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Sunday, February 14, 2010

What is Endemism?

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A number of species of plants are found growing together in a particular habitat. The group of plant species sharing a common habitat is called as a plant community. Many species of insects, worms, nematodes and even higher animals live in association with the plant community. They share the same habitat. Thus communities of plants and animals are found merged together to form the biodiversity of a habitat. This assemblage of plants and animals in a particular habitat is called as a Biota or the Biotic Community.

The mixing of plant and animal communities may take place either gradually or sharply. Those species of plants or animals that have best adaptations in respect of the habitat and the environment always grow and develop in better ways. Others remain unable to enjoy healthy conditions. Thus some species may be abundant in a particular habitat while others may be rare. The colonization of numerous organisms in a particular place is affected by several factors. A number of factors affect the habitation of organisms and all the habitats do not provide particular facilities required by particular type of organisms. These are the reasons why plants and animals are not found distributed uniformly in all types of habitats. Different plants and animals exhibit different patterns of distribution; like Continuous Distribution, Discontinuous Distribution, and
Endemic Distribution.

Some species remain confined to a particular locality due to some or the other reasons. One important reason behind this story is the habitat that alone favors the development and welfare of these species. Good and favorable habitat conditions of river plains attracted human beings to form settlements. That’s why all the civilizations emerged and developed in these areas. Other important reasons behind this may be the Ecological Barriers (like mountain range), geographical locations and extension of the arm of sea etc.

A Mountain Barrier

The species that are confined only to a particular locality or region are called as endemic species. This condition represents a unique step in the process of evolution. The phenomenon of occurrence of particular species only in a particular habitat is called as endemism.For example Bali Mynah is distributed and endemic to the island of Bali, where it is the island's only surviving endemic species.  This rare bird was discovered in 1910 and is one of the world's most critically endangered birds.   In fact, it has been hovering immediately above extinction in the wild for several years. The endemic species are prone to extinction due to several reasons. 

Table of endemic species in India

The Bali Maina

The endemic species remain restricted to a small area, and these are not found elsewhere. It is due to following reasons-

oEndemic species of plants and animals remain poor in adaptation to different types of environmental conditions,

oThese remain restricted to a particular place due to geographical barriers like sea, mountain etc., 

oTheir reproductive organs produce less efficient reproductive cells like propagules, seeds etc. due to which they become unable to disseminate up to far off places.

The above reasons combined with certain environmental factors cause the living Gymnosperm the Metasequoia to remain  endemic to China; the Sequoia or the red wood tree to remain endemic to the coastal valleys in California (USA); the Primulla and the Potentilla remain endemic to high altitudes of Himalayas; and the Ginkgo biloba , to remain endemic to Japan and China.



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