About 3.7 billion years ago during chemical evolution on our planet there were first connections which were capable to reproduce similar to molecules. On modern scientific representations these molecules also gave rise to life on Earth.
Instruction
1. At the moment the biochemical theory of origin of life is considered recognized. It was developed by the Soviet scientist Alexander Oparin in 1924. According to this theory the emergence and further evolution of living organisms are impossible without the previous long chemical evolution which consists in emergence and development of organic molecules.
2. About 4 billion years ago Earth already had the solid bark and the atmosphere significantly differing from present, in it there was practically no oxygen, but there were a hydrogen, ammonia, methane, nitrogen and vapors of water much. The lack of oxygen without which it is impossible to present modern life at the first stage of chemical evolution was the benefit as oxygen is strong oxidizer, and at its large number the organic molecules just could not be formed.
3. After Earth cooled down enough, in its atmosphere processes of synthesis of organic molecules began to happen, and these processes took place abiogenno, that is synthesis went not by means of living organisms which were not yet, but thanks to accidental reactions between chemical compounds. For synthesis lightnings, the space radiation and, first of all, rigid ultra-violet radiation of the Sun gave energy. The possibility of abiogenous synthesis is completely proved as it manages to be repeated easily in laboratory, besides, it is observed now at volcanic activity.
4. Gradually temperature of primary atmosphere fell, some substances began to pass from gaseous state into liquid, rains began, the first oceans saturated with plain organic compounds which began to interact actively were formed, creating harder and harder connections.
5. In 1986 the theory of the world of RNA according to which molecules of ribonucleic acid were the first connections capable to reproduce similar to molecules, was formulated. It is impossible to call molecules RNA living organisms as they had no cover separating them from the environment.
6. It is supposed that covers appeared at the first RNA when they in a random way got to spheres from fatty acids. In covers the emergence of difficult biochemical processes of a metabolism became possible. In the course of evolution there were more viable connections, the first simplest living organisms as a result appeared.
7. There are several other theories of origin of life on Earth: - the theory of self-generation of life is known from antiquity, it was supposed that living organisms in a random way appear from lifeless matter, for example, of a fly - from the decaying meat, a bird - from leaves, etc.; - the theory of creationism says that living beings were created by superreason - an alien civilization, God, the absolute idea; - there is a theory according to which life on our planet was brought from space, but this theory just transfers emergence of life to other place and does not explain its mechanism.