Is water really necessary for life? Discuss

7/30/2019 Is water really necessary for life? Discuss

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Sinead DarmaninMonday Group

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IS WATER REALLY NECESSARY FOR LIFE? DISCUSS.

Every known form of life on Earth, from the largest mammals to the smallest microbes,

is made up of water. It is a substance with a chemical formula of H2O and, as can beseen in the diagram below, is made up of two hydrogen atoms bonded covalently with

an oxygen atom.

The water molecule is not linear and the oxygen atom is the most electronegative atom,

and thus it exerts the most attraction. As a result, water has polar covalent bonds. This

polarity leads to strong attractive forces between molecules of water, giving rise to

water's high surface tension and capillary forces. The capillary action refers to the

tendency of water to move up a narrow tube against the force of gravity. Such strong

cohesive and adhesive properties enable water to perform transpiration in plants, and

for a larger flow of blood through narrow blood vessels in organisms.

Waters high surface tension enables small animals to walk on the surface of the water.A high surface tension means that the surface of the liquid water exposed to the air is

diffcult to puncture.

No organism can remain biologically active without water. Within cells, water partakes in

many chemical reactions, and is the medium in which most biological reactions take

place.

Due to its atomic structure, water has other various advantageous properties. wo of

waters physical properties are quite unique to a chemical substance it remains in liquid

form over an extremely broad range of temperatures between and and itdecreases in density when converted to solid phase (ice). In fact, water is the only

known substance on Earth that exhibits its three physical states of matter; which are the

gas, liquid and solid states.

Water has a high specific heat capacity, that of 4200J. This is favourable in, for

example; the human body. As the human body is made up of about 70% of water, a low


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specific heat capacity would lead to the death of all body cells in the event of slight

fluctuation in temperature.

Water as acts as an insulator as it needs a lot of energy (since it has a high specific

heat capacity) to change in temperature. In pregnancy, for example, the amniotic fluid

does not experience changes in temperature as such, and thus the baby is insulated.

Water also has a high heat of vapourisation, which means that a lot of heat is required

to change water from its liquid state to its gaseous state. Evapouration thus has a

cooling effect on the environment. Thus effect explains why sweating cools the human

body; as sweat evaporates off the skin, it uses up some of the adjacent body heat. Also,

plants are cooled by means of transpiration.

For many large mammals in various climates, getting rid of excess heat can pose as a

serious problem, expecially during exercise. Having water in contact with the skin

greatly increases heat loss because water has a much higher heat capacity forabsorbing heat than air does. However, since water is heavy, animals do not tend to

carry an excess supply of it. Evaporation of water by sweating or panting is usually at a

last resort. This is usually done by animals adapted to hot environments.

Water also an exhibits aberrant property during its freezing temperature, mainly due to

its density. When water molecules undergo freezing, there is less molecules per unit

volume. These molecules expand in a hexagonal shape structure by around 9%, and air

becomes trapped within. This makes ice less dense than liquid water. If ice was denser

than water, and the Earth cooled slightly, ice formed on the oceans would sink and push

the already cold water from the bottom to the surface, where it too would freeze andsink, repeating the cycle until all water on the planet was frozen.

In reality, when water comes into contact with freezing temperatures, such as in lakes,

only a top layer of water freezes, and hence insulates the water trapped underneath.

The fact that water remains in liquid form, is advantageous to aquatic life, as it helps

them to remain alive in their natural medium. Water, in comparison with other liquids,

does not form a block of solid stuff, hence helping organisms to survive in extreme

temperatures with a lack of heat energy.


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The specific heat capacity of wateralso attributes to a species survival, due to its ability

to keep water temperatures from fluctuating; hence acting as a buffer. This is one of the

main reasons why life originated from water! Also, in animals, such a property is

particuarily favourable due to the fact that it helps in the regulation of body temperature.

Also this property goes alongside the property of a high heat of vapourization, both of

which are a result of the extensive hydrogen bonding between water molecules. These

two unusual properties allow water to moderate Earth's climate by buffering large

fluctuations in temperature.

Water is also commonly referred to as a universal solvent. Substances that dissolve in

water, like salts, sugars and various gases are known as hydrophilic (water-loving)

substances, whilst those that do not mix well with water such as fats and oils, are known

as hydrophobic (water-fearing) substances. The fact that oxygen dissolves in water

solves the problem that aquatic organisms would have to face in order to obtain oxygen

for respiration. This is as a fish cannot break the strong bonds that exist in a water

molecule in order to obtain the oxygen atom; as its strong covalent bonds make it

impossible. Thus; it takes up the oxygen that is dissolves in water.

In other land-living organisms, the solvent effect of water is also beneficial, as the

respiratory system has organs; mainly the trachea and te lungs, which have water on

the surface as the dissolving of gases in water facilitates gaseous excange.

As can be concluded, water is basically the molecule of life. Its molecular structure

gives rise to various unique properties making it one of Earths bare necessities.

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Is water really necessary for life? Discuss