December 5, 2011 18:34
Scientists estimate that over 3 billion years ago, simple organisms evolved into complex life forms. But for scientists is still a mystery how life began on earth. And they set out one theory after another in an attempt to explain this phenomenon.
According to the new theory, the first form of life on Earth was a mega-organism, which filled all the world's oceans, and then divided into parts, which later gave rise to the ancestors of all living things. The latest research indicates that the mega-organism has been the struggle of the early forms of life to survive. Cells that have struggled to survive, exchanged useful parts with each other and created a global mega-organism, writes infoniac.ru.
About 3 billion years ago, the mega-organism is divided into three areas of life: single-celled bacteria, archaea and eukaryotes Bole complex that gave rise to all the animals and plants. It is difficult to know what happened before the separation, the researchers wrote in the journal Newscientist.
Practically did not have any fossil evidence from the time, and any genes that date back to the time likely to have mutated beyond recognition.
Although gene sequence changes so fast, three-dimensional structure of the protein can withstand the test of time. Thus, if all organisms on Earth today produce a protein with the same general structure, it is likely that this structure is present in the mega-organism.
Scientists can not say with certainty whether it was so in fact, but for computing the mega-organism coincides with the appearance of oxygen in the atmosphere, which happened about 3 billion years ago.
Meanwhile, researchers are still discussing the seven traditional theories about the origin of life on Earth.
1. Electrical sparks
In the famous Miller-Urey experiment (Miller-Urey Experiment), scientists have proved that lightning could contribute to the emergence of the basic substances needed for life: electrical spark was the amino acid in the atmosphere, which consists of a huge amount of water, methane, ammonia and hydrogen. Then, from the amino acid developed more advanced forms of life. This theory was little changed after the researchers found that the atmosphere of the planet billions of years ago was poor hydrogen. Scientists have suggested that methane, ammonia and hydrogen contained in volcanic clouds, saturated electric charges, writes livescience.com http://www.livescience.com/.
Chemist Alexander Graham Cairns-Smith (Alexander Graham Cairns-Smith) from the University of Glasgow, Scotland, has put forward the theory that at the dawn of life in the clay contained many organic compounds that are close to each other, and that the clay facilitated the organization of these substances in structures similar to our genes.
DNA stores information about the structure of molecules, DNA and gene sequences indicates that the amino acids have to build into proteins. Cairns-Smith suggests that clay crystals contributed to the organization of organic molecules into ordered structures, and later it became engaged in the molecules themselves, "without the help of" clay.
3. Deep-sea vents
According to this theory, life began in submarine hydrothermal vents emitting molecule, hydrogen-rich. Their rocky surface, these molecules could come together and become a mineral catalysts for reactions that led to the origin of life. Even now, these hydrothermal vents rich chemical and thermal energy, lives a fairly large number of living beings.
4. Icy start
3 billion years ago The sun is not as bright as it is now, and, accordingly, the heat from the Earth came less. It is possible that the earth's surface covered with a thick layer of ice that protects the fragile organic matter in the water under it from ultraviolet rays and cosmic influences. In addition, the cold helped molecules longer exist, resulting in the reactions were that led to the origin of life.
5. RNA world
DNA needed for the formation of proteins, and proteins necessary for the formation of DNA. How could they be formed without each other? Scientists have suggested that this process involved RNA, which, as well as DNA stores information. Of RNA, respectively, formed proteins and DNA, which replaced it is because of its greater efficiency.
There was a different question: "How did the RNA?" Some people think that it spontaneously appeared on the planet, and others deny this possibility.
6. "Simple" theory
Some scientists have suggested that life evolved not from complex molecules such as RNA, from simple to interact with each other. They may have been in a simple interface, similar to cell membranes. As a result of the interaction of simple molecules appeared difficult to effectively react.
After all, life could have arisen not on our planet, and brought from space: in science, this phenomenon is called panspermia. This theory is quite solid foundation: the impact of space because of Mars periodically separated fragments of stones, which flies up to Earth. Once they found Martian meteorites on Earth, they suggested that these objects and brought bacteria. If we believe it, we all Martians. Other researchers have suggested that comets brought life from other star systems. Even if they are right, then mankind will seek the answer to another question: "How life began in space?"