The concept of the evolution of the organic world seminar. Theories of evolution of the organic world. The origin of life on earth
Until the end of the 17th century. most Europeans believed that everything in nature has been unchanged since the day of creation, that all kinds of plants and animals are still the way God created them. However, in the XVIII century. new scientific data cast doubt on this. People began to find evidence that plant and animal species change over long periods of time. This process is called evolution.
The first theories of evolution
Jean-Baptiste de Monnet (1744-1829), Chevalier de Lamarck, was born in France. He was the eleventh child in an impoverished aristocratic family. Lamarck lived a difficult life, died a poor blind man, his works were forgotten. At 16, he joined the army, but soon retired due to poor health. Need forced him to work in a bank, instead of doing what he loved - medicine.
royal botanist
AT free time Lamarck studied plants and acquired such extensive knowledge in this that in 1781 he was appointed chief botanist of the French king. Ten years later, after Lamarck was elected professor of zoology at the Museum of Natural History in Paris. Here he gave lectures and arranged exhibitions. Noticing the differences between fossils and modern animal species, Lamarck came to the conclusion that the species and characteristics of animals and plants are not unchanged, but, on the contrary, change from generation to generation. This conclusion was suggested to him not only by fossils, but also by geological evidence of changes in the landscape over long millions of years.
Lamarck came to the conclusion that throughout life, the characteristics of an animal can change depending on external conditions. He proved that these changes are inherited. Thus, the neck of a giraffe may have lengthened during its life due to the fact that it had to reach for the leaves of trees, and this change was passed on to its offspring. Today, this theory is recognized as erroneous, although it was used in the theory of evolution of Darwin and Wallace that appeared 50 years later.
Expedition to South America
Charles Darwin (1809-1882) was born in Shrewsbury, England. He was the son of a doctor. After graduating from school, Darwin went to study medicine at the University of Edinburgh, but soon became disillusioned with this subject and, at the insistence of his father, left for Cambridge University to prepare for the priesthood. And although the preparation was successful, Darwin was once again disappointed in the career ahead of him. At the same time, he became interested in botany and entomology (the science of insects). In 1831, botanist John Henslow noticed Darwin's abilities and offered him a job as a naturalist on an expedition to South America. Before sailing, Darwin read the works of the geologist Charles Lyell (see the article ""). They struck the young scientist and influenced his own views.
Darwin's discoveries
The expedition sailed on the ship "Beagle" and lasted 5 years. During this time, the researchers visited Brazil, Argentina, Chile, Peru and the Galapagos Islands - ten rocky islands off the coast of Ecuador in the Pacific Ocean, each of which has its own fauna. On this expedition, Darwin collected a huge collection of rock fossils, made herbariums and a collection of stuffed animals. He kept a detailed diary of the expedition and subsequently used much of the material from the Galapagos Islands to present his theory of evolution.
In October 1836, the Beagle returned to England. Darwin devoted the next 20 years to processing the collected materials. In 1858 he received a manuscript from Alfred Wallace (1823-1913) with ideas very close to his own. And although both naturalists were co-authors, the role of Darwin in putting forward a new theory is much more significant. In 1859, Darwin published The Origin of Species by Means of Natural Selection, in which he outlined the theory of evolution. The book was a huge success and made a lot of noise, as it contradicted traditional ideas about the origin of life on Earth. One of the boldest thoughts was the assertion that evolution continued for many millions of years. This was contrary to the Bible's teaching that the world was created in 6 days and has not changed since then. Today, most scientists use a modernized version of Darwin's theory to explain changes in living organisms. Some reject his theory on religious grounds.
Natural selection
Darwin discovered that organisms fight each other for food and habitat. He noticed that even within the same species there are individuals with special features that increase their chances of survival. The offspring of such individuals inherit these traits, and they gradually become common. Individuals that do not have these traits die out. So, after many generations, the whole species acquires useful features. This process is called natural selection. Let's see, for example, how the moth adapted to changes in its environment. At first, all moths had a silvery color and were invisible on the branches of trees. But then the trees darkened from the smoke - and the moths became more noticeable, they were more actively eaten by birds. The moths that were darker in color survived. This dark coloration was passed on to their offspring and subsequently spread to the whole species.
The role of the works of Charles Darwin in the creation of scientific evolutionary theory
By the middle of the XIX century. objective conditions arose for the creation of a scientific evolutionary theory. They boil down to the following.
1. By this time, a lot of factual material had accumulated in biology, proving the ability of organisms to change, and the first evolutionary theory was created.
2. All the most important geographical discoveries were made, as a result of which the most important representatives of the organic world were described in more or less detail; a wide variety of animal and plant species has been discovered, and some intermediate forms of organisms have been identified.
3. The rapid development of capitalism required the study of sources of raw materials (including biological ones) and markets, which intensified the development of biological research.
4. Great success has been achieved in the selection of plants and animals, which contributed to the identification of the causes of variability and the consolidation of the characteristics that have arisen in organisms.
5. Intensive development of minerals made it possible to discover cemeteries of prehistoric animals, prints of ancient plants and animals, which confirmed evolutionary ideas.
The creator of the foundations of scientific evolutionary theory was Charles Darwin (1809-1882). Its main propositions were published in 1859 in the book The Origin of Species by Means of Natural Selection, or the Preservation of Favorable Races in the Struggle for Life. C. Darwin continued to work on the development of evolutionary theory and published the books The Change in Domestic Animals and Cultivated Plants (1868) and The Origin of Man and Sexual Selection (1871). The evolutionary theory is constantly developing, supplemented, but its foundations were outlined in the above-mentioned books.
The creation of Darwin's theory was facilitated by the situation prevailing in biology at the time of the beginning scientific activity scientist, the fact that he lived in the most developed (at that time) capitalist country - England, the ability to travel (Ch. Darwin made a trip around the world on the Beagle ship), as well as the personal qualities of a scientist.
When developing the scientific evolutionary theory, Charles Darwin created his own definition of "species", put forward new principles for the systematization of the organic world, consisting in finding kindred (genetic) ties that arose due to the same origin of the entire organic world; defined evolution as the ability of species to slow, gradual development in the course of their historical existence. He correctly revealed the cause of evolution, which consists in the manifestation of hereditary variability, and also correctly revealed the factors (driving forces) of evolution, including natural selection and the struggle for existence, through which natural selection is realized.
The theory of evolution of the organic world, developed in the works of Charles Darwin, was the foundation for the creation of modern synthetic evolutionary theory.
The synthetic theory of the evolution of the organic world is a set of scientifically based provisions and principles that explain the emergence of the modern organic world of the Earth. In developing this theory, the results of research in the field of genetics, breeding, molecular biology and other biological sciences obtained in the second half of the 19th and throughout the 20th century were used.
Carl Linnaeus and the role of his work in the development of evolutionary theory
Man has always been interested in where such a wonderful world of animals and plants came from, whether it has always been the same as it is now, whether the organisms that exist in nature change. With the eyes of one generation it is difficult, and sometimes impossible, to detect significant changes in the surrounding world, therefore, a person initially formed an idea of the immutability of the surrounding world, especially the world of animals (fauna) and plants (flora).
Ideas about the immutability of the organic world are called metaphysical, and people (including scientists) who share these views are called metaphysicians.
The most ardent metaphysicians, who believe that all living things are created by God and do not change from the day of creation, are called creationists, and the pseudo-teaching about the divine creation of living things and its immutability is called creationism. This is an extremely reactionary doctrine, it hinders the development of science, interferes with the normal activity of man both in the development of civilization and in ordinary life.
Creationism was widespread in the Middle Ages, but even now believers and church leaders adhere to this doctrine, however, and now the church recognizes the variability of the living and believes that only the soul was created by God.
With the accumulation of knowledge about nature, the systematization of knowledge, it was revealed that the world is changing, and this further led to the creation and development of evolutionary theory.
An outstanding biologist who was a metaphysician and creationist, but whose work prepared the possibility of developing an evolutionary theory, was the Swedish naturalist Carl Linnaeus (1707-1778).
K. Linnaeus created the most perfect artificial system of the organic world. It was artificial because Linnaeus based it on signs that often did not reflect the relationship between organisms (which at that time was impossible due to incomplete knowledge about organisms). So, he classified lilac and fragrant ear (plants of completely different classes and families) in one group because both of these plants have two stamens (the fragrant ear belongs to the class of monocots, the family of cereals, and lilac belongs to the class of dicots, the family of olives) .
The system proposed by K. Linnaeus was practical and convenient. It used the binary nomenclature introduced by Linnaeus and which is still used today because of its rationality. In this system, the class was the highest taxon. Plants were divided into 24 classes, and animals - into six. The scientific feat of K. Linnaeus was the inclusion of man in the kingdom of Animals, which, during the undivided domination of religion, was far from safe for a scientist. The significance of the system of K. Linnaeus for the further development of biology is as follows:
1) it created the basis for scientific systematization, since it clearly showed that there is an interconnection and family relationship between organizations;
2) this system set the task of finding out the causes of similarities between organisms, which was an incentive to study the underlying features of similarities and explain the reasons for such similarities.
Towards the end of his life, K. Linnaeus abandoned the idea of the immutability of species, since the system of the organic world he proposed did not fit into the framework of metaphysical and creational ideas.
General characteristics of the evolutionary theory developed by J. B. Lamarck
At the end of XVIII - early XIX in. the idea of the variability of the organic world is increasingly winning the minds of scientists. The first evolutionary theories appear.
Evolution is a gradual long-term development of the organic world, accompanied by its change and the emergence of new forms of organisms.
The first, more or less substantiated evolutionary theory was created by the French naturalist Jean Baptiste Lamarck (1744-1829). He was a prominent representative of Transformism. J. Buffon (France), Erasmus Darwin - the grandfather of Charles Darwin (England), J. V. Goethe (Germany), K. F. Roulier (Russia) were also transformists.
Transformism - the doctrine of the variability of species of various organisms, including animals, plants and humans.
J. B. Lamarck outlined the foundations of his theory of evolution in the book Philosophy of Zoology. The essence of this theory is that organisms change in the process of historical existence. Changes in plants occur under the direct influence of environmental conditions; these conditions affect animals indirectly.
The reason for the appearance of new forms of organisms (especially animals) is the internal desire of the organism for perfection, and the changes that have appeared are fixed due to the exercise or non-exercise of the organs. The changes that occur are inherited by the organism under successive exposure to the conditions that caused these changes, if these conditions act for several generations.
The central position of Lamarck's evolutionary theory is the idea of the types of organisms, their gradation and the desire of the species to move from a lower level (gradation) to a higher one (hence the desire for perfection).
An example illustrating the exercise of the organs is the stretching of the neck by a giraffe to get food, which leads to its lengthening. If the giraffe does not stretch its neck, then it will become shorter.
The factors of evolution (according to Lamarck) are:
1) adaptation to environmental conditions, due to which various changes occur in organisms;
2) inheritance of acquired traits.
The driving forces of evolution (according to Lamarck) consist in the striving of organisms for perfection.
The main achievement of Lamarck's theory was that for the first time an attempt was made to prove the existence of evolution in the organic world in the process of historical existence, however, the scientist was unable to correctly reveal the causes and driving forces of evolution (at that stage in the development of scientific thought, this was impossible due to lack of scientific knowledge). ).
Similar views on the development of the organic world were also expressed by Professor of Moscow University K. F. Rul'e. In his theoretical positions, he went further than J. B. Lamarck, since he denied the idea that organisms strive for improvement. But he published his theory later than Lamarck and could not create an evolutionary theory in the form in which it was developed by Charles Darwin.
General characteristics of evidence for the evolution of the organic world
The study of organisms over a long historical time human development showed that organisms were subject to changes, were in a state of constant development, i.e. evolved. There are four groups of evidence for evolutionary theory: cytological, paleontological, comparative anatomical and embryological. In this subsection, we consider these proofs in general terms.
General characteristics of cytological evidence for the evolution of organisms
The essence of cytological evidence is that almost all organisms (except viruses) have a cellular structure. Animal and plant cells are characterized by a general structural plan and organelles that are common in form and function (cytoplasm, endoplasmic reticulum, cell center, etc.). However, plant cells differ from animal cells in a different way of feeding and different adaptability to the environment compared to animals.
Cells have the same chemical and elemental composition, regardless of belonging to any organism, having specificity associated with the peculiarity of the organism.
The existence in nature of an intermediate type of unicellular organisms - flagella, combining the signs of plant and animal organisms (as plants they are capable of photosynthesis, and as animals they are capable of heterotrophic nutrition), testifies to the unity of the origin of animals and plants.
Overview of embryological evidence for evolution
It is known that in individual development (ontogenesis) all organisms go through the stage of embryonic (intrauterine - for viviparous organisms) development. The study of the embryonic period of different organisms shows the common origin of all multicellular organisms and their ability to evolve.
The first embryological evidence is that the development of all (both animal and plant) organisms begins with a single cell - the zygote.
The second most important proof is the biogenetic law discovered by F. Müller and E. Haeckel, supplemented by A. N. Severtsov, A. O. Kovalevsky and I. I. Schmalhausen. This law states: "In the embryonic development of ontogenesis, organisms pass through the main embryonic stages of the phylogenetic (historical) development of the species." So, individual individuals of a species, regardless of the level of its organization, go through the stage of zygote, morula, blastula, gastrula, three germ layers, organogenesis; moreover, both fish and man have a fish-like larval stage, and the human embryo has gills and gill slits (this applies to animals).
The clarification of the biogenetic law by Russian scientists refers to the fact that organisms go through the main stages of phylogenetic development, repeating the stages characteristic of the embryonic period of development, and not of the adult states of organisms.
Comparative Anatomical Evidence for Evolution
This evidence relates to the evolution of animals and is based on information obtained by comparative anatomy.
Comparative anatomy is a science that studies internal structure different organisms in their comparison with each other ( highest value this science has for animals and man).
As a result of studying the structural features of chordates, it was found that these organisms have bilateral (bilateral) symmetry. They have a musculoskeletal system that has a single structural plan common to all (compare the human skeleton and the skeleton of a lizard or frog). This testifies to the common origin of man, reptiles and amphibians.
Different organisms have homologous and similar organs.
Organs are called homologous if they are general plan structures, unity of origin, but they may have a different structure due to the performance of different functions.
Examples of homologous organs are the pectoral fin of a fish, the forelimb of a frog, the wing of a bird, and the human hand.
Analogous are those organs that have approximately the same structure (external form) due to the performance of similar functions, but have a different structural plan and different origins.
Similar organs include the burrowing limb of a mole and a bear (an insect that leads an underground lifestyle), a bird's wing and a butterfly's wing, etc.
Comparative anatomical evidence also includes the presence of rudiments and atavisms in organisms.
Rudiments are called residual organs that are not used by these organisms. Examples of rudiments are the appendix (caecum), coccygeal vertebrae, etc. Rudiments are the remains of those organs that were once necessary, but at this stage of phylogenesis have lost their significance.
Atavisms are signs that were previously inherent and characteristic of a given organism, but at this stage of evolution have lost their significance for most individuals, but manifested in this particular individual in its ontogenesis. Atavisms include the tailing of some people, human polymastia (multiple nipples), excessive development of the hairline. Superstitious people give some religious meaning to tailing and increased development of the hairline, they consider such people close to the devil, and in the Middle Ages they were even burned at the stake.
Paleontological evidence for evolution
Paleontology is the science of the organic world of past geological epochs, that is, of organisms that once lived on Earth and are now extinct. In paleontology, paleozoology and paleobotany are distinguished.
Paleozoology studies the remains of fossil animals, while paleobotany studies the remains of fossil plants.
Paleontology directly proves that the organic world of the Earth in different geological epochs was different, it changed and developed from primitive forms of organisms to more highly organized forms.
Paleontological studies make it possible to establish the history of the development of various forms of organisms on Earth, to identify related (genetic) relationships between individual organisms, which contributes to the creation natural system organic world of the Earth.
In conclusion, we can conclude that the briefly considered phenomena prove that the organic world of the Earth is in a state of constant slow gradual development, i.e. evolution, while development has gone and goes from simple to complex.
The role of heredity and variability in the evolution of the organic world
The most important factors of evolution are variability and heredity. The role of heredity in evolution consists in the transmission of traits, including those that have arisen in ontogeny, from parents to offspring.
The variability of organisms leads to the appearance of individuals with different levels of differences from each other. Is every change that has arisen in ontogeny inherited? Probably not. Modification changes that do not affect the genome are not inherited. Their role in evolution is that such changes allow the organism to survive in difficult, sometimes extreme environmental conditions. So, small leaves help reduce transpiration ( evaporation), which allows the plant to survive in conditions of lack of moisture.
An important role in the processes of evolution is played by hereditary (mutational) variability affecting the genome of gametes. In this case, the resulting changes are transmitted from parents to offspring, and a new trait is either fixed in the offspring (if it is useful to the organism), or the organism dies if this trait worsens its adaptability to the environment.
Thus, hereditary variability "creates" material for natural selection, and heredity fixes the changes that have arisen and leads to their accumulation.
Evolution (from Latin evolutio - deployment), in a broad sense - a synonym for development; processes of change (predominantly irreversible) occurring in animate and inanimate nature, as well as in social systems. Evolution can lead to complication, differentiation, an increase in the level of organization of the system (progress) or, conversely, to a decrease in this level (regression). In a narrow sense, the concept of evolution includes only gradual quantitative changes, opposing it to development as a qualitative shift, that is, revolution. In real development processes, revolution and evolution (in the narrow sense) are equally necessary components and form a contradictory unity.
Evolution in the broadest sense of the word refers to the gradual change complex systems in time. They talk about the evolution of stars and galaxies, landscapes and biocenoses, languages and social systems.
Biological evolution is a hereditary change in the properties and characteristics of living organisms over a number of generations. In the course of biological evolution, an agreement is achieved and constantly maintained between the properties of living organisms and the conditions of the environment in which they live. Since conditions are constantly changing, including as a result of the vital activity of the organisms themselves, and only those individuals that are best adapted to life in changed environmental conditions survive and reproduce, the properties and signs of living beings are constantly changing. The conditions of life on Earth are infinitely diverse, so the adaptation of organisms to life in these different conditions has given rise in the course of evolution to a fantastic variety of life forms.
Driving forces of evolution, their relationship.
1. The teachings of Ch. Darwin about driving forces evolution. Driving forces of evolution: hereditary variability, struggle for existence, natural selection.
2. Hereditary variability. The reason for hereditary changes is a change in genes and chromosomes, a recombination (combination) of parental traits in offspring. Beneficial, harmful and neutral hereditary changes. Random, undirected nature of hereditary changes. The role of hereditary variation in evolution: the supply of material for the action of natural selection.
4. Forms of struggle for existence:
Fight against unfavorable conditions of inanimate nature (abiotic factors). Impact on any organism adverse conditions: excess or lack of moisture, light, high or low air temperature. Example: death or oppression of individuals of a light-loving plant in low light conditions;
Intraspecific struggle for existence - the relationship between individuals of the same species. The greatest intensity of intraspecific struggle due to the similarity of needs in individuals of the same species (the need for similar food, lighting, soil, etc.).
5. Natural selection - the process of survival of individuals with hereditary changes that are useful in given environmental conditions and their subsequent reproduction. Selection is a consequence of the struggle for existence, the main factor of evolution, preserving individuals mainly with hereditary changes that are useful in certain environmental conditions. Selecting factor - conditions external environment: high or low air temperature; excess or lack of moisture, light, food.
6. The mechanism of action of natural selection:
The appearance of hereditary changes in individuals (beneficial, harmful, neutral);
Preservation as a result of the struggle for existence, natural selection, predominantly individuals with hereditary changes that are useful in given environmental conditions;
Reproduction of individuals with useful changes, increase in their number;
Preferential survival of individuals with changes corresponding to the environment among the offspring, their reproduction and transmission of useful changes to a part of the offspring;
Distribution of hereditary changes useful in given environmental conditions.
7. The relationship of the driving forces of evolution. Heterogeneity of individuals of a species due to hereditary variability, supplying material for the action of the struggle for existence and for natural selection. Exacerbation of relationships between individuals as a result of the struggle for existence. Preservation of individuals predominantly with beneficial hereditary changes by natural selection as a consequence of the struggle for existence.
It is important to note that Charles Darwin laid the foundations of the scientific theory of evolution. As the dominant evolutionary doctrine, Darwinism existed from 1859 to 1900, i.e. before the rediscovery of G. Mendel's laws. Until the end of the 20s of the current century, genetic data were opposed to evolutionary theory, hereditary variability (mutational, combinative) was considered as the main factor in evolution, natural selection was assigned a secondary role. Thus, already in the initial period of its formation, genetics was used to create new concepts of evolution. In itself, this fact is significant: it testified to the close connection of genetics with evolutionary theory, but the time for their unification was yet to come. Various kinds of criticism of Darwinism were widespread until the emergence of STE.
An exceptional role in the development of evolutionary theory was played by population genetics, which studies microevolutionary processes in natural populations. It was founded by outstanding domestic scientists S.S. Chetverikov and N.V. Timofeev-Resovsky.
The unification of Darwinism and genetics, which began in the 1920s, contributed to the expansion and deepening of the synthesis of Darwinism with other sciences. The 1930s and 1940s are considered to be the period of formation of the synthetic theory of evolution.
In Western countries, the renewed Darwinism, or the synthetic theory of evolution, gained wide recognition among scientists already in the 40s, although there have always been and are some major researchers who take anti-Darwinian positions.
Modern science has very many facts proving the existence of the evolutionary process. These are data from biochemistry, genetics, embryology, anatomy, taxonomy, biogeography, paleontology and many other disciplines. The main evidence to date is:
taxonomy data reflecting the course of evolutionary transformations;
embryological evidence obtained in the study of the development of chordate embryos, confirming the validity of the law of germinal similarity of K. Baer. Moreover, it has been shown that during the individual development the organism goes through stages reflecting the phylogenesis of the given species. Based on these data, the biogenetic law was formulated (F. Muller, E. Haeckel);
cellular structure;
comparative anatomy data;
data obtained during selection work;
evidence of the existence of natural selection in nature (melanization of insects);
universality of the genetic code;
the unity of the organization of genetic material and the implementation of genetic information;
the universality of the energy accumulator in a living cell - ATP;
genetic evidence. Phylogenetically close species have similarities in the structure of genes;
similarity in the structure of proteins of organisms belonging to close taxonomic groups;
experimental evidence. Modeling of evolutionary processes on living organisms (models).
Modern ideas about the factors of evolution are the result of the development of Darwinism, genetics and ecology. Charles Darwin in his classic work "The Origin of Species" solved the problem of the main driving forces (factors) of the evolutionary process. He singled out the following factors: heredity, variability and natural selection. In addition, Charles Darwin pointed out the important role of limiting the free interbreeding of individuals due to their isolation from each other, which arose in the process of evolutionary divergence of species.
In the modern view, the factors of the evolutionary process are hereditary variability, natural selection, genetic drift, isolation, migration of individuals, etc. All organisms form natural groups with similar anatomical features of the individuals included in them. Large groups are successively divided into smaller ones, the representatives of which have an increasing number of common features. It has long been known that organisms of a similar anatomical structure are similar in their embryonic development. However, sometimes even significantly different species, such as turtles and birds, are almost indistinguishable in the early stages of individual development. The embryology and anatomy of organisms are so closely correlated with each other that taxonomists (specialists in the field of classification) use the data of both these sciences equally in developing schemes for the distribution of species into orders and families. Such a correlation is not surprising, since the anatomical structure - final result embryonic development.
The direction of evolution of each systematic group is determined by the relationship between the features of the environment in which the evolution of a given taxon takes place and its genetic organization, which has developed in the course of its previous evolution.
Divergence. Most often in the course of evolution, we observe divergence or divergence of characters in species descending from a common ancestor. Divergence begins at the population level. It is due to differences in the environmental conditions in which the daughter species live and to which the daughter species adapt differently under the influence of natural selection. Genetic drift also plays a certain role in divergence. Divergence causes an increase in the number of species and continues at the level of supraspecific taxa. It is divergent evolution that accounts for the amazing diversity of living beings.
A striking example of divergence is the change in the limbs of mammals in the course of their adaptation to different environmental conditions.
Convergence (convergence of characters) is observed when unrelated taxa adapt to the same conditions. Convergence is spoken of in those cases when an external similarity is found in the structure and functioning of an organ that has completely different origins in the compared groups of living organisms. For example, the wing of a dragonfly and a bat have common features in structure and function, but are formed during embryonic development from completely different cellular elements and are controlled by different groups of genes. Such bodies are called similar. They are outwardly similar, but different in origin, they do not have a phylogenetic commonality. The similarity in eye structure between mammals and cephalopods is another example of convergence. They arose independently in the course of evolution and are formed in ontogeny from different rudiments.
General and private fixtures. Questions about the possible paths of the evolutionary process were developed by A. N. Severtsov. One of the main such ways, according to Severtsov, is aromorphosis (arogenesis), or the emergence in the course of evolution of adaptations that significantly increase the level of organization of living organisms and open up completely new evolutionary possibilities for them. Such adaptations were, for example, the emergence of photosynthesis, sexual reproduction, multicellularity, pulmonary respiration in the ancestors of amphibians, amniotic membranes in the ancestors of reptiles, warm-bloodedness in the ancestors of birds and mammals, etc. Aromorphoses are a natural result of evolutionary processes. They open up opportunities for species to explore new, previously inaccessible habitats.
Aromorphoses do not occur instantly; when they appear, they are practically indistinguishable from ordinary adaptations. Only in the process of their evolutionary "polishing" by natural selection, coordination with numerous signs of the organism and widespread in many species they become aromorphoses. For example, the appearance of pulmonary respiration in the ancient inhabitants of fresh water did not fundamentally change their lifestyle, level of organization, etc. However, as a result of this adaptation, it became possible to develop land - a vast habitat. This opportunity was actively used in subsequent evolution, many thousands of species of amphibians, reptiles, birds and mammals appeared, filling various habitat niches. Therefore, the acquisition of lungs by vertebrates is a major aromorphosis, which led to an increase in the level of organization of many species.
There are also smaller aromorphoses. There were several of them in the evolution of mammals: the appearance of a coat, live birth, feeding of young with milk, the acquisition constant temperature body, progressive development of the brain, etc. High level organization of mammals, achieved thanks to the listed aromorphoses, allowed them to master new habitats.
In addition to such a major transformation as aromorphosis, in the course of the evolution of individual groups, a large number of small adaptations to certain environmental conditions arise. A. N. Severtsov called such adaptations idioadaptation.
Idioadaptations are adaptations of organisms to environment without a fundamental restructuring of the biological organization. An example of idioadaptation is the variety of forms in insectivorous mammals, different species of which, having a common initial level of organization, were able to acquire properties that allowed them to occupy different habitats in nature.
The paths of evolution of the organic world either combine with each other or replace each other, and aromorphoses occur much less often than idioadaptation. But it is aromorphoses that determine new stages in the development of the organic world. Having arisen by aromorphosis, new, higher in organization groups of organisms occupy a different habitat. Further, evolution follows the path of idioadaptation, and sometimes degeneration, which provide organisms with the development of a new habitat for them.
2. CHANGES IN BASIC INDUSTRIES
With the beginning of the transition to a post-industrial society, the share of industry in world GDP and employment of the economically active population decreases. industry still remains the most important branch of material production. Large investments are directed to industrial production, large expenses for research and development work are associated with it. Manufactured goods retain unconditional primacy in world trade. Industry continues to have a great impact not only on the economy, but also on other aspects of public life. And the territorial structure of industry to the greatest extent determines the territorial structure of the entire world economy, forming, as it were, its framework. Therefore, it is sometimes not without reason continue to be called the engine of economic development.
Big shifts are taking place in the sectoral structure of world industry. At the mesostructure level, they are expressed primarily in a change in the proportion between the extractive and manufacturing industries. Throughout the second half of the twentieth century. there was a steady trend towards a decrease in the share of extractive industries in the total industrial production; now it is about 1/10. But the changes also affected the internal proportions in the mining and manufacturing industries.
The extractive industry is a whole complex of industries and sub-sectors, which includes not only mining, but also the logging industry. It also includes marine fishing, water supply, hunting and fishing facilities. Approximately 3/4 of the total output of this industry falls on its main sub-sector - the mining industry. In turn, in the structure of the mining industry, 3/5 of the products (by value) are provided by the oil and gas industry, and the rest, in approximately equal shares, by coal and ore mining.
The manufacturing industry is structurally a much more complex complex, including more than 300 different industries and sub-sectors, which are usually divided into four blocks: 1) production of structural materials and chemical products; 2) mechanical engineering and metalworking; 3) light industry; 4) food industry. In the structure of manufacturing industries, heavy and light industries are also distinguished: if in the 60s the ratio between them was 60:40, then in the mid-90s it was already 70:30. The first place in the structure of the world manufacturing industry is occupied by mechanical engineering (40% of all products), the second place is occupied by the chemical industry (more than 15%). This is followed by food (14%), light industry (9%), metallurgy (7%) and other industries. The ratio between them changes somewhat with time, but in general remains relatively stable. On the other hand, the shifts taking place in the structure of each of these industries are usually more noticeable. First of all, this applies to mechanical engineering, as the most diversified branch of industrial production.
The fastest growing branch of world engineering has been and remains the electronic and electrical industry, whose share in all manufacturing products has already grown to 1/10. The general engineering industry as a whole is characterized by moderate growth, and changes are also taking place in its structure: the production of agricultural, textile machinery and equipment is decreasing, and the production of road transport machines is increasing, and especially robots, office equipment, etc. The share of transport engineering in The structure of the manufacturing industry as a whole remains relatively stable, but this also hides internal differences: the share of shipbuilding and rolling stock is declining, but the share of the automotive industry is generally maintained.
Along with shifts in the sectoral structure of world industry, there are changes in its territorial proportions. Usually these changes are considered at different hierarchical levels, ranging from the comparison of North and South to individual countries.
Exercise
The relic radiation discovered in the 1970s, that is, the microwave background radiation, began to be considered an experimental confirmation of the model: ...?
and the historical development of living systems.Anthropogenesis
Theories of Ch. Darwin, E. Bauer, L. Berg, modern understanding of the mechanisms of evolution organic world.
Stages of anthropogenesis. Representation of the noosphere: scientists VI Vernadsky, P. Teilhard de Chardin.
Origin of life on earth.Theory of Ch. Darwin.
Modern understanding
mechanisms of evolutionorganic world
Evolution is a historical change in the form of organization and behavior of living beings in a series of generations. Evolutionary theory provides an explanation for the totality of features that characterize all life on Earth.
In various fields of natural science (geology, paleontology, biogeography, embryology, comparative anatomy, the study of the cellular structure of organisms), the materials collected by scientists contradicted the ideas of the divine origin and the immutability of nature. The great English scientist C. Darwin was able to correctly explain all these facts, generalize them, and create a theory of evolution.
Basic principles of the evolutionary theory of Ch. Darwin
Within each species of living organisms, there is a huge range of individual heredity of variability (according to morphological, physiological, behavioral and any other characteristics). It is impossible to find two individuals that are completely identical in terms of the totality of signs.
All living organisms have the ability to increase in numbers.
Life resources for any kind of living organisms are limited, and therefore, with a large production of individuals, a struggle for existence must arise either between individuals of the same species or individuals of different species, or with natural conditions.
Only adapted individuals survive, having those deviations that turned out to be adaptive to given environmental conditions. The natural selection of individual isolated varieties under different conditions of existence gradually leads to a divergence (divergence) of the characteristics of these varieties.
The data of geology, paleontology, embryology and other sciences also pointed to the variability of the organic world. However, most scientists did not recognize evolution: no one observed the transformation of one species into another. Intensive work was carried out on the selection of new breeds of animals and varieties of cultivated plants.
Supporters of the permanence of species argued that each variety, each breed has a special wild ancestor. Darwin proved that this was not the case. All breeds of chickens are descended from wild Banking chickens, domestic ducks from wild mallard ducks, rabbit breeds from wild European rabbits. The ancestors of cattle were two types of wild tours, and dogs - the wolf and, for some breeds, possibly the jackal. At the same time, animal breeds and plant varieties can differ very sharply.
The process of creating new breeds of animals and varieties of cultivated plants through the systematic conservation and reproduction of individuals with certain traits and properties valuable to humans in a number of generations is called artificial selection.
Darwin identified two forms of artificial selection: conscious or methodical (the breeder sets himself a specific task and selects for one or two characteristics) and unconscious (a primitive form of artificial selection). Each pair of organisms produces many more offspring than they survive to adulthood. Most of the organisms that are born die before reaching puberty. The causes of death are varied (attack by enemies, lack of food, etc.). In nature there is a continuous struggle for existence. This term should be understood in a broad sense, as any dependence of organisms on the whole complex of conditions of the animate and inanimate nature surrounding it. In other words, the struggle for existence is a set of diverse and complex relationships that exist between organisms and environmental conditions.
Ch. Darwin singled out three main forms of the struggle of existence: interspecific, intraspecific and struggle with adverse conditions.
After the creation of Darwin's theory of evolution, years have passed, the historical era has changed, but the discussion on the problems of evolution does not stop.
Now such ideas are being actively promoted and widely discussed, which a few years ago would have been recognized as absurd. This is the undoubted merit of "scientific" creationists. The question arises whether all this is connected with the objective falsity or non-scientific nature of the theory of evolution? Is it not a fruitless dead end in the development of science? It is obvious that this is not the case. This is partly convinced by the successes achieved in recent decades by many biologists working in the field of empirical study of evolution, and partly by the study of those critical remarks that are most often expressed by opponents of evolutionism.
Let's consider the most widespread positions of modern evolution criticized by its opponents. It is often argued that we can observe microevolutionary change, but we never see speciation and macroevolution. Indeed, usually these processes proceed so slowly that they cannot be the object of direct observation. Nevertheless, speciation can be fixed empirically from direct or indirect data. Quite a lot of such data is given in general reports on speciation. There are also more private works on individual groups of animals or plants. Sometimes speciation can be repeated experimentally. For example, the studies of V. A. Rybin showed that the ancestor of the common plum, in all likelihood, was a natural hybrid of cherry plum and blackthorn. As a result of experimental crossing of these plants with subsequent doubling of chromosomes, hybrids were obtained - quite viable, very similar to real plums, and well crossing both with them and with each other. Some differences between the synthesized plums and the real ones were also found. It can be assumed that since their appearance, these latter have had time to change somewhat in the course of further evolution.
Man-made species appear to be most of our domestic animals and agricultural plants. Sometimes paleontological data allow us to trace how, through gradual transformations, one species turned into another. For example, the polar bear appears to have evolved in the Late Pleistocene from the brown bear. The whole process is documented by paleontological data; the transitional stages of the process are known.
Other examples of speciation could be cited. Actually, they are known to creationists. However, modern creationists argue that speciation always proceeds through the loss or redistribution of certain already existing hereditary factors and only within the framework of some primary type of structure, the so-called "baramin". The emergence of new hereditary information, and, consequently, new phenotypic structures, according to creationists, is impossible. The emergence of new "baramins" is also impossible. These latter were created directly by the creator.
Regarding these concepts, the following should be noted. In evolution, indeed, old structures are used more often than new ones arise. Reduction processes are very common. Therefore, it will not be a problem to find examples that do not contradict the views of creationists. For example, plum originated from blackthorn and cherry plum by hybridization followed by polyploidy, that is, without the emergence of new genetic information. Some changes to this information may have occurred in the course of further transformations. However, fundamentally new structures also appear quite often in evolution.
In the evolution of the polar bear, new traits arose (a complex of comprehensive morphological, physiological, and behavioral adaptations associated with the transition to life in the extreme conditions of the Far North and to a semi-aquatic lifestyle), which were definitely absent in the brown bear. Genetically, these two species remained very similar (in zoo conditions they can form fertile hybrids), but their morphological and ecological differences are so great that some scientists even recommended that the polar bear be separated into a separate genus. At the same time, the polar bear is at the same high level of organization as the brown bear. He has an equally, if not more, complex lifestyle and behavior. The results of reduction (in the creationist understanding) were among its signs, except that the transition from omnivorous to eating purely animal food, some simplification of the dental system associated with this, and even depigmentation of the coat.
Let's pass from the reduction evolution to the progressive one. Creationists and some evolutionists argue that the current theory of evolution cannot explain the early stages of organ formation, as well as the emergence of structures of a high level of perfection, such as humans. In fact, the problems that arise here are associated only with insufficient knowledge of the structure and functioning of these organs, as well as factologists and the evolutionary process. For well-studied organs, we tend to present in in general terms how they could have been formed in the process of evolution.
The hereditary information of living organisms, according to creationists, was created by God in the course of creation, and later can only be lost. Creationists quite clearly draw an analogy between the creative activity of God and human creativity, seeing in the human mind, albeit imperfect, but still a semblance of the mind of God. However, the available data rather suggest that the creative activity of the human mind is based on completely natural processes.
In their opinion, the fact that the existing laws of the universe can be revealed with the help of the human mind, in itself indicates the presence of a reasonable legislator. Indeed, we can agree that there is some correspondence between the logic of our thinking and the logic of processes occurring in nature. This correspondence is not absolute, therefore the process of cognition is always accompanied by errors, and the information obtained as a result of cognition is never exhaustive. Nevertheless, it is the existence of this correspondence that makes it possible in principle to know the surrounding world. There is, however, no logical necessity to explain this correspondence by the fact that the mind of beings who cognize the world is similar to the mind of the creator who created this world.
Much easier and more convincingly, it can be explained by the fact that in human evolution, the carriers of such mental structures that better corresponded to the reality of our world received an adaptive advantage. So our ability to know the world gradually improved. It was based on the same process of natural selection.
7.2.1. Evidence for the evolution of the organic world
Evidence of evolution - evidence of the common origin of all organisms from common ancestors, the variability of species and the emergence of some species from others
The evidence for evolution is divided into groups.
1. Cytological. All organisms (except viruses) are made up of cells that have general structure and functions.
2. Biochemical. All organisms are made up of the same chemicals: proteins, nucleic acids, and so on.
3. Comparative anatomical:
the unity of the structure of organisms within a type, class, genus, etc. For example, all representatives of the class of mammals are characterized by a highly developed cortex of the cerebral hemispheres, intrauterine development, feeding of young with milk, hairline, four-chamber heart and complete separation of arterial and venous blood, warm-bloodedness, lungs of an alveolar structure:
homologous organs - organs that have a common origin, regardless of the functions performed. For example, the limbs of vertebrates, modifications of the root, stem and leaves of plants;
rudiments - the remains of the organs (signs) that were available to the ancestors. For example, a person has such rudiments as the coccyx, appendix, third eyelid, wisdom teeth, muscles that move the auricle, etc.;
atavisms - the sudden appearance in individual individuals of the organs (signs) of their ancestors. For example, the birth of people with a tail, thick body hair, extra nipples, highly developed fangs, etc.
4. Embryological evidence. These include: the similarity of gametogenesis, the presence in the development of a unicellular stage - the zygote; similarity of embryos in the early stages of development; relationship between ontogeny and phylogeny.
The embryos of organisms of many systematic groups are similar to each other, and the closer the organisms, the more this similarity remains until a later stage in the development of the embryo (Fig. 7.8). Based on these observations, E. Haeckel and F. Müller formulated a biogenetic law - each individual repeats some of the main structural features of its ancestors in the early stages of ontogenesis. Thus, ontogenesis (individual development) is a brief repetition of phylogenesis (evolutionary development).
6. Relic evidence. At present, there are descendants of transitional forms (Fig. 7.11), for example, the lobe-finned coelacanth fish is a descendant of the transitional form between fish and amphibians, the tuatara is a descendant of the transitional form between amphibians and reptiles; platypus - a descendant of a transitional form between reptiles and mammals
7. Biogeographic evidence. Similarities and differences between organisms living in different biogeographic zones. For example, marsupials survived only in Australia.
7.2.2. Origin of life
Development of views on the origin of life. From ancient times to this day, mankind has been looking for an answer to the question of the origin of life on Earth. Previously, it was believed that spontaneous generation of life from inanimate matter was possible. According to scientists of the Middle Ages, fish could be born from silt, worms from soil, mice from dirty rags, flies from rotten
meat. In the 17th century the Italian scientist F. Redi conducted an original experiment: he placed pieces of meat in glass vessels, he left some of them open, and covered some with muslin. Fly larvae appeared only in open vessels (Fig. 7.12). In the middle of the XIX century. the French microbiologist L. Pasteur placed the sterilized broth in a flask with a long narrow B-shaped neck. Bacteria and other airborne organisms settled by gravity in the lower curve of the neck and did not reach the broth, while the air entered the flask itself (Fig. 7.13).
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These and other similar experiments convincingly proved that living organisms in the modern era come only from other living organisms. The impossibility of spontaneous generation of life from non-living things was called Redi's principle. As a result, the question of the origin of the first living organisms is natural.
A variety of approaches to the question of the origin of life. On the question of the origin of life, as well as on the question of the essence of life, there is no consensus among scientists. There are several approaches to solving the problem of the origin of life, which are closely intertwined. They can be classified as follows.
1) according to the principle that the idea, mind are primary, and matter is secondary (idealistic hypotheses) or matter is primary, and the idea, mind are secondary (materialistic hypotheses);
2) according to the principle that life has always existed and will exist forever (stationary state hypotheses) or life arises at a certain stage in the development of the world;
3) according to the principle that the living is only from the living (the hypothesis of biogenesis) or spontaneous generation of the living from the non-living is possible (the hypothesis of abiogenesis)",
4) on the principle that life originated on Earth or was brought from space (panspermia hypotheses).
Consider the most significant of the hypotheses.
Creationism. According to this hypothesis, life was created by the Creator. The Creator is God, the Idea, the Higher Mind, or others.
Stationary State Pshothesis. Life, like the Universe itself, has always existed and will exist forever, for what has no beginning has no end. At the same time, the existence of individual bodies and formations (stars, planets, organisms) is limited in time: they arise, are born and die. At present, this hypothesis is mainly of historical significance, since the “Big Bang theory” is generally recognized, according to which the Universe exists for a limited time; it formed from a single point about 15 billion years ago.
Pshothesis of panspermia. Life was brought to Earth from outer space and took root here after favorable conditions for this developed on Earth. This assumption was made by the German scientist G. Rikhur in 1865, and finally formulated by the Swedish scientist S. Arrhenius in 1895. With meteorites and cosmic dust, bacteria spores, which are largely resistant to radiation, vacuum, and low temperatures, could get to Earth about how life arose in space due to objective difficulties is postponed indefinitely. It could have been created by the Creator, always existed, or emerged from inanimate matter. Recently, more and more supporters of the panspermia hypothesis have appeared among scientists.
Pshothesis of abiogenesis (spontaneous generation of living things from non-living things and subsequent biochemical evolution). In 1924, the Russian biochemist A. I. Oparin, and later in 1929 the English scientist J. Haldane suggested that life arose on Earth from non-living matter as a result of chemical evolution - complex chemical transformations of molecules. This event was favored by the conditions prevailing on Earth at that time.
According to this hypothesis, four stages can be distinguished in the process of the formation of life on Earth -
1) synthesis of low molecular weight organic compounds from gases of the primary atmosphere;
2) polymerization of monomers with the formation of chains of proteins and nucleic acids;
3) the formation of phase-separated systems of organic substances, separated from the external environment by membranes;
4) the emergence of the simplest cells that have the properties of a living, including the reproductive apparatus, carrying out
giving the daughter cells all the chemical and metabolic properties of the parent cells.
The first three stages are attributed to the period of chemical evolution, from the fourth - biological evolution begins.
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The ideas about the possible chemical evolution of matter have been confirmed by a number of model experiments. In 1953, the American chemist S. Miller and physicist G. Urey simulated in laboratory conditions the composition of the Earth's primary atmosphere, which consisted of methane, ammonia and water vapor, and, acting on it with a spark discharge, obtained simple organic substances - the amino acids glycine, alanine and others (Fig. 7.14). Thus, the fundamental possibility of the abiogenic synthesis of organic compounds (but not living organisms) from inorganic substances was proved.
Thus, organic matter could have been created in the primordial ocean from simple inorganic compounds. As a result of the accumulation of organic matter in the ocean, the so-called "primary soup" was formed. Then, combining, proteins and other organic molecules formed drops of coacervates, which served as a prototype
cells Drops of coacervates were subjected to natural selection and evolved. The first organisms were heterotrophic. As the reserves of the "primary broth" were used up, autotrophs arose.
It should be noted that from the point of view of probability theory, the probability of synthesizing supercomplex biomolecules under the condition of random combinations of their constituent parts is extremely low.
IN AND. Vernadsky on the origin and essence of life and the biosphere. IN AND. Vernadsky outlined his views on the origin of life in the following theses.
1. There was no beginning of life in the cosmos that we observe, since there was no beginning of this cosmos. Life is eternal, because the cosmos is eternal, and has always been transmitted through biogenesis.
2. Life, eternally inherent in the Universe, was new on Earth, its germs were constantly brought from outside, but were strengthened on Earth only when opportunities were favorable for this.
3. There has always been life on Earth. The lifetime of a planet is only the lifetime of life on it. Life is geologically (planetary) eternal. The age of the planet is indeterminate.
4. Life has never been something random, nestling in some separate oases. It was distributed everywhere and always living matter existed in the form of the biosphere.
5. The most ancient forms of life - pellets - are able to perform all functions in the biosphere. This means that a biosphere consisting of only prokaryotes is possible. It is likely that this is how it was in the past.
6. Living matter could not come from inert. There are no intermediate steps between these two states of matter. On the contrary, as a result of the influence of life, the evolution of the earth's crust took place.
Thus, it must be recognized that to date, none of the existing hypotheses about the origin of life has direct evidence, and modern science There is no single answer to the question of the origin of life.
7.2.3. Short story development of the organic world
The age of the Earth is about 4.6 billion years. Life on Earth originated in the ocean more than 3.5 billion years ago.
A brief history of the development of the organic world is given in Table. 7.2. The phylogeny of the main groups of organisms is shown in fig. 7.15. The organic world of bygone eras is recreated in fig. 7.16-7.21.
Geochronological scale and the history of the development of living organisms
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| Era, age, million years | Climate and geological processes | Animal world | plant world | The most important aromorphoses | |
| Mesozoic, 240 | archeopteryx; ancient cartilaginous fish die out | gymnosperms | |||
| Triassic | Weakening of climatic zonality Beginning of movement of continents | Amphibians, cephalopods, herbivores and predatory reptiles predominate; bony fish, oviparous and marsupial mammals appear | Ancient gymnosperms predominate; modern gymnosperms appear, seed ferns die out | The appearance of a four-chambered heart; complete separation of arterial and venous blood flow, the appearance of warm-bloodedness, the appearance of mammary glands | |
| Paleozoic | Permian (Permian), 50± 10 | Sharp climate zoning, completion of mountain building processes | Marine invertebrates, sharks dominate; reptiles and insects develop rapidly; there are animal-toothed and herbivorous reptiles; stegocephalians and trilobites are dying out | Rich flora of seed and herbaceous ferns; ancient gymnosperms appear; tree-like horsetails, club mosses and ferns die out | Pollen tube and seed formation |
| Carbon (carbon), b5± 10 | Distribution of forest swamps. Uniformly moist | Amphibians, molluscs, sharks, lungfish dominate, and | The abundance of dendritic | The appearance of internal fertilization 1 |
| Era, age, million years | Period, duration, million years | Climate and geological processes | Animal world | plant world | The most important aromorphoses |
| The mild climate is replaced by a dry one at the end of the period. | winged forms of insects, spiders, scorpions develop rapidly, the first reptiles appear; trilobites and stegocephals are noticeably reduced | ferns, forming "carboniferous forests", seed ferns appear, lsilophytes disappear | the appearance of dense egg shells; keratinization of the skin | ||
| Devonian (Devonian). | Change of dry and rainy seasons, glaciation in the territory of modern South Africa and America | Armored, molluscs, trilobites, corals prevail; Kisteler, lungfish and ray-finned fish, stegocephals appear | Rich flora l forces ophites, mosses, ferns, mushrooms appear | The dismemberment of the body of plants into organs; transformation of fins into terrestrial limbs; the emergence of respiratory organs | |
| Silurian | Initially dry, then humid climate, mountain building | A rich fauna of trilobites, molluscs, crustaceans, corals, armored fish appear, the first terrestrial invertebrates: centipedes, scorpions, wingless insects | Abundance of algae; plants come to land - PS or ophites appear | Differentiation of the plant body into tissues, division of the animal body into sections, formation of jaws and limb belts in vertebrates |
| Era, age, million years | Period, duration, million years | Climate and geological processes | Animal world | plant world | The most important aromorphoses |
| Paleozoic | Ordovician (Ordovician), \ 55± 10 | Cambrian) (Cambrian), I 80±20) | Glaciation is replaced by a moderately humid, then dry climate. Most of the land is occupied by the sea, mountain building | Sponges, coelenterates, worms, echinoderms, trilobites predominate; jawless vertebrates (scutes), molluscs appear | Prosperity of all departments of algae | |
| Prothero | The surface of the planet is bare desert. Frequent glaciations, active rock formation | Protozoa are widespread; all types of invertebrates, echinoderms appear: primary chordates - subtype Cranial | Bacteria, blue-green and green algae are widespread; red algae appear | The emergence of bilateral symmetry | |
| Archeyskaya, 3 500 (3 800) | Active volcanic activity Anaerobic living conditions in shallow water | The emergence of life, prokaryotes (bacteria, blue-green algae), eukaryotes (green algae, protozoa), primitive metazoans | Emergence of photosynthesis, aerobic respiration, eukaryotic cells, sexual process, multicellular™ | ||
The history of the development of life on Earth is studied by the fossil remains of organisms or traces of their vital activity. They are found in rocks of different ages.
The geochronological scale of the history of the development of the organic world of the Earth includes eras and periods (see Table 7.2). The following eras are distinguished: Archean (Archean) - the era of ancient life, Proterozoic (Proterozoic) - the era of primary life, Paleozoic (Paleozoic) - the era of ancient life, Mesozoic (Mesozoic) - the era average life, Cenozoic (Cenozoic) - the era of new life. The names of the periods are formed either from the names of the localities where the corresponding deposits were first found (the city of Perm, Devon County), or from the processes taking place at that time (during the coal period - Carboniferous - deposits of coal were laid, in the Cretaceous - chalk, etc. .).
Archean era (era of ancient life: 3500 (3800-2600 million years ago). According to various sources, the first living organisms on Earth appeared 3.8-3.2 billion years ago. These were prokaryotic heterotrophic anaerobes (pre-nuclear, feeding on ready-made organic substances, not They lived in the primordial ocean and fed on organic substances dissolved in its water, created abiogenically from inorganic substances under the action of the energy of the ultraviolet rays of the Sun and lightning discharges.
The Earth's atmosphere consisted mainly of CO 2 , CO, H 2 , N7, water vapor, small amounts of N113, H 2 5 , CH 4 and almost did not contain free oxygen 0 2 . The absence of free oxygen made it possible for abiogenically created organic substances to accumulate in the ocean, otherwise they would immediately be broken down by oxygen.
The first heterotrophs carried out the oxidation of organic substances anaerobically - without the participation of oxygen by fermentation. During fermentation, organic matter is not completely broken down, and little energy is generated. For this reason, evolution in the early stages of the development of life was very slow.
Over time, heterotrophs greatly multiplied and they began to lack abiogenically created organic matter. Then prokaryotic autotrophic anaerobes arose. They could synthesize organic substances from inorganic substances on their own, first through chemosynthesis, and then through photosynthesis.
The first was anaerobic photosynthesis, which was not accompanied by the release of oxygen:
6С0 2 + 12Н 2 5 -> С(,Н 12 0 6 + 125 + 6 Н,0
Then came aerobic photosynthesis:
6С0 2 + 6Н 2 0 -> СбН, 2 0 6 + 60,
Aerobic photosynthesis was characteristic of creatures similar to modern cyanobacteria.
The free oxygen released during photosynthesis began to oxidize divalent iron, sulfur compounds and manganese dissolved in ocean water. These substances turned into insoluble forms and settled on the ocean floor, where they formed deposits of iron, sulfur and manganese ores, which are currently used by man.
Oxidation of substances dissolved in the ocean took place over hundreds of millions of years, and only when their reserves in the ocean were exhausted did oxygen begin to accumulate in the water and diffuse into the atmosphere.
It should be noted that a mandatory condition for the accumulation of oxygen in the ocean and atmosphere was the burial of some part of the organic matter synthesized by organisms at the bottom of the ocean. Otherwise, if all organics were split with the participation of oxygen, there would be no excess of it and oxygen could not accumulate. Undecomposed bodies of organisms settled on the bottom of the ocean, where they formed deposits of fossil fuels - oil and gas.
The accumulation of free oxygen in the ocean made possible the emergence of autotrophic and heterotrophic aerobes. This happened when the concentration of 0 2 in the atmosphere reached 1% of the current level (and it is equal to 21 6C0 2 + 6H 2 0 + 38ATP.
Since much more energy began to be released during aerobic processes, the evolution of organisms accelerated significantly.
As a result of the symbiosis of various prokaryotic cells, the first eukaryotes (nuclear) appeared.
As a result of the evolution of eukaryotes, the sexual process arose - the exchange of organisms with genetic material - DNA. Thanks to the sexual process, evolution went even faster, since combinative variability was added to the mutational variability.
At first, eukaryotes were unicellular, and then the first multicellular organisms appeared. The transition to multicellularity in plants, animals and fungi occurred independently of each other.
Multicellular organisms have received a number of advantages over unicellular ones:
1) a long duration of ontogenesis, since in the course of the individual development of the organism, some cells are replaced by others;
2) numerous offspring, since the organism can produce more cells for reproduction;
3) significant size and diverse body structure, which provides greater resistance to external environmental factors due to the stability of the internal environment of the organism.
Scientists do not have a common opinion on the question of when the sexual process and multicellularity arose - in the Archean or Proterozoic era.
Proterozoic era (era of primary life: 2600-570 million years ago). The appearance of multicellular organisms accelerated evolution even more and, in a relatively short period (on a geological time scale), different kinds living organisms adapted to different conditions of existence. New forms of life occupied and formed ever new ecological niches in different areas and depths of the ocean. Rocks 580 million years old already contain the imprints of creatures with hard skeletons, and therefore it is much easier to study evolution from this period. Solid skeletons serve as a support for the bodies of organisms and contribute to an increase in their size.
By the end of the Proterozoic era (570 million years ago), a producer-consumer system was formed and an oxygen-carbon biogeochemical cycle of substances was formed.
Paleozoic era (era of ancient life: 570-240 million years ago).
In the first period of the Paleozoic era - the Cambrian (570-505 million years ago) - there was a so-called "evolutionary explosion": in a short time, almost all currently known types of animals were formed. All the evolutionary time preceding this period was called the Precambrian, or cryptozoic (“the era hidden life”) is 7/jj of the Earth's history. The time after the Cambrian was called the Phanerozoic (“era of manifest life”).
As more and more oxygen was formed, the atmosphere gradually acquired oxidizing properties. When did the concentration of 0 2 in the atmosphere reach lOfS? from the current level (on the border of the Silurian and Devonian), at an altitude of 20-25 km, the ozone layer began to form in the atmosphere. It was formed from 0 2 molecules under the influence of the energy of the ultraviolet rays of the Sun:
o 2 + o -> o,
Ozone molecules (0 3) have the ability to reflect ultraviolet rays. As a result, the ozone screen has become a protection for living organisms from harmful to them in large doses of ultraviolet rays. Before that, an ox served as sewn up. Now life has the opportunity to move out of the ocean onto land.
The emergence of living beings on land began in the Cambrian period: bacteria were the first to enter it, and then fungi and lower plants. As a result, soil was formed on land, and in the Silurian period (435-400 million years ago), the first vascular plants, psilophytes, appeared on land. Exit to land contributed to the appearance in plants of tissues (integumentary, conductive, mechanical, etc.) and organs (root, stem, leaves). As a result, higher plants appeared. The first land animals were arthropods, descended from marine crustaceans.
At this time, chordates evolved in the marine environment: vertebrate fish originated from invertebrate chordates, and amphibians originated from lobe-finned fish in the Devonian. They dominated the land for 75 million years and were represented by very large forms. In the Permian period, when the climate became colder and drier, reptiles gained superiority over amphibians.
Mesozoic era (era of middle life: 240-66 million years ago). In the Mesozoic era, the “era of the dinosaurs”, reptiles reached their peak (their numerous forms were formed) and decline. In the Triassic, crocodiles and turtles appeared, and the class Mammals originated from the animal-toothed reptiles. Throughout the Mesozoic era, mammals were small and not widely distributed. At the end of the Cretaceous, a cooling set in and a mass extinction of reptiles occurred, the final causes of which have not been fully elucidated. AT Cretaceous angiosperms (flowering) appeared.
Cenozoic era (era of new life: 66 million years ago - present). In the Cenozoic era, mammals, birds, arthropods, and flowering plants were widely distributed. A man appeared.
At present, human activity has become an important factor development of the biosphere.
“... you must firmly remember
that visible bodily things on Earth
and the whole world is not in this state
were from the beginning from creation,
as we now find
but the great ones happened
there are changes in it ... "
M. V. LOMONOSOV
The mass of the Earth is about 4´10 18 tons, and the age is about 4.5-5 billion years. It is believed that life arose on Earth about 3.5-3.8 billion years ago.
It had a significant effect on the atmosphere, which changed from oxidizing to non-oxidizing.
The huge variety of living forms that now inhabit the Earth is the result of a long process of evolution, which is understood as the development of organisms in time or the process of historical transformation on Earth, the result of which is the diversity of the modern living world. The term "evolution" (from Latin evolutio - deploy) was introduced into science in 1762 by the Swiss naturalist C. Bonn (1720-1793).
In the beginning, evolution was very slow. Microorganisms were the first and only living inhabitants of the Earth for 3 billion years. Multicellular organisms appeared after four-fifths of the time the Earth began to exist. Human evolution has taken the last few million years. The central point of evolution is phylogeny (from the Greek phyle - tribe, genesis - development), - the process of the emergence and development of a species, i.e., the evolution of a species.
Ideas about the development of life are reflected in the theory of evolution, which is based on data on the general laws and driving forces of the development of living nature. It is a synthesis of the achievements of Darwinism, biology, genetics, morphology, physiology, ecology, biogeocenology and other sciences. In our time, the theory of evolution, based on Darwinism, is the science of the general laws of the development of organic nature, the methodological basis of all special biological disciplines.
In this section, we will consider the theory of evolution. Data on the origin of life, microevolution and speciation, as well as the course, main directions and evidence of evolution will also be given. In separate chapters, we present information about the evolution of animal organ systems and the origin of man.
Chapter XIV
EVOLUTION THEORY
Ideas about evolution before
Charles Darwin
Evolution proceeds at all levels of the organization of living matter and at each level is characterized by the formation of new structures and the emergence of new functions. The unification of structures and functions of one level is accompanied by the transition of living systems to a higher evolutionary level.
The problems of the origin and evolution of life on Earth were and still are among the greatest problems of natural science. These problems have attracted the attention of the human mind since time immemorial. They were the subject of interest of all philosophical and religious systems. However, in different epochs and at different stages of the development of human culture, the problems of the origin and evolution of life were solved in different ways.
The modern theory of evolution is based on the theory of Ch. Darwin. But evolutionism existed even before Charles Darwin. Therefore, in order to better understand the modern theory of evolution, it is important to know about the views on the world before Charles Darwin, about how the ideas of evolutionism developed.
The most ancient views of nature were mystical, according to which life was associated with the forces of nature. But already at the very origins of culture in ancient greece the mystical interpretations of nature are replaced by the beginnings of other ideas. During that period, the doctrine of abiogenesis and spontaneous spontaneous generation arose and began to develop, in accordance with which it was recognized that living organisms arise spontaneously from inanimate material. At the same time, evolutionary ideas appeared. For example, Empedocles (490-430 BC) believed that the first living beings arose from the four elements of world matter (fire, air, water and earth) and that natural development is characteristic of nature, the survival of those organisms that are most harmoniously (appropriately) arranged. These thoughts were very important for the further dissemination of the idea of the natural origin of living beings.
Democritus (460-370 BC) believed that the world consists of many tiny particles that are in motion, and that life is not the result of creation, but the result of action mechanical forces nature itself, leading to spontaneous generation. According to Democritus, the spontaneous generation of living beings occurs from silt and water as a result of the combination of atoms during their mechanical movement, when the smallest particles of moist earth meet and combine with the atoms of fire. Spontaneous generation seemed to be a random process.
Assuming that worms, mites and other organisms arise from dew, silt, manure, hair, sweat, meat, mollusks from moist earth, and fish from sea mud, etc., Plato (427-347 BC .) argued that living beings are formed as a result of the combination of passive matter with an active principle (form), which is a soul, which then moves the body.
Aristotle (384-322 BC) argued that plants and animals arise from non-living material. In particular, he argued that some animals arise from decomposed meat. Recognizing the reality of the material world and the constancy of its movement, comparing organisms with each other, Aristotle came to the conclusion about the "ladder of nature", reflecting the sequence of organisms, starting with inorganic bodies and continuing through plants to sponges and ascidians, and then to free-living marine organisms. However, while recognizing development, Aristotle did not allow the idea of the development of lower organisms to higher ones.
The views of Aristotle influenced the centuries, for subsequent Greek and Roman philosophical schools fully shared the idea of spontaneous generation, which was more and more filled with mystical content. Descriptions of various cases of spontaneous generation are given by Cicero, Ovid, later Seneca, Pliny, Plutarch and Apuleius. The idea of variability can be traced in the views of the ancient philosophers of India, China, Mesopotamia, and Egypt. Early Christianity substantiated the doctrine of abiogenesis with examples from the Bible. It was emphasized that spontaneous generation operates from the creation of the world to the present day.
During the Middle Ages (5th-15th centuries), belief in spontaneous spontaneous generation was dominant among scientists of that time, because philosophical thought then could exist only as a theological thought. Therefore, the writings of medieval scientists contain numerous descriptions of the spontaneous generation of insects, worms, and fish. Then it was often believed that even lions arose from the stones of the desert. The famous physician of the Middle Ages Paracelsus (1498-1541) gave a recipe for the "production" of a homunculus (man) by placing human sperm in a pumpkin. As you know, Mephistopheles from Goethe's tragedy "Faust" called himself the master of rats, mice, flies, frogs, bedbugs and lice, which I. Goethe emphasized the extraordinary possibilities of spontaneous generation.
The Middle Ages did not introduce new ideas into the ideas about the development of the organic world. On the contrary, during that period, the creationist idea reigned about the emergence of the living as a result of the act of creation, about the constancy and immutability of existing living forms. The pinnacle of creationism was the creation of a ladder of bodies of nature: god - angel - man - animals, plants, micelles.
Harvey (1578-1667) admitted that worms, insects and other animals could be born as a result of decay, but under the action of special forces. F. Bacon (1561-1626) believed that flies, ants and frogs can spontaneously arise during decay, but he approached the issue materialistically, denying the insurmountable line between inorganic and organic. R. Descartes (1596-1650) also recognized spontaneous generation, but denied participation in it spirituality. According to R. Descartes, spontaneous generation is a natural process that occurs under certain (incomprehensible) conditions.
Assessing the views of prominent figures of the past, we can say that the doctrine of spontaneous generation was not questioned until mid-seventeenth in. Metaphysical views in the XVII-XVIII centuries. especially manifested in the ideas of the immutability of species and organic expediency, which were considered the result of the creator's wisdom and vitality.
However, despite the dominance of metaphysical ideas in the XVI-XVII centuries. nevertheless, the dogmatic thinking of the Middle Ages is being broken, the struggle against the spiritual dictatorship of the church is intensifying, the process of cognition arises and deepens, which led in the 18th century. to substantial arguments against the theory of abiogenesis and to arouse interest in evolutionism.
Having carried out a series of experiments with meat and flies in 1665, F. Redi (1626-1697) came to the conclusion that the larvae that appear in rotting meat are insect larvae, and that such larvae will never occur if the meat is placed in a closed container , inaccessible to insects, i.e. for laying eggs. With these experiments, F. Redi refuted the doctrine of spontaneous generation of higher organisms from inanimate material. However, in the materials and reasoning of F. Redi, the idea of spontaneous spontaneous generation of microorganisms and helminths in the intestines of humans and animals was not ruled out. Consequently, the very idea of spontaneous generation still continued to exist.
In 1765, L. Spalanzani (1729-1799) in many experiments showed that the development of microbes in vegetable and meat infusions is excluded by boiling the latter. He also revealed the importance of boiling time and tightness of vessels. His conclusion boiled down to the fact that if sealed vessels with infusions were boiled for a sufficient time and the penetration of air into them was excluded, then microorganisms would never arise in such infusions. However, L. Spalanzani failed to convince his contemporaries of the impossibility of spontaneous generation of microorganisms. The idea of spontaneous generation of life continued to be defended by many prominent philosophers and natural scientists of that time (I. Kant, G. Hegel, X. Gay-Lussac, and others).
In 1861-1862. L. Pasteur presented detailed evidence of the impossibility of spontaneous generation in infusions and solutions of organic substances. Experimentally, he proved that the source of contamination of all solutions are bacteria in the air. The studies of L. Pasteur made a great impression on his contemporaries. The Englishman D. Tyndall (1820-1893) found that some forms of microbes are very resistant, withstanding heating for up to 5 hours. Therefore, he developed a method of fractional sterilization, now called tyndalization.
The refutation of the doctrine of abiogenesis was accompanied by the formation of ideas about the eternity of life. Indeed, if spontaneous generation of life is impossible, many philosophers and scientists reasoned, then life is eternal, autonomous, scattered in the Universe. But how did she get to Earth? To answer this question, the Swedish scientist Arrhenius (1859-1927) at the beginning of our century (1912) formulated the panspermia hypothesis, according to which life exists in the universe and is transferred in the simplest forms from one celestial body to another, including the Earth, under the pressure of light rays. Proponents of this hypothesis believed that the transfer of life to Earth is possible with the help of meteorites. However, the panspermia hypothesis was objected to in the sense that factors in outer space act that are detrimental to microorganisms and that these factors exclude the circulation of microorganisms outside the Earth's atmosphere. It became more and more clear that life is unique, that the origins of life should be sought on Earth.
No less important at that time was the question of the "natural relationship" of organisms. It was about grouping organisms on the basis of their natural relationship, about the assumption that individual organisms could come from common ancestors. For example, J. Buffon believed that there could be "common ancestors" for several families, in particular for mammals, he allowed 38 common ancestors. In Russia, the idea of the origin of organisms of a number of species from common ancestors was developed by PS Pallas (1741-1811).
Further, attention was drawn to the question of the time factor in the change of organisms. In particular, the importance of the time factor for the existence of the Earth and the formation of organic forms on the Earth was recognized by I. Kant (1724-1804), D. Diderot, J. Buffon, M. V. Lomonosov (1711-1765), A. N. Radishchev ( 1749-1802), A. A. Kaverznev (1748-?). I. Kant determined the age of the Earth at several million years, and M. V. Lomonosov wrote that the time that was necessary for the creation of organisms is large in church calculus. The recognition of the time factor was of undoubted importance for the historical understanding of the development of organisms. However, ideas about time in that period were reduced only to the idea of the non-simultaneity of the appearance of organisms different types, but not to the recognition of the development of organisms in time.
At that time, the question of the sequence of natural bodies was of great importance. A significant contribution to the formation of the idea of a sequence of natural bodies belongs to S. Bonnet and G. Leibniz. In Russia this idea was supported by A. N. Radishchev. Not having sufficient knowledge about organisms, S. Bonnet, G. Leibniz and other naturalists of that time revived the Aristotelian "ladder of nature". By arranging the organisms on it in steps (man was on the main step), they created a "ladder of beings" in which there were continuous transitions from the Earth and stones to God. There were as many steps in the stairs as there are animals. Reflecting the idea of the unity and connection of living forms, of the complication of organisms, the “ladder of beings” as a whole was a product of metaphysical thinking, because its steps reflected a simple neighborhood, but not the result historical development.
Significant attention in those days was attracted by the question of the "prototype" and the unity of the plan of the structure of organisms. Assuming the existence of the original being, many recognized a single plan for the structure of organisms. Discussions on this issue were important for subsequent ideas about the common origin.
For many, great interest was attracted by the question of the transformation of organisms. For example, the French naturalist B. de Mais (1696-1738) believed that eternal seeds of life live in the sea, which give rise to marine living forms, which then transform into terrestrial organisms. Noting the positive role of transformism in evolutionism, it should nevertheless be noted that it was mechanical and excluded the idea of development, of historicism.
Finally, the focus of attention at that time was the question of the emergence of organic expediency. Many philosophers and naturalists have recognized that expediency is not primordial, that it arose naturally as a result of the rejection of disharmonic organisms. The discussion of this question promoted evolutionism, but did not achieve a significant result, because the appearance of one form was considered independently of the appearance of another.
So, by the end of the XVIII century. ideas appeared that contradicted the ideas about the immutability of species, but they did not develop into a system of views, and the metaphysical thinking prevented us from completely rejecting religion and looking at nature in a new way. The first who specifically turned to the study of the problems of evolution was the French scientist J.-B. Lamarck (1744-1829). The doctrine he created was the completion of the previous searches of many naturalists and philosophers who tried to comprehend the emergence and development of the organic world.
J.-B. Lamarck was a deist, because he believed that the creator is the root cause of matter and motion, but further development occurs due to natural causes. According to Lamarck, the creator carried out only the first act, creating the simplest forms, which then developed, giving rise to all diversity based on natural laws. Lamarck was also an anti-vitalist. Considering that the living arises from the inanimate, he considered spontaneous generation as a natural regular process, which is the starting point of evolution. Recognizing the development from the simple to the complex and relying on the "ladder of beings", Lamarck came to the conclusion about the gradation, in which he saw a reflection of the history of life, the development of some forms from others. Lamarck believed that the development from the simplest forms to the most complex is the main content of the history of the entire organic world, including the history of man. However, proving the evolution of species, Lamarck believed that they are fluid and there are no boundaries between them, that is, in fact, he denied the existence of species.
The main reasons for the development of wildlife according to Lamarck is the innate desire of organisms to complicate through improvement. According to Lamarck, evolution proceeds on the basis of an internal desire for progress, and the provisions on the exercises and non-exercise of organs and on the transmission by inheritance of signs acquired under the influence of the environment are laws. As Lamarck thought, environmental factors affect plants and simple organisms directly, "sculpting" them, as if from clay, desired forms, i.e. changes in the environment lead to a change in species. Environmental factors affect animals indirectly.
Changes in the environment lead to a change in the needs of animals, a change in needs leads to a change in habits, and a change in habits is accompanied by the use or non-use of certain organs. In support of these views, Lamarck cited many examples. For example, the shape of the body of snakes, he believed, is the result of the habit of these animals to crawl on the ground, and the long neck of the giraffe is due to the need to get fruit on the trees.
The use (exercise) of an organ is accompanied by its further development, while the non-use of an organ is accompanied by degradation. Changes induced by external conditions (circumstances) are inherited by offspring, accumulate and lead to the transition of one species to another.
Historical merits of Lamarck lie in the fact that he was able to show the development from simple to complex and draw attention to the inseparable connection of the organism with the environment. However, Lamarck still failed to substantiate the evolutionary doctrine, because he failed to find out the true mechanisms of evolution. As K. A. Timiryazev (1843-1920) noted, Lamarck failed to explain the most important issue concerning the expediency of organisms. Lamarck's teaching contained elements of natural philosophy and idealism, so he failed to convince his contemporaries that evolution does indeed take place in nature.
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