Briefly explain Oparin-Haldane theory of origin of life.

Explanation

Theory of Chemical Evolution and Biological Evolution proposed by Oparin and Haldane.
First form of life, originated from pre-existing non-living organic molecules. Organic molecules were formed from inorganic molecules under the special conditions, i.e., high temperature, volcanic storms, energy from electric discharges, and high energy radiations, prevailing on the earth at that time.

(a) Methane, ammonia, etc. forming the reducing atmosphere changed into simple organic compounds such as sugars, bases, amino acids, glycerol, fatty acids, etc.
Stanley Miller 1953, created similar conditions in a laboratory and passed electric discharges in a closed flask containing `CH_(4),H_(2)`, NHs, water vapours at `800^(@)C` and observed formation of amino acids. Sugar, bases, pigments and fats were also observed. The formation of organic molecules from inorganic molecules is chemical evolution.
(b) Simple organic molecules formed complex organic compounds by polymerisation.
(c ) Organic molecules aggregated to form the first non-cellular forms of life- protobionts also called coacervates, 3 billion years back. Coacervates would have been giant moleculer of RNA, proteins and polysaccharides etc. They produced a lipid bilayer and termed as microphere and started reproducing their molecules.