Question 1
Paper 4 short-answer style1 markState what is meant by biodiversity. (1 mark)
Model answer
Biodiversity is the number of different species that live in an area.
Why this scores
One mark for 'the number of different species in an area'.
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Detailed notes on Human Influences on Ecosystems for Cambridge IGCSE Biology, covering key concepts, explanations, examples, and exam-focused revision points.
The leading cause of biodiversity loss. Cambridge wants the causes and the chain of consequences for ecosystems and climate.
Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).
Forests cleared, lands urbanised, oceans polluted, mines dug.
1. Deforestation.
2. Urbanisation.
3. Agriculture.
4. Mining.
5. Dams + flooding.
6. Coastal development.
Worked qualitative. Why is the AMAZON RAINFOREST particularly important?
Cambridge tip. When asked causes of habitat destruction, give 4-5 different ones. Cambridge marks each.
Extinction, soil erosion, climate change, flooding — all linked.
1. Loss of biodiversity → extinction.
2. Soil erosion.
3. Climate change.
4. Flooding.
5. Reduced local rainfall.
6. Ecosystem services lost.
Worked qualitative. Why might cutting forests for agriculture eventually REDUCE agricultural productivity?
Cambridge tip. Always link causes to multiple consequences. 'Deforestation causes climate change' is partial; 'deforestation releases CO₂ which contributes to climate change' is full.
Current extinction rates 100-1000× the natural background rate.
Background extinction rate.
Current rate.
Why humans are particularly bad for biodiversity:
Why extinction matters:
1. Medical. Many medicines come from natural compounds. Quinine (malaria) from Cinchona bark; aspirin from willow; many cancer drugs from plants. Extinct species = lost medicines.
2. Ecological. Species are interconnected. Extinction can cascade through food webs.
3. Ethical. Humans cause the harm; many feel responsible to prevent it.
4. Economic. Tourism (safaris, reef diving), fisheries, pollination — all depend on biodiversity.
5. Aesthetic + cultural. Many cultures value certain species; biodiversity is part of natural beauty.
Worked qualitative. Why is the GIANT PANDA's situation so concerning?
Cambridge tip. When asked why we should preserve species, give 3-4 reasons (medical, ecological, ethical, economic). Cambridge marks the diversity of reasons.
Verbatim phrases and definitions Cambridge mark schemes credit.
Habitat destruction appears Paper 4 (5-7 marks: causes, consequences). Examiner reports flag students missing chain of consequences.
Sources: Cambridge IGCSE Biology 0610 syllabus 2026-2028 (20.2); 0610/42 Oct/Nov 2024 — Q21 (deforestation); 0610 Examiner Reports 2022-2024. Last reviewed 2026-05-07.
Step-by-step solutions to past-paper-style questions on habitat destruction, written exactly the way a tutor would explain them at the board.
Question
State what is meant by biodiversity and give three reasons why habitats are destroyed.
Step-by-step solution
Step 1
Biodiversity is the number of different species that live in an area.
Step 2
Reason 1: clearing land for housing, growing crops and rearing livestock.
Step 3
Reason 2: the extraction of natural resources (e.g. mining, logging).
Step 4
Reason 3: pollution of freshwater and the sea, which damages aquatic habitats.
Answer
Biodiversity = the number of different species in an area. Habitats are destroyed for housing/farming, by extracting resources, and by freshwater and marine pollution.
Question
Deforestation has several harmful effects. State the effect caused by each: (a) removing the trees that organisms live in; (b) removing the roots that hold the soil; (c) burning the trees.
Step-by-step solution
Step 1
(a) Removing the trees organisms live in → loss of habitat → reduced biodiversity and extinction.
Step 2
(b) Removing the roots that hold the soil → soil erosion (loss of soil), and faster run-off causing flooding.
Step 3
(c) Burning the trees → release of carbon dioxide into the atmosphere.
Answer
(a) Reduced biodiversity/extinction; (b) soil loss and flooding; (c) increased carbon dioxide.
Question
Describe four undesirable effects of large-scale deforestation.
Step-by-step solution
Step 1
Reduced biodiversity and extinction: the forest organisms lose their habitat, so many die and some species become extinct.
Step 2
Loss of soil (soil erosion): without the tree roots to hold the soil, rain washes it away.
Step 3
Flooding: without the trees to take up and intercept rainwater, water runs off the land quickly, causing flooding.
Step 4
Increased carbon dioxide: the trees no longer remove carbon dioxide by photosynthesis, and burning them releases stored carbon as carbon dioxide, adding to the greenhouse effect.
Answer
Reduced biodiversity and extinction, loss of soil (erosion), flooding, and an increase in atmospheric carbon dioxide.
Examiner tip
The syllabus names exactly these effects: reduced biodiversity, extinction, loss of soil, flooding and increased carbon dioxide.
Question
Explain how destroying part of a habitat can harm species that did not live in the part destroyed.
Step-by-step solution
Step 1
Organisms in an ecosystem are linked together in food chains and food webs.
Step 2
If a habitat is destroyed, the species that lived there die or move away, removing them from the food web.
Step 3
Other species that fed on them lose a food source, and species they used to eat may increase without their predator.
Step 4
These knock-on effects spread through the food web, so species far from the destroyed area can also be affected — humans can harm habitats by altering food webs in this way.
Answer
Species are connected in food webs. Removing one species removes a food source for others and lets its prey increase, so the effects spread through the web, harming species beyond the area destroyed.
Question
Explain why habitat destruction is a major cause of extinction, and why preventing extinction is important.
Step-by-step solution
Step 1
Each species is adapted to live in its particular habitat, which provides its food, shelter and breeding sites.
Step 2
If the habitat is destroyed, the species cannot survive there, and may have nowhere else suitable to live — so it dies out (extinction).
Step 3
Extinction is permanent — once a species is gone, its genes are lost forever, reducing biodiversity.
Step 4
Preventing extinction is important to maintain biodiversity, because species are valuable as sources of food, drugs, fuel and useful genes, and they keep ecosystems functioning (e.g. nutrient cycling).
Answer
Species are adapted to their habitats, so destroying a habitat can cause a species to die out. Extinction is permanent and loses genes forever, so it matters because biodiversity provides food, drugs, fuel, genes and stable ecosystems.
Examiner tip
Reasons to prevent extinction (syllabus): maintaining biodiversity, reducing extinction, protecting ecosystems, and ecosystem functions including resources such as food, drugs, fuel and genes.
Question
Explain how the pollution of rivers and the sea can destroy aquatic habitats.
Step-by-step solution
Step 1
Pollutants such as sewage, fertiliser run-off, oil and plastics enter rivers and the sea.
Step 2
Sewage and fertiliser cause eutrophication, which uses up the oxygen in the water, killing fish and other organisms.
Step 3
Oil coats and poisons organisms, and plastics are eaten by or trap animals, harming or killing them.
Step 4
As organisms die and conditions become unsuitable, the habitat is destroyed and its biodiversity falls.
Answer
Sewage and fertiliser cause eutrophication (low oxygen); oil poisons organisms; plastics harm animals. As organisms die and conditions worsen, the aquatic habitat is destroyed and biodiversity falls.
Examiner tip
Freshwater and marine pollution is a named cause of habitat destruction in the syllabus (20.2).
High-scoring sample answers for habitat destruction on the Cambridge IGCSE 0610 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.
State what is meant by biodiversity. (1 mark)
Model answer
Biodiversity is the number of different species that live in an area.
Why this scores
One mark for 'the number of different species in an area'.
State two reasons why natural habitats are destroyed by humans. (2 marks)
Model answer
Any two of: clearing land for housing, crop production or rearing livestock; the extraction of natural resources (such as mining or logging); and pollution of freshwater and the sea.
Why this scores
Two distinct reasons from the syllabus list (housing/farming; resource extraction; freshwater/marine pollution).
Explain how deforestation reduces biodiversity and can cause extinction. (3 marks)
Model answer
Deforestation destroys the habitat of the organisms that live in the forest, removing their food and shelter. Many of these organisms die because they cannot survive without the forest, so the number of different species falls (biodiversity is reduced). If all the members of a species die without reproducing, that species becomes extinct.
Why this scores
Three marks: destroys habitat / removes food and shelter; organisms die / biodiversity reduced; species can become extinct.
Explain four undesirable effects of large-scale deforestation. (4 marks)
Model answer
Deforestation reduces biodiversity and can cause extinction, because the forest organisms lose their habitat and die. It causes loss of soil (soil erosion), because there are no longer tree roots to hold the soil and rain washes it away. It causes flooding, because the trees no longer take up and intercept rainwater, so water runs off the land quickly. It also increases the carbon dioxide in the atmosphere, because the trees no longer remove it by photosynthesis and burning them releases stored carbon — adding to the greenhouse effect.
Why this scores
Four marks: reduced biodiversity/extinction; loss of soil/erosion; flooding; increased carbon dioxide (each briefly explained).
Explain how, by altering food chains and food webs, humans can have a negative impact on an ecosystem beyond the area they directly affect. (5 marks)
Model answer
The organisms in an ecosystem are linked together in food chains and food webs, so they depend on one another for food. If humans destroy a habitat or remove a species (for example by overharvesting), that species is lost from the food web. The animals that fed on it lose a food source, so their numbers may fall, while the organisms it used to eat may increase without their predator. These changes have knock-on effects that pass along the connected food chains, so species that were not directly affected can also increase or decrease. In this way, a human impact in one place spreads through the food web and can damage the whole ecosystem.
Why this scores
Five marks: organisms linked in food webs; removing a species removes a food source; its prey may increase; knock-on effects through the web; species beyond the affected area are harmed.
Describe the undesirable effects of clearing a large area of tropical rainforest. (6 marks)
Model answer
Clearing a large area of rainforest destroys the habitat of the many organisms that live there. Because they lose their food and shelter, large numbers die, so the biodiversity (number of different species) is reduced, and species found only in that forest may become extinct, losing their genes forever. With the trees gone, there are no longer roots to hold the soil, so heavy rain washes the soil away (soil erosion), leaving the land infertile. The trees also normally take up and intercept rainwater, so without them the water runs off the land quickly, causing flooding. Finally, the trees no longer remove carbon dioxide from the atmosphere by photosynthesis, and burning the felled trees releases the carbon they stored as carbon dioxide; so the concentration of carbon dioxide in the atmosphere rises, adding to the greenhouse effect and global warming. Together these effects make deforestation very damaging to both wildlife and the wider environment.
Why this scores
Up to 6 marks: destroys habitat → organisms die → reduced biodiversity; extinction; loss of soil/erosion; flooding; less CO₂ removed by photosynthesis; burning releases CO₂ → increased atmospheric CO₂/greenhouse effect.
Definitions to memorise and the exact keywords mark schemes credit for habitat destruction answers — sharpened from recent examiner reports for the 2026 0610 sitting.
The number of different species that live in an area.
The removal of large areas of forest. Causes reduced biodiversity, extinction, soil loss, flooding and increased carbon dioxide.
The permanent loss of a species — its last members die without reproducing. Cannot be reversed.
The washing or blowing away of soil when there are no plant roots to hold it in place.
The traps other students keep falling into on habitat destruction questions — taken from recent Cambridge IGCSE 0610 examiner reports and mark schemes — and how to avoid them.
Why it happens
The animals are the obvious victims.
How to avoid it
Deforestation has many effects: loss of biodiversity AND soil erosion, flooding, and increased carbon dioxide. Cover the wider effects too.
Why it happens
Captive breeding can recover endangered species.
How to avoid it
Extinction is PERMANENT — once the last individuals die, the species and its genes are gone forever. Endangered (not yet extinct) species can sometimes be recovered.
Why it happens
Burning obviously releases CO₂.
How to avoid it
There are TWO effects: the trees no longer REMOVE CO₂ by photosynthesis, AND burning them RELEASES stored carbon as CO₂.
The things students keep getting wrong in this sub-topic, answered.