Explain how resource partitioning allows closely related species to coexist within the same habitat without violating the competitive exclusion principle.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The competitive exclusion principle states that two species that occupy the same ecological niche cannot coexist indefinitely, as one will outcompete the other to local extinction.
Resource partitioning occurs when closely related species divide or differentiate their use of resources (e.g. food, space, time) so that their realised niches only partially overlap.
By subdividing resources, each species occupies a distinct realised niche, reducing interspecific competition sufficiently to allow stable coexistence.
An example is MacArthur’s warblers, which feed at different heights within the same tree, or anole lizards that use different perch heights and microhabitats.
Resource partitioning occurs when closely related species divide or differentiate their use of resources (e.g. food, space, time) so that their realised niches only partially overlap.
By subdividing resources, each species occupies a distinct realised niche, reducing interspecific competition sufficiently to allow stable coexistence.
An example is MacArthur’s warblers, which feed at different heights within the same tree, or anole lizards that use different perch heights and microhabitats.
Examiner tips
- Use the phrase "competitive exclusion principle" first. Show that partitioning reduces niche overlap. Give a clear example with specific resource differences. Keep answer concise and to the point.
Common mistakes
- Confusing potential niche with realised niche. Failing to mention that partitioning reduces competition. Giving an example that does not involve closely related species or the same habitat.
Mark scheme (4 marks)
- The competitive exclusion principle states that two species occupying the same ecological niche cannot coexist indefinitely, as one will outcompete the other to local extinction.
- Resource partitioning occurs when closely related species divide or differentiate their use of resources (e.g. food, space, time) so that their realised niches only partially overlap.
- By subdividing resources, each species occupies a distinct realised niche, reducing interspecific competition sufficiently to allow stable coexistence.
- A named or described example illustrating resource partitioning, such as MacArthur's warblers feeding at different heights/zones within the same tree, or anole lizards using different perch heights/microhabitats.
Key terms in this question
competitive exclusion principle · resource partitioning
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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