Oparin and Haldane’s Theory:
The chemical evolution of life is the most widely accepted theory of origin of life. It is based on the fact that primitive earth was different from the earth which is present today. It was proposed by Russian bio-chemist, A.I Oparin (1923) and was supported by Englishman J.B.S Haldane (1928). This theory can be well-explained under the following headings: i.
Formation of the earth:
When the earth was formed, it was extremely hot with temperature of 5000 centigrades. Everything in the atmosphere was in molten state. ii.
Gradually, the constituents of the earth cooled down and formed primitive atmosphere. 2.
Formation of simple molecules:
Even after the formation of the earth, there existed certain simple molecules like hydrogen, nitrogen, etc. ii.
These elements were arranged under different strata according to their densities in the atmosphere. iii.
Soon, these reactive elements combined to form simple molecules like water, methane, ammonia, hydrogen cyanide, etc. iv.
These compounds settled in the atmosphere when the earth began to cool and condensation of water occurred to give rise to water cycle. v.
These molecules got mixed with the rain water and settled in the water resources formed by the water cycle. 3.
Formation of simple organic compounds:
The chemical synthesis of the organic compounds was supposed to occur in the warm primeval oceans or primordial soup. ii.
The energy for the synthesis of these chemicals were abundantly provided by the UV radiation from the sun as well as the rocks, heat energy from the volcanoes and electric energy from the lightening. iii.
Different organic molecules like amino acids, simple sugars and nucleic acid were formed spontaneously from the methane, ammonia and water. iv.
Since there were no organisms to consume these compounds and no oxygen for the oxidation of intermediate compounds, the organic compounds slowly accumulated in the...
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