Carbon enters the atmosphere from respiration and combustion.
Carbon dioxide & sunlight are absorbed by plants to produce carbohydrates for photosynthesis.
Animals then feed on the plant which passes the carbon from the plant to the animal.
The animal exhales the carbon in the form of carbon dioxide and releases it in the atmosphere through respiration.
Eventually, the animal will die. :((
In some cases, the ability to decompose is gone and the plant/animal may be available as a fossil fuel for future combustion.
The dead animal will be eaten by decomposers which will release the carbon back into the atmosphere.
Importance of Carbon . . .
Carbon is important for many reasons including that all living things have and need carbon to survive. Carbon is a part of an organic compound that all living things need to live. Even plants need Carbon to survive because they use carbon and sunlight to create the process of photosynthesis which is how they produce nutrients they need to survive.