Given below are two statements:
Statement I : The primary source of energy in an ecosystem is solar

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Question

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 (NPP).
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Statement I is incorrect but statement II is correct
(2) Both statement I and statement II are correct
(3) Both statement I and statement II are incorrect
(4) Statement I is correct but statement II is incorrect

Accepted Answer

Correct Answer: D — Statement I is correct but statement II is incorrectStep-by-step Solution:Statement I — CORRECT: Solar (sun) energy is the primary (ultimate) source of energy for the overwhelming majority of ecosystems on Earth. Photosynthetic organisms (producers/autotrophs) capture solar radiation and convert it into chemical energy stored in organic compounds. This energy then flows through the food chain to all heterotrophs. The only exceptions are chemosynthetic ecosystems (e.g., deep-sea hydrothermal vents) where energy comes from chemical oxidation reactions.Statement II — INCORRECT: The rate of production of organic matter during photosynthesis is called Gross Primary Productivity (GPP), not Net Primary Productivity. GPP is the total rate of photosynthesis, including the organic matter used in respiration by the producers themselves during the measurement period. Net Primary Productivity (NPP) is defined as: NPP = GPP − Respiration (R). NPP represents the rate of accumulation of organic matter in producer biomass that is actually available to consumers. It is NPP that is harvested by herbivores and enters the food chain.Extended Explanation:Key productivity concepts: GPP (Gross Primary Productivity) — total photosynthetic rate; all organic matter produced; NPP (Net Primary Productivity) — GPP minus plant/producer respiration; organic matter stored in plant tissues; available to consumers; Secondary Productivity — rate of energy storage at consumer levels (herbivore, carnivore etc.); Net Ecosystem Productivity (NEP) — GPP minus total ecosystem respiration (producers + consumers + decomposers). Values: Tropical rainforests have highest NPP (~2000 g dry weight m⁻² yr⁻¹); Open oceans have low productivity but cover vast area so contribute significantly to global productivity. Units: g (dry weight) m⁻² yr⁻¹ or KCal m⁻² yr⁻¹.Key Concepts: Ecosystem energy source, solar energy, primary productivity, GPP vs NPP, productivity definitions, respiration correction.

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