Darwin And Natural Selection

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The importance attributed to natural selection as a cause of evolution varies widely. The operations of natural selection, real or imagined, are not accessible to the human eye. Natural selection is usually meant, the belief that random variation can, when subjected to selective pressure for long periods of time, culminate in new forms, and that it therefore provides an explanation for the origins of morphological diversity, adaptation, and when extended as far as Darwin proposed, speciation Darwin's definition of natural selection was the preservation of favorable individual differences and variations, and the destruction of those which are injurious, and the survival of the fittest.
The theory that natural selection is the major driving force of evolution is based on the fact that not all conceptions result in births, and only a certain percentage of animals that are born alive survive to adulthood, and even less are able to successfully reproduce. It is also assumed that those that survive to reproduce are more likely to be better adapted to the environment, and are generally biologically superior. As a result, each generation is assumed to produce animals that are slightly better adapted to local conditions than the previous one. Slight genetic mistakes or imperfections called mutations may result in some new traits. Although most mutations are neutral or maladaptive, it is believed that a very few may aid a given population's adaptation, and these may eventually change the composition of the gene pool, slowly producing more and more variety. This process of natural selection is the means of selecting the best of this variety, causing evolution.
Although many researchers conclude that natural selection is the major cause of evolution, most ascribe varying degrees of importance to other factors. Some of these include chance recombination of existing genes which produce positive, negative or neutral characteristics, the neutral mean...