LIFE

From Big Medical Encyclopedia

LIFE — one of the highest forms of motion and organization of matter. On Earth life arose as result of evolution of carbonaceous connections and is presented by various organisms — the individual complete systems possessing a certain complex structure and the metabolism determined by order mutually agreed biochemical, reactions.

Thousand-year history of knowledge of essence. was always the arena of ideological fight between materialism and idealism, science and religion. Difficulty of a scientific solution. was premises of the fact that the religion and idealism found the strongest shelter here. To the religious concept about the divine nature of creation of living beings there correspond idealistic views creationism (see), vitalism (see) etc. At the heart of all these doctrines, despite their variety, one idea lies —. by the nature it is non-material and is result of an animation of matter by «the vital force». Matter, being lifeless and inert, serves only as material, from to-rogo soul (or spirit) creates living beings, purposefully manages their vital processes. The course of vital processes nevertheless submits to the fixed laws not connected with direct and extraordinary interventions of transcendental (supernatural) forces. Therefore studying of these processes by perhaps objective methods of a research, but this studying is not enough for understanding of the essence., since within the specified laws all phenomena. and all its development is predetermined by the predefined plan which is put in matter by god at the emergence.

Materialists of primary consider matter, i.e. that objective reality, to-ruyu it is possible to observe directly and to study by practical consideration. From these positions Zh., as well as the rest of the world, it is material by the nature and for her understanding there is no need for recognition of any spiritual beginning incomprehensible by practical consideration.

From positions of dialectic materialism emergence. is considered as natural, material process, as a natural stage in development of matter as a special step of development in succession of forms of motion of matter.

Matter is in the constant movement which is concerning matter not something external, and it is necessary connected with its essence. At the same time the movement of matter cannot be considered only as movement of material bodies in space; also other, more irregular shapes of the movement arising in development of matter as its new qualities are inherent in numerous objects of reality. This development has forward character, is directed to emergence of more and more high forms of motion of matter, is observed everywhere in the world surrounding us. The arising new qualities of material objects are quite real, but they did not predsushchestvovat before the emergence in some hidden look, they really appear again only at this stage of development of matter as more difficult, diverse and more differentiated forms of motion. At emergence at matter of new qualities former forms of motion do not disappear, but as if recede into the background. Their value for the subsequent development of qualitatively new objects becomes rather small in comparison with value of new forms of motion. The future of qualitatively new natural bodies is defined generally already by their special characteristics and new objective patterns which cannot be reduced by the simple analysis to former more primitive forms.

Rational knowledge of new forms can be reached only on the way of studying of those new qualities which arise during historical development of matter. Therefore from positions of dialectic materialism a problem of knowledge. it is formulated differently, than from positions of a mekhanitsizm. If for mekhanitsist it comes down to an explanation. only laws of physics and chemistry, for representatives of dialectic materialism the main thing for knowledge. — this establishment of its qualitative difference from other forms of motion of matter.

F. Engels gave the following definition to life: «Life is mode of existence of proteinaceous bodies, and this mode of existence consists on the being in continuous updating of their chemical components by food and allocation» (F. Engels, Anti-Dyuring, 1969, Art. 350). Thus, Engels characterized proteinaceous bodies as material carriers Zh., and a metabolism — as their main function, from a cut all other signs of life are removed. At the same time F. Engels made the following reservation: «Our definition of life, certainly, is very insufficient as it is far from capturing all phenomena of life, and, on the contrary, is limited the most general and the simplest among them... To gain really exhaustive impression about life, we should track all forms of its manifestation, from the lowest to the highest» (in the same place, p. 80).

Only studying of all new qualities of matter which consistently arose in the course of its historical development — from inorganic forms of motion to biological, and their subsequent evolution can give the rational answer to a question of why these qualities arose and why they such what are observed now.

Representatives of mechanical materialism did not manage to resolve a problem of an origin of life. Therefore one of them claimed that. on Earth at all never arose, and it was brought from other worlds where it exists eternally. Others considered that emergence. was some unique «lucky coincidence», edges could occur only once for all the time of existence of Earth and therefore it cannot be reproduced in experience.

Only dialektiko-materialistic approach considering. as one of forms of motion of matter which arose in the course of its evolution allows to resolve a problem of essence.

The world surrounding the person continuously changes, evolves. This development has forward character and leads to emergence everything the new, harder and harder, diverse and more differentiated forms of reality. At the same time it cannot be carried out at the same time and equally everywhere. Therefore in scales of the Universe on its various objects evolutionary development of matter is carried out in various ways and various rates that it is schematically possible to present in the form of a bunch of various ways which separate branches can lead to very irregular and perfect forms of the organization and movement of matter, many of which still are not known, and in some cases we even do not suspect about their existence.

At the same time it is known. only in the only option — only terrestrial. and only from it it is necessary to proceed in the ideas of other possible forms biol, the organizations of matter. Therefore Earth and events which were taking place on it shall serve to a certain extent as model for more sweeping generalization about possible forms Zh. on other objects of the Universe.

On Earth. arose as result of progressive development of carbonaceous connections, organic matters and the supramolecular systems formed of them. Initial stages of this evolution had abiotic character and still are eurysynusic in space.

Radio-astronomical researches of various areas of interstellar space indicate existence in them of various carbonaceous connections: formaldehyde, cyanides, cyanoacetylene, etc. It is undoubted that in interstellar dust clouds, strongly radiiruyemy star radiations, form also more complicated organic molecules.

There are data allowing to consider that the atmosphere of stars, accumulations of dust matter, cometary clots and interstellar space contain a large amount of carbon and its connections, i.e. abiotic organic matters which can provide chemical evolution on the way of formation.

The existing ideas of emergence of Solar system show that space organic matters had to be a part of Earth already at its emergence. Part of them disappeared in world space, a part underwent disintegration at the subsequent local warming up of Earth. But along with this decomposition, during the formation of crust, the hydrosphere and the atmosphere there was also a catalytic synthesis of more and more complex organic matters.

Thus, from the moment of formation of Earth on its surface there already had to be various organic matters which were exposed to the further changes and complications which made in total a chemical stage of evolution of matter on the way to Zh.

Provedeno's emergence a large number of the laboratory experiments imitating the conditions existing on the surface still of lifeless Earth. These experiences convincingly show that in a subsoil of crust, in the atmosphere and the hydrosphere there had to be a formation of many organic matters, in particular amino acids, the purine and pirimidinovy bases, a ribose and desoxyribose, i.e. the chemical connections playing a paramount role in metabolism of modern organisms.

It is important that in such conditions emergence not only the listed above monomers, but also their polymers — polypeptides and polynucleotides is possible. Fox (S. W. Fox, 1960), imitating volcanic conditions, received the belkovopodobny high-molecular «proteinoida» having intramolecular orderliness, the repeating sequence of the amino-acid remains and insignificant euzymatic activity.

Synthesis of such substances can go already on purely catalytic basis, but is especially successful due to energy of the natural sources which are available on the Earth's surface — electric discharges, ionizing radiation, heat of volcanic eruptions, and also the short-wave ultraviolet radiation which is easily getting through the atmosphere of that time deprived of the ozone screen. At the same time there had to be not only a synthesis, but also disintegration of complex organic matters, and according to laws of thermodynamics this process shall prevail. Calculation of a thermodynamic equilibrium, a cut would have to step on the surfaces of primary ocean which is exposed to long influence of short-wave ultraviolet radiation shows that at approach of a thermodynamic equilibrium only a minute quantity of organic matters could remain here. However in nature on the Earth's surface there could not come the thermodynamic equilibrium since there was a continuous movement of the substances synthesized in one place to other conditions. On the basis of a big geol. material it is possible to present as follows a picture of the land surface of the period of origin. on Earth. Strongly leveled land only slightly rose over the level of the shallow-water seas. The ratio of water and sushi changed; the waters impregnating terrestrial soil, came, receded, continuously moving the substances dissolved in them from places of their education to the places of accumulation protected from the decomposing action of ultraviolet radiation or other similar influence. There was a further complication of organic molecules to the subsequent transition from a chemical phase of evolution to it biol, to a stage. This transition was connected with consecutive emergence of the main characteristic of all live properties: 1) abilities to overcome increase of entropy; 2) so-called expediency of the organization, fitness to existence in these conditions of the environment, and also fitness of all parts of an organism (molecules, cells and bodies) to the functions which are carried out in vital process; 3) abilities to preservation and transfer of the hereditary information based on the intramolecular organization of high-molecular compounds (a nucleinic code).

The first question following solutions of a problem of transition of chemical evolution in biol., comes down to how could arise characteristic for. an order from random chaotic thermal agitation of organic molecules in «primary broth». At first sight it seems that such event in general is impossible since it contradicts the second law of thermodynamics, on Krom the system consisting of a large number of chaotically moving particles is characterized by a tendency to spontaneous transition from conditions of less probable in more probable. However this contradiction can be considered overcome on the basis of the doctrine about open circuits which thermodynamics significantly differs from classical thermodynamics (see).

In open circuits continuously there is an intake of substances and the related energy from the environment in the system delimited from it in one way or another and removal from system of the chemical connections arising in it back. Therefore constancy of properties of such open circuit in time is characterized not by a thermodynamic equilibrium (as it is observed in loop systems), and emergence of a stationary state, at Krom constancy of speeds unilaterally of the proceeding chemical changes and diffusion of substances in system, provided with receipt of free energy from the outside is observed.

Emergence of open circuits first of all requires existence of multiphase, allocation from initial homogeneous solution of the individual multimolecular educations which stood apart from the environment a certain interface. This phenomenon is extremely widespread in the nature, is observed at laboratory experiments, in particular during the work with high-molecular organic substances. There is no doubt that such processes in grandiose scales repeatedly happened also on the surface of lifeless Earth in places of concentration of organic polymers — in so-called subvital territories. In such way there were predecessors of live systems here — «pro-bionts».

It is possible to monitor their education and further evolution on the basis of model experiences with various open circuits, in particular with coacervate drops. These drops are easily allocated from solutions of high-molecular organic substances, and the molecules which are earlier evenly distributed in solution combine in the whole Molecular swarms forming the drops seen under a microscope delimited from the environment (solution) surrounding them distinct by the expressed interface, but capable to interact with this Wednesday as open circuits. Model experiences show that in such systems various chemical transformations can be made. Drops are absorbed from the environment by attendees of substance in it (in particular, makroergichesky) and turn them into polymers of the body. At the expense of it drops can increase in the volume and weight — grow as individual educations; growth rate depends on the internal organization of this drop, in particular on availability in it catalystically of active ingredients and a harmonious combination of their action. Therefore the drops with various sets of catalysts which are in identical solution behave differently. One of them grow quickly whereas growth of others is slowed down and oppressed; there can be even their full disintegration. Thus, model experiences show a possibility of primitive selection of drops depending on their interaction with the environment.

In nature at a certain stage of evolution in these or those «subvital territories» primitive natural selection of pro-bionts had to arise similarly.

The opinion is expressed, it agrees to - it is necessary for rum for initial formation of live systems that in water solution of the terrestrial hydrosphere originally (at molecular level) there were internally organized and reasonablly constructed proteic matters and nucleinic to - you. Self-assembly of their molecules as if also led to formation of primary organisms, like that as the car is mounted from in advance made details. Of course, such representation is an echo of the former mechanistic views assimilating an organism to the mechanism. Fitness of details to work in the complete car is caused by the fact that they are produced according to in advance provided plan or the drawing. At emergence of living beings it is impossible to recognize preexistence of any «plan of creation», but then it is absolutely unclear how could arise in «primary broth» of a molecule of proteins or nucleinic to - the t possessing an intramolecular structure not only strictly certain and perfect, but also adapted for implementation of those functions which they will perform in the complete live system formed of them.

It is known that already in primitive abiogenous conditions the high-molecular polypeptides possessing the known intramolecular structure (the sequence of the amino-acid remains) could be formed and nek-dig euzymatic activity. However this activity in itself does not bear yet any expediency since for the protein it has no value. Such expediency is gained in complete system (in a pro-biont) and only in only that case when the reaction catalyzed by this protein is an important link in the progressing metabolism of a pro-biont causing dynamic stability and rapid growth of all complete system.

The pro-bionts arising in various «subvital territories» could be formed of the polymers (in particular, belkovopodobny substances) which were not possessing any natural intramolecular structure. Both on the chemical structure, and by the principle of the space organization they had to differ strongly among themselves. But only those from them which had dynamic stability could not only is long to remain in these conditions, but also to expand, and then to be split up for affiliated educations under the influence of external mechanical factors.

Thus, already at this stage of evolution natural selection of pro-bionts, in initial Darvinian understanding of this term as survival of systems fittest to conditions of the environment is carried out. Safety, the known constancy of the organization of these systems could be based on this stage only on the dynamic bases, on improvement of an interconsistency made in system of metabolic reactions. Therefore the proteic matters possessing catalytic functions played a crucial role.

On the basis of the latest experimental data it is possible to present emergence of purely proteinaceous evolving pro-bionts theoretically. However in such systems reproduction of proteins was imperfect and easy was broken.

Contrary to proteins nucleinic to - you do not bear catalytic functions, but they have ability to very perfect reproduction.

Extremely important advantage, from the evolutionary point of view, was received by those pro-bionts which included not only reasonablly constructed belkovopodobny polymers, but also polynucleotides, capable to molecular reproduction, that caused very perfect transfer of properties from ancestors to descendants. Already at simple mixing of unorganized polypeptides and polynucleotides (yet not bearing any genetic information) there is an association of these substances in fazovoobosoblenny educations. In them also there had to be an interaction of originally independent proteins and nucleinic to - t and the subsequent evolution of the so-called genetic code which defined further preservation and perfect transfer of hereditary information.

Emergence of fitness of an intramolecular structure of proteins and nucleinic to - t to the functions which are carried out by them in an organism and improvement of this fitness could happen only on the basis of natural selection. But not these or those polynucleotides, capable to replication, and even reasonablly constructed proteins-enzymes which were not arising under their influence, and the complete evolving systems — pro-bionts and the living beings arising from them were exposed to this selection. Therefore, not parts defined the organization whole, and whole in the development created expediency of a structure of parts.

In process of further improvement. there were all new and new properties inherent in already only more developed living beings: ability to autotrophic food, photosynthesis, oxygen breath, cellular structure, mitosis, multicellularity, sexual process, ability to the movement, irritation and many others.

See also Darwinism , Theory of evolution .



Bibliography: Marx K. and Engels F. Compositions, 2nd prod., t. 20, M., 1955; B D. Zh er-cash. Emergence of life, the lane with English, M., 1969; The Horizons of biochemistry, under the editorship of L. A. Tumerman, the lane with English, M., 1964; Oparin A. I. Life, its nature, origin and development, M., 1968; P at t of t of e of N of M. An origin of life (a natural way), the lane with English, M., 1973; Schrödinger E. What is life from the point of view of physics, the lane with English, M., 1947.

A. I. Oparin.

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