Lecture: Natural selection as the leading factor of evolution. Modern ideas about the forms of natural selection

Living in natural conditions, there is individual variability, which can manifest itself in three types- useful, neutral and harmful. Typically, organisms with harmful variability die at various stages of individual development. Neutral variability of organisms does not affect their viability. Individuals with beneficial variability survive due to advantages in intraspecific, interspecific competition, or in the fight against unfavorable conditions environment.

Driving selection

When environmental conditions change, those individuals of the species that have exhibited hereditary variability and, as a result, developed characteristics and properties corresponding to the new conditions, survive, and those individuals that did not have such variability die. During his voyage, Darwin discovered that on oceanic islands, where strong winds prevail, there are few long-winged insects and many insects with vestigial wings and wingless insects. As Darwin explains, insects with normal wings could not withstand the strong winds on these islands and died. But insects with rudimentary wings and wingless ones did not rise into the air at all and hid in crevices, finding shelter there. This process, which was accompanied by hereditary variability and natural selection and continued for many thousands of years, led to a reduction in the number of long-winged insects on these islands and to the appearance of individuals with vestigial wings and wingless insects. Natural selection, which ensures the emergence and development of new characteristics and properties of organisms, is called driving selection.

Disruptive selection

Disruptive selection is a form of natural selection that leads to the formation of a number of polymorphic forms that differ from each other within the same population.

Among organisms of a certain species, individuals with two or more different forms are sometimes found. This is the result of a special form of natural selection - disruptive selection. Yes, y ladybugs There are two forms of hard wings - with a dark red and reddish color. Beetles with reddish wings are less likely to die from the cold in winter, but produce few offspring in the summer, while those with dark red wings, on the contrary, more often die in winter, being unable to withstand the cold, but produce numerous offspring in the summer. Consequently, these two forms of ladybugs, due to their different adaptations to different seasons, managed to preserve their offspring for centuries.

Natural selection is a process originally defined by Charles Darwin as leading to the survival and preferential reproduction of individuals more adapted to given environmental conditions and possessing useful hereditary traits. In accordance with Darwin's theory and the modern synthetic theory of evolution, the main material for natural selection is random hereditary changes - recombination of genotypes, mutations and their combinations.

In the absence of the sexual process, natural selection leads to an increase in the proportion of a given genotype in the next generation. However, natural selection is “blind” in the sense that it “evaluates” phenotypes rather than genotypes, and the preferential transmission of the genes of an individual with useful traits to the next generation occurs regardless of whether these traits are heritable.

There are different classifications of selection forms. A classification based on the nature of the influence of forms of selection on the variability of a trait in a population is widely used.

Driving selection- a form of natural selection that operates under directed changes in environmental conditions. Described by Darwin and Wallace. In this case, individuals with traits that deviate in a certain direction from the average value receive advantages. In this case, other variations of the trait (its deviations in the opposite direction from the average value) are subject to negative selection. As a result, in a population from generation to generation there is a shift in the average value of the trait in a certain direction. In this case, the pressure of driving selection must correspond to the adaptive capabilities of the population and the rate of mutational changes (otherwise, environmental pressure can lead to extinction).

An example of the action of driving selection is “industrial melanism” in insects. “Industrial melanism” is a sharp increase in the proportion of melanistic (dark-colored) individuals in those populations of insects (for example, butterflies) that live in industrial areas. Due to industrial impact, the tree trunks darkened significantly, and light-colored lichens also died, which is why light-colored butterflies became better visible to birds, and dark-colored ones became less visible. In the 20th century, the proportion of dark-colored butterflies in some well-studied moth populations in England reached 95%, while for the first time dark butterfly(morpha carbonaria) was captured in 1848.

Driving selection occurs when the environment changes or adapts to new conditions when the range expands. It preserves hereditary changes in a certain direction, moving the reaction rate accordingly. For example, during the development of soil as a habitat, various unrelated groups of animals developed limbs that turned into burrowing limbs.

Stabilizing selection- a form of natural selection in which its action is directed against individuals that have extreme deviations from average norm, in favor of individuals with average expression of the trait. The concept of stabilizing selection was introduced into science and analyzed by I.I. Schmalhausen.

Many examples of the action of stabilizing selection in nature have been described. For example, at first glance it seems that the greatest contribution to the gene pool of the next generation should be made by individuals with maximum fertility. However, observations of natural populations of birds and mammals show that this is not the case. The more chicks or cubs in the nest, the more difficult it is to feed them, the smaller and weaker each of them is. As a result, individuals with average fertility are the most fit.

Selection toward the mean has been found for a variety of traits. In mammals, very low-weight and very high-weight newborns are more likely to die at birth or in the first weeks of life than average-weight newborns. Taking into account the size of the wings of sparrows that died after a storm in the 50s near Leningrad showed that most of them had wings that were too small or too large. And in this case, the average individuals turned out to be the most adapted.

Disruptive selection- a form of natural selection in which conditions favor two or more extreme variants (directions) of variability, but do not favor the intermediate, average state of a trait. As a result, several new forms may appear from one original one. Darwin described the action of disruptive selection, believing that it underlies divergence, although he could not provide evidence of its existence in nature. Disruptive selection contributes to the emergence and maintenance of population polymorphism, and in some cases can cause speciation.

One of the possible situations in nature in which disruptive selection comes into play is when a polymorphic population occupies a heterogeneous habitat. Wherein different shapes adapt to different ecological niches or sub-niches.

An example of disruptive selection is the formation of two races in the greater rattle in hay meadows. Under normal conditions, the flowering and seed ripening periods of this plant cover the entire summer. But in hay meadows, seeds are produced mainly by those plants that manage to bloom and ripen either before the mowing period, or bloom at the end of summer, after mowing. As a result, two races of rattle are formed - early and late flowering.

Disruptive selection was carried out artificially in experiments with Drosophila. The selection was carried out according to the number of bristles; only individuals with a small and large number of bristles were retained. As a result, from about the 30th generation, the two lines diverged very much, despite the fact that the flies continued to interbreed with each other, exchanging genes. In a number of other experiments (with plants), intensive crossing prevented the effective action of disruptive selection.

Sexual selection - This is natural selection for reproductive success. The survival of organisms is an important, but not the only component of natural selection. Another important component is attractiveness to individuals of the opposite sex. Darwin called this phenomenon sexual selection. “This form of selection is determined not by the struggle for existence in the relations of organic beings among themselves or with external conditions, but by the competition between individuals of one sex, usually males, for the possession of individuals of the other sex.” Traits that reduce the viability of their hosts can emerge and spread if the advantages they provide for reproductive success are significantly greater than their disadvantages for survival. Two main hypotheses about the mechanisms of sexual selection have been proposed. According to the “good genes” hypothesis, the female “reasons” as follows: “If this male, despite his bright plumage and long tail, somehow managed not to die in the clutches of a predator and survive to puberty, then, therefore, he has good genes.” genes that allowed him to do this. This means that he should be chosen as a father for his children: he will pass on his good genes to them.” By choosing colorful males, females are choosing good genes for their offspring. According to the “attractive sons” hypothesis, the logic of female choice is somewhat different. If brightly colored males, for whatever reason, are attractive to females, then it is worth choosing a brightly colored father for his future sons, because his sons will inherit the brightly colored genes and will be attractive to females in the next generation. Thus, a positive feedback arises, which leads to the fact that from generation to generation the brightness of the plumage of males becomes more and more intense. The process continues to grow until it reaches the limit of viability. In the choice of males, females are no more and no less logical than in all their other behavior. When an animal feels thirsty, it does not reason that it should drink water in order to restore the water-salt balance in the body - it goes to a watering hole because it feels thirsty. In the same way, females, when choosing bright males, follow their instincts - they like bright tails. All those to whom instinct suggested a different behavior, all of them did not leave offspring. Thus, we were discussing not the logic of females, but the logic of the struggle for existence and natural selection - a blind and automatic process that, acting constantly from generation to generation, has formed all the amazing diversity of shapes, colors and instincts that we observe in the world of living nature .

Natural selection- the result of the struggle for existence; it is based on the preferential survival and leaving of offspring with the most adapted individuals of each species and the death of less adapted organisms.

The mutation process, fluctuations in population numbers, and isolation create genetic heterogeneity within a species. But their action is undirected. Evolution is a directed process associated with the development of adaptations, with the progressive complication of the structure and functions of animals and plants. There is only one directed evolutionary factor - natural selection.

Either certain individuals or entire groups can be subject to selection. As a result of group selection, traits and properties often accumulate that are unfavorable for an individual, but useful for the population and the whole species (a bee that stings dies, but by attacking an enemy, it saves the family). In any case, selection preserves the organisms most adapted to a given environment and operates within populations. Thus, it is populations that are the field of selection.

Natural selection should be understood as the selective (differential) reproduction of genotypes (or gene complexes). In the process of natural selection, it is not so much the survival or death of individuals that is important, but rather their differential reproduction. Success in the reproduction of different individuals can serve as an objective genetic-evolutionary criterion of natural selection. The biological significance of an individual that produces offspring is determined by the contribution of its genotype to the gene pool of the population. Selection from generation to generation based on phenotypes leads to the selection of genotypes, since it is not traits, but gene complexes that are passed on to descendants. For evolution, not only genotypes matter, but also phenotypes and phenotypic variability.

During expression, a gene can influence many traits. Therefore, the scope of selection may include not only properties that increase the likelihood of leaving offspring, but also characteristics that are not directly related to reproduction. They are selected indirectly as a result of correlations.

a) Destabilizing selection

Destabilizing selection- this is the destruction of correlations in the body with intensive selection in each specific direction. An example is the case when selection aimed at reducing aggressiveness leads to destabilization of the breeding cycle.

Stabilizing selection narrows the reaction norm. However, in nature there are often cases when the ecological niche of a species may become wider over time. In this case, individuals and populations with a wider reaction norm receive a selective advantage, while at the same time maintaining the same average value of the trait. This form of natural selection was first described by American evolutionist George G. Simpson under the name centrifugal selection. As a result, a process occurs that is the opposite of stabilizing selection: mutations with a wider reaction rate receive an advantage.

Thus, populations of lake frogs living in ponds with heterogeneous illumination, with alternating areas overgrown with duckweed, reeds, cattails, and with “windows” of open water, are characterized by a wide range of color variability (the result of a destabilizing form of natural selection). On the contrary, in bodies of water with uniform illumination and color (ponds completely overgrown with duckweed, or open ponds), the range of color variability of frogs is narrow (the result of the action of a stabilizing form of natural selection).

Thus, a destabilizing form of selection leads to an expansion of the reaction norm.

b) Sexual selection

Sexual selection- natural selection within one sex, aimed at developing characteristics that primarily give the opportunity to leave the largest number of descendants.

Males of many species display clearly expressed secondary sexual characteristics that at first glance seem non-adaptive: the tail of a peacock, the bright feathers of birds of paradise and parrots, the scarlet crests of roosters, the enchanting colors of tropical fish, the songs of birds and frogs, etc. Many of these features complicate the life of their carriers and make them easily noticeable to predators. It would seem that these characteristics do not provide any advantages to their carriers in the struggle for existence, and yet they are very widespread in nature. What role did natural selection play in their emergence and spread?

We already know that the survival of organisms is an important, but not the only component of natural selection. Another important component is attractiveness to individuals of the opposite sex. Charles Darwin called this phenomenon sexual selection. He first mentioned this form of selection in On the Origin of Species and then analyzed it in detail in The Descent of Man and Sexual Selection. He believed that “this form of selection is determined not by the struggle for existence in the relations of organic beings among themselves or with external conditions, but by the competition between individuals of one sex, usually males, for the possession of individuals of the other sex.”

Sexual selection is natural selection for reproductive success. Traits that reduce the viability of their hosts can emerge and spread if the advantages they provide for reproductive success are significantly greater than their disadvantages for survival. A male who lives short but is liked by females and therefore produces many offspring has much higher overall fitness than one who lives long but produces few offspring. In many animal species, the vast majority of males do not participate in reproduction at all. In each generation, fierce competition arises between males for females. This competition can be direct, and manifest itself in the form of struggle for territory or tournament battles. It can also occur in an indirect form and be determined by the choice of females. In cases where females choose males, male competition manifests itself in the display of their striking appearance or challenging behavior courtship. Females choose the males they like best. As a rule, these are the brightest males. But why do females like bright males?

Rice. 7.

The fitness of a female depends on how objectively she is able to assess the potential fitness of the future father of her children. She must choose a male whose sons will be highly adaptable and attractive to females.

Two main hypotheses about the mechanisms of sexual selection have been proposed.

According to the “attractive sons” hypothesis, the logic of female choice is somewhat different. If brightly colored males, for whatever reason, are attractive to females, then it is worth choosing a brightly colored father for his future sons, because his sons will inherit the brightly colored genes and will be attractive to females in the next generation. Thus, a positive feedback arises, which leads to the fact that from generation to generation the brightness of the plumage of males becomes more and more intense. The process continues to grow until it reaches the limit of viability. Let's imagine a situation where females choose males with a longer tail. Long-tailed males produce more offspring than males with short and medium tails. From generation to generation, the length of the tail increases because females choose males not with a certain tail size, but with a larger than average size. Eventually, the tail reaches a length where its detriment to the male's vitality is balanced by its attractiveness in the eyes of females.

In explaining these hypotheses, we tried to understand the logic of the actions of female birds. It may seem that we expect too much from them, that such complex calculations of fitness are hardly possible for them. In fact, females are no more or less logical in their choice of males than in all their other behavior. When an animal feels thirsty, it does not reason that it should drink water in order to restore the water-salt balance in the body - it goes to a watering hole because it feels thirsty. When a worker bee stings a predator attacking a hive, she does not calculate how much with this self-sacrifice she increases the overall fitness of her sisters - she follows instinct. In the same way, females, when choosing bright males, follow their instincts - they like bright tails. All those to whom instinct suggested a different behavior, all of them did not leave offspring. Thus, we were discussing not the logic of females, but the logic of the struggle for existence and natural selection - a blind and automatic process that, acting constantly from generation to generation, has formed all the amazing diversity of shapes, colors and instincts that we observe in the world of living nature .

c) Group selection

Group selection, often also called group selection, is the differential reproduction of different local populations. W. Wright compares two types of population systems - a large continuous population and a series of small semi-isolated colonies - with respect to the theoretical efficiency of selection. It is assumed that the overall size of both population systems is the same and organisms interbreed freely.

In a large continuous population, selection is relatively ineffective in increasing the frequency of favorable but rare recessive mutations. Moreover, any tendency toward an increase in the frequency of any favorable allele in one part of a given large population is counteracted by interbreeding with neighboring subpopulations in which that allele is rare. In the same way, favorable new gene combinations that managed to form in some local lobe of a given population are broken down into parts and eliminated as a result of crossing with individuals from neighboring lobes.

All these difficulties are largely eliminated in a population system whose structure resembles a series of individual islands. Here selection, or selection together with genetic drift, can quickly and efficiently increase the frequency of some rare favorable allele in one or more small colonies. New favorable gene combinations can also easily become established in one or more small colonies. Isolation protects the gene pools of these colonies from being “flooded” as a result of migration from other colonies that do not have such favorable genes, and from crossing with them. Up to this point, the model has included only individual selection or, for some colonies, individual selection combined with genetic drift.

Let us now assume that the environment in which this population system is located has changed, as a result of which the adaptability of the previous genotypes has decreased. In a new environment, new favorable genes or combinations of genes that become established in some colonies have high potential adaptive value for the population system as a whole. Now all the conditions are in place for group selection to come into play. Less adapted colonies gradually decline and die out, and colonies that are more adapted expand and replace them throughout the area occupied by a given population system. Such a subdivided population system acquires a new set of adaptive characteristics as a result of individual selection within some colonies, followed by differential reproduction of different colonies. The combination of group and individual selection can produce results that cannot be achieved by individual selection alone.

It has been established that group selection is a second-order process that complements the main process of individual selection. As a second-order process, group selection must proceed slowly, probably much more slowly than individual selection. Renewing populations takes longer than updating individuals.

The concept of group selection has found wide acceptance in some circles, but has been rejected by other scientists. They argue that different possible patterns of individual selection are capable of producing all the effects attributed to group selection. Wade conducted a series of breeding experiments with mealy beetles (Tribolium castaneum) to investigate the effectiveness of group selection and found that the beetles responded to this type of selection. In addition, when individual and group selection simultaneously act on a trait, and in the same direction, the rate of change of this trait is higher than in the case of individual selection alone (Even moderate immigration (6 and 12%) does not prevent differentiation populations caused by group selection.

One of the features of the organic world that is difficult to explain on the basis of individual selection, but can be considered as the result of group selection, is sexual reproduction. Although models have been created in which sexual reproduction is favored by individual selection, they appear to be unrealistic. Sexual reproduction is the process that creates recombination variation in interbreeding populations. What benefits from sexual reproduction is not the parental genotypes, which decay during the process of recombination, but the population of future generations, in which the stock of variability increases. This implies participation as one of the factors in the selective process at the population level.

G) Directional selection (driving)

Rice. 1.

Directional selection (driving) was described by Charles Darwin, and the modern doctrine of driving selection was developed by J. Simpson.

The essence of this form of selection is that it causes a progressive or unidirectional change in the genetic composition of populations, which is manifested in a shift in the average values of selected traits towards their strengthening or weakening. It occurs in cases where a population is in the process of adapting to a new environment or when there is a gradual change in the environment, followed by a gradual change in the population.

With a long-term change in the external environment, an advantage in life activity and reproduction may be obtained by some individuals of the species with some deviations from the average norm. This will lead to a change in the genetic structure, the emergence of evolutionarily new adaptations and a restructuring of the organization of the species. The variation curve shifts in the direction of adaptation to new conditions of existence.

Fig 2. Dependence of the frequency of dark forms of the birch moth on the degree of atmospheric pollution

Light-colored forms were invisible on birch trunks covered with lichens. With the intensive development of industry, sulfur dioxide produced by burning coal caused the death of lichens in industrial areas, and as a result dark bark of trees was discovered. Against a dark background, light-colored moths were pecked by robins and thrushes, while melanic forms, which are less noticeable against a dark background, survived and successfully reproduced. Over the past 100 years, more than 80 species of butterflies have evolved dark forms. This phenomenon is now known as industrial melanism. Driving selection leads to the emergence of a new species.

Rice. 3.

Insects, lizards and a number of other grass inhabitants are green or brown in color; desert inhabitants are the color of sand. The fur of animals living in forests, such as a leopard, is colored with small spots reminiscent of sun glare, and that of a tiger imitates the color and shadow of the stems of reeds or reeds. This coloring is called protective.

In predators, it was established due to the fact that its owners could sneak up on prey unnoticed, and in organisms that are prey, due to the fact that the prey remained less noticeable to predators. How did she appear? Numerous mutations have given and continue to give a wide variety of forms, differing in color. In a number of cases, the color of the animal turned out to be close to the background of the environment, i.e. hid the animal, played a protective role. Those animals whose protective coloring was weakly expressed were left without food or became victims themselves, and their relatives, who had better protective coloring, emerged victorious in the interspecific struggle for existence.

Directional selection underlies artificial selection, in which selective mating of individuals possessing desirable phenotypic traits increases the frequency of those traits in a population. In a series of experiments, Falconer selected the heaviest individuals from a population of six-week-old mice and allowed them to mate with each other. He did the same with the lightest mice. Such selective crossing based on body weight led to the creation of two populations, in one of which the weight increased, and in the other it decreased.

After the selection was stopped, neither group returned to their original weight (approximately 22 grams). This shows that artificial selection for phenotypic traits led to some genotypic selection and partial loss of some alleles by both populations.

d) Stabilizing selection

Rice. 4.

Stabilizing selection under relatively constant environmental conditions, natural selection is directed against individuals whose characteristics deviate from the average norm in one direction or another.

Stabilizing selection preserves the state of the population that ensures its maximum fitness under constant conditions of existence. In each generation, individuals that deviate from the average optimal value for adaptive traits are removed.

However, observations of natural populations of birds and mammals show that this is not the case. The more chicks or cubs in the nest, the more difficult it is to feed them, the smaller and weaker each of them is. As a result, individuals with average fertility are the most fit.

Selection toward the mean has been found for a variety of traits. In mammals, very low- and very-high-weight newborns are more likely to die at birth or in the first weeks of life than average-weight newborns. A study of the size of the wings of birds that died after the storm showed that most of them had wings that were too small or too large. And in this case, the average individuals turned out to be the most adapted.

What is the reason for the constant appearance of poorly adapted forms in constant conditions of existence? Why is natural selection not able to once and for all clear a population of unwanted deviant forms? The reason is not only and not so much the constant emergence of more and more new mutations. The reason is that heterozygous genotypes are often the fittest. When crossed, they constantly split and their offspring produce homozygous offspring with reduced fitness. This phenomenon is called balanced polymorphism.

Fig.5.

The most widely known example of such a polymorphism is sickle cell anemia. This severe blood disease occurs in people homozygous for the mutant hemoglobin alley (Hb S) and leads to their death at an early age. In most human populations, the frequency of this alley is very low and approximately equal to the frequency of its occurrence due to mutations. However, it is quite common in areas of the world where malaria is common. It turned out that heterozygotes for Hb S have higher resistance to malaria than homozygotes for the normal alley. Thanks to this, in populations inhabiting malarial areas, heterozygosity for this lethal homozygous alley is created and stably maintained.

Stabilizing selection is a mechanism for the accumulation of variability in natural populations. The outstanding scientist I.I. Shmalgauzen was the first to draw attention to this feature of stabilizing selection. He showed that even in stable conditions of existence neither natural selection nor evolution ceases. Even if it remains phenotypically unchanged, the population does not stop evolving. Its genetic makeup is constantly changing. Stabilizing selection creates genetic systems that ensure the formation of similar optimal phenotypes on the basis of a wide variety of genotypes. Such genetic mechanisms as dominance, epistasis, complementary action of genes, incomplete penetrance and other means of hiding genetic variability owe their existence to stabilizing selection.

The stabilizing form of natural selection protects the existing genotype from the destructive influence of the mutation process, which explains, for example, the existence of such ancient forms as hatteria and ginkgo.

Thanks to stabilizing selection, “living fossils” living in relatively constant environmental conditions have survived to this day:

hatteria, bearing the features of reptiles of the Mesozoic era;

coelacanth, a descendant of lobe-finned fish, widespread in the Paleozoic era;

the North American opossum is a marsupial known since the Cretaceous period;

The stabilizing form of selection operates as long as the conditions that led to the formation of a particular trait or property remain.

It is important to note here that the constancy of conditions does not mean their immutability. Environmental conditions change regularly throughout the year. Stabilizing selection adapts populations to these seasonal changes. Reproduction cycles are timed to coincide with them, so that young animals are born at that season of the year when food resources are maximum. All deviations from this optimal cycle, which is reproduced from year to year, are eliminated by stabilizing selection. Descendants born too early die from lack of food; offspring born too late do not have time to prepare for winter. How do animals and plants know that winter is coming? Upon the onset of frost? No, this is not a very reliable pointer. Short-term temperature fluctuations can be very misleading. If in some year it gets warmer earlier than usual, this does not mean that spring has come. Those who react too quickly to this unreliable signal risk being left without offspring. It is better to wait for a more reliable sign of spring - increasing daylight hours. In most animal species, it is this signal that triggers the mechanisms of seasonal changes in vital functions: cycles of reproduction, molting, migration, etc. I.I. Schmalhausen convincingly showed that these universal adaptations arise as a result of stabilizing selection.

Thus, stabilizing selection, sweeping aside deviations from the norm, actively shapes genetic mechanisms that ensure the stable development of organisms and the formation of optimal phenotypes based on various genotypes. It ensures the stable functioning of organisms in a wide range of fluctuations in external conditions familiar to the species.

f) Disruptive (dismembering) selection

Rice. 6.

Disruptive selection favors the preservation of extreme types and the elimination of intermediate ones. As a result, it leads to the preservation and enhancement of polymorphism. Discontinuous selection operates under a variety of environmental conditions found in the same territory and maintains several phenotypic various forms due to individuals with an average norm. If environmental conditions have changed so much that the bulk of the species loses its fitness, then individuals with extreme deviations from the average norm gain an advantage. Such forms multiply quickly and several new ones are formed on the basis of one group.

A model of disruptive selection could be the situation of the emergence of dwarf predatory fish in a body of food with little food. Often, underyearling squirrels do not have enough food in the form of fish fry. In this case, the advantage goes to the fastest growing ones, which very quickly reach a size that allows them to eat their fellows. On the other hand, the bee-eater with the maximum delay in growth rate will be in an advantageous position, since their small size allows them to remain planktivores for a long time. Such a situation, through stabilizing selection, can lead to the emergence of two predatory fish.

An interesting example is given by Darwin regarding insects - inhabitants of small oceanic islands. They fly beautifully or have no wings at all. Apparently, the insects were carried out to sea by sudden gusts of wind; Only those that could either withstand the wind or did not fly at all survived. Selection in this direction has led to the fact that on the island of Madeira, out of 550 species of beetles, 200 are flightless.

Another example: in forests where the soil is brown, individuals of the earth snail often have brown and pink colored shells, in areas with coarse and yellow grass yellow color predominates, etc.

Populations adapted to ecologically dissimilar habitats may occupy adjacent geographic areas; for example, in the coastal regions of California, the plant Gilia achilleaefolia is represented by two races. One race, the “sun” race, grows on open, grassy, south-facing slopes, while the “shade” race is found in shady oak and redwood groves. These races differ in the size of the petals - a genetically determined feature.

The main result of this selection is the formation of population polymorphism, i.e. the presence of several groups differing in some characteristic or in isolation of populations differing in their properties, which may be the cause of divergence.

Conclusion

Like other elementary evolutionary factors, natural selection causes changes in the ratio of alleles in the gene pools of populations. In evolution, natural selection plays a creative role. By excluding genotypes with low adaptive value from reproduction, preserving favorable gene combinations of different merits, he transforms the picture of genotypic variability, which initially develops under the influence of random factors, in a biologically expedient direction.

Bibliography

Vlasova Z.A. Biology. Student's Handbook - Moscow, 1997

Green N. Biology - Moscow, 2003

Kamlyuk L.V. Biology in questions and answers - Minsk, 1994

Lemeza N.A. A manual on biology - Minsk, 1998

It is a holistic doctrine about the historical development of the organic world.

The essence of evolutionary teaching lies in the following basic principles:

1. All types of living beings inhabiting the Earth were never created by anyone.

2. Having arisen naturally, organic forms were slowly and gradually transformed and improved in accordance with environmental conditions.

3. The transformation of species in nature is based on such properties of organisms as heredity and variability, as well as natural selection that constantly occurs in nature. Natural selection occurs through the complex interaction of organisms with each other and with factors of inanimate nature; Darwin called this relationship the struggle for existence.

4. The result of evolution is the adaptability of organisms to their living conditions and the diversity of species in nature.

Natural selection. However, Darwin's main merit in creating the theory of evolution lies in the fact that he developed the doctrine of natural selection as the leading and directing factor of evolution. Natural selection, according to Darwin, is a set of changes occurring in nature that ensure the survival of the most adapted individuals and the predominance of their offspring, as well as the selective destruction of organisms that are unadapted to existing or changed environmental conditions.

In the process of natural selection, organisms adapt, i.e. they develop necessary equipment to the conditions of existence. As a result of competition between different species that have similar vital needs, less adapted species become extinct. Improving the mechanism of adaptation of organisms leads to the fact that the level of their organization gradually becomes more complex and thus the evolutionary process is carried out. At the same time, Darwin paid attention to such characteristics natural selection, as the gradual and slow process of change and the ability to summarize these changes into large, decisive causes leading to the formation of new species.

Based on the fact that natural selection operates among diverse and unequal individuals, it is considered as a combined interaction of hereditary variability, preferential survival and reproduction of individuals and groups of individuals better adapted than others to given conditions of existence. Therefore, the doctrine of natural selection as a driving and directing factor historical development the organic world is central to Darwin's theory of evolution.

Forms of natural selection:

Driving selection is a form of natural selection that operates under directed changes in environmental conditions. Described by Darwin and Wallace. In this case, individuals with traits that deviate in a certain direction from the average value receive advantages. In this case, other variations of the trait (its deviations in the opposite direction from the average value) are subject to negative selection.

As a result, in a population from generation to generation there is a shift in the average value of the trait in a certain direction. In this case, the pressure of driving selection must correspond to the adaptive capabilities of the population and the rate of mutational changes (otherwise, environmental pressure can lead to extinction).

In the 20th century, the proportion of dark-colored butterflies in some well-studied moth populations in England reached 95% in some areas, while the first dark-colored butterfly (morfa carbonaria) was captured in 1848.

Stabilizing selection- a form of natural selection in which its action is directed against individuals with extreme deviations from the average norm, in favor of individuals with an average expression of the trait. The concept of stabilizing selection was introduced into science and analyzed by I. I. Shmalgauzen.

Disruptive selection- a form of natural selection in which conditions favor two or more extreme variants (directions) of variability, but do not favor the intermediate, average state of a trait. As a result, several new forms may appear from one original one. Darwin described the action of disruptive selection, believing that it underlies divergence, although he could not provide evidence of its existence in nature. Disruptive selection contributes to the emergence and maintenance of population polymorphism, and in some cases can cause speciation.

One of the possible situations in nature in which disruptive selection comes into play is when a polymorphic population occupies a heterogeneous habitat. At the same time, different forms adapt to different ecological niches or subniches.

Sexual selection is natural selection for reproductive success. The survival of organisms is an important, but not the only component of natural selection. To others an important component is attractive to individuals of the opposite sex. Darwin called this phenomenon sexual selection. “This form of selection is determined not by the struggle for existence in the relations of organic beings among themselves or with external conditions, but by the competition between individuals of one sex, usually males, for the possession of individuals of the other sex.”

Traits that reduce the viability of their hosts can emerge and spread if the advantages they provide for reproductive success are significantly greater than their disadvantages for survival. When choosing males, females do not think about the reasons for their behavior. When an animal feels thirsty, it does not reason that it should drink water in order to restore the water-salt balance in the body - it goes to a watering hole because it feels thirsty.

In the same way, females, when choosing bright males, follow their instincts - they like bright tails. Those for whom instinct suggested different behavior did not leave offspring. The logic of the struggle for existence and natural selection is the logic of a blind and automatic process, which, acting constantly from generation to generation, has formed the amazing variety of forms, colors and instincts that we observe in the world of living nature.

When analyzing the reasons for the increase in the organization of organisms or their adaptability to living conditions, Darwin drew attention to the fact that selection does not necessarily require the selection of the best, it can only come down to the destruction of the worst. This is exactly what happens during unconscious selection. But the destruction (elimination) of the worst, less adapted organisms in nature can be observed at every step. Consequently, natural selection can be carried out by “blind” forces of nature.

Darwin emphasized that the expression “natural selection” should in no case be understood in the sense that someone is conducting this selection, since this term speaks of the action of spontaneous forces of nature, as a result of which organisms adapted to given conditions survive and die unadapted. The accumulation of beneficial changes leads first to small and then to large changes. This is how new varieties, species, genera and other systematic units of a higher rank appear. This is the leading, creative role of natural selection in evolution.

Elementary evolutionary factors. Mutation process and genetic combinatorics. Population waves, isolation, genetic drift, natural selection. Interaction of elementary evolutionary factors.

Elementary evolutionary factors are stochastic (probabilistic) processes occurring in populations that serve as sources of primary intrapopulation variability.

3. Periodic with high amplitude. Found in a wide variety of organisms. Often they are periodic in nature, for example, in the “predator-prey” system. May be associated with exogenous rhythms. It is this type of population waves that plays the greatest role in evolution.

Historical reference. The expression “wave of life” was probably first used by the explorer of the South American pampas, W.H. Hudson (1872-1873). Hudson noted that favorable conditions(light, frequent showers) vegetation that usually burns out has been preserved; the abundance of flowers gave rise to an abundance of bumblebees, then mice, and then birds that fed on mice (including cuckoos, storks, short-eared owls).

S.S. Chetverikov drew attention to the waves of life, noting the appearance in 1903 in the Moscow province of certain species of butterflies that had not been found there for 30...50 years. Before this, in 1897 and somewhat later, there was a massive appearance of the gypsy moth, which denuded vast areas of forests and caused significant damage to orchards. In 1901, the admiral butterfly appeared in significant numbers. He presented the results of his observations in a short essay “Waves of Life” (1905).

If during the period of maximum population size (for example, a million individuals) a mutation appears with a frequency of 10-6, then the probability of its phenotypic manifestation will be 10-12. If, during a period of population decline to 1000 individuals, the carrier of this mutation survives completely by chance, then the frequency of the mutant allele will increase to 10-3. The same frequency will continue during the period of subsequent population growth, then the probability of the phenotypic manifestation of the mutation will be 10-6.

Insulation. Provides manifestation of the Baldwin effect in space.

In a large population (for example, one million diploid individuals), a mutation rate of the order of 10-6 means that approximately one in a million individuals are carriers of the new mutant allele. Accordingly, the probability of phenotypic manifestation of this allele in a diploid recessive homozygote is 10-12 (one trillionth).

If this population is divided into 1000 small isolated populations of 1000 individuals, then in one of the isolated populations there will most likely be one mutant allele, and its frequency will be 0.001. The probability of its phenotypic manifestation in the next subsequent generations will be (10 - 3)2 = 10 - 6 (one millionth). In ultra-small populations (tens of individuals), the probability of a mutant allele manifesting itself in the phenotype increases to (10 - 2)2 = 10 - 4 (one ten-thousandth).

Thus, only by isolating small and ultra-small populations will the chances of a phenotypic manifestation of a mutation in the coming generations increase thousands of times. At the same time, it is difficult to imagine that the same mutant allele would appear in the phenotype completely randomly in different small populations. Most likely, each small population will be characterized by a high frequency of one or a few mutant alleles: either a, or b, or c, etc.

Material from Wikipedia - the free encyclopedia

Natural selection- the main evolutionary process, as a result of which in a population the number of individuals with maximum fitness (the most favorable traits) increases, while the number of individuals with unfavorable traits decreases. In the light of the modern synthetic theory of evolution, natural selection is considered as the main reason for the development of adaptations, speciation and the origin of supraspecific taxa. Natural selection is the only known cause adaptations, but not the only reason for evolution. Maladaptive causes include genetic drift, gene flow, and mutations.

The term "Natural selection" was popularized by Charles Darwin, comparing the process with artificial selection. modern form which is selection. The idea of comparing artificial and natural selection is that in nature the selection of the most “successful”, “best” organisms also occurs, but in this case the role of “evaluator” of the usefulness of properties is not a person, but the environment. In addition, the material for both natural and artificial selection is small hereditary changes that accumulate from generation to generation.

Mechanism of natural selection

In the process of natural selection, mutations are fixed that increase the fitness of organisms. Natural selection is often called a "self-evident" mechanism because it follows from such simple facts as:

Organisms produce more offspring than can survive;
There is heritable variation in the population of these organisms;
Organisms with different genetic traits have different survival rates and ability to reproduce.

The central concept of the concept of natural selection is the fitness of organisms. Fitness is defined as an organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next generation. However, the main thing in determining fitness is not the total number of descendants, but the number of descendants with a given genotype (relative fitness). For example, if the offspring of a successful and rapidly reproducing organism are weak and do not reproduce well, then the genetic contribution and therefore the fitness of that organism will be low.

Natural selection for traits that can vary over some range of values (such as the size of an organism) can be divided into three types:

Directional selection- changes in the average value of a trait over time, for example an increase in body size;
Disruptive selection- selection for extreme values of a trait and against average values, for example, large and small body sizes;
Stabilizing selection- selection against extreme values of a trait, which leads to a decrease in the variance of the trait.

A special case of natural selection is sexual selection, the substrate of which is any trait that increases the success of mating by increasing the attractiveness of the individual to potential partners. Traits that have evolved through sexual selection are especially noticeable in the males of some animal species. Characteristics such as large horns and bright coloring, on the one hand, can attract predators and reduce the survival rate of males, and on the other hand, this is balanced by the reproductive success of males with similar pronounced characteristics.

Selection can operate at different levels of organization, such as genes, cells, individual organisms, groups of organisms, and species. Moreover, selection can act simultaneously at different levels. Selection at levels above the individual, for example group selection, can lead to cooperation (see Evolution#Cooperation).

Forms of natural selection

There are different classifications of selection forms. A classification based on the nature of the influence of forms of selection on the variability of a trait in a population is widely used.

Driving selection

Driving selection- a form of natural selection that operates when directed changing environmental conditions. Described by Darwin and Wallace. In this case, individuals with traits that deviate in a certain direction from the average value receive advantages. In this case, other variations of the trait (its deviations in the opposite direction from the average value) are subject to negative selection. As a result, in a population from generation to generation there is a shift in the average value of the trait in a certain direction. In this case, the pressure of driving selection must correspond to the adaptive capabilities of the population and the rate of mutational changes (otherwise, environmental pressure can lead to extinction).

An example of the action of driving selection is “industrial melanism” in insects. “Industrial melanism” is a sharp increase in the proportion of melanistic (dark-colored) individuals in those populations of insects (for example, butterflies) that live in industrial areas. Due to industrial impact, the tree trunks darkened significantly, and light-colored lichens also died, which is why light-colored butterflies became better visible to birds, and dark-colored ones became less visible. In the 20th century, in some areas, the proportion of dark-colored butterflies in some well-studied moth populations in England reached 95%, while for the first time the dark-colored butterfly ( morpha carbonaria) was captured in 1848.

Stabilizing selection

Stabilizing selection- a form of natural selection in which its action is directed against individuals with extreme deviations from the average norm, in favor of individuals with an average expression of the trait. The concept of stabilizing selection was introduced into science and analyzed by I. I. Shmalgauzen.

Disruptive selection

Disruptive selection- a form of natural selection in which conditions favor two or more extreme variants (directions) of variability, but do not favor the intermediate, average state of a trait. As a result, several new forms may appear from one original one. Darwin described the action of disruptive selection, believing that it underlies divergence, although he could not provide evidence for its existence in nature. Disruptive selection contributes to the emergence and maintenance of population polymorphism, and in some cases can cause speciation.

Sexual selection

Two hypotheses about the mechanisms of sexual selection are common.

According to the “good genes” hypothesis, the female “reasons” as follows: “If a given male, despite his bright plumage and long tail, managed not to die in the clutches of a predator and survive to sexual maturity, then he has good genes that allowed him to do this. Therefore, he should be chosen as the father of his children: he will pass on his good genes to them.” By choosing colorful males, females are choosing good genes for their offspring.
According to the “attractive sons” hypothesis, the logic of female choice is somewhat different. If brightly colored males, for whatever reason, are attractive to females, it is worth choosing a brightly colored father for his future sons, because his sons will inherit the brightly colored genes and will be attractive to females in the next generation. Thus, a positive feedback occurs, which leads to the fact that from generation to generation the brightness of the plumage of males is increasingly increasing. The process continues to grow until it reaches the limit of viability.

When choosing males, females do not think about the reasons for their behavior. When an animal feels thirsty, it does not reason that it should drink water in order to restore the water-salt balance in the body - it goes to a watering hole because it feels thirsty. In the same way, females, when choosing bright males, follow their instincts - they like bright tails. Those for whom instinct suggested different behavior did not leave offspring. The logic of the struggle for existence and natural selection is the logic of a blind and automatic process, which, acting constantly from generation to generation, has formed the amazing variety of forms, colors and instincts that we observe in the world of living nature.

Selection methods: positive and negative selection

There are two forms of artificial selection: Positive And Cut-off (negative) selection.

Positive selection increases the number of individuals in a population that have useful traits that increase the viability of the species as a whole.

Eliminating selection eliminates from a population the vast majority of individuals that carry traits that sharply reduce viability under given environmental conditions. Using selection selection, highly deleterious alleles are removed from the population. Also, individuals with chromosomal rearrangements and a set of chromosomes that sharply disrupt the normal functioning of the genetic apparatus can be subjected to cutting selection.

The role of natural selection in evolution

In the example of the worker ant we have an insect extremely different from its parents, yet absolutely sterile and, therefore, unable to transmit from generation to generation acquired modifications of structure or instincts. You can set good question- How is it possible to reconcile this case with the theory of natural selection?
- Origin of Species (1859)

Darwin assumed that selection could apply not only to an individual organism, but also to a family. He also said that perhaps, to one degree or another, this could explain people's behavior. He was right, but it was only with the advent of genetics that it became possible to provide a more expanded view of the concept. The first sketch of the “theory of kin selection” was made by the English biologist William Hamilton in 1963, who was the first to propose considering natural selection not only at the level of an individual or an entire family, but also at the gene level.

Write a review about the article "Natural selection"

Notes

, With. 43-47.
, p. 251-252.
Orr H.A.// Nat Rev Genet. - 2009. - Vol. 10(8). - P. 531-539.
Haldane J//Nature. - 1959. - Vol. 183. - P. 710-713.
Lande R, Arnold SJ The measurement of selection on correlated characters // Evolution. - 1983. - Vol. 37. - P. 1210–26. - DOI:10.2307/2408842.
.
, Chapter 14.
Andersson M, Simmons L// Trends Ecol Evol. - 2001. - Vol. 21(6). - P. 296-302.
Kokko H, Brooks R, McNamara J, Houston A// Proc Biol Sci. - 2002. - Vol. 269. - P. 1331-1340.
Hunt J, Brooks R, Jennions MD, Smith MJ, Bentsen CL, Bussière LF//Nature. - 2004. - Vol. 432. - P. 1024-1027.
Okasha, S. Evolution and the Levels of Selection. - Oxford University Press, 2007. - 263 p. - ISBN 0-19-926797-9.
Mayr E// Philos. Trans. R. Soc. Lond., B, Biol. Sci. - 1998. - T. 353. - P. 307–14.
Maynard Smith J// Novartis Found. Symp. - 1998. - T. 213. - pp. 211–217.
Gould SJ, Lloyd EA//Proc. Natl. Acad. Sci. U.S.A. - 1999. - T. 96, No. 21. - pp. 11904–11909.

Literature

Lua error: attempt to index local "entity" (a nil value).

Links

- an article with well-known examples: the color of butterflies, human resistance to malaria, etc.
- Chapter 4, Natural Selection
- Modeling for Understanding in Science Education, University of Wisconsin
from University of Berkeley education website
Evolution: Education and Outreach





Evolutionary processes

Factors of evolution

Population genetics

Origin of life

Historical concepts

Modern theories

Evolution of taxa

Excerpt describing Natural selection

- They killed me three times, three times I rose from the dead. They stoned me, crucified me... I will rise... I will rise... I will rise. They tore my body apart. The kingdom of God will be destroyed... I will destroy it three times and build it up three times,” he shouted, raising his voice more and more. Count Rastopchin suddenly turned pale, just as he had turned pale when the crowd rushed at Vereshchagin. He turned away.
- Let's go... let's go quickly! - he shouted at the coachman in a trembling voice.
The carriage rushed at all the horses' feet; but for a long time behind him, Count Rastopchin heard a distant, insane, desperate cry, and before his eyes he saw one surprised, frightened, bloody face of a traitor in a fur sheepskin coat.
No matter how fresh this memory was, Rostopchin now felt that it had cut deep into his heart, to the point of bleeding. He now clearly felt that the bloody trail of this memory would never heal, but that, on the contrary, the further, the more evil, the more painful this terrible memory would live in his heart for the rest of his life. He heard, it seemed to him now, the sounds of his words:
“Cut him, you will answer me with your head!” - “Why did I say these words! Somehow I accidentally said... I could not have said them (he thought): then nothing would have happened.” He saw the frightened and then suddenly hardened face of the dragoon who struck and the look of silent, timid reproach that this boy in a fox sheepskin coat threw at him... “But I didn’t do it for myself. I should have done this. La plebe, le traitre... le bien publique", [The mob, the villain... public good.] - he thought.
The army was still crowded at the Yauzsky Bridge. It was hot. Kutuzov, frowning and despondent, was sitting on a bench near the bridge and playing with a whip in the sand, when a carriage noisily galloped up to him. A man in a general's uniform, wearing a hat with a plume, with darting eyes that were either angry or frightened, approached Kutuzov and began telling him something in French. It was Count Rastopchin. He told Kutuzov that he came here because Moscow and the capital no longer exist and there is only one army.
“It would have been different if your lordship had not told me that you would not surrender Moscow without fighting: all this would not have happened!” - he said.
Kutuzov looked at Rastopchin and, as if not understanding the meaning of the words addressed to him, carefully tried to read something special written at that moment on the face of the person speaking to him. Rastopchin, embarrassed, fell silent. Kutuzov shook his head slightly and, without taking his searching gaze off Rastopchin’s face, said quietly:
– Yes, I will not give up Moscow without giving a battle.
Was Kutuzov thinking about something completely different when he said these words, or did he say them on purpose, knowing their meaninglessness, but Count Rostopchin did not answer anything and hastily walked away from Kutuzov. And a strange thing! The commander-in-chief of Moscow, the proud Count Rostopchin, taking a whip in his hands, approached the bridge and began to disperse the crowded carts with a shout.

At four o'clock in the afternoon, Murat's troops entered Moscow. A detachment of Wirtemberg hussars rode ahead, and the Neapolitan king himself rode behind on horseback with a large retinue.
Near the middle of the Arbat, near St. Nicholas the Revealed, Murat stopped, awaiting news from the advance detachment about the situation of the city fortress “le Kremlin”.
A small group of people from the residents remaining in Moscow gathered around Murat. Everyone looked with timid bewilderment at the strange, long-haired boss adorned with feathers and gold.
- Well, is this their king himself? Nothing! – quiet voices were heard.
The translator approached a group of people.
“Take off your hat... take off your hat,” they said in the crowd, turning to each other. The translator turned to one old janitor and asked how far it was from the Kremlin? The janitor, listening in bewilderment to the alien Polish accent and not recognizing the sounds of the translator's dialect as Russian speech, did not understand what was being said to him and hid behind others.
Murat moved towards the translator and ordered to ask where the Russian troops were. One of the Russian people understood what was being asked of him, and several voices suddenly began to answer the translator. A French officer from the advance detachment rode up to Murat and reported that the gates to the fortress were sealed and that there was probably an ambush there.
“Okay,” said Murat and, turning to one of the gentlemen of his retinue, he ordered four light guns to be brought forward and fired at the gate.
The artillery came out at a trot from behind the column following Murat and rode along the Arbat. Having descended to the end of Vzdvizhenka, the artillery stopped and lined up in the square. Several French officers controlled the cannons, positioning them, and looked into the Kremlin through a telescope.
The bell for Vespers was heard in the Kremlin, and this ringing confused the French. They assumed it was a call to arms. Several infantry soldiers ran to the Kutafyevsky Gate. There were logs and planks at the gate. Two rifle shots rang out from under the gate as soon as the officer and his team began to run up to them. The general standing at the cannons shouted command words to the officer, and the officer and the soldiers ran back.
Three more shots were heard from the gate.
One shot hit a French soldier in the leg, and a strange cry of a few voices was heard from behind the shields. On the faces of the French general, officers and soldiers at the same time, as if on command, the previous expression of gaiety and calm was replaced by a stubborn, concentrated expression of readiness to fight and suffer. For all of them, from the marshal to the last soldier, this place was not Vzdvizhenka, Mokhovaya, Kutafya and Trinity Gate, but this was a new area of a new field, probably a bloody battle. And everyone prepared for this battle. The screams from the gate died down. The guns were deployed. The artillerymen blew off the burnt blazers. The officer commanded “feu!” [fallen!], and two whistling sounds of tins were heard one after another. Grapeshot bullets crackled against the stone of the gate, logs and shields; and two clouds of smoke wavered in the square.
A few moments after the rolling of shots across the stone Kremlin died down, a strange sound was heard above the heads of the French. A huge flock of jackdaws rose above the walls and, cawing and rustling with thousands of wings, circled in the air. Along with this sound, a lonely human cry was heard at the gate, and from behind the smoke the figure of a man without a hat, in a caftan, appeared. Holding a gun, he aimed at the French. Feu! - the artillery officer repeated, and at the same time one rifle and two cannon shots were heard. The smoke closed the gate again.
Nothing else moved behind the shields, and the French infantry soldiers and officers went to the gate. There were three wounded and four dead people lying at the gate. Two people in caftans were running away from below, along the walls, towards Znamenka.
“Enlevez moi ca, [Take it away,” said the officer, pointing to the logs and corpses; and the French, having finished off the wounded, threw the corpses down beyond the fence. Nobody knew who these people were. “Enlevez moi ca,” was the only word said about them, and they were thrown away and cleaned up later so they wouldn’t stink. Thiers alone dedicated several eloquent lines to their memory: “Ces miserables avaient envahi la citadelle sacree, s"etaient empares des fusils de l"arsenal, et tiraient (ces miserables) sur les Francais. On en sabra quelques "uns et on purgea le Kremlin de leur presence. [These unfortunates filled the sacred fortress, took possession of the guns of the arsenal and shot at the French. Some of them were cut down with sabers, and cleared the Kremlin of their presence.]
Murat was informed that the path had been cleared. The French entered the gates and began to camp on Senate Square. The soldiers threw chairs out of the Senate windows into the square and laid out fires.
Other detachments passed through the Kremlin and were stationed along Maroseyka, Lubyanka, and Pokrovka. Still others were located along Vzdvizhenka, Znamenka, Nikolskaya, Tverskaya. Everywhere, not finding owners, the French settled not as in apartments in the city, but as in a camp located in the city.
Although ragged, hungry, exhausted and reduced to 1/3 of their previous strength, the French soldiers entered Moscow in orderly order. It was an exhausted, exhausted, but still fighting and formidable army. But it was an army only until the minute the soldiers of this army went to their apartments. As soon as the people of the regiments began to disperse to empty and rich houses, the army was destroyed forever and neither residents nor soldiers were formed, but something in between, called marauders. When, five weeks later, the same people left Moscow, they no longer constituted an army. It was a crowd of marauders, each of whom carried or carried with him a bunch of things that seemed valuable and necessary to him. The goal of each of these people when leaving Moscow was not, as before, to conquer, but only to retain what they had acquired. Like that monkey who, having put his hand into the narrow neck of a jug and grabbed a handful of nuts, does not unclench his fist so as not to lose what he has grabbed, and thereby destroys himself, the French, when leaving Moscow, obviously had to die due to the fact that they were dragging with the loot, but it was as impossible for him to throw away this loot as it is impossible for a monkey to unclench a handful of nuts. Ten minutes after each French regiment entered some quarter of Moscow, not a single soldier or officer remained. In the windows of the houses people in greatcoats and boots could be seen walking around the rooms laughing; in the cellars and basements the same people managed the provisions; in the courtyards the same people unlocked or beat down the gates of barns and stables; they lit fires in the kitchens, baked, kneaded and cooked with their hands rolled up, scared, made them laugh and caressed women and children. And there were many of these people everywhere, in shops and in homes; but the army was no longer there.
On the same day, order after order was given by the French commanders to prohibit troops from dispersing throughout the city, to strictly prohibit violence against residents and looting, and to make a general roll call that same evening; but, despite any measures. the people who had previously made up the army dispersed throughout the rich, empty city, abundant in amenities and supplies. Just as a hungry herd walks in a heap across a bare field, but immediately scatters uncontrollably as soon as it attacks rich pastures, so the army scattered uncontrollably throughout the rich city.
There were no inhabitants in Moscow, and the soldiers, like water into sand, were sucked into it and, like an unstoppable star, spread out in all directions from the Kremlin, which they entered first of all. The cavalry soldiers, entering a merchant's house abandoned with all its goods and finding stalls not only for their horses, but also extra ones, still went nearby to occupy another house, which seemed better to them. Many occupied several houses, writing in chalk who occupied it, and arguing and even fighting with other teams. Before they could fit in, the soldiers ran outside to inspect the city and, hearing that everything had been abandoned, rushed to where they could take away valuables for nothing. The commanders went to stop the soldiers and themselves unwittingly became involved in the same actions. In Carriage Row there were shops with carriages, and the generals crowded there, choosing carriages and carriages for themselves. The remaining residents invited their leaders to their place, hoping to thereby protect themselves from robbery. There was an abyss of wealth, and there was no end in sight; everywhere, around the place that the French occupied, there were still unexplored, unoccupied places, in which, as it seemed to the French, there was even more wealth. And Moscow sucked them in further and further. Just as when water pours onto dry land, water and dry land disappear; in the same way, due to the fact that a hungry army entered an abundant, empty city, the army was destroyed, and the abundant city was destroyed; and there was dirt, fires and looting.

The French attributed the fire of Moscow to au patriotisme feroce de Rastopchine [to Rastopchin's wild patriotism]; Russians – to the fanaticism of the French. In essence, there were no reasons for the fire of Moscow in the sense that this fire could be attributed to the responsibility of one or several persons. Moscow burned down due to the fact that it was placed in such conditions under which every wooden city should burn down, regardless of whether the city had one hundred and thirty bad fire pipes or not. Moscow had to burn due to the fact that the inhabitants left it, and just as inevitably as a heap of shavings should catch fire, on which sparks of fire would rain down for several days. A wooden city, in which there are fires almost every day in the summer under the residents, house owners and under the police, cannot help but burn down when there are no inhabitants in it, but live troops smoking pipes, making fires on Senate Square from Senate chairs and cooking themselves two once a day. In peacetime, as soon as troops settle into quarters in villages in a certain area, the number of fires in this area immediately increases. To what extent should the probability of fires increase in an empty wooden city in which an alien army is stationed? Le patriotisme feroce de Rastopchine and the fanaticism of the French are not to blame for anything here. Moscow caught fire from pipes, from kitchens, from fires, from the sloppiness of enemy soldiers and residents - not the owners of the houses. If there were arson (which is very doubtful, because there was no reason for anyone to set fire, and, in any case, it was troublesome and dangerous), then the arson cannot be taken as the cause, since without the arson it would have been the same.
No matter how flattering it was for the French to blame the atrocity of Rostopchin and for the Russians to blame the villain Bonaparte or then to place the heroic torch in the hands of their people, one cannot help but see that there could not have been such a direct cause of the fire, because Moscow had to burn, just as every village and factory had to burn , every house from which the owners will come out and into which strangers will be allowed to run the house and cook their own porridge. Moscow was burned by its inhabitants, it’s true; but not by those residents who remained in it, but by those who left it. Moscow, occupied by the enemy, did not remain intact, like Berlin, Vienna and other cities, only due to the fact that its inhabitants did not offer bread, salt and keys to the French, but left it.

The influx of Frenchmen, spreading like a star across Moscow on the day of September 2, reached the block in which Pierre now lived only in the evening.
After the last two days, spent alone and unusually, Pierre was in a state close to madness. His whole being was taken over by one persistent thought. He himself did not know how and when, but this thought now took possession of him so that he did not remember anything from the past, did not understand anything from the present; and everything that he saw and heard happened before him as in a dream.
Pierre left his home only to get rid of the complex tangle of life's demands that gripped him, and which, in his then state, he was able to unravel. He went to Joseph Alekseevich’s apartment under the pretext of sorting through the books and papers of the deceased only because he was looking for peace from life’s anxiety - and with the memory of Joseph Alekseevich, a world of eternal, calm and solemn thoughts was associated in his soul, completely opposite to the anxious confusion in which he felt himself being drawn in. He was looking for a quiet refuge and really found it in the office of Joseph Alekseevich. When, in the dead silence of the office, he sat down, leaning on his hands, over the dusty desk of the deceased, memories began to appear in his imagination, calmly and significantly, one after another. last days, especially the Battle of Borodino and that indefinable feeling for him of his insignificance and deceit in comparison with the truth, simplicity and strength of that category of people who were imprinted in his soul under the name they. When Gerasim woke him from his reverie, the thought occurred to Pierre that he would take part in the supposed - as he knew - people's defense Moscow. And for this purpose, he immediately asked Gerasim to get him a caftan and a pistol and announced to him his intention, hiding his name, to stay in the house of Joseph Alekseevich. Then, during the first solitary and idle day (Pierre tried several times and could not stop his attention on the Masonic manuscripts), he vaguely imagined several times the previously thought about the cabalistic meaning of his name in connection with the name of Bonaparte; but this thought that he, l "Russe Besuhof, was destined to put a limit to the power of the beast, came to him only as one of the dreams that run through his imagination for no reason and without a trace.
When, having bought a caftan (with the sole purpose of participating in the people's defense of Moscow), Pierre met the Rostovs and Natasha said to him: “Are you staying? Oh, how good it is!” – the thought flashed through his head that it would really be good, even if they took Moscow, for him to stay in it and fulfill what was predetermined for him.
The next day, with one thought not to feel sorry for himself and not to lag behind them in anything, he walked with the people beyond the Trekhgornaya Gate. But when he returned home, making sure that Moscow would not be defended, he suddenly felt that what had previously seemed to him only a possibility had now become a necessity and an inevitability. He had to, hiding his name, stay in Moscow, meet Napoleon and kill him in order to either die or stop the misfortune of all of Europe, which, in Pierre's opinion, originated from Napoleon alone.
Pierre knew all the details of the attempt by a German student on the life of Bonaparte in Vienna in 1809 and knew that this student had been shot. And the danger to which he exposed his life in fulfilling his intention excited him even more.
Two equally strong feelings irresistibly attracted Pierre to his intention. The first was a feeling of the need for sacrifice and suffering with the awareness of general misfortune, that feeling, as a result of which he went to Mozhaisk on the 25th and arrived in the very heat of battle, now ran away from his home and, instead of the usual luxury and comforts of life, slept without undressing, on on a hard sofa and ate the same food with Gerasim; the other was that vague, exclusively Russian feeling of contempt for everything conventional, artificial, human, for everything that is considered by most people to be the highest good of the world. For the first time, Pierre experienced this strange and charming feeling in the Slobodsky Palace, when he suddenly felt that wealth, power, and life, everything that people so diligently arrange and protect - if all this is worth something, then only by the pleasure with which you can give it all up.
It was that feeling as a result of which a hunter recruit drinks his last penny, a drunken man breaks mirrors and glass without any apparent reason and knowing that it would cost him his last money; that feeling as a result of which a person, doing (in the vulgar sense) crazy things, seems to be testing his personal power and strength, declaring the presence of a higher, standing outside human conditions, judgment over life.
From the very day when Pierre first experienced this feeling in the Slobodsky Palace, he was constantly under its influence, but now he only found complete satisfaction with it. In addition, at the moment Pierre was supported in his intention and deprived of the opportunity to renounce him by what he had already done along this path. And his flight from home, and his caftan, and the pistol, and his statement to Rostov that he remained in Moscow - everything would have lost not only its meaning, but all this would have been despicable and ridiculous (to which Pierre was sensitive), if After all this, like others, he left Moscow.

Lecture: Natural selection as the leading factor of evolution. Modern ideas about the forms of natural selection

Driving selection

Disruptive selection

Insulation. Provides manifestation of the Baldwin effect in space.

Mechanism of natural selection

Forms of natural selection

Driving selection

Stabilizing selection

Disruptive selection

Sexual selection

Selection methods: positive and negative selection

The role of natural selection in evolution

see also

Write a review about the article "Natural selection"

Notes

Literature

Links

Excerpt describing Natural selection

Latest

You need to know this