6.17 Extinction
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What is meant by extinction?
Mark scheme
there are no individuals of the species left alive
Model answer
Extinction is when no individuals of a species remain alive.
Give three possible causes of extinction.
Mark scheme
Any three from:
- new predators (1)
- new diseases (1)
- new / more successful competitors (1)
- catastrophic event (1)
- environmental change / climate change / habitat loss (1)
Model answer
New predators, new diseases and a catastrophic event such as an asteroid strike.
The dodo became extinct after humans brought rats and pigs to its island. Suggest why.
Mark scheme
- rats / pigs were new predators (1)
- ate eggs / young, and the dodo could not fly / had no defences (1)
Model answer
The rats and pigs were new predators that ate the dodo's eggs, and the dodo could not fly away or defend its nest.
Suggest why a species with little genetic variation is more likely to become extinct when its environment changes.
Mark scheme
- fewer / no individuals likely to have characteristics suited to the new conditions (1)
- so few survive to reproduce / natural selection cannot act (1)
Model answer
With little variation, it is unlikely that any individuals have characteristics suited to the new conditions, so few survive and reproduce.
Which event is thought to have caused the extinction of the dinosaurs?
Choose one answer.
Correct Not quite: the answer is An asteroid collision
Mark scheme
B
Model answer
B: an asteroid collision about 66 million years ago.
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