SAT Subject Biology Practice Question 344: Answer and Explanation

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Question: 344

14. Acid rain is formed after the burning of fossil fuels releases compounds containing nitrogen and sulfur into the atmosphere. Sunlight and rain bring about chemical reactions that convert these compounds into nitric acid and sulfur dioxide, which combine with water droplets to form acid rain. Acid rain typically has a pH of approximately 5.5.

The higher acidity of soil and water affects many living organisms adversely. As the pH of lake water falls, fish become ill and die. Table 1 shows the effects of pH on the size of adult fish.

Table 1

Mycorrhizal fungi, which form a mutualistic association with many plant roots, are particularly sensitive to the effects of acid rain. These fungi facilitate the absorption of water and nutrients by the plants; in turn, the plants provide sugars and amino acids without which the fungi could not survive.

The effect of acid rain on fish size is b


Correct Answer: D


D As the acidity increases (pH goes down), the average mass of the fish decreases. However, it does not decrease linearly; rather, it stays constant for a while, then gradually drops off, then rapidly drops off as acidity becomes severe. The best representation of this is choice D.

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