Differentiate between gross and net primary production.

• A. GPP is total energy captured by photosynthesis; NPP is GPP minus the energy used by producers for respiration.
• B. GPP is energy lost as heat; NPP is energy stored in glucose.
• C. GPP is the energy used by consumers; NPP is energy stored in glucose.
• D. GPP is net production; NPP is gross production.

Answer: (C)

The main idea here is how plants convert light into stored energy and what remains after they fuel their own metabolism. Gross primary production is the total amount of energy captured by photosynthesis and turned into chemical energy in plant tissue. But plants don’t keep all of that energy for themselves; a portion is used to power their own respiration and maintenance. Net primary production is what’s left after subtracting those respiratory losses. That remaining energy is stored in plant biomass and can be passed on to herbivores and higher consumers.

So the correct idea is that GPP represents the total energy captured by photosynthesis, and NPP represents the energy that stays in the plants as biomass after respiration. The other descriptions either swap who uses the energy or describe a different form of energy storage (like glucose) rather than the usable biomass produced.