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November 20.doc

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Biology (Sci)
BIOL 111

Bio 111 Alanna Houston November 20, 2007 - Look at amniote phylogeny for lab The Ancestor of Birds: - a dinosaur - lived on land - walked with legs under body (quadrapedal or bipedal) - ancestor to birds was probably a theropod dinosaur o bipedal, 3 hind toes o carnivorous o 4-chambered heart o similar lungs o endothermic o feathered o hollow bones o parental care of eggs and juveniles Archaeopteryx - ancient wing - oldest bird fossil found - ~150 mya (Jurassic) - 11 fossil specimens - crow-sized - feathers (avian) - wings (avian) - teeth (non-avian) - bony tail (non-avian) - not a direct ancestor of common birds Birds (Aves) - ~9600 species - amniotes - endothermic - 4-chambered heart - feathers - diverse beaks o diverse diets - most fly - High amount of parental care o Most build nests o Incubate eggs o Feed juveniles Body Temperature Control - thermoregulation - source of body heat o ectotherms  absorb external heat Bio 111 Alanna Houston  body temperature change with water  MR increase with increasing temperature o endotherms  generate heat internally through metabolic processes  leaky ion channels may have led to the evolution of endothermy  maintain relatively constant body temperature  MR increases when temperatures are outside of the optimal range Thermoregulation - mechanisms to maintain optimal body temperature - physiological: o too hot: increase blood flow to periphery, sweating, panting o Too cold: decrease blood flow to periphery, shiver - behavioural o orientation relative to heat source, basking, huddling o moving locations throughout day - physical o insulation (fur, feathers, fat) o surface area: volume Physiological Thermoregulation - Example: counter-current heat exchanger o Fast, pelagic fish (tunas, sharks) o Heat generated by swim muscles o Heat retained in muscles o - Example: human thermostat o In hypothalamus o Negative feedback system o If temperature is too high: Bio 111 Alanna Houston  Sweat – evaporative cooling o If temperature is too low:  Shiver – generate metabolic heat o A fever is an adaptive response to pathogens Behavioural Thermoregulation - orient body to/away from radiation source o maximize or minimize infrared absorption - Vary degree of contact with substrate o Direct conduction of heat to and from body - A lizard maintains its body temperature between upper and lower limits by moving between hot and cold microhabitats
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