The hypothesis of the emergence of life on earth oparin. The Origin of Life on Earth: Oparin's Theory in Simple Words

The most fully developed, reasoned and widely recognized hypothesis of the origin of life should be recognized. biochemical evolutionor " oparin-Haldane hypothesis».

A. I. Oparin, Russian biochemist, academician, as early as 1924, published his first book on this problem. J. Haldane, an English geneticist and biochemist, since 1929 developed ideas that were consonant with the ideas of A. I. Oparin.

She postulates that life arose on Earth precisely from inanimate matter, under conditions that took place on the planet billions of years ago. These conditions included the availability of energy sources, a certain temperature regime, water and other inorganic substances - precursors of organic compounds. The atmosphere at that time was oxygen-free (plants are the current source of oxygen, but then they were not).

In the framework of this theory, five main stages can be distinguished on the path to the emergence of life, which are given in table. 1.

Table 1

Stages of development of life on Earth according to the hypothesisOparina Haldane

The ideas about the formation and composition of the primary atmosphere of the Earth are based on objective data from various sciences, on the study of the gas shells of other planets of the solar system. Very convincing evidence of the possibility of carrying out the 2nd and 3rd stages of the development of life was obtained as a result of numerous experiments on the artificial synthesis of biological monomers. So, for the first time in 1953, S. Miller (USA) created a fairly simple installation, on which he was able to synthesize a number of amino acids and other organic compounds from a mixture of gases and water vapor under the influence of ultraviolet radiation and electric discharges (Fig. 1).

Fig. 1.Stanley Miller installation in which he synthesized amino acids from gases, creating conditions supposedlyexisted in the atmosphere of the primeval Earth. Gases and watervapors circulating in a high-pressure installation,subjected to high voltage for a week.After this, the substances collected in the "trap" were investigated.chromatography on paper. In total there was15 amino acids were isolated, including glycine, alanineand aspartic acid

In the experiment of S. Miller in his installation, the conditions that existed on Earth at the estimated time were reproduced. The device contained a mixture of gases: hydrogen, ammonia, methane and water vapor. Electrodes were introduced into one of the chambers to obtain discharges simulating lightning as a possible source of energy for chemical reactions. Water was poured in another chamber, and this chamber was heated (to saturate the gas mixture with water vapor). Another chamber was subjected to cooling, and here the water condenses (“rainfall”). Within a week, various organic substances were found in the condensate.

In the following decades, artificial synthesis of various amino acids, nucleotides, simple sugars, and then more complex organic compounds was carried out in many laboratories around the world. All this confirms the possibility of the formation of organic substances on Earth in remote times without the participation of living organisms. In the absence of free oxygen (which would destroy them) and living organisms (which could use them as food), these substances accumulated in the primary ocean in high concentrations.

The next stage was the formation of more complex compounds - protein-like substances (chains of amino acids) and short polynucleotide molecules. The likelihood of this is repeatedly confirmed: today, such is obtained experimentally. Upon reaching a certain concentration of organic substances in the primary ocean, complex aggregates of various compounds could arise - coacervates, small spherical formations.

A study of artificially created coacervates (very widely studied by A.I. Oparin and his collaborators) showed that they exhibit some properties of living systems. Having a densified outer layer, a kind of cell membrane, coacervates are able to selectively absorb various substances from the environment that are involved in chemical reactions inside coacervate drops, and some of the products of these reactions are released back into the medium. Accumulating substances, coacervates “grow” and, having increased in size, can fall into several parts - “multiply”.

Coacervates, different in composition, are characterized by varying degrees of stability. More stable are preserved, others disappear, are destroyed.

These observations gave reason to A.I. Oparin to suggest the possibility of action natural selection(see below) already at this stage of becoming living.

Nevertheless, the coacervates, for all the complexity of their organization, cannot be considered living beings, primarily because they do not have stable self-reproduction.

At the next stage, coacervates formed the relationship of nucleic acids and proteins. The synthesis of proteins of a certain composition began to be carried out on the basis of information contained in nucleic acids.

The ability of nucleic acids to self-reproductionwith the participation of specific proteins - enzymes. That is, we can talk about the appearance protobionts- primary life forms that do not yet have cellular organization, but are capable of self-reproduction and metabolism.

Further development of protobionts, the complexity of their organization led to the appearance of organisms with a cellular structure, - primary prokaryotesbacteria. From this moment, biological evolution begins. Apparently, heterotrophic organisms originally existed (since the primary ocean contained many different organic substances). As their number increased, food resources decreased and competition between them increased. This led to the appearance of autotrophs - organisms that synthesize the organic substances they need from inorganic ones.

At first, organisms appeared that used the energy derived from the oxidation of minerals. This process is known as chemosynthesis, and organisms are called chemosynthetics. Then, during subsequent evolutionary transformations, autotrophic organisms appeared that use the energy of sunlight - these are photosynthetic organisms ( photosynthetics) Further biological evolution led to the formation of the diverse world of wildlife that we see today.

Species diversity as a result of biological evolutiontion.Evolutionary doctrine (theory of evolution) is a biological discipline that studies the causes and driving forces, laws and mechanisms of development of living organisms.

Under biological evolutionthey understand the irreversible and regular process of the historical development of living things from simple to more complex, starting from the moment the first living organisms appeared on Earth.

During evolution, some species were replaced by others, there was a complication and increase in the organization of living organisms, their diversity increased, a man appeared.

The great worldview value of evolutionary doctrine: it approves the idea of \u200b\u200bthe unity of origin of all living things, explains the reasons for the diversity of species,living on earth the expediency of organizing living things(i.e., the conformity of the structure and functioning of all their systems and organs to the conditions of existence), the simultaneous presence in nature of both simple and highly organized organisms.

Evolutionary doctrine serves as the theoretical basis of modern biology, combining, generalizing the results obtained by numerous private biological sciences.

Obviously, its importance for humans in solving problems of interaction with the biosphere.

Finally, knowledge of the laws and mechanisms of evolution is the basis for the development of selection, a science that develops methods for creating and improving varieties of cultivated plants and domestic animal breeds.

The history of the development of ideas about the natural origin of life and the evolution of organisms can be divided into three stages: the Darwin, Darwin, and Post-Darwin (modern).

The problem of life and living is the object of study of many natural disciplines, starting with biology and ending with philosophy, mathematics, considering abstract models of the phenomenon of living, as well as physics, which determines life from the standpoint of physical laws.

Around this main problem, all other more particular problems and questions are concentrated, and philosophical generalizations and conclusions are built.

In accordance with two worldviews - materialistic and idealistic - even in ancient philosophy, opposing concepts of the origin of life developed: creationism and materialistic theory of origin  organic nature from inorganic.

Supporters   creationism  claim that life arose as a result of an act of divine creation, evidence of which is the presence in living organisms of a special force that controls all biological processes.

Proponents of the origin of life from inanimate nature claim that organic nature arose through the action of natural laws. Later, this concept was specified in the idea of \u200b\u200bspontaneous generation of life.

The concept of spontaneous generation, despite the fallacy, played a positive role; experiments designed to confirm it provided rich empirical material for developing biological science. The final rejection of the idea of \u200b\u200bspontaneous generation occurred only in the 19th century.

In the XIX century. was also put forward   hypothesis of the eternal existence of life  and its cosmic origin on Earth. It has been suggested that life exists in space and is transferred from one planet to another.

At the beginning of the XX century. the idea   space origin  biological systems on Earth and the eternity of the existence of life in space was developed by a Russian scientist academician IN AND. Vernadsky.

The hypothesis of academician A.I. Oparina

A fundamentally new hypothesis of the origin of life was presented by the academician   A.I. Oparin  in the book   "The origin of life”, Published in 1924. He argued that redi principleintroducing a monopoly of biotic synthesis of organic substances, is valid only for the modern era of the existence of our planet. At the beginning of its existence, when the Earth was lifeless, abiotic syntheses of carbon compounds and their subsequent prebiological evolution took place on it.

The essence of the Oparin hypothesis consists in the following: the birth of life on Earth is a long evolutionary process of the formation of living matter in the bowels of inanimate. This happened through chemical evolution, as a result of which the simplest organic substances formed from inorganic under the influence of potent physico-chemical processes.

He regarded the emergence of life as a single natural process, which consisted of the initial chemical evolution that took place in the conditions of the early Earth, which gradually passed to a qualitatively new level - biochemical evolution.

Considering the problem of the origin of life through biochemical evolution, Oparin identifies three stages of the transition from inanimate matter to living.

The first stage is chemical evolution.  When the Earth was still lifeless (about 4 billion years ago), abiotic synthesis of carbon compounds took place on it and their subsequent   prebiological evolution.

For this period of the Earth's evolution, numerous volcanic eruptions were characteristic with the release of a huge amount of hot lava. As the planet cools, water vapor in the atmosphere condenses and rains down on the Earth, forming huge water spaces (primary ocean). These processes have been going on for millions of years. Various inorganic salts were dissolved in the waters of the primary ocean. In addition, various organic compounds that continuously form in the atmosphere under the influence of ultraviolet radiation, high temperature, and active volcanic activity fell into the ocean.

The concentration of organic compounds was constantly increasing, and in the end, the waters of the ocean became broth»Of protein-like substances - peptides.

The second stage is the appearance of protein substances.  As the conditions on Earth softened, under the influence of electric discharges, thermal energy and ultraviolet rays on the chemical mixtures of the primary ocean, it became possible to form complex organic compounds - biopolymers and nucleotides, which, gradually uniting and becoming more complex, turned into   protobionts(precellular ancestors of living organisms). The evolution of complex organic substances resulted in   koatservatov, or coacervate drops.

Coacervates - complexes of colloidal particles, the solution of which is divided into two layers: a layer rich in colloidal particles, and a liquid almost free of them. Coacervates had the ability to absorb various substances dissolved in the waters of the primary ocean. As a result, the internal structure of the coacervates changed in the direction of increasing their stability under constantly changing conditions.

The theory of biochemical evolution considers coacervates as prebiological systems, which are groups of molecules surrounded by an aqueous shell.

So, for example, coacervates can absorb substances from the environment, interact with each other, increase in size, etc. However, unlike living creatures, coacervate drops are not capable of self-reproduction and self-regulation, therefore, they cannot be attributed to biological systems.

The third stage is the formation of the ability to self-reproduction, the emergence of a living cell.  During this period, natural selection, i.e. in the mass of coacervate droplets, coacsquats were selected that were most resistant to these environmental conditions. The selection process has been going on for many millions of years. The surviving coacervate drops already had the ability to primary metabolism - the main property of life.

At the same time, reaching a certain size, the mother droplet disintegrated into daughter ones, which retain the features of the mother structure.

Thus, we can talk about the acquisition by the coacervates of the property itself about its production - one of the most important signs of life. In fact, at this stage, the coacervates turned into simple living organisms.

Further evolution of these prebiological structures was possible only with the complication of metabolic processes within the coacervate.

The internal environment of the coacervate needed to be protected from environmental influences. Therefore, around coacervates rich in organic compounds, lipid layers arose, separating the coacervate from its surrounding aqueous medium. During evolution, lipids were transformed into the outer membrane, which significantly increased the viability and stability of organisms.

The appearance of the membrane predetermined the direction of further biological evolution along the path of more and more perfect autoregulation, culminating in the formation of the primary cell — the archaelet. A cell is an elementary biological unit, the structural and functional basis of all living things. Cells carry out an independent metabolism, are capable of division and self-regulation, i.e. possess all the properties of a living. The formation of new cells from non-cellular material is impossible, cell reproduction occurs only due to division. Organic development is considered as a universal process of cell formation.

In the structure of the cell there are: a membrane that delimits the contents of the cell from the external environment; cytoplasm, which is a saline solution with soluble and suspended enzymes and RNA molecules; a nucleus containing chromosomes consisting of DNA molecules and proteins attached to them.

Therefore, the beginning of life should be considered the emergence of a stable self-reproducing organic system (cells) with a constant sequence of nucleotides. Only after the emergence of such systems can we talk about the beginning of biological evolution.

The possibility of abiogenic synthesis of biopolymers was experimentally proven in the middle of the 20th century. In 1953, an American scientist S. Miller  simulated the primary atmosphere of the Earth and synthesized acetic and formic acids, urea and amino acids by passing electric charges through a mixture of inert gases. Thus, it was demonstrated how synthesis of complex organic compounds is possible under the influence of abiogenic factors.

Despite theoretical and experimental validity, Oparin's concept has both strengths and weaknesses.

The strength of the concept is a fairly accurate experimental substantiation of chemical evolution, according to which the origin of life is a logical result of the prebiological evolution of matter.

A convincing argument in favor of this concept is the possibility of experimental verification of its main provisions.

The weakness of the concept is the impossibility of explaining the very moment of the jump from complex organic compounds to living organisms.

One of the versions of the transition from prebiological to biological evolution is offered by a German scientist   M. Eigen. According to his hypothesis, the occurrence of life is explained by the interaction of nucleic acids and proteins. Nucleic acids are carriers of genetic information, and proteins serve as catalysts for chemical reactions. Nucleic acids reproduce themselves and transmit information to proteins. There is a closed circuit - a hypercycle, in which the processes of chemical reactions are self-accelerating due to the presence of catal and congestion.

In hypercycles, the reaction product simultaneously acts as both a catalyst and a starting reagent. Such reactions are called autocatalytic.

Another theory within which one can explain the transition from prebiological to biological evolution is synergetics. The patterns discovered by synergetics make it possible to clarify the mechanism of the emergence of organic matter from inorganic in terms of self-organization through the spontaneous emergence of new structures during the interaction of an open system with the environment.

Remarks on the theory of the origin of life and the emergence of the biosphere

In modern science, the hypothesis of the abiogenic (non-biological) origin of life under the influence of natural causes as a result of a long process of cosmic, geological and chemical evolution - abiogenesis, based on the hypothesis of academician A.I. Oparin, is accepted. The abiogenetic concept does not exclude the possibility of the existence of life in space and its cosmic origin on Earth.

However, based on the modern achievements of science, to the hypothesis of A.I. Oparina begs the following clarifications.

Life could not have arisen on the surface (or near it) of the water of the Ocean, since in those distant times the Moon was much closer to the Earth than at present. The tidal waves were supposed to be of great height, of great destructive power. Under these conditions, protobionts simply could not form.

Due to the lack of the ozone layer under the influence of hard ultraviolet radiation, protobionts also could not exist. This suggests that life could only appear in the water column.

Due to special conditions, life could appear only in the water of the primary Ocean, but not on the surface, but at the bottom in thin films of organic matter adsorbed by the surfaces of pyrite and apatite crystals, apparently near geothermal sources. Since it was found that organic compounds are formed in the products of volcanic eruptions, and volcanic activity near the Ocean in ancient times was very active. There was no dissolved oxygen in the ancient Ocean capable of oxidizing organic compounds.

Today, it is believed that protobionts were RNA molecules, but not DNA, since it was proved that the process of evolution went from RNA to protein, and then to the formation of a DNA molecule in which C-H bonds were stronger than C-OH bonds in RNA However, it is clear that RNA molecules could not arise as a result of a smooth evolutionary development. Probably, there was a leap with all the features of the self-organization of the substance, the mechanism of which is currently not clear.

The primary biosphere in the water column was probably represented by rich functional diversity. And the first appearance of life was to happen not in the form of any one kind of organism, but in the aggregate of organisms. Many primary biocenoses should have appeared immediately. They consisted of the simplest unicellular organisms capable of performing, without exception, all the functions of living matter in the biosphere.

These simple organisms were heterotrophs (fed on ready-made organic compounds), were prokaryotes (organisms without a nucleus), were anaerobes (used yeast fermentation as a source of energy).

Due to the special properties of carbon, life appeared on this basis. However, no current data contradict the likelihood of life not only on a carbon basis.

Some future directions for studying the origin of life

In the XXI century. in order to clarify the problems of the origin of life, researchers show increased interest in two objects -   to the satellite of Jupiter,  discovered back in 1610   G. Galileo.It is located at a distance from the Earth, equal to 671,000 km. Its diameter is 3100 km. It is covered with a multi-kilometer layer of ice. However, under the cover of ice is the ocean, and it may have preserved the simplest forms of ancient life.

Another object is   East Lake, which is called a relict pond. It is located in Antarctica under a four-kilometer layer of ice. Our researchers discovered it as a result of deep water drilling. At present, an international program is being developed with the goal of penetrating the waters of this lake without violating its relict purity. It is possible that there are relic organisms that are several million years old.

Great interest is also shown in   discovered in Romania cave,  no access light. When they drilled the entrance to this cave, they discovered the existence of blind living organisms such as bugs that feed on microorganisms. These microorganisms use for their existence inorganic compounds containing hydrogen sulfide coming from the inside of the bottom of this cave. No light penetrates this cave, but there is water.

Of particular interest   microorganisms  recently discovered by American scientists in a study   one of the salt lakes.  These microorganisms are exceptionally resistant to the environment. They can live even in a purely arsenic environment.

Organisms living in the so-called “black smokers” also attract a lot of attention (Fig. 2.1).

Fig. 2.1. "Black smokers" of the ocean floor (jets of hot water are shown by arrows)

“Black smokers” - numerous hydrothermal springs operating on the bottom of the oceans, confined to the axial parts of the mid-ocean ridges. Of these, to the oceans under high pressure of 250 atm. highly mineralized hot water (350 ° C) is supplied. Their contribution to the heat flux of the Earth is about 20%.

Hydrothermal ocean sources carry dissolved elements from the oceanic crust into the oceans, changing the crust and making a very significant contribution to the chemical composition of the oceans. Together with the cycle of generation of the oceanic crust in oceanic ridges and its recycling to the mantle, the hydrothermal change represents a two-stage system of transfer of elements between the mantle and the oceans. The oceanic crust recycled into the mantle is apparently responsible for part of the mantle inhomogeneities.

Hydrothermal springs in mid-ocean ridges are the habitat of unusual biological communities that receive energy from the decomposition of hydrothermal fluid compounds (black color of the jet).

In the oceanic crust, apparently, there are the deepest parts of the biosphere, reaching a depth of 2500 m.

Hydrothermal springs make a significant contribution to the thermal balance of the Earth. Under the middle ridges, the mantle comes closest to the surface. Seawater through cracks penetrates into the oceanic crust to a considerable depth, due to thermal conductivity it is heated by mantle heat and concentrated in magma chambers.

A thorough study of the above “special” objects will undoubtedly lead scientists to a more objective understanding of the problem of the origin of life on our planet and the formation of its biosphere.

However, it should be pointed out that, to date, it is not possible to obtain life experimentally.

Subject: A. I. Oparin hypothesis on the origin of life on Earth

Performed:

1. Introduction

2. The main part

2.1   The hypothesis of A. I. Oparin about the origin of life on Earth

2.2   Strengths and weaknesses of the concept

3. Conclusion

4. Used literature

Introduction

Life is such an understandable and at the same time such a mysterious word for every thinking person. It would seem that the meaning of this word should be clear and unambiguous for all times and all peoples. However, we know that over many centuries the views on the problem of the origin of life have changed, and a large number of the most diverse hypotheses and concepts have been expressed. Some of them were widespread and dominated during various periods of the development of natural science.

One of the main obstacles that stood at the beginning of the XX century. on the way to solving the problem of the origin of life, there was a prevailing in science and based on everyday experience belief that there is no relationship between organic and inorganic compounds. Until the middle of the 20th century. many scientists believed that organic compounds can occur only in a living organism, biogenic. That is why they were called organic compounds in contrast to inanimate substances - minerals, which are called inorganic compounds. It was believed that the nature of inorganic substances is completely different, and therefore the emergence of even the simplest organisms from inorganic substances is fundamentally impossible. However, after the first organic compound was synthesized from ordinary chemical elements, the idea of \u200b\u200btwo different essences of organic and inorganic substances turned out to be untenable. As a result of this discovery, organic chemistry and biochemistry have arisen that study the chemical processes in living organisms.

In addition, this scientific discovery made it possible to create the concept of biochemical evolution, according to which life on Earth arose as a result of physical and chemical processes. The initial basis of this hypothesis was data on the similarity of substances that make up plants and animals, as well as on the possibility in the laboratory to synthesize the organic substances that make up protein.

These discoveries formed the basis of the concept of A. I. Oparin, published in 1924 in the book “The Origin of Life”, where a fundamentally new hypothesis of the origin of life was presented.

Main part

2.1. The hypothesis of A. I. Oparin about the origin of life on Earth

In 1924, the Russian scientist Alexander Ivanovich Oparin for the first time formulated the main provisions of the concept of prebiological evolution.

He regarded the emergence of life as a single natural process, which consisted of the initial chemical evolution that took place in the conditions of the early Earth, which gradually passed to a qualitatively new level - biochemical evolution. The essence of the hypothesis was as follows: the birth of life on Earth is a long evolutionary process of the formation of living matter in the bowels of inanimate. And this happened through chemical evolution, as a result of which the simplest organic substances were formed from inorganic under the influence of potent physico-chemical factors.

Considering the problem of the emergence of life through biochemical evolution, Oparin identifies three stages of the transition from inanimate matter to living:

1) the stage of synthesis of the starting organic compounds from inorganic substances in the primary atmosphere of the early Earth;

2) the stage of formation in the primary reservoirs of the Earth from the accumulated organic compounds of biopolymers, lipids, hydrocarbons;

3) the stage of self-organization of complex organic compounds, the emergence on their basis and evolutionary improvement of the processes of metabolism and reproduction of organic structures, culminating in the formation of a simple cell.

On the the first stage About 4 billion years ago, when the Earth was lifeless, abiotic synthesis of carbon compounds and their subsequent prebiological evolution took place on it. For this period of the Earth's evolution, numerous volcanic eruptions were characteristic with the release of a huge amount of hot lava. As the planet cools, water vapor in the atmosphere condenses and rains down on Earth, forming vast expanses of water. Since the Earth’s surface still remained hot, the water evaporated, and then, cooling in the upper atmosphere, fell again to the surface of the planet. These processes have been going on for millions of years. Thus, various salts were dissolved in the waters of the primary ocean. In addition, organic compounds also fell into it: sugars, amino acids, nitrogenous bases, organic acids, etc., continuously formed in the atmosphere under the influence of ultraviolet radiation, high temperature and active volcanic activity.

The primary ocean probably contained various organic and inorganic molecules dissolved in it from the atmosphere and surface layers of the Earth. The concentration of organic compounds was constantly increasing, and, in the end, ocean water became a “broth” of protein-like substances - peptides.

On the second stage  as the Earth conditions softened, under the influence of electric discharges, thermal energy and ultraviolet rays on the chemical mixtures of the primary ocean, it became possible to form complex organic compounds - biopolymers and nucleotides, which, gradually uniting and becoming more complex, turned into protobionts (pre-cellular ancestors of living organisms). The evolution of complex organic substances resulted in the appearance of coacervates, or coacervate drops.

Coacervates are complexes of colloidal particles, the solution of which is divided into two layers: a layer rich in colloidal particles, and a liquid that is almost free of them. Coacervates had the ability to absorb various substances dissolved in the waters of the primary ocean. As a result, the internal structure of the coacervates changed, which led either to their decay or to the accumulation of substances, i.e. to the growth and change in chemical composition, increasing their stability in constantly changing conditions. The theory of biochemical evolution considers coacervates as prebiological systems, which are groups of molecules surrounded by an aqueous shell. Coacervates were able to absorb various organic substances from the external environment, which provided the possibility of primary metabolism with the environment.

On the third stage  as Oparin suggested, natural selection began to operate. In the mass of coacervate drops, coacervates most resistant to these environmental conditions were selected. The selection process has been going on for many millions of years, as a result of which only a small part of the coacervates has survived. However, the preserved coacervate drops had the ability to primary metabolism. And metabolism is the first property of life. At the same time, having reached a certain size, the mother drop could break up into daughter ones, which retained the features of the mother structure. Thus, we can talk about the acquisition by coacervates of the property of self-reproduction - one of the most important signs of life. In fact, at this stage, the coacervates turned into simple living organisms.

Further evolution of these prebiological structures was possible only with the complication of metabolic and energy processes within the coacervate. Only the membrane could provide a stronger insulation of the internal environment from external influences. Around coacervates rich in organic compounds, lipid layers arose, separating the coacervate from its surrounding aquatic environment. During evolution, lipids were transformed into the outer membrane, which significantly increased the viability and stability of organisms.

In protocells like coacervates or microspheres, nucleotide polymerization reactions took place until a protogen, the primary gene capable of catalyzing the appearance of a specific amino acid sequence, the first protein, was formed from them. Probably the first such protein was the precursor of an enzyme that catalyzes the synthesis of DNA or RNA. Those protocells in which the primitive mechanism of heredity and protein synthesis arose quickly shared and absorbed all the organic matter of the primary ocean. At this stage there was already a natural selection for the rate of reproduction; any improvement in biosynthesis was picked up, and new protocells replaced all previous ones.

Schematic representation of the path of the origin of life according to the protein-coacervate theory A.I. Oparina

Oparin's theory was warmly supported by Cambridge professor Haldane. He opened a polemic on the origin of life in an article published in the Rationalist Annual in 1929. In it, Halden hypothesized that huge amounts of organic compounds had accumulated on the primeval Earth, forming what he called hot dilute soup (later called the primary broth or protobouillon - primeval soup).

The modern two-pronged concept of primitive broth and the spontaneous generation of life proceeds from the theory of Oparin-Haldane on the origin of life.

The greatest success of the Oparin-Haldane theory was the widely publicized experiment conducted in 1953 by American graduate student Stanley Miller.

Miller's experiment

Charles Darwin believed that inanimate matter can be transformed into living matter with the help of electricity - after all, his grandfather, Erasmus Darwin, was greatly impressed by Frankenstein, who came out from Mary Shelley's pen. The idea that pyrotechnic exercises with electricity can give rise to life was of great appeal; so it’s not surprising that the interest in the Stanley Miller experiment, the results of which were published in 1953, is not surprising.

The hypothesis of the origin of life through biochemical evolution, or the “Oparin-Haldane hypothesis” should be recognized as the most fully developed, reasoned and widely recognized.

A. I. Oparin, Russian biochemist, academician, as early as c. published his first book on this issue. J. Haldane, English geneticist and biochemist, p. developed ideas in tune with the ideas of A. I. Oparin.

She postulates that life arose on Earth precisely from inanimate matter, under conditions that took place on the planet billions of years ago. These conditions included the availability of energy sources, a certain temperature regime, water and other inorganic substances - precursors of organic compounds. The atmosphere at that time was oxygen-free (plants are the current source of oxygen, but then they were not).

In the framework of this theory, five main stages can be distinguished on the path to the emergence of life, which are given in table. 1.

Table 1

Stages of development of life on Earth according to the hypothesisOparina Haldane

The ideas about the formation and composition of the primary atmosphere of the Earth are based on objective data from various sciences, on the study of the gas shells of other planets of the solar system. Very convincing evidence of the possibility of carrying out the 2nd and 3rd stages of the development of life was obtained as a result of numerous experiments on the artificial synthesis of biological monomers. So, for the first time in. S. Miller (USA) created a fairly simple installation, on which he was able to synthesize a number of amino acids and other organic compounds from a mixture of gases and water vapor under the influence of ultraviolet radiation and electric discharges (Fig. 1).

Fig. 1.The Stanley Miller installation, in which he synthesized amino acids from gases, creating conditions that supposedly existed in the atmosphere of the primeval Earth. Gases and water vapor circulating in the high-pressure unit were exposed to high voltage for a week. After this, substances collected in a "trap" were investigated by chromatography on paper. A total of 15 amino acids were isolated, including glycine, alanine and aspartic acid.

In the experiment of S. Miller in his installation, the conditions that existed on Earth at the estimated time were reproduced. The device contained a mixture of gases: hydrogen, ammonia, methane and water vapor. Electrodes were introduced into one of the chambers to obtain discharges simulating lightning as a possible source of energy for chemical reactions. Water was poured in another chamber, and this chamber was heated (to saturate the gas mixture with water vapor). Another chamber was subjected to cooling, and here the water condenses (“rainfall”). Within a week, various organic substances were found in the condensate.

In the following decades, artificial synthesis of various amino acids, nucleotides, simple sugars, and then more complex organic compounds was carried out in many laboratories around the world. All this confirms the possibility of the formation of organic substances on Earth in remote times without the participation of living organisms.

In the absence of free oxygen (which would destroy them) and living organisms (which could use them as food), these substances accumulated in the primary ocean in high concentrations.

The next stage was the formation of more complex compounds - protein-like substances (chains of amino acids) and short polynucleotide molecules. The likelihood of this is repeatedly confirmed: today, such is obtained experimentally. Upon reaching a certain concentration of organic substances in the primary ocean, complex aggregates of various compounds — coacervates, small spherical formations — could arise.

A study of artificially created coacervates (very widely studied by A.I. Oparin and his collaborators) showed that they exhibit some properties of living systems. Having a densified outer layer, a kind of cell membrane, coacervates are able to selectively absorb various substances from the environment that are involved in chemical reactions inside coacervate drops, and some of the products of these reactions are released back into the medium. Accumulating substances, coacervates “grow” and, having increased in size, can fall into several parts - “multiply”.

Coacervates, different in composition, are characterized by varying degrees of stability. More stable are preserved, others disappear, are destroyed.

These observations gave reason to A.I. Oparin to suggest the possibility of natural selection (see below) already at this stage of the formation of living things.

Nevertheless, the coacervates, for all the complexity of their organization, cannot be considered living beings, primarily because they do not have stable self-reproduction.

At the next stage, coacervates formed the relationship of nucleic acids and proteins. The synthesis of proteins of a certain composition began to be carried out on the basis of information contained in nucleic acids.

The ability of nucleic acids to reproduce with the participation of specific proteins - enzymes. That is, we can talk about the appearance of protobionts - primary life forms that do not yet have cellular organization, but are capable of self-reproduction and metabolism.

Further development of protobionts, the complexity of their organization led to the appearance of organisms with a cellular structure - primary prokaryotes, bacteria. From this moment, biological evolution begins. Apparently, heterotrophic organisms originally existed (since the primary ocean contained many different organic substances). As their number increased, food resources decreased and competition between them increased. This led to the appearance of autotrophs - organisms that synthesize the organic substances they need from inorganic ones.

At first, organisms appeared that used the energy derived from the oxidation of minerals. This process is known as chemosynthesis, and organisms are called chemosynthetics. Then, during subsequent evolutionary transformations, autotrophic organisms appeared that use the energy of sunlight - these are photosynthetic organisms (photosynthetics). Further biological evolution led to the formation of the diverse world of wildlife that we see today.

Species diversity as a result of biological evolutiontion.Evolutionary doctrine (theory of evolution) is a biological discipline that studies the causes and driving forces, laws and mechanisms of development of living organisms.

Under biological evolutionthey understand the irreversible and regular process of the historical development of living things from simple to more complex, starting from the moment the first living organisms appeared on Earth.

During evolution, some species were replaced by others, there was a complication and increase in the organization of living organisms, their diversity increased, a man appeared.

The worldview significance of evolutionary doctrine is great: it affirms the idea of \u200b\u200bthe unity of origin of all living things, explains the reasons for the diversity of species that live on Earth, the expediency of organizing living beings (i.e., the structure and functioning of all their systems and organs according to the conditions of existence), the simultaneous presence in nature and simple and highly organized organisms.

Evolutionary doctrine serves as the theoretical basis of modern biology, combining, generalizing the results obtained by numerous private biological sciences.

Obviously, its importance for humans in solving problems of interaction with the biosphere.

Finally, knowledge of the laws and mechanisms of evolution is the basis for the development of selection, a science that develops methods for creating and improving varieties of cultivated plants and domestic animal breeds.

The history of the development of ideas about the natural origin of life and the evolution of organisms can be divided into three stages: the Darwin, Darwin, and Post-Darwin (modern).

Krasnodembsky E. G. "General Biology: A Handbook for High School Students and University Applicants"

Introduction

Life is one of the most complex natural phenomena. Since ancient times, it seemed to people mysterious and unknowable. Adherents of religious idealistic views considered life to be a spiritual, intangible principle that arose as a result of divine creation. In the Middle Ages, life was associated with the presence of a certain “life force” in organisms, inaccessible to knowledge by means of science and practice.

The problem of the emergence of life on Earth has long been haunted by many scientists. Since a person began to wonder where all life came from, many years have passed, and during this time many hypotheses and assumptions about the origin of life have been considered. Religious theory, the theory of spontaneous generation, the theory of panspermia, the theory of the eternal existence of life ... Mankind still cannot fully solve this riddle. I have always been interested in questions whose answers are definitely unknown and exist only in the form of assumptions, theories. One of these problems is the origin of life. We were introduced to the brief content of these theories at school, now I have the opportunity to consider one of them, the one closest to me, the most probable, more detailed and deeper, to understand its provisions, the evidence provided.

In the development of the doctrines about the origin of life, a significant place is occupied by the theory that all life comes from living alone - the theory of biogenesis. This theory in the middle of the nineteenth century was opposed to unscientific ideas about the spontaneous generation of organisms (worms, flies, etc.). However, as a theory of the origin of life, biogenesis is untenable, since it fundamentally contrasts the living with the non-living, and affirms the idea of \u200b\u200beternity of life rejected by science.

The theory proposed by A. I. Oparin in the first half of the twentieth century is based on the assumption of chemical evolution, which gradually turns to biochemical and then biological evolution. Cell formation was a complex phenomenon. But it laid the foundation for the development of life and all its diversity. Abiogenesis - the idea of \u200b\u200bthe origin of living from nonliving - the initial hypothesis of the modern theory of the origin of life. This led to a revival of the theory of spontaneous generation. The new version is called the theory of chemical evolution.

Alexander Ivanovich Oparin was born on March 2, 1894 in the city of Uglich. In 1912 graduated from the Second Moscow Grammar School.

1912-1917 - Student of the Natural Department of the Physics and Mathematics Faculty of Moscow University.

1915 - Chemist at the pharmaceutical factory of the All-Russian Union of Cities.

1917 - He graduated from the Natural Department of the Physics and Mathematics Faculty of Moscow University and was left at the Department of Plant Physiology to prepare for the professorship.

Alexander Ivanovich Oparin - the creator of the internationally recognized theory of the origin of life, the provisions of which brilliantly withstood more than half a century of testing by time; one of the largest Soviet biochemists, laying the foundation for research in the field of evolutionary and comparative biochemistry, enzymology, plant biochemistry and subcellular structures, the founder of Soviet technical biochemistry; outstanding teacher, organizer of science, public figure and brilliant popularizer of scientific knowledge.

Proceedings A.I. Oparina is devoted to the study of the biochemical principles of processing plant materials, the action of enzymes in a living organism, and the problem of the emergence of life on Earth. His work laid the foundations of the technical biochemistry of the USSR. Exploring the action of enzymes in various plants, A.I. Oparin came to the conclusion that the basis of the technology of a number of industries dealing with raw materials of plant origin, lies biological catalysis.

Developing the theoretical foundations of biology, A.I.

Oparin put forward the theory of the origin of life on Earth. Based on actual materials from the field of astronomy, chemistry, geology and biology A.I. Oparin proposed a hypothesis of the development of matter, explaining the emergence of life on Earth. He considered the problem of the origin of life from a materialistic point of view and explained the emergence of life as a definite and regular qualitative stage in the historical development of matter.

Already the early research of A.I. Oparin in the field of comparative biochemistry of redox processes in simplest algae led him to study the evolutionary development of life and to develop the basic principles of the problem of the origin of life on Earth. In those years (at the beginning of the 20th century) among natural scientists, the problem of the origin of life was considered a problem that did not allow an experimental approach and was not solved by the methods of the natural sciences. The largest scientific servant of A.I. Oparin is that he convincingly shows the possibility of a scientific experimental approach to the study of the problem of the origin of life. He set forth his ideas in the book The Origin of Life, published in the Soviet Union in 1924 and translated into English in 1938. The peak of research by A. I. Oparin and his co-authors was in the 1950s and 1960s, although his book The Origin of Life was published earlier.

The appearance of life A.I. Oparin considered as a single natural process, which consisted of the initial chemical evolution that took place in the conditions of the early Earth, which gradually passed to a qualitatively new level - biochemical evolution.

1. The primeval Earth had a rarefied (that is, deprived of oxygen) atmosphere. When various natural sources of energy began to influence this atmosphere - for example, thunderstorms and volcanic eruptions - then the basic chemical compounds necessary for organic life began to spontaneously form.

From the very beginning, this process has been associated with geological evolution. Currently, it is believed that the age of our planet is approximately 4.3 billion years. In the distant past, the Earth was very hot (4000-8000 ° C). As the earth cools, a crust forms, and the atmosphere of water, ammonia, carbon dioxide and methane. Such an atmosphere is called “reducing” because it does not contain free oxygen. When the temperature on the Earth's surface drops below 1000C, primary water bodies formed. Under the influence of electric discharges, thermal energy, and ultraviolet rays on gas mixtures, a synthesis of organic monomer substances took place, which locally accumulated and connected to each other, forming polymers. It can be assumed that at the same time, with polymerization, the formation of supramolecular membrane complexes proceeded.

2. Over time, molecules of organic matter accumulated in the oceans until they reached the consistency of hot diluted broth. However, in some areas, the concentration of molecules necessary for the origin of life was especially high, and nucleic acids and proteins formed there.

By the same type of rules, polymers of all types were synthesized in the “primary broth” of the Earth’s hydrosphere: amino acids, polysaccharides, fatty acids, nucleic acids, resins, essential oils, etc. This assumption was verified experimentally in 1953 using a Stanley Miller installation.

Miller's experiment, which became a turning point in this area, was extremely simple. The apparatus consisted of two glass flasks connected in a closed circuit. A device imitating thunderstorm effects is placed in one of the flasks - two electrodes between which a discharge occurs at a voltage of about 60 thousand volts; in another flask, water is constantly boiling. Then the apparatus is filled with the atmosphere, which supposedly existed on the ancient Earth: methane, hydrogen and ammonia. The device worked for a week, after which the reaction products were investigated. Mostly a viscous mess of random compounds; a certain amount of organic substances was also found in the solution, including the simplest amino acids glycine and alanine.

Primary cells are thought to have arisen using fat molecules (lipids).

Water molecules, wetting only the hydrophilic ends of fat molecules, put them, as it were, “on the head”, with hydrophobic ends up. In this way, a complex of ordered fat molecules was created, which, due to the addition of new molecules to them, gradually delimited some space from the whole environment, which became the primary cell, or coacervate - a spatially isolated integral system. Coacervates were able to absorb various organic substances from the external environment, which provided the possibility of primary metabolism with the environment.

3. The first cells were heterotrophs, they could not reproduce their components on their own and received them from the broth. But over time, many compounds began to disappear from the broth, and the cells were forced to reproduce them on their own. So the cells developed their own metabolism for self-reproduction.

Thus, according to Oparin, the primary cell structure was an open chemical microstructure, which was endowed with the ability to primary metabolism, but did not yet have a system for transmitting genetic information based on nucleic acids. Such systems, drawing substances and energy from the environment, can resist the growth of entropy and contribute to its decrease during its growth and development, which is a characteristic feature of all living systems. A single molecule, even a very complex one, cannot be alive. This means that not separate parts determine the organization of the whole, but the whole, continuing to evolve, determines the expediency of the structure of the parts.

Natural selection was preserved by those systems in which the metabolic function and the fitness of the organism as a whole to exist under the given environmental conditions were more perfect. The gradual complication of protobionts was carried out by the selection of such coacervate drops, which had the advantage in the best use of matter and energy of the medium. Selection as the main reason for the improvement of coacervates to primary living beings is a central position in the Oparin hypothesis.

Oparin's Theory of the Origin of Life on Earth

Currently, the hypothesis about the origin of life on Earth, developed by the Soviet scientist academician A.I. Oparin, has received the widest recognition. This hypothesis is based on the assumption that the gradual emergence of life on Earth from inorganic substances through prolonged abiogenic (non-biological) molecular evolution.

It is believed that the Earth and other planets of the solar system formed from a gas-dust cloud about 4.5 billion years ago. At the first stages of its formation, the Earth had a high temperature. As the planet cools, heavy elements moved to its center, while lighter ones remained on the surface. The atmosphere consisted of free hydrogen and its compounds (H2O, CH4, NH3, HCN) and therefore was of a reducing nature. This circumstance served as an important prerequisite for the appearance of organic molecules in a non-biological way. Compounds that are reducing agents easily enter into chemical reactions, giving off hydrogen, and at the same time they themselves are oxidized. The components of the atmosphere were exposed to various energy sources: hard, close to X-ray, short-wave radiation from the Sun, lightning discharges, high temperature in the region of lightning discharges and in areas of active volcanic activity, etc. As a result of these effects, the chemically simple components of the atmosphere interacted, changing and becoming more complicated. Molecules of sugars, amino acids, nitrogenous bases, organic acids (acetic, formic, lactic, etc.) and other simple organic compounds arose.

Scientists were able to reproduce some of these reactions in the laboratory. In 1935, the American scientist L.S. Miller, passing an electric discharge through a mixture of H2, H2O, CH4 and NH3, obtained a mixture of several amino acids and organic acids. Later it turned out that in the absence of oxygen, many simple organic compounds that are part of biological polymers — proteins, nucleic acids, and polysaccharides — can be synthesized in an abiogenic way. In an aqueous medium, under certain conditions, amino acids may arise from hydrocyanic acid, ammonia, and certain other compounds. From nitrogen bases in the presence of inorganic phosphorus compounds, adenosine monophosphate (AMP) is formed, as well as adenosine diphosphate (ADP) and adenosine triphosphate (ATP), sugar, amino acids.

The possibility of abiogenic synthesis of organic compounds is proved by the fact that they are found in outer space. In space, hydrogen cyanide, formaldehyde, formic acid, methyl and ethyl alcohols, and other substances were found. Some meteorites contain fatty acids, sugars, amino acids. All this indicates that organic compounds could have arisen purely chemically under the conditions that existed on Earth about 4 billion years ago.

Thus, the conditions for the abiogenic occurrence of organic compounds can be considered the restorative nature of the Earth’s atmosphere, high temperature, lightning discharges and powerful ultraviolet radiation of the Sun, which was not yet delayed by the ozone screen.

As the Earth cools, the water vapor contained in the atmosphere condenses, rains fall on the Earth's surface, forming large water spaces on it. Ammonia, carbon dioxide, hydrocyanic acid, methane and more complex organic compounds formed in the atmosphere were dissolved in water. Organic molecules, such as amino acids or nucleotides, in the aqueous medium can bind to each other (condense) to form polymers. In this case, water is released. Two amino acids can be joined by a peptide bond, and two nucleotides can be joined by a phosphodiester bond. It should be noted that for the synthesis of simple compounds more stringent conditions are required than for the emergence of complex ones. For example, the synthesis of amino acids occurs at a temperature of about 1000 C, and their condensation into polypeptides at a temperature of 160 C.

However, these reactions in the absence of protein enzymes are very slow. Among randomly formed polypeptides, there are those that have catalytic activity and could accelerate the processes of matrix synthesis of polynucleotides. Therefore, the next important step in prebiological evolution was the combination of the ability of nucleotides to reproduce themselves with the ability of polypeptides to catalytic activity. Stability, stability of “successful” combinations of amino acids - polypeptides is ensured only by storing information about them in nucleic acids. In turn, polypeptides or proteins synthesized based on information embedded in RNA molecules can facilitate the reduction of these molecules. Thus, through selection, a genetic code, or “dictionary”, was established, establishing a correspondence between triplets of nucleotides and amino acids.

A further complication of metabolism could occur only under conditions of spatial proximity of the genetic code and the proteins encoded by it, as well as isolation of the reacting components from the external environment. Indeed, the selection of RNA molecules by the quality of the protein encoded by it is carried out only if the protein does not diffuse in any direction, but is stored in some isolated space, where it participates in metabolic processes. The possibility of separating the protein synthesizing system from the external environment lies in the physicochemical properties of the molecules. Organic molecules are also surrounded by an aqueous shell, the thickness of which depends on the magnitude of the charge of the molecule, the concentration of salts in the solution, temperature, etc.

Under certain conditions, the water shell acquires clear boundaries and is separated from the surrounding solution. Molecules surrounded by an aqueous shell can combine to form multimolecular complexes - coacervates. In the primary ocean, coacervate, or coacervate droplets, had the ability to absorb various substances. As a result, the internal composition of the coacervate underwent changes, which led either to the decay or accumulation of substances, i.e. to growth and to a change in the chemical composition that increases the stability of the coacervate drop. The fate of the drop was determined by the predominance of one of these processes. Academician A.I. Oparin noted that in the mass of coacervate drops, the selection of the most stable under the given specific conditions should go. Having reached a certain size, the maternal coacervate drop could break up into daughter ones. Subsidiary coacervates, the structure of which differed little from the mother, continued to grow, and sharply differing drops disintegrated. Only those coacervate drops continued to exist, which, entering into some elementary forms of exchange with the medium, retained a relative constancy of their composition. Subsequently, they acquired the ability to absorb not any substances from the environment, but only those that provided them with stability, as well as the ability to excrete metabolic products. The differences between the chemical composition of the droplet and the environment gradually increased. In the process of long selection (it is called chemical evolution), only those drops were preserved that, when decayed into daughter ones, did not lose their structural features, i.e. acquired the property of self-reproduction. The coacervate evolution ended with the formation of a membrane that separates them from the environment and consists of phospholipids. Similar artificial membranes bordering bubbles from 1 to 10 microns in size are now easily created under experimental conditions. The formation of the outer membrane predetermined the direction of further chemical evolution along the path of the development of more and more advanced self-regulating systems up to the appearance of the first primitive cells. Once inside the enclosed membrane space, RNA molecules evolved, and the sign of selection was not their own RNA structure, but mainly the properties of the proteins encoded by them.

Thus, the nucleotide sequence of RNA began to manifest itself in the properties of the cell as a whole. The key event in the emergence of the cell was the combination of the matrix function of RNA and the catalytic function of peptides. At some later stage of evolution, DNA replaced RNA as a substance of heredity.

The appearance of the first cellular organisms laid the foundation for biological evolution. This happened 3 to 3.5 billion years ago. The first living organisms possessed the ability to reproduce themselves and other basic characteristics of living things, existed in a reducing environment and had an anaerobic type of metabolism. In their structure, they resembled modern bacteria.

The theory of the origin of life, proposed by the Soviet scientist Alexander Oparin (1894-1980) for a long time became one of the most influential in the scientific world. This theory describes life from the standpoint of materialistic methodology and postulates the spontaneous generation of life under the influence of physicochemical processes taking place in the primeval Earth.

Oparin's theory is a theory of chemical evolution. The scientist first set forth his ideas in the book The Origin of Life, published in the Soviet Union in 1924 and translated into English in 1938. Oparin’s theory was warmly supported by a Cambridge professor, a militant atheist, and the long-time editor-in-chief of the Daily Worker communist newspaper. Haldane opened a polemic on the origin of life in an article published in the 1929 Rationalist Annual Announcement. In it, Halden hypothesized that huge amounts of organic compounds had accumulated on the primeval Earth, forming what was called the “primary broth” or “protobulon”.

The modern concepts of "primitive broth" and "spontaneous generation of life" come from the theory of Oparin-Haldane about the origin of life. The essence of the theory is as follows:

1. The primeval Earth had a rarefied (that is, deprived of oxygen) atmosphere.

2. When various natural sources of energy began to influence this atmosphere - for example, thunderstorms and volcanic eruptions - then the basic chemical compounds necessary for organic life began to spontaneously form.

3. Over time, molecules of organic matter accumulated in the oceans until they reached the consistency of hot diluted broth. However, in some areas, the concentration of molecules necessary for the origin of life was especially high, and nucleic acids and proteins formed there.

4. Some of these molecules have been shown to be capable of self-reproduction.

5. The interaction between the resulting nucleic acids and proteins ultimately led to the emergence of a genetic code.

6. Subsequently, these molecules combined, and the first living cell appeared.

7. The first cells were heterotrophs, they could not reproduce their components on their own and received them from the broth. But over time, many compounds began to disappear from the broth, and the cells were forced to reproduce them on their own. So the cells developed their own metabolism for self-reproduction.

8. Thanks to the process of natural selection from these first cells, all living organisms that exist on Earth have appeared.

The greatest success of the Oparin-Haldane theory was the well-known experiment conducted in 1953 by American graduate student Stanley Miller.

Miller's experiment

He tested the theory of Stanley Miller in 1953. The Miller-Yuri experiment, which became a turning point in this area, was extremely simple. The apparatus consisted of two glass flasks connected in a closed circuit. A device imitating thunderstorm effects is placed in one of the flasks - two electrodes between which a discharge occurs at a voltage of about 60 thousand volts; in another flask, water is constantly boiling. Then the apparatus is filled with the atmosphere, which supposedly existed on the ancient Earth: methane, hydrogen and ammonia. The device worked for a week, after which the reaction products were investigated. Mostly a viscous mess of random compounds; a certain amount of organic substances was also found in the solution, including the simplest amino acids glycine and alanine. Later, sugars and nucleotides were also obtained under different conditions. Miller concluded that evolution can occur in a phase-separated state from a solution (coacervates). However, such a system cannot reproduce itself.

The publication of the Miller experiment data aroused unprecedented interest, and soon many other scientists began to repeat this experiment. It was found that modification of the experimental conditions makes it possible to obtain a small amount of other amino acids. However, it was difficult to repeat the experiment, and many results were obtained only after many unsuccessful attempts.

It was reported that during the experiments, the basic components necessary for life arose. So, in some biology textbooks it is said that during the experiments representatives of all the most important types of molecules found in cells were obtained. This statement is absolutely incorrect, because of the many biochemical substances present in the cells, only two are similar to those obtained in experiments of the Millerovsky type - glycine and alanine. But they were also presented in very small concentrations. In addition, in the course of experiments, nucleic acids, protein, lipid and polysaccharide were never obtained - more than 90% of the substances that make up a living cell.

Almost all specialists in the field of the origin of life have long turned a blind eye to several problems of the Oparin – Haldane theory. Even if spontaneously, through random matrix-free syntheses in the coacervate, single successful constructs of protein molecules appeared (for example, effective catalysts that provide this coacervate with an advantage in growth and reproduction), the mechanism by which they could be copied for distribution inside the coacervate remains unknown. especially for transmission to coacervates descendants.

The theory was unable to propose a solution to the problem of exact reproduction - within the coacervate and in generations - of single, randomly appearing effective protein structures. However, it was shown that the first coacervates could spontaneously form from lipids synthesized abiogenously, and they could enter into symbiosis with “living solutions” - colonies of self-reproducing RNA molecules, among which were ribozymes that catalyze lipid synthesis, and such a community can already be call an organism.

Theory (it would be more correct to speak of a hypothesis) Oparin causes a lot of controversy, but is still the main one in biology.

Russian Civilization

1. What is life?

Answer. Life is a way of being of entities (living organisms) endowed with internal activity, the process of developing bodies of organic structure with a steady predominance of synthesis processes over decay processes, a special state of matter, achieved due to the following properties. Life is a way of existence of protein bodies and nucleic acids, the essential point of which is a constant metabolism with the environment, and with the cessation of this exchange, life ceases.

2. What hypotheses of the origin of life do you know?

Answer. Different ideas about the origin of life can be combined into five hypotheses:

1) creationism - the divine creation of the living;

2) spontaneous nucleation - living organisms arise spontaneously from inanimate matter;

3) the hypothesis of a stationary state - life has always existed;

4) the hypothesis of panspermia - life is brought to our planet from the outside;

5) the hypothesis of biochemical evolution - life arose as a result of processes obeying chemical and physical laws. Currently, most scientists support the idea of \u200b\u200babiogenic origin of life in the process of biochemical evolution.

3. What is the basic principle of the scientific method?

Answer. The scientific method is a set of techniques and operations used in building a system of scientific knowledge. The basic principle of the scientific method is not to take anything for granted. Any statement or refutation of something should be checked.

Questions after § 89

1. Why can not the idea of \u200b\u200bthe divine origin of life be either confirmed or refuted?

Answer. The process of the Divine creation of the world is conceived as having taken place only once and therefore inaccessible to research. Science deals only with those phenomena that are observable and experimental research. Therefore, from a scientific point of view, the hypothesis of the divine occurrence of the living cannot be neither proved nor refuted. The main principle of the scientific method is "do not take anything for granted." Therefore, logically there can be no contradiction between the scientific and religious explanation of the origin of life, since these two areas of thought mutually exclude one another.

2. What are the main points of the Oparin – Haldane hypothesis?

Answer. In modern conditions, the emergence of living beings from inanimate nature is impossible. The abiogenic (i.e., without the participation of living organisms) occurrence of living matter was possible only in the conditions of the ancient atmosphere and the absence of living organisms. The composition of the ancient atmosphere included methane, ammonia, carbon dioxide, hydrogen, water vapor and other inorganic compounds. Under the influence of powerful electric discharges, ultraviolet radiation and high radiation, organic compounds could arise from these substances, which accumulated in the ocean, forming the “primary broth”. In the “primary broth”, multimolecular complexes — coacervates — were formed from biopolymers. Metal ions acting as the first catalysts fell into coacervate droplets from the external environment. From the huge number of chemical compounds present in the “primary broth”, the most catalytic combinations of molecules were selected, which ultimately led to the appearance of enzymes. On the border between the coacervates and the external environment, lipid molecules were lined up, which led to the formation of a primitive cell membrane. At a certain stage, protein probionts included nucleic acids, creating single complexes, which led to the emergence of living properties such as self-reproduction, preservation of hereditary information and its transmission to subsequent generations. Probionts, in which metabolism was combined with the ability to reproduce themselves, can already be considered as primitive cells, the further development of which took place according to the laws of evolution of living matter.

3. What experimental evidence can be given in favor of this hypothesis?

Answer. In 1953, this hypothesis of A.I. Oparin was experimentally confirmed by the experiments of the American scientist S. Miller. In the installation he created, the conditions that supposedly existed in the primary atmosphere of the Earth were modeled. As a result of the experiments, amino acids were obtained. Similar experiments were repeated many times in various laboratories and made it possible to prove that it is possible in principle to synthesize practically all the monomers of the main biopolymers under such conditions. It was further established that, under certain conditions, it is possible to synthesize more complex organic biopolymers from monomers: polypeptides, polynucleotides, polysaccharides and lipids.

4. What are the differences between the A. I. Oparin hypothesis and the J. Haldane hypothesis?

Answer. J. Haldane also put forward the hypothesis of the abiogenic origin of life, but, unlike A.I. Oparin, he did not give priority to proteins - coacervate systems capable of metabolism, but nucleic acids, that is, macromolecular systems capable of self-reproduction.

5. What arguments do opponents make when they criticize the Oparin – Haldane hypothesis?

Answer. The Oparin – Haldane hypothesis also has a weak side, which its opponents point to. In the framework of this hypothesis, it is not possible to explain the main problem: how did a qualitative leap from non-living to living occurred. Indeed, for the self-reproduction of nucleic acids, enzyme proteins are necessary, and for the synthesis of proteins, nucleic acids are necessary.

  Give possible pros and cons of the panspermia hypothesis.

Answer. Arguments for:

Life at the level of prokaryotes appeared on Earth almost immediately after its formation, although the distance (in terms of the difference in the level of complexity of the organization) between prokaryotes and mammals is comparable to the distance from the primary broth to pokaryotes;

In the case of the origin of life on any planet of our galaxy, it, as shown, for example, by the estimates of A.D. Panov, can “infect” the entire galaxy in a period of only about several hundred million years;

Finds in some meteorites of artifacts that can be interpreted as the result of the activity of microorganisms (even before the meteorite hit the Earth).

The panspermia hypothesis (life is brought to our planet from the outside) does not answer the main question of how life came about, but transfers this problem to some other place in the Universe;

Complete radio silence of the universe;

Since it turned out that our entire Universe is only 13 billion years old (i.e., our entire Universe is only 3 times older (!) Than the planet Earth), there is very little time left for the origin of life somewhere far away ... The distance to the nearest a-centauri star is 4 St. of the year. A modern fighter (4 speeds of sound) will fly to this star ~ 800,000 years.

C. Darwin wrote in 1871: “But if now ... in a warm body of water containing all the necessary salts of ammonium and phosphorus and accessible to light, heat, electricity, etc., a protein capable of further , increasingly complex transformations, then this substance would immediately be destroyed or absorbed, which was impossible in the period before the emergence of living beings. "

Confirm or refute this statement of C. Darwin.

Answer. The process of the emergence of living organisms from simple organic compounds was extremely long. For life to begin on Earth, an evolutionary process that took many millions of years was required, during which complex molecular structures, primarily nucleic acids and proteins, were selected for stability, for the ability to reproduce their own kind.

If now on Earth somewhere in areas of intense volcanic activity and quite complex organic compounds can arise, then the likelihood of any continued existence of these compounds is negligible. The possibility of the re-emergence of life on Earth is excluded. Now living things appear only as a result of reproduction.