BCOR 12 1st Edition Lecture 18 Outline of Last Lecture I Ecdyozoans II Nematodes III Arthropods IV Subphyla of arthropods V Echinoderms Major Characters Outline of Current Lecture I Shared Derived Characters of Chordates II Cephalochordates III Tunicates IV Vertebrates V Gnathostomes VI Bony Fish VII Tetrapods Current Lecture Chapter 34 Origin and evolution of the Chordates Shared Derived Characters of Chordates I Notochord longitudinal flexible rod that runs the length of the dorsal part of the body a Advantage gives skeletal support against gravity and provides a place for muscles attachment II Dorsal hollow nerve cord develops into central nervous system III Pharyngeal clef develops into gills important for gas exchange These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV Muscular post anal tail propels aquatic species through water In land animals this is seen more in the embryos Cephalochordates Lancelet is the most basal chordate o Do not have head or vertebrae o Are filter feeders Tunicates Larvae show chordate characteristics Have lost 4 important Hox genes which causes them to lose chordate characteristics in development Vertebrates chordates with a backbone 52 000 animals species are vertebrates Shared Derived Characters I Complex nervous system II More elaborate skeleton III Cranium emergence All of these are advantageous for they allow for a better ability to capture prey and avoid predators Cranium head which contains brain skull and other sensory organs o Advantage coordinates complex movements very good for predators Most basal are the jawless fishes hagfish and lampreys Gnathostomes vertebrates with jaws Most basal are sharks and rays they have to keep moving so they don t sink Shared Derived Characters I Jaws II Additional duplication of Hox genes enabled the origin of jaws III Enhanced smell and vision IV Lateral line system bodes that sense an electrical field generated by muscles contraction of nearby animals Bony Fish Shared Derived Characters I Ossified bony skeleton includes collagen and a hard matrix of calcium phosphate II Operculum protective bony flap that covers and protects the gills III Swim bladder an air sac that enables the bony fish to control buoyancy in the water Tetrapods Gnathostomes with 4 limbs Emerged about 377 MYA Shared Derived Characters I Four limbs with digits II Neck allows for head movement from side to side III Pelvic girdle fused to the backbone creating a force from the hind legs IV Adults to not have gills breathe out of water These allowed for many advantages for a terrestrial organism
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