Dispersion (biology)

Genotypic variance

Dispersion of the genetic material of a population or species . Includes genetic information of the nucleus , mitochondria , ribosomes and other organelles . New genetic diversity is due to mutations that can take the form of recombination , migration, and / or karyotype abnormalities (number, shape, size, and internal distribution of chromosomes ). Genetic drift is a statistical measure of the rate of genotypic change in a population.

Phenotypic variance

The same gene under different environmental conditions can be realized in 1, 2, several or a whole range of values ​​of the trait (phenes). In the same way, the same genotype under different environmental conditions can be realized in a whole spectrum of potential phenotypes , but in each specific ontogenesis only one is realized from this spectrum of phenotypes. By the hereditary norm of the reaction we understand the maximum possible width of this spectrum. The reaction rate characterizes the share of the environment in the implementation of the trait. The wider the reaction rate, the greater the influence of the environment and the less the influence of the genotype in ontogenesis. Usually, the more varied the living conditions of a species, the wider its rate of reaction.

For the population to “feel” the approach of the front of a harmful environmental factor, a contact of the population mortality curve with this front is necessary. That is, the population has to pay a certain victim for the information received all the time in the form of elimination of the most sensitive individuals to this factor. Moreover, the fee is proportional to the information received and is closely related to the phenotypic dispersion of the population. If the phenotypic dispersion is small, then in a stable environment there is no elimination and there is no information contact between the population and the environment. In this case, another sudden change in the environment may take the population by surprise and destroy it entirely. On the contrary, if the phenotypic variance is very large, then the fee for new information is growing excessively. Consequently, there is a certain amount of phenotypic dispersion that is optimal for a given population in a given environment, which ensures that the necessary information is obtained in advance with a minimum payment for it.

Negative feedback regulating population variance

The well-known genetic mechanisms of diploidy , homo- , heterozygosity and gametism are able to regulate dispersion and automatically maintain its optimum due to the negative feedback mechanism. Heterozygosity plays a conservative role in protecting recessive traits from the effects of selection. The dispersion is reduced. Homozygosity plays an operational role, exhibits recessive traits and increases dispersion. In the simplest case of monohybrid crosses : 2Aa ↔ AA + aa, an increase in dispersion means an increase in the proportion of homozygotes, while a decrease in it, on the contrary, is associated with an increase in the proportion of heterozygotes. It was shown that a change in equilibrium to the left ( hybridization , outbreeding ) increases heterozygosity, increases potential variability and narrows the variance. ^{[1] [2] [3]} On the other hand, a change in equilibrium to the right ( inbreeding ) reduces heterozygosity, increases free variability and dispersion. The transition to more complex polyallelic cases does not change the main conclusions. ^[four]

• Mutation
• Population
• Genotype
• Phenotype
• Reaction rate
• The evolutionary theory of sex V. A. Geodakyan