Combinatorial, mutational and modification variability

Modification variability - this is quite an important feature of organisms to adapt to the external environment.This set of reactions that are physiological adaptation of the organism or the whole population of a change in environmental conditions.For example, under the sun, the skin is more or less dark each person.

Modification variability and its properties

organisms This property has some characteristic features:

  • Modification variability affects only the phenotype (outward signs), but has no effect on the genotype (genetic information of an individual set).
  • She wears a group character - if certain environmental conditions affect the group of organisms, then all of its representatives observed the appearance of the same symptoms.
  • reversibility - changes appear under constant influence of certain factors.If you move the body to the other terms and conditions or to eliminate the influence of the factor, the phenotypic changes disappear.
  • The changes under the influence of external factors, not inherited.

should be noted that modification variability is crucial to the process of natural selection.The fact that the nature of those surviving organisms which are most suited to the conditions, particularly when a sudden change of external factors.Combinatorial and mutational variability is not fully provides the body with the ability to adapt.

Modification variability: examples

In nature you can find countless examples of such changes in the body.Below you will find the most common.

  • When climbing in the mountains, where the environmental conditions change, in human or animal blood, an increase the number of red blood cells, allowing normal oxygen supply.
  • When exposed to ultraviolet rays in the skin tissue begins an accelerated accumulation of pigments.
  • a result of constant intensive training muscle mass increases significantly.After the termination of training the body gradually loses its elasticity, the muscles decrease in size.
  • If white Himalayan rabbit move in moderate climatic conditions and the shaved area of ​​the body, the new hair will be gray.
  • If the trees are already fully expanded leaves, and at night they will be affected by temperatures below zero, in the morning you will notice a characteristic reddish color.

In order to understand the nature of modification devices, it is necessary to consider other forms of variability.

Combinatorial variability

This variability is a result of the recombination of genes during gamete fusion.Now look at an example: if the father's green eyes and dark hair, and her mother - blond hair and blue eyes.A child may be born in a green eyes and blond hair or dark hair and blue eyes.Such phenotypic changes progeny provided a combinatorial variability.

mutational variability

Changes occur when exposed to the body of mutagens chemical, physical or biological nature.Mutational variability unlike Modification:

  • arises spontaneously, and it is almost impossible to predict;
  • cause changes in the genetic material;
  • mutational changes resistant and are inherited;
  • mutations can be both benign and cause disease or death;
  • they do not depend on the environmental conditions;
  • occur in some individuals;

As can be seen, the variability - this is a very complex process that involves both the genotype and phenotype characteristics.It is due to modifications, combinations and mutations of the organisms gradually changed, improving and adapting to change.