Question

What do you understand by primary and secondary productivity?

Answer 1

Productivity in an ecosystem means the rate of production of biomass. It is the quantity of organic matter accumulated at any time. The primary producers in an ecosystem are the producers or the autotrophs. The secondary producers are the heterotrophs which feed on the autotrophs.

Complete answer:
To solve this question, we must know about the productivity and flow of energy in the ecosystem.
We know that in an ecosystem, plants are the primary producers or the autotrophs which can prepare its own food or make organic compounds. This is being consumed by the consumers. The energy produced by the autotrophs are transferred from one trophic level to another. Let us discuss the productivity of these organisms.

The production of the organic matter by the photoautotrophs is known as primary productivity. The autotrophs produce energy by the process of photosynthesis. The primary productivity is mainly of two types-
- Gross productivity- It is the amount of the sunlight trapped during photosynthesis.
- Net productivity- It is the rate at which energy is stored by the producers as biomass. This energy is transmitted to the consumers who feed on the producers.

The secondary productivity refers to the rate at which the consumers convert the chemical energy present in the food into their own biomass. The consumers are the herbivores, carnivores, decomposers etc. The secondary productivity also shows the mass of new tissue created by consuming the food.

Note: The other means of primary productivity is through lithoautotrophy. In this the primary production takes place without light as in case of ground-water ecosystem or hydrothermal vents or cave ecosystem. The lithoautotrophs use reduced chemical compounds like hydrogen, hydrogen sulphide or methane to fix carbon and produce biomass.