Vertebrates

One of the main reasons that arthropods are so diverse is the adaptability of their exoskeletons. Vertebrates, though not as diverse as arthropods, also have a high amount of diversity, which can also be attributed to their skeletal structure.

Vertebrates all have the same basic structure: a skull, a long back bone which usually ends in a post-anal tail, and a pelvic and pectoral girdle. Modifications to this basic body plan can lead to adaptations for swimming, walking, slithering, and even flying. Modifications to the skull allow for the powerful jaws of a wolf, the grinding jaws of a horse, the cutting beak of an eagle, and the wide gulping mouth of a bass.

The post-anal tail is also a structure unique to vertebrates. Most likely, its first adaptation was for swimming. This can be seen in modern fishes, especially sharks, which are powerful swimmers. But the tail has also been modified to allow for other adaptations such as balance, grasping, control in flight, and protection from the cold.