Lamarck's theory of inheritance of acquired traits.
Lamarck distributed all animals into six steps, levels (or, as he said, "gradations") according to the complexity of their organization. The farthest from a person are ciliates, the closest to him are mammals. At the same time, all living things have an inherent desire to develop from simple to complex, to move up the "steps".
The living world is constantly evolving smoothly. Based on this, Lamarck came to the conclusion that species in nature do not actually exist, there are only individual individuals. Lamarck consistently applied in his theory the famous Leibniz principle: "Nature does not make leaps." Denying the existence of species, Lamarck referred to his vast experience in taxonomy.
When asked why a person does not notice the constant transformation of some species into others, Lamarck replied: “Suppose that human life lasts no more than one second in comparison with the life of the universe, in this case not a single person who contemplates the hour hand will see how she gets out of her position. " Even after tens of generations, its movement will not be noticeable.
While improving, organisms are forced to adapt to environmental conditions.
To explain this, the scientist formulated several "laws". First of all, it is “ the law of exercise and no exercise of organs ". The most famous of the examples given by Lamarck is that of giraffes. Giraffes have to constantly stretch their necks to reach the leaves growing above their heads. Therefore, their necks become longer, stretched. The anteater, in order to catch ants in the depths of the anthill, has to constantly stretch out its tongue, and it becomes long and thin. On the other hand, the eyes only interfere with the mole under the ground, and they gradually disappear.
If the organ is exercised frequently, it develops. If the organ is not exercised, it gradually dies off.
Another "law" of Lamarck is " law of inheritance of acquired characteristics ". Useful traits acquired by animals, according to Lamarck, are passed on to offspring. Giraffes passed on to their descendants an elongated neck, anteaters inherited a long tongue, and so on.
Basic principles of the evolutionary theory of Charles Darwin.
The essence of the Darwinian concept of evolution comes down to a number of logical, experimentally verified and confirmed by a huge amount of factual data:
1 ... Within each species of living organisms, there is a huge range of individual hereditary variability in morphological, physiological, behavioral and any other characteristics. This variability can be continuous, quantitative, or intermittent qualitative, but it always exists.
2 ... All living organisms multiply exponentially.
3 ... Vital resources for any kind of living organisms are limited, and therefore there must be a struggle for existence either between individuals of the same species, or between individuals different types, or with natural conditions... In the concept of "struggle for existence" Darwin included not only the actual struggle of an individual for life, but also the struggle for success in reproduction.
4 ... Under the conditions of the struggle for existence, the most adapted individuals survive and give offspring, having those deviations that accidentally turned out to be adaptive to the given environmental conditions. This is a fundamentally important point in Darwin's argument. Deviations do not arise directionally - in response to the action of the environment, but randomly. Few of them prove to be useful in specific conditions. The descendants of the surviving individual who inherit the beneficial deviation that allowed their ancestor to survive are more adapted to the given environment than other members of the population.
5 ... Survival and preferential reproduction of adapted individuals Darwin called natural selection.
6 . Natural selection separate isolated varieties in different conditions of existence gradually leads to divergence (divergence) of the characteristics of these varieties and, ultimately, to speciation.
On these postulates, flawless from the point of view of logic and supported by a huge number of facts, was created modern theory evolution.
Darwin's main merit is that he established the mechanism of evolution that explains both the diversity of living beings and their amazing expediency, adaptation to the conditions of existence. This mechanism - gradual natural selection of random undirected hereditary changes.
Synthetic theory of evolution (STE).
This is a modern evolutionary theory, which is a synthesis of various disciplines, primarily genetics and Darwinism. STE also relies on paleontology, taxonomy, molecular biology and others.
The “core” of ST is an article by SS Chetverikov “On some aspects of the evolutionary process from the point of view of modern genetics” (1926). It shows the compatibility of the principles of genetics with the theory of natural selection, and also gives the beginning of the foundations of evolutionary genetics.
In the 1930s and 1940s, a wide synthesis of genetics and Darwinism took place. Genetic ideas have penetrated into taxonomy, paleontology, embryology, biogeography. The term "modern" or "evolutionary synthesis" comes from the title of the book by J. Huxley "Evolution: The Modern synthesis" (1942). The expression "synthetic theory of evolution" in its exact application to this theory was first used by J. Simpson in 1949.
- the elementary unit of evolution is a local population;
- material for evolution is mutational and recombination variability;
- natural selection is considered as the main reason for the development of adaptations, speciation and the origin of supraspecific taxa;
- gene drift and the founder principle are the reasons for the formation of neutral traits;
- a species is a system of populations reproductively isolated from populations of other species, and each species is ecologically isolated;
- speciation consists in the emergence of genetic isolating mechanisms and is carried out mainly in conditions of geographical isolation.
Thus, the synthetic theory of evolution can be characterized as a theory of organic evolution by natural selection of genetically determined traits.
| SIGNS | K. LINNEY's evolutionary theory (metaphysician: nature was created by God and is unchangeable) | The evolutionary theory of J.-B. LAMARK
| Evolutionary theory CH. DARWIN 1809-1882
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| Theory creation | In the XVIII century. K. Linnaeus created artificial system nature in whichthe species was recognized as the smallest systematic unit ... He introducednomenclature of double species names (binary) in Latin, which made it possible to systematize the organisms of different kingdoms known by that time by taxonomic groups. In 1751 his book "Philosophy of Botany" was published, where he outlined the binomial (binary) nomenclature developed by him. Scientistdivided all living organisms known to him into groups, based on anatomical-morphological and partly physiological criteria(the work "System of Nature", described 10 thousand species of plants and 4.5 thousand species alive); in other words, its classification was artificial. Therefore, in this system, systematically distant organisms sometimes found themselves in one class, and related ones in different ones. K. Linnaeusfor the first time placed a man and a great ape in one detachment, but he did not think that man was descended from apes.The species was identified and recognized as a really existing unit of taxonomy. Realized the shortcomings of his system. | In 1794 - the term "Zoology of invertebrates" (the foundations of the taxonomy of invertebrates), 1802 - "Biology". In 1809 he proposedthe first holistic theory of evolution (book "Philosophy of Zoology"), was evaluated only after 50 years. Analyzed and listed the similarities and differences between living and nonliving matter. Basic position:matter and the laws of its development were created by the creator . The first factor of evolution – gradation of internal "striving for improvement". How and why this desire arose, Lamarck did not explain and did not even consider this issue worthy of attention. The result of the graduation is the simultaneous existence in nature of organisms of different levels of complexity.The second factor of evolution – the constant influence of the external environment determines the formation of the whole variety of adaptations of living beings.The third factor of evolution – heredity. Evolution according to Lamarck was presented as a continuous translational motion from lower forms life to the highest ladder of beings). To explain the varying degrees of complexity of the structure observed among modern species, he admitted the constant spontaneous generation of life: the ancestors of more highly organized forms were born earlier, and therefore their descendants went further along the path of progress.2 laws: the law of exercise and non-exercise, the law of inheritance of acquired characteristics. | Proposed in 1859 by the English naturalist Charles Darwin Charles Darwin's evolutionary doctrine includes three major components: 1. Evidence for the historical development of the organic world 2. Statement on the driving forces of evolution 3. Concept of the ways of evolutionary transformations. |
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| The emergence of life | K. Linnaeus shared metaphysical views on nature, seeing in it the original purposefulness, the wisdom of the Creator. | Life arose and arises through repeated spontaneous generation from inanimate nature (polyphilia). | Life arose, from the very beginning, formed by the creator in one or more forms (monophilia) |
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| Starting point of evolution | Initial expediency, the wisdom of the Creator. | Matter and the laws of its development, created by the creator. Single-celled organisms are capable of spontaneous generation, while organisms with a higher organization appeared as a result of long-term development. | Inborn personality, variability |
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| The influence of the environment on the body | At the end of his life, he recognized that species can arise by crossing or by changing the environment. | The environment, having caused a change in habits, causes a change in the functional activity of the body (repositioning of organs). The functional activity of organs causes changes in their nutrition, as a result of which their size and shape change. | The environment (for example, hunger, etc.) causes massive death of organisms and the survival of the fittest. Natural selection occurs |
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| Variability | The species of plants and animals do not change, they have retained their characteristics from the moment of creation. While reproducing, they retain all the characteristics of the ancestral pair. Different species are not related by kinship. | Lamarck believed that changes arising under the influence of the environment can be inherited. He believed that increased exercise of organs leads to their enlargement, and failure to exercise leads to degeneration. So Lamarck explained the long nose of the anteater by the fact that his ancestors from generation to generation exercised their nose, sniffing in search of ants. He considered the reduction of eyes in moles as a consequence of their failure to exercise in a number of generations. Neither Lamarck nor his followers asked the question, why, in fact, intensive exercise, the use of an organ must necessarily lead to its improvement, improvement, and not, for example, to wear, how do machine parts wear out? | Natural selection, supported by sexual selection, gives progressive and progressive variability in descending generations |
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| Formation of new species | "There are as many species as the Almighty created at the beginning of life" | The views are realnot exists , this is a purely speculative concept invented forin order to make it easier to consider in aggregate moreindividuals, since according to Lamarck, “in nature there is nowhat other than individuals. "Individual variability is continuous, therefore, the border between species can be drawn here and there - where it is more convenient. Hereditary variability leads to the formation of progressive and degrading series of organisms, in accordance with the nature of the habitat. Explained the origin of man from the highest "four-armed monkeys". | Increasing variability leads to divergence of characters and the formation of new species |
Other scientists: J. Cuvier, J. de Saint-Hilaire, the first Russian evolutionists
The main features of the evolutionary theory of Charles Darwin
1. Evidence for evolution. Charles Darwin finds evidence of the evolutionary process in many areas of biology, of which the main provisions are laid down in three groups of scientifically based facts.Paleontological data. Darwin provides evidence of numerous scientific facts showing that ancient forms of organisms are very different from modern ones, but as we approach modernity, there is an increase in the similarity of fossil forms. This indicates the sequence of evolutionary transformations of living forms. Embryological materials. Comparison of the embryos of modern animals, which are very distant in their morphological similarity, shows a great similarity between them. This can only be explained by the unity of origin and kinship relationships. Biogeographic materials. Comparison of the faunas of oceanic islands separated from the continents long ago, on the one hand, shows the commonality of their origin, and on the other hand, significant changes in the structure of organisms, which indicate different directions of evolution, depending on the unequal conditions of existence.
2. The driving forces of evolution. Darwin attributed such phenomena to the factors of the evolutionary process asvariability, heredity and natural selection.
Among the phenomena of variability, he especially singled out definite and indefinite forms. Of themonly indefinite variability is capable of providing material for evolutionary transformations since it arises by chance, its manifestations are multidirectional, and they can also be inherited, i.e. persist for generations. Charles Darwin considered natural selection to be the main and guiding force in the evolution of organic forms. AT short form the theory of natural selection can be summarized as follows:
and. All species of animals and plants tend to increase their numbers. In this case, the value of variability also increases, i.e. the number of individuals carrying small, i.e. relatively harmless to life, deviations in inherited traits. This leads to the appearance of a large number of individuals of different quality, with one or another trait. Inhabited in natural environment they find themselves in a state of struggle for existence, both among themselves and between individuals of other species. In the harsh environmental conditions, some organisms survive better than others and leave offspring with more beneficial hereditary traits.
at. The process of accumulation of useful deviations as a result of such a selective average statistical survival of individuals in the course of the struggle, Darwin called the existence of natural selection. Nothing is created anew by natural selection. It takes place on the basis of existing devices. When environmental conditions remain relatively stable, natural selection maintains existing accommodations. When the conditions of existence change, the average values \u200b\u200bof the survival of organisms change. Let's assume that the climate in the northern region has warmed sharply. Such phenomena have happened before and are possible in the future. At the same time, the mortality of individuals with thick fur may be higher than that of individuals with a genotype that gives less dense fur. Then the population can accumulate individuals with hereditary properties, which give a lower density of fur. The thinning of fur in warm environmental conditions can be assessed as the emergence of a new adaptation.
Natural selection is the main driving force behind evolution ... On its basis, in the course of the emergence of more and more adaptations of organisms that contribute to their better survival and reproduction, a process arisesdivergences (discrepancies in the characteristics of intraspecific groups, the emergence of new species and on this basis the identification of genera, families, classes and types). In the constructions of Charles Darwin, the concept of monophyletic evolution was formed, showing that all organisms on Earth have the same roots of origin. The unity of the whole world of living organisms on our planet is the result biological evolution based on natural selection.
3. Difficulties which Charles Darwin experienced when creating his theory:1. Lack of scientifically developed theory of heredity. At the time of the writing of Darwin's book, nothing was known about the inheritance of traits. Mendel published his work in 1865, but at that time information spread very slowly, and very few understood the significance of Mendel's work. His work never reached Darwin. In his experiments, he observed similar phenomena. But he did not pay due attention to this. Therefore, Charles Darwin adhered to the then widespread ideas about that. That the traits of the parents are transmitted to the offspring in half (the theory of mixed inheritance). Because of this, there were complications with Jenkin's nightmare, forcing Darwin to partially allow the inheritance of useful devices. He even had to invent a hypothesis of pangenesis (about the existence of gemmules that penetrate the germ cells and cause variability), which he himself soon abandoned.
2. A small amount of data confirming the work of selection in natural conditions. There was little such evidence in Darwin's writings. Therefore, he had to first prove the theory of artificial selection, and then go on to prove the theory of natural selection. The theory of artificial selection was the cardinal issue of his evolutionary theory, which proves that human activity can quickly and effectively change the characteristics of animals and plants in the direction he needs.
4. Darwin about the sight. A consequence of the passage of natural selection is the emergence of adaptations that allow species to exist more efficiently in the environment. On the basis of adaptations, it becomes possible to distinguish between varieties, i.e. within a species, different groups of organisms appear, and then subspecies appear. Thus, instead of the old concept of an absolutely unchanging, stable and morphologically isolated species, Darwin put forward new ideas about a changing species. In his concept, he considered the view as if from two projections:
In a given period of time, he represents a species as a really existing natural unit. However, according to Charles Darwin, the species as a real natural unit possesses high degree variability, so that sometimes it is very difficult to distinguish not only the varieties within the species. But also one view from another. A number of transitional forms can be found between the two types. Therefore, Darwin believed that species are distinct varieties and varieties are nascent species.
A species in the course of a long historical period of time is a really evolving unit, in its morphological development passing through a number of adaptive transformations. At the same time, the specific characters become even more variable and difficult to subdivide, because evolution is slow and gradual.
After Charles Darwin's works, the evolutionary idea was first united by the concept of a really existing and developing species.
5 ... Evolutionary transformation paths Charles Darwin depicted in the form of a diagram showing the course of divergent evolution, i.e. evolution with divergence of signs. In this scheme, the importance of random factors in evolution is especially emphasized, on the basis of which a natural historical process is formed, leading to a progressive complication of organisms.
Carl Linnaeus
To systematize a huge number of descriptions of animals and plants, some kind of unit of taxonomy was required. Such a unit, common to all living things, Linnaeus took the form. Linnaeus called a group of individuals similar to each other, like the children of the same parents and their children. The species consists of many similar individuals, giving fertile offspring. The entire organic world consists of various types of plants and animals.
Linnaeus began to name species in Latin, which was at that time the international language of science. Thus, Linnaeus solved a difficult problem: after all, when the names were given in different languages, the same species could be described under many names.
A very important merit of Linnaeus was the introduction into the practice of double names of species (binary nomenclature). He suggested calling each species in two words. The first is the name of the genus, which includes closely related species. For example, lion, tiger, domestic cat belong to the genus Felis (Cat). The second word is the name of the species itself (respectively Felis leo, Felis tigris, Felis domestica).
Man (whom he christened "Homo sapiens", Homo sapiens) Linnaeus quite boldly for his time placed in the class of mammals and a detachment of primates along with apes. He did it 120 years before Charles Darwin. He did not believe that humans were descended from other primates, but saw great similarities in their structure.
The system of plants and animals of Linnaeus was largely artificial; it did not reflect the course of the historical development of the world. Linnaeus was aware of this flaw in his system and believed that future naturalists should create a natural system of plants and animals, which should take into account all the characteristics of organisms, and not one or two signs. The science of that time did not have the knowledge necessary for this.
Linnaeus believed that the species of plants and animals do not change; they have retained their characteristics "from the moment of creation." According to Linnaeus, each modern look is the offspring of the original god-created parental couple. Each species multiplies, but, in his opinion, retains all the features of this ancestor couple unchanged.
As a good observer, Linnaeus could not help but see the contradiction between the concept of the complete immutability of plants and animals with what is observed in nature. He allowed the formation of varieties within a species due to the influence on organisms of climate change and other external conditions.
Jean Baptiste Lamarck
Jean Baptiste Lamarck, a French researcher, became the first biologist who tried to create a coherent and holistic theory of the evolution of the living world. Not appreciated by his contemporaries, half a century later, his theory became the subject of heated debate, which has not stopped in our time.
The most important work of Lamarck was the book "Philosophy of Zoology", published in 1809, in which he outlined his theory of the evolution of the living world. The basis of Lamarck's views was the provision that matter and the laws of its development were created by the creator. Lamarck analyzed the similarities and differences between living and nonliving matter and listed them. The most important of these differences is the ability to respond to external stimuli. In his opinion, the cause of life lies not in the living body itself, but outside it.
Lamarck introduced the concept of gradation - the internal "striving for improvement" inherent in all living things; the action of this factor of evolution determines the development of living nature, a gradual but steady increase in the organization of living beings - from the simplest to the most perfect. The result of graduation is the simultaneous existence in nature of organisms of varying degrees of complexity, as if forming a hierarchical ladder of beings. Considering the gradation to be a reflection of the main trend in the development of nature, Lamarck tried to give this process a materialistic interpretation: in a number of cases, he associated the complication of organization with the action of fluids entering the body from the external environment.
Another factor of evolution is the constant influence of the external environment, leading to a violation of the correct gradation and causing the formation of the whole variety of organisms' adaptations to environmental conditions. Environmental change is the main cause of speciation; while the environment is unchanged, the species remain constant; if there is a shift in it, the views change.
Life, according to Lamarck, can spontaneously arise on Earth and continues to emerge at the present time. In the 17th century, there were ideas that darkness and grain were needed for the spontaneous generation of mice, and rotten meat for the spontaneous generation of worms. Lamarck suggests that unicellular organisms are capable of spontaneous generation, and all animals and plants with a higher organization appeared as a result of long-term development of living organisms.
Lamarck introduces two laws of the development of living nature: "The law of exercise and non-exercise of organs" and "The law of inheritance of acquired characteristics."
The first law can be called the law of variability, in which Lamarck focuses on the fact that the degree of development of an organ depends on its function, the intensity of exercise, that young animals that are still developing are more capable of changing. The scientist opposes the metaphysical explanation of the form of animals as unchanging, created for a specific environment. At the same time, Lamarck overestimates the importance of function and considers that the exercise or non-exercise of the organ is an important factor in changing species.
The second law can be called the law of heredity; attention should be paid to the fact that Lamarck associates the inheritance of individual changes with the duration of the influence of the conditions that cause these changes, and as a result of their reproduction, their intensification in a number of generations. It is necessary to emphasize the fact that Lamarck was one of the first to analyze heredity as an important factor in evolution. At the same time, it should be noted that Lamarck's position on the inheritance of all traits acquired during life was erroneous: further research showed that only hereditary changes are of decisive importance in evolution.
Lamarck extends the provisions of these two laws to the problem of the origin of breeds of domestic animals and varieties of cultivated plants, and also uses them to explain the animal origin of man. Human Origins.
Charles Darwin's theory of evolution
At the end of 1831, the Beagle began a five-year round the world voyage. This journey was an important event in my life. Darwin. He collected a huge and very valuable scientific material, which played an exceptional role in the development of the evolutionary idea.
Darwin owns a number of interesting paleontological finds. After analyzing numerous facts, Darwin came to the conclusion that extinct and current animals have a common origin, but the latter have changed significantly. The reason for this could be changes that occurred over time for earth surface... They could also be the cause of the extinction of species, the remains of which are found in the earth's strata.
After returning from the trip, Darwin processes and publishes the collected geological, zoological and other materials in detail and works on the development of the idea of \u200b\u200bthe historical development of the organic world, which originated during the trip. For over 20 years he has been persistently developing and substantiating this idea, continues to collect and generalize facts, especially from the practice of plant growing and animal husbandry.
After the publication of "The Origin of Species", Darwin continues to actively work on substantiating the problem of evolution, comprehensively analyzing the patterns of variability, heredity, and artificial selection. Darwin extended the idea of \u200b\u200bthe historical development of plants and animals to the problem of the origin of man. In 1871, his book "The Descent of Man and Sexual Selection" was published, which analyzed in detail the numerous evidence of the animal origin of man. "The Origin of Species" and the next two books constitute a single scientific trilogy, they provide irrefutable evidence of the historical development of the organic world, establish the driving forces of evolution, determine the paths of evolutionary transformations, and finally show how and from what positions one should study complex phenomena and processes of nature. Darwin published 12 volumes of his writings.
Variability and heredity
In the conditions of the dominance of the idea of \u200b\u200bconstancy, immutability of species, it was important for Darwin to show how their diversity is formed. Therefore, first of all, he substantiates in detail the position on the variability of living beings. The first section of the book "The Origin of Species" is devoted to the analysis of this very problem. Darwin draws attention to a wide variety of plant varieties and animal breeds, the ancestors of which are one species or a limited number of wild species.
Under a certain (group) variability, Darwin understood a similar change in all individuals of the offspring in one direction due to the influence of certain conditions (change in growth with a change in the quantity and quality of food, thickness of the skin and thickness of the coat from climate change, etc.); under indefinite (individual) variability - the appearance of various insignificant differences in individuals of the same variety, breed, species, which, while existing in similar conditions, one individual differs from others (the descendants of one pair of animals are not completely similar, although they develop in similar conditions). Such variability is a consequence of the uncertain influence of the conditions of existence on each individual individual. A significant diversity of individuals due to individual variability is an important material for the evolutionary process. Noting that individual variability, as a rule, leads to minor changes, Darwin does not exclude the possibility of sharp deviations.
Darwin understood the organism as an integral system, the individual parts of which are closely interconnected. Therefore, a change in the structure or function of one part often leads to a change in another or others. Compensatory variability is that the development of some organs or functions is often the cause of the oppression of others, that is, there is an inverse correlation, for example, between milkiness and meatiness of cattle.
The second important factor in evolution is heredity, that is, the ability of all organisms to transmit structural features, functions, and development to their offspring. This feature was well known. Practitioners have always paid attention to the ability of organisms to reproduce their own kind, and breeders paid large sums for good animals. Darwin analyzed in detail the importance of heredity in the evolutionary process. He drew attention to cases of uniformity of hybrids of the first generation and splitting of traits in the second generation, he was aware of heredity associated with sex, hybrid atavisms and a number of other phenomena of heredity.
Artificial selection
Artificial selection is understood as a system of measures implemented by man to improve existing and create new breeds of animals and plant varieties with economically useful hereditary traits.
The creative function of artificial selection is based on the cumulative interaction in a number of generations of variability, heredity, selection, directional rearing, predominant reproduction of individuals with useful traits and culling of unwanted individuals. Thanks to this, from generation to generation, the development of useful traits is enhanced, and due to correlative variability, the whole organism is restructured. Artificial selection leads to divergence - a divergence of characters in breeds and varieties, the formation of a large variety of them.
When analyzing artificial selection and the process of shaping, Darwin emphasizes that an important condition for success is the predominant reproduction of some individuals or groups of individuals, which leads to an increase in the number of such individuals, the enhanced development of their traits in subsequent generations and the elimination of other individuals or groups of individuals from reproduction.
Darwin identified two forms of artificial selection - methodical and unconscious. Methodical selection - purposeful breeding of a breed or variety. The breeder sets a goal, determines the direction of work, fixes attention on those desirable traits that should be characteristic of the breed, variety. He uses the natural variability of organisms, conducts selection of pairs for mating, ensures the maximum development and consolidation of the desired traits in each subsequent generation, gradually approaches the goal and reaches it.
The oldest form of artificial selection was unconscious selection. With unconscious selection, a person does not set the goal of creating a new breed, variety, but only leaves it to the tribe and mainly reproduces the best individuals. Thanks to this differentiated approach, in a number of generations, certain characteristics of the reproduced individuals gradually increase, which ultimately, albeit slowly, leads to the formation of new breeds and varieties. Consequently, in this case, a person does not seek to develop a new breed, variety, but, using natural variability and heredity, through the reproduction of some individuals and culling of others, he slowly changes organisms.
Darwin stresses the special importance of unconscious selection from a theoretical point of view, because this form of selection also sheds light on the process of speciation. It can be seen as a bridge between artificial and natural selection.
Struggle for existence
Darwin drew attention to the extremely 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 complex and varied, multifaceted forms of dependence of organisms on environmental conditions and on other living beings a struggle for existence, or a struggle for life. Darwin was aware that the term was unfortunate, and warned that he was using it in a broad metaphorical sense, and not literally.
The relationship of organisms and species with physical conditions life, abiotic environment arise depending on climatic and soil conditions, temperature, humidity, illumination and other factors that affect the life of organisms. In the process of evolution, species of animals and plants develop a number of adaptations to unfavorable conditions. But the relativity of these adaptations, as well as the gradual changes in the environment, require constant improvement in adaptation to abiotic living conditions. On the other hand, living things also affect non wildlifechanging it.
Interspecies relationships are extremely diverse and rather complex. Of great importance are the relationships that are formed on the basis of food (trophic) connections, as well as the relationships that arise between different species in the struggle for habitats. The extreme expression of interspecific relationships is interspecific struggle, when one form displaces another or limits its number in a certain area.
Natural selection
Natural selection is also associated with the struggle for existence, the competition in life and the dependence of organisms on the environment, conditions of existence. The doctrine of natural selection as a driving and directing factor in the historical development of the organic world is a central part of Darwin's theory of evolution.
Darwin gives the following definition of natural selection: "The preservation of useful individual differences or changes, the elimination of harmful ones, I called natural selection, or the experience of the fittest." He warns that the selection of species should be understood as a metaphor, as a fact of survival, and not as a conscious choice.
So, natural selection is understood as the process of conservation and predominant reproduction in nature in a number of generations of organisms and groups of organisms that have adaptive characteristics useful for their life and development, which arose as a result of multidirectional individual variability. The opposite process - the extinction of the unadapted - is called elimination.
As a result of the competition in life in nature, there is a constant selective elimination of some individuals and the predominant survival and reproduction of individuals and groups of individuals, which, changing, have acquired useful features. As a result of crossing, the characteristics of one form are combined with the characteristics of another. So, from generation to generation, minor beneficial hereditary changes and their combinations accumulate, which over time become characteristic features population, variety, species. Selection constantly affects the entire organism, all its external and internal organs, their structure and function. This rather delicate and precise mechanism gradually accumulates new things, rebuilds, adapts, polishes organisms.
Jean Baptiste Lamarck is rightfully considered the founder of the evolutionary theory, which he expressed in his book "The Philosophy of Zoology", published in the early 19th century.
Lamarck's theory is based on the idea of \u200b\u200bgradation - an internal "striving for improvement" inherent in all living things; the action of this factor of evolution determines the development of living nature, a gradual but steady increase in the organization of living beings - from the simplest to the most perfect. The result of gradation is the simultaneous existence in nature of organisms of varying degrees of complexity, as if forming a hierarchical ladder of beings. The gradation is easily traced when comparing representatives of large systematic categories of organisms (for example, classes) and on organs of primary importance.
The main factor in the variability of species, he considered the influence of the external environment, which violates the correctness of the gradation: “The increasing complexity of the organization is subjected here and there throughout the general row of animals to deviations caused by the influence of habitat conditions and learned habits.” The gradation, so to speak, “in pure form "manifests itself with the invariability, stability of the external environment; any change in the conditions of existence forces organisms to adapt to the new environment in order not to perish. This disrupts the uniform and steady change of organisms on the path of progress, and various evolutionary lines deviate to the side, linger at primitive levels of organization. This is how Lamarck explained the simultaneous existence on Earth of highly organized and simple groups, as well as the variety of forms of animals and plants.
Lamarck on the highest level in comparison with his predecessors, he developed the problem of unlimited variability (transformism) of living forms under the influence of the conditions of existence: nutrition, climate, soil characteristics, moisture, temperature, etc. He supported his thought with examples such as the change in the shape of leaves in plants that live in water and air environment (arrowhead, buttercup), in plants of wet and dry, low-lying and mountainous areas.
Based on the level of organization of living things, Lamarck identified two forms of variability:
- direct, immediate variability of plants and lower animals under the influence of environmental conditions;
- indirect variability of higher animals, which have a developed nervous system, with the participation of which the influence of the conditions of existence is perceived, habits, means of self-preservation, protection are developed.
Lamarck formalizes his thoughts on the issues considered in the form of two laws:
First law. “In every animal that has not reached the limit of its development, a more frequent and longer use of an organ gradually strengthens this organ, develops and increases it and gives it strength commensurate with the duration of use, while the constant non-use of one or another organ gradually weakens it, leads to decline, continuously diminishes its ability and finally causes its disappearance. " This law can be called the law of variability, in it Lamarck focuses on the fact that the degree of development of this or that organ depends on its function, the intensity of exercise, that young animals that are still developing are more capable of changing. The scientist opposes the metaphysical explanation of the form of animals as unchanging, created for a specific environment. At the same time, Lamarck overestimates the importance of function and considers that the exercise or non-exercise of the organ is an important factor in changing species.
The second law can be called the law of heredity.
Lamarck extends the provisions of these two laws to the problem of the origin of breeds of domestic animals and varieties of cultivated plants. Lacking sufficient factual material, with a still low level of knowledge of this issue, Lamarck was unable to reach a correct understanding of the phenomena of variability.
Darwin's theory is opposite to Lamarck's theory not only in its consistently materialistic conclusions, but also in its entire structure. She is a wonderful example scientific research, based on a huge number of reliable scientific facts, the analysis of which leads Darwin to a coherent system of proportionate conclusions.
Darwin collected ample evidence of the variability of animal and plant species. By the time of Darwin, the practice of breeders had created numerous breeds of various domestic animals and varieties of agricultural plants. Since the work of breeders leading to changes in the breed and varietal qualities of organisms was conscious and purposeful, and it was obvious that at least many of the breeds of domestic animals were created by this activity in a relatively recent time, Darwin turned to the study of the variability of organisms in the domesticated state.
First of all, the very fact of changes in animals and plants under the influence of domestication and selection was important, which, in fact, is already evidence of the changeability of species of organisms. “At the beginning of my research, wrote Charles Darwin in the introduction to his book On the Origin of Species,“ it seemed to me likely that a thorough study of domesticated animals and cultivated plants would provide the best opportunity to understand this obscure problem. And I was not wrong; in this and all the other confusing cases, I have invariably found that our knowledge of variation in domestication, though incomplete, is always the best and surest clue. I can afford to express my belief in the exceptional value of such studies, despite the fact that naturalists usually neglected them. "
According to Darwin, the stimulus for these changes is the impact on organisms of new conditions to which they are subjected in the hands of man. At the same time, Darwin stressed that the nature of the organism in the phenomena of variability is more important than the nature of the conditions, since the same conditions often lead to different changes in different individuals, and similar changes in the latter can occur under completely different conditions. In this regard, Darwin identified two main forms of variability of organisms under the influence of changes in environmental conditions: indefinite and definite.
Changes can be recognized as definite if all or almost all of the offspring of individuals subjected to certain conditions change in the same way (this is how a number of shallow changes arise: growth depends on the amount of food, skin thickness and hairiness - from climate, etc.).
By indeterminate variability, Darwin understood those infinitely varied weak differences that distinguish individuals of the same species from each other and which could not be inherited from either their parents or from more distant ancestors. Darwin concludes that uncertain variability is a much more common result of changing conditions than specific variability and played a more important role in the formation of domestic animal breeds. In this case, changes in external conditions play the role of a stimulus that enhances the uncertain variability, but does not in any way affect its specificity, i.e., the quality of changes.
An organism that has changed in any direction conveys to the offspring a tendency to change further in the same direction in the presence of the conditions that caused this change. This is the so-called continuous variability, which plays an important role in evolutionary transformations.
Finally, Darwin drew attention to the existence in organisms of certain correlations (correlations) between various structures, when one of which changes, the other, relative, or correlative, variability naturally also changes. Examples of such correlations are, according to Darwin, the deafness of white cats with blue eyes; toxicity for white sheep and pigs of some plants, harmless for black individuals of the same breeds, etc.
Darwin collected numerous data indicating that the variability of various types of organisms in nature is very great, and its forms are fundamentally similar to the forms of variability of domestic animals and plants. Diverse and fluctuating differences between individuals of the same species form, as it were, a smooth transition to more stable differences between the varieties of this species; in turn, the latter just as gradually pass into more distinct distinctions of even larger groups - subspecies, and the differences between subspecies - into quite definite interspecific differences. Thus, individual variability smoothly transforms into group differences. From this, Darwin concluded that individual differences between individuals are the basis for the emergence of varieties. Varieties, with the accumulation of differences between them, turn into subspecies, and those, in turn, into separate species. Consequently, a clearly defined variety can be viewed as the first step towards the isolation of a new species (variety - "incipient species").
Darwin believed that there is no qualitative difference between a species and a variety - these are just different stages of the gradual accumulation of differences between groups of individuals of different sizes. More widespread species living in more diverse conditions are characterized by greater variability. In nature, just as in the domesticated state, the main form of variation in organisms is indeterminate, which serves as a universal material for the process of speciation. It should be emphasized here that Darwin was the first to place the focus of evolutionary theory not on individual organisms (as was typical of his transformist predecessors, including Lamarck), but on biological species, i.e., speaking modern language, populations of organisms.
Having considered Darwin's evolutionary views on the variability of organisms, we briefly list his main ideas:
1.
Organisms, both tamed and wild, are characterized by hereditary variability. The most common and important form of variability is indeterminate. Changes in the external environment serve as a stimulus for the emergence of variability in organisms, but the nature of variability is determined by the specifics of the organism itself, and not by the direction of changes in external conditions, in contrast to Lamarck's view.
2.
The focus of evolutionary theory should not be on individual organisms, but on biological species and intraspecific groups (populations).
The concept of J. B. Lamarck is considered unscientific today. However, the significance of Lamarck's theory cannot be denied, since it was precisely the scientific polemic with the conclusions and concepts of the French naturalist that triggered the emergence of Charles Darwin's theory.
The conclusions of the English scientist were also subjected to further criticism and detailed revision, which was caused primarily by the fact that many factors, mechanisms and patterns of the evolutionary process unknown at the time of Darwin were identified and new ideas were formed that were significantly different from classical theory Darwin.
Nevertheless, there is no doubt that the modern theory of evolution is the development of the basic ideas of Darwin, which are still relevant and productive.
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Goal.To acquaint students with the emergence and development of evolutionary ideas, the evolutionary teachings of Charles Darwin.
Methods... Lesson-lecture.
During the classes
1. Explanation
- Lecture plan.
- Terms
- Aristotle and organic evolution
- Karl Linnaeus is the forerunner of evolutionism.
- The evolutionary doctrine of Zh.B. Lamarck.
- The evolutionary doctrine of Charles Darwin
First, let's get acquainted with the new terms of the topic.
Creationism - the teaching that life was created by a supernatural being at a certain time.
Metaphysical worldview- (Greek “phisis” - nature; “meta” - over) - initial and absolute expediency, and therefore the constancy and invariability of all nature.
Transformism- the doctrine of the transformation of one species into another.
Evolution- (Latin evolvo - deploy / evolution / - deployment) a historical change in the form of organization and behavior of living beings in a number of generations.
Aristotle and organic evolution
The new branch of biology is called evolutionary doctrine, or Darwinism, since the theory of evolution was established in biology thanks to the work of the outstanding English scientist Charles Darwin. However, the very idea of \u200b\u200bevolution is as old as the world. The myths of many peoples are permeated with ideas about the possibility of transformation (transformation) of one species into another. The rudiments of evolutionary concepts can be found both in the writings of the thinkers of the Ancient East and in the statements of ancient philosophers. 1000 BC e. in India and Chinabelieved that man descended from a monkey.
Why do you think?
Similarly, in India, a monkey is a sacred animal and it is even honorable.
Ancient Greek thinker, philosopher, founder of biology, father of zoology Aristotle (384-322 BC)formulated a theory of continuous and gradual development of living things from nonliving matter, based on his observations of animals. In doing so, he proceeded from a metaphysical concept about the striving of nature from the simple and imperfect to the more complex and perfect. Aristotle recognized the evolution of terrestrial layers, but there are no living organisms in the evolution, although in his “Ladder of Nature” he grouped and arranged inanimate matter and all living organisms in a certain order from primitive to more complex, which suggested a relationship between living organisms.
Karl Linnaeus is the forerunner of evolutionism.
Karl Linnaeus - Swedish scientist (1707-1778) - the father of botany, the king of flowers, the great systematizer of Nature.
He proposed a simple classification scheme for animals and plants, the best of all the previous ones.
a) Linnaeus considered the main systematic unit to be a species (a set of individuals similar in structure and giving fertile offspring). The species exists and does not change.
b) He combined all species into genera, genera into detachments, detachments into classes.
c) Linnaeus classified the whale as a mammal, although in the 17th century the whale was considered a fish.
d) Linnaeus, for the first time in the history of science, put man first in the order of primates in the class of mammals, together with monkeys and semi-monkeys on the basis of the similarity between man and ape.
Linnaeus applied a clear, convenient double-naming principle.
Before Linnaeus, scientists gave plants only generic names. Called: oak, maple, rose, pine, nettle, etc. Science used the names of plants by genus, just as it is usually done in colloquial everyday language, in relation to plants and animals, to designate a species, they used long descriptions of characters. So, before Linnaeus the dog rose was called "An ordinary forest rose with a fragrant pink flower".
Linnaeus left the generic names. He suggested giving the names of species in words (most often adjectives) denoting the characteristics of a given plant or animal. The name of plants or animals now consisted of 2 words: in the first place was the generic name (noun), in the second place was the specific name (usually an adjective). For example, Linnaeus named the dog rose in Latin Rosа canina L (Dog rose). L stood for the name of the author who gave the name to this species. In this case, Linnaeus.
The very idea of \u200b\u200bdouble names was proposed by Kaspar Baugin, i.e. 100 years before Linnaeus, but only Linnaeus realized it.
Linnaeus created the science of botany in the place of the former chaos.
a) Made a huge reform in the botanical language. In the book "Fundamentals of Botany", he lists about 1000 botanical terms, clearly explaining where and how to use each of them. In fact, Linnaeus invented, albeit with the same terminology, new language for natural science.
b) Worked on plant biology. It is enough to recall the "Flora Calendar"
"Flora Clock", "Plant Dream". He was the first to propose to conduct phenological observations to determine the best terms of work for agricultural plants.
c) Wrote several large textbooks and tutorials on botany.
Linnaeus's system aroused tremendous interest in the study and description of plants and animals. Thanks to this, the number of known plant species has increased from 7,000 to 10,000 over several decades. Linnaeus himself discovered and described about 1.5 thousand species of plants, about 2000 species of insects.
The line aroused interest in the study of biology. Many famous scientists, philosophers, and writers became interested in the study of nature thanks to their acquaintance with the works of K. Linnaeus. Goethe said: "After Shakespeare and Spinoza, Linnaeus had the strongest impression on me."
Despite the fact that Karl Linnaeus was a creationist, the system he developed is a living
nature was built on the principle of similarity, had a hierarchical structure and suggested a relationship between closely related species of living organisms. Analyzing these facts, scientists came to the conclusion about the variability of species. The authors of these ideas considered the change in species in time as a result of the unfolding (from the Latin “evolvo” - I unroll) of some preliminary design of the Creator, a pre-compiled program in the course of historical development. This point of view was named evolutionary.Such views were expressed in the 18th century. and at the beginning of the 19th century. J. Buffon, W. Goethe, C. Baer, \u200b\u200bErasmus Darwin - Charles Darwin's grandfather. But none of them offered a satisfactory explanation of why and how the species changed.
The evolutionary doctrine of Zh.B. Lamarck.
The first holistic concept of evolution was expressed by the French naturalist Jean Baptiste Pierre Antoine de Monier Chevalier de Lamarck (1744-1829).
Lamarck was a deist and believed that the creator created matter to the laws of its motion, this stopped the creative activity of the creator, and all further development nature took place in accordance with its laws. Lamarck believed that the most primitive and simple organisms arise through spontaneous generation, and such spontaneous generation has occurred many times in the distant past, occurs at the present time and will occur in the future. Organisms, according to Lamarck, could arise from inanimate matter under the influence of light, heat, electricity.
After their appearance, primitive living organisms do not remain unchanged. They change under the influence of the external environment, adapting to it. As a result of such a change, living organisms gradually improve over time in a long series of successive generations, becoming more and more complex and highly organized. As a result, the more time passes from the moment a certain form appears through spontaneous generation, the more perfect and complexly organized its modern descendants are. The most primitive modern living organisms, in his opinion, arose quite recently and simply did not have time to become more perfect and highly organized as a result of gradual complication. All these changes occur over a long period of time, therefore they are invisible. But carried away by the denial of the constancy of species, Lamarck begins to represent living nature as continuous rows of changing individuals, he considers species to be an imaginary unit of classification convenient for the nomenclature of organisms, and only individuals exist in nature. The species is constantly changing, and therefore does not exist - he writes in "Philosophy of Zoology" (1809) Lamarck called the gradual nature of complication the organization of living beings a gradation. Another new term.
Gradation (lat. ascent) - increasing the organization of living beings from the lowest to the highest in the process of evolution.
Driving forces of evolution according to Lamarck.
Inner desire for progressthat is, every living creature has an innate internal desire to complicate and improve its organization, this property is inherent in them from the very beginning of nature.
The influence of the external environment, due to which, within the same stage of organization, various species are formed, adapted to the conditions of life in the environment.
Any change in the external environment causes organisms only usefulchanges traits inheritedas innate properties and only adequate changes, that is, those that correspond to the changed conditions.
In plants, lower animals the reason for the continuous complication and improvement is direct impact of the external environment, causing changes that provide a better adaptation to these conditions. Lamarck gives such examples. If the spring was very dry, then meadow grasses grow poorly; spring, with alternating warm and rainy days, causes a lush growth of the same grasses. Getting from natural conditions into gardens, plants change greatly: some lose thorns and thorns, others change the shape of the stem, the woody stem of plants in hot countries becomes herbaceous in our country in temperate climates.
The external environment on higher animals acts indirectly with nervous system... The external environment has changed - and the animals have new needs. If the new conditions last for a long time, then the animals acquire the corresponding habits. At the same time, some organs exercise more, others less or completely inactive. An organ that acts with vigor develops more strongly, becomes stronger, and an organ that has been little used for a long time gradually atrophies.
The formation of the swimming membrane between the toes in waterfowl was explained by Lamarck by stretching of the skin; the absence of legs in snakes is explained by the habit of stretching the body when crawling on the ground, without using the limbs; long front legs of a giraffe - by constant efforts of the animal to reach the leaves on the trees.
J. B. Lamarck also admitted that the desire, the desire of the animal leads to an increased flow of blood and other "fluids" to the part of the body to which this desire is directed, which causes an increased growth of this part of the body, which is then transmitted by inheritance.
Lamarck was the first to use the terms "kinship", "kinship ties" to denote the unity of the origin of living beings.
He quite correctly believed that environmental conditions have an important influence on the course of the evolutionary process.
Lamarck was one of the first to correctly assess the importance of time in the process of evolution and noted the extraordinary duration of the development of life on earth.
Lamarck's ideas about the ramification of the "ladder of creatures" and the non-linear nature of evolution paved the way for the concept of "genealogical trees" developed in the 1860s.
J.B. Lamarck developed the hypothesis of the natural origin of man, he assumed that the ancestors of man were monkeys who switched to a terrestrial lifestyle and walking on the ground from climbing trees. This group (breed) used hind limbs for walking for a number of generations and eventually from four-handed became two-handed. If this breed stopped using its jaws for tearing prey, and began to chew it, this could lead to a decrease in the size of the jaw. Such the most developed breed took possession of all convenient places on the earth, displacing the less developed breeds. Individuals of this dominant breed gradually accumulated ideas about the world around them, they had a need to convey these ideas to their own kind, which led to the development of various gestures, and then speech. Lamarck pointed out the important role of the hand in the formation of a person.
He tried to explain the origin of domestic animals and cultivated plants. Lamarck said that the ancestors of domestic animals and cultivated plants were taken by humans from the wild, but domestic maintenance, dietary changes and interbreeding made these forms unrecognizable compared to wild forms.
Evolutionary doctrine of Charles Darwin.
2. Charles Darwin about the species.
The species exists and changes
The driving forces of evolution according to Charles Darwin.
- Heredity.
- Variability.
- Natural selection based on the struggle for existence.
3. Assignment at home. Paragraphs 41, 42 to art.
4. Anchoring.
- What did Aristotle think about the evolution of living organisms?
- Why is Karl Linnaeus called the herald of evolutionism?
- Why the evolutionary doctrine of Zh.B. Lamarck was not recognized by his contemporaries?
- What do you know about the evolutionary teachings of Charles Darwin?