Nov 29 - Animals Lecture #21 - Aves (Birds)1

Upstroke open barbules linking adjacent barbs by

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Upstroke = open Barbules, linking adjacent barbs by overlapping hooks Vanes separate the 2 sides o If barbules detach, can be easily rehook by preening (running beak parallel to axis of barb) Feathers are homologous to reptile scales Feathers develop from an epidermal … Rather than flattening they role into a cylinder and sink into the follicle from which it grows Pigments added during growth then (1) shaft and barbs keratinize for strength & (2) protective sheath splits open Feathers are dead material like nails or hair o Have to shed feathers Symmetrical shedding, new ones will grow back Only when those new ones that grew, will old ones continue to shed Shedding (molting) is a highly ordered process o Periodic Down Feathers (insulation) o Used in jackets since it keeps heat o Soft turfs hidden beneath contour feathers o Don’t normally see them o Sot because barbules lack hooks o Abundance life-style/-stage dependent of bird Numerous on breast & abdomen of water birds prime region for heat displacement cover entire body of some juvenile birds (penguins in early stage or chick in early stages of life) To help regulate temperature Substance Conductivity * Copper 0.99 Glass 0.0025 Water 0.0014 Sheep wool Down feather Still air 0.000025 0.00016 – very effective insulator Anything that trap airs is good insulator Filoplumes (sensory) o Fine hair like feathers with a few short barbs at end o Usually not exposed above contour feathers o Nobody entirely sure what they do o Numerous nerve endings at base Communicate information about position and movement of contour feathers Most likely sensory functions EVOLUTION
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Dromeosaur – dinosaur that is more advanced than thestle therapod (t rex) Archaeoptyres Modern bird o
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