BIL 160 Lecture Notes - Lecture 13: Yolk Sac, Yolk, Tetrapod
28 Apr 2016
School
Department
Course
Professor
Document Summary
Bilaterian animals that belong to the deuterostome clade. Flexible rod b/w nerve cord and digestive tissues. Muscles attach to it: post anal tail. Muscular and helps with locomotion: dorsal, hollow nerve cord. Develops into cns (brain and spinal cord: pharyngeal slits/clefts. Water goes in through the mouth and out through the slits (gills) In mammals it becomes part of head (ears, neck) Lancelets: filter feeders, tiny, marine animals, oldest chordate ancestor of non-vertebrate chordates. Tunicates: sucks in water, filters it through pharynx for food and squirts it out of siphon, only has 1 feature of chordate (pharynx) The larvae of them have all 4 characters however: non vertebrate. Vertebrates: skeletal system and have a backbone, 2 sets hox genes (lancelets and tunicates have 1 set, derived characters. Fin rays in aquatic versions: class myxini hagfishes. Enlarged forebrain associated with better smell and vision. Lateral line system (sensitive to vibrations: earliest ones 440 mya, chondrichthyes.
