Biology · Ecosystems · NEET
Because energy transfer follows the 10 per cent law. Only about 10% of the energy at one trophic level is passed to the next level. The other 90% is lost as heat during respiration and in life activities. After 4 or 5 levels, so little energy is left that it cannot support another trophic level. So the chain must stop.
Most food chains have only 4 or 5 trophic levels. For example: producer, then herbivore (primary consumer), then primary carnivore, then secondary carnivore. NCERT states it is possible to have producer, herbivore, primary carnivore and secondary carnivore in the grazing food chain.
Energy is lost mainly as heat during respiration. Organisms use energy to move, grow, and stay alive, and this energy leaves as heat and cannot be reused. This follows the second law of thermodynamics. Only the small amount stored in body tissue (about 10%) can pass to the next level.
No. Ten per cent is an average figure used for NEET. The real transfer can be a little more or less. NCERT uses 10% as the standard rule to explain why energy drops sharply and why trophic levels are few.
Yes. The pyramid of energy is always upright because energy decreases at each higher level. This same energy loss is exactly why the number of trophic levels is limited. Both facts come from the 10 per cent law.
Energy flows only one way, from the Sun to producers to consumers. It is never sent back. Because it is not recycled and keeps leaking as heat, the supply at each higher level keeps shrinking until it cannot support one more level.
In an ecosystem if the Net Primary Productivity (NPP) of the first trophic level is 100x kcal m⁻² yr⁻¹, what would be the GPP (Gross Primary Productivity) of the third trophic level of the same ecosystem?
Which of the following statements are correct? (a) Energy flow from producers to consumers is unidirectional; (b) Energy pyramid can never be inverted; (c) Transfer of energy follows the 1% law.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Because only about 10% of energy passes to each next level. After 4 or 5 levels, the leftover energy is too small to support another trophic level, so the chain ends.
The 10 per cent law of energy transfer. At each step only 10% of energy moves up, and 90% is lost mostly as heat during respiration.
NCERT asks students to think about this. The strict restriction is described for the grazing food chain, where energy transfer follows the 10 per cent law from level to level.
It is lost as heat during respiration and in daily activities like movement and maintaining body functions. This heat cannot be reused, following the second law of thermodynamics.
Yes. Because energy keeps dropping at each level, top carnivores get very little energy. This is why big predators are few in number and why no further level can exist above them.
