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Environment Book Summary Presented Bu Aartee Mishra
CHAPTER 7 diversit
BIODIVERSITY .The land, air and seas of our planet are home to the tiniest insects and the largest animals which make up a rich tapestry of interconnecting and BIODIVERSITY All ing beings that inhabit the planet. ecosystens that host theni and the relathonships they establich with each other interdependent forces. . Biodiversity found on Earth today consists of many millions of distinct biological species the product of four billion years of evolution. Biodiversity is measured by two major components: 1. species richness. 2. species evenness.
MEASUREMENT OF BIODIVERSITY Species richness It is the measure of number of species found in a community Alpha diversity It refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species (i.e., species richness) in that ecosystem. Beta diversity It is a comparison of diversity between ecosystems, usually measured as the change in amount of species between the ecosystems. Gamma diversity It is a measure of the overall diversity for the different ecosystems within a region.
Species evenness It measures the proportion of species at a given site, e.g. low evenness indicates that a few species dominate the site. Genetic diversity .Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. A single species might show high diversity at the genetic level [E.g. Man: Chinese, Indian American, African etc.]. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango. Genetic diversity allows species to adapt to changing environments. This diversity aims to ensure that some species survive drastic changes and thus carry on desirable genes.
Species diversity It is the ratio of one species population over total number of organism:s across all species in the given biome. 'Zero' would be infinite diversity, and 'one' represents only one species present. Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a community) and the evenness of species. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. There are more than 200000 species in India of which several are confined to India (endemic). .Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere.
A particular type of animal or plant may be endemic to a zone, a state or a country. The extreme opposite of endemism is cosmopolitarn distribution. Species differ from one another, markedly in their genetic makeup, do not inter-breed in nature. Closely-related species however have in common much of their hereditary characteristics. For instance, about 98.4 per cent of the genes of humans and chimpanzees are the same. According to the IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but we have no clear idea of how many species are yet to be discovered and described A large proportion of the species waiting to be discovered are in the tropics. Estimate place the global species diversity at about 7 million