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Skin

Skin. Leslie Muller Feb 25 th – EEB 413. Evolution.  endothermy Req : good external insulation of body Result: hair & feathers Hair follicles Located in dermis Humans have just as much hair as apes Associated with complex sensory receptors and sebaceous glands Cat & mouse whiskers

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Skin

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  1. Skin Leslie Muller Feb 25th– EEB 413

  2. Evolution •  endothermy • Req: good external insulation of body • Result: hair & feathers • Hair follicles • Located in dermis • Humans have just as much hair as apes • Associated with complex sensory receptors and sebaceous glands • Cat & mouse whiskers • specialized hairs called vibrissae • Follicles dense with nerve receptos • Send information to animal’s brain about what it is touching • Human solution: sensitive hands • Piloerection • Raising of hairs • Occurs when an animal is angry, excited, scared • Body hair becomes less obvious in humans  communicate critical emotion quickly through universally recognized facial expressions Example of piloerection by chimpanzee

  3. Evolution,cont. • Reptilian lineage  birds • Scales  feathers • Adaptations: protection against desiccation, abrasion, heat loss • The move to dry land • Variable surfaces and textures of vegetation • Adaptation: claws – specialized modification of skin at end of appendages to ensure secure footing for different angles and textures • Some amphibians, most reptiles, all birds • Mammals: claws  nails or hooves • Nails • Distinguishing feature of primates • Development related to heightened sensitivity on pads at ends of finger and toes

  4. Evolution, cont • Importance of sweat  hairlessness • In hot environment, a naked and actively-sweating body is the best way to maintain body temperature and keep head cool

  5. Ecology • Mummification • Good: body either dries out or freeze-dries before all of the skin has decomposed • Ex: Mummies of the Silk Road – fair complexion, European features  These residents of Xinjiang Province migrated from Caucus region of Western Asia • Better: fast-frozen – body completely frozen immediately after death • Ex: ‘Dima’ - Late Pleistocene baby mammoth • ‘Otzi’ – Neolithic iceman found in 1991 between Italy and Austria • Best: peat bog – cold, acidic water inhibits growth of microorganisms that potentially cause decay • Ex: ‘Bog people’ of England, Denmark, Germany

  6. Physiology • Input • Precise sense of touch crucial to primates • ALL primates use fingers & toes to pick appropriate foods (integration) and communicate (output) through grooming or other reassuring gestures

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