AQA GCSE Combined Science

Biology

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Paper 1

Topic 1 – Cell Biology

4.1.1.1 Eukaryotes and Prokaryotes

1.

What is the difference between a eukaryotic cell and a prokaryotic cell?

Eukaryotic cells have a nucleus and membrane-bound organelles. Prokaryotic cells do not.
2.

Which type of cell has its genetic material enclosed inside a nucleus?

Eukaryotic cells.
3.

What is the function of a bacterial plasmid?

It contains extra small rings of DNA that can carry useful genes, such as antibiotic resistance.
4.

State two structures found in both bacterial and animal cells.

Cell membrane and cytoplasm.
5.

Why are bacterial cells described as prokaryotic?

They have no nucleus, so their genetic material is free in the cytoplasm.
6.

Explain one way that bacterial cells differ from plant cells.

Plant cells have a nucleus, mitochondria, a cell wall and chloroplasts, whereas bacterial cells have no nucleus or chloroplasts.

4.1.1.2 Animal and Plant Cells

1.

Name the five main sub-cellular structures found in an animal cell.

Nucleus, cell membrane, cytoplasm, mitochondria and ribosomes.
2.

Which three structures are found in plant cells but not animal cells?

Cell wall, chloroplasts and permanent vacuole.
3.

What is the function of the nucleus?

Controls the activities of the cell and contains the genetic material (DNA).
4.

What is the function of mitochondria?

Site of aerobic respiration where energy is released.
5.

Explain why plant cells contain chloroplasts but animal cells do not.

Plant cells photosynthesise, so they need chloroplasts containing chlorophyll. Animals do not photosynthesise.
6.

Explain why a plant cell needs a cellulose cell wall.

It strengthens and supports the cell and maintains its shape.

Required Practical 1: Using a Light Microscope

1.

What type of microscope is used in the required practical to observe plant and animal cells?

A light microscope.
2.

Which two types of cells are commonly observed in the microscopy required practical?

Onion epidermal cells and human cheek cells.
3.

What must always be included with a biological drawing made using a microscope?

A title and magnification (or scale).
4.

Why is iodine stain used when observing plant cells under a light microscope?

To make structures easier to see by increasing contrast.
5.

Explain why the microscope should be focused using the low-power objective lens before switching to a higher magnification.

It makes it easier to find and focus the specimen before increasing magnification.
6.

Explain why biological drawings should be drawn using clear, continuous lines without shading.

To produce an accurate scientific drawing that clearly shows the structures.

4.1.1.3 Cell Specialisation

1.

What is meant by a specialised cell?

A cell adapted to carry out a particular function.
2.

State one adaptation of a sperm cell.

A long tail (flagellum) to swim to the egg.
3.

State one adaptation of a nerve cell.

A long axon to carry electrical impulses over long distances.
4.

State one adaptation of a root hair cell.

A large surface area for absorbing water and mineral ions.
5.

Explain how the structure of a muscle cell helps it carry out its function.

Muscle cells contain many mitochondria to provide energy for contraction.
6.

Explain why xylem cells are adapted for transporting water.

Xylem cells are hollow with no end walls, allowing water to flow through them.

4.1.1.4 Cell Differentiation

1.

What is meant by cell differentiation?

The process by which a cell changes to become specialised for a particular function.
2.

At what stage do most animal cells differentiate?

At an early stage of development.
3.

Why can many plant cells continue to differentiate throughout their lives?

They contain meristems where cells continue to divide and differentiate.
4.

Why is cell division in mature animals mainly restricted to repair and replacement?

Most cells have already differentiated, so cell division is mainly for growth, repair and replacement.
5.

Explain how differentiation produces specialised cells.

Different genes are switched on and off, producing cells with different structures and functions.
6.

Explain why specialised cells contain different sub-cellular structures.

Different specialised cells require different structures to carry out their functions efficiently.

4.1.1.5 Microscopy

1.

Which type of microscope has the greatest magnification?

An electron microscope.
2.

Which type of microscope has the greatest resolving power?

An electron microscope.
3.

What is meant by the resolution of a microscope?

The ability to distinguish between two points that are close together.
4.

What equation is used to calculate magnification?

Magnification = Image size ÷ Real size
5.

Explain why electron microscopes have improved scientists' understanding of cell structure.

They have much greater magnification and resolution, allowing smaller cell structures to be seen.
6.

Calculate the magnification of an image that is 20 mm long if the real object is 0.02 mm long.

Magnification = Image size ÷ Real size = 20 mm ÷ 0.02 mm = 1000

4.1.2.1 Chromosomes

1.

Where are chromosomes found in a cell?

In the nucleus.
2.

What molecule are chromosomes made from?

DNA.
3.

What is a gene?

A section of DNA that codes for a protein.
4.

How are chromosomes usually arranged in human body cells?

In 23 pairs.
5.

Explain why chromosomes are important.

They contain the genetic information needed to control cell activities and inheritance.
6.

Explain the relationship between DNA, chromosomes and genes.

Chromosomes are made of DNA, and genes are sections of DNA found on chromosomes.

4.1.2.2 Mitosis and the Cell Cycle

1.

What is mitosis?

A type of cell division that produces two genetically identical daughter cells.
2.

What happens to the DNA before a cell divides?

It is copied so there are two copies of each chromosome.
3.

How many genetically identical cells are produced by mitosis?

Two.
4.

Why do cells increase the number of mitochondria and ribosomes before dividing?

To prepare the new cells so they can make proteins and release energy.
5.

Explain why mitosis is important for growth and repair.

It produces identical cells needed for growth and replacing damaged or worn-out cells.
6.

Describe the three main stages of the cell cycle.

DNA is replicated → Cell grows and increases sub-cellular structures → Mitosis and cell division produce two identical daughter cells.

4.1.2.3 Stem Cells

1.

What is a stem cell?

An undifferentiated cell that can divide and differentiate into different types of specialised cells.
2.

Where are stem cells found in human embryos?

In embryos.
3.

Where are stem cells found in adult humans?

In bone marrow.
4.

How can stem cells from plant meristems be useful in agriculture?

They can produce clones of plants quickly and cheaply with desired characteristics.
5.

Explain one medical use of stem cells.

They can replace damaged cells, for example treating leukaemia using bone marrow stem cells.
6.

Explain one ethical concern about the use of embryonic stem cells.

Destroying embryos to obtain stem cells raises ethical concerns because some believe embryos are potential human life.

4.1.3.1 Diffusion

1.

What is diffusion?

The net movement of particles from an area of higher concentration to an area of lower concentration.
2.

In which direction do particles move during diffusion?

Down a concentration gradient (from high to low concentration).
3.

State three factors that affect the rate of diffusion.

Concentration gradient, temperature and surface area.
4.

Why do single-celled organisms not need specialised exchange surfaces?

They have a large surface area to volume ratio, so diffusion is fast enough.
5.

Explain why multicellular organisms need specialised exchange surfaces.

They have a small surface area to volume ratio and diffusion alone is too slow.
6.

Explain how the lungs are adapted for efficient diffusion.

The lungs have a large surface area, thin walls and a good blood supply.

4.1.3.2 Osmosis

1.

What is osmosis?

The net movement of water molecules through a partially permeable membrane from a dilute solution to a more concentrated solution.
2.

Through what type of membrane does osmosis occur?

A partially permeable membrane.
3.

In which direction does water move during osmosis?

From a dilute solution (high water concentration) to a concentrated solution (low water concentration).
4.

Explain what happens to a plant cell placed in a very dilute solution.

Water enters the cell by osmosis and it becomes turgid.
5.

Explain what happens to a plant cell placed in a concentrated sugar solution.

Water leaves the cell by osmosis and it becomes flaccid (or plasmolysed if enough water is lost).
6.

Explain the difference between diffusion and osmosis.

Diffusion is the movement of any particles. Osmosis is the movement of water molecules only through a partially permeable membrane.

Required Practical 2: Osmosis

1.

Which plant tissue is commonly used in the osmosis required practical?

Potato tissue.
2.

In the potato osmosis required practical, which variable is deliberately changed?

The concentration of the sugar solution.
3.

In the potato osmosis required practical, what measurement is recorded before and after placing the potato cylinders in solution?

The mass of the potato cylinders.
4.

Why should all potato cylinders be cut to the same size in the potato osmosis required practical?

To ensure it is a fair test because they all have the same surface area to volume ratio.
5.

Explain why the mass of potato cylinders changes when they are placed in different sugar solutions.

Water moves into or out of the potato cells by osmosis depending on the concentration of the solution.
6.

Explain how the results of the potato osmosis required practical can be used to estimate the concentration of the potato cells.

The concentration where there is no change in mass is the estimated concentration of the potato cells.

4.1.3.3 Active Transport

1.

What is active transport?

The movement of substances from a low concentration to a high concentration against the concentration gradient using energy from respiration.
2.

In which direction do substances move during active transport?

From low concentration to high concentration.
3.

Why does active transport require energy?

Because substances are moved against the concentration gradient.
4.

Give one example of where active transport occurs in plants.

Absorption of mineral ions by root hair cells.
5.

Give one example of where active transport occurs in humans.

Absorption of glucose in the small intestine.
6.

Explain two differences between diffusion and active transport.

Diffusion moves substances down the concentration gradient and does not require energy. Active transport moves substances against the concentration gradient and requires energy.

Topic 2: Organisation

4.2.1 Principles of Organisation

1.

What is a cell?

A cell is the basic unit of structure and function in living organisms.
2.

What is a tissue?

A tissue is a group of similar cells working together to carry out a particular function.
3.

What is an organ?

An organ is a group of different tissues working together to perform a particular function.
4.

What is an organ system?

An organ system is a group of organs working together to perform a particular function.
5.

Put these in order from smallest to largest: organ, organism, tissue, cell, organ system.

Cell → Tissue → Organ → Organ system → Organism.
6.

Explain how cells are organised to form an organism.

Similar cells form tissues, tissues form organs, organs work together in organ systems, and organ systems make up an organism.

4.2.2.1 The Human Digestive System

1.

What is the main function of the digestive system?

To break down food into small soluble molecules that can be absorbed into the blood.
2.

Where does digestion begin in the human body?

The mouth.
3.

Name the organ where most absorption of digested food occurs.

The small intestine.
4.

State the role of the small intestine in digestion and absorption.

Completes digestion and absorbs soluble products of digestion into the bloodstream.
5.

Explain why digestion produces small soluble molecules.

Small soluble molecules can pass through the walls of the small intestine into the blood.
6.

Explain how the digestive system and circulatory system work together.

The digestive system breaks food into soluble molecules, which the circulatory system transports to cells throughout the body.

Enzymes and Metabolism

1.

What type of biological molecule are enzymes?

Proteins.
2.

What is the function of enzymes?

To act as biological catalysts that speed up chemical reactions.
3.

What is the active site of an enzyme?

The part of the enzyme where the substrate binds.
4.

Explain why enzymes are specific to their substrates.

Each enzyme has an active site with a specific shape that only fits one substrate.
5.

Describe the lock and key model of enzyme action.

The substrate has a complementary shape to the enzyme's active site.
6.

Explain why changes in temperature can affect enzyme activity.

High temperatures change the shape of the active site (denature the enzyme), reducing or stopping enzyme activity.

Digestive Enzymes

1.

Which enzyme breaks down starch?

Amylase.
2.

Which enzyme breaks down proteins?

Protease.
3.

Which enzyme breaks down lipids?

Lipase.
4.

What are the products of protein digestion?

Amino acids.
5.

What are the products of lipid digestion?

Fatty acids and glycerol.
6.

Explain why the products of digestion can be absorbed into the bloodstream.

They are small and soluble, so they can pass through the wall of the small intestine into the bloodstream.

Bile

1.

Where is bile produced?

The liver.
2.

Where is bile stored?

The gall bladder.
3.

What is the role of bile in digestion?

Neutralises stomach acid and emulsifies fats.
4.

Why does bile neutralise stomach acid?

To provide the optimum alkaline pH for enzymes in the small intestine.
5.

Explain how bile increases the rate of fat digestion.

It breaks large fat droplets into smaller droplets, increasing the surface area for lipase.
6.

Explain why lipase works more effectively after bile has acted on fats.

Emulsification increases the surface area, allowing lipase to digest fats more quickly.

Required Practical – Food Tests

1.

What reagent is used to test for reducing sugars?

Benedict's solution.
2.

Describe the method and positive result for the test for reducing sugars.

Add Benedict's solution to the food sample and heat in a water bath. A positive result changes from blue to green, yellow, orange or brick-red depending on the amount of reducing sugar present.
3.

What reagent is used to test for starch, and what is the positive result?

Iodine solution. A positive result changes from orange-brown to blue-black.
4.

What reagent is used to test for protein, and what is the positive result?

Biuret reagent. A positive result changes from blue to lilac/purple.
5.

Describe the method and positive result for the test for lipids.

Add ethanol to the food sample and shake. Pour the mixture into water. A positive result is a cloudy white (milky) emulsion.
6.

Why should clean test tubes and equal sample volumes be used in food tests?

To ensure a fair test by preventing contamination and allowing valid comparisons between samples.

4.2.2.2 The Heart and Blood Vessels

1.

What is the main function of the heart?

To pump blood around the body.
2.

What type of circulatory system do humans have?

A double circulatory system.
3.

Which side of the heart pumps blood to the lungs?

The right side.
4.

Which side of the heart pumps blood around the body?

The left side.
5.

Name the five main blood vessels associated with the heart.

Aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries.
6.

Explain why the heart is described as a double circulatory system.

Blood passes through the heart twice during one complete circulation of the body.

Structure of the Heart

7.

Which organ pumps blood around the body?

The heart.
8.

What is the function of the ventricles?

To pump blood out of the heart.
9.

What is the function of the atria?

To receive blood returning to the heart.
10.

Why is the left ventricle thicker than the right ventricle?

It pumps blood at higher pressure around the whole body.
11.

Explain why the heart muscle needs its own blood supply.

The heart muscle needs oxygen and glucose for aerobic respiration.
12.

Explain the role of the natural pacemaker and state where it is found.

It generates electrical impulses that control the heart rate and is found in the right atrium of the heart.

The Lungs and Gas Exchange

1.

What gas enters the blood in the lungs?

Oxygen.
2.

What gas leaves the blood in the lungs?

Carbon dioxide.
3.

What structure in the lungs is adapted for gas exchange?

Alveoli.
4.

Name the blood vessels surrounding alveoli.

Capillaries.
5.

Explain how alveoli are adapted for gas exchange.

Large surface area, moist surface, thin walls (one cell thick) and a good blood supply.
6.

Explain why a good blood supply increases the efficiency of gas exchange.

It maintains a steep concentration gradient for rapid diffusion.

Blood Vessels

1.

Name the three types of blood vessel.

Arteries, veins and capillaries.
2.

Which blood vessel carries blood away from the heart?

Arteries.
3.

Which blood vessel carries blood towards the heart?

Veins.
4.

Explain why arteries have thick muscular walls.

To withstand the high pressure of blood pumped from the heart.
5.

Explain why capillaries have thin walls.

To provide a short diffusion distance for substances.
6.

Compare the structures of arteries, veins and capillaries.

Arteries have thick muscular, elastic walls and a small lumen; veins have thinner walls, a large lumen and valves; capillaries have walls one cell thick for efficient exchange.

4.2.2.3 Blood

1.

What is plasma?

Plasma is the liquid part of the blood that transports cells and dissolved substances.
2.

What is the function of red blood cells?

To transport oxygen.
3.

What is the function of white blood cells?

To defend the body against pathogens.
4.

What is the function of platelets?

To help blood clot.
5.

Explain how red blood cells are adapted to their function.

They contain haemoglobin, have no nucleus and have a biconcave shape, giving a large surface area for oxygen transport.
6.

Explain why blood is described as a tissue.

It is made up of different specialised cells working together to carry out a function.

4.2.2.4 Coronary Heart Disease

1.

What causes coronary heart disease?

Fatty deposits build up in the coronary arteries, reducing blood flow to the heart muscle.
2.

Why is reduced blood flow to the heart dangerous?

The heart muscle receives less oxygen, increasing the risk of a heart attack.
3.

What is the function of a stent?

To keep a narrowed coronary artery open.
4.

What do statins do?

They reduce blood cholesterol levels.
5.

What is the difference between a biological valve and a mechanical valve?

Biological valves are made from animal or human tissue and usually do not require lifelong anticoagulants. Mechanical valves are artificial, last longer but require lifelong anticoagulants.
6.

Evaluate the advantages and disadvantages of heart transplants and artificial hearts.

Heart transplants can greatly improve quality of life but there is a shortage of donors and risk of rejection. Artificial hearts can keep patients alive while waiting for a transplant but can increase the risk of blood clots and infection.

4.2.2.5 Health Issues

1.

What is health?

Health is the state of physical and mental wellbeing.
2.

What is the difference between a communicable and a non-communicable disease?

Communicable diseases are caused by pathogens and can spread between organisms. Non-communicable diseases cannot be spread.
3.

Give two factors other than disease that affect health.

Diet, stress, life situation or exercise (any two).
4.

How can a weakened immune system affect health?

It makes a person more likely to develop infectious diseases.
5.

Explain how viruses can increase the risk of cancer.

Some viruses damage DNA in cells, increasing the risk of uncontrolled cell division and cancer.
6.

Explain how different diseases can interact with one another.

One disease can trigger another or make it more likely, for example a weakened immune system increasing susceptibility to infectious diseases.

4.2.2.6 Effect of Lifestyle on Non-Communicable Diseases

1.

What is a risk factor?

A risk factor is something that increases the chance of developing a disease.
2.

How does smoking affect the lungs?

Smoking damages the lungs and can cause lung disease and lung cancer.
3.

How does alcohol affect the liver?

Alcohol can damage liver cells, causing cirrhosis.
4.

Why is obesity a risk factor for Type 2 diabetes?

Obesity increases insulin resistance, increasing the risk of Type 2 diabetes.
5.

How can smoking affect an unborn baby?

It increases the risk of premature birth, low birth weight and developmental problems.
6.

Explain why many non-communicable diseases have more than one risk factor.

Most non-communicable diseases result from a combination of lifestyle, environmental and genetic risk factors.

4.2.2.7 Cancer

1.

What is a tumour?

A tumour is a mass of abnormal cells formed by uncontrolled cell division.
2.

What is a benign tumour?

A benign tumour is contained in one place and does not spread.
3.

What is a malignant tumour?

A malignant tumour invades surrounding tissues and spreads to other parts of the body.
4.

How do malignant tumours spread around the body?

Through the blood or lymphatic system.
5.

Give one lifestyle risk factor for cancer.

Smoking.
6.

Compare benign and malignant tumours.

Benign tumours remain in one place and are usually not cancerous, whereas malignant tumours spread around the body and are cancerous.

4.2.3.1 Plant Tissues

1.

What is the function of epidermal tissue?

Epidermal tissue covers and protects the plant.
2.

What is the function of palisade mesophyll cells?

To carry out photosynthesis.
3.

What is the function of spongy mesophyll?

It allows gases to diffuse through air spaces.
4.

What is the function of xylem tissue?

To transport water and mineral ions from the roots to the leaves and provide support.
5.

What is the function of phloem tissue?

To transport dissolved sugars produced by photosynthesis.
6.

Explain why meristem tissue is important for plant growth.

Meristem tissue contains unspecialised cells that divide and differentiate, allowing the plant to grow.

4.2.3.2 Plant Organ System

1.

What is transpiration?

The loss of water vapour from the leaves.
2.

What is translocation?

The transport of dissolved sugars around the plant.
3.

How are root hair cells adapted for absorbing water?

They have a large surface area, thin walls and many mitochondria for active transport.
4.

How is xylem adapted for transporting water?

Xylem vessels are dead, hollow cells joined end to end with no end walls and strengthened with lignin.
5.

What is the role of guard cells?

Guard cells open and close the stomata to control gas exchange and water loss.
6.

Explain how temperature, light intensity, humidity and wind speed affect the rate of transpiration.

Higher temperature, higher light intensity and higher wind speed increase transpiration. Higher humidity decreases transpiration.

Topic 3: Infection and Response

4.3.1.1 Communicable (Infectious) Diseases

1.

What is a pathogen?

A disease caused by a pathogen that can be passed from one organism to another.
2.

Name the four types of pathogen.

Bacteria, viruses, fungi and protists.
3.

Give three ways pathogens can spread.

Air, water and direct contact. (Also acceptable: contaminated food.)
4.

How do bacteria make us ill?

They produce toxins that damage tissues and make us ill.
5.

How do viruses cause disease?

They reproduce inside living cells, damaging or destroying the cells.
6.

Explain how the spread of communicable diseases can be reduced.

Good hygiene, isolating infected individuals, destroying vectors and vaccination.

4.3.1.2 Viral Diseases

1.

What type of pathogen causes measles?

A virus.
2.

How is measles spread?

By droplets from coughs and sneezes.
3.

Why are children vaccinated against measles?

To develop immunity and prevent the spread of the disease.
4.

How is HIV spread?

Through sexual contact or exchange of body fluids, including infected blood.
5.

How does HIV damage the body?

It attacks and damages the immune system.
6.

Explain how tobacco mosaic virus affects plant growth.

It causes discolouration of leaves, reducing photosynthesis and stunting growth.

4.3.1.3 Bacterial Diseases

1.

What type of pathogen causes salmonella?

Bacteria.
2.

How is salmonella spread?

By eating contaminated food.
3.

Name two symptoms of salmonella food poisoning.

Fever, stomach cramps, vomiting or diarrhoea. (Any two.)
4.

How is salmonella controlled in UK poultry?

Poultry are vaccinated against salmonella.
5.

How is gonorrhoea spread?

Through sexual contact.
6.

Explain why gonorrhoea has become more difficult to treat.

Some bacteria have become antibiotic resistant.

4.3.1.4 Fungal Diseases

1.

Which fungus causes rose black spot?

Rose black spot fungus.
2.

What are the symptoms of rose black spot?

Purple or black spots on leaves and early leaf loss.
3.

How is rose black spot spread?

By spores carried in the wind or water.
4.

Why does rose black spot reduce plant growth?

Less photosynthesis occurs because leaves are damaged or lost.
5.

How can rose black spot be treated?

Using fungicides and removing infected leaves.
6.

Explain why removing infected leaves helps control the disease.

It reduces the spread of fungal spores to healthy plants.

4.3.1.5 Protist Diseases

1.

What type of pathogen causes malaria?

A protist.
2.

Which organism carries malaria?

The mosquito.
3.

Name one symptom of malaria.

Fever. (Also acceptable: chills or flu-like symptoms.)
4.

Why is the mosquito called a vector?

It carries the pathogen from one host to another.
5.

How can mosquito nets reduce malaria?

They prevent mosquito bites.
6.

Explain two methods used to control the spread of malaria.

Use insecticides and remove mosquito breeding sites/use mosquito nets.

4.3.1.6 Human Defence Systems

1.

How does the skin help prevent infection?

The skin acts as a physical barrier and secretes antimicrobial substances.
2.

How does the nose help stop pathogens entering the body?

The nose contains hairs and mucus that trap pathogens.
3.

What is the function of mucus in the trachea and bronchi?

Mucus traps pathogens and cilia move the mucus to the throat where it is swallowed.
4.

How does stomach acid protect the body?

Hydrochloric acid kills many pathogens that enter the stomach.
5.

Name the three ways white blood cells defend the body.

Phagocytosis, producing antibodies and producing antitoxins.
6.

Explain the roles of phagocytosis, antibodies and antitoxins in defending against disease.

Phagocytes engulf and digest pathogens, antibodies bind to specific pathogens to destroy them, and antitoxins neutralise toxins released by bacteria.

4.3.1.7 Vaccination

1.

What is a vaccine?

A way of protecting people against disease by stimulating the immune system.
2.

What does a vaccine contain?

Dead or inactive pathogens, or parts of pathogens (antigens).
3.

Why are vaccines given before a person catches a disease?

So the body develops immunity before infection occurs.
4.

How do white blood cells respond after vaccination?

They produce specific antibodies and memory cells.
5.

Why does vaccination usually provide long-term protection?

Memory cells remain in the body and produce antibodies quickly if the pathogen enters again.
6.

Explain how vaccinating a large proportion of the population reduces the spread of disease.

It reduces the number of people who can catch and spread the disease, reducing transmission (herd immunity).

4.3.1.8 Antibiotics and Painkillers

1.

What are antibiotics used to treat?

Bacterial diseases.
2.

Give one example of an antibiotic.

Penicillin.
3.

Why can't antibiotics treat viral diseases?

Viruses reproduce inside body cells, so antibiotics cannot destroy them.
4.

What do painkillers do?

They relieve symptoms such as pain but do not kill pathogens.
5.

What is antibiotic resistance?

When bacteria are no longer killed by antibiotics.
6.

Explain why antibiotic-resistant bacteria are a serious problem.

Infections become harder to treat, increasing the risk of illness and death.

4.3.1.9 Discovery and Development of Drugs

1.

Which plant is the source of aspirin?

Willow.
2.

Which plant is the source of digitalis?

Foxglove.
3.

Who discovered penicillin?

Alexander Fleming.
4.

What is tested during preclinical drug testing?

Toxicity, efficacy and dosage are tested using cells, tissues and live animals.
5.

Why are double-blind clinical trials used?

To reduce bias and produce valid, reliable results.
6.

Explain why new drugs must be tested for toxicity, efficacy and optimum dose before they are approved.

To ensure the drug is safe, works effectively and the correct dose is identified before it is licensed.

Topic 4: Bioenergetics

4.4.1.1 Photosynthetic Reaction

1.

What is photosynthesis?

Photosynthesis is the process by which plants use light energy to produce glucose from carbon dioxide and water.
2.

What are the two reactants in photosynthesis?

Carbon dioxide and water.
3.

What are the two products of photosynthesis?

Glucose and oxygen.
4.

In which organelle does photosynthesis take place?

Chloroplasts.
5.

Why is photosynthesis described as an endothermic reaction?

Because it absorbs energy from light.
6.

Write the word equation for photosynthesis.

Carbon dioxide + water → glucose + oxygen (light energy and chlorophyll required).

4.4.1.2 Rate of Photosynthesis

1.

Name four factors that affect the rate of photosynthesis.

Light intensity, carbon dioxide concentration, temperature and chlorophyll concentration.
2.

What is meant by a limiting factor?

A factor that is in shortest supply and therefore limits the rate of photosynthesis.
3.

How does increasing light intensity affect the rate of photosynthesis?

The rate increases until another factor becomes limiting.
4.

How does increasing carbon dioxide concentration affect photosynthesis?

The rate increases until another factor becomes limiting.
5.

Explain how temperature affects the rate of photosynthesis.

Increasing temperature increases the rate up to the optimum temperature; above this, enzymes denature and the rate decreases.
6.

Explain how growers use limiting factors to increase crop yield in greenhouses.

They increase light intensity, carbon dioxide concentration and temperature to maximise the rate of photosynthesis and crop yield.

4.4.1.3 Uses of Glucose from Photosynthesis

1.

What process uses glucose to release energy?

Respiration.
2.

Why is glucose converted into starch?

Starch is insoluble, so it can be stored.
3.

How is glucose used to make cellulose?

It is converted into cellulose to make cell walls.
4.

How is glucose used to produce fats and oils?

It is converted into lipids for energy storage.
5.

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

Nitrate ions.
6.

Explain five different uses of glucose made during photosynthesis.

Respiration, making starch, making cellulose, making amino acids (with nitrate ions) and making fats and oils.

4.4.2.1 Aerobic and Anaerobic Respiration

1.

What is respiration?

Respiration is the process that transfers energy from glucose.
2.

What type of reaction is respiration?

An exothermic reaction.
3.

What is the word equation for aerobic respiration?

Glucose + oxygen → carbon dioxide + water.
4.

What is the word equation for anaerobic respiration in muscles?

Glucose → lactic acid.
5.

What are the products of anaerobic respiration in yeast?

Ethanol and carbon dioxide.
6.

Compare aerobic and anaerobic respiration in terms of oxygen required, products and energy released.

Aerobic respiration requires oxygen, releases more energy and produces carbon dioxide and water. Anaerobic respiration does not require oxygen, releases less energy and produces lactic acid in animals or ethanol and carbon dioxide in yeast.

4.4.2.2 Response to Exercise

1.

What happens to heart rate during exercise?

It increases.
2.

What happens to breathing rate during exercise?

It increases.
3.

Why do muscles carry out anaerobic respiration during vigorous exercise?

The muscles cannot receive enough oxygen for aerobic respiration.
4.

What causes muscles to become fatigued?

Lactic acid builds up in the muscles.
5.

What is oxygen debt?

The extra oxygen needed to react with the lactic acid produced during anaerobic respiration.
6.

Explain how the body removes lactic acid after exercise.

Lactic acid is carried by the blood to the liver, where it is broken down using oxygen.

4.4.2.3 Metabolism

1.

What is metabolism?

Metabolism is the sum of all the chemical reactions that take place in a cell or the body.
2.

What process provides the energy needed for metabolism?

Respiration.
3.

What is glucose converted into for storage in animals?

Glycogen.
4.

What is glucose converted into for storage in plants?

Starch.
5.

How are amino acids used in metabolism?

Amino acids are used to make proteins.
6.

Describe the main reactions that are part of metabolism.

The conversion of glucose to starch, glycogen and cellulose. The formation of lipids from glycerol and fatty acids. The use of glucose and nitrate ions to make amino acids, which are then used to make proteins. Respiration, where glucose is broken down to transfer energy. The breakdown of excess proteins to form urea for excretion.

Paper 2

Topic 5: Homeostasis and Response

4.5.1 Homeostasis

1.

What is homeostasis?

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
2.

Name three conditions controlled by homeostasis.

Body temperature, blood glucose concentration and water content.
3.

What is a receptor?

A cell or group of cells that detect a stimulus.
4.

What is an effector?

A muscle or gland that brings about a response.
5.

Name three coordination centres in the body.

The brain, spinal cord and pancreas.
6.

Explain how receptors, coordination centres and effectors work together to maintain homeostasis.

Receptors detect a stimulus, coordination centres process the information, and effectors produce a response to restore optimum conditions.

4.5.2 The Human Nervous System

1.

What is the function of the nervous system?

To detect stimuli and coordinate the body's responses.
2.

What does CNS stand for?

Central Nervous System.
3.

Which two organs make up the central nervous system?

The brain and spinal cord.
4.

Put these in order: stimulus, receptor, coordinator, effector, response.

Stimulus → Receptor → Coordinator → Effector → Response.
5.

What is a reflex action?

A rapid, automatic response to a stimulus that does not involve conscious thought.
6.

Explain how a reflex arc produces a rapid response.

A stimulus is detected by receptors, impulses travel along sensory neurones to the CNS, then along motor neurones to an effector, which produces a rapid response.

4.5.3.1 Human Endocrine System

1.

What is a hormone?

A chemical messenger produced by a gland and carried in the blood.
2.

What is the endocrine system?

A system of glands that produce and release hormones.
3.

How are hormones transported around the body?

In the bloodstream.
4.

Why is the pituitary gland called the "master gland"?

It releases hormones that control other endocrine glands.
5.

State one difference between the endocrine system and the nervous system.

Hormones act more slowly but have longer-lasting effects than nerve impulses.
6.

Compare hormonal coordination with nervous coordination.

Hormonal coordination is slower, carried in the blood and longer lasting, whereas nervous coordination is rapid, carried by neurones and usually has short-lived effects.

4.5.3.2 Control of Blood Glucose Concentration

1.

Which organ monitors blood glucose concentration?

The pancreas.
2.

Which hormone lowers blood glucose concentration?

Insulin.
3.

What is glycogen?

A stored form of glucose.
4.

What causes Type 1 diabetes?

The pancreas produces little or no insulin.
5.

How is Type 2 diabetes commonly treated?

By a carbohydrate-controlled diet, exercise and weight loss (sometimes medication).
6.

Compare Type 1 and Type 2 diabetes.

Type 1 diabetes is caused by little or no insulin production and requires insulin therapy. Type 2 diabetes is linked to lifestyle and insulin resistance and is often managed with diet, exercise and medication.

4.5.3.3 Hormones in Human Reproduction

1.

Which hormone is the main female reproductive hormone?

Oestrogen.
2.

Which hormone is the main male reproductive hormone?

Testosterone.
3.

What is ovulation?

The release of an egg from an ovary.
4.

What is the function of FSH?

FSH stimulates the maturation of an egg in an ovary.
5.

What is the function of LH?

LH stimulates ovulation.
6.

Explain the roles of FSH, LH, oestrogen and progesterone in the menstrual cycle.

FSH stimulates egg maturation, oestrogen inhibits FSH and stimulates LH, LH triggers ovulation, and progesterone maintains the lining of the uterus and inhibits FSH and LH.

4.5.3.4 Contraception

1.

What is contraception?

The prevention of pregnancy.
2.

Give one hormonal method of contraception.

The contraceptive pill. (Also acceptable: contraceptive patch, implant or injection.)
3.

Give one non-hormonal method of contraception.

Condoms. (Also acceptable: diaphragm or abstinence.)
4.

How does the contraceptive pill prevent pregnancy?

It contains hormones that inhibit FSH so no egg matures, and/or prevent ovulation.
5.

How do condoms prevent pregnancy?

They act as a barrier to stop sperm reaching the egg.
6.

Compare hormonal and non-hormonal methods of contraception.

Hormonal methods use hormones to prevent ovulation or fertilisation and are usually highly effective but may have side effects. Non-hormonal methods do not use hormones and include barrier methods such as condoms, which also reduce the spread of STIs.

4.5.3.5 The Use of Hormones to Treat Infertility (HT)

1.

What is infertility?

The inability to conceive naturally after regular unprotected intercourse.
2.

Which two hormones are used in fertility drugs?

FSH and LH.
3.

What does IVF stand for?

In Vitro Fertilisation.
4.

Why are FSH and LH given before IVF?

FSH stimulates egg maturation and LH triggers ovulation.
5.

Describe the main stages of IVF treatment.

FSH and LH are given to mature eggs, eggs are collected from the ovaries, sperm are used to fertilise the eggs in a laboratory, and one or two embryos are transferred into the uterus.
6.

Evaluate the advantages and disadvantages of IVF.

Advantages: can help infertile couples have children. Disadvantages: expensive, emotionally stressful, success rates are not guaranteed and there is an increased chance of multiple births.

4.5.3.6 Feedback Systems (HT)

1.

Which gland produces adrenaline?

The adrenal glands.
2.

Which gland produces thyroxine?

The thyroid gland.
3.

What is the function of adrenaline?

It prepares the body for a "fight or flight" response by increasing heart rate and blood flow to muscles.
4.

What is the function of thyroxine?

It controls the body's metabolic rate.
5.

What is negative feedback?

A control mechanism that reverses a change to keep internal conditions stable.
6.

Explain how negative feedback helps control thyroxine levels.

If thyroxine levels are too low, the pituitary releases more TSH to stimulate the thyroid. If thyroxine levels are too high, less TSH is released, reducing thyroxine production.

Topic 6: Inheritance, Variation and Evolution

4.6.1.1 Sexual and Asexual Reproduction

1.

What is sexual reproduction?

Reproduction involving the fusion of male and female gametes.
2.

What is asexual reproduction?

Reproduction involving only one parent with no fusion of gametes.
3.

Which type of cell division produces gametes?

Meiosis.
4.

Which type of cell division produces genetically identical cells?

Mitosis.
5.

Why does sexual reproduction produce variation?

Offspring inherit a mixture of alleles from both parents, creating genetic variation.
6.

Compare sexual and asexual reproduction.

Sexual reproduction produces genetically varied offspring and involves two parents. Asexual reproduction produces genetically identical offspring (clones) and involves one parent.

4.6.1.2 Meiosis

1.

What is meiosis?

Cell division that produces gametes.
2.

Where does meiosis take place?

In the reproductive organs (ovaries and testes).
3.

How many gametes are produced from one cell?

Four.
4.

Why are gametes genetically different?

Because chromosomes are mixed and separated randomly.
5.

What happens to chromosome number during meiosis and fertilisation?

Meiosis halves the chromosome number to 23; fertilisation restores it to 46.
6.

Explain how meiosis and fertilisation produce variation.

Meiosis produces genetically different gametes, and fertilisation combines genes from two parents, producing variation.

4.6.1.3 DNA and the Genome

1.

What does DNA stand for?

Deoxyribonucleic acid.
2.

What is a chromosome?

A long molecule of DNA containing many genes.
3.

What is a gene?

A section of DNA that codes for a protein.
4.

What is a genome?

The entire genetic material of an organism.
5.

What does a gene code for?

A specific sequence of amino acids to make a protein.
6.

Give three benefits of understanding the human genome.

Identify genes linked to disease, understand inherited disorders and develop new treatments.

4.6.1.4 Genetic Inheritance

1.

What is an allele?

An alternative version of a gene.
2.

What is the difference between dominant and recessive alleles?

A dominant allele is expressed if present; a recessive allele is only expressed if two copies are present.
3.

What is meant by homozygous?

Having two identical alleles.
4.

What is meant by heterozygous?

Having two different alleles.
5.

What is the difference between genotype and phenotype?

Genotype is the genetic makeup; phenotype is the observable characteristics.
6.

Complete and interpret a simple Punnett square for a single gene cross.

Use the parental alleles to complete the Punnett square, determine the possible offspring genotypes and phenotypes, and calculate the probabilities.

4.6.1.5 Inherited Disorders

1.

What is an inherited disorder?

A disorder caused by inheriting one or more faulty alleles from parents.
2.

Which inherited disorder is caused by a dominant allele?

Polydactyly.
3.

Which inherited disorder is caused by a recessive allele?

Cystic fibrosis.
4.

What is polydactyly?

An inherited disorder in which a person is born with extra fingers or toes.
5.

What is cystic fibrosis?

An inherited disorder that causes thick, sticky mucus to build up in the lungs and digestive system.
6.

Explain the ethical issues surrounding embryo screening.

Embryo screening can prevent serious inherited disorders, but some people believe it is unethical because embryos may be destroyed and it could be used to select preferred characteristics rather than prevent disease.

4.6.1.6 Sex Determination

1.

How many pairs of chromosomes do humans have?

23 pairs (46 chromosomes).
2.

What are the female sex chromosomes?

XX.
3.

What are the male sex chromosomes?

XY.
4.

Which parent determines the sex of a baby?

The father, because sperm carry either an X or a Y chromosome.
5.

What is the probability of having a male child?

50% (1 in 2).
6.

Complete a genetic cross for sex determination.

The mother always passes on an X chromosome. The father passes on either an X or a Y chromosome. XX produces a female and XY produces a male, giving a 50% chance of each.

4.6.2.1 Variation

1.

What is variation?

Differences between individuals of the same species.
2.

Name two causes of variation.

Genetic factors (inherited alleles) and environmental factors.
3.

What is a mutation?

A random change in the DNA sequence of a gene.
4.

Do most mutations affect phenotype?

No, most mutations have little or no effect on the phenotype.
5.

How can environmental factors affect phenotype?

Environmental factors such as diet, climate and lifestyle can influence characteristics.
6.

Explain how mutations can lead to evolution.

Mutations create new alleles. If a mutation gives an advantage, individuals are more likely to survive and reproduce, passing the allele on through natural selection.

4.6.2.2 Evolution

1.

What is evolution?

The gradual change in the inherited characteristics of a population over time.
2.

What is natural selection?

The process where organisms with advantageous characteristics are more likely to survive and reproduce.
3.

Why are some organisms more likely to survive and reproduce?

Because they have advantageous adaptations that make them better suited to their environment.
4.

How can a new species form?

When populations become isolated and evolve differently until they can no longer interbreed.
5.

What is meant by "survival of the fittest"?

Individuals with advantageous characteristics are more likely to survive, reproduce and pass on their alleles.
6.

Explain evolution by natural selection.

Variation exists within a population. Individuals with advantageous characteristics are more likely to survive and reproduce, passing on their alleles. Over many generations these alleles become more common, causing the population to evolve.

4.6.2.3 Selective Breeding

1.

What is selective breeding?

The process of breeding plants or animals with desirable characteristics to produce offspring with those characteristics.
2.

Why do humans selectively breed plants and animals?

To produce organisms with useful characteristics such as disease resistance, higher yield or a good temperament.
3.

Give one example of selective breeding.

Breeding dairy cattle to produce more milk.
4.

How is selective breeding carried out?

Select parents with the desired characteristic, breed them, then select offspring with the characteristic and repeat over many generations.
5.

Give one disadvantage of selective breeding.

It reduces genetic variation, making populations more vulnerable to disease or environmental change.
6.

Evaluate the advantages and disadvantages of selective breeding.

Selective breeding can increase food production and improve desirable traits, but it reduces genetic variation and may increase the chance of inherited health problems.

4.6.2.4 Genetic Engineering

1.

What is genetic engineering?

Changing the genetic material of an organism by inserting a gene from another organism.
2.

What is a genetically modified (GM) crop?

A crop that has had its genes altered using genetic engineering.
3.

Give one medical use of genetic engineering.

Producing human insulin using genetically modified bacteria.
4.

Give one agricultural use of genetic engineering.

Producing crops that are resistant to insects or herbicides.
5.

Give one advantage and one disadvantage of GM crops.

Advantage: Higher crop yields or reduced pesticide use. Disadvantage: Concerns about environmental impacts and the spread of modified genes.
6.

Explain how genetic engineering can benefit medicine and agriculture.

Genetic engineering can produce medicines such as insulin and improve crops by increasing yield, disease resistance or nutritional value, although there are ethical and environmental concerns.

4.6.3.1 Evidence for Evolution

1.

Who proposed the theory of evolution by natural selection?

Charles Darwin.
2.

Name two pieces of evidence for evolution.

Fossils and antibiotic-resistant bacteria.
3.

How do fossils provide evidence for evolution?

Fossils show how organisms have changed over millions of years and provide evidence of extinct species.
4.

How does antibiotic resistance support evolution?

Bacteria evolve resistance through natural selection, showing evolution can occur over short timescales.
5.

Why is evolution widely accepted today?

Because there is now extensive evidence from fossils, genetics and observations of evolution.
6.

Explain how evidence supports the theory of evolution.

Fossils, DNA evidence and observations such as antibiotic resistance all support Darwin's theory that species evolve over time by natural selection.

4.6.3.2 Fossils

1.

What is a fossil?

The preserved remains or traces of ancient organisms.
2.

Give one way fossils can form.

When hard parts do not decay because they are replaced by minerals over millions of years.
3.

Why is the fossil record incomplete?

Many early organisms were soft-bodied and decayed before fossilising, and geological activity has destroyed some fossils.
4.

What can scientists learn from fossils?

They can learn what extinct organisms looked like, how they lived and how species have changed over time.
5.

Why are there few fossils of early soft-bodied organisms?

Soft tissues usually decay before fossilisation can occur.
6.

Explain why fossils are important evidence for evolution.

Fossils provide evidence of organisms that lived in the past and show how species have evolved over time.

4.6.3.3 Extinction

1.

What is extinction?

The permanent loss of a species when no individuals remain alive.
2.

What does it mean if a species is extinct?

It means every member of the species has died.
3.

Give one cause of extinction.

Environmental change.
4.

How can environmental change lead to extinction?

Rapid environmental changes may prevent species from adapting quickly enough to survive.
5.

How can competition contribute to extinction?

Better-adapted species may outcompete others for food, space or mates, causing their numbers to fall.
6.

Explain why species become extinct.

Species become extinct because of factors such as environmental change, new diseases, competition, new predators or catastrophic events, preventing them from surviving and reproducing.

4.6.3.4 Resistant Bacteria

1.

What is antibiotic resistance?

The ability of bacteria to survive treatment with antibiotics.
2.

Why do bacteria evolve quickly?

Because they reproduce rapidly and mutations can occur frequently.
3.

What is MRSA?

A type of bacteria that is resistant to many common antibiotics (Methicillin-resistant Staphylococcus aureus).
4.

Why should antibiotics not be prescribed for viral infections?

Because antibiotics do not kill viruses and are ineffective against viral infections.
5.

Why should patients finish their course of antibiotics?

To ensure all bacteria are killed and reduce the chance of resistant bacteria surviving and reproducing.
6.

Explain how antibiotic-resistant bacteria evolve.

Mutations make some bacteria resistant to an antibiotic. These bacteria survive treatment, reproduce and pass on the resistance gene. Over time, the resistant strain becomes more common through natural selection.

4.6.4 Classification of Living Organisms

1.

Who developed the traditional classification system?

Carl Linnaeus.
2.

What is binomial naming?

The system of giving each organism a two-part Latin name consisting of its genus and species.
3.

List the seven taxonomic groups in order.

Kingdom, Phylum, Class, Order, Family, Genus, Species.
4.

Who developed the three-domain system?

Carl Woese.
5.

Name the three domains.

Archaea, Bacteria and Eukaryota.
6.

Explain why classification systems have changed over time.

Classification systems have changed because new evidence, including DNA analysis and improved technology, has shown that some organisms are more or less closely related than previously thought.

Topic 7: Ecology

4.7.1.1 Communities

1.

What is an ecosystem?

An ecosystem is the interaction of a community of organisms with the non-living parts of their environment.
2.

What is a community?

All the populations of different species living together in a habitat.
3.

Put these in order: organism, population, community, ecosystem.

Organism → Population → Community → Ecosystem.
4.

What is meant by interdependence?

Organisms depend on each other for food, shelter, pollination, seed dispersal and other resources.
5.

What do plants compete for?

Light, space, water and mineral ions.
6.

Explain why removing one species can affect the whole community.

Removing one species can disrupt food chains and interdependence, affecting the survival of other organisms in the community.

4.7.1.2 Abiotic Factors

1.

What is an abiotic factor?

A non-living factor that affects organisms in an ecosystem.
2.

Name four abiotic factors.

Light intensity, temperature, moisture levels and soil pH.
3.

How does light intensity affect plants?

Higher light intensity generally increases the rate of photosynthesis and plant growth.
4.

Why is soil pH important for plants?

Soil pH affects the availability of mineral ions needed for healthy plant growth.
5.

Why are oxygen levels important for aquatic animals?

Aquatic animals need dissolved oxygen for aerobic respiration.
6.

Explain how a change in one abiotic factor can affect a community.

Changes in abiotic factors can affect the survival and distribution of organisms, changing population sizes and the whole community.

4.7.1.3 Biotic Factors

1.

What is a biotic factor?

A living factor that affects organisms in an ecosystem.
2.

Name four biotic factors.

Competition, predation, disease and food availability.
3.

How does food availability affect populations?

More food generally increases population size, while less food causes populations to decrease.
4.

How can a new predator affect a community?

It can reduce the population of prey species and affect the whole food web.
5.

What happens if one species outcompetes another?

The less successful species may decrease in number or be forced out of the habitat.
6.

Explain how changes in biotic factors affect ecosystems.

Changes in biotic factors affect survival and reproduction, altering population sizes and ecosystem balance.

4.7.1.4 Adaptations

1.

What is an adaptation?

A feature that helps an organism survive and reproduce in its environment.
2.

Name the three types of adaptation.

Structural, behavioural and functional.
3.

What is a structural adaptation?

A physical feature that helps an organism survive.
4.

What is a behavioural adaptation?

A way an organism acts that helps it survive.
5.

What is a functional adaptation?

A process inside an organism's body that helps it survive.
6.

Explain why extremophiles are able to survive in extreme environments.

Extremophiles have adaptations that allow their enzymes and cells to function in extreme conditions such as very high temperatures, high salt concentrations or high pressures.

4.7.2.1 Levels of Organisation

1.

What is a producer?

An organism that makes its own food, usually by photosynthesis.
2.

What is a primary consumer?

An organism that eats producers.
3.

What is a predator?

An animal that hunts and eats other animals.
4.

What is prey?

An animal that is hunted and eaten by another animal.
5.

Which sampling methods are used to estimate population size?

Quadrats and transects.
6.

Explain why predator and prey populations rise and fall in cycles.

As prey numbers increase, predator numbers increase because there is more food. More predators then reduce the prey population, causing predator numbers to fall. This cycle then repeats.

4.7.2.2 How Materials are Cycled

1.

Name the two cycles studied in ecology.

The carbon cycle and the water cycle.
2.

Why are materials recycled?

Because materials are needed continuously by living organisms and are present in limited amounts.
3.

What process returns carbon dioxide to the atmosphere?

Respiration.
4.

What process removes carbon dioxide from the atmosphere?

Photosynthesis.
5.

What is the role of microorganisms in the carbon cycle?

They act as decomposers, breaking down dead organisms and waste, releasing carbon dioxide through respiration.
6.

Explain the importance of the carbon and water cycles.

The carbon cycle recycles carbon needed to make carbohydrates, proteins and fats, while the water cycle continually supplies fresh water needed for life.

4.7.3.1 Biodiversity

1.

What is biodiversity?

The variety of all the different species of organisms on Earth or within an ecosystem.
2.

Why is biodiversity important?

It helps maintain stable ecosystems and provides resources such as food and medicines.
3.

Name one human activity that reduces biodiversity.

Deforestation.
4.

How does biodiversity help keep ecosystems stable?

A greater variety of species makes ecosystems more stable because organisms depend on each other.
5.

Why is biodiversity important for humans?

It provides food, medicines, raw materials and helps maintain stable ecosystems.
6.

Explain how human activities reduce biodiversity.

Human activities such as deforestation, pollution, peat extraction and global warming destroy habitats and reduce the variety of species.

4.7.3.2 Waste Management

1.

Name three types of pollution.

Air pollution, water pollution and land pollution.
2.

How can sewage pollute water?

It releases harmful microorganisms and chemicals into rivers and lakes.
3.

How can air pollution be caused?

Burning fossil fuels and releasing smoke or harmful gases.
4.

How does landfill affect the environment?

Landfill uses land, can pollute soil and water, and produces methane gas.
5.

How does pollution affect biodiversity?

Pollution damages habitats, kills organisms and reduces the variety of species.
6.

Explain why increasing human population leads to more pollution.

A growing population produces more waste, increases pollution and destroys more habitats, reducing biodiversity.

4.7.3.3 Land Use

1.

Name four ways humans use land.

Building, farming, quarrying and landfill.
2.

What is a peat bog?

A wetland where dead plant material builds up to form peat.
3.

Why are peat bogs important?

They provide unique habitats and store large amounts of carbon.
4.

What happens when peat is burned?

Carbon dioxide is released into the atmosphere.
5.

How does destroying peat bogs reduce biodiversity?

Habitats are destroyed and stored carbon is released, contributing to climate change.
6.

Explain the conflict between using peat for compost and conserving peat bogs.

Using peat provides compost for gardening, but destroying peat bogs damages habitats, reduces biodiversity and releases carbon dioxide, so conservation is generally more sustainable.

4.7.3.4 Deforestation

1.

What is deforestation?

The clearing of forests.
2.

Give two reasons for deforestation.

To provide land for cattle farming and to grow crops such as biofuels.
3.

Why are forests cleared for cattle farming?

To create grazing land for cattle.
4.

Why are forests cleared to grow biofuel crops?

To produce crops that can be used as renewable fuels.
5.

How does deforestation reduce biodiversity?

It destroys habitats, reduces food sources and can lead to species becoming extinct.
6.

Explain the environmental impacts of deforestation.

Deforestation destroys habitats, reduces biodiversity, increases carbon dioxide levels in the atmosphere and contributes to global warming.

4.7.3.5 Global Warming

1.

Name two greenhouse gases.

Carbon dioxide and methane.
2.

What is global warming?

The long-term increase in the Earth's average temperature caused by increased greenhouse gases.
3.

How does carbon dioxide contribute to global warming?

Carbon dioxide absorbs infrared radiation, trapping heat in the atmosphere.
4.

Name one biological consequence of global warming.

Changes in the distribution of species.
5.

How can global warming affect species distribution?

Species may move to cooler areas or become extinct if they cannot adapt.
6.

Explain how increasing greenhouse gases can affect ecosystems.

Increased greenhouse gases raise global temperatures, causing habitat loss, changes in species distribution, reduced biodiversity and disruption of ecosystems.

4.7.3.6 Maintaining Biodiversity

1.

What is a breeding programme?

A programme where endangered species are bred in captivity to increase their population.
2.

Why are rare habitats protected?

To conserve biodiversity and prevent species from becoming extinct.
3.

Why are hedgerows and field margins important?

They provide habitats, food and shelter for wildlife.
4.

How does recycling help biodiversity?

It reduces the need for landfill and the use of raw materials, helping to protect habitats.
5.

How can reducing deforestation protect biodiversity?

It preserves habitats and prevents species from losing their homes.
6.

Explain how humans can maintain biodiversity.

Humans can maintain biodiversity by protecting habitats, reducing deforestation, running breeding programmes, recycling resources, reducing pollution, creating field margins and hedgerows, and reducing greenhouse gas emissions.