Describe how water contributes to the fitness of the environment as it supports life?

Answer 1

"In a classic book called The Fitness of the Environment, ecologist Lawrence Henderson highlights the importance of water to life. While acknowledging that life adapts to its environment through natural selection, Henderson emphasizes that for life to exist at all, the environment must first be a suitable abode.

Life on Earth began in water and evolved there for 3 billion years before spreading onto land. Modern life, even terrestrial life, remains tied to water. All living organisms require water more than any other substance. Human beings, for example can survive for quite a few weeks without food, but only a week or so without water. Molecules of water participate in many chemical reactions necessary to sustain life. Most cells are surrounded by water, and cells themselves are about 70-95% water."

and paraphrased from the same source:

"....four emergent properties of water that contribute to Earth's suitability as an environment for life: cohesive behavior(hydrogen bonds+this property's surface tension phenomena+adhesion), ability to moderate temperature (the ability to absorb heat with only a slight change to its own temperature), expansion upon freezing (few substances are less dense in solid form than in liquid), and use as a solvent (behavioral characteristics of H+ and OH+ ions when mixed with an acid or base)."

-Taken from

Cambell, Reece. Biology 8th Edition. Pearson. Page 46

Water also has a high specific heat which is the amount of heat (1 calorie [cal]or 4.184 joules [J]) that must be absorbed or lost for 1 gram of water(or any other substance) to change its temperature by 1degree Celsius. Because of this the 3/4 or so of the earth covered in water regulates the heat energy from the sun, making the temperatures ideal for life to exist. Water also evaporates at a large range of temperatures causing evaporative cooling to occur on the surface of water and on the surface of our skin. Some species of ant develop "air conditioners" in their colonies by creating an evaporative bottom layer that uses the evaporation of the water table to infuse the entire colony with oxygen molecules and cool it off. Naturally occurring ice also insulates the water below it to make the habitat below ideal for aquatic life to survive the winter. If there were no ice on these bodies of water, the life contained within would all freeze with the water around it as the ice would constantly sink until the body of water is completely frozen. North American Tree Frogs can actually completely freeze and thaw in the spring due to an "antifreeze" in their blood.

Water is not a universal solvent. This is good because if it was it would completely dissolve our bodies. It is more versatile as a solvent than anything else on earth due to the polarity of its molecules. This makes it easy classify most substances as either acids or bases based on their pH scale (the amount of either OH- or H+ ions released during dissociation in water). Hydrophobic substances (oils, molecules containg C and H but NOT O atoms) form cell membranes to contain water in our bodies.