Natural selection takes the raw material of variations with a population and moulds it over a long period of time into a population that can compete most effectively with other species. This selection will favor the fittest individuals in a species to fit a particular biological niche. Any given environment will have a large number of niches, for example small variations in the temperature, humidity and exposure to sunlight will affect the ability of certain plants to grow and compete with other plants. Species that fit these niches will represent a very diverse population and therefore will have extensive genetic diversity. This diversity will be both at the level of an individual species and also at level of different species which co-evolved to fit a particular biological niche. Within a niche there are numerous different solutions to the problem of adaptation to that environment, and it is likely that different species will develop different methods of adaptation that enable them to survive in any particular niche. In summary, natural selection will drive the adaptation of any given population to fit the number of available niches, and this will create the biodiversity that is present in nature. Explain
Continued evolution requires a diverse population, which provides the raw material on which natural selection can act. As natural selection is the accumulation of random, small genetic changes, the chances of any of these changes resulting in an organism capable of better fitness for a given environment is magnified if the initial population is diverse. A more restricted starting population would limit the genetic diversity and make it less likely to generate individuals with improved fitness to adapt to new environments. Therefore a restriction in biodiversity, as may be occurring by the large numbers of species becoming extinct currently, will severely limit the ability of the remaining population to adapt. This is particularly a problem as the environment changes, since that will require plant an animal species to change to fit these new environments. Without a large gene pool to draw upon, the number of solutions to the problem of survival in a new biological niche will be limits, perhaps resulting in the inability of some species to compete and survive.
Edward O.Wilson, editor, Frances M.Peter, associate editor, Biodiversity, National Academy Press, March 1988 Biodiversity: An Introdution by Kevin J. Gaston and John I. Spicer
Genetics, Evolution and Biodiversity by John Adds, Erica Larkcom, and Ruth Miller Evolution by Jean-Baptiste de Panafieu, Patrick Gries, and Linda Asher