Question

________ is the available biomass for consumption by heterotrophs in an ecosystem.

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

Answer 1

The correct option is B Net primary productivity

A self-sustained stable system formed by the interactions between the biotic (living) and abiotic (non-living) factors present in it, is known as an ecosystem.

Productivity of an ecosystem refers to the rate of biomass or organic matter production.

Primary productivity refers to the rate of production of organic matter (biomass), by the process of photosynthesis by the plants per unit area over a time period.

It is expressed either in terms of weight (g^-2yr^-1) or energy (Kcal m^-2)yr^-1

Primary productivity can be categorised as gross primary productivity (GPP) and net primary productivity (NPP).

Gross primary productivity refers to the rate of production of organic matter during photosynthesis.

Net primary productivity refers to the remainder of the gross production which is 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.

Secondary productivity is the rate at which the consumers/heterotrophs synthesise new organic matter.

The mass of living material in a particular trophic level at a particular time is called the standing crop. It is measured either in number or biomass (mass of living organisms) in a unit area.