How many molecules of ozone can be decomposed by one atom of chlorine?

Which trophic level has the highest energy in an ecosystem?

Define ecosystem.

Pesticides like $DDT$ which are sprayed to kill pests on crops are found to be present in the soil,groundwater,water bodies etc. Explain how do they reach these places.

During heavy rain in a village,rainwater carried excessive fertilizers to a pond. How will it affect the fish population in the pond in the long run?

State two methods to get rid of non-biodegradable wastes.