BCOR 12 1st Edition Lecture 18Outline of Last Lecture I. EcdyozoansII. NematodesIII. ArthropodsIV. Subphyla of arthropodsV. Echinoderms Major CharactersOutline of Current Lecture I. Shared Derived Characters of ChordatesII. CephalochordatesIII. TunicatesIV. VertebratesV. GnathostomesVI. Bony FishVII. TetrapodsCurrent LectureChapter 34 – Origin and evolution of the ChordatesShared Derived Characters of ChordatesI. Notochord – longitudinal, flexible rod that runs the length of the dorsal part of the bodya. Advantage: gives skeletal support against gravity and provides a place for musclesattachmentII. Dorsal, hollow nerve cord – develops into central nervous systemIII. 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 embryosCephalochordates- Lancelet is the most basal chordateo Do not have head or vertebraeo Are filter feedersTunicates- Larvae show chordate characteristics- Have lost 4 important Hox genes which causes them to lose chordate characteristics in developmentVertebrates – chordates with a backbone- 52,000 animals species are vertebratesShared Derived Characters:I. Complex nervous systemII. More elaborate skeletonIII. Cranium emergenceAll 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 organso Advantage: coordinates complex movements (very good for predators)Most basal are the jawless fishes: hagfish and lampreysGnathostomes – vertebrates with jaws- Most basal are sharks and rays, they have to keep moving so they don’t sinkShared Derived Characters:I. JawsII. Additional duplication of Hox genes (enabled the origin of jaws)III. Enhanced smell and visionIV. Lateral line system – bodes that sense an electrical field generated by muscles contraction of nearby animalsBony FishShared Derived Characters:I. Ossified (bony) skeleton – includes collagen and a hard matrix of calcium phosphateII. Operculum – protective bony flap that covers and protects the gillsIII. Swim bladder – an air sac that enables the bony fish to control buoyancy in the waterTetrapods – Gnathostomes with 4 limbsEmerged about 377 MYAShared Derived Characters:I. Four limbs with digitsII. Neck – allows for head movement from side-to-sideIII. Pelvic girdle – fused to the backbone creating a force from the hind legsIV. Adults to not have gills (breathe out of water)These allowed for many advantages for a terrestrial
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