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Lecture 8 – Evolution of Ear Ossicles

Semicircular Canals Sensory cells for balance. 3 Ear Ossicles Malleus Incus Stapes. Chochlea Sensory cells for hearing. Tympanum. Lecture 8 – Evolution of Ear Ossicles. Characteristics of Evolution Demonstrated by Ear Ossicles /Jaw Joint .

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Lecture 8 – Evolution of Ear Ossicles

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  1. Semicircular Canals Sensory cells for balance 3 Ear Ossicles Malleus Incus Stapes Chochlea Sensory cells for hearing Tympanum Lecture 8 – Evolution of Ear Ossicles

  2. Characteristics of Evolution Demonstrated by Ear Ossicles/Jaw Joint 1. Gradualism  Evolution is often very gradual. We’ll see change from one morphology to a very different one in a finely graded set of steps. 2. Modification of existing structures  For the most part, evolution modifies what’s already there, and when new structures arise (masseter) they split off existing structures. 3. Constraints & Exaptations Organisms are integrated wholes, and changes to a particular system don’t occur in a vacuum; characters are non-independent and functions change over time. Functional Morphology In equilibrium, any force that is being exerted is resisted by an equal and opposite force. 2. Resolve force vectors.

  3. Early Synapsids Chain of transmission: Dentary Angular Articular {JJ}  Quadrate Stapes Inner Ear

  4. Malleus Meckle’s cartilage Development of Ear Ossicles in Didelphis

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