What is the carbon cycle?
The carbon cycle shows the circulation and recycling of the chemical element carbon in nature as a result of the action of living beings.
Photosynthetic beings absorb carbon as carbon dioxide available in the atmosphere and the carbon atoms become kind of glucose molecules. During the cellular respiration of these beings part of this organic material is consumed to make ATP and in this process carbon dioxide is returned to the atmosphere. The other part is incorporated by the photosynthetic organisms into the molecules that compose their structure. The carbon atoms incorporated into the producers are transferred to the next trophic level and again part is liberated by the cellular respiration of the consumers, part becomes a constituent of the consumer body and part is excreted as uric acid or urea (excretes later recycled by decomposer bacteria). Thus carbon absorbed by the producers in photosynthesis returns to the atmosphere by cellular respiration along the food chain unless the decomposers that also liberate carbon dioxide in their energetic metabolism. Under special conditions in a process that takes millions of years carbon incorporated into organisms might also constitute fossil fuels stored in deposits under the surface of the planet; as fossil fuels burn the carbon atoms return to the atmosphere as carbon dioxide or carbon monoxide.