Biodiversity or biological diversity is the diversity of life.
There are a number of definitions and measures of biodiversity.
Biodiversity is commonly identified at three levels.
First there is genetic diversity, which is the diversity of genes within a species.
There is a genetic variability among the populations and the individuals of the same species.
Secondly there is species diversity, or diversity among species in an ecosystem. "Biodiversity hotspots" are excellent examples of species diversity.
Third there is ecosystem diversity, diversity at a higher level of organization, the ecosystem.
This has to do with the variety of ecosystems on Earth.
Since 1986 the terms and the concept have achieved widespread use among biologists, environmentalists, political leaders, and concerned citizens worldwide.
This use has coincided with the expansion of concern over extinction observed in the last decades of the 20th century.