AIPMT Biology Aspirants, read out the next topic AIPMT Biology Study material/ Notes of Productivity of Ecosystem, useful for AIPMT Biology.

Sun is the only source of energy for all ecosystems on Earth. Out of which, less than 50% of the total incident solar radiation is useful for photosynthesis, which is called as Photosynthetically Active Radiation (PAR). Plants capture only 2-10 per cent of the PAR for photosynthesis.

• Biomass: Mass of living organisms. Biomass of species is expressed in terms of fresh or dry weight.
• Standing Crop: Mass of living material at each trophic level at a particular time. The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area.
• Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis, i.e., light energy converted to chemical energy.It is expressed in terms of weight (g ^–2) or energy (kcal m^–2).
• Productivity: Rate of biomass production. It is expressed in terms of g^–2 yr ^–1 or (kcal m^–2) yr^–1.  Productivity can be divided into Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).

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

A considerable amount of GPP is utilised by plants in respiration. Gross primary productivity minus respiration losses (R) is the net primary productivity (NPP).

                                                                              GPP – R = NPP

• Net primary productivity is the available biomass for the consumption to heterotrophs (herbivores and decomposers).
• Secondary productivity is defined as the rate of formation of new organic matter by consumers.
• Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants.
• Temperature and moisture are the main factors controlling primary production in terrestrial ecosystems.
• Tropical rain forests are among the most productive terrestrial ecosystems and contribute a large portion of the planet’s NPP.