What statement do you agree with about the origin of life and why?

A German-French joint research team from the University of Bremen in Germany recently found that meteorites contain more than 80 amino acids by analyzing their components. Researchers believe that amino acids play a decisive role in the origin of life on earth, and this meteorite has thus become a strong evidence of the "extraterrestrial theory of life on earth."

Three ways to trace the origin of life

Since man landed on the moon and overlooked our home, the beautiful blue planet in the solar system is full of vitality everywhere. As the only human being with ideology on earth, he is full of curiosity about himself and the origin of life. Where did life originate? Is it bred by the unique environment of the earth, or is it from distant space?

Because the traces of the early formation and evolution of the earth were basically changed by various geological processes in the later period, human exploration of the above problems mainly depends on the following methods: the first one is from hypothesis and inference to direct experimental observation. Secondly, with the rapid development of space science, especially the progress of deep space exploration technology, probes or spacecraft are launched to detect or sample planets or comets in the solar system. The third method is to study and analyze the most precious and primitive "fossils" from space-meteorites.

Solve the occurrence and composition of life

There are differences in the scientific community on the occurrence and composition of life. One view is that life is made of silicon or germanium instead of carbon, and the solvent is ethylene glycol instead of water. Another point of view is that the concept of life and the standard of whether there is life should be based on the concept of life on earth. All living things are composed of hydrocarbons, exist in the form of protein, and are based on nucleic acid. Most of the exploration of extraterrestrial life is based on the latter.

Then, for the origin and evolution of life, there must be basic elements such as carbon, hydrogen, oxygen and nitrogen. Synthetic organic matter, these elements are everywhere in the universe. Under the proper temperature and time, with the participation of the necessary medium liquid water and the protection of the planetary atmosphere, various biochemical reactions take place, forming the most basic material components of life-small molecular organic compounds such as amino acids and fatty acids, and these compounds form composite protein under appropriate conditions. Where did life on earth come from? The question about the origin of life in the universe remains a mystery. Scientists have their own opinions according to their own research results, and they can't generalize. To sum up, there are mainly two schools of thought. One school of scholars believes that life is the product of the earth itself. As early as 1955, harold urey of the United States claimed that life originated from the earth itself. He and his student Stanley Le designed a simulated primitive atmosphere to study whether substances related to life can be produced under natural conditions. Another school of scholars thinks that when the earth was born, it was a hot sphere and there could be no life. They suggested that comets and meteorites brought the embryos of cosmic life to the earth, so there was life on the earth. The theory of extraterrestrial origin includes the theory of Martian life, the theory of comet origin and the theory of meteorite origin. This theory is gradually affirmed by more and more researchers. Are earthlings from Mars? Among the nine planets in the solar system, Mars, the sister star of the earth, seems to have the most conditions for life. 1784, German scientist William Schell discovered the polar cap and atmosphere of Mars. The polar cap of Mars is mainly composed of solid carbon dioxide and water ice. The atmosphere of Mars is very thin, mainly composed of carbon dioxide, nitrogen and argon, and trace elements are oxygen, carbon monoxide and water vapor, which are close to the stratosphere of the earth. At the beginning of the 20th century, some scientists found that the surface of Mars was covered with a canal system extending in all directions, and there seemed to be a highly developed extraterrestrial civilization on Mars. The Viking, Mars and Mariner spacecraft made a comprehensive and systematic exploration of Mars. So far, no life similar to that on earth has been found on Mars, but the possibility of life in the past cannot be ruled out.

1996, in the Martian meteorite ALH8400 1, a primitive microbial fossil with microtubule structure and composed of carbonate with a diameter smaller than that of human hair1100 was found. Mars Global Explorer, Spirit and Opportunity also proved the existence of water. All these studies show the possibility of life on Mars in the past, and the medium of "spreading" life is meteorites.

Most meteorites come from the asteroid belt between Mars and Jupiter, where there are thousands of asteroids of different sizes orbiting the sun. Through collision and gravity, some asteroids sometimes enter the earth's orbit and eventually land on the earth in the form of meteorites. In the study of some meteorites, it is found that they are rich in organic matter, sugars and amino acids, and these molecules may be the pioneers of life on earth.

During the period from 1997 to 1998, American and Russian scientists discovered biological fossil particles and a very simple microorganism in meteorites. In 2000, British scientists discovered water-bearing crystalline salt rocks 4.6 billion years ago in the meteorite that crashed in Morocco in 1998. Isotope detection proves that it was formed within 2 million years after the birth of the solar system and is the oldest substance in the solar system. The discovery that water is a key factor in life shows that life conditions may appear in the universe much earlier than previously thought. Another Possibility of the Origin of Life-Comet Dust

Other scientists believe that organic molecules brought by comet dust help the earth to produce life, and in the right environment, it initially evolved into a vibrant life substance. So whether the first seed from space is produced from this requires us to fully study the chemical composition of comets. Comets are mainly composed of ice, dust and rocks, which absorb and wrap a considerable amount of volatile components. They were formed in the lower temperature region of the outer layer of the solar system, retaining the chemical composition and structural characteristics of many solar nebula condensates. Therefore, comets are of great significance for studying the origin and early state of the solar system.

Not long ago, with the help of a new spectrometer installed on the American stardust spacecraft, scientists discovered that there is a coenzyme called PQQ in comet dust, which is one of the necessary prerequisites for the generation of genetic material and provides new evidence for the theory of the origin of comet life.

After more than a billion years of changes, the earth is ready for the birth of life. Whether it comes from distant space or from the earth itself, the first seed of life begins to sprout, reproduce and evolve. From the birth of the first organism to the life and death of human beings, this complex and confusing life development process lasted for 3 billion years.

Did life on earth originate from land or sea, or was it carried by an asteroid in a distant place in the universe? So far, the origin of life on earth is still a mystery that scientists try their best to solve. They often disagree. The planet we live on was formed about 4.6 billion years ago. To some extent, something must have happened at an uncertain time, because this lifeless celestial body began to accept something completely different from rocks and water. Nitrogen and carbon molecules evolved into DNA, and a microorganism traveled in the universe ... There is no doubt that millions of years after the appearance of this tiny molecule, primitive single-celled organisms were born, and then more and more complex aquatic organisms gradually appeared, and they finally landed on land. Since then, various organisms have proliferated on a large scale on the earth.

Today, there are about 2 million different creatures on the earth. But all kinds of living things originated from the same substance-a substance that can start the course of life to some extent. What substance is this? This paper will expound the latest theories and research results about life on earth. Fragments of some celestial bodies cruising in space, like a group of "robbers" in the universe, will collide with a celestial body sooner or later. But some comets and asteroids that collide with the earth may become the creators of life on earth. It is likely that a comet (a celestial body composed of rocks and ice) brought a lot of water to the earth. If there is no water, the earth may always be a dry planet.

Cristiano Cosmovici, coordinator of 27 Italian scientific research groups engaged in space biology research, said: "Comets and asteroids certainly played a vital role in the birth and evolution of life. Recently, organic molecules, that is, molecules that make up living things, have been found on asteroids. These latest findings make people have to reconsider the embryo hypothesis put forward by Agnes in 1907. This hypothesis holds that celestial bodies such as comets and asteroids have sown the seeds of life on the earth. These celestial bodies are a bit like buses, transporting organic substances, sometimes even very complicated substances, from one planet in the solar system to another. Some people think that they also bring bacteria. "

However, biologists from outer space added that huge meteorites also caused real natural disasters, which really fell from the sky. "On the one hand, these phenomena led to the extinction of many biological species such as dinosaurs, but at the same time they also promoted the development of life forms. For example, the extinction of dinosaurs allowed mammals to reproduce faster, and then humans prospered. " RNA and DNA: the chain of life

Some creatures, besides maintaining their own existence, can reproduce almost the same offspring as themselves. This ability to preserve and copy oneself constitutes the essential difference between life and matter. However, life is only made up of ordinary atoms like carbon and nitrogen. How can such an ordinary element shoulder the heavy responsibility of creating all kinds of creatures?

Martino Rizzotti, a biologist at the University of Padua and a scholar studying the origin of cells, said: "In fact, the biggest problem is to find out how organic molecules become complete cells composed of protein, fat or lipid compounds, sugar and nucleic acids (RNA and DNA). All the components of the cell are perfectly combined and can function normally with each other. At present, there are three theories to explain this process. One theory is based on the binding capacity of lipids. In fact, these molecules can spontaneously form growing spheres in an environment with water. When these spheres reach a certain size, they may divide and produce two smaller spheres. If other molecules bind to similar lipids, this process can explain the formation of some cell-like structures. The second theory is based on the fact that nucleic acids (especially RNA) can promote some chemical reactions, which are still the key to the life process today. The starting point of the third theory is protein. The basic component of protein, amino acids, is easily formed in the warm primitive ocean, and then polymerized to form some compounds called microspheres, which show the typical characteristics of cells. "

However, paul davis, a physicist at the University of Adelaide and the author of several best-selling books about life and the origin of the universe, thinks that the above explanation is unconvincing. He pointed out: "The key to the problem is not how all the components of a cell are formed, but how they are integrated. We are far from uncovering the mystery of life. "

Secrets in the dark sea

Since the late 1970s, oceanographers have explored mid-ocean ridges and rifts through submersibles. They found a vast area near the Pacific submarine mountains and the Galapagos Ridge, where boiling water gushed from the bottom of the sea and the temperature reached 380℃. The cold water of the ocean seeps into the ridge from the cracks in the earth's crust and becomes hot seawater, which reacts strongly with basalt to leach metal ions such as manganese, zinc, copper and iron from rocks. This undersea hot spring also releases a lot of gases, including methane, hydrogen sulfide and hydrogen. Bacteria multiply around the hot spring mouth. They obtain the energy necessary for life by oxidizing hydrogen sulfide and make chemical synthesis to form primary organisms. Bacteria and other more complex creatures like "tubular worms", mollusks with shells, crabs and shrimps were born here.

After laboratory verification, this is a generalized ecosystem, and its environment is dark, which is completely different from the terrestrial environment based on photosynthesis. Recently, it is believed that it is these deep-sea environments that led to the birth of life on earth.

The possibility of this hypothesis has been confirmed by experiments simulating the same environment in the laboratory. The test tubes filled with aqueous solutions of amino acids (glycine, alanine and asparagine) were heated at 134 atmospheric pressure and 250℃ for 6 hours, and it was found that they formed some tiny spheres with membrane structure, with diameters ranging from 1.5 ‰ to 2.5 ‰ mm, from which scientists inferred that primitive cells might have been generated from these spheres.

3 billion years of growth

With the passage of time, life is constantly evolving and its forms are becoming more and more complex. The second drastic change in the history of life development is the appearance of nuclear membrane, or the membrane that wraps the nucleus. Cells are part of the whole "biological system" of organisms. The nuclear membrane contains DNA, that is, a substance that contains all the information necessary for maintaining life and self-reproduction. This form of protection can protect DNA from the external environment, so that cells can survive and withstand the test of environmental changes. The third great change in the history of life development is the emergence of multicellular organisms.

350℃ undersea hot spring: Cold water from the ocean seeps into cracks in the earth's crust. When it comes into contact with hot magma, the temperature of seawater will rise. When the seawater rises again, it reacts with the basalt covering the inner surface of the volcanic jet channel, and then metal ions are injected into the seawater.

Life is starting to be different.

The slow and continuous aggregation of cells leads to more and more specialized functions of organisms. In fact, the cells of these creatures began to be different in morphology, and each cell assumed various functions necessary for maintaining life and self-reproduction. Different life forms may be flooding the earth in this way. However, if life forms are very different, the basis of biological systems is the same. Every living thing has an element to transmit genetic information and a system to maintain and breed according to this information. As the picture shows, from left to right, the primitive creatures that appeared on the earth about 3.5 billion to 4 billion years ago were single-celled creatures. They have no nuclear membrane, that is, they are naked and their DNA is completely exposed to the external environment.

About 2.6 billion years ago, a revolutionary event happened in the history of biology. Some types of stromatolites (layered or dome-shaped calcium deposits formed by algae, which can capture and precipitate calcium) began to produce oxygen with the help of primitive photosynthesis systems, just like what happens in plants today. But until then, oxygen is still a toxic gas for living things. With the gradual increase of oxygen concentration, only those life forms that have withstood the test of oxygen existence can survive after a natural selection. 65.438+0.6 billion years ago, cellular organisms with real nuclear membranes finally appeared on the earth, and then multicellular organisms also appeared.

700 million years ago, after 3 billion years of long evolution, life forms have grown long enough to be observed with the naked eye.

The celestial debris carrying the seeds of life is an asteroid that attacked the earth and brought the original life form to the earth. RNA is a molecule, which consists of alternating units of ribose and phosphate molecules, and these units are connected with each other through a matrix to form a long chain. DNA has two helical strands, each of which is similar to RNA. The sugar component of RNA is ribose, and the sugar component of DNA is deoxyribose. Life at the bottom of the ocean may have been formed in this way: amino acids gathered in protein, while protein created RNA, then DNA and protocells. 350℃ undersea hot spring: Cold water from the ocean seeps into cracks in the earth's crust. When it comes into contact with hot magma, the temperature of seawater will rise. When the seawater rises again, it reacts with the basalt covering the inner surface of the volcanic jet channel, and then metal ions are injected into the seawater.