SAT Subject Biology Practice Question 345: Answer and Explanation

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Question: 345

15. 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 relationship between mycorrhizal fung

A. one partner benefits from the association and the other partner is harmed
B. one partner benefits from the association and the other partner is neither harmed nor helped
C. one partner preys upon the other partner
D. both partners benefit from the association
E. neither partner benefits from the association

Correct Answer: D


D The plant benefits by easier availability of water and phosphorus, and the fungi benefit by receiving amino acids and sugars. Another term for this type of relationship is mutualism.

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