In a sample, how many organisms there are and how abundant (richness and evenness)

It is used to measure the diversity within a sample. It is calculated as a value for each sample. Different metrics were developed to calculate diversity in different ways.

Count of different microbes (OTU count) – Richness: richness is a measure of the number of species present in a sample.

Distribution of different microbes – Evenness: evenness is a measure of the relative abundance of different species that make up the richness in that area.