The identification of variability in individuals of one species made it possible to take an important step in the development of evolutionary doctrine. The concept and value of this property for adaptation we will consider in our article.
What is volatility?
Variability is understood as the ability of organisms to acquire new signs and properties in the process of their individual and historical development. This property is the result of their adaptation to environmental conditions. Thus, the variability in individuals of one species, examples of which are shown in the photo below, led to the emergence of human races. A narrow section of the eyes of the Mongoloids and a yellow skin color formed and entrenched in the genotype of people living in the Asian steppes, where strong sandy winds constantly blew. And black skin of Negroids is the result of life in African deserts.
Types of variability
The identification of variability in individuals of one species showed that new characters may not be inherited. This was proven during the experiment. Tails were cut off to laboratory mice, and then they were crossed among themselves. In such individuals, tailed children were always born. Such variability is called non-hereditary, or modification. If new features affect the genetic apparatus, changing it at a certain level, the variability is hereditary.
Modification Variability
Remember the children's riddle: "In winter, white, and in summer gray"? This is the identification of variability in individuals of one species. Scientists have proved that the signal for changing the color of the hare's hair is not the temperature of the air, but the amount of sunlight. This is easy to prove. If in the warm season the cage or aviary with hares is darkened, after a while they "put on white fur coats".
Modification variability in individuals of one plant species can be considered by the example of an arrow leaf. It grows in water. The leaves of this plant, which are under water, have a ribbon-like shape, and above it - arrow-shaped. A change in living conditions leads to a modification of their shape. If the whole plant is under water, all leaves take the form of a ribbon.
Not all features may change due to environmental conditions. So, skin color can be changed under the influence of solar radiation. But the blood group is not affected by any conditions. This trait, like many others, is inherited.
Hereditary Volatility
Changes affecting the genetic apparatus are hereditary. They are independent of environmental conditions and are caused by recombination of genes or mutations. Their feature is random and non-directional. The identification of variability in individuals of one species and their closely related organisms has become the subject of research by the famous scientist N. I. Vavilov. Their result was the law of homological series. Its essence lies in the fact that the hereditary changes that are observed in some species can occur in others that are close to them by origin. For example, albinism is characteristic of representatives of all classes of vertebrate animals. This mutation is found in both fish and mammals.
So, living organisms can exist in different forms. This property is called variability. It can be of two types. Modification depends on the living conditions of individuals and is not fixed in the genotype. Hereditary variation is associated with a change in hereditary material. Such signs are transmitted in a series of generations. Variability is an important factor in the emergence of adaptations and evolutionary transformations.