6.1a Energy flows through ecosystems in one direction, usually from the Sun, through
producers to consumers and then to decomposers. This process may be visualized with
food chains or energy pyramids.
6.1b Food webs identify feeding relationships among producers, consumers, and
decomposers in an ecosystem.
6.1c Matter is transferred from one organism to another and between organisms and
their physical environment. Water, nitrogen, carbon dioxide, and oxygen are examples
of substances cycled between the living and nonliving environment.