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GCSE Biology · GCSEChapter 18 · Biodiversity and the effect of humans
GCSE · Chapter 18

Biodiversity and the effect of humans

By the end of this chapter you will be able to

  • Explain what biodiversity is and why it matters
  • Evaluate the effect of a human activity on biodiversity
  • Explain bioaccumulation along a food chain
  • Describe conservation methods, and how they protect species
  • [H] Explain eutrophication step by step, and interpret a population graph

You should already know

  • Food chains, energy and cycles (Chapter 17)
  • Organisms and their habitats (KS3 Biology)
  • Extinction and natural selection (Chapter 16)

Where this leads

  • Revision across the course
  • Climate and the carbon cycle (Chapter 17)
  • The microorganisms of the nitrogen cycle (Chapter 17)

GCSE Biology. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Describe biodiversity and why it matters for food, medicines and ecosystem stability, Describe the impact of humans on biodiversity, including deforestation, pollution, global warming and overfishing, Describe pesticides and bioaccumulation, and the methods that protect biodiversity, [H] Explain eutrophication, and interpret population data over time, Describe the effects of climate change on ecosystems.

Exercise P  Do you remember?

1
FName the process by which decomposers return carbon dioxide to the air. Write the word.
2
FWhat is the name of a food chain’s first organism, which makes its own food? Write the word.
3
FWhat is 60 minus 12? Write the number.
4
FWhat is the name of a chemical sprayed on crops to kill pests? Write the word. Accept pesticide.
5
FName the process by which water vapour leaves plants. Write the word.
18.1

Biodiversity and why it matters

GCSE
Describe biodiversity, Explain why biodiversity matters for food, medicines and ecosystem stability
Video lesson: Biodiversity and why it mattersComing soon
Context. Ali walks through two habitats: a rainforest edge with many kinds of plants and animals, and a farm field with one crop. “Which of these has more biodiversity?” he asks. The answer depends on how many different kinds of living things live there.

Biodiversity is the variety of living organisms in an area. It includes the number of different species (species richness) and the variety of genes within each species. Biodiversity matters because it provides food, a source of medicines (many drugs come from plants and microorganisms), and ecosystem stability: an ecosystem with many species can cope better with change, because if one species declines another may take its place.

HabitatSpecies found in the survey (invented)
rainforest edge60
farmland field12
Species found in two habitats (invented data)

Key ideas

  • Biodiversity is the variety of living organisms, including species and genes.
  • Biodiversity provides food and sources of medicines.
  • A variety of species gives ecosystem stability.
  • A habitat with more species generally has higher biodiversity.
Worked example 18.1.1
In the survey, which habitat has more species? Write the words.

Method. Compare the two numbers.

  1. Compare. The rainforest edge has 60 species, and the farmland field has 12.
    60 and 12
  2. Name it. So the rainforest edge has more species.
    rainforest edge
  3. Write the answer.
    rainforest edge

Check. More species means higher biodiversity. ✓

Worked example 18.1.2
Name the variety within a species, in its genes. Write the word.

Method. Recall the genetic variety.

  1. Recall. Genetic diversity is the variety of alleles within a species.
    variety of alleles
  2. Name it. This variety is genetic diversity.
    genetic diversity
  3. Write the answer.
    genetic diversity

Check. Biodiversity includes genetic diversity. ✓

Worked example 18.1.3
Name one medicine that comes from plants or microorganisms. Write the words. Accept aspirin (from willow bark) or penicillin (from a fungus).

Method. Recall a source of medicines.

  1. Recall. Many medicines come from plants and microorganisms.
    from plants and microorganisms
  2. Name one. Penicillin comes from a fungus, and aspirin was first obtained from willow bark.
    penicillin
  3. Write the answer.
    Accept aspirin (from willow bark) or penicillin (from a fungus).

Check. Biodiversity is a store of useful chemicals. ✓

Watch out

Watch out: biodiversity is not the same as the number of individuals. A habitat can have many individuals of one species and very low biodiversity.

Exam tip

Exam tip. When you explain why biodiversity matters, give a named benefit: food, medicines or ecosystem stability.

Try it (with your teacher). With your teacher, count the different kinds of plants in a patch of grass or a school garden in five minutes. Compare your count with a classmate’s, and explain any difference.

Exercise 18A  Biodiversity and why it matters

1
FWhat is biodiversity? Write the words.
2
FName the level of biodiversity that is the variety of genes within a species. Write the words.
3
FName one benefit of biodiversity for food. Write one sentence. Accept any sentence that says a variety of crops and animals gives food security.
4
FWhy does a species-rich ecosystem tend to be more stable? Write one sentence. Accept any sentence that says if one species declines, another can fill its role.
5
FWhich habitat in the survey has fewer species: the rainforest edge or the farmland field? Write the words.
6
FName the group of organisms from which many medicines are obtained, other than animals. Write the words.
7
PSWhat is the difference between species diversity and genetic diversity? Write one sentence. Accept any sentence that says species diversity is the number of species, and genetic diversity is the variety of alleles within a species.
8
PSA habitat has many individuals of one species. Does this mean it has high biodiversity? Write yes or no.
9
RChallenge: explain why losing a single species from a food web can affect many others, in two sentences. Accept any answer that says other species depend on it for food, and the food web changes as a result.
18.2

Human impacts on biodiversity

GCSE
Describe the impact of deforestation, pollution, global warming, habitat destruction, overfishing and hunting, Evaluate the effect of a human activity
Video lesson: Human impacts on biodiversityComing soon
Context. A logging company clears a forest to make room for farmland. “The trees are gone, so what happens to the animals that lived there?” asks Hana. Human activities are one of the largest causes of loss of biodiversity today.

Human activities affect biodiversity in several ways. Deforestation and habitat destruction remove the homes and food sources of many species. Pollution of air, water and land harms organisms and their food chains. Global warming changes the places where species can live. Overfishing and hunting reduce populations, and some species may become extinct.

When the effect is evaluated, it is helpful to ask: how many species are affected, how severe is the change, and can the habitat recover?

Human activityEffect on biodiversity
deforestationhabitat is lost; many species lose their homes
pollution of air, water and landharms organisms and food chains
global warmingshifts habitats and can cause species to decline
overfishing and huntingreduces populations, and some species may become extinct
pesticides and fertiliserscan harm organisms and cause eutrophication in water
Human activities and their effects on biodiversity

Key ideas

  • Deforestation and habitat destruction remove homes and food.
  • Pollution harms organisms and food chains.
  • Global warming shifts the places where species can live.
  • Overfishing and hunting reduce populations and can cause extinction.
Worked example 18.2.1
Name the human activity that removes large areas of trees. Write the word.

Method. Recall the activity.

  1. Recall. Clearing large areas of trees is deforestation.
    clearing large areas
  2. Name it. So the activity is deforestation.
    deforestation
  3. Write the answer.
    deforestation

Check. Deforestation destroys habitats. ✓

Worked example 18.2.2
Name one effect of overfishing on biodiversity. Write one sentence. Accept any sentence that says it reduces fish populations, and some species may become extinct.

Method. Think about the fish.

  1. Think. Overfishing removes fish faster than they can breed.
    faster than they can breed
  2. Conclude. So fish populations fall, and some species may become extinct.
    may become extinct
  3. Write the answer.
    Overfishing reduces fish populations, and some species may become extinct.

Check. The effect spreads through the food chain. ✓

Worked example 18.2.3
Name the human activity that changes the temperature of the planet over time. Write the words.

Method. Recall the activity.

  1. Recall. Global warming is caused by increases in greenhouse gases.
    greenhouse gases
  2. Name it. The effect is global warming.
    global warming
  3. Write the answer.
    global warming

Check. Global warming changes habitats. ✓

Watch out

Watch out: a human activity can have several effects at once. Evaluate it by naming more than one effect, and saying how serious each one is.

Exam tip

Exam tip. When you evaluate a human activity, name an effect on biodiversity, and then say whether it is reversible, and how far it reaches.

Try it (with your teacher). With your teacher, discuss one human activity that affects a local habitat. List two effects on the species there, and suggest one way to reduce the impact.

Exercise 18B  Human impacts on biodiversity

1
FName the human activity that removes forests. Write the word.
2
FName the human activity that releases substances harming air, water or land. Write the word.
3
FName the human-caused change in the climate that shifts habitats. Write the words.
4
FName one activity that reduces fish populations. Write the word. Accept overfishing.
5
FName the process that removes the homes and food sources of many species. Write the words. Accept habitat destruction.
6
FDoes deforestation affect biodiversity? Write yes or no.
7
PSGive one way that pollution of water affects organisms. Write one sentence. Accept any sentence that says it harms the organisms that live in the water, or their food chains.
8
PSName the organisms that are most at risk when a forest is cleared. Write the words. Accept animals that live in the forest.
9
PSWhy does overfishing put a species at risk of extinction? Write one sentence. Accept any sentence that says fish are removed faster than they can breed to replace them.
10
RChallenge: a government says that a new road through a forest will have no effect on biodiversity because only a small area is lost. Write yes or no, and give two reasons. Accept no, with reasons such as that roads fragment habitats and disturb species beyond the area lost.
18.3

Pesticides, bioaccumulation and eutrophication

GCSE
Describe bioaccumulation along a food chain, [H] Describe eutrophication step by step
Video lesson: Pesticides, bioaccumulation and eutrophicationComing soon
Context. A farmer sprays a pesticide on a field. Some of it washes into a river. “The concentration in the water is tiny,” the farmer says. “Why would the fish at the top of the river have a much larger amount of it?” asks the student.

Bioaccumulation is the build-up of a substance, such as a pesticide, in the tissues of organisms. A substance that is not broken down or excreted is stored in each organism that eats contaminated food. Because each predator eats many prey, the concentration increases at each level of a food chain.

[H] Eutrophication is the enrichment of water with nutrients, such as nitrates and phosphates from fertilisers. Algae grow rapidly and form a bloom that blocks light. The plants below die, and decomposers use up the oxygen as they break them down. Fish and other aquatic animals then die from lack of oxygen.

Pesticide concentration along a food chain (invented data)02004006008001000wateralgaesmall fishlarge fishtrophic levelrelative concentration
Pesticide concentration increasing at each level of a food chain (invented data)
LevelRelative pesticide concentration (invented)
water1
algae10
small fish100
large fish1000
Relative pesticide concentration at each level
fertiliser runs into waternitrates and phosphatesalgae grow fastan algal bloom covers the surfacelight is blockedplants below diebacteria decompose the dead materialthey use up oxygenfish dieno oxygen left in the watereutrophication: excess nutrients cause a chain of events that kills aquatic life
[H] Eutrophication: nutrients cause algal growth, blocked light, decomposition, and loss of oxygen

Key ideas

  • Bioaccumulation: a substance builds up in organisms along a food chain.
  • Each level eats many organisms from the level below, so the concentration rises.
  • [H] Eutrophication: excess nutrients cause algal blooms, which use up oxygen.
  • [H] Fish die when there is no oxygen left in the water.
Worked example 18.3.1
In the table, how many times more pesticide is in the small fish than in the algae? Write the number.

Method. Divide the small fish value by the algae value.

  1. Read. The small fish have 100 and the algae have 10.
    100 and 10
  2. Divide. 100 / 10 = 10 times more.
    100 / 10 = 10
  3. Write the answer.
    10

Check. 10 x 10 = 100. ✓

Worked example 18.3.2
Name the process by which a substance builds up in organisms along a food chain. Write the word.

Method. Recall the process.

  1. Recall. The build-up of a substance in organisms is bioaccumulation.
    build-up
  2. Name it. So the process is bioaccumulation.
    bioaccumulation
  3. Write the answer.
    bioaccumulation

Check. Each level eats many prey. ✓

Worked example 18.3.3
[H] Name the nutrients from fertilisers that cause eutrophication. Write the words.

Method. Recall the nutrients.

  1. Recall. Fertilisers add nitrates and phosphates to water.
    nitrates and phosphates
  2. Name them. These nutrients cause algae to grow rapidly.
    algae to grow
  3. Write the answer.
    nitrates and phosphates

Check. Algae are the first to grow. ✓

Watch out

Watch out: bioaccumulation is about a substance that is not broken down or excreted, building up in tissues. It is not the same as the pesticide being diluted in water.

Exam tip

Exam tip. [H] When you describe eutrophication, give the steps in order: nutrients, algal bloom, blocked light, decomposition, oxygen loss, fish death.

Try it (with your teacher). With your teacher, use a table of concentrations to show bioaccumulation. Draw a simple food chain with four levels, and write the concentration at each level.

Exercise 18C  Pesticides, bioaccumulation and eutrophication

1
FName the process by which a substance builds up along a food chain. Write the word.
2
FIn the table, what is the pesticide concentration in large fish? Write the number.
3
PSHow many times more pesticide is in large fish than in water? Write the number.
4
PSWhy does the concentration rise along the food chain? Write one sentence. Accept any sentence that says each predator eats many prey, so it accumulates all of their stored pesticide.
5
F[H] Name the nutrients in fertilisers that cause eutrophication. Write the words.
6
F[H] Name the organisms that grow rapidly in eutrophic water and form a bloom. Write the word.
7
F[H] Name the gas whose level falls, causing fish to die in eutrophication. Write the word.
8
PS[H] Put these in order for eutrophication: fish die, algae bloom, nutrients enter water, decomposition uses oxygen. Write the order.
9
PSExplain why a pesticide that is not broken down is more harmful to a top predator than to a plant, in one sentence. Accept any sentence that says the pesticide builds up in the predator, which eats many contaminated prey.
10
RChallenge: explain why a pesticide sprayed in one field can harm birds that live far away, in two sentences. Accept any answer that says the pesticide can wash into water and be taken up by food chains, and it builds up in the birds that eat contaminated prey.
18.4

Protecting biodiversity: conservation and reforestation

GCSE
Describe conservation methods: reforestation, protected areas, breeding programmes and seed banks, Describe fishing quotas
Video lesson: Protecting biodiversity: conservation and reforestationComing soon
Context. A conservation group plants trees on land that was cleared years ago. “Why bother, when the forest will take many years to recover?” asks Dan. The group explains that every method protects biodiversity in a different way, and some work best together.

Reforestation plants trees to restore a habitat. Conservation areas protect habitats from damage. Breeding programmes breed endangered species in captivity, so they can later be released into the wild. Seed banks store the seeds of many plant species, so that they can be grown again if the wild population is lost. Fishing quotas limit the catch, so fish stocks can recover.

MethodHow it helps
reforestationplants new trees to restore habitat
conservation areas and protected siteskeep habitats safe from damage
breeding programmesbreed endangered species in captivity, to reintroduce them later
seed banksstore seeds of many plant species, to protect them from loss
fishing quotaslimit the catch, so fish stocks can recover
Conservation methods and how they help

Key ideas

  • Reforestation restores habitat by planting trees.
  • Conservation areas protect habitats from damage.
  • Breeding programmes and seed banks protect species from being lost.
  • Fishing quotas let fish stocks recover.
Worked example 18.4.1
Name the method that stores seeds of many plant species for the future. Write the words.

Method. Recall the method.

  1. Recall. Seed banks store seeds of many plant species.
    store seeds
  2. Name it. So the method is a seed bank.
    seed bank
  3. Write the answer.
    seed bank

Check. Seeds can be grown again later. ✓

Worked example 18.4.2
Name the method that breeds endangered animals so they can be released later. Write the words.

Method. Recall the method.

  1. Recall. Breeding programmes breed endangered species in captivity.
    in captivity
  2. Name it. So the method is a breeding programme.
    breeding programme
  3. Write the answer.
    breeding programme

Check. The animals are released when it is safe. ✓

Worked example 18.4.3
Name the method that limits how many fish are caught. Write the words.

Method. Recall the method.

  1. Recall. A limit on the number of fish that may be caught is a fishing quota.
    limit on the number
  2. Name it. So the method is a fishing quota.
    fishing quota
  3. Write the answer.
    fishing quota

Check. Quotas help fish stocks recover. ✓

Watch out

Watch out: planting trees does not replace a mature forest at once. Reforestation takes many years, so it is a long-term method.

Exam tip

Exam tip. When you describe a conservation method, say how it protects the species or habitat, and whether it is quick or slow.

Try it (with your teacher). With your teacher, look at a seed bank or a conservation area on a website chosen by your teacher. Write one sentence about what it protects.

Exercise 18D  Protecting biodiversity: conservation and reforestation

1
FName the method of planting trees to restore a habitat. Write the word.
2
FName the method that breeds endangered species in captivity. Write the words.
3
FName the store of seeds that can protect plant species. Write the words.
4
FWhat does a fishing quota limit? Write the words.
5
FName the method that protects habitats from damage by setting them aside. Write the words.
6
FIs reforestation a quick way to restore a habitat? Write yes or no.
7
PSWhy are seed banks useful? Write one sentence. Accept any sentence that says they keep seeds safe, so a species can be grown again if the wild population is lost.
8
PSWhy might a breeding programme and a conservation area work best together? Write one sentence. Accept any sentence that says the area protects the habitat while the programme restores the population.
9
RChallenge: explain why a single method of conservation is rarely enough to protect biodiversity, in two sentences. Accept any answer that says different threats need different methods, and several methods together give more protection.
18.5

Climate change, population data and biodiversity [H]

GCSE
Describe the effects of climate change on ecosystems, [H] Interpret population data over time
Video lesson: Climate change, population data and biodiversity [H]Coming soon
Context. A scientist counts a species in the same habitat every two years. The numbers fall steadily. “Is this a sign of trouble, or just a normal change?” asks Priya. To answer, she needs to read the graph carefully, and to think about the cause.

[H] Higher tier only. This section is higher-tier content. It covers reading a population graph over time, and the link to climate change.

Climate change can shift the range of a species, alter the timing of seasons, and change the food supply. Species that cannot move or adapt may decline, and some may become extinct. Changes in biodiversity can therefore be an early sign of climate change.

[H] When reading population data over time, look at the trend, the rate of change, and the size of the change. A fall of 52% over ten years, for example, is a large decline. The data show a pattern, but the cause still needs to be investigated.

Population of a species in a habitat (invented data)01002003004005006000246810years after 2000number of individuals
Population of a species over ten years (invented data)
Years after 2000Number of individuals
0500
2460
4380
6300
8260
10240
Population counts over ten years (invented data)

Key ideas

  • [H] Read population data by looking at the trend, the rate and the size of the change.
  • Climate change can shift ranges, timing and food supply.
  • A decline shows a pattern; the cause must be investigated.
  • Changes in biodiversity can be an early sign of climate change.
Worked example 18.5.1
[H] By how much did the population fall from 500 to 240? Write the number of individuals.

Method. Subtract the final count from the first.

  1. Read. The population was 500 at 0 years and 240 at 10 years.
    500 and 240
  2. Subtract. 500 - 240 = 260.
    500 - 240 = 260
  3. Write the answer.
    260

Check. 240 + 260 = 500. ✓

Worked example 18.5.2
[H] What was the percentage fall in the population over 10 years? Write the number, with the percentage sign.

Method. Divide the fall by the starting population, then multiply by 100.

  1. Fall. The fall is 260 individuals.
    260
  2. Divide. Divide by the starting population: 260 / 500 = 0.52.
    260 / 500 = 0.52
  3. Multiply. Multiply by 100 to give 52%.
    52%
  4. Write the answer.
    52%

Check. 52% of 500 is 260. ✓

Worked example 18.5.3
[H] Name one effect of climate change on ecosystems. Write one sentence. Accept any sentence that says it can shift the range of species, or change the food supply.

Method. Think about the habitat change.

  1. Think. Warmer temperatures change where species can live.
    where species can live
  2. Conclude. So climate change can shift the range of species, or change the food supply.
    shift the range
  3. Write the answer.
    Accept any sentence that says it can shift the range of species, or change the food supply.

Check. Species that cannot move may decline. ✓

Watch out

Watch out: a population graph shows a pattern, not the cause. Do not say that climate change is the cause from population data alone; other factors may also be involved.

Exam tip

Exam tip. [H] When you interpret a population graph, quote two values, give the change, and say what the data cannot show.

Try it (with your teacher). With your teacher, plot the population graph on squared paper, and mark the points where the population falls fastest. Describe the pattern in one sentence.

Exercise 18E  [H] Climate change, population data and biodiversity

1
F[H] What was the population at 6 years? Write the number.
2
F[H] What was the population at 8 years? Write the number.
3
PS[H] Between which two readings is the fall the largest? Write the two years. Accept 2 and 4, or 4 and 6.
4
PS[H] Calculate the fall in population from 2 years to 6 years. Write the number of individuals.
5
PS[H] Is the population falling at a steady rate or does the rate change? Write the word.
6
PS[H] Name one way climate change can change an ecosystem. Write one sentence. Accept any sentence that says it changes the food supply or the timing of seasons for species.
7
R[H] Explain why a population graph cannot show the cause of a decline by itself. Write one sentence. Accept any sentence that says other factors, such as disease or habitat loss, may also be involved.
8
R[H] Challenge: explain why a species that cannot move to a new habitat is at more risk from climate change than one that can, in two sentences. Accept any answer that says a species that cannot move may lose its habitat, while a mobile species can find a suitable new one.

Chapter summary

SkillMethod
BiodiversityVariety of living organisms: species and genes; it gives food, medicines and stability.
Human impactsDeforestation, pollution, global warming, habitat destruction, overfishing and hunting.
BioaccumulationA substance that is not broken down builds up at each level of a food chain.
[H] EutrophicationNutrients cause algal blooms, blocked light, decomposition, oxygen loss and fish death.
ConservationReforestation, conservation areas, breeding programmes, seed banks, fishing quotas.
Climate changeShifts ranges, seasons and food supply; a decline shows a pattern, not the cause alone.
[H] Population dataRead the trend, the rate and the size of the change; compare values to calculate the change.

Can you…?

  • I can describe biodiversity and explain why it matters
  • I can evaluate the effect of a human activity on biodiversity
  • I can explain bioaccumulation along a food chain
  • I can describe conservation methods and how they protect species
  • [H] I can explain eutrophication and interpret a population graph

Key terms

biodiversity
the variety of living organisms in an area, including species and genes
deforestation
the clearing of forests
pollution
the release of harmful substances into air, water or land
bioaccumulation
the build-up of a substance in organisms along a food chain
pesticide
a chemical used to kill pests
reforestation
planting trees to restore a habitat
seed bank
a store of seeds, kept for the future
fishing quota
a limit on the number of fish that may be caught
[H] eutrophication
the enrichment of water with nutrients, which causes algal blooms and loss of oxygen
[H] algal bloom
a rapid growth of algae that covers the surface of water

Exercise 18Z  Check-up

1
What is biodiversity? Write the words.
2
Name the human activity that removes forests. Write the word.
3
Name the process by which a substance builds up along a food chain. Write the word.
4
Name the method that breeds endangered species in captivity. Write the words.
5
Name the store of seeds used to protect plant species. Write the words.
6
Name the method that limits the number of fish caught. Write the words.
7
In the pesticide table, how many times more pesticide is in small fish than in algae? Write the number.
8
Name the human activity that changes the climate and shifts habitats. Write the words.
9
Name the method of planting trees to restore a habitat. Write the word.
10
Explain in one sentence why a conservation area helps biodiversity. Accept any sentence that says it protects habitats from damage, so the species there can survive.

Total 29 marks. Allow about 29 minutes.

Exercise 18X  Exam-style questions

1
FName the human activity that releases substances harming air, water or land. Write the word.[1 mark]
2
FName the method that protects plant species by storing their seeds. Write the words.[1 mark]
3
FName the process that is most likely to cause bioaccumulation in top predators. Write the word.[1 mark]
4
FDescribe two ways that humans reduce biodiversity. Write two points. Accept any two of: deforestation; pollution; global warming; overfishing; hunting; habitat destruction.[2 marks]
5
RExplain how bioaccumulation causes a pesticide to reach a higher concentration in a top predator than in the water. Write three sentences. Accept any answer that says the pesticide is not broken down or excreted, each predator eats many prey, and the stored amount builds up at each level.[3 marks]
6
REvaluate deforestation as a human activity, naming one effect on biodiversity and one effect on the climate. Write three sentences. Accept any answer that gives a habitat loss effect, and an effect on carbon dioxide levels, such as trees removed reduce photosynthesis.[3 marks]
7
FDescribe the conservation methods that protect a threatened species, naming three and saying how each helps. Write four sentences. Accept any answer that names three of: a breeding programme, a conservation area, a seed bank, a fishing quota, reforestation, each with its effect.[4 marks]
8
F[H] Describe how eutrophication happens, from the input of fertiliser to the death of fish. Write five sentences. Accept any answer giving nutrients entering the water, algae growing into a bloom, light being blocked, decomposition using oxygen, and fish dying from lack of oxygen.[5 marks]
9
PS[H] A population of a species falls from 500 to 240 in ten years. Calculate the percentage fall, and explain why this data alone cannot show the cause. Write four sentences. Accept 52%, and an answer that says other factors such as disease or habitat change may also be involved.[4 marks]
10
R[H] Challenge: a government says that protecting one forest is enough to protect biodiversity in a whole country. Evaluate this claim. Write five sentences. Accept any answer that says one forest protects only some species; biodiversity needs a range of habitats; corridors and other sites are needed; threats such as climate change and pollution affect all habitats; so the claim is not correct.[5 marks]
← Chapter 17: Food chains, energy and the cycles

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