INTEGBI N33 Lecture Notes - Lecture 11: Eardrum, Middle Ear, Theria
31 Mar 2018
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Document Summary
Having 1 bone instead of 3 in jaw hinge makes mammals have stronger, more precise bite, which is good for animals with only 1 set of teeth throughout adulthood. Early mammals identified by 3 middle ear bones because they preserve unlike mammary glands. All tetrapods have one bone in middle ear (chamber on other side of ear drum) Two bones part of ancestral amniote jaw shrank down to become other two middle ear bones. Mammals (as well as therapsids) had specialized teeth. Incisors - large teeth at front center of mouth. Canines - sharp teeth at front of mouth. Cheek teeth - flat premolars and molars at back of mouth. Early mammals are small because endothermy is metabolically demanding and being small means they don"t need to eat as much food. Were insectivorous and nocturnal (active out at night) Less energy investment for mothers;easy to get pregnant again if have to throw baby away.
