Conventional wisdom has it that for any given niche there should be a best species, the fittest, that will eventually dominate to exclude all others.(University of Exeter)
This is the principle of survival of the fittest.From protozoans to mammals, evolution has created more and more complex structures and better-adapted organisms."A single base change can create a devastating genetic disorder or a beneficial adaptation, or it might have no effect. How do mutations happen, and how do they influence the future of a species?
The DNA in any cell can be altered through environmental exposure to certain chemicals, ultraviolet radiation, other genetic insults, or even errors that occur during the process of replication. If a mutation occurs in a germ-line cell then this mutation can be passed to an organism's offspring. This means that every cell in the developing embryo will carry the mutation. Together, these different classes of mutations and their causes serve to place organisms at risk for disease and to provide the raw material for evolution. Thus, mutations are often detrimental to individuals, but they serve to diversify the overall population. Now researchers are uncovering how mutations actually work and that may help us find cures for life threatening diseases. As we understand more about mutation we may discover more secrets of the history and future of life on this planet."(http://www.nature.com).