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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
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