Question: 150. Which of the following is the unit of productivity of an Ecosystem?
(1) \mathrm{gm}^{-2}
(2) \mathrm{KCal}\,\mathrm{m}^{-2}
(3) \mathrm{KCal}\,\mathrm{m}^{-3}
(4) \left(\mathrm{KCal}\,\mathrm{m}^{-2}\right)\mathrm{yr}^{-1}
Answer: Option (4)
Explanation:
Productivity of an ecosystem refers to the rate at which biomass or energy is produced per unit area over a given time period. Therefore, its unit must include:
– Energy: \mathrm{KCal}
– Area: \mathrm{m}^{-2}
– Time: \mathrm{yr}^{-1}
This matches the unit \left(\mathrm{KCal}\,\mathrm{m}^{-2}\right)\mathrm{yr}^{-1}, which correctly expresses energy fixed per unit area per year. Hence, option (4) is the correct unit of productivity.