State the direction of flow of energy in a food chain. Can food and energy from a trophic level move back to the previous level? Give reasons for your answer.

(N/A) $(i)$ The flow of energy in a food chain is unidirectional, moving from producers to primary consumers, then to secondary consumers, and finally to top carnivores.
$(ii)$ No, food and energy cannot move back to the previous trophic level. This is because energy is lost as heat at each trophic level during metabolic activities, as per the $10\%$ law of energy transfer. Once energy is transferred to a higher trophic level, it is no longer available to the previous level.