The driving forces of evolution are 1 hereditary. Theory H

Darwin considered artificial selection to be the main mechanism for the emergence and diversity of cultivated plants and domestic animals. In the process of studying artificial selection, the scientist came to the conclusion that there is a similar phenomenon in nature. What are the driving forces behind the evolution of species? Darwin saw the answer to this question in two parts.

First, he pointed to the presence of an indefinite (individual) variability of organisms in the natural conditions of their habitat.

Darwin identified the presence of individual variability in nature by a number of facts. For example, bees distinguish bees from their own and neighboring hives. Plants grown from the acorns of one oak tree differ in many small external features, etc.

Secondly, Darwin came to the conclusion that the fitness of wild species, as well as cultivated forms, is the result of selection. But this selection is not made by man, but by the environment. Individual variability in nature is the material for selection. Just as animal breeds and plant varieties are expediently adapted to human needs, species are adapted to life in certain environmental conditions.

As already mentioned, organisms tend to reproduce exponentially. However, not all born individuals survive to adulthood. The reasons for this are varied. The death of organisms can be observed from a lack of food resources, adverse environmental factors, diseases, enemies, etc. Based on this, Darwin came to the conclusion that there is a constant struggle for existence between organisms in nature.

The struggle for existence is a set of diverse and complex interactions of organisms with each other and with the environmental conditions surrounding them.

Darwin singled out three forms of the struggle for existence: intraspecific, interspecific and struggle with adverse environmental conditions.

Intraspecific struggle- Relationships between individuals of the same species. Darwin considered intraspecific struggle the most intense. Undoubtedly, organisms belonging to the same species have similar requirements for food, breeding conditions, shelters, etc. Such a struggle is most acute with a significant increase in the number of individuals of a species and deterioration of living conditions. This leads to the death of some individuals or to their elimination from reproduction. For example, intraspecific struggle manifests itself in the form of competition for nesting sites in birds or for a sexual partner in animals of the same species. Germinated seeds of plants, such as birches, often die because the soil is already densely overgrown with seedlings of the same species. At the same time, young seedlings experience a lack of illumination, nutrition, etc. In the flour beetle, an excess of the permissible number of individuals per unit of food substrate leads to disruption of sexual cycles and cannibalism.

Fight against adverse environmental conditions- survival of the fittest individuals, populations and species in the changed conditions of inanimate nature. This form of struggle is more acute when any of the abiotic environmental factors is in deficit or excess. Such situations develop during severe droughts, floods, frosts, fires, volcanic eruptions, etc. For example, in deserts, the struggle for existence among plants is aimed at economical use of moisture. As a result, some plants developed adaptations in the form of fleshy leaves or stems to store water. Others have spiny leaves to reduce evaporation, deeply penetrating roots to use groundwater, etc. Another example of combating adverse environmental conditions is the migration of migratory birds to warm countries when cold weather sets in.

The natural result of all forms of struggle is the reduction from generation to generation of the number of the least adapted individuals. This is due both to their immediate death and to a smaller number of descendants produced. On the other hand, more adapted individuals increase their numbers. At the same time, in each next generation, they take away from the less adapted more and more resources necessary for life. This gradually leads to the complete displacement of the latter from the biotope. This process, constantly occurring in nature, Darwin called natural selection.

According to Darwin, natural selection is the process of survival and reproduction of the most adapted to the living conditions of individuals and the death of the less adapted.

Selection occurs continuously in a number of generations and retains mainly those forms that are most adapted to given environmental conditions. Natural selection and the struggle for existence are inextricably linked and are the driving forces behind the evolution of species. These driving forces contribute to the improvement of organisms, the result of which is their adaptability to the environment and the diversity of species in nature.

Main results of evolution

According to Darwin, the results of evolution are the adaptability of organisms to their environment and the diversity of species in nature. Fitness- a set of adaptations (features of the external and internal structure and behavior of organisms) that provide this species with an advantage in survival and leaving offspring under certain environmental conditions.

Variety of species- the second important result of evolution. First, indeterminate variability and the natural selection flowing on its basis lead to a variety of relationships between organisms. Secondly, our planet is characterized by a multitude of biotopes differing in strength of environmental factors. Based on the above, the diversity of species in nature is formed. The advantage in this case is obtained by the most highly organized and adapted to environmental conditions forms. Darwin emphasized that the simultaneous existence of species of living organisms with different levels of organization is explained by the fact that their evolution went simultaneously in several directions.

The struggle for existence is a set of diverse and complex interactions of organisms with each other and with the environmental conditions surrounding them. The result of the struggle for existence is natural selection. As a result of the action of natural selection, the main results of evolution are achieved: the fitness of organisms and the diversity of species in nature.

Question 1

The main driving forces (factors) of the evolutionary process, according to Ch. Darwin, are the hereditary variability of individuals, the struggle for existence and natural selection. Evolutionary biology research has now confirmed this claim and has identified a number of other factors that play an important role in the evolutionary process.

The idea of ​​the existence of natural selection was arrived at independently and almost simultaneously by several English naturalists: V.

Wells (1813), P. Matthew (1831), E. Blythe (1835, 1837), A. Wallace (1858), C. Darwin (1858, 1859); but only Darwin was able to reveal the significance of this phenomenon as the main factor in evolution and created the theory of natural selection. Unlike artificial selection carried out by man, natural selection is determined by the influence on organisms of the environment.

According to Darwin, natural selection is the “survival of the fittest” organisms, as a result of which evolution takes place on the basis of indefinite hereditary variability in a number of generations.

Natural selection is the main driving force of evolution, and every kind of living organism that has ever lived on Earth has been shaped in one way or another by natural selection.

Evolutionary theory states that each biological species purposefully develops and changes in order to best adapt to the environment.

In the process of evolution, many species of insects and fish acquired a protective coloration, the hedgehog became invulnerable thanks to needles, and man became the owner of a complex nervous system.

We can say that evolution is the process of optimizing all living organisms and the main mechanism of evolution is natural selection. Its essence lies in the fact that more adapted individuals have more opportunities for survival and reproduction and, therefore, bring more offspring than ill-adapted individuals.

At the same time, due to the transfer of genetic information ( genetic inheritance) descendants inherit from their parents their main qualities. Thus, the descendants of strong individuals will also be relatively well adapted, and their proportion 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 markedly.

Natural selection happens automatically. All living organisms from generation to generation are subjected to a severe test of all the smallest details of their structure, the functioning of all their systems in a variety of conditions.

Only those who pass this test are selected and give rise to the next generation. Darwin wrote: “Natural selection daily and hourly investigates the smallest variations all over the world, discarding the bad ones, preserving and adding up the good ones, working inaudibly and imperceptibly, wherever and whenever the opportunity presents itself, on the improvement of every organic being in relation to conditions. his life, organic and inorganic.

We do not notice anything in these slow changes in development until the hand of time marks the past centuries.

Thus, natural selection is the only factor that ensures the adaptation of all living organisms to constantly changing environmental conditions and regulates the harmonious interactions between genes within each organism.

Question 2

Any cell, like any living system, despite the continuous processes of decay and synthesis, the intake and release of various chemical compounds, has the ability to maintain its composition and all its properties at a relatively constant level.

This constancy is preserved only in living cells, and when they die, it is broken very quickly.

The high stability of living systems cannot be explained by the properties of the materials from which they are built, since proteins, fats and carbohydrates have little stability.

The stability of cells (as well as other living systems) is actively maintained as a result of complex processes of self-regulation or auto-regulation.

The basis for the regulation of cell activity is information processes, i.e., processes in which communication between the individual links of the system is carried out using signals. The signal is a change that occurs in some part of the system.

In response to the signal, a process is started, as a result of which the change that has occurred is eliminated. When the normal state of the system is restored, this serves as a new signal to shut down the process.

How does the cell signaling system work, how does it provide autoregulation processes in it? The reception of signals inside the cell is carried out by its enzymes. Enzymes, like most proteins, have an unstable structure. Under the influence of a number of factors, including many chemical agents, the structure of the enzyme is disturbed and its catalytic activity is lost.

This change, as a rule, is reversible, i.e., after the removal of the active factor, the structure of the enzyme returns to normal and its catalytic function is restored.

As a result of this interaction, the structure of the enzyme is deformed and its catalytic activity is lost.

Question 3

Artificial mutagenesis is an important new source of starting material in plant breeding. Artificially induced mutations are the starting material for obtaining new varieties of plants, microorganisms and, less often, animals.

Mutations lead to the emergence of new hereditary traits, from which breeders select those properties that are useful to humans.

In nature, mutations are relatively rare, so breeders widely use artificial mutations. Influences that increase the frequency of mutations are called mutagenic. The frequency of mutations is increased by ultraviolet and X-rays, as well as chemicals that act on DNA or the machinery that ensures division.

The importance of experimental mutagenesis for plant breeding was not immediately understood.

L. Stadler, who in 1928 was the first to obtain artificial mutations in cultivated plants under the action of X-rays, believed that they would have no significance for practical selection.

He concluded that the likelihood of experimentally obtaining changes by mutagenesis that would be superior to forms found in nature is negligible. Many other scientists were also negative about mutagenesis.

A. A. Sapegin and L. N. Delaunay were the first researchers to show the importance of artificial mutations for plant breeding.

In their experiments, conducted in 1928-1932. in Odessa and Kharkov, a series of economically useful mutant forms in wheat was obtained. In 1934, A. A. Sapegin published the article "X-Ray Mutations as a Source of New Forms of Agricultural Plants", which indicated new ways of creating starting material in plant breeding, based on the use of ionizing radiation.

But even after that, the use of experimental mutagenesis in plant breeding continued to be viewed negatively for a long time.

Only at the end of the 1950s was increased interest shown in the problem of using experimental mutagenesis in breeding. It was associated, firstly, with major advances in nuclear physics and chemistry, which made it possible to use various sources of ionizing radiation (nuclear reactors, particle accelerators, radioactive isotopes, etc.) and highly reactive chemicals to obtain mutations, and, secondly, with the production of practically valuable hereditary changes by these methods on a wide variety of cultures.

Works on experimental mutagenesis in plant breeding have developed especially widely in recent years.

They are carried out very intensively in Sweden, Russia, Japan, the USA, India, Czechoslovakia, France and some other countries.

Of great value are mutations that are resistant to fungal (rust, smut, powdery mildew, sclerotinia) and other diseases. The creation of immune varieties is one of the main tasks of breeding, and methods of radiation and chemical mutagenesis should play an important role in its successful solution.

With the help of ionizing radiation and chemical mutagens, it is possible to eliminate certain shortcomings in crop varieties and create forms with economically useful features: non-lodging, frost-resistant, cold-resistant, early maturing, with a high content of protein and gluten.

There are two main ways of selective application of artificial mutations: 1) direct use of mutations obtained from the best zoned varieties; 2) the use of mutations in the process of hybridization.

In the first case, the task is to improve the existing varieties according to some economic and biological characteristics, to correct their individual shortcomings.

This method is considered promising in breeding for disease resistance. It is assumed that resistance mutations can be quickly obtained in any valuable variety and its other economic and biological characteristics can be preserved intact.

The method of direct use of mutations is designed to quickly create the source material with the desired features and properties.

However, the direct and rapid use of mutations, given the high requirements that are placed on modern breeding varieties, does not always give positive results.

To date, more than 300 mutant varieties of agricultural plants have been created in the world.

Some of them have significant advantages over the original varieties. Valuable mutant forms of wheat, corn, soybeans, and other field and vegetable crops have been obtained in recent years at research institutions in our country.

Development of evolutionary ideas. Evidence for evolution.

Evolution is the process of historical development of the organic world.

The essence of this process consists in the continuous adaptation of living things to diverse and constantly changing environmental conditions, in the increasing complexity of the organization of living beings over time. In the course of evolution, one species is transformed into another.

Major in evolutionary theory- the idea of ​​historical development from relatively simple forms of life to more highly organized ones.

The foundations of the scientific materialistic theory of evolution were laid by the great English naturalist Charles Darwin. Before Darwin, biology was largely dominated by the misconception that species are historically immutable, that there are as many of them as God created them. Even before Darwin, however, the most astute biologists understood the inconsistency of religious views on nature, and some of them speculatively came to evolutionary ideas.

The largest naturalist, the predecessor of Ch.

Darwin was the famous French scientist Jean Baptiste Lamarck. In his famous book "Philosophy of Zoology" he proved the variability of species. Lamarck emphasized that the constancy of species is only an apparent phenomenon, it is associated with the short duration of observations of species. The higher forms of life, according to Lamarck, evolved from the lower ones in the process of evolution.

The evolutionary doctrine of Lamarck was not sufficiently demonstrative and did not receive wide recognition among his contemporaries. Only after the outstanding works of Charles Darwin did the evolutionary idea become generally accepted.

Modern science has very many facts proving the existence of the evolutionary process.

These are data from biochemistry, genetics, embryology, anatomy, taxonomy, biography, paleontology and many other disciplines.

Embryological evidence- the similarity of the initial stages of the embryonic development of animals. Studying the embryonic period of development in various groups of vertebrates, K. M. Baer discovered the similarity of these processes in various groups of organisms, especially in the early stages of development. Later, based on these findings, E.

Haeckel suggests that this similarity has an evolutionary significance and on its basis the "biogenetic law" is formulated - ontogenesis is a brief reflection of phylogeny. Each individual in its individual development (ontogenesis) passes through the embryonic stages of ancestral forms. The study of only the early stages of development of the embryo of any vertebrate does not allow us to determine with accuracy which group they belong to. Differences are formed at later stages of development.

The closer the groups to which the studied organisms belong, the longer the common features will remain in embryogenesis.?

Morphological- many forms combine the features of several large systematic units. When studying various groups of organisms, it becomes obvious that they are fundamentally similar in a number of features.

For example, the structure of the limb in all four-legged animals is based on a five-fingered limb. This basic structure in different species has been transformed in connection with different conditions of existence: this is the limb of a equid-hoofed animal, which, when walking, rests on just one finger, and the flippers of a marine mammal, and the burrowing limb of a mole, and the wing of a bat.

Organs built according to a single plan and developing from single primordia are called homologous.

Homologous organs cannot in themselves serve as evidence of evolution, but their presence indicates the origin of similar groups of organisms from a common ancestor. A striking example of evolution is the presence of rudimentary organs and atavisms. Rudimentary organs are organs that have lost their original function, but remain in the body. Examples of rudiments are: the human appendix, which performs a digestive function in ruminant mammals; pelvic bones of snakes and whales, which perform no function in them; coccygeal vertebrae in humans, which are considered vestiges of the tail that our distant ancestors had.

Atavisms are the manifestation in organisms of structures and organs characteristic of ancestral forms. Classical examples of atavisms are multi-nipples and tailing in humans.

paleontological- the fossil remains of many animals can be compared with each other and find similarities. Based on the study of fossil remains of organisms and comparison with living forms. They have their advantages and disadvantages. The advantages include the opportunity to see firsthand how a given group of organisms changed in different periods.

The disadvantages include that the paleontological data are very incomplete due to a variety of reasons. These include such as the rapid reproduction of dead organisms by animals that feed on carrion; soft-bodied organisms are extremely poorly preserved; and, finally, that only a small part of the fossil remains are found.

In view of this, there are many gaps in paleontological data, which are the main object of criticism of opponents of the theory of evolution.

Biogeographic- distribution of animals and plants on the surface of our planet. Comparison of the animal and plant world of different continents, showing that the differences between their flora and fauna are greater, the older and stronger their isolation from each other.

As you know, the state of the earth's crust is constantly undergoing changes, and the current position of the continents was formed in recent (geological) time.

Prior to this, all the continents were brought together and united into one mainland.

The separation of the continents proceeded gradually, some separated earlier, others later. Each new highly organized species sought to settle on the maximum possible territory. The absence of more highly organized forms in any territory indicates that this territory separated earlier than some species formed or had time to settle on it. By itself, this does not explain the mechanism of the origin of species, but it indicates that different species formed in different areas and at different times.

The modern classification of organisms was proposed by Linnaeus long before the theory of evolution proposed by Darwin.

Of course, it can be assumed that the entire variety of plant and animal species was created simultaneously, and each of them was created independently of each other.

However, taxonomy, based on the morphological similarities of organisms, combines them into groups. The existence of such groups (genera, families, orders) suggests that each taxonomic group is the result of adaptation of various species to specific environmental conditions.

The evolutionary doctrine of Ch. Darwin.

Its main provisions and significance.
Type, type criteria. Populations.

The presuppositions of evolution by themselves cannot lead to evolution. For the evolutionary process leading to the appearance of adaptations and the formation of new species and other taxa, the driving forces of evolution are necessary.

At present, the doctrine created by Darwin about the driving forces of evolution (the struggle for existence and natural selection) is supplemented with new facts thanks to the achievements of modern genetics and ecology.

The struggle for existence and its forms

According to the ideas of modern ecology, individuals of the same species are united in populations, and populations of different species exist in certain ecosystems.

The relationships of individuals within populations and with individuals of populations of other species, as well as with environmental conditions in ecosystems, are considered as struggle for existence.

Darwin believed that the struggle for existence is the result of exponential reproduction of species and the appearance of an excess number of individuals with limited food resources.

That is, the word "struggle" essentially meant competition for food in conditions of overcrowding.

According to modern ideas, any relationship can be elements of the struggle for existence - both competitive and mutually beneficial (caring for offspring, mutual assistance). Overpopulation is not a necessary condition for the struggle for existence. Consequently, at present the struggle for existence is understood in a broader sense than according to Darwin, and is not reduced to a competitive struggle in the literal sense of the word.

There are two main forms of struggle for existence: direct struggle and indirect struggle.

Straight wrestling- any relationship in which between individuals of the same or different species in their populations there is physical contact expressed to one degree or another.

The consequences of this struggle can be very different for the interacting parties. Direct struggle can be both intraspecific and interspecific.

Examples of direct intraspecific struggle can be: rivalry between families of rooks for nesting places, between wolves for prey, between males for territory.

This is also the feeding of young with milk in mammals, mutual assistance in the construction of nests in birds, protection from enemies, etc.

Indirect struggle- any relationship between individuals of different populations that use common food resources, territory, environmental conditions without direct contact with each other.

Indirect struggle can be intraspecific, interspecific and with abiotic environmental factors.

Examples of indirect struggle can be the relationship between individual birches in a thickened birch grove (intraspecific struggle), between polar bears and arctic foxes, lions and hyenas for prey, light-loving and shade-loving plants (interspecific struggle).

Also, an indirect struggle is the different resistance of plants to the provision of soil with moisture and minerals, animals - to the temperature regime (the fight against abiotic environmental factors).

The result of the struggle for existence is the success or failure of these individuals in surviving and leaving offspring, i.e. natural selection, as well as changing territories, changing environmental needs, etc.

Natural selection and its forms

According to Darwin, natural selection is expressed in the preferential survival and leaving offspring of the most adapted individuals and the death of the less adapted.

Modern genetics has expanded this view. The diversity of genotypes in populations, resulting from the action of the prerequisites of evolution, leads to the appearance of phenotypic differences between individuals. As a result of the struggle for existence in each population, individuals with useful phenotypes and genotypes survive and leave offspring.

Therefore, the action of selection is to differentiate (selectively preserve) phenotypes and reproduce adaptive genotypes. Since selection occurs according to phenotypes, this determines the significance of phenotypic (modification) variability in evolution.

The variety of modifications affects the degree of diversity of phenotypes analyzed by natural selection and allows the species to survive in changing environmental conditions. However, modification variability cannot be a prerequisite for evolution, since it does not affect the gene pool of a population.

Natural selection is a directed historical process of differentiation (selective preservation) of phenotypes and reproduction of adaptive genotypes in populations.

Depending on the environmental conditions of populations in nature, two main forms of natural selection can be observed: driving and stabilizing.

driving selection operates in conditions of the environment gradually changing in a certain direction.

It retains beneficial deviant phenotypes and removes old and useless deviant phenotypes. In this case, there is a shift in the average value of the norm of the reaction of signs and a shift in their variation curve in a specific direction without changing its limits.

If selection acts in this way in a series of generations (F1 → F2 → F3), then it leads to the formation of a new norm for the reaction of traits.

It does not overlap with the previous reaction rate. As a result, new adaptive genotypes are formed in the population. This is the reason for the gradual transformation of the population into a new species. It was this form of selection that Darwin considered the driving force behind evolution.

As a result of the action of driving selection, some features may disappear under new conditions, while others may develop and improve.

The unidirectional action of natural selection leads to elongation of the roots in sclerophytes, an increase in visual acuity, hearing, and smell in predators and their prey.

Stabilizing selection operates under constant and optimal environmental conditions for populations.

It retains the old phenotype and removes any deviant phenotypes. In this case, the average value of the reaction norm of the signs does not change, but the limits of their variation curve narrow. Consequently, the genotypic and phenotypic diversity that arises as a result of the action of the prerequisites of evolution is reduced.

This contributes to the consolidation of the old genotypes and the preservation of the existing species. The result of this form of selection is the existence of ancient (relict) organisms at the present time.

relic(from lat. relictum - remnant) kinds- living organisms preserved in modern flora and fauna or in a certain region as a remnant of an ancestral group. In past geological epochs, they were widespread and played an important role in ecosystems.

The driving forces of evolution are natural selection and the struggle for existence.

There are two forms of struggle for existence: direct and indirect struggle. In nature, there are two main forms of natural selection: driving and stabilizing.

Directing factor of evolution according to Darwin

All our dignity lies in thought. It is not space or time, which we cannot fill, that elevates us, but it is she, our thought.

Let us learn to think well: this is the basic principle of morality.

Charles Darwin was born in the cold winter of 1809 in England. His father was Robert Waring, the son of the famous scientist and talented poet Erasmus Darwin.

The mother of little Charles died when he was not even 8 years old.

Soon Charles was sent to study at an elementary school, and after one year he was transferred to Dr. Betler, the head of the gymnasium. Ch. Darwin studied very mediocrely, although he very early "woke up" a love for nature, as well as a "lively" interest in flora and fauna. Directing factor of evolution according to Darwin He enjoyed collecting insects, various minerals, flowers and shells.

After graduating from high school in 1825, young Darwin brilliantly enters the University of Edinburgh. There he studied for only two years. After an unsuccessful attempt to become a doctor, Darwin decides to try his hand at being a priest. For this, the young man enters Cambridge. He graduated from his studies, completely standing out from the rest of the students. He was attracted by something completely different: societies of naturalists and botanists, excursions dedicated to the natural sciences. During these years, the first work came out from the pen of the scientist, which contained his notes and observations of the natural world.

In 1831, Darwin begins a trip around the world, in which for 5 years he gets acquainted with the nature of the most diverse points on the planet. As a result of the observations he made during his travels, he wrote several works on geological observations of volcanic islands and coral reefs.

They brought Darwin fame in scientific circles.

In 1839 Darwin marries, which makes him stay in London. Charles's failing health leads to a move to Dawn, where Darwin remains for the rest of his days. There he develops the question of the origin of species and formulates the idea of ​​natural selection. The Directing Factor of Evolution According to Darwin The essay "The Origin of Species by Means of Natural Selection" is published, in which his theory is carefully proved, and indisputable evidence is given.

His name has gained recognition and fame throughout the world. All subsequent works of Darwin are further developments of his teachings. For example, some explanations for the origin of man from monkeys.

After spreading his theory, C. Darwin received a number of awards for his work, becoming an honorary member of numerous scientific societies.

The scientist died in 1882, having lived to the age of 74. Darwin's teaching glorified his name for centuries, marking a new approach to the doctrine of the emergence of mankind.

In order for the upbringing of children to be successful, it is necessary that the educators, without ceasing, educate themselves.

Elementary Factors of Evolution- factors that change the frequency of alleles and genotypes in the population (the genetic structure of the population). There are several basic elementary factors of evolution: the mutation process, combinative variability, population waves and gene drift, isolation, natural selection.

mutation process leads to the emergence of new alleles (or genes) and their combinations as a result of mutations.

As a result of a mutation, a gene can move from one allelic state to another (A → a) or change the gene in general (A → C). The mutation process, due to the randomness of mutations, does not have a direction and, without the participation of other evolutionary factors, cannot direct the change in the natural population.

It only supplies the elementary evolutionary material for natural selection. Recessive mutations in the heterozygous state constitute a hidden reserve of variability, which can be used by natural selection when the conditions of existence change.

Combination variability occurs as a result of the formation in the offspring of new combinations of already existing genes inherited from parents.

The reasons for combinative variability are: chromosome crossing (recombination); random segregation of homologous chromosomes during meiosis; random combination of gametes during fertilization.

Waves of life- periodic and non-periodic fluctuations in the population size, both upward and downward.

Population waves can be caused by:

• periodic changes in environmental environmental factors (seasonal fluctuations in temperature, humidity, etc.);
• non-periodic changes (natural disasters);
• colonization of new territories by the species (accompanied by a sharp increase in numbers).

Population waves act as an evolutionary factor in small populations where gene drift is possible.

Gene drift- random non-directional change in the frequencies of alleles and genotypes in populations. In small populations, the action of random processes leads to noticeable consequences. If the population is small in size, then as a result of random events, some individuals, regardless of their genetic constitution, may or may not leave offspring, as a result of which the frequencies of some alleles may change significantly over one or several generations.

So, with a sharp reduction in the population size (for example, due to seasonal fluctuations, reduction of food resources, fire, etc.), rare genotypes may be among the few survivors.

If in the future the population is restored due to these individuals, then this will lead to a random change in the frequencies of alleles in the gene pool of the population. Thus, population waves serve as a supplier of evolutionary material.

Insulation due to the emergence of various factors that prevent free crossing.

Between the formed populations, the exchange of genetic information ceases, as a result of which the initial differences in the gene pools of these populations increase and become fixed. Isolated populations can undergo various evolutionary changes, gradually turning into different species.

Distinguish between spatial and biological isolation. Spatial (geographical) isolation is associated with geographical obstacles (water barriers, mountains, deserts, etc.), and for sedentary populations, simply with large distances.

Biological isolation is due to the impossibility of mating and fertilization (due to a change in the timing of reproduction, structure or other factors that prevent crossing), the death of zygotes (due to biochemical differences in gametes), the sterility of the offspring (as a result of impaired chromosome conjugation during gametogenesis).

The evolutionary significance of isolation is that it perpetuates and reinforces genetic differences between populations.

Changes in the frequencies of genes and genotypes caused by the factors of evolution discussed above are of a random, non-directional nature.

The guiding factor of evolution is natural selection.

Natural selection- the process, as a result of which, predominantly individuals with traits useful for the population survive and leave behind offspring. Selection operates in populations; its objects are the phenotypes of individual individuals. However, selection by phenotypes is a selection of genotypes, since not traits, but genes are transmitted to offspring.

As a result, in the population there is an increase in the relative number of individuals with a certain property or quality. Thus, natural selection is a process of differential (selective) reproduction of genotypes.

Not only properties that increase the likelihood of leaving offspring are subjected to selection, but also traits that are not directly related to reproduction. In a number of cases, selection can be aimed at creating mutual adaptations of species to each other (flowers of plants and insects visiting them).

There may also be signs that are harmful to an individual, but ensure the survival of the species as a whole (a stinging bee dies, but attacking the enemy, it saves the family). On the whole, selection plays a creative role in nature, since from undirected hereditary changes those are fixed that can lead to the formation of new groups of individuals that are more perfect in the given conditions of existence.

There are three main forms of natural selection: stabilizing, moving and tearing (disruptive).

Stabilizing selection is aimed at preserving mutations leading to less variability in the average value of the trait.

Operates under relatively constant environmental conditions, i.e. while the conditions that led to the formation of one or another sign (property) persist.

For example, the preservation of the size and shape of a flower in insect-pollinated plants, since the flowers must correspond to the size of the body of the pollinating insect.

Conservation of relic species.

Driving selection is aimed at maintaining mutations that change the average value of the trait. Occurs when environmental conditions change. Individuals of a population have some differences in genotype and phenotype, and with a long-term change in the external environment, a part of the species with some deviations from the norm may receive an advantage in life and reproduction.

The variation curve shifts in the direction of adaptation to new conditions of existence. For example, the emergence of resistance to pesticides in insects and rodents, and resistance to antibiotics in microorganisms.

Or industrial melanism, for example, the darkening of the color of the birch moth moth in the developed industrial regions of England. In these areas, the bark of trees becomes dark due to the disappearance of lichens sensitive to atmospheric pollution, and dark butterflies are less visible on tree trunks.

Disruptive (disruptive) selection is aimed at preserving mutations that lead to the greatest deviation from the average value of the trait.

Disruptive selection is manifested in the event that environmental conditions change in such a way that individuals with extreme deviations from the norm acquire an advantage. As a result of tearing selection, population polymorphism is formed, i.e. the presence of several groups that differ in some way. For example, with frequent strong winds, insects with either well-developed wings or rudimentary ones persist on oceanic islands.

MAIN PROVISIONS OF DARWIN'S EVOLUTIONARY DOCTRINE.

All kinds of living beings have never been created by anyone.

Having arisen in a natural way, organic forms were slowly and gradually transformed and improved.

The evolutionary process is determined by the conditions of existence and manifests itself in the formation of species adapted to these conditions.

Driving forces of evolution: hereditary variability, struggle for existence, natural selection.

Natural selection plays the role of a guiding factor in evolution.

The material for natural selection is supplied by the variability of organisms.

Natural selection is a consequence of the struggle for existence, which is divided into intraspecific, interspecific and struggle with environmental conditions.

The result of natural selection is:

― preservation of any adaptations that ensure the survival and reproduction of offspring;

― divergence - the process of genetic and phenotypic divergence of groups of individuals and the formation of new species;

― progressive evolution of the organic world.

THE SIGNIFICANCE OF THE THEORY OF EVOLUTION FOR NATURAL SCIENCE.

Evolution theoryrevealed the underlying mechanisms of the evolutionary process , has accumulated a lot of facts and evidence of the evolution of living organisms,combined data from many biological sciences . Darwin marked the beginning of a new era in the development of natural science. The doctrine of the variability of living beings causeda heavy blow to metaphysics and idealism provided materialistic explanations for evolution.

DRIVING FORCES OF EVOLUTION: heredity, struggle for existence, variability, natural selection.

HEREDITY – the ability of organisms to retain certain traits over generations.

VARIABILITY – the ability of organisms to acquire new traits and properties in a number of generations and lose old ones.

Darwin singled outTHREE FORMS OF VARIABILITY : definite, indefinite, correlative.

● CERTAIN VARIABILITY (group, modification, phenotypic, non-hereditary) - arises under the influence of some environmental factor that acts equally on all individuals of a variety, breed, species.

Example: weight gain with good nutrition in all individuals of the breed. Changes in hairline under the influence of climate.

This variation is not hereditary. In offspring placed in other environmental conditions, these signs do not appear.

● UNCERTAIN VARIABILITY (individual, hereditary) - manifests itself individually in each individual.

Example: in one variety of plants appear specimens with different colors of flowers.

● CORRELATIVE VARIABILITY Changes in one organ cause changes in other organs.

Example: long-billed pigeons usually have long legs.

HEREDITY AND VARIABILITY are preconditions for evolution .

The driving forces of evolution are the struggle for existence and natural selection.

STRUGGLE FOR EXISTENCE - any relationship of the organism with factors of living inanimate nature (biotic and abiotic)

The result of the struggle for existence is the death of less adapted individuals.

TYPES OF STRUGGLE FOR EXISTENCE :

Interspecific 2. Intraspecific 3. Fight against abiotic factors.

● INTERSPECIES FIGHT.

- protective coloration (mushrooms are painted in the color of fallen leaves)

- mimicry (the similarity in shape and color with different objects and organisms). Praying mantises look like leaves, and non-venomous snakes look like poisonous ones.

- special protection agencies : thorns in a cactus, needles in a hedgehog.

- menacing coloration (fly agaric, wasps).

● INTRA-SPECIES FIGHT.

This is competitionbetween individuals of the same species for food, light, air, living space, the possibility of reproduction .

● FIGHT AGAINST ABIOTIC FACTORS.

itthe relationship of the organism with the environment . In this case, only those forms that are better adapted to the conditions survive.

Example : Arctic animals have thick fur and a thick layer of fat.

LEADING ROLE OF NATURAL SELECTION IN EVOLUTION.

Evolution is a directed process . There is onlyone directed evolutionary factor is natural selection. He is the driving force behind evolution .

Mutations and the sexual process create genetic heterogeneity within a species (for example, different colors of caterpillars). Their action is not directed. These individual deviations can be beneficial, neutral or harmful to the organism.

NATURAL SELECTION preserves the organisms most adapted to the environment .

The selection factors are complex of abiotic and biotic environmental conditions . Depending on these conditions, selection acts in different directions and leads to unequal evolutionary results.

Allocate three forms of natural selection : moving, stabilizing, disruptive - tearing (and sexual).

SEXUAL SELECTION is the competition of males for the possibility of reproduction. Active, healthy and strong males leave offspring, the rest are removed from reproduction and their genotypes disappear from the gene pool of the species.

SYNTHETIC THEORY OF EVOLUTION.

Synthetic theory of evolution -modern darvi nism - originated in the early 1940sXXin. She representscothe battlethe doctrine of the evolution of the organic world, developed on based on the data of modern genetics, ecology and classical Darwinism . Into the development of a synthetic theoryevolution was contributed by Chetverikov, Timofeev-Ressovsky, Vavilov, Schmalhausen, Gauze, Huxley, Haldane, and others.

MAIN PROVISIONS OF THE SYNTHETIC THEORY OF EVOLUTION

1. The material for evolution is hereditary changes. nia - mutations (usually genetic) and their combinations.

2. The main driver of evolution is natural selection , arising from the struggle for existence.

3. The smallest unit of evolution is the population .

4. Evolution is in most cases divergent. , i.e. one taxon can become the ancestor of several daughtersthem taxa.

5. Evolution is gradual and continuous . vidoeducation as a stage of the evolutionary process is a successive change of one temporary population by a succession of subsequent temporary populations.

6. A view consists of many subordinate , morphologically, physiologically, ecologically, biochemically and geneticallygreat, butreproductively non-isolated units - subspecies and populations.

7. The species exists as a holistic and closed formation . Tsethe density of the species is maintained by migrations of individuals from onepopulation to another, in which there is an exchange of allelemi ("gene flow").

8. Macroevolution at a higher level than the species (genus, semeystvo, detachment, class, etc.),goes through microevolution . In other words, macroevolution is characterized by the same prerequisites and driving forces asfor microevolution.

9. Any real (not prefabricated)the taxon is monophyletic ancestry .

10. Evolution is undirected , i.e. does not go in onthe rule of some end goal.

View, its criteria. A population is a structural unit of a species and an elementary unit of evolution. Microevolution. Formation of new species. Speciation methods. Conservation of species diversity as a basis for the sustainability of the biosphere

View, its criteria

The founder of modern taxonomy, K. Linnaeus, considered a species as a group of organisms similar in morphological features that freely interbreed with each other. As biology developed, evidence was obtained that the differences between species are much deeper, and affect the chemical composition and concentration of substances in tissues, the direction and speed of chemical reactions, the nature and intensity of vital processes, the number and shape of chromosomes, i.e. the species is the smallest a group of organisms that reflects their close relationship. In addition, species do not exist forever - they arise, develop, give rise to new species and disappear.

View- this is a collection of individuals that are similar in structure and features of life processes, have a common origin, freely interbreed among themselves in nature and give fertile offspring.

All individuals of the same species have the same karyotype and occupy a certain geographical area in nature - area.

Signs of similarity of individuals of the same species are called type criteria. Since none of the criteria is absolute, it is necessary to use a set of criteria to correctly determine the species.

The main criteria of a species are morphological, physiological, biochemical, ecological, geographical, ethological (behavioral) and genetic.

1. Morphological- a set of external and internal features of organisms of the same species. Although some species have unique characters, it is often very difficult to distinguish between closely related species using morphological features alone. Thus, recently a number of twin species living in the same territory have been discovered, for example, the house and mound mice, so it is unacceptable to use only a morphological criterion to determine the species.
2. Physiological- the similarity of life processes in organisms, primarily reproduction. It is also not universal, since some species interbreed in nature and produce fertile offspring.
3. Biochemical- the similarity of the chemical composition and the course of metabolic processes. Despite the fact that these indicators can vary significantly in different individuals of the same species, they are currently receiving much attention, since the features of the structure and composition of biopolymers help to identify species even at the molecular level and establish the degree of their relationship.
4. Ecological- the difference between species according to their belonging to certain ecosystems and the ecological niches they occupy. However, many unrelated species occupy similar ecological niches, so this criterion can be used to distinguish a species only in combination with other characters.
5. Geographical- the existence of a population of each species in a certain part of the biosphere - an area that differs from the areas of all other species. Due to the fact that for many species the boundaries of the ranges coincide, and there are also a number of cosmopolitan species whose range covers vast areas, the geographical criterion also cannot serve as a marker "species" feature.
6. Genetic- the constancy of the signs of the chromosome set - the karyotype - and the nucleotide composition of DNA in individuals of the same species. Due to the fact that non-homologous chromosomes cannot conjugate during meiosis, offspring from crossing individuals of different species with an unequal set of chromosomes either do not appear at all or are not fertile. This creates the reproductive isolation of the species, maintains its integrity and ensures the reality of existence in nature. This rule may be violated in the case of crossing species of similar origin with the same karyotype or the occurrence of various mutations, however, the exception only confirms the general rule, and species should be considered as stable genetic systems. The genetic criterion is the main one in the system of species criteria, but also not exhaustive.

For all the complexity of the system of criteria, a species cannot be represented as a group of absolutely identical organisms in all respects, that is, clones. On the contrary, many species are characterized by a significant variety of even external features, as, for example, some populations of ladybugs are characterized by a predominance of red in color, while others are black.

Population - a structural unit of a species and an elementary unit of evolution

It is difficult to imagine that in reality, individuals of the same species would be evenly distributed over the earth's surface within the range, since, for example, the lake frog lives mainly in rather rare stagnant fresh water bodies, and it is unlikely to be found in fields and forests. Species in nature most often break up into separate groups, depending on the combination of conditions suitable for habitats - populations.

population- a group of individuals of the same species occupying part of its range, freely interbreeding and relatively isolated from other populations of individuals of the same species for a more or less long time.

Populations can be separated not only spatially, they can even live in the same territory, but have differences in food preferences, breeding times, etc.

Thus, a species is a collection of populations of individuals that have a number of common morphological, physiological, biochemical characteristics and types of relationships with the environment, inhabiting a certain area, and also able to interbreed with each other to form fertile offspring, but almost or not at all interbreeding with other groups individuals of the same species.

Within species with large ranges covering territories with different living conditions, sometimes there are subspecies- large populations or groups of neighboring populations that have persistent morphological differences from other populations.

Populations are scattered over the earth's surface not randomly, they are tied to specific areas of it. The totality of all factors of inanimate nature necessary for the living of individuals of a given species is called habitat. However, these factors alone may not be enough to occupy this area with a population, since it must also be involved in close interaction with populations of other species, that is, take a certain place in the community of living organisms - ecological niche. So, the Australian marsupial bear koala, all other things being equal, cannot exist without its main source of nutrition - eucalyptus.

Forming an inseparable unity in the same habitats, populations of various species usually provide a more or less closed circulation of substances and are elementary ecological systems (ecosystems) - biogeocenoses.

For all their demanding environmental conditions, populations of the same species are heterogeneous in terms of area, number, density and spatial distribution of individuals, often forming smaller groups (families, flocks, herds, etc.), sex, age, gene pool, etc. , therefore, their size, age, gender, spatial, genetic, ethological and other structures, as well as dynamics, are distinguished.

Important characteristics of a population are gene pool- a set of genes characteristic of individuals of a given population or species, as well as the frequency of certain alleles and genotypes. Different populations of the same species initially have an unequal gene pool, since individuals with random rather than specially selected genes master new territories. Under the influence of internal and external factors, the gene pool undergoes even more significant changes: it is enriched due to the occurrence of mutations and a new combination of traits and depleted as a result of the loss of individual alleles during the death or migration of a certain number of individuals.

New traits and their combinations can be beneficial, neutral, or harmful; therefore, only individuals adapted to given environmental conditions survive and successfully reproduce in a population. However, at two different points on the earth's surface, environmental conditions are never completely identical, and therefore the direction of changes even in two neighboring populations can be completely opposite or they will proceed at different rates. The result of changes in the gene pool is the divergence of populations according to morphological, physiological, biochemical and other characteristics. If the populations are also isolated from each other, then they can give rise to new species.

Thus, the emergence of any obstacles in the crossing of individuals of different populations of the same species, for example, due to the formation of mountain ranges, changes in river beds, differences in breeding periods, etc., leads to the fact that populations gradually acquire more and more differences and, in eventually become different species. For some time, crossing of individuals occurs at the boundaries of these populations and hybrids arise, however, over time, these contacts also disappear, i.e., populations from open genetic systems become closed.

Despite the fact that individual individuals are primarily affected by environmental factors, the change in the genetic composition of a single organism is insignificant and will manifest itself, at best, only in its descendants. Subspecies, species and larger taxa are also not suitable for the role of elementary units of evolution, since they do not differ in morphological, physiological, biochemical, ecological, geographical and genetic unity, while populations, as the smallest structural units of a species, accumulate a variety of random changes, the worst of which will be eliminated, meet this condition and are the elementary units of evolution.

microevolution

Changing the genetic structure of populations does not always lead to the formation of a new species, but can only improve the adaptation of the population to specific environmental conditions, however, species are not eternal and unchanged - they are able to develop. This process of irreversible historical change of the living is called evolution. Primary evolutionary transformations occur within a species at the population level. They are based, first of all, on the mutation process and natural selection, leading to a change in the gene pool of populations and the species as a whole, or even to the formation of new species. The totality of these elementary evolutionary events is called microevolution.

Populations are characterized by enormous genetic diversity, which often does not manifest itself phenotypically. Genetic diversity arises due to spontaneous mutagenesis, which occurs continuously. Most mutations are unfavorable for the organism and reduce the viability of the population as a whole, but if they are recessive, they can remain in the heterozygote for a long time. Some mutations that do not have adaptive value under the given conditions of existence are able to acquire such value in the future or during the development of new ecological niches, thus creating a reserve of hereditary variability.

Fluctuations in the number of individuals in populations, migrations and catastrophes, as well as isolation of populations and species have a significant impact on microevolutionary processes.

A new species is an intermediate result of evolution, but by no means its outcome, since microevolution does not stop there - it continues on. Emerging new species, in the case of a successful combination of characters, inhabit new habitats, and, in turn, give rise to new species. Such groups of closely related species are combined into genera, families, etc. Evolutionary processes occurring in supraspecific groups are already called macroevolution. Unlike macroevolution, microevolution proceeds in a much shorter time, while the first requires tens and hundreds of thousands and millions of years, as, for example, the evolution of man.

As a result of microevolution, all the variety of species of living organisms that have ever existed and now live on Earth is formed.

However, evolution is irreversible, and already extinct species never reappear. Emerging species consolidate everything achieved in the process of evolution, but this does not guarantee that new species will not appear in the future, which will have more perfect adaptations to environmental conditions.

Formation of new species

In a broad sense, the formation of new species is understood not only as the splitting off of the main stem of a new species or the disintegration of the parent species into several daughter species, but also the general development of the species as an integral system, leading to significant changes in its morphostructural organization. However, more often than not speciation considered as a process of formation of new species through the branching of the "pedigree tree" of the species.

The fundamental solution to the problem of speciation was proposed by Ch. Darwin. According to his theory, the dispersal of individuals of the same species leads to the formation of populations, which, due to differences in environmental conditions, are forced to adapt to them. This, in turn, entails an aggravation of the intraspecific struggle for existence, directed by natural selection. At present, it is believed that the struggle for existence is not at all an obligatory factor in speciation; on the contrary, the selection pressure in a number of populations may decrease. The difference in the conditions of existence contributes to the emergence of unequal adaptive changes in the populations of the species, the consequence of which is the divergence of the characteristics and properties of the populations - divergence.

However, the accumulation of differences, even at the genetic level, is by no means sufficient for the emergence of a new species. As long as populations that differ in some way not only contact, but are also capable of interbreeding with the formation of fertile offspring, they belong to the same species. Only the impossibility of the flow of genes from one group of individuals to another, even in the case of the destruction of the barriers separating them, i.e., crossing, means the completion of the most complex evolutionary process of the formation of a new species.

Speciation is a continuation of microevolutionary processes. There is a point of view that speciation cannot be reduced to microevolution, it represents a qualitative stage of evolution and is carried out due to other mechanisms.

Speciation methods

There are two main modes of speciation: allopatric and sympatric.

allopatric, or geographical speciation is a consequence of the spatial separation of populations by physical barriers (mountain ranges, seas and rivers) due to their emergence or settlement in new habitats (geographical isolation). Since in this case the gene pool of the separated population differs significantly from the parent one, and the conditions in its habitat will not coincide with the original ones, over time this will lead to divergence and the formation of a new species. A striking example of geographic speciation is the variety of finches discovered by C. Darwin during a voyage on the Beagle ship on the Galapagos Islands off the coast of Ecuador. Apparently, individual individuals of the only finches living on the South American continent somehow got to the islands, and, due to the difference in conditions (primarily the availability of food) and geographical isolation, they gradually evolved, forming a group of related species.

At the core sympatric, or biological speciation some form of reproductive isolation lies, with new species appearing within the range of the original species. A prerequisite for sympatric speciation is the rapid isolation of the formed forms. This is a faster process than allopatric speciation, and the new forms are similar to the original ancestors.

Sympatric speciation can be caused by rapid changes in the chromosome set (polyploidization) or chromosomal rearrangements. Sometimes new species arise as a result of hybridization of two original species, as, for example, in domestic plum, which is a hybrid of blackthorn and cherry plum. In some cases, sympatric speciation is associated with the division of ecological niches in populations of the same species within a single range or seasonal isolation - discrepancies in the timing of reproduction in plants (different types of pine in California dust in February and April) and the timing of reproduction in animals.

Of all the variety of newly emerging species, only a few, the most adapted, can exist for a long time and give rise to new species. The reasons for the death of most species are still unknown, most likely this is due to abrupt climate changes, geological processes and their displacement by more adapted organisms. At present, one of the reasons for the death of a significant number of species is a person who exterminates the largest animals and the most beautiful plants, and if in the 17th century this process only began with the extermination of the last round, then in the 21st century more than 10 species disappear every hour.

Conservation of species diversity as a basis for the sustainability of the biosphere

Despite the fact that, according to various estimates, there are 5-10 million species of organisms that have not yet been described on the planet, we will never know about the existence of most of them, since about 50 species disappear from the face of the Earth every hour. The disappearance of living organisms at the present time is not necessarily associated with their physical extermination, more often it is due to the destruction of their natural habitats as a result of human activity. The death of an individual species is unlikely to lead to fatal consequences for the biosphere, however, it has long been established that the extinction of one plant species entails the death of 10–12 animal species, and this already poses a threat both to the existence of individual biogeocenoses and to the global ecosystem in in general.

The sad facts accumulated over the previous decades forced the International Union for the Conservation of Nature and Natural Resources (IUCN) to begin in 1949 the collection of information on rare and endangered species of plants and animals. In 1966, the IUCN published the first "Red Book of Facts".

Red Book is an official document containing regularly updated data on the status and distribution of rare and endangered species of plants, animals and fungi.

This document adopted a five-stage scale of the status of a protected species, and the first stage of protection includes species whose salvation is impossible without the implementation of special measures, and the fifth - restored species, the state of which, thanks to the measures taken, does not cause concern, but they are not yet subject to industrial use. The development of such a scale makes it possible to direct priority efforts in the field of protection to the rarest species, such as Amur tigers.

In addition to the international version of the Red Book, there are also national and regional versions. In the USSR, the Red Book was established in 1974, and in the Russian Federation, the procedure for maintaining it is regulated by the Federal Laws "On Environmental Protection", "On the Fauna" and the Decree of the Government of the Russian Federation "On the Red Book of the Russian Federation". Today, 610 species of plants, 247 species of animals, 42 species of lichens and 24 species of fungi are listed in the Red Book of the Russian Federation. The populations of some of them, which at one time were under the threat of extinction (European beaver, bison), have already been quite successfully restored.

The following species of animals are taken under protection in Russia: Russian muskrat, tarbagan (Mongolian marmot), polar bear, Caucasian European mink, sea otter, manul, Amur tiger, leopard, snow leopard, sea lion, walrus, seals, dolphins, whales, Przewalski's horse, kulan, pink pelican, common flamingo, black stork, small swan, steppe eagle, golden eagle, black crane, Siberian Crane, bustard, eagle owl, white gull, Mediterranean tortoise, Japanese snake, gyurza, cane toad, Caspian lamprey, all types of sturgeon fish, lake salmon, stag beetle, unusual bumblebee, common Apollo, mantis shrimp, common pearl mussel, etc.

The plants of the Red Book of the Russian Federation include 7 types of snowdrops, some types of wormwood, real ginseng, 7 types of bluebells, toothed oak, blueberry, 11 types of killer whales, Russian hazel grouse, Schrenk's tulip, walnut lotus, real lady's slipper, thin-leaved peony, pinnate feather grass, primrose of Julia, backache (sleep-grass) meadow, belladonna belladonna, Pitsunda pine, yew berry, Chinese thyroid gland, lake half grass, soft sphagnum, curly phyllophora, filiform hara, etc.

Rare mushrooms are represented by summer truffle, or Russian black truffle, varnished tinder fungus, etc.

The protection of rare species in most cases is associated with the prohibition of their destruction, their preservation in an artificially created habitat (zoos), the protection of their habitats and the creation of low-temperature genetic banks.

The most effective measure for the protection of rare species is the conservation of their habitats, which is achieved by organizing a network of specially protected protected areas, which, in accordance with the Federal Law "On Specially Protected Natural Territories" (1995), have international, federal, regional or local significance. These include state nature reserves, national parks, nature parks, state nature reserves, natural monuments, dendrological parks, botanical gardens, etc.

State natural reserve- it is a specially protected natural complex (land, water bodies, subsoil, flora and fauna) completely withdrawn from economic use, which has environmental, scientific, environmental and educational significance as an example of the natural environment, typical or rare landscapes, places of conservation of the plant genetic fund and the animal world.

Reserves that are part of the international system of biosphere reserves that carry out global environmental monitoring have the status state natural biosphere reserves. The reserve is a nature protection, research and environmental education institution with the aim of preserving and studying the natural course of natural processes and phenomena, the genetic fund of flora and fauna, individual species and communities of plants and animals, typical and unique ecological systems.

At present, there are about 100 state nature reserves in Russia, 19 of which have the status of a biosphere reserve, including Baikalsky, Barguzinsky, Caucasian, Kedrovaya Pad, Kronotsky, Prioksko-Terrasny and others.

Unlike nature reserves, territories (water areas) national parks include natural complexes and objects of special ecological, historical and aesthetic value, and are intended for use in environmental protection, educational, scientific and cultural purposes and for regulated tourism. This status has 39 specially protected natural areas, including the Zabaikalsky and Sochi national parks, as well as the national parks "Curonian Spit", "Russian North", "Shushensky Bor", etc.

natural parks are environmental recreational institutions under the jurisdiction of the constituent entities of the Russian Federation, the territories (water areas) of which include natural complexes and objects of significant environmental and aesthetic value, and are intended for use in environmental, educational and recreational purposes.

State natural reserves are areas (water areas) of particular importance for the conservation or restoration of natural complexes or their components and maintaining the ecological balance.

Development of evolutionary ideas. The value of the evolutionary theory of Ch. Darwin. The relationship of the driving forces of evolution. Forms of natural selection, types of struggle for existence. Synthetic theory of evolution. Elementary factors of evolution. Research by S. S. Chetverikov. The role of evolutionary theory in the formation of the modern natural-science picture of the world

Development of evolutionary ideas

All theories of the origin and development of the organic world can be reduced to three main areas: creationism, transformism and evolutionism. creationism- this is the concept of the constancy of species, considering the diversity of the organic world as a result of its creation by God. This direction was formed as a result of the establishment of the dominance of the Christian Church in Europe, based on biblical texts. Prominent representatives of creationism were C. Linnaeus and J. Cuvier.

The "prince of botanists" K. Linnaeus, who discovered and described hundreds of new plant species, and created their first coherent system, nevertheless, proved that the total number of species of organisms has not changed since the creation of the Earth, that is, they not only do not appear again, but and don't disappear. Only towards the end of his life did he come to the conclusion that the work of God was childbirth, while species could develop as a result of adaptation to local conditions.

The contribution of the outstanding French zoologist J. Cuvier (1769–1832) to biology was based on numerous data of paleontology, comparative anatomy and physiology the doctrine of correlations- interconnections of body parts. Thanks to this, it became possible to reconstruct the appearance of the animal in separate parts. However, in the process of paleontological research, J. Cuvier could not help but pay attention both to the obvious abundance of fossil forms and to the sharp changes in animal groups over the course of geological history. These data served as the starting point for formulating catastrophe theory, according to which all or almost all organisms on Earth repeatedly died as a result of periodic natural disasters, and then the planet was repopulated by species that survived the catastrophe. The followers of J. Cuvier counted up to 27 such catastrophes in the history of the Earth. Considerations about evolution seemed to J. Cuvier divorced from reality.

The contradictions in the initial positions of creationism, which became more and more obvious as scientific facts accumulated, served as the starting point for the formation of another system of views - transformism which recognizes the real existence of species and their historical development. Representatives of this trend - J. Buffon, I. Goethe, E. Darwin and E. Geoffroy Saint-Hilaire, being unable to reveal the true causes of evolution, reduced them to adaptation to environmental conditions and the inheritance of acquired traits. The roots of transformism can be found in the works of ancient Greek and medieval philosophers who recognized the historical changes in the organic world. Thus, Aristotle expressed the idea of ​​the unity of nature and the gradual transition from bodies of inanimate nature to plants, and from them to animals - the “ladder of nature”. He considered the main reason for the changes in living organisms to be their inner striving for perfection.

The French naturalist J. Buffon (1707-1788), whose main work of life was the 36-volume "Natural History", contrary to the ideas of creationists, pushed the boundaries of the history of the Earth to 80-90 thousand years. At the same time, he stated the unity of flora and fauna, as well as the possibility of changing related organisms under the influence of environmental factors as a result of domestication and hybridization.

The English physician, philosopher and poet E. Darwin (1731–1802), grandfather of Charles Darwin, believed that the history of the organic world is millions of years old, and the diversity of the animal world is the result of a mixture of several “natural” groups, the influence of the external environment, exercise and non-exercise organs, and other factors.

E. Geoffroy Saint-Hilaire (1772–1844) considered the unity of the structural plan of animal groups to be one of the main proofs of the development of the living world. However, unlike his predecessors, he was inclined to believe that the change in species is due to the influence of environmental factors not on adults, but on embryos.

Despite the fact that in the discussion that broke out in 1831 between J. Cuvier and E. Geoffroy Saint-Hilaire in the form of a series of reports at the Academy of Sciences, a clear advantage remained on the side of the first, it was transformism that became the forerunner of evolutionism. Evolutionism(the theory of evolution, evolutionary doctrine) is a system of views that recognizes the development of nature according to certain laws. It is the theoretical pinnacle of biology, which allows us to explain the diversity and complexity of living systems that we observe. However, due to the fact that evolutionary teaching describes phenomena that are difficult to observe, it encounters significant difficulties. Sometimes the theory of evolution is called "Darwinism" and identified with the teachings of Ch. Darwin, which is fundamentally wrong, because, although Ch. Darwin's theory made an invaluable contribution to the development of not only evolutionary doctrine, but also biology in general (as well as many other sciences ), the foundations of evolutionary theory were laid by other scientists, it continues to develop to this day, and "Darwinism" in many aspects has only historical significance.

The creator of the first evolutionary theory - Lamarckism - was the French naturalist J. B. Lamarck (1744–1829). He considered the internal striving of organisms for perfection as the driving force of evolution ( gradation law), but adaptation to environmental conditions forces them to deviate from this main line. At the same time, the organs that are intensively used by the animal in the process of life develop, while those that are unnecessary to it, on the contrary, weaken and may even disappear ( law of exercise and non-exercise organs). Acquired in the process of life, signs are fixed and transmitted to descendants. So, he explained the presence of membranes between the toes of waterfowl by the attempts of their ancestors to move in the aquatic environment, and the long neck of giraffes, according to Lamarck, is a consequence of the fact that their ancestors tried to get leaves from the tops of trees.

The disadvantages of Lamarckism were the theoretical nature of many constructions, as well as the assumption of the Creator's intervention in evolution. During the development of biology, it became clear that the individual changes acquired by organisms in the course of life, for the most part, fit within the limits of phenotypic variability, and their transmission is practically impossible. For example, the German zoologist and evolutionary theorist A. Weismann (1834–1914) cut off the tails of mice for many generations and always produced only tailed rodents in the offspring. The theory of J. B. Lamarck was not accepted by his contemporaries, but at the turn of the century formed the basis of the so-called neo-Lamarckism.

The value of the evolutionary theory of Charles Darwin

The prerequisites for the creation of the most famous evolutionary theory of Charles Darwin, or Darwinism, were the publication in 1778 of the work of the English economist T. Malthus "Treatise on Population", the work of the geologist Ch. Lyell, the formulation of the cell theory, the success of selection in England and Ch. Darwin (1809–1882), made during his years of study at Cambridge, during and after his expedition as a naturalist on the Beagle.

So, T. Malthus argued that the population of the Earth is increasing exponentially, which significantly exceeds the planet's ability to provide it with food and leads to the death of part of the offspring. The parallels drawn by C. Darwin and his co-author A. Wallace (1823–1913) indicated that in nature, individuals reproduce at a very high rate, but the population size remains relatively constant. The studies of the English geologist C. Lyell made it possible to establish that the surface of the Earth was far from always the same as at present, and its changes were caused by the influence of water, wind, volcanic eruptions and the activity of living organisms. Ch. Darwin himself, even in his student years, was struck by the extreme degree of variability of beetles, and during the trip - the similarity of the flora and fauna of continental South America and the Galapagos Islands lying near it, and at the same time a significant diversity of species, such as finches and turtles. In addition, on the expedition, he could observe the skeletons of giant extinct mammals, similar to modern armadillos and sloths, which significantly shook his belief in the creation of species.

The main provisions of the theory of evolution were expressed by Charles Darwin in 1859 at a meeting of the Royal Society of London, and subsequently developed in the books “The Origin of Species by Means of Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life” (1859), “Change in Domestic Animals and Cultivated Plants "(1868), "The Origin of Man and Sexual Selection" (1871), "The Expression of Emotions in Man and Animals" (1872), etc.

The essence of the developed by Ch. Darwin evolution concepts can be reduced to a number of provisions arising from each other, having corresponding proof of:

1. The individuals that make up any population produce many more offspring than is necessary to maintain the population size.
2. Due to the fact that life resources for any kind of living organisms are limited, between them inevitably arises struggle for existence. Ch. Darwin distinguished between intraspecific and interspecific struggle, as well as the struggle with environmental factors. At the same time, he also pointed out that it is not only about the struggle of a particular individual for existence, but also for leaving offspring.
3. The result of the struggle for existence is natural selection- the prevailing survival and reproduction of organisms that accidentally turned out to be the most adapted to the given conditions of existence. Natural selection is in many ways similar to artificial selection, which man has been using since ancient times to develop new varieties of plants and breeds of domestic animals. By selecting individuals that have some desirable trait, man preserves those traits by artificial breeding through selective propagation or pollination. A special form of natural selection is sexual selection for traits that usually have no direct adaptive value (long feathers, huge horns, etc.), but contribute to success in reproduction, since they make an individual more attractive to the opposite sex or more formidable to rivals the same gender.
4. The material for evolution is the differences in organisms that arise as a result of their variability. C. Darwin distinguished between indefinite and definite variability. Certain(group) variability manifests itself in all individuals of a species in the same way under the influence of a certain factor and disappears in descendants when the action of this factor ceases. indefinite(individual) variability is the changes that occur in each individual, regardless of fluctuations in the values ​​of environmental factors, and are transmitted to descendants. Such variability does not have an adaptive (adaptive) character. Subsequently, it turned out that a certain variability is non-hereditary, and an indefinite one is hereditary.
5. Natural selection ultimately leads to a divergence of the characteristics of individual isolated varieties - divergence, and, in the end, to the formation of new species.

Ch. Darwin's theory of evolution not only postulated the process of the emergence and development of species, but also revealed the very mechanism of evolution, which is based on the principle of natural selection. Darwinism also denied the programming of evolution and postulated its continuous nature.

At the same time, Charles Darwin's evolutionary theory could not answer a number of questions, for example, about the nature of genetic material and its properties, the essence of hereditary and non-hereditary variability, and their evolutionary role. This led to the crisis of Darwinism and the emergence of new theories: neo-Lamarckism, saltationism, the concept of nomogenesis, etc. Neo-Lamarckism is based on the position of the theory of J. B. Lamarck on the inheritance of acquired characteristics. saltationism- this is a system of views on the process of evolution as spasmodic changes leading to the rapid emergence of new species, genera and larger systematic groups. Concept nomogenesis postulates the programmed direction of evolution and the development of various features based on internal laws. Only the synthesis of Darwinism and genetics in the 20-30s of the twentieth century was able to overcome the contradictions that inevitably arose when explaining a number of facts.

The relationship of the driving forces of evolution

Evolution cannot be associated with the action of any one factor, since mutations themselves are random and undirected changes, and cannot ensure the adaptation of individuals to environmental factors, while natural selection already sorts these changes. In the same way, selection itself cannot be the only factor in evolution, since selection requires the appropriate material supplied by mutations.

However, it can be noted that the mutation process and gene flow create variability, while natural selection and gene drift sort this variability. This means that the factors that create variability start the process of microevolution, and those that sort variability continue it, leading to the establishment of new frequencies of variants. Thus, evolutionary change within a population can be seen as the result of opposing forces that create and sort genotypic variation.

An example of the interaction between the mutation process and selection is hemophilia in humans. Hemophilia is a disease caused by reduced blood clotting. Previously, it led to death in the pre-reproductive period, since any damage to the soft tissues could potentially lead to large blood loss. This disease is caused by a recessive mutation in the sex-linked H (Xh) gene. Women suffer from hemophilia extremely rarely, they are more often heterozygous carriers, but their sons can inherit the disease. Theoretically, within several generations, such men die before puberty and gradually this allele should disappear from the population, however, the frequency of occurrence of this disease does not decrease due to repeated mutations in this locus, as happened in Queen Victoria, who transmitted the disease to three generations of the royal houses of Europe. The constant frequency of this disease indicates a balance between the mutation process and selection pressure.

Forms of natural selection, types of struggle for existence

natural selection called selective survival and the abandonment of offspring by the fittest individuals and the death of the least fit.

The essence of natural selection in the theory of evolution lies in the differentiated (non-random) preservation of certain genotypes in a population and their selective participation in the transfer of genes to the next generation. At the same time, it does not affect a single trait (or gene), but the entire phenotype, which is formed as a result of the interaction of the genotype with environmental factors. Natural selection in different environmental conditions will be of a different nature. Currently, there are several forms of natural selection: stabilizing, moving and tearing.

Stabilizing selection aimed at consolidating a narrow norm of reaction, which turned out to be the most favorable under the given conditions of existence. It is typical for those cases when phenotypic traits are optimal for unchanging environmental conditions. A striking example of the action of stabilizing selection is the maintenance of a relatively constant body temperature in warm-blooded animals. This form of selection was studied in detail by the outstanding Russian zoologist I. I. Shmalgauzen.

driving selection arises in response to changes in environmental conditions, as a result of which mutations that deviate from the average value of the trait are preserved, while the previously dominant form is destroyed, since it does not adequately meet the new conditions of existence. For example, in England as a result of air pollution by industrial emissions hitherto unseen in many places moth butterflies with dark wings, which were less visible to birds against the background of smoked birch trunks, widely spread. Driving selection does not contribute to the complete destruction of the form against which it acts, because due to the measures taken by the government and environmental organizations, the situation with atmospheric pollution has improved dramatically, and the color of the wings of butterflies is returning to the original version.

Tearing, or disruptive selection favors the preservation of extreme variants of a trait and removes intermediate ones, such as, for example, as a result of the use of pesticides, groups of insects resistant to it appear. By its mechanism, disruptive selection is the opposite of stabilizing selection. Through this form of selection, several sharply demarcated phenotypes arise in a population. This phenomenon is called polymorphism. The emergence of reproductive isolation between distinct forms can lead to speciation.

Sometimes also considered separately destabilizing selection, which retains mutations that lead to a wide variety of any trait, for example, the color and structure of the shells of some mollusks living in heterogeneous microenvironments of the rocky surf of the sea. This form of selection was discovered by D.K. Belyaev while studying the domestication of animals.

In nature, none of the forms of natural selection exists in its pure form, but on the contrary, there are various combinations of them, and as environmental conditions change, one or the other of them comes to the fore. So, upon completion of changes in the environment, the driving selection is replaced by a stabilizing one, which optimizes the group of individuals in the new conditions of existence.

Natural selection occurs at various levels, in connection with which there are also individual, group and sexual selection. Individual selection eliminates less adapted individuals from participating in reproduction, while group selection is aimed at preserving a trait that is useful not for an individual, but for the group as a whole. Under pressure group selection can completely die out entire populations, species and larger groups of organisms without leaving offspring. Unlike individual selection, group selection reduces the diversity of forms in nature.

sexual selection carried out within the same floor. It contributes to the development of traits that ensure success in leaving the largest offspring. Thanks to this form of natural selection, sexual dimorphism has developed, expressed in the size and color of the tail of a peacock, the horns of deer, etc.

Natural selection is the result struggle for existence based on genetic variation. The struggle for existence is understood as the totality of relationships between individuals of one's own and other species, as well as with abiotic environmental factors. These relationships determine the success or failure of a certain individual in surviving and leaving offspring. The reason for the struggle for existence is the appearance of an excess number of individuals in relation to the available resources. In addition to competition, mutual assistance should also be included in these relationships, which increases the chances of individuals for survival.

Interaction with environmental factors can also lead to the death of the vast majority of individuals, for example, in insects, only a small part of which survives the winter.

Synthetic theory of evolution

The successes of genetics at the beginning of the 20th century, for example, the discovery of mutations, suggested that hereditary changes in the phenotype of organisms occur suddenly, and do not form for a long time, as postulated by the evolutionary theory of Charles Darwin. However, further research in the field of population genetics led to the formulation in the 20-50s of the twentieth century of a new system of evolutionary views - synthetic theory of evolution. A significant contribution to its creation was made by scientists from different countries: Soviet scientists S. S. Chetverikov, I. I. Shmalgauzen and A. N. Severtsov, English biochemist and geneticist D. Haldane, American geneticists S. Wright and F. Dobzhansky, evolutionist D. Huxley, paleontologist D. Simpson and zoologist E. Mayr.

The main provisions of the synthetic theory of evolution:

1. The elementary material of evolution is hereditary variability (mutational and combinative) in individuals of a population.
2. The elementary unit of evolution is the population in which all evolutionary changes take place.
3. An elementary evolutionary phenomenon is a change in the genetic structure of a population.
4. The elementary factors of evolution - the drift of genes, the waves of life, the flow of genes - have an undirected, random character.
5. The only directional factor in evolution is natural selection, which is creative. Natural selection is stabilizing, moving and tearing (disruptive).
6. Evolution is divergent, that is, one taxon can give rise to several new taxa, while each species has only one ancestor (species, population).
7. Evolution is gradual and continuous. Speciation as a stage of the evolutionary process is a successive change of one population by a series of other temporary populations.
8. There are two types of evolutionary process: microevolution and macroevolution. Macroevolution does not have its own special mechanisms and is carried out only thanks to microevolutionary mechanisms.
9. Any systematic group can either flourish (biological progress) or die out (biological regression). Biological progress is achieved through changes in the structure of organisms: aromorphosis, idioadaptation or general degeneration.
10. The main laws of evolution are its irreversible nature, the progressive complication of life forms and the development of the adaptability of species to the environment. At the same time, evolution does not have an ultimate goal, i.e., the process is undirected.

Despite the fact that evolutionary theory over the past decades has been enriched with data from related sciences - genetics, selection, etc., it still does not take into account a number of aspects, for example, a directed change in hereditary material, therefore, in the future, it is possible to create a new concept of evolution that will replace the synthetic theory .

Elementary Factors of Evolution

According to the synthetic theory of evolution, an elementary evolutionary phenomenon is a change in the genetic composition of a population, and events and processes that lead to a change in gene pools are called elementary factors of evolution. These include the mutation process, population waves, genetic drift, isolation, and natural selection. In view of the exclusive significance of natural selection in evolution, it will be considered separately.

mutation process, which is as continuous as evolution itself, maintains the genetic heterogeneity of the population through the emergence of more and more new variants of genes. Mutations that occur under the influence of external and internal factors are classified as gene, chromosomal and genomic.

Gene mutations occur with a frequency of 10 -4 -10 -7 per gamete, however, due to the fact that in humans and most higher organisms the total number of genes can reach several tens of thousands, it is impossible to imagine that two organisms are absolutely identical. Most of the resulting mutations are recessive, especially since dominant mutations are immediately subjected to natural selection. Recessive mutations create the very reserve of hereditary variability, however, before they appear in the phenotype, they must be fixed in many individuals in a heterozygous state due to free crossing in the population.

Chromosomal mutations, associated with the loss or transfer of part of a chromosome (a whole chromosome) to another, are also quite common in various organisms, for example, the difference between some species of rats is in a single pair of chromosomes, which makes it difficult to cross them.

Genomic mutations associated with polyploidization also lead to reproductive isolation of the newly emerged population due to disturbances in mitosis of the first division of the zygote. Nevertheless, they are quite widespread in plants and such plants can grow in the Arctic and in alpine meadows due to their greater resistance to environmental factors.

Combination variability, which ensures the emergence of new options for combining genes in the genotype, and, accordingly, increases the likelihood of the emergence of new phenotypes, also contributes to evolutionary processes, since only in humans the number of variants of chromosome combinations is 2 23, that is, the appearance of an organism similar to the already existing is practically impossible.

population waves. The opposite result (depletion of the gene composition) is often caused by fluctuations in the number of organisms in natural populations, which in some species (insects, fish, etc.) can change tens and hundreds of times - population waves, or "waves of life". An increase or decrease in the number of individuals in populations can be either periodical, and non-periodic. The former are seasonal or perennial, such as migrations in migratory birds, or reproduction in daphnia, which have only females in spring and summer, and by autumn males appear, which are necessary for sexual reproduction. Non-periodic fluctuations in numbers are often due to a sharp increase in the amount of food in a favorable year, violation of habitat conditions, reproduction of pests or predators.

Since the restoration of the population size occurs due to a small number of individuals that do not have the entire set of alleles, the new and original populations will have an unequal genetic structure. The change in the frequency of genes in a population under the influence of random factors is called genetic drift, or genetically automatic processes. It also takes place during the development of new territories, because they get an extremely limited number of individuals of this species, which can give rise to a new population. Therefore, the genotypes of these individuals are of particular importance here ( founder effect). As a result of gene drift, new homozygous forms (according to mutant alleles) are often split out, which may turn out to be adaptively valuable, and will be subsequently picked up by natural selection.

Thus, among the Indian population of the American continent and the Laplanders, there is a very high proportion of people with I (0) blood group, while III and IV groups are extremely rare. Probably, in the first case, the founders of the population were individuals who did not have the I B allele, or it was lost during the selection process.

Up to a certain point, alleles are exchanged between neighboring populations as a result of crossing between individuals of different populations - gene flow, which reduces the discrepancy between individual populations, but with the onset of isolation, it stops. Essentially, gene flow is a delayed mutation process.

Insulation. Any changes in the genetic structure of the population must be fixed, which is due to isolation- the emergence of any barriers (geographical, ecological, behavioral, reproductive, etc.) that make it difficult and impossible for individuals of different populations to interbreed. Although isolation does not in itself create new forms, it nevertheless preserves the genetic differences between populations subjected to natural selection. There are two forms of isolation: geographical and biological.

Geographic isolation arises as a result of the division of the range by physical barriers (water obstacles for terrestrial organisms, land areas for hydrobiont species, alternation of elevated areas and plains); this is facilitated by a sedentary or attached (in plants) lifestyle. Sometimes geographic isolation can be caused by the expansion of the range of a species, followed by the extinction of its populations in intermediate territories.

biological isolation is the result of certain divergences of organisms within the same species, which somehow prevent free interbreeding. There are several types of biological isolation: ecological, seasonal, ethological, morphological and genetic. Environmental isolation achieved through the division of ecological niches (for example, the preference for certain habitats or the nature of food, as in spruce crossbill and pine crossbill). Seasonal(temporary) isolation is observed in the case of reproduction of individuals of the same species at different times (different herring herds). Ethological isolation depends on the characteristics of behavior (features of the courtship ritual, coloration, "singing" of females and males from different populations). At morphological isolation An obstacle to crossing is the discrepancy in the structure of the reproductive organs or even the size of the body (Pekingese and Great Dane). genetic isolation has the greatest influence and is manifested in the incompatibility of germ cells (death of the zygote after fertilization), sterility or reduced viability of hybrids. The reasons for this are the peculiarities of the number and shape of chromosomes, as a result of which full cell division (mitosis and meiosis) becomes impossible.

Violating free interbreeding between populations, isolation thus fixes in them those differences that have arisen at the genotypic level due to mutations and population fluctuations. In this case, each of the populations is subjected to the action of natural selection separately from the other, and this ultimately leads to divergence.

Creative role of natural selection in evolution

Natural selection performs the function of a kind of "sieve" that sorts genotypes according to the degree of fitness. However, even Ch. Darwin emphasized that selection is not only and not so much aimed at preserving only the best, but at removing the worst, that is, it allows you to save multivariance. The function of natural selection is not limited to this, since it ensures the reproduction of adapted genotypes, and thus determines the direction of evolution by successively adding up random and numerous deviations. Natural selection does not have a specific goal: on the basis of the same material (hereditary variability), different results can be obtained under different conditions.

In this regard, the factor of evolution under consideration cannot be compared with the work of a sculptor who cuts a marble block; rather, it acts as a distant ancestor of man, making a tool from a stone fragment, without imagining the final result, which depends not only on the nature of the stone and its shape, but and on the strength, direction of impact, etc. However, in case of failure, selection, like a humanoid creature, rejects the “wrong” shape.

The price of selection is the occurrence genetic cargo, that is, the accumulation of mutations in the population, which over time may become predominant due to the sudden death of most of the individuals or the migration of a small number of them.

Under the pressure of natural selection, not only the diversity of species is formed, but also their level of organization increases, including their complication or specialization. However, unlike artificial selection carried out by man only for economically valuable traits, often to the detriment of adaptive properties, natural selection cannot contribute to this, since not a single adaptation in nature can compensate for the harm from a decrease in the viability of a population.

Research by S. S. Chetverikov

One of the important steps towards the reconciliation of Darwinism and genetics was made by the Moscow zoologist S. S. Chetverikov (1880–1959). Based on the results of a study of the genetic composition of the natural populations of the Drosophila fruit fly, he proved that they carry many recessive mutations in the heterozygous form that do not violate phenotypic uniformity. Most of these mutations are unfavorable for the organism and create the so-called genetic cargo, which reduces the adaptability of the population as a whole to the environment. Some mutations that do not have an adaptive value at a given moment in the development of a species may acquire a certain value later, and thus are reserve of hereditary variability. The spread of such mutations among the individuals of the population due to successive free crossings can ultimately lead to their transition to a homozygous state and manifestation in the phenotype. If the given state of the feature is hair dryer- is adaptive, then in a few generations it will completely displace the dominant phene, which is less suitable for these conditions, together with its carriers, from the population. Thus, due to such evolutionary changes, only the recessive mutant allele remains, and its dominant allele disappears.

Let's try to prove this with a specific example. In the study of any particular population, it can be found that not only its phenotypic, but also its genotypic structures can remain unchanged for a long time, which is due to free crossing, or panmixia diploid organisms.

This phenomenon is described by the law Hardy - Weinberg, according to which, in an ideal population of unlimited size, in the absence of mutations, migrations, population waves, genetic drift, natural selection, and subject to free crossing, the frequencies of alleles and genotypes of diploid organisms will not change over a number of generations.

For example, in a population, a certain trait is encoded by two alleles of the same gene - dominant ( BUT) and recessive ( a). The frequency of the dominant allele is denoted as R, and recessive - q. The sum of the frequencies of these alleles is 1: p + q= 1. Therefore, if we know the frequency of the dominant allele, then we can determine the frequency of the recessive allele: q = 1 – p. In fact, the allele frequencies are equal to the probabilities of the formation of the corresponding gametes. Then, after the formation of zygotes, the frequencies of genotypes in the first generation will be:

(pA + qa) 2 = p 2 AA + 2pqAa + q 2 aa = 1,

where p 2 AA- frequency of dominant homozygotes;

2pqAa- frequency of heterozygotes;

q 2 aa- the frequency of recessive homozygotes.

It is easy to calculate that in subsequent generations the genotype frequencies will remain the same, maintaining the genetic diversity of the population. But ideal populations do not exist in nature, and therefore mutant alleles in them can not only be preserved, but also spread, and even replace previously more common alleles.

S. S. Chetverikov was clearly aware that natural selection not only eliminates individual less successful traits, and, accordingly, the alleles encoding them, but also acts on the entire complex of genes that affect the manifestation of a particular gene in the phenotype, or genotypic environment. As a genotypic environment, the entire genotype is currently considered as a set of genes that can enhance or weaken the manifestation of specific alleles.

No less important in the development of evolutionary teaching are the studies of S. S. Chetverikov in the field of population dynamics, in particular, "waves of life", or population waves. While still a student, in 1905 he published an article on the possibility of insect outbreaks and an equally rapid decline in their numbers.

The role of evolutionary theory in the formation of the modern natural-science picture of the world

The importance of evolutionary theory in the development of biology and other natural sciences can hardly be overestimated, since it was the first to explain the conditions, causes, mechanisms, and results of the historical development of life on our planet, i.e., it gave a materialistic explanation for the development of the organic world. In addition, the theory of natural selection was the first truly scientific theory of biological evolution, since when creating it, Charles Darwin did not rely on speculative constructions, but proceeded from his own observations and relied on the real properties of living organisms. At the same time, she enriched the biological toolkit with the historical method.

The formulation of evolutionary theory not only caused a heated scientific discussion, but also gave impetus to the development of such sciences as general biology, genetics, breeding, anthropology and a number of others. In this regard, one cannot but agree with the statement that the theory of evolution crowned the next stage in the development of biology and became the starting point for its progress in the 20th century.

Evidence for the evolution of wildlife. Results of evolution: adaptability of organisms to the environment, diversity of species

Evidence for the evolution of wildlife

In various fields of biology, even before Charles Darwin and after the publication of his theory of evolution, a number of evidence was obtained to support it. These testimonies are called evidence of evolution. Paleontological, biogeographical, comparative embryological, comparative anatomical, and comparative biochemical evidence of evolution is most frequently cited, although taxonomy data, as well as plant and animal breeding, cannot be discounted.

paleontological evidence based on the study of fossil remains of organisms. These include not only well-preserved organisms frozen in ice or encased in amber, but also “mummies” found in acidic peat bogs, as well as remains of organisms and fossils preserved in sedimentary rocks. The presence of simpler organisms in ancient rocks than in later layers, and the fact that species found at one level disappear at another, is considered one of the most significant evidence of evolution and is explained by the emergence and extinction of species in corresponding epochs due to changes in environmental conditions.

Despite the fact that few fossils have been found so far and many fragments are missing in the fossil record due to the low probability of preserving organic remains, forms of organisms have nevertheless been found that have signs of both evolutionarily older and younger groups of organisms. These types of organisms are called transitional forms. Prominent representatives of transitional forms, illustrating the transition from fish to terrestrial vertebrates, are lobe-finned fish and stegocephals, and Archeopteryx occupies a certain place between reptiles and birds.

Rows of fossil forms, successively interconnected in the process of evolution, not only by common, but also by particular features of the structure, are called phylogenetic series. They may be represented by fossils from different continents, and claim to be more or less complete, but their study is impossible without comparison with living forms to demonstrate the progress of the evolutionary process. A classic example of a phylogenetic series is the evolution of the ancestors of the horse, studied by the founder of evolutionary paleontology, V. O. Kovalevsky.

biogeographic evidence. biogeography how science studies the patterns of distribution and distribution over the surface of our planet of species, genera and other groups of living organisms, as well as their communities.

The absence in any part of the earth's surface of species of organisms that are adapted to such a habitat and take root well with artificial importation, like rabbits in Australia, as well as the presence of similar forms of organisms in parts of the land separated at considerable distances from each other, testify, first of all, that the appearance of the Earth was not always like this, and geological transformations, in particular, the drift of continents, the formation of mountains, the rise and fall of the level of the World Ocean, affect the evolution of organisms. For example, in the tropical regions of South America, in South Africa and Australia, four similar species of lungfish live, while the ranges of camels and llamas belonging to the same order are located in North Africa, most of Asia and South America. Paleontological studies have shown that camels and llamas are descended from a common ancestor that once lived in North America, and then spread to Asia through the pre-existing isthmus at the site of the Bering Strait, and also through the Isthmus of Panama to South America. Subsequently, all representatives of this family in the intermediate areas became extinct, and in the marginal areas, new species formed in the process of evolution. The earlier separation of Australia from the rest of the land masses allowed the formation of a very special flora and fauna there, in which such forms of mammals as monotremes, the platypus and echidna, were preserved.

From the point of view of biogeography, one can also explain the diversity of Darwin's finches on the Galapagos Islands, which are 1200 km away from the coast of South America and are of volcanic origin. Apparently, representatives of the only species of finches in Ecuador once flew or were brought to them, and then, as they reproduced, some of the individuals settled on the rest of the islands. On the central large islands, the struggle for existence (food, nesting sites, etc.) was the most acute, and therefore species slightly different from each other in appearance were formed, consuming various foods (seeds, fruits, nectar, insects, etc.). .).

They influenced the distribution of various groups of organisms and changes in climatic conditions on Earth, which contributed to the prosperity of some groups and the extinction of others. Individual species or groups of organisms that have survived from previously widespread floras and faunas are called relics. These include ginkgo, sequoia, tulip tree, coelacanth coelacanth fish, etc. In a broader sense, plant and animal species that live in limited areas of a territory or water area are called endemic, or endemic. For example, all representatives of the native flora and fauna of Australia are endemic, and in the flora and fauna of Lake Baikal they are up to 75%.

Comparative anatomical evidence. The study of the anatomy of related groups of animals and plants provides convincing evidence of the similarity in the structure of their organs. Despite the fact that environmental factors, of course, leave their mark on the structure of organs, in angiosperms, with all their amazing diversity, flowers have sepals, petals, stamens and pistils, and in terrestrial vertebrates, the limb is built according to a five-fingered plan. Organs that have a similar structure, occupy the same position in the body and develop from the same rudiments in related organisms, but perform different functions, are called homologous. Thus, the auditory ossicles (hammer, anvil and stirrup) are homologous to the gill arches of fish, the poisonous glands of snakes to the salivary glands of other vertebrates, the mammary glands of mammals to the sweat glands, the flippers of seals and cetaceans to the wings of birds, the limbs of horses and moles.

Non-functioning organs for a long time, most likely, in the process of evolution turn into rudimentary (rudiments)- structures that are underdeveloped in comparison with ancestral forms, which have lost their main significance. These include the fibula in birds, the eyes of moles and mole rats, hairline, coccyx and appendix in humans, etc.

Individuals, however, may show signs that are absent in this species, but were present in distant ancestors - atavisms, for example, three-toedness in modern horses, the development of additional pairs of mammary glands, a tail and hairline throughout the human body.

If homologous organs are evidence in favor of the relationship of organisms and divergence in the process of evolution, then similar bodies- similar structures in organisms of different groups that perform the same functions, on the contrary, refer to examples convergence(convergence is generally called the independent development of similar traits in different groups of organisms that exist under the same conditions) and confirm the fact that the environment leaves a significant imprint on the organism. Analogues are the wings of insects and birds, the eyes of vertebrates and cephalopods (squid, octopus), the jointed limbs of arthropods and terrestrial vertebrates.

Comparative embryological evidence. Studying embryonic development in representatives of different groups of vertebrates, K. Baer discovered their striking structural unity, especially in the early stages of development ( law of germinal resemblance). Later E. Haeckel formulated biogenetic law, according to which ontogenesis is a brief repetition of phylogenesis, i.e., the stages that an organism goes through in the process of its individual development repeat the historical development of the group to which it belongs.

Thus, in the first stages of development, the embryo of a vertebrate acquires structural features characteristic of fish, and then of amphibians, and, finally, of the group to which it belongs. This transformation is explained by the fact that each of the above classes has common ancestors with modern reptiles, birds and mammals.

However, the biogenetic law has a number of limitations, and therefore the Russian scientist A.N. Severtsov significantly limited the scope of its application to the repetition in ontogenesis exclusively of the features of the embryonic stages of development of ancestral forms.

Comparative biochemical evidence. The development of more accurate methods of biochemical analysis has provided evolutionary scientists with a new body of evidence in favor of the historical development of the organic world, since the presence of the same substances in all organisms indicates a possible biochemical homology similar to that at the level of organs and tissues. Comparative biochemical studies of the primary structure of such widespread proteins as cytochrome With and hemoglobin, as well as nucleic acids, especially rRNA, showed that many of them have almost the same structure and perform the same functions in representatives of different species, while the closer the relationship, the greater the similarity in the structure of the studied substances.

Thus, the theory of evolution is confirmed by a significant amount of data from various sources, which once again indicates its reliability, but it will still change and be refined, since many aspects of the life of organisms remain out of the field of view of researchers.

Results of evolution: adaptability of organisms to the environment, diversity of species

In addition to the general features characteristic of representatives of a particular kingdom, the species of living organisms are characterized by an amazing variety of features of the external and internal structure, life activity and even behavior that appeared and were selected in the process of evolution and ensure adaptation to living conditions. However, it should not be assumed that since birds and insects have wings, this is due to the direct action of the air environment, because there are plenty of wingless insects and birds. The aforementioned adaptations have been selected through a process of natural selection from the full range of available mutations.

Epiphytic plants that do not live on soil, but on trees, have adapted to the absorption of atmospheric moisture with the help of roots without root hairs, but with a special hygroscopic tissue - velamen. Some bromeliads can absorb water vapor in the humid atmosphere of the tropics using hairs on their leaves.

Insectivorous plants (sunflower, Venus flytrap) living on soils where nitrogen is not available for one reason or another have developed a mechanism for attracting and absorbing small animals, most often insects, which are the source of the desired element for them.

To protect against being eaten by herbivores, many plants leading an attached way of life have developed passive defenses, such as thorns (hawthorn), thorns (rose), burning hairs (nettle), accumulation of calcium oxalate crystals (sorrel), biologically active substances in tissues (coffee, hawthorn), etc. In some of them, even the seeds in unripe fruits are surrounded by stony cells that prevent pests from reaching them, and only by autumn does the process of wooding occur, which allows the seeds to get into the soil and germinate (pear).

The environment also has a shaping effect on animals. So, many fish and aquatic mammals have a streamlined body shape, which facilitates their movement in its thickness. However, one should not assume that water directly affects the shape of the body, just in the process of evolution, those animals that possessed this trait turned out to be the most adapted to it.

At the same time, the body of whales and dolphins is not covered with hair, while the related group of pinnipeds has a reduced coat to one degree or another, since, unlike the former, they spend part of their time on land, where without wool their skin would immediately freeze .

The body of most fish is covered with scales, which are lighter colored on the underside than on the top, as a result of which these animals are hardly noticeable from above for natural enemies against the background of the bottom, and from below - against the sky. The coloration that makes animals invisible to their enemies or prey is called patronizing. It is widely distributed in nature. A vivid example of such coloration is the coloring of the underside of the wings of the callima butterfly, which, sitting on a twig and folding its wings together, turns out to be like a dry leaf. Other insects, such as stick insects, disguise themselves as plant branches.

Spotted or striped coloration also has an adaptive value, since birds such as quail or eiders are not visible against the background of the soil even at close range. Imperceptible and spotted eggs of birds nesting on the ground.

The coloration of animals is not always as constant as that of a zebra, for example, a flounder and a chameleon are able to change it depending on the nature of the place where they are. Cuckoos, laying their eggs in the nests of various birds, can vary the color of their shells in such a way that the “owners” of the nest do not notice the differences between it and their own eggs.

The coloring of animals can not always make them invisible - many of them are simply striking, which should warn of danger. Most of these insects and reptiles are poisonous to some extent, such as, for example, a ladybug or a wasp, so the predator, having experienced discomfort several times after eating such an object, avoids it. Nonetheless, warning coloration is not universal, since some birds have adapted to eat them (honey buzzard).

The increased chance of survival for individuals with warning coloration has contributed to its appearance in representatives of other species without proper reason. This phenomenon is called mimicry. So, non-poisonous caterpillars of some species of butterflies imitate poisonous ones, and ladybugs - one of the types of cockroaches. However, birds can quickly learn to distinguish poisonous organisms from non-poisonous ones and consume the latter, avoiding individuals that served as a role model.

In some cases, the opposite phenomenon can also be observed - predatory animals imitate harmless ones in color, which allows them to approach the victim at close range and then attack (saber-toothed blennies).

Protection for many species is also provided by adaptive behavior, which is associated with storing food for the winter, caring for offspring, freezing in place, or vice versa, adopting a threatening posture. So, river beavers prepare several cubic meters of branches, parts of trunks and other plant food for the winter, flooding it in the water near the "huts".

Care for offspring is inherent mainly in mammals and birds, however, it is also found in representatives of other classes of chordates. For example, the aggressive behavior of stickleback males is known, driving away all enemies from the nest in which the eggs are located. Male clawed frogs wrap eggs around their paws and carry them until tadpoles hatch from them.

Even some insects are able to provide their offspring with a more favorable habitat. For example, bees feed their larvae, and young bees at first "work" only in the hive. Ants carry their pupae up and down in the anthill, depending on the temperature and humidity, and if there is a threat of flooding, they generally take them with them. Scarab beetles prepare special balls for their larvae from animal waste.

Many insects, when threatened with an attack, freeze in place and take the form of dry sticks, twigs and leaves. Vipers, on the other hand, rise and puff out their hood, while the rattlesnake makes a special sound with a rattle at the end of its tail.

Behavioral adaptations are supplemented by physiological adaptations associated with the characteristics of the environment. So, a person is able to stay under water without scuba gear for only a few minutes, after which he can lose consciousness and die due to lack of oxygen, and whales do not emerge for a sufficiently long time. Their lung volume is not too large, but there are other physiological adaptations, for example, in the muscles there is a high concentration of the respiratory pigment - myoglobin, which, as it were, stores oxygen and releases it during a dive. In addition, whales have a special formation - a "wonderful network", which allows the use of oxygen even in venous blood.

Animals in hot habitats, such as deserts, are constantly at risk of overheating and losing excess moisture. Therefore, the fennec fox has extremely large auricles that allow it to radiate heat. Amphibians of desert regions, in order to avoid moisture loss through the skin, are forced to switch to a nocturnal lifestyle, when humidity rises and dew appears.

Birds that have mastered the air habitat, in addition to anatomical and morphological adaptations for flight, also have important physiological features. For example, due to the fact that movement in the air requires extremely high energy expenditure, this group of vertebrates is characterized by a high metabolic rate, and the excreted metabolic products are excreted immediately, which contributes to a decrease in the specific density of the body.

Adaptations to the environment, despite all their perfection, are relative. So, some types of milkweed produce alkaloids that are poisonous to most animals, but the caterpillars of one of the species of butterflies - danaids - not only feed on milkweed tissues, but also accumulate these alkaloids, becoming inedible for birds.

In addition, adaptations are useful only in a particular environment and are useless in another environment. For example, the Ussuri tiger, a rare and large predator, like all cats, has soft pads on its paws and retractable sharp claws, sharp teeth, excellent vision even in the dark, sharp hearing and strong muscles, which allows it to detect prey, sneak up on it unnoticed and ambush. However, its striped coloring masks it only in spring, summer and autumn, while on the snow it becomes clearly visible and the tiger can only count on a lightning attack.

The inflorescences of figs, which give valuable seedlings, have such a specific structure that they are pollinated only by blastophage wasps, and therefore, introduced into the culture, they did not bear fruit for a long time. Only the breeding of parthenocarpic varieties of figs (forming fruits without fertilization) could save the situation.

Despite the fact that examples of speciation over very short periods of time are described, as in the case of the rattle in the Caucasian meadows, which, due to regular mowing, first divided into two populations - early-flowering and fruit-bearing and late-flowering, in fact, microevolution is most likely requires much longer periods - many centuries, because humanity, whose different groups have been cut off from each other for thousands of years, nevertheless, has not been divided into different species. However, since evolution has practically unlimited time, for hundreds of millions and billions of years, several billion species have already lived on Earth, most of which have died out, and those that have come down to us are qualitative stages of this ongoing process.

According to modern data, there are over 2 million species of living organisms on Earth, most of which (approximately 1.5 million species) belong to the animal kingdom, about 400 thousand to the plant kingdom, over 100 thousand to the fungi kingdom, and the rest - to bacteria. Such a striking diversity is the result of divergence (divergence) of species according to various morphological, physiological, biochemical, ecological, genetic and reproductive traits. For example, one of the largest genera of plants belonging to the Orchid family - dendrobium - includes over 1,400 species, and the genus of kaloed beetles - over 1,600 species.

The classification of organisms is the task of systematics, which for the past 2 thousand years has been trying to build not just a coherent hierarchy, but a “natural” system that reflects the degree of relatedness of organisms. However, all attempts to do this have not yet been successful, since in a number of cases, in the process of evolution, not only divergence of characters was observed, but also convergence (convergence), as a result of which, in very distant groups, organs acquired similarities, such as the eye of cephalopods. and mammalian eyes.

Macroevolution. Directions and paths of evolution (A. N. Severtsov, I. I. Shmalgauzen). Biological progress and regression, aromorphosis, idioadaptation, degeneration. Causes of biological progress and regression. Hypotheses for the origin of life on Earth. The main aromorphoses in the evolution of plants and animals. Complication of living organisms in the process of evolution

macroevolution

The formation of a species marks a new round in the evolutionary process, since individuals of this species, being more adapted to environmental conditions than individuals of the parent species, gradually settle into new territories, and already in its populations mutagenesis, population waves, isolation and natural selection play their creative role . Over time, these populations give rise to new species, which, due to genetic isolation, have much more signs of similarity with each other than with the species of the genus from which the parent species budded, and thus a new genus arises, then a new family, order (order) , class, etc. The set of evolutionary processes that lead to the emergence of supraspecific taxa (genera, families, orders, classes, etc.) is called macroevolution. Macroevolutionary processes, as it were, generalize microevolutionary changes that occur over a long time, while revealing the main trends, directions and patterns of evolution of the organic world, which cannot be observed at a lower level. Until now, no specific mechanisms of macroevolution have been identified, therefore it is believed that it is carried out only through microevolutionary processes, however, this position is constantly subjected to well-founded criticism.

The emergence of a complex hierarchical system of the organic world is largely the result of the unequal rate of evolution of different groups of organisms. So, the already mentioned Ginkgo biloba, as it were, was “mothballed” for thousands of years, while the pines close enough to it have changed significantly during this time.

Directions and paths of evolution (A. N. Severtsov, I. I. Shmalgauzen). Biological progress and regression, aromorphosis, idioadaptation, degeneration

Analyzing the history of the organic world, one can notice that at certain intervals certain groups of organisms dominated, which then tended to decline or disappeared altogether. Thus, it is possible to distinguish three main directions of evolution: biological progress, biological regression and biological stabilization. A significant contribution to the development of the doctrine of the directions and paths of evolution was made by the Russian evolutionists A. N. Severtsov and I. I. Shmalgauzen.

biological progress associated with the biological prosperity of the group as a whole and characterizes its evolutionary success. It reflects the natural development of living nature from simple to complex, from a lower degree of organization to a higher one. According to A.N. Severtsov, the criteria for biological progress are an increase in the number of individuals of a given group, the expansion of its range, as well as the appearance and development of groups of a lower rank in its composition (transformation of a species into a genus, a genus into a family, etc.). Currently, biological progress is observed in angiosperms, insects, bony fish and mammals.

According to A. N. Severtsov, biological progress can be achieved as a result of certain morphophysiological transformations of organisms, while he identified three main ways to achieve: arogenesis, allogenesis and catagenesis.

Arogenesis, or morphophysiological progress, is associated with a significant expansion of the range of this group of organisms due to the acquisition of large structural changes - aromorphoses.

Aromorphosis called the evolutionary transformation of the structure and functions of the body, which increases its level of organization and opens up new opportunities for adapting to various conditions of existence.

Examples of aromorphoses are the emergence of a eukaryotic cell, multicellularity, the appearance of a heart in fish and its separation by a complete septum in birds and mammals, the formation of a flower in angiosperms, etc.

allogenesis, unlike arogenesis, is not accompanied by an expansion of the range, however, within the old, a significant variety of forms arise that have particular adaptations to the habitat - idioadaptation.

Idioadaptation- this is a small morphophysiological adaptation to special environmental conditions, useful in the struggle for existence, but not changing the level of organization. These changes are illustrated by the protective coloration in animals, the variety of mouthparts in insects, the spines of plants, etc. An equally successful example is Darwin's finches, specializing in various types of food, in which the transformations first affected the beak, and then other parts of the body - plumage, tail etc.

Paradoxically, the simplification of organization can also lead to biological progress. This path is called catagenesis.

Degeneration- this is the simplification of organisms in the process of evolution, which is accompanied by the loss of certain functions or organs.

The phase of biological progress is replaced by the phase biological stabilization, the essence of which is to preserve the characteristics of a given species as the most favorable in a given microenvironment. According to I. I. Schmalhausen, it does not at all “mean the cessation of evolution, on the contrary, it means the maximum consistency of the organism with changes in the environment.” In the phase of biological stabilization are "living fossils" coelacanth, gingko, etc.

The opposite of biological progress is biological regression- the evolutionary decline of this group due to the inability to adapt to changes in the environment. It manifests itself in a decrease in the number of populations, narrowing of areas, and a decrease in the number of groups of a lower rank in the composition of a higher taxon. A group of organisms that is in a state of biological regression is threatened with extinction. In the history of the organic world, many examples of this phenomenon can be seen, and at present regression is characteristic of some ferns, amphibians and reptiles. With the advent of man, biological regression is often due to his economic activity.

The directions and paths of evolution of the organic world are not mutually exclusive, that is, the appearance of aromorphosis does not mean that idioadaptation or degeneration can no longer occur. On the contrary, according to the developed by A. N. Severtsov and I. I. Shmalgauzen phase change rule, different directions of the evolutionary process and ways of achieving biological progress naturally replace each other. In the course of evolution, these paths are combined: rather rare aromorphoses transfer a group of organisms to a qualitatively new level of organization, and further historical development follows the path of idioadaptation or degeneration, providing adaptation to specific environmental conditions.

Causes of Biological Progress and Regression

In the process of evolution, the bar of natural selection is overcome and, accordingly, only those groups of organisms progress in which hereditary variability creates a sufficient number of combinations that can ensure the survival of the group as a whole.

The same groups that for some reason do not have such a reserve are in most cases doomed to extinction. Often this is due to low selection pressure at previous stages of the evolutionary process, which led to a narrow specialization of the group or even degenerative phenomena. The consequence of this is the inability to adapt to new environmental conditions with its sudden changes. A striking example of this is the sudden death of dinosaurs due to the fall of a giant celestial body to Earth 65 million years ago, which caused an earthquake, raising millions of tons of dust into the air, a sharp cold snap, and the death of most of the plants and herbivorous animals. At the same time, the ancestors of modern mammals, having no narrow preferences for food sources and being warm-blooded, were able to survive these conditions and take on a dominant position on the planet.

Hypotheses of the origin of life on Earth

Of the entire spectrum of hypotheses for the formation of the Earth, the largest number of facts testify in favor of the Big Bang theory. In view of the fact that this scientific assumption is based mainly on theoretical calculations, the Large Hadron Collider built at the European Center for Nuclear Research near Geneva (Switzerland) is called upon to confirm it experimentally. According to the Big Bang theory, the Earth was formed over 4.5 billion years ago together with the Sun and other planets of the solar system as a result of the condensation of a gas and dust cloud. The decrease in the temperature of the planet and the migration of chemical elements on it contributed to its stratification into the core, mantle and crust, and the subsequent geological processes (movement of tectonic plates, volcanic activity, etc.) caused the formation of the atmosphere and hydrosphere.

Life has also existed on Earth for a very long time, as evidenced by the fossil remains of various organisms in rocks, but physical theories cannot answer the question of the time and causes of its occurrence. There are two opposite points of view on the origin of life on Earth: the theory of abiogenesis and biogenesis. Theories of abiogenesis assert the possibility of the origin of the living from the non-living. These include creationism, the hypothesis of spontaneous generation and the theory of biochemical evolution by A. I. Oparin.

fundamental position creationism was the creation of the world by a certain supernatural being (Creator), which was reflected in the myths of the peoples of the world and religious cults, however, the age of the planet and life on it far exceeds the dates indicated in these sources, and there are plenty of inconsistencies in them.

Founder theories of spontaneous generation life is considered to be the ancient Greek scientist Aristotle, who argued that the repeated appearance of new creatures is possible, for example, earthworms from puddles, and worms and flies from rotten meat. However, these views were refuted in the 17th-19th centuries by the bold experiments of F. Redi and L. Pasteur.

The Italian physician Francesco Redi in 1688 placed pieces of meat in pots and sealed them tightly, but no worms started in them, while they appeared in open pots. In order to refute the then prevailing belief that the vital principle is contained in the air, he repeated his experiments, but he did not seal the pots, but covered them with several layers of muslin, and again life did not appear. Despite the convincing data obtained by F. Redi, A. van Leeuwenhoek's research provided new food for discussions about the "life beginning", which continued throughout the next century.

Another Italian researcher - Lazzaro Spallanzani - in 1765 modified the experiments of F. Redi, boiling meat and vegetable broths for several hours and sealing them. After a few days, he also did not find any signs of life there and concluded that the living can only arise from the living.

The final blow to the theory of spontaneous generation was dealt by the great French microbiologist Louis Pasteur in 1860, when he placed the boiled broth in a flask with an S-shaped neck and did not receive any germs. It would seem that this testified in favor of the theories of biogenesis, but the question remained open of how the very, very first organism arose.

The Soviet biochemist A. I. Oparin tried to answer it, and he came to the conclusion that the composition of the Earth's atmosphere in the early stages of its existence was not at all the same as in our time. Most likely, it consisted of ammonia, methane, carbon dioxide and water vapor, but did not contain free oxygen. Under the influence of electric discharges of high power and at high temperature, the simplest organic compounds could be synthesized in it, which was confirmed by the experiments of S. Miller and G. Urey in 1953, who obtained several amino acids, simple carbohydrates, adenine, urea, and also the simplest fatty, formic and acetic acids.

Nevertheless, the synthesis of organic substances does not yet mean the emergence of life, therefore A. I. Oparin put forward hypothesis of biochemical evolution, according to which various organic substances arose and combined into larger molecules in the shallow waters of the seas and oceans, where conditions for chemical synthesis and polymerization are most favorable. RNA molecules are currently considered the first carriers of life.

Some of these substances gradually formed stable complexes in water - coacervates, or coacervate drops, resembling drops of fat in the broth. These coacervates received a variety of substances from the surrounding solution, which were subjected to chemical transformations occurring in drops. Like organic substances, coacervates themselves were not living beings, but were the next step in their emergence.

Those of the coacervates that had a good ratio of substances in their composition, especially proteins and nucleic acids, due to the catalytic properties of protein enzymes, over time acquired the ability to reproduce their own kind and carry out metabolic reactions, while the structure of proteins was encoded by nucleic acids.

However, in addition to reproduction, living systems are characterized by dependence on energy from outside. This problem was initially solved by oxygen-free splitting of organic substances from the environment (there was no oxygen in the atmosphere at that time), i.e.

heterotrophic nutrition. Some of the absorbed organic substances turned out to be able to accumulate the energy of sunlight, such as chlorophyll, which made it possible for a number of organisms to switch to autotrophic nutrition. The release of oxygen into the atmosphere during photosynthesis led to the emergence of more efficient oxygen respiration, the emergence of the ozone layer and, ultimately, the release of organisms to land.

Thus, the result of chemical evolution was the appearance protobionts- primary living organisms, from which, as a result of biological evolution, all currently existing species originated.

The theory of biochemical evolution in our time is the most confirmed, but the idea of ​​the specific mechanisms of the origin of life has changed. For example, it turned out that the formation of organic substances begins even in space, and organic substances play an important role even in the very formation of planets, ensuring the adhesion of small parts. The formation of organic matter also occurs in the bowels of the planet: with one eruption, the volcano ejects up to 15 tons of organic matter. There are other hypotheses regarding the mechanisms of concentration of organic substances: solution freezing, absorption (binding) on ​​the surface of certain mineral compounds, the action of natural catalysts, etc. The emergence of life on Earth is currently impossible, since any organic substances spontaneously formed at any point planets would immediately be oxidized by the free oxygen of the atmosphere or used by heterotrophic organisms. Charles Darwin understood this as early as 1871.

Theories of biogenesis deny the spontaneous generation of life. The main ones are the steady state hypothesis and the panspermia hypothesis. The first of them is based on the fact that life exists forever, however, there are very ancient rocks on our planet in which there are no traces of the activity of the organic world.

Panspermia hypothesis claims that the germs of life were brought to Earth from outer space by some aliens or divine providence. Two facts testify in favor of this hypothesis: the need for all living things, which is quite rare on the planet, but often found in meteorites, molybdenum, as well as the discovery of organisms similar to bacteria on meteorites from Mars. However, how life arose on other planets remains unclear.

The main aromorphoses in the evolution of plants and animals

Plant and animal organisms, representing different branches of the evolution of the organic world, in the process of historical development independently acquired certain structural features, which will be described below.

In plants, the most important of these are the transition from haploidy to diploidy, independence from water during fertilization, the transition from external to internal fertilization and the occurrence of double fertilization, the division of the body into organs, the development of the conducting system, the complication and improvement of tissues, and the specialization of pollination with the help of insects and dispersal of seeds and fruits.

The transition from haploid to diploid made plants more resistant to environmental factors due to a reduced risk of recessive mutations. Apparently, this transformation affected the ancestors of vascular plants, which do not include bryophytes, which are characterized by the predominance of the gametophyte in the life cycle.

The main aromorphoses in the evolution of animals are associated with the emergence of multicellularity and the increasing dismemberment of all organ systems, the emergence of a strong skeleton, the development of the central nervous system, as well as social behavior in various groups of highly organized animals, which gave impetus to human progress.

Complication of living organisms in the process of evolution

The history of the organic world on Earth is studied by the preserved remains, prints and other traces of the vital activity of living organisms. She is the subject of science paleontology. Based on the fact that the remains of different organisms are located in different rock layers, a geochronological scale was created, according to which the history of the Earth was divided into certain periods of time: eons, eras, periods and centuries.

aeon called a large period of time in geological history, uniting several eras. Currently, only two eons are distinguished: cryptozoic (hidden life) and phanerosa (manifest life). Era- this is a period of time in geological history, which is a subdivision of an eon, uniting, in turn, periods. In the Cryptozoic, two eras are distinguished (Archaean and Proterozoic), while in the Phanerozoic there are three (Paleozoic, Mesozoic and Cenozoic).

An important role in the creation of the geochronological scale was played by guidance fossils- the remains of organisms that were numerous at certain intervals and well preserved.

Development of life in the cryptozoic. Archean and Proterozoic make up most of the history of life (period 4.6 billion years - 0.6 billion years ago), but there is not enough information about life in that period. The first remains of organic substances of biogenic origin are about 3.8 billion years old, and prokaryotic organisms existed already 3.5 billion years ago. The first prokaryotes were part of specific ecosystems - cyanobacterial mats, due to the activity of which specific sedimentary rocks stromatolites ("stone carpets") were formed.

The discovery of their modern analogues - stromatolites in Shark Bay in Australia and specific films on the soil surface in Sivash Bay in Ukraine - helped to understand the life of ancient prokaryotic ecosystems. Photosynthetic cyanobacteria are located on the surface of cyanobacterial mats, and extremely diverse bacteria of other groups and archaea are located under their layer. Minerals that settle on the surface of the mat and are formed due to its vital activity are deposited in layers (approximately 0.3 mm per year). Such primitive ecosystems can exist only in places unsuitable for the life of other organisms, and indeed, both of the above-mentioned habitats are characterized by extremely high salinity.

Numerous data indicate that at first the Earth had a renewable atmosphere, which included: carbon dioxide, water vapor, sulfur oxide, as well as carbon monoxide, hydrogen, hydrogen sulfide, ammonia, methane, etc. The first organisms of the Earth were anaerobes However, due to the photosynthesis of cyanobacteria, free oxygen was released into the medium, which at first quickly bound to the reducing agents in the medium, and only after the binding of all reducing agents did the medium begin to acquire oxidizing properties. This transition is evidenced by the deposition of oxidized forms of iron - hematite and magnetite.

About 2 billion years ago, as a result of geophysical processes, almost all iron unbound in sedimentary rocks moved to the planet's core, and oxygen began to accumulate in the atmosphere due to the absence of this element - an "oxygen revolution" took place. It was a turning point in the history of the Earth, which entailed not only a change in the composition of the atmosphere and the formation of an ozone screen in the atmosphere - the main prerequisite for the settlement of land, but also the composition of rocks formed on the surface of the Earth.

Another important event took place in the Proterozoic - the emergence of eukaryotes. In recent years, convincing evidence has been collected for the theory of the endosymbiogenetic origin of the eukaryotic cell - through the symbiosis of several prokaryotic cells. Probably, the "main" ancestor of eukaryotes was the archaea, which switched to the absorption of food particles by phagocytosis. The hereditary apparatus moved deep into the cell, retaining, however, its connection with the membrane due to the transition of the outer membrane of the resulting nuclear envelope to the membranes of the endoplasmic reticulum.

Geochronological history of the Earth Aeon Era Period Beginning, million years ago Duration, million years life development Phanerozoic Cenozoic Anthropogenic 1.5 1.5 Four ice ages followed by floods led to the formation of cold-resistant flora and fauna (mammoths, musk oxen, reindeer, lemmings). The exchange of animals and plants between the continents due to the emergence of land bridges. Dominance of placental mammals. Extinction of many large mammals. The formation of man as a biological species and its resettlement. Domestication of animals and cultivation of plants. Disappearance of many species of living organisms due to human activities Neogene 25 23.5 Distribution of cereals. Formation of all modern orders of mammals. Emergence of great apes Paleogene 65 40 Dominance of flowering plants, mammals and birds. The emergence of ungulates, carnivores, pinnipeds, primates, etc. Mesozoic Cretaceous 135 70 The emergence of angiosperms, mammals and birds become numerous Jura 195 60 The era of reptiles and cephalopods. The emergence of marsupials and placental mammals. Dominance of gymnosperms Triassic 225 30 The first mammals and birds. Reptiles are numerous. Distribution of herbaceous spores Paleozoic Perm 280 55 Emergence of modern insects. The development of reptiles. Extinction of a number of groups of invertebrates. Distribution of conifers Carbon 345 65 The first reptiles. The emergence of winged insects. Ferns and horsetails predominate Devon 395 50 Fish are numerous. The first amphibians The emergence of the main groups of spores, the first gymnosperms and fungi Silur 430 35 Abundant algae. The first land plants and animals (spiders). Ordovician 500 70 Ordovician 500 70 Abundant corals and trilobites. The flowering of green, brown and red algae. Emergence of the first chordates Cambrians 570 70 Numerous fish fossils. Sea urchins and trilobites are common. Emergence of multicellular algae by Cryptotose Proterozoic 2600 2000 Emergence of eukaryotes. Mainly unicellular green algae are distributed. The emergence of multicellularity. An outbreak of diversity of multicellular animals (the emergence of all types of invertebrates) Archaea 3500 1500 The first traces of life on Earth are bacteria and cyanobacteria. The emergence of photosynthesis

Bacteria absorbed by the cell could not be digested, but remained alive and continued their functioning. It is believed that mitochondria originate from purple bacteria that have lost the ability to photosynthesize and have switched to the oxidation of organic substances. Symbiosis with other photosynthetic cells led to the emergence of plastids in plant cells. Probably, the flagella of eukaryotic cells arose as a result of symbiosis with bacteria, which, like modern spirochetes, were capable of wriggling movements. At first, the hereditary apparatus of eukaryotic cells was arranged in approximately the same way as in prokaryotes, and only later, due to the need to control a large and complex cell, chromosomes were formed. The genomes of intracellular symbionts (mitochondria, plastids, and flagella) generally retained their prokaryotic organization, but most of their functions were transferred to the nuclear genome.

Eukaryotic cells arose repeatedly and independently of each other. For example, red algae arose as a result of symbiogenesis with cyanobacteria, and green algae - with prochlorophyte bacteria.

The remaining single-membrane organelles and the nucleus of the eukaryotic cell, according to the endomembrane theory, arose from invaginations of the membrane of the prokaryotic cell.

The exact time of the appearance of eukaryotes is unknown, since already in deposits about 3 billion years old there are imprints of cells with similar sizes. Precisely, eukaryotes were recorded in rocks about 1.5–2 billion years old, but only after the oxygen revolution (about 1 billion years ago) did conditions favorable for them develop.

At the end of the Proterozoic era (at least 1.5 billion years ago), multicellular eukaryotic organisms already existed. Multicellularity, like the eukaryotic cell, has repeatedly arisen in different groups of organisms.

There are different views on the origin of multicellular animals. According to some data, their ancestors were multinuclear, similar to ciliates, cells, which then disintegrated into separate single-nuclear cells.

Other hypotheses link the origin of multicellular animals with the differentiation of colonial unicellular cells. The discrepancies between them concern the origin of cell layers in the original multicellular animal. According to E. Haeckel's hypothesis of gastrea, this occurs by invagination of one of the walls of a single-layer multicellular organism, as in intestinal cavities. In contrast, I. I. Mechnikov formulated the phagocytella hypothesis, considering the ancestors of multicellular organisms to be single-layer spherical colonies like Volvox, which absorbed food particles by phagocytosis. The cell that captured the particle lost its flagellum and moved deep into the body, where it carried out digestion, and at the end of the process returned to the surface. Over time, there was a division of cells into two layers with certain functions - the outer one provided movement, and the inner one - phagocytosis. I. I. Mechnikov called such an organism a phagocytella.

For a long time, multicellular eukaryotes lost out in competition with prokaryotic organisms, but at the end of the Proterozoic (800-600 million years ago) due to a sharp change in conditions on Earth - a decrease in sea level, an increase in oxygen concentration, a decrease in the concentration of carbonates in sea water, regular cycles cooling - multicellular eukaryotes gained advantages over prokaryotes. If until that time only individual multicellular plants and, possibly, fungi were found, then from that moment animals are also known in the history of the Earth. Of the faunas that emerged at the end of the Proterozoic, the Ediacaran and Vendian faunas are the best studied. Animals of the Vendian period are usually included in a special group of organisms or attributed to such types as coelenterates, flatworms, arthropods, etc. However, none of these groups have skeletons, which may indicate the absence of predators.

Development of life in the Paleozoic era. The Paleozoic era, which lasted more than 300 million years, is divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous (Carboniferous) and Permian.

AT Cambrian period land consisted of several continents, located mainly in the southern hemisphere. The most numerous photosynthetic organisms during this period were cyanobacteria and red algae. Foraminifera and radiolarians lived in the water column. In the Cambrian, a huge number of skeletal animal organisms appear, as evidenced by numerous fossil remains. These organisms belonged to about 100 types of multicellular animals, both modern (sponges, coelenterates, worms, arthropods, molluscs) and extinct, for example: a huge predator anomalocaris and colonial graptolites that floated in the water column or were attached to the bottom. The land during the Cambrian remained almost uninhabited, but bacteria, fungi and, possibly, lichens had already begun the process of soil formation, and at the end of the period, oligochaete worms and centipedes came to land.

AT Ordovician period The level of the waters of the oceans rose, which led to the flooding of the continental lowlands. The main producers during this period were green, brown and red algae. In contrast to the Cambrian, in which reefs were built by sponges, in the Ordovician they are replaced by coral polyps. The heyday was experienced by gastropods and cephalopods, as well as trilobites (now extinct relatives of arachnids). In this period, chordates, in particular jawless ones, were also recorded for the first time. At the end of the Ordovician, a grandiose extinction occurred, which destroyed about 35% of the families and more than 50% of the genera of marine animals.

Silurian characterized by increased mountain building, which led to the drying of continental platforms. The leading role in the invertebrate fauna of the Silurian was played by cephalopods, echinoderms, and giant crustaceans, while among the vertebrates a wide variety of jawless animals remained and fish appeared. At the end of the period, the first vascular plants, rhinophytes and lycopods, came to land, which began colonization of shallow water and the tidal zone of the coasts. The first representatives of the arachnid class also came to land.

AT Devonian as a result of the uplift of the land, large shallow waters were formed, which dried up and even froze, as the climate became even more continental than in the Silurian. The seas are dominated by corals and echinoderms, while cephalopods are represented by spirally twisted ammonites. Among the Devonian vertebrates, fish reached their peak, and cartilaginous and bone ones, as well as lungfish and lobe-finned ones, replaced the armored ones. At the end of the period, the first amphibians appear, which first lived in the water.

In the Middle Devonian, the first forests of ferns, club mosses and horsetails appeared on land, which were inhabited by worms and numerous arthropods (centipedes, spiders, scorpions, wingless insects). At the end of the Devonian, the first gymnosperms appeared. The development of land by plants has led to a decrease in weathering and an increase in soil formation. Soil fixation led to the emergence of river beds.

AT carboniferous period the land was represented by two continents separated by an ocean, and the climate became noticeably warmer and more humid. By the end of the period, there was a slight uplift of the land, and the climate changed to a more continental one. The seas were dominated by foraminifera, corals, echinoderms, cartilaginous and bony fishes, while freshwater bodies were inhabited by bivalves, crustaceans and various amphibians. In the middle of the Carboniferous, small insectivorous reptiles arose, and winged reptiles (cockroaches, dragonflies) appeared among insects.

The tropics were characterized by swampy forests dominated by giant horsetails, club mosses and ferns, the dead remains of which later formed deposits of coal. In the middle of the period in the temperate zone, due to their independence from water in the process of fertilization and the presence of a seed, the spread of gymnosperms began.

Permian period was distinguished by the merging of all the continents into a single supercontinent Pangea, the retreat of the seas and the strengthening of the continental climate to such an extent that deserts formed in the interior of Pangea. By the end of the period, tree ferns, horsetails and club mosses almost disappeared on land, and drought-resistant gymnosperms occupied a dominant position. Despite the fact that large amphibians still continued to exist, different groups of reptiles arose, including large herbivores and predators. At the end of the Permian, the largest extinction in the history of life occurred, as many groups of corals, trilobites, most cephalopods, fish (primarily cartilaginous and crossopterans), and amphibians disappeared. At the same time, the marine fauna lost 40–50% of families and about 70% of genera.

Development of life in the Mesozoic. The Mesozoic era lasted about 165 million years and was characterized by land uplift, intense mountain building, and a decrease in climate humidity. It is divided into three periods: Triassic, Jurassic and Cretaceous.

At the beginning Triassic period the climate was arid, but later, due to rising sea levels, it became more humid. Gymnosperms, ferns and horsetails predominated among plants, but arboreal forms of spores almost completely died out. Some corals, ammonites, new groups of foraminifers, bivalves and echinoderms have reached a high development, while the diversity of cartilaginous fish has decreased, and groups of bony fish have also changed. The reptiles that dominated the land began to master the aquatic environment, like ichthyosaurs and plesiosaurs. Of the reptiles of the Triassic, crocodiles, tuatara and turtles have survived to our time. At the end of the Triassic, dinosaurs, mammals and birds appeared.

AT jurassic The supercontinent Pangea has split into several smaller ones. Most of the Jura was very humid, and towards the end of the Jura the climate became more arid. The dominant group of plants were gymnosperms, of which sequoias have survived from that time. Mollusks flourished in the seas (ammonites and belemnites, bivalves and gastropods), sponges, sea urchins, cartilaginous and bone fish. Large amphibians almost completely died out in the Jurassic, but modern groups of amphibians (tailed and anurans) and scaly (lizards and snakes) appeared, and the diversity of mammals increased. By the end of the period, the possible ancestors of the first birds, the Archeopteryx, also arose. However, all ecosystems were dominated by reptiles - ichthyosaurs and plesiosaurs, dinosaurs and flying pangolins - pterosaurs.

Cretaceous period got its name in connection with the formation of chalk in the sedimentary rocks of that time. Throughout the Earth, except for the polar regions, there was a persistent warm and humid climate. In this period, angiosperms arose and became widespread, replacing the gymnosperms, which led to a sharp increase in the diversity of insects. In the seas, in addition to mollusks, bony fish, plesiosaurs, a huge number of foraminifera reappeared, the shells of which formed chalk deposits, and dinosaurs prevailed on land. Better adapted to the air, the birds began to gradually replace the flying lizards.

At the end of the period, a global extinction occurred, as a result of which ammonites, belemnites, dinosaurs, pterosaurs and sea lizards, ancient groups of birds, as well as some gymnosperms, disappeared. About 16% of families and 50% of animal genera disappeared from the face of the Earth as a whole. The crisis at the end of the Cretaceous is associated with the fall of a large meteorite into the Gulf of Mexico, but it most likely was not the only cause of global changes. During the subsequent cooling, only small reptiles and warm-blooded mammals survived.

Development of life in the Cenozoic. The Cenozoic era began about 66 million years ago and continues to the present. It is characterized by the dominance of insects, birds, mammals and angiosperms. The Cenozoic is divided into three periods - paleogene, Neogene and Anthropogen - the last of which is the shortest in the history of the Earth.

In the early and middle Paleogene, the climate remained warm and humid, but by the end of the period it became cooler and drier. Angiosperms became the dominant group of plants, however, if at the beginning of the period evergreen forests prevailed, then at the end many deciduous ones appeared, and steppes formed in arid zones.

Among the fish, bony fish occupied a dominant position, and the number of cartilaginous species, despite their significant role in salt water bodies, is insignificant. On land, only scaly, crocodiles and turtles have survived from reptiles, while mammals have occupied most of their ecological niches. In the middle of the period, the main orders of mammals appeared, including insectivores, carnivores, pinnipeds, cetaceans, ungulates and primates. The isolation of the continents made the fauna and flora geographically more diverse: South America and Australia became centers for the development of marsupials, and other continents for placental mammals.

Neogene period. The earth's surface in the Neogene acquired a modern look. The climate became cooler and drier. In the Neogene, all orders of modern mammals had already formed, and in the African shrouds, the Hominid family and the genus Man arose. By the end of the period, coniferous forests spread in the polar regions of the continents, tundras appeared, and grasses occupied the steppes of the temperate zone.

Quaternary period(anthropogen) is characterized by periodic changes of glaciation and warming. During glaciations, high latitudes were covered with glaciers, the level of the ocean dropped sharply, and the tropical and subtropical belts narrowed. A cold and dry climate was established in the territories adjacent to the glaciers, which contributed to the formation of cold-resistant groups of animals - mammoths, giant deer, cave lions, etc. The decrease in the level of the World Ocean that accompanied the glaciation process led to the formation of land bridges between Asia and North America, Europe and the British Isles etc. Animal migrations, on the one hand, led to the mutual enrichment of floras and faunas, and, on the other hand, to the displacement of relics by newcomers, for example, marsupials and ungulates in South America. These processes, however, did not affect Australia, which remained isolated.

In general, periodic climate changes led to the formation of an extremely abundant species diversity, which is characteristic of the current stage of biosphere evolution, and also influenced human evolution. During the Anthropogen, several species of the genus Man spread from Africa to Eurasia. Approximately 200 thousand years ago, the species Homo sapiens arose in Africa, which, after a long period of existence in Africa, about 70 thousand years ago, entered Eurasia and about 35–40 thousand years ago - to America. After a period of coexistence with closely related species, he pushed them out and spread throughout the globe. About 10 thousand years ago, human economic activity in moderately warm regions of the globe began to influence both the appearance of the planet (plowing land, burning forests, overgrazing pastures, desertification, etc.), and the animal and plant world due to the reduction of habitats their habitat and extermination, and the anthropogenic factor came into play.

Human Origins. Man as a species, his place in the system of the organic world. Hypotheses of the origin of man. Driving forces and stages of human evolution. Human races, their genetic relationship. biosocial nature of man. Social and natural environment, human adaptation to it

Human Origins

Even 100 years ago, the vast majority of people on the planet did not even think that a person could come from such “unrespectable” animals as monkeys. In a discussion with one of the defenders of the Darwinian theory of evolution, Professor Thomas Huxley, his ardent opponent, Bishop Samuel Wilberforce of Oxford, who relied on religious dogma, even asked him if he considered himself connected with ape ancestors through a grandfather or grandmother.

Nevertheless, ancient philosophers expressed thoughts about the evolutionary origin, and the great Swedish taxonomist K. Linnaeus in the 18th century, based on the totality of signs, gave a person a species name Homo sapiens L.(reasonable man) and carried him, along with monkeys, to the same detachment - Primates. J. B. Lamarck supported K. Linnaeus and believed that man even had common ancestors with modern apes, but at some point in his history he descended from a tree, which was one of the reasons for the formation of man as a species.

Ch. Darwin also did not ignore this issue and in the 70s of the XIX century published the works “The Origin of Man and Sexual Selection” and “On the Expression of Emotions in Animals and Man”, in which he provided no less convincing evidence of the common origin of man and monkeys, than the German researcher E. Haeckel (“Natural History of Creation”, 1868; “Anthropogenesis, or the History of the Origin of Man”, 1874), who even compiled the genealogy of the animal kingdom. However, these studies concerned only the biological side of the formation of man as a species, while the social aspects were revealed by the classic of historical materialism - the German philosopher F. Engels.

At present, the origin and development of man as a biological species, as well as the diversity of populations of modern man and the patterns of their interaction are studied by science. anthropology.

Man as a species, his place in the system of the organic world

reasonable man ( Homo sapiens) as a biological species refers to the animal kingdom, sub-kingdom of multicellular. The presence of a notochord, gill slits in the pharynx, neural tube and bilateral symmetry in the process of embryonic development allows us to attribute it to the chordate type, while the development of the spine, the presence of two pairs of limbs and the location of the heart on the ventral side of the body indicate its relationship with other representatives of the vertebrate subtype.

The feeding of young with milk secreted by the mammary glands, warm-bloodedness, a four-chambered heart, the presence of hair on the surface of the body, seven vertebrae in the cervical spine, the vestibule of the mouth, alveolar teeth and the change of milk teeth to permanent ones are signs of the class of mammals, and the intrauterine development of the embryo and its relationship with the mother's body through the placenta - a subclass of placental.

More specific features, such as grasping limbs with opposable thumbs and fingernails, the development of clavicles, forward-facing eyes, an increase in the size of the skull and brain, and the presence of all groups of teeth (incisors, canines and molars) leave no doubt that that his place is in the order of primates.

Significant development of the brain and facial muscles, as well as structural features of the teeth, make it possible to classify a person as a suborder of higher primates, or monkeys.

The absence of a tail, the presence of curves of the spine, the development of the cerebral hemispheres, covered with a bark with numerous furrows and convolutions, the presence of the upper lip and the sparseness of the hairline give reason to place it among the representatives of the family of higher narrow-nosed, or anthropoid apes.

However, even the most highly organized human monkeys are distinguished by a sharp increase in the volume of the brain, upright posture, a wide pelvis, a protruding chin, articulate speech, and the presence of 46 chromosomes in the karyotype and determine its belonging to the genus Man.

The use of the upper limbs for labor activity, the manufacture of tools, abstract thinking, collective activity and development based on social rather than biological laws are the species characteristics of Homo sapiens.

All modern people belong to the same species - Homo sapiens ( Homo sapiens), and subspecies H. sapiens sapiens. This species is a collection of populations that produce fertile offspring when crossed. Despite the rather significant variety of morphophysiological features, they are not evidence of a higher or lower degree of organization of certain groups of people - they are all at the same level of development.

In our time, a sufficient number of scientific facts have already been collected in the interests of the formation of man as a species in the process of evolution - anthropogenesis. The specific course of anthropogenesis has not yet been fully elucidated, but thanks to new paleontological findings and modern research methods, we can hope that a clear picture will appear quite soon.

Hypotheses of the origin of man

If we do not take into account the non-biological hypotheses of the divine creation of man and his penetration from other planets, then all more or less consistent hypotheses of the origin of man trace him to common ancestors with modern primates.

So, hypothesis of the origin of man from the ancient tropical primate tarsier, or tarsial hypothesis, formulated by the English biologist F. Wood Jones in 1929, is based on the similarity of the proportions of the bodies of humans and tarsiers, the features of the hairline, the shortening of the facial section of the latter's skull, etc. However, the differences in the structure and vital activity of these organisms are so great that it did not win universal recognition.

With anthropoid apes, humans even have too many similarities. So, in addition to the anatomical and morphological features already mentioned above, attention should be focused on their postembryonic development. For example, little chimpanzees have much thinner hair, a much larger brain-to-body ratio, and slightly better hind-limbed locomotion than adults. Even puberty in higher primates occurs much later than in representatives of other orders of mammals with similar body sizes.

In the course of cytogenetic studies, it was revealed that one of the human chromosomes was formed as a result of the fusion of chromosomes of two different pairs present in the karyotype of great apes, and this explains the difference in the number of their chromosomes (in humans 2n = 46, and in large great apes 2n = 48 ), and is also another evidence of the relationship of these organisms.

The similarity between humans and great apes is also very high in terms of molecular biochemical data, since humans and chimpanzees have the same ABO and Rhesus blood group proteins, many enzymes, and the amino acid sequences of hemoglobin chains have only 1.6% differences, while this discrepancy with other monkeys a few more. And at the genetic level, differences in DNA nucleotide sequences between these two organisms are less than 1%. If we take into account the average rate of evolution of such proteins in related groups of organisms, it can be determined that human ancestors separated from other groups of primates about 6–8 million years ago.

The behavior of monkeys in many ways resembles that of humans, as they live in groups in which social roles are clearly distributed. Joint protection, mutual assistance and hunting are not the only goals for creating a group, since inside it monkeys feel affection for each other, express it in every possible way, and emotionally react to various stimuli. In addition, in groups there is an exchange of experience between individuals.

Thus, the similarity of man with other primates, especially the higher narrow-nosed monkeys, is found at different levels of biological organization, and the differences between man as a species are largely determined by the characteristics of this group of mammals.

The group of hypotheses that do not question the origin of man from common ancestors with modern great apes include the hypotheses of polycentrism and monocentrism.

starting position hypotheses of polycentrism is the emergence and parallel evolution of the modern type of man in several regions of the globe at once from different forms of ancient or even ancient man, but this contradicts the basic provisions of the synthetic theory of evolution.

The hypotheses of the single origin of modern man, on the contrary, postulate the emergence of man in one place, but differ in where this happened. So, hypothesis of extratropical origin of man is based on the fact that only the harsh climatic conditions of the high latitudes of Eurasia could contribute to the "humanization" of monkeys. In its favor was the discovery on the territory of Yakutia of sites from the time of the most ancient Paleolithic - the Diringa culture, but later it was established that the age of these finds is not 1.8-3.2 million years, but 260-370 thousand years. Thus, this hypothesis is also insufficiently confirmed.

Most of the evidence to date is in favor of African origin hypotheses, but it is not without shortcomings, which is designed to take into account the integrated broad monocentrism hypothesis, which combines the arguments of the hypotheses of polycentrism and monocentrism.

Driving Forces and Stages in Human Evolution

Unlike other representatives of the animal world, man in the course of his evolution was exposed not only to biological factors of evolution, but also to social factors, which contributed to the emergence of a species of qualitatively new creatures with biosocial properties. Social factors led to a breakthrough into a fundamentally new adaptive environment, which gave huge advantages for the survival of human populations and dramatically accelerated the pace of its evolution.

The biological factors of evolution that play a certain role in anthropogenesis to this day are hereditary variability, as well as the flow of genes that supply the primary material for natural selection. At the same time, isolation, population waves and genetic drift have almost completely lost their significance as a result of scientific and technological progress. This gives reason to some scientists to believe that in the future even minimal differences between representatives of different races will disappear due to their mixing.

Since the change in environmental conditions forced the human ancestors to descend from the trees into the open space, and switch to movement on two limbs, the released upper limbs were used by them to carry food and children, as well as to make and use tools. However, it is possible to make such a tool only if there is a clear idea of ​​the final result - the image of the object, therefore, abstract thinking also developed. It is well known that complex movements and thinking processes are necessary for the development of certain areas of the cerebral cortex, which happened in the process of evolution. However, it is impossible to inherit such knowledge and skills, they can only be transferred from one individual to another throughout the life of the latter, which resulted in the creation of a special form of communication - articulate speech.

Thus, human labor activity, abstract thinking and articulate speech should be attributed to the social factors of evolution. We should not discard the manifestations of altruism of primitive man, who cared for children, women and the elderly.

The labor activity of a person not only influenced the appearance of himself, but also made it possible at first to partially alleviate the conditions of existence through the use of fire, the manufacture of clothing, the construction of housing, and later actively change them through deforestation, plowing, etc. In our time, uncontrolled economic activity has put humanity in front of a global catastrophe as a result of soil erosion, drying up of freshwater reservoirs, destruction of the ozone screen, which, in turn, can increase the pressure of biological factors of evolution.

Dryopithecus, who lived about 24 million years ago, most likely was the common ancestor of humans and great apes. Despite the fact that he climbed trees and ran on all four limbs, he could move on two legs, and carry food in his hands. The complete separation of the higher apes and the line leading to man occurred about 5–8 million years ago.

Australopithecus. From dryopithecus, apparently, the genus ardipithecus, which was formed over 4 million years ago in the savannahs of Africa as a result of cooling and forest retreat, which forced these monkeys to switch to moving on their hind limbs. This small animal, apparently, gave rise to a rather numerous genus australopithecines("southern monkey").

Australopithecus appeared about 4 million years ago and lived in the African savannas and dry forests, where the advantages of bipedal movement were fully affected. Two branches went from Australopithecus - large herbivores with powerful jaws paranthropes and smaller and less specialized people. For a certain time, these two genera developed in parallel, which, in particular, manifested itself in an increase in the volume of the brain, and the complication of the tools used. The peculiarities of our genus are the manufacture of stone tools (paranthropus used only bone) and a relatively large brain.

The first representatives of the genus Man appeared about 2.4 million years ago. They belonged to the kind of man of skill (Homo habilis) and were short creatures (about 1.5 m) with a brain volume of approximately 670 cm 3 . They used crude pebble tools. Apparently, the representatives of this species had well-developed facial expressions and had rudimentary speech. A skilled man left the historical scene about 1.5 million years ago, giving rise to the following species - upright man.

Straight man (H. erectus) as a biological species formed in Africa about 1.6 million years ago and existed for 1.5 million years, quickly spreading over vast territories in Asia and Europe. A representative of this species from the island of Java was once described as Pithecanthropus("monkey-man"), discovered in China, was called Sinanthropus, while their European "colleague" is heidelberg man.

All these forms are also called archanthropes(earliest people). The straight man was distinguished by a low forehead, large superciliary arches and a chin sloping back, his brain volume was 900-1200 cm 3. The torso and limbs of a straightened man resembled those of modern man. Without a doubt, representatives of this genus used fire and made double-edged axes. As recent finds have shown, this species even mastered navigation, for its descendants were found on remote islands.

Paleoanthropist. About 200 thousand years ago, from the Heidelberg man came Neanderthal Man (H. neandertalensis), which is attributed to paleoanthropists(ancient people) who lived in Europe and Western Asia within 200-28 thousand years ago, including during the epoch of glaciation. They were strong, physically quite strong and hardy people with a large brain volume (even larger than that of a modern person). They had articulate speech, made complex tools and clothes, buried their dead, and may even have had some rudiments of art. Neanderthals were not the ancestors of Homo sapiens, this group developed in parallel. Their extinction is associated with the disappearance of the mammoth fauna after the last glaciation, and may also be the result of competitive displacement by our species.

The oldest find of a representative Homo sapiens (homo sapiens) is 195 thousand years old and comes from Africa. Most likely, the ancestors of modern man are not Neanderthals, but some form of archanthropes, such as Heidelberg man.

Neoanthrope. About 60 thousand years ago, as a result of unknown events, our species almost died out, so all the following people are descendants of a small group that numbered only a few dozen individuals. Having overcome this crisis, our species began to spread across Africa and Eurasia. It differs from other species in its more slender physique, higher reproduction rate, aggressiveness and, of course, the most complex and most flexible behavior. People of the modern type who inhabited Europe 40 thousand years ago are called Cro-Magnons and refer to neoanthropes(modern people). They did not differ biologically from modern people: height 170–180 cm, brain volume about 1600 cm3. The Cro-Magnon people developed art and religion, they domesticated many types of wild animals and cultivated many types of plants. Cro-Magnons are descended from modern humans.

Human races, their genetic relationship

During the settlement of mankind on the planet between different groups of people, certain discrepancies arose regarding skin color, facial features, the nature of the hair, as well as the frequencies of occurrence of certain biochemical characteristics. The totality of such hereditary traits characterizes a group of individuals of the same species, the differences between which are less significant than subspecies - race.

The study and classification of races is complicated by the lack of clear boundaries between them. All modern humanity belongs to one species, within which there are three large races: Australo-Negroid (black), Caucasoid (white) and Mongoloid (yellow). Each of them is divided into small races. Differences between races come down to features of skin color, hair, nose shape, lips, etc.

Australo-Negroid, or equatorial race characterized by dark skin color, wavy or curly hair, a wide and slightly protruding nose, transverse nostrils, thick lips, and a number of cranial features. Caucasoid, or Eurasian race characterized by light or dark skin, straight or wavy soft hair, good development of hair on the face of men (beard and mustache), a narrow protruding nose, thin lips and a number of cranial features. Mongoloid(Asian American) race characterized by dark or fair skin, often coarse hair, medium width of the nose and lips, flattening of the face, strong protrusion of the cheekbones, relatively large face size, noticeable development of the "third eyelid".

These three races also differ in settlement. Prior to the era of European colonization, the Australo-Negroid race was common in the Old World south of the Tropic of Cancer; Caucasian race - in Europe, North Africa, Western Asia and North India; Mongoloid race - in Southeast, North, Central and East Asia, Indonesia, North and South America.

However, the differences between races concern only minor features that have adaptive significance. Thus, the skin of Negroids gets burned at a tenfold higher dose of ultraviolet radiation than the skin of Caucasians, but Caucasians suffer less from rickets in high latitudes, where there may be a shortage of ultraviolet radiation necessary for the formation of vitamin D.

Previously, some people sought to prove the perfection of one of the races in order to gain a moral edge over others. It is now clear that racial characteristics reflect only different historical paths of groups of people, but have nothing to do with the advantage or biological backwardness of one or another group. Human races are less clearly defined than the subspecies and races of other animals, and cannot be compared in any way, for example, with breeds of domestic animals (which are the result of purposeful selection). As biomedical studies show, the consequences of interracial marriage depend on the individual characteristics of a man and a woman, and not on their race. Therefore, any prohibitions against interracial marriages or certain superstitions are unscientific and inhumane.

More specific than races, groups of people are nationalities- historically formed linguistic, territorial, economic and cultural communities of people. The population of a particular country forms its people. With the interaction of many nationalities, a nation can arise as part of a people. Now on Earth there are no "pure" races, and each sufficiently large nation is represented by people who belong to different races.

Biosocial nature of man

Undoubtedly, man as a biological species must be under the pressure of evolutionary factors such as mutagenesis, population waves and isolation. However, as human society develops, some of them weaken, while others, on the contrary, increase, because on the planet captured by the processes of globalization, there are almost no isolated human populations in which closely related crossings are carried out, and the number of populations themselves is not subject to sharp fluctuations. Accordingly, the driving factor of evolution - natural selection - thanks to the successes of medicine, no longer plays the role in human populations that is characteristic of it in populations of other organisms.

Unfortunately, the weakening of selection pressure leads to an increase in the frequency of hereditary diseases in populations. For example, in industrialized countries, up to 5% of the population suffer from color blindness (color blindness), while in less developed countries this figure is up to 2%. The negative consequences of this phenomenon can be overcome through preventive measures and progress in such areas of science as gene therapy.

However, this does not mean that human evolution has ended, since natural selection continues to act, eliminating, for example, gametes and individuals with unfavorable combinations of genes even at the pre-embryonic and embryonic periods of ontogenesis, as well as resistance to pathogens of various diseases. In addition, the material for natural selection is supplied not only by the mutation process, but also by the accumulation of knowledge, the ability to learn, the perception of culture and other traits that can be transmitted from person to person. Unlike genetic information, the experience accumulated in the process of individual development is transmitted both from parents to descendants and vice versa. And competition already arises between communities that differ culturally. This form of evolution, peculiar exclusively to man, is called cultural, or social evolution.

However, cultural evolution does not exclude biological evolution, since it became possible only due to the formation of the human brain, and human biology itself is currently determined by cultural evolution, since in the absence of society and a variety of movements, certain zones do not form in the brain.

Thus, a person has a biosocial nature, which leaves an imprint on the manifestation of biological, including genetic patterns, to which his individual and evolutionary development is subject.

Social and natural environment, human adaptation to it

Under social environment understand, first of all, the social material and spiritual conditions surrounding a person for his existence and activity. In addition to the economic system, social relations, social consciousness and culture, it also includes the immediate environment of a person - the family, work and student teams, as well as other groups. The environment, on the one hand, has a decisive influence on the formation and development of the personality, and on the other hand, it itself changes under the influence of a person, which entails new changes in people, etc.

Adaptation of individuals or their groups to the social environment for the realization of their own needs, interests, life goals and includes adaptation to the conditions and nature of study, work, interpersonal relationships, ecological and cultural environment, leisure and life conditions, as well as their active change for satisfaction of their needs. A big role in this is played by a change in oneself, one's motives, values, needs, behavior, etc.

Information loads and emotional experiences in modern society are often the main cause of stress, which can be overcome with the help of clear self-organization, physical training and auto-training. In some, especially severe cases, an appeal to a psychotherapist is required. An attempt to find oblivion of these problems in overeating, smoking, drinking alcohol and other bad habits does not lead to the desired result, but only aggravates the condition of the body.

The natural environment has no less influence on a person, despite the fact that a person has been trying to create a comfortable artificial environment for himself for about 10 thousand years. Thus, climbing to a considerable height due to a decrease in the concentration of oxygen in the air leads to an increase in the number of red blood cells in the blood, increased respiration and heart rate, and prolonged exposure to the open sun contributes to increased skin pigmentation - sunburn. However, these changes are within the norm of the reaction and are not inherited. However, peoples living in such conditions for a long time may have some adaptations. So, among the northern peoples, the nasal sinuses have a much larger volume to warm the air, and the size of the protruding parts of the body decreases to reduce heat loss. Africans are distinguished by darker skin color and curly hair, since the pigment melanin protects the organs of the body from the penetration of harmful ultraviolet rays, and the hair cap has thermal insulating properties. The light eyes of Europeans are an adaptation to a more acute perception of visual information at dusk and in fog, and the Mongoloid eye shape is the result of natural selection for the action of winds and dust storms.

These changes require centuries and millennia, but life in a civilized society entails some changes. Thus, a decrease in physical activity leads to simplification of the skeleton and a decrease in its strength, a decrease in muscle mass. Low mobility, an excess of high-calorie foods, stress lead to an increase in the number of overweight people, and high-grade protein nutrition and the continuation of daylight hours with the help of artificial lighting contribute to acceleration - accelerating growth and puberty, increasing body size.

1. Heredity is the property of organisms to transmit structural features and

life from generation to generation.

2. The material foundations of heredity are chromosomes and genes, which store information about the characteristics of an organism. Transfer of genes and chromosomes from generation to generation

thanks to reproduction. Development of a daughter organism from one cell - a zygote

or groups of cells of the mother's organism in the process of reproduction. Localization in

nuclei of cells involved in reproduction, genes and chromosomes that determine

the similarity of the daughter organism with the parent.

3. Heredity is a factor in evolution, the basis of the similarity of parents and offspring, individuals of the same species.

4. Variability is a common property of all organisms to acquire new features in the process of individual development.

5. Types of variability: non-hereditary (modification) and hereditary (combinative, mutational).

6. Non-inherited changes are not associated with changes

genes and chromosomes, are not inherited, arise under the influence of factors

external environment, disappear with time. The manifestation of similar modification

changes in all individuals of the species (for example, in the cold in horses, wool becomes

thicker). The disappearance of modification changes upon termination of the factor,

that caused this change (sunburn disappears in winter, when conditions worsen

modification variability: the appearance of a tan in the summer, an increase in body weight

animals with good feeding and maintenance, the development of certain muscle groups

when playing sports.

7. Hereditary changes are due to changes

genes and chromosomes, are inherited, differ in individuals within

of the same species, persist throughout the life of the individual.

8. Combination variability. Manifestation

combinative variability during crossing, its conditionality by the appearance of new

combinations (combinations) of genes in offspring. Sources of combinative

variability: exchange of sites between homologous chromosomes, random

the combination of germ cells during fertilization and the formation of a zygote. Diverse

combinations of genes - the reason for the recombination (new combination) of parental

traits in offspring.

9. Mutations are sudden, persistent changes.

genes or chromosomes. The result of mutations is the appearance of new traits in the child

organisms that were absent from his parents, such as short legs in

sheep, lack of plumage in chickens, albinism (lack of pigment). useful,

harmful and neutral mutations. The harm of most mutations for the body

due to the manifestation of new signs that do not correspond to its habitat.

10. Hereditary variability is a factor in evolution.

The emergence of new features in organisms and their diversity is the material for

actions of natural selection, preservation of individuals with changes,

corresponding to the environment, the formation of the adaptability of organisms to

changing environmental conditions.

2. Natural and artificial ecosystems, their features.

1. Ecosystem - a collection of living organisms of different species, interconnected

and with the components of inanimate nature by the metabolism and transformation of energy into

certain area of ​​the biosphere.

2. Ecosystem structure:

Species - the number of species living in the ecosystem and

the ratio of their numbers. Example: about 30 species growing in a coniferous forest

plants, in an oak forest - 40-50 species, in a meadow - 30-50 species, in a wet

tropical forest - over 100 species;

Spatial - the placement of organisms in

vertical (tiered) and horizontal (mosaic) directions. Examples:

the presence in the broad-leaved forest of 5-6 tiers; differences in plant composition

the edge and in the thicket of the forest, in dry and moist areas.

3. Community components: abiotic and biotic.

Abiotic components of inanimate nature - light, pressure, humidity, wind,

relief, soil composition, etc. Biotic components: organisms - producers,

consumers and destroyers.

4. Producers - plants and some bacteria,

creating organic substances from inorganic using energy

sunlight.

5. Consumers - animals, some plants and

bacteria that feed on ready-made organic substances and use

6. Destroyers - fungi and some bacteria,

destroying organic matter to inorganic, feeding on corpses,

plant residues.

7. The cycle of matter and the transformation of energy -

a necessary condition for the existence of any ecosystem. The transfer of matter and energy in

food chains in an ecosystem.

8. Ecosystem sustainability. Resilience dependency

ecosystems on the number of species living in them and the length of food chains: the more

species, food chains, the more stable the ecosystem from the cycle of substances.

9. Artificial ecosystem - created as a result

human activities. Examples of artificial ecosystems: park, field, garden,

10. Differences between an artificial ecosystem and a natural one:

A small number of species (e.g. wheat and some

weed species in a wheat field and related animals)

Predominance of organisms of one or more species

(wheat in the field);

Short food chains due to the small number of species;

Unclosed circulation of substances due to

significant removal of organic substances and their removal from the circulation in the form of

Low stability and inability to

independent existence without human support.

TICKET#12

Living organisms are capable of "compensatory phenotypic modifications", i.e. such lifetime changes that compensate for the effects of various injuries (regeneration is a typical example). This ability, which arises in the course of evolution, can itself influence further evolution, since compensatory modifications arise not only in response to injuries, but also in response to mutations that disrupt the normal course of development of the organism. Compensatory modifications can promote the perpetuation of such mutations, leading to rapid evolutionary changes.

Two kinds of variability. Biological evolution is based on the famous "Darwinian triad": heredity, variability and selection. Today, behind each of these three concepts are well-developed, complex and highly detailed theories, supported by countless facts, experiments and observations. These theories are not static at all: they continue to evolve rapidly as new data (as well as older insights) become available.

With regard to variability, the main focus of evolutionary biology has traditionally been on so-called hereditary (i.e., genetically determined) variability. Hereditary variability is determined by differences in the genotype of individuals, it is transmitted from parents to offspring, and natural selection directly “works” with it. However, there is also the so-called modification variability, which is not hereditary in the strict sense of the word. Modification variability is a change in the structure (phenotype) that occurs in response to changes in the conditions in which the development of the organism takes place (one of the striking examples, see the note "A caterpillar that changes color when heated" has been bred. "Elements", 9.02.06).

Modification variability is one of those natural phenomena that seem to exist on purpose in order to confuse theorists. An erroneous understanding of the nature of modification variability and its causal relationships with the evolutionary process in the past often led to various misunderstandings and inadequate conclusions. Currently, the following key provisions are generally recognized:

• The genotype determines not the phenotype as such, but the norm of the reaction: a certain range of developmental possibilities. Which of these possibilities will be realized depends no longer on genes, but on the conditions in which the development of the organism will take place. Variations in the phenotype within the norm of the reaction - this is the modification variability.
• Modifications are not inherited (they are not "recorded" in the genes), however ability to them, of course, is inherited, i.e. is genetically determined.
• Modification variability is often expedient (adaptive). For example, tanning from the sun's rays protects us from the harmful effects of ultraviolet radiation. However, the ability to adaptive modifications did not fall on us from the sky. There is nothing mystical about it, it is not a manifestation of some incomprehensible "internal expediency of nature" or the result of the intervention of supernatural forces. The ability for adaptive modifications develops under the influence of selection, on the basis of fixing certain hereditary changes (mutations), just like any other adaptive properties of an organism.
• The ability for modification variability, on the one hand, is the result of evolution, on the other hand, it can itself have a significant impact on evolution. In the article under discussion by N.N. Iordansky, it is precisely one of the aspects of this influence that is discussed.

The evolutionary role of modification variability. Already at the end of the 19th century, some biologists began to think about the fact that the ability to modify variability that arises in the course of evolution (in the broad sense, including the ability to change behavior, learning, etc. in life) can have an inverse effect on the course of the evolutionary process, moreover the nature of this influence may be different.

On the one hand, the ability to adaptive modifications can slow down evolution. If an organism, without changing its genotype, can adapt to different conditions of existence during its life, this can lead to a weakening of the effect of selection when the latter change.

On the other hand, this ability may partly predetermine further paths of evolutionary transformations. If conditions have changed “seriously and for a long time”, so that organisms from generation to generation have to undergo the same modification transformations in the course of their development, this can lead to the fact that mutations leading to a rigid genetic “fixation” of these transformations will be supported. selection, and then the modification will turn into a hereditary change. In this case, the illusion of Lamarck's "inheritance of an acquired trait" may arise. This phenomenon is known as the "Baldwin effect" (see about it in the note "Genes control behavior, and behavior - genes". "Elements", 12.11.08). In this way, for example, some skill acquired by an animal during its life as a result of training can eventually turn into a hereditary instinct. In addition, a new behavior - no matter if it is instinctive or “conscious”, the main thing is that this behavior is reproduced for many generations - creates new selection vectors and can lead to the fixation of mutations that “make life easier” precisely with this behavior. For example, the development of animal husbandry has led to the spread of a specific mutation in “livestock” human populations that allows adults to digest the milk sugar lactose (initially, people had this ability only in infancy). Again we see the illusion of Lamarckian inheritance: our ancestors "trained" for a long time to drink milk as adults, and eventually the "results of training" became hereditary. In fact, of course, the mechanism of this evolutionary change is completely different: the changed behavior (drinking milk of domestic animals) has led to the fact that periodically occurring mutations that disable the mechanism for shutting down (in order to save) the synthesis of the lactase enzyme in adults have ceased to be harmful and have, on the contrary, become useful. People with this mutation ate better and left more offspring. Therefore, these mutations began to spread in the population in strict accordance with the laws of population genetics.

As early as the beginning of the 20th century, it was established that for almost any modification one can find a mutation that will lead to similar phenotypic consequences, only now strictly determined, not dependent on external conditions. This is called "genocopying modifications". As N.N. Iordansky notes, this is not surprising in essence. The genotype determines the "reaction rate", i.e. a set of possible ways of individual development. If there are such variants of external conditions that lead to the choice of one of these paths, then there may be such mutations that will make this path the only possible (or most probable) regardless of external conditions. Ultimately, modifications are due to a change in the activity (expression) of certain genes in certain cells of the body. It is well known that changes in gene expression can be caused by both fluctuations in environmental conditions and mutations. The evolutionary significance of "genecopying modifications" is discussed at length in the works of Waddington, Kirpichnikov, Shishkin, and other evolutionists; these ideas are used in Schmalhausen's theory of stabilizing selection; an attempt has even been made to formulate on this basis a special "epigenetic theory of evolution".

compensatory modifications. N.N. Iordansky draws attention to a special group of adaptive modifications, namely, compensatory reactions of organisms to various violations of ontogenesis processes and traumatic injuries of adult organisms. For example, many cases have been described in which an amphibian, reptile, bird, or mammal lost one of its limbs, but compensated for the consequences of the injury through a change in behavior and safely produced offspring from year to year. Many times, fish have been observed that have completely lost their tail fin (sometimes along with part of the spine), but at the same time are in good physical shape. In such fish, the dorsal and anal fins often grow back, which form around the damaged area a kind of dorsal and ventral lobes of the caudal fin.

This suggests that in natural biocenoses the struggle for existence and selection are not always so cruel. In any case, selective "survival of the fittest" is a statistical process, and injured individuals often have a chance of surviving and even reproducing.

The main idea of ​​N.N. Iordansky's article is that the ability for compensatory modifications can lead to rapid evolutionary transformations due to the fact that the effect of many harmful mutations can be smoothed out due to compensatory modifications. As a result, such mutations can sometimes persist and even spread in a population. The fact is that compensatory modifications can compensate not only for injuries, but also for the consequences of harmful mutations.

Imagine that a fish has a mutation that prevents it from developing a tail fin. It is quite possible that during the ontogeny of such a fish, the same mechanism of compensatory modification will be activated, which is activated when the tail is lost as a result of an injury. In other words, the dorsal and anal fins will begin to grow back and form a kind of lost caudal fin. Of course, this will lead to a serious change in the structure of the fish. But this change need not be wholly incompatible with life, because it is based on a "desirable" compensatory modification, the capacity for which has been honed by selection in millions of previous generations of fish.

Perhaps it was in this way that the moonfish and its relatives arose, in which the structure of the fins is very similar to that obtained in other fish as a result of the traumatic loss of the caudal fin.

Thus, the ability to make compensatory modifications increases the likelihood of fixing large mutations, the evolutionary significance of which is usually considered extremely insignificant (because the probability that a large mutation will be beneficial or even not very harmful) is extremely small. However, taking into account compensatory modifications forces us to reconsider this estimate of probabilities.

N.N. Iordansky emphasizes that the idea he proposes is not an argument in favor of the so-called. saltationist model of evolution. Saltationists see saltations (jump-like structural changes) as the main mechanism of evolution, which ensures the emergence of evolutionary innovations without the participation of selection. In contrast, N.N. Iordansky suggests that large changes in the body that have arisen through mutations “along with more frequently occurring small variations can serve as elementary evolutionary material from which, under the influence of selection, new adaptations and new types of organization are formed” .

It should be noted that the evolutionary role of compensatory mechanisms (including various negative feedbacks) is clearly manifested at the molecular genetic level as well. This is reflected in the concept of "evolutionary swing", developed by N.A. Kolchanov and his colleagues from the Novosibirsk Institute of Cytology and Genetics (see: N.A. Kolchanov, V.V. Suslov, K.V. Gunbin. Modeling of biological evolution: Regulatory genetic systems and coding for the complexity of biological organization). According to the researchers, in the networks of intergenic interactions, as a result of the action of stabilizing selection, under relatively constant conditions, the development of compensating mechanisms based on the principle of negative feedback occurs. In essence, these mechanisms provide the ability for compensatory modifications at the molecular level. They make the system more stable, better able to compensate for fluctuations in external conditions. But the development of compensatory mechanisms also leads to the fact that many mutations that could turn out to be harmful and unbalance the system do not really do any harm, because their effects are compensated in the same way as external influences. As a result, such mutations are not eliminated by selection and can accumulate. This continues until some very large changes (for example, a transition to a new habitat) disable the compensating mechanisms - and then "hidden" mutations can suddenly appear, which will lead to an explosive increase in the variability of organisms.

Thus, the ability to compensatory modifications that arises in the course of evolution is an important factor guiding (limiting, “channelling”) possible paths for further evolution.