Darwin's theory of evolution is one of the basic theories of the development of the organic world. According to Darwin, the driving forces of evolution are natural selection, variability, heredity. New signs arise in the functions and structure of organisms in connection with variability. The latter is definite and indefinite. Certain (directed) variability occurs when environmental conditions have the same effect on all or most individuals of a particular species. It is not fixed hereditarily in future generations. Individual individuals may experience indefinite (non-directional) changes that are random and hereditary. Uncertain variability is of two types - combinational and mutational. In the first case, during meiosis, when offspring are formed, new combinations of paternal and maternal chromosomes appear, which sometimes exchange parts, and with each generation the combination of genes increases. In the second case, the genetic structure of the organism changes: the number of chromosomes, their structure or the structure of genes.
Darwin's theory of evolution and its representatives believe that changes in organisms occur under the influence of the environment. As a result of natural selection, the offspring of carriers of useful traits that have arisen as a result of recombination or mutation of genes survive. Selection is the main factor in evolution that determines speciation of organisms. It can be expressed in three forms: driving, stabilizing and disruptive. The first leads to the emergence of new adaptations. The greatest likelihood of leaving offspring is in individuals that have changed in some way compared to the average value. In the second form, the formed adaptations are preserved under constant environmental conditions. In this case, individuals with an average value of characters are preserved in the population. In the third form, polymorphism occurs under the influence of multidirectional environmental changes. That is, selection takes place according to two or more types of deviation.
Darwin's theory of evolution has proven that the main driving force behind evolution is natural selection. Now, as a result of interspecific crossing, new types of populations are being produced. The theory was used in various branches of knowledge, including in history (Karl Marx), and in psychology (Sigmund Freud).
The modern theory of evolution has undergone significant changes. Unlike the initial Darwinian theory, it clearly distinguishes the elementary structure (population) with which evolution began. The modern theory is more reasoned, it reasonably and clearly interprets the driving forces and factors, highlighting the main and non-basic. An elementary manifestation of the process is a steady change in the genotype of populations. The main task of modern teaching is to study the mechanism of evolutionary processes, the ability to predict transformations.
Darwin's theory of evolution is closely interconnected with the theory of biochemical evolution, which consists in the fact that the first organic substances in the formation of the planet were hydrocarbons formed from simple compounds in the ocean. As a result of further hydrocarbon compounds with a number of chemical elements, complex organic substances formed. These processes developed under the influence of intense solar radiation and lightning electrical discharges, emitting the necessary amount of ultraviolet radiation. Organic matter accumulating in the ocean has created strong molecular bonds that are resistant to the damaging effects of ultraviolet radiation. After a long evolution of carbon compounds, life arose. The theory of biochemical evolution was developed by Alexei Oparin, Stanley Miller, John Haldane and others.