Life comes from energy: Energy → plants, microorganism Animals, etc. Living individual They all go through birth, growth and death. The living population in the succession of individuals from generation to generation, relying on the random variation of genes to continue to reality Convergent evolution . Cosmological philosophy holds that life repeats itself spontaneously in conjunction with law Cosmic spirit . ^[1]

But to include the impossible, the unknown Life form The definition of life must be general enough or even vague enough to encompass the widest possible range of life forms. And life itself is a process, Living entity It's the process carrier This makes the definition of life and living entities very difficult. There is no single, widely accepted definition of life. Here's a try:

Life is designed to reproduce, to be spontaneous Entropy change For specific ways of evolution and Adaptive process . (Of course, living things degrade themselves Entropy value But this is not always successful: sometimes because their homeostasis is disrupted, such as aging; Sometimes because they cannot fully resist the high entropy pressure of the outside world. Entropy change should be primarily oriented towards metabolism and the processes that regulate it: material, energy, information.

Chinese name: HP
Foreign name: life, albumoxy
alias: Life pulsation, miracle

General reference: stable matter and Energy metabolism phenomenon
longitude: Be born , Grow up and Death
synonym: life

catalogue

Life definition

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EDITOR

Essence of life

Process. From a macro point of view: everything is life, that is, the process, the process basically has three stages: occurrence, survival, death, its basic characteristics are: Immortality of matter ( Nuclear reaction Except, in fact, so does this one Godel's theorem But the structure of matter changes (at whatever stage), so that what is called life (which we care about) is logically the structure of matter, in the term information.

The three stages of life are actually the process by which matter changes from disorder to order and finally back to disorder.

The participants are matter and energy (both are actually energy), and what changes is the structure of matter (because matter is in motion).

The life we talk about every day actually refers to: organic life, but it still meets the basic definition of life, the difference (the extension of the class) is the ability to react dynamically to the outside world.

Life is a material system of growth and change. Organic life is a material system unique to the astral environment such as the earth, composed of water as a carrier, with the ability of self-creation, precision replication, gentle division, etc., irreversible but always continue to repeat or continue these abilities. An organic being such as a cell, an animal, a plant, etc.

According to human convention, organic life is simply life. It is not difficult for the average person to distinguish between what is animate and what is inanimate. But it took thousands of years to come up with a scientific definition of life Hard problem It's not completely resolved. This question is directly related to man's understanding of himself.

Biological definition

Life is made of Nucleic acid and protein Such substances constitute a molecular system that it has continuously propagate Offspring and the ability to react to the outside world.

The general scientific definition of modern biology goes something like this: Life is the manifestation of self-reproduction, Growth and development , metabolism, Genetic variation And react to stimuli and other complex phenomena. Here, none of these single phenomena is unique to living things. Flame can also metabolize and reproduce, but most people wouldn't think of it as life. The seeds of many plants can be preserved for a long time without appearing Vital signature For example Ancient lotus seed , A tardigrade It may not be metabolized for a considerable period of time, and it will come to life when the conditions are right. The complex phenomenon of self-reproduction, growth and development, metabolism, genetic variation and response to stimulation shown by organisms is called "life".

Biological individuals in some Critical period It doesn't manifest at all Life phenomenon Like fertilized eggs, bacteria in the air, virus All kinds of seeds, even hibernating snakes and so on. They have no metabolism, no growth and development and other life characteristics, but they are also the category of life, we can not call them "non-life", each life has its way of survival, they are part of life, without them, life will end. Things like eating, things like human communication, things that animals do before coitus.

Let's learn about life by listing some of the changes and characteristics of living things.

identity

In terms of elemental composition, more than 110 species have been found Chemical element The elements necessary for all kinds of organisms are almost specific ten or twenty, among which C, H, O, N, P, S, Ca Mg, K accounted for supermajority .

From the point of view of molecular composition, the important characteristic of living organisms is that they basically contain what is called biomolecule Proteins, nucleic acids, lipin These organic molecules are the same in all kinds of organisms Structural model And function. Like all living things Genetic material All are DNA and RNA In the body of life catalysis Enzymes are all kinds of proteins that all kinds of organisms use High-energy compound ( ATP , NADH ...) Etc., all stated Biological kingdom in Chemical composition There is a high degree of identity.

structure

The various chemical components of an organism are not piled together randomly in the body, but are strictly ordered (strictly structured). biotic Basic unit Is a cell (virus, viroid , prion There's a debate about whether they belong in the realm of life, but they all need to be Cell structure Inside can complete normally Vital activity ). Intracellular each Structural unit Have a specific structure and function. biomacromolecule No matter how complicated, is not life, only when macromolecule Form a certain structure, or The formation of such an orderly system as cells can show the phenomenon of life . Loss of order, as when cells are beaten homogenate Life is over.

The biological world is a multi-layered one Ordered structure . On top of the cells are tissues, organs, systems, entity , population, community , ecosystem And so on. The individual structural units in each level, such as The nine systems of the human body Each organ in the system has its own specific structure and function, and their coordinated activities constitute a complex system Living system .

metabolism

The organism is Open system , organisms and Surrounding environment Go on Material exchange and Energy flow . After some substances are absorbed by the organism, a series of changes occur in it, becoming the final product and being excreted from the body, which is called metabolism. Metabolism is an orderly process, a series of enzymes Chemical reaction The reaction network. If the order of the metabolic process is destroyed, such as certain links are blocked, the entire metabolic process may be disrupted, life will be threatened, and even lead to the disappearance of life characteristics.

irritability

bioenergy To respond to external stimuli. It involves two processes: perception and response. The result of the reaction is to make the organism "seek advantage and avoid harm". In a drop paramecium Drop a small drop of acetic acid in the suspension, and the paramecia swim away. A piece of carrion Can attract fly ; plant Stem apex Growing to the light, that's all irritability .

Irritability is a universal characteristic of living things. However, the stress of animals is more obvious and more diverse. animalistic Sensory organ and Motor organ It is the product of highly developed irritability.

Steady state

No matter how the environment changes, the organism must remain Internal environment The stability to maintain normal life activities. Over 100 years ago, Bernard (C. Bernard) found that although the external environment fluctuates greatly, but mammal There is always some mechanism that keeps its internal environment constant, and W. B. Cannon later developed this concept under the name homeostasis. Later, it was found that not only mammals, but all living organisms, cells, communities, and even ecosystems are stable in the absence of violent external factors, and each has its own specific mechanism to ensure the stability of its own dynamics.

Growth and development

All living things can grow and develop through metabolism. A seed can become a tree, a tadpole can become a frog. though Environmental condition It can affect the growth and development of organisms, but the growth and development of each organism is carried out in accordance with a certain size range, a certain pattern and a stable procedure.

Heredity and evolution

No individual organism can exist for a long time, they produce children through reproduction so that life can continue. Progeny and Parental generation The similarity in morphology, structure and physiological function is the result of heredity. The differences between parents and children are caused by variation. The evolution of life from about 3.8 billion years ago, from simple to complex, from low to high is the result of evolution.

Adapt to

Every living thing has its own unique Living environment Specific structures and functions are always suitable for survival and continuation under such environmental conditions. For example, the structure of gills is suitable for fish to breathe in water, on land vertebrate The lung structure is adapted to land respiration . Adaptation is a unique phenomenon of life.

The adaptation of any organism to its environment is always relative. Because of genetic and phenotypic differences, individuals of the same species always have different degrees of adaptation to the environment. As long as there is such a difference, even a slight one, Natural selection It works, pushing the group to evolve in a way that makes it better suited to its environment.

Other definitions

Life consists of nucleic acids, proteins, etc biomacromolecule Is composed of organisms, constantly carrying out material, information and Energy exchange A synthesis of Motion form . Man's life is for certain Social environment Have in relation self-awareness The biological entity. Human life is a biological attribute with Social attribute High unity, human sociality It is the most essential feature of human life that is different from other animals, and life should be emphasized in human survival Material value , Spiritual value And the unity of human values.

Because of the complexity of life, life does not have an accurate definition, can only be grasped Essence of life Complexity to define life.

Some people define life as "life is having. autocatalysis Characteristic cyclic reaction molecular system, can co-cycle with the environment; pass Synergistic effect , integration ; Is a functionally coupled hypercyclic organization." According to this definition, the cyclic reactions of a large number of molecular systems can be coherently evolved through synergies and thus maintained Steady state . The information of life can be stored in large molecules of DNA, and can also be copied, transcribed, and translated biochemistry Loop Reaction structure And to enlarge, to form individuals, that is life. By the traditional definition, a virus is not a complete life; By this definition, a virus is a complete "life." Viruses must depend on cells to survive; For the virus, the cell is its survival "environment", and can co-cycle with the environment.

Common cycle The concept goes beyond" irritability The concept of homeostasis and evolution is fundamental, while heredity is not necessary (co-cycles can be understood in ecological terms as coevolution ).

(1)[life] : the ability of an organism to exist and act

(2)[vitality] : The quality of a thing that enables it to exist

(3)[condition] : means the qualification and ability to participate in a certain activity

Basic attribute

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EDITOR

self-regulation

Self-regulation is one of life Essential attribute . Any life at every moment of its existence , They are constantly adjusting their internal functions and adjusting their relationship with the external environment. hyperbiotic self-regulation Be multi-layered Including molecular, cellular, and global regulation. Even if prokaryote There is also self-regulation, and it is also achieved in a variety of ways. For example, bacteria have the ability to synthesize many of the molecules they need, and whether a molecule is synthesized, and how fast it is synthesized, depends on their internal state and environment. The molecules needed inside bacteria are neither produced in abundance nor felt lacking, but depend on themselves Regulatory mechanism Finished. The first enzyme in a molecular pathway Structural gene Both the function of regulation, that is, the first enzyme has the function of enzyme, but also plays Repressor protein Qualitative effect.

In genetics and biochemistry, this function is called Self-regulating system . This regulatory system was originally developed in salmonella histidine biosynthesis Found in, and subsequently in bacteriophage , mold It is also found in mammals. In fact, Feedback suppression The regulation of inductive and repressive systems can also be regarded as a way of biological self-regulation. Because in feedback suppression, Biosynthetic pathway The first of these enzymes occurs by binding to the end products of metabolism reversibility inactivation The synthesis rate of many compounds can be adjusted. In both the induction system and the repression system, even the production of the enzyme itself is regulated. The difference is that in the induction system, the enzyme required for the substrate is produced only when the substrate is present, in the way that the substrate and repressor Bind and inactivate the repressor, thereby turning on structural genes to induce gene activity; In a repressing system, End product inhibition The enzyme is produced by combining the repressor with the end product to be activated, and then with Operator gene Combine, thus turning off structural genes to Repressible enzyme The production of. Many biological regulatory systems are complex, and they often have both positive and negative regulatory effects. The regulation mechanism of the body is a process of self-completion, and the regulation program or instruction is inherited and inherent in itself, so this kind of self-regulation system is unique to life.

self-replication

It is a characteristic of living systems that differs from chemical systems. In a narrow sense, self-replication Refer to DNA molecule the unwinding The two chains are separated and respectively synthesized Complementary chain To form two new but identical molecules. Broadly speaking, it includes Cell division Reproduce inside. As far as the basis is concerned, division and reproduction are also carried out on the basis of molecular replication; As a result, two identical individuals are formed. Due to the periodicity of biological reproduction, some organisms will be lost due to diseases, hybridization and other reasons fertility Therefore, reproduction cannot be regarded as an essential attribute of life. But self-replication is different, as long as life is not in a state of disintegration, there is always self-replication. As such, it is an attribute that runs through the life process. in In vitro experiment Under certain conditions, the cell cleavage products still maintain the synthesis of DNA, and some single-stranded DNA can also be transformed into DNA under artificial conditions duplex The form. However, non-living systems cannot do this on their own DNA replication Although given under artificial conditions as necessary nucleotide Unspirase, polymerase , ligase DNA can also replicate, but the process is short-lived. Self-replication is an inherent feature of living systems .

Selective reaction

Bacterial fossil

In vivo External environment Selective response is another important feature of living systems. Reactions are properties of both non-living matter and living matter. The difference is that the physical and chemical reactions that occur in non-living matter are not self-completing processes. Only biological organisms react independently, and this independent reaction is selective, under the control of the organism itself, and varies with internal and external environmental conditions. Cells exchange materials with the outside world, of course, there is also diffusion and osmosis For sure, but Cell membrane What to absorb and what to exclude, but highly selective. An obvious example is the cell membrane Active transport Medium, material inverse Concentration gradient And run. For another example, E. coli available glucose Can also be used lactose Act as Carbon source . When there is both glucose and lactose in the environment, E. coli Metabolic reaction First, glucose is used instead of lactose, and only the constituent enzymes are involved Inducible enzyme The system is irrelevant.

Biological selective responses are also the result of coordinated activities of several systems. easy prokaryote This is true of the selective responses of higher organisms. Because there are a variety of different enzyme systems in higher organisms, these enzymes are not only incomparable to inorganic catalysts for their high efficiency, but also have strict selectivity. At the same time, organisms entoenzyme The activity of the enzyme is regulated and controlled by many factors, the interaction between enzymes and enzymes, enzymes and other proteins will affect the activity of the enzyme, and the product of an enzyme has a positive or negative impact on the activity of another enzyme.

In the external behavior, the biological selective response is more obvious. For example, animals in a satiated state do not respond to food; The novel agent initially attracts the animal's attention, but over time the response becomes weak, and so on. In fact, every living thing responds to its environment in some way and in some way, or the same cause appears sometimes in one form of response and sometimes in another.

purposefulness

The 19th century German philosopher Schopenhauer (1996) listed the three instincts of life - survival, reproduction and maternal love ^[2] . Xie Ping (2014) ^[3] Point out that about maternal love, in the lower life is no meaning, like a lot Unicellular organism Their life behavior is constantly splitting in two, repeating Cell growth - The simple process of division - growth. A mother's love should be Higher animal One of the most common in China Instinctive behavior And in some species, they can even outperform themselves.

Monod (1977) that plants and animals have such nature and purposefulness :" Plant growth Seeking sunshine, death; Animals spy on prey, attack enemies, feed and protect their young, males fight for possession of females...... These creatures all have one goal: to live and to keep their descendants alive, even at the cost of death." ^[4] .

It has also been argued that "the purpose of a creature is Survival, competition and reproduction ', development and evolution transform the universe and energy ' "Competition can be seen as a way to survive, of course, Cooperative phenomenon It can also be seen as a generalized form of competition, and such cooperation can occur between species (such as reciprocity) symbiosis Phenomena), can also occur within species (such as hunting in groups of animals or Defensive behavior ) ^[3] . As Williams (2001) argues, groups composed of interacting individuals may be adaptively organized in such a way that individual interests pass through a functional subordination Submit to Group interest ^[5] .

Therefore, Xie Ping (2014) ^[3] It is believed that all life (belonging to a particular species) must have three innate primordial purposes, relating to food, survival and reproduction. They are:

The enjoyment of the sun bath (of course, under the premise of the presence of appropriate nutrients and water) is the intrinsic purpose of all plants, and the acquisition of organic matter synthesized by plants (yes carnivore It is all animals and many Heterotrophic microorganism Intrinsic purpose.

Survival (at least until reproduction is successful) is everything Living individual The second intrinsic purpose, though, is that males of many species die immediately after mating (what a cruel life procedure that is). Survival is an individual. Survival competition And the basis for adaptation to exist.

Reproduction or mating is the third intrinsic purpose of all life, whether by asexual or sexual means. Without it, there may be no brilliant flowers and butterflies in nature, and there will be no charming Birds' songs Chirp, no male fight to the death for love... . Of course, without reproduction, no species would exist.

Just as Ancient Rome POEMS Lucretius It says, "That divine joy, that which the guide of life draws men to." She is the guide of the way, with the aim that, by the cunning of her love, the human race may forever reproduce a new generation, lest it perish "(Lucretius 1981). ^[6] .

Self-regulation, self-replication, selective response and purposefulness are the important characteristics that distinguish life from non-life. ^[7] These characteristics of living systems, as far as their basis is concerned, are undoubtedly physicochemical processes, subject to physicochemical laws. But these Physicochemical change As a result, what is transformed into life becomes a property peculiar to life. Although one of these four basic properties, or some aspect of a property, may also exist in the inorganic world, it is only in life that these four properties can be connected and combined in a system.

Ancient view of life

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EDITOR

Ancient Greek Philosophers tend to call all as yet unknown causes of motion "forces." Later scholars borrowed this concept of "force" to study various motions, such as "gravity" and "electromagnetic force" in physics, and "affinity" in chemistry. Research has yielded a lot of results, but it is not clear Ancient Greek philosophers What is called "vitality" or "life force" was proposed very early on.

Ancient Chinese philosophers tend to ascribe the unknown causes of movement to "qi", and life is regarded as the activity of "qi". For example, "the life of a person is also, the gathering of gas is also, the gathering is living, and the scattering is death... Therefore, it is said that the world is a gas ear." "Qi" is also an unclear concept, and different scholars have very different interpretations, such as: "Human life is like ice, and water condenses into ice. pneumatosis To be human." Here, the formation of life is compared to the process of icing, and there are those who compare life to fire, such as: "People are born with air, and they die when they are exhausted. For example, when the salary is exhausted and the fire is extinguished, there is no light. Therefore, fire extinguishment, all inflammation; When you die, you die." This view emphasizes that life is an ignorant metabolic process. Ancient Chinese philosophers regarded life as one Motion of matter Process, often linked to the discussion of life and death, this is also Chinese philosophy The characteristics of integrated thinking, such as "there is blood, there is no birth, there is no death, live by it, know it is dead", regards life as the opposite of death.

Theory of special creation

That life is made up of superbeings Material force Created by a god or other, or determined by something beyond matter. This is an idea that arose in the context of man's low ability to understand nature, and was later socialized ideology Occasionally or unintentionally used to convince those who believe in spiritual absolute supremacy Theory of special creation .

authigenism

Ancient times People's ability to understand nature is low, but they have been able to carry out abstract thinking activities and draw the conclusion that life is spontaneous according to phenomena. On behalf of the ancient Chinese thought "meat rot maggots, fish withered 蠧", Greece Aristotle "Some fish are developed from silt and gravel".

heterogenesis

As people became more aware that maggots were laid by flies, Louis Pasteur Later, it was thought that life was produced by parents and spores, that life could not have arisen naturally. however biogenesis It doesn't answer how the first life came into being.

Buddhist life theory

Sun, moon, stars, dust. Wind, fire, thunder, electricity, magnetism. Gold, wood, water, fire, earth, is the low embodiment of the universe Yin and Yang energy flow, with the basic Natural element Conditions, can give birth to life.

Buddha Sakyamuni said, "All beings are equal." Life here generally refers to: having the ability to breathe, the ability to continue. Breathing is the advanced way of expressing Yin and Yang in living organisms.

Spiritual fatalism

All things in the universe are composed of "spirit", all things are constructed by God's will, and man is Cosmic spirit The secret of the universe lies within man himself, to be deciphered. Man himself is a single cosmic entity, temple It corresponds to the position of the sun, and the heart corresponds to the position of the Earth. The ancients' "unity of heaven and man" means that all things change will have the corresponding inherent connection, and the traditional Chinese medicine's "three flowers gathering the top five Qi toward the Yuan" is, in a sense, human and the universe Kinematic change development The relationship. The whole universe and the world is a harmonious unity, and nothing can escape this harmonious law and cannot exist in isolation. Life is "qi" in heaven, "Qi + type" on earth, "Qi + type + emotion" in things, and "Qi + type + emotion + righteousness" in man. Man exists in heaven and earth and is different from other things in love. "If man is different from animals, the common people will go away, and the gentleman will remain. Mencius The famous saying, not in love and not for animistic also.

Cosmic spirit

single Life carrier The birth is not simply a single cell composition, it is the external reflection of the inner spiritual individual. This spiritual individual is contrary to other things and is born with individual differences. Life is not from nothing, but gradually unfold the process, each step is thrilling, are extremely painful. any Vital sign In the existence and individual composition, only the spirit is an indispensable and important part, the spirit can give all things the upward momentum, and dominate the whole Cosmic space The change and evolution of... A seed, a grass, a tree, all living things on the earth are interpreted by the definition of the spirit. Without spirit, the world is doomed.

The universal closed breath theory holds that the present corresponds to the future or It is a point in the past, the future is not impossible to pass through, history is not impossible to change, but it lacks the necessary conditions. with Future human With the deepening of cognition, the interpretation of life and death and the understanding of human self will become more and more true and perfect.

Modern view of life

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EDITOR

According to the characteristics of life forms, life is defined in Modern science After the appearance, people to Natural phenomenon Study them in different categories. Different sciences study life from different angles, so the view of life is not the same. Before the 1950s, people were common from all life forms Surface feature To summarize a definition of "life" : Life is a material system with the characteristics of material and energy exchange with the environment, growth and reproduction, genetic variation and response to stimuli . This definition, which describes the general characteristics of life activities, has certain Scientific understanding The value. However, with the development of science, people increasingly feel that this definition has great limitations. Because all of these characteristics can have some exceptions. ^[8]

Chemical evolution

The earth

It is advocated to study the origin of life from the law of movement and change of matter. Place on Primitive earth Under the conditions, Inorganic substance Can be transformed into organic matter, organic matter can develop into biological macromolecules and Multimolecular system Until finally the original Living entity . The year 1924 The Soviet Union This view was first proposed by the scholar A.N. Oparin, and in 1929 by the British scholar J.B.S. Haldane made a similar argument. They both believe that life on Earth evolved from non-living matter over a long period of time, a process known as Chemical evolution In order to be different from the emergence of living organisms Biological evolution .

Oparin's The Origin of Life on Earth, published in 1936, was the world's first comprehensive treatise Origin of life A monograph of the problem. He believed that there was no free oxygen reducing atmosphere on the primordial Earth Shortwave ultraviolet Under the action of energy, simple organic matter can be generated (biological micromolecule ), simple organic matter can generate complex organic matter ( biomacromolecule ), and in Primitive ocean In the formation of a polymolecular system aggregate After a long period of evolution and "natural selection", the latter finally emerged Primitive life The protozoa. Chemical evolution More and more experimental evidence has been accepted by the vast majority of scientists.

Hegelian view of life

The concept of "life" is in Hegel There is a core concept that was addressed in the early days Human alienation Hegel put forward the concept of "life", which is the unity of soul and body, subjective and objective, to make life free. Later Hegel sees life as logical, as immediacy At the same time, it puts forward three kinds of logical life, natural life and spiritual life View of life To make the concept of life generalized, to put the whole world as well as the whole Ideological system As an organic organism. Marx thought Hegelian thought Rational kernel Because of his dialectic thought, Hegel bundles dialectics and ideas together to discuss, so the discussion of dialectic thought in Hegel's works, the space is not very much. But there's no denying it. dialectics In Hegel's thought, dialectics is the soul and core of Hegel's thought, dialectics is inherent in the idea, is the most internal link of life and spirit. The idea of immediacy, that is, the movement of what Hegel calls "life", makes dialectics a speculative dialectic, a dialectic of free movement capable of self-reflection, self-sublation, and return to self. For Hegel, life or concept is a spiritual thing, Hegelian dialectics The soul is the self-motion of life and spirit, that is, the active negative motion of the conceptual self, negativity Makes possible conceptual or dialectical movement. ^[9]

Engels' view of life

Engels wrote in his book Anti-duhring theory A definition of life is given: life is proteome The form of existence. this Existence form the Basic factor It is in constant metabolism with the external nature around it, and once this metabolism stops, life stops with it, and the result is the breakdown of proteins. ^[10]

Engels put forward this definition on the basis of criticizing Duhring's definition of life. Duhring defined life as "the metabolic activity of the cell." Engels believed that the higher organisms were indeed composed of simple types of "cells", but there were organisms below the cells, which were as good as the higher ones biofacies They are connected only because their basic building blocks are proteins, and thus they perform the functions of proteins - life and death.

Plant cell

Engels' definition of life is unified with his thoughts on the form of motion of matter. Engels believed that there are five forms of movement in nature: i.e Mechanical motion , Physical motion , chemical movement, Life movement and Social movement . From a historical point of view, these five forms of movement reflect the order of evolution and development of nature, and each subsequent form of movement is evolved from the previous form of movement. Different forms of movement have different material bearers and different movement laws, and the higher forms of movement include the lower forms of movement. The movement of life is a kind of advanced movement, it is developed from the chemical movement, its material bearer and its movement law are different from the chemical movement, but the movement of life includes the chemical movement. Engels put a lot of emphasis on the natural world continuity . If you define life as Cell structure On top of that, it's hard to explain the origin of life. Engels paid special attention to the dialectical development process from the inorganic to the organic world, so Engels chose proteome As living matter.

vitality

"Here the proteome is understood in the sense of modern chemistry, which includes within the concept of the proteome everything that is structurally similar to a common protein, or protein as it is called. The name proteome is not appropriate, for the ordinary protein is the most inanimate and passive of all the substances close to it, and together with eggs it is merely Embryonic development But when the chemical composition of the proteome is not at all known, this name is better than all the others, because it is more general." It can be seen that the proteome referred to by Engels is generalized, it is not even a polymer in the modern sense, but a material system. Engels used the term on various occasions, sometimes even referring to cells as "protein bits". Like he said, "Everything organism All but the lowest grade are made of cells, and all are made of tiny, only highly magnified, internal nucleus Is made of small pieces of protein." In short, Engels equated life with proteome. Life is "inherent in proteins, born with them, and without this process proteins cannot exist."

In the first half of the 20th century, with the progress of biochemistry research, people have more and more clear understanding of the structure and function of proteins. Proteins have complex forms and different functions, and play an extremely important role in the process of life activities. All this has reinforced many people's belief that the molecular basis of life is proteins.

By "proteome" Engels means nucleic acid and protein. So without protein, there would be no life. This fundamentally negates the creation theory that God created man. Engels' definition of life, to a certain extent, reveals the material basis of life, that is, proteome with metabolic function. For 100 years, this definition has guided the idea of life.

Engels also boldly proposed that since life is Motion of matter If the conditions are right, then of course the flower of life can also bloom on other planets. modern astronomer Confirms this statement. ^[11]

Cosmic germ theory

With the great development of astronomy, people proposed that life on Earth came from other planets or the "germ seed" of the universe, which was popular in the 19th century.

All living things are unified Genetic code , and Rare element Molybdenum in Enzyme system Some support for this argument is provided by the fact that there is a special important role in...

Molecular biology

Biological diversity

The definition of life is summarized from the commonness of the microscopic composition of living matter. On the basis of Molecular biology The study of the people have a more detailed understanding of the basic substances constituting the activities of life. Living things can vary in shape, size and structure, but they are all made of Deoxyribonucleic acid (DNA), Ribonucleic acid Large molecules, such as RNA and proteins, form the backbone.

DNA is made up of four different things called deoxynucleotide A very long chain of small molecules (monomers) arranged in a certain order. For example E. coli DNA is made up of about 20,000 deoxynucleotide molecules Long chain . In all the different forms of life, DNA is equivalent to the same letters written in different lengths, in different orders, and therefore with different meanings. RNA It's also made up of four different things called deoxyribonucleotide A chain of molecules connected by monomers. The situation is similar to DNA, but the strand is shorter. All kinds of different forms Living entity It has a variety of molecular chains of varying lengths. RNA proteins are made up of 20 different kinds Amino acid Monomers connect long chains of molecules in a certain order. A variety of different living organisms have a variety of monomers arranged in different length of protein chains, chain folding, curling shape is also different. In short, the DNA, RNA, and proteins of various organisms are composed of four deoxynucleotides, four deoxyribonucleotides, and 20 amino acid monomers, respectively, which means that they are all composed of universal "components." These nucleic acids and proteins play basically the same role in the life activities of various organisms.

Because DNA can replicate itself, it gives living matter the ability to reproduce and inherit. Because DNA determines the structure of RNA and proteins through transcription and translation, it controls biological processes Morphological structure and Physiological function These processes of replication, transcription and translation require the participation of protein enzymes and RNA. So, there's one Molecular biology Definition of life: Life is produced by the interaction of nucleic acids and proteins, especially enzymes, which can constantly reproduce material feedback Circulatory system . ^[11]

This statement is about life matter the microstructure And the description of its motion process. It Outlines some important theoretical breakthroughs in molecular biology, but still leaves some boundaries unclear. There is a class of things in nature called "viruses", viruses are just some naked annular Nucleic acid, which is made up of nucleic acid chains and protein shells, when alone, it resembles a pure chemical substance and can crystallize, while once in the living specific Host cell It can reproduce itself using the "machine" of replication, transcription and translation of the energy supply of the monomer in the host cell. In addition, a similar situation applies to viroids. Are these things alive? It has been argued that anything that can control its own reproduction and genetic variation and respond independently to evolutionary forces should be called life. If so, then the virus, bacteriophage Objects such as plasmids can be classified as living organisms. Some people also believe that life must be able to independently replicate, transcribe, translate, and viroids and plasmids are an incomplete life form, they are parasitic, can not exist independently. Nor can the latter be a clear-cut demarcation of the definition of life. Because life is never an isolated being, life and its surroundings are inextricably linked to other life. This leaves no clear sense of what is independent life and what is parasitic life. Therefore, we also need to start from a macro perspective, that is, from ecology To study View of life .

biophysics

biophysics Emphasize from Motion of matter the General law Upper specification Vital signature .

Solar system

Order and entropy. Matter and energy are conserved. The earth is not connected to the outside world Material exchange Only from Solar radiation The energy obtained is reflected and radiated into space, and the energy that the sun radiates to the earth is equal to the energy that the Earth reflects and radiates into space. Although the matter and energy of the Earth have not significantly changed, the various elements on the Earth have different reactions due to solar radiation, and these movements have led to the material on the Earth Uniform distribution . The influence of the energy flow caused by solar radiation on the earth is stable, rhythmic and regular over a long period of time, so the uneven distribution of the earth's material is also rhythmic and regular. This produces an ordered state of distribution and motion of the Earth's material.

Second law of thermodynamics The uniformity of a system is measured by a function called entropy. single Isolated system In other words, a system with no exchange of matter and energy with the outside world, the total entropy (disorder value) increases as a result of motion. When entropy reaches Maximum value When the macroscopic motion of matter will stop and reach Thermodynamic equilibrium . At this point, the system is in a uniform, disordered state. The Earth is not an isolated system, but a closed system, that is, a system with only energy exchange and no matter exchange with the outside world, which receives the energy of the sun's radiation and at the same time reflects the energy into space Radiant energy . The energy radiated by the sun causes the surface of the sun to be in a high temperature state (about 5800 ° C). According to the definition of entropy, the sun is relative Low entropy Area, due to the earth Surface temperature Far below the Sun, the Earth reflects radiation to the Sun in a relatively high entropy region, which can be described by this formula:

Energy state

Here S represents entropy, and dS/dt represents the rate of change of entropy with time. Q stands for energy, and dQ/dt is the rate of change of energy over time. T Sun and T Earth stand for the surface temperature of the Sun and the surface temperature of the Earth. A formula less than zero means that the Earth's entropy is decreasing during the solar transformation. The matter and energy of the Earth are thus in an uneven and ordered state.

Life is an open system, with which there is not only a change of energy, but also an exchange of matter. Living entity Actually take matter and energy from the environment in a high entropy state in the form of food and convert them into Low entropy State and expel waste from the body, thereby maintaining its own entropy at a lower level than the environment, that is, maintaining its own orderly state. The order of life is obvious from the molecular level, and large molecules such as nucleic acids and proteins have a certain order in various cells, even one ecosystem All have certain Spatial structure . Order is not only shown in Spatial distribution It is also reflected in the activity laws of living organisms: growth, development, reproduction, aging, death, and regular responses to external stimuli. from thermodynamics From the point of view, these phenomena are from the role of solar radiation, but only the Earth has life activities, the emergence of life must also have its own internal factors. ^[12]

mechanism with vitalism . On the origin of life, Essence of life There has been a debate for a long time. Mechanics is sometimes called reductionism It believes that the phenomena of life can be clarified by the laws of physical science, and the advanced complex laws can be reduced to simpler and more basic laws. Vitalism sees life as a machine that takes different forms of expression at different times. Clock machinery was fashionable in the 16th and 17th centuries, and some people thought that microbes were nothing more than machines like clocks, invented in the 19th century Steam engine Others think that living things are nothing more than" Heat engine ".

ecology

biosphere

As far as we know, Solar system Within, life is active only in the Earth's biosphere - from a height of about 20 kilometers above the surface atmosphere To a depth of more than a dozen kilometers below the surface, this is relatively not thick Spatial composition .

In the biosphere, some life has chlorophyll Can be carried out photosynthesis , most plants, cyanobacteria And some bacteria belong to this class of life. Other organisms do not have chlorophyll, do not photosynthesize, and must rely on uptake autotroph Or other living things that live for food, called heterotroph . Fungi, animals (including humans), and most bacteria belong to this group of organisms. The inorganic substances in the biosphere enter the organism through the photosynthesis of autotrophs, some of which return to the inorganic world through the metabolic activities of the autotrophs themselves, and some of which are ingested by heterotrophs and return to the inorganic world through their metabolic activities. And most plant stalks and animal carcasses end up dead saprophyte Degradation (also for heterotrophs) and eventual return to the inorganic world. This creates a cycle of material movement in the biosphere. This circular movement is unilateral, irreversible, in this circular movement, which ring is missing or which ring is not smooth, will affect the whole Biological kingdom . There are no autotrophs or insufficient autotrophs, and heterotrophs are certainly difficult to survive; But only autotrophs, no heterotrophs, lots of them Organic matter After accumulation, it cannot be degraded, and it will also block the road of continued survival of autotrophs.

In simple forms of matter, as in the atmosphere Carbon dioxide formal carbon The elements enter the living body through the photosynthesis of autotrophs and the synthesis of sugars by hydration; some of them return to the atmosphere as carbon dioxide through the respiration of autotrophs themselves; the rest are used by various heterotrophs and return to the inorganic world through their respiration. This forms a carbon cycle, which must also be coupled with the cycle of many other elements (such as hydrogen, oxygen, nitrogen, phosphorus, sulfur, etc.) in life, through chemical reactions, and at the same time push these elements to circulate in space. Such cycles exist not only in the macrobiosphere, but also in the microcosmic movements of organisms. Ecological handle HP Regard as It is the central link of various irreversible material cycles in the biosphere . But it only describes the external conditions of life and its place, and does not specify the qualitative characteristics of life itself.

On contradiction

The string is created every time it vibrates Elementary particle and Natural forces The combination of the two further generates everything in the universe. The effect of the inertia of elementary particles and the action of natural forces is just a pair of contradictions - the inertia maintains balance and the effect causes change. Therefore, the inertia to maintain balance and the effect of change is the most basic attribute contradiction of matter, and it is this contradiction that promotes the evolution of matter from inorganic matter to organic matter to primitive life to animals and plants to human beings.

Inertial maintenance balance externalization Out of the metabolism of life, internalized out of the inheritance of life; The effect of the change externalizes the birth and death of life, and internalizes the variation of life. Inertia maintains balance and effects, resulting in changes in metabolism, aging, disease and death that appear in the survival and growth of life, and inheritances and variations that are internalized are reflected in life Multiply and prosper Up. In this way, survival and reproduction have become the two major attributes of life, and death and variation have become the two major necessities of life. It is inertia that maintains the balance of the demand for performance, the pleasure of struggle, and the desire for reproduction, which causes the pain of birth, old age, illness and death, and the short life of alienation and degeneration, which supports and maintains the survival and reproduction of life, and further derives the survival level of human life Natural attribute And social attributes at the level of population continuation. ^[13]

Life quote

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EDITOR

1, life, that is nature to human beings to carve Gem . -- Nobel

Life is a dangerous narrow valley, only the brave can pass. -- Michepin

3, a great soul will strengthen the mind and life. -- Ralph Waldo Emerson

4. There's only one in the world heroism That is the person who understands life and loves life. - Romain Rolland

We can only get life if we give it. -- Rabindranath Tagore

A full life is a long life. We must measure our lives by deeds, not by time. -- Seneca Jr

If you can use it well, life is long. -- Seneca

Life is brilliant in the shine, real in the ordinary. -- Burke

The shortening of life is proportional to the waste of thought. -- Charles Darwin

Cherish life to cherish today. -- Proverbs

Who can enrich every moment with profound content, who is in the infinite extension of their lives. -- Kurz

We only have one life, but if we can use it correctly, once is enough. -- British proverb

Life can not be twice, but many people are not good at spending it even once. -- Luckett

Life is like running water, only in his rapids and rush forward, only beautiful, only meaningful. -- Zhang Wentian

Respect for life, respect for others and respect for their own life, is the concomitant in the process of life, is also Mental health A condition of.

-- Fromm

There are two tragedies in life: one is hopeless, the other is complacent. - Bernard shaw

People who know the true meaning of life can prolong the short life. -- Cicero

Make a person's limited life, more effective, that is, to extend the life of people. - Lu Xun

Should face life with a smile, no matter what. -- Volchik

Prime not again, a day difficult morning. - Tao Qian

Life, as long as you make full use of it, it is long. -- Seneca

Before we know what life is, we have spent half of it. -- Herbert

Life does not sell back and forth tickets, once set off, can never return. -- Romain Rolland

24, life is the form of the protein body. -- Engels

The most precious thing is life. Everyone has only one life. A man's life should be spent in this way: recalling the past, he will not regret for wasting his time, nor will he be ashamed of being mean and vulgar; On his deathbed he was able to say: "All my life and all my energies have been devoted to the most magnificent cause in the world - the struggle for the liberation of all mankind." -- Ostrovsky," How is steel made "

The chapters that praise life are Wang Guozhen 's Love life French thinker Montaigne's Love of Life, and the United States Jack London The short story "Love Life".

Love Life by Wang Guozhen

I don't think about whether I can succeed

Since we chose the distance

I just go through the storm

I don't think about winning love

In love with Rose

Be brave enough to speak the truth

I don't think about the cold wind and rain coming behind me

Since the target is the horizon

What we leave to the world is only our back

I don't think about whether the future will be flat or muddy

Just love life

Everything, as expected

26, born, also As I wish Righteousness, also I want also, both Cannot have both Give up life and take righteousness. Life is what I want, so desire Better than the living, so do not get also. I hate death more than the dead, so I do not shy away from something. If people want more than life, then who can get life why not use it. Make people worse than the dead, then where can avoid patients why not also! By is born without use also; So you can avoid trouble and have not also. hence What you desire more than the living, what you hate more than the dead. Not only the sage is the heart also, everyone has it, the sage can not lose the ear. -- Ancient Chinese thinker Mencius

Scientific research

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EDITOR

In September 2022, according to the UK's" New scientist Magazine's website, the United States aerospace Office ( NASA ) the "Perseverance" Mars rover in It's found in abundance on Mars Organic molecule The discovery of carbon-containing molecules thought to be the building blocks of life could make Mars's dried-up river deltas an ideal place to look for life And help shed light on the central question of whether life existed on Mars. ^[14]

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