CBSE Class 10 Science 2022 · Paper 31/4/2 · Question 13

Diagram: Sun (solar input) → Producers (green plants, 1st trophic level) → Herbivores (2nd) → Carnivores (3rd) → Top carnivores (4th), with energy lost as heat at every level and only about one-tenth passed on at each step, for example 10,000 J → 1,000 J → 100 J → 10 J (see the diagram). Inferences (any two): (i) The flow of energy is unidirectional: energy captured by the producers does not return to the solar input, and energy passed to the herbivores does not come back to the producers. (ii) The energy available decreases at each successive trophic level: only about 10% of the energy of one level reaches the next, the rest being used in life processes and lost as heat. (iii) Because of this loss, very little usable energy remains after four trophic levels, so food chains generally have only three or four steps.