Nitrogen cycle and Carbon cycle

Nitrogen Cycle:

Nitrogen is necessary for the formation of proteins. Certain bacteria can change the nitrogen in the air to nitrates in the soil. Green plants absorb the nitrates from the soil and use them to make proteins. Animals fed on plants and use their proteins for growth. When the plants and the animals die, their bodies decay or get broken down by the bacteria and fungi. In this way, nitrates are released  back into soil. 

Carbon Cycle:

The carbon cycle refers to the circulation of carbon through the ecosystem. Carbon dioxide from the air is used up by green plants to make sugar and other
substances. When animals eat the plants, they take these carbon compounds. Eventually, the plants and animals die. Bacteria and fungi obtain the carbon compounds from the dead bodies of these plants and animals. Respiration in living organisms release carbon dioxide back into the air.