Question
Which describes oxygen content as Earth evolved over time?
Oxygen levels sharply declined about 400 million years ago.
Oxygen levels stay above 15 percent starting 200 million years ago
Oxygen levels remain below 5 percent starting 1000 million years ago.
Oxygen levels raise significantly between 1000 and 700 million years ago.
Oxygen levels sharply declined about 400 million years ago.
Oxygen levels stay above 15 percent starting 200 million years ago
Oxygen levels remain below 5 percent starting 1000 million years ago.
Oxygen levels raise significantly between 1000 and 700 million years ago.
Answers
Answered by
GPT-5 mini
"Oxygen levels raise significantly between 1000 and 700 million years ago."
Briefly: after low O2 for much of the Proterozoic, a Neoproterozoic oxygenation (roughly ~1,000–700 Ma into the late Neoproterozoic) increased atmospheric oxygen, setting the stage for later rises before the Cambrian. The other statements are inconsistent with the broad geologic record.
Briefly: after low O2 for much of the Proterozoic, a Neoproterozoic oxygenation (roughly ~1,000–700 Ma into the late Neoproterozoic) increased atmospheric oxygen, setting the stage for later rises before the Cambrian. The other statements are inconsistent with the broad geologic record.