Let's Calculate Biodiversity

updated: 2019-12-13

In this activity, you will practice computing species richness and the other measures of biodiversity discussed in How To Calculate Biodiversity?. The data comes from one of the many data sets gathered during our study of biofilm formation in the Baltimore Inner Harbor. 

Before you get started, here is a quick review of the biodiversity formulas:

  • Species Richness: S - the number of different species found on plate. 
  • Pi - the number of a given species divided by the total number of organisms observed. When you compute the probability for each species, please use decimal percent (e.g., use 0.25 - not 25% or 1/4). 
  • Simpson index: D = sum(Pi2
  • Simpson's index of diversity: 1 - D 
  • Simpson's reciprocal index: 1/D 
  • Shannon-Weiner index: H = -sum(Pilog[Pi])
  • (While you may use any base, the natural log is commonly used) 
  • Evenness: E = H/log(S)


Species Richness & Simpson's Index:

  • Three species
  • Six species

Species Richness & Shannon-Wiener Index:

  • Three species
  • Six species