Today it is one of the most commonly used expressions in the biological sciences and subsequently has become a household word.
Biologists are inclined to agree that it is, in one sense, everything.
Biodiversity is defined as all hereditarily based variation at all levels of organization, from the genes within a single local population or species, to the species composing all or part of a local community, and finally to the communities themselves that compose the living parts of the multifarious ecosystems of the world. Even though the study of biodiversity can be traced back as far as Aristotle, what finally has given it such extraordinarily widespread attention is the realization that it is disappearing. In the late 1970s and through the 1980s, the first convincing estimates were made of the rate of tropical deforestation, which translates to the areal loss of habitat where most of living diversity is concentrated. This information led to disturbingly high estimates of the rates of loss of species in these forests. The magnitude of erosion also drew attention to ongoing extinction in other habitats, from deserts to coral reefs, at all levels of biological organization from alleles to entire local ecosystems.