Explain how resource partitioning allows two species with overlapping fundamental niches to coexist within the same habitat.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. Without partitioning, species with overlapping fundamental niches would compete for the same resources, leading to competitive exclusion.
2. Resource partitioning means each species uses a different subset of resources (e.g. different food sizes, foraging heights, or activity times), reducing niche overlap.
3. The realised niche of each species is therefore narrower than its fundamental niche, but coexistence is possible because direct competition is minimised.
4. Over time, natural selection can reinforce partitioning through character displacement, where traits such as beak size or body size diverge, making resource use differences more pronounced and stable.
2. Resource partitioning means each species uses a different subset of resources (e.g. different food sizes, foraging heights, or activity times), reducing niche overlap.
3. The realised niche of each species is therefore narrower than its fundamental niche, but coexistence is possible because direct competition is minimised.
4. Over time, natural selection can reinforce partitioning through character displacement, where traits such as beak size or body size diverge, making resource use differences more pronounced and stable.
Examiner tips
- Use the word "partitioning" early; link to niche overlap and competitive exclusion. Show the sequence: competition → partitioning → reduced overlap → coexistence. Mention evolutionary reinforcement (character displacement).
Common mistakes
- Confusing fundamental and realised niche; not explaining why partitioning reduces competition. Omitting the evolutionary aspect of character displacement.
Mark scheme (4 marks)
- Species with overlapping fundamental niches would, without partitioning, compete for the same resources, potentially leading to competitive exclusion of one species.
- Resource partitioning involves each species utilising a different subset of the available resources (e.g. different food sizes, foraging heights, or activity times), thereby reducing niche overlap.
- The realised niche of each species is narrower than its fundamental niche as a result of this differentiation, but coexistence is possible because direct competition is minimised.
- Over evolutionary time, natural selection may reinforce partitioning through character displacement, where traits (e.g. beak size, body size) diverge, making resource use differences more pronounced and stable.
Key terms in this question
resource partitioning · fundamental niche
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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