Extinction — AQA GCSE Combined Science
Test yourself on Extinction with AQA GCSE practice questions.
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Extinction explained
Extinction is the permanent loss of a species: it occurs when there are no remaining individuals of that species still alive anywhere.
Read the full explanation
A species is a group of organisms that can interbreed to produce fertile offspring, so extinction means every member of that group has died and no breeding population remains. For example, if the last pair of a bird species dies without producing surviving offspring, the species is extinct. Extinction differs from a local disappearance, where individuals survive elsewhere, and from endangerment, where some individuals remain. Once a species is extinct, its genetic information is lost forever and it cannot reappear naturally.
Students should be able to describe factors which may contribute to the extinction of a species.
Many factors can contribute to extinction by reducing a species' population until no individuals remain alive. These include environmental changes such as climate change, habitat loss and pollution; new predators or competitors; new diseases; and hunting or overexploitation by humans. A single factor may be enough, but often several combine. For example, deforestation removes nesting sites and food, while a new predator or disease may then kill the survivors. Small populations are especially at risk because they have less genetic variation and are more vulnerable to chance events. Describing factors means explaining how each one reduces numbers or survival until the species dies out.
Your focus
- Define extinction as the situation where no individuals of a species remain alive.
- Distinguish extinction from endangerment and local disappearance.
- Apply the definition to a simple example of a species dying out.
Show all 6 objectives
- Identify a range of factors that can contribute to extinction.
- Describe how each factor reduces the survival or reproduction of a species.
- Explain how combined factors can lead to no remaining individuals of a species.
Extinction exam tips
Marking Points
- States that extinction means no individuals of the species remain alive anywhere.
- Distinguishes extinction from endangerment, where some individuals of the species are still alive.
- Distinguishes extinction from local disappearance, where the species survives in another area.
- Uses the idea of a species as a breeding group, so extinction occurs when no breeding population remains.
- Applies the definition to an example, such as the death of the last known individual of a species.
- Describes environmental change, such as climate change, as a factor that can make conditions unsuitable for a species.
- Describes habitat loss or destruction, such as deforestation, as removing food, shelter or breeding sites.
- Describes the introduction of new predators or competitors that reduce survival or resources.
- Describes new diseases that can spread rapidly through a population and cause many deaths.
- Describes human activities such as hunting, overfishing or pollution that reduce population numbers.
- Explains that several factors can act together and that small populations are more vulnerable.
Examiner Tips
- 💡Define extinction precisely using the phrase 'no remaining individuals of a species still alive'.
- 💡Contrast extinction with endangerment in one sentence to show secure understanding.
- 💡Use a named or described example to make the definition concrete.
- 💡Use the command word 'describe' by giving a clear account of each factor and its effect.
- 💡Include at least three different factors to show breadth.
- 💡Link each factor to a reduction in the number of individuals until none remain.
Common Mistakes
- Saying a species is extinct when it is only endangered: correct this by noting that endangered species still have living individuals.
- Confusing extinction with a local disappearance: correct this by checking whether any individuals survive elsewhere.
- Thinking an extinct species can reappear naturally: correct this by explaining that extinction is permanent because the genetic information is lost.
- Listing factors without explaining how they lead to extinction: correct this by linking each factor to reduced survival or reproduction.
- Assuming only one factor can cause extinction: correct this by noting that factors often combine.
- Confusing extinction with a temporary population decrease: correct this by explaining that extinction requires no individuals to remain alive.