What is the difference between epics and folk tales briefly. Difference between epic and fairy tale

Natural selection tests organisms for compliance with living conditions and is carried out in different 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 driving selection:

• transitive (transitive);
• directed.

Transitional selection is the development of an initially small form that gains an advantage under changed 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 because they became less noticeable 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 directed selection, the formation and reproduction of forms differ in some characteristic from the original form. Such selection occurs under conditions of unidirectional environmental changes.

Rice. 1. Driving selection.

Unlike transitional selection, with 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, it is the preservation of average norms.

The condition for stabilizing selection is constant environmental parameters, and in this it is the opposite of driving selection.

Rice. 2. Stabilizing selection.

Each species has an optimal average rate of fertility and weight of the cubs born.

If birds lay fewer eggs than normal, 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 action 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.

Disruptive selection

A disruptive, or disruptive, form of selection splits a previously single population into two or more new ones.

Thus, female African swallowtail butterflies have evolved into three forms, imitating three different inedible butterfly species.

Rice. 3. Three forms of female African swallowtails.

Having such similarities is more beneficial to a population than imitating just one species.

Disruptive selection drives 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”

What have we learned?

While studying the three forms of natural selection in biology, we gave them a brief description. Forms of selection differ in: conditions, focus, results. Stabilizing selection preserves old adaptations, while disruptive and driving selection preserves new ones. At the same time, the purpose of all forms is to adapt organisms to the conditions of existence.

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There are three main forms of natural selection - stabilizing, driving (or directed), and disruptive (fragmenting). This division is quite arbitrary, and it is often not always possible to accurately determine which form a given example of natural selection belongs to.

Stabilizing selection is aimed at maintaining the average, previously established value of a trait or property in populations. It operates under relatively constant (fluctuating within certain limits) environmental conditions. With stabilizing selection, the advantage in reproduction is given to the most typical individuals in the population, while individuals that noticeably deviate from the established norm are eliminated by natural selection. This form of selection is the most common, but it is difficult to notice, since in this case there is no change in the morphological appearance of organisms in the population.

Moving or directed is called selection that promotes a shift in the average value of a trait or property in a population. This form of selection occurs when the conditions of existence change and leads to the establishment of a new norm to replace the previously existing one.

Disruptive or fragmenting selection (disrupt - tear, crush, English) call selection that occurs simultaneously in favor of several evading options against individuals with an intermediate value of the trait. This form of selection occurs in cases where no one group of genotypes receives a decisive advantage in the struggle for existence due to the diversity of conditions simultaneously occurring in one territory. Disruptive selection contributes to the emergence and maintenance of population polymorphism, and in some cases can cause speciation.

Evolutionary process

Evolutionary theory states that each species purposefully develops and changes in order to best adapt to its environment. In the process of evolution, many species of insects and fish acquired protective colors, the hedgehog became invulnerable thanks to its needles, and man became the owner of a very complex nervous system. We can say that evolution is the process of optimization of all living organisms. Let us consider by what means nature solves this optimization problem.

The main mechanism of evolution is natural selection. Its essence is that more adapted individuals have more opportunities for survival and reproduction and, therefore, produce more offspring than poorly adapted individuals. Moreover, thanks to the transfer of genetic information ( genetic inheritance) descendants inherit their basic qualities from their parents.

Thus, the descendants of strong individuals will also be relatively well adapted, and their share in the total mass of individuals will increase. After a change of several tens or hundreds of generations, the average fitness of individuals of a given species increases noticeably.

To make the operating principles of genetic algorithms clear, we will also explain how the mechanisms of genetic inheritance in nature work. Each cell of any animal contains all the genetic information of that individual. This information is written in the form of a set of very long DNA (Deoxyribonucleic Acid) molecules. Each DNA molecule is a chain consisting of four types of nucleotide molecules, designated A, T, C and G. Actually, the information is carried by the order of nucleotides in DNA. Thus, an individual's genetic code is simply a very long string of characters using only 4 letters. In an animal cell, each DNA molecule is surrounded by a membrane - this formation is called a chromosome.

Each innate quality of an individual (eye color, hereditary diseases, hair type, etc.) is encoded by a certain part of the chromosome, which is called the gene for this property. For example, the eye color gene contains information that codes for a specific eye color. The different meanings of a gene are called its alleles.

When animals reproduce, two parental germ cells merge and their DNA interacts to form the DNA of the offspring. The main method of interaction is crossover. In a crossover, the DNA of ancestors is divided into two parts, and then their halves are exchanged.

During inheritance, mutations are possible due to radioactivity or other influences, as a result of which some genes in the germ cells of one of the parents may change. The changed genes are passed on to the offspring and give it new properties. If these new properties are useful, they are likely to be retained in a given species - and there will be a stepwise increase in the fitness of the species.

At the beginning of the 20th century, at the dawn of genetics, many researchers denied the role of natural selection as a creative factor. The mutation process was considered the main evolutionary force as the sole cause of the emergence of new characteristics and properties of the organism. Since mutation is an extremely rare phenomenon (it has been established that on average one gene in a million mutates), natural selection was assigned the role of a simple “controller”, coming into action only after the appearance of a new genetic deviation.

However, further research has shown that in natural populations of any species there is a huge reserve of genetic variability for a wide variety of traits. Thus, natural selection always has a wealth of material to work with. In laboratory experiments, it was possible to establish that with the help of selection it is possible to change almost any properties of an organism, even such as the dominance or recessivity of certain traits.

Indeed, the only source of “evolutionary material” (hereditary variability) is the mutation process. But this does not deny the creative role of natural selection: it can be compared to a sculptor who creates beautiful objects of art only by cutting off “unnecessary” pieces from a block of marble.

Question 1. What forms of natural selection exist?
There are several forms of natural selection, which depend on environmental conditions.
Stabilizing selection leads to the preservation of mutations that reduce the variability of the average value of the trait, that is, it preserves the average value of the trait. Operates under constant environmental conditions. Selection pressure is directed against individuals that have deviations from the average norm, both in the direction of increasing and decreasing the expression of the trait. Organisms with average values ​​of the trait receive an advantage. The stabilizing form of selection protects the genotype from the destructive effects of the mutation process. The stabilizing form of natural selection is characteristic of species that live for a long time in constant conditions, for example, cave bats and deep-sea fish. For example: in flowering plants, flowers change little, but the vegetative parts of the plant are more variable. The flower proportions in this example were influenced by stabilizing selection. It is also characteristic of the modern stage of human evolution.
Another form of selection is driving selection, in which there is a change in the reaction norm in a certain direction; such selection changes the average value of the trait. Operates under smoothly changing environmental conditions. Selection pressure is directed against individuals that have deviations from the average norm either in the direction of strengthening or weakening the expression of the trait. As a result, a shift in the average norm occurs - a new average norm arises instead of the old one, which no longer meets the updated conditions of existence. An example of such selection is the gradual replacement of light-colored individuals of the birch moth butterfly with dark-colored ones in industrial areas. For example, resistance to a poison that causes bleeding quickly spread among rats, as individuals that were resistant to this poison initially survived and subsequently gave rise to a new population. Another example of driving selection is the loss of a trait in a mole - reduction of eyes. As a result of the action of the driving form of natural selection, new species can arise.
Another form - disruptive selection- provides an advantage for the survival of individuals with extreme manifestations of this trait. Such selection is directed against middle and intermediate forms. At the same time, the parts of the population that deviate most from the average values ​​of the trait are preserved; As a rule, this occurs in connection with very sudden changes in the environment. For example, due to the massive use of pesticides, groups of insects resistant to these chemicals have survived. Each such group has become an independent selective center, within which stabilizing selection maintains resistance to pesticides. Disruptive selection can be illustrated by the example of the emergence of two races of rattles - early flowering and late flowering. Their occurrence is the result of mowing carried out in mid-summer, as a result of which a single population is divided into two non-overlapping populations.

Question 2. Under what environmental conditions does each form of natural selection operate?
The driving form of natural selection operates when conditions of existence change. Driving selection contributes to a shift in the average value of a trait or property and leads to the emergence of a new average norm instead of the old one, which no longer corresponds to the newly emerged environmental conditions. Thus, the leading role in the spread of new characteristics within a given species when environmental conditions change belongs to the driving form of natural selection.
Stabilizing selection operates under constant environmental conditions. Organisms with average expression of the trait receive an advantage. The stabilizing form of selection protects the genotype from the destructive effects of the mutation process.
Discontinuous selection acts when conditions of existence change. Selection pressure is directed against organisms with average expression of the trait. As a result, two new average norms arise instead of the old one, which no longer meets the conditions of existence. There is a divergence between the old and new average standards. Such divergence (divergence) can lead to the formation of new species.

Question 3. What is the reason for the emergence of resistance to pesticides in microorganisms - agricultural pests and other organisms?
The development of resistance (tolerance) to pesticides in a number of organisms serves as an example of the action of driving selection, when a new average norm of a trait arises instead of the old one. Thus, after exposure to poisons, individuals that accidentally turn out to be resistant to this toxic substance survive. They have a reproductive advantage, due to which the resistance trait spreads and becomes predominant among individuals of a given species.

Question 4. What is sexual selection?
Sexual selection is based on competition between males for a sexual partner - a female. As a result of sexual selection, the most active, healthy and strong males leave offspring. The rest are excluded from reproduction, and their genotypes disappear from the gene pool of the species. This form of selection should be considered as a special case of intraspecific competition.

NATURAL SELECTION is the result of the struggle for existence; it is based on the preferential survival and leaving of offspring by the most adapted individuals of each species and the death of less adapted organisms

IN Under conditions of constant environmental change, natural selection eliminates unadapted forms and preserves hereditary deviations that coincide with the direction of the changed conditions of existence. There is either a change in the reaction norm or its expansion (norm of reaction called the ability of the body to respond with adaptive changes to the action of environmental factors; reaction norm is the limits of modification variability controlled by the genotype of a given organism). This form of selection was discovered by Charles Darwin and was called driving .

An example is the displacement of the original light-colored form of the birch moth butterfly by a dark-colored form. In the southeast of England, in the past, along with the light-colored form of the butterfly, dark-colored ones were occasionally found. In rural areas, light coloring on birch bark turns out to be protective; they are invisible, while dark-colored ones, on the contrary, stand out against a light background and become easy prey for birds. In industrial zones, due to environmental pollution with industrial soot, dark-colored forms gain an advantage and quickly replace light-colored ones. Thus, out of 700 species of butterflies in this country, over the past 120 years, 70 species of moths have changed their light color to dark. The same picture is observed in other industrial zones of Europe. Similar examples include the emergence of insecticide-resistant insects, antibiotic-resistant forms of microorganisms, the spread of poison-resistant rats, etc.

Domestic scientist I. I. Shmalgauzen discovered stabilizing form selection, which operates under constant conditions of existence. This form of selection is aimed at maintaining the existing norm. In this case, the constancy of the reaction norm is maintained as long as the environment remains stable, while individuals deviating from the average norm disappear from the population. For example, during snowfall and strong winds, short-winged and long-winged sparrows died, but individuals with average wing sizes survived. Or another example: the stable constancy of the parts of a flower in comparison with the vegetative organs of the plant, since the proportions of the flower are adapted to the size of pollinating insects (a bumblebee cannot penetrate a too narrow corolla of a flower, the proboscis of a butterfly cannot touch the too short stamens of flowers with a long corolla). Over millions of years, stabilizing selection protects species from significant changes, but only as long as living conditions do not change significantly.

Also distinguished tearing, ordisruptive , selection operating in a diverse environment: not just one trait is selected, but several different ones, each of which favors survival within narrow limits of the population’s range. Because of this, the population is divided into several groups. For example, some wolves in the Kitskill Mountains of the USA look like a light greyhound and hunt deer, while other wolves in the same area, heavier, with short legs, usually attack herds of sheep. Disruptive selection operates under conditions of a sharp change in the environment: forms with multidirectional changes survive on the periphery of the population; they give rise to a new group in which stabilizing selection comes into effect. None of the forms of selection occurs in nature in its pure form, since environmental factors change and act together as a whole. However, at certain historical periods of time, one of the forms of selection may become leading.

All forms of natural selection constitute a single mechanism, which, acting on a statistical basis as a cybernetic regulator, maintains the balance of populations with the surrounding environmental conditions. The creative role of natural selection is not only to eliminate the unadapted, but also to direct the emerging adaptations (the result of mutations and recombinations), “selecting” in a long series of generations only those of them that are most suitable in the given conditions of existence , which leads to the emergence of more and more new life forms.

Forms of natural selection (T.A. Kozlova, V.S. Kuchmenko. Biology in tables. M., 2000)

Bylina- a special epic song genre that developed in Russian folklore at the turn of the 10th-11th centuries. As in a folk tale, the epic contains ethnic elements of everyday life and myth-making, but its distinctive feature is not the entertaining or moralizing plot on which the fairy-tale narrative is based, but the description of historically significant events that embodied the folk idea of ​​heroic strength and valor.

IN fairy tale the characters lost their direct connection with real heroes and acquired an abstract meaning, expressed in the confrontation between good and evil. The plot of fairy tales is fiction, created as a transformation of reality into a wonderful image associated with the mystical ideas of a certain ethnic group about the world around them.

The epic specifies heroes who played an important role in historical events or became famous among their fellow tribesmen for their special merits and military merits.

The style of narration in fairy tales and epics is also significantly different. The content of the tale is conveyed in the usual narrative manner, close to colloquial speech. Epic poems are performed with a solemn recitative to string accompaniment, thanks to which the narrator is able to preserve the rhythm of syllabic-tonic verse inherent in the epic text.

The means of artistic expression characteristic of the epic also differ from the traditional tropes used in the fairy tale. Hyperbole, repetition of stable phrases, exaggeration of synonymous words, abundance of epithets, antithesis - all these formative techniques are used in epics to emphasize solemnity and preserve the storyline. For example, situations of the same type in the heroic epics of the Kyiv cycle are repeated three times; "valiant strength" "glorious" hero Ilya Muromets resists deceit “the kingdom of the filthy”; in Novgorod epics, Vasily Buslaevich has incredible strength, and Sadko is able to sink to the bottom of the sea and come out unscathed.

Fairy tales were created as instructive and entertaining stories at the same time. They were told among family members and could have an ending with the subtext: “The fairy tale is a lie, but there is a hint in it - a lesson for good fellows.”

Epics glorified heroic heroes. They were performed in front of large crowds of people, in squares and near city walls.

An epic about the beautiful Vasilisa Mikulishna

Conclusions website

1. The epic is a folk epic song, and the fairy tale belongs to the small narrative epic genres.
2. The plot of fairy tales is fiction; epics always have a historical basis and a real prototype of the hero.
3. The tale uses a conversational style of narration; the epic is performed in recitative.
4. A fairy tale is a prosaic work of oral folk art; an epic has a poetic meter.
5. The main technique of the epic is hyperbole, repetition, stable formulas and speech patterns.