BSC 116 Lecture Notes - Lecture 17: Acanthopterygii, Triploblasty, Gnathostomata
4 Jun 2016
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Includes two basal groups of invertebrate, the lancelets and the tunicates, as well as vertebrates. Difficult to see chordates traits when adult but present in the larvae stage. Sedentary suspension feeders: basket like pharynx with mucus that traps food. Notochord: long, flexible rod of cells provides skeletal support something for muscles to pull against when swimming may be replaces by other skeletal elements. Pharyngeal slits pharynx: posterior to mouth water enters mouth passes thru slits: suspension feeding. 2 clades of jawless vertebrates: the cyclostomes: hagfishes (myxini) No jaws, sucks up worms and dead fish. Gnathostomes evolved by modification of the skeletal rods that had previously supported the anterior pharyngeal (gill) slits. Lateral line system, organs that form a row along each side of the body and are sensitive to vibrations in the surrounding water. Skelton ossified with hard matrix of calcium phosphate (bones) Chondrichthyes: sharks ad rays un-mineralized skeletons buoyancy by storing oil in its liver.
