Carbon cycle involves the exchange of components between the hydrosphere, biosphere and atmosphere. During carbon cycle, materials such as gases, minerals which are necessary for life are interchange. For example, animals pass out faeces on the soil which is rich in urea. Urea decomposes to provide nitrogen into the soil through bioactive bacterials. The nitrogen is used up by plants to grow. During photosynthesis, plants uses carbon dioxide and water to produce glucose and release oxygen for animals to use. It's like a purification system where one waste product from one organism is used by the other to survive.
