This essay develops the processes of micro- and macroevolution. Microevolution is a complex of evolutionary processes that occur within species, alter the genetic structure of populations and lead to formation of new species. The processes, which provide the intraspecific alterations of microevolution, are: mutation, natural selection and genetic drift. Macroevolution is a process of evolutionary transformation of supraspecific scale, which leads to the generation of higher taxonomic groups: from species - new genuses, from new genuses - new families, etc. the driving forces of macroevolution are the same of microevolution: natural selection, speciation, variation, and isolating mechanisms (or reproductive isolation).
Species is a main structural unit of wildlife. It appears, develops, and can become extinct, or transform itself into other species if its life conditions modify. Species is an ensemble of homogeneous individuals, with similar morpho-physiological characteristics; it occupies the same area, the species can freely interbreed and produce a copious geniture. The main characteristic of species is the relative stability of its gene pool, which is sustained by reproductive isolation from other species. Population is a totality of individuals of the same species that long-exists on a specific territory, freely interbreeds, and is relatively isolated from other individuals of the same species. All the evolutionary processes proceed from the population, not from the species (which, in addition, originates within a population), that is why population is the basic unit of evolution.
The concept of evolution comprises natural processes of the wildlife`s development, according to Charles Darwin, there are the four ‘driving forces’: selection, migration (or gene flow), genetic drift, and mutation. Populations always undertake mutations, as it stipulates its genetic heterogeneity. In certain environments, mutations that promote the adaptation of the organism, are supported and reinforced by natural selection, and mutations that reduce adaptability, are eliminated. Thus, spontaneous mutations give elementary material for natural selection. Selection itself is the process, by which a population increases the number of individuals that possess the maximum adaptiveness (the most favorable traits), while the number of individuals with unfavorable traits decreases. Gene flow is a change of genes frequency in the gene pool of a population, under the influence of emigration and immigration. Genetic drift comprises various changes that occur in the genetic connections of small isolated populations in the process of breeding within the same species. Such populations are genetically different from the original population from which they came.
Variation, along with isolating mechanisms and speciation is one of the driving forces of macro- and microevolution. Variation is the ability of subsidiary organisms to differ from their parent forms; it is also an ability of living organisms to acquire new features and qualities. It is a very important property that plays a significant role in evolution of species. Variation can be of two types – variability between populations and inside populations. The first type of variation reflects differences between species within a section, between sections within the subgenus, between subgenera within the genus. Variation inside populations is the variability between individuals, represented by a single species. Variation consists of mutations, gene flow and recombination of genetic material.
Isolating mechanisms are mechanisms that prevent the exchange of genes between populations. The morphological differences between closely related species that live in one area are saved by the fact that they do not interbreed. Therefore, the formation of isolating mechanisms is the most obligatory stage of speciation. Speciation is the process of change of the old forms and formation of new forms, as a result of the accumulation of new features.
Evolution is a continual process in the universe. Nature creates new types of systems, and selects the most stable ones. Common to any level of development is the interaction, which leads to competition, to destruction and reproduction of systems, to formation of systems with new structure, to formation of new species, and, finally, to selection of more stable and more perfect of the latter.