A vertebrate is an animal that has a backbone, also known as a vertebral column, spine, or backbone, which is a column of bones that supports the body and protects the spinal cord. Vertebrates are a subphylum of chordates, which are animals that have a notochord, a dorsal nerve cord, and pharyngeal slits at some point in their lives. The vertebrates consist of all the taxa within the subphylum Vertebrata (chordates with backbones) and represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described.
Vertebrates are characterized by several features, including:
- Backbone: This is the most obvious feature of vertebrates, and it is a column of bones that supports the body and protects the spinal cord.
- Muscular system: Vertebrates have a muscular system consisting primarily of bilaterally paired masses and a central nervous system partly enclosed within the backbone.
- Distinct head: Vertebrates have a distinct head, with a differentiated tubular brain and three pairs of sense organs (nasal, optic, and otic).
- Pharyngeal slits with gills: The presence of pharyngeal slits with gills indicates a relatively high metabolic rate.
- Bilateral symmetry: Vertebrates have bilateral symmetry, which means that their left and right sides are mirror images of each other.
- Two pairs of appendages: Vertebrates have two pairs of appendages, such as arms and legs.
Approximately 45,000 living species constitute the vertebrates, ranging in size from minute fishes to elephants and whales (of up to 100 tons), the largest animals ever to have existed. Vertebrates are adapted to life underground, on the surface, and in the air, and they feed upon plants, invertebrate animals, and one another.
