Biodiversity can be subdivided into three levels as follows:
1. Genetic Diversity
At finer levels of organisation, biodiversity includes the genetic variation within species, both among geographically separated populations and among individuals within the single population.
Differences between individual organisms have two causes: variation in the genetic material which all organisms possess and which is passed on from generation to generation; and variation caused by environmental influence on each individual organism. New genetic variation, which arises by gene and chromosome mutation in individuals and in sexually reproducing organisms, is spread in the population by a recombination of genetic material during cell division preceding sexual reproduction.
A great deal of work needs to be done on the conservation of genetic diversity within wild species in India. Protecting the Gir Habitat, for instance, has saved the Asiatic Lion. India also has a long tradition of domestic animal breeding for specific qualities. These include cattle, goats and sheep as well as horses and pigeons for sport.
The replacement of numerous locally adapted varieties with a few high yielding strains in the large contiguous areas presents the danger of the spread of serious diseases capable of wiping out the entire crop, as happened prior to the Bengal rice famine in 1942.
A productive and stable agriculture requires genetic diversity on the farm. Genetically diverse crop varieties enable farmers to fit their cropping systems to heterogeneous conditions, to enhance the food security of their households and to exploit a range of crop products.
The challenges are at least two-fold; to meet farmers’ needs for wide genetic diversity whether through enhanced access to local varieties or newly introduced genetic resources; and to find strategies for linking longer-term conservation goals with immediate product needs.
2. Species Diversity
Biodiversity at its most basic level includes the full range of species on earth from micro- orgnisms such as viruses, bacteria through the multicellular kingdom of plants, animals and fungi. Thus, it refers to the variety of species within a region. It measured on the basis of number of species in the region. Species’ richness varies geographically. Out of an estimation 30 million species on earth, only one-sixth has been identified and authenticated in the past 200 years. Only 250,000 species of the total stock are plants.
Keystone species have an important role in maintaining the diversity of a whole community of other species. Keystone species would include pollinators, top predators and the decomposer organisms and so-forth. The wild species are of considerable potential benefit to man in medicine, agriculture and industry as a natural source of drugs, food, fuel, fibre, industrial base compounds and additives.
3. Ecosystem Diversity
On the wider scale, biodiversity includes variations in the biological communities in which species live, the ecosystem in which communities exist, and the interactions among these levels.
In the living world, interdependence and interaction between organisms and their environment are a very common practice to assert one’s existence on this planet. On the other hand, nature always tries to remain in homeostatic state and various life forms help to maintain this equilibrium.
For both these cases, biodiversity serves as the source of livestock. To human beings, it opens avenues for understanding the laws and ways of nature and for making the optimum sustainable use of life support systems gifted to man by nature.
The regulation of biogeochemical cycles, maintenance of predator-prey relationships by various types of food chains and food webs and finally the balance of nature are maintained through biodiversity. Again it indirectly influences the climatic factors, soil nature, chemistry of air etc. that are the abiotic elements of an ecosystem.
Ecosystem diversity could be best understood if one studies the communities in various ecological niches within the given ecosystem.