Hypotheses of life. The origin of life on Earth: theories, hypotheses, concepts

Municipal educational institution

Secondary school No. 45

Theories of the origin of life on Earth

Performed : student of 11th grade "B"

Nigmatullina Maria

Proveila : biology teacher

Trapueva L. S.

Chelyabinsk

2010

Introduction

Hypotheses about the origin of life

Genobiosis and holobiosis

Oparin–Haldane theory

The RNA World as a Precursor to Modern Life

Panspermia

Spontaneous generation of life

Steady State Theory

Creationism

Evolution theory

Darwinian theory

Conclusion

Introduction

Theories concerning the origin of the Earth and life on it, and indeed the entire Universe, are varied and far from reliable. According to the steady state theory, the universe has existed forever. According to other hypotheses, the Universe could have arisen from a bunch of neutrons as a result of the “Big Bang”, was born in one of the black holes, or was created by the Creator. Contrary to popular belief, science cannot refute the thesis of the divine creation of the Universe, just as theological views do not necessarily reject the possibility that life in the process of its development acquired features that can be explained on the basis of the laws of nature.

Hypotheses about the origin of life

At different times, the following hypotheses were put forward regarding the origin of life on Earth:

Biochemical evolution hypothesis

Panspermia hypothesis

Stationary State of Life Hypothesis

Spontaneous generation hypothesis

Theories spontaneous generation And steady state are of historical or philosophical interest only, since the results of scientific research contradict the conclusions of these theories.

Theory panspermia does not solve the fundamental question of the origin of life, it only pushes it into the even more nebulous past of the Universe, although it cannot be excluded as a hypothesis about the beginning of life on Earth.

Genobiosis and holobiosis

Depending on what is considered primary, there are two methodological approaches to the question of the origin of life:

Genobiosis- a methodological approach to the question of the origin of life, based on the belief in the primacy of a molecular system with the properties of a primary genetic code.

Holobiosis- a methodological approach to the question of the origin of life, based on the idea of the primacy of structures endowed with the ability to elementary metabolism with the participation of an enzymatic mechanism.

Oparin–Haldane theory

In 1924, the future academician Oparin published an article “The Origin of Life,” which was translated into English in 1938 and revived interest in the theory of spontaneous generation. Oparin suggested that in solutions of high molecular weight compounds they can spontaneously zones of increased concentration are formed, which are relatively separated from the external environment and can maintain exchange with it. He called them Coacervate drops, or simply coacervates.

According to his theory, the process that led to the emergence of life on Earth can be divided into three stages:

The emergence of organic substances

The emergence of proteins

The emergence of protein bodies

Astronomical studies show that both stars and planetary systems arose from gas and dust matter. Along with metals and their oxides, it contained hydrogen, ammonia, water and the simplest hydrocarbon - methane.

The conditions for the beginning of the process of formation of protein structures were established from the moment the primary ocean appeared. In the aquatic environment, hydrocarbon derivatives could undergo complex chemical changes and transformations. As a result of this complication of molecules, more complex organic substances could be formed, namely carbohydrates.

Science has proven that as a result of the use of ultraviolet rays, it is possible to artificially synthesize not only amino acids, but also other biochemical substances. According to Oparin's theory, a further step towards the emergence of protein bodies could be the formation of coacervate droplets. Under certain conditions, the aqueous shell of organic molecules acquired clear boundaries and separated the molecule from the surrounding solution. Molecules surrounded by a water shell united, forming multimolecular complexes - coacervates.

Coacervate droplets could also arise from simply mixing different polymers. In this case, self-assembly of polymer molecules into multimolecular formations occurred - droplets visible under an optical microscope.

The drops were capable of absorbing substances from outside like open systems. When various catalysts (including enzymes) were included in coacervate droplets, various reactions occurred in them, in particular the polymerization of monomers coming from the external environment. Due to this, the drops could increase in volume and weight, and then split into daughter formations. Thus, coacervates could grow, multiply, and carry out metabolism.

British biologist John Haldane also expressed similar views.

The theory was tested by Stanley Miller in 1953 in the Miller-Urey experiment. He placed a mixture of H 2 O, NH 3, CH 4, CO 2, CO in a closed vessel (Fig. 1) and began to pass electrical discharges through it. It turned out that amino acids are formed. Later, other sugars and nucleotides were obtained under different conditions. He concluded that evolution can occur in a phase-separated state from solution (coacervates). However, such a system cannot reproduce itself.

The theory was justified, except for one problem, to which almost all experts in the field of the origin of life had long turned a blind eye. If spontaneously, through random template-free syntheses, single successful designs of protein molecules arose in the coacervate (for example, effective catalysts that provide an advantage for a given coacervate in growth and reproduction), then how could they be copied for distribution within the coacervate, and even more so for transmission to descendant coacervates? The theory turned out to be unable to offer a solution to the problem of exact reproduction - within a coacervate and in generations - of single, randomly appearing effective protein structures. However, it was shown that the first coacervates could be formed spontaneously from lipids synthesized abiogenically, and they could enter into symbiosis with “living solutions” - colonies of self-replicating RNA molecules, among which were ribozymes that catalyze the synthesis of lipids, and such a community is already possible call it an organism.

Alexander Oparin (right) in the laboratory

The RNA World as a Precursor to Modern Life

By the 21st century, the Oparin-Haldane theory, which assumes the initial emergence of proteins, has practically given way to a more modern one. The impetus for its development was the discovery of ribozymes - RNA molecules with enzymatic activity and therefore capable of combining functions that in real cells are mainly performed separately by proteins and DNA, that is, catalyzing biochemical reactions and storing hereditary information. Thus, it is assumed that the first living beings were RNA organisms without proteins and DNA, and their prototype could be an autocatalytic cycle formed by those very ribozymes capable of catalyzing the synthesis of their own copies.

Panspermia

According to the theory of Panspermia, proposed in 1865 by the German scientist G. Richter and finally formulated by the Swedish scientist Arrhenius in 1895, life could have been brought to Earth from space. Living organisms of extraterrestrial origin are most likely to enter with meteorites and cosmic dust. This assumption is based on data on the high resistance of some organisms and their spores to radiation, high vacuum, low temperatures and other influences. However, there are still no reliable facts confirming the extraterrestrial origin of microorganisms found in meteorites. But even if they got to Earth and gave rise to life on our planet, the question of the original origin of life would remain unanswered.

Francis Crick and Leslie Orgel proposed another option in 1973 - controlled panspermia, that is, the deliberate “infection” of the Earth (along with other planetary systems) with microorganisms delivered on unmanned spacecraft by an advanced alien civilization, which may have been facing a global catastrophe or simply hoped to terraform other planets for future colonization. They gave two main arguments in favor of their theory - the universality of the genetic code (known other variations of the code are used much less frequently in the biosphere and differ little from the universal one) and the significant role of molybdenum in some enzymes. Molybdenum is a very rare element throughout the solar system. According to the authors, the original civilization may have lived near a star enriched in molybdenum.

Against the objection that the theory of panspermia (including controlled) does not solve the question of the origin of life, they put forward the following argument: on planets of another type unknown to us, the probability of the origin of life may initially be much higher than on Earth, for example, due to the presence of special minerals with high catalytic activity.

In 1981, F. Crick wrote the book “Life itself: its origin and nature,” in which he sets out the hypothesis of controlled panspermia in more detail than in the article and in a popular form.

Spontaneous generation of life

This theory was common in Ancient China, Babylon and Ancient Egypt as an alternative to creationism, with which it coexisted. Aristotle (384-322 BC), often hailed as the founder of biology, maintained the theory of the spontaneous origin of life. According to this hypothesis, certain “particles” of a substance contain a certain “active principle” that, under suitable conditions, can create a living organism. Aristotle was right in believing that this active principle was contained in the fertilized egg, but he erroneously believed that it was also present in sunlight, mud and rotting meat.

With the spread of Christianity, the theory of the spontaneous origin of life fell out of favor, but this idea continued to exist somewhere in the background for many more centuries.

The famous scientist Van Helmont described an experiment in which he allegedly created mice in three weeks. For this you needed a dirty shirt, a dark closet and a handful of wheat. Van Helmont considered human sweat to be the active principle in the process of mouse generation.

In 1688, the Italian biologist and physician Francesco Redi approached the problem of the origin of life more rigorously and questioned the theory of spontaneous generation. Redi discovered that the small white worms that appear on rotting meat are fly larvae. After conducting a series of experiments, he obtained data supporting the idea that life can only arise from previous life (the concept of biogenesis).

These experiments, however, did not lead to the abandonment of the idea of spontaneous generation, and although this idea faded somewhat into the background, it continued to be the main version of the origin of life.

While Redi's experiments seemed to disprove spontaneous generation in flies, early microscopic studies by Antonie van Leeuwenhoek strengthened the theory as it applied to microorganisms. Leeuwenhoek himself did not enter into disputes between supporters of biogenesis and spontaneous generation, but his observations under the microscope provided food for both theories.

In 1860, the French chemist Louis Pasteur took up the problem of the origin of life. Through his experiments, he proved that bacteria are ubiquitous and that non-living materials can easily be contaminated by living things if they are not properly sterilized. The scientist boiled various media in water in which microorganisms could form. With additional boiling, microorganisms and their spores died. Pasteur attached a sealed flask with a free end to an S-shaped tube. Microorganism spores settled on the curved tube and could not penetrate the nutrient medium. A well-boiled nutrient medium remained sterile; the origin of life was not detected in it, despite the fact that air access was provided.

As a result of a series of experiments, Pasteur proved the validity of the theory of biogenesis and finally refuted the theory of spontaneous generation.

Steady State Theory

According to the steady state theory, the Earth never came into being, but existed forever; it was always capable of supporting life, and if it changed, it was very little. According to this version, species also never arose, they always existed, and each species has only two possibilities - either a change in numbers or extinction.

However, the stationary state hypothesis fundamentally contradicts the data of modern astronomy, which indicate a finite lifetime of any stars and, accordingly, planetary systems around stars. According to modern estimates, based on taking into account the rates of radioactive decay, the age of the Earth, the Sun and the Solar System is ~4.6 billion years. Therefore, this hypothesis is not usually considered by academic science.

Proponents of this theory do not recognize that the presence or absence of certain fossil remains may indicate the time of appearance or extinction of a particular species, and cite as an example a representative of lobe-finned fish - coelacanth (coelacanth). According to paleontological data, lobe-finned animals became extinct at the end of the Cretaceous period. However, this conclusion had to be reconsidered when living representatives of lobe-fins were found in the Madagascar region. Proponents of the steady state theory argue that only by studying living species and comparing them with fossil remains can one draw a conclusion about extinction, and even then it is very likely that it will be incorrect. Using paleontological data to support the steady state theory, its proponents interpret the appearance of fossils in ecological terms. For example, they explain the sudden appearance of a fossil species in a certain layer by an increase in the size of its population or its movement to places favorable for the preservation of remains.

Creationism

Creationism (from English. creation- creation) is a religious and philosophical concept within which the entire diversity of the organic world, humanity, planet Earth, as well as the world as a whole, are considered as intentionally created by some supreme being or deity. Theory creationism, referring the answer to the question of the origin of life to religion (the creation of life by God), according to Popper’s criterion is outside the field of scientific research (since it is irrefutable: it is impossible to prove by scientific methods both that God did not create life and that God created it). In addition, this theory does not provide a satisfactory answer to the question of the reasons for the emergence and existence of the supreme being itself, usually simply postulating its beginninglessness.

Evolution theory

Until now, in the scientific and general educational environment, the theory of evolution was considered the main theory of the origin of life on Earth in all its diversity. This theory arose from the work of the Darwin family: the physician, naturalist and poet Erasmus Darwin (1731-1802), who proposed the theory of evolution in the 1790s, and especially his naturalist grandson Charles Darwin (1809-1882), who published in 1859 his now famous book “On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life.”
The theory of evolution, often called Darwinian theory or Darwinism, did not arise out of nowhere. By the time of Darwin, the cosmological theory of Emmanuel Kant, with his infinite Universe in space and time, subject to the laws of mechanics described by Isaac Newton, had become generally accepted. In addition, the English scientist Charles Lyell (1797-1875) confirmed the theory of so-called uniformitarianism, proposed by the 18th century scientist Jason Hutton (1726-1797), according to which the Earth was formed over millions of years as a result of slow and gradual processes that are still occurring today. Lyell substantiated this conclusion in 3 volumes of “Fundamentals of Geology,” published in 1830-1833.
Thus, the foundation of the theory of evolution was created, on which Charles Darwin created the harmonious edifice of his theory by publishing the books: “The Origin of Species”, “Change in Domestic Animals and Cultivated Plants”, “The Descent of Man and Sexual Selection” and others

Darwinian theory

According to Darwin, evolution, i.e. the history of the development of the organic world of the Earth is carried out as a result of the interaction of three main factors: variability, heredity and natural selection. Thanks to these factors, organisms accumulate new adaptive characteristics during the development process, which ultimately leads to the formation of new species.
In support of Darwin's theory, two arguments were immediately proposed: vestigial organs and the theory of embryonic recapitulation.
Thus, a list was compiled of 180 human rudiments - organs that lost their purpose in the process of its development from lower forms, i.e. organs that a person no longer needs and can be removed. However, as they studied these vestiges (for example, the appendix), scientists crossed organ after organ off the list until they crossed everything off. After 100 years, physiologists do not consider any of the human organs useless.
Quite soon, the theory of embryonic recapitulation, proposed in 1868 by the German zoologist Ernst Haeckel, a supporter and propagandist of Darwin's teachings, also died out for a long time. This theory is based on the apparent similarity between human and dog embryos at 4 weeks of age, as well as the presence of so-called “gill slits” and a “tail” in the human embryo.
In fact, it turned out that Haeckel forged the illustrations (retouched them), for which the academic council of the University of Jena found Haeckel guilty of scientific fraud and his theory unfounded. But in the USSR, almost before its collapse, textbooks persistently presented pictures of embryos, supposedly confirming the theory of recapitulation, long rejected by embryologists in the rest of the world.

Conclusion

Many of these “theories” and their proposed explanations for existing species diversity use the same data but emphasize different aspects of it. Scientific theories can be super-fantastic on the one hand, and super-skeptical on the other. Theological considerations may also find a place within this framework, depending on the religious views of their authors. One of the main points of disagreement, even in pre-Darwinian times, was the question of the relationship between scientific and theological views on the history of life.

(9) life on Earth in the historical past as a result... a huge number of different hypotheses and theories about the cause of occurrence life on Earth, none of them...

Life is the greatest miracle that exists on our planet. The problems of its study are currently occupied not only by biologists, but also by physicists, mathematicians, philosophers and other scientists. Of course, the most difficult mystery is the very origin of life on Earth.

Researchers are still arguing about how this happened. Oddly enough, philosophy has made a significant contribution to the study of this phenomenon: this science allows one to draw correct conclusions by summarizing huge amounts of information. What versions are guiding scientists around the world today? Here are the current theories of the origin of life on Earth:

The concept of spontaneous generation.
Creationism, or the theory of divine creation.
The principle of stationary state.
Panspermia, whose proponents claim the natural “productivity” of any planet where suitable conditions exist. In particular, this idea was once developed by the well-known academician Vernadsky.
Biochemical evolution according to A.I. Oparin.

Let us consider all these theories of the origin of life on Earth in a little more detail.

Materialism and idealism

Back in the Middle Ages and earlier, in the Arab world, some scientists, even at the risk of their own lives, assumed that the world could be created as a result of some natural processes, without the participation of a divine essence. These were the first materialists. Accordingly, all other points of view that provided for Divine intervention in the creation of all things were considered idealistic. Accordingly, it is quite possible to consider the origin of life on Earth from these two positions.

Creationists argue that life could only have been created by God, while materialists promote the theory of the emergence of the first organic compounds and life from inorganic substances. Their version is based on the complexity or impossibility of understanding those processes that resulted in life in its modern form. Interestingly, the modern Church only partially supports this hypothesis. From the point of view of the most scientist-friendly figures, it is truly impossible to understand the main Plan of the Creator, but we can determine the phenomena and processes due to which life arose. However, this is still very far from a truly scientific approach.

Currently, the materialist point of view prevails. However, they did not always put forward modern theories of the origin of life. Thus, the hypothesis that the origin and evolution of life on Earth occurred spontaneously was initially popular, and supporters of this phenomenon were found back in the early 19th century.

Proponents of this concept argued that there are certain laws of natural nature that determine the possibility of the arbitrary transition of inorganic compounds into organic ones with the subsequent arbitrary formation of life. This also includes the theory of the creation of a “homunculus,” an artificial person. In general, the spontaneous origin of life on Earth is still considered seriously by some “experts”... At least it’s good that they talk about bacteria and viruses.

Of course, this approach was later proven to be wrong, but it played an important role, providing a huge amount of valuable empirical material. Note that the final rejection of the version of the independent origin of life occurred only in the middle of the 19th century. In principle, the impossibility of such a process was proven by Louis Pasteur. For this, the scientist even received a considerable prize from the French Academy of Sciences. Soon the main theories of the origin of life on Earth come to the fore, which we will describe below.

Academician Oparin's theory

Modern ideas about the origin of life on Earth are based on a theory that was put forward by a domestic researcher, Academician Oparin, back in 1924. He refuted Redi's principle, which spoke about the possibility of only biogenic synthesis of organic substances, pointing out that this concept is valid only for the current state of affairs. The scientist pointed out that at the very beginning of its existence, our planet was a giant rocky ball, on which, in principle, there was no organic matter.

Oparin's hypothesis was that the origin of life on planet Earth is a long-term biochemical process, the raw materials for which are common compounds that can be found on any planet. The academician suggested that the transition of these substances into more complex ones was possible under the influence of extremely strong physical and chemical factors. Oparin was the first to put forward a hypothesis about the continuous transformation and interaction of organic and inorganic compounds. He called it "biochemical evolution." Below are the main stages of the origin of life on Earth according to Oparin.

Stage of chemical evolution

About four billion years ago, when our planet was a huge and lifeless rock in the depths of space, the process of non-biological synthesis of carbon compounds was already underway on its surface. During this period, volcanoes emitted titanic amounts of lava and hot gases. Cooling in the primary atmosphere, the gases turned into clouds, from which torrential rains fell incessantly. All these processes took place over millions of years. But, excuse me, when did the origin of life on Earth begin?

At the same time, the showers gave rise to huge primary oceans, the waters of which were extremely saturated with salts. The first organic compounds got there, the formation of which took place in the atmosphere under the influence of strong electrical discharges and UV irradiation. Gradually their concentration increased until the seas turned into a kind of “broth” saturated with peptides. But what happened next and how did the first cells arise from this “soup”?

Formation of protein compounds, fats and carbohydrates

And only at the second stage do true proteins and other compounds from which life is built appear in the “broth”. Conditions on Earth softened, carbohydrates, proteins and fats, the first biopolymers, and nucleotides appeared. This is how coacervate droplets formed, which were the prototype of real cells. Roughly speaking, this was the name given to drops of proteins, fats, and carbohydrates (as in soup). These formations could absorb and absorb those substances that were dissolved in the waters of the primary oceans. At the same time, a kind of evolution took place, the result of which were drops with increased resistance and stability to environmental influences.

Appearance of the first cells

Actually, at the third stage, this amorphous formation turned into something more “meaningful.” That is, into a living cell capable of the process of self-reproduction. The natural selection of drops, which we have already discussed above, became more and more stringent. The first “advanced” coacervates already had, albeit primitive, metabolism. Scientists suggest that the drop, having reached a certain size, disintegrated into smaller formations that had all the features of the mother “cell”.

Gradually, a layer of lipids appeared around the core of the coacervate, giving rise to a full-fledged cell membrane. This is how the primary cells, archecells, were formed. It is this moment that can rightfully be considered as the origin of life on Earth.

Is non-biological synthesis of organic matter real?

As for the hypothesis of the origin of life on Earth from Oparin... Many people immediately have a question: “How realistic is the formation of organic matter from inorganic matter under natural conditions?” Many researchers have had such thoughts!

In 1953, American scientist Miller modeled the Earth's primordial atmosphere, with its incredible temperatures and electrical discharges. Simple inorganic compounds were placed in this medium. As a result, acetic and formic acids and other organic compounds were formed there. This is how the origin of life on Earth took place. Briefly, this process can be characterized by the philosophical law of “Transition of quantity into quality.” Simply put, with the accumulation of a certain amount of proteins and other substances in the primary ocean, these compounds acquire different properties and the ability to self-organize.

Strengths and weaknesses of Oparin's theory

The concept we have considered has not only strong but also weak points. The strength of the theory is its logic and experimental confirmation of the abiotic synthesis of organic compounds. In principle, this could be the origin and development of life on Earth. A huge weakness is the fact that so far no one can explain how coacervates were able to degenerate into a complex biological structure. Even supporters of the theory admit that the transition from a protein-fat drop to a full-fledged cell is very doubtful. We are probably missing something by not taking into account factors unknown to us. Currently, all scientists recognize that there was some kind of sharp jump, as a result of which the self-organization of matter became possible. How could this even happen? It is still unclear... What other main theories of the origin of life on Earth exist?

Theory of panspermia and steady state

As we have already said, at one time this version was ardently supported and “promoted” by the famous academician Vernadsky. In general, the theory of panspermia cannot be discussed in isolation from the concept of a stationary state, since they consider the principle of the origin of life from the same point of view. You should know that this concept was first proposed by the German Richter at the end of the 19th century. In 1907, he was supported by the Swedish researcher Arrhenius.

Scientists who adhere to this concept believe that life simply existed in the Universe and will always exist. It is transferred from planet to planet with the help of comets and meteorites, which play the role of peculiar “seeds”. The disadvantage of this theory is that the Universe itself is believed to have formed approximately 15-25 billion years ago. It doesn't look like Eternity at all. Considering that the planets potentially suitable for the formation of life are many times smaller than ordinary rocky planetoids, it is quite natural for the question to arise: “When and where did life form and how did it spread throughout the Universe at such a speed, taking into account the unrealistic distances?”

It should be remembered that the age of our planet is no more than 5 billion years. Comets and asteroids fly much slower than the speed of light, so they simply might not have enough time to plant the “seeds” of life on Earth. Proponents of panspermia suggest that certain seeds (spores of microorganisms, for example) are transported “on light rays” at an appropriate speed... But decades of spacecraft have made it possible to prove that there are quite a few free particles in space. The probability of this method of spreading living organisms is too low.

Some researchers today suggest that any planet that is suitable for life may eventually form protein bodies, but the mechanism of this process is unknown to us. Other scientists say that in the Universe, perhaps, there are some “cradles”, planets on which life can form. It sounds, of course, like some kind of science fiction... However, who knows. In recent years, here and abroad, a theory has gradually begun to take shape, the provisions of which speak about the information initially encoded in the atoms of substances...

Allegedly, these data provide the very impetus that leads to the transformation of the simplest coacervates into archecells. If we think logically, then this is the same theory of the spontaneous origin of life on Earth! In general, the concept of panspermia is difficult to consider as a complete scientific thesis. Its supporters can only say that life was brought to Earth from other planets. But how did it form there? There is no answer to this.

"Gift" from Mars?

Today it is known for certain that there was indeed water on the Red Planet and there were all conditions favorable to the development of protein life. The data that confirms this was obtained thanks to the work on the surface of two landers at once: Spirit and Curiosity. But scientists are still passionately arguing: was there life there? The fact is that information received from the same rovers indicates the short-term (in geological aspect) existence of water on this planet. How high is the probability that, in principle, full-fledged protein organisms managed to develop there? Again, there is no answer to this question. Again, even if life came to our planet from Mars, this in no way explains the process of its development there (which we have already written about).

So, we have examined the basic concepts of the origin of life on Earth. Which of them are absolutely true is unknown. The problem is that there is not yet a single experimentally confirmed test that could confirm or refute at least Oparin’s concept, not to mention other theses. Yes, we can synthesize protein without any problems, but we cannot obtain protein life. So scientists have work in store for many decades to come.

There is another problem. The fact is that we are intensely looking for carbon-based life and trying to understand exactly how it came to be. What if the concept of life is much broader? What if it could be based on silicon? In principle, this point of view does not contradict the principles of chemistry and biology. So on the way to finding answers we are met with more and more new questions. Currently, scientists have put forward several fundamental theses, guided by which people are looking for potentially habitable planets. Here they are:

The planet should orbit in the so-called “comfort zone” around the star: its surface should not be too hot or too cold. In principle, at least one or two planets in each star system meet this requirement (Earth and Mars, in particular).
The mass of such a body should be average (within one and a half times the size of the Earth). Planets that are too large either have unrealistically high gravity or are gas giants.
More or less highly organized life can only exist near fairly old stars (at least three to four billion years).
The star should not seriously change its parameters. It is useless to look for life near white dwarfs or red giants: if it was there, it would have died long ago due to extremely unfavorable environmental conditions.
It is desirable that the star system be single. In principle, modern researchers object to this thesis. It is possible that a binary system with two stars located at opposite ends could contain even more potentially habitable planets. Moreover, today there is more and more talk that somewhere on the outskirts of the solar system there is a gas-dust cloud, the forerunner of the unborn second Sun.

Final conclusions

So, what can we say in conclusion? First, we urgently lack data on the exact environmental conditions on the newly formed Earth. To obtain this information, ideally one should observe the development of a planet that is similar to ours in other respects. In addition, researchers are still finding it difficult to say exactly what factors stimulate the transition of coacervate archecapelles into full-fledged cells. Perhaps further in-depth studies of the genome of living beings will provide some answers.

MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUS

BSPU IM. M. TANK

FACULTY OF SPECIAL EDUCATION

DEPARTMENT OF FUNDAMENTALS OF DEFECTOLOGY

Essay

in the discipline "Natural Science"

on the topic of:

"The main hypotheses about the origin of life on Earth."

Performed:

1st year student of group 101

correspondence department (budgetary

form of training)

………Irina Anatolyevna

INTRODUCTION………………………………………………………………………………..….1

1. CREATIONISM……………………………………………………….…….1

2. THEORY OF STEADY STATE…………..……………….….2

3. THEORY OF SPONTANEOUS GENERATION…………..…3

4. THE THEORY OF PANSPERMIA……………………………………………………......7

5. THEORY OF A.I. OPARIN……………...…………………………..……10

6. MODERN VIEWS ON THE ORIGIN OF LIFE ON EARTH……………………………………………………………………………………….....12

CONCLUSION…………………………………………………………...…..14

LITERATURE …………………………………………………………...……...15

INTRODUCTION.

The problem of the origin of life on Earth and the possibility of its existence in other areas of the Universe has long attracted the attention of both scientists and philosophers, and ordinary people. In recent years, interest in this “eternal problem” has increased significantly.

This is due to two circumstances: firstly, significant advances in laboratory modeling of some stages of the evolution of matter that led to the origin of life, and secondly, the rapid development of space research, making the direct search for any forms of life on the planets of the solar system more and more realistic , and in the future beyond.

The origin of life is one of the most mysterious questions, a comprehensive answer to which is unlikely to ever be obtained. Many hypotheses and even theories about the origin of life, explaining various aspects of this phenomenon, are so far unable to overcome the essential circumstance - experimentally confirm the fact of the appearance of life. Modern science does not have direct evidence of how and where life arose. There are only logical constructions and indirect evidence obtained through model experiments, and data in the field of paleontology, geology, astronomy, etc.

Theories regarding the origin of life on Earth are varied and far from reliable. The most common theories of the origin of life on Earth are the following:

1. Life was created by a supernatural being (Creator) at a specific time (creationism).

2. Life has always existed (stationary state theory).

3. Life arose repeatedly from nonliving matter (spontaneous generation).

4. Life was brought to our planet from outside (panspermia).

5. Life arose as a result of processes that obey chemical and physical laws (biochemical evolution).

1. CREATIONISM.

Creationism (from the Latin creaсio - creation) is a philosophical and methodological concept within the framework of which the entire diversity of the organic world, humanity, planet Earth, as well as the world as a whole, are considered as intentionally created by some superbeing (Creator) or deity. There is no scientific evidence for this point of view: in religion, truth is comprehended through divine revelation and faith. The process of creation of the world is thought of as having taken place only once and therefore inaccessible to observation.

The theory of creationism is adhered to by followers of almost all the most common religious teachings (especially Christians, Muslims, Jews). According to this theory, the origin of life refers to some specific supernatural event in the past that can be calculated. In 1650, Archbishop Usher of Armagh (Ireland) calculated that God created the world in October 4004 BC. e. and finished his work on October 23 at 9 a.m., creating man. Asher obtained this date by adding up the ages of all the people mentioned in the Biblical genealogy, from Adam to Christ (“who begat whom”). From an arithmetic point of view, this makes sense, but it means that Adam lived at a time when, as archaeological finds show, a well-developed urban civilization already existed in the Middle East.

The traditional Judeo-Christian view of creation, as set out in the Book of Genesis, has been and continues to be controversial. However, existing contradictions do not refute the concept of creation. The creation hypothesis can neither be proven nor disproved and will always exist along with scientific hypotheses of the origin of life.

Creationism is thought of as God's Creation. However, at present, some view it as the result of the activity of a highly developed civilization, creating various forms of life and observing their development.

2. THEORY OF STATIONARY STATE.

According to this theory, the Earth never came into being, but existed forever; it was always capable of supporting life, and if it changed, it was very little. According to this version, species also never arose, they always existed, and each species has only two possibilities - either a change in numbers or extinction.

According to modern estimates, based on the rate of radioactive decay, the age of the Earth is 4.6 billion years. More advanced dating methods provide ever higher estimates of the age of the Earth, leading proponents of the steady state theory to believe that the Earth has always existed.

Many other animals that were considered extinct were also found, for example, the lingula - a small sea animal, supposedly extinct 500 million years ago, is alive today and like other "living fossils": the solendon - a shrew, the tuatara - a lizard. For millions of years they have not undergone any evolutionary changes.

Another example of a misconception is Archeopteryx - a creature that connects birds and reptiles, a transitional form on the way to transforming reptiles into birds. But in 1977, fossils of birds were discovered in Colorado, the age of which is commensurate with and even exceeds the age of the remains of Archeopteryx, i.e. it is not a transitional form.

Proponents of the steady state theory argue that only by studying living species and comparing them with fossil remains can one draw a conclusion about extinction, and even then it is very likely that it will be incorrect. Using paleontological data to support the steady state theory, its proponents interpret the appearance of fossils in ecological terms.

For example, they explain the sudden appearance of a fossil species in a certain layer by an increase in the size of its population or its movement to places favorable for the preservation of remains.

Much of the argument for this theory has to do with obscure aspects of evolution such as the significance of breaks in the fossil record, and it is along these lines that it has been most extensively developed.

The steady state hypothesis is sometimes called the eternism hypothesis (from the Latin eternus - eternal). The hypothesis of eternism was put forward by the German scientist W. Preyer in 1880.

Preyer's views were supported by academician Vladimir Ivanovich Vernadsky (1864 - 1945), the author of the doctrine of the biosphere. Vernadsky believed that life is the same eternal basis of the cosmos, which are matter and energy. “We know, and we know it scientifically,” he insisted, “that the Cosmos cannot exist without matter, without energy. And is there enough matter, even without the manifestation of life, to build the Cosmos, that Universe that is accessible to the human mind? He answered this question in the negative, referring specifically to scientific facts, and not to personal sympathies, philosophical or religious beliefs. “...We can talk about the eternity of life and the manifestations of its organisms, just as we can talk about the eternity of the material substrate of celestial bodies, their thermal, electrical, magnetic properties and their manifestations. From this point of view, the question of the beginning of life will be as far from scientific research as the question of the beginning of matter, heat, electricity, magnetism, and motion.”

Based on the idea of the biosphere as an earthly, but at the same time a cosmic mechanism, Vernadsky connected its formation and evolution with the organization of the Cosmos. “It becomes clear to us,” he wrote, “that life is a cosmic phenomenon, and not a purely earthly one.” Vernadsky repeated this idea many times: “... 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.”

3. THEORY OF SPONTANEOUS GENERATION.

This theory was common in ancient China, Babylon and Egypt as an alternative to creationism, with which it coexisted. Religious teachings of all times and all peoples usually attributed the appearance of life to one or another creative act of a deity. The first researchers of nature also resolved this issue very naively. Aristotle (384 – 322 BC), often hailed as the founder of biology, adhered to the theory of the spontaneous origin of life. Even for such an outstanding mind of antiquity as Aristotle, it was not particularly difficult to accept the idea that animals - worms, insects and even fish - could arise from silt. On the contrary, this philosopher argued that every dry body, becoming wet, and, conversely, every wet body, becoming dry, will give birth to animals.

According to Aristotle's hypothesis of spontaneous generation, certain “particles” of matter contain a certain “active principle” that, under suitable conditions, can create a living organism. Aristotle was right in believing that this active principle was contained in the fertilized egg, but he erroneously believed that it was also present in sunlight, mud and rotting meat.

“These are the facts - living things can arise not only through the mating of animals, but also through the decomposition of the soil. The same is the case with plants: some develop from seeds, while others seem to spontaneously generate under the influence of all nature, arising from decaying earth or certain parts of plants” (Aristotle).

The authority of Aristotle had an exceptional influence on the views of medieval scientists. The opinion of this philosopher in their minds was intricately intertwined with the teachings of the church fathers, often giving ideas that were absurd and even funny in modern eyes. The preparation of a living person or his likeness, a “homunculus,” in a flask, by mixing and distilling various chemicals, was considered in the Middle Ages, although very difficult and lawless, but, without a doubt, doable. The production of animals from non-living materials seemed so simple and common to scientists of that time that the famous alchemist and physician Van Helmont (1577 - 1644) directly gives a recipe, following which you can artificially prepare mice by covering a vessel with grain with wet and dirty rags. This very successful scientist described an experiment in which he allegedly created mice in three weeks. All you needed was a dirty shirt, a dark closet and a handful of wheat. Van Helmont considered human sweat to be the active principle in the process of mouse generation.

A number of works dating back to the 16th and 17th centuries describe in detail the transformation of water, stones and other inanimate objects into reptiles, birds and animals. Grindel von Ach even gives a picture of frogs being formed from the May dew, and Aldrovand gives drawings showing how birds and insects are born from the branches and fruits of trees.

The further natural science developed, the more important accurate observation and experience, and not mere reasoning and philosophizing, acquired in the knowledge of nature, the more the scope of application of the theory of spontaneous generation narrowed. Already in 1688, the Italian biologist and physician Francesco Redi, who lived in Florence, approached the problem of the origin of life more strictly and questioned the theory of spontaneous generation. Dr. Redi, through simple experiments, proved the unfoundedness of opinions about the spontaneous generation of worms in rotting meat. He established that the small white worms are fly larvae. After conducting a series of experiments, he obtained data supporting the idea that life can only arise from previous life (the concept of biogenesis).

“Conviction would be futile if it could not be confirmed by experiment. Therefore, in mid-July, I took four large wide-mouthed vessels, placed earth in one of them, some fish in another, eels from the Arno in the third, a piece of dairy veal in the fourth, closed them tightly and sealed them. Then I placed the same thing in four other vessels, leaving them open... Soon the meat and fish in the unsealed vessels were wormed; one could see flies freely flying into and out of the vessels. But I did not see a single worm in the sealed vessels, although many days had passed since the dead fish were placed in them” (Redi).

Thus, with regard to living beings visible to the naked eye, the assumption of spontaneous generation turned out to be untenable. But at the end of the 17th century. Kircher and Leeuwenhoek discovered a world of tiny creatures, invisible to the naked eye and visible only through a microscope. These “smallest living animals” (as Leeuwenhoek called the bacteria and ciliates he discovered) could be found wherever decay occurred, in long-standing decoctions and infusions of plants, in rotting meat, broth, in sour milk, in feces, in dental plaque . “In my mouth,” Leeuwenhoek wrote, “there are more of them (microbes) than there are people in the United Kingdom.” One has only to place perishable and easily rotting substances in a warm place for a while, and microscopic living beings that were not there before immediately develop in them. Where do these creatures come from? Did they really come from embryos that accidentally fell into a rotting liquid? How many of these embryos there must be everywhere! The thought involuntarily appeared that it was here, in rotting decoctions and infusions, that the spontaneous generation of living microbes from inanimate matter took place. This is the opinion in the middle of the 18th century. received strong confirmation in the experiments of the Scottish priest Needham. Needham took meat broth or decoctions of plant substances, placed them in tightly sealed vessels and boiled them for a short time. In this case, according to Needham, all the embryos should have died, but new ones could not enter from the outside, since the vessels were tightly closed. However, after some time, microbes appeared in the liquids. From this the said scientist concluded that it is present during the phenomenon of spontaneous generation.

However, another scientist, the Italian Spallanzani, opposed this opinion. Repeating Needham's experiments, he became convinced that longer heating of vessels containing organic liquids completely sterilizes them. In 1765, Lazzaro Spallanzani conducted the following experiment: after boiling meat and vegetable broths for several hours, he immediately sealed them and then removed them from the heat. Having examined the liquids a few days later, Spallanzani did not find any signs of life in them. From this he concluded that high temperatures destroyed all forms of living beings and that without them nothing living could arise.

A fierce dispute broke out between representatives of two opposing views. Spallanzani argued that the liquids in Needham's experiments were not sufficiently heated and embryos of living beings remained there. To this, Needham objected that it was not he who heated the liquids too little, but, on the contrary, Spallanzani heated them too much and with such a crude method destroyed the “generative power” of organic infusions, which is very capricious and fickle.

Thus, each of the disputants remained unconvinced, and the question of the spontaneous generation of microbes in rotting liquids was not resolved in either direction for a whole century. During this time, many attempts were made to experimentally prove or disprove spontaneous generation, but none of them led to definite results.

The question became more and more confused, and only in the half of the 19th century. it was finally resolved thanks to the brilliant research of the brilliant French scientist Pasteur.

LOUIS PASTER

Louis Pasteur took up the problem of the origin of life in 1860. By this time, he had already done a lot in the field of microbiology and managed to solve problems that threatened sericulture and winemaking. He also proved that bacteria are ubiquitous and that non-living materials can easily be contaminated by living things if they are not properly sterilized. Through a series of experiments, he showed that everywhere, and especially near human habitation, tiny embryos are floating in the air. They are so light that they float freely in the air, only very slowly and gradually falling to the ground.

As a result of a series of experiments based on Splanzani's methods, Pasteur proved the validity of the theory of biogenesis and finally refuted the theory of spontaneous generation.

Pasteur explained the mysterious appearance of microorganisms in the experiments of previous researchers either by incomplete sterilization of the environment, or by insufficient protection of liquids from the penetration of germs. If you thoroughly boil the contents of the flask and then protect it from germs that could get in with the air flowing into the flask, then in one hundred cases out of a hundred, rotting of the liquid and the formation of microbes will not occur.

To dehydrate the air flowing into the flask, Pasteur used a variety of techniques: he either calcined the air in glass and metal tubes, or protected the neck of the flask with a cotton plug, in which all the smallest particles suspended in the air are retained, or, finally, he passed the air through a thin glass tube , curved in the shape of the letter S - in this case, all the embryos were mechanically retained on the wet surfaces of the bends of the tube.

S-neck flasks used in Louis Pasteur's experiments:

A – in a flask with a curved neck, the broth remains transparent (sterile) for a long time; B – after removing the S-shaped neck, rapid growth of microorganisms is observed in the flask (the broth becomes cloudy).

Wherever the protection was sufficiently reliable, the appearance of microbes in the liquid was not observed. But maybe prolonged heating chemically changed the environment and made it unsuitable for supporting life? Pasteur easily refuted this objection too. He threw a cotton plug into the liquid, deprived of heat, through which air was passed and which, therefore, contained embryos - the liquid quickly rotted. Consequently, boiled infusions are quite suitable soil for the development of microbes. This development does not occur just because there is no embryo. As soon as the embryo enters the liquid, it immediately germinates and produces a lush harvest.

Pasteur's experiments showed beyond doubt that spontaneous generation of microbes does not occur in organic infusions. All living organisms develop from embryos, that is, they originate from other living beings. However, confirmation of the biogenesis theory gave rise to another problem. Since another living organism is necessary for the emergence of a living organism, then where did the very first living organism come from? Only the steady state theory does not require an answer to this question, and all other theories imply that at some stage in the history of life there was a transition from nonliving to living. So how did life begin on Earth?

4. THEORY OF PANSPERMIA.

Pasteur is rightly considered the father of the science of simple organisms - microbiology. Thanks to his work, an impetus was given to extensive research into the world of the smallest creatures that inhabit the earth, water and air, invisible to the naked eye. These studies were no longer aimed, as before, at merely describing the forms of microorganisms; bacteria, yeast, ciliates, amoebas, etc. were studied from the point of view of their living conditions, their nutrition, breathing, reproduction, from the point of view of the changes that they make in their environment, and, finally, from the point of view of their internal structure, their finest structure. The further these studies went, the more and more it was discovered that the simplest organisms are not at all as simple as previously thought.

The body of every organism - plant, snail, worm, fish, bird, animal, human - consists of tiny bubbles, visible only through a microscope. It is made up of these bubble-cells, just like a house is made up of bricks. Different organs of different animals and plants contain cells that differ from each other in appearance. Adapting to the work assigned to a given organ, the cells that make it up, one way or another, change, but in principle, all cells of all organisms are similar to each other. Microorganisms differ only in that their entire body consists of just one single cell. This fundamental similarity of all organisms confirms the now generally accepted idea in science that everything living on Earth is connected, so to speak, by blood. More complex organisms evolved from simpler ones, gradually changing and improving. Thus, one has only to explain to oneself the formation of some simple organism - and the origin of all animals and plants becomes clear.

But, as already mentioned, even the simplest, consisting of just one cell, are very complex formations. Their main component, the so-called protoplasm, is a semi-liquid, viscous gelatinous substance, saturated with water, but insoluble in water. The composition of protoplasm includes a number of extremely complex chemical compounds (mainly proteins and their derivatives), which are not found anywhere else, only in organisms. These substances are not just mixed, but are in a special, little-studied state, due to which protoplasm has the finest structure, difficult to distinguish even with a microscope, but extremely complex. The assumption that such a complex formation with a very specific fine organization could spontaneously arise within a few hours in structureless solutions, such as broths and infusions, is as wild as the assumption that frogs are formed from May dew or mice from grain.

The exceptional complexity of the structure of even the simplest organisms so amazed the minds of some scientists that they came to the conclusion that there was an impassable gap between living and nonliving things. The transition of the inanimate into the living, organized seemed to them absolutely impossible, either in the present or in the past. “The impossibility of spontaneous generation at any time,” says the famous English physicist W. Thomson, “should be considered as firmly established as the law of universal gravitation.”

But how then did life originate on Earth? After all, there was a time when the Earth, according to the now generally accepted view in science, was a white-hot ball. Data from astronomy, geology, mineralogy, and other exact sciences speak for this - this is certain. This means that conditions existed on Earth under which life was impossible and unthinkable. Only after the globe lost a significant part of its heat, dissipating it into cold interplanetary space, only after cooled water vapor formed the first thermal seas, did the existence of organisms like those that we now observe become possible. To clarify this contradiction, a theory was created that bears a rather complex name - the theory of panspermia (Greek panspermía - a mixture of all kinds of seeds, from pán - all, everyone and spérma - seed).

One of the first to express the idea of cosmic rudiments was in 1865 the German doctor G. E. Richter, who argued that life is eternal and its rudiments can be transferred from one planet to another. This hypothesis is closely related to the stationary state hypothesis. Based on the idea that small particles of solid matter (cosmozoans), separated from celestial bodies, are floating around everywhere in the cosmos, this author assumed that simultaneously with these particles, perhaps clinging to them, viable germs of microorganisms are flying around. Thus, these embryos can be transferred from one celestial body inhabited by organisms to another, where there is no life yet. If favorable living conditions have already been created on this latter, in the sense of suitable temperature and humidity, then the embryos begin to germinate, develop and subsequently become the ancestors of the entire organic world of a given planet.

This theory gained many supporters in the scientific world, among whom there were even such outstanding minds as G. Helmholtz, S. Arrhenius, J. Thomson, P. P. Lazarev and others. Its defenders sought mainly to scientifically substantiate the possibility of such a transfer embryos from one celestial body to another, which would preserve the viability of these embryos. Indeed, in fact, in the end, the main question is precisely whether a spore can make such a long and dangerous journey as flying from one world to another without dying, retaining the ability to germinate and develop into a new organism. Let us examine in detail what dangers are encountered on the path of the embryo.

First of all, this is the cold of interplanetary space (220° below zero). Having separated from its home planet, the embryo is doomed to float for many years, centuries and even millennia at such a terrifying temperature before a lucky chance gives it the opportunity to land on a new earth. One cannot help but doubt whether the embryo is capable of withstanding such a test. To solve this issue, we turned to the study of resistance to cold in modern spores. Experiments carried out in this direction have shown that germs of microorganisms tolerate cold excellently. They remain viable even after six months at 200° below zero. Of course, 6 months is not 1000 years, but experience still gives us the right to assume that at least some of the embryos can survive the terrible cold of interplanetary space.

A much greater danger for embryos is their complete lack of protection from light rays. Their path between planets is penetrated by the rays of the suns, destructive for most microbes. Some bacteria die from direct sunlight within a few hours, others are more resistant, but very strong lighting has an adverse effect on all microbes without exception. However, this unfavorable effect is significantly weakened in the absence of atmospheric oxygen, and we know that there is no air in interplanetary space, and therefore we can reasonably assume that the embryos of life will withstand this test.

But a lucky chance makes it possible for the embryo to fall into the sphere of gravity of a planet with conditions of temperature and humidity favorable for the development of life. The wanderer could only, obeying the force of gravity, fall to his new Earth. But just here, almost already in a peaceful harbor, a terrible danger awaits him. Previously, the embryo rushed in airless space, but now, before falling on the surface of the planet, it must fly through a rather thick layer of air that envelops this planet on all sides.

Everyone, of course, is well aware of the phenomenon of “falling stars” - meteors. Modern science explains this phenomenon as follows. Solid bodies and particles of various sizes are floating around in interplanetary space, possibly fragments of planets or comets that have flown into our solar system from the most distant places in the Universe. Flying close to the globe, they are attracted by this latter, but before falling on its surface, they must fly through the airy atmosphere. Due to friction with the air, a rapidly falling meteorite heats up to white heat and becomes visible in the dark vault of heaven. Only a few of the meteorites reach the earth; most burn up from intense heat while still far from its surface.

The embryos must suffer a similar fate. However, various considerations show that this kind of death is not necessary. There is reason to assume that at least some of the embryos that enter the atmosphere of a particular planet will reach its surface viable.

At the same time, we must not forget about those colossal astronomical periods of time during which the Earth could be seeded with embryos from other worlds. These intervals are calculated in millions of years! If during this time, out of many billions of embryos, at least one reached safely the surface of the Earth and found here conditions suitable for its development, then this would already be enough for the formation of the entire organic world. This possibility, given the current state of science, seems unlikely, but acceptable; in any case, we have no facts that would directly contradict it.

However, the theory of panspermia is an answer only to the question of the origin of earthly life, and not at all to the question of the origin of life in general, transferring the problem to another place in the Universe.

“One of two things,” says Helmholtz. “Organic life either ever began (originated) or exists forever.” If we admit the first, then the theory of panspermia loses all logical meaning, since if life could have originated anywhere in the Universe, then, based on the uniformity of the world, we have no reason to say that it could not have originated on Earth. Therefore, supporters of the theory under consideration accept the position of the eternity of life. They admit that “life only changes its form, but is never created from dead matter.”

In the late 60s, the popularity of this theory resumed. This was due to the fact that during the study of meteorites and comets, many “precursors of living things” were discovered - organic compounds, hydrocyanic acid, water, formaldehyde, cyanogens. In 1975, amino acid precursors were found in lunar soil and meteorites. Proponents of panspermia consider them "seeds sown on Earth." In 1992, works by American scientists appeared, where, based on a study of material collected in Antarctica, they describe the presence in meteorites of the remains of living creatures resembling bacteria.

Modern adherents of the concept of panspermia (including Nobel Prize winner English biophysicist F. Crick) believe that life was brought to Earth either accidentally or intentionally by space aliens using aircraft. Proof of this is the repeated appearances of UFOs, rock paintings of objects similar to spaceports, as well as reports of encounters with aliens.

The panspermia hypothesis is supported by the point of view of astronomers Ch. Wickramasinghe (Sri Lanka) and F. Hoyle (Great Britain). They believe that microorganisms are present in large numbers in outer space, mainly in gas and dust clouds. Next, these microorganisms are captured by comets, which then, passing near the planets, “sow the germs of life.”

Other scientists have expressed the idea of transferring “spores of life” to Earth by light (under the pressure of light).

In general, interest in the theory of panspermia has not waned to this day.

5. THEORY OF A.I. OPARIN.

The first scientific theory regarding the origin of living organisms on Earth was created by the Soviet biochemist A. I. Oparin (born 1894). In 1924, he published works in which he outlined ideas about how life on Earth could have arisen. According to this theory, life arose in the specific conditions of the ancient Earth and is considered by Oparin as a natural result of the chemical evolution of carbon compounds in the Universe.

According to Oparin, the process that led to the emergence of life on Earth can be divided into three stages:

1. The emergence of organic substances.

2. Formation of biopolymers (proteins, nucleic acids, polysaccharides, lipids, etc.) from simpler organic substances.

3. The emergence of primitive self-reproducing organisms.

The theory of biochemical evolution has the largest number of supporters among modern scientists. The earth originated about five billion years ago; Initially, its surface temperature was very high (4000 - 80000C). As it cooled, a solid surface (the earth's crust - lithosphere) formed. The atmosphere, originally consisting of light gases (hydrogen, helium), could not be effectively contained by the insufficiently dense Earth, and these gases were replaced by heavier ones: water vapor, carbon dioxide, ammonia and methane. When the Earth's temperature dropped below 1000C, water vapor began to condense, forming the world's oceans. At this time, in accordance with the ideas of A.I. Oparin, abiogenic synthesis took place, that is, in the original earth’s oceans, saturated with various simple chemical compounds, “in the primary broth” under the influence of volcanic heat, lightning discharges, intense ultraviolet radiation and other factors environment began the synthesis of more complex organic compounds, and then biopolymers. The formation of organic substances was facilitated by the absence of living organisms - consumers of organic matter - and the main... oxidizing agent... -... oxygen. Complex amino acid molecules randomly combined into peptides, which in turn created the original proteins. From these proteins, primary living beings of microscopic size were synthesized.

The most difficult problem in the modern theory of evolution is the transformation of complex organic substances into simple living organisms. Oparin believed that the decisive role in the transformation of non-living things into living things belongs to proteins. Apparently, protein molecules, attracting water molecules, formed colloidal hydrophilic complexes. Further fusion of such complexes with each other led to the separation of colloids from the aqueous medium (coacervation). At the boundary between the coacervate (from the Latin coacervus - clot, heap) and the environment, lipid molecules were built - a primitive cell membrane. It is assumed that colloids could exchange molecules with the environment (a prototype of heterotrophic nutrition) and accumulate certain substances. Another type of molecule provided the ability to reproduce itself.

A. I. Oparin’s system of views was called the “coacervate hypothesis.”

6. MODERN VIEWS ON THE ORIGIN OF LIFE ON EARTH.

The theory of A.I. Oparin and other similar hypotheses have one significant drawback: there is not a single fact that would confirm the possibility of abiogenic synthesis on Earth of even the simplest living organism from lifeless compounds. Thousands of attempts at such synthesis have been carried out in numerous laboratories around the world. For example, the American scientist S. Miller, based on assumptions regarding the composition of the Earth's primary atmosphere, passed electrical discharges through a mixture of methane, ammonia, hydrogen and water vapor in a special device. He managed to obtain molecules of amino acids - those basic “building blocks” that make up the basis of life - proteins. These experiments were repeated many times, and some scientists managed to obtain fairly long chains of peptides (simple proteins). But only! No one has been lucky enough to synthesize even the simplest living organism. Nowadays, Redi’s principle is popular among scientists: “Living things come only from living things.”

But let's assume that such attempts will one day be crowned with success. What will such an experience prove? Only that the synthesis of life requires the human mind, complex, developed science and modern technology. None of this existed on the original Earth. Moreover, the synthesis of complex organic compounds from simple ones contradicts the second law of thermodynamics, which prohibits the transition of material systems from a state of greater probability to a state of lesser probability, and the development from simple organic compounds to complex ones, then from bacteria to humans, occurred precisely in this direction. Here we observe nothing more than a creative process. The second law of thermodynamics is an immutable law, the only law that has never been questioned, violated or refuted. Therefore, order (gene information) cannot spontaneously arise from the disorder of random processes, which is confirmed by the theory of probability.

Recently, mathematical research has dealt a crushing blow to the hypothesis of abiogenic synthesis. Mathematicians have calculated that the probability of spontaneous generation of a living organism from lifeless blocks is practically zero. Thus, L. Blumenfeld proved that the probability of the random formation of at least one DNA molecule (deoxyribonucleic acid - one of the most important components of the genetic code) during the entire existence of the Earth is 1/10800. Think about the negligible magnitude of this number! After all, in its denominator there is a figure where after one there is a row of 800 zeros, and this number is an incredible number of times greater than the total number of all atoms in the Universe. Contemporary American astrophysicist C. Wickramasinghe expressed the impossibility of abiogenic synthesis in the following way: “It’s faster for a hurricane that sweeps over an old airplane cemetery to assemble a brand new superliner from pieces of scrap than for life to emerge from its components as a result of a random process.”

The theories of abiogenic synthesis and geological data contradict. No matter how far we penetrate into the depths of geological history, we find no traces of the “Azoic era,” that is, the period when life did not exist on Earth.

Now paleontologists have found fossil remains of quite complexly organized creatures - bacteria, blue-green algae, simple fungi. V. Vernadsky was sure that life is geologically eternal, that is, in geological history there was no era when our planet was lifeless. “The problem of abiogenesis (spontaneous generation of living organisms),” the scientist wrote in 1938, “remains fruitless and paralyzes truly urgent scientific work.”

The terrestrial form of life is extremely closely related to the hydrosphere. This is evidenced by the fact that water is the main part of the mass of any terrestrial organism (a person, for example, consists of more than 70% water, and organisms such as jellyfish - 97-98%). It is obvious that life on Earth formed only when the hydrosphere appeared on it, and this, according to geological data, happened almost from the beginning of the existence of our planet. Many of the properties of living organisms are determined precisely by the properties of water, but water itself is a phenomenal compound. Thus, according to P. Privalov, water is a cooperative system in which any action spreads in a “relay race” way over thousands of interatomic distances, that is, “long-range action” takes place.

Some scientists believe that the entire hydrosphere of the Earth is, in essence, one giant “molecule” of water. It has been established that water can be activated by natural electromagnetic fields of terrestrial and cosmic origin (in particular artificial). The recent discovery by French scientists of the “memory of water” was extremely interesting. Perhaps the fact that the Earth's biosphere is a single superorganism is due to these properties of water? After all, all organisms are components, “drops” of this supermolecule of earthly water.

Although we still know only terrestrial protein-nucleic acid-water life, this does not mean that other forms cannot exist in the boundless Cosmos. Some scientists, in particular American ones, G. Feinberg and R. Shapiro, model the following hypothetically possible options:

plasmoids - life in stellar atmospheres due to magnetic forces associated with groups of moving electric charges;

radiobs - life in interstellar clouds based on aggregates of atoms that are in different states of excitation;

Lavobs - life based on silicon compounds, which can exist in lakes of molten lava on very hot planets;

water sparrows - life that can exist at low temperatures on planets covered with “reservoirs” of liquid methane, and draw energy from the transformation of orthohydrogen to parahydrogen;

Thermophages are a type of space life that obtains energy from the temperature gradient in the atmosphere or oceans of planets.

Of course, such exotic life forms currently exist only in the imagination of scientists and science fiction writers. However, the possibility of the real existence of some of them, in particular plasmoids, cannot be ruled out. There is some reason to believe that on Earth, in parallel with “our” form of life, there is another type of life, similar to the mentioned plasmoids. These include some types of UFOs (unidentified flying objects), formations similar to ball lightning, as well as energy “clumps” flying in the atmosphere invisible to the eye, but recorded by color photographic film, which in some cases exhibited intelligent behavior.

Thus, there is now reason to assert that life on Earth appeared from the very beginning of its existence and arose, in the words of Ch. Wickramasinghe, “from an all-pervasive pan-galactic living system.”

CONCLUSION.

Do we have a logical right to recognize the fundamental difference between living and nonliving? Are there facts in the nature around us that convince us that life exists forever and has so little in common with inanimate nature that under no circumstances could it ever be formed or separated from it? Can we recognize organisms as entities completely, fundamentally different from the rest of the world?

Biology of the XX century. deepened the understanding of the essential features of living things, revealing the molecular basis of life. The modern biological picture of the world is based on the idea that the living world is a grandiose System of highly organized systems.

Undoubtedly, new knowledge will be included in models of the origin of life, and it will become increasingly valid. But the more qualitatively the new differs from the old, the more difficult it is to explain its emergence.

After reviewing the main theories of the origin of life on Earth, the theory of creation seemed to me personally the most likely. The Bible states that God created everything out of nothing. Surprisingly, modern science admits that everything could have been created out of nothing. “Nothing” in scientific terminology is called a vacuum. Vacuum, which is the physics of the 19th century. considered emptiness, according to modern scientific concepts it is a unique form of matter, capable of “giving birth” to material particles under certain conditions. Modern quantum mechanics allows that the vacuum can come into an “excited state”, as a result of which a field can form in it, and from it - matter.

LITERATURE.

1. Bernal D. “The Emergence of Life” Appendix No. 1: Oparin A.I. "The Origin of Life". - M.: "Mir", 1969.

2. Vernadsky V.I. Living matter. - M., 1978.

3. Naydysh V. M. Concepts of modern natural science. – M., 1999.

4. General biology./ Ed. N. D. Lisova. – Mn., 1999.

5. Ponnamperuma S. “The Origin of Life.” - M.: "Mir", 1977.

6. Smirnov I.N., Titov V.F. Philosophy. Textbook for students of higher educational institutions. - M.: Russian Economic Academy named after. Plekhanov, 1998.

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Currently, there are several concepts regarding the origin of life on earth. Let us dwell only on some of the main theories that help to form a fairly complete picture of this complex process.

Creationism (Latin sgea - creation).

According to this concept, life and all species of living beings inhabiting the Earth are the result of a creative act of a supreme being at some specific time.

The main principles of creationism are set out in the Bible, in the Book of Genesis. The process of divine creation of the world is conceived as having taken place only once and therefore inaccessible to observation.

This is enough to take the entire concept of divine creation beyond the scope of scientific research. Science deals only with those phenomena that can be observed, and therefore it will never be able to either prove or disprove the concept.

Spontaneous(spontaneous) generation.

The ideas of the origin of living beings from inanimate matter were widespread in Ancient China, Babylon, and Egypt. The greatest philosopher of Ancient Greece, Aristotle, expressed the idea that certain “particles” of a substance contain a certain “active principle”, which, under suitable conditions, can create a living organism.

Van Helmont (1579–1644), a Dutch physician and natural philosopher, described an experiment in which he allegedly created mice in three weeks. All you needed was a dirty shirt, a dark closet and a handful of wheat. Van Helmont considered human sweat to be the active principle in the process of mouse generation.

In the 17th-18th centuries, thanks to advances in the study of lower organisms, fertilization and development of animals, as well as the observations and experiments of the Italian naturalist F. Redi (1626-1697), the Dutch microscopist A. Leeuwenhoek (1632-1723), and the Italian scientist L. Spallanzani ( 1729-1799), Russian microscopist M. M. Terekhovsky (1740-1796) and others, the belief in spontaneous generation was thoroughly undermined.

However, until the appearance of the works of the founder of microbiology, Louis Pasteur, in the middle of the 10th century, this teaching continued to find adherents.

The development of the idea of spontaneous generation essentially dates back to the era when religious ideas dominated the public consciousness.

Those philosophers and naturalists who did not want to accept the church teaching about the “creation of life,” at the then level of knowledge, easily came to the idea of its spontaneous generation.

To the extent that, in contrast to the belief in creation, the idea of the natural origin of organisms was emphasized, the idea of spontaneous generation had at a certain stage a progressive meaning. Therefore, the Church and theologians often opposed this idea.

Panspermia hypothesis.

According to this hypothesis, proposed in 1865. by the German scientist G. Richter and finally formulated by the Swedish scientist Arrhenius in 1895, life could have been brought to Earth from space.

Living organisms of extraterrestrial origin are most likely to enter with meteorites and cosmic dust. This assumption is based on data on the high resistance of some organisms and their spores to radiation, high vacuum, low temperatures and other influences.

However, there are still no reliable facts confirming the extraterrestrial origin of microorganisms found in meteorites.

But even if they got to Earth and gave rise to life on our planet, the question of the original origin of life would remain unanswered.

Hypothesis biochemical evolution.

In 1924, the biochemist A.I. Oparin, and later the English scientist J. Haldane (1929), formulated a hypothesis that considered life as the result of a long evolution of carbon compounds.

The modern theory of the origin of life on Earth, called the theory of biopoiesis, was formulated in 1947 by the English scientist J. Bernal.

Currently, the process of life formation is conventionally divided into four stages:

1. Synthesis of low molecular weight organic compounds (biological monomers) from gases of the primary atmosphere.
2. Formation of biological polymers.
3. Formation of phase-separated systems of organic substances, separated from the external environment by membranes (protobionts).
4. The emergence of the simplest cells with the properties of living things, including a reproductive apparatus that ensures the transfer of the properties of parent cells to daughter cells.

The first three stages belong to the period of chemical evolution, and from the fourth, biological evolution begins.

Let us consider in more detail the processes as a result of which life could arise on Earth. According to modern ideas, the Earth was formed about 4.6 billion years ago. The temperature of its surface was very high (4000-8000 ° C), and as the planet cooled and gravitational forces acted, the earth's crust was formed from compounds of various elements.

Degassing processes led to the creation of an atmosphere enriched, possibly, with nitrogen, ammonia, water vapor, carbon dioxide and carbon monoxide. Such an atmosphere was apparently reducing, as evidenced by the presence in the most ancient rocks of the Earth of metals in a reduced form, such as, for example, divalent iron.

It is important to note that in the atmosphere there were atoms of hydrogen, carbon, oxygen and nitrogen, constituting 99% of the atoms included in the soft tissues of any living organism.

However, for atoms to turn into complex molecules, simple collisions were not enough. Additional energy was needed, which was available on Earth as a result of volcanic activity, electrical lightning discharges, radioactivity, and ultraviolet radiation from the Sun.

The absence of free oxygen was probably not a sufficient condition for the emergence of life. If free oxygen were present on Earth in the prebiotic period, then, on the one hand, it would oxidize synthesized organic substances, and on the other, forming the ozone layer in the upper atmosphere, it would absorb high-energy ultraviolet radiation from the Sun.

During the considered period of the origin of life, which lasted approximately 1000 million years, ultraviolet radiation was probably the main source of energy for the synthesis of organic substances.

Oparin A.I.

From hydrogen, nitrogen and carbon compounds, in the presence of free energy on Earth, simple molecules (ammonia, methane and similar simple compounds) should first have arisen.

Subsequently, these simple molecules in the primary ocean could react with each other and with other substances, forming new compounds.

In 1953, American researcher Stanley Miller, in a series of experiments, simulated the conditions that existed on Earth approximately 4 billion years ago.

By passing electrical discharges through a mixture of ammonia, methane, hydrogen and water vapor, he obtained a number of amino acids, aldehydes, lactic, acetic and other organic acids. American biochemist Cyril Ponnaperuma achieved the formation of nucleotides and ATP. During these and similar reactions, the waters of the primary ocean could be saturated with various substances, forming the so-called “primary broth.”

The second stage consisted of further transformations of organic substances and the abiogenic formation of more complex organic compounds, including biological polymers.

The American chemist S. Fox prepared mixtures of amino acids, subjected them to heat and obtained protein-like substances. On primitive earth, protein synthesis could take place on the surface of the earth's crust. In small depressions in the solidifying lava, reservoirs appeared containing small molecules dissolved in water, including amino acids.

When the water evaporated or splashed onto the hot rocks, the amino acids reacted to form protenoids. Then the rains washed the protenoids into the water. If some of these protenoids had catalytic activity, then the synthesis of polymers, that is, protein-like molecules, could begin.

The third stage was characterized by the release in the primary “nutrient broth” of special coacervate droplets, which are groups of polymer compounds. It has been shown in a number of experiments that the formation of coacervate suspensions, or microspheres, is typical for many biological polymers in solution.

Coacervate drops have some properties characteristic of living protoplasm, such as, for example, selectively adsorbing substances from the surrounding solution and, due to this, “grow” and increase their size.

Due to the fact that the concentration of substances in coacervate droplets was tens of times greater than in the surrounding solution, the possibility of interaction between individual molecules increased significantly.

It is known that the molecules of many substances, in particular polypeptides and fats, consist of parts that have different relationships to water. The hydrophilic parts of the molecules located at the boundary between the coacervates and the solution turn towards the solution, where the water content is higher.

The hydrophobic parts are oriented inside the coacervates, where the water concentration is lower. As a result, the surface of the coacervates acquires a certain structure and, in connection with this, the ability to allow certain substances to pass through in a certain direction and not others.

Due to this property, the concentration of some substances inside the coacervates increases even more, while the concentration of others decreases, and the reactions between the components of the coacervates acquire a certain direction. Coacervate droplets become systems isolated from the environment. Protocells or protobionts arise.

An important stage in chemical evolution was the formation of a membrane structure. In parallel with the appearance of the membrane, there was an ordering and improvement of metabolism. In the further complication of metabolism in such systems, catalysts were to play a significant role.

One of the main characteristics of living things is the ability to replicate, that is, to create copies that are indistinguishable from the parent molecules. This property is possessed by nucleic acids, which, unlike proteins, are capable of replication.

A protenoid capable of catalyzing the polymerization of nucleotides with the formation of short RNA chains could be formed in coacervates. These chains could serve as both a primitive gene and messenger RNA. Neither DNA, nor ribosomes, nor transfer RNAs, nor protein synthesis enzymes have yet participated in this process. They all appeared later.

Already at the stage of formation of protobionts, natural selection probably took place, i.e., the preservation of some forms and the elimination (death) of others. Thus, progressive changes in the structure of protobionts were fixed due to selection.

The appearance of structures capable of self-reproduction, replication, and variability apparently determines the fourth stage in the formation of life.

So, in the late Archean (approximately 3.5 billion years ago), at the bottom of small reservoirs or shallow, warm and nutrient-rich seas, the first primitive living organisms arose, which were heterotrophic in their type of nutrition, i.e., they fed on ready-made organic substances, synthesized during chemical evolution.

Their method of metabolism was probably fermentation, a process of enzymatic transformation of organic substances in which other organic substances serve as electron acceptors.

Part of the energy released in these processes is stored in the form of ATP. It is possible that some organisms also used the energy of redox reactions for life processes, i.e. they were chemosynthetics.

Over time, the reserves of free organic matter in the environment decreased and organisms capable of synthesizing organic compounds from inorganic ones gained an advantage.

In this way, probably about 2 billion years ago, the first phototrophic organisms such as cyanobacteria arose, capable of using light energy to synthesize organic compounds from CO2 and H2O, releasing free oxygen.

The transition to autotrophic nutrition was of great importance for the evolution of life on Earth, not only from the point of view of creating reserves of organic matter, but also for saturating the atmosphere with oxygen. At the same time, the atmosphere began to acquire an oxidizing character.

The appearance of the ozone screen protected primary organisms from the harmful effects of ultraviolet rays and put an end to the abiogenic (non-biological) synthesis of organic substances.

These are modern scientific ideas about the main stages of the origin and formation of life on Earth.

A visual diagram of the development of life on Earth (clickable)

Addition:

The wonderful world of “black smokers”

In science, it has long been believed that living organisms can exist only from the energy of the Sun. Jules Verne, in his novel Journey to the Center of the Earth, described an underground world with dinosaurs and ancient plants. However, this is fiction. But who would have thought that there would be a world isolated from the energy of the Sun with absolutely different living organisms. And he was found at the bottom of the Pacific Ocean.

Back in the fifties of the twentieth century, it was believed that life could not exist in the ocean depths. The invention of the bathyscaphe by Auguste Piccard dispelled these doubts.

His son, Jacques Picard, together with Don Walsh, descended in the bathyscaphe Trieste into the Mariana Trench to a depth of over ten thousand meters. At the very bottom, the dive participants saw live fish.

After this, oceanographic expeditions from many countries began to comb the ocean abyss with deep-sea nets and discover new species of animals, families, orders and even classes!

Bathyscaphe diving has improved. Jacques-Yves Cousteau and scientists from many countries made expensive dives to the bottom of the oceans.
In the 70s, a discovery was made that changed many scientists' ideas. Near the Galapagos Islands, faults were discovered at a depth of two to four thousand meters.
And at the bottom, small volcanoes were discovered - hydrotherms. Sea water, falling into fractures in the earth's crust, evaporated along with various minerals through small volcanoes up to 40 meters high.
These volcanoes were called “black smokers” because the water coming out of them was black.

However, the most incredible thing is that in such water, filled with hydrogen sulfide, heavy metals and various toxic substances, vibrant life flourishes.

The temperature of the water coming out of the black smokers reaches 300° C. The sun's rays do not penetrate to a depth of four thousand meters, and, therefore, there cannot be rich life here.
Even in shallower depths, benthic organisms are very rarely found, let alone in deep abysses. There, animals feed on organic debris that falls from above. And the greater the depth, the less poor the bottom life.
Chemoautotrophic bacteria were found on the surfaces of black smokers, which break down sulfur compounds erupted from the depths of the planet. Bacteria cover the bottom surface with a continuous layer and live in aggressive conditions.
They became food for many other animal species. In total, about 500 species of animals living in the extreme conditions of “black smokers” have been described.

Another discovery was vestimentifera, which belongs to the class of bizarre animals - pogonophora.

These are small tubes from which long tubes with tentacles protrude at the ends. The unusual thing about these animals is that they do not have a digestive system! They entered into symbiosis with bacteria. Inside the vestimentifera there is an organ - the trophosome, where many sulfur bacteria live.

Bacteria receive hydrogen sulfide and carbon dioxide for life; the excess of reproducing bacteria is eaten by the vestimentifera itself. In addition, bivalve mollusks of the genera Calyptogena and Bathymodiolus were found nearby, which also entered into symbiosis with bacteria and ceased to depend on searching for food.

One of the most unusual creatures of the deep-sea hydrothermal world is the Alvinella pompeian worm.

They are named because of the analogy with the eruption of the Pompeii volcano - these creatures live in a zone of hot water reaching 50 ° C, and ash from sulfur particles constantly falls on them. Worms, together with vestimentifera, form real “gardens” that provide food and shelter for many organisms.

Among the colonies of vestimentifera and pompeii worms live crabs and decapods that feed on them. Also among these “gardens” there are octopuses and fish from the eelpout family. The world of black smokers also harbored long-extinct animals that were driven out of other parts of the ocean, such as the Neolepas barnacles.

These animals were widespread 250 million years ago, but then became extinct. Here representatives of barnacles feel calm.

The discovery of black smoker ecosystems has become the most significant event in biology. Such ecosystems have been discovered in different parts of the World Ocean and even at the bottom of Lake Baikal.

Pompeian worm. Photo: life-grind-style.blogspot.com

The question of the origin of life is one of the most difficult questions in modern natural science. However, great interest was attracted to him at all times. The difficulty in obtaining an answer to this question is that it is difficult to accurately reproduce the processes and phenomena that occurred in the Universe billions of years ago. At the same time, the current diversity of forms and manifestations of life on Earth attracts the closest attention to this problem. Today, the following main hypotheses of the origin of life are distinguished.

Creationism

According to this hypothesis, life and all species of living beings inhabiting the Earth were created by God. Moreover, the divine creation of the world occurred simultaneously, so the process of creating life itself is not accessible to observation in time. In addition, creationism does not provide a clear interpretation of the origin of God the Creator himself and therefore has the character of a postulate. The famous Swedish naturalist K. Linnaeus, as well as the outstanding Russian chemist M.V. Lomonosov, supported this dogma of the origin of life.

Spontaneous generation hypothesis

This hypothesis is a variation abiogenesis- the origin of life from nonliving matter. This hypothesis was an alternative to creationism, when the accumulated knowledge of people about living nature questioned the creation of life by God. Philosophers of Ancient Greece and naturalists of medieval Europe believed in the emergence of living organisms from inanimate matter. They believed and tried to prove that frogs and insects breed in damp soil, flies in rotten meat, etc. Views about the spontaneous origin of life were widespread almost until the end of the 18th century. Only in the middle of the 19th century. French scientist Louis Pasteur proved that bacteria are ubiquitous. Moreover, any non-living objects become “infected” with them if sterilization is not carried out. Thus, Pasteur confirmed the theory biogenesis- Life can only arise from a previous life. The scientist finally refuted the concept of the spontaneous origin of life.

Panspermia hypothesis

In 1865, the German scientist G. Richter proposed a hypothesis panspermia, according to which life could have been brought to Earth from space along with meteorites and cosmic dust. A supporter of this hypothesis was the great Russian scientist, creator of the modern doctrine of the biosphere, V. I. Vernadsky. Modern research confirms the high resistance of some microorganisms and their spores to radiation and low temperatures. Recently there have been reports that traces of organic matter have been found in meteorites. When studying the closest planet to Earth, Mars, structures similar to bacteria and traces of water were found. However, these findings do not answer the question of the origin of life.

Biochemical hypothesis of the origin of life is the most common at present. This hypothesis was proposed in the 20s. last century, Russian biochemist A.I. Oparin and English biologist J. Haldane. It formed the basis of scientific ideas about the origin of life.

The essence of this hypothesis is that in the early stages of the development of the Earth there was a long period of abiogenesis. Living organisms did not take part in it. For the synthesis of organic compounds, the energy source was ultraviolet radiation from the Sun. Solar radiation was not retained by the ozone layer because there was no ozone or oxygen in the atmosphere of the ancient Earth. Synthesized amino acids, sugars and other organic compounds were stored in the ancient ocean for tens of millions of years. Their accumulation eventually led to the formation of a homogeneous mass, which Oparin called the “primary broth.” According to Oparin, it was in the “primordial broth” that life arose.

Oparin believed that the decisive role in the transformation of non-living things into living things belongs to proteins. It is proteins that are capable of forming colloidal complexes that attract water molecules. Such complexes, merging with each other, formed coacervates- structures isolated from the rest of the water mass.

Coacervates had some properties of life. They could selectively absorb substances from the surrounding solution and increase in size - a certain semblance of nutrition and growth. When the coacervates were crushed, new droplets were formed that retained the basic properties of the original formation - semblance of reproduction. But to transform into the first living organisms, coacervates lacked biological membranes and genetic information to ensure reproduction.

The next step in the origin of life was the appearance of membranes. They could be formed from lipid films covering the surface of water bodies. Next, proteins dissolved in water were added to such lipid formations. As a result, the surface of the coacervates acquired the structure and properties of a biological membrane. Such a membrane could already allow some substances to pass through and not others.

Further combination of coacervates with nucleic acids led to the formation of self-regulating and self-reproducing first living organisms - protobionts. These primitive primary organisms were anaerobes and heterotrophs that fed on substances from the “primordial broth.” Thus, after 1 billion years, according to this hypothesis, the origin of life on Earth was completed.

Currently, the following main hypotheses of the origin of life are distinguished: the hypotheses of creationism, spontaneous generation, panspermia and biochemical. Among modern views of scientists on the origin of life, the biochemical hypothesis occupies the most important place. According to it, life on Earth arose over a long period of time in the absence of oxygen in the presence of chemicals and a constant source of energy.