Characteristic features of the structure of vertebrates.

The subtype of vertebrates is rich in a variety of living organisms and includes several classes: fish, amphibians, reptiles, birds and mammals. All representatives are united by common features characteristic of this subtype. In all vertebrates, the notochord has turned into a spinal column, which at one end passes into the skull. This greatly improved the survival rate of the animals. Their heart has several chambers, consisting of the atria and ventricles. The circulation circles have become closed.