Digestion is a complex process in which the raw food is converted into the energy needed to live and grow.
Animals take in oxygen and water as well as food.
A series of complex chemical reactions takes place to produce the necessary energy. Waste products, in particular carbon dioxide, are then exhaled through lungs, gills, pores or spiracles. This life process is known as respiration. Plants, too, require energy in order to live and grow. Because plants have chlorophyll, they have the ability to produce their own food.