Question

Assertion: Net primary productivity (NPP) is always more than gross primary productivity.
Reason: Net primary productivity (NPP) is the amount of organic matter that is lost by the producers during respiration.

• A. Both assertion and reason are true and the reason is the correct explanation for the assertion
• B. Both assertion and reason are true but the reason is not the correct explanation for the assertion
• C. Only assertion is true
• D. Both assertion and reason are false

Answer 1

The correct option is D Both assertion and reason are false

Productivity of an ecosystem refers to the rate at which biomass (total mass of all living organic matter) is produced per unit area.

Gross primary productivity (GPP) is the rate at which organic matter is produced by the producers via the process of photosynthesis, per unit area.

It is expressed in terms of weight (g/m²/year) or energy (kcal/m²/year).

A part of the organic matter is used up by the producers during respiration to produce energy for bodily functions.

Net primary productivity (NPP) refers to the remainder of the gross production left after its use by the producers in the process of respiration.

Thus, net primary productivity is the biomass that is available to the heterotrophs in an ecosystem for consumption and is always less than GPP.

NPP = GPP - Respiration losses (R)

Thus, both assertion and reason are false.