The following questions refer to the evolutionary tree shown below.
The horizontal axis of the cladogram depicted below is a timeline that extends from? 100 000 years ago to the present; the vertical axis represents nothing in particular. The labelled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since? 50 000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

-According to this tree, what percentage of the species seem to be extant (in other words, not extinct)?
A)25%
B)33%
C)50%
D)66%
E)75%

Question

The following questions refer to the evolutionary tree shown below.
The horizontal axis of the cladogram depicted below is a timeline that extends from? 100 000 years ago to the present; the vertical axis represents nothing in particular. The labelled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since? 50 000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.
 
-According to this tree, what percentage of the species seem to be extant (in other words, not extinct)?
A)25% 
B)33% 
C)50% 
D)66% 
E)75%

Quizplus · Accepted Answer

Since only the tips of the branches represent distinct species, we can count the number of tips and compare it to the total number of branches in the tree. From the diagram, there are 4 distinct species at the tips of the branches, out of a total of 6 branches in the tree. Therefore, 4/6 or 66% of the species seem to be extant. Choice D is the correct answer.

The Following Questions Refer to the Evolutionary Tree Shown Below