Earth Sciences 2266F/G Lecture Notes - Lecture 6: Pharyngeal Arch, Branchial Arch, Object Manipulation

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 2266F/G
• Professor: Jisuo Jin

Document Summary

Function of jaws: larger mouth gape formation of teeth (allow eat larger foods = larger body, grasp/hold prey, object manipulation, nest building, mating/care for young. Mandibular arch (main jaws): upper (palatoquadrate) + lower (meckels cartilage) Hypoid arch (connect mandibular to cranium): upper (hyomandibular) + lower (cetaohyal) Hypothesis (3: gill arch hypothesis to support gill arch opening need hard structure first 2-3 pairs of gill arch lost (become incorporated into basal of cranium, next gill arches evolved into jaws/support. *spiracle near eye used for breathing (those that live bottom) Problems: no fossil evidence showing transition, gill arch-gill opposite b/w jawless and jawed jawless: gill support outside & gill inside jawed: gill support inside & gill outside, ventilation hypothesis. Jaws first evolved to improve breathing jawless modified to form mandibular arch (increase mouth for o2 intake: muscle organization in mouth area (involved in primary feeding apparatus) Spiracle = first gill opening lower mandibular arch = meckel"s cartilage: velum hypothesis.