The genotype of the population is influenced to a great extent by natural selection and it is essentially the effect of the environment on the specific phenotype that describes the definition of the fittest. Specific genetic variation plays an important role in the prevailing genome so that the polygenic mannerisms and relevant characteristics function in uniformity. Polygenic inheritance enables the provision of a continuous mannerism of expressions like the color of hair.
Certain human species are polymorphic which means that some dominating phenotypes are commonly conveyed by the natural process. The selection by direction implies that a single phenotype is selected by ignoring other phenotype extremes.
This process enables the progeny of the extreme that is favored to indulge in reproductive activities more effectively thus creating dominance in the entire population. This enables the phenotypes of the succeeding generation to move in a specific direction due to the adoption of the process of natural selection. This process becomes quite common when the population takes over a new area or region and when the environment is transformed by way of, for example, herbicide applications brought about in the existing systems (Simpson, 1967).
This kind of directional selection accounts for some of the diseases becoming resistant to medicines that have been constantly used over time. Surprisingly, such an occurrence happens not because the related germs multiplied and became immune to the medicine, but because as the medicines are used over a period of time by a large population, the innate variables in the germs will breed germs that do not get impacted by the medicine.
In due course, the older germs die and the newer ones can survive the impact of the medicine and breed more germs that are resistant. Thus the phenotype of the given germ shifted to a course that was distinctively a result of the natural selection which functioned on and was in favor of the extreme phenotypes. Conversely, the diversifying selection process supports the phenotype extreme by ignoring the ranges of intermediate phenotypes.
The process of diversified selection creates different phenotypes which result in a booming breeding season within the population. The reverse situation of the diversifying selections is depicted by the stabilizing selection since it is in favor of the intermediate phenotypes at the cost of the different extremes. While the diversifying mechanisms signal a changed environment, stabilizing selections indicate a steady environment, which appears to lessen phenotypic variations (Moulton, 2004).
Sexual selection implies the fondness of a given mate over others and sometimes entails an effusive demonstration by way of a mating dance or graceful plumage. Sometimes the mental, physical, and overall size qualities can impact the decisions to pair off with a particular individual.
In contrasting distinction to the ambiguous and obscure behavior and in order to keep away from predation, such actions mostly are in the nature of being ostentatious irrespective of the possible damaging consequences, for example, the increasing levels of predation. As a result, some individuals will partner and send on their genes while others will not do so. The effect of this kind of selection is very strongly related to the diversifying and directional selections as it influences the overall arrangement of the populations.
Hence sexual selection becomes different in that the forms of selection are created by issues inside other members belonging to similar groups as against external events. When a particular phenotype is preferred over the other in terms of the biotic issues in the environment, inconsistent reproductive patterns are created for the entities in the given populations. Essentially survival of the fittest in this regard pertains to those individuals who can reproduce in the largest numbers. Therefore, success in reproduction becomes the essence of natural selection.
References
Moulton Glen, The Complete Idiot’s Guide to Biology, 2004, Alpha Publishers.
Simpson George Gaylord, The Meaning of Evolution, 1967, Yale University Press.