Life is inseparable from water. This dependence of life on water can be attributed to the unique properties of water, water is directly intimately involved in all details of animal physiology but because it is so common, water is often regarded with indifference as an inert space, filter in living system. The special properties of water are so important to life stem directly from its molecular structure. Therefore it is important that we should begin by understanding its molecular structure. Not only that water is also a driving force of all living organisms, hence the saying “water is life, conserve it.”
MOLECULAR STRUCTURE OF WATER
The shape of water and of all organic molecules is necessary to the structure and functional roles they playin living organisms, for example, hormones having specific shapes that allow them to be recognized by the cells in the body. We can stay well only when the antibiotics combine with disease- causing agents like a key fits into a lock, similarly homeostasis is only maintained when enzymes have the proper shape to carry out their particular reactions in cells. The shape of a water molecule and its polarity makes hydrogen bonding possible. Water’s shape also enables it to support life as shown below
Water has several functions due to its unique properties that make it vital to living organisms. The following are some of the properties of water which can either be physical or chemical and its significance to living organisms. Water is said to be;
Water is said to be an excellent universal solvent for polar substances like salts which contains charged particles, as shown below;
From the diagram above of a salt molecule it can be seen that water is able to surround a salt molecule, which makes it to be dissolved by a water molecule, hence the reason for water being a universal solvent that is enabling it to dissolve nutrients in other living organisms, also water being a universal solvent means that more substances both organic and inorganic are dissolved in water than in any other solvent. For this reason water is rarely pure, being almost always in solution containing dissolved substances. (Lacksonetal 1995:14) Hence because of water being a universal solvent it plays an important role in living organisms, it is suitable for life in which diffusion and osmosis occur easily, that is it helps in the diffusion of gases to facilitate gaseous exchange in insects as well as in fish which usually uses oxygen that has dissolved in water.
Aquatic organisms such as fish, amoeba and so on benefit from water by making use of the dissolved oxygen in water for their respiration. Water also acts as a transport medium as in the blood, lymphatic and excretory systems, such as in the removal of water products in the body such as urine, as well as in the alimentary canal of a living organism and in the xylem to transport mineral salts in plants and in the phloem to transport manufactured food.
It is also an important solvent in which most of the bodily solute are dissolved, it also plays an important part in metabolism processes as well as helping organisms to transport nutrients and oxygen throughout the body.
The tendency of water to cause amphipathic molecules to form in cells is important in the formation of biological membranes in living cells and may have provided the basis for the first cell-like organisms of living system in the organic-rich shallow seas in which the beginning of life is believed to have undergone its first stages (Eckert and Randi 1978:20)
DENSITY AND FREEZING PROPERTIES OF WATER
When we consider this property of water having less density when in solid state (ice) than liquid water which has a maximum density at a temperature of 40c we see that ice tends to float on water. When water is cooled to form ice the hydrogen bonds become more rigid but also more open causing water to expand thus increasing in volume. This reason explains why a cans containing water bursts when placed in a freezer for a long period of time. It is generally observed that matter expands upon heating hence the behavior of water to expand when heated is sometimes referred to as “the abnormal behavior of water.”
The ability of ice to float on water prevents the whole body of water (ponds, rivers, lakes and oceans) from freezing solid because it acts as in insulator on the water surface, as a result this property of water protects aquatic organisms and enables them to survive through the winter.
HIGH HEAT CAPACITY
Heat capacity is the amount of energy required to change the temperature of a substance by 1oc. water is said to have a high heat capacity because water has the ability to retain a good amount of energy with only a little fluctuation in its own temperature. This means that for water to have a change in its temperature it requires a lot of energy. This property of water is important not only to aquatic life but for all living organisms because the temperature of water rises and falls slowly organisms are better able to maintain their normal internal temperature and are protected from rapid temperature changes.
COHESIVE AND ADHESIEVE
Cohesion refers to the ability of water molecules to cling to other water molecules due to hydrogen bonding. Because of cohesion, water exists as a liquid under ordinary conditions of temperature and pressure. Cohesion in water contributes to the transport of water in plants living because water molecules are strongly attracted to each other, and its surface tension makes it possible for water striders, a common insect to walk on the surface of a pond (Mader 2010:29)
Furthermore, high surface tension and cohesion are also important properties of water which makes water molecules to stick together. The high surface tension or cohesion of water molecules is important in cells and many organisms such as insects which rely on surface tension to settle on water. Below is a diagram illustrating the structure of water that makes it cling to other water molecules due to hydrogen bonding.
δ+ H H δ+
δ+ H O ………………..…. H O 2δ–
δ+ : slightly positively charged H : Hydrogen atom
δ– : slightly negatively charged O : Oxygen atom
HIGH HEAT OF VAPORIZATION
High heat of vaporization is also another important property of water. Latent heat of vaporization is the measure of the heat energy required to vaporize a liquid- that is the energy needed to overcome the attractive forces between its molecules that they can escape as a gas. The energy transferred to water molecules to allow them to vaporize results in the loss of energy from surrounding that is cooling taking place. As a result this property is made use of in the cooling of the temperature of living organisms through sweating and panting.
It can be concluded that the properties of water are vital to all living organisms and it plays important roles by ensuring that living organisms survive. It can be seen that the properties of water outlined in this discussion have a direct link to the survival of living organisms and that without water life on earth as we know would not exist. Therefore water is life conserve it.
Berner E. eatal (1987), The global water cycle. prentice- Hall inc: New Jersey.
Eckert and Rand (1978), Animal physiology 2nd edition. C.B.S publishers: New Delhi.
Raven J. (2000), Science of biology. Cambridge university press: New York
Silver Mader .S. (2010), Biology 10th edition McCraw Hill Companies: New York.
Taylor DJ.T. etal (1997), Biological Science 1st and 2nd edition. Cambridge University press: New York.