Which of the following best describes the net primary productivity (NPP) of an ecosystem?

• A. The amount of energy captured by producers through photosynthesis minus the energy lost as heat through respiration.
• B. The total biomass of all organisms present in an ecosystem at a given time.
• C. The total amount of energy captured by all organisms in the ecosystem.
• D. The energy available to primary consumers after accounting for energy lost by producers through respiration.

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of Net Primary Productivity (NPP). NPP is a measure of the energy available to an ecosystem's primary consumers after accounting for the energy lost by producers through respiration. It represents the energy captured by producers (plants, algae, etc.) through photosynthesis minus the energy they use for their own metabolic processes.
2. Step 2: Break down the options provided in the question. Analyze each statement to determine if it aligns with the definition of NPP. For example, the first option mentions energy captured by producers minus energy lost as heat through respiration, which matches the definition of NPP.
3. Step 3: Evaluate the second option, which refers to the total biomass of all organisms present in an ecosystem at a given time. This describes a different concept known as 'standing crop biomass,' not NPP.
4. Step 4: Assess the third option, which mentions the total amount of energy captured by all organisms in the ecosystem. This describes 'gross primary productivity' (GPP), not NPP.
5. Step 5: Finally, analyze the fourth option, which states the energy available to primary consumers after accounting for energy lost by producers through respiration. This aligns with the definition of NPP, as it represents the energy flow available to the next trophic level after producers have used some energy for their own needs.