Explain the process of origin of life as given by different scientists.

Explanation

(1) Darwin : His theory of evolution tells us how life evolved from simple to more complex forms. Darwin.s theory is called "Theory of Natural Selection".
But he could not explain about how life began on earth.
(2) J. B. S. Haldane : He was a British scientist who suggested in 1929 that life must have developed from the simple inorganic molecules which were present on primitive earth. He speculated that the conditions on the earth at that time could have given rise to more complex organic molecules that were necessary for life. The first primitive organisms arose further by chemical synthesis.
(3) Stanley L. Miller and Harold C. Urey : In 1953, they assembled an experiment in which primitive atmosphere was simulated.
It had compounds like ammonia, methane, hydrogen and water vapour but no oxygen. This was maintained at a temperature just below `100^(@)C` and electric sparks were passed through the mixture of gases to simulate lightning. At the end of a week, `15%` of the carbon had been converted to simple compounds of carbon including amino acids which are monomers of protein molecules.