Question

In primordial atmosphere when the living organism evolved the respiration process was
A. Anaerobic as it released more energy.
B. Aerobic as it was more complex.
C. Aerobic as it released more energy.
D. Anaerobic because early atmosphere contained little or no oxygen.

Answer 1

Hint:- Origin of the universe was the most important phenomenon in the origin of life. The Big Bang Theory attempts to explain the origin of the universe. This theory proposes that the universe is very old and its origin took place almost 20 billion (20 x 10) years ago. It explains the condition that a single huge explosion (i.e., Big Bang) took place in space which was so powerful that it is unimaginable in physical terms.

Complete Answer:- The gaseous packets or atmosphere was absent on the early earth. Due to volcanic eruptions, the molten mass was released which slowly covered the surface of earth. From this molten mass, various gases released into the surroundings like methane $(\mathop {CH}\nolimits_4 )$, ammonia $(\mathop {NH}\nolimits_3 )$, carbon dioxide $(\mathop {CO}\nolimits_2 )$, water vapour etc. The ultraviolet (UV) radiations present in the sunlight acted upon water and broke up water into hydrogen and oxygen and lighter $\mathop H\nolimits_2$, escaped. Oxygen readily combined with other gases like $(\mathop {NH}\nolimits_3 )$, and $(\mathop {CH}\nolimits_4 )$, to form again $\mathop H\nolimits_2$,$\mathop O\nolimits_{}$, $(\mathop {CO}\nolimits_2 )$, and other gases. Thus the free and nascent oxygen (like today's environment) was not present on the early earth.
Now let us match this with given options:-
Anaerobic as it released more energy. :- when respiration takes place without the presence of oxygen it is said to be anaerobic respiration , it is true that in early atmosphere organisms perform anaerobic respiration but this respiration do not releases more energy
Aerobic as it was more complex. :- when respiration takes place in the supply of oxygen it is termed as aerobic respiration but earth in the early times has no atmosphere so no oxygen thus they can not perform aerobic respiration
Aerobic as it released more energy. when respiration takes place in the supply of oxygen it is termed as aerobic respiration and it release more energy as occur in presence of oxygen but earth in the early times has no atmosphere so no oxygen thus they cannot perform aerobic respiration
Anaerobic because early atmosphere contained little or no oxygen. :- when respiration takes place without the presence of oxygen it is said to be anaerobic respiration so in early times earth has no oxygen it is reducing in nature thus organisms perform anaerobic respiration.

**Our required option is d that is Anaerobic because early atmosphere contained little or no oxygen
**

Note:- The early atmosphere was reducing unlike today's oxidising atmosphere. It was only present in the form of compounds like $\mathop H\nolimits_2 \mathop O\nolimits_{}$, $\mathop {CO}\nolimits_2$etc. Oxygen also participated in the formation of ozone $\mathop O\nolimits_3$ molecules due to action of UV rays on it. These oxygen molecules clustered together to form the ozone layer which acts as a shield to save our present atmosphere from harmful UV rays. The water vapour condensed to form water drops which fell as rain and slowly filled the depressions present on the surface of earth which is supposed to be the origin of large oceans seen today.