What happens to energy as it moves through trophic levels?

• A. Energy decreases as it moves up trophic levels.
• B. Energy increases as it moves up trophic levels.
• C. Energy stays the same at all levels.
• D. Energy is created at higher levels.

Answer: (A)

Energy in ecosystems flows from the sun into producers and then into higher trophic levels, but with losses at every step. Much of the energy captured by producers is used for metabolism, reproduction, movement, and other activities, and is released as heat. Only a small portion—roughly about one-tenth—is stored in the biomass of the next trophic level. Because of this continual energy loss, the amount of usable energy decreases as you move up the levels, creating a pyramid of energy that narrows toward the top. Energy isn’t created at higher levels and isn’t preserved intact from one level to the next; it must be continuously supplied by the sun and is progressively dissipated as heat and used for life processes.