What process is responsible for the accumulation of oxygen in Earth's atmosphere according to scientists?

Photosynthesis is the key process responsible for the accumulation of oxygen in Earth’s atmosphere. During photosynthesis, plants, algae, and some bacteria use sunlight to convert carbon dioxide and water into glucose and oxygen. The chemical equation for photosynthesis can be summarized as:

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

This indicates that for every six molecules of carbon dioxide and six molecules of water used, six molecules of oxygen are produced. This oxygen is then released into the atmosphere, significantly increasing its presence over geological time.

Early Earth had a very different atmosphere, predominantly composed of carbon dioxide. However, as photosynthetic organisms evolved and flourished, the oxygen produced began to accumulate, leading to significant changes in the planet's atmospheric composition. This buildup of oxygen not only allowed for the development of aerobic (oxygen-dependent) life forms but also played a crucial role in shaping the Earth’s environment.

The other processes mentioned do not contribute to the accumulation of oxygen in the atmosphere. Decomposition of organic matter primarily breaks down compounds and releases carbon dioxide rather than oxygen. Respiration, performed by both plants and animals, consumes oxygen and releases carbon dioxide. Nitrogen fixation is focused on converting