About 1.5 billion years ago, oxygen began to accumulate as a byproduct of ____, drastically changing the composition of the Earth's atmosphere.
A) biosynthesis
B) cellular respiration
C) methane synthesis
D) photosynthesis

Question

Quizplus · Accepted Answer

Oxygen began to accumulate as a byproduct of photosynthesis, specifically from cyanobacteria, which drastically changed the composition of the Earth's atmosphere. Prior to this, the atmosphere was mainly composed of methane, ammonia, and water vapor. The accumulation of oxygen allowed for the emergence of more complex life forms.

About 15 Billion Years Ago, Oxygen Began to Accumulate as a a Byproduct