Natural selection is always the maintransformation factor of living organisms. It operates according to one mechanism - the strongest survive and leave offspring, i.e. the most adapted individuals. However, depending on its efficiency, orientation, and peculiarities of the conditions of existence of organisms, the forms of natural selection can be different. Thus, one of its forms is moving selection (directed), which is a response to changes in habitat and contributes to a shift in the average value of a trait or property. For quantitative traits, the average value is equal to the arithmetic mean value, for example, the average number of children born. And to describe the qualitative properties, the frequency (percentage) of individuals with a necessary attribute is determined, for example, the frequency of horned and horny cows.
Data analysis of properties allows to judge aboutchanges that appeared in the population due to adaptation to the changed habitat conditions. At the same time, motive selection can contribute to both strengthening and weakening the changed properties of the organism. An example of the enhancement of a trait is the so-called industrial melanism. The species of the butterfly 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 that lived on the bark of trees and served as a settlement for butterflies (patronizing coloring). The change in color of the scales increased the chance of butterflies to survive. In this case, the so-called selection criteria worked out - the preservation and distribution of a new species of butterflies, which under the changed conditions are able to continue the genus, i.e. give offspring.
An example of the weakening of a trait is the loss or reduction of an organ and its part in
due to the fact that it does not carry the functional load - the wings of the ostrich (does not fly), the lack of limbs in snakes.
Driving selection is the basis of artificial.At the same time, a person, choosing individuals by certain parameters (phenotype), increases the frequency of this property. It has been experimentally proven that such selection by external features 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, as it were, on an intuitive level. The result of such a sample is the emergence of new breeds and varieties characteristic of a particular area. The methodical principle is used in breeding to obtain new species of plants and animals adapted to specific conditions of growth and residence (frost-resistant types of rats).
So motivational selection is one of the formsnatural selection, the result of which is the emergence of a new, adapted species of organisms that can survive and continue its kind in the changed environmental conditions.
