Answer:
•Photosynthesis removes carbon dioxide from the atmosphere, and cellular respiration puts it back.
Step-by-step explanation:
Photosynthesis: 
It is the process in which in the presence of sun light and chlorophyll by using carbon dioxide and water plants produce the oxygen and glucose. 
Carbon dioxide + water + energy → glucose + oxygen 
water is supplied through the roots, carbon dioxide collected through stomata and sun light is capture by chloroplast. 
Cellular respiration:
It is the breakdown of glucose molecule in the presence of oxygen to yield large amount of energy. Water and carbon dioxide are also produced as a byproduct. 
Glucose + oxygen → carbon dioxide + water + 38ATP 
In this way it release the carbon dioxide back into atmosphere.