Question

With the origin of aerobic phototrophs the atmosphere of the earth became ______.

Options

• oxidizing

• reducing

• devoid of nitrogen

• devoid of carbon dioxide

Answer 1

With the origin of aerobic phototrophs the atmosphere of the earth became oxidizing.

Explanation:

The origin of aerobic phototrophs led to the liberation of free oxygen into the atmosphere, which gradually changed the primitive reducing atmosphere into an oxidizing atmosphere. This rise in oxygen also resulted in the formation of the ozone layer and supported the evolution of aerobic respiration.