Kaplan Nursing Entrance Practice Exam

Which of the following characteristics is NOT typically associated with mammals?

1. Warm-blooded

2. Two pairs of limbs

3. Feathers

4. Three middle ear bones

The correct answer is: Feathers

Mammals are a distinct group of animals characterized by several key features. Among these, being warm-blooded (endothermic), having two pairs of limbs (which correspond to their evolutionary adaptations), and possessing three middle ear bones (important for hearing) are all typical characteristics found in mammals. However, feathers are not associated with mammals; instead, they are a feature exclusive to birds. This distinction arises from the evolutionary lineage of these classes of animals—while mammals evolved from ancient synapsids, birds evolved from theropod dinosaurs, which developed feathers for insulation and other purposes. Thus, the presence of feathers is a defining trait of birds, making the choice that includes feathers the correct answer as not being typically associated with mammals.