Question

Assertion (A) : Net Primary Productivity (NPP) is always less than Gross Primary Productivity (GPP).

Reason (R) : A portion of Gross Primary Productivity (GPP) is used by plants for respiration.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

NPP equals GPP minus plant respiration, so NPP is always smaller and the Reason explains the Assertion.

Answer 1

The Correct Option is A

Step 1: Recall the definitions:
Gross primary productivity (GPP) is the total organic matter made by producers in photosynthesis.
Plants use a part of it in respiration.
Net primary productivity (NPP) is what remains: \( \mathrm{NPP} = \mathrm{GPP} - R \), where R is the respiratory loss.

Step 2: Check the Assertion:
Plants always respire, so R is always above zero.
So NPP is always smaller than GPP. The Assertion is TRUE.

Step 3: Check the Reason:
It is true that a share of GPP is spent by plants in respiration. The Reason is TRUE.

Step 4: Link the two:
NPP is lower than GPP exactly because of this respiratory loss. So R explains A.

Step 5: Pick the code:
Option (B) fails because R is the correct explanation. Options (C) and (D) fail because both statements are true.

Final Answer:
Both statements are true and R explains A, so option (A) is correct.