Where does most energy go during cellular respiration, and how does this limit energy available to higher trophic levels?

Where does most energy go during cellular respiration, and how does this limit energy available to higher trophic levels?

• A. Most energy is stored as chemical energy in ATP at higher levels.
• B. Most energy is released as heat during cellular respiration; only a portion is transferred to the next trophic level.
• C. All energy from the previous level is transferred to the next trophic level.
• D. Energy is never lost and accumulates at each step.

Answer: (B)

During cellular respiration, energy stored in organic molecules is released to power life processes, but most of that energy leaves as heat. The energy that remains in chemical bonds—what’s captured as ATP and what ends up in the organism’s biomass—can be passed on when the organism is eaten, but only a portion of it is. The rest is lost as heat from metabolism, movement, digestion, and maintaining body temperature. Because this heat loss happens at every step, energy transfer between trophic levels is inefficient, typically only about a tenth of the energy from one level becomes usable energy for the next. That’s why higher levels receive less energy, and ecosystems tend to have fewer food-web levels and a shrinking amount of energy as you move up.

During cellular respiration, energy stored in organic molecules is released to power life processes, but most of that energy leaves as heat. The energy that remains in chemical bonds—what’s captured as ATP and what ends up in the organism’s biomass—can be passed on when the organism is eaten, but only a portion of it is. The rest is lost as heat from metabolism, movement, digestion, and maintaining body temperature. Because this heat loss happens at every step, energy transfer between trophic levels is inefficient, typically only about a tenth of the energy from one level becomes usable energy for the next. That’s why higher levels receive less energy, and ecosystems tend to have fewer food-web levels and a shrinking amount of energy as you move up.