Explain how the introduction of a non-native predator species to an island can reduce the biodiversity of that island's ecosystem.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Conservation scientists have warned that non-native species introduced to island ecosystems can cause a rapid decline in the variety of living organisms found there.
Model answer (4 marks)
A non‑native predator arrives with no natural enemies, so its numbers grow unchecked.
The native prey species have not evolved defence mechanisms against it and are therefore heavily preyed upon.
As a result, the populations of those prey species fall, and some may even go extinct.
The loss of these species means fewer different organisms are present, so the island’s biodiversity declines.
The native prey species have not evolved defence mechanisms against it and are therefore heavily preyed upon.
As a result, the populations of those prey species fall, and some may even go extinct.
The loss of these species means fewer different organisms are present, so the island’s biodiversity declines.
Examiner tips
- Use the exact wording from the mark scheme – e.g. ‘no natural predators’, ‘not adapted’, ‘decrease’, ‘reduce biodiversity’.
- Show the causal chain: predator → no control → heavy predation → population loss → lower biodiversity.
Common mistakes
- Failing to mention that the predator has no natural predators on the island.
- Using vague terms like ‘many animals’ instead of ‘native prey species’.
- Omitting the final link that fewer species equals lower biodiversity.
Mark scheme (4 marks)
- The non-native predator has no natural predators on the island, so its population increases rapidly / is not controlled.
- Native prey species are not adapted to the new predator so are preyed upon more heavily / cannot escape it effectively.
- Native prey populations decrease / species may become extinct.
- Loss of native species reduces biodiversity because there is less variety of living organisms in the ecosystem.
Key terms in this question
biodiversity · predator · ecosystem
Related
- Revision notes: Biodiversity and the effect of human interaction on ecosystems →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →