Sunlight and CO2 from the atmosphere are used by plants such as the date palm tree, wheat, and many others to create sugars and oxygen. These sugars are kept by the plants and used for energy. These plants then release carbon through cellular respiration back into the atmosphere. The plants are then eaten by animals (like pigeons, humans, bugs, mosquitoes) or decompose into waste in the ground and the ocean may take some of the dead waste and carbon or the carbon may be used for fossil fuels. The animals that eat the plants release carbon dioxide into the atmosphere through cellular respiration and other animals (like fish, crocodiles, hawks) may eat them or they may die and decompose. Factories also release carbon dioxide into the atmosphere.