Extinction — AQA GCSE Biology
Test yourself on Extinction with AQA GCSE practice questions.
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Extinction explained
A species becomes extinct when its last individual dies, so no living members remain to reproduce.
Read the full explanation
Extinction can follow a gradual decline or a sudden event. Causes include environmental change such as climate shift or habitat loss, new predators or competitors, and catastrophic events such as volcanic eruptions or asteroid impacts. Small populations are especially vulnerable because inbreeding, disease or a skewed sex ratio can reduce survival and reproduction further. Once numbers fall below a critical level, the species may be unable to recover even if conditions improve. Extinction is permanent: the species' gene pool is lost, although its fossils may still be studied.
Students should be able to describe factors which may contribute to the extinction of a species.
Extinction means no members of a species remain alive anywhere. Several factors can contribute, often acting together. A new predator or competitor may outcompete native species for food and territory. A new disease can spread rapidly through a population with little resistance. Environmental change, such as climate shifts, drought or habitat destruction, may remove breeding sites and food sources. Human activity, including deforestation, pollution and overhunting, accelerates these pressures. For example, introduced rats on islands prey on ground-nesting birds, while habitat loss removes their nesting cover, so the population cannot replace itself and eventually disappears. Describing means naming each factor and explaining how it reduces numbers until reproduction fails and the species is lost.
Your focus
- State the meaning of extinction in terms of no surviving individuals of a species.
- Explain how environmental change, predators, competitors or catastrophes can cause extinction.
- Distinguish between extinct, endangered and vulnerable species using population evidence.
Show all 6 objectives
- State at least three factors that may contribute to extinction.
- Explain how a named factor reduces a population until the species is lost.
- Apply the concept to an unfamiliar example and predict the likely outcome.
Extinction exam tips
Marking Points
- Extinction means that no individuals of a species remain alive anywhere, so the species can no longer reproduce.
- Environmental changes such as climate change, habitat destruction or pollution can make conditions unsuitable for a species.
- New predators, competitors or diseases can reduce a population until no breeding individuals survive.
- Catastrophic events such as volcanic eruptions, asteroid impacts or major fires can destroy habitats or food sources rapidly.
- Small populations are at greater risk because genetic variation is low and chance events can remove the remaining individuals.
- Identifies a named factor such as a new predator, competitor, disease, environmental change or human activity.
- Explains the mechanism by which the factor reduces the population, for example competition for limited food or destruction of breeding habitat.
- Links the factor to a fall in population size until no breeding individuals remain.
- Uses a specific example, such as an introduced predator or habitat loss, to support the description.
- Recognises that several factors often act together rather than in isolation.
Examiner Tips
- 💡Define extinction precisely in terms of no remaining living individuals before explaining a cause.
- 💡Link each cause to a mechanism, such as loss of food or failure to breed, rather than naming the cause alone.
- 💡Use examples of past mass extinctions or named endangered species to show the difference between extinct and at risk.
- 💡Use the command word describe: give clear points about each factor and how it acts.
- 💡Support each factor with a brief named example to show understanding.
- 💡Link factors to population decline and loss of breeding, not just to harm to individuals.
Common Mistakes
- Saying a species is extinct when only a local population has disappeared; correct this by checking that no individuals survive anywhere.
- Confusing endangered with extinct; correct this by stating that endangered species still have living individuals.
- Listing only one cause of extinction when asked to explain; correct this by giving several causes and linking each to a fall in population.
- Confusing extinction with a species becoming endangered; the correction is that extinction means no living members remain.
- Treating a single factor as always sufficient; the correction is that factors often combine and interact.
- Describing extinction as an instant event; the correction is that it is usually a gradual decline over generations.