Theory of Asynchronous Evolution

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The Evolutionary Theory of Sex: Receiving the Ecological Information from the Environment

The ecological information is required for the regulation of population parameters, such as the density, rates of mutations, sex ratio, variation and sexual dimorphism. Individuals of a population need some kind of “sensors” reacting to the changes of ecological factors of environment. The received information then will be transformed on the organism and chromosomal levels.

First, change of factors of environment can eliminate most sensitive to the given factor part of individuals, as a result of natural selection. Second, environmental changes create discomfort conditions. As a result other part of a population can be partially or completely discharged from duplication, due to sexual selection. Third, the changed environment modifies survived part of a population, creating morpho-physiological, behavioral and other non inherited adaptations, due to a norm of reaction. For example in a cold conditions the animal’s tails are shortened, the fur becomes thicker, the hypodermic fat layer increases, humans use caves, clothes, fire.

First two processes (elimination and discrimination) remove some genotypes from a reproduction pool. The third process (modification), on the contrary, allows some genotypes to survive under the shell of the modified phenotype and to get in genes of posterity. That is someone should be broken, killed, discharged, and someone—bended, “educated”, and altered. Both processes occur, not in a zone of comfort, but in zones of elimination and discomfort.

All these processes result, finally that the genotypic distribution in two adjacent generations changes. The generation n receives one spectrum of genotypes from generation n - 1, and transfers another spectrum to generation n + 1. And this is a reception of the ecological information from the environment. So, the ecological information from the environment such as frost, heat, predators, and parasites, is perceived by a population in the form of elimination or modification of phenotypes. It changes phenotypical distribution of a population. Besides, conditions of environment define reproductive success, by discriminating some phenotypes and giving the privileges to others. The result is that the genotypic distribution of posterity changes.

Informativity of individuals on the ends of a genotypic distribution curve (areas E1 and E2) is maximal, because they can cause the maximal shift of genotypes in the following generation (Figure 1). The further a genotype from a median, the more original it is, the higher its informativity.

Figure 1

Distribution of phenotypes (p), their informativity (-lgp) and information efficiency (-plgp) in a population.
X—generalized attribute (or a phenotype), p—probability of its presence in a population,
G—genetic part of a population, E1, E2 —ecological parts.

However the number of such individuals is very small and their contribution to a gene pool of posterity is insignificant. Therefore the real contribution will be defined by product of a degree of originality on concentration of individuals with the given value of an attribute, and also on cross section of their liaison channel with posterity. As the section of a male liaison channel with posterity is much more than that of a female, their contribution also will be higher.

Variation of Sexes

In order to “feel” the approaching of the harmful environmental factor, the population mortality curve should be in close contact with this factor. This means that population always has to pay for the information in the form of elimination of organisms most sensitive to the given factor. The “payment” is directly proportional to the amount of information received and is related to population’s phenotypic variation. If phenotypic variation is insufficient, in a stable environment there is no elimination, and hence no information contact with the environment. In this case the next unexpected change of environmental conditions can extinguish population completely. On the other hand, if phenotypic variation is too big, the payment for the new information is too high, which is uneconomical. So, for a given population in a given environment there must exist some optimal value of phenotypic variation, which provides the necessary information with minimal payment for it.

Let’s divide a phenotypic distribution curve of the population into three parts, as shown in Figure 2A. In well-known old environmental conditions, the organisms from the central part of a population (G) are most adapted to them. They live under comfort conditions and are maximally involved in the transmission of genetic (specific) information to their progeny. This part can be named the “genetic” part of the population. The peripheral parts E1 and E2 are in discomfort, suffering from alternative values of the same factor. For example, if part E1 suffers from cold, then part E2 will suffer from heat. Therefore their reproduction is limited. It means, that even in populations of the animals living in tropics, monkeys for example, some animals are dying not only from heat, but also from cold, while in populations of penguins or polar bears, some animals are perish from heat.

Figure 2

Relationship of population and environment. Zones of: □—comfort; ░—discomfort; █—elimination.
A—under stabilizing, B—under directional selection (→ —direction of the selection); X—generalized
character (resistance to environmental factor), p—probability (or concentration) of the character in
population, G—genetical part of the population, E1, E2—ecological parts.
 

When the environmental conditions change, one of the peripheral parts (E1 ) gets shifted into the elimination zone and perishes. Part G moves into discomfort zone, and part E2—into comfort zone accordingly (Figure 2B). Individuals of the E2 group, which suffered from discomfort in the past, are now in comfort and can therefore reproduce more successfully. Their useful genes spread around and help population to adapt. This means that population received the ecological information from the environment. Therefore we can call the peripheral parts of the population—“ecological”.

Consequently, the informational roles of different population parts differ. The “genetic”, past oriented, part (G) “works” more for storing the genetic information, as it realizes more of a conservative trend. At the same time the “ecological” parts E1 and E2 “work” more for alteration. They realize mainly the relations with the environment and are more oriented towards the future. In other words, distinct specialization of the parts exists in the population, “division of labor” of some kind—performing relationship with preceding generations (inheritance) and with the environment (variability).

Mechanisms of Regulation of the Population Parameters (stress, sex hormones, pollen amount)

Two sexes — two streams of information

 

 

Copyright 2005-2009 S. Geodakyan. All rights reserved.

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