SAT Subject Biology Practice Question 297: Answer and Explanation

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Question: 297

7. A population of birds lives in an area with many insects upon which it feeds. The insects live inside trees, burrowing into the bark. Over many hundreds of years, the average beak size in the bird population has increased. This is due to

A. increased fitness of the birds, leading to speciation
B. decreased fitness of the insects, allowing the birds to catch them more easily
C. increased fitness of large-beaked birds, leading to evolution
D. decreased fitness of small-beaked birds, leading to speciation
E. random mutation and genetic recombination

Correct Answer: C


C A change in a population that occurs over a long period of time is evolution. This alone is a good tip-off that choice C, the only choice that mentions evolution, is correct. Speciation has not occurred, only a change in the characteristic of the birds, thus choices A and D can be eliminated. Any change in the fitness of the insects would change the characteristics of the insect population, not the bird population (B is wrong), and random mutation would not produce a specific, directed effect (E is wrong). Birds with large beaks had greater fitness because they could more easily obtain food, thus they had an advantage over birds with smaller beaks, which died out as time passed.

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