A conservation team is comparing the biodiversity of two woodland sites, Site A and Site B. Site A is an ancient semi-natural woodland with a wide variety of tree species, ground flora, insects and fungi. Site B is a recently planted commercial conifer plantation with a single tree species and very little ground flora. Explain why Site A has greater biodiversity than Site B, using the concept of species richness and species evenness in your answer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Site A: ancient semi-natural woodland containing 24 different plant species, 61 invertebrate species and 15 fungal species, with no single species dominating. Site B: commercial conifer plantation containing 1 tree species and 4 invertebrate species, with the conifer accounting for over 95% of all individual organisms recorded.
Model answer (4 marks)
Site A has a higher species richness – it contains many more species (24 plant, 61 invertebrate, 15 fungal) than Site B (1 tree, 4 invertebrate).
Site A also has greater species evenness – the individuals are more evenly distributed among the many species, whereas in Site B the conifer accounts for >95 % of all organisms.
The larger number of plant species in Site A creates a wider range of ecological niches and habitats, supporting more diverse invertebrate and fungal communities.
In contrast, the monoculture of Site B provides very few habitats, limiting the species that can survive there.
Site A also has greater species evenness – the individuals are more evenly distributed among the many species, whereas in Site B the conifer accounts for >95 % of all organisms.
The larger number of plant species in Site A creates a wider range of ecological niches and habitats, supporting more diverse invertebrate and fungal communities.
In contrast, the monoculture of Site B provides very few habitats, limiting the species that can survive there.
Examiner tips
- State both richness and evenness explicitly; link evenness to the dominance of the conifer.
- Explain how more plant species give more niches; mention habitat diversity.
Mark scheme (4 marks)
- Site A has greater species richness than Site B
- Site A has greater species evenness than Site B
- Greater variety of plant species in Site A provides more ecological niches / habitats
- The monoculture in Site B reduces habitat diversity, limiting the species that can survive there
Key terms in this question
biodiversity · species richness · species evenness
Related
- All OCR A-Level Biology A (H420) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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