The Net Primary Productivity (NPP) is :

The correct answer is Option (1) → Gross Primary Productivity − Respiration losses

Gross primary productivity (GPP) is the rate at which plants make organic matter in photosynthesis. Plants use part of it in their own respiration (R). What is left, NPP = GPP − R, is the biomass available to herbivores and decomposers.

Option (1) Gross Primary Productivity − Respiration losses — Correct. Gross primary productivity is the rate of production of biomass in photosynthesis, and part of it is used up in respiration. So NPP = GPP − R; NPP is the biomass available to heterotrophs.

Option (2) Gross Primary Productivity + Respiration losses — Incorrect. Respiration uses up organic matter, so it must be taken away, not added; NPP is always less than GPP.

Option (3) Gross Primary Productivity × Respiration losses — Incorrect. Productivities are amounts of biomass; multiplying them has no meaning.

Option (4) Respiration losses − Gross Primary Productivity — Incorrect. This is the subtraction the wrong way round; it would give a negative value.

Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 2).

NCERT Extract:
Productivity – “… Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration. Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP). GPP – R = NPP Net primary productivity is the available biomass for the consumption to heterotrophs (herbiviores and decomposers).”