Question

How do plants and animals rely on each other to maintain the atmospheric oxygen and carbon dioxide content?

Answer 1

It has already been known that the animals breathe oxygen inside and exhale carbon dioxide, while plants take in carbon dioxide during the day and then release oxygen.

Complete answer:
Photosynthesis can be defined as the process in which plants use the energy in sunlight to convert carbon dioxide and water into sugar and oxygen.
The carbon dioxide–oxygen cycle regulates the balancing of these gases present within the atmosphere so that all plants and animals do have what they need in order to survive.
Photosynthesis, respiration, and decomposition are the three important processes that are responsible for maintaining the carbon dioxide–oxygen cycle. The process of photosynthesis in plants leads to release of oxygen into the atmosphere. Respiration by plants and animals occurs since they use the energy stored in food, and the process of decomposition of dead decaying organisms releases carbon dioxide into the atmosphere. All these three work together to regulate the carbon dioxide-oxygen cycle.
If it is assumed that most of the plants suddenly died, then the amount of oxygen present in the atmosphere would decrease whereas the level of carbon dioxide would increase.

Note: The carbon cycle and oxygen cycle is mainly maintained by the plants as well as animals.
Oxygen is released into the environment from the plants by the process of photosynthesis. Even though, oxygen is utilised by both plants and the animals for the process of respiration.
Photosynthesis and respiration are two opposite metabolic activities to each other. In photosynthesis, carbon dioxide is used up, whereas in respiration oxygen is used up.
-In photosynthesis, the carbon dioxide is used from the atmosphere and oxygen is released from the water by the process known as photolysis of water.
-In respiration, both carbon dioxide and water is released from the product of photosynthesis i.e., glucose.