Approximately what percentage of energy is transferred from one trophic level to the next in ecological pyramids?

• A. About 50 percent.
• B. About 1 percent.
• C. About 10 percent.
• D. About 90 percent.

Answer: (C)

Energy moves through ecosystems in a one-way flow from the sun to producers to consumers, and at each step only a fraction of the available energy is passed on. When an organism at one level is eaten, much of the energy stored in the food is used for metabolism, maintenance, and movement, or is lost in waste and undigested material. The energy that actually becomes new biomass for the next level is typically about 10% of what was available at the previous level. That ~10% transfer creates a noticeable drop in available energy as you move up the food chain, which is why food webs tend to have only a few trophic levels. Remember, this is an average; some systems transfer a bit more or less, but ten percent is the common rule of thumb.