PRODUCTIVITY IN ECOLOGY
PRODUCTIVITY IN ECOLOGY
- In ecology, productivity or production refers to the rate of generation of biomass in an ecosystem.
- It is usually expressed in units of mass per unit area (or volume) per unit time, for instance, grams per square metre per day.
- Productivity of autotrophs such as plants is called primary productivity, while that of heterotrophs such as animals is called secondary productivity.
Primary Production
- Primary production is the synthesis of new organic material from inorganic molecules such as water and carbon dioxide.
- It is dominated by the process of photosynthesis which uses sunlight to synthesise organic molecules such as sugars.
- Organisms responsible for primary production include plants, algae and some bacteria (including cyanobacteria).
Gross Primary Production (GPP)
- It is the amount of organic matter synthesised by producers per unit area in unit time.
- In other words, it refers to the total production including the energy utilised for respiration by the producers. Mathematically,
- GPP = Rate of increase in body weight or rate of organic matter synthesised by producers + the rate of respiration (R) and other utilisation of mass by primary producers.
Net Primary Production (NPP)
- It is the amount of organic matter stored by producers per unit area in unit time. PRODUCTIVITY IN ECOLOGY
- In other words, it refers to the net productivity that is converted to organic matter excluding the energy utilised for respiration and other purposes by the producers.
Mathematically,
NPP = Rate of organic matter synthesised by photosynthesis by producers – the rate of energy utilised for respiration and other purposes.
Secondary Production
- Secondary production is the generation of biomass by heterotrophic (consumer) organisms in a system.
- This is driven by the transfer of organic materials between trophic levels, and represents the quantity of new tissue created through the use of assimilated food.
- Organisms responsible for secondary production include animals, protists, fungi and many bacteria. PRODUCTIVITY IN ECOLOGY
- Compounds that are considered organic must contain carbon bound to hydrogen, and possibly, other elements. By this definition, carbon dioxide is inorganic in nature.
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