the importance of water to life

You might not realize the significance of water to enable life to exist on Earth. The following is a summary of the importance of water to life. 

1.Water remains a liquid over a very wide temperature range, namely, a range of 100C°  between freezing and vaporization.   This spans the temperatures of most parts of the Earth where life can occur. 

2.Water has a very high specific heat, which means that it can absorb or lose much heat before its temperature changes.  This is important in maintaining body heat in mammals, such as ourselves.

3.Water has a high latent heat of vaporization.  For this reason, water evaporates slowly from ponds and lakes, where many life forms are dependent on it. 

4.Water is less dense in its solid state than in its liquid state, so that ice floats instead  of sinking.  This property permits life to develop in polar regions and subpolar regions where ice floats and allows life to continue living below the surface.  If ice were heavier than water, it would sink, and more ice would form on top of it.  As a result, all life in the waters would be trapped in the ice in the many areas of the world where it gets cold enough to freeze water.

5.Water is a remarkable solvent not only for the reasons mentioned above but also for gases such as oxygen and carbon dioxide.  The oxygen must be soluble in the water phase of the living cell in order for it to be used for oxidation of food.  At the same time, another gas, carbon dioxide, must also be soluble to escape to the outside of the cell, from where it travels to the lungs to get expired.

6.Water exhibits surface tension.  The molecules of water on the surface of a calm and quiet pond tend to be drawn into the liquid, so that the liquid surface is taut, like a sheet of rubber drawn over the open mouth of a jar.  This tautness is called surface tension.  It can support small objects like a sewing needle.  This "skin" on the water can also cause a handicap to mayflies and caddisflies that try to emerge from their juvenile images.  It also can trap flying insects that accidentally fall into the water and are unable to fly out. 

7.Water exhibits viscosity.  One can observe the effects of viscosity alongside a stream or river with uniform banks.  The water along the banks is nearly still, while the current in the center may be swift.  This resistance between the layers is called viscosity.   This property allows smaller fish to live near the shore, while larger fish are able to swim efficiently in strong currents.  Viscosity is also responsible for the formation of eddies, creating turbulence that leads to good mixing of air in the water and more uniform  distribution of microscopic organisms.