In these situations it is possible to count the diversity of families rather than species. This is much faster, but should only be used when a fast comparison is needed between two sample sites. Calculation Very often, biodiversity indices are used when comparing one habitat to another or the diversity of an area before and after disturbance. Therefore they are extremely useful tools to the biologist looking at the environmental impact of a motorway or helping to decide where new houses should be built. A number of biologists have devised indices with different biases towards abundance, richness etc.
None is applicable universally.
Shannons Index , French's Hierachical Richness Index and Simpsons index are all good examples. For practice, I have chosen Margalef's Diversity Index. The number of species. A - Has 15 plant species and 32 individuals. B - Has 10 plant species comprising 40 individuals.