Passage I

Table 1 indicates the presence or absence of 6 traits in 7 dinosaur genera (genera is the plural of genus).

Figure 1 is a cladogram (a diagram showing evolutionary relationships) for these dinosaur genera based on the 6 traits in Table 1. Figure 1 also includes 6 dinosaurs (A-F) at 6 nodes (branch points).The dinosaur at each node represents the most recent common ancestor (MRCA) of the dinosaur genera extending upward from that node. Each MRCA had all traits that were shared by all of the genera extending upward from it.

Table 1 and Figure 1 adapted from Neil A. Campbell, Biology, 4th ed. @1996 by The Benjamin/Cummings Publishing Company, lnc.

Table 2 indicates when each of the 7 dinosaur genera in Table 1 existed.

1. If a row in Table 1 were made for Dinosaur A, it would most likely appear as which of the following?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

From the cladogram in Figure 1, it can be seen that Dinosaur A is the most recent common ancestor of Archaeopteryx and Allosaurus, so the characteristics of this common ancestor should be very close to the above two types of dinosaurs. According to Table 1, it can be seen that the two Dinosaurs are all +———++, so Dinosaur A should be too.