<p>This was an essay prompt from Cliff's Ap Bio 3rd Edition that I responded to. I did as recommended and discussed how each of the 5 major properties of water facilitated life, but my actual reasoning was different than theirs in a couple of the paragraphs. Without further adieu...</p>
<p>Prompt: Describe why water is an ideal medium for living things.</p>
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<p>Water is a versatile substance which gives it 5 major properties, each having certain benefits for sustaining life. First, water is an excellent solvent. Because hydrogen and oxygen have different electronegativities, water (H20) is a polar covalent molecule. This causes water to have positive poles (centered around the hydrogen atoms) and negative poles (centered around the oxygen). These poles may interact with the poles of other polar covalent molecules and ionic compounds in order to dissolve them. This allows for the existence of oceanic saltwater which facilitates a large portion of Earths life.
Secondly, water has a high "heat capacity". This term describes the amount of heat energy it takes to raise the temperature of a substance. Because water's is high, it takes very much heat energy to warm up water. Animals are able to use this property to keep their body temperature regulated. When their metabolic processes produce large amounts of heat as products, it is sweat out in water. The water's temperature is not high, but it contains much heat energy, which it releases when it evaporates.
Unlike other substances which become more dense in solid form, water expands. This is because the weak hydrogen bonds between molecules of H20, which normally separate and reattach easily, become rigid in the cold and push apart from each other, to form crystals. Because ice is less dense than water, it floats. This has huge implications as if ice did not float, oceanic ice would sink to the bottom of the ocean and it would be forever frozen due to the insulating layer of water above it. Because ice does float, it provides a habitat at the north and south polar ice caps for organisms to surface, such as walruses, penguins, etc.
Also, water has very strong cohesion, which is an attraction between like substances. This means that water sticks together with much force, providing high surface tension. High surface tension allows many insects to walk on top of water, which facilitates life for them, and allows them to reproduce and feed in the water.
Lastly, water has strong adhesion, which is an attraction between unlike substances. This usage as an adhesive facilitates various human activities. For example, humans may lick their finger to pick up a metal pin or a piece of paper. This is because water demonstrates capillary action as a result of its adhesion, as it courses through the fibers in paper and the ridges in one's finger, it causes them to adhere together. This makes it an important medium for various activities such as this. In these ways, water facilitates daily processes for life which are necessary for survival. </p>
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<p>So, feel free to destroy it if you must. The most notable difference between mine and the example response in the Cliff's book is that theirs is much more sophisticated, particularly in that it draws upon outside examples not given in the book. Are my supporting examples too basic, or are they sufficient enough to prove my point? Basically I'm not in AP Bio, I'm self studying, so I don't have someone to explain in detail all of the finer points of writing a paper for bio. I know that in World History there was more of a focus on facts and proving one's thesis statement than on being sophisticated and using outside examples, and being stylistic, but I'm not sure if they carries over into Bio essays.</p>
<p>Anyway, please let me know what you would change, no matter how little the detail may seem. Thank you!</p>