What happens to most energy as it moves through trophic levels?

• A. It is released as heat.
• B. It is recycled by decomposers back to producers.
• C. It is stored indefinitely in biomass.
• D. It is converted into electricity.

Answer: (A)

Energy flow through ecosystems is inefficient: as energy moves from producers to higher trophic levels, most of it is used for life processes and released as heat. Metabolic activities like respiration, movement, and digestion burn energy, so only a small portion remains to be stored in the biomass of the next level. That’s why energy available to successive levels drops, and why food chains are relatively short. In general, about 90% of the energy is lost at each transfer, leaving only around 10% to be passed on. Decomposers recycle nutrients, not energy, and the energy they release eventually leaves the ecosystem as heat. Energy is not stored indefinitely in biomass; it is largely dissipated as heat as it moves through the ecosystem.