Question

In an ecosystem, the rate of production of organic matter during photosynthesis is termed as
(a) Secondary productivity
(b) Net productivity
(c) Net primary productivity
(d) Gross primary productivity

Answer 1

Hint: Plants are the main producers on Earth. The energy that plants trap to photosynthesize is the energy that sustains whole life on Earth. The energy trapped by plants is 2-10% of photosynthetically active radiation (PAR) given by the Sun. So, plants that are the primary producers produce organic matter out of which a part is consumed by primary consumers, and others are used up in the respiratory activities of the plants.

Complete answer:
In an ecosystem, the rate of production of organic matter during photosynthesis is termed as Gross primary productivity. Gross means total and thus gross primary productivity is the total organic matter produced by plants through photosynthesis. Plants have their respiratory needs so we use the term net primary productivity to define the organic matter that is consumed by primary consumers.

Additional Information: - The ecosystem has four important functions- productivity, decomposition, energy flow, and nutrient cycling. Productivity is the rate at which organic matter is produced when plants capture sunlight and use it to make food. Decomposition is the physical and chemical breakdown of organic remains or detritus with the help of decomposers or detritivores.
- Half of the total incident radiation from the Sun is photosynthetically active radiation or PAR and only 2-10 % of PAR is used by plants to photosynthesize. Nutrient cycling is the cycling of nutrients in an ecosystem that is used repeatedly by different components of the ecosystem.
So, the correct answer is `Gross primary productivity`.

Note: Gross primary productivity accounts for the total amount of organic matter produced by the plants. Net primary productivity accounts for the amount of organic matter left for use of consumers. Respiratory activities of the plants consume some energy and thus the left energy is consumed by primary consumers. Whereas, secondary productivity is the amount of organic matter produced by consumers.