SSC CGL 2022 PYQ — Question 29

The correct answer is Option 4. i.e. Net primary productivity and gross primary productivity.

The rate of biomass production is called productivity. The portion of fixed energy, a trophic level passes on to the next trophic level is called production.

Productivity in ecosystems is of two kinds, i.e., primary and secondary. Green plants fix solar energy and accumulate it in organic forms as chemical energy. As this is the first and basic form of energy storage, the rate at which the energy accumulates in the green plants or producers is known as primary productivity.

Primary productivity has two aspects:

(i) Gross and

(ii) Net.

1. The amount of energy-bound organic matter created per unit area and time that is left after respiration is net primary productivity (NPP).

            Net productivity of energy = Gross productivity — Energy lost in respiration.

        2.  The rates at which the heterotrophic organisms resynthesise the energy-yielding substances                 are called secondary productivity. Here, the net primary productivity (NPP) results in the                       accumulation of plant biomass, which serves the food of herbivores and decomposers.