The chlorophyll stores the sun's energy. Then carbon dioxide, which people and animals breathe out, enters the plants' leaves through tiny holes. The carbon dioxide combines with the stored energy in the chlorophyll and makes a simple sugar. This sugar is transported to the plants' stems, roots, seeds and fruit. People and animals eat the plant itself or its parts, like carrots, rice or potatoes.
Photosynthesis is the first step in the food chain that connects all living things.
Every creature on earth depends on green plants in some way. Even animals who do not eat plants eat smaller animals who do eat plants. But people and animals don't need green plants just for food. While the plant is making sugar through photosynthesis, it is also putting oxygen into the air. Human beings, as well as animals, must have oxygen in order to live.