Question

Which of the following represents the correct formula for Net Primary Productivity (NPP)?

• A. GPP – R
• B. GPP + R
• C. R – GPP
• D. GPP × R

Hint:

Remember: - GPP = Total energy fixed by photosynthesis - R = Energy used in respiration - NPP = GPP – R (Energy available for ecosystem growth and storage)

Answer 1

The Correct Option is A

Step 1: Understand the meaning of NPP
Net Primary Productivity (NPP) refers to the rate at which producers (such as plants) convert solar energy into chemical energy stored in organic compounds, minus the energy used by the plants for respiration. Step 2: Define related terms GPP (Gross Primary Productivity):
The total amount of energy or biomass produced by photosynthesis in autotrophs. R (Respiration):
The amount of energy used by plants for metabolic activities such as growth and maintenance. Step 3: Use the standard formula
The relationship between these terms is given by the formula: $$ \text{NPP} = \text{GPP} - R $$ This means that Net Primary Productivity is obtained by subtracting the energy used in respiration from the total energy captured during photosynthesis. Step 4: Analyze each option (A) GPP – R
This matches the standard formula for NPP. (B) GPP + R
This would give a value greater than GPP, which is not correct. (C) R – GPP
This could result in a negative value, which does not represent productivity. (D) GPP × R
This is not a valid expression for NPP. Step 5: Conclusion
The correct formula for Net Primary Productivity is: $$ (A) GPP – R $$