CBSE Class 10 Science 2020 · Paper 31/3/1 · Question 18(a)

(a) Cereal plant $\to$ Human being. Feeding directly on the producer, human beings stand at the end of the shortest chain; since only about $10\%$ of the energy passes from one trophic level to the next, the most energy reaches them this way. (b) Pesticides in the soil are absorbed by the cereal plant and enter the food chain. Being non-biodegradable, they accumulate progressively at each trophic level (biological magnification), so human beings and other top consumers receive the highest concentration, which harms their health. (c) Food web: Cereal plant $\to$ Rat $\to$ Snake $\to$ Hawk; Rat $\to$ Hawk; Cereal plant $\to$ Goat $\to$ Human being; Cereal plant $\to$ Human being (as drawn in the figure).