Final answer:
Photosynthesis and respiration are the two processes upon which the amount of carbon in the atmosphere depends, as they are integral parts of the carbon cycle.
Step-by-step explanation:
The amount of carbon in the atmosphere is dependent on the processes of photosynthesis and respiration. Photosynthesis is a process that consumes carbon dioxide and produces oxygen, performed by plants and other photosynthetic organisms. It removes carbon dioxide from the atmosphere and uses it to create energy-rich organic compounds. On the other hand, cellular respiration is a process by which living organisms, including plants at night, consume oxygen and release carbon dioxide back into the atmosphere as a byproduct of energy production. These two processes are central to the carbon cycle, which is the recycling pathway of carbon through the biosphere and atmosphere. In aquatic environments, carbon dioxide dissolves in water, forming carbonic acid that can ionize to carbonate and bicarbonate ions, contributing to oceanic carbon reservoirs that eventually lead to geological formations like limestone.