Forms of natural selection

In the process of natural selection, the individuals that are most adapted to survival are kept and grow in the population, the most adapted. This term was made at one time by Charles Darwin. He introduced it to compare with artificial selection and to show that in principle, in both cases the process is the same. The difference is only in who evaluates the need or the uselessness of certain properties - the habitat or the person.

The forms of natural selection are classified on the basis of many criteria. The typology proposed by II Shmalhausen was widely used. Defining 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 remains unclear. But the main three in biological science are the following three forms of natural selection: tearing (disruptive), guiding (driving) and stabilizing. The more diverse genotypes are the species, the more successfully the process takes place.

The result of the driving selection is the consolidation of deviating characteristics from the norm. It was first described by Wallace and Darwin. In the case of this selection, those individuals who have signs that deviate strongly in one direction or another are given advantages.

It manifests itself when the range is expanding or the environment changes. Then the living beings are forced to change in a certain direction in order to adapt to the new conditions. For example, if terrestrial mammals are forced to go underground, their limbs will gradually adapt to new conditions and become diggers.

The stabilizing form of natural selection is focused on the preservation of individuals in whom a certain sign is expressed with an average degree, and at the same time to reject those in which it is too far from the norm. For example, there are more chances to survive in birds that have a standard wing size, rather than too big or small.

The effect of the disruptive selection is opposite to that of the previous two. It occurs when the conditions are ideal for the further development of some feature 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, a dysfunctional selection may be the cause of the appearance of absolutely new, previously not existing species.

In nature, often there is a situation where the same population lives in different places. Accordingly, its representatives adapt to their own, different ecological niches.

An example of artificially conducted disruptive selection is the experiment known to all with Drosophila. After only individuals having either a maximum or a minimum number of bristles were selected to be crossed, the two groups began to differ very much from the thirtieth generation, although they continued to interbreed.

Separated from the three main forms, sexual selection is considered in biology. His influence is important. After all, any individual should not just adapt and survive, but also like the partner to continue his family.

There are two hypotheses explaining the mechanism of the action of sexual selection.

According to the first, the female chooses the male for the fact that he managed to survive to the stage of maturity, despite the 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, the bright partner of a female is chosen for an attractive coloring, considering that the next generation should have the same, so that they are also chosen for reproduction.

In addition to the three listed above, there is still an individual and group form of natural selection. The first is aimed at preserving individuals who have signs that allow them to survive and exist within their populations. A group fixes qualities that are useful for the whole species.

All existing forms of natural selection do not act chaotically, randomly and simultaneously, but gradually, when from generation to generation the population retains certain characteristics.