Natural selection


August 14, 2022

Natural selection or natural selection refers to traits characteristic of individuals - phenotypes - that can be assigned to individuals. Organisms with a more favorable phenotype are more likely to survive or reproduce than individuals with a less favorable phenotype. If the beneficial phenotype is inherited, the frequency of the alleles (gene variants) responsible for its formation will in most cases be higher in the next generation. The selection process itself is usually called adaptation, and the beneficial properties that spread during the selection process are usually called adaptive properties. Natural selection is a process that takes place in populations of organisms, which can take place as follows: 1. the frequency of certain inherited variants tends to increase from generation to generation until only one variant remains in the population (the case of the spread of advantageous variants), 2. the frequency of certain inherited variants tends to increase from generation to generation until two reproductively isolated, different populations are created (species formation, selection for divergence) 3. the frequency of some inherited variants changes similarly in each generation within one generation, while remaining constant in the long term (e.g. case of balanced polymorphism, frequency-dependent selection). For example, the hemoglobin variant responsible for the development of sickle cell anemia is more common in adults than in newborns in areas affected by malaria, while the frequency of occurrence among newborns in the same areas has been constant for a long time. The reason for this is that in the first years of life, children with both the defective and the normal molecule version are more likely to survive the infection than their peers with only the normal hemoglobin molecule. In contrast to natural selection, the equivalent, so-called the frequency of neutral heritable variants varies randomly in populations, both in the short and long term. This process is called genetic drift. The neutral theory of molecular evolution examines the effect of genetic drift resulting from finite population size on molecular evolution. Understanding the mechanisms of adaptations, i.e. natural selection, is the basis of modern biology. The inevitability of natural selection processes was recognized and deduced by Charles Darwin in his 1859 book On the Origin of Species, in which he described natural selection as an analogy to artificial selection (during artificial selection, breeders give preference to animals and plants based on their own ideas during reproduction). In nature, hereditary variants incapable of life or reproduction fall out of populations. Environmental factors (e.g. temperature, quality of available food, natural enemies, etc.) can select among the other inherited variants. Darwin's description of the process of natural selection is still valid today among organisms that reproduce asexually. Since the mechanisms of inheritance were not yet known when his theory of evolution was born, Darwin could not yet describe certain selection processes (e.g. the case of heterozygous advantage). The modern evolutionary synthesis was born during a kind of unification and formalization of the classical and Darwinian selection theory. Although different mechanisms of molecular evolution (for example the neutral theory of molecular evolution described by Motoo Kimura) can also play an important role in genetics