"Energy flow in food chains is always unidirectional". Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

Explanation

(i) In a food chain the energy moves progressively through the various trophic levels and is no longer available to the organisms of the previous trophic level/ energy captured by the autotrophs does not revert back to the solar input. Hence, the flow of energy is unidirectional.
(ii) Pesticides used for crop protection when washed away/down into the soil/water bodies absorbed by plants/ producers.
(iii) On consumption they enter our food chain and being non-biodegradable, these chemicals get accumulated progressively and enter our body.