CHORDATA: FISH, AMPHIBIANS, REPTILES, BIRDS, AND MAMMALS
diagram of a Chordata embryo
The phylum Chordata is the one you probably know most about- you’re part of it! In fact, fish, amphibians, reptiles, birds, and mammals are all chordates. Chordates are related by four embryotic features:
dorsal hollow nerve chord, notochord, pharyngeal gill slits, and tail. The dorsal hollow nerve chord is a tube-like structure which will later develop into the brain and spinal chord, which process sensory information. The nerve chord sits just above the notochord. The notochord supports the animal and is flexible yet firm. In most chordates, the notochord is replaced by a backbone, but in a few chordates, it is kept. Extending from the notochord is a postanal tail, a muscular structure which can be seen at the posterior end of the embryo. This tail continues to develop in most chordates but is lost in humans. Pharyngeal gill slits are openings to the animal’s surrounding. They can be found between the mouth and the digestive tube. In fish, these slits become gills which lie under the skin, but they disappear in humans. Click on a button below to learn more about a specific class!