Question

biodiversity and classification
all mammals have a spine, or backbone, made of vertebrae. is the trait of a backbone made of vertebrae an example of a derived character in mammals?
a. yes, because all mammals have this trait.
b. yes, because the trait evolved in a mammal ancestor and was passed to its descendants.
c. no, because the presence of the trait is not explained by the theory of evolution.
d. no, because the trait evolved in a vertebrate ancestor and was passed to all vertebrates, and not mammals only.

Explanation:

A derived character is a trait that evolved in a specific group's ancestor and is passed to its descendants, distinguishing that group from earlier relatives. The backbone (vertebrae) evolved in a common vertebrate ancestor, not a mammal-specific ancestor, so it is not a derived character for mammals alone.

Answer:

D. No, because the trait evolved in a vertebrate ancestor and was passed to all vertebrates, and not mammals only.