Lecture 16 - cordates I - immunity) 1. Sharks and rays -...

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Lecture 17 – Chordates I I. What are chordates? A. Four pleisiomorpic characters: 1. Notochord - flexible rod of fluid filled cells; skeletal support 2. Dorsal Hollow nerve chord - Develops into CNS (nerve cord can be ventral in non-chordates) 3. Pharyngeal slits - involved in filter feeding and respiration (as gills) 4. Muscular post-anal tail – propulsion B. All chordates exhibit these traits at some point during ontogeny. II. Simple Chordates A. Lancelets 1. Fish-like, use cilia to feed; adults have all 4 characters B. Tunicates (aka sea squirts) 1. Only larvae have characters III. Craniates A. Evolution of head 1. Hagfish - Cartilaginous skull; lack jaws and vertebrae III. Vertebrates A. Evolution of vertebral column 1. Lampreys - cartilaginous vertebral column; lack jaws IV. Gnathostomes A. Evolution of jaws (from skeletal rods supporting gill slits; paired fins; adaptive
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Unformatted text preview: immunity) 1. Sharks and rays - cartilaginous skeleton w/ some bones VI. Osteichthyans A. Evolution of bony endoskeleton 1. Ray finned fish - rudimentary lungs and swim bladder VII. Lobe-fins Lecture 17 Chordates I A. Evolution of fins with rod-shaped bones supporting muscle 1. Coelacanth - thought extinct for 75 my B. Evolution of lungs or lung derivatives 2. Lung fish - have gills; survival terrestrial desiccation via estivating in mud VIII. Tetrapods A. Evolution of legs from lobe-finned lung fish 1. Tiktaalik fossil a. possess both tetrapod and fish characteristics; b. possess important intermediates 1. Fins with wrists 2. Head disconnected from shoulder (neck) 3. Expanded ribs...
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Lecture 16 - cordates I - immunity) 1. Sharks and rays -...

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