Question

explain the difference between gross primary productivity and net primary productivity. Which is larger, and why? Why is total primary production always greater than total secondary production?

Answer 1

Gross primary productivity is the rate of production of organic matter during photosynthesis in primary producers.

Whereas, net primary productivity is the Gross primary productivity minus the respiratory loss. That means, plant utilizes some amount of Gross primary productivity for their own use (for respiration to obtain -ATP).

So NPP =GPP ? R

Where NPP is the Net primary productivity

GPP is the Gross primary productivity and

R is the respiration loss.

Gross primary productivity is larger than net primary productivity. GPP is larger because it is the total amount of biomass accumulated during photosynthesis but Net primary productivity is obtained after the loss of some amount of GPP. So GPP is larger than NPP.

Total primary production is always larger than total secondary production. Because, primary productivity is accumulated during photosynthesis in all producers but secondary productivity is the rate of accumulation of biomass in consumers.

In any ecosystem number of producers are more than consumers so primary productivity is larger than secondary productivity.