Answer:
Natural selection is differential reproduction of some genetic variants with respect to others. We can define it more rigorously as the process that occurs in a population of biological entities when the following three conditions are met: (1) phenotypic variation between the individuals of a population, that is, the different individuals of a population differ in their observable characters -your phenotype- presenting differences in their morphology, physiology or behavior; (2) differential biological efficacy associated with the variation; that is, certain phenotypes or variants are associated with greater offspring and / or longer survival; and (3) the inheritance of the variation, which requires that the phenotypic variation is due, at least in part, to an underlying genetic variation that allows the transmission of the selected phenotypes to the next generation. If these three conditions occur in a population of organisms, then a change in the genetic composition of the population by natural selection is necessarily followed.
Explanation:
The theory of evolution by natural selection (TESN) was formulated by Darwin in the work on the origin of species through natural selection: “To the conservation of favorable individual differences and variations and the destruction of harmful ones I have called 'natural selection' or 'survival of the fittest' ”(Darwin 1860, 147). The eloquent subtitle of this work is "The preservation of the preferred races in the struggle for life", and in it Darwin exposes the hypothesis of a "battle for existence", of a struggle for life existing in nature, in which only the best manage to survive. Nature itself provides the means to win this battle through random changes, and among these, there are some that increase the chance of survival. Therefore, these changes are selected and transmitted to the progeny, thus allowing the evolution of the species. A change that is advantageous will be preserved and transmitted to the offspring, while one that is harmful will be eliminated. The term "selection" was used by Darwin to compare what happens in nature with livestock. In effect, farmers select their own cattle by eliminating the worst and allowing only the best to survive and reproduce. In contrast to this "artificial selection," Darwin called his hypothesis "natural selection."
Therefore, evolution must be considered as the result of a process with two phases: one of changes and another of selection. The changes are verified completely randomly, so the objective of the selection is to guarantee reproductive success. The whole set of genes is called the genotype of an organism, while its manifestations constitute the phenotype. Therefore, some phenotypic features that develop casually are then selected if they allow greater reproductive success. However, in order to talk about evolution, the following conditions must be met: phenotypic variation, differential reproductive success and heritability.
