Which portion of energy is actually passed to the next trophic level as biomass?

• A. Energy lost as heat
• B. Energy in waste
• C. Biomass energy remaining after losses
• D. All energy ingested

Answer: (C)

When energy moves from one trophic level to the next, only the energy that remains stored in an organism’s tissues after accounting for uses and wastes can be passed on. Much of the ingested energy is spent on metabolism and lost as heat, and some is lost in waste products or is not assimilated. The energy that actually moves forward is the energy still stored as biomass in the consumer after these losses. That is why biomass energy remaining after losses best describes what gets passed to the next level. In practice, only a fraction (often around 10%) of the energy at one level becomes new biomass at the next.