The Accumulation of Free Oxygen in the Atmosphere ____

Question

The accumulation of free oxygen in the atmosphere ____.  
A) was a result of the accumulation of a by-product of a type of photosynthesis
B) caused the further spontaneous generation of life
C) provided the opportunity to extract more energy through anaerobic respiration
D) occurred immediately after the earth was formed
E) allowed for DNA to replace RNA as the primary data storage molecule

Accepted Answer

The accumulation of free oxygen in the atmosphere was a result of the accumulation of a by-product of a type of photosynthesis known as oxygenic photosynthesis, which is performed by cyanobacteria, algae, and plants. This process releases oxygen as a by-product, leading to an increase in atmospheric oxygen levels over time.