Elementary unit of evolution - what is it? Definition of an elementary unit of evolution

Modern man, in general, is familiar with the concept of evolution as a process of the continuous development of life on the planet. It is commonly believed that evolution is the process of adaptability and changeability of all forms of living organisms throughout their long existence. You can argue a lot about the theories of the origin of life on the planet, about how it all began. But the generally accepted concept is that it is all taught in school. At the same time, what is an elementary unit of evolution - an individual, a group of organisms, a species - is far from known and understood by all.

The development of theory

At the word "evolution" we immediately recall Charles Darwin (1809-1882). But long before him the idea of a gradual development of life and such a concept as an elementary unit of evolution appeared in the philosophical thought of mankind. But it is Charles Darwin who belongs to the introduction to the scientific community ... no, not concepts of evolution, but those driving forces that will lead to significant, sometimes significant changes in organisms that result in the formation of new species. Species as a biological community of organisms that are similar in a whole complex of features that are capable of free crossing with the appearance of reproductive progeny. So, the subject of this article is the definition of the smallest unit in which a long and qualitative change can occur, leading to the appearance of something new and different from the parent forms.

Before Darwin

The point of view on the development of the organic world, which existed before the theory of the origin of Darwin's species , is called the pre-Darwinian theory. Without going into the jungle of evolutionary theory, the dominant theory was theological (everything from God) and the theological-naturalistic (organisms strive for perfection, which again is from God). These theories consider an individual as an elementary unit of evolution. For example, Jean Baptiste Lamarck (1744-1829) explained the occurrence of a long neck in giraffes by their desire to reach the upper branches and the transfer of this desire to the descendants.

The Revolution of Darwin

The merit of Charles Darwin is that in his work "The Origin of Species" he explained all the unthinkable variety of living forms on the planet by the result of the struggle for existence, natural selection. And the result of this process was the victory of the most powerful and adapted individuals. Darwin specifically noted that the elementary unit of evolution is a group of individuals, and not just single individuals. Natural selection works exactly when it affects both individuals and their natural groups. It is in the group, according to Darwin, that today the signs that are unnecessary can remain, but tomorrow they become decisive in the adaptability of organisms to the ever-changing conditions of life. In Darwin, such a group is a species as an elementary unit of evolution.

Darwinism plus genetics

What Charles Darwin could not explain in his "Origin ..." is how these random changes are transmitted and fixed in the offspring. After all, special signs must be blurred in the course of a successive change of generations. And it is at this time that the genetics science appears with its inheritance laws and the recessive and dominant alleles accumulated in the group of organisms. Three laws of the generality of the first generation of G. Mendel hybrids, the double helix of the genetic information of J. Watson and F. Crick's DNA, molecular biology and the structure of the gene, the development of embryology and cytology, ethology and paleontology, biochemistry and ecology - and the birth of a synthetic theory of evolution, Prevailing in today's scientific environment.

Symbiosis of Darwinism and Modernity

Synthetic theory of evolution was formed in the middle of the twentieth century. The contribution of all evolutionary biologists to its development will not be enough for three pages. We note biologists SS Chetverikov (1880-1959), FG Dobrozhansky (1900-1975) and II Shmalhausen (1884-1963). The main postulate of the theory - the elementary unit of evolution is the population as a separate group of one species, living in one territory and in a certain way isolated from other populations of a given species. It is the isolation of populations (ecological, geographic, reproductive) that leads to the formation of new species. To explain the mechanisms of this speciation, the synthetic theory of evolution brings certain positions, which also explain why the population is considered an elementary unit of evolution.

The main provisions of the synthetic theory of evolution

The data given below do not pretend to full and comprehensive information about the provisions of modern theory, but are considered in the context of the postulate that the population is an elementary unit of evolution.

Russian biologist and geneticist NV Timofeev-Resovskii (1900-1981) formulated the main provisions of the STE on elementary units, phenomena and factors of biological evolution.

• An elementary unit of evolution is a population.
• The phenomenon of evolution in action is the changes in the gene pool (a common set of genes of all individuals) in the population.
• The gene pool of the population is the hereditary material of evolution.
• Factors of evolution are mutational processes, isolation, population waves (fluctuations in numbers) and selection.

Why the population

Only a population as a group of individuals of one species represents a single entity that can exist indefinitely as an integrity in space and time. And only within this generality the probability of free crossing of individuals is always higher than the probability of crossing individuals from different populations. Only the population meets the requirements of the evolutionary process, and therefore it is the elementary unit of evolution. Only within this group with a different set of genotypes, individuals are selected for phenotypic traits. Only in such a closed system can the phenotypically successful conditions for the existence of symptoms persist in the genotype of the whole group, in the gene pool of the population. And, accumulating in the gene pool, change the individual genotypes of individuals, leading to phenotypic (external) differences.

Why is not the species an elementary unit of evolution?

The view can also be regarded as an integral closed system, which exists for a long time. But each species, inhabiting a certain area, is distributed unevenly across the territory. And each part of it is a population that can theoretically give rise to the process of speciation. And maybe not give. Some species, for example endemics, generally inhabit fairly limited areas and are represented by a single population (Arctic polar bear or Baikal seal). And there are species, for example, forty ordinary, represented by hundreds of populations in various parts of the world.

Why is not a single individual an elementary unit of evolution?

The evolutionary process implies the development and emergence of new signs and properties of the organism, leading to its greater fitness. And then you need a chain of generations - evolutionary history or evolutionary destiny. One organism does not exist for a long time, in order to develop and consolidate a trait throughout life. Therefore, a herd or a flock can not be an elementary unit - this group is not sufficiently isolated and exists, as a rule, not very long term in the context of the number of generations. It is worth noting that this statement does not quite fit with prokaryotes (nuclear-free) as the simplest with a high rate of reproduction.