A History of Evolutionary Conceptions Before Darwin. The theory of evolutionary development. Aristotle and organic evolution
11.1. BecomingideasdevelopmentvbiologyEvolutionarytheoryandhermeaning
It is impossible to understand the essence of life as a specific form of motion of matter without studying the theories of biological evolution. When a scientist uses the term "evolution" in relation to biological processes and phenomena, then most often he means a process of long and gradual changes that lead to fundamental qualitative changes in living organisms, accompanied by the emergence of new biological systems, forms and species.
The evolutionary theory, created on the basis of the historical method, whose task is to study the factors, driving forces and laws of organic evolution, rightfully occupies a central place in the system of the sciences of living nature. It is a generalizing biological concept. There are practically no branches of biology for which evolutionary theory would not provide methodological principles of research. For this reason, evolutionary biology is one of the three most important directions in the development of biological science.
Historydevelopmentevolutionaryideas
The development of evolutionary ideas in biology has a fairly long history. The beginning of the consideration of the issues of the evolution of the organic world was laid back in ancient philosophy and continued for more than two thousand years, until the first independent biological disciplines arose in the science of modern times. The main content of this period is the collection of information about the organic world, as well as the formation of two main points of view explaining the diversity of species in wildlife.
The first of them arose on the basis of ancient dialectics, which affirmed the idea of development and change of the surrounding world. Second
The paradise point of view appeared along with the Christian worldview based on the ideas of creationism. At that time, the idea dominated in the minds of many scientists that God created the entire world around us, including all types of life that have existed since then in an unchanged form.
Throughout the initial stage of the development of the evolutionary idea, there was a constant struggle between these two points of view, and the creationist version had a serious advantage. After all, naively transformist ideas about the spontaneous generation of living beings and the emergence of complex organisms through a random combination of individual organs, in which non-viable combinations die out, and successful ones remain (Empedocles), a sudden transformation of species (Anaximenes), etc. cannot even be regarded as a prototype of an evolutionary approach to the cognition of living nature.
Nevertheless, during this period, a number of valuable ideas were expressed, necessary for the approval of the evolutionary approach. Among them, the conclusions of Aristotle were of particular importance, who in his work "On the parts of animals" noted that nature gradually passes from inanimate objects to plants, and then to animals, and this transition goes on continuously. Unfortunately, Aristotle did not speak about the development of nature in its modern understanding, but about the fact that at the same time a number of juxtaposed living forms, devoid of a genetic connection, coexist. Therefore, first of all, his idea of the “ladder of living beings” is valuable, showing the existence of organisms of varying degrees of complexity - the emergence of evolutionary theories would have been impossible without realizing this fact.
Interest in biology increased markedly in the era of the great geographical discoveries. Intensive trade and the discovery of new lands expanded knowledge of animals and plants. The need to streamline the rapidly accumulating knowledge led to the need for their systematization and the appearance of the first classifications of species, among which a special place belongs to the classification of K. Linnaeus. In his ideas about living nature, Linnaeus proceeded from the idea of the immutability of species. But in the same XVIII century. other ideas appeared related to the recognition not only of gradation, but also of the gradual complication of organic forms. These views became known as transformism, and many famous scientists of that time belonged to this direction. All transformists recognized the changeability of species of organisms under the influence of environmental changes, but most of them did not yet have a holistic and consistent concept of evolution.
This is how the concept of evolution as a long-term process was first used in the works of the Swiss biologist Charles Bonnet.
gradual change leading to the emergence of new species. However, in the works of most scientists of that time, the ideas of the gradation of living beings and the idea of evolution existed separately. They were formed into a unified theory only in the 19th century, when the evolutionary theory of J. B. Lamarck appeared.
ConceptdevelopmentF. B. Lamarck
The first attempt to construct a holistic concept of the development of the organic world was undertaken by the French naturalist J. B. Lamarck. In his work "Philosophy of Zoology" Lamarck summarized all biological knowledge of the early 19th century. He developed the foundations of the natural taxonomy of animals and for the first time substantiated a holistic theory of the evolution of the organic world, the progressive historical development of plants and animals.
To create an evolutionary theory, it was necessary to answer the following questions: "What is the basic unit of evolution?", "What are the factors and driving forces of evolution?"
The evolutionary theory was based on Lamarck's idea of development, gradual and slow, from simple to complex, taking into account the role of the external environment in the transformation of organisms. Lamarck believed that the first spontaneous organisms gave rise to the whole variety of existing organic forms. By this time, the idea of the "ladder of living beings" as a successive series of independent, unchanging forms created by the Creator had already been firmly established in science. He saw in the gradation of these forms a reflection of the history of life, the real process of the development of some forms from others. Development from the simplest to the most perfect organisms is the main content of the history of the organic world. Man is also a part of this story, he evolved from monkeys.
Lamarck believed that the main reason for evolution is inherent in living nature primordial(laid down by the Creator) the pursuit of complication and self-improvement your organization. It manifests itself in the innate ability of each individual to complicate the organism. He called the second factor of evolution influence of externalWednesday: as long as it does not change, the species are constant, as soon as it becomes different, the species also begin to change. At the same time Lamarck is at a higher level on Compared with his predecessors, he developed the problem of unlimited variability of living forms under the influence of living conditions: nutrition, climate, soil characteristics, moisture, temperature, etc.
Based on the level of organization of living beings, Lamarck identified two forms of variability:
1) direct - direct variability of plants and bottom
their animals under the influence of environmental conditions;
2) indirect - the variability of higher animals, which
have a developed nervous system that perceives the impact
living conditions and developing habits, means
self-preservation and protection.
Having shown the origin of variability, Lamarck analyzed the second factor of evolution - heredity. He noted that individual changes, if they are repeated in a number of generations, during reproduction are inherited by descendants and become characteristics of the species. At the same time, if some organs of animals develop, then others, not involved in the process of changes, atrophy. So, for example, as a result of exercise, a giraffe developed a long neck, because the ancestors of the giraffe, feeding on the leaves of trees, stretched after them and in each generation the neck and legs grew. Thus, Lamarck suggested that the changes that plants and animals acquire during life are hereditarily fixed and transmitted by inheritance to descendants. In this case, the offspring continues to develop in the same direction, and one species turns into another.
Lamarck believed that the historical development of organisms is not random, but natural and occurs in the direction of gradual and steady improvement, an increase in the general level of organization. In addition, he analyzed in detail the prerequisites for evolution and formulated the main directions of the evolutionary process and the causes of evolution. He also developed the problem of species variability under the influence of natural causes, showed the importance of time and environmental conditions in evolution, which he considered as a manifestation of the general law of the development of nature. The merit of Lamarck is that he was the first to propose a genealogical classification of animals, based on the principles of kinship of organisms, and not just their similarities.
The essence of Lamarck's theory is that animals and plants were not always the way we see them now. He proved that they developed by virtue of the natural laws of nature, following the evolution of the entire organic world. Lamarckism is characterized by two main methodological features:
teleologism as a striving for improvement inherent in organisms;
organismocentrism is the recognition of an organism as an elementary unit of evolution, directly adapting to changes in external conditions and transmitting these changes by inheritance.
From the point of view of modern science, these positions are fundamentally wrong, they are refuted by the facts and laws of genetics. In addition, Lamarck's evidence for the reasons for species variation was not convincing enough. Therefore, Lamarck's theory did not receive recognition from contemporaries. But it was not refuted either, it was only forgotten for a while in order to return to its ideas in the second half of the 19th century, putting them at the basis of all anti-Darwinian concepts.
TheorydisastersF. Cuvier
The rapid development of natural science and selection work, the expansion and deepening of research in various branches of biology, the intensive accumulation of new scientific facts in the 19th century. created favorable conditions for new generalizations in the theory of the evolution of living nature. One of the attempts of this kind of generalization was the theory of catastrophes by the French zoologist J.L. Cuvier.
The methodological basic theory of catastrophes has been great advances in such areas of biological science as comparative anatomy and paleontology. Cuvier systematically compared the structure and functions of one and the same organ or a whole system of organs in a wide variety of animal species. Investigating the structure of the organs of vertebrates, he established that all organs of any living organism are parts of a single integral system. As a result, the structure of each organ is naturally correlated with the structure of all others. No part of the body can change without corresponding changes in other parts. This means that every part of the body reflects the principles of the structure of the whole organism.
So, herbivores that eat poorly nutritious plant foods must have a large stomach capable of digesting this food in large quantities. The size of the stomach determines the size of other internal organs: the spine, chest. The massive body must be supported by powerful legs, equipped with hard hooves, and the length of the legs determines the length of the neck, which makes it possible to freely grasp the grass. Predators have more nutritious food, so they have a smaller stomach. In addition, they need soft paws with movable clawed fingers in order to sneak up on prey and grab it imperceptibly, so the neck of predators should be short, teeth are sharp, etc.
Cuvier called this correspondence of animal organs to each other correlation principle(relativity). Guided by the principle of correlations, Cuvier successfully applied the acquired knowledge,
being able to restore the appearance of an animal by a single tooth, because, according to Cuvier, in any fragment of the organism, as in a mirror, the entire animal was reflected.
Cuvier's undoubted merit was the application of the principle of correlations in paleontology, which made it possible to restore the appearance of animals that have long disappeared from the face of the Earth. Thanks to Cuvier's work, today we imagine what dinosaurs, mammoths and mastodons looked like - the whole world of fossil animals. Thus, Cuvier, who himself proceeded from the idea of the constancy of species, not seeing the transitional forms between modern animals and animals that lived earlier, made a great contribution to the formation of the evolutionary theory that appeared half a century later.
In the course of his research, Cuvier became interested in the history of the Earth, terrestrial animals and plants. He spent many years studying it, while making many valuable discoveries. In particular, he found that the remains of some species are confined to the same geological strata, while completely different organisms are found in adjacent strata. On this basis, he concluded that the animals that inhabited our planet died almost instantly from unknown reasons, and then completely different species appeared in their place. In addition, he found that many modern land areas used to be the seabed, and the change of sea and land occurred more than once.
As a result of his research, Cuvier came to the conclusion that gigantic cataclysms periodically occurred on Earth, destroying entire continents, and with them their inhabitants. Later, new organisms appeared in their place. This is how the famous catastrophe theory, which was very popular in the 19th century.
Cuvier's followers and disciples, developing his teaching, went even further, arguing that catastrophes covered the entire globe. Each catastrophe was followed by a new act of divine creation. They numbered twenty-seven such catastrophes and, consequently, acts of creation.
The position of the theory of catastrophes was shaken only in the middle of the 19th century. A significant role in this was played by a new approach to the study of geological phenomena by Charles Lyell - the principle of actualism. He proceeded from the fact that in order to know the past of the Earth, it is necessary to study its present. Thus, Lyell came to the conclusion that slow, tiny changes on Earth, if they go in one direction for a long time, can lead to amazing results. So one more step was made towards the evolutionary theory, the creators of which were Charles Darwin and A. Wallace.
11.2. TheoryevolutionH. Darwin
The idea of a gradual and continuous change in all types of plants and animals was expressed by many scientists long before Darwin. Therefore, the very concept of evolution - a process of long, gradual, slow changes, ultimately leading to radical, qualitative changes - the emergence of new organisms, structures, forms and species, penetrated into science at the end of the 18th century. However, it was Darwin who created a completely new doctrine of living nature, generalizing individual evolutionary ideas into one coherent theory of evolution. Based on a huge amount of factual material and the practice of breeding work on the development of new varieties of plants and animal breeds, he formulated the main provisions of his theory, which he outlined in the book "The Origin of Species by Natural Selection" (1859).
The maindrivingfactorsevolutionvtheoryDarwin
Darwin came to the conclusion that in nature any species of animals and plants tends to reproduce exponentially. At the same time, the number of adults of each species remains relatively constant. Thus, a female cod lays seven million eggs, of which only 2% survive. Consequently, a struggle for existence takes place in nature, as a result of which traits that are useful for the organism and the species as a whole accumulate, as well as new species and varieties are formed. The rest of the organisms die in unfavorable environmental conditions. Thus, the struggle for existence is a collection of diverse, complex relationships that exist between organisms and environmental conditions.
In the struggle for existence, only those individuals survive and leave offspring that have a complex of traits and properties that allow them to most successfully compete with other individuals. Thus, in nature there is a process of selective destruction of some individuals and the predominant reproduction of others, i.e. natural selection, or survival of the fittest.
When environmental conditions change, some other signs may be useful for survival. As a result, the direction of selection changes, the structure of the species is rebuilt, thanks to reproduction, new characters are widely distributed - a new species appears. Useful signs are preserved and passed on to subsequent generations, as in a living
kind of acts factor of heredity, ensuring the sustainability of species.
However, in nature it is impossible to find two identical, completely identical organisms. All the diversity of living nature is the result process of variability, those. transformations of organisms under the influence of the external environment.
So, Darwin's concept is based on the recognition of objectively existing processes as factors and causes of the development of living things. The main driving forces behind evolution are variability, heredity, and natural selection.
Variability. The first link in evolution is variability (change and transformation of organisms under the influence of the external environment), which is an integral property of living things. Due to the variability of traits and properties, even in the offspring of one pair of parents, the same individuals are almost never found. The more carefully and deeply nature is studied, the more the belief in the general universal character of variability is formed. In nature, it is impossible to find two completely identical, identical organisms. Under favorable conditions, these differences may not have a noticeable effect on the development of organisms, but under unfavorable conditions, every smallest difference can become decisive in whether this organism will remain alive and give birth to or die.
Darwin distinguished two types of variability: 1) hereditary (uncertain) and 2) non-hereditary (definite).
Under certain (group) variability it is understood a similar change in all individuals of the offspring in one direction due to the influence of certain conditions (change in growth depending on the quantity and quality of food, change in the thickness of the skin and the density of the coat with climate change, etc.).
Under uncertain (individual) variability the appearance of various insignificant differences in individuals of the same species, by which one individual differs from others, is understood. In the future, "undefined" changes were called mutations, and "definite" - modifications.
Heredity. The next factor of evolution is heredity - the property of organisms to ensure the continuity of signs and properties between generations, as well as to determine the nature of the development of an organism in specific environmental conditions. This property is not absolute: children are never exact copies of their parents, but only wheat always grows from wheat seeds, etc. In the process of reproduction from generation to generation, not traits are transmitted, but the code of hereditary information, which determines only the possibility of the development of future traits.
characters in a certain range. It is not a trait that is inherited, but the rate of reaction of a developing individual to the action of the external environment.
Darwin analyzed in detail the importance of heredity in the evolutionary process and showed that by themselves variability and heredity do not yet explain the emergence of new breeds of animals, varieties of plants, their adaptability, since the variability of different characteristics of organisms is carried out in a wide variety of directions. Each organism is the result of interaction between the genetic program of its development and the conditions for its implementation.
Struggle for existence. Considering the issues of variability and heredity, Darwin drew attention to the complex relationship between the organism and the environment, to the different forms of dependence of plants and animals on living conditions, to their adaptation to unfavorable conditions. He called such various forms of dependence of organisms on environmental conditions and other living beings struggle for existence. The struggle for existence, according to Darwin, is a set of relationships between organisms of a given species with each other, with other types of living organisms and non-living factors of the external environment.
The struggle for existence means all forms of manifestation of the activity of a given type of organisms, aimed at maintaining the life of their offspring. Darwin identified three main forms of struggle for existence: 1) interspecific, 2) intraspecific, and 3) struggle with unfavorable environmental conditions.
Examples of interspecies struggle are often found in nature and are well known to everyone. It manifests itself most vividly in the struggle of predators and herbivores. Herbivores can survive and leave offspring only if they manage to avoid predators and are provided with food. But different types of mammals also feed on vegetation, and in addition - insects and mollusks. And here a situation arises: what went to one, did not go to the other. Therefore, in the interspecies struggle, the success of one species means the failure of the other.
Intraspecific struggle means competition between individuals of the same species, in which the need for food, territory and other conditions of existence is the same. Darwin considered the intraspecific struggle to be the most intense. Therefore, in process During evolution, populations have developed various adaptations that reduce the severity of competition: marking boundaries, threatening postures, etc.
Dealing with harsh environmental conditions it is expressed in the desire of living organisms to survive during sudden changes in weather conditions. In this case, only the individuals most adapted to the changed conditions survive. They form a new population
which generally contributes to the survival of the species. In the struggle for existence, individuals and individuals survive and leave offspring, possessing such a complex of signs and properties that allow them to successfully resist unfavorable environmental conditions.
Natural selection. However, Darwin's main merit in creating the theory of evolution is that he developed the doctrine of natural selection as the leading and directing factor in evolution. Natural selection, according to Darwin, is a set of changes occurring in nature that ensure the survival of the most adapted individuals and their predominant leaving of offspring, as well as the selective destruction of organisms that have turned out to be unadapted to existing or changed environmental conditions.
In the process of natural selection, organisms adapt, i.e. they develop the necessary adaptations to the conditions of existence. As a result of competition between different species with similar vital needs, the less adapted species die out. Improvement of the mechanism of adaptation of organisms leads to the fact that the level of their organization is gradually becoming more complicated and thus the evolutionary process is carried out. At the same time, Darwin drew attention to such characteristic features of natural selection as the gradualness and slowness of the process of change and the ability to summarize these changes into large, decisive causes leading to the formation of new species.
Proceeding from the fact that natural selection acts among diverse and unequal individuals, it is considered as a cumulative interaction of hereditary variability, predominant survival and reproduction of individuals and groups of individuals better adapted than others to given conditions of existence. Therefore, the doctrine of natural selection as a driving and directing factor in the historical development of the organic world is central to Darwin's theory of evolution.
MeaningevolutionarytheoryDarwin
Thus, Darwin consistently solved the problem of the determination of organic evolution as a whole, explained the expediency of the structure of living organisms as a result of natural selection, and not as a result of their striving for self-improvement. He also showed that the expediency of the structure is always relative, since any adaptation is useful only in specific conditions of existence. By this he dealt a serious blow to the ideas of teleologism in natural science.
In addition, Darwin emphasized that the elementary unit of evolution is not a separate individual, as in Lamarck's, but a group of individuals - a species. In other words, both individuals and whole groups can fall under the influence of natural selection. Then selection preserves traits and properties that are unfavorable for an individual, but useful for a group of individuals or a species as a whole. An example of such a device is a bee sting - a sting bee leaves a sting in the enemy's body and dies, but the death of an individual helps to preserve the bee colony. This approach led to the emergence of population thinking in biology, which is the basis of modern ideas about evolution.
Along with the undoubted advantages, there were significant shortcomings in Darwin's theory. One of the earlier objections to this theory was that it could not explain the reasons for the appearance in organisms of many structures that seem useless. However, as it turned out later, many morphological differences between species that are not important for survival are side effects actions of genes that determine physiological signs that are imperceptible, but very important for survival.
A weak point in Darwin's theory was also the concept of heredity, which was severely criticized by his opponents. Indeed, if evolution is associated with the random appearance of changes and the hereditary transmission of acquired traits to offspring, then how can they persist and even intensify in the future? Indeed, as a result of crossing individuals with useful traits with other individuals that do not possess them, they will transmit these traits in a weakened form. In the end, over a number of generations, these randomly occurring changes will have to weaken, and then disappear altogether. So a glass of milk will dissolve in a barrel of water almost without a trace. This conclusion was obtained with the help of elementary arithmetic calculations by the British engineer and physicist F. Jenkin in 1867. Darwin himself was forced to admit these arguments convincing, given the then ideas of heredity it was impossible to refute them. That is why in the last years of his life he began to emphasize more and more the influence on the evolutionary process of directed changes occurring under the influence of certain environmental factors.
Subsequently, some other shortcomings of Darwin's theory were identified, concerning the main causes and factors of organic evolution. It was clear that his theory needed further development and substantiation, taking into account the subsequent achievements of biological science.
11.3. Furtherdevelopmentevolutionarytheory. Antidarvinism
With the emergence of Darwinism, several tasks have come to the fore in biological research:
collecting evidence of the very fact of evolution;
accumulation of data on the adaptive nature of evolution;
experimental study of the interaction of hereditary variability, the struggle for existence and natural selection as the driving force of evolution;
study of the patterns of speciation and macroevolution.
Complexevidencetheoryevolution
Information confirming the Darwinian theory of evolution was obtained from a variety of sources, among which paleontology, biogeography, taxonomy, plant and animal breeding, morphology, comparative embryology, and comparative biochemistry occupy the most important place.
Paleontology is engaged in the study of fossil remains, i.e. any traces of previously living organisms preserved in the earth's crust. Among them are whole organisms, solid skeletal structures, fossils, prints.
Such traces were well known to scientists long before the emergence of paleontology as an independent science. They were considered either the remains of creatures created earlier than others, or artifacts placed in rocks by God.
In the XIX century. these findings have been interpreted in terms of the theory of evolution. The fact is that in the most ancient rocks there are traces of very few simple organisms. A variety of organisms with a more complex structure are found in young rocks. In addition, there are many examples of the existence of species only at one of the stages of the geological history of the Earth, after which they disappear. This is understood as the emergence and extinction of species over time.
Gradually, scientists began to find traces of an increasing number of "missing links" in the evolution of life - either in the form of fossils (for example, Archeopteryx, a transitional form between reptiles and birds), or in the form of living organisms similar in structure to fossil forms ( for example, the coelacanth, which is a long-extinct cross-finned fish). Of course, scientists managed to find far from all transitional forms, so the fossil record of our planet is not continuous, and this argument is used by opponents of evolution.
tional theory. Nevertheless, scientists find convincing explanations for this fact. In particular, it is believed that not all deceased organisms end up in conditions favorable for their preservation. Most of the dead individuals are eaten by scavengers, decomposed, leaving no traces, and returned to the cycle of substances in nature.
Paleontologists managed to discover some patterns of evolution. In particular, with an increase in the complexity of an organism, the duration of the existence of a species decreases, and the rate of evolution increases. Thus, bird species exist on average for 2 million years, mammals - 800 thousand years old, human ancestors - about 200 thousand years. We also found out that the lifespan of a species depends on the size of its representatives.
Geographical distribution (biography). All organisms are adapted to their environment. Therefore, all species arose in a certain area, and from there they could spread to areas with similar natural conditions. The degree of dispersal depends on how successfully these organisms can settle in new places, how complex are the natural barriers standing in the way of the dispersal of this species (oceans, mountains, deserts). Therefore, usually the distribution of species occurs only if the suitable territories are located close to each other. So, in the distant past, land masses were located closer to each other than now, and this contributed to the wide dispersal of many species. If in some area there are no more developed species, then this indicates an early separation of this territory from the place of the original origin of the species. That is why a large number of marsupials have survived in Australia, which are absent in Europe, Africa and Asia.
These facts do not explain the mechanism of the emergence of new species, but indicate that different groups arose at different times and in different areas, thus confirming the theory of evolution.
Systematics. The first taxonomic classification, which included the distinguished units-taxa, which are in relations of hierarchical subordination, was created by K. Linnaeus. Linnaeus distinguished as units-taxa: species, genus, family, order, class, type and kingdom. He based his classification on the structural similarity between organisms, which can be represented as the result of their adaptation to certain environmental conditions over a certain period. Thus, this classification fits well with evolutionary theory, illustrating the process of evolution on Earth.
Selection of plants and animals. In addition to natural selection, there is artificial selection associated with purposeful
human activities to preserve and create required types... This is how, through selection, all cultivated plant varieties and breeds of domestic animals were bred from wild ancestors. The reference to artificial selection gave Darwin the opportunity to draw an analogy with natural selection in nature.
With the creation of genetics, it became clear that in the course of artificial selection, genes that are useful from the point of view of a person are preserved, and genes that do not suit him are removed.
Comparative anatomy deals with the comparison of various groups of plants and animals with each other. At the same time, common structural features inherent in them are revealed. So, all flowering plants have sepals, petals, stamens, stigma, column and ovary, although in different species they can have different sizes, colors, the number of their constituent parts and some features of their structure. The same can be said for animals.
Thus, comparative anatomy reveals homologous organs, built according to the same plan, occupying a similar position and developing from the same primordia. The existence of such organs, as well as the appearance of rudimentary organs that are preserved in organisms, but do not perform any function, can only be explained from the standpoint of the theory of evolution.
Comparative embryology. One of the founders of this science was K. Baer, who studied embryonic development in representatives of different groups of vertebrates. In doing so, he found striking similarities in the development of the embryos of all groups, especially in the early stages of their development.
After that, E. Haeckel expressed the idea that the early stages of development of the embryo repeat the evolutionary history of their group. He formulated the law of recapitulation, according to which ontogeny repeats phylogeny. In other words, the individual development of an organism repeats the development of the entire species. Thus, the embryo of vertebrates at different stages of its development has the features of a fish, amphibian, reptile, bird and mammal. Therefore, in the early stages of embryo development, it can be very difficult to determine which species it belongs to. Only at the later stages does the embryo acquire a resemblance to the adult form.
The law of recapitulation can only be explained by the presence of common ancestors in all living organisms, which confirms the evolutionary theory.
Comparative biochemistry. With its emergence, evolutionary theory had rigorous scientific evidence. It was comparative biochemistry that showed the presence of the same substances in all organisms, confirming their obvious biochemical relationship. First, the relationship of all proteins was proved, and later - of nucleic acids.
Immune responses also support evolutionary links. If proteins contained in blood serum are introduced into the blood of animals that do not have these proteins, then they act as antigens, prompting animal organisms to produce antibodies.
Openinglawsandmechanismsevolution
Researchers have identified two classes of evolutionary mechanisms: adaptive and catastrophic, or threshold.
Adaptation mechanisms associated with the adaptation of organisms to the environment. In this case, self-tuning of the system occurs, ensuring its stability in certain conditions... Thus, by studying the features of the environment, it is possible to predict in which direction the adaptation mechanisms will act. This is used by breeders by conducting artificial selection.
We can say that no internal or external disturbances are able to bring the system under study beyond the limits of the channel of evolution that is provided for it by nature. Therefore, all possible changes in the system, its development can be predicted with great accuracy. Thus, from the point of view of nonequilibrium thermodynamics, the adaptation mechanism refers to one of the evolutionary stages in the development of systems.
Catastrophic mechanisms evolutions are of a different nature. They are associated with a leap in the development of systems that occurs when passing through the bifurcation point. This is usually due to a sudden change in environmental conditions. In this case, the old structure of the system is destroyed and a qualitatively new structure is formed. The transition through the bifurcation point is always random. It is impossible to predict in advance how the development will go. Therefore, catastrophic events periodically occur in the Earth's biosphere, stimulating the extinction of old plant and animal species and the emergence of new ones.
Evolution laws. Nevertheless, the general rule is the continuous complication and growth of the diversity of the organic world after each transition through critical points in the development of the biosphere. This rule is called divergence law, which explains why originally closely related groups of organisms diverged in the process of evolution, creating a huge variety of species.
By the beginning of the XX century. other laws of evolution were also discovered. So, in 1876 S. Delere established rule of progressive specializationtion, in accordance with which a group that has embarked on the path of specialization, as a rule, in its further development will follow the path of ever deeper specialization.
I.I. Schmalhausen discovered the process of autonomization of ontogenesis, which speaks of the preservation of the defining value of the physical
chemical factors of the external environment, which leads to the emergence of a relative stability of development.
K. Waldington formulated the principle of homeostasis, showing the ability of organisms to self-regulate and maintain the stability of the internal environment of the body.
Finally, L. Dollo discovered the rule of irreversibility, according to which evolution is an irreversible process, and the organism cannot return to the previous state in which its ancestors were.
Antidarvinism
Criticism of Darwinism has been conducted almost since its inception and had objective grounds, since a number of important questions initially dropped out of the field of vision of Darwinists. These include questions about the reasons for the preservation of the systemic unity of organisms in the historical development, the mechanisms of inclusion in the evolutionary process of ontogenetic rearrangements, the uneven pace of evolution, the causes of progressive macroevolution, the causes and mechanisms of biotic crises, etc.
Anti-Darwinism of the second half of the 19th - early 20th centuries. was represented by two main currents - neo-Lamarckism and the concepts of telogenesis. The fight against them, as well as the search for experimental evidence of individual factors of natural selection, were the main content of the biology of this time.
Neo-Lamarckism. The first major anti-Darwinian doctrine was neo-Lamarckism, which arose at the end of the 19th century. This doctrine was based on the recognition of adequate variability arising under the direct or indirect influence of environmental factors that cause the body to directly adapt to them. Neo-Lamarckians also spoke about the inheritance of traits acquired in this way, denied the creative role of natural selection.
As the name of this direction suggests, the basis of neo-Lamarckism was formed by Lamarck's ideas, which scientists forgot at the beginning of the century, but remembered about them after the appearance of the Darwinian theory of evolution. Neo-Lamarckism was not a single trend, but united in itself several directions, each of which tried to develop one or another side of Lamarck's teachings. In neo-Lamarckism, the following are distinguished:
. mechanolamarkism- the concept of evolution, according to which a purposeful organization is created by adaptation, or according to Lamarck, the exercise of organs. This concept explained the evolutionary transformations of organisms by their initial ability to expediently respond to changes in the external environment, changing
while learning their structures and functions. The entire complexity of the evolutionary process, thus, was reduced to a simple theory of the balance of forces, borrowed, in essence, from Newtonian mechanics. Supporters of this trend were G. Spencer and T. Aymer;
psycholamarkism - the basis of this direction was the idea of Lamarck about the importance in the evolution of animals of such factors as habits, efforts of will, consciousness. It was believed that these factors are inherent not only in the body of the animal as a whole, but also in its constituent cells. Thus, evolution was presented as a gradual increase in the role of consciousness in the movement from primitive creatures to intelligent life forms. This developed the doctrine of panpsychism, universal animation. A. Pauli and A. Wagner were supporters of this trend;
Ortholamarckism - a set of hypotheses that develop Lamarck's idea of the desire of organisms to improve as the driving force of evolution inherent in all living things. The supporters of ortolamarkism were K. Nageli, E. Cope, G. Osborne, who believed that the direction of evolution is due to the intrinsic primordial properties of organisms. These views are related to the ideas of autogenesis, which considers evolution as a process of unfolding preexisting inclinations, which is purposeful and occurs on the basis of initial internal potentialities.
The teleological concept of evolution, or telogenesis, was ideologically closely associated with ortholamarckism, since it proceeded from the same idea of Lamarck about the inner striving of all living organisms for progress. The most prominent representative of this trend was the Russian naturalist, founder of embryology K. Baer.
A kind of modification of telogenesis was represented by the views of supporters saltationism, laid down in the 60-70s. XIX century. A. Suess and A. Kelliker. In their opinion, already at the dawn of the emergence of life, the whole plan of the future development of nature emerged, and the influence of the external environment determined only particular moments of evolution. All major evolutionary events - from the emergence of new species to the change of biota in the geological history of the Earth - occur as a result of abrupt changes, saltations, or macromutations. In fact, it was catastrophism, reinforced by additional arguments. These views still exist today.
Genetic anti-Darwinism. V early XX century. genetics arose - the doctrine of heredity and variability. It would seem that its appearance should have solved many questions of evolutionary theory that have remained unanswered until now. But the first geneticists opposed the data of their research to Darwinism, as a result
which in evolutionary theory has arisen a deep crisis. The speech of geneticists against Darwin's teachings resulted in a broad front uniting several trends: mutationism, hybridogenesis, pre-adaptationism, etc. All of them united under the general name of genetic anti-Darwinism.
Thus, the discovery of gene resistance was interpreted as their immutability. This contributed to the spread anti-evolutionism(W. Betson). Mutational variability was identified with evolutionary transformations, which eliminated the need for selection as the main cause of evolution.
The culmination of these constructions was the theory of nomogenesis by L.S. Berg, created in 1922. It was based on the idea that evolution is a programmed process of realization of internal laws inherent in all living things. He believed that organisms have an internal force of unknown nature, acting purposefully, regardless of the external environment, towards the complication of the organization. To prove this, Berg cited a lot of data on the convergent and parallel evolution of different groups of plants and animals.
From all these controversies, it was clear that genetics and Darwinism had to find a common language. But before proceeding to consider the further development of the theory of evolution, one should dwell in more detail on the basic provisions of genetics, without which modern Darwinism would be impossible.
11.4. The basicsgenetics
Genetics arose at the beginning of the 20th century, although the first steps in the study of heredity were made in the second half of the 19th century. by the Czech naturalist G. Mendel, who, with his experiments, laid the foundations of modern genetics. In 1868, he set up experiments on crossing peas, in which he proved that heredity has no intermediate character, but is transmitted by discrete particles. Today we call these particles genes. Mendel reflected the results of his observations in a scientific article published by him, which, unfortunately, went unnoticed.
The same conclusions were again obtained in 1900, when three researchers - H. De Vries, K. Correns and E. Cermak - conducted their experiments in which they rediscovered the rules of inheritance of traits. Therefore, the aforementioned scientists are considered the founders of the new science, and this science received its name in 1906, it was given by the English biologist W. Betson.
A huge role in the development of genetics was played by the Danish researcher V. Johansen, who introduced the main
terms and definitions used in this science. Among them, the most important concept is "gene"- an elementary unit of heredity. It is an intracellular molecular structure. As we know today, a gene is a section of a DNA molecule located in the chromosome, in the nucleus of a cell, as well as in its cytoplasm and organelles. The gene determines the possibility of the development of one elementary trait or the synthesis of one protein molecule. As noted earlier, the number of genes in a large organism can reach many billions. In the body, genes are a kind of "brain center". They record the signs and properties of the organism, which are inherited.
The collection of all genes of one organism is called genotype.
The set of all variants of each of the genes that make up the genotypes of a certain group of individuals or a species as a whole is called gene pool. For example, the Drosophila fly has a whole series of 12 genes for eye color (red, coral, cherry, apricot, etc., up to white). The gene pool is a species, not an individual trait.
The totality of all the signs of one organism is called fenootype. The phenotype is the result of the interaction of the genotype and the environment.
Genetics studies two fundamental properties of living systems - heredity and variability, i.e. the ability of living organisms to pass on their characteristics and properties from generation to generation, as well as acquire new qualities. Heredity creates a continuous succession of traits, properties and developmental characteristics in a number of generations. Variability provides material for natural selection, creating both new variants of traits and countless combinations of previously existing and new traits of living organisms.
GeneticsOheredity
Genetics was based on the laws of heredity discovered by Mendel when he conducted a series of experiments on crossing various varieties of peas. In the course of these studies, he discovered the quantitative patterns of inheritance of traits, later named after the discoverer Mendel's laws. These three laws are known as the first generation law of uniformity.
hybrids, the law of splitting and the law of independent combination of traits.
Mendel's first law- the law of uniformity of the first generation of hybrids - establishes that when two individuals are crossed, differing in one pair of alternative traits, hybrids of the first generation are uniform, showing only one trait. For example, when two varieties of peas with yellow and green seeds are crossed in the first generation of hybrids, all the seeds are yellow in color. This trait, which appears in the first generation of hybrids, is called dominant. The second sign (green color) is called recessive and in the first generation of hybrids it is suppressed.
Mendel's second law- the law of splitting - states that when crossing hybrids of the first generation, their offspring (second generation of hybrids) splits according to the analyzed trait in a ratio of 3: 1 by phenotype, 1: 2: 1 by genotype, or Aa + Aa = AA + 2Aa + aa ... In the same example of crossing two varieties of peas with yellow and green seeds in the second generation of hybrids, splitting will occur: plants with green seeds will appear (recessive trait), but the number of green seeds will be three times less than the number of yellow ones (dominant trait).
Mendel's third law- the law of independent combination of traits - states that when crossing organisms that differ from each other in two or more pairs of alternative traits, genes and their corresponding traits are inherited independently of each other and are combined in all possible combinations. So, when dihybrid crossing of two varieties of peas with yellow smooth and green wrinkled seeds in the second generation of hybrids, four groups of individuals (yellow smooth seeds, yellow wrinkled, green smooth, green wrinkled) in a quantitative ratio - 9: 3: 3: 1.
Chromosomal theory of heredity. Mendel's third law does not apply in all cases. Therefore, an important stage in the development of genetics was the creation at the beginning of the 20th century. American scientist G. Morgan chromosome theory of heredity. Observing cell division, Morgan came to the conclusion that the main role in the transmission of hereditary information belongs to the chromosomes of the cell nucleus. The American scientist was able to identify the patterns of inheritance of traits, the genes of which are located on the same chromosome - they are inherited together. It is called clutchgenes, or Morgan's law. Morgan logically concluded that any organism has many characteristics, and the number of chromosomes is small. Therefore, there must be many genes on each chromosome.
Each chromosome consists of a central thread called lame, along which the structures are located - chromomeres. Chromosomes acquire this appearance only during cell division, at other times they look like thin dark-colored filaments. Each cell of any organism of a given species contains a certain number of chromosomes, but their number is different for each species. For example, the fruit fly Drosophila has 8, the garden pea has 14, the toad has 22, the rat has 42, the duck has 80, and the microscopic marine animal radiolaria has 1600. The human genome consists of 46 chromosomes. In other animal species, the number of chromosomes may be different, but certain and constant for a given species. Chromosomes are always paired, i.e. there are always two chromosomes of each type in a cell. So, a person has 23 pairs of chromosomes. Pairs differ from each other in length, shape and presence of thickenings and constrictions.
Genetics also answered the question of the origin of sex differences. So, in a person, out of 23 pairs of chromosomes, 22 pairs are the same in both male and female organisms, and one pair is different. It is thanks to this pair that sex differences are determined, which is why it is called sex chromosomes, unlike identical chromosomes named autosomes. The sex chromosomes in women are the same, they are called X chromosomes. In men, the sex chromosomes are different - one X chromosome and one Y chromosome. For each person, the Y-chromosome plays a decisive role in determining sex. If the egg is fertilized by a sperm carrying the X chromosome, it develops female body, if a sperm containing the Y-chromosome enters the egg, a male body develops.
Next important stage in the development of genetics began in the 1930s. and is associated with the discovery of the role of DNA in the transmission of hereditary information. The discovery of genetic patterns at the molecular level began, a new discipline was born - molecular genetics. At the same time, in the course of research, it was found that the main function of genes is to encode protein synthesis. Then, in 1950, S. Benzer established the fine structure of genes, discovered the molecular mechanism of functioning of the genetic code, and understood the language in which genetic information is recorded. For this, four nitrogenous bases (adenine, thymine, guanine and cytosine), a pentaatomic sugar and a phosphoric acid residue are used. And finally, the mechanism of DNA replication (transmission of hereditary information) was deciphered. It is known that the sequence of bases in one strand exactly predetermines the sequence of bases in another - this is the so-called the principle of complementarity, acting like a matrix.
During reproduction, two spirals of the old DNA molecule diverge, and each becomes a matrix for the reproduction of new DNA strands. Each of the two daughter molecules necessarily includes one old polynucleotide chain and one new one. Doubling of DNA molecules occurs with amazing precision, which is facilitated by the double-stranded structure of the molecule - the new molecule is absolutely identical to the old one. This is a deep meaning, because a violation of the DNA structure, leading to a distortion of the genetic code, would make it impossible to preserve and inherit genetic information that ensures the development of the characteristics inherent in the body. The triggering mechanism of replication is the presence of a special enzyme - DNA polymerase.
Geneticsaboutvariability
The genetic mechanisms of heredity are closely related to the genetic mechanisms of variability, i.e. with the ability of living organisms to acquire new signs and properties in the process of interaction of the organism with the environment. Variability is the basis for natural selection and evolution of organisms.
According to the mechanisms of occurrence and the nature of changes in traits, genetics distinguishes between two main forms of variability: 1) hereditary (genotypic) and 2) non-hereditary (phenotypic), or modification variability. Modification variability depends on the specific conditions of the environment in which a separate organism exists, and makes it possible to adapt to these conditions, but within the limits of the reaction norm. Thus, a European who has lived for a long time in Africa will acquire a strong tan, but his skin color will still not be the same as that of the indigenous inhabitants of this continent. These changes are not inherited.
The variability associated with a change in the genotype is called genotypic variability.
Genetic variability is inherited and subdivided into combinative and mutational.
The most vividly hereditary variability is manifested in mutations - restructuring of the hereditary basis, the genotype of the organism. Mutational variability - it is an abrupt and persistent change in genetic material that is inherited. Although the process of DNA replication and cell division is usually extremely accurate, sometimes, about once in a thousand or a million cases, this process is disrupted, and then the chromosomes of the new cell differ from those in the old one. Thus,
mutation occurs due to a change in the structure of genes or chromosomes and serves as the only source of genetic diversity. There are different types of gene and chromosomal mutations.
Factors that can cause mutations are called mutagenmi. They are divided into physical (various types of radiation, high or low temperatures), chemical (some drugs, etc.) and biological (viruses, bacteria). According to their importance for the organism, mutations are subdivided into negative ones - lethal (incompatible with life), semi-lethal (reducing the organism's viability), neutral and positive (increasing the organism's adaptability and vitality). Positive mutations are extremely rare, but they are the basis of progressive evolution.
Combinative variability associated with obtaining new combinations of genes present in the genotype. In this case, the genes themselves do not change, but new combinations of them arise, which leads to the emergence of organisms with a different genotype and, therefore, a phenotype. Mendel's experiments on dihybrid crossing are an example of the manifestation of variability due to recombination of genes, i.e. combinative variability. Another example of such variability is genetic recombination that occurs during sexual reproduction. That is why children are like their parents, but they are not an exact copy of them. In addition, recombination can occur due to the inclusion in the cell genome of new genetic elements introduced from the outside - migrating genetic elements. Recently, it was found that even their very introduction into the cell gives a powerful impetus to multiple mutations.
Such an impetus can be given by viruses - one of the most dangerous mutagens. Viruses are the smallest living things. They do not have a cellular structure, they are not able to synthesize protein themselves, therefore they receive the substances necessary for their life, penetrating into a living cell and using foreign organic substances and energy. In humans, as in plants and animals, viruses cause many diseases.
Although mutations are the main suppliers of evolutionary material, they refer to random changes obeying probabilistic, or statistical, laws. Therefore, they cannot serve as a determining factor in the evolutionary process. True, some scientists consider mutations as the main evolutionary factor, forgetting that in this case it is necessary to recognize the initial usefulness and suitability of absolutely all random changes that arise. And this contradicts observations in nature and experiments in selection.
In fact, apart from selection, natural or artificial, there is no other means of regulating hereditary variation. Only selection on the part of nature or man can preserve randomly occurring changes that turned out to be useful in certain conditions and use them for further evolution.
Nevertheless, the idea of the leading role of mutations in the evolutionary process formed the basis the theory of neutral mutations, created in the 70's and 80's. XX century Japanese scientists M. Kimura and T. Ota. According to this theory, changes in the functions of the protein synthesizing apparatus are the result of random mutations that are neutral in their evolutionary consequences. Their true role is to provoke genetic drift - a change in the frequency of genes in a population under the influence of completely random factors. On this basis, a neutralist concept of non-Darwinian evolution was proclaimed, the essence of which lies in the idea that natural selection does not work at the molecular-genetic level. And although these ideas are not generally accepted among biologists, it is obvious that the immediate arena of natural selection is the phenotype, i.e. living organism, ontogenetic level of life organization.
11.5. Synthetictheoryevolution
Considering the main factors of evolution, it is easy to make sure that the initial ideas of Darwin's theory of evolution were subsequently subjected to significant refinements, additions and corrections. A special role in the formation of new ideas about development was played by genetics, which formed the basis of neo-Darwinism - the theory of organic evolution through natural selection of genetically determined traits. Another common name for neo-Darwinism is synthetic (based on data from many areas of natural science), or general, theory of evolution (STE). The synthetic theory of evolution is a synthesis of Darwin's basic evolutionary ideas and, above all, natural selection with new research results in the field of heredity and variability.
The works of the Russian geneticist S.S. Chetverikov on population genetics, then about 50 scientists from eight countries joined this work. In their works, it was shown that not individual traits or individuals, but the genotype of the entire population are subjected to selection, however, it is carried out through phenotypic traits
individual individuals. This leads to the spread of beneficial changes throughout the population. The usefulness of variability will be determined by the natural selection of a group of individuals most adapted to life under certain conditions. Thus, the elementary unit of evolution is no longer an individual (as Lamarck believed), not a species (as Darwin believed), but a set of individuals of the same species capable of interbreeding with each other, i.e. population.
A mutated gene creates a new trait in an individual, which, if useful for the population, is fixed in it. The efficiency of the process is determined by the frequency of occurrence of a trait in the population and the state of individuals in the population.
A significant contribution to the formation of STE was made by the Russian scientist N.V. Timofeev-Resovsky. He formulated a provision on elementary phenomena and factors of evolution. In his opinion:
the elementary evolutionary structure is the population;
an elementary evolutionary phenomenon is a change in the genotypic composition of a population;
the elementary hereditary material is the population's gene pool;
elementary evolutionary factors are mutation, "waves of life", isolation and natural selection.
The mainfactorsevolutionSTE
Darwin and his followers attributed variability, heredity and natural selection to the main factors of evolution. Currently, many other additional, non-basic factors are added to them, which, nevertheless, have an impact on the evolutionary process, and the basic factors themselves are now understood in a new way.
Leading Factors of Evolution. Currently, the leading factors of evolution include mutational processes, population waves of numbers, isolation and natural selection.
Insofar as mutations arise by chance, insofar as their result becomes uncertain, but a random change becomes necessary when it turns out to be useful for the organism, helps it to survive in the struggle for existence. Fixing and repeating in a number of generations, random changes cause rearrangements in the structure of living organisms and their populations and thus lead to the emergence of new species. Populations saturated with mutations have ample opportunities to improve existing and develop new adaptations in changing environmental conditions. However, the mutation process itself, without the participation of other evolutionary factors, cannot
to guide the change in the natural population. He is only a supplier of elementary evolutionary material.
Population waves called fluctuations in the number of individuals in a population. The reasons for these fluctuations can be different. For example, a sharp decline in population size can occur due to depletion of food resources. Among the few surviving individuals, there may be rare genotypes. If in the future the number is restored at the expense of these individuals, then this will lead to a random change in the frequencies of genes in the gene pool of this population. Thus, population waves are the supplier of evolutionary material.
STE recognizes as the third main factor in the evolution isolation (isolation) of a group of organisms. This feature was pointed out by Darwin, who believed that for the formation of a new species, a certain group of the old species must separate, but he could not explain the need for this requirement from the point of view of heredity. It has now been established that the isolation and isolation of a certain group of organisms is necessary so that it cannot interbreed with other species and thereby transmit and receive genetic information from them. Isolation of different groups of organisms in nature, as well as in the practice of breeding work, is carried out in different ways, but their goal is the same - to exclude the exchange of genetic information with other species.
Guiding factor STE is natural selection. However, at present, the concept of natural selection has been supplemented by new facts, significantly expanded and deepened. Natural selection should be understood as selective survival and the possibility of individual individuals leaving offspring. The biological significance of an individual that gave offspring is determined by its contribution to the population's gene pool. Selection operates in a population; its objects are the phenotypes of individual individuals. The phenotype of an organism is formed on the basis of the realization of genotype information under certain environmental conditions. Thus, selection from generation to generation according to phenotypes leads to selection of genotypes, since not traits, but gene complexes are transmitted to descendants.
In STE, there are three main forms of natural selection: 1) stabilizing, 2) driving, and 3) disruptive.
Stabilizing selection contributes to the preservation of the characteristics of the species in relatively constant environmental conditions. It maintains average values, rejecting mutational deviations from the previously formed norm. The stabilizing form of selection is valid as long as the conditions that led to the formation of this or that trait or property persist. An example of a stabilizing
The first selection is the selective death of house sparrows under unfavorable weather conditions. In surviving birds, various traits are close to the mean. Among the dead, these signs varied greatly. An example of the action of this form of selection in human populations is the high survival rate of children with an average weight.
Driving selection favors a change in the mean value of a trait under changed environmental conditions. It conditions the constant transformation of the adaptations of species in accordance with changes in the conditions of existence. Individuals of the population have some differences in genotype and phenotype. With a prolonged change in the external environment, mainly in life and reproduction, a part of the species may appear with some deviations from the average norm. This will lead to a change in the genetic structure, the emergence of evolutionarily new adaptations and a reorganization of the organization of the species. One example of this form of selection is the darkening of the color of the moth moth in the industrialized regions of England. In agricultural areas, light-colored forms are common, and near industrial centers the bark of trees becomes dark due to the disappearance of lichens, therefore the form of dark-colored butterflies predominates there.
Disruptive selection acts in a variety of environmental conditions found on the same territory, and supports several phenotypically different forms at the expense of individuals with an average norm. If environmental conditions have changed so much that the bulk of the species loses its fitness, then individuals with extreme deviations from the average rate gain advantage. Such forms multiply rapidly, and several new ones are formed on the basis of one group. The main result of this selection consists in the presence of several groups, differing in some characteristic, as if tearing the population apart.
It should be noted that the listed types of selection are very rarely found in their pure form. As a rule, complex, complex types of selection are observed in living nature, and special efforts are required to distinguish simpler types from them.
Conceptsmicro- andmacroevolution
An important component of the synthetic theory of evolution is the concept of micro- and macroevolution.
Microevolution is understood as a set of evolutionary processes occurring in populations, leading to changes in the gene pool of these populations and the formation of new species.
It is believed that microevolution proceeds on the basis of mutational variability under the control of natural selection. Mutations are the only source of qualitatively new traits, and natural selection is the only creative factor in microevolution, directing elementary evolutionary changes along the path of the formation of adaptation of organisms to changing environmental conditions. The nature of microevolutionary processes is influenced by fluctuations in the number of populations ("waves of life"), the exchange of genetic information between them, their isolation and gene drift. Microevolution leads either to a change in the entire gene pool of a biological species as a whole, or to their isolation from the parental species as new forms.
Under macroevolution understand evolutionary transformations leading to the formation of taxa of a higher rank than the species (genera, orders, classes).
It is believed that macroevolution has no specific mechanisms and is carried out only through the processes of microevolution, being their integrated expression. Accumulating, microevolutionary processes are expressed externally in macro-evolutionary phenomena, i.e. macroevolution is a generalized picture of evolutionary change. Therefore, at the level of macroevolution, general tendencies, directions and regularities of the evolution of living nature are revealed, which cannot be observed at the level of microevolution.
The mainprovisionsSTE
Based on the above, the main provisions of the synthetic theory of evolution are reduced to four statements:
the main factor of evolution is natural selection, which integrates and regulates the action of all other factors (mutagenesis, hybridization, migration, isolation, etc.);
evolution proceeds divergently, gradually, through the selection of random mutations, and new forms are formed through hereditary changes;
evolutionary changes are random and undirected; mutations are the source material for them; the original organization of the population and changes in external conditions limit and direct hereditary changes;
macroevolution, leading to the formation of supraspecific groups, is carried out only through the processes of microevolution, and
there are no specific mechanisms for the emergence of new life forms.
The synthetic theory of evolution is not a frozen and complete concept. It has a number of difficulties on which non-Darwinian concepts of evolution are based, both already mentioned above and recently arisen. Thus, it allows for the possibility of changing the genomes of organisms as a result of mutations. But the genome of any organism contains a huge amount of nucleotides, so mutations cannot affect it in such a way that a different genome is obtained. Most likely, a change in the genome of one cell or several cells will lead to a mismatch in the behavior of cells, and the cell population will not form.
According to a number of scientists, the fitness of organisms, natural selection and mutations operate in living nature, but they do not work on the scale required for the formation of new forms.
Thus, another concept of non-Darwinian evolution has recently emerged - punctualism. Its supporters believe that the process of evolution follows the path of rare and rapid leaps, and in 99% of its time the species is in a stable state - stasis. In extreme cases, a jump to a new species can take place in a population of only ten individuals within one or several generations. This hypothesis is based on a broad genetic base, laid down by a number of fundamental discoveries in molecular genetics and biochemistry. Punctualism rejected the genetic-population model of speciation, Darwin's idea of varieties and subspecies as emerging species, and focused its attention on the molecular genetics of an individual as a carrier of all the properties of a species. The value of this concept lies in the idea of dissociation of micro- and macroevolution and the independence of the factors controlled by them.
Perhaps, in the future, STE and non-Darwinian concepts of evolution, complementing each other, will unite into a new unified theory of life and development of living nature.
Literatureforindependentstudying
Afanasyev V.G. The world of the living: consistency, evolution and management. M., 1986.
Vorontsov N.N. Evolution Theory: Origins, Postulates and Problems. M., 1984.
Darwinism: history and modernity. L., 1988.
Dubinin N.P. Essays on genetics. M., 1985.
Zakharov V.B., Mamontov S.G., Sivoglazov V.I. Biology: general patterns. M., 1996.
Kivenko N.V. The principles of knowing the living. Kiev, 1991.
KrisachenkoB.C. Philosophical analysis of evolutionism. Kiev, 1990.
Ruse M. Philosophy of Biology. M., 1997.
Severtsov A.S. Foundations of the theory of evolution. M., 1987.
Timofeev-Resovsky N.V., Vorontsov N.N., Yablokov A.V. A brief outline of the theory of evolution. M., 1969.
Shmalgauzen I.I. Questions of Darwinism. M., 1990.
Yugay G.A. General theory of life. M., 1985.
Yablokov A.V., Yusufov A.G. Evolutionary teaching. M., 1998.
Ministry of Education of the Russian Federation
North Caucasus Humanitarian Technical Institute
in the discipline "Concepts modern natural science»
on the topic: "Darwin's evolutionary theory"
Completed by: G.V. Chaplina
Work supervisor:
Goncharova S.N.
Stavropol 2002
Content
Introduction. 3
1. Prerequisites for the creation of the evolutionary theory of Charles Darwin. 4
2. Evolutionary studies of Charles Darwin. 7
3. The main provisions of the evolutionary teachings of Charles Darwin. eight
4. Preconditions and driving forces of evolution according to Charles Darwin. nine
5. The main results of evolution (according to Charles Darwin) 14
Conclusion. 17
Literature. eighteen
Introduction
For the first time the term "evolution" (from the Latin evolutio - deployment) was used in one of the embryological works by the Swiss naturalist Charles Bonnet in 1762. At present, evolution is understood as an irreversible process of change in a system that occurs in time, due to which something arises. something new, heterogeneous, standing at a higher stage of development.
The evolutionary process concerns many phenomena occurring in nature. For example, an astronomer talks about the evolution of planetary systems and stars, a geologist - about the evolution of the Earth, a biologist - about the evolution of living things. At the same time, the term "evolution" is often applied to phenomena that are not directly related to nature in the narrow sense of the word. For example, they talk about the evolution of social systems, views, any machines or materials, etc.
The concept of evolution in natural science acquires special meaning, where biological evolution is mainly studied. Biological evolution is an irreversible and, to a certain extent, directed historical development of living nature, accompanied by a change in the genetic composition of populations, the formation of adaptations, the formation and extinction of species, transformations of biogeocenoses and the biosphere as a whole. In other words, biological evolution should be understood as the process of adaptive historical development of living forms at all levels of organization of living things.
The theory of evolution was developed by Charles Darwin (1809-1882) and outlined by him in the book "The Origin of Species by Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life" (1859).
1. Prerequisites for the creation of the evolutionary theory of Charles Darwin
By the middle of the XIX century. a number of important generalizations and discoveries were made that contradicted creationist views and contributed to the strengthening and further development of evolution, constituting the scientific prerequisites for the creation of the evolutionary theory of Charles Darwin.
The first gap in the metaphysical worldview was made by the philosopher E. Kant (1724-1804), who in his famous work "General Natural History and Theory of Heaven" rejected the myth of the first shock and came to the conclusion that the entire Earth and the solar system are something that arose in time. Thanks to the works of E. Kant, P. Laplace and W. Hertel, the Earth and the entire solar system began to be considered as developing in time.
In 1830, the English naturalist Charles Lyell (1797-1875) substantiated the idea of the variability of the Earth's surface under the influence of various natural causes and laws: climate, water, volcanic forces, organic factors. Lyell expressed the idea that the organic world is gradually changing, which was confirmed by the results of paleontological studies of the French zoologist J. Cuvier (1769-1832).
In the first half of the 19th century, the idea of the unity of all nature was developed. The Swedish chemist I. Berzelius (1779-1848) proved that all animals and plants consist of the same elements that are found in inanimate nature, and the German chemist F. Wöhler (1800-1882) for the first time in 1824 chemically synthesized in a laboratory oxalic acid, in 1828 - urea, thus showing that the formation of organic substances is carried out without the participation of some "vital force".
In the 18th-19th centuries, as a result of the colonization of vast territories and their exploration, the Europeans significantly expanded their ideas about the diversity of the organic world, about the patterns of its distribution over the continents of the globe. Systematics is developing intensively: all the diversity of the organic world required its classification and reduction into a certain system, which was important for the development of the idea of the kinship of living beings, and then of the unity of their origin.
In the first half of the 19th century, a detailed study of the geographic distribution of organisms began; biogeography and ecology begin to develop, the first generalizations of which were important for substantiating the idea of evolution. So, in 1807, the German naturalist A. Humboldt (1769-1859) expressed the idea of the dependence of the geographical distribution of organisms on the conditions of existence. The Russian scientist K.F.Rulier (1814-1858) tries to interpret the historical change in the face of the Earth and living conditions on it and the impact of these changes on the change in animals and plants. His student N.A. Severtsov (1827-1885) expressed ideas about the relationship of organisms with the environment, about the formation of new species as an adaptive (adaptive) process.
At the same time, comparative morphology and anatomy were developing. Her successes helped to clarify not only the similarity of the structure of various animal species, but also such a similarity in their organization, which suggested a deep connection between them, about their unity. Comparative embryology begins to take shape. In 1817-1818. THEIR. Pander discovered the germ layers and the universality of their laying in the embryogenesis of multicellular animals. The German researcher M. Rathke applied the theory of germ layers to invertebrates (1829).
At the end of the 20s of the 19th century, the Russian embryologist K.M.Ber (1792-1870) established the main types of embryonic development and proved that all vertebrates develop according to a single plan. similarities ”and were used by him to prove evolution). A remarkable sign of embryonic similarity is, for example, the presence of branchial slits in the embryos of all vertebrates, including humans.
In 1839, T. Schwann created a cell theory, which substantiated the generality of the microstructure and development of animals and plants. Thus, the intensive development of science, the accumulation in various fields of natural science of a large number of facts incompatible with creationist concepts, prepared the basis on which Darwin's teaching was successfully developed.
This was also facilitated by the socio-economic conditions of the first half of the 19th century. The establishment of the capitalist mode of production along with the expansion of the British colonial empire was accompanied by intensive restructuring Agriculture, which contributed to the development of selection. The achievements of breeders testified that a person can change breeds and varieties, adapt them to their needs through artificial selection. Breeders of the first half of the 19th century not only practically proved the power of artificial selection, but also tried to theoretically substantiate it. This significantly influenced the formation of the idea of evolution in Darwin, and most importantly, relying on the results of breeding practice as a kind of model, he was able to move on to the analysis of the process of speciation in nature.
The formation of Charles Darwin's ideas was also facilitated by some political and economic ideas, primarily the views of A. Smith and T. Malthus. A. Smith (1723-1790) proceeded from the then consolidated idea of natural laws and created the doctrine of "free competition". He believed that the engine of free competition is "natural self-interest or" natural selfishness "of a person, and this is the source of national wealth. The unadapted in the process of free competition are eliminated. The idea of competitive relations also influenced the formation of ideas about the development of wildlife. These ideas, in all likelihood, prompted Darwin to think about the existence of some analogies in nature and contributed to the creation of evolutionary theory.
Reached by the middle of the nineteenth century. major successes in the development of various directions in natural science, as well as in society, the conditions that stimulated the development of selection and created opportunities for the advancement of ideas of competition and selection, and were the prerequisites that paved the way for the formulation of the scientific concept of biological evolution.
2. Evolutionary research of Charles Darwin
From 1837 to 1839 Darwin created the series notebooks, in which he sketched in a short and fragmentary form thoughts about evolution based on his studies in zoology. In 1842 and 1844. in two steps he summarized a sketch and an outline of the origin of species. These works already contain many of the ideas that were later published by him in 1859.
In 1854-1855. Darwin begins to work closely on an evolutionary work, collects materials on the variability, heredity and evolution of wild species of animals and plants, as well as data on the methods of breeding domestic animals and cultivated plants, comparing the results of the action of artificial and natural selection. He began to write a work, the volume of which he estimated at 3-4 volumes. By the summer of 1858, he had written ten chapters of this work. This work was never completed and was first published in the UK in 1975. The work was stopped due to the receipt of A. Wallace's manuscript, in which, independently of Darwin, the foundations of the theory of natural selection and its role in evolution were outlined on the basis of Wallace's own research on the flora and fauna of the Malay Archipelago. Darwin began to write a short extract and completed the work with unusual haste in 8 months. On November 24, 1859, The Origin of Species by Natural Selection, or the Conservation of Favored Breeds in the Struggle for Life, was published.
The historical merit of Darwin is that he, together with Wallace, revealed the driving factor of evolution - natural selection and thereby revealed the reasons for the course of biological evolution.
Passions raged throughout the world, there was a struggle for Darwin, for Darwinism, on the one hand, against Darwinism, on the other. Audiences buzzed, scientists and publicists were worried, some branded Darwin, others admired him.
Darwin wrote three more books on evolution. In 1868, Darwin published a large work on the theory of artificial selection "Change in domestic animals and cultivated plants." In this book, not without the influence of criticism, Darwin asked the question of how favorable deviations in the offspring can be recorded, and put forward a "temporary hypothesis of pangenesis." The hypothesis assumed the transfer by means of hypothetical particles - "gemmules" - acquired properties from the organs of the body to the reproductive cells and was a tribute to Lamarckism. Darwin and his contemporaries did not know that in 1865 the Austro-Czech naturalist Abbot Gregor Mendel discovered the laws of heredity. The pangenesis hypothesis was no longer broadly in need of creation.
In 1871, when Darwinism was already accepted as a natural science concept, Darwin's book "The Descent of Man and Sexual Selection" was published, which showed not only an undeniable similarity, but also the relationship between man and primates. Darwin argued that the ancestor of man can be found by modern classification, among forms that may be even lower than great apes. Humans and monkeys undergo similar psychological and physiological processes in courtship, reproduction, fertility and offspring. A Russian translation of this book appeared in the same year. Next year, Darwin's book "Expression of Emotions in Man and Animals" is published, in which, based on the study of facial muscles and the means of expressing emotions in humans and animals, their relationship is proved by another example.
3. The main provisions of the evolutionary teachings of Charles Darwin
Darwin's evolutionary theory is a holistic teaching about the historical development of the organic world. It covers a wide range of problems, the most important of which are evidence of evolution, identification of the driving forces of evolution, determination of the paths and patterns of the evolutionary process, etc.
The essence of evolutionary doctrine consists in the following basic provisions:
1. All kinds of living beings inhabiting the Earth have never been created by someone.
2. Having arisen naturally, organic forms were slowly and gradually transformed and improved in accordance with the surrounding conditions.
3. The transformation of species in nature is based on such properties of organisms as variability and heredity, as well as natural selection constantly occurring in nature. Natural selection is carried out through the complex interaction of organisms with each other and with factors of inanimate nature; this relationship Darwin called the struggle for existence.
4. The result of evolution is the adaptability of organisms to the conditions of their habitation and the diversity of species in nature.
4. Prerequisites and driving forces of evolution according to Charles Darwin
In Darwin's evolutionary theory, the premise of evolution is hereditary variability, and the driving forces of evolution are the struggle for existence and natural selection. When creating an evolutionary theory, Charles Darwin repeatedly refers to the results of breeding practice. He tries to find out the origin of domestic animal breeds and plant varieties, to reveal the reasons for the diversity of breeds and varieties and to identify the methods by which they were obtained. Darwin proceeded from the fact that cultivated plants and domestic animals are similar in a number of ways to certain wild species, and this cannot be explained from the standpoint of the theory of creation. Hence the hypothesis that cultural forms evolved from wild species. On the other hand, the plants and tamed animals introduced into culture did not remain unchanged: man not only chose the species of interest from the wild flora and fauna, but also significantly changed them in the right direction, while creating a large number of plant varieties and breeds from a few wild species animals. Darwin showed that the basis for the diversity of varieties and breeds is variability - the process of the appearance of differences in descendants in comparison with ancestors, which determine the diversity of individuals within a variety, breed. Darwin believes that the causes of variability are the impact on organisms of environmental factors (direct and indirect, through the "reproductive system"), as well as the nature of the organisms themselves (since each of them specifically reacts to the impact of the external environment). Having determined for himself his attitude to the question of the causes of the change, Darwin analyzes the forms of variability and distinguishes three of them: definite, indefinite and correlative.
Certain, or group, variability is variability that arises under the influence of some environmental factor that acts equally on all individuals of a variety or breed and changes in a certain direction. An example of such variability is an increase in body weight in all animals with good nutrition, changes in hairline under the influence of climate, etc. A certain variability is massive, covers the entire generation and is expressed in each individual in a similar way. She is not hereditary, i.e. in the descendants of the changed group, when placed in other environmental conditions, the characters acquired by the parents are not inherited.
Uncertain, or individual, variability manifests itself specifically in each individual, that is, it is single, individual in nature. With indefinite variability, various differences appear in individuals of the same variety, breed, in which, under similar conditions, one individual differs from others. This form of variability is uncertain, i.e. a sign under the same conditions can change in different directions. For example, in one plant variety, specimens appear with different color of flowers, different intensity of color of petals, etc. The reason for this phenomenon was unknown to Darwin. Uncertain, or individual, variability is hereditary in nature, i.e. steadily transmitted to offspring. This is its great importance for evolution.
With correlative, or relative variability, a change in any one organ is the cause of changes in other organs. For example, dogs with a poorly developed coat usually have underdeveloped teeth, pigeons with feathered legs have membranes between the toes, pigeons with a long beak usually have long legs, white cats with blue eyes are usually deaf, etc. From the factors of correlative variability, Darwin draws an important conclusion: a person, selecting any feature of the structure, will almost "probably inadvertently change other parts of the body on the basis of the mysterious laws of correlation."
Having determined the form of variability, Darwin comes to the conclusion that only inherited changes are important for the evolutionary process, since only they can accumulate from generation to generation. According to Darwin, the main factors in the evolution of cultural forms are hereditary variability and selection made by man (Darwin called such selection artificial).
What are the driving forces behind the evolution of species in nature? Darwin considered it possible to explain the historical variability of species only through the disclosure of the reasons for adaptability to certain conditions. Darwin came to the conclusion that the adaptability of natural species, as well as of cultural forms, is the result of selection, but it was produced not by man, but by environmental conditions.
To the factors limiting the number of species (this means, causing the struggle for existence), Darwin refers to the amount of food, the presence of predators, various diseases and unfavorable climatic conditions. These factors can influence the abundance of species directly and indirectly, through the goal of complex relationships. Mutual contradictions between organisms play a very important role in limiting the number of species. For example, germinated seeds die more often because they sprouted on soil already densely overgrown with other plants. These contradictions take on an especially acute character in those cases when the question is about the relationship between organisms with similar needs and similar organization. Therefore, the struggle for existence between species of the same genus is tougher than between species of different genera. The contradictions between individuals of the same species (intraspecific struggle) are even more intense.
The natural result of the contradictions between organisms and the external environment is the extermination of some of the individuals of the species. If some of the individuals of each species die in the struggle for existence, then the rest are able to overcome unfavorable conditions.
Selection occurs continuously over the course of an endless series of successive generations and preserves mainly those forms that are more consistent with these conditions. Natural selection and the elimination of a part of a particular species are inextricably linked and are necessary condition evolution of species in nature.
The scheme of action of natural selection in a species system, according to Darwin, is as follows:
1. Variability is inherent in any group of animals and plants, and organisms differ from each other in many different ways.
2. The number of organisms of each species that are born into the world is greater than the number that can find food and survive. However, since the abundance of each species in natural conditions is constant, it should be assumed that most of the offspring perishes. If all descendants of any species survived and reproduced, they would very soon supplant all other species on the globe.
3. Since more individuals are born than can survive, there is a struggle for existence, competition for food and habitat. It can be an active life-and-death struggle, or less obvious; but no less effective competition, as, for example, when plants experience drought or cold.
4. Among the many changes observed in living things, some facilitate survival in the struggle for existence, while others lead to the fact that their owners perish. Survival of the fittest is at the core of natural selection theory.
5. Surviving individuals give rise to the next generation, and thus "successful" changes are passed on to subsequent generations. As a result, each subsequent generation turns out to be more and more adapted to the environment; as the environment changes, further adaptations arise. If natural selection has been in effect for many years, then the last offspring may turn out to be so dissimilar from their ancestors that they can be distinguished into an independent species.
It may also happen that some members of a given group of individuals will acquire some changes and will be adapted to the environment in one way, while other members, possessing a different complex of changes, will be adapted differently; In this way, from one ancestral species, provided that such groups are isolated, two or more species may arise.
5. The main results of evolution (according to Charles Darwin)
The main result of evolution is the improvement of the adaptability of organisms to living conditions, which entails the improvement of their organization. As a result of the action of natural selection, individuals with traits useful for their prosperity are preserved. Darwin provides a lot of evidence for the increase in the fitness of organisms due to natural selection. This, for example, is widespread among animals of the cover color (according to the color of the area in which the animals live, or according to the color of individual objects. or inedible animals.) Some animals have a threatening color in the form of bright repelling spots. , shell, scales, etc. All these adaptations could appear only as a result of natural selection, ensuring the existence of the species in certain conditions. Among plants, a wide variety of adaptations to cross-pollination, the spread of fruits and seeds are widespread. different kinds of instincts play (the instinct of caring about offspring, instincts associated with obtaining food, etc.).
At the same time, Darwin notes that the adaptability of organisms to the environment (their expediency), along with perfection, is of a relative nature. When conditions change abruptly, useful traits can be useless or even harmful. For example, in aquatic plants that absorb water and substances dissolved in it, the entire surface of the body has a poorly developed root system, but the surface of the shoot and the airborne tissue - aerenchyma, formed by the system of intercellular spaces that permeate the entire body of the plant are well developed. This increases the surface of contact with the environment, providing better gas exchange, and allows plants to more fully utilize light and absorb carbon dioxide. But when the reservoir dries up, such plants will die very quickly. All their adaptive traits that ensure their prosperity in aquatic environment, turn out to be useless outside of it.
Another important result of evolution is the increase in the diversity of species of natural groups, that is, the systematic differentiation of species. The general increase in the variety of organic forms greatly complicates the relationships that arise between organisms in nature. Therefore, in the course of historical development, the most highly organized forms, as a rule, gain the greatest advantage. Thus, the progressive development of the organic world on Earth from lower to higher is carried out. At the same time, stating the fact of progressive evolution, Darwin does not deny morphophysiological regression (that is, the evolution of forms, adaptation of which to environmental conditions go through simplifying the organization), as well as such a direction of evolution that does not lead to either complication or simplification of organization. living forms. The combination of different directions of evolution leads to the simultaneous existence of forms that differ in terms of the level of organization.
Conclusion
The driving forces of evolution, according to Darwin, are hereditary variability and natural selection. Variability serves as the basis for the formation of new traits in the structure and functions of organisms, and heredity fixes these traits. As a result of the struggle for existence, the most adapted individuals survive and participate in reproduction, that is, natural selection, the consequence of which is the emergence of new species. It is essential that the adaptability of organisms to the environment is relative.
Independently of Darwin, A. Wallace came to similar conclusions. T. Huxley (who proposed the term "Darwinism" in 1860), F. Müller and E. Haeckel, A.O. and V.O. Kovalevskiy, N.A. and A.N. Severtsov, I.I. Mechnikov, K.A. Timiryazev, I.I. Schmalhausen and others. In the 20-30s. XX century the so-called synthetic theory of evolution was formed, combining classical Darwinism and the achievements of genetics.
As a holistic materialistic doctrine, Darwinism made a revolution in biology, undermined the positions of creationism and vitalism, and rendered it in the 2nd floor. XIX century. a huge impact on the natural and social sciences, culture in general. However, even during Darwin's lifetime, along with the wide acceptance of his theory, various currents of anti-Darwinism arose in biology, denying or sharply limiting the role of natural selection in evolution and putting forward other factors as the main forces leading to speciation. The controversy on the main problems of the evolution of teaching continues in modern science.
Literature
1. Danilova V.S., Kozhevnikov N.N. Basic concepts of natural science. - M .: Aspect Press, 2000 .-- 256 p.
2. Concepts of modern natural science / Ed. V.N. Lavrinenko, V.P. Ratnikova. - M .: UNITI, 2000 .-- 203 p.
3. Concepts of modern natural science / S.I. Samygin. and others - Rostov n / D .: Phoenix, 1997 .-- 448 p.
4. Lemeza N.A., Kamlyuk L.V., Lisov N.D. Biology in exam questions and answers. - M .: Rolf, Iris-press, 1998 .-- 496 p.
5. Ruzavin G.I. Concepts of modern natural science: A course of lectures. - M .: Project, 2002 .-- 336 p.
6. Solopov E.F. Concepts of modern natural science. - M .: Vlados, 1999 .-- 232 p.
7. Horoshavina S.G. Concepts of modern natural science: A course of lectures. - Rostov n / D .: Phoenix, 2002 .-- 480 p.
Evolution means a gradual, natural transition from one state to another. Biological evolution is understood as the change in populations of plants and animals in a series of generations, directed by natural selection. For many millions of years, since the emergence of life on Earth, as a result of the continuous, irreversible, natural process of replacing some species with others, animal and plant forms that exist at the present time have been formed.
The idea that organisms evolve over generations has interested many naturalists. The idea that modern living organisms evolved from simpler, more primitive ones has long lived in the minds of people.
The first systematization of material about plants and animals was made by the famous Swedish scientist Karl Linnaeus in 1735. On the basis of one or two characters (mainly morphological), he classified plants and animals into species, genera, and classes. He took the species as the unit of classification.
K. Linnaeus's contribution to the progressive development of natural science is enormous: he proposed a system of animals and plants; introduced a binary system of double names; described about 1,200 genera and more than 8,000 plant species; reformed the botanical language and established up to 1,000 terms, many of which he introduced for the first time.
The works of K. Linnaeus helped his followers to organize the scattered factual material and improve it.
At the beginning of the 18th century. French scientist Jean-Baptisto Lamarck created the first evolutionary theory, which he set forth in the work "Philosophy of Zoology" (1809). According to Lamarck, some organisms evolved from others in the process of long evolution, gradually changing and improving under the influence of the external environment. The changes were consolidated and passed on by inheritance, which was the main factor that determined evolution.
J.-B. Lamarck was the first to expound the ideas of the evolution of living nature, which affirmed the historical development from the simple to the complex. Evidence for evolutionary theory put forward by J.-B. Lamarck, turned out to be insufficient for their complete acceptance, since no answers were given to the questions: how to explain the great variety of species in nature; what is the reason for the improvement of the organization of living beings; how to explain the adaptability of organisms to environmental conditions?
In Russia in the 18th century. notable for the emergence of new scientific ideas. The brilliant Russian scientist MV Lomonosov, materialist philosopher AN Radishchev, academician KF Wolf and other prominent scientists expressed ideas about the evolutionary development and changeability of nature.
MV Lomonosov argued that changes in the landscape of the Earth caused climate changes, in connection with which the animals and plants inhabiting it changed.
KF Wolff argued that during the development of the embryo of a chicken, all organs appear as a result of development, and not predetermined in advance (the theory of epigenesis), and all changes are associated with nutrition and climate. Not having yet sufficient scientific material, KF Wolff made an assumption that brilliantly anticipated the complete scientific evolutionary doctrine of the future.
In the XIX century. more and more metaphysical ideas about the immutability of living beings are criticized. In Russia, evolutionary ideas have been constantly expressed.
For example, Afanasy Kaverznev (late 18th - early 19th centuries) in his work "On the Rebirth of Animals" argued that species do exist in nature, but they are changeable. The factors of variability are changes in the environment: food, climate, temperature, humidity, relief, etc. He raised the question of the origin of species from one another and their relationship. A. Kaverznev confirmed his reasoning with examples from human practice in breeding animal breeds.
KF Roulier (1814-1858), 10-15 years before the publication of Charles Darwin's work "The Origin of Species", wrote about the historical development of nature, sharply criticizing the metaphysical views on the immutability and constancy of species and the descriptive direction in science ... He linked the origin of species with their struggle for existence.
Progressive evolutionary ideas were expressed by K. M. Baer (1792-1876), engaged in research in the field of embryology.
And another scientist - A. I. Herzen (1812-1870) in his works "Dilettantism in Science" and "Letters on the Study of Nature" wrote about the need to study the origin of organisms, their family ties, to consider the structure of animals in unity with physiological characteristics and that mental activity should also be studied in development - from the lowest to the highest, including humans. He saw the main task in revealing the reasons for the unity of the organic world with all its diversity and in explaining the origin of animals.
NG Chernyshevsky (1828-1889) in his works dwelled on the causes of variability and the question of the unity of the origin of man and animals.
The greatest English naturalist Charles Darwin (1809-1882), with his evolutionary theory, marked the beginning of a new era in the development of natural science.
The emergence of the evolutionary doctrine of Charles Darwin was facilitated by the socio-economic prerequisites - the intensive development of capitalism, which gave impetus to the development of science, industry, technology, and agriculture.
After a five-year voyage as a naturalist on the Beagle ship around the world and almost 20 years of generalization and comprehension of a large amount of evidence, he wrote the book "The Origin of Species by Natural Selection or Conservation of Favored Breeds in the Struggle for Life", published in 1859. , exactly 50 years after Lamarck's book.
During this journey, Darwin conceived the idea of evolution - a fresh concept of his own, correcting or improving the views and arguments of his predecessors. Darwin's idea explained the laws of the development of life better than any other theory.
Charles Darwin in this book outlined an evolutionary theory that revolutionized biological thinking and became a historical research method in biology.
Darwin's main merit is that he explained the mechanism of the evolutionary process, created the theory of natural selection. Darwin linked numerous individual phenomena of organic life into a logical whole, due to which the kingdom of living nature appeared before people as something continuously changing, striving for constant improvement.
Darwin's theory of natural selection was so reasonable and so well founded that most biologists soon recognized it. Darwin linked numerous individual phenomena of organic life into a logical whole, due to which the kingdom of living nature appeared before people as something continuously changing, striving for constant improvement.
Russian evolutionists prepared the ground for the acceptance of Darwin's theory, so in Russia it found its followers. However, at the time of Darwin, many areas of biological science were not well developed enough to give him little in developing his theory.
The main discoveries of Gregor Mendel in the doctrine of heredity (in genetics) were not known to Darwin (although they were created at the same time), nor to most scientists of his time. Cytology, which studies cells, did not yet know how cells divide. Paleontology, the science of fossils, was a young science, and the beautiful examples of fossil animals and plants that came later were not yet discovered.
The discreteness of the factual material and the absence of scientific achievements at that time, which appeared later, allowed Darwin's opponents to express an opinion about the lack of evidence of the correctness of the provisions of the theory of evolution.
Due to the lack of these and some other data, the development of the theory of evolution by natural selection in the 19th century. was an even more remarkable achievement than if it had taken place in the middle of the 20th century.
Thus, existed in the XVII-XVIII centuries. metaphysical ideas in science and philosophy have left a deep imprint on the study of physiological problems: all phenomena in nature were considered constant and unchanging. The evolutionary doctrine of Charles Darwin dealt a powerful blow to the metaphysical view of nature.
In general, the greatest achievement of biology in the 19th century. was the development of a cell theory, according to which the structure and development of animals and plant organisms there is a single form of organization of living matter - the cell. The cell theory was the basis for the subsequent development of evolutionary theory.
Evolutionary concepts before Charles Darwin
The traditional historical description of the pre-Darwinian period in the development of evolutionary doctrine begins with the name
Swedish naturalist Karl Linnaeus. However, Linnaeus himself did not assume the existence of a process of historical transformation of living things. He considered all living organisms to be permanent and unchanging, that is, as they were created by the Creator. Linnaeus entered science as the creator of the classification of flora and fauna.
Linnaeus also proposed a way to describe the belonging of a particular species in a particular taxonomic group - a binary (double) nomenclature. At his suggestion, the species began to be called two words, the first of which defines the genus, and the second - the species. All species names are given in Latin. After the species name, the surname of the author who gave the name is indicated in abbreviated form. For example, the field sparrow - Passer montanus L. (L. - Linnaeus). The binary nomenclature proposed by Linnaeus turned out to be so successful that it is still used today. Linnaeus described and named more than 1,000 previously unknown species
plants and animals, introduced over 100 scientific terms (eg pistil and stamen).
French zoologist Jean Baptiste Lamarck in 1809 proposed the first concept of evolution. It was based on two main premises: the internal desire of organisms for self-improvement, laid down by the Creator, and the inheritance of acquired traits. The scientist believed that all the diversity of species on Earth appeared due to the fact that the Creator created the simplest single-celled organisms and set their further gradation (development by complication). The adaptation of species to environmental conditions is the result of the activity or inactivity of organs. According to Lamarck, the long neck and legs of the giraffe are the result of the fact that many generations of its short-necked and short-legged ancestors ate the leaves of trees, after which they had to reach higher and higher. The slight lengthening of the neck and legs, which occurs in each generation, was inherited until the length of these parts of the body reached the present. Thus, according to Lamarck, the emergence of a new species is based on the following mechanisms:
Under the influence of the environment, changes that are beneficial to the body occur;
These changes are inherited by descendants;
The activity or inactivity of organs accelerates the process of speciation.
Lamarck's theory paved the way for modern evolutionary theory, but his views on the mechanisms of variability are widely accepted. It has been found that environmental conditions affect the phenotype without affecting the genotype.
State educational institution
Secondary vocational education of the city of Moscow
Medical College №7
Department of Health of the city of Moscow
Abstract on the topic: The history of the development of evolutionary ideas of Charles Darwin
Performed:
1st year student of 11 group
Syrovatskaya Lily
Moscow 2010
TABLE OF CONTENTS
INTRODUCTION
3
BACKGROUND OF THE CREATION OF THE EVOLUTIONARY THEORY OF CH.DARWIN
4
-
7
- DRIVING FORCES OF EVOLUTION ACCORDING TO CH.DARWIN
8
- BIBLIOGRAPHY
13
INTRODUCTION
Man has always sought to know the world around him and determine the place that he occupies in it. How did modern animals and plants come about? What led to their astounding diversity? What are the reasons for the disappearance of fauna and flora, far from us? What are the further paths for the development of life on Earth? Here are just a few questions from the huge number of riddles, the solution of which has always worried mankind. One of them is the very beginning of life. The question of the origin of life at all times, throughout the entire history of mankind, was not only of cognitive interest, but of great importance for the formation of the worldview of people.For the first time, the term "evolution" (from the Latin evolutio - deployment) was used in one of the embryological works by the Swiss naturalist Charles Bonnet in 1762. At present, evolution is understood as an irreversible process of change in a system that occurs in time, due to which something arises - something new, heterogeneous, worth no higher degree of development.
The theory of evolution is designed to explain the past, present and future, which Darwin does in the simplest possible way. His work "The Origin of Species by Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life" (1859) is available to any literate person who is ready to enjoy a book whose language borders on poetry: "... from such a simple beginning, an infinite number of the most beautiful and most amazing forms ”.
BACKGROUND OF THE CREATION OF THE EVOLUTIONARY THEORY OF CH.DARWIN
To appreciate the full significance of the upheaval in biological science accomplished by Charles Darwin, it is necessary to pay attention to the state of science and socio-economic conditions of the first half of the 19th century, when the theory of natural selection was created.The 19th century was a period of discovery of the fundamental laws of the universe. By the middle of the century, many major discoveries were made in natural science. The French scientist P. Laplace mathematically substantiated I. Kant's theory of the development of the solar system. The idea of development is introduced into philosophy by G. Hegel. AI Herzen in "Letters on the Study of Nature", published in 1845 - 1846, outlined the idea of the historical development of nature from inorganic bodies to man. He argued that in natural science, only those that are based on the principle of historical development can be correct generalizations. The laws of conservation of chemical elements were discovered. A little time will pass and D.I.Mendeleev will publish (1869) his famous Periodic Table of Elements. In 1830, the English naturalist Charles Lyell (1797 - 1875) substantiated the idea of the variability of the Earth's surface under the influence of various natural causes and laws: climate, water, volcanic forces, organic factors. Lyell expressed the idea that the organic world is gradually changing, which was confirmed by the results of paleontological studies of the French zoologist J. Cuvier (1769 - 1832). Lyell's theory had a great influence on the formation of Charles Darwin's worldview.
In the first half of the 19th century, the idea of the unity of all nature was developed. The Swedish chemist I. Berzelius (1779 - 1848) proved that all animals and plants consist of the same elements that are found in inanimate nature, and the German chemist F. Wöhler (1800 - 1882) for the first time in 1824 chemically synthesized in a laboratory oxalic acid, in 1828 - urea, thus showing that the formation of organic substances is carried out without the participation of some "vital force".
In the 18th - 19th centuries, as a result of the colonization of vast territories and their exploration, the Europeans significantly expanded their ideas about the diversity of the organic world, about the patterns of its distribution over the continents of the globe. Systematics is developing intensively: all the diversity of the organic world required its classification and reduction into a certain system, which was important for the development of the idea of the kinship of living beings, and then of the unity of their origin.
In the first half of the 19th century, a detailed study of the geographical distribution of organisms began; biogeography and ecology begin to develop, the first generalizations of which were important for substantiating the idea of evolution. So, in 1807, the German naturalist A. Humboldt (1769 - 1859) expressed the idea of the dependence of the geographical distribution of organisms on the conditions of existence. The Russian scientist K.F.Rul'e (1814 - 1858) tries to interpret the historical change in the face of the Earth and the conditions of life on it and the influence of these changes on the change in animals and plants. His student N. A. Severtsov (1827 - 1885) expressed ideas about the relationship of organisms with the environment, about the formation of new species as an adaptive (adaptive) process.
At the same time, comparative morphology and anatomy were developing. Her successes helped to clarify not only the similarity of the structure of various animal species, but also such a similarity in their organization, which suggested a deep connection between them, about their unity. Comparative embryology begins to take shape. In 1817 - 1818. I. Kh. Pander discovered the germ layers and the universality of their establishment in the embryogenesis of multicellular animals. The German researcher M. Rathke applied the theory of germ layers to invertebrates (1829).
At the end of the 20s of the XIX century, the Russian academician K.M.Ber (1792 - 1870) showed that the development of all organisms begins with the egg, and that at the early stages of development, a striking similarity is found in the structure of the embryos of animals belonging to different classes (later Baire's generalizations were called by Charles Darwin "the law of embryonic similarity" and were used by him to prove evolution). A remarkable sign of embryonic similarity is, for example, the presence of branchial slits in the embryos of all vertebrates, including humans.
In 1839, T. Schwann created a cell theory, which substantiated the generality of the microstructure and development of animals and plants. Thus, the intensive development of science, the accumulation in various fields of natural science of a large number of facts incompatible with creationist concepts, prepared the basis on which Darwin's teaching was successfully developed.
The socio-economic conditions of the first half of the 19th century also contributed to the development of evolutionary theory. The establishment of the capitalist mode of production, together with the expansion of the British colonial empire, was accompanied by an intensive restructuring of agriculture, which contributed to the development of selection. The achievements of breeders testified that a person can change breeds and varieties, adapt them to their needs through artificial selection. Breeders of the first half of the 19th century not only practically proved the power of artificial selection, but also tried to theoretically substantiate it. This significantly influenced the formation of the idea of evolution in Darwin, and most importantly, relying on the results of breeding practice as a kind of model, he was able to move on to the analysis of the process of speciation in nature.
The formation of Charles Darwin's ideas was also facilitated by some political and economic ideas, primarily the views of A. Smith and T. Malthus. A. Smith (1723 - 1790) proceeded from the then consolidated idea of natural laws and created the doctrine of "free competition". He believed that the engine of free competition is "natural self-interest or" natural selfishness "of a person, and this is the source of national wealth. The unadapted in the process of free competition are eliminated. The idea of competitive relations also influenced the formation of ideas about the development of wildlife. These ideas, in all likelihood, prompted Darwin to think about the existence of some analogies in nature and contributed to the creation of evolutionary theory.
So, in the most diverse areas of natural science (geology, paleontology, biogeography, embryology, comparative anatomy, the doctrine of the cellular structure of organisms), the materials collected by scientists contradicted the ideas of divine origin and the immutability of nature. The English scientist Charles Darwin was able to correctly explain all these facts, generalize them, and create a theory of evolution.
CH. DARWIN'S FORWARDING MATERIAL
Let's trace the main stages of life, the formation of Darwin's worldview and his system of evidence. Like many genius personalities, Charles Darwin was a man who lived by his own laws. He showed no early desire to learn. Young Charles, born into a well-to-do family, was considered a very mediocre student at school and hated the monotony of the curriculum focused on the study of classical languages. Fulfilling the will of his father, Darwin entered the Faculty of Medicine at the University of Edinburgh, but classes in the anatomical disgust, and he interrupted the course of study. Darwin's father insisted on his training in the theological department of the University of Cambridge, which would give him the right to become a pastor later. Thus, a person whose ideas were considered by some churchmen as a grave insult to the holy faith received a theological education. Soon Darwin accepted an offer to participate as a naturalist on the voyage of the research vessel Beagle; he later called this experience "the first real teaching or enlightenment of my mind." During the five-year journey, observations made with great precision and professionalism made Darwin ponder the reasons for the similarities and differences between species. His main find, found in the geological deposits of South America, is the skeletons of extinct giant non-toothed, very similar to modern armadillos and sloths. Darwin was even more impressed by the study of the species composition of animals in the Galapagos Islands, where he was able to observe closely related species of turtles and thrush - mockingbirds that lived on separate neighboring islands. Moreover, as can be assumed, each of these two groups descended from one common ancestor. It would be absurd to assume that for each newly emerging volcanic island, the creator creates his own special types of animals. It is more reasonable to draw another conclusion: the birds came to the island from the mainland and changed as a result of adaptation to new living conditions. Thus, Darwin raises the question of the role of environmental conditions in speciation. Darwin observed a similar picture off the coast of Africa. The animals living on the Cape Verde Islands, despite some similarities with the mainland species, still differ from them in essential features. These and many other facts have shaken Darwin's faith in the creation of species. Returning to England, he set himself the task: to resolve the issue of the origin of the species.DRIVING FORCES OF EVOLUTION ACCORDING TO CH.DARWIN
In Darwin's evolutionary theory, the premise of evolution is hereditary variability, and the driving forces of evolution are the struggle for existence and natural selection. When creating an evolutionary theory, Charles Darwin repeatedly refers to the results of breeding practice. He tries to find out the origin of domestic animal breeds and plant varieties, to reveal the reasons for the diversity of breeds and varieties and to identify the methods by which they were obtained. Darwin proceeded from the fact that cultivated plants and domestic animals are similar in a number of ways to certain wild species, and this cannot be explained from the standpoint of the theory of creation. Hence the hypothesis that cultural forms evolved from wild species. On the other hand, the plants and tamed animals introduced into culture did not remain unchanged: man not only chose the species of interest from the wild flora and fauna, but also significantly changed them in the right direction, while creating a large number of plant varieties from a few wild species and animal breeds. Darwin showed that the basis for the diversity of varieties and breeds is variability - the process of the appearance of differences in descendants in comparison with ancestors, which determine the diversity of individuals within a variety, breed. Darwin believes that the causes of variability are the impact on organisms of environmental factors (direct and indirect, through the "reproductive system"), as well as the nature of the organisms themselves (since each of them specifically reacts to the impact of the external environment). Having determined for himself his attitude to the question of the causes of variability, Darwin analyzes the forms of variability and distinguishes three of them: definite, indefinite and correlative.Certain, or group, variability is variability that occurs under the influence of some environmental factor that acts equally on all individuals of a variety or breed and changes in a certain direction. An example of such variability is an increase in body weight in all animal individuals with good nutrition, changes in hairline under the influence of climate, etc. A certain variability is massive, covers the entire generation and is expressed in each individual in a similar way. It is not hereditary, that is, when the descendants of the changed group, when placed in other environmental conditions, acquired by their parents, the traits are not inherited.
Uncertain, or individual, variability manifests itself specifically in each individual, that is, it is single, individual in character. With indeterminate variability, various differences appear in individuals of the same variety, breed, in which, under similar conditions, one individual differs from others. This form of variability is indefinite, that is, a sign under the same conditions can change in different directions. For example, in one variety of plants, specimens appear with different color of flowers, different intensity of color of petals, etc. The reason for this phenomenon was unknown to Darwin. Uncertain, or individual, variability has a hereditary character, that is, it is steadily transmitted to offspring. This is its great importance for evolution.
With correlative, or relative variability, a change in any one organ is the cause of changes in other organs. For example, dogs with a poorly developed coat usually have underdeveloped teeth, pigeons with feathered legs have membranes between the toes, pigeons with a long beak usually have long legs, white cats with blue eyes are usually deaf, etc. Of the factors of correlative variability, Darwin makes an important conclusion: a person, selecting any feature of the structure, almost "probably will inadvertently change other parts of the body on the basis of the mysterious laws of correlation."
etc.................
