Revision questions

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Biology review questions
1. Cell biology
1.1 Cell structure
1.1.1 Eukaryotes and prokaryotes
Name the two main classes of cells.

Eukaryotic and prokaryotic

Describe the main features found in prokaryotic cells. 

Cytoplasm, cell membrane, cell wall, loop of DNA and plasmid

Describe the main features found in eukaryotic cells.

Cell membrane, cytoplasm and nucleus

Explain how a scientist could distinguish between a prokaryotic cell and a eukaryotic cell.

Eukaryotes are larger and have a nucleus. Prokaryotes are smaller and have no nucleus.

Give an example of a eukaryotic cell and a prokaryotic cell.

Eukaryote: e.g. palisade cell, white blood cell, nerve cell etc. Prokaryote: bacteria.

1.1.2 Animal and plant cells
What is the function of the nucleus?

Control the functions of the cell and is the location of chromosomes in eukaryotic cells.

What is the function of the ribosome?

Protein synthesis.

What is the function of the mitochondria? 

Site of aerobic respiration.

What is the function of the chloroplast?

Site of photosynthesis.

What is the function of the cell membrane? 

The selective transport of substances in and out of the cell.

What is the function of the cell wall?

Supports the cell.

What is the function of the vacuole?

Involved with keeping plant cells turgid by osmosis.

Explain how a scientist could distinguish between an animal and plant cell. 

A plant cell has a cell wall, chloroplasts and a vacuole in addition to the parts of an animal cell.

Calculate the order of magnitude between a eukaryotic cell (100μm) and a prokaryotic cell (1μm)


1.1.3 Cell specialisation
Describe how the structure of a nerve cell relates to its function.

It is long to connect to the central nervous system. It is surrounded in fat to insulate the electrical signal.

Describe how the structure of a sperm cell relates to its function. 

The sperm cell has a tail to allow it to swim. It is packed with mitochondria to provide energy.  The nucleus contains only half the chromosomes.

Describe how the structure of a muscle cell relates to its function. 

The muscle cells contain fibres to contract. It has many mitochondria to provide energy.

Describe how the structure of a root hair cell relates to its function. 

The root hair cell has thin projections which increase the surface area to volume ratio of the cell to allow efficient transport of water by osmosis.

Describe how the structure of xylem relates to its function. 

Xylem consists of hollow tubes strengthened by lignin to allow the transport of water.

Describe how the structure of phloem relates to its function. 

Phloem is composed of tubes of elongated cells with sieve plates.  Cell sap can move from one phloem cell to another through the sieve plates in the end cell walls.

1.1.4 Cell differentiation
Describe the stages of the cell cycle and mitosis. 

The cell will grow and increase the sub cellular structures such as ribosomes and mitochondria. The DNA will divide to form two copies of each chromosome. In mitosis the chromosome pairs are pulled apart to each end of the cell. The cytoplasm and cell membrane then divide to form two identical cells.

Explain the importance of mitosis in a multicellular organism.

Mitosis is important in the growth and development of multicellular organisms.

1.1.5 Microscopy
Describe how technological advances in microscopes have improved our understanding of the cell.

Light microscopes allowed for the discovery of cells and electron microscopes allowed for the discovery of organelles within the cell.

Compare the light microscope and electron microscope with regards to magnification and resolution. 

electron microscopes have high magnification and high resolution (detail). Light microscopes have low resolution and low magnification.

What is the formula to calculate magnification. 

Magnification = size of image / size of real object

1.2 Cell division
1.2.1 Chromosomes
Describe how the genetic material is organised in eukaryotic cells.

Genetic material is made from DNA and organised in to chromosomes.

1.2.2 Mitosis and the cell cycle
Describe the stages of the cell cycle and mitosis.

The cell will grow and increase the sub cellular structures such as ribosomes and mitochondria. The DNA will divide to form two copies of each chromosome. In mitosis the chromosome pairs are pulled apart to each end of the cell. The cytoplasm and cell membrane then divide to form two identical cells.

Explain the importance of mitosis in a multicellular organism.

Mitosis is important in the growth and development of multicellular organisms.

1.2.3 Stem cells
What is a stem cell? 

It is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can develop by differentiation.

Describe a use of human embryonic stem cells. 

Stem cells from embryos can be cloned and made to differentiate into most different types of human cells

Describe a use for adult stem cells from bone marrow. 

Stem cells from bone marrow can form many different types of cells including blood cells.

What is meristem tissue?

Meristems tissue is found in plants and can differentiate into any type of plant cell throughout the life of the plant.

Name two potential conditions that embryonic stem cells may help to treat in the future. 

Diabetes and paralysis

Describe therapeutic cloning.

n embryo is produced with the same genes as the patient. The stem cells removed from the embryo will not be rejected by the patient’s body so may be used for medical treatment.

Name some disadvantages of using embryonic stem cells. 

Risk of transfer of viral infections.  Religious or ethical objections to using embryos for research.

Name two uses of stem cells from meristems.

Rare species can be cloned to protect from extinction and crop plants with special characteristics such as disease resistance or drought resistance, can be cloned to produce large numbers of identical plants for farmers.

1.3 Transport in cells
1.3.1 Diffusion
What is diffusion?

The net movement of particles from an area of higher concentration to an area of lower concentration.

Give two examples of diffusion. 

Gaseous exchange of carbon dioxide and oxygen in the lungs and muscles, the removal of urea from cells into the blood.

Name three factors which affect the rate of diffusion. 

The difference in concentration (concentration gradient), the temperature and the surface area of the membrane.

Describe the surface area to volume ratio of a single cell organism. 

A single cell organism has a large surface area to volume ratio. This allows the transport of substances in and out of the organism to meet its metabolic needs.

Name five exchange surfaces found in animals and plants. 

Small intestine, lungs, gills, roots and leaves.

Name four ways the efficiency of an exchange surface can be increased. 

Having a large surface area, a thin membrane (for a short diffusion path), an efficient blood supply (animals), being ventilated (animals for gaseous exchange).

1.3.2 Osmosis
What is osmosis? 

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

What is the effect of placing a plant cell in a solution which has a higher concentration than inside the cell?

Water will move from inside the cell (dilute solution) to outside the cell (concentrated solution).

What is the effect of placing a plant cell in a solution which has a lower concentration than inside the cell? 

Water will move from outside the cell (dilute solution) to inside the cell (concentrated solution)

What is the effect of placing a red blood cell in water? 

Water will move inside the cell by osmosis. The blood cell will swell up and burst.

Describe an experiment to investigate the effect of salt concentration on plant tissue. 

Cut 5 pieces of potato to equal size. Weigh each piece of potato. Place a piece of potato in 5mL of the following solutions: 0M, 0.2M, 0.4M, 0.6M, 0.8M and1M. Incubate the solutions for 1hr. Remove each piece of potato, pat it dry with tissue paper and weigh.  Calculate the change in mass of each potato. Calculate the percentage change in mass by dividing the change in mass by the mass of the potato at the start. 

1.3.3 Active transport
What is active transport? 

The movement of substances from a dilute solution to a more concentrated solution, against the concentration gradient. This process requires energy from respiration.

Compare active transport and diffusion. 

Active transport moves substances against the concentration gradient while diffusion moves substances down the concentration gradient.  Active transport requires energy for the process, diffusion is a passive process and does not require energy.

Give two examples of active transport.

Mineral ions are absorbed by root hair cells into the plant from low concentrations in the soil.  Sugar are absorbed into the blood (which has a high concentration of sugar) from the small intestine (which has a lower concentration of sugar).

2. Organisation
2.1 Principles of organisation
What do all living organisms consist of? 


What is a tissue?

A group of cells with a similar structure and function

What are organs?

Organs are aggregations of tissues which perform a similar function

Put the following in order of size (smallest first): 

ribosome, mitochondria, nucleus, vacuole, palisade cell.

2.2 Animal tissues, organs and organ systems
2.2.1 The human digestive system
Name the parts of the digestive system. 

Mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus.

What happens to enzymes at low temperature? 

They have low kinetic energy and will rarely collide with substrate molecules which results in a low rate of reaction.

What happens to enzymes at high temperatures?

The enzyme loses its shape and the active site no longer binds to the substrate. 

Explain the term optimal pH using a protease produced in the stomach as an example. 

Optimal pH is the pH at which the rate of reaction is the fastest. In the stomach the protease enzymes work best at pH3.

Explain enzyme action using the lock and key hypothesis. 

Enzymes action depends on the shape of the active site (the lock) fitting to substrate (the key).  When the enzyme and substrate are joined together the enzyme can breakdown the substrate.  When the enzyme is denatures, the active site no longer fits the substrate.

Where is amylase produced?

Salivary glands, pancreas and small intestine.

Where is protease produced? 

Stomach, pancreas and small intestine.

Where is lipase produced?

Pancreas and small intestine.

What are the products of amylase digestion?

Starch is broken down into glucose.

What are the products of protease digestion?

Protein is broken down into amino acids.

What are the products of lipase digestion?

Lipids are broken down in fatty acids and glycerol

Where is bile made?


Where is bile stored?

Gall bladder

Name two functions of bile.

It is alkaline to neutralise hydrochloride acid from the stomach. Bile emulsified fat to form small droplets which increases the surface area of lipid for quicker digestion.

What is the food test for glucose? 

Benedict’s test

What is the positive result for the test for glucose? 

Green, orange or red.

What is the food test for starch?

Iodine test

What is the positive result for the test for starch?


What is the food test for protein?

Biuret test

What is the positive result for the test for protein? 


What is the food test for lipids? 

Sudan III

What is the positive result for the test for lipids?

A red layer

2.2.2 The heart and blood vessels
Name the two blood vessels which carry blood into the heart. 

Vena cava and pulmonary vein

Name the two blood vessels which carry blood away from the heart.

Pulmonary artery and aorta

Which blood vessels entering or leaving the heart contain oxygenated blood. 

Pulmonary vein and aorta.

Which blood vessels entering or leaving the heart contain deoxygenated blood.

Pulmonary artery and vena cava

Which chamber of the heart pumps blood to the lungs?

Right ventricle

Which chamber of the heart pumps blood to the body?

Left ventricle

Explain the term “double circulatory” system.

The circulatory system consists of a deoxygenated loop which passes the the lungs and an oxygenated loop which passes through the body. Blood passes through the heart twice as it travels through each loop.

How is the natural resting heart rate controlled. 

It is controlled by a group of cells in the right atrium which act as a pacemaker.

What is the function of an artificial pacemaker. 

An artificial pacemaker is an electrical device used to correct irregularities in the heart.

2.2.3 Blood
Name the three types of blood vessels found in the body. 

Artery, vein and capillary.

Compare the structure of the blood vessels found in the body. 

Arteries have thick walls with large muscle layers. Veins have thinner walls but contain valves to ensure blood flows in one direction. Capillaries are much small than arteries and veins and are only a one cell thick. They have gaps in their walls to allow plasma to leak out.

What is blood made of? 

Red blood cells, white blood cells, platelets and plasma.

What part of the blood carries oxygen? 

Red blood cells

What part of the blood is involved with clotting? 


What part of the blood carries dissolved glucose? 


What part of the blood is involved with the immune response.

White blood cells

What part of blood has granulated cytoplasm with an irregular shaped nucleus?

White blood cells

What part of blood is made from cell fragments? 


What part of blood is a yellow liquid? 


What part of blood has no nucleus? 

Red blood cells

2.2.4 Coronary heart disease: a non-communicable disease
What type of disease is coronary heart disease?

A non-communicable disease

Describe how coronary heart disease develops. 

Layers of fatty material build up inside coronary arteries, narrowing them. This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle.

Describe how a mechanical device can treat coronary heart disease. 

Stents are inserted through veins into the coronary arteries. A ballon is then inflated to open the stent which keeps the coronary artery open.

Describe how drugs can treat coronary heart disease. 

Statins are drugs which reduce blood cholesterol levels and slow down the rate of fatty material deposit.

Describe how a heart may be replaced. 

If heart failure occurs a heart can be transplanted. Sometimes an artificial heart can be used to keep patients alive while waiting for a transplant or to allow a heart to rest to aid recovery.

Describe the benefits and risks associated with drug and mechanical device treatments. 

Stents lower the risk of coronary heart disease, are a long term solution and recovery from surgery is quick. The is a risk of infection from the surgery and for patients to develop a blood clot (thrombosis) near the stent. Statins reduce the risk of strokes, heart disease and heart attacks. Can cause negative side effects such as headaches, kidney failure and liver damage. It can take time for statins to have an effect.

Describe two problems which can occur with heart valves. 

Heart valves may not fully open or they may leak.

Describe the consequences of a faulty valve. 

Blood does not circulate as effectively. Lack of oxygen in circulation around the body.

Describe the treatment for faulty valves. 

Replacement with biological valves (from humans or other animals or synthetic valves (made from metal and plastic).

2.2.5 Health issues
What is health?

Health is the state of physical and mental well being.

Name four factors which cause ill health. 

Diseases, diet, stress and life situations.

Name two types of diseases. 

Communicable and non-communicable

What can defects in the immune system lead to?

Infectious disease

What may viral infections trigger? 


What can immune reactions caused by pathogens trigger? 

Allergies such as skin rashes or cancer

What can severe physical ill health lead to?

Depression and other mental illness

2.2.6 The effect of lifestyle on some non-communicable diseases
Discuss the human and financial cost of non-communicable disease to an individual, a local community and nationally. 

Many millions of human die each year from non-communicable disease. Their short life span and lower quality of life will also have an impact on their families. Treating illness costs money to fund health services and research. 

List three lifestyle factors which affect the incidence of non-communicable disease. 

Diet, alcohol and smoking.

Name three risk factors for cardiovascular disease. 

Diet, smoking and lack of exercise.

Name a risk factor for type 2 diabetes.


Name a risk factor for liver disease. 


Name a risk factor for lung disease and cancer. 


Name two risks factors which can affect the health of unborn children. 

Smoking and alcohol.

Name two risk factors in cancer. 

Carcinogens (in chemicals) and ionising radiation.

2.2.7 Cancer
What is cancer?

Cancer is a result of changes (mutations) in cells which lead to uncontrolled growth and division.

Describe benign tumours. 

Growths of abnormal cells that are contained in one area usually within a membrane. They do not move to other parts of the body.

Describe malignant tumours.

Malignant tumour cells are cancerous. They invade neighbouring tissue and spread to different parts of the body through the blood where they grow to form secondary tumours.

2.3 Plant tissues, organs and systems
2.3.1 Plant tissues
Name six plant tissues. 

Epidermal, palisade mesophyll, spongy mesophyll, xylem, phloem and meristem

Name a plant organ involved with photosynthesis. 


Starting from the top, name the layers of the leaf in order. 

Waxy cuticle (not a tissue), upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis (containing guard cells).

2.3.2 Plant organ system
Describe the process of transpiration. 

Root hairs cells take up water from the soil by osmosis. Xylem vessels transport the water up the plant to the leaves. Water evaporates from the stomata of leaves. It is the evaporation which pulls water up through the plant. The movement of water through the plant is called the transpiration stream.

Explain the effects of changing temperature, humidity, air movement and light intensity on the rate of transpiration in plants. 

Increasing the temperature and air movement will increase the rate of transpiration in a plant (more water evaporates from the stomata). Increasing humidity will decrease the rate of transpiration (less water evaporates from the stomata). The stomata open during the day (transpiration) but close at night (no transpiration)

Describe an experiment to measure the rate of transpiration. 

Use a potometer.  To look at the effect of wind set up the potometer and measure how far the bubble travels in 15 minutes.  Use a hair drier on low power setting without the heater and blow plant for 15 minutes.  Measure how far the bubble travels. Use the hair drier on the highest power setting and blow plant for 15 minutes. Record how far the bubble travels. 

Where are stomata located in leaves? 

Stomata are located in the lower epidermis of the leaf in most terrestrial plants.  Water lily leaves float on water, so their stomata are on the upper epidermis of the leaf.

Which plant organs are involved in the transport of substances. 

Xylem (water and mineral ions) and phloem (sugar)

What is translocation?

This is the process where phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage.

Describe the role of stomata in transpiration.

Stomata are located in the lower epidermis of the leaf in most terrestrial plants.  Water lily leaves float on water, so their stomata are on the upper epidermis of the leaf.

How are root hair cells adapted for their function?

Root hair cells have a long thread like structure which increases the surface area to volume ratio of the cell.  This allows for the efficient uptake of water and mineral ions.

What is phloem?

Phloem is composed of tubes of elongated cells with sieve plates.  Cell sap can move from one phloem cell to another through the sieve plates in the end cell walls.

What is xylem? 

Hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream

How do root hair cells absorb water and mineral ions? 

Water is absorbed by osmosis and mineral ions are absorbed by active transport.

3. Infection and response
3.1 Communicable diseases
3.1.1 Communicable (infectious) diseases
What are pathogens? 

Pathogens are microorganisms that cause infectious disease.

Name four types of pathogens. 

Viruses, bacteria, protists and fungi.

Name three ways pathogens can be spread. 

Direct contact, by water or by air.

How do bacteria cause disease? 

They reproduce rapidly inside the body. They may produce toxins (poison) that damage tissue and cause illness.

How do viruses cause disease? 

They live and reproduce inside cells, causing cell damage.

3.1.2 Viral diseases
Name three viral diseases.

Measles, HIV and tobacco mosaic virus.

What are the symptoms of measles?

Fever and a red skin rash.

What are the consequences of measles?

Measles can be fatal if there are complications.

How is the measles virus spread?

Inhalation of droplets from coughing and sneezing.

How can the measles virus be controlled?

Vaccination of young children.

What are the symptoms of HIV?

Flu-like illness.

What are the effects of HIV? 

The virus attacks and destroys the cells of the body’s immune system.What is AIDS? The late stage of HIV when the body’s immune system is so badly damaged it can no longer cope with other infections or cancers.

What is AIDS? 

The late stage of HIV when the body’s immune system is so badly damaged it can no longer cope with other infections or cancers.

How is the HIV spread? 

HIV is spread by sexual contact or the exchange of body fluids (e.g. blood when drug users share needles)

How can the HIV virus be treated?

By the use of antiretroviral drugs which slow down the replication of the virus.

What organisms does tobacco mosaic virus (TMV) infect?

Many species of plants, including tomatoes.

What are the symptoms of TMV? 

A distinctive mosaic pattern of discolouration on the leaves.

What are the effects of TMV? 

TMV affects the growth of a plant due to the lack of photosynthesis.

3.1.3 Bacterial diseases
Name two bacterial diseases?

Salmonella food poisoning and gonorrhoea.

What are the symptoms of salmonella food poisoning? 

Fever, abdominal cramps, vomiting and diarrhoea.

What causes the symptoms of salmonella food poisoning? 

The bacteria and the toxins they produce.

How is the salmonella bacteria spread?

By ingesting contaminated food or on food prepared in unhygienic conditions (dirty hands and surfaces).

How can the salmonella bacteria be controlled?

In the UK poultry (chickens) are vaccinated against salmonella.

What are the symptoms of gonorrhoea? 

A thick yellow or green discharge from the vagina or penis and pain when urinating.

How is the gonorrhoea bacteria spread? 

Gonorrhoea is a sexually transmitted disease (STD).

How can the gonorrhoea bacteria be controlled? 

Gonorrhoea is treated with antibiotics. The risk of transmission can be reduced by using barrier methods of contraception such as condoms.

Why is the treatment for gonorrhoea no longer as effective?

Many antibiotic resistant strains have appeared.

3.1.4 Fungal diseases
Name a fungal disease.

Rose black spot.

What are the symptoms of rose black spot? 

Purple or black spots develop on leaves which turn yellow and drop early.

What are the effects of rose black spot?

The growth of plants is affected as photosynthesis is reduced.

How is rose black spot spread?

The fungal spores are spread by water or wind.

How can rose black spot be controlled?

It can be treated using fungicides and by removing and destroying (by burning) the affected leaves.

3.1.5 Protist diseases
Name a protist disease. 


What are the symptoms of malaria?

Recurrent episodes of fever.

What are the effects of malaria?

It can be fatal.

What is a vector?

An organism that transports the pathogen from one host to another. 

How is the malaria protist spread?

It is spread from host to host by a mosquito.

How can the malaria protist be controlled?

By targeting the mosquito. This is achieved by disrupting its habitat (draining swamps), disrupting its breeding and using mosquito nets to prevent being bitten.

3.1.6 Human defence systems
Name four non-specific defence systems of the human body against pathogens. 

Skin, nose, trachea and bronchi and stomach.

How does the skin help prevent infection?

A layer of dead cells which cannot be infected.

How does the nose help prevent infection?

Hairs and mucus prevent pathogens entering the lungs.

How do the trachea and bronchi help prevent infection? 

Cilia and mucus, in the trachea and bronchi, trap then remove pathogens.

How does the stomach help prevent infection? 

The acid in the stomach kills pathogens.

What is the role of the immune system? 

The immune system detects and destroys pathogens that enter the blood and tissues.

Name three methods by which white blood cells defend against pathogens? 

phagocytosis, antibody production and antitoxin production.

3.1.7 Vaccination
Describe vaccination. 

Vaccination involves the introduction of dead or inactive pathogens into an organism which stimulates the white blood cells to produce antibodies.  If the organism is reinfected by a live pathogen it will activate the antibodies to eradicate the pathogens quickly and so prevent infection.

What has been the effect of vaccination in reducing disease? 

Vaccination on a global scale has helped to eradicate a number of diseases.  This only happens when the majority of the population is vaccinated.

3.1.8 Antibiotics and painkillers
What are antibiotics?

Antibiotics are medicines used to treat bacterial infections by killing the bacteria inside the body.

What has been the effect of antibiotics? 

The overall effect of antibiotics has been to significantly reduce death from infections. However misuse of antibiotics has lead to the emergence of resistant strains. 

What do antibiotics target? 

They target bacteria (prokaryotic cells) only. They do not kill viruses.

What are painkillers? 

A type of drug that treats symptoms of a disease but does not affect the pathogens themselves.

Why is it difficult to develop drugs that target viruses. 

Viruses live inside cells so any treatment can also damage host cells as well.

3.1.9 Discovery and development of drugs
Name three drugs that were extracted from plants or microorganisms. 

Digitalis, aspirin and penicillin.

Who discovered penicillin? 

Alexander Fleming.

How are most new drugs made today? 

Most pharmaceuticals (drugs) are synthesised by chemists in laboratories.

Why do drugs have to be tested? 

Drugs are tested to ensure that they are safe and effective.

Name three factors which drugs are tested for. 

Drugs are tested for toxicity (side effects), efficacy (effectiveness) and dose (most effective amount which balances maximum efficacy with minimal toxicity.

What is preclinical testing?

Preclinical testing occurs in the laboratory and can use cells, tissues and live animals.

Describe the process of clinical testing. 

Clinical trials are carried out in healthy volunteers and patients. Low doses are given at the start of testing to ensure toxicity is low. Further trials are then carried out at different doses to find out the optimum dose of the drug. To check if a drug is effective a double blind trial will be used.  In this case half the patients receive the drug and the other half will be given a placebo.  The results of trials are published after peer review.

What is a placebo?

Phloem is composed of tubes of elongated cells with sieve plates.  Cell sap can move from one phloem cell to another through the sieve plates in the end cell walls.

4. Bioenergetics
4.1 Photosynthesis
4.1.1 Photosynthetic reaction
Write the word equation for photosynthesis? 

Carbon dioxide + water → glucose + oxygen

What is the symbol for carbon dioxide?


What is the symbol for water? 


What is the symbol for oxygen? 


What is the symbol for glucose?


Write the balanced chemical equation for photosynthesis. 

6CO2 + 6H2O → C6H12O6 + 6O2

Describe the process of photosynthesis. 

Photosynthesis is an endothermic reaction in which energy from sunlight is transferred to chloroplasts.

4.1.2 Rate of photosynthesis
Name four factors which affect the rate of photosynthesis.

Temperature, light intensity, carbon dioxide concentration and chlorophyll.

How does temperature affect photosynthesis?

Photosynthesis is controlled by enzymes. Temperature affects the rate of collisions between the enzymes and the substrates. If the temperature is too high the enzymes will denature and no longer bind to the substrate.

How does carbon dioxide affect photosynthesis?

Carbon dioxide is required to make the glucose.  If the carbon dioxide concentration is too low the amount of glucose that can be produce is reduced.

How does light affect photosynthesis?

Light transfers energy to the chloroplasts for the reactions.  A reduction in light intensity will reduce the energy available for the reaction.

Describe an experiment to measure the rate of photosynthesis using pondweed. 

Pondweed is placed in a beaker of water at a constant temperature.  Sodium carbonate is added to the water to ensure there is enough dissolved carbon dioxide. The plant is left for ten minutes to acclimatise. A glass filter funnel is placed over the plant. Any oxygen given off is collected in a graduated test tube placed on top of the funnel. A light source is placed at 100cm from the plant. A glass plate is placed between the light source and the plant. This prevents the water from heating up from the light.  The light is turned on and the volume of gas collected over 5 minutes is measured. The experiment is repeated at 90cm, 80cm, 70cm, 60cm, 40cm, 30cm, 20cm and 10cm.  A graph is plotted of distance vs volume of oxygen collected.

What is a limiting factor? (HT only) 

A limiting factor is a resource or environmental factor whose absence prevents an increase in the rate of a reaction. If the limiting factor is increased, the rate of reaction will increase as well.

Draw a graph to show the effect of increasing light intensity on the rate of photosynthesis. (HT only)
Draw a graph to show the effect of increasing carbon dioxide concentration on the rate of photosynthesis. (HT only)
Draw a graph to show the effect of increasing temperature on the rate of photosynthesis. (HT only)
Use the inverse square to calculate the light intensity of a lamp when placed 10cm away from a plant.Use the formula light intensity = 1 / distance2. (HT only)

ight intensity = 1 / 102 : light intensity = 0.01 au (arbitrary units)

Describe what happens to the light intensity when you half the distance between lamp and the plant. (HT only) 

if you halve the distance the light intensity will be four times greater.

Explain how the conditions of a commercial greenhouse can be maintained to gain maximum rate of growth and maintain a profit. (HT only) 

Greenhouses control light intensity (artificial light), temperature (heating) and carbon dioxide concentration (ventilation). The cost effectiveness of each factor is related to the maximum growth rate.

What is the limiting factor in this graphs? (HT only)

Carbon dioxide

4.1.3 Uses of glucose from photosynthesis
State five uses of glucose produced by photosynthesis. 

Respiration, converted to starch for storage, converted to fat or oil for storage, converted to cellulose to make the cell wall, used to make amino acids for protein synthesis.

As well as glucose, what else do plants need to make proteins?

Plants absorb nitrate ions from the soil which are used to make proteins.

4.2 Respiration
4.2.1 Aerobic and anaerobic respiration
Describe the process of cellular respiration. 

Cellular respiration is an exothermic reaction which is continually happening inside all living cells.

Which type of respiration requires oxygen?

Aerobic respiration.

Which type of respiration does not require oxygen?

Anaerobic respiration.

What is the word equation for aerobic respiration? 

Glucose + oxygen → carbon dioxide + water

What is the balanced symbol equation for aerobic respiration? 

C6H12O6 + 6O2  → 6CO2 + 6H2O

What is the word equation for anaerobic respiration in muscles?

Glucose → lactic acid

What is the word equation for anaerobic respiration in plant cells and yeast? 

Glucose → ethanol and carbon dioxide

What is another term to describe anaerobic respiration in plant cells and yeast? 


Give three uses for the energy transferred by cellular respiration. 

Chemical reactions to synthesise large molecules (eg proteins).

Compare the processes of anaerobic and aerobic respiration with regard to oxygen. 

Aerobic respiration requires oxygen, anaerobic respiration does not require oxygen.

Compare the processes of anaerobic and aerobic respiration with regard to their products. 

Anaerobic respiration will produce lactic acid in humans or ethanol and carbon dioxide in yeast.  Aerobic respiration produces carbon dioxide and water.

Compare the processes of anaerobic and aerobic respiration with regard to the relative amounts of energy transferred.

Aerobic respiration produces large amounts of energy slowly, from a molecule of glucose. Anaerobic respiration produces a small amount of energy quickly, from a molecule of glucose.

What is the economic importance of anaerobic respiration in yeast?

Anaerobic respiration is important in the manufacture of bread and alcoholic drinks.

4.2.2 Response to exercise
What three processes will increase during exercise to provide the muscles with an increase in oxygenated blood? 

Heart rate, breathing rate and breath volume.

What will happen if there is insufficient oxygen in the blood? 

Anaerobic respiration will take place in muscles.

Describe the consequences of the incomplete oxidation of glucose in anaerobic respiration in the muscles. 

Incomplete oxidation of glucose will lead to a build up of lactic acid in the muscles and creates an oxygen debt.

What is the effect on the muscles of long periods of vigorous activity? 

The muscles will become fatigued and will stop contracting efficiently.

What is the metabolic fate of the lactic acid produced during anaerobic respiration? (HT only)

Lactic acid is removed from the muscles and transported via the circulatory system to the liver. The liver converts the lactic acid back to glucose.

Define oxygen debt. (HT only) 

Oxygen debt is the amount of extra oxygen the liver uses after exercise to convert lactic acid back to glucose.

4.2.3 Metabolism
What is metabolism? 

The sum of all the reactions in a cell or organism.

How is the energy transferred by cellular respiration used by organisms? 

The energy transferred by respiration, is used by a cell or organism for enzyme controlled processes of metabolism that synthesise new molecules.

Name three compounds that glucose can be converted into in plants and animals.  

Starch and cellulose in plants and glycogen in humans.

What are lipid molecules formed from?

One molecule of glycerol and three molecules of fatty acids.

What are amino acids formed from? 

Glucose and nitrate ions.

How are proteins synthesised?

From amino acids.

What happens to excess proteins in the body? 

They are broken down to form urea which is removed by excretion.

What products are formed by the breakdown of carbohydrates?


What products are formed by the breakdown of protein? 

Amino acids.

What products are formed by the breakdown of lipids? 

Glycerol and fatty acids.

5. Homeostasis and response
5.1 Homeostasis
What is homeostasis? 

Homeostasis is the regulation of the internal environment of an organism to maintain optimal conditions for life processes (e.g. enzyme action).

Name three factors which need to be controlled by the human body. 

Blood glucose concentration, body temperature and water levels.

Name the three parts of a control system. 

Receptors, coordination centres and effectors

What is the function of a receptor? 

To detect stimuli (a change in the internal or external environment)

Give three examples of coordination centres. 

Brain, spinal cord and pancreas

What is the function of a coordination centre?

To receive and process information from receptors.

Give two examples of effectors. 

Muscles and glands 

What is the function of an effector? 

To bring about responses which restore the internal environment to optimal levels.

5.2 The human nervous system
What is the function of the nervous system?

To enable organisms to react to changes in the environment and to coordinate their behaviour.

Name the two parts of the nervous system. 

Neurones and central nervous system (CNS)

Name the two parts of the CNS. 

Brain and spinal cord

What is the role of the CNS? 

To process information form receptors and coordinate responses by the effectors (e.g. contracting muscles or glands secreting hormones).

What is the reflex arc?

A protective nervous pathway.

What neurone connects the receptor to the coordinator? 

Sensory neurone.

What neurone connects the coordinator to the effector?

Motor neurone.

Where is the relay neurone found? 

In the spinal cord.

What neurone does the sensory neurone connect to?

The relay neurone.

What neurone connects to the motor neurone? 

The relay neurone.

What neurones does the relay neurone connect to? 

The sensory neurone and the motor neurone.

What is the gap between neurones called? 


How is information transmitted across the gaps between the neurones? 

By the release of chemicals called neurotransmitters.

What are the properties of a reflex action? 

They are rapid and automatic. They are involuntary (they do not involve the conscious part of the brain)

Describe an experiment to investigate the effect of caffeine on reaction times.

Select a subject. Ensure the subject does not drink caffeine for 24 hours prior to the test.  Hold a ruler above the subjects hand. When you release the ruler the subject will grab it. Measure the distance the ruler falls.  Repeat the test 10 times and calculate the average distance the ruler fell.  Give the subject a known amount of caffeine in a drink.  Allow 30 minutes for the caffeine to be absorbed. Repeat the experiment.  Compare the effect of caffeine on the distance the ruler falls. The experiment can be repeated with more subjects but they should be the same sex, height and weight to ensure the results can be compared.

Describe the reflex arc 


5.3 Hormonal coordination in humans
5.3.1 Human endocrine system
What is the endocrine system? 

The endocrine system is made up of different glands which release chemical messengers called hormones into the blood.

What is a target organ? 

The target organ is the organ where the hormone has an effect. 

Compare the effects of the endocrine system to the nervous system. 

The endocrine system is slower than the nervous system but it has a longer lasting effect.

What is the master gland? 

The pituitary.

Where is the master gland found? 

The brain.

Describe the role of the master gland. 

In response to changes in the body, the pituitary secretes a number of hormones into the blood. These hormones then stimulate other glands to release hormones and bring about other effects.

Name six endocrine glands found in the human body. 

Pituitary, pancreas, thyroid, adrenal gland, ovary and testes

State where each of the glands are found in the human body. 

Pituitary - brain, pancreas - abdomen, thyroid - neck, adrenal gland - on top of kidney, ovary - female lower abdomen and testes - male scrotum.

5.3.2 Control of blood glucose concentration
Which organ monitors and controls blood glucose concentration? 


Name the two carbohydrates involved in the control of blood sugar concentration. 

Glucose and glycogen

Name the two hormones involve in the control of blood sugar concentration. 

Insulin and glucagon

Name three of the organs involved in the control of blood sugar concentration. 

Pancreas, liver and muscle.

If blood glucose concentration is too high, what hormone is released by the pancreas? 


What are the target organs for the hormone released? 

Liver and muscle.

What is the effect of this hormone on the target organs?

Insulin triggers the liver and muscle to take up the excess glucose in the blood.

How do the target organs process the excess glucose?

The liver and muscle convert the glucose into glycogen for storage.

What is type 1 diabetes? 

A disorder where the pancreas does not produce enough insulin.

How is type 1 diabetes characterised? 

High levels of blood glucose concentration.

How is type 1 diabetes treated? 

Insulin injections.

What is type 2 diabetes? 

A condition where the body cells (target organs) no longer respond to insulin.

How is type 2 diabetes treated? 

A carbohydrate controlled diet and more exercise.

What is a risk factor for type 2 diabetes? 


If blood glucose concentration is too low, what hormone is released by the pancreas? (HT only) 


What are the target organs for the hormone released? (HT only)

Liver and muscle.

What is the effect of this hormone on the target organs? (HT only)

It stimulates the liver and muscles cells to breakdown glycogen into glucose and release the glucose into the blood.

Describe how the negative feedback cycle maintains the blood glucose concentration within normal levels. (HT only)

As a result of exercise blood glucose concentration will fall.  The fall is detected by the pancreas which releases glucagon to counteract the lower levels of glucose. The target organs for the glucagon are liver and muscle. The liver and muscle respond to the glucagon by breaking down the glycogen they have stored and releasing the glucose into the blood. This causes the blood glucose concentration to return to normal.

5.3.3 Hormones in human reproduction
What is the role of reproductive hormones during puberty? 

To stimulate the development of the secondary sexual characteristics

Name the main female reproductive hormone. 


Where is the main female reproductive hormone made?


Name the main male reproductive hormone. 


Where is the main male reproductive hormone made? 


What is ovulation? 

The release of an egg cell from the ovary.

When does ovulation start?

At puberty.

How often does ovulation occur?

Approximately every 28 days.

Give the full names of the four hormones involved the menstrual cycle of a woman? 

Oestrogen, progesterone, Luteinising hormone and follicle stimulating hormone.

What is the function of FSH?

It causes the maturation of an egg cell from a follicle in the ovary.

What is the function of LH?

It stimulates ovulation.

What is function of oestrogen and progesterone. 

They are involved in stimulating and maintaining the thickness of the uterine lining.

What is the order of secretion of the four hormones during the menstrual cycle? 

FSH → oestrogen → LH → progesterone

Name the hormones labelled A, B, C and D on a graph of the menstrual cycle? 

A - oestrogen, B - LH, C - progesterone and D - FSH

What event occurs between days 1 and 4 of the menstrual cycle?

Breakdown of the uterine lining (menstruation).

What event occurs at approximately 14 days of the menstrual cycle? 


Name the hormone that inhibits FSH at the start of the cycle. 


How does oestrogen affect the uterine lining? 

It stimulates the uterine lining to thicken.

Which hormone does oestrogen stimulate? 


How does progesterone affect the uterine lining? 

It maintains the thickness of the uterine lining.

5.3.4 Contraception
What are the two main methods of contraception?

Hormonal and non-hormonal

How does the contraceptive pill work? 

It contains progesterone which inhibits the production of FSH so no eggs can mature and be released.

How do methods of slow release progesterone work? 

These inhibit FSH and prevent eggs maturing  for months or even years.

Name two barrier methods. 

Condoms and the diaphragm

How do barrier methods work? 

They prevent the sperm from reaching the egg.

How do IUDs work?

They prevent the implantation of an embryo into the uterine lining.

How do spermicidal agents work? 

They kill or disable sperm.

How does abstinence work?

Couples refrain from sex during the most fertile days of the cycle.

How do surgical methods for male and female sterilisation work? 

Tubes which transport sperm or eggs are tied off or cut to prevent passage.

5.3.5 The use of hormones to treat infertility (HT only)
Name two hormones which can be used as fertility drugs? 

LH and FSH.

What does IVF stand for? 

In vitro fertilisation 

Describe the process of IVF. 

The prospective mother is given FSH and LH to stimulate the maturing of several eggs. The eggs are collected from the prospective mother and fertilised with spree from the prospective father in the laboratory. The fertilised eggs develop into embryos.  Some of the developed embryos are selected and inserted into the prospective mothers uterus.

What are negative effects of IVF.

The success rate is not very high. It is very emotional and physical stressful for the prospective parents. It can lead to multiple births which are a risk to both the babies and the mother. The destruction of embryos inside and outside the body is considered unethical by religious groups.

5.3.6 Negative feedback (HT only)
What is the basal metabolic rate? 

The sum of all the reactions in the body when it is at rest.

Where is thyroxine produced? 

Thyroid gland.

What is the role of thyroxine in the body? 

Stimulates the basal metabolic rate. Thyroxine also plays a role in growth and development.

How are thyroxine levels controlled? 

Thyroxine levels are controlled by negative feedback.

Where is adrenaline produced? 

Adrenal glands

When is adrenaline produced? 

It is produced at times of fear or stress (fight or flight response)

What is the effect of adrenaline on the body? 

Adrenaline increases the heart rate and increases the oxygen and glucose delivered to the muscles.

6. Inheritance, variation and evolution
6.1 Reproduction
6.1.1 Sexual and asexual reproduction
What does meiosis lead to the formation of? 

Non identical cells.

What does mitosis lead to the formation of?

Identical cells.

What is sexual reproduction? 

The fusing of male and female gametes.

Name the two gametes involved in sexual reproduction in flowering plants. 

Egg (female) and pollen (male).

Name the two gametes involved in the sexual reproduction in animals. 

Egg (female) and sperm (male).

Describe how variation occurs in sexual reproduction. 

During the formation of gametes by meiosis and the mixing of genetic material during sexual reproduction.

Describe why clones are formed in asexual reproduction.

There is only one parent cell and the is no fusion of gametes. As a result there is no mixing of genetic information. 

6.1.2 Meiosis
Describe what happens to the number of chromosomes during meiosis and fertilisation? 

Meiosis halves the number of chromosomes during the formation of the gametes. During fertilisation the full number of chromosomes is restored in the fertilised egg.

How are gametes formed?

By meiosis.

Describe the process of gamete formation?

Genetic information is copied. The cell divides twice to form single cells with half the number of chromosomes. All the gametes are genetically different.

Describe how an embryo develops from gametes?

Gametes fuse during fertilisation and restore the normal number of chromosomes. The new cell divides by mitosis. This increases the number of cells. Once the cells differentiate an embryo is formed.

6.1.3 DNA and the genome
Where is the genetic material found in the cell? 


What is the genetic material made of?


Describe the structure of DNA.

A polymer made of two strands forming a double helix.

What structures in the nucleus are made from DNA? 


What is a gene?

A small section of DNA on a chromosome. 

What does a gene code for?

A sequence of amino acids which make a specific protein.

What is the genome of an organism? 

The entire genetic material of an organism.

List three ways which demonstrate the importance of understanding the human genome. 

Search for genes linked to disease, understanding and treating inherited diseases and tracing human migration patterns from the past.

6.1.4 Genetic inheritance
Define gamete. 

A sex cell.

Define chromosome. 

A long strand of DNA folded into structure.

Define gene. 

A section of DNA that codes for a specific protein.

Define allele. 

A different form of the same gene (e.g. blue and brown alleles for eye colour).

Define dominant. 

A dominant allele is always expressed in the phenotype even if only one copy is present.

Define recessive. 

A recessive allele is only expressed if two copies are present.

Define homozygous. 

Two copies of the same allele.

Define heterozygous. 

Different copies of an allele.

Define genotype. 

The alleles present in an organism. e.g. TT or Tt.

Define phenotype. 

The physical expression of the genotype. E.g. Tall or short.

Give two examples of characteristics governed by a single gene? 

Fur colour in mice and red-green colour blindness in humans.

At what level do alleles operate? 

Molecular level.

6.1.5 Inherited disorders
Name an inherited disorder caused by a dominant allele. 


Name an inherited disorder caused by a recessive allele. 

Cystic fibrosis.

Name two methods that could alleviate suffering caused by genetic disorders. 

Embryonic screening and gene therapy.

Discuss a social and an ethical issue around the issue of embryo screening. 

Embryonic screening can be used to terminate an unwanted foetus due to gender. E.g. some societies value male children more than female children for economic reasons.  Many religious groups consider the termination of babies to be immoral.

6.1.6 Sex determination
How many chromosomes do ordinary human body cells contain? 


What are the two sex chromosomes? 

X and Y.

What combination of sex chromosomes produce a female?


What combination of sex chromosomes produce a male? 


6.2 Variation and evolution
6.2.1 Variation
What is variation?

The difference of characteristics of individuals in a population.

Name three causes of differences in characteristics of individuals in a population. 

Genes, the environment in which the individual developed or a combination of both.

Describe the variation usually found in a population of a species.

There is usually extensive variation within a population of a species.

What causes variants in a genome?


How do mutations affect the phenotype? 

Most have no effect, some influence the phenotype and a small proportion determine the phenotype.

How often do mutations occur? 


What will happen if a new phenotype is suited to an environmental change? 

It will lead to a rapid change in the species.

6.2.2 Evolution
What is evolution? 

A change in the inherited characteristics of a population over time.

By what process is evolution thought to occur?

Natural selection.

What does the theory of evolution by natural selection state? 

All species of living organisms have evolved from simple life forms that first developed 3 billion years ago.

How does natural selection occur?

By the selection of variants with phenotypes that are best suited to their environment.

What is a species?

A group of individuals which can interbreed and produce fertile offspring.

Describe how two populations of one species could form two new species. 

The phenotypes of a species may become so different that the population can no longer interbreed.

6.2.3 Selective breeding
What is another term for selective breeding? 

Artificial selection.

Why do humans carry out selective breeding? 

To select useful genetic characteristics.

For how long have humans carried out selective breeding?

Thousands of years.

Describe the process of selective breeding.

Parents with the desired characteristics are bred together. The offspring which show the desired characteristics are then bred together. This happens over many generations until all the offspring show the desired characteristics.

List four examples of selective breeding. 

Disease resistance in food crops, animals which produce more milk or meat, domestic dogs with a gentle nature and large or unusual flowers.

What problems can arise from selective breeding? 

Problems can arise from inbreeding and lead to some breeds which are prone to disease or inherited defects.

6.2.4 Genetic engineering
What is genetic engineering?

The process of modifying the genome of an organism by introducing a gene from another organism to transfer a desired characteristic.

Give two examples of how plant crops have been genetically engineered. 

Disease resistant and to produce larger fruit.

Give an example of how bacteria have been genetically engineered. 

Bacteria are used to produce human insulin to treat diabetes.

How are useful genes used in genetic engineering. 

Genes are cut out of chromosomes and transferred to the cells of other organisms.

What is a genetically modified (GM) crop? 

Crop plants (e.g. wheat or rice) which have had genes from other organisms transferred into them.

Give three examples of GM crops. 

Resistant to insects, resistant to herbicides and increased yields.

Describe the concerns about the use of GM crops. 

Their effect on wild populations of animals, plants and insects. The effect of eating GM crops on human health.

How could genetic modification be useful in humans? 

To treat inherited disorders.

Describe the main steps in the process of genetic engineering (HT)

Enzymes are used to cut out the required gene. This gene is then inserted into a vector (a plasmid or virus). The vector then inserts the gene into the required cells. If this occurs in the early stage of an organisms development (e.g. fertilised egg) the organism will develop with the desired characteristics.

6.3 The development of understanding of genetics and evolution
6.3.1 Evidence for evolution
Name two pieces of evidence for evolution. 

Fossils and antibiotic resistance in bacteria.

6.3.2 Fossils
What are fossils? 

The remains of organisms from millions of years ago found buried in rocks.

Describe three ways fossils may be formed. 

From parts of organisms that have not decayed, when parts of organisms are replaced by minerals as they decay and as preserved traces of organisms such as footprints, burrows and rootlet traces.

Explain why the fossil record is incomplete.

Early forms of life where soft bodied which left behind few traces. Many of these traces where destroyed by geologic activity.

Why are fossils useful? 

They inform us how organisms have changed or stayed the same as life has developed on earth.

6.3.3 Extinction
What is extinction? 

Extinction occurs when there are no remaining individuals of a species still alive.

Describe the factors which may contribute to the extinction of a species. 

Changes to the environment over a long period of time, new predators, new diseases, competition or a single catastrophic event.

6.3.4 Resistant bacteria
Why can evolution in bacteria be studied?

Because they reproduce rapidly (e.g. every 20 minutes).

Describe how an antibiotic resistant strain of bacteria could arise.

A mutation to a non resistant bacteria could lead to resistance. The resistant strain is not killed by antibiotics but the non resistant strains are. The resistant strains survive and reproduce. The population of the resistant strain increases.

What is MRSA? 

A strain of bacteria resistant to antibiotics.

Describe three steps which would reduce the development of antibiotic resistant strains. 

Doctors should not prescribe antibiotics inappropriately, patients should complete their course of antibiotics and the agricultural use of antibiotics should be restricted.

Why is the development of new antibiotics unlikely to keep up with the emergence of new resistant strains? 

The development of new antibiotics is costly and slow.

6.4 Classification of living organisms
Who first developed a classification system? 

Carl Linnaeus

How did he group organisms together? 

Their structure and characteristics.

Name the 7 levels of classification used by Linnaeus.

Kingdom, phylum, class, order, family, genus and species.

What is the binomial system? 

A system of naming organisms using their genus and species e.g. Homo sapiens.

Why were new models of classification proposed? 

An increase in our understanding of the internal structures of the cell and increased understanding of biochemical processes.

What system did Carl Woese develop? 

The three domain system.

Why did Carl Woese propose a new system? 

Due to evidence from chemical analysis.

How are organisms divided up in the three domain system? 

Archaea (primitive bacteria), Bacteria (true bacteria) and Eukaryota (includes protists, fungi, plants and animals).

What is an evolutionary tree? 

A diagram used by scientists to show how organisms are thought to be related.

7. Ecology
7.1 Adaptations, interdependence and competition
7.1.1 Communities
What does abiotic mean?

The non living parts of an environment.

What is an ecosystem? 

The interaction of a community of living organisms with the non living parts of their environment.

What is a habitat? 

An environment in which a particular species lives.

What do organisms need to survive and reproduce?

A supply of materials from their surroundings and from other living organisms living there. 

What do plants compete for in a habitat? 

Light, space, water and mineral ions.

What do animals compete for in a habitat? 

Food, mates and territory.

What is a population?

A group of individuals from the same species living in an environment.

What is a community? 

A group of populations living within the same environment.

Name 4 ways in which species in a community depend on each. 

Food, shelter, pollination and seed dispersal.

What is a stable community? 

A community where the species and environmental factors are in balance so that population sizes remain fairly constant.

7.1.2 Abiotic factors
List seven abiotic 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) and oxygen levels (for aquatic animals).

7.1.3 Biotic factors
List four biotic factors which can affect a community.

Availability of food, new predators, new diseases and competition between species.

7.1.4 Adaptations
What is an adaptation? 

A feature that enables an organism to survive in the conditions they normally live.

Name the three types of adaptations.

Structural, behavioural and functional.

Give an example of a structural adaptation. 

Spines in a cactus instead of leaves prevent water loss.

Give an example of a behavioural adaptation. 

Mating rituals in birds such as peacock feathers in males to attract females.

Give an example of a functional adaptation. 

Formation of venom in plants and animals such as nettles and snakes.

Name three factors which can cause extreme environments? 

High temperature, pressure and salt concentration.

What are organisms that live in extreme environments called? 


Give an example of an organism that lives in an extreme environment? 

Bacteria living in deep sea vents (high temperature and pressure).

7.2 Organisation of an ecosystem
7.2.1 Levels of organisation
Who are the producers of biomass for life on Earth?

Photosynthetic organisms.

How are feeding relationships within a community represented? 

Food chains.

What are producers? 

An organism that synthesises molecules.

Give two examples of producers. 

Green plants and algae.

What are transects and quadrants used to measure? 

Distribution and abundance of a species in an ecosystem.

What is the mean? 

The average number (of species in ecosystem).

What is the mode? 

The value which appears the most often.

What is the median?

The value in the middle of a range of data.

Describe how energy is passed along a food chain. 

Producers are eaten by primary consumers which in turn are eaten by secondary consumers which are then eaten by tertiary consumers.

What are predators? 

Consumers that kill and eat other organisms.

What are prey?

Animals eaten by by other organisms.

What is a stable community? 

A community where the numbers of predator and prey fall and rise in cycles.

Describe a method to measure the population size of buttercups in a large field and then describe how you would measure the effect of light intensity on the distribution of the buttercups. 

One method is to assign a grid to the area of interest. Squares in the grid are randomly selected and the abundance of a species is noted.  An alternate method is to use a transect square which is thrown randomly and the abundance of a species is counted.  In each square a light meter is used to measure light intensity. The abundance of each square is then plotted against the light intensity to see if the is any relationship.

7.2.2 How materials are cycled
What is the name of the process in the carbon cycle that turns atmospheric CO2 into carbon compounds in plants? 


What is the name of the process in the carbon cycle that converts carbon compounds in plants into carbon compounds in animals? 


What is the name of the process in animals and plants which converts carbon compounds into atmospheric CO2?


How are carbon compounds in plants and animals converted into carbon compounds in microorganisms. 

By death and decay.

How are carbon compounds in animals and plants converted into fossil fuels? 


How are carbon compounds in fossil fuels converted into atmospheric CO2? 


Name two ways water enters the atmosphere from groundwater and oceans. 

Evaporation and transpiration

What is transport in the water cycle? 

The moment of water through the atmosphere, usually from over oceans to over land.

What is the process of cloud formation called? 


What is precipitation? 

Rain, snow, sleet or hail.

What is infiltration in the water cycle? 

The process by which water soaks in to the soil and rocks to form groundwater.

What is the effect of deforestation on the water cycle? 

Deforestation reduces transpiration, the lack of soil reduces infiltration and increases the amount of run off.

7.3 Biodiversity and the effect of human interaction on ecosystems
7.3.1 Biodiversity
What is biodiversity? 

The variety of different species of organisms in an ecosystem.

How does high biodiversity ensure the stability of an ecosystem? 

High biodiversity increases the the stability of ecosystems by reducing the dependence of one species on another.

Name three ways human activity have reduced biodiversity? 

Waste, deforestation and global warming.

7.3.2 Waste management
Name two reasons why the production of waste has increased.

Rapid growth in population and an increase in the standard of living.

Name three ways pollution can occur. 

In water from sewage, fertilisers and toxic chemicals. In air from smoke and acidic gases. On land from landfill and toxic chemicals.

How does pollution affect biodiversity? 

Pollution kills plants and animals which reduces biodiversity.

7.3.3 Land use
Name 4 ways humans reduce the amount of land available for other animals and plants.

Building, quarrying, farming and dumping waste.

What natural resource is used to make garden compost? 


How does the production of garden compost affect biodiversity? 

Reduces the area of peat bog and as a result it reduces the biodiversity of the habitat.

How does the use of peat contribute to global warming? 

The decay or burning of peat release carbon dioxide into the atmosphere.

7.3.4 Deforestation
Name two reasons for large scale deforestation in tropical areas. 

To provide land for cattle or rice fields and to grow crops for biofuels.

How does deforestation affect global warming? 

Burning of timber increases the carbon dioxide being released into the atmosphere. The destruction of trees leads to less photosynthesis removing carbon dioxide from the atmosphere.

How does deforestation affect biodiversity? 

The destruction of habitat reduces the number of species living in a habitat.

How does deforestation affect the water cycle? 

Deforestation reduces transpiration, the lack of soil reduces infiltration and increases the amount of run off.

7.3.5 Global warming
Name the biological consequences of global warming. 

Melting polar ice caps, rising sea levels, flooding and climate change (violent storms and extended droughts).

Name two gases which contribute to global warming.

Carbon dioxide and methane.

7.3.6 Maintaining biodiversity
Name one method of saving endangered species (e.g. Snow leopards)?

Breeding programs.

How can rare habitats (e.g. mangrove swamps) be saved? 

Protection and regeneration

How can biodiversity be increased in a field growing only one type of food crop (e.g. wheat)? 

Reintroduction of field margins and hedgerows.

How can governments help to protect the environment? 

Legislate (make laws) to reduce deforestation and cut carbon dioxide emissions.

How can resources be more efficiently used? 

Legislate (make laws) to reduce deforestation and cut carbon dioxide emissions.