Published on 14/05/2011
First Update 17/03/2017
Evolution has proceeded from simpler to complex organisms and evolutionary history has provided ample evidence to establish that it has also proceeded in the direction of increasing Biological diversity. Mutations and recombinations are constantly producing new genotypes and providing species with a constant input of physical and chemical variations, some of which improve the efficiency with which the species selects and harvests resources. Mutations may even lead to the creation of separate gene pools, which eventually give rise to non-interbreeding pools – the species. The Darwinian concept of natural selection, which favours the fittest, and the most adaptable species to dominate has an important role to play in the establishment of diversity. Diversity in a population is eliminated by natural selection. Every genetic variation, from a simple mutant to a complete species, will disappear eventually but the rate varies. Species that have survived for extended periods include the horseshoe crabs, which have been round for 200 million years and the cockroaches which have evolved even earlier, during the carboniferous.
This vast library of millions of different species and billions of genetically distinct populations is what is biotic diversity or biodiversity. Any assessment of the number of species on this planet is only guess work. It is estimated that there are between 8 million and 10 million different species on this planet. Of these only 1.5 million have been identified. About 90 percent of the named species occur on land and are identified from the temperate region of North America, Europe, Russia and Australia. May be, because this is where most scientists are located. Indian biodiversity is rich. With just two percent of the world’s landmass, it has about 5 % of living resources, one third of which are land bound. It has been designated as one of the 12 mega diversity states in the world. The living resources include 45,000 species of plants, about 370 mammals, 1200 birds, 60,000 insects, 180 amphibians, 1700 fishes and 400 reptiles. India has more than 75 % of the 425 families of flowering plants found all over the world and has a very large network of 497 sanctuaries and89 national parks.