Scientists say that life arose on the primitive earth because of the conditions then existent on our planet. Explain this statement & comment whether life would have originated on our present day earth?
1 Answer
Our present atmosphere of 21% Oxygen would make the formation of DNA and other organic molecules impossible. So Scientists propose conditions different from what we see today
Explanation:
The award winning experiment of Miller and Urey postulated an early atmosphere of Hydrogen , Methane, Ammonia and Water vapor as proposed by Oparin and Haldane.
By shooting an electric spark through this combination of gases the experimenters were able to produce biologically significant amino acids such as glycine and alanine.
If Oxygen had been present in the combination of gases used by Miller and Urey the reaction flask would have exploded.
If the molecules necessary for life were to be produced by natural causes alone, Oxygen can not have been present in the early atmosphere.
However many scientists today believe that the early atmosphere came from volcano's not the interstellar gas clouds. So the atmosphere in the early earth was not the composition used in the Miller and Urey experiments.
Michael Kimberly wrote in 1979 said that there was no evidence "that an oxygen-free atmosphere has existed at any time during the span of geological history recorded in well preserved sedimentary rocks".
The evidence is inconclusive. If life ( living cells) occurred by natural causes then the atmosphere must have been different than the present atmosphere with significant percentages of Oxygen. However there no evidence that indicates the atmosphere postulated by Miller and Urey ever existed.
