Q.102 A typical food chain involves producers, herbivores, primary carnivores and
secondary carnivores. Based on Lindeman’s law of trophic efficiency, if producers
have 40 kJ of energy, the energy that will be stored in secondary carnivores
is _____ kJ. (round off to two decimal places)
roducers capture 40 kJ of energy in a typical food chain. According to Lindeman’s 10% law of trophic efficiency, only 10% of energy transfers to each successive trophic level, so secondary carnivores receive 0.04 kJ.
Trophic Levels
Producers form the first trophic level with 40 kJ. Herbivores (primary consumers) receive 10% of that, or 4 kJ. Primary carnivores (secondary consumers) get 10% of herbivores’ energy (0.4 kJ), and secondary carnivores (tertiary consumers) get 10% of primary carnivores’ energy (0.04 kJ).
Calculation
Energy at secondary carnivores = 40 × 0.1³ = 40 × 0.001 = 0.04 kJ (rounded to two decimal places). This follows the unidirectional energy flow where 90% is lost as heat at each step per the second law of thermodynamics.
Introduction
Lindeman’s law of trophic efficiency explains the 10% energy transfer rule in food chains, crucial for understanding energy flow from producers to herbivores, primary carnivores, and secondary carnivores. In ecosystems, if producers capture 40 kJ of energy, students preparing for CSIR NET Life Sciences often calculate how much reaches secondary carnivores using this principle. This guide breaks down the calculation, trophic levels, and exam applications for optimal SEO on “Lindeman’s law trophic efficiency food chain.”
Food Chain Structure
A typical food chain follows: producers (plants) → herbivores (primary consumers) → primary carnivores (secondary consumers) → secondary carnivores (tertiary consumers). Energy decreases unidirectionally, with no backflow.
-
Producers fix solar energy into biomass.
-
Herbivores consume plants.
-
Primary carnivores eat herbivores.
-
Secondary carnivores prey on primary carnivores.
Lindeman’s 10% Law Explained
Proposed by Raymond Lindeman in 1942, the law states ~10% of energy from one trophic level transfers to the next as chemical energy in biomass; 90% loses as heat via respiration. This trophic efficiency limits food chain length to 4-5 levels.
Step-by-Step Calculation
Start with producers: 40 kJ.
| Trophic Level | Energy (kJ) | Transfer Calculation |
|---|---|---|
| Producers | 40.00 | Given |
| Herbivores | 4.00 | 40 × 0.1 |
| Primary Carnivores | 0.40 | 4 × 0.1 |
| Secondary Carnivores | 0.04 | 0.40 × 0.1 (round to 2 decimals) |
Answer: 0.04 kJ. Verify with formula: Energyₙ = Energy₁ × (0.1)^(n-1), where n=4 for secondary carnivores.
CSIR NET Exam Tips
For competitive exams like CSIR NET, recognize “Lindeman’s law of trophic efficiency” as the 10% rule. Common traps: confusing gross vs. net productivity or assuming 100% transfer. Practice with variations like 1000 kJ producers (secondary carnivores: 1 kJ).
