Approximately 10 percent of energy is transferred to the next trophic level because

• A. Most energy is used for metabolism and lost as heat, leaving only a fraction stored as biomass
• B. All energy is stored as biomass for the next level
• C. Energy is not transferred between levels
• D. Energy is destroyed as heat completely

Answer: (A)

The main idea here is that energy transfer between trophic levels is inefficient because organisms use much of the energy they obtain for metabolism and life processes, releasing it as heat. Only a small portion is captured in new biomass that can be passed to the next level. In daily activities, growth, reproduction, and respiration consume energy, and a lot is lost as heat. Some energy is also lost in waste products and gut processing, so not all of what’s ingested ends up as biomass to be transferred onward. This combination of metabolic costs and energy losses means only about 10% of the energy at one level becomes available to the next. This is also why energy pyramids slope downward as you move up the trophic levels. The other statements aren’t correct because energy isn’t stored entirely as biomass, energy is transferred (though not completely), and energy isn’t destroyed—it's transformed, mainly into heat and waste, while some remains in the biomass that can be passed on.