Essay on AP biology 2009 free response

1073 Words Sep 1st, 2014 5 Pages
Question 3
Water is essential to all living things.
(a) Discuss THREE properties of water.
(b) Explain each of the following in terms of the properties of water. You are not limited to the three properties discussed in part (a):

the role of water as a medium for the metabolic processes of cells the ability of water to moderate temperature within living organisms and in organisms’ environments the movement of water from the roots to the leaves of plants

(a) Discuss THREE properties of water (6 points maximum):
Name of property and correct description (2 points). Points MUST provide both property and description. Property
Polarity of water
Specific heat/high heat
…show more content…
The first property the response describes is the polar nature of water, earning 2 points. The response also earned
1 point for describing a use of water as a medium when it includes a solvent, which comes from part (b) but was awarded the point here. This happened often in students’ responses, as students would mix in statements from part (b) during a description of a property in part (a). The response describes the properties of specific heat (2 points) and cohesion (2 points). The property of adhesion was also described, but the response had already earned the maximum 6 points in part (a) so this property was not counted in the score.
The response addresses part (b) by explaining each of the three bullets. One point was earned for describing the ability of the high heat of vaporizations to regulate temperature. Two points were earned for addressing the role of the properties of water in the roots and leaves of plants. One point was earned for explaining how root pressure is acquired from diffusion in the root, and 1 point was earned for explaining that capillary action assists water as it rises in the plant by adhesion and cohesion.
Sample: 3B
Score: 8
The response earned all 6 available points for the discussion of three properties of water and 2 points for the explanation of how those properties play out in the biological world.
The response earned its first 2 property points by identifying and describing the polarity of water. The next
2 property

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