Currently, one of the leading sciences is selection. Its theoretical basis is the doctrine of artificial selection. The main characteristics, types and features of this concept we will analyze in our article.
Drivers of Evolution
According to evolutionary theory, modern species have arisen as a result of a number of adaptive changes in wild animals. Under the influence of what processes did this happen? These include hereditary variability and the struggle for existence, the result of which is natural selection. The essence of the latter lies in the predominant survival of the fittest species. In nature, it is happening now.
Characteristics of Artificial Selection
Man has long learned to use selection to obtain species with useful properties. To do this, he saves the descendants of the most productive individuals. This type of selection is called artificial. Its purpose is the breeding of economically valuable animal breeds, plant varieties and strains of microorganisms.
Their formation began with the taming and cultivation of wild species. For example, all modern dog breeds have a single ancestor, which is the wolf. Initially, the main characteristic of artificial selection was its unconscious nature. This means that a person carried it out without a specific goal. He left the largest animals for breeding, and the best seeds for sowing next year. Less valuable specimens were used as food. The results of this process will be visible only after a long time.
How to achieve the appearance of new signs in self-pollinated plants and animals that are capable of self-fertilization? In this case, breeders apply mutations - sharp abrupt changes in the genotype that occur as a result of certain factors. They are called mutagenic. This has been proven empirically. If self-pollination of plants with the largest seeds is carried out, then useful signs do not appear even after six generations.
More effective is conscious selection. It is also called methodological. At the same time, a person consciously displays an artificial appearance with specific properties. This selection is conducted in a series of generations until the desired result is achieved.
Comparative characteristics of artificial and natural selection
Both types of selection have a number of similar features. Their basis is hereditary variability - the property of organisms to transmit certain signs and characteristics of development to descendants. In both cases, properties that increase the viability of individuals are valuable. In natural selection, species that do not have favorable changes die as a result of the struggle for existence. And with artificial, they are rejected or destroyed.
The main characteristic of artificial selection is the direct participation of a person and the high rate of obtaining results. Necessary changes can be achieved over a period of 10 to 20 years. In nature, these processes take place hundreds or even millions of years.
Mass selection
There are two forms of artificial selection. One of them is massive. In this case, the useful properties of the starting material are determined only on the basis of phenotypic characters. Thus, a person visually determines which species to use for further reproduction and cultivation.
Such artificial selection is an example of the use of simple methods in breeding. It is used quite often, but has a number of disadvantages. Despite the external similarity, individuals can be genetically heterogeneous: heterozygous or homozygous for the dominant allele. In this case, the selection efficiency is significantly reduced. The expected result will appear only if heterozygotes are crossed. But in future generations, the manifestation of beneficial traits will decrease, as the number of homozygous organisms will increase.
Individual selection
This form has several advantages. Individual artificial selection, the examples of which we are considering, is carried out taking into account the genotype of the source material. To do this, use the method of analyzing crosses, as well as the study of pedigrees.
After the choice of parental pairs, a hybridization system is used - hybridization. It can be carried out within one or different types. In any case, breeders are faced with a number of difficulties. So, after a series of related crosses, the homozygosity of the offspring increases. The consequence of this is the degeneration, weakening and death of the line. But this method is ideal for obtaining clean lines.
When unrelated crossing initially increases heterozygosity. This leads to the emergence of the descendants of the first generation of hybrid power. This phenomenon is called heterosis. Hybrids at the same time have greater viability in comparison with parents. But in subsequent generations, this effect is weakened.
So, the main characteristics of artificial selection include directed human activities, the fast pace of obtaining results, taking into account the characteristics of the genotype of selection material.