Question

An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to ________.

(A) make life on land difficult for aerobic organisms.
(B) change the atmosphere from oxidizing to reducing.
(C) make it easier to maintain reduced molecules.
(D) cause iron in ocean water and terrestrial rocks to rust (oxidize).
(E) prevent the formation of an ozone layer.

Answer 1

Answer:

(D) cause iron in ocean water and terrestrial rocks to rust (oxidize).

Explanation:

The primitive atmosphere on the earth was reducing since free molecular oxygen was not present in it. Evolution of autotrophic organisms that split water during photosynthesis and release oxygen as a by-product changed the atmosphere into an oxidizing one. Plants and bacteria were some of these autotrophs. The addition of oxygen to the atmosphere led to oxidation of metal ions such as iron present in the water of oceans and rocks. Oxidation of iron led to the formation of iron oxide that formed rust layer on it.