Jan 312013
 

In terms of biology, productivity can be defined as the rate of production of amount of organic matter (food) which is accumulated in the living components of the ecosystem in unit area and time. We can classify productivity in two types. They are:

1. Primary Productivity
2. Secondary Productivity


1. Primary Productivity: Primary productivity is associated with the producers which are autotrophic. The autotrophic producers include both chemoautotrophs and photoautotrophs. Primary productivity is defined as the rate at which radiant energy of the sun is stored or used by producers to form organic matter, i.e. food. Primary productivity can also be classified into two different types which are described below:

    • Gross Primary Productivity (G.P.P): Gross Primary Productivity is the total organic matter synthesized by producers during photosynthesis. It can also be defined as the total rate of photosynthesis including the organic matter used up in the process of respiration during the period of measurement. This is also called total photosynthesis or total assimilation.
    • Net Primary Productivity (N.P.P): Net Primary Productivity can be defined as the rate of storage of organic matter by producers, excluding the organic matter which is used up in respiration process during the period of measurement. This is also called apparent photosynthesis or net assimilation. For calculating Net Primary Productivity, we can use the following formula:

Net Primary Productivity = Gross Primary Productivity – Rate of respiration

2. Secondary Productivity: Secondary productivity is the productivity which is associated with consumers or heterotrophs. Consumers feed on other organisms for their survival. They use the organic matter which is present in food for the resynthesis of new organic matter. The resynthesis of organic matter by consumers is called secondary productivity. Secondary productivity can also be defined as the rate of energy storage at consumers’ level for the resynthesis of new organic matter. It can be calculated by using the following formula:

Secondary Productivity = Net Primary Productivity – Heterotrophic consumption