Chordata => Vertebrata

Phylum: Chordata    51,000 species

(Animals with a notocord)

Chordata contains the most familiar species, including humans. All chordates have several things in common that occur at some stage of development. They have pharyngeal slits, which are openings that connect the inside of the throat to the outside of the neck.

These are often used as gills. Their main feature, what they are named after, is the notochord, which is a rod that supports the nerve cord. The nerve cord is also present in all species. This is a bundle of nerve fibers which connect the brain with the muscles and organs, and is through which messages from the brain are sent.

A tail is also present, which extends past the anal opening. In most species, at least some of these features disappear with age. For example, the pharyngeal slits are only present in the human fetus.

SubPhylum: Vertebrata   41,700 species

  (Vertebrates – Animals with backbones)

This is the largest subphylum and the focus of this website. It contains the more well-known land animals, including humans, reptiles, fish, marine mammals, and birds. Every animal with a backbone is present in this subphylum.

The notochord is developed at an early age, and is replaced with vertebrate. All vertebrates have a skeleton of either bone or cartilage. Their brain is protected by a boney cranium, and consists of three parts.

They all have well-developed hearts with 2-4 chambers and have a closed circulatory system.