BIOL 1902 Lecture : Wk 4.doc
29 Mar 2012
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Problem: below freezing = subzero temperatures make water freeze it. If water in cells of living animal, it freezes and expands and cells burst and. Two different ways animals generate their internal temperatures: Ectotherms: largely controlled by the temperature of the external. Two main solutions to the cold problem: escape the cold either by leaving = migration) or by going dormant, stay active and deal with the subzero temperatures. Endotherms that remain active stay warm by: increasing body insulation to trap air and body heat. Mammals: on the outside of their bodies grow extra hair - two coats: outer coat gets thicker - longer coarser guard hairs, put on long johns = woolly underfur; example: foxes. Birds: increase feather mass in two layers: contour feathers outside, down feathers underneath contour. Some increase total feather mass by 50% examples: goldfinches. Birds also trap even more body heat when fluff up their feathers.
