10% Energy Law & Trophic Levels — NEET Biology
✅ Asked in NEET 2024(NEET 2024) Consider the pyramid of energy of an ecosystem given below: If T4 = 1000 J, what is the value of T1?
(NEET 2024) Consider the pyramid of energy of an ecosystem given below: If T4 = 1000 J, what is the value of T1?
(NEET 2024) In an ecosystem, if the Net Primary Productivity (NPP) of the first trophic level is 100x (kcal/m²/year), what would be the Gross Primary Productivity (GPP) of the third trophic level of the same ecosystem?
Answer & NCERT explanation
Correct answer: D — 10,00,000 J
In ecological pyramids, energy transfer follows the 10% rule. Only 10% of energy is transferred from one trophic level to the next. If T4 = 1000 J, then T3 = 10,000 J, T2 = 100,000 J, and T1 = 1,000,000 J. This is based on NCERT principle that energy decreases by 90% at each level due to metabolic losses, respiration, and heat production.
Read more NCERT concept on the PYQ
The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law – only 10 per cent of the energy is transferred to each trophic level from the lower trophic level. In nature, it is possible to have so many levels – producer, herbivore, primary carnivore, secondary carnivore in the grazing food chain. Do you think there is any such limitation in a detritus food chain?
The 10% law limits trophic levels in grazing food chains because only 10% of energy transfers upward at each level, making it impossible to sustain many levels. Students often confuse this with detritus food chains, which can have more levels because decomposers recycle energy more efficiently from dead organic matter. The key distinction NTA tests: grazing chains are energy-limited while detritus chains are not similarly restricted. Remember—in grazing chains, energy progressively decreases (100→10→1→0.1%), but in detritus chains, decomposers work longer to extract energy, allowing additional levels to persist despite the 10% rule.
What does NCERT say about number trophic levels grazing?
Has this concept appeared in NEET?
Which chapter is this from?
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.