Combinatorial, mutational and modification variability

Modification variability is a rather important property of organisms to adapt to the external environment. This is a complex of reactions that are physiological adaptation of the organism or an entire population to a change in environmental conditions. For example, under the sun the skin more or less darkens in every person.

Modification variability and its properties

This property of organisms has some characteristic features:

• Modification variability affects exclusively the phenotype (external signs), but does not affect the genotype (an individual set of genetic information).
• It has a group character - if some environmental conditions affect a group of organisms, then all its representatives observe the appearance of the same signs.
• Reversibility - changes occur with the constant influence of certain factors. If you transfer the organism to other conditions or eliminate the influence of the factor, then the phenotypic changes disappear.
• Changes that occur under the influence of external factors are not inherited.

It should be noted that the modification variability is of great importance for the process of natural selection. The fact is that nature survives those organisms that are most adapted to the conditions, especially with a sharp change in external factors. Combinatorial and mutational variability does not fully provide the body with the ability to adapt.

Modification variability: examples

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

• When climbing mountains, where environmental conditions change, an increase in the number of red blood cells is observed in the blood of a person or animal, which ensures normal oxygen supply.
• When exposed to ultraviolet rays in the skin tissues, intensified release of pigments begins.
• As a result of constant intense training, muscle mass increases significantly. After the termination of employment the body gradually loses elasticity, muscles decrease in size.
• If the white Himalayan hare is moved to moderate climatic conditions and shaved the body, the new coat will be gray.
• If the trees already have fully blossoming leaves, and at night they will be affected by the minus temperature, then in the morning you can see a characteristic reddish hue.

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

Combinatorial variability

Such variability appears as a result of recombination of genes during the fusion of gametes. Now consider the example: if the father of the child has green eyes and dark hair, and the mother has blond hair and blue eyes. The child can be born in green eyes and blond hair, or dark hair and blue eyes. It is these phenotypic changes in offspring that are provided by combinatorial variability.

Mutational variability

Changes occur when the organism is exposed to chemical, physical or biological mutagens. Mutational variability in contrast to the modification:

• Arises spontaneously, and it is practically impossible to predict it;
• Causes changes in genetic material;
• Mutational changes are persistent and are inherited;
• Mutations can be both benign, and cause pathology up to a lethal outcome;
• They do not depend on environmental conditions;
• Arise in individual individuals;

As you can see, variability is a very complex process that affects both the genotype and the phenotypic characteristics. It is thanks to modifications, combinations and mutations that organisms gradually changed, improving and adapting to changes.