Describe the usefulness of water in the biosphere and biological systems.

$A$ major part of all living organisms is made up of water. The human body contains about $65 \%$ water,and some plants contain as much as $95 \%$ water.
It is a crucial compound for the survival of all life forms.
It acts as a solvent of great importance.
The high heat of vaporization and high heat capacity of water are responsible for the moderation of the climate and the regulation of body temperature in living beings.
It serves as an excellent solvent for the transportation of ions and molecules required for plant and animal metabolism.
The distribution of water over the earth's surface is not uniform. The estimated world water supply is given in the following table:

Source	$\%$ of Total
Oceans	$97.33$
Saline lakes and inland seas	$0.008$
Polar ice and glaciers	$2.04$
Ground water	$0.61$
Lakes	$0.009$
Soil moisture	$0.005$
Atmospheric water vapour	$0.001$
Rivers	$0.0001$