Moving selection - microevolution in the population of organisms

Natural selection always acts as the main factor in the transformation of living organisms. It operates by a single mechanism - they survive and retain the strongest offspring. The most adapted individuals. However, depending on its effectiveness, orientation, and specific conditions of existence of organisms, the forms of natural selection may be different. So, one of its forms is the driving selection (directional), which is a response to changes in the habitat and contributes to a shift in the mean value of the feature or property. For quantitative characteristics, the average value is equal to the arithmetic mean value, for example, the average number of descendants to be born. And to describe the qualitative properties, the frequency (percentage) of individuals with the necessary trait is determined, for example, the frequency of horned and littered cows.

Analysis of these properties allows us to judge the changes that have appeared in the population in connection with the adaptation to the changed habitat conditions. In this case, the driving selection can promote both strengthening and weakening of the changed properties of the organism. An example of strengthening the trait can serve as a so-called industrial melanism. The species of a butterfly, a birch moth in non-industrial areas, has a light color of scales covering the body, and wings, and in areas with a large number of plants and factories their color changes to black. The appearance of moths of an unusual color is due to the fact that harmful industrial emissions led to the death of lichens living on the bark of trees and served as a place for the settlement of butterflies (patronizing coloring). Changing the color of scales increased the chance of butterflies to survive. In this case, the so-called selection criteria worked - the conservation and distribution of a new species of butterflies, which, under changed conditions, can continue the genus, i.e. Give offspring.

An example of a weakening of a trait is the loss or reduction of an organ and its part in Connection with the fact that it does not carry a functional load - the wings of an ostrich (does not fly), the absence of limbs in snakes.

Motion selection is the basis of the artificial. Thus the person, choosing individuals on certain parameters (phenotype), increases the frequency of this property. It has been proven by experience that such selection by external characteristics leads to some changes in the genotype, and, possibly, the loss of some alleles. There are such forms of artificial selection - unconscious and methodical. When using unconscious selection, a person, as if on an intuitive level, selects the best. The result of such a sample is the emergence of new breeds and varieties characteristic of a particular locality. Methodological principle is used in breeding for obtaining new species of plants and animals adapted to certain conditions of growth and residence (frost-resistant types of plants).

Thus, moving selection is one of the forms of natural selection, the result of which is the emergence of a new, adapted species of organisms that can survive and continue its genus under changed environmental conditions.