The next few questions refer to the following evolutionary tree, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change.

-Which of these five species is the extant (i.e., not extinct)species that is most closely related to species X, and why is this so?
A) V; shared a common ancestor with X most recently
B) W; shared a common ancestor with X most recently
C) Y; arose in the same fashion (i.e., at the same tempo) as X
D) Z; shared a common ancestor with X most recently, and arose in the same fashion as X
E) This tree does not provide enough information to answer this question.

Question

The next few questions refer to the following evolutionary tree, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change.
 
-Which of these five species is the extant (i.e., not extinct)species that is most closely related to species X, and why is this so?
A) V; shared a common ancestor with X most recently 
B) W; shared a common ancestor with X most recently 
C) Y; arose in the same fashion (i.e., at the same tempo) as X 
D) Z; shared a common ancestor with X most recently, and arose in the same fashion as X 
E) This tree does not provide enough information to answer this question.

Quizplus · Accepted Answer

The species that is most closely related to another species is the one that shared a common ancestor with it most recently. Choices B, C, and D are incorrect because they either do not specify this crucial detail or add irrelevant information. Choice E is incorrect because the question assumes the existence of a phylogenetic tree or some form of lineage information that allows for the determination of relationships based on common ancestry.

The Next Few Questions Refer to the Following Evolutionary Tree