Index of Diversity

Laura Armstrong

Teacher

Laura Armstrong

Recall Questions

This topic requires prior knowledge of biodiversity. You can test your knowledge on this below.

What is biodiversity?

Biodiversity is the variety of living organisms in an ecosystem. It includes species diversity, genetic diversity, and habitat diversity.

What are the two main components of species diversity?

  • Species richness 
  • Species evenness

What is species richness?

The number of different species within an area.

Topic Explainer Video

Check out this @LauraDoesBiology video that explains index of diversity or read the full notes below. Once you've gone through the whole note, try out the practice questions!

What is Index Diversity?

  • The Index of Diversity (D) is a mathematical measure used to quantify biodiversity within a habitat.

  • It considers both species richness (number of species) and species evenness (the abundance of each species).

  • To calculate the index of diversity, you need to know:

    • The total number of all species.

    • The individual number of organisms in each species.

Formula for Index of Diversity

Where:

  • D = Index of Diversity.

  • N = Total number of organisms of all species.

  • n = Number of individuals of each species.

How to Calculate Index of Diversity Step-by-Step

  1. Count the total number of organisms (N) in the community.

  2. For each species, count the number of individuals (n).

  3. Calculate n(n−1) for each species.

  4. Find the sum ∑n(n−1) of all species.

  5. Substitute into the formula and calculate D.

  6. Interpretations: 

    • Higher D = Greater biodiversity.

    • Lower D = Lower biodiversity (fewer species or dominance of one species).

Example Calculation

Species Number of Individuals (n)n (n-1)
Species A1090
Species B520
Species C36
Total (N)18∑ = 116

Interpretation: A higher value indicates greater species diversity, meaning the habitat is more stable and less likely to be affected by changes.

Key Terms 

  • Biodiversity: Biodiversity is the variety of living organisms in an ecosystem. It includes species diversity, genetic diversity, and habitat diversity.

  • Species richness: The number of different species in an area.

  • Species evenness: The relative abundance of individuals within each species.

  • Index of Diversity (D): A numerical value that represents biodiversity within a community.

No answer provided.

Exam Tips

Don't confuse species richness with species diversity:  Species richness is just the number of different species in an area, whereas species diversity also considers how evenly individuals are distributed.

Use the formula correctly: Ensure you correctly apply the Index of Diversity formula in calculations. Make sure to practice with me in the video question below!

No answer provided.

A student collected data on insect species in two different fields. The results are shown below:

SpeciesField A (Number of Individuals)Field B (Number of Individuals)
Beetles 2015
Butterflies105
Grasshoppers53
Spiders21
Total (N)3724

(a) Calculate the Index of Diversity (D) for Field A and Field B. (4 marks)
(b) Suggest a reason why Field A has a higher index of diversity than Field B. (2 marks)

(a)

  • Field A Calculation:

D= 37(36) / 492 ​= 1332 / 492 ​= 2.71

  • Field B Calculation:

D= 24(23) / 236 ​= 552 / 236 ​= 2.34

(b)

  • Field A has a higher Index of Diversity than Field B because it has more species and a greater species evenness.

  • Field B may have fewer species due to habitat destruction, pesticide use, or human activity such as deforestation.

Practice Question

Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!