Photosynthesis: energy from the sun is captured by plants and used to make food. Most of this energy is used to carry on the plant's life activities, the rest of the energy is passed on as food to the next level of the food chain.
Energy flows in a simple food chain. At each level of the food chain, about 90% of the energy is lost in the form of heat. Therefore, as you move up the food chain, there is less energy available.
NOTE!! Each organism in the food chain is only transfering one-tenth of its energy to the next organism.