Limiting Factors & Ecosystem Cycles — NEET Biology
📚 Practice ConceptIn aquatic ecosystems, the limiting factor for the productivity is________. (d) Common detritivores in our ecosystem are________. (e) The major reservoir of carbon on earth is________.
Which of the following statements regarding energy flow in an ecosystem are correct? S1: Photosynthetically active radiation (PAR) constitutes less than 50% of the incident solar radiation, and plants capture approximately 2-10% of this PAR. S2: Net Primary Productivity (NPP) represents the rate of production of organic matter during photosynthesis and is entirely available for consumption by heterotrophs. S3: The number of trophic levels is generally restricted because only about 10% of the energy from a lower trophic level is transferred to the next higher trophic level. S4: Ecosystems do not conform to the Second Law of Thermodynamics, as they maintain highly ordered structures through constant energy input. S5: In a terrestrial ecosystem, the grazing food chain (GFC) is typically the major conduit for energy flow, unlike in aquatic ecosystems where the detritus food chain (DFC) dominates. S6: Energy flow in an ecosystem is unidirectional, beginning with producers and eventually dissipating as heat to the environment.
View solution & NCERT explanation
Correct answer: A — S1, S3 and S6 are correct.
The core concept here is the flow of energy through different trophic levels and its governing principles. S1: Correct. NCERT states that less than 50% of incident solar radiation is PAR, and plants capture only 2-10% of this PAR (Page 209, Para 1). S2: Incorrect. NPP (Net Primary Productivity) is GPP (Gross Primary Productivity) minus respiration losses (R). GPP is the rate of production of organic matter during photosynthesis. NPP is the available biomass for heterotrophs, not the rate of production of organic matter during photosynthesis itself (Page 207, Para 1). S3: Correct. The 10 per cent law states that only 10% of the energy is transferred from one trophic level to the next, which restricts the number of trophic levels (Page 211, Para 2). S4: Incorrect. Ecosystems are not exempt from the Second Law of Thermodynamics. They require a constant energy supply to counteract the universal tendency towards increasing disorderliness (Page 209, Para 2). S5: Incorrect. In an aquatic ecosystem, GFC is the major conduit for energy flow, whereas in a terrestrial ecosystem, a much larger fraction of energy flows through the DFC (Page 210, Para 2). S6: Correct. Energy flow in an ecosystem is unidirectional, moving from the sun to producers and then to consumers, with dissipation and loss as heat to the environment (Page 206, Para 3; Page 209, Para 3). Therefore, statements S1, S3, and S6 are correct. The final answer is A.
What does NCERT say about aquatic ecosystems limiting factor?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.