In a Comparison of Birds and Mammals, Having Four Limbs

Question

In a comparison of birds and mammals, having four limbs is
A) a shared ancestral character.
B) a shared derived character.
C) a character useful for distinguishing birds from mammals.
D) an example of analogy rather than homology.
E) a character useful for sorting bird species.

Accepted Answer

Having four limbs is a shared ancestral character, meaning that it was present in the common ancestor of both birds and mammals, and is not a useful characteristic for distinguishing between the two groups.