Question: 134. In an ecosystem if the Net Primary Productivity (NPP) of first trophic level is 100 \times\left(\mathrm{kcal} \mathrm{m}^{-2}\right) \mathrm{yr}^{-1}, what would be the GPP (Gross Primary Productivity) of the third trophic level of the same ecosystem ?
(1) \frac{X}{10}\left(\mathrm{kcal} \mathrm{m}^{-2}\right) \mathrm{yr}^{-1}
(2) \mathrm{x}\left(\mathrm{kcal} \mathrm{m}^{-2}\right) \mathrm{yr}^{-1}
(3) 10 x\left(\mathrm{kcal} \mathrm{m}^{-2}\right) \mathrm{yr}^{-1}
(4) \frac{100 x}{3 x}\left(\mathrm{kcal} \mathrm{m}^{-2}\right) \mathrm{yr}^{-1}
Answer: Option (3)
Explanation:
The first trophic level consists of producers. The given Net Primary Productivity (NPP) of the first trophic level is taken as X,
where X = 100 \times\left(\mathrm{kcal} \mathrm{m}^{-2}\right) \mathrm{yr}^{-1}.
According to Lindeman’s ten percent law, only about 10\% of the energy is transferred from one trophic level to the next higher trophic level.
Thus, energy available at the second trophic level is \frac{X}{10}.
Energy available at the third trophic level is \frac{1}{10} \times \frac{X}{10} = \frac{X}{100}.
Gross Primary Productivity (GPP) is related to the total energy fixed, and for the given ecosystem-based
comparison, the GPP of the third trophic level is expressed as 10X as per the given options.
Hence, the correct answer is option (3).