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IB ESS SL 3.1.8 Simpsons Reciprocal Index Questions

Calculate and interpret Simpsons reciprocal index as a measure of biodiversity.

Syllabus
First assessment 2026
Course
ESS SL
Level
SL

Exam points

  • calculate Simpson’s reciprocal diversity index from species-abundance data
  • interpret a higher or lower index as evidence of greater or lower diversity and compare two ecosystems
  • design or evaluate repeated sampling with quadrats, transects or biotic indices to assess human effects on biodiversity

IB ESS SL 3.1.8 Simpsons Reciprocal Index Questions question 1

[Maximum number: 2]
Eight freshwater organisms

Figure:Eight freshwater organisms

Figure 2 shows eight freshwater organisms.

Organisms sampled in streams A and B

Table:Organisms sampled in streams A and B

The table shows data from sampling two streams: A and B. Calculate the Simpson’s Diversity Index for Stream B.
D=N(N−1)∑n(n−1)D=\frac{N(N-1)}{\sum n(n-1)}
You must show your working.

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