Explain how the ecological niche concept can be used to predict the likely impact of removing a top predator from an ecosystem.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A top predator occupies a niche that regulates the population size of its prey species. Removing it allows prey populations to expand, increasing their realised niche and often exceeding the carrying capacity of shared resources. Mesopredators or other competitors that were suppressed by the top predator can also expand their niches – a mesopredator release – intensifying competition with other species. This trophic cascade alters the niches of many species, reducing biodiversity and restructuring community composition, showing that niches are interdependent and dynamically linked within an ecosystem.
Examiner tips
- Use the word ‘regulates’ to show predator’s role in the niche. Mention ‘mesopredator release’ as a key mechanism. Explain how niche expansion leads to competition and biodiversity loss. Show the link to trophic cascade to demonstrate interdependence.
Common mistakes
- Confusing the predator’s niche with that of its prey. Failing to mention mesopredator release. Using vague terms like ‘changes’ without explaining the mechanism.
Mark scheme (4 marks)
- A top predator occupies a niche that involves regulating the population size / abundance of prey species below it in the food web.
- Without the top predator, prey species can expand their realised niche / population, potentially exceeding the carrying capacity of shared resources.
- Mesopredators / competing species previously suppressed by the top predator may also expand their niches, intensifying competition with other species (mesopredator release).
- This cascading alteration of niches (trophic cascade) can reduce biodiversity / restructure community composition, demonstrating that niches are interdependent and dynamically linked within an ecosystem.
Key terms in this question
ecological niche · top predator
Related
- All IB DP Biology Higher Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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