“... 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 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 were 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 the action of the mechanical forces of 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, dung, 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 thought 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 scholars 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 the participation of the spiritual principle in it. 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 the middle of the 17th century. 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 breaking down, 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 pressure 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 a large church calculation. 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 of different species, 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 of 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 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 form 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 addressed 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, into the necessary 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 the simple to the 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.
Similar information.
THE THEORY OF EVOLUTION OF THE ORGANIC WORLD
In 1909, there was a great celebration in Paris: a monument to the great French naturalist Jean-Baptiste Lamarck was unveiled to commemorate the centenary of the publication of his famous work, The Philosophy of Zoology. One of the bas-reliefs of this monument depicts a touching scene: a blind old man sits in an armchair in a sad pose - this is Lamarck himself, who lost his sight in old age, and a young girl stands nearby - his daughter, who consoles her father and addresses him with the words:
"Your offspring will admire you, my father, they will avenge you."
Jean-Baptiste de Monet Chevalier de Lamarck was born on August 1, 1744 in France, in a small town. He was the eleventh child in an impoverished aristocratic family. His parents wanted to make him a priest and assigned him to a Jesuit school, but after the death of his father, sixteen-year-old Lamarck left school and joined the army in 1761 as a volunteer. There he showed great courage and received the rank of officer. After the end of the war, Lamarck came to Paris, a neck injury forced him to leave military service. He began to study medicine. But he was more interested in the natural sciences, especially botany. Receiving a small pension, he entered one of the banking houses to earn money.
After a number of years of intense studies, the hardworking and talented young scientist wrote a large work in three volumes - "The Flora of France", published in 1778. It describes many plants and provides guidance for identifying them. This book made Lamarck famous, and the following year he was elected a member of the Paris Academy of Sciences. At the Academy, he successfully continued to engage in botany and gained great authority in this science. In 1781 he was appointed chief botanist of the French king.
Another passion of Lamarck was meteorology. From 1799 to 1810 he published eleven volumes devoted to this science. He studied physics and chemistry.
In 1793, when Lamarck was already close to fifty, his scientific activity changed radically. The Royal Botanic Gardens, where Lamarck worked, was transformed into the Museum of Natural History. There were no free departments of botany in the museum, and he was offered to study zoology. It was difficult for an elderly man to leave his old job and move on to a new one, but Lamarck's great diligence and brilliant abilities overcame everything. About ten years later he became the same expert in the field of zoology as he was in botany.
A lot of time passed, Lamarck grew old, crossed the line of sixty years. He now knew almost everything about animals and plants that was known to the science of that time. Lamarck decided to write a book that would not describe individual organisms, but would explain the laws of development of living nature. Lamarck wanted to show how animals and plants appeared, how they changed and developed, and how they reached their present state. Speaking in the language of science, he wanted to show that animals and plants were not created as they are, but developed by virtue of the natural laws of nature, that is, to show the evolution of the organic world.
It was not an easy task. Only a few scientists before Lamarck had speculated about the variability of species, but only Lamarck, with his enormous store of knowledge, managed to solve this problem. Therefore, Lamarck is deservedly considered the creator of the first evolutionary theory.
Ideas about the variability of the surrounding world (including living beings) were formed in antiquity. For example, the ancient Greek philosophers Heraclitus of Ephesus, Empedocles, Democritus, the ancient Roman philosopher Titus Lucretius Carus thought about the changeability of the world. Later, a system of worldview appeared, based on religious dogmas about the immutability of the world created by the Creator - creationism. Then, in the 17th-18th centuries, new ideas about the variability of the world and the possibility of historical changes in the types of organisms were formed, which were called transformism.
Among naturalists and transforming philosophers, the names of Robert Hooke, Georges Louis Leclerc Buffon, Denis Diderot, Julien Offret de La Mettrie, Johann Wolfgang Goethe, Erasmus Darwin, Etienne Geoffroy Saint-Hilaire became known. All transformists recognized the variability of species of organisms under the influence of environmental changes. At the same time, most transformists did not yet have a holistic and consistent concept of evolution.
Lamarck published his revolutionary book in 1809 and called it "Philosophy of Zoology", although it deals not only with animals, but also with all living nature. It should not be thought that all those interested in science at that time were delighted with this book and understood that Lamarck had set a great task for scientists. It often happened in the history of science that great ideas remained incomprehensible to contemporaries and received recognition only many years later.
So it happened with the ideas of Lamarck. Some scientists did not pay any attention to his book, others laughed at it. Napoleon, to whom Lamarck took it into his head to present his book, scolded him so much that he could not refrain from tears.
At the end of his life, Lamarck went blind and, forgotten by everyone, died on December 18, 1829, 85 years old. Only his daughter Cornelia remained with him. She took care of him until her death and wrote under his dictation.
The words of Cornelia, imprinted on the monument to Lamarck, turned out to be prophetic; posterity really appreciated the works of Lamarck and recognized him as a great scientist. But this did not happen soon, many years after Lamarck's death, after Darwin's remarkable work On the Origin of Species appeared in 1859. Darwin confirmed the correctness of the evolutionary theory, proved it on many facts and made him remember his forgotten predecessor.
The essence of Lamarck's theory is that animals and plants were not always the way we see them now. In times gone by, they were arranged differently and much more simply than they are now. Life on Earth arose naturally in the form of very simple organisms. Over time, they gradually changed, improved, until they reached the modern, familiar state. Thus, all living beings come from ancestors unlike them, more simply and primitively arranged.
Why, then, did the organic world, or, in other words, all animals and plants, not stand still, like a watch without winding, but move forward, develop, change, as it is changing now? Lamarck answered this question as well.
He gives two basic laws of evolution.
"First law. In every animal that has not reached the limit of its development, the more frequent and longer use of any organ gradually strengthens this organ, develops and enlarges it and gives it a strength commensurate with the duration of use, while the constant non-use of this or that organ gradually weakens him, causes him to decline, continuously diminishes his powers, and finally causes him to disappear.
Second law. Everything that nature has forced individuals to gain or lose under the influence of the conditions in which their breed has long been located, and, consequently, under the influence of the predominance of the use or disuse of one or another part (of the body), - all this nature preserves through reproduction in new individuals. which are descended from the former, provided that the acquired changes are common to both sexes or to those individuals from which the new individuals are descended.
Improving and refining his theory, Lamarck in his "Introduction" to the "Natural History of the Invertebrates" gave a new, somewhat expanded edition of his laws of evolution.
"one. Life, by its own forces, tends to continuously increase the volume of all its bodies and expand their dimensions to the limits established by it.
2. The formation of a new organ in the body of an animal comes from a new need that has appeared and continues to be felt, and from a new movement that this need generates and maintains.
3. The development of organs and the strength of their action always depends on the use of these organs.
4. Everything that is acquired, noted, or changed in the organization of individuals during their life, is preserved by generation and transmitted to new species that are descended from those who experienced this change.
Lamarck illustrated his theoretical construction with examples.
“The bird, drawn to the water by the need to find the prey it needs to sustain life, spreads its toes when it wants to row and move on the surface of the water. Due to these constantly repeated movements of the fingers, the skin connecting the fingers at their bases acquires the habit of stretching. Thus, over time, those wide membranes between the toes were formed, which we now see in ducks, geese, etc.
“... A coastal bird, which does not like to swim, but which is still forced to look for food near the shore, is constantly in danger of sinking into silt. And so, in an effort to avoid the need to dip the body into the water, the bird makes every effort to stretch and lengthen its legs. As a result of a long habit, acquired by this bird and other individuals of its breed, to constantly stretch and lengthen its legs, all individuals of this breed, as it were, stand on stilts, since little by little they formed long bare legs ... "
As Nikolai Iordansky notes: “Lamarck first identified two of the most general directions of evolution: ascending development from the simplest forms of life to more and more complex and perfect ones and the formation of adaptations in organisms depending on changes in the external environment (development “vertically” and “horizontally”) . Oddly enough, when discussing Lamarck's views, modern biologists more often recall only the second part of his theory (the development of adaptations in organisms), which was very close to the views of the transformists - Lamarck's predecessors and contemporaries, and leave its first part in the shade. However, it is the idea of ascending or progressive evolution that is the most original part of Lamarck's theory. The scientist believed that the historical development of organisms is not random, but natural in nature and occurs in the direction of gradual and steady improvement, an increase in the overall level of organization, which Lamarck called gradation. Lamarck considered the driving force of gradations to be “nature’s striving for progress”, inherent in all organisms and embedded in them by the Creator…
... Lamarck believed that the changes that plants and animals acquire during life are hereditarily fixed and transmitted to descendants; scientists call them modifications.
Contemporaries considered Lamarck's arguments contradictory and shaky and did not accept his theory. However, some of Lamarck's ideas still attract the attention of the cured and in the 20th century gave rise to several neo-Lamarckian concepts.
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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
In his spare 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 in biology at the time the scientist began his scientific activity, 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 the 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 the XVIII - beginning of the XIX century. 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 emergence 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, but 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 period of human development has shown that organisms have undergone 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 - flagellates, 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 the internal structure of various organisms in their comparison with each other (this science is of the greatest importance for animals and humans).
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.
Homologous organs are those characterized by a common structural plan, 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 research makes 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 of a natural system of the 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.
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 a common structure and function.
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 coelacanth 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 curved part of the neck and did not reach the broth, while 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. Bacterial spores, which are largely resistant to radiation, vacuum, low temperatures, could get to Earth with meteorites and cosmic dust. 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 a 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 does not have an unambiguous answer to the question of the origin of life.
7.2.3. A Brief History of the 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 of middle 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 the obligatory 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) various types of living organisms appeared, 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 of hidden life”) - this is 7 / jj of the history of the Earth. 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. In the Cretaceous period, 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 in the development of the biosphere.
The concept of evolution Evolution is a process of long-term and gradual changes that lead to fundamental qualitative changes in living organisms, accompanied by the emergence of new biological systems, forms and species. Created on the basis of the historical method, evolutionary theory, whose task is to study the factors, driving forces and patterns of organic evolution, occupies a central place in the system of the sciences of living nature.
History of development of evolutionary ideas Two points of view explaining the diversity of species in wildlife: The first of them arose on the basis of ancient dialectics, which affirmed the idea of development and change in the surrounding world; The second point of view appeared along with the Christian worldview based on the ideas of creationism.
The most important achievements of antiquity and modern times Aristotle "On parts of animals" - the idea of "ladder of living beings"; Carl Linnaeus and his classification of species; The formation of the doctrine of "transformism" - the idea of variability of species of organisms under the influence of environmental changes in the absence of a holistic and consistent concept of evolution.
The concept of development of J. B. Lamarck Three questions: 1) What is the basic unit of evolution? 2) What are the factors and driving forces (1744-1829) of evolution? 3) How is the transmission of newly acquired traits to the next generations?
The unit of evolution according to Lamarck The unit of evolution is the organism. Lamarck's evolutionary theory was based on the concept of development, gradual and slow, from simple to complex, taking into account the role of the external environment in the transformation of organisms. Lamarck believed that the first spontaneously generated organisms gave rise to the whole variety of organic forms that currently exist. Development from the simplest to the most perfect organisms is the main content of the history of the organic world.
Factors and driving forces of evolution Inherent in living nature, the original (laid by the Creator) desire for the complication and self-improvement of its organization; the influence of the external environment and living conditions: nutrition, climate, soil characteristics, moisture, temperature, etc.
The mechanism of transmission of acquired characteristics to the next generations The mechanism of heredity: individual changes, if they are repeated in a number of generations, are transmitted by inheritance to descendants during reproduction and become signs of the species; at the same time, if some organs of animals develop, then others, not involved in the process of changes, atrophy.
The theory of catastrophes by J. Cuvier Identification of the principle of correlations - each part of the body reflects the principles of the structure of the whole organism. Development of the theory of catastrophes - Cuvier came to the conclusion that gigantic cataclysms periodically occurred on Earth, destroying entire continents, and with them their inhabitants. Later, new organisms appeared in their place.
Ch. Darwin's Theory of Evolution Darwin formulated the main provisions of his theory of evolution and presented them in the book "The Origin of Species by Means of Natural Selection" (1859). (1809 - 1882)
The main driving factors of evolution in Darwin's theory Factors: Variability; Heredity; Struggle for existence; Natural selection.
Variability A certain (group) variability is a similar change in all individuals of the offspring in one direction due to the influence of certain conditions. \u003d modification Indefinite (individual) variability - the appearance of various minor differences in individuals of the same species, by which one individual differs from others. = mutation
Heredity is the property of organisms to ensure the continuity of signs and properties between generations, as well as to determine the nature of the development of an organism in specific environmental conditions. In the process of reproduction, not traits are transmitted from generation to generation, but a code of hereditary information (the norm of the reaction of a developing individual to the action of the external environment), which determines only the possibility of developing future traits in a certain range.
The struggle for existence is a set of relationships between organisms of a given species with each other, with other types of living organisms and inanimate environmental factors. Darwin singled out three main forms of struggle for existence: 1) interspecific, 2) intraspecific, 3) struggle with adverse environmental conditions.
Natural selection is a set of changes occurring in nature that ensure the survival of the fittest individuals and their predominant offspring, as well as the selective destruction of organisms that are unadapted to existing or changed environmental conditions.
Disadvantages of Darwin's theory According to the theory of evolution, mutations should occur very often, and for the most part they should be beneficial (in reality, almost all mutations are harmful) or, in extreme cases, useless; Also, according to the theory of evolution, in one place and at one time there should be two individuals of the same species and with the same mutations, and they should be of different sexes. They must survive, interbreed, and their descendants must have the same mutant features (descendants must also survive, find the same mutant of the opposite sex, etc.). So far, this has never happened in the natural environment.
Disadvantages of Darwin's theory The following questions also fell out of the field of view of Darwinists: About the reasons for the preservation of the systemic unity of organisms in the historical development; On the mechanisms of inclusion in the evolutionary process of ontogenetic rearrangements; On the uneven pace of evolution; On the causes and mechanisms of biotic crises, etc. In addition, there is no evidence that man descended from a monkey, since not a single evidence (fossil) has been found confirming the existence of an intermediate stage between man and ape.
Neo-Lamarckism mechanolamarckism - this concept explained the evolutionary transformations of organisms by their original ability to respond appropriately to changes in the external environment, while changing their structures and functions; psycho-Lamarckism - evolution was presented as a gradual strengthening of the role of consciousness in the movement from primitive beings to intelligent life forms; ortholamarckism - the direction of evolution is due to the internal initial properties of organisms.
The concept of teleogenesis This concept is ideologically close to ortholamarckism, as it comes from Lamarck's idea of the inner striving of all living organisms for progress. Within the concept of teleogenesis, the doctrine of saltationism stands out, according to which all major evolutionary events - from the emergence of new species to the change of biota in the geological history of the Earth - occur as a result of spasmodic changes, saltations, or macromutations.
Genetic anti-Darwinism At the beginning of the 20th century. genetics arose - the doctrine of heredity and variability; The spread of anti-evolutionism (W. Betson), according to which mutational variability was identified with evolutionary transformations, which eliminated the need for selection as the main cause of evolution.
The theory of nomogenesis L. S. Berg's theory of nomogenesis, created in 1922, was based on the idea that evolution is a programmed process of realizing internal patterns inherent in all living things (1876-1950). Berg believed that organisms have an internal force of an unknown nature, acting purposefully, regardless of the external environment, in the direction of complicating the organization.
Synthetic theory of evolution = general theory of evolution = neo-Darwinism is the theory of organic evolution by natural selection of genetically determined traits. The elementary evolutionary structure is the population; An elementary evolutionary phenomenon is a change in the genotypic composition of a population; The elementary hereditary material is the gene pool of the population; The elementary evolutionary factors are mutation processes, population waves of abundance, isolation and natural selection.
Concepts of micro- and macroevolution Microevolution is understood as a set of evolutionary processes occurring in populations, leading to changes in the gene pool of these populations and the formation of new species. Macroevolution is understood as evolutionary transformations leading to the formation of taxa of a higher rank than the species (genera, orders, classes).
The main provisions of STE 1. The main factor of evolution is natural selection, integrating and regulating the action of all other factors (mutagenesis, hybridization, migration, isolation, etc.); 2. Evolution proceeds divergently, gradually, through the selection of random mutations, and new forms are formed through hereditary changes; 3. Evolutionary changes are random and undirected; the source material for them are mutations; the original organization of the population and changes in external conditions limit and direct hereditary changes; 4. Macroevolution leading to the formation of supraspecific groups is carried out only through microevolutionary processes, and there are no specific mechanisms for the emergence of new life forms.
