Final answer:
Species richness and Simpson's diversity index are used in biology (ecology) to measure biodiversity and the relative abundance of species.
Step-by-step explanation:
Ecologists have extensively studied one of the fundamental characteristics of communities: biodiversity. One measure of biodiversity used by ecologists is the number of different species in a particular area and their relative abundance. Species richness is the term used to describe the number of species living in a habitat or other unit. Species richness can be corrected for total abundance to produce Simpson's diversity index, a measure of diversity that takes into account both the number of species and their relative abundance.