What best describes the transfer of energy between trophic levels?

• A. All energy is transferred perfectly; no energy is lost as heat.
• B. Energy is created anew at higher levels.
• C. Only a portion of energy is transferred to the next trophic level; the rest is lost as heat.
• D. Energy is stored indefinitely in the next trophic level.

Answer: (C)

Energy moves through an ecosystem in a one-way flow from producers to higher-level consumers. At each step, only part of the energy available at the current level is captured and passed on to the next level, because much of it powers the organism’s life processes—growth, movement, respiration, and maintaining body heat. That energy is released as heat or used in other ways and becomes unavailable to the next trophic level. This is why energy (and biomass) declines as you move up the food chain, and why energy is not stored indefinitely at higher levels.

The idea that energy is created anew at higher levels isn’t correct, nor is the idea that all energy is transferred perfectly without heat loss. Energy is also not stored forever in the next level; it’s continually used and dissipated. The commonly cited rule is that only a fraction—often around 10%—of the energy at one level is available to the next, with the rest lost as heat or used up.