Natural selection checks organisms for compliance with living conditions and is carried out in various forms that have their own characteristics. What form or mechanism of selection acts on a given group of organisms depends on climatic, geological and other conditions.
The driving form of natural selection preserves useful deviations from the average norm.
This deviation can be any trait that increases the survival and fertility of some organisms compared to others.
There are two types of motive selection:
- transitive (transitive);
- directed.
Transitional selection is the development of an initially small form that has gained an advantage under changing environmental conditions.
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An example of such selection is the development of industrial melanism in Lepidoptera.
Thus, the birch moth previously had about 98% of light-colored individuals in populations. As the bark of trees darkened in industrial areas, dark-colored moths began to predominate, since they became less visible to birds.
The action of transitive selection is reversible, and when external conditions change, the ratio of dark and light individuals will also change.
With directional selection, the formation and reproduction of forms that differ in some way from the original form occur. Such selection takes place under conditions of unidirectional changes in the environment.
Rice. 1. Driving selection.
Unlike transitional selection, in this type of selection there is no ready-made different form, and useful changes accumulate in ordinary representatives of the species.
For example, bacteria can mutate when exposed to antibiotics. The resulting mutants are resistant to doses much higher than the original.
Stabilizing selection
If we talk briefly about the stabilizing form of natural selection, then this is the preservation of average norms.
The condition of stabilizing selection is the constant parameters of the environment, and in this it is opposite to the driving one.
Rice. 2. Stabilizing selection.
Each species has an optimal average fecundity rate and the weight of cubs born.
If birds lay eggs below the norm, this may not be enough to maintain the population. If the chicks hatch more than the average norm, then the parents risk not feeding them.
In this case, we see the effect of stabilizing selection. Increased fertility is not an advantage in conditions of competition and lack of food.
Driving and stabilizing are the two main forms of natural selection, which are essentially two sides of the same process.
Tearing selection
The tearing, or disruptive, form of selection divides a previously single population into two or more new ones.
Thus, the female butterflies of the African sailboat developed three forms, imitating three different inedible species of butterflies.
Rice. 3. Three forms of females of the African swallowtail.
Having such a similarity is more beneficial to a population than mimicking just one species.
Disruptive Selection Guides Stratifying Evolution , as a result of which new groups of organisms are formed, for example, many orders in the class of mammals.
Table "Forms of natural selection"
|
driving |
Stabilizing |
Tearing |
|
|
Validity conditions |
Gradual environmental changes |
Constant environmental conditions |
Several options for adapting to the environment |
|
Orientation |
In favor of individuals with useful, different from the original, features |
Against the extreme values of the trait in favor of the average |
Against the mean values of the feature in favor of the extreme |
|
Result |
Create a new average rate |
Preservation of the average rate |
Creation of two or more new rules |
|
The emergence of populations resistant to pesticides, antibiotics, etc. |
Preservation of the shape and size of the flower in insect-pollinated plants to match the size of the pollinator; relict species |
Persistence of groups of insects with either strongly developed or small wings in conditions of frequent windy weather |
What have we learned?
Studying in biology the three forms of natural selection, we gave a brief description of them. Forms of selection differ in: conditions, focus, results. Stabilizing selection preserves old adaptations, while disruptive and motive selection preserves new ones. At the same time, the purpose of all forms is the adaptation of organisms to the conditions of existence.
Topic quiz
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1. The stabilizing form of natural selection is manifested in
A) constant environmental conditions
B) change in the average reaction rate
C) the preservation of adapted individuals in the original habitat
D) culling of individuals with deviations from the norm
E) preservation of individuals with mutations
E) the preservation of individuals with new phenotypes
Answer
3. Establish a correspondence between the example and the type of evidence for the evolution of the animal world that it illustrates: 1-comparative anatomical, 2-paleontological
A) the phylogenetic series of the horse
B) the presence of the coccyx in the human skeleton
C) bird feather and lizard scales
D) Archeopteryx prints
D) multi-faciality in humans
Answer
A2 B1 C1 D2 D1
4. Determine the sequence of processes characteristic of geographic speciation
A) the formation of a population with a new gene pool
B) the appearance of a geographical barrier between populations
C) natural selection of individuals with traits adaptive to given conditions
D) the emergence of individuals with new traits in an isolated population
Answer
4+. Specify the correct sequence of stages of geographical speciation
A) distribution of a trait in a population
B) the appearance of mutations
C) isolation of populations
D) preservation as a result of the struggle for existence of natural selection of individuals with useful changes
Answer
4++. Specify the sequence of processes in geographic speciation
A) accumulation of mutations in new conditions
B) territorial isolation of the population
B) reproductive isolation
D) the formation of a new species
Answer
4+++. Specify the sequence of stages of geographical speciation
A) divergence of traits in isolated populations
B) reproductive isolation of populations
C) the emergence of physical barriers in the range of the original species
D) the emergence of new species
D) the formation of isolated populations
Answer
4A. Under the influence of what evolutionary factors does the process of ecological speciation occur??
A) modification variability
B) fitness
B) natural selection
D) mutational variability
D) struggle for existence
E) convergence
Answer
4B. Set the correspondence between the example and the mode of speciation that this example illustrates: 1-geographic, 2-ecological
A) the habitation of two populations of common perch in the coastal zone and at a great depth of the lake
B) the habitation of different populations of blackbirds in dense forests and near human habitation
C) the disintegration of the range of the May lily of the valley into isolated areas due to glaciation
D) the formation of different types of tits on the basis of food specialization
E) the formation of Dahurian larch as a result of the expansion of the range of Siberian larch to the east
Answer
A2 B2 C1 D2 D1
4B. Establish a correspondence between the causes and methods of speciation: 1-geographic, 2-ecological
A) expansion of the range of the original species
B) the stability of the range of the original species
C) division of the species range by various barriers
D) the diversity of variability of individuals within the range
E) variety of habitats within a stable range
Answer
A1 B2 C1 D2 D2
5. Establish a correspondence between the example and the type of evidence of evolution to which this example belongs: 1 - paleontological, 2 - comparative anatomical
A) transitional forms
B) homologous organs
B) rudiments
D) a single plan for the structure of organs
D) fossils
E) atavisms
Answer
A1 B2 C2 D2 E1 E2
6. Establish the sequence of formation of aromorphoses in animals
A) appearance of tissue
B) the emergence of sexual reproduction
B) the formation of a chord
D) the formation of five-fingered limbs
Answer
6a. Establish the sequence of formation of aromorphoses in the evolution of chordates
A) the appearance of the lungs
B) the formation of the brain and spinal cord
B) the formation of a chord
D) the emergence of a four-chambered heart
Answer
6a+. Establish the sequence of formation of aromorphoses in the evolution of invertebrates
A) the appearance of bilateral symmetry of the body
B) the emergence of multicellularity
C) the appearance of jointed limbs covered with chitin
D) division of the body into many segments
Answer
6b. Set the sequence of complication of the organization of these animals in the process of evolution
A) earthworm
B) common amoeba
B) white planaria
D) May beetle
Answer
7. What factors are the driving forces of evolution?
A) modification variability
B) mutation process
B) natural selection
D) adaptation of organisms to the environment
D) population waves
E) abiotic environmental factors
Answer
7+. The driving forces of evolution are
A) crossing over
B) mutation process
B) modification variability
D) insulation
D) variety of species
E) natural selection
Answer
9. Establish a correspondence between the example and the anthropogenesis factor that illustrates it: 1-biological, 2-social
A) spatial isolation
B) genetic drift
B) speech
D) abstract thinking
D) social labor activity
E) population waves
Answer
A1 B1 C2 D2 E2 E1
9a. Establish a correspondence between the example and the factor of anthropogenesis for which it is characteristic: 1-biological, 2-social
A) work activity
B) abstract thinking
B) isolation
D) mutational variability
D) population waves
E) second signaling system
Answer
A2 B2 C1 D1 E1 E2
11. Establish a correspondence between the characteristic of natural selection and its form: 1-moving, 2-stabilizing
A) preserves the mean value of the feature
B) contributes to adaptation to changing environmental conditions
C) retains individuals with a trait that deviates from its average value
D) contributes to an increase in the diversity of organisms
D) contributes to the preservation of species characteristics
Answer
A2 B1 C1 D1 D2
11+. Specify the features that characterize the driving form of natural selection
A) provides the appearance of a new species
B) manifests itself in changing environmental conditions
C) the adaptation of individuals to the original environment is improved
D) individuals with a deviation from the norm are culled
E) the number of individuals with the average value of the trait increases
E) individuals with new traits are preserved
Answer
11++. What are the characteristics of motive selection?
A) operates under relatively constant living conditions
B) eliminates individuals with an average value of the trait
C) promotes the reproduction of individuals with an altered genotype
D) preserves individuals with deviations from the average values of the trait
E) preserves individuals with the established norm of the reaction of the trait
E) contributes to the appearance of mutations in the population
Answer
12. What did the idioadaptation lead to in the Birds class?
A) the overall growth of the organization
B) an increase in the number of populations and species
B) widespread
D) simplifying the organization
D) the emergence of private adaptations to environmental conditions
E) decreased fertility
Answer
13. Establish a correspondence between the animal and the type of coloring of the integument of its body: 1-protective, 2-warning
A) honey bee
B) river perch
B) ladybug
D) Colorado potato beetle
D) white partridge
E) white hare
Answer
A2 B1 C2 D2 E1 E1
14. Indicate the historical sequence of the main stages of anthropogenesis
A) modern man
B) Australopithecus
B) Cro-Magnon
D) Pithecanthropus
D) Neanderthal
Answer
16. Establish a correspondence between the process occurring in nature and the form of the struggle for existence: 1-intraspecific, 2-interspecific
A) competition between individuals of a population for territory
B) the use of one species by another
C) rivalry between individuals for a female
D) displacement of the black rat by the gray rat
D) predation
Answer
A1 B2 C1 D2 D2
17. Establish a correspondence between the characteristic of evolution and its feature: 1-factor, 2-result
A) natural selection
B) adaptation of organisms to the environment
C) the formation of new species
D) combinative variability
E) conservation of species in stable conditions
E) struggle for existence
Answer
A1 B2 C2 D1 E2 E1
18. Establish a correspondence between the sign of a quick lizard and the criterion of the species that it illustrates: 1-morphological, 2-ecological
A) winter torpor
B) body length - 25–28 cm
B) spindle-shaped body
D) differences in the color of males and females
D) living on the edges of forests, in ravines and gardens
E) feeding on insects
Answer
A2 B1 C1 D1 E2 E2
18+. Establish a correspondence between the trait that characterizes the agile lizard and the species criterion: 1-morphological, 2-ecological
A) the body is brown
B) eats insects
B) is inactive at low temperatures
D) respiratory organs - lungs
D) breeds on land
E) the skin does not have glands
Answer
A1 B2 C2 D1 E2 E1
18++. Establish a correspondence between the characteristic of the species Common dolphin (dolphin-dolphin) and the criterion of the species to which this characteristic belongs: 1-morphological, 2-physiological, 3-ecological
a) Predators eat different types of fish.
B) Males are 6–10 cm larger than females.
C) Animals have mastered the aquatic habitat.
D) The size of the body is 160–260 centimeters.
E) Pregnancy of females lasts 10-11 months.
E) Animals lead a herd life.
Answer
A3 B1 C3 D1 E2 E3
19. Establish the sequence of appearance of animal types in the process of evolution
A) ringed worms
B) Intestinal
B) roundworms
D) flatworms
Answer
20. Establish a correspondence between the type of organisms and the direction of evolution along which its development is currently taking place: 1-biological progress, 2-biological regression
A) common dandelion
B) house mouse
B) coelacanth
D) walnut lotus
D) platypus
E) hare
Answer
A1 B1 C2 D2 E2 E1
21. What statements refer to the theory of Charles Darwin?
A) Within the species, the divergence of features leads to speciation.
B) The species is heterogeneous and is represented by many populations.
C) Natural selection is the guiding factor of evolution.
D) When creating varieties and breeds, artificial selection serves as a guiding factor.
E) The inner striving for perfection is a factor in evolution.
E) A population is a unit of evolution.
Answer
22. Establish a correspondence between aromorphosis of chordates and the era in which it appeared: 1-Paleozoic, 2-Mesozoic
A) a four-chambered heart in birds
B) bone jaws in armored fish
C) pulmonary respiration in lungfish
D) five-fingered limb in stegocephalians
D) uterus and placenta in mammals
E) an egg covered with a dense shell in reptiles
Answer
A2 B1 C1 D1 E2 E1
23. Set the sequence of evolutionary processes on Earth in chronological order
A) the release of organisms on land
B) the occurrence of photosynthesis
C) the formation of an ozone screen
D) the formation of coacervates in water
D) the emergence of cellular life forms
Answer
23+. Set the sequence of evolutionary processes on Earth in chronological order
A) the emergence of prokaryotic cells
B) the formation of coacervates in water
C) the emergence of eukaryotic cells
D) the release of organisms on land
D) the emergence of multicellular organisms
Answer
24. Establish a correspondence between the characteristics of selection and its type: 1-natural, 2-artificial
A) operates in nature constantly
B) preserves individuals with features that are of interest to humans
B) preserves individuals with traits that are useful to them
D) provides the formation of fitness
D) leads to the emergence of new species
E) contributes to the creation of new breeds of animals
Answer
A1 B2 C1 D1 E1 E2
Answer
26. Set the chronological sequence of anthropogenesis
A) a skilled person
B) erect man
B) driopithecus
D) intelligent person
The situation, but you can act at random. It is enough to create a wide range of diverse individuals - and, ultimately, the fittest will survive.
- At first an individual appears with new, completely random properties
- Then she is or is not able to leave offspring, depending on these properties
- Finally, if the outcome of the previous stage is positive, then she leaves offspring and her descendants inherit the newly acquired properties
At present, the partly naive views of Darwin himself have been partly reworked. So, Darwin imagined that changes should occur very smoothly, and the spectrum of variability is continuous. Today, however, the mechanisms of natural selection are explained with the help of genetics, which brings some originality to this picture. Mutations in the genes that operate in the first step of the above process are essentially discrete. It is clear, however, that the basic essence of Darwin's idea has remained unchanged.
Forms of natural selection
driving selection
Driving selection - a form of natural selection, when environmental conditions contribute to a certain direction of change in any trait or group of traits. At the same time, other possibilities for changing the trait are subjected 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. At the same time, 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).
A modern case of motive selection is the "industrial melanism of English butterflies". "Industrial melanism" is a sharp increase in the proportion of melanistic (having a dark color) individuals in those butterfly populations that live in industrial areas. Due to industrial impact, tree trunks darkened significantly, and light lichens also died, which made light butterflies more visible to birds, and dark ones worse. In the 20th century, in a number of regions, the proportion of dark-colored butterflies reached 95%, while for the first time a dark butterfly (Morfa carbonaria) was caught in 1848.
Driving selection is carried out when the environment changes or adapts to new conditions with the expansion of the range. It preserves hereditary changes in a certain direction, shifting the rate of reaction accordingly. For example, when developing the soil as a habitat for various unrelated groups of animals, the limbs turned into burrowing ones.
Stabilizing selection
Stabilizing selection- a form of natural selection, in which the action is directed against individuals with extreme deviations from the average norm, in favor of individuals with an average severity of the trait.
Many examples of the action of stabilizing selection in nature have been described. For example, at first glance it seems that individuals with maximum fecundity should make the greatest contribution to the gene pool of the next generation. 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. As a result, individuals with average fecundity turn out to be the most adapted.
Selection in favor of averages has been found for a variety of traits. In mammals, very low and very high birth weight newborns are more likely to die at birth or in the first weeks of life than middle weight newborns. Accounting for the size of the wings of birds that died after the storm showed that most of them had too small or too large wings. And in this case, the average individuals turned out to be the most adapted.
Disruptive selection
Disruptive (tearing) 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 the trait. As a result, several new forms may appear from one initial one. 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.
An example of disruptive selection is the formation of two races in the meadow rattle in hay meadows. Under normal conditions, the flowering and seed ripening periods of this plant cover the whole summer. But in hay meadows, seeds are produced mainly by those plants that have time to bloom and ripen either before the mowing period, or bloom at the end of summer, after mowing. As a result, two races of the 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 setae, leaving only individuals with a small and large number of setae. As a result, from about the 30th generation, the two lines diverged very strongly, 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.
Cut-off selection
Cut-off selection is a form of natural selection. Its action is opposite to positive selection. Cut-off selection culls out from the population the vast majority of individuals that carry traits that sharply reduce viability under given environmental conditions. With the help of cut-off selection, strongly harmful alleles are removed from the population. Also, individuals with chromosomal rearrangements and a set of chromosomes that sharply disrupt the normal operation of the genetic apparatus can be subjected to cutting selection.
positive selection
positive selection is a form of natural selection. Its action is the opposite of clipping selection. Positive selection increases the number of individuals in the population that have useful traits that increase the viability of the species as a whole. With the help of positive selection and cutting selection, a change in species is carried out (and not only through the destruction of unnecessary individuals, then any development should stop, but this does not happen).
Examples of positive selection include: a stuffed Archeopteryx can be used as a glider, but a stuffed swallow or seagull cannot. But the first birds flew better than Archeopteryx. Another example of positive selection is the emergence of predators that outperform many other warm-blooded creatures in their "mental abilities". Or the emergence of reptiles such as crocodiles, which have a four-chambered heart and are able to live both on land and in water.
Private directions of natural selection
- Survival of the most adapted species and populations, for example, species with gills in the water, since fitness allows you to win the fight for survival.
- Survival of physically healthy organisms.
- The survival of the physically strongest organisms, since the physical struggle for resources is an integral part of life. It is important in intraspecific struggle.
- Survival of the most sexually successful organisms, as sexual reproduction is the dominant mode of reproduction. This is where sexual selection comes into play.
However, all these cases are particular, and the main thing is the successful preservation in time. Therefore, sometimes these directions are violated in order to follow the main goal.
The role of natural selection in evolution
Darwin did not dare to publish his theory for a long time, because. I saw the problem of ants, which could only be explained from the standpoint of genetics.
see also
Links
- "Problems of macroevolution" - website of paleontologist A. V. Markov
- "Forms of natural selection" - an article with well-known examples: the color of butterflies, people's resistance to malaria, and more
- "Evolution based on patterns" - an article about whether the role of mutations in the evolutionary process is great, or some signs exist in advance, and then develop under the influence of driving selection
| evolutionary biology | |
|---|---|
| Mechanisms and processes | Adaptation Speciation Genetic drift Natural selection Heredity Variability Microevolution Macroevolution Mutations Gene transfer |
| The emergence of life | Chemical evolution RNA world hypothesis Biological evolution |
| History of evolutionary doctrine | |
Natural selection- the result of the struggle for existence; it is based on preferential survival and leaving offspring with the most adapted individuals of each species and the death of less adapted organisms.
The mutation process, population fluctuations, isolation create genetic heterogeneity within a species. But their action is not directed. Evolution, on the other hand, is a directed process associated with the development of adaptations, with a 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 are often accumulated that are unfavorable for an individual, but useful for the population and the whole species (a stinging bee dies, but attacking the 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 action of selection.
Natural selection should be understood as 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 their differential reproduction. Success in reproduction of different individuals can serve as an objective genetic-evolutionary criterion of natural selection. The biological significance of an individual that has given offspring is determined by the contribution of its genotype to the gene pool of the population. Selection from generation to generation according to phenotypes leads to the selection of genotypes, since not traits, but gene complexes are transmitted to descendants. For evolution, not only genotypes are important, but also phenotypes and phenotypic variability.
During expression, a gene can influence many traits. Therefore, the scope of selection can include not only properties that increase the likelihood of leaving offspring, but also traits 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 rate. However, in nature there are cases when the ecological niche of a species may become wider over time. In this case, the selective advantage is obtained by individuals and populations with a wider reaction rate, while maintaining the same average value of the trait. This form of natural selection was first described by the American evolutionist George G. Simpson under the name centrifugal selection. As a result, a process occurs that is the reverse of stabilizing selection: mutations with a wider reaction rate gain an advantage.
Thus, populations of marsh frogs living in ponds with heterogeneous illumination, with alternating areas overgrown with duckweed, reed, cattail, 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 water bodies with uniform illumination and coloration (ponds completely overgrown with duckweed, or open ponds), the range of variability in frog coloration 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 rate.
b) sexual selection
sexual selection- natural selection within the same sex, aimed at developing traits that give mainly the opportunity to leave the largest number of descendants.
In males of many species, pronounced secondary sexual characteristics are found that at first glance seem maladaptive: the tail of a peacock, the bright feathers of birds of paradise and parrots, the scarlet combs of roosters, the enchanting colors of tropical fish, the songs of birds and frogs, etc. Many of these features make life difficult for their carriers, making them easily visible to predators. It would seem that these signs do not give 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 origin 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 members of the opposite sex. Charles Darwin called this phenomenon sexual selection. He first mentioned this form of selection in The Origin of Species and later 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 relationship of organic beings among themselves or with external conditions, but by the rivalry between individuals of the same sex, usually males, for the possession of individuals of the other sex."
Sexual selection is natural selection for success in reproduction. Traits that reduce the viability of their carriers can emerge and spread if the advantages they provide in breeding success are significantly greater than their disadvantages for survival. A male that lives a short time but is liked by females and therefore produces many offspring has a much higher cumulative fitness than one that lives long but leaves few offspring. In many animal species, the vast majority of males do not participate in reproduction at all. In each generation, fierce competition for females arises between males. This competition can be direct, and manifest itself in the form of a struggle for territories or tournament fights. It can also occur in an indirect form and be determined by the choice of females. In cases where females choose males, male competition is shown in displaying their flamboyant appearance or complex courtship behavior. Females choose those males that they like the most. As a rule, these are the brightest males. But why do females like bright males?
Rice. 7.
The fitness of the 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 selection is somewhat different. If bright males, for whatever reason, are attractive to females, then it is worth choosing a bright father for your future sons, because his sons will inherit the bright color 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 more and more enhanced. The process goes on increasing until it reaches the limit of viability. 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. In the end, the tail reaches such a length that its harm to the viability of the male is balanced by its attractiveness in the eyes of females.
In explaining these hypotheses, we tried to understand the logic of the action of female birds. It may seem that we expect too much from them, that such complex fitness calculations are hardly accessible to them. In fact, in choosing males, females are no more and no less logical than in all other behaviors. 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 the watering hole because it feels thirsty. When a worker bee stings a predator attacking a hive, she does not calculate how much by this self-sacrifice she increases the cumulative fitness of her sisters - she follows instinct. In the same way, females, choosing bright males, follow their instincts - they like bright tails. All those who instinctively prompted a different behavior, all of them left no offspring. Thus, we discussed 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, formed all that amazing variety of shapes, colors and instincts that we observe in the world of wildlife. .
c) Group selection
Group selection is often also called group selection, it is the differential reproduction of different local populations. Wright compares population systems of two types - a large continuous population and a number of small semi-isolated colonies - in relation to the theoretical efficiency of selection. It is assumed that the total size of both population systems is the same and the organisms interbreed freely.
In a large contiguous population, selection is relatively inefficient in terms of increasing the frequency of favorable but rare recessive mutations. In addition, any tendency to increase the frequency of any favorable allele in one part of a given large population is counteracted by crossing with neighboring subpopulations in which that allele is rare. In the same way, favorable new gene combinations that manage to form in some local fraction of a given population are broken apart and eliminated as a result of crossing with individuals of neighboring fractions.
All these difficulties are eliminated to a large extent in a population system that resembles in its structure a series of separate islands. Here, selection, or selection in conjunction with genetic drift, can quickly and effectively increase the frequency of some rare favorable allele in one or more small colonies. New favorable combinations of genes can also easily gain a foothold in one or more small colonies. Isolation protects the gene pools of these colonies from "flooding" as a result of migration from other colonies that do not have such favorable genes, and from crossing with them. Up to this point, only individual selection or, for some colonies, individual selection combined with genetic drift has been included in the model.
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 former genotypes has decreased. In a new environment, new favorable genes or combinations of genes that are fixed in some colonies have a high potential adaptive value for the population system as a whole. All conditions are now in place for group selection to take effect. The less fit colonies gradually shrink and die out, while the more fit colonies expand and replace them throughout the area occupied by a given population system. Such a subdivided population system acquires a new set of adaptive traits as a result of individual selection within certain colonies, followed by differential reproduction of different colonies. The combination of group and individual selection can lead to results that cannot be achieved through 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 be slow, probably much slower than individual selection. Updating populations takes more time than updating individuals.
The concept of group selection has been widely accepted in some circles, but has been rejected by other scientists. They argue that the various possible patterns of individual selection are capable of producing all the effects attributed to group selection. Wade conducted a series of breeding experiments with the flour beetle (Tribolium castaneum) in order to ascertain the effectiveness of group selection, and found that the beetles responded to this type of selection. In addition, when any trait is simultaneously affected by individual and group selection and, moreover, 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, which 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. It is not the parental genotypes that break up in the process of recombination that benefit from sexual reproduction, but the population of future generations, in which the margin of variability increases. This implies participation as one of the factors of the selective process at the population level.
G) Directional selection (moving)
Rice. one.
Directed selection (moving) was described by Ch. 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 unilateral change in the genetic composition of populations, which manifests itself in a shift in the average values of the selected traits in the direction of their strengthening or weakening. It occurs when 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, a part of the individuals of the species with some deviations from the average norm may gain an advantage in life and reproduction. 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. The 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. On a dark background, light-colored moths were pecked by robins and thrushes, while melanic forms survived and successfully reproduced, which are less noticeable against a dark background. Over the past 100 years, more than 80 species of butterflies have developed dark forms. This phenomenon is now known under the name of industrial (industrial) melanism. Driving selection leads to the emergence of a new species.
Rice. 3.
Insects, lizards and a number of other inhabitants of the grass are green or brown in color, the inhabitants of the desert are the color of sand. The fur of animals living in the forests, such as a leopard, is colored with small spots resembling sun glare, while in a tiger it imitates the color and shadow from the stems of reeds or reeds. This coloring is called patronizing.
In predators, it was fixed 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 gave and give a wide variety of forms that differ in color. In a number of cases, the coloring of the animal turned out to be close to the background of the environment, i.e. hid the animal, played the role of a patron. Those animals in which the protective coloration was weakly expressed were left without food or became victims themselves, and their relatives with the best protective coloration emerged victorious in the interspecific struggle for existence.
Directed selection underlies artificial selection, in which selective breeding of individuals with desirable phenotypic traits increases the frequency of those traits in a population. In a series of experiments, Falconer chose the heaviest individuals from a population of six-week-old mice and let them mate with each other. He did the same with the lightest mice. Such selective crossing on the basis of body weight led to the creation of two populations, in one of which the mass increased, and in the other it decreased.
After the selection was stopped, neither group returned to its original weight (approximately 22 grams). This shows that artificial selection for phenotypic traits has led to some genotypic selection and partial loss of some alleles by both populations.
e) Stabilizing selection
Rice. 4.
Stabilizing selection in relatively constant environmental conditions, natural selection is directed against individuals whose characters deviate from the average norm in one direction or another.
Stabilizing selection preserves the state of the population, which ensures its maximum fitness under constant conditions of existence. In each generation, individuals that deviate from the average optimal value in terms of adaptive characteristics are removed.
Many examples of the action of stabilizing selection in nature have been described. For example, at first glance it seems that individuals with maximum fecundity should make the greatest contribution to the gene pool of the next generation.
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. As a result, individuals with average fecundity turn out to be the most adapted.
Selection in favor of averages has been found for a variety of traits. In mammals, very low and very high birth weight newborns are more likely to die at birth or in the first weeks of life than middle weight newborns. Accounting for the size of the wings of birds that died after the storm showed that most of them had too small or too large wings. 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 unable to once and for all clear a population of unwanted evasive forms? The reason is not only and not so much in the constant emergence of more and more new mutations. The reason is that heterozygous genotypes are often the fittest. When crossing, they constantly give splitting and homozygous descendants with reduced fitness appear in their offspring. 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 allele (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 a higher resistance to malaria than homozygotes for the normal alley. Due to this, in populations inhabiting malarial areas, heterozygosity is created and stably maintained for this lethal alley in the homozygote.
Stabilizing selection is a mechanism for the accumulation of variability in natural populations. The outstanding scientist I. I. Shmalgauzen was the first to pay attention to this feature of stabilizing selection. He showed that even under stable conditions of existence, neither natural selection nor evolution ceases. Even remaining phenotypically unchanged, the population does not cease to evolve. Its genetic makeup is constantly changing. Stabilizing selection creates such genetic systems that provide 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 the tuatara and ginkgo.
Thanks to stabilizing selection, "living fossils" that live in relatively constant environmental conditions have survived to this day:
tuatara, 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 from the Cretaceous period;
The stabilizing form of selection acts as long as the conditions that led to the formation of a particular trait or property persist.
It is important to note here that the constancy of conditions does not mean their immutability. During the year, environmental conditions change regularly. Stabilizing selection adapts populations to these seasonal changes. Breeding cycles are timed to them, so that the young are born in that season of the year when food resources are maximum. All deviations from this optimal cycle, reproducible from year to year, are eliminated by stabilizing selection. Descendants born too early die from starvation, too late - they do not have time to prepare for winter. How do animals and plants know when winter is coming? On the onset of frost? No, it's not a very reliable pointer. Short-term temperature fluctuations can be very deceptive. If in some year it gets warmer earlier than usual, this does not mean at all 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 - an increase in 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 forms 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 (dismembering) selection favors the preservation of extreme types and the elimination of intermediate ones. As a result, it leads to the preservation and strengthening of polymorphism. Disruptive selection operates in a variety of environmental conditions found in the same area, and maintains several phenotypically different forms at the expense of individuals with an average norm. If environmental conditions have changed so much that the bulk of the species loses fitness, then individuals with extreme deviations from the average norm acquire an advantage. Such forms multiply rapidly and on the basis of one group several new ones are formed.
A model of disruptive selection can be the situation of the emergence of dwarf races of predatory fish in a water body with little food. Often, juveniles of the year do not have enough food in the form of fish fry. In this case, the advantage is gained by the fastest growing ones, which very quickly reach a size that allows them to eat their fellows. On the other hand, squints with the maximum delay in growth rate will be in an advantageous position, since their small size allows them to remain planktivorous for a long time. A similar situation through stabilizing selection can lead to the emergence of two races of predatory fish.
An interesting example is given by Darwin regarding insects - inhabitants of small oceanic islands. They fly well or are completely devoid of wings. Apparently, the insects were blown out to sea by sudden gusts of wind; only those that could either resist the wind or not fly at all survived. Selection in this direction has led to the fact that out of 550 species of beetles on the island of Madeira, 200 are flightless.
Another example: in forests where soils are brown, earth snail specimens often have brown and pink shells, in areas with coarse and yellow grass, yellow color prevails, etc.
Populations adapted to ecologically dissimilar habitats may occupy contiguous geographic areas; for example, in coastal areas of California, the plant Gilia achilleaefolia is represented by two races. One race - "sunny" - grows on open grassy southern slopes, while the "shady" race is found in shady oak forests and sequoia groves. These races differ in the size of the petals - a trait determined genetically.
The main result of this selection is the formation of population polymorphism, i.e. the presence of several groups that differ in some way or in the isolation of populations that differ 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. Natural selection plays a creative role in evolution. By excluding genotypes with low adaptive value from reproduction, while preserving favorable gene combinations of different merits, he transforms the picture of genotypic variability, which is formed initially under the influence of random factors, in a biologically expedient direction.
Bibliography
Vlasova Z.A. Biology. Student Handbook - Moscow, 1997
Green N. Biology - Moscow, 2003
Kamlyuk L.V. Biology in questions and answers - Minsk, 1994
Lemeza N.A. Biology manual - Minsk, 1998
Natural selection is the driving force behind evolution. Selection mechanism. Forms of selection in populations (I.I. Shmalgauzen).
Natural selection- the process by which the number of individuals with the maximum fitness (the most favorable traits) increases in the population, 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 of adaptations, but not the only cause of evolution. Non-adaptive causes include genetic drift, gene flow, and mutations.
The term "natural selection" was popularized by Charles Darwin, comparing this process with artificial selection, the modern form of which is selection. The idea of comparing artificial and natural selection is that in nature the selection of the most “successful”, “best” organisms also takes place, but in this case it is not a person who acts as an “appraiser” of the usefulness of properties, but the environment. In addition, the material for both natural and artificial selection are 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 referred to as a "self-evident" mechanism because it follows from simple facts such as:
Organisms produce more offspring than can survive;
In the population of these organisms, there is hereditary variability;
Organisms that have different genetic traits have different survival rates and ability to reproduce.
Such conditions create competition between organisms for survival and reproduction and are the minimum necessary conditions for evolution through natural selection. Thus, organisms with inherited traits that give them a competitive advantage are more likely to pass them on to their offspring than organisms with inherited traits that do not.
The central concept of the concept of natural selection is the fitness of organisms. Fitness is defined as the ability of an organism 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 offspring, but the number of offspring 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, accordingly, the fitness of this organism will be low.
If any allele increases the fitness of an organism more than other alleles of this gene, then with each generation the share of this allele in the population will increase. That is, selection occurs in favor of this allele. And vice versa, for less beneficial or harmful alleles, their share in populations will decrease, that is, selection will act against these alleles. It is important to note that the influence of certain alleles on the fitness of an organism is not constant - when environmental conditions change, harmful or neutral alleles can become beneficial, and beneficial ones can become harmful.
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:
Directed Selection- changes in the average value of the trait over time, for example, an increase in body size;
Disruptive selection- selection for the extreme values of the trait and against the average values, for example, large and small body sizes;
Stabilizing selection- selection against the extreme values of the 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 mating success by increasing the individual's attractiveness to potential partners. Traits that have evolved through sexual selection are particularly evident in the males of certain animal species. Such traits as large horns, bright coloration, 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 traits.
Selection can operate at various 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, such as group selection, can lead to cooperation.
Forms of natural selection
There are different classifications of forms of selection. A classification based on the nature of the influence of selection forms on the variability of a trait in a population is widely used.
driving selection- a form of natural selection that operates under 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. At the same time, other variations of the trait (its deviations in the opposite direction from the average value) are subjected to negative selection. As a result, in the population from generation to generation, there is a shift in the average value of the trait in a certain direction. At the same time, 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).
A classic example of motive selection is the evolution of color in the birch moth. The color of the wings of this butterfly imitates the color of the bark of trees covered with lichens, on which it spends daylight hours. Obviously, such a protective coloration was formed over many generations of previous evolution. However, with the beginning of the industrial revolution in England, this device began to lose its importance. Atmospheric pollution has led to the mass death of lichens and the darkening of tree trunks. Light butterflies on a dark background became easily visible to birds. Since the middle of the 19th century, mutant dark (melanistic) forms of butterflies began to appear in populations of the birch moth. Their frequency increased rapidly. By the end of the 19th century, some urban populations of the moth were almost entirely composed of dark forms, while light forms still predominated in rural populations. This phenomenon has been called industrial melanism. Scientists have found that in polluted areas, birds are more likely to eat light forms, and in clean areas - dark ones. The imposition of restrictions on atmospheric pollution in the 1950s caused natural selection to change direction again, and the frequency of dark forms in urban populations began to decline. They are almost as rare today as they were before the Industrial Revolution.
Driving selection is carried out when the environment changes or adapts to new conditions with the expansion of the range. It preserves hereditary changes in a certain direction, shifting the rate of reaction accordingly. For example, during the development of the soil as a habitat for various unrelated groups of animals, the limbs turned into burrowing ones.
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 severity of the trait. The concept of stabilizing selection was introduced into science and analyzed by I. I. Shmalgauzen.
Many examples of the action of stabilizing selection in nature have been described. For example, at first glance it seems that individuals with maximum fecundity should make the greatest contribution to the gene pool of the next generation. 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. As a result, individuals with average fecundity turn out to be the most adapted.
Selection in favor of averages has been found for a variety of traits. In mammals, very low and very high birth weight newborns are more likely to die at birth or in the first weeks of life than middle weight newborns. Accounting for the size of the wings of sparrows that died after a storm in the 50s near Leningrad showed that most of them had too small or too large wings. And in this case, the average individuals turned out to be the most adapted.
The most widely known example of such a polymorphism is sickle cell anemia. This severe blood disease occurs in people homozygous for a mutant hemoglobin allele ( Hb S) and leads to their death at an early age. In most human populations, the frequency of this allele 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 a higher resistance to malaria than homozygotes for the normal allele. Due to this, heterozygosity for this lethal allele in the homozygote is created and stably maintained in populations inhabiting malaria areas.
Stabilizing selection is a mechanism for the accumulation of variability in natural populations. The outstanding scientist I. I. Shmalgauzen was the first to pay attention to this feature of stabilizing selection. He showed that even under stable conditions of existence, neither natural selection nor evolution ceases. Even remaining phenotypically unchanged, the population does not cease to evolve. Its genetic makeup is constantly changing. Stabilizing selection creates such genetic systems that provide 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 concealing genetic variation owe their existence to stabilizing selection.
Thus, stabilizing selection, sweeping aside deviations from the norm, actively forms 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.
Disruptive (tearing) 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 the trait. As a result, several new forms may appear from one initial one. Darwin described the operation 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.
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.
The formation of seasonal races in some weeds is explained by the action of disruptive selection. It was shown that the timing of flowering and seed ripening in one of the species of such plants - meadow rattle - stretched almost all summer, and most of the plants bloom and bear fruit in the middle of summer. However, in hay meadows, those plants that have time to bloom and produce seeds before mowing, and those that produce seeds at the end of summer, after mowing, receive advantages. 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 setae, leaving only individuals with a small and large number of setae. As a result, from about the 30th generation, the two lines diverged very strongly, 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 success in reproduction. The survival of organisms is an important but not the only component of natural selection. Another important component is attractiveness to members 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 rivalry between individuals of the same sex, usually males, for the possession of individuals of the other sex." Traits that reduce the viability of their carriers can emerge and spread if the advantages they provide in breeding success are significantly greater than their disadvantages for survival.
Two hypotheses about the mechanisms of sexual selection are common.
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 the genes that let him do it. So, he should be chosen as a father for his children: he will pass on his good genes to them. By choosing bright males, females choose good genes for their offspring.
According to the “attractive sons” hypothesis, the logic of female selection is somewhat different. If bright males, for whatever reason, are attractive to females, then it is worth choosing a bright father for your future sons, because his sons will inherit the bright color 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 more and more enhanced. The process goes on increasing until it reaches the limit of viability.
In choosing males, females are no more and no less logical than in all 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 the watering hole because it feels thirsty. In the same way, females, choosing bright males, follow their instincts - they like bright tails. All those who instinctively prompted a different behavior, all of them left no offspring. Thus, we discussed 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, formed all that amazing variety of shapes, colors and instincts that we observe in the world of wildlife. .
positive and negative selection
There are two forms of natural selection: Positive and Clipping (negative) selection.
Positive selection increases the number of individuals in the population that have useful traits that increase the viability of the species as a whole.
Cut-off selection culls out from the population the vast majority of individuals that carry traits that sharply reduce viability under given environmental conditions. With the help of cut-off selection, strongly harmful alleles are removed from the population. Also, individuals with chromosomal rearrangements and a set of chromosomes that sharply disrupt the normal operation of the genetic apparatus can be subjected to cutting selection.
The role of natural selection in evolution
Charles Darwin considered natural selection to be the main driving force of evolution; in the modern synthetic theory of evolution, it is also the main regulator of the development and adaptation of populations, the mechanism for the emergence of species and supraspecific taxa, although the accumulation of information on genetics in the late 19th and early 20th centuries, in particular, the discovery of a discrete nature inheritance of phenotypic traits, led some researchers to deny the importance of natural selection, and as an alternative proposed concepts based on the assessment of the genotype mutation factor as extremely important. The authors of such theories postulated not a gradual, but a very fast (over several generations) spasmodic nature of evolution (the mutationism of Hugo de Vries, the saltationism of Richard Goldschmitt, and other less well-known concepts). The discovery of well-known correlations among the traits of related species (the law of homological series) by N. I. Vavilov prompted some researchers to formulate the next “anti-Darwinian” hypotheses about evolution, such as nomogenesis, batmogenesis, autogenesis, ontogenesis, and others. In the 1920s and 1940s in evolutionary biology, those who rejected Darwin's idea of evolution by natural selection (sometimes theories that emphasized natural selection were called "selectionist") revived interest in this theory due to the revision of classical Darwinism in the light of relatively young science of genetics. The synthetic theory of evolution developed as a result, often incorrectly called neo-Darwinism, relies, among other things, on the quantitative analysis of the frequency of alleles in populations, changing under the influence of natural selection. There are debates where people with a radical approach, as an argument against the synthetic theory of evolution and the role of natural selection, argue that "the discoveries of the last decades in various fields of scientific knowledge - from molecular biology with her theory of neutral mutationsMotoo Kimura and paleontology with her theory of punctuated equilibrium Stephen Jay Gould and Niles Eldredge (wherein view understood as a relatively static phase of the evolutionary process) until mathematics with her theorybifurcations and phase transitions- testify to the insufficiency of the classical synthetic theory of evolution for an adequate description of all aspects of biological evolution". The discussion about the role of various factors in evolution began more than 30 years ago and continues to this day, and it is sometimes said that "evolutionary biology (meaning the theory of evolution, of course) has come to the need for its next, third synthesis."
