In the process of natural selection in the population, those individuals that are most adapted to survival, most adapted, are preserved and increased. This term made Charles Darwin common at the time. He introduced it to compare with artificial selection and show that, in principle, in both cases the process is the same. The difference lies only in who evaluates the necessity or unnecessaryness of certain properties - the environment or a person.
Forms of natural selection are classified based on many criteria. The typology proposed by I. I. Schmalhausen was widely used. Determining the types of natural selection, he relied on how they affect the variability or stability of the trait in a particular population. The question of their number is still unclear. But the following three forms of natural selection are still considered basic in biological science : tearing (disruptive), guiding (moving), and stabilizing. The more diverse the genotypes the species possess, the more successful the process.
The result of moving selection is the consolidation of abnormal signs. It was first described by Wallace and Darwin. In the case of this selection, those individuals who have traits that deviate strongly in one direction or another get advantages.
It manifests itself when the area is expanding or the environment changes. Then living beings are forced to change in a certain direction in order to adapt to new conditions. For example, if terrestrial mammals are forced to go underground, their limbs will gradually adapt to new conditions and turn into burrows.
The stabilizing form of natural selection is focused on the preservation of individuals in which a certain trait is expressed with an average degree, and at the same time on the deviation of those in which it is too far from the norm. For example, birds with a standard wing size are more likely to survive rather than being too large or small.
The action of disruptive selection is the opposite of the two previous ones. It occurs when the conditions are ideal for the further development of some attribute in its extreme manifestation, but not on average. As a result, not one, but even several new ones may appear from the initial form. Thus, disruptive selection may be the reason for the appearance of completely new, previously non-existent species.
In nature, a situation often arises when the same population lives in different places. Accordingly, its representatives adapt to their differing ecological niches.
An example of artificially conducted disruptive selection is the well-known experiment with Drosophila. After only individuals having either the maximum or minimum number of bristles were selected for crossing, these two groups began, beginning in the thirtieth generation, to differ very much from each other, although they continued to cross with each other.
Separately from the three main forms, biology is considered in biology. Its influence is important. After all, any individual must not only adapt and survive, but also like the partner to continue his race.
There are two hypotheses that explain the mechanism of action of sexual selection.
According to the first, the female chooses the male already because he managed to survive to the stage of maturity, despite his bright appearance. This means that he has good genes and will pass them on to the next generation.
The second hypothesis explains the choice of pairs differently. According to her, females choose a bright partner precisely because of their attractive color, believing that the next generation should have the same one so that they are chosen for reproduction.
In addition to the three listed above, there is also an individual and group form of natural selection. The first is aimed at preserving individual individuals that have signs that allow them to survive and exist within their population. A group fixes qualities that are useful for the whole species.
All existing forms of natural selection do not act randomly, randomly and simultaneously, but gradually, when the population retains certain signs from generation to generation.