Simulation · Biology · Class 12
Gross and net primary productivity
From the lesson Productivity in Ecosystem. Change the values and watch what happens.
Gross and net primary productivityBiology · Class 12
The idea behind it
NCERT §12.2
- Every ecosystem needs a steady supply of solar energy to keep working.
- Primary production is the organic matter (biomass) that plants make by photosynthesis on a unit of area over a stated period. It is expressed as weight (g m⁻²) or energy (kcal m⁻²).
- Productivity is the rate of biomass production, expressed as g m⁻² yr⁻¹ or kcal m⁻² yr⁻¹, so that different ecosystems can be compared.
- Gross primary productivity (GPP) is the rate at which organic matter is made in photosynthesis. Plants use a considerable part of it in respiration.
- Net primary productivity: GPP − R = NPP, where R is the respiration loss. NPP is the biomass available to heterotrophs (herbivores and decomposers).
- Secondary productivity is the rate at which consumers form new organic matter.
- Primary productivity depends on the plant species of an area, environmental factors, nutrient availability and the photosynthetic capacity of plants, so it differs between ecosystems.
- The annual NPP of the whole biosphere is about 170 billion tons (dry weight) of organic matter.
- Oceans cover about 70 per cent of the surface but produce only 55 billion tons of it; the rest is produced on land.