What is the approximate energy transfer efficiency between trophic levels in most ecosystems?

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

Answer: (A)

Energy transfer efficiency between trophic levels is about how much energy available at one level becomes useful biomass for the next. In most ecosystems, only roughly 10 percent of the energy at one level is passed on to the next, because the rest is lost as heat during metabolism, used for respiration and daily activity, or remains unavailable in undigested material. This pervasive energy loss creates the typical pyramid shape of ecosystems, with much less energy at higher levels. While the exact value varies, around ten percent is the standard rule of thumb. The other options aren’t right because transferring nearly all energy (about 90 percent) or half of it (about 50 percent) would require far less loss to metabolism and waste than actually occurs, and transferring only about 1 percent is unusually low for most systems.