Answer:
Carbon is passed in the form of carbon dioxide from the atmosphere to the living species. It is then circulated from one organism to another and is ultimately returned back to the atmosphere in the form of carbon dioxide again.
The plants utilize carbon dioxide from the atmosphere for undergoing the process of photosynthesis. The carbon becomes a component of composite molecules in plants like fats, proteins, and carbohydrates.
The carbon dioxide is returned back to the atmosphere through the process of respiration by animals, plants and microbes. The decomposition of dead and decaying plants and animal components also discharges carbon dioxide, the process involves microorganisms.