Which statement best describes energy flow in an energy pyramid?

• A. Energy flows from producers to consumers, but most energy is retained at higher trophic levels.
• B. Energy flows from consumers to producers, and energy increases at higher levels.
• C. Energy flows from producers to consumers, but only a portion transfers to higher trophic levels, and most is lost as heat.
• D. Energy is created at each trophic level to sustain higher levels.

Answer: (C)

Energy moves through an ecosystem in one direction—from producers at the base up to consumers above—and most of the energy is used for life processes and released as heat at every step. Producers capture energy from the sun and store it as chemical energy. When a consumer eats, only a fraction of that energy is converted into new biomass that the next level can use; the rest is lost as heat through metabolism, respiration, movement, and digestion. Because of this, the amount of energy available decreases as you go higher in the pyramid, which is why higher trophic levels have less energy and fewer individuals. The idea that energy flows from producers to consumers, with only some transferred and most lost as heat, best describes the energy pyramid.