[Campbell Biology P.583] Based on Figure 25.9 and the accompanying text, which statement abo... | Practice Question
Based on Figure 25.9 and the accompanying text, which statement about the "Oxygen Revolution" is accurate?
A: The "Oxygen Revolution" refers to a period when atmospheric O2 levels gradually increased from 2.7 to 2.4 billion years ago, followed by a rapid rise.
B: Before the "Oxygen Revolution," free O2 dissolved directly into the atmosphere, bypassing the aquatic environment.
C: The graph in Figure 25.9 shows that atmospheric O2 levels reached 100% of present-day levels around 2 billion years ago.
D: The "Oxygen Revolution" had a limited impact, as most prokaryotic groups adapted easily to the new oxygenic environment.
Explanation
The text explicitly states: "As shown in Figure 25.9, the amount of atmospheric O2 increased gradually from about 2.7 to 2.4 billion years ago, but then shot up relatively rapidly to between 1% and 10% of its present level. This “oxygen revolution” had an enormous impact on life."