ExtinctionSpec 4.6.3.6
In short
Extinction occurs when there are no remaining individuals of a species still alive. Factors that may contribute include a change to the environment over geological time, new predators, new diseases, new, more successful competitors, and a single catastrophic event, such as a massive volcanic eruption or an asteroid collision. Each can reduce numbers until none are left.
Extinction occurs when there are no remaining individuals of a species still alive.
You need to be able to describe factors that may contribute to the extinction of a species. A species may become extinct because of:
- a change to the environment over geological time
- new predators
- new diseases
- new, more successful competitors
- a single catastrophic event, such as a massive volcanic eruption or an asteroid collision.
Exam tip:Always link the factor to the species: for example, a new disease kills individuals faster than they can reproduce, so the numbers fall until none are left.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026
Frequently asked questions
What is the evidence for evolution?
The evidence for evolution includes the fossil record, which shows how much or how little organisms have changed as life developed on Earth, the discovery that characteristics are passed on to offspring in genes, and antibiotic resistance in bacteria, which shows natural selection happening in a short time. This is why the theory is now widely accepted.
How are fossils formed?
Fossils form in three ways: from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent, from parts that are replaced by minerals as they decay, or as preserved traces such as footprints, burrows and rootlet traces. Fossils are found in rocks and show how organisms have changed.
How does antibiotic resistance develop in bacteria?
Antibiotic resistance develops by natural selection. A mutation produces a strain of bacteria that is resistant to antibiotics. When antibiotics are used, non-resistant bacteria are killed but the resistant bacteria survive and reproduce, so the resistant population rises. Because bacteria reproduce at a fast rate, resistant strains such as MRSA can spread quickly, with no effective treatment.
All 4 questions on The development of understanding of genetics and evolution
