Natural selection is always the main factor in the transformation of living organisms. He acts according to one mechanism - the strongest survive and reserve offspring, i.e. most fit individuals. However, depending on its effectiveness, orientation, characteristics of the living conditions of organisms, the forms of natural selection can be different. So, one of its forms is driving selection (directional), which is a response to changes in the environment and contributes to a shift in the average value of a trait or property. For quantitative characters, the average value is equal to the arithmetic mean value, for example, the average number of descendants 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 hornless cows.
Analysis of these properties allows us to judge the changes that have appeared in the population in connection with adaptation to changing living conditions. At the same time, driving selection can contribute to both strengthening and weakening the changed properties of the body. An example of enhancing a trait is the so-called industrial melanism. The butterfly species, the
birch moth in non-industrial areas, has a light colored 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 that lived on the bark of trees and served as a place for the settlement of butterflies
(protective color). Changing the color of the flakes increased the butterflies' chance of survival. In this case, the so-called selection criteria worked out - the conservation and dissemination of a new species of butterflies, which under the changed conditions are able to continue the genus, i.e. give offspring.
An example of a weakening of a sign is the loss or reduction of an organ and its part in
due to the fact that it does not carry a functional load - the wings of an ostrich (does not fly), the absence of limbs in snakes.
Driving selection is the basis of the artificial. At the same time, a person choosing individuals according to certain parameters (phenotype) increases the frequency of this property. It has been experimentally proved 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 selects the best on an intuitive level. The result of this selection is the emergence of new breeds and varieties characteristic of a particular area. The methodological principle is used in breeding to obtain new species of plants and animals adapted to certain growing and living conditions (frost-resistant species of ratshenia).
Thus, driving 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 their species in changing environmental conditions.