What was one ecological consequence of the Great Oxidation Event?

• A. Oxygen-enabled life evolved; aerobes thrived, while anaerobes diminished
• B. Oxygen caused Earth to become completely uninhabitable
• C. Oxygen had no influence on life
• D. Oxygen instantly produced continents

Answer: (A)

The key idea is that the Great Oxidation Event raised atmospheric oxygen, which changed how organisms obtain energy. With more oxygen available, aerobic respiration became possible—organisms could extract much more energy from the same amount of nutrients than in anaerobic metabolism. This extra energy powered the evolution and diversification of aerobes and eventually more complex life, while many anaerobic microbes struggled or declined in the oxygen-rich environment. So, a major ecological consequence was a shift toward living systems that rely on oxygen, enabling larger, more energy-demanding life forms to emerge.

Oxygen didn’t make Earth uninhabitable; life persisted and adapted to the new conditions, and the rise of oxygen also drove other long-term geochemical changes. Oxygen didn’t instantly create continents; the formation of continents is driven by plate tectonics, not atmospheric oxygen.