Measure biodiversity at three levels
Compare ecosystem diversity, species diversity and genetic variation within a species.
A Level; Cambridge International Biology 9700, 2028–2030. Written responses are self-checked; this does not certify supervised fieldwork or practical competence.
Before you begin
- Classification compares shared characteristics; populations occupy environments and contain variation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Name one level of biodiversity within a single species.
What you will learn
- Describe biodiversity across ecosystems and habitats
- Describe species abundance and within-species genetic variation
Build the explanation
Biodiversity can be assessed as the number and range of ecosystems and habitats; the number of species and their relative abundance; and genetic variation within each species. These levels describe different scales of biological variety. A species count alone does not capture differences in abundance or genetic variation.
Use evidence within scope
Use the level matched to the question. Two sites may contain the same number of species but differ in evenness; two populations of one species may differ genetically even when species richness is unchanged.
Pause and explain
Two populations belong to the same species and occupy similar habitat. What additional diversity could differ between them?
Worked example
Two grassland samples contain equal species counts, but one is dominated by a single species. Which biodiversity information differs?
Show the worked solution
- Compare relative abundance, not only species count.
- Dominance affects evenness.
Answer Their species richness is the same, but relative abundance and evenness differ; biodiversity is not fully described by the count alone.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A report compares the range of habitat types in two regions. Which biodiversity level is being assessed?
Give me a hint
Identify the required evidence and sequence the reasoning.
Compare my reasoning
- The comparison is among habitats.
- This is ecosystem or habitat diversity.
Ecosystem and habitat diversity.
Look for these in your work
- Relevant evidence selected
- Reasoning linked to conclusion
A site lists 12 species but gives no abundance data. What biodiversity feature cannot be assessed fully?
Give me a hint
Use the supplied example or data to justify a conclusion.
Compare my reasoning
- The species count gives richness.
- Relative abundance is missing.
Relative abundance and evenness cannot be assessed from the species count alone.
Look for these in your work
- Concept applied
- Limit or assumption stated
Two populations belong to the same species and occupy similar habitat. What additional diversity could differ between them?
Give me a hint
Apply the concept in a new context and qualify its limits.
Compare my reasoning
- Variation among alleles or genotypes within the species.
- That is genetic diversity.
Their genetic variation may differ, even if the species and habitat categories are the same.
Look for these in your work
- New context handled
- Conclusion appropriately bounded
Common mistakes
- Equating species richness with all biodiversity
- Assuming identical species counts mean identical communities
What can you explain now?
Name one level of biodiversity within a single species.
Compare with the explanation
Genetic variation
The other levels include ecosystem/habitat and species diversity.
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Make it stick
What three levels can be used to assess biodiversity?
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