What percentage of energy is usually transferred from one trophic level to the next?

• A. 10%
• B. 90%
• C. 50%
• D. Size of the organism

Answer: (A)

Energy transfer between trophic levels is inefficient because organisms use energy for life processes and release much of it as heat, plus not all of the energy stored by producers is consumed or digested at the next level. This means only a small portion moves up to the next level. The usual figure is about ten percent of the energy available at one level becomes available to the next. For example, if producers capture 1000 energy units, roughly 100 units are passed to herbivores, and about 10 units reach the next level of carnivores. The other options don’t fit: 90% would imply most energy is passed on, which isn’t supported; 50% would still be too high; and the size of the organism doesn’t determine this energy-transfer percentage.