Life in the Earth appeared more than three billion years ago, having passeda long way from the simplest microbes to the dazzling complexity of organisms like us. But how did the first organisms on the only inhabited planet known to us originate in the primary broth? Here are some basic theories of the origin of life on Earth.
- 1 Electric sparks
- 2 Clay Society
- 3 Deep-sea sources
- 4 RNA World
- 5 Simple Beginnings
- 6 Panspermia
Electric sparks can generate amino acids and sugar froman atmosphere filled with water, methane, ammonia and hydrogen, as was shown in the famous 1953 Miller-Yuri experiment. There was an idea that lightning could contribute to the appearance of the first building blocks at the initial stage of the origin of life. Over millions of years, more complex and complex molecules have formed. Although the researchers found that the atmosphere of the young Earth was not very saturated with hydrogen, over time, volcanic activity could saturate it with methane, ammonia and hydrogen, and then leave the case of lightning.
First molecules of life could come from clayif you believe the organic chemist Alexander GrahamCairns Smith of Glazko University in Scotland. This substance not only collected organic compounds together, but also contributed to their organization, similar to how our genes work today.
The main role of DNA is to store information about howother molecules can be organized. Genetic chains in DNA are essentially instructions on how amino acids should be located in proteins. Cairns-Smith suggested that the mineral crystals in clay probably lined up organic molecules in ordered patterns. After some time, organic molecules took over this work and self-organized.
Deep water sources
Theory of deep sea ventilation suggests that life may have appeared inunderwater hydrothermal springs that spew important hydrogen-rich molecules. Rocky clefts probably held these molecules together, and mineral catalysts promoted key reactions. Even now, these “tailpipes”, rich in chemical and thermal energy, support vibrant ecosystems.
A layer of ice may have covered the oceans threebillion years ago, when the sun gave a third less light than now. This layer, hundreds of meters thick, probably protected the fragile organic compounds in the water from ultraviolet and cosmic effects. Cold, most likely, helped these molecules survive, allowing them to carry out key reactions.
Currently DNA proteins are needed to form, and proteins need DNA. How could they exist without each other? The answer may be RNA, which can store information, like DNA, serve as an enzyme, like protein, and contribute to the formation of DNA and proteins. DNA and proteins later violated this “RNA world” because they were more effective. RNA still exists and performs several functions in organisms, including the inclusion and deactivation of certain genes. But then the question arises, how did RNA appear? And although some scientists believe that this molecule could spontaneously appear on Earth, others say that this is unlikely.
Exposed to other nucleic acids, in addition to RNA, exotic PNA or TNA.
Instead of evolving from complex moleculeslike RNA, life could begin with smaller molecules interacting with each other in cyclic reactions. They could be stored in simple capsules such as cell membranes, and over time increase the complexity of the structure. That is, the scenario “first metabolism” in this case prevails over the scenario “first genes” in the model of the “RNA world”.
Perhaps life did not appear on Earth at all, but was delivered from outer space. This concept is called panspermia. For example, even Martians were found on Earth.meteorites knocked out of the surface of the Red Planet by a cosmic collision, which means there could well have been more exotic "guests" who brought the first seeds of life. Other scientists believe that life could have hitchhiked on a comet. But if this concept is correct, the basic question is not solved: how did life in general originate? The complexity of this issue is not yet easier than the question of what happened before the Big Bang?