SAT Subject Biology Practice Question 224: Answer and Explanation
14. 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 nitrogen a limiting factor on algae growth?
A. 1 only
B. 1 and 2
C. 1, 2, and 3
D. 4 and 5
E. 5 only
Correct Answer: C
The growth of algae in response to the addition of nitrogen indicates that this nutrient was a limiting factor. Algae at locations 4 and 5 exhibited growth in response to fertilization with nitrogen.