What term describes the total mass of living matter at each trophic level, which decreases as trophic level rises?

• A. Biomass
• B. Energy
• C. Sediment
• D. Joules

Answer: (A)

Biomass is the total mass of living matter at a trophic level. In most ecosystems, the amount of living material available decreases as you move up the food chain because energy transfer between levels is inefficient: only a fraction of the energy captured by organisms at one level becomes new biomass at the next, while the rest is lost as heat, used for metabolism, or excreted. This creates a biomass pyramid that typically narrows with each higher trophic level. Biomass is usually expressed as dry mass per area (for example, g/m^2). The other terms refer to energy or non-living material, so they don’t describe the mass of living matter.