Answer:
Carbon dioxide is also generated by cellular metabolism and must be removed from the cell. There must be an exchange of gases: carbon dioxide leaving the cell, oxygen entering. Animals have organ systems involved in facilitating this exchange as well as the transport of gases to and from exchange areas.
Animals and plants need oxygen. When an animal breathes, it takes in oxygen gas and releases carbon dioxide gas into the atmosphere. This carbon dioxide is a waste product produced by the animal's cells during cellular respiration. Cellular respiration occurs in the individual cells.
