BIOL 2200 Chapter Notes - Chapter 34: Gnathostomata, Endoskeleton, Swim Bladder
31 Mar 2017
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34. 1 chordates have a notochord and a dorsal, hollow nerve cord. Chordates bilaterian animals belonging to the clade dueterostomia. Longitudinal flexible rod between digestive tube and nerve cord. Made of large-fluid filled cells encased in stiff fibrous tissue. In many adult vertebrates, a more complex skeleton develops around notochord while only remnants of the embryonic vertebrae remain: dorsal, hollow nerve cord. The fact that the nerve cord is dorsal is unique to chordates. Develops into the central nervous system: brain and spinal cord: pharyngeal slits or cleft. Pharyngeal clefts (grooves) develop into slits that open into the pharynx. The slits allow water entering through to mouth to exit without fully passing through the digestive tract. Function as suspension feeding devices for many invertebrates. In tetrapods, slits develop and become part of ear, head and neck: muscular, post anal tail. In nonchordates, in contrast, have a digestive tract that runs the full length of the body.
