Answer: Gross primary productivity (GPP) minus autotroph respiration (Ra) -- energy available to consumers.
- A The total combined photosynthetic output across an entire ecosystem without subtracting any respiratory losses
- B Gross primary productivity (GPP) minus autotroph respiration (Ra) -- energy available to consumers
- C Mainly the total biomass produced by animal consumers each year excluding any contribution from producers
- D Mainly the total organic matter generated by decomposer organisms excluding any net production from autotrophs
Correct answer: B. Gross primary productivity (GPP) minus autotroph respiration (Ra) -- energy available to consumers
Explanation: NPP = GPP - Ra (autotroph respiration). NPP represents the organic matter actually available to consumers. Globally, terrestrial NPP ~60 Pg C/yr; ocean ~50 Pg C/yr.
Energy pyramid showing a simple food chain (producer to herbivore to carnivore) with energy decreasing roughly tenfold at each trophic level.
Concept context
Ecosystems, food chains, energy flow, nutrient cycles, biodiversity, and conservation.