SAT Subject Biology Practice Question 455: Answer and Explanation
5. A buck with a large, impressive rack of antlers sires four offspring, three males and one female. The three male offspring also have large, impressive antlers, but before being able to reproduce, two of the male offspring get their antlers tangled in a low-hanging tree and are caught and killed by wolves. A second buck with a smaller set of antlers sires three male offspring; all of these males have smaller antlers like their father. They are more effective at escaping predators and successfully reproduce. In terms of evolution, which of the original bucks is more fit?
A. The buck with the larger antlers because he sired more offspring.
B. The buck with the smaller antlers because more of his offspring survived.
C. The buck with the larger antlers because he will be more successful at attracting a mate and continuing to reproduce.
D. The buck with the smaller antlers because he is more effective at escaping predators and will continue to reproduce.
E. Both bucks are equally fit.
Correct Answer: B
B Remember, the key to fitness is not how many children you produce or how long you live, but how much you contribute to the next generation's gene pool. Because the buck with smaller antlers sired three surviving offspring, and the buck with larger antlers sired only two surviving offspring, the buck with smaller antlers is more "fit" in the evolutionary sense.