Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): To compare the productivity of different ecosystems, it is expressed in terms of g m ⁻² yr ⁻¹ or ( kcal m ⁻²) yr ⁻¹ . Reason (R): Productivity is the rate of biomass production, whereas standing crop is the mass of living material present at a particular time. In the light of the above statements,

Step-by-step solution

Assertion (A) is true because productivity is expressed in units that include both area and time, such as g m ⁻² yr ⁻¹ , to allow for comparison between different ecosystems. Reason (R) is also true and correctly explains the Assertion. Productivity is defined as the rate of biomass production, which inherently requires a time dimension (per year). In contrast, standing crop is a static measurement of biomass at a specific time and is expressed without a time dimension (e.g., g m ⁻² ). Therefore, the time component