Which statement about energy transfer is true?

Which statement about energy transfer is true?

• A. Energy moves equally through all trophic levels.
• B. Energy is stored entirely in biomass at higher levels.
• C. Each transfer is 100% efficient.
• D. Only about 10% of energy is transferred to the next level because most energy is used for metabolism, movement, growth, reproduction, and heat loss.

Answer: (D)

When energy moves from one trophic level to the next, most of it is used to power life processes rather than being carried forward as usable biomass. Organisms must fuel cellular respiration, movement, digestion, growth, and reproduction, and a lot of energy is lost as heat during these processes. Because of this, only a fraction—about 10% on average—of the energy available at one level becomes new biomass at the next level. This is why energy pyramids slope upward and higher levels tend to have less energy and fewer individuals. The 10% rule is an average; the exact amount can vary, but energy transfer is never 100% efficient, and energy is not stored entirely in biomass at higher levels.

When energy moves from one trophic level to the next, most of it is used to power life processes rather than being carried forward as usable biomass. Organisms must fuel cellular respiration, movement, digestion, growth, and reproduction, and a lot of energy is lost as heat during these processes. Because of this, only a fraction—about 10% on average—of the energy available at one level becomes new biomass at the next level. This is why energy pyramids slope upward and higher levels tend to have less energy and fewer individuals. The 10% rule is an average; the exact amount can vary, but energy transfer is never 100% efficient, and energy is not stored entirely in biomass at higher levels.