life

Ming Sheng

English:

life

exist

All of a person.

Silver rope

What is life like? Usually, you can tell what is alive and what is not without much effort, but when you really want to express what is life in words or words, things are no longer so simple. In fact, it is extremely difficult to give a scientific definition of life. This problem has never been solved by human beings before, although there have been many sayings since ancient times.

For example, Engels gave a definition of life: "Life is the way of existence of protein Group, and the basic factor of this way of existence lies in its constant metabolism with the surrounding outside world. Once this metabolism stops, life will stop, and the result is the decomposition of protein." Engels' definition of life reveals the material basis of life to some extent, that is, the protein body with metabolic function. However, this definition has great defects:

1. According to this definition, life is Tao, which means that a living person means that this person is Tao, which is totally illogical.

Second, the seeds of many plants can be preserved for a long time without life characteristics, such as ancient lotus seeds and slow-moving animals. They may not undergo metabolism for a long time and will have vitality when conditions are right.

In Introduction to Molecular Biology, life is defined as a multi-molecular system composed of nucleic acid and protein, which has the ability of self-renewal, reproduction and reaction to the outside world. However, this definition still has great defects:

First, this definition is closer to the definition of biology than life.

Second, worker bees, cows and mules are alive, but they have no reproductive ability at all.

Third, both sperm and eggs are alive, but they are not fertile, because the new individuals produced by fertilization and development of sperm and eggs are neither sperm nor eggs.

Fourth, the heart to be transplanted must be alive, that is, alive, but the heart is obviously infertile.

A raw egg is alive, but it obviously has no ability to respond to the outside world.

The general scientific definition given by modern biology is that life is a compound phenomenon of self-reproduction, growth and development, metabolism, genetic variation and response to stimuli.

First of all, the statement that life is a phenomenon is illogical in itself. Secondly, here, any single phenomenon is not unique to living things. Flame can also metabolize and reproduce, but normal people don't think it has life. The seeds of many plants can be preserved for a long time and have no life characteristics, such as ancient lotus seeds and slow-moving animals, which may not be metabolized for a long time and will have vitality when conditions are right. When it comes to reproduction, we simply have nothing to say in the face of such things as cows and mules! The same is true of growth, and the crystallization process of many inorganic substances can show this characteristic well. The situation of external stimuli is also obvious. For example, your computer is a very sensitive guy.

It is illogical to define life as: pattern, system and phenomenon.

Zhou defined life in On the Definition of Life: Life refers to the "self-replication ability" of things.

Life is a kind of ability, and a living person means that he has some kind of ability. This statement is not illogical. Living people do have many abilities, such as sports ability, reproductive ability, growth and development ability, metabolism ability, stress ability, adaptability to a certain environment, and even genetic variation ability; On the contrary, a dead person, that is, a lifeless person, does not have these abilities. Living mules have sports ability, growth and development ability, metabolism ability, stress ability, adaptability to a certain environment and so on. Dead mules don't have this ability. Living poplar has the ability of reproduction, growth and development, metabolism, adversity and adaptation to a certain environment. Dead poplars do not have these abilities.

It is not difficult to find that all living animals have the ability of growth, metabolism, stress and adaptation to a certain environment; None of the dead animals have these abilities. Living plants have the ability of reproduction, growth, metabolism, stress and adaptation to a certain environment. None of the dead plants have these abilities. Living microorganisms have the ability of reproduction, growth, metabolism, stress and adaptation to a certain environment; No inanimate microorganism has these abilities. All living protozoa except Ruan virus have the ability of reproduction, growth, metabolism and adaptation to a certain environment. All inanimate protozoa except Ruan virus do not have these abilities. Viruses do not necessarily have the ability to stress.

Ruan virus is special, and it may be just a protein molecule of Ruan virus, which has reproductive ability. If Nguyen virus is only a protein molecule, it has no metabolic ability and growth and development ability, because it is impossible for a single protein molecule to have these phenomena.

So far, we can conclude that all living things except Nguyen virus have the ability of growth, metabolism and adaptation to a certain environment. However, in nature, not only creatures have life, but also some parts of them have life. For example, a living leaf is said to be alive because it has life. Similarly, the heart to be transplanted, red blood cells and white blood cells in the blood, sperm and eggs are all alive. However, they do not necessarily have the ability to grow, metabolize and adapt to a certain environment.

Therefore, the ability to grow and develop, the ability to metabolize, and the ability to adapt to a certain environment are not shared by all living things. Therefore, we can't define life and the ability to adapt to a certain environment by the ability of growth and development and metabolism.

So, what ability is shared by all living objects, and this ability is not possessed by all inanimate objects? If we can find the ability that all living things have in common, but all inanimate things don't, then this ability is life.

In order to solve this problem, we need to start with special life forms. Ruan virus, heart to be transplanted, red blood cells and white blood cells in blood, sperm and eggs are all living special objects. After careful analysis, they all have the ability to make new living substances (including protein, nucleic acids, sugars and lipids, etc. ) by copying or according to the information template (nucleic acid).

The ability of growth, development and metabolism shared by all organisms except Ruan virus is precisely because they have the ability to make new biological substances (including protein, nucleic acid, sugar and lipid) through replication or according to information template (nucleic acid), and the reproductive ability of Ruan virus is precisely because it can make new protein through replication. Therefore, Ruan virus also has the ability to create new life forms (including protein, nucleic acid, sugar and lipid) by replication or according to information template (nucleic acid).

And it is not difficult to find that the ability to make new living substances (including protein, nucleic acids, sugars and lipids, etc. ) by copying or according to information template (nucleic acid) is what any inanimate object does not have.

At this point, we can give a logical and complete definition of the concept of life in the biological world.

Life in a narrow sense refers to the ability of an object to make new living substances (including protein, nucleic acid, sugar and lipid, etc.). ) by copying or according to the information template (nucleic acid).

Life in a narrow sense is the only life in the biological world. An object has life, which means that it has the ability to produce new life by copying or according to information templates; On the contrary, an object is inanimate, which means that it has no ability to produce new living substances by copying or according to information templates.

This narrow definition of life applies not only to all creatures in nature, but also to all parts of nature.

Life in a broad sense refers to the unique function or ability of something different from other things.

A thing is no longer such a thing, it has no unique function or ability to distinguish it from other things, so it can be said that it is dead, that is, there is no life (referring to life in a broad sense). When a volcano stops erupting, it becomes an extinct volcano, or it can be said that a volcano has no life (life in a broad sense). When the lake stops flowing, it becomes stagnant water.

conception of history

In the process of understanding life, human beings have also had difficult thinking. In ancient Greece, the reason of exercise-whether people can understand it or not-was called "force", so the great concepts of vitality and vigor were put forward. In ancient China, people tend to call the cause of exercise "Qi", and the activity of life is of course the activity of "Qi", for example, "Since birth, it is still produced, water condenses into ice, and Qi accumulates into human beings". Like force, qi is an ambiguous concept, and different people will have different interpretations. Fire is a violent material movement, which will certainly arouse people's great concern. Therefore, some ancient people in the East believed that life came from "fire" and emphasized the metabolic process of life. In addition, China ancients discussed life in an ingenious way, that is "death". Studying life and death together in this opposition is probably a major feature of China's philosophy.