Question

Following are the two statements regarding the origin of life:
(i) The first organisms that appeared on earth were non-green and presumably anaerobes.
(ii) The first autotrophic organisms were chemoautotrophs that never released oxygen.
Which of the following options are correct regarding the above statements?

• A. (i) is correct but (ii) is false
• B. (i) is false but (ii) is correct
• C. Both (i) and (ii) are correct
• D. Both (i) and (ii) are false

Answer 1

The correct option is C Both (i) and (ii) are correct

The first form of life that appeared on earth came from pre-existing non-living organic molecules (e.g. RNA, protein, polysaccharides, etc.). The formation of life was preceded by chemical evolution, i.e. formation of diverse organic molecules from inorganic constituents. So the first life forms were nucleoproteins that lack chlorophyll i.e. they were non-green.
The first forms of life that appeared on earth used these organic compounds as their carbon and energy source hence they were anaerobic chemoheterotrophs.
The conditions on earth were – high temperature, volcanic storms, reducing atmosphere containing ${\mathrm{CH}}_4$, ${\mathrm{NH}}_3$ since there was no oxygen available therefore the first life forms would be anaerobes which performed anaerobic breakdown of organic compounds to release energy.
Due to the absence of oxygen, the first autotrophic organisms were dependent on chemicals. Hence, they were chemoautotrophs.