(i) Genetic biodiversity enables a population to adapt to its environment and to respond to natural selection. Genetic diversity within a species increases with environmental variability which results in the formation of polymorphs, races and subspecies in geographically isolated populations. Therefore, it provides the raw material for adaptation and evolution of new life forms (speciation). The different varieties of a given plant may differ in the concentration and activity of an important chemical compound that the plant may be producing (e.g., reserpine in Rauwolfia vomitoria). Similarly, the genetic diversity of rice in India is reflected in having more than 50,000 strains and in having more than 1000 varieties of mango.
(ii) Species biodiversity refers to the variety of species within a region. Species diversity has three qualities: (a) Species richness (the total number of species), (b) Species evenness (the relative abundance of species) and (c) species dominance (the most abundant species). Species diversity is the sum total of relative chance of seeing species as well as the actual number of species present.
(iii) Ecological biodiversity describes the number of niches, trophic levels and various ecological processes that sustain energy flow, food webs and the recycling of nutrients. Ecological biodiversity helps in producing more productive and stable ecosystems which can tolerate various stresses like prolonged drought
