Vertebrates are animals with an internal backbone or spinal column. There are over 85,000 species of vertebrate animals such as amphibians, birds, fish, mammals and reptiles. Most large land animals are vertebrates. Even large sea animals, such as the whale, are vertebrates. However, only about 5% of all animal species are vertebrates. The remaining 95% of animals are invertebrates that don’t have an internal backbone (e.g., insects, mollusks and arthropods).
The defining characteristic of all vertebrates is the vertebral column or backbone. This vertebral column is a strong series of bones extending through the core of the body. Near the front end of the backbone is the mouth, with the anus opening near the back end of the backbone. In vertebrates with a tail, the vertebral column extends beyond the anus to the end of the tail. Above the backbone is the spinal cord, a major component of the nervous system. Below the backbone is the gastrointestinal or digestive tract.
The vertebral column is made up of many individual vertebrae interconnected with intervertebral discs. These vertebrae and intervertebral discs provide for flexibility and movement of the spine.