Question

The biomass available in plants for consumption by herbivores and decomposers, is called :

• A. Gross primary productivity
• B. Net primary productivity
• C. Standing crop
• D. Secondary productivity

Hint:

NPP = GPP minus plant respiration, and it is the biomass available to herbivores and decomposers.

Answer 1

The Correct Option is B

Step 1: Recall the definitions:
Gross primary productivity (GPP) is the total rate of organic matter produced by photosynthesis.
Plants use part of GPP in their own respiration, R.

Step 2: Write the relation:
The part left after respiration is net primary productivity.
\[ \mathrm{NPP} = \mathrm{GPP} - R \]
This is the biomass available to consumers.

Step 3: Match to the question:
Herbivores and decomposers feed on plant biomass that is left after plant respiration.
That is the net primary productivity.

Step 4: Check other options:
GPP includes the portion plants burn in respiration, so it is not fully available.
Standing crop is the amount of living material present at a given time.
Secondary productivity is the rate of new organic matter formed by consumers.

Final Answer:
The biomass available to herbivores and decomposers is net primary productivity, option (B).