'Ozone-hole' means:

The two forms of oxygen found in the atmosphere are

$(i)$ An increase in temperature of the water bodies would lead to water pollution: Explain.
$(ii)$ Suggest any two methods to prevent water pollution.

State whether the following statement is True or False:
Nitrogen gas makes up $78 \%$ of our atmosphere and nitrogen is also a part of many molecules essential to life like proteins,nucleic acids ($DNA$ and $RNA$) and some vitamins.

State whether the following statement is True or False:
Nitrogen is also found in other biologically important compounds such as alkaloids and urea.

The process of nitrogen-fixation by bacteria does not take place in the presence of