Q.43 Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Y-shaped or 2-channel energy flow model of E.P. Odum is more realistic than linear energy flow
model of Lindeman.
Reason R: Y-shaped model is realistic because it has both grazing and detritus food chains.
In the light of the above statements, choose the most appropriate answer from the options given below:
l. Both A and R are tme and R is the conect explanation of A
2. Both A and R are true but R is NOT the correct explanation of A
3. A is true but R is false
4. A is not false but R is true
Both Assertion A and Reason R are true, and R is the correct explanation of A. The correct answer is option 1.
Option Analysis
Option 1: Both A and R true, R explains A
This is correct. E.P. Odum’s Y-shaped model incorporates dual pathways—grazing (herbivores consuming live plants) and detritus (decomposers processing dead matter)—making it more realistic than Lindeman’s 1942 linear model, which assumes a single unidirectional flow from producers to top carnivores. The dual channels explain the realism by reflecting natural ecosystems where ~10-20% energy enters grazing chains and 80-90% via detritus.
Option 2: Both true, R not explanation
Incorrect. R directly justifies A’s claim, as the Y-shape’s dual channels capture energy partitioning absent in Lindeman’s single-channel oversimplification.
Option 3: A true, R false
Incorrect. R accurately describes the model’s structure: one arm for grazing, the other for detritus, converging at higher trophic levels.
Option 4: A false, R true (noted as “A is not false but R is true” likely a typo)
Incorrect. A is true—Odum’s 1983 model applies to aquatic/terrestrial systems, outperforming Lindeman’s idealized linear flow.
Y-shaped energy flow model Odum Lindeman highlights ecosystem energy dynamics in NEET exams. E.P. Odum’s dual-channel approach trumps Lindeman’s linear model by integrating grazing and detritus paths for realistic energy transfer.
Lindeman’s Linear Model
Lindeman’s 1942 single-channel depicts unidirectional flow: sun → producers → herbivores → carnivores. Realistic for short grazing chains but ignores detritus dominance (~90% organic matter).
Odum’s Y-Shaped Realism
Odum’s inverted Y starts with shared producers splitting into grazing (live biomass) and detritus (dead matter) arms, reconverging at decomposers/carnivores. Applicable to forests, lakes—captures ~50% efficiency loss per trophic level across paths.
Why R Explains A
Dual chains prevent energy “waste” oversight in linear models; detritus recycling sustains ecosystems, explaining Y-shape’s superiority.
