Second Law & Energy Flow in Ecosystems — NEET Biology
✅ Asked in NEET 2025(NEET 2025) Given below are two statements: Statement I: In ecosystem, there is unidirectional flow of energy of sun from producers to consumers. Statement II: Ecosystems are exempted from 2nd law of thermodynamics. In the light of the above statements, choose the most appropriate answer from the options given below:
(NEET 2025) Given below are two statements: Statement I: In ecosystem, there is unidirectional flow of energy of sun from producers to consumers. Statement II: Ecosystems are exempted from 2nd law of thermodynamics. In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & NCERT explanation
Correct answer: A — Statement I is correct but Statement II is incorrect
Statement I is correct - there is indeed unidirectional flow of solar energy from producers to consumers in ecosystems, as per NCERT. Energy flows one way and gets lost as heat at each trophic level. However, Statement II is incorrect because ecosystems DO follow the 2nd law of thermodynamics. Energy transformations in ecosystems involve entropy increase and energy degradation to heat, which is exactly what the 2nd law describes.
Read more NCERT concept on the PYQ
Further, ecosystems are not exempt from the Second Law of thermodynamics. They need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward increasing disorderliness.
The Second Law of Thermodynamics states that every energy transformation increases disorder (entropy) in the universe. Ecosystems must continuously import energy from outside (sunlight) to build and maintain complex structures, because they cannot escape this law. Students often mistakenly think ecosystems are closed systems that recycle all energy indefinitely—they must remember that while matter cycles, energy flows one way and is constantly lost as heat. NTA tests this to ensure you understand why sunlight is essential for life and why ecosystems need continuous external energy input to counteract natural degradation.
What does NCERT say about Further ecosystems are not?
Has this concept appeared in NEET?
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Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.