Extinction
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of the terms extinct and endangered.
What does extinction mean?
Extinction is when no individuals of a species remain alive anywhere on Earth.
What is meant by an endangered species?
An endangered species is one that is at risk of becoming extinct in the near future.
Give two natural causes of extinction.
Examples include new diseases and new predators.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains extinction, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
What Is Extinction?
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Extinction occurs when the last individual of a species dies.
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No individuals of that species remain alive anywhere on Earth.
Causes of Extinction
Extinction can happen naturally or be caused by human activity. Key causes include:
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New predators
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Introduction of a new predator can outcompete or hunt a species to extinction.
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New diseases
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Species may have no immunity to new diseases, leading to rapid population decline.
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Competition
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A new species may arrive and outcompete an existing one for food, shelter, or mates.
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Changes in the environment
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Climate change, natural disasters, or loss of habitat (e.g., due to deforestation) can make survival impossible.
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Catastrophic events
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E.g., asteroid impacts like the one believed to have caused the extinction of dinosaurs.
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Human activities
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Hunting, habitat destruction, and climate change all contribute to modern extinctions.
Endangered Species
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A species becomes endangered when numbers are very low or their habitat is severely threatened.
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Conservation efforts include breeding programmes, protected habitats, and legal protection against hunting.
Scientists often cannot be certain why a species became extinct because:
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Lack of complete fossil records
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Many organisms, especially soft-bodied ones, did not fossilise well, or their fossils have been destroyed by geological activity like earthquakes or erosion.
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Multiple possible causes
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Extinction is often caused by a combination of factors- like climate change, new predators, and disease- making it hard to identify one specific reason.
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No direct observations
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Extinctions that happened millions of years ago weren’t witnessed by humans, so scientists must infer causes from limited evidence.
Key Terms
- Extinction – When a species no longer exists anywhere on Earth.
- Endangered – A species at risk of becoming extinct.
- Biodiversity – The variety of living organisms in an area.
- Conservation – Steps taken to protect and preserve biodiversity and endangered species.
No answer provided.
Exam Tip
Always refer to specific causes of extinction and use examples. Don’t just say "humans cause extinction"- explain how (e.g. loss of habitat or hunting).
Make sure the cause of extinction is suitable for the organism in question. For example – if the question is asking why a species of plant became extinct, do not suggest it is due to hunting!
No answer provided.
Practice Question
Species can become extinct.
Give two possible causes of extinction. (2 marks)
any two from:
- drought
- ice age
- global warming
- volcanic activity
- asteroid collision
- new predators / hunting
- new disease / pathogen
- competition for food
- competition for mates
- loss of habitat or habitat change
More Practice
Try to answer the practice question from the TikTok video on your own, then watch the video to see how well you did!