All nutritional energy comes from the Sun: plants use chlorophyll to photosynthesize the Sun's energy into plant energy, and then animals either feed on plants for that energy or they feed on the animals that have eaten that plant energy. The food chain begins with the Sun and then the energy flows to producers. The chloroplasts collect energy from the sun and use carbon dioxide and water in the process called photosynthesis to produce sugars. Animals can make use of the sugars provided by the plants in their own cellular energy factories, the mitochondria. ... The energy cycle for life is fueled by the Sun.
