The total annual net primary productivity of the whole biosphere is:

The rate at which energy is stored at the level of primary consumers is known as:

What is $NPP$?

Total energy fixed by an ecosystem is called

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:

In the equation $GPP - R = NPP$,what does $R$ represent?