Biodiversity and Species Richness

Biodiversity is a measure of the variety of life on Earth. It encompasses the diversity within species, between species, and of ecosystems. Understanding biodiversity — what it is, why it matters, and how it varies — is central to ecology and conservation biology.

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What Is Biodiversity?

Biodiversity (biological diversity) can be defined at three levels:

Level	Definition	Example
Genetic diversity	The variety of alleles (gene variants) within a species or population	Different alleles for coat colour in a population of mice
Species diversity	The variety of species in an area, encompassing both the number of species and their relative abundance	A tropical rainforest containing thousands of plant, animal, fungal and microbial species
Ecosystem diversity	The variety of different ecosystems (habitats) in a region	A landscape containing forests, wetlands, grasslands and rivers

All three levels are interconnected. High genetic diversity within species contributes to species diversity, and diverse ecosystems support greater species diversity.