They must eat plants like lettuce and potatoes, or meat, like pork and beef, to live.
Humans can have meat only because animals like cows and pigs eat plants.
Green plants are the only living things that can make their own food. During the process of photosynthesis, the energy from the sun is turned into chemical energy. The chemical energy is used to join carbon dioxide and water. In the process, sugar and oxygen are created. This process takes place mainly in the leaves of the plant.