SAT Subject Biology Practice Question 342: Answer and Explanation
A population of birds (Population A) on a remote, isolated island is studied to determine beak length. The resulting data are plotted in Figure 1.
Suppose that 200 years later, the beaks of the birds on the island were again measured (Population B). The data, when plotted, yielded a graph as in Figure 2.
Suppose that a researcher studying Population B found that birds with beaks of 20 mm were unable to mate with birds that had 40 mm beaks. These two groups of birds would now be classified as
A. occupying different niches
B. separate species
E. separate populations
Correct Answer: B
B The defining characteristic for speciation is an inability to interbreed.