Final answer:
Gas exchange in photosynthesis and cellular respiration helps maintain balanced levels through the regulation of carbon dioxide and oxygen.
Step-by-step explanation:
Gas exchange in photosynthesis and cellular respiration helps to keep the levels balanced as a constant percentage. Photosynthesis pulls carbon dioxide out of the atmosphere and produces oxygen, while cellular respiration releases carbon dioxide and uses oxygen. These interconnected processes work together to maintain a balance by regulating the levels of carbon dioxide and oxygen in the environment.