The increasing concentration of atmospheric oxygen in Earth's early atmosphere
A) was favorable to most prokaryotes because of their small size.
B) was fatal to numerous eukaryotes because they possessed mitochondria
C) conferred a selective advantage to a eukaryote that possessed a mitochondrion.
D) conferred a selective advantage to a eukaryote that possessed a chloroplast.
E) conferred a selective advantage to prokaryotes because of their stiff membranes.

Question

Quizplus · Accepted Answer

As the concentration of atmospheric oxygen increased during the Great Oxygenation Event, aerobic respiration became possible. This conferred a selective advantage to eukaryotes possessing mitochondria. These eukaryotes could produce more ATP from the same amount of nutrients as compared to anaerobic eukaryotes or prokaryotes. This increased energy availability likely gave these eukaryotes an advantage in competition for resources. The increase in atmospheric oxygen had no direct effect on chloroplasts, as they are thought to have evolved from photosynthetic bacteria that were already adapted to the low-oxygen atmosphere. Oxygen toxicity was a challenge for many anaerobic prokaryotes, and some lineages likely went extinct as a result, but the selective advantage conferred by increased energy availability is likely to have outweighed this disadvantage for many other prokaryotes. Therefore, choices A, B, D, and E are incorrect.

The Increasing Concentration of Atmospheric Oxygen in Earth's Early Atmosphere