SAT Subject Biology Practice Question 150: Answer and Explanation

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Question: 150

20. In a long-running ecological study, the species richness of mosses, shrubs, and trees was calculated for one hectare (10,000 m2) of land every 50 years for 200 years. The data are shown in the table.

YEARMOSSESSHRUBSTREES
18001620
18502174
19001053
195013126
2000172814

According to the data, has this community reached a climax?

A. Yes; all densities continue to change.
B. No; there is continual change in species' densities.
C. Yes; moss species are constantly present throughout time.
D. No; moss species are always present in high densities.
E. Yes; in 1800 there are relatively many more tree species found.

Correct Answer: B

Explanation:

Because these data continue to change every time they are collected, one can infer that this community has yet to reach its climax. If numbers were to remain the same between two data collection periods, this would suggest a climax had been reached.

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