All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food.
Food webs identify the relationships among producers, consumers, and decomposers in an ecosystem.
For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. To explore the transfer of energy and introduce food webs, begin by asking your students how they get their energy. Discuss sources of food and the role that food plays in the human energy cycle. Draw upon student examples to draw simple food chains or webs.