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The Biological Significance of Water.

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Introduction

The Biological Significance of Water Water, H2O is the basis of all life on earth. Without it, there would be no life at all. That fact alone makes this substance biologically important. Why it is that this substance is so important, will now be explained. The water molecule consists of two Hydrogen atoms and one Oxygen atom, and these bond together by covalent bonding. However, both the oxygen and the hydrogen atoms are left with a slight charge. Oxygen has a slight negative charge, and hydrogen has a slight positive charge. When balanced out over the molecule, there is no net charge. However, in liquid water, the hydrogen from one molecule is electrically attracted to the oxygen in another. This makes water a dipolar molecule, and an oxygen atom from one molecule and a hydrogen atom from another molecule form a weak hydrogen bond. ...read more.

Middle

Even lipids, which are immiscible with water, are useful, because they can be used as membranes, to separate aqueous solutions. Water is also the source of hydrogen and oxygen for many forms of life, most notably in autotrophic plants, where water along with carbon dioxide is synthesised into glucose. Life is also based on water due to its high specific heat capacity. For warm- blooded animals, this means that a stable internal environment is possible; to change the internal temperature, a lot a heat must be acquired or lost. In oceans and seas, the water temperature varies little; around Britain, the sea temperature varies between 7�C and 16�C annually, which is very stable, relative to the air, which can vary from -10�C to 30�C. This means that for cold- blooded aquatic life, their external environment is stable, and therefore there is less chance of death due to extremes of temperature. ...read more.

Conclusion

The density of most liquids decreases as temperature increases, but when the temperature of water rises from 0�C to 4�C, its density actually increases. This means that ponds and lakes do not freeze from the bottom up, because the coldest water is also the least dense, so it stays at the top. This means that a layer of ice forms at the top. This layer of ice actually acts as an insulator, so the remaining liquid water stays liquid for longer (i.e. in Britain, ponds and lakes never freeze through; the thickest ice found is about six inches). This property means that aquatic life in freshwater lakes can survive air temperatures of -10�C. The diagram below explains this, which is one of the many reasons why living organisms consist of at least 70% water. Sources The research sources used were Biological Science 1, by N.P.O. Green, G.W. Stout and D.J. Taylor, Advanced Biology by Mary and Geoff Jones. The websites http://vava.essoetment.com/watersolventhy_rgqx.htm and www.bbc.co.uk/asguru were used, as were sections from the New Scientist and Biological Sciences magazines HPorkess 08/05/07 ...read more.

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