Write an explanatory note on origin of life.
 

If you go back in the history approx. $4500$ million years back when atmosphere was reducing the organism were

Give scientific reasons : Life originated from the earths inorganic atmosphere is the post but this no longer happens today
 

An experiment to prove that organic compounds were the basis of life, was performed by

Formation of which complex molecules was noticed by Urey and Miller when they subjected substances like $N{H_3},C{H_4},{H_2}O$ etc. to electric discharge