Did you know that modification variability, in contrast to mutational variability, is caused solely by environmental factors? Which of these changes is more important for the adaptation of organisms? You will find answers to these and many other questions in our article.
Organism Variability: The Importance
Variability is a universal biological phenomenon. Its essence lies in the ability of organisms to acquire new features in the process of individual development. The result of variability is the emergence of new traits and species. And when viewed globally, the development of the biosphere as a whole. Variability is a factor of evolution, provides the ability of organisms to adapt, genetic diversity and material for selection.
The appearance of modifications
One of the main areas of genetics is to elucidate the mechanisms of interaction of the genotype with the environment. It has long been known: if two identical individuals develop in different conditions, they have a number of external differences. This is a manifestation of non-hereditary or modification variability. The study of this property of living organisms allows us to determine how hereditary traits are manifested in these conditions.
Modification variability, in contrast to mutational variability, is a response to the intensity of certain factors. Non-hereditary changes are the same for all genotypically homogeneous creatures. Proof of this is the arrowhead, whose leaves in the water have a leaf shape, and on land - arrow-shaped. Such changes protect the plant from flow damage.
In the case of modification variability, new traits do not cause changes in genetic material. So, if the tails are cut off in mice, the tail tailed offspring will appear. Such an experiment was first conducted by the German scientist August Weisman.
Usually, modifications disappear when the action of the factor causing them ceases. So, the summer tan by the autumn-winter period is already almost invisible. But in some cases, such signs persist throughout life or are even inherited in a series of generations. For example, at high temperatures in the cells of pupae of the Colorado potato beetle, molecules of informational RNA accumulate, which determine the dark color. But from generation to generation, the number of these molecules decreases, and the trait gradually disappears.
Reaction rate
Modification variability, in contrast to mutational variability, is subject to some statistical laws. Its limits are called the reaction rate. A narrower reaction rate is characteristic of the signs that determine viability. For example, the relative position of internal organs. For signs that are not so important, it can be wider.
Causes of mutations
Mutation mutation, unlike modification, arises due to the formation of new structures in the genotype of organisms. They are called mutations. Such modifications may have a different character. Mutations can be associated with a change in the number or structure of chromosomes, the number of chromosome sets, as well as with a violation of the sequence of nucleotides in the nucleic acid molecules. In any case, there is a violation of the hereditary programs of cells and the body as a whole. As a result, a phenotype change that is not always beneficial for individuals.
Modifications and mutations: signs for comparison
All types of variability are a source of evolutionary neoplasms and a universal property of living matter. But modification variability, unlike mutational variability, is not inherited and does not affect DNA. The body acquires new signs of the external structure, which are useful in certain conditions.
Mutational variability, in contrast to modification, is uncertain. It is impossible to determine in advance exactly what signs will appear in the body. Modifications can be predicted. And they will be the same for all organisms in the group. For example, if several rabbits are placed in low temperature conditions, they will all change color. If you irradiate a bag of seeds with radiation, mutations will appear in everyone, but will be completely different.
The vast majority of modifications are adaptive in nature. A tan appears to protect the skin from the harmful effects of solar radiation, thick coat of animals during autumn molt - from the action of the cold. Although this does not always happen. So, if you obscure the lower part of the potato shoot, overhead tubers will begin to appear. Mutations can be harmful, neutral and beneficial.
So, variability is the universal ability of all living things to acquire new attributes. Mutational variation, unlike modification, is due to sudden changes in the genetic material and is inherited.