(a) Define trophic level. Draw the food chain with four trophic levels. (b) What will happen if we kill all the organisms in one trophic level?

(a) The various steps in a food chain at which the transfer of food and energy takes place are known as trophic levels.

A food chain with four trophic levels can be shown as follows.

Grass → Insect → Butterfly → Crow

(b) If we kill all the organisms in one trophic level, there will be no food for the organisms of the next trophic level, and this may cause the death of those animals. Also, the organisms of the previous trophic levels may increase in number as there will be no organism to consume them as food which leads to an imbalance in the ecosystem.