๐Ÿงฌap biology review

Atmospheric Oxygen (O2)

Written by the Fiveable Content Team โ€ข Last updated August 2025
Verified for the 2026 exam
Verified for the 2026 examโ€ขWritten by the Fiveable Content Team โ€ข Last updated August 2025

Definition

Atmospheric oxygen refers to the oxygen present in Earth's atmosphere. It makes up about 21% of our atmosphere and is essential for aerobic respiration in many organisms.

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