The most obvious definition of biodiversity is the variety of species on Earth. Biodiversity or biological diversity refers to the variety of life forms: the different form. This plants, animals and microorganisms, the genes they contain, and the ecosystems they living wealth is the product of hundreds of millions of years of evolutionary history. Biological diversity is usually considered at three different levels: genetic diversity, species diversity and ecosystem diversity.
Genetic diversity refers to the variety of genetic information contained in all of the individual plants, animals and microorganisms. Genetic diversity occurs both within and between distinct populations of the same species, as well as between species in one particular population. New genetic variation is produced in populations of organisms that can reproduce sexually by recombination and in individuals by gene and chromosome mutations. The pool of genetic variation present in an interbreeding population is shaped by selection, leading to certain genetic attributes being preferred thus resulting in changes to the frequency of genes within this pool.
The enormous variety and complexity of habitats and the different ways organisms obtain their living can be responsible for the large differences in the amount and distribution of genetic variation.
Species diversity refers to the variety of species. Aspects of species diversity can be measured in a number of ways. Most of these ways can be classified into three groups of measurement: species richness, species abundance and taxonomic or phylogenetic diversity. On a broad scale species diversity is not evenly distributed across the globe. The single most obvious pattern in the global distribution of species is that overall species richness is concentrated in equatorial regions, tending to decrease as one moves from equatorial to Polar Regions. In general, there are more species per unit area in the tropics than in temperate regions,