Natural selection is always the main factor in the transformation of living organisms.He acts by the same mechanism - survive and retain the strongest offspring, ie,fittest.However, depending on its efficiency, directivity characteristics of the conditions of existence of organisms - forms of natural selection can be different.Thus, one of its forms is the dynamic selection (directional), which is a response to changes in the environment and contributes to a shift of the mean value of a characteristic or property.For quantitative characteristics the average value is equal to the arithmetic mean, for example - the average number of offspring being born.But to describe the qualitative properties is determined by frequency (percentage) of individuals with the necessary sign, for example - the frequency of horned and hornless cows.
analysis of these properties gives an indication of the changes that have emerged in the population due to the adaptation to changing environmental conditions.This dynamic selection can contribute to both strengthen and weaken the changed characteristics of the organism.An example of the gain characteristic is the so-called industrial melanism.Kind of butterfly peppered moth in non-industrial areas, has a light color scales covering the body and wings, and in areas with a large number of factories of their color turns black.The emergence of moths unusual for them to color due to the fact that the harmful industrial emissions have led to the death of lichens that lived on bark of trees and serves as a place of settlement of butterflies (protective coloration).Change the color of the flakes increase the chances of survival of butterflies.In this case, it triggered the so-called selection criteria - the preservation and promotion of a new species of butterflies that in the changed circumstances are able to continue the race, that is,give birth.
attenuation characteristic example is the loss or reduction of the body and its parts due to the fact that he does not bear the functional load - the wings of the ostrich (not flying), lack of limbs in snakes.
dynamic selection is based on artificial.At the same man choosing individuals according to certain parameters (phenotype), increases the frequency of a given property.Empirically it proved that such selection by their appearance leads to some changes in genotype, and perhaps the loss of some alleles.There are some forms of artificial selection - unconscious and methodical.When using the selection of the unconscious man as if intuitively selects the best.The result of such a sample is the emergence of new breeds and varieties specific to certain areas.Methodological principles used in breeding to produce new species of plants and animals adapted to the specific growing conditions and accommodation (hardy species ratseny).
thus driving the selection - is a form of natural selection, the result of which is the appearance of a new, adapted species of organisms that can survive and continue their family in the changed environment.
