In the equation $GPP - R = NPP$ (where $GPP$ is Gross Primary Productivity and $NPP$ is Net Primary Productivity),$R$ represents:

Which of the following has the highest value in a grassland ecosystem?

State whether the following statements are True or False:
$I.$ The total organic matter synthesized by the producers in the process of photosynthesis per unit time and area is known as gross primary productivity.
$II.$ Net primary productivity is the weight of the organic matter stored by the producers in a unit area/volume per unit time.

The annual net primary productivity of the whole biosphere is approximately $...........$ (dry weight) of organic matter.

Identify the ecosystem with the lowest productivity.

Given below are two statements:
Statement $I$: The primary source of energy in an ecosystem is solar energy.
Statement $II$: The rate of production of organic matter during photosynthesis in an ecosystem is called net primary productivity $\text{(NPP)}$.
In the light of the above statements,choose the most appropriate answer from the options given below: