ABSTRACT
The biodiversity of a place or region is a measure of the number of species present and of their abundance. Each species occupies a niche a specific location, relationship with its physical surroundings and mode of interaction with other species. Organisms of a single species in one place are called a population, and together populations form a community. The precise cause of each mass extinction is difficult to assess. Catastrophes such as meteorite impacts and comet showers may have been responsible for some mass extinction. Global climate change, fluctuation in the concentration of various gases, and other gradual environmental trends may have caused others. Modern humans are the last survivors of the Hominini tribe, whose many branches evolved as a result of geographic isolation, possibly brought about by climate change. It is this use of tools and technology, from clothing and housing to sophisticated farming methods, that has served as a buffer between Homo sapiens and the changing environment.
