A coral reef is an ecosystem where clownfish live among the tentacles of sea anemones. The anemone's stinging tentacles protect the clownfish from predators, whilst the clownfish chases away fish that would otherwise eat the anemone. Describe the relationship between the clownfish and the sea anemone, and explain how the removal of all clownfish from the reef could affect the sea anemone population.

OCR GCSE Biology A: Gateway Science (J247) — B4.1 Ecosystems · Describe · 4 marks · View as Markdown

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

A coral reef is an ecosystem where clownfish live among the tentacles of sea anemones. The anemone's stinging tentacles protect the clownfish from predators, whilst the clownfish chases away fish that would otherwise eat the anemone.

Model answer (4 marks)

The clownfish and sea anemone have a mutualistic relationship – both benefit. The clownfish gains protection from predators by living in the anemone’s stinging tentacles, while the anemone is protected from its own predators because the clownfish chases them away.

If all clownfish were removed, the fish that normally prey on sea anemones would no longer be chased away. Their numbers would increase, leading to more predation on the anemones. Consequently, the sea anemone population would decline as more individuals are eaten.

Examiner tips

  • Use the term "mutualism" first; examiners look for correct terminology. Explain the benefit to each organism in one sentence. Show the causal chain: removal → more predators → more predation → population decline.
  • common_mistakes
  • :
  • Calling the relationship commensalism or parasitism. Failing to mention the benefit to the anemone. Not linking removal of clownfish to increased predation and population decline.

Mark scheme (4 marks)

  1. The relationship between clownfish and sea anemone is mutualism
  2. Both organisms benefit from the relationship / clownfish gains protection and anemone gains protection from its predators
  3. Without clownfish, the fish that eat sea anemones would no longer be chased away / the anemone's predators would increase in number
  4. The sea anemone population would decrease / sea anemones would be eaten in greater numbers and their population would fall

Key terms in this question

ecosystem · population

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