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Biodiversity is measured by two major components:
i. species richness, and
ii. species evenness.
(i) Species richness
It is the measure of number of species found in a community
a) Alpha diversity
It refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species (i.e., species richness) in that ecosystem.
b) Beta diversity
It is a comparison of diversity between ecosystems, usually measured as the change in amount of species between the ecosystems
c) Gamma diversity
It is a measure of the overall diversity for the different ecosystems within a region.
(ii) Species evenness
It measures the proportion of species at a given site, e.g. low evenness indicates that a few species dominate the site.