Photosynthesis is a process plants use to create glucose. In this process, carbon dioxide is being used up and oxygen is created as a byproduct, and this oxygen released into the atmosphere through the leaves of the plant.
Cellular respiration is a process cells use to create ATP, which is energy for cells. Cellular respiration uses up oxygen and has a byproduct of carbon dioxide, which is released into the atmosphere through our lungs and other ways (depending on the organism).
Thus, photosynthesis creates oxygen and reduces carbon dioxide, and cellular respiration creates carbon dioxide and uses up oxygen. Thus, <span>"photosynthesis and cellular respiration have opposite effects on gases in the atmosphere."</span>
Put simply, Photosynthesis uses carbon dioxide and outputs oxygen while cellular respiration takes in oxygen and outputs carbon dioxide. I hope this helped.
