Answer:
They increase the amount of carbon in the atmosphere
Step-by-step explanation:
Carbon is usually introduced into the atmosphere in a gaseous form. The atmosphere is the gaseous envelope round the earth.
When animals respire, they take up food materials from plants and other sources. They then metabolically break it down.
Oxygen is needed for respiration and in turn, the waste product is usually carbon dioxide.
So, respiration by animals releases carbon dioxide as a by product.