The total rate of photosynthesis,including the organic matter used up in respiration during a definite period,is known as:

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:

Which of the following ecosystems has the highest productivity?

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

The annual net primary productivity of the biosphere is approximately

Secondary productivity is the rate of formation of new organic matter by: