What type of creature is characterized as having a backbone?

A creature characterized as having a backbone is defined as a vertebrate. Vertebrates belong to the subphylum Vertebrata within the phylum Chordata and include animals such as mammals, birds, reptiles, amphibians, and fish. The backbone, or vertebral column, provides structural support and protects the spinal cord, which is crucial for the nervous system function in these animals.

In contrast, invertebrates are animals that do not have a backbone, which accounts for the majority of animal species. While amphibians are indeed vertebrates, the term specifically refers to a class within vertebrates that includes frogs and salamanders rather than the general characteristic of having a backbone. Aquatic, on the other hand, refers to creatures that live in water, which can include both vertebrates and invertebrates, making it too broad to specifically denote creatures with backbones. Thus, vertebrate is the correct and specific classification for creatures with a backbone.