Explain how both abiotic and biotic factors can affect the size of a population of rabbits living in a grassland ecosystem.

Edexcel GCSE Biology (1BI0) — 9.1 Ecosystems · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. Temperature – an abiotic factor.
A rise in temperature increases rabbit metabolism and breeding rate, so the population grows, while a drop in temperature reduces activity and breeding, decreasing the population.
2. Predation – a biotic factor.
More predators (e.g. foxes) increase rabbit mortality, lowering the population size; fewer predators allow more rabbits to survive and reproduce, raising the population size.

Examiner tips

  • Use the word ‘abiotic’ and ‘biotic’ to show you know the categories.
  • Explain the mechanism (e.g. temperature affecting metabolism or predators affecting mortality).
  • Give a clear example for each factor.
  • Keep the answer concise – one sentence per point is enough for full marks.

Common mistakes

  • Confusing abiotic with biotic (e.g. using ‘food’ as abiotic).
  • Failing to explain the effect – just naming the factor is insufficient.
  • Using vague terms like ‘weather’ without specifying temperature or humidity.

Mark scheme (4 marks)

  1. Correct identification of a relevant abiotic factor
  2. Explanation of how the named abiotic factor affects rabbit population size
  3. Correct identification of a relevant biotic factor
  4. Explanation of how the named biotic factor affects rabbit population size

Key terms in this question

biotic factors · ecosystem · population

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