NEETBotanyEcosystem
In a forest ecosystem, the Gross Primary Productivity (GPP) is 50,000 J m ⁻² yr ⁻¹ . If the respiration losses (R) at the producer level are 20% of the GPP, what amount of energy will be available to the primary carnivores?
Options
- A4,000 J m ⁻² yr ⁻¹
- B500 J m ⁻² yr ⁻¹
- C400 J m ⁻² yr ⁻¹
- D40 J m ⁻² yr ⁻¹
Correct answer
C. 400 J m ⁻² yr ⁻¹
Step-by-step solution
Gross Primary Productivity (GPP) = 50,000 J m ⁻² yr ⁻¹ . Respiration losses (R) = 20% of GPP = 0.20 50,000 = 10,000 J m ⁻² yr ⁻¹ . Net Primary Productivity (NPP) is the energy available to the first trophic level (producers). NPP = GPP - R = 50,000 - 10,000 = 40,000 J m ⁻² yr ⁻¹ . According to the 10% law of energy transfer: Energy available to primary consumers (herbivores, T₂ ) = 10% of NPP = 4,000 J m ⁻² yr ⁻¹ . Energy available to primary carnivores (secondary consumers, T₃ ) = 10% of 4,000 = 400 J m ⁻² yr ⁻¹ .