Which of the following pairs is correctly matched?

The correct answer is Option (4) → Net primary productivity – Available biomass for the consumption to heterotrophs

Productivity terms differ in who makes the organic matter and in what is measured. Gross primary productivity (GPP) is the rate of production of organic matter by plants during photosynthesis. Net primary productivity (NPP) is what is left after respiration and is the biomass available to heterotrophs. Secondary productivity is the rate of formation of new organic matter by consumers.

Option (1) Gross primary productivity – Rate of formation of new organic matter by consumers — Incorrect. This describes secondary productivity. GPP is the rate of production of organic matter during photosynthesis.

Option (2) Secondary productivity – Rate of production of organic matter during photosynthesis — Incorrect. This describes gross primary productivity. Secondary productivity is the formation of new organic matter by consumers.

Option (3) Standing crop – Rate of biomass production — Incorrect. The rate of biomass production is called productivity. The standing crop is the mass of living material at a trophic level at a particular time.

Option (4) Net primary productivity – Available biomass for the consumption to heterotrophs — Correct. NPP (GPP minus respiration losses) is the biomass available for consumption by heterotrophs, that is, herbivores and decomposers.

NCERT Extract:
Productivity – “… The rate of biomass production is called 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). Secondary productivity is defined as the rate of formation of new organic matter by consumers.”
Energy Flow – “Each trophic level has a certain mass of living material at a particular time called as the standing crop.”