Energy transfer is inefficient between trophic levels primarily because molecules are fully digested from each trophic level.
However, the most accurate explanation for energy inefficiency is that a large portion of energy is lost as metabolic heat, not fully captured by digestion or consumption. Further, not all parts of organisms are consumed or digested, and energy is lost through processes like respiration and waste excretion. This means that a typical answer regarding inefficiency would emphasize the loss of energy at each level due to various biological processes and not simply focus on digestion.
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