Energy flow is unidirectional as the plants convert the 1% of solar energy into chemical energy by the process of photosynthesis. This energy is transferred to the next trophic level.This energy cannot be passed back to the plant and then to environment.It is not possible. Hence food chain is unidirectional.
The pesticides are sprayed on the crops for protection from pests. These pesticides dissolve in water and the plant absorbs these chemicals dissolved in water through roots. This chemicals enter the food chain through producers. In turn these producers are consumed by the organisms present in the next trophic level.Accumulation of harmful chemicals increases as we go up the trophic level. The organisms constituting the top level of the food chain has the maximum concentration of chemicals. This process is called biomagnification.
