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

WJEC GCSE Biology (Wales) — 1.6.1 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)

Temperature is an abiotic factor. If the temperature is too low, rabbits have a harder time maintaining body heat and breeding rates fall, reducing the population size.

Predation is a biotic factor. When there are more foxes, rabbits are eaten more often, which lowers the number of rabbits that survive to reproduce, thereby decreasing the population size.

Examiner tips

Identify a specific abiotic and biotic factor; explain the effect on population size in one sentence each.
Use terms like ‘temperature’, ‘predation’, ‘breeding rates’ and ‘survival’ to show understanding.
Keep each explanation short but clear – one sentence per factor is enough for 1 mark.

Common mistakes

Choosing a factor that is not clearly abiotic or biotic (e.g. ‘food’ as abiotic).
Giving a vague explanation such as ‘it affects the rabbits’ without showing the mechanism.
Writing more than one factor for each part, which splits the marks.

Mark scheme (4 marks)

Abiotic factor correctly identified (e.g. temperature, rainfall, light intensity, soil type)
Explanation of how the named abiotic factor affects rabbit population size
Biotic factor correctly identified (e.g. predators, food availability, disease, competition)
Explanation of how the named biotic factor affects rabbit population size

Key terms in this question

abiotic factor · biotic factor · population · ecosystem