Key Ecosystem Distinctions — NEET Biology
📚 Practice ConceptDistinguish between (a) Grazing food chain and detritus food chain (b) Production and decomposition (c) Upright and inverted pyramid (d) Food chain and Food web (e) Litter and detritus (f) Primary and secondary productivity
Which of the above statements about energy flow and ecological pyramids are correct? S1: The flow of energy in an ecosystem is unidirectional, with a significant amount of energy being lost as heat at each successive trophic level according to the second law of thermodynamics. S2: Primary productivity is defined as the rate of formation of new organic matter by consumers, and it is expressed in terms of gm⁻² or kcal m⁻². S3: A given species, like a human being, can occupy multiple trophic levels simultaneously depending on its feeding habits. S4: In an aquatic ecosystem, the grazing food chain (GFC) is often the major conduit for energy flow, while in terrestrial ecosystems, the detritus food chain (DFC) typically accounts for a larger fraction of energy flow. S5: Ecological pyramids of number and biomass can sometimes be inverted, but the pyramid of energy is always upright because of the 10% law. S6: Plants typically capture 50% of photosynthetically active radiation (PAR) to sustain the entire living world.
View solution & NCERT explanation
Correct answer: B — S1, S3, S4, and S5 only
The core concept tested is various aspects of energy flow, trophic levels, productivity, and ecological pyramids. S1: This statement is correct. Energy flow is unidirectional, and a substantial amount is lost as heat at each trophic level, consistent with the second law of thermodynamics. S2: This statement is incorrect. Primary productivity refers to the biomass production by *plants (producers)*, not consumers. Secondary productivity is the rate of new organic matter formation by consumers. S3: This statement is correct. Organisms like human beings can function at different trophic levels (e.g., primary consumer when eating plants, secondary consumer when eating herbivores). S4: This statement is correct. The grazing food chain is dominant in aquatic ecosystems, whereas the detritus food chain typically carries more energy in terrestrial ecosystems. S5: This statement is correct. Pyramids of number and biomass can be inverted (e.g., biomass in the sea), but the energy pyramid is always upright due to energy loss at each step. S6: This statement is incorrect. Plants capture only 2-10% of the photosynthetically active radiation (PAR), not 50%. Therefore, statements S1, S3, S4, and S5 are correct. This question integrates multiple concepts related to energy dynamics within an ecosystem.
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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.