How life originated on earth hypotheses. The most interesting theories of the origin of life on Earth: the main versions

12.10.2019

The history of life on Earth hides many secrets. Whether they will ever be revealed, the future development of science will show.

We confine ourselves to a cultural-historical consideration of all hypotheses for the origin of life on Earth. Within the framework of the natural-science concept, we will pay special attention to the constructive-theoretical models of the theory of biochemical evolution.

Since biological time - age has an "arrow of time" directed from the past to the future and is described by the triad: birth - aging - death, the evolutionary idea arose already in mythology and was formed in ancient natural philosophy in theory of spontaneous generation life from inanimate matter, while it was assumed multiple generation based on naive transformism through a random combination of individual organs (Empedocles, 495-435 BC), a sudden transformation of species (Anaksimen, 384-322 BC). Aristotle (384-322 BC) formalized the theory of the spontaneous generation of life into the theory of the gradual development of living forms (from simple to complex), which intersects in the Middle Ages with creationist theory.

creationism(creation, creation) - contains the thesis about the divine creation of the world and man. According to this theory, life is the result of supernatural events in the past. Many scientists in the aesthetics of thinking actually combine the evolutionary idea with creationism. It seems to us that the aesthetics of thinking of the Russian philosopher of the 20th century Merab Mamardashvili, leading to the intersection of sacred and secular thinking at the “meeting point at which we thought a thought, which cannot be had by the will or desire of thought, seems justified. She thinks or she doesn't. And if we think about it, if we are at this point of intersection in the fullness of the collected being, it will not pass us by. Then we are worthy of this thought, or in other words, worthy of the gift. The gift does not follow from our merits, we are worthy of it only when it happens to us, and this is a path along an arc, and not horizontally, since we are linked and merged with the higher, superconscious.

In the seventeenth century there was theory of biogenesis, which boils down to the assertion that life can only arise from a previous life, i.e., "the living from the living." It was formed by the Italian physician and biologist F. Redi and is known in the literature as the "Redi principle". The French biologist Louis Pasteur in 1862, by convincing experiments, proved the impossibility of spontaneous generation of the simplest organisms in modern conditions and approved the principle of "everything living from living things." The aesthetics of thinking of the founder of modern microbiology and immunology, L. Pasteur, clearly intersects with creationism in the following statement: “The more I study nature, the more I stop in reverent amazement before the deeds of the Creator. I pray during my work in the laboratory.”

The principle of complementarity of evolutionary ideas with creationism is also characteristic of the principle of development of J.B. Lamarck (1744-1829), who postulated the following provisions: organisms are changeable; species (and other taxonomic categories) are conditional and are gradually transformed into new species; the general trend of historical changes in organisms is the gradual improvement of their organization (gradation), the driving force of which is the initial (laid down by the Creator) desire of nature for progress. For Lamarckism, two complementary features are characteristic: teleologism - as the desire for improvement inherent in organisms, organismocentrism - the recognition of an organism as an elementary unit of evolution.

Charles Darwin (1809 - 1882), summarizing individual evolutionary ideas, created a coherent, detailed theory of evolution. He considered the driving forces of evolution to be hereditary variability and natural selection, and as the elementary unit of evolution the organism of each species, i.e., in fact, individual individuals. Surviving individuals give rise to the next generation, and thus "fortunate" positive changes are transmitted to the next generations. Very often, Charles Darwin's theory of natural selection is opposed to creationism. However, let's turn to the aesthetics of Charles Darwin's thinking: "The world rests on patterns and in its manifestations it appears as a product of the mind - this is an indication of its Creator."

“God, truly dues ex machine, allows you to jump over the abyss between the living and the dead, nature and spirit, while maintaining the abyss.” God (Creator) is a complex, creative construction of our mind, demonstrating the ability of civilizing humanity to think abstractly. In the Middle Ages, the theory of creationism takes shape in confessional philosophical theologies and religions, which are based on the thesis: “God is known only through faith”, thereby religion separated faith in the divine creation of the world from science, i.e. from the scientific method of knowing the world, based on on a set of empirical and theoretical methods. At the same time, good and evil receive sacred sanction in religion, and a person finds inner peace and light for work in our imperfect world. This is most clearly expressed in the following teaching by M.V. Lomonosov: “A mathematician is not sensible if he wants to measure the Divine will with a compass. Such is the theology teacher, if he thinks that one can learn astronomy and chemistry from the Psalter.

They tried to explain the appearance of life on Earth by introducing it from other cosmic worlds. In 1865, the German physician G. Richter put forward the hypothesis of cosmozoans (cosmic germs), according to which life is eternal and the germs that inhabit the world space can be transferred from one planet to another. arose steady state theory, according to which life has always existed, based to a certain extent on the “Redi principle”. This hypothesis was supported by many scientists of the XIX century - W. Thompson, G. Helmholtz and others. To a certain extent, our great scientist V.I. Vernadsky, who believed that life on Earth appeared simultaneously with the appearance of the Earth.

The steady state theory in the Richter model intersects with panspermia theory, which was put forward in 1907 by the famous Swedish naturalist S. Arrhenius: “In the Universe, there are always germs of life that move in outer space under the pressure of light rays; falling into the sphere of attraction of the planet, they settle on its surface and lay the beginning of life on this planet. Structurally - theoretical possibilities of panspermia are confirmed by a number of experiments: the detection of traces of organic compounds in meteorite and cometary substances, amino acid precursors in lunar soil, traces of microorganisms in a meteorite of presumably Martian origin. Obviously, these discoveries of the second half of the 20th century will be expanded as man explores outer space.

However, within the framework of the natural science principle of global evolution, the theory of the steady state is not productive, and the theory of panspermia also does not offer any mechanism to explain the primary origin of life; it simply transfers the problem of the origin of life to some other place in the universe.

So, within the framework of the evolutionary “arrows of time”, based on the principle of complementarity, there remain two mutually exclusive, and possibly complementary, at least in the aesthetics of thinking, the theory of creationism and theory of biochemical evolution. In our opinion, in the intersection of these theories, both belief in religious fanaticism and scientific absolutism seem unjustified. It seems to us that the feeling of “religious faith in the higher, superconscious and worship” before the harmony of nature on Earth and in the Cosmos and the conviction that in the “conceptual fund (as well as in the gene pool) of the Earth” all elements are significant and important is the basis not only spiritual, but and material culture of human civilization.

The anthropic principle, formulated in the 70s of the 20th century, speaks in favor of the non-random nature of the process of both the origin and development of life. Its essence lies in the fact that even a slight deviation of the value of any of the fundamental constants leads to the impossibility of the appearance of highly ordered structures in the Universe. For example, an increase in Planck's constant by 10% makes it impossible for a proton to combine with a neutron, that is, nucleosynthesis becomes impossible. A decrease in Planck's constant by 10% would lead to the formation of a stable 2 He nucleus, which would result in the burning out of all hydrogen in the early stages of the expansion of the Universe, or the collapse of stars in the later stages. Science has come across a large group of facts, the separate consideration of which creates the impression of inexplicable coincidences bordering on a miracle. (for more details: Barron J.D., Tipler F.J. The antropic cosmological principle, Oxford, 2-nd., ed., 1986). According to physicist J. Wheeler: "The life-giving factor lies at the center of the whole mechanism and constructs the world."

At the same time, constructive-theoretical models of biochemical evolution are based on the hypothesis that life arose as a result of processes that obey chemical and physical laws. Thus, we put, justifiably or not, the laws of physics and chemistry at the center of "the whole mechanism that constructs the world."

The first three stages are attributed to the period of chemical evolution, the fourth begins biological evolution. The concept of chemical evolution has been confirmed by a number of experiments. The beginning of this work was laid in 1953 by S. Miller and G. Ury, who, when exposed to a spark charge on a gas mixture of methane and water vapor, obtained a set of small organic molecules, for the first time showing the possibility of abiogenic synthesis of organic compounds in systems that mimic the supposed composition the earth's primary atmosphere.

The complex processes of chemical evolution leading to biochemical and biological evolution can be expressed as a simple sequence: atoms
simple molecules
complex macromolecules and ultramolecular systems (probionts)

unicellular organisms.

The first cells are considered the prototype of all living organisms of plants, animals, bacteria.

However, in this physical and chemical construction of all living things, the anthropic principle is naturally present, i.e. belief in the non-random nature of the process of both the origin and development of life on Earth. In addition, the possibility of the intersection of the theory of biochemical evolution of terrestrial matter with the theory of panspermia is not removed. The theory of biochemical evolution itself acquired the scientific nature of the theoretical construction of models, confirmed experimentally by the geochronological history of the Earth only in the 20th century after the discovery of the molecular genetic level of the biological level of matter and the formation of evolutionary chemistry.

The theory of biochemical evolution is based on the concept of abiogenesis - the formation of organic compounds common in living nature outside the body, without the participation of enzymes.

All the numerous hypotheses that were put forward in the 60-80s of the 20th century had a clearly expressed opposition on the issue of the characteristics of the protobiological system, i.e., the precellular ancestor. The problem was that between the chemical form of matter, which is not yet life, and the biological form of matter, which is already life, there is a prebiotic structure associated with the transition from physicochemical evolution to biological. It was necessary to find some kind of pre-cellular structure that could evolve, so that it was subject to genetic transformations and natural selection. As a result, two hypotheses were identified - coacervant and genetic.

The basis of the coacervant hypothesis is the assertion that the initial stages of biogenesis were associated with the formation of protein structures from the "primary ocean" due to coacervation - the spontaneous separation of an aqueous solution of polymers into phases with different concentrations. The main provisions of this hypothesis were first formulated by A.I. Oparin in 1924 (see: Oparin A.I. Life, its nature, origin and development. M., 1968). Selection as the main reason for the improvement of coacervants to primary living beings is the most important provision of Oparin's hypothesis.

Within the framework of the coacervant hypothesis, a methodological principle arose, called holobiose, i.e. the primacy of cellular-type structures endowed with the ability for elemental metabolism, including enzymatic catalysis.

However, if we rely on equilibrium thermodynamics, then the molecules of living beings do not arise spontaneously, their formation requires a complex mechanism for the continuous and coordinated action of the "heater" and "refrigerator" in accordance with the second law of thermodynamics. The probability that a protein molecule, consisting of 20 types of amino acids, will be randomly formed according to a certain pattern is

The number in the denominator is too large to be grasped by the mind. "The probability - according to the astronomer Freud Hoyle, is blatantly small, so small that it would be unthinkable even if the entire universe consisted of organic soup." However, if we pass to non-equilibrium thermodynamics, then the radiation entropy S rad. much more than the entropy of matter S real. (S izl >> S real.), then the probability of formation of ordered structures from crystals to proteins and nucleic acids increases sharply.

However, for this hardly enough natural selection, which is aimed at cleansing the gene pool of a population from “defective” genes, modification occurs only within the framework of the existing genetic material, as an adaptive response to environmental changes.

Coming to the fore genetic hypothesis, according to which nucleic acids first arose as a matrix basis for protein synthesis. This hypothesis was first put forward in 1929 by the American geneticist G. Meller.

Within the framework of the genetic hypothesis, a methodological principle arose, called genobiosis, asserting the primacy of the emergence as a result of biochemical evolution of a molecular system with the properties of the genetic code.

The idea of discrete splitting of genetic traits was added to natural selection, to a certain extent based on the main position of quantum mechanics: "Everything: matter, energy, quantum characteristics of particles - are discrete quantities, and none of them can be measured without changing it." The genetic hypothesis links the theory of biochemical evolution with global evolutionism, and the theory of the origin of life on Earth is associated with the belief in the existence of "super-rational, super-rational" teleologism - as the desire for improvement inherent in the entire Universe up to the creation of a "reasonable observer".

The genetic concept is now widely accepted as a result of discoveries made in the 1980s. It has been experimentally proved that simple nucleic acids can be replicated without enzymes. The ability of nucleic acids to serve as templates in the formation of complementary chains is the most convincing argument in favor of the concept of the leading role in the process of biogenesis of the hereditary mechanism and, consequently, in favor of the genetic hypothesis of the origin of life.

By the beginning of the 1980s, it became clear that only ribonucleic acid (RNA) could be the primary nucleic acid.

In other words, it was the RNA molecule that could constitute the macromolecular substrate of the precellular ancestor. The decisive discovery regarding the role of the RNA molecule in the origin of life boils down to the following. First, this is the establishment of the ability of RNA to self-reproduce in the absence of protein enzymes. Secondly, the establishment of the fact that one of the small RNA molecules (ribosine) itself has the functions of an enzyme. Finally, thirdly, it was found that RNA has autocatalytic properties.

Thus, it can be considered that ancient RNA combined both functions: catalytic and information-genetic, which provided the possibility of self-reproduction of a macromolecular object. In other words, it met all the requirements of the mechanism of evolution in combining the theory of natural selection with hereditary (genetic) discrete splitting of traits (allelic genes), and with the theory of linkage of non-allelic genes. This contributed to the subsequent evolution of the RNA-based macromolecular system into a more efficient DNA-based macromolecular system in terms of protein synthesis. In the course of such evolution, in most cases, there was a separation of information-genetic and catalytic functions. The essential role of the "right-left" asymmetry of both nucleic and protein molecules, the origin of which has many hypotheses and has not yet been experimentally substantiated, should be especially emphasized. It is possible that the emergence of such a dissymmetry had as profound consequences for the origin of life as the emergence of baryon-antibaryon dissymmetry had for the evolution of the Universe.

The problem is also is the time and place of action- Earth about 4.5 billion years ago- unique arena for biochemical evolution. Or this process took place and is taking place spontaneously and at the same time on the basis of “super-rational, super-rational” teleologism in various parts of outer space, and the Earth only provided favorable conditions for the development of life that had already arisen.

Moving on to the ontogenetic (organismal) level of living nature, starting from the 1940s, the cell, the plant of life, has been considered a structural feature of a living organism. In other words, The cell is recognized as the lowest object of living nature either as an independent unicellular organism or as an autonomous part of a multicellular organism. Pre-cellular forms of life - viruses - occupy an intermediate place between living and non-living.

Only in the early 60s of the 20th century did the genetic concept of the cellular organization of living matter appear, which made it possible to discretely divide all living things into two over-kingdoms - prokaryotes and eukaryotes. The most fundamental differences between the two types of organisms concerns the nature of organization and replication at the genetic level; structures of the apparatus that synthesizes proteins; the nature of the "starting" mechanisms of protein biosynthesis; structures of the RNA molecule; organization and nature of the photosynthetic apparatus, etc. At the same time, neither prokaryotes nor eukaryotes have certain evolutionary advantages. This suggests that both these types of organisms are descended from a common ancestor, or archecells, combining features of prokaryotes and eukaryotes.

In the 1970s, this view was strongly confirmed by the discovery archaebacteria, which, being prokaryotes according to the type of organization of the genetic apparatus, have signs that bring them closer to eukaryotes. Most popular at present symbiotic the hypothesis that a eukaryotic cell is the result of a symbiosis of several prokaryotic cells.

An important concept of the functioning of living nature at the ontogenetic level is its functional system. According to this concept, functional systemicity is due to the fact that the components of systems not only interact, but also cooperate.

The concept of functional consistency is universal at all structural levels of living nature. It is based on the interaction of mutational (genetically hereditary splitting of alternative traits (allelic genes) and the linkage of non-allelic genes in the genetics of sex) selection with natural selection, when processes on lower levels as if organized by functional connections at higher levels, and some by specialized regulatory apparatus (homeostasis), such as hormonal and the first systems in the animal body.

The concept of functional consistency could appear at the molecular-genetic level and in the form of a symbiosis of the methodological principles of holobiosis and genobiosis.

This approach, to a certain extent, removes the problem of the primacy of protein or DNA / RNA in the emergence of probionts. It is believed that life evolved on the basis of a dynamic interplay of small molecules (organic and inorganic) and the first biopolymers could be the result of autocatalytic reactions of small molecules in raindrops illuminated by the ultraviolet of the primordial Sun. However, there is a problem of maturation of these droplets into coacervant droplets in accordance with the oparin scenario of the “primary soup” or into primary double-stranded RNAs in accordance with the genetic hypothesis and their subsequent symbiosis into an archecell.

In our opinion, based on the put forward by N.V. Timofeev-Resovsky axiom that the evolution of living nature is fundamentally unpredictable, then this axiom points to a rather difficult way to study the origin of life on Earth and anthropological study of the human genealogy, which, in our opinion, leads to the intersection of at least three theories (concepts) , namely the natural science concept of biochemical evolution with the concepts of panspermia and creationism based on the anthropic principle and the principle of global evolutionism.

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 steady 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, citing scientific facts, and not on personal sympathies, philosophical or religious beliefs. “... One can talk about the eternity of life and the manifestations of its organisms, just as one 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 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 has been circulated in Ancient China, Babylon and Egypt as an alternative to the creationism with which it co-existed. 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.

If we analyze all the data that scientists managed to obtain in the course of various studies, it becomes obvious that life on Earth is amazing. incredible fact. The chances of its occurrence in our universe are negligible. All stages of the emergence of life contained the possibility of an alternative development of events, as a result of which the world would have remained a cold cosmic abyss without a hint not only of the human mind, but even of the smallest microbe. Creationists attribute this incredible event to divine intervention. However, the existence of God cannot be proved or disproved, and modern ideas about the origin of life, like all science in general, are based on experimental data and theoretical developments that can be questioned or confirmed.

Vitalism

Human knowledge is undergoing an evolution that is somewhat similar in its main points to the process described by Darwin. Theories pass and survive the strongest, who managed to withstand the onslaught of counterarguments or adapt, change to suit them. Hypotheses of the origin of life have also gone a long way of formation, the completion of which has not even been marked yet, since new facts are discovered daily, forcing to correct already established views.

Vitalism, the theory of constant spontaneous generation of life, became a major milestone on this road. According to its provisions, mice appeared in old rags, worms - in rotting food remnants. Vitalism dominated science until the experiments of Louis Pasteur in 1860, when he proved the impossibility of spontaneous generation of living organisms. The results triggered paradoxical events: they strengthened faith in the divine principle and forced scientists to look for evidence of what they had recently refuted. Science sought to explain that the independent origin of life took place, but a very long time ago and happened in stages, taking millions of years.

Synthesis of carbons

The situation seemed hopeless until, in 1864, A.M. Butlerov did not make an important discovery.

He managed to get (carbon) from inorganic (in his experiment it was formaldehyde). The data obtained destroyed the imposing wall that until now delimited living organisms and the world of dead matter. After a while, scientists were able to obtain other variants of organics from organic matter. From that moment, modern ideas about the origin of life began to form. They absorbed data not only from biology, but also from cosmology and physics.

Consequences of the Big Bang

Theories of the origin of life cover a huge period: scientists find the first prerequisites for the future formation of organisms as far back as early stages the birth of the universe. Modern physics counts the existence of the world from the Big Bang, when almost everything appeared from nothing. In the rapidly expanding and cooling Universe, first atoms and molecules were formed, then they began to combine, forming the first generation of stars. They became the place of formation of most of the elements known to science today. New atoms filled space after the explosions of stars and became the basis for the next generation of objects, including our Sun. Modern data suggest that the first could have appeared in protoplanetary clouds surrounding new stars. Planets soon formed from them. It turns out that the first stages of the emergence of life on Earth took place even before its formation.

Autocatalytic cycles

The processes that took place on the Blue Planet in its “childhood years” were supported by substances that make up its interior and come from space as meteorites. Hypotheses of the origin of life one of the important foundations for the origin of organic matter on Earth is called catalysts chemical reactions who got here with fragments of these "aliens". They led to the fact that the fastest processes began to play an overwhelming role in the formation of new substances on the planet.

The next step is autocatalytic cycles. In such processes, substances are formed that increase the rate of the reaction, as well as renew the substrate - the elements that interact. The cycle thus closed: the processes accelerated themselves and “cooked food” for themselves, that is, substances that again reacted, again catalyzing themselves and again forming a substrate, and so on.

Doubts

Modern ideas about the origin of life have long contained conflicting opinions. The stumbling block is the chicken and egg problem. What arose first: proteins that carry out all processes in the cell, or DNA that determines the structure of these proteins, storing all hereditary information. The former are necessary for the body, as they contribute to the self-maintenance of the system, without which life is impossible. DNA contains a record of the structure of the cell, which also determines viability. The opinions of scientists were divided and there was no answer to the question until the moment when it became known that not DNA, but RNA, the third class of organic compounds, which was usually assigned only a secondary role in the theory of the origin of life, acts as a repository of hereditary information in viruses.

RNA world

Gradually, facts began to accumulate, and in the 80s of the last century, data appeared that overturned ideas about the initial stages of the formation of living matter. Ribozymes, RNA molecules, have been discovered that have the ability of proteins, in particular, to catalyze reactions. The first forms of life, therefore, could have arisen without the participation of proteins and DNA. They have the function of storing information, as well as all inner work made by RNA. Life on Earth now descended from proto-organisms, which are autocatalytic cycles composed of self-replicating ribozymes. The theory was called "RNA World".

coacervates

Today it is difficult to imagine the life of that period, since it did not have one important feature - a shell or a border. In fact, it was a solution containing autocatalytic cycles from RNA. The problem of the lack of boundaries necessary for the correct flow of processes was solved by improvised methods. Protoorganisms found shelter near zeolite minerals, which had a network structure of the crystal lattice. Their surface was able to catalyze the formation of RNA chains and give them a certain configuration.

Further - more: coacervates or water-lipid drops appear on the stage. Hypotheses of both recent times and modernity are largely based on the theory of A.I. Oparin, who studied the properties of such formations. Coacervates are drops of solution enclosed in a shell of fats (lipids). Their membranes are also characterized by the ability to carry out metabolism. Some of them, apparently, combined with chains of self-replicating RNA, including those that catalyzed the synthesis of lipids themselves. Thus, new forms of life arose, having overcome the path from the pre-organismal level to the proper organismic one. The possibility of such formations was confirmed quite recently: scientists experimentally confirmed the ability of RNA in combination with calcium ions to attach to lipid membranes and regulate their permeability.

Skilled Helpers

The origin of life at the next stage was the process of improving the functions of the resulting organisms. RNA acquired the ability to catalyze the synthesis of amino acid polymers, initially quite simple. The crowning achievement of the new mechanism was the ability to synthesize proteins. The resulting formations coped with biological processes several times more effectively than ribozymes.

Initially, the synthesis of peptides was not ordered. The process happened "haphazardly", leaving the direction of the sequence of amino acids in new chains to chance. Over time, exact copying became entrenched, since it was it that contributed to the greater stability of the entire system. This is how it appeared allowing to synthesize certain proteins with the necessary functions.

Perfection

Honing the ability to synthesize the necessary proteins took place gradually. The first step was the emergence special kind RNA that could connect amino acids. The next phase was accompanied by the construction of the process of formation of peptide molecules with the help of bases lined up in a certain order. The sequence was set by the RNA template. Correlating the "instruction" of informative RNA and the elements of future proteins was taken up by a new type of RNA, called transport. As well as informational, it is still an important part of peptide synthesis to this day.

DNA

The complication of organisms further followed the path of improving the ways of storing information. It is assumed that originally DNA was one of the phases of the life cycle of RNA colonies. She had a more stable structure. Its degree of information protection was an order of magnitude higher, so after some, quite a long time, DNA became the main repository of the genetic code.

One of the properties of the new formation, which at one time did not allow placing DNA at the head of the theory of the origin of life, is the inability to take active actions. It has become a kind of payment for the improved functions of the information storage. All the "work" was left to proteins and RNA.

Symbiosis

Modern ideas about the origin of life do not deduce as an ancestor an organism that is closed and fenced off from the rest. Scientists are more in favor of the assumption that in the early stages there were communities of microscopic similarities of cells that performed different functions. Such a symbiosis is not difficult to find in nature today. The simplest example is cyano-bacterial mats, which are both a community of microorganisms and a single whole living being.

Biology on present stage sees its development as a process characterized not by constant struggle and competition, but rather by the ever-increasing rallying of certain diverse structures, which ultimately led to the emergence of a living cell, as we imagine it today.

Generalization

Summing up, we can briefly list all the stages of the formation of life, which, according to modern theories, are the most likely version of the appearance and development of organisms on Earth:

Formation of primary organic compounds in protoplanetary clouds.

Gradual coming to the forefront of self-accelerating reactions and autocatalytic cycles.

Emergence of autocatalytic cycles consisting of RNA.

Union of RNA and lipid membranes.

The acquisition of RNA's ability to synthesize protein.

The emergence of DNA and its establishment as the main repository of information.

The formation of the first unicellular organisms based on symbiosis.

Understanding the processes that led to the emergence of life is still imperfect. Scientists are left with a lot of questions. It is not known exactly how RNA originated, many intermediate phases remain only theoretical. However, new experiments are being set up every day, facts and hypotheses are being tested. We can say with confidence that our century will give the world a lot more discoveries related to the prehistoric era.

The question of the origin of life is one of the most difficult questions of modern natural science. However, great interest was riveted to him at all times. The difficulty in obtaining an answer to this question lies in the fact that it is difficult to accurately reproduce the processes and phenomena that took place 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 for the origin of life are distinguished.

creationism

According to this hypothesis, life and all species of living creatures inhabiting the Earth were created by God. Moreover, the divine creation of the world happened at once, so the very process of creating life is not available for observation in time. In addition, creationism does not give a clear interpretation of the origin of the Creator God 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 kind abiogenesis- the origin of life from non-living matter. This hypothesis was an alternative to creationism, when the accumulated knowledge of people about wildlife questioned the creation of life by God. The philosophers of ancient Greece and the naturalists of medieval Europe believed in the emergence of living organisms from inanimate matter. They believed and tried to prove that frogs and insects start in damp soil, flies in rotten meat, etc. Views about the spontaneous generation of life were widespread almost until the end of the 18th century. Only in the middle of the XIX century. French scientist Louis Pasteur proved that bacteria are ubiquitous. At the same time, any inanimate objects are “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 spontaneous generation of life.

Panspermia hypothesis

In 1865, the German scientist G. Richter proposed a hypothesis panspermia, according to which life could be brought to Earth from space along with meteorites and cosmic dust. A supporter of this hypothesis was the great Russian scientist, creator modern teaching about the biosphere V. I. Vernadsky. Modern research confirm 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 1920s. of the last century, the Russian biochemist A. I. Oparin and the 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 Earth's development there was a long period of abiogenesis. Living organisms did not participate in it. For the synthesis of organic compounds, the energy source was ultraviolet radiation Sun. Solar radiation was not retained by the ozone layer, because there was neither ozone nor 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 "primary broth". According to Oparin, it was in the "primordial soup" that life arose.

Oparin believed that the decisive role in the transformation of the inanimate into the living belongs to proteins. It is proteins that are able to form colloidal complexes that attract water molecules to themselves. Such complexes, merging with each other, formed coacervates- structures isolated from the rest of the body of water.

Coacervates possessed some properties of the living. They could selectively absorb matter from the surrounding solution and increase in size - a certain semblance of nutrition and growth. During the crushing of coacervates, new drops were formed that retained the main 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. Further, proteins dissolved in water were attached to such lipid formations. As a result, the surface of coacervates acquired the structure and properties biological membrane. Such a membrane could already pass some substances inside and not let others through.

Further association 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, feeding on the substances of the "primordial soup". 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: creationism, spontaneous generation, panspermia and biochemical hypotheses. Among the modern views of scientists on the origin of life, the most important place is occupied by the biochemical hypothesis. According to her, 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.

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

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 areas of the Universe has long attracted the attention of both scientists and philosophers, as well as ordinary people. In recent years, interest in this "eternal problem" has increased significantly.

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 steady 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 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 of life and monitors their development.

2. THE THEORY OF A STATIONARY STATE.

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.

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. “... One can talk about the eternity of life and the manifestations of its organisms, just as one 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 just as far from scientific research as the question of the beginning of matter, heat, electricity, magnetism, motion.

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.

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 the decomposition of the soil. It is the same 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).

The authority of Aristotle had an exceptional influence on the views of medieval scholars. The opinion of this philosopher in their minds was intricately intertwined with the teachings of the Church Fathers, often giving absurd and even ridiculous ideas from a modern point of view. The preparation of a living person or his likeness, "homunculus", in a flask, by mixing and distilling various chemicals, was considered in the Middle Ages, although very difficult and lawless, but no doubt doable. Obtaining animals from non-living materials seemed the scientists of that time is so simple and common that the famous alchemist and physician Van Helmont (1577 - 1644) directly gives a recipe, following which one 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. For this, a dirty shirt, a dark closet and a handful of wheat were needed. Van Helmont considered human sweat to be the active principle in the process of the birth of a mouse.

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

The further natural science developed, the more important accurate observation and experience became in the knowledge of nature, and not just reasoning and sophistication, the more narrowed was the scope of the theory of spontaneous generation. 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, by simple experiments, proved the groundlessness of opinions about the spontaneous generation of worms in rotting meat. He found that the little white worms were fly larvae. After conducting a series of experiments, he received data confirming the idea that life can only arise from a previous life (the concept of biogenesis).

“Conviction would be futile if it could not be confirmed by experiment. So in the middle of July I took four large, wide-mouthed vessels, put earth in one of them, some fish in another, Arno eels in the third, and a piece of veal in the fourth, closed them tightly and sealed them. Then I placed the same in four other vessels, leaving them open... Soon the meat and fish in the unsealed vessels were wormed; flies could be seen flying freely into and out of the vessels. But I did not see a single worm in the sealed vessels, although many days passed after dead fish” (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 XVII century. Kircher and Leeuwenhoek discovered the world of the smallest creatures, invisible to the naked eye and distinguishable only through a microscope. These “tiniest living animals” (this is how Leeuwenhoek called the bacteria and ciliates he discovered) could be found wherever decay occurred, in decoctions and infusions of plants that had stood for a long time, in rotting meat, broth, in sour milk, in feces, in plaque . “In my mouth,” Leeuwenhoek wrote, “there are more of them (germs) than there are people in the United Kingdom.” One has only to put perishable and easily rotting substances in a warm place for some time, as microscopic living creatures immediately develop in them, which were not there before. Where do these creatures come from? Could they really come from embryos that accidentally fell into the rotting liquid? How many of these germs must be everywhere! The thought involuntarily appeared that it was here, in rotting decoctions and infusions, that spontaneous generation of living microbes from inanimate matter took place. This opinion in the middle of the XVIII century. received strong confirmation in the experiments of the Scottish priest Needham. Needham took meat broth or concoctions vegetable matter, placed them in tightly closed vessels and boiled for a short time. At the same time, according to Needham, all the embryos should have died, while new ones could not get in from the outside, since the vessels were tightly closed. However, after a while, microbes appeared in the liquids. From this, the said scientist concluded that he was present at the phenomenon of spontaneous generation.

However, this opinion was opposed by another scientist, the Italian Spallanzani. Repeating Needham's experiments, he became convinced that a longer heating of vessels containing organic liquids completely dehydrates them. In 1765, Lazzaro Spallanzani conducted the following experiment: having boiled meat and vegetable broths for several hours, he immediately sealed them, after which he removed them from the fire. After examining the liquids a few days later, Spallanzani found no signs of life in them. From this, he concluded that the high temperature destroyed all forms of living beings and that without them, nothing living could have arisen.

A fierce dispute broke out between representatives of two opposing views. Spallanzani argued that the liquids in Needham's experiments were not heated enough and the embryos of living beings remained there. To this, Needham objected that he did not heat the liquids too little, but, on the contrary, Spallanzani heated them too much and by such a rude method destroyed the “generating force” 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 decaying liquids was not resolved either way for a whole century. During this time, many attempts have been made empirically to prove or disprove spontaneous generation, but none of them has led to definite results.

The question became more and more confused, and only in the middle 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 was able to solve the 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. In a number of experiments, he showed that everywhere, and especially near human habitation, the smallest germs rush in the air. They are so light that they float freely in the air, only very slowly and gradually sinking to the ground.

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

The mysterious appearance of microorganisms in the experiments of previous researchers was explained by Pasteur either by incomplete desolvation of the medium, 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 into the flask with air flowing into the flask, then in a hundred cases out of a hundred the liquid will not rot and the formation of microbes does not occur.

Pasteur used a wide variety of methods to dehydrate the air flowing into the flask: 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 were trapped, or, finally, passed the air through a thin glass tube , bent in the form of the letter S; in this case, all the nuclei were mechanically retained on the wet surfaces of the tube bends.

S-necked 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 removal of the S-shaped neck in the flask, a rapid growth of microorganisms is observed (the broth becomes cloudy).

Wherever the protection was sufficiently reliable, the appearance of microbes in the liquid was not observed. But perhaps prolonged heating has chemically changed the environment and made it unsuitable for supporting life? Pasteur easily refuted this objection as well. He threw a cotton plug into a liquid that had not been heated, through which air was passed and which, consequently, contained germs - the liquid quickly rotted. Therefore, boiled infusions are quite suitable soil for the development of microbes. This development does not take place just because there is no germ. As soon as the embryo enters the liquid, it immediately germinates and gives a lush harvest.

Pasteur's experiments showed with certainty that spontaneous generation of microbes in organic infusions does not occur. All living organisms develop from embryos, that is, they originate from other living beings. However, the confirmation of the theory of biogenesis gave rise to another problem. Since another living organism is needed 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 in all other theories it is assumed that at some stage in the history of life there was a transition from inanimate to living. So how did life originate on Earth?

4. THEORY OF PANSPERMIA.

Pasteur is rightly considered the father of the science of the simplest organisms - microbiology. Thanks to his work, an impetus was given to the most extensive studies of the world invisible to the naked eye of the smallest creatures inhabiting the earth, water and air. These studies were no longer directed, as before, to a mere description of the forms of microorganisms; bacteria, yeast, ciliates, amoeba, etc. studied from the point of view of their living conditions, their nutrition, respiration, reproduction, from the point of view of the changes that they produce 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 they thought before.

The body of any organism - a plant, a snail, a worm, a fish, a bird, an animal, a person - consists of the smallest bubbles visible only under a microscope. It is made up of these bubble cells, just as a house is made of bricks. Different organs of various animals and plants contain cells that differ from each other in their appearance. Adapting to the work that is assigned to this organ, the cells, its components, 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 only 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 relationship. 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 only 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 protoplasm contains whole line extremely complex chemical compounds (mainly proteins and their derivatives), which are not found anywhere else, only in organisms. These substances are not simply mixed, but are in a special state, little studied until now, due to which the protoplasm has the thinnest, poorly distinguishable even with a microscope, but extremely complex structure. The suggestion that such a complex formation with a well-defined fine organization could spontaneously arise within a few hours in structureless solutions, such as broths and infusions, is as wild as the suggestion that frogs form from May dew or mice from grain.

The exceptional complexity of the structure of even the simplest organisms so struck the minds of some scientists that they came to the conclusion that there was an impassable abyss between the living and the non-living. 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 occur 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. This is supported by the data of astronomy, and geology, and mineralogy, and other exact sciences - this is undoubtedly. This means that on Earth there were such conditions under which life was impossible, unthinkable. Only after the globe lost a significant part of its heat, scattering it into cold interplanetary space, only after the first thermal seas formed the first thermal seas, did the existence of organisms become possible, similar topics that we are currently observing. To clarify this contradiction, a theory was created that has a rather complicated 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 the German physician G. E. Richter in 1865, who argued that life is eternal and its rudiments can be transferred from one planet to another. This hypothesis is closely related to the steady state hypothesis. Proceeding from the idea that small particles of solid matter (cosmozoans), separated from celestial bodies, are everywhere in the world space, the above author assumed that simultaneously with these particles, perhaps, having stuck to them, viable germs of microorganisms are carried. Thus, these embryos can be transferred from one inhabited by organisms celestial body to another where there is no life yet. If favorable living conditions have already been created on this latter, in the sense of a suitable temperature and humidity, then the embryos begin to germinate, develop and subsequently become the ancestors of the entire organic world of this planet.

This theory has acquired 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, in which the viability of these embryos would be preserved. After all, in fact, in the end, the main question is precisely whether a spore can make such a long and dangerous journey as a flight from one world to another without dying, retaining the ability to germinate and develop into a new organism. Let us analyze in detail what dangers are encountered on the way of the embryo.

First of all, it is the coldness of interplanetary space (220° below zero). Separated from its home planet, the embryo is doomed to rush for many years, centuries and even millennia in such terrifying temperatures before a happy chance gives it the opportunity to descend to a new earth. Involuntarily there is a doubt whether the embryo is capable of withstanding such a test. To resolve this issue, we turned to the study of resistance to cold of modern spores. Experiments carried out in this direction have shown that the germs of micro-organisms endure cold very well. They remain viable even after six months at 200° below zero. Of course, 6 months is not 1000 years, but still experience gives us the right to assume that at least some of the embryos can survive terrible cold interplanetary space.

A much greater danger to the embryos is their complete exposure to light rays. Their path between the planets is permeated with the rays of the sun, which are detrimental to most microbes. Some bacteria die from the action of direct sunlight within a few hours, others are more resistant, but all microbes, without exception, are adversely affected by very strong lighting. However, this unfavorable effect is greatly 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 germs of life will pass this test as well.

But a lucky chance gives the embryo the opportunity to fall into the sphere of attraction of some planet with favorable temperature and humidity conditions for the development of life. The only thing left for the wanderer, obeying the force of gravity, is to fall to his new Earth. But just here, almost already in a peaceful harbor, a formidable danger awaits him. Previously, the embryo hovered in a vacuum, but now, before falling to 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 “shooting stars” - meteors. Modern science explains this phenomenon as follows. In interplanetary space, solid bodies and particles of various sizes are worn, perhaps fragments of planets or comets that have flown into our solar system from the farthest places in the universe. Flying near the globe, they are attracted by this latter, but before falling on its surface, they must fly through the air atmosphere. Due to air friction, a rapidly falling meteorite heats up to a white heat and becomes visible in the dark firmament. Only a few of the meteorites reach the earth, most of them burn out from the intense heat still far from its surface.

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

At the same time, one should not forget about those colossal astronomical periods of time during which the Earth could be sown with germs 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 the surface of the Earth safely and found conditions suitable for its development here, then this would already be enough for the formation of the entire organic world. This possibility with state of the art science seems, although unlikely, but permissible; in any case, we have no facts that directly contradict it.

However, the theory of panspermia is only an answer to the question of the origin of life on earth, and by no means to the question of the origin of life in general, transferring the problem to another place in the Universe.

“One of the two,” says Helmholtz. “Organic life has either ever begun (originated), or exists forever.” If we admit the first, then the theory of panspermia loses all logical meaning, since if life could originate somewhere in the Universe, then, based on the uniformity of the world, we have no reason to assert that it could not originate 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 in the study of meteorites and comets, many "precursors of the living" 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 the Earth." In 1992, the works of American scientists appeared, where, based on a study of material collected in Antarctica, they describe the presence in meteorites of the remains of living beings resembling bacteria.

Modern adherents of the concept of panspermia (including the Nobel Prize winner English biophysicist F. Crick) believe that life on Earth was brought by accident or intentionally by space aliens with the help of aircraft. Evidence of this is the repeated appearances of UFOs, rock carvings of objects similar to spaceports, as well as reports of meetings with aliens.

The point of view of astronomers C. Wickramasingh (Sri Lanka) and F. Hoyle (Great Britain) adjoins the panspermia hypothesis. They believe that in outer space, mainly in gas and dust clouds, in in large numbers microorganisms are present. Further, these microorganisms are captured by comets, which then, passing near the planets, "sow the germs of life."

Other scientists express the idea of transferring the "spores of life" to Earth by light (under the pressure of light).

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

5. THE 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 (b. 1894). In 1924, he published works in which he outlined ideas about how life could have arisen on Earth. 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. The formation of biopolymers (proteins, nucleic acids, polysaccharides, lipids, etc.) from simpler organic substances.

3. Emergence of primitive self-reproducing organisms.

The theory of biochemical evolution has the largest number of supporters among modern scientists. The earth arose about five billion years ago; Initially, its surface temperature was very high (4000 - 80000C). As it cooled, a solid surface was formed (the earth's crust - the lithosphere). The atmosphere, which originally consisted of light gases (hydrogen, helium), could not be effectively retained by the insufficiently dense Earth, and these gases were replaced by heavier gases: 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 soup" 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, the primary living creatures 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 the inanimate into the living belongs to proteins. Apparently, protein molecules, attracting water molecules, formed colloidal hydrophilic complexes. Further merging of such complexes with each other led to the separation of colloids from the aqueous medium (coacervation). On the border between the coacervate (from the Latin coacervus - clot, heap) and the environment, lipid molecules lined up - a primitive cell membrane. It is assumed that colloids could exchange molecules with 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”.

The theory was substantiated, except for one problem, which for a long time turned a blind eye to almost all experts in the field of the origin of life. If single successful constructions of protein molecules (for example, effective catalysts that provide an advantage for this coacervate in growth and reproduction) arose spontaneously, by means of random template-free syntheses in a coacervate, how could they be copied for distribution within the coacervate, and even more so for transmission to descendant coacervates? The theory has been unable to offer a solution to the problem of exact reproduction - within the coacervate and in generations - of single, randomly appearing effective protein structures.

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 a synthesis have been made in numerous laboratories around the world. For example, the American scientist S. Miller, based on assumptions about 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, some of the scientists managed to get quite long chains of peptides (simple proteins). Only! No one has been lucky enough to synthesize even the simplest living organism. Nowadays Redi's principle is popular among scientists: "The living - only from the living."

But suppose that such attempts will someday be crowned with success. What will such an experience prove? Only that for the synthesis of life, the human mind, a 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, took place in this direction. Here we observe nothing but the creative process. The second law of thermodynamics is an immutable law, the only law that has never been questioned, violated or refuted. Therefore, the 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. So, L. Blumenfeld proved that the probability of the random formation of at least one DNA molecule (deoxyribonucleic acid - one of the most important constituent parts genetic code) is 1/10800 Think about the negligible amount of this number! Indeed, in its denominator there is a figure, where after one there is a series of 800 zeros, and this number is an incredible number of times greater than the total number of all atoms in the Universe. The modern American astrophysicist C. Wickramasinghe figuratively expressed the impossibility of abiogenic synthesis: “It is faster for a hurricane that sweeps over a cemetery of old aircraft to assemble a brand new superliner from pieces of scrap than as a result of a random process life will arise from its components.”

Contradict the theory of abiogenic synthesis and geological data. No matter how far we penetrate into the depths of geological history, we do not find traces of the "Azoic era", that is, the period when life did not exist on Earth.

Now paleontologists in rocks whose age reaches 3.8 billion years, that is, close to the time of the formation of the Earth (4-4.5 billion years ago, according to recent estimates), have found fossils of rather complexly organized creatures - bacteria, algae, simple fungi. V. Vernadsky was sure that life is geologically eternal, that is, there was no era in geological history when our planet was lifeless. “The problem of abiogenesis (spontaneous generation of living organisms),” the scientist wrote in 1938, “remains fruitless and paralyzes really overdue scientific work.”

The terrestrial form of life is extremely closely related to the hydrosphere. This is evidenced at least 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%). Obviously, life on Earth was formed only when the hydrosphere appeared on it, and this, according to geological information, happened almost from the beginning of the existence of our planet. Many of the properties of living organisms are due precisely to the properties of water, while water itself is a phenomenal compound. So, according to P. Privalov, water is a cooperative system in which any action is distributed by a "relay" way over thousands of interatomic distances, that is, there is a "far action".

Some scientists believe that the entire hydrosphere of the Earth, in essence, is one giant "molecule" of water. It has been established that water can be activated by natural electromagnetic fields 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 constituent parts, “drops” of this supermolecule of terrestrial water.

Although we still know only terrestrial protein-nucleic-aquatic life, this does not mean that its other forms cannot exist in the boundless Cosmos. Some scientists, in particular American ones, G. Feinberg and R. Shapiro, model such hypothetically possible variants of it:

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

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

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

waterfowl - life that can exist at low temperatures on planets covered with "reservoirs" of liquid methane, and draw energy from the conversion of orthohydrogen to parahydrogen;

thermophages are a type of cosmic life that derives energy from the temperature gradient in the atmosphere or oceans of planets.

Of course, such exotic life forms so far exist only in the imagination of scientists and science fiction writers. Nevertheless, the possibility of the real existence of some of them, in particular plasmoids, is not ruled out. There are some reasons to believe that on Earth, in parallel with "our" form of life, there is another kind of it, similar to the mentioned plasmoids. These include some types of UFOs (unidentified flying objects), formations similar to ball lightning, as well as invisible to the eye, but fixed by color photographic film, energy “clots” flying in the atmosphere, which in some cases showed reasonable behavior.

Thus, now there is reason to assert that life on Earth appeared from the very beginning of its existence and arose, according to C. Wickramasinghe, "from an all-penetrating general galactic living system."

CONCLUSION.

Do we have a logical right to recognize the fundamental difference between the living and the non-living? Are there facts in the nature surrounding us that convince us that life exists forever and has so little in common with inanimate nature that under no circumstances could it ever form, stand out from it? Can we recognize organisms as formations completely, fundamentally different from the rest of the world?

Biology of the 20th century deepened the understanding of the essential features of the living, revealing the molecular foundations of life. At the heart of the modern biological picture of the world lies the idea that the living world is a grandiose system of highly organized systems.

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

After reviewing the main theories of the origin of life on Earth, the creation theory seemed to me personally the most likely. The Bible states that God created everything out of nothing. Surprisingly, modern science admits that everything could be created from nothing. "Nothing" in scientific terminology is called a vacuum. Vacuum, which the physics of the nineteenth century. considered emptiness, according to modern scientific concepts, it is a peculiar form of matter, capable of “giving birth” to material particles under certain conditions. Modern quantum mechanics admits 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 substance. - 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 higher students educational institutions. - M.: Russian Economic Academy. Plekhanov, 1998.

Tutoring

Need help learning a topic?

Our experts will advise or provide tutoring services on topics of interest to you.
Submit an application indicating the topic right now to find out about the possibility of obtaining a consultation.