Productivity: It is the rate of production of biomass per unit area over a period of time by plants during photosynthesis. Gross Productivity: It is the rate of production of organic matter by green plants per unit time per unit area. Net Primary Productivity: Net primary productivity is the available biomass for the consumption of heterotrophs. Net primary Productivity: Gross Primary Productivity-Respiratory losses, `N_(PP) = G_(PP) – R.` Secondary Productivity: It is the rate of formation of new organic matter by consumers.