2:01 A vertebrate is an animal with a backbone. (An invertebrate is an animal without a backbone.) Fishes, amphibians, reptiles, birds, and mammals, including humans, are all vertebrates. Vertebrates share some basic characteristics. A hollow backbone and the cranium, or skull, protect the spinal cord and brain of most vertebrates.

Solution. Verified by Toppr. Both mammals and birds are warm-blooded animals i.e they maintain a constant body temperature despite the changes in the surrounding temperature. Therefore, it is necessary to keep the oxygenated and deoxygenated blood separate to maintain constant body temperature.

The lower jawbone of mammals is composed of a single piece that attaches directly to the skull. This bone is called the dentary because it holds the teeth of the lower jaw. In other vertebrates, the dentary is only one of several bones in the lower jaw and does not attach directly to the skull. Why is this important?