. There are also mechanical adaptations to deter
animals from eating or touching them.
80. Mechanical adaptations include: thorns and
hairs to deter animals; leaves which droop or
curl when touched; mimicry to trick animals.
GCSE Biology
Bioenergetics
Photosynthesis
light
1.
Carbon dioxide + water  glucose + oxygen.
2.
3.
6CO2 + 6H2O  C6H12O6 + 6O2
Photosynthesis takes place in the palisade cells in the
leaf.
Photosynthesis is an endothermic reaction in which
energy is transferred from the environment into the
chloroplasts by light.
4.
light
Rate of photosynthesis
5.
The rate of photosynthesis may be limited by:
• low temperature
• shortage of CO2
• shortage of light
• shortage of chlorophyll.
6.
7.
When the graph has a slope, the investigated factor is
limiting.
8. When the slope levels out, another factor has started to
limit photosynthesis.
9. The rate of photosynthesis can be measured by counting
the number of oxygen bubbles produced by a plant in
water.
10. Factors that can limit the rate of photosynthesis are
called limiting factors.
11. Limiting factors are important economically in
greenhouses. They help us work out the optimum
conditions for growing plants.
12. Glucose produced in photosynthesis may be:
• used for respiration
• converted into starch for storage
• used to produce fats and oils for storage or cellulose
to strengthen cell walls
• used to produce amino acids for protein synthesis.
Biology 4
Respiration
13. Respiration can take place aerobically or
anaerobically to transfer energy.
14. Respiration is an exothermic reaction.
15. Respiration takes place in the mitochondria.
16. Organisms need energy for chemical reactions,
movement and to keep warm.
Aerobic respiration
17. During aerobic respiration glucose and oxygen
react to release energy.
18. Glucose + oxygen  carbon dioxide + water.
19. C6H12O6 + 6O2  6CO2 + 6H2O
Anaerobic respiration
20. Anaerobic respiration is the incomplete
oxidation of glucose so less energy is released
than in aerobic respiration.
21. In muscle cells: Glucose  lactic acid
22. C6H12O6  2C3H6O3
23. In some plant and yeast cells:
Glucose  ethanol + carbon dioxide
24. C6H12O6  2C2H5OH + 2CO2
25. Anaerobic respiration in yeast cells is called
fermentation and has economic importance in
the manufacture of bread and alcoholic drinks.
Response to exercise
26. During exercise the heart and breathing rates
increase and breath volume increases to supply
oxygen to muscle cells faster.
27. Muscle cells can respire anaerobically if there is
insufficient oxygen. This produces lactic acid
and creates an oxygen debt.
28. Lactic acid can cause muscle fatigue. The cells
stop contracting efficiently.
29. When exercise stops, the oxygen debt must be
repaid by continuing to breathe deeply.
30. Blood transports lactic acid to the liver where it
is converted back into glucose.
31. The oxygen debt is the amount of oxygen
needed to oxidise lactic acid.
Metabolism
32. Metabolism means all the chemical reactions
happening in a living organism.
33. Metabolism includes:
• the conversion of glucose to starch,
glycogen and cellulose
• the formation of lipids
• the formation of amino-acids and proteins
• respiration
• the breakdown of excess proteins to form
urea for excretion.
GCSE Biology
Homeostasis and response – Biology only
Brain function
The brain
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Biology 5
The brain controls complex behaviour.
The brain has billions of interconnected neurones.
Different areas of the brain control different functions.
Investigating and treating brain damage and disorders is
difficult.
5.
Neuroscientists have been able to map
the regions of the brain to particular
functions by studying patients with brain
damage, electrically stimulating different
parts of the brain and using MRI scans.
6. The complexity and delicacy of the brain
makes investigating and treating brain
disorders very difficult.
7. The cerebral cortex is the largest part of
the mammal brain.
8. It is divided into four lobes, the parietal,
occipital, temporal and frontal. Each has
a different function.
9. It is responsible for intelligence,
language, memory and consciousness.
10. The cerebellum receives information
from the sensory systems, spinal cord
and other parts of the brain to regulate
movement.
11. The medulla oblongata is the centre for
respiration and circulation.
12. It regulates breathing, heart and blood
vessel function, digestion, sneezing and
swallowing.
The eye
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The eye contains receptors sensitive to light and colour.
The cornea refracts (bends) light as it enters the eye.
The sclera is the front part of the cornea. It is a tough outer coat.
The iris is the coloured part of your eye, it contains pigments so light cannot pass through.
Ciliary muscles connected to the iris contract and relax to alter the size of the pupil (the hole) to change the amount
of light entering the eye.
The lens is a transparent, bi-concave, flexible disc behind the iris which focuses light onto the retina.
Accommodation is the process of changing the shape of the lens to focus on near and far objects.
The lens is held in place by suspensory ligaments to the ciliary muscles.
The retina is the lining on the back of the eye.
The retina contains two types of photoreceptor cells: rods (sensitive to dim light and black and white) and cones
(sensitive to colour).
The optic nerve is a bundle of sensory neurones at the back of the eye that carries electrical impulses to the brain.
To focus on a near object: the ciliary muscle contract, suspensory ligaments loosed and the lens becomes thicker to
refract the light more strongly.
To focus on a distant object: the ciliary muscles relax, the suspensory ligaments are pulled tight and the lens becomes
thin so it only slightly refracts the light.
To common defects of the eye are myopia (short sightedness) and hyperopia (long sightedness) in which rays do not
focus on the retina.
These defects are treated with glasses which refract the light so that it focusses on the retina.
New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and
replacements lenses in the eye.
GCSE Biology
Homeostasis and response – Biology only
Biology 5
Maintaining water and nitrogen balance
Control of body temperature
29. Body temperature is monitored and controlled
by the thermoregulatory centre in the brain. It
has receptors sensitive to the temperature of
the blood.
30. Temperature receptors in the skin send impulses
to the thermoregulatory centre.
31. If the body temperature is too high, blood vessels
dilate (vasodilation) and sweat is produced
from skin glands.
32. Sweat cools the body as it evaporates from the
skin.
33. If the body temperature is too low, blood vessels
constrict (vasoconstriction), sweating stops and
skeletal muscles contract (shiver).
34. Water leaves the body via the lungs during exhalation.
35. Water, ions and urea are lost from the skin in sweat.
36. There is no control over water, ion or urea loss by the
lungs or skin.
37. Excess water, ions and urea are removed via the kidneys
in the urine.
38. If body cells lose or gain too much water by osmosis they
do not function efficiently.
39. Urea is produced in the liver by the breakdown of excess
amino acids.
40. In the liver, amino acids are deaminated to form
ammonia.
41. Ammonia is toxic and is immediately converted to urea
for safe excretion.
Kidneys
42. The kidneys produce urine by filtration of the blood and
selective reabsorption of useful substances.
43. All the sugar and dissolved ions needed by the body and
as much water as the body needs are selectively
reabsorbed.
44. Urea, excess ions and water are excreted in urine.
45. ADH is released by the pituitary gland when the blood is
too concentrated. It causes more water to be reabsorbed
back into the blood.
46. ADH control of water in the blood is an example of
negative feedback.
47. Kidney failure can be treated by kidney transplant or by
using kidney dialysis.
48. Kidney dialysis is a procedure to remove waste products
and excess fluid from the blood.
49. Blood is diverted to a machine to be cleaned and pumped
back into the body.
Plant hormones
50. Hormones control and coordinate
growth and responses to light and gravity
in plants.
51. Auxin is a powerful growth hormone
produced naturally by plants.
52. Responses to light and gravity are
controlled by the unequal distribution of
auxin which causes unequal growth rates
in shoots and roots.
53. Auxin moves away from the light which
makes that part of the shoot grow. It
makes the stem grow towards the light.
54. Gibberellins are important in initiating
seed germination.
55. Ethene controls cell division and ripening
of fruits.
Plant hormones
56. Plant hormones are used in
agriculture and horticulture.
57. Auxins are used as weed
killers,, as rooting powders
and for promoting growth
tissue culture.
58. Giberellins can be used to end
seed dormancy, promote
flowering and increase fruit
size.
59. Ethene is used in the food
industry to control the
ripening of fruit during
storage and transport.
GCSE Biology
Homeostasis and response
Biology 5
Homeostasis
Homeostasis is the regulation of internal conditions to
maintain optimal conditions for enzyme action and cell
function.
2. Automatic control systems involve nervous responses and
chemical responses.
3. Control systems have receptors, a coordination centre and
effectors.
1.
Nervous system
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Reflex arc
The functions of the nervous system are to detect and react to
stimuli; to coordinate behaviour.
The structure of the central nervous system (CNS): receptors;
different types of neurones, coordinator (brain or spinal cord);
effectors, synapses.
Sensory neurones carry impulses (electrical signals) from the
sense organ to the relay neurone.
The relay neurone carries electrical impulses in the CNS.
The motor neurone carries electrical impulses from the relay
neurone to the muscle or gland (effector) to make it respond.
Neurones line up end to end throughout the CNS.
Synapses are the gaps between each neurone.
Electrical impulses cannot cross a synapse.
At the end of the neurone, the electrical impulse causes a
chemical to be released.
The chemical diffuses across the synapse and triggers an
electrical impulse in the next neurone.
Diffusion of the chemical is slower than the electrical impulse.
Human endocrine system
22. The system is composed of endocrine
glands that secrete hormones into the
blood to be carried to a target organ where
it has an effect.
23. The pituitary is the master gland. It
secretes many hormones that affect other
glands.
24. Hormones are chemical messengers.
25.
26.
27.
28.
29.
30.
31.
15. Some of your reactions happen without you
thinking about them, e.g. moving your hand
when you touch something hot. These are
called reflex actions.
16. Reflex actions are automatic and rapid to
protect the body from harm.
17. A stimulus is a change in the environment that
can be detected by the body.
18. A receptor is a cell that detects the stimulus.
19. The effector is the area that makes the
response.
20. The reflex action is a reflex arc that doesn’t
involve the brain, it is very fast.
21. The brain is informed after the action has
happened.
GCSE Biology
Homeostasis and response
Biology 5
Control of blood glucose concentration
32. Blood glucose concentration is monitored and controlled by the pancreas. It produces insulin, which causes glucose
from the blood to enter cells.
33. Glucose is converted to glycogen in liver and muscle cells for storage.
34. Glucagon is also produced by the pancreas to convert stored glycogen back into glucose when blood glucose levels
fall.
35. In Type 1 diabetes the pancreas does not produce enough insulin. Glucose levels may rise too high.
36. Type 1 diabetes is usually treated with insulin injections.
37. In Type 2 diabetes the cells do not respond properly to insulin.
38. Type 2 diabetes is usually treated by diet, exercise and drugs. Obesity is a risk factor for Type 2 diabetes.
39.
Contraception
Hormones in human reproduction
40. During puberty hormones cause sexual characteristics
to develop.
41. In females oestrogen is produced by the ovaries. Eggs
mature and are released (ovulation) every 28 days.
42. In males testosterone is produced by the testes and
stimulates sperm production.
43. Follicle stimulating hormone (FSH) causes the eggs in
the ovary to mature (the eggs grow surrounded by cells
called the follicle).
44. Luteinising hormone (LH) stimulates the release of the
egg at ovulation.
45. Oestrogen and progesterone stimulate the build-up
and maintenance of the uterus lining.
46.
47. Fertility can be controlled using hormonal and nonhormonal contraceptives.
48. Hormonal
• oral contraceptives
• injection
• implant or skin patch.
49. Non-hormonal
• barrier methods
• IUDs
• spermicides
• abstinence
• sterilisation
• surgery.
Hormones for infertility
50. Infertility is when an animal or plant is unable to
reproduce.
51. Women can be given a ‘fertility drug’ containing
FSH and LH to stimulate ovulation.
52. In IVF treatment, FSH and LH are given to stimulate
many eggs to mature. These are collected and
fertilised by sperm in a lab. Embryos form, and
some are inserted into the woman’s uterus.
53. There are many advantages and disadvantages to
fertility treatment: healthy baby; multiple births;
cost; stress.
Negative feedback
54. Adrenaline is produced by the adrenal glands in
times of stress. It increases heart rate so oxygen
and glucose are supplied to the brain and muscles
faster.
55. Thyroxine is produced by the thyroid gland. It
stimulates the basal metabolic rate and plays an
important role in physical and mental development.
56. Adrenaline and thyroxine secretions are controlled
by negative feedback mechanisms.
GCSE Biology
Inheritance, variation and evolution
Sexual and asexual reproduction
1.
2.
3.
4.
5.
6.
7.
Sexual reproduction involves the joining (fusion) of
male and female gametes (sperm and egg) in animals
and pollen and ovule cells in flowering plants.
This mixing of genetic information leads to variation in
the offspring.
Only mitosis is involved.
Gametes are produced by meiosis.
Asexual reproduction involves only one parent and no
fusion of gametes.
There is no mixing of genetic information.
This leads to genetically identical offspring (clones).
Biology 6
Meiosis
Cells in reproductive organs divide by meiosis
to form gametes.
9. When a cell divides to form gametes: copies
of the genetic information are made and the
cell divides twice to form four gametes, each
with a single set of chromosomes.
10. All gametes are genetically different from
each other.
11. Gametes join at fertilisation to restore the
normal number of chromosomes. The new
cell divides by mitosis, and as the embryo
develops, cells differentiate.
8.
DNA and the genome
Genetic inheritance
12. DNA is a polymer made up of two strands
forming a double helix.
13. DNA is found in chromosomes in the nucleus of a
cell.
14. A gene is a small section of DNA.
15. Each gene codes for a sequence of amino acids to
form a particular protein.
16. The genome is all the genetic material of an
organism.
18. A gamete is the male or female sex cell which
contains the genetic information.
19. Some characteristics are controlled by a single
gene. Each gene may have different forms called
alleles.
20. The genes present, or genotype, operate at a
molecular level to develop characteristics that are
expressed as a phenotype.
21. A dominant allele is expressed if only present on
one chromosome.
22. A recessive allele is only expressed if present on
both chromosomes.
23. If the two alleles present are the same the person
is homozygous for that trait, but if the alleles are
different they are heterozygous.
24. ‘Homo’ means the same. ‘Hetero’ means
different.
25. Most characteristics are a result of multiple genes
interacting.
26. Some disorders are inherited, eg polydactyly
(caused by a dominant allele) and cystic fibrosis
(caused by a recessive allele).
27. A Punnett square can be constructed to predict
the outcome of a monohybrid cross.
17. The human genome has been studied and will be
important for medicine in the future.
Sex determination
28. Human body cells contain 23 pairs of
chromosomes.
29. 22 pairs control characteristics only.
rd
30. The 23 pair carries the genes that determine
sex.
31. In females the sex chromosomes are the same
(XX).
32. In males the chromosomes are different (XY).
GCSE Biology
Inheritance, variation and evolution
Biology 6
Genetic engineering
Variation
33. Genetic engineering involves modifying the genome
of an organism to introduce a desired characteristic.
34. Genes can be cut from the chromosome of a human
or other organism and transferred into the cells of
other organisms.
35. Enzymes are used to cut the gene from a
chromosome.
36. The gene is inserted into a vector, eg bacterial
plasmid or virus.
37. The vector is used to insert gene into cell.
38. The cell then makes a new protein to produce the
desired characteristic.
39. Examples of genetic engineering are: weed killer
resistance soya beans; golden rice; humalin (insulin
made in bacteria).
40. Concerns about GM crops, eg effect on populations
of wild flowers and insects, and uncertainty about
safety of eating them.
41. Differences in the characteristics of individuals
may be due to:
• genes they have inherited
• environmental causes
• a combination of genetic and environmental
causes.
42. There is usually extensive genetic variation within
a population of a species.
43. All variants arise from mutations.
44. Most mutations have no effect on the phenotype.
45. Some mutations influence phenotype.
46. A few mutations determine the phenotype.
47. Mutations occur continuously but it is only very
rarely that a mutation leads to a new phenotype.
48. If the phenotype is suited to an environmental
change, it can lead to a relatively rapid change in
the species.
Selective breeding
Evolution
49. Selective breeding (artificial selection) is the
process by which humans breed plants and animals
for useful characteristics.
50. Selective breeding of food plants has produced
disease or weather resistant crops, more attractive
or better flavoured fruits and crops that are easier
to harvest.
51. Selective breeding of animals has produced cows
that produce more milk, animals that produce
more, better flavoured or leaner meat.
52. Selective breeding can lead to inbreeding, where
some breeds are particularly prone to disease or
inherited defects. Some breeds of dogs suffer from
inbred defects.
53. Darwin’s theory of evolution by natural selection
states that all species evolved from simple life
forms that first developed more than three billion
years ago.
54. Characteristics favourable to the environment are
passed on because the animal is more likely to
survive and reproduce.
55. Mutations are changes in the DNA code. They
may lead to more rapid evolution, although
mutations resulting in a new phenotype are rare.
56. Organisms of the same species can interbreed to
produce fertile offspring.
Extinction
33. Extinction may be caused by:
• changes to the environment over geological time
• new predators
• new diseases
• new, more successful competitors
• a single catastrophic event, eg massive volcanic
eruptions or collisions with asteroids.
Evidence for evolution
57. The theory of evolution by natural selection is
now widely accepted. At the time, it contested
with religious belief.
58. Fossils are the ‘remains’ of organisms from many
years ago, which are found in rocks.
59. Scientists can’t be certain about how life began
on Earth as many early forms of life were softbodied, so few traces remain. What traces there
were have been destroyed by geological activity.
60. Fossils show how much, or how little, organisms
have changed over time.
61. Bacteria can evolve rapidly because they
reproduce at a fast rate.
62. Mutations produce new strains. Resistant strains
are not killed by antibiotics, so they survive and
reproduce. Resistant strains spread because
people are not immune and there is no effective
treatment.
63. MRSA is resistant to antibiotics.
GCSE Biology
Inheritance, variation and evolution
Advantages and disadvantages of
sexual and asexual reproduction
64. Advantages of sexual reproduction:
• produces variation
• survival advantage if the environment
changes
• used in selective breeding to produce
organisms with desired characteristics.
65. Advantages of asexual reproduction:
• only one parent needed
• time and energy efficient as do not need to
find a mate
• faster than sexual reproduction
• many identical offspring produced when
conditions are favourable.
66. Some organisms can reproduce by either method,
depending on conditions.
67. Some organisms reproduce by both methods
depending on the circumstances.
• Malarial parasites reproduce asexually in the
human host but sexually in the mosquito.
• Many fungi reproduce asexually by spores
but also reproduce sexually to give variation.
• Many plants produce seeds sexually but also
reproduce asexually by runners, such as
strawberry plants, or bulb division, such as
daffodils.
DNA structure
77. Cloning techniques include taking
cuttings, tissue culture, embryo
transplants and adult cell cloning.
78. Tissue culture uses small groups of
cells from part of a plant to grow
identical new plants. It is important in
preserving rare plant species or for
nurseries.
79. Taking cuttings is an older but simpler
method used by gardeners to produce
many identical new plants from a
parent plant.
80. Embryo transplants are splitting apart
cells from a developing animal embryo
before they become specialised, then
transplanting the identical embryos
into host mothers.
81. Adult cell cloning
Biology 6
DNA structure
68. DNA is made up of four different nucleotides. Each
nucleotide consists of a sugar, a phosphate group and
one of four different bases attached to the sugar. The
bases are A, C, G and T.
69. A = adenosine, C = cytosine, G = guanine, T = thymine.
70. The bases on the two strands always join together in
the same pairs: C with G and T with A.
71. The DNA polymer is made up of repeating nucleotide
units.
72. Proteins are synthesised on ribosomes, according to a
template. Carrier molecules bring specific amino acids
to add to the growing protein chain in the correct
order.
73. When the protein chain is complete it folds up to form
a unique shape. This unique shape enables the proteins
to do their job as enzymes, hormones or forming
structures in the body such as collagen.
74. Mutations occur continuously. Most do not alter the
protein, or only alter it slightly so that its appearance or
function is not changed.
75. A few mutations code for an altered protein with a
different shape. For example an enzyme may no longer
fit the substrate binding site or a structural protein may
lose its strength.
76. Not all parts of DNA code for proteins. Non-coding
parts of DNA can switch genes on and off, so variations
in these areas of DNA may affect how genes are
expressed.
The theory of evolution
82. Charles Darwin published his theory of evolution by natural
selection (On the Origin of Species) in 1859. It raised much
controversy.
83. The theory of evolution by natural selection was only gradually
accepted.
84. There were other scientists who tried to explain evolution, eg
Alfred Russell Wallace and Jean-Baptiste Lamarck.
85. The work of Alfred Russel Wallace on natural selection, the theory
of speciation and warning colouration in animals.
86. New species arise as a result of isolation, genetic variation,
natural selection and speciation.
Mendel
87. In the mid-19th century Gregor Mendel carried out breeding
experiments using plants. He proposed the idea of separately
inherited factors that we now call genes.
88. In the late 19th century behaviour of chromosomes during cell
division was observed.
89. In the early 20th century it was observed that chromosomes and
Mendel’s factors behaved in similar ways, leading to the idea that
the factors (genes) were located on chromosomes.
90. In the mid-20th century the structure of DNA was determined and
the mechanism of gene function worked out.
GCSE Biology
Ecology
Classification
1.
Traditionally organisms have
been classified into groups
depending on their structure and
characteristics.
2. Classification can be described
by: Kingdom; Phylum; Class;
Order; Family; Genus; Species.
3. Organisms were classified into
smaller and smaller groups.
4. Carl Linnaeus studied the
similarities and differences
between organisms to classify
them. He developed the binomial
system to name organisms by
genus and species.
5. Today powerful microscopes are
used to see internal structures.
This and biochemical analysis has
led to new classification systems.
6. Carl Woese developed the three
domain system to classify
organisms as:
• Archaea (primitive bacteria)
• Bacteria (true bacteria)
• Eukaryota (protists, fungi,
plants and animals).
Sampling
15. Quantitative data on the
distribution and abundance of
organisms can be obtained by:
• random sampling with quadrats
• sampling along a transect.
16.
Adaptations
22. Organisms have adaptations for
survival; they may be structural,
behavioural or functional.
23. Extremophiles can survive in very
extreme environments, such as
high temperature or pressure, or
in high salt concentration.
Biology 7
Communities
An ecosystem is the interaction of a community of living
organisms (biotic) within the non-living (abiotic) parts of their
environment.
8. Organisms need a supply of materials from their surroundings and
other organisms to survive and reproduce.
9. Plants compete for light, space, water and mineral ions.
10. Animals compete for food, mates and territory.
11. One species depends on others for food, shelter, pollination, seed
dispersal etc. This is called interdependence.
12. A stable community is one where all the species and
environmental factors are in balance so that population sizes
remain fairly constant.
7.
Biotic and abiotic factors
13. Biotic factors are living factors that can affect a community:
• availability of food
• new predators arriving
• new disease organisms
• one species out-competing another so the numbers are no
longer sufficient to breed.
14. Abiotic factors are non-living factors which can affect a
community:
• light intensity
• temperature
• moisture levels
• soil pH and mineral content
• wind intensity and direction
• carbon dioxide levels for plants
• oxygen levels for aquatic animals
Food chains
17. Feeding relationships can be
represented by food chains.
18. A food chain begins with a producer
which synthesises molecules, which is
usually a green plant or alga which
makes glucose by photosynthesis.
19. Producers are eaten by consumers.
20. Consumers that eat other animals are
predators, and those eaten are prey.
21. In a stable community the numbers of
predators and prey rise and fall in
cycles.
Biodiversity
24. Biodiversity is the variety of all life on
Earth.
25. A great biodiversity ensures stability of
ecosystems.
26. The future of the human species relies
on us maintaining a good level of
biodiversity.
27. Human activities can reduce biodiversity
and we should try to stop this.
GCSE Biology
Ecology
Biology 7
Material recycling
Waste management
28. Materials are recycled to provide the
building blocks for future organisms.
29. The carbon cycle returns carbon to the
atmosphere as carbon dioxide and mineral
ions to the soil.
31. Rapid growth in the human population means more
resources are used and more wastes are produced, which
could lead to more pollution.
32. Pollution kills plants and animals which can reduce
biodiversity.
33. Waste may pollute water with sewage, fertilisers or toxic
chemicals.
34. Waste may pollute air with smoke and gases such as
sulfur dioxide, which contributes to acid rain.
35. Waste may pollute land with toxic chemicals such as
pesticides and herbicides, which may be washed from
the land into water.
Land use and deforestation
30. The water cycle provides fresh water for
plants and animals on land before draining
into the seas. Water is continuously
evaporated and precipitated.
Global warming
40. Levels of carbon dioxide and methane in
the atmosphere are increasing and
contribute to global warming.
41. Consequences of global warming include:
• loss of habitat when low lying areas
flood
• changes in the distribution of species
where temperature of rainfall changes
• changes in migration patterns.
36. Humans reduce the amount of land available for other
plants and animals by building, quarrying, farming and
dumping waste.
37. The destruction of peat bogs to produce compost
releases carbon dioxide into the atmosphere. It destroys
habitats and reduces biodiversity.
38. Large scale deforestation occurred to:
• provide land for cattle and rice fields to provide more
food
• grow crops from which biofuel can be produced.
39. This destruction of large areas of trees has:
• increased the release of carbon dioxide by burning
and microbial activity
• reduced the rate at which carbon dioxide is removed
from the atmosphere by photosynthesis to be ‘locked
up’ in wood
• led to a reduction in biodiversity.
Programmes
42. Programmes have been put in place to reduce the
negative effects on ecosystems and biodiversity.
• breeding programmes for endangered species
• protection and regeneration of rare habitats, eg coral
reefs, mangroves, heathland
• reintroduction of field margins and hedgerows in
agricultural areas
• reduction of deforestation and carbon dioxide
emissions by some governments
• recycling resources rather than dumping waste in
landfill.
GCSE Biology
Ecology
Biology 7
Trophic levels
Pyramid of biomass
43. Organisms obtain food as producers, consumers
or decomposers.
44. Producers are mostly plants and algae. They
transfer about 1% of incident light for
photosynthesis.
45. Consumers include herbivores, carnivores and
omnivores.
46. Decomposers break down dead plant and
animal matter.
47. The stages in a food chain are called trophic levels. The
producer is at level 1.
48. Level 2 is herbivores (eat plants and algae) and are
called primary consumers.
49. Level 3 is carnivores that eat herbivores (secondary
consumers).
50. Level 3 is carnivores that eat other carnivores (tertiary
consumers).
51. Apex predators are carnivores with no predators
52. Pyramids of biomass can be constructed to represent
the relative amount of biomass at each level in a food
chain.
53. Trophic level 1 is at the bottom of a pyramid of
biomass.
54. Only about 10% of the biomass at each trophic level is
transferred to the level above.
55. They are always a pyramid shape.
Decomposition
56. Decomposition is the process of rotting or
decay.
57. Factors which affect the rate of decay of organic
matter:
• temperature
• availability of oxygen
• availability of moisture
• availability of microorganisms to carry out
decay
• pH
• build-up of toxic substances.
58. Compost provides gardeners and farmers with a
natural fertiliser for plants and crops.
59. Anaerobic decay produces methane gas. It
occurs without the presence of oxygen.
60. Biogas is a mixture of different gases produced
by the anaerobic decay of organic matter.
61. Biogas generators can produce methane which
can be used as a fuel.
Impact of environmental changes
62. Environmental changes affect the distribution of
species in an ecosystem.
63. These changes include:
• Temperature
• Availability of water
• Composition of atmospheric gases
64. These changes may be seasonal, geographic or caused
by human interaction.
Food security
68. Factors affecting food security include:
• the increasing human population
• changing diets in developed countries means scarce food resources are transported around the world
• new pests and pathogens affect farming
• environmental changes affect food production
• cost of agricultural inputs
• conflicts in some parts of the world over the availability of water or food.
69. New ways must be found to feed all people without endangering the ecological balance of the planet.
Farming techniques
Sustainable fish
Biotechnology
70. The efficiency of food production
can be improved by restricting
energy transfer from food
animals.
71. Battery chickens and calves
raised in pens are examples of
‘factory farming’.
72. Fish grown in cages can be fed
high protein food and have
restricted movement.
73. There are moral and ethical
objections to some ‘factory
farming’ techniques.
74. Fish stocks are
declining and need to
be maintained at
levels where
breeding continues
or some species may
disappear.
75. Net size and fishing
quotas play
important roles in
conservation of fish
stocks.
65. Modern biotechnology techniques enable
large quantities of microorganisms to be
cultured in industrially controlled vats for food
or medical purposes.
66. The fungus Fusarium is useful for producing
mycoprotein, a protein-rich food suitable for
vegetarians. The fungus is grown on glucose
syrup, in aerobic conditions, and the biomass
is harvested and purified.
67. GM crops could provide more food or food
with improved nutritional value, eg Golden
rice.