Question

Who said "abiogenesis first but biogenesis ever since"?
A. Haldane
B. Pasteur
C. Fox
D. Oparin

Answer 1

Hint: This theory talks about the concept that the first living organism evolved from non- living material. It is also called primary abiogenesis. They also suggest that the sequence of events that might have occured. This theory was put forward when life on earth was imagined to come from in-organic material.

Complete answer: Abiogenesis is the idea that life arose from non- life more than 3.5 billion years ago. This proposes that the first life - form generated were very simple and through a gradual process became increasingly complex. Biogenesis is that in which life is derived from the reproduction of other life. It precedes abiogenesis.
In 1920, British scientist J.B.S. Haldane and Russian biochemist Aleksandr Oparin explained the idea of life on earth. Both of them believed that the concerning conditions required for the origin of life on earth are similar.
According to their theory, spontaneous generation of early molecules might have taken place if the earth was reducing the atmosphere compared to the present oxidising atmosphere. They both agreed that the early atmosphere contained little or no oxygen in free form. As there was no ozone layer so there could not be absorption of UV rays that are lethal for the lives on earth. Moreover, the atmospheric water vapour condensed into droplets and fell as rain which rolled down on earth.
Atmospheric chemicals produce amino acids, nitrogen bases etc. These molecules combine to form the products like amino acid, polysaccharides and nucleic acids. The energy source for the reaction of organic synthesis were UV radiations, cosmic rays, intense dry, heat and radioactive decay of various elements that are present on the earth. Once these organic molecules are formed and accumulated in water due to degradation it is extremely slow in absence of catalysts of enzymes. Such transformation is possible in an oxidising atmosphere.
In 1923, Oparin postulated that life originated on earth at a remote place at some time under conditions no longer observed. In his book, The origin of life in 1938, he submitted the thesis that abiogenesis first, but biogenesis ever since. It is also known as primary abiogenesis.

So, the correct answer is option D, Oparin.

Note: The origin of life is considered a unique event in the history of the universe. Relatively speaking, the universe is 20 billion years old. Oparin of Russia and Haldane of England proposed that the first form of life could come from pre - existing non- living organic molecules and that formation of life was preceded by chemical evolution.