Ecosystem
If the producers in a grassland fix 10,000 kJ of energy, approximately how much of this energy is expected to be available at the level of secondary consumers following the ten percent law?
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Solution
100 kJ
Lindeman's ten percent law states that only about ten percent of the energy stored at one trophic level is transferred and stored at the next higher trophic level, the rest being lost mainly as heat during respiration and metabolism. Starting from producers with 10,000 kJ, the primary consumers (herbivores) receive about 10 percent, that is 1,000 kJ. The secondary consumers feed on primary consumers and again receive about 10 percent of 1,000 kJ, which equals 100 kJ. Therefore 100 kJ is available at the secondary consumer level. The value 1,000 kJ is wrong because it represents the primary consumer level, only one transfer down. The value 10 kJ corresponds to tertiary consumers, one level too far. The value 5,000 kJ wrongly assumes 50 percent efficiency, which contradicts the ten percent rule. As described in NCERT Class 12, Chapter 14 (Ecosystem), energy flow is unidirectional and diminishes sharply at each step. Plausibility check: two successive ten percent transfers give 0.1 multiplied by 0.1 equals 0.01 of the original 10,000 kJ, confirming 100 kJ.
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About This Question
- Subject
- biology
- Chapter
- ecology and environment
- Topic
- ecosystem
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
100 kJ
Lindeman's ten percent law states that only about ten percent of the energy stored at one trophic level is transferred and stored at the next higher trophic level, the rest being lost mainly as heat during respiration and metabolism. Starting from producers with 10,000 kJ, the primary consumers (herbivores) receive about 10 percent, that is 1,000 kJ. The secondary consumers feed on primary consumers and again receive about 10 percent of 1,000 kJ, which equals 100 kJ. Therefore 100 kJ is available at the secondary consumer level. The value 1,000 kJ is wrong because it represents the primary consumer level, only one transfer down. The value 10 kJ corresponds to tertiary consumers, one level too far. The value 5,000 kJ wrongly assumes 50 percent efficiency, which contradicts the ten percent rule. As described in NCERT Class 12, Chapter 14 (Ecosystem), energy flow is unidirectional and diminishes sharply at each step. Plausibility check: two successive ten percent transfers give 0.1 multiplied by 0.1 equals 0.01 of the original 10,000 kJ, confirming 100 kJ.
This easy difficulty biology question is from the chapter ecology and environment, covering the topic of ecosystem. It appeared in the 2025 exam.
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