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CHAPTER 3: Water And The Fitness of the Environment
I.
The Effects of Water’s Polarity
A. The Polarity of Water Molecules Results in Hydrogen Bonding
 Be able to integrate this information with the H bonding info from the last
chapter. Diagram 3.1 is excellent.
B. Organisms Depend on the Cohesion of Water Molecules
 So this is where you now need to focus on the role of H bonding in
biological systems.
1. Cohesion- Adhesion-Surface Tension: When you are done taking notes
and / or reading this section just sit back and explain to yourself how these
3 properties of water, all caused by H bonding are important in biology.
This will help prepare you for essay questions.
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C. Water Moderates Temperatures on Earth
1. Heat and Temperature
2. Water’s High Specific Heat
a. Definition and pay attention to how this property affects living
situations. That is, What is the relevance of water’s high specific heat
to life on Earth?
3. Evaporative Cooling
a) So if you have a hot car with no AC or you are staying in a dorm
room that is really hot (but not humid) why does it make some sense to
spray water into these two enclosed areas? Which way is the heat
flowing?
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b) Heat of Vaporization
c) Evaporative Cooling and Its Relevance to Biological Systems
D. Oceans and Lakes Don’t Freeze Solid Because Ice Floats
 How does life in a pond or lake or ocean benefit because ice floats? What
property allows ice to float? What happens to water as it gets colder and
colder, doesn’t it sink? And then it eventually floats? Why is that or how
does that happen?
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E. Water Is The Solvent of Life
1. Solute-Solvent-Solution-Aqueous Solution
2. Hydration Shell
 I like to refer to this simply as the hydration of ions or molecules. You
see this is very important because some things would be insoluble in
your blood stream because they are nonpolar unless they were
hydrated by water. Do sugars get hydrated or just ions? Proteins?
a) Hydrophilic and Hydrophobic Substances: these are very
important terms, so know them well.
b) Solute Concentration in Aqueous Solutions
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 So at this point you should again ask yourself about the role of water in biological
systems. Since our cells are mostly water, since our cells are surrounded by water,
since organisms need to take in water, you’ve got to understand what its role is.
II.
The Dissociation of Water Molecules
A. Introduction
1. Hydrogen and Hydroxide Ions
B. Organisms Are Sensitive to Changes in pH.
1. Acids and Bases: hopefully this is all a review
2. The pH Scale
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3. Buffers
 So these are pretty important. How is it that the pH of your blood
remains fairly constant while you are strenuously exercising and
producing bunches of lactic acid?
C. Acid Precipitation Threatens the Fitness of the Environment
 Well I hope you didn’t think buffers were only inside of your body?
Where do the buffers come from that are in the lakes, oceans, etc.?
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