Phylum Chordata (General Characteristics and Overview of Chordates)

Phylum Chordata
The phylum Chordata consists of animals with a flexible rod supporting their dorsal or back sides. The phylum name derives from the Greek root word chord- meaning string. Most species within the phylum Chordata are vertebrates, or animals with backbones (subphylum Vertebrata). Examples of vertebrate chordates include fishes, amphibians, reptiles, birds, and mammals. A modern human—one species of mammal—is a familiar example of a chordate. However, we share this phylum with two groups of invertebrates as well.

All chordates share the following common features that are unique to the group:

The notochord is a stiff but flexible rod of cells and connective tissue (from the Greek root words noto meaning back and chord meaning string) that gives the phylum its name, Chordata. In some chordates the notochord is a major support structure.

Pharyngeal slits are in the pharynx, the region of the digestive tract just behind the mouth.

The dorsal hollow nerve tube lies above the notochord and sends branches of nerve tissue into muscles and other organs. As the nerve tube grows, its walls thicken, almost eliminating the central hollow space. A dorsal hollow nerve tube is a common feature of all chordates, including humans, in both embryonic and mature stages.

All chordates have a post-anal tail that is located posterior to the anal opening. In humans, our tail is reduced to a small nub of bone (the tailbone) that does not protrude significantly outside the body.

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