Class 12 Biology Ecosystem Productivity


The rate of biomass production is called productivity.

Productivity is of two types-

  • Primary productivity
  • Secondary productivity.

Primary productivity is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.

Primary productivity is expressed in terms of weight (g–2) or energy (kcal m–2 ).

Primary productivity can be divided into

  • gross primary productivity (GPP)
  • net primary productivity (NPP).

Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis.

Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP).

GPP – R = NPP      

Secondary productivity is defined as the rate of formation of new organic matter by consumers.

The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter.

Fig. productivity

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