$A$ biological community and its associated physical components interact to form a system. What is this system called?

The decomposers in an ecosystem

Why is improper disposal of waste a curse to the environment?

In a certain study conducted on the occurrence of $DDT$ along food chains in an ecosystem,the concentration of $DDT$ in grass was found to be $0.5\, ppm$ (parts per million),in sheep it was $2\, ppm$,and in man it was $10\, ppm$. Why was the concentration of $DDT$ maximum in the case of man?

What is meant by biological magnification?

List two causes of depletion of the ozone layer. Mention any two harmful effects of the depletion of this layer.