The law, which was discovered by the outstanding domestic scientist N. I. Vavilov, is a powerful stimulator for the selection of new plant and animal species that are beneficial to humans. Even at the present time, this regularity plays an important role in the study of evolutionary processes and the development of an acclimatization base. The results of Vavilov's research are also important for the interpretation of various biogeographic phenomena.
The essence of the law
In short, the law of homological series is as follows: the spectra of variability in related types of plants are similar to each other (often this is a strictly fixed number of certain variations). Vavilov presented his ideas at the III Selection Congress, which was held in 1920 in Saratov. To demonstrate the operation of the law of homologous series, he collected the entire set of hereditary characteristics of cultivated plants, arranged them in one table and compared the varieties and subspecies known at that time.
Exploring Plants
Together with cereals, Vavilov also considered legumes. In many cases parallelism was found. Despite the fact that each family had different phenotypic characters, they had their own characteristics, form of expression. For example, the color of the seeds of almost any cultivated plant ranged from the lightest to black. In cultivated plants well studied by researchers, up to several hundred traits were found. Others, which were at that time less studied or wild relatives of cultivated plants, showed much less signs.
Geographic centers of species distribution
The basis for the discovery of the law of homological series was the material that Vavilov collected during his expedition to the countries of Africa, Asia, Europe and America. The first assumption that there are certain geographical centers from which biological species originate was made by the Swiss scientist A. Decandol. According to his ideas, once these species covered large territories, sometimes entire continents. However, it was Vavilov who was the researcher who was able to study the diversity of plants on a scientific basis. He used a method called differential. The entire collection that was collected by the researcher during the expeditions was subjected to a thorough analysis using morphological and genetic methods. So it was possible to determine the final area of concentration of the diversity of forms and features.
Plant Map
During these trips, the scientist did not get confused invariety of plant species. He put all the information with colored pencils on maps, then translating the material into a schematic form. Thus, he was able to discover that on the entire planet there are only a few centers of diversity of cultivated plants. The scientist showed directly with the help of maps how species "spread" from these centers to other geographical regions. Some of them go a short distance. Others are taking over the world, as happened with wheat and peas.
Consequences
According to the law of homological variability, all genetically close plant varieties have approximately equal series of hereditary variability. At the same time, the scientist admitted that even outwardly similar signs may have a different hereditary basis. Given the fact that each of the genes has the ability to mutate in different directions and that this process can proceed without a specific direction, Vavilov made the assumption that the number of gene mutations in related species will be approximately the same. The law of homological series by N. I. Vavilov reflects the general patterns of gene mutation processes, as well as the formation of various organisms. It is the main basis for the study of biological species.
Vavilov also showed the corollary that followed from the law of homologous series. It sounds like this: hereditary variability in almost all plant species varies in parallel. The closer to each otherare species, the more this homology of characters is manifested. Now this law is universally applied in the selection of agricultural crops, as well as animals. The discovery of the law of homologous series is one of the greatest achievements of the scientist, which brought him worldwide fame.
Origin of plants
The scientist created a theory about the origin of cultivated plants in distant from each other in different prehistoric epochs of the globe. According to Vavilov's law of homologous series, related plant and animal species exhibit similar variations in trait variability. The role of this law in crop and animal husbandry can be compared with the role played by D. Mendeleev's table of periodic elements in chemistry. Using his discovery, Vavilov came to the conclusion about which territories are the primary sources of certain types of plants.
- The world owes the origin of rice, millet, naked forms of oats, many types of apple trees to the Sino-Japanese region. Also, the territories of this region are home to valuable varieties of plums, oriental persimmons.
- The birthplace of bananas, coconut palms and sugarcane is the Indonesian-Indochinese center.
- With the help of the law of homological series of variability, Vavilov managed to prove the great importance of the Hindustan Peninsula in the development of crop production. These territories are home to some types of beans, eggplants, cucumbers.
- Traditionally grown on the territory of the Central Asian regionwalnuts, almonds, pistachios. Vavilov discovered that this territory is the birthplace of onions, as well as the primary types of carrots. In ancient times, the inhabitants of Tajikistan grew apricots. Some of the best in the world are melons, which were bred in the territories of Central Asia.
- Vine first appeared in the Mediterranean territories. The process of evolution of wheat, flax, various varieties of oats also took place here. Also fairly typical elements of the Mediterranean flora is the olive tree. The cultivation of lupine, clover and flax also began here.
- Flora of the Australian continent gave the world eucalyptus, acacia, cotton.
- The African region is home to all types of watermelon.
- In the European-Siberian territories, the cultivation of sugar beets, Siberian apple trees, forest grapes took place.
- South America is the birthplace of cotton. The Andean territory is home to potatoes and some types of tomatoes. In the territories of ancient Mexico, corn and some types of beans grew. Tobacco also originated here.
- In the territories of Africa, the ancient man first used only local plant species. The black continent is the birthplace of coffee. Wheat appeared for the first time in Ethiopia.
Using the law of homological series of variability, a scientist can identify the center of origin of plants by those features that are similar to the forms of species from another geographical area. In addition to the necessary diversity of flora, in order for a large center of diverse cultivated plants to arise, it is also necessaryagricultural civilization. N. I. Vavilov thought so.
Domestication of animals
Thanks to the discovery of the law of homologous series of hereditary variability, it became possible to discover those places where animals were first domesticated. It is believed that it happened in three ways. This is the rapprochement of man and animals; forcible domestication of young individuals; domestication of adults. Territories where domestication of wild animals took place are presumably in the habitats of their wild relatives.
Taming in different eras
It is believed that the dog was domesticated in the Mesolithic era. People began to breed pigs and goats in the Neolithic era, and a little later wild horses were tamed. However, the question of who the ancestors of modern domestic animals were is still not clear enough. It is believed that the ancestors of cattle were tours, horses - tarpans and Przewalski's horses, domestic goose - wild gray goose. Now the process of domestication of animals cannot be called complete. For example, arctic foxes and wild foxes are in the process of taming.
The meaning of the law of homologous series
With the help of this law, it is possible not only to establish the origin of certain plant species and the centers of domestication of animals. It allows you to predict the occurrence of mutations by comparing patterns of mutation in other types. Also, using this law, one can predict the variability of a trait,the possibility of new mutations appearing by analogy with those genetic abnormalities that were found in other species related to this plant.
