notes-2-22 - ZOL 328 notes 2/22 CLASS MAMMALIA Arose from...

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ZOL 328 notes 2/22 CLASS MAMMALIA Arose from synapsid reptiles (birds-diapsid) Co-existed with large reptiles Small Probably nocturnal Well developed nasal passages, acute hearing Endothermic perhaps advantage when temp drops at night ~65 mya, asteroid off yucatan peninsula – largest impact structure known - Demise of dinosaurs? Mammals expanded geographically and into niches Characters (synapomorhies) 1. Hair Insulation Coloration- protection by crypsis (quills) Sensory function Sensory hairs- vibrissae (whiskers) Associated with hair: sebaceous and sweat glands Condition hair and skin Evaporative water loss for cooling 2. Mammary glands Embryologically like sweat glands – probably derived from them 3. RBCs lack nucleus (except in monotremes) Sacs of hemoglobin 4. Most retain young in uterus for at least part of development, except monotremes 5. Endothermic (like birds) Skeletal Specializations 6. Lower jaw composed of dentary 7. Jaw articulation- dentary and squamosal Quadrate articular bones freed – join in stapes in transmittin sound from tymp. Membrane – sensory app 8. 3 middle ear bones that conduct sound Quadrate- incus
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This note was uploaded on 03/27/2010 for the course ZOL 328 taught by Professor Hill during the Spring '08 term at Michigan State University.

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notes-2-22 - ZOL 328 notes 2/22 CLASS MAMMALIA Arose from...

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