BIO 200 Lecture Notes - Lecture 21: Actinopterygii, Swim Bladder, Gnathostomata
20 Nov 2018
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Outline: fish, diversity: over vert species; only fully aquatic species, 5 traits of all fish: Agnathans/extinct placoderms/modern gnathostomes= show evo and importance of jaws from jawless agnathans to placoderm (gill arches modified to jaw) and gnathostomes w jaw supporting teeth. Paired appendages: pectoral (shoulder) & pelvic (hip) stabilize position in water and allow propulsion; evolve to be jointed. Single loop blood circ: oxy blood pumped from heart to gills to body, deoxy returns to heart [we have double loop- lung & rest of. Gas filled sac to supplement gill based gas exchange when o2 scarce. Evolved into lungs in 2 groups: locomotion. Ray finned fish: parallel bony rays to support + stiffen fin w/o muscle; int muscle control fin movement in concert. Lobe finned fish: land animals evolved here; few survive today. Lungfish= gills & vestigial lungs (functions more like swim bladder now)
