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Molecular evolution: origin of life on earth
The origin of life as a spontaneous event from lifeless matter seems like an absurd idea. It seems, but only now.
For many philosophers of the past this was an irrefutable truth. The hypothesis called spontaneous generation prevailed. In the nineteenth century there was evidence that enabled researchers to overturn this hypothesis and create another. Since then, it has been known that chemical reactions and physical events were essential for the emergence of the first living organisms on the planet.
Main features of the origin of life hypothesis
The hypothesis to explain the origin of life currently believed to be called abiogenic molecular evolution. It is based on evidence obtained from experiments conducted in the chemistry laboratory. She also considers the findings obtained by paleontologists.
One piece of evidence shows that Earth's early atmosphere contained little oxygen. A considerable proportion of this oxygen reacted with hydrogen ions to form water. In this atmosphere were also gases and compounds such as methane and ammonia. The gases and compounds were exposed to ultraviolet radiation from the sun as well as frequent volcanic activity. Conditions thus triggered the formation of organic compounds: carbohydrates (sugars), amino acids and nitrogenous bases.
What happened next was the condensation of these organic compounds. But condensation reactions require substrates to be in high concentration. Therefore, the formation of complex molecules, which in the future would be part of living organisms, occurred in restricted places. A very important component in this phase of chemical evolution was ribonucleic acid (RNA). It has been shown that some RNAs act as enzymes during the binding of one amino acid to another in protein formation.
Who were the protagonists in the origin of life?
Researchers estimate that the first living organisms appeared about 4 billion years ago. They were unicellular beings of very simple structure. Over time, these organisms acquire the power of self-replication, that is, to make copies similar to themselves. Then natural selection worked upon them: the most efficient in those environmental conditions remained alive and reproduced.
- The branch of Biological Sciences that studies the origin of life is evolutionary biology.
Reading the book “Wonderful Life,” written by paleontologist Stephen Jay Gould, is a good way to understand biological evolution.