Do you know the origin of life?
3. What is the basic principle of the scientific method?

The problem of the origin of life on our planet is one of the central ones in modern natural science. Since ancient times, people have tried to find the answer to this question.

Creationism (lat, sgeatio - creation).

At different times, different peoples had their own ideas about the origin of life. They are reflected in the sacred books of various religions, which explain the emergence of life as an act of the Creator (the will of God). The hypothesis of the divine origin of living things can only be accepted on faith, since it cannot be experimentally verified or refuted. Therefore, it cannot be considered scientific points of view.

The hypothesis of spontaneous origin of life.

From ancient times to the middle of the 17th century. scientists did not doubt the possibility of spontaneous generation of life. It was believed that living beings can appear from inanimate matter, for example, fish - from silt, worms - from soil, mice - from rags, flies - from rotten meat, and also that some forms can give rise to others, for example, animals can form from fruits (see, p. 343).

So, the great Aristotle, studying eels, found that among them there are no individuals with caviar or milk. Based on this, he suggested that eels are born from "sausages" of silt, formed from the friction of an adult fish against the bottom.

The first blow to the idea of ​​spontaneous generation was caused by the experiments of the Italian scientist Francesc Redi, who in 1668 proved the impossibility of spontaneous generation of flies in rotting meat.

Despite this, the ideas of spontaneous generation of life persisted until the middle of the 19th century. Only in 1862 did the French scientist Louis Pasteur finally disprove the hypothesis of spontaneous generation of life.

The works of the Master made it possible to assert that the principle "All living things - from living things" is true for all known organisms on our planet, but they did not resolve the question of the origin of life.

Panspermia hypothesis.

Proof of the impossibility of spontaneous generation of life gave rise to another problem. If another living organism is needed for the emergence of a living organism, then where did the first living organism come from? This gave impetus to the emergence of the panspermia hypothesis, which had and has many supporters, including among prominent scientists. They believe that for the first time life did not originate on Earth, but was somehow introduced to our planet.

However, the panspermia hypothesis only attempts to explain the emergence of life on Earth. It does not answer the question of how life began.

The denial of the fact of spontaneous generation of life at the present time does not contradict the ideas about the fundamental possibility of the development of life in the past from inorganic matter.

The hypothesis of biochemical evolution.

In the 1920s, the Russian scientist A. I. Oparin and the Englishman J. Haldane put forward a hypothesis about the origin of life in the process of biochemical evolution carbon compounds, which formed the basis of modern ideas.

In 1924, AI Oparin published the main provisions of his hypothesis of the origin of life on Earth. He proceeded from the fact that in modern conditions the emergence of living beings from inanimate nature is impossible. Abiogenic (i.e., without the participation of living organisms) the emergence of living matter was possible only in the conditions of the ancient atmosphere and the absence of living organisms.

According to A. I. Oparin, in the primary atmosphere of the planet, saturated with various gases, with powerful electrical discharges, as well as under the influence of ultraviolet radiation (there was no oxygen in the atmosphere and, therefore, there was no protective ozone screen, the atmosphere was reducing) and high radiation organic compounds could be formed that accumulated in the ocean, forming a "primordial soup".

It is known that in concentrated solutions of organic substances (proteins, nucleic acids, lipids) under certain conditions, clots called coacervate drops, or coacervates, can form. Coacervates did not break down in a reducing atmosphere. From the solution, they received chemicals, they synthesized new compounds, as a result of which they grew and became more complex.

Coacervates already resembled living organisms, but they were not yet such, since they did not have an ordered internal structure inherent in living organisms, and were not able to reproduce. Protein coacervates were considered by A.I., Oparin as probionts - the precursors of a living organism. He assumed that at a certain stage, protein probionts included nucleic acids, creating single complexes.
The interaction of proteins and nucleic acids has led to the emergence of such living properties as self-reproduction, the preservation of hereditary information and its transmission to subsequent generations.
Probionts, in which metabolism was combined with the ability to reproduce themselves, can already be considered as primitive procells.

In 1929, the English scientist J. Haldane also put forward the hypothesis of the abiogenic origin of life, but according to his views, the primary was not a coarcervate system capable of exchanging substances with the environment, but a macromolecular system capable of self-reproduction. In other words, A. I. Oparin gave priority to proteins, and J. Haldane - to nucleic acids.

The Oparin-Holdein hypothesis won many supporters, as it received experimental confirmation of the possibility of abiogenic synthesis of organic biopolymers.

In 1953, the American scientist Stanley Miller, in the installation he created (Fig. 141), simulated the conditions that presumably existed in the Earth's primary atmosphere. As a result of the experiments, amino acids were obtained. Similar experiments were repeated many times in various laboratories and made it possible to prove the fundamental possibility of synthesizing practically all monomers of the main biopolymers under such conditions. Subsequently, it was found that, under certain conditions, it is possible to synthesize more complex organic biopolymers from monomers: polypeptides, polynucleotides, polysaccharides, and lipids.

But the Oparin-Haldane hypothesis also has a weak side, which is pointed out by its opponents. This hypothesis fails to explain main problem: how the qualitative leap from non-living to living took place. Indeed, for the self-reproduction of nucleic acids, enzyme proteins are needed, and for the synthesis of proteins, nucleic acids.

Creationism. Spontaneous generation. Panspermia hypothesis. The hypothesis of biochemical evolution. Coacervates. Probionts.

1. Why can the notion of the divine origin of life be neither confirmed nor refuted?
2. What are the main provisions of the Oparin-Haldane hypothesis?
3. What experimental evidence can be given in favor of this hypothesis?
4. What is the difference between the hypothesis of A. I. Oparin and the hypothesis of J. Haldane?
5. What arguments do opponents give when criticizing the Oparin-Haldane hypothesis?

Give possible arguments "for" and "against" the hypothesis of panspermia.

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

Confirm or refute this statement of Charles Darwin.

In understanding the essence of life and its origin in the culture of human civilization, there have long been two ideas - biogenesis and abiogenesis. The idea of ​​biogenesis (the origin of living things from living things) comes from ancient Eastern religious constructions, for which the idea of ​​the absence of the beginning and end of natural phenomena was common. Reality eternal life for these cultures is logically acceptable, as well as the eternity of matter, the Cosmos.
An alternative idea - abiogenesis (the origin of life from non-life) goes back to civilizations that existed long before our era in the valleys of the Tigris and Euphrates rivers. This area was subject to constant flooding, and it is not surprising that it became the birthplace of catastrophism, which influenced European civilization through Judaism and Christianity. Catastrophes, as it were, interrupt the connection, the chain of generations, suggest its creation, reappearance. In this regard, the belief in the periodic spontaneous generation of an organism under the influence of natural or supernatural causes was widespread in European culture.

Kamensky A. A., Kriksunov E. V., Pasechnik V. V. Biology Grade 10
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Life is the greatest miracle that only 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.

Until now, researchers are arguing about how this happened. Oddly enough, philosophy has made a significant contribution to the study of this phenomenon: this science allows you to draw the right conclusions by summarizing huge amounts of information. What versions are guided by scientists all over 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.
• Steady state principle.
• Panspermia, whose proponents claim the natural "productivity" of any planet where the right conditions exist. In particular, this idea was once developed by the notorious academician Vernadsky.
• Biochemical evolution according to A. I. Oparin.

Let us consider all these theories of the origin of life on Earth in somewhat 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, suggested 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, which provided for Divine intervention in the creation of all things, were 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 first organic compounds and life from inorganic substances. Their version is based on the complexity or impossibility of understanding the processes that resulted in life in its modern form. Interesting but modern church this hypothesis is only partially supported. From the point of view of the figures most friendly to scientists, it is really impossible to understand the main Intention 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.

At the present time, the point of view of the materialists 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 met as early as the beginning of the 19th century.

Proponents of this concept argued that there are certain laws of natural nature that determine the possibility of an arbitrary transition of inorganic compounds into organic ones, followed by the 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 by some "specialists" seriously ... It's good at least what they say about bacteria and viruses.

Of course, the fallacy of this approach was subsequently proved, 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 proved by Louis Pasteur. For this, the scientist even received a considerable award from the French Academy of Sciences. Soon on foreground the main theories of the origin of life on Earth are put forward, 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 Russian researcher, Academician Oparin, back in 1924. He refuted Redi's principle, which spoke of the possibility of only a 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 biochemical process, the raw materials for which are ordinary 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 stone in the depths of space, the process of non-biological synthesis of carbon compounds was already going on on its surface. During this period, volcanoes threw out a titanic amount of lava and hot gases. Cooling in the primary atmosphere, the gases turned into clouds, from which it rained 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 primordial oceans, the waters of which were extremely saturated with salts. The first organic compounds also got there, the formation of which took place in the atmosphere under the influence of the strongest electrical discharges and UV radiation. 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 emerge from this “soup”?

Formation of proteins, fats and carbohydrates

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

The 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 mentioned above, became more and more rigid. The first "advanced" coacervates already had a primitive, but a metabolism. Scientists suggest that the drop, having reached a certain size, broke up into smaller formations that had all the features of the mother's "cell".

Gradually, a layer of lipids appeared around the core of the coacervate, giving rise to a full-fledged cell membrane. Thus, primary cells, archecells, were formed. It is this moment that can rightfully be considered as the birth 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 in natural conditions?” Such thoughts visited many researchers!

In 1953, the American scientist Miller modeled the Earth's primordial atmosphere, with its incredible temperatures and electrical discharges. Simple inorganic compounds were placed into this medium. As a result, acetic and formic acids and other organic compounds were formed there. This is how life originated on Earth. Briefly, this process can be described philosophical law"The 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 other properties and the ability to self-organize.

Strengths and weaknesses of Oparin's theory

The concept we have considered has not only strengths, but also weaknesses. Strong point 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 the coacervates could be reborn 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. At present, all scientists admit that there was some kind of a sharp jump, as a result of which the self-organization of matter became possible. How could this even happen? It is not yet clear... What other main theories of the origin of life on Earth exist?

The 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 steady state, since they consider the principle of the origin of life from the same point of view. You should know that for the first time this concept was proposed by the German Richter at the end of the 19th century. In 1907 he was supported by the Swedish explorer 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 a kind of “seeds”. The downside of this theory is that the universe itself is thought to have formed about 15 to 25 billion years ago. It doesn't look like Eternity. Considering the fact that planets potentially suitable for the formation of life are many times smaller than ordinary stony planetoids, the question can be considered quite natural: “When and where did life form and how did it spread across the Universe with such speed, given the unrealistic distances?”

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

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 kind of "cradles", planets on which life can form. It sounds, of course, like some kind of science fiction ... However, who knows. AT last years in our country and abroad, a theory gradually began to take shape, the provisions of which speak of information initially encoded in the atoms of substances ...

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

"Gift" from Mars?

Today it is known for certain that there really was water on the Red Planet and there were all the conditions conducive to the development of protein life. The data that confirm this was obtained due to the work on the surface of two descent vehicles at once: Spirit and Curiosity. But until now, scientists are arguing with fervor: was there life there? The fact is that the information received from the same rovers indicates a short-term (in the 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 does not explain the process of its development there (which we have already written about).

So, we have considered the basic concepts of the origin of life on Earth. Which of them are absolutely true, is unknown. The problem is also that so far there is not 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 get protein life. So the work of scientists is in store for many decades to come.

There is another problem. The fact is that we are intensely looking for life based on carbon, and trying to understand exactly how it arose. But 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 provisions 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 either 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 dimensions of the Earth). Too big planets or have unrealistic high strength gravity, or are gas giants.
• More or less highly organized life can exist only near sufficiently old stars (at least three or four billion years old).
• 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 has long since died 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 more and more people are talking about the fact that somewhere on the outskirts of the solar system there is a gas and dust cloud, the forerunner of the unborn second Sun.

Final conclusions

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

The main hypotheses of the origin of life on earth.

Biochemical evolution

Among astronomers, geologists and biologists, it is generally accepted that the age of the Earth is approximately 4.5 - 5 billion years.

According to many biologists, in the past the state of our planet was little like the current one: the temperature on the surface was probably very high (4000 - 8000 ° C), and as the Earth cooled, carbon and more refractory metals condensed and formed the earth's crust. ; the surface of the planet was probably bare and uneven, since as a result of volcanic activity, movements and contractions of the crust caused by cooling, the formation of folds and ruptures occurred on it.

It is believed that the gravitational field of the still insufficiently dense planet could not hold light gases: hydrogen, oxygen, nitrogen, helium and argon, and they left the atmosphere. But simple compounds containing among others these elements (water, ammonia, CO2 and methane). Until the Earth's temperature dropped below 100°C, all water was in a vapor state. The absence of oxygen was probably a necessary condition for the origin of life; as laboratory experiments show, organic substances (the basis of life) are much easier to form in an oxygen-poor atmosphere.

In 1923 A.I. Oparin, based on theoretical considerations, expressed the opinion that organic substances, possibly hydrocarbons, could be created in the ocean from simpler compounds. The energy for these processes was supplied by intense solar radiation, mainly ultraviolet radiation, which fell on the Earth before the ozone layer formed, which began to trap most of it. According to Oparin, the variety of simple compounds found in the oceans, the surface area of ​​the Earth, the availability of energy and time scales suggest that organic matter gradually accumulated in the oceans and formed a "primordial soup" in which life could arise.

It is impossible to understand the origin of man without understanding the origin of life. And to understand the origin of life is possible only by understanding the origin of the universe.

First there was a big bang. This explosion of energy took place fifteen billion years ago.

Evolution can be thought of as the Eiffel Tower. At the base - energy, above - matter, planets, then life. And finally, at the very top - a man, the most complex and the last animal to appear.

The course of evolution:

15 billion years ago: the birth of the universe;

5 billion years ago: birth of the solar system;

4 billion years ago: birth of the Earth;

3 billion years ago: the first traces of life on Earth;

500 million years ago: first vertebrates;

200 Ma: First mammals;

70 million years ago: the first primates.

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 be brought to Earth from space. The most likely hit of living organisms of extraterrestrial origin 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.

In 1969, the Murchison meteorite was found in Australia. It contained 70 intact amino acids, eight of which are part of the human protein!

Many scientists could argue that the squirrels that petrified upon re-entry into the atmosphere were dead. However, a prion, a protein that can withstand very high temperatures, has recently been discovered. The prion is stronger than the virus and is able to transmit the disease much faster. According to the Panspermia theory, man somehow originates from a virus of extraterrestrial origin that struck monkeys, which mutated as a result.

Theory of spontaneous generation of life

This theory has been circulated in Ancient China, Babylon and Egypt as an alternative to the creationism with which it co-existed.

Aristotle (384-322 BC), often hailed as the founder of biology, held to the theory of the spontaneous generation of life. Based on his own observations, he developed this theory further, linking all organisms in a continuous series - the "ladder of nature." “For nature makes the transition from lifeless objects to animals with such a smooth succession, placing between them creatures that live, while not being animals, that between neighboring groups, due to their close proximity, one can hardly notice the differences” (Aristotle).

According to Aristotle's hypothesis of spontaneous generation, certain "particles" of matter contain some kind of "active principle", which, when suitable conditions can create a living organism. Aristotle was right in thinking that this active principle is contained in a fertilized egg, but mistakenly believed that it is also present in sunlight, mud and rotting meat.

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

With the spread of Christianity, the theory of the spontaneous origin of life was not honored: it was recognized only by those who believed in witchcraft and worshiped evil spirits, but this idea continued to exist somewhere in the background for many more centuries.

Steady State Theory

According to this theory, the Earth never arose, but existed forever, it is always capable of supporting life, and if it has changed, then very little. Species have also always existed.

Estimates of the age of the earth have varied greatly, from about 6,000 years according to Archbishop Ussher's calculations to 5,000 106 years according to modern estimates based on radioactive decay rates. Improved dating methods give increasingly higher estimates of the age of the Earth, which allows the proponents of the steady state theory to believe that the Earth has existed forever. According to this theory, species also never arose, they have always existed, and each species has only two alternatives - either a change in numbers or extinction.

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. Proponents of the steady state theory argue that only by studying living species and comparing them with fossil remains can one conclude about extinction, and in this case it is very likely that it will turn out to be wrong. Using paleontological data to confirm the steady state theory, its few supporters interpret the appearance of fossils in an ecological aspect (increase in abundance, migration to places favorable for the preservation of remains, etc.). Much of the argument in favor of this theory has to do with obscure aspects of evolution, such as the significance of gaps in the fossil record, and it has been most elaborate in this direction.

creationism

Creationism (lat. 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 higher being at some specific time. The main provisions of creationism are set out in the Bible, in the Book of Genesis. The process of the divine creation of the world is conceived as having taken place only once and therefore inaccessible to observation. This is enough to take the whole concept of divine creation beyond scientific research. Science deals only with observable phenomena and therefore will never be able to either prove or reject this concept.

The theory of water origin of man

It says: man came directly from the water. Those. we were once something like marine primates, or humanoid fish.

The "Water Theory" of human origins was put forward by Alistair Hardy (1960) and developed by Elaine Morgan. After that, the idea was broadcast by many popularizers, for example, Jan Lindblad and the legendary submariner Jacques Maillol. According to Hardy and Morgan, one of our ancestors was a Miocene great ape of the proconsul family, which lived in the water for many millions of years before becoming terrestrial.

In favor of the origin of the "water monkey", the following human features are given:

1. The ability to hold your breath, apnea (including during vocalization) makes a person a diver.

2. Working with dexterous brushes and using tools is similar to the behavior of the raccoon and sea otter.

3. When wading water bodies, primates stand on their hind limbs. The semi-aquatic lifestyle contributed to the development of bipedal locomotion.

4. Loss of hairline and development of subcutaneous fat (normally thicker in humans than in other primates) are characteristic of aquatic mammals.

5. big breasts helped keep the body in the water and warm the heart.

6. Hair on the head helped keep the baby.

7. An elongated foot helped swim.

8. There is a skin fold between the fingers.

9. By wrinkling the nose, a person can close the nostrils (monkeys - no)

10. The human ear takes in less water.

And for example, if a newborn is placed in water immediately after he leaves the mother's womb, he will feel great. He already knows how to swim. After all, in order for a newborn to move from the stage of a fish to the stage of an air-breathing mammal, it needs to be patted on the back.

MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUS

BSPU IM. M. TANKA

FACULTY OF SPECIAL EDUCATION

DEPARTMENT OF THE FUNDAMENTALS OF DEFECTOLOGY

abstract

in the discipline "Natural Science"

on the topic:

"Basic hypotheses about the origin of life on Earth".

Performed:

1st year student of group 101

correspondence department (budget

form of education)

……… Irina Anatolyevna

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

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

2. STATION STATE THEORY…………..……………….….2

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

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

5. A. I. OPARIN’S THEORY………………………………………………..……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 regions 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 progress in laboratory modeling of some stages of the evolution of matter, which led to the origin of life, and, secondly, the rapid development of space research, making it increasingly possible to directly search for any life forms on the planets of the solar system. and in the future and beyond.

The origin of life is one of the most mysterious questions, the exhaustive answer to which is unlikely to ever be received. Many hypotheses and even theories about the origin of life, explaining the various aspects of this phenomenon, are not yet able to overcome an essential circumstance - to 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 for the origin of life on Earth are as follows:

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

2. Life has always existed (the theory of a stationary state).

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

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

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

1. Creationism.

Creationism (from Latin creaсio - creation) is a philosophical and methodological concept, within which the entire diversity of the organic world, humanity, the 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 confirmation of this point of view: in religion, the truth is comprehended through divine revelation and faith. The process of creation of the world is conceived as having taken place only once and therefore inaccessible to observation.

The followers of almost all the most common religious teachings adhere to theories of creationism (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 Ussher of Armagh, Ireland, calculated that God created the world in October 4004 BC. e. and finished his work on October 23 at 9 o'clock in the morning, creating man. Asher got this date by adding up the ages of all the people mentioned in the Biblical genealogy, from Adam to Christ (“who bore whom”). From the point of view of arithmetic, this makes sense, but it turns out 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 idea of ​​the creation of the world, set forth in the Book of Genesis, has caused and continues to cause controversy. However, the existing contradictions do not refute the concept of creation. The hypothesis of creation can neither be proved nor disproved and will always exist together with scientific hypotheses of the origin of life.

Creationism is thought of as God's Creation. However, at present, some consider it as the result of the activities of a highly developed civilization that creates various forms life and watching their development.

2. THE THEORY OF A STATIONARY STATE.

According to this theory, the Earth never came into being, but existed forever; it has always been capable of sustaining life, and if it has changed, it has changed 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 estimated at 4.6 billion years. Improved dating methods give increasingly higher estimates of the age of the Earth, leading steady state theorists to believe that the Earth has always existed.

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 the cross-finned fish - coelacanth (coelacanth). It was believed that the brush-finned fish (coelacanth) is a transitional form from fish to amphibians and died out 60-90 million years ago (at the end of the Cretaceous period). However, this conclusion had to be revised when, in 1939, off the coast of about. Madagascar, the 1st live coelacanth was caught, and then other specimens. Thus, coelacanth is not a transitional form.

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

Another example of delusion is Archeopteryx - a creature that binds birds and reptiles, a transitional form on the way to turning 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 the living species and comparing them with fossil remains, one can conclude about extinction, and in this case it is very likely that it will turn out to be wrong. Using paleontological data to support the steady state theory, its proponents interpret the appearance of fossils in an ecological sense.

Thus, for example, the sudden appearance of a fossil species in a particular stratum is explained by an increase in its population or its movement to places favorable for the preservation of remains.

Much of the argument in favor of this theory has to do with obscure aspects of evolution, such as the significance of gaps in the fossil record, and it has been most elaborate in this direction.

The hypothesis of a stationary state is sometimes called the hypothesis of eternism (from 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 this scientifically,” he repeated, “that the Cosmos cannot exist without matter, without energy. And is there enough matter even without revealing life - to build the Cosmos, that Universe, which is accessible to the human mind? He answered this question in the negative, referring precisely to scientific facts, and not to personal sympathies, philosophical or religious convictions. “... You can talk about the eternity of life and the manifestations of its organisms, just as you can talk about the eternity of the material substrate celestial bodies, their thermal, electrical, magnetic properties and their manifestations. From this point of view, the question of the beginning of life will be just as far from scientific research as the question of the beginning of matter, heat, electricity, magnetism, motion.

Proceeding from the concept 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 purely earthly.” Vernadsky repeated this thought 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 eternal Cosmos.

3. THE THEORY OF SPONTANEOUS GENERATION.

This theory was circulated in ancient China, Babylon, and Egypt as an alternative to the 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 the deity. Very naively solved this question and the first researchers of nature. Aristotle (384-322 BC), often hailed as the founder of biology, held to the theory of the spontaneous generation of life. Even for such an outstanding mind of antiquity as Aristotle, it was not difficult to accept the idea that animals - worms, insects, and even fish - could arise from mud. On the contrary, this philosopher argued that every dry body, becoming wet, and, conversely, every wet body, becoming dry, give birth to animals.

Hypotheses of the origin of life on Earth

The problem of life and the living is the object of study of many natural disciplines, starting with biology and ending with philosophy, mathematics, which consider abstract models of the living phenomenon, as well as physics, which defines life from the standpoint of physical laws. Centuries of research and attempts to resolve these issues have given rise to various hypotheses of the origin of life.

In accordance with two worldview positions - materialistic and idealistic - even in ancient philosophy, opposite concepts of the origin of life developed: creationism and the materialistic theory of the origin of organic nature from inorganic. Proponents of creationism argue that life arose as a result of an act of divine creation, evidence of which is the presence in living organisms of a special force that controls all biological processes. Proponents of the origin of life from inanimate nature argue that organic nature arose due to the action of natural laws. Later, this concept was concretized in the idea of ​​spontaneous generation of life.

So, there are the following hypotheses of the origin of life.

1. creationism . According to the concept of creationism, life arose as a result of supernatural, i.e., violating the laws of physics, events in the past. The concept of creationism is followed by followers of almost all the most common religions. According to the traditional Judeo-Christian ideas about the creation of the world, set out in the Book of Genesis, the world and all the organisms inhabiting it were created by the almighty Creator in 6 days lasting 24 hours. However, at present, many Christians do not treat the Bible as a scientific book and believe that it contains the theological revelation about the creation of all living beings by God in a form understandable to all people of all times.

Logically, there can be no contradiction between the scientific and theological explanations of the creation of the world. these two realms of thought are mutually exclusive. Theology recognizes truth through divine revelation and faith and recognizes things for which there is no evidence in the scientific sense of the word. Science makes extensive use of observation and experiment, scientific truth always contains an element of hypothesis, while for the believer theological truth is absolute. The process of the divine creation of the world is conceived as having taken place once, therefore it is not available for observation. The concept of the divine creation of the world is outside the scope of scientific research, so science dealing with phenomena that can be observed can never prove or disprove this concept.

The anthropic principle, formulated in the 70s of our century, speaks in favor of the non-random nature of the process of the origin and development of life. Its essence lies in the fact that even slight deviations in the value of any of the fundamental constants leads to the impossibility of the appearance in the Universe of highly ordered structures and, consequently, of life. Thus, an increase in Planck's constant by 10% makes it impossible for a proton to combine with a neutron, i.e. makes nucleosynthesis impossible. A decrease in Planck's constant by 10% would lead to the formation of a stable isotope 2 He, which would result in the burning out of all hydrogen in the early stages of the expansion of the Universe. The non-random nature of the values ​​of the fundamental constants may indicate the presence of a “creative plan” from the very beginning of the formation of the Universe, which implies the presence of the Creator, the author of this plan.

2. Hypothesis of spontaneous origin of life . According to Aristotle, certain “particles” of matter contain some kind of “active principle”, which, under suitable conditions, can create a living organism.

The hypothesis of spontaneous origin of life was widespread in ancient China, Babylon and Egypt as an alternative to creationism. Following Empedocles, one of the first to express the idea of ​​organic evolution, Aristotle adhered to the concept of spontaneous origin of life, linking all organisms into a single “ladder of nature“. According to Aristotle, certain “particles” of matter contain some kind of “active principle”, which, under suitable conditions, can create a living organism. This beginning, according to Aristotle, is present in a fertilized egg, in sunlight, mud and rotting meat. In 1688, the Italian physician Francesco Redi questioned the theory of spontaneous generation of life and conducted a series of experiments in which he showed that life can only arise from a previous life (the concept of biogenesis). Louis Pasteur (1860) finally refuted the theory of spontaneous origin of life and proved the validity of the theory of biogenesis. The experiments of L. Pasteur showed that microorganisms appear in organic solutions due to the fact that their embryos were previously introduced there. If a vessel with a nutrient medium is protected from entering microbes into it, then no spontaneous generation of life occurs.

The concept of spontaneous generation, though fallacious, has played a positive role; experiments designed to confirm it provided rich empirical material for the developing biological science. The final rejection of the idea of ​​spontaneous generation occurred only in the 19th century.

Confirmation of the theory of biogenesis gave rise to the problem of the first living organism from which all the others arose. In all theories (except the theory of a stationary state) it is implied that at some stage in the history of life there was a transition from inanimate to living. How did it happen?

3. Steady State Hypothesis . According to this hypothesis, the Earth never came into being, but existed forever; The earth has always been capable of supporting life. Species have always existed, each species has only two possibilities: change in numbers or extinction.

4. Panspermia hypothesis claims that life could have arisen one or more times in different time and in different parts of the universe. This hypothesis arose in the 60s of the XIX century and is associated with the name of the German scientist G. Richter. Later, the concept of panspermia was shared by such prominent scientists as S. Arrhenius, G. Helmholtz, V.I. Vernadsky. To substantiate this theory, UFO sightings, rock paintings of ancient, rocket-like and aliens, etc. are used. Soviet and American space research allows us to consider the probability of finding extraterrestrial life within the solar system as negligible, but they do not provide grounds for confirming or refuting the existence of life outside it. When studying the material of meteorites and comets, many “precursors of the living” (cyanogens, hydrocyanic acid, etc.) were found in them, which could play the role of “seeds” of life. Be that as it may, the theory of panspermia is not a theory of the origin of life as such; it simply transfers the problem of the origin of life to another place in the universe.

At the beginning of the XX century. The idea of ​​the cosmic origin of biological systems on Earth and the eternity of the existence of life in space was developed by the Russian scientist Academician V.I. Vernadsky.

5. The hypothesis of the eternal existence of life . It was put forward in the 19th century. It has been suggested that life exists in space and travels from one planet to another.

6. Hypothesis of biochemical evolution. The age of the Earth is estimated at 4.5–5 billion years. In the distant past, the temperature on the surface of our planet was 4000-8000 degrees Celsius. As it cooled, carbon and more refractory metals condensed to form the earth's crust; as a result of volcanic activity, continuous movements of the crust and compression caused by cooling, the formation of folds and ruptures occurred. The atmosphere of the Earth in ancient times was obviously reducing (in the most ancient rocks of the Earth there are metals in a reducing form, for example, ferrous iron, younger rocks contain metals in an oxidized form, for example, ferric iron). There was practically no oxygen in the atmosphere. The emergence of life is closely related to the emergence of the Earth's oceans, which happened about 3.8 billion years ago. Paleontological data indicate that the water temperature in them was not too low, but did not exceed 58 °C. Traces of the most ancient organisms have been found in the strata, whose age is estimated at 3.2-3.5 billion years.

The hypothesis of biochemical evolution was presented by Academician A.I. Oparin (1894-1980) in the book "The Origin of Life", published in 1924. He made the statement that the Redi principle, introducing a monopoly of the biotic synthesis of organic substances, is valid only for modern era the existence of our planet. At the beginning of its existence, when the Earth was lifeless, abiotic synthesis of carbon compounds and their subsequent prebiological evolution took place on it.

The essence of Oparin's hypothesis is as follows: the origin of life on Earth is a long evolutionary process of the formation of living matter in the depths of inanimate matter. This happened through chemical evolution, as a result of which the simplest organic substances were formed from inorganic ones under the influence of potent physicochemical factors.

The emergence of life A.I. Oparin considered as a single natural process, which consisted of the initial chemical evolution proceeding in the conditions of the early Earth, which gradually passed to a qualitatively new level - biochemical evolution. Considering the problem of the emergence of life through biochemical evolution, Oparin distinguishes three stages of the transition from inanimate to living matter.

First stage - chemical evolution . When the Earth was still lifeless (about 4 billion years ago), abiotic synthesis of carbon compounds and their subsequent prebiological evolution took place on it. This period of the Earth's evolution was characterized by numerous volcanic eruptions with the release of a huge amount of red-hot lava. As the planet cooled, the water vapor in the atmosphere condensed and fell on the Earth in showers, forming huge expanses of water (the primary ocean). These processes continued for many millions of years. Various inorganic salts were dissolved in the waters of the primary ocean. In addition, various organic compounds, which are continuously formed in the atmosphere under the influence of ultraviolet radiation, high temperature, and active volcanic activity, also entered the ocean. The concentration of organic compounds was constantly increasing, and, in the end, the waters of the ocean became " broth» from protein-like substances - peptides.

Figure 26 - Scheme of the origin of life according to Oparin

Second phase - appearance of proteins . As conditions on Earth soften, under the influence of electrical discharges, thermal energy and ultraviolet rays it became possible to form complex organic compounds - biopolymers and nucleotides, which, gradually combining and becoming more complex, turned into protobionts (precellular ancestors of living organisms). The result of the evolution of complex organic substances was the appearance of coacervates, or coacervate drops. coacervates - complexes of colloidal particles, the solution of which is divided into two layers: a layer rich in colloidal particles and a liquid almost free of them. Coacervates had the ability to absorb various substances dissolved in the waters of the primary ocean. As a result, the internal structure of coacervates changed in the direction of increasing their stability in constantly changing conditions. The theory of biochemical evolution considers coacervates as prebiological systems, which are groups of molecules surrounded by a water shell. For example, coacervates are able to absorb substances from environment, interact with each other, increase in size, etc. However, unlike living beings, coacervate drops are not capable of self-reproduction and self-regulation, so they cannot be classified as biological systems.

The third stage is the formation of the ability to self-reproduce, appearance of a living cell . During this period, natural selection began to act, i.e. in the mass of coacervate drops, the selection of coacervates, the most resistant to given environmental conditions, took place. The selection process has been going on for many millions of years. The surviving coacervate drops already possessed the ability for primary metabolism, the main property of life. At the same time, having reached a certain size, the parent drop broke up into child droplets that retained the features of the parent structure. Thus, we can talk about the acquisition by coacervates of the property of self-reproduction - one of the most important signs of life. In fact, at this stage, coacervates have become the simplest living organisms. Further evolution of these prebiological structures was possible only with the complication of metabolic processes inside the coacervate.

The internal environment of the coacervate needed protection from environmental influences. Therefore, around the coacervates, rich in organic compounds, layers of lipids arose, separating the coacervates from the surrounding aquatic environment. In the process of evolution, lipids were transformed into the outer membrane, which significantly increased the viability and resistance of organisms. The appearance of the membrane predetermined the direction of further biological evolution along the path of more and more perfect autoregulation, culminating in the formation of the primary cell - the archecell. A cell is an elementary biological unit, the structural and functional basis of all living things. Cells carry out an independent metabolism, are capable of division and self-regulation, i.e. have all the properties of living things. The formation of new cells from non-cellular material is impossible, cell reproduction occurs only due to division. Organic development is considered as a universal process of cell formation.

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

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

The transition from the inanimate to the living took place after the rudiments of two fundamental life systems arose and developed on the basis of the predecessors: the system of metabolism and the system of reproduction of the material foundations of the living cell.

The probability that a protein molecule consisting of 100 amino acids of 20 types will be randomly formed according to a certain pattern is 1/20 100 ≈ 1/10 130 . A living cell is a complex of interacting proteins, lipids and nucleotides that form the genetic code. The simplest cell contains more than 2000 enzymes. The probability of random formation of such complex structures is small.

The possibility of abiogenic synthesis of biopolymers was experimentally proven in the middle of the 20th century. In 1953, the American scientist S. Miller modeled the primary atmosphere of the Earth and synthesized acetic and formic acids, urea and amino acids by passing electric charges through a mixture of gases (water, carbon dioxide, hydrogen, nitrogen, methane). Thus, it was demonstrated how the synthesis of complex organic compounds is possible under the action of abiogenic factors.

Despite the theoretical and experimental validity, Oparin's concept has both strong and weak sides. The strength of the concept is a fairly accurate experimental substantiation of chemical evolution, according to which the origin of life is a natural result of the prebiological evolution of matter. A convincing argument in favor of this concept is also the possibility of experimental verification of its main provisions. Weak side concept is the impossibility of explaining the very moment of the jump from complex organic compounds to living organisms.

One of the versions of the transition from prebiological to biological evolution is offered by the German scientist M. Eigen. According to his hypothesis, the origin of life is explained by the interaction of nucleic acids and proteins. Nucleic acids are carriers of genetic information, and proteins serve as catalysts chemical reactions. Nucleic acids reproduce themselves and transmit information to proteins. A closed chain appears - a hypercycle, in which the processes of chemical reactions are self-accelerated due to the presence of catalysts. In hypercycles, the reaction product simultaneously acts as both a catalyst and an initial reactant. Such reactions are called autocatalytic.

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