The Question Refers to the Following Evolutionary Tree, in Which

Multiple Choice

The question refers to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) , and the vertical axis represents morphological change.

Which conclusion can be drawn from this evolutionary tree?

A) A single clade (that is, a group of species that share a common ancestor) can include species that formed by gradualism and other species that formed by punctuated equilibrium.
B) A single clade (that is, a group of species that share a common ancestor) will either include species that formed by gradualism or species that formed by punctuated equilibrium.
C) Assuming that the tip of each line represents a species, there are five extant (that is, not extinct) species resulting from the earliest common ancestor.
D) Species X and Z best represent species that evolved by punctuated equilibrium.