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Phylogenetics, Background Info (continued) and Craniates

Phylogenetics, Background Info (continued) and Craniates. Discussion of article Next article Additional Reading Schedule Changes Lecture material. Cladistic Classification / Phylogenetic systematics. The science of evolutionary grouping based on shared derived characteristics

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Phylogenetics, Background Info (continued) and Craniates

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  1. Phylogenetics, Background Info (continued) and Craniates

  2. Discussion of article • Next article • Additional Reading • Schedule Changes • Lecture material

  3. Cladistic Classification / Phylogenetic systematics • The science of evolutionary grouping based on shared derived characteristics • The naming of organisms based on these groups • Plesiomorphy: • Synapomorphy: • Autapomorphy: • Monophyly: • Paraphyly: • Polyphyly:

  4. M N A B C Cladogram Branch Node Internode Root OTU Ingroup Outgroup Autapomorphy Plesiomorphy Synapomorphy spizit

  5. The five synapomorphies of the Chordates • In combination: • Notochord • Hydroskeleton • Liquid-filled cells encased in a fibrous CT sheath • Allows for lateral undulation • Dorsal-hollow CNS (cf. paired structures of annelids and arthropods) • Post-anal tail • Extension of the body caudal to the anus • Increases the length of the body associated with locomotion

  6. Endostyle • Longitudinal groove in the floor of the pharynx • Lined with glandular cells • Bind iodine in matrix (homologous to thyroid gland) • Transports food to esophagus • Pharyngeal slits • Filter feeding • Respiratory

  7. Characteristics and Phylogenetic Relationships of Chordates • Tunicates • 2000 species • Mostly Ascidians (sessile adults) • Hermaphroditic • In larvae – locomotion • Notochord absorbed in the adult • Tubular nerve cord • Ependyma only • Integrates locomotion • Retained to some degree in adult • Eyespot, balancing organ • Cerebral vesicle becomes a ganglion in adult

  8. Tunicate Adult

  9. Tunicate larvae Cf. vertebrate

  10. Cephalochordates • 45 species, mostly Branchiostomata (Amphioxus) • World-wide distribution • Motile • Short, post-anal tails • Distinct anterior end • Not well developed head • Notochord extends entire length of body • Dioeceous

  11. The Parade of the Craniates • 50,000 known living species • Plus extinctions since 500 MYA • Mostly marine • Hagfish + Vertebrata • Clearly exhibit all 5 chordate synapomorphies • Some only in the embryonic stages • Thyroid gland in all craniate adults • Paired, cephalized sensory organs • Nose, lateral eyes, ears • Major organ systems

  12. “Cephalized” Why the concentration of paired sensory organs here?

  13. Developmental Neural crest Neurogenic placodes Nervous System Above Braincase (skeletal) Complex sense organs Cranial nerves Tripartite brain Endocrine system is complex Gut Muscularization Regionalization Differentiated organs Cardiovascular Gills Heart Hemoglobin Major synapomorphies of the Craniates

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