Which term means the rate at which autotrophs convert energy to biomass?

• A. Net Primary Production
• B. Ecological Models
• C. Hydrologic Cycle
• D. Productivity

Answer: (D)

This question is about primary productivity—the rate at which autotrophs convert light energy into biomass. Productivity is the broad term ecologists use for how fast energy captured by photosynthesis ends up as new plant biomass per unit area per unit time. Net Primary Production is related but refers to the amount of biomass that remains after plants use some energy for their own respiration, i.e., the net gain. The other options describe a process or tool (the hydrologic cycle and ecological models) rather than the rate of biomass production by autotrophs. So productivity best captures the idea of how quickly energy is turned into biomass.