What is the number of possible unrooted trees for 5 taxa?
A)5
B)10
C)15
D)20
E)25

Question

Quizplus · Accepted Answer

The number of unrooted trees can be found by Cayley's formula, which is "N^(N-2)", where N is the number of taxa. Thus, for 5 taxa, the number of possible unrooted trees is 5^(5-2), which is equal to 125. However, this includes both rooted and unrooted trees. To get only the number of unrooted trees, we divide 125 by 2^4 (as there are 4 possible ways to root a tree with 5 taxa). This gives us 15 possible unrooted trees for 5 taxa.

What Is the Number of Possible Unrooted Trees for 5