NSES Content Standard C  Life Science: Populations and ecosystems Grades 5-8, page 158 For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. That energy then passes from organism to organism in food webs.

 
Benchmark 5E The Living Environment: Flow of Matter and Energy
Grades 6-8, page 120
Food provides the molecules that serve as fuel and building material for all organisms. Plants use the energy from light to make sugars from carbon dioxide and water. This food can be used immediately or stored for later use. Organisms that eat plants break down the plant structures to produce the materials and energy they need to survive. Then they are consumed by other organisms.

Benchmark 5E The Living Environment: Flow of Matter and Energy
Grades 6-8, page 120
Energy can change from one form to another in living things. Animals get energy from oxidizing their food, releasing some of its energy as heat. Almost all food energy comes originally from sunlight.