Which equation correctly calculates the percent energy transferred to the next trophic level?

• A. Biomass energy divided by energy ingested, times 100
• B. Energy ingested divided by biomass energy, times 100
• C. (Biomass energy plus energy ingested) times 100
• D. Energy lost divided by energy ingested times 100

Answer: (A)

Percent energy transferred between trophic levels shows how efficiently energy from food is converted into new biomass at the next level. It is calculated by taking the energy stored as biomass in the next level (the energy that remains as growth and reproduction) and dividing it by the energy the organisms ingested from the previous level, then multiplying by 100 to express it as a percent. This is the best form because it compares what was consumed (energy available) to what actually becomes new biomass (the transferred energy). The other options mix the terms incorrectly or refer to energy lost, which isn’t the measure of transfer efficiency.