Correct Response: C. Evidence suggests that at least for certain genes the rate of mutation is fairly constant among different species, thus providing a sort of molecular clock. This means that the amount of time that has elapsed since two species diverged can be approximated by examining the number of differences in the DNA and protein sequences of the two species. These estimates can be made using tissue from living organisms, rather than relying on fossil evidence. In convergent evolution (A), two species that are not closely related evolve similar traits as a result of living in similar environments. These similar structures may tend to obscure when the two species diverged in the absence of other types of evidence. The Hardy-Weinberg equilibrium (B) assumes a stable population in which natural selection, and hence evolution, is not occurring. Thus, it provides no information about speciation. The biological species concept (D) defines a species as organisms that are capable in interbreeding with each other. It provides criteria for whether two organisms belong to the same or different species but does not provide evidence about when speciation might have occurred.
