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AP Biology 8.5.A: Species Composition and Diversity

Practise AP Biology 8.5.A questions by comparing species richness, relative abundance and community diversity using ecological data.

Syllabus
Effective Fall 2025
Course
AP Biology

Exam points

  • distinguish species richness from relative abundance when describing community structure
  • calculate and interpret Simpson’s Diversity Index from species-abundance data
  • explain how changes in plant diversity and community structure can alter animal species composition

8.5.A—Describe the structure of a community according to its species composition and diversity question 1

[Maximum number: 1]

Biological communities containing a large number of species that are evenly distributed exhibit high species diversity-a concept that encompasses both species richness (the number of different species present) and relative abundance (the number of individuals of each species). One measure of species diversity is Simpson's index of diversity, which is represented by the following mathematical equation.

Ds=1−∑ni(ni−1)N(N−1)D_{s}=1-\frac{\sum n_{i}\left(n_{i}-1\right)}{N(N-1)}

Where Ds=D_{s}= index of diversity for a community
N= total number of individuals of all species
ni=n_{i}= number of individuals in each individual species
The following data were collected from a community of trees.

Species

Number of
Individuals

1

20

2

34

3

4

4

10

Calculate the Simpson's index of diversity for the community of trees. Enter your answer as a value between 0 and 1 to the nearest hundredth.

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