All life forms need energy to survive. Energy is the resource that allows organisms to do things. What kinds of things might an organism do with energy? This answer to this question is as varied as the life forms that use energy. Some, like the African Lion, use energy to chase after prey. Other life forms, like many creatures we find in the depths of the Earth's oceans use energy to create their own light. Living things use energy to grow, to defend themselves, and to move around.

With so many living things around us using energy every day, you might ask where all this energy comes from. The main source of energy on the Earth today is the Sun. The energy found in your body, that you use to run, jump, and play sports, was originally produced by the Sun.