What is a vertebrate?

A vertebrate is defined as an animal that has a backbone or spinal column, which is part of an internal skeleton known as an endoskeleton. This characteristic is crucial as it supports the body, houses the central nervous system, and allows for greater mobility and complexity in various life forms. Vertebrates include categories such as mammals, birds, reptiles, amphibians, and fish.

In contrast, options referring to animals without backbones or skeletons, or specifically misclassifying vertebrates as invertebrates, do not accurately reflect the defining features of vertebrates. The key distinction lies in the presence of a backbone, which forms the basis of the classification and biological structure in these animals.