The essence of the concept of the evolution of C. Darwin is reduced to a line of logical, confirmed by experiments and other studies. So, it was proved to him that all types of living organisms are characterized by individual hereditary variability in any way; all of them multiply exponentially; within species there is a struggle for existence due to the limitation of vital resources; Only adapted individuals survive and continue to breed in this struggle.
Thus, the main driving forces of evolution are hereditary variability, natural selection and the struggle for existence. Let us consider in more detail each of them.
1. Hereditary variation is the improvement of chromosomes and genes, as well as the appearance of various combinations in the offspring of parental traits, that is, it arises from mutations. The variety of inherited traits is explained by the repetition of mutations and the contact of individuals among themselves; their habitat also plays a role here.
The evolution of living organisms involves a change in the genetic environment and the creation of those living units whose chromosomes form successful combinations. An increase in the number of carriers of these genes leads to hereditary changes in the traits of the organism, manifested in mutations, so these individuals become more resilient.
Variability is of three types:
a) certain - the acquisition by a certain number of units of one type of new features;
b) indefinite variability - the appearance of a variety of insignificant features that cannot be explained among representatives of the same species;
c) correlative - the interdependence of acquired attributes of the body.
Thus, the driving forces of evolution, namely, hereditary variability, arise as a result of the interaction of hereditary information and the conditions of a particular external environment. At the same time, the acquired traits persist for many generations.
2. The struggle for existence is a mechanism of the relationship between organisms and factors of inanimate nature, due to the ability of individuals to reproduce (increase their number) and limited resources (territory, food, etc.). The following forms are distinguished:
a) the fight against critical environmental conditions, such as excess or lack of light, moisture, changes in air temperature;
b) the struggle within a particular species - arises as a result of the similarity of the needs of representatives of this species;
c) interspecific struggle - is expressed in the relationship between representatives of different species.
Thus, such the driving forces of evolution, like variability and the battle for existence, are closely interconnected, since the former helps the species adapt to the conditions of inanimate nature, which leads to biological progress.
3. Natural selection - identifies the survival mechanism of units with the necessary hereditary changes and their further reproduction. Selection is the result of a struggle for existence. The following mechanisms are distinguished:
a) the formation of hereditary changes;
b) the survival and preservation of individuals with these changes in the appropriate habitat;
c) the reproduction of these units, the growth of their numbers and the spread of useful hereditary changes.
The driving forces of evolution, interacting with each other, can explain the formation of other species in nature. Materials accumulated in different branches of biology have a logical conclusion only when they comply with the principle of evolution.
A huge merit of C. Darwin lies in explaining the development and formation of species. It was this fact that made Darwin's evolutionary doctrine a generally accepted theory.