SAT Subject Biology Practice Question 223: Answer and Explanation

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Question: 223

13. Scientists examined the effects of adding nutrients to waters off the Eastern coast of the United States. The graph shows the nutrient added and the resulting algae counts at six locations. No nutrients were added in the control condition.

At which locations was a sufficient supply of phosphorus present before the experiment was conducted?

A. 1 only
B. 1 and 2
C. 1, 2, and 3
D. 4 and 5
E. 5 only

Correct Answer: D


If the addition of phosphorus does not result in increased growth, this indicates that phosphorus was not a limiting nutrient. Algae at locations 4 and 5 did not exhibit growth in response to the addition of phosphorus.

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