‘Biological diversity’ or biodiversity is that part of nature which includes the differences in genes among the individuals of a species, the variety and richness of all the plant and animal species at different scales in space, locally, in a region, in the country and the world, and various types of ecosystems, both terrestrial and aquatic, within a defined area.

Biological diversity deals with the degree of nature’s variety in the biosphere. This variety can be observed at three levels:
1. The genetic variability within a species,
2. The variety of species within a community, and
3. The organization of species in an area into distinctive plant and animal com-munities constitutes  ecosystem diversity

Genetic diversity:
 Each member of any animal or plant species differs widely from other individuals in its genetic makeup  because of the large number of combinations possible in the genes that give every individual specific characteristic.
 Thus, for example, each human being is very different from all others. This genetic variability is essential for a healthy breeding population of a species.
 If the number of breeding individuals is reduced, the dissimilarity of genetic makeup is reduced and inbreeding occurs. Eventually this can lead to the extinction of the species.

 The diversity in wild species forms the ‘gene pool’ from which our crops and domestic animals have been developed over thousands of years.

Species diversity: 
 The number of species of plants and animals that are present in a region constitutes its species diversity. This diversity is seen both in natural ecosystems and in agricultural ecosystems. Some areas are richer in species than others.
 Natural undisturbed tropical forests have much greater species richness than plantations developed by the Forest Department for timber production.
 Modern intensive agricultural ecosystems have a relatively lower diversity of crops than traditional agropastoral farming systems where multiple crops were planted.
 Areas that are rich in species diversity are called ‘hotspots’ of diversity. India is among the world’s 15 nations that are exceptionally rich in species diversity.

Ecosystem diversity:
 There are a large variety of different ecosystems on earth, which have their own complement of  distinctive inter linked species based on the differences in the habitat.
 Ecosystem diversity can be described for a specific geographical region, or a political entity such as a  country, a State or a taluka.
 Distinctive ecosystems include landscapes such as forests, grasslands, deserts, mountains, etc., as well  as aquatic ecosystems such as rivers, lakes, and the sea.
 Each region also has man-modified areas such as farmland or grazing pastures. An ecosystem is referred  to as ‘natural’ when it is relatively undisturbed by human activities or ‘modified’ when it is changed to other types of uses, such as farmland or urban areas. Ecosystems are most natural in wilderness areas.