Question

Net primary productivity (NPP) in an ecosystem is
A. GPP – R = NPP
B. GPP + R = NPP
C. GPP – NPP = R
D. R – NPP = GPP

Answer 1

Hint: In the ecosystem, the energy of the sun helps the plants to produce their own food through the process of photosynthesis. During this process, the plants convert the raw materials which are the inorganic materials and convert them into organic compounds.

Complete answer:
Primary productivity is distinguished in two forms such as gross productivity and net productivity. Gross primary productivity (GPP) is the amount of energy produced by the plants at a given time. It is the amount of energy that is expressed as carbon biomass.
Some amount of the energy is utilized by the plants for the maintenance of themselves. The plants use a portion of the fixed energy that is used in cellular respiration and in the growth. The remaining fixed energy that remains after the expenditure of the energy used for maintenance of the cells is known as net primary productivity.
The respiration energy is used by the organism to perform several cellular and tissue level respiration. The net primary productivity production is calculated as the rate at which the plants produce net useful chemical energy that is available to the next level in an ecosystem.
Net primary productivity is calculated as the difference between the gross primary productivity and the respiration energy utilized. It is equal to differences between the rate at which the autotrophs produce energy and the rate at which some of the produced energy is utilized during respiration.

Hence, the correct answer is option (A).

Additional information:
The plants are known as the primary producers as they manufacture organic compounds by utilizing light as the source of energy. The sole source of light energy of the ecosystem is the sun. The plants convert the light energy into organic compounds and the plants are consumed by other animals or consumers. The rate of energy which is converted into organic substances by the photosynthetic process by the green plants is referred to as primary productivity. Primary productivity is determined by calculating by measuring the uptake of carbon dioxide or as the release of oxygen. The plants are the principal organism that are the producers of primary productivity. The production of primary productivity requires other micronutrients such as nitrogen and phosphorus. These materials are available as nutrients in the soil, lakes, ocean etc.

Note: The plants produce chemical energy from the energy of the sun. The amount of energy produced that the plants produce over a particular period of time is known as gross primary productivity. Some amount of the energy produced by the plants are utilized to maintain the cell growth and development in the form of cellular respiration. The remaining energy after the use of energy as respiration energy is known as net primary productivity. Net primary productivity(NPP) is calculated as the differences between gross primary productivity(GPP) and respiration(R).