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Lecture 6

BIOL 1902 Lecture Notes - Lecture 6: Pennaceous Feather, Subcutaneous Tissue, Fluffing

Course Code
BIOL 1902
Michael Runtz

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Lecture 6 Natural History
Second challenge that all living things face
Environmental Stress
ECTOTHERMS (insects)
The internal body temperature is controlled by the external temperature around them
- The environment controls their body temperatures
ENDOTHERMS (mammals/ birds)
Internal body temperature is mostly controlled by themselves
1. Add layers externally
- Mammals grow more hair
o guard hairs grow longer and thicker
o dense underfur traps the heat
- Birds grow more and bulkier feathers
o contour feathers on outside
o Down underneath
2. Add layers internally
- Mammals have two types of fat
o subcutaneous fat a layer of fat just under skin for insulation (white)
o internal brown fat that generates more heat internally (internal) (only mammals)
- Birds only have one fat + generate heat by shivering
o Add subcutaneous fat for fuel NOT insulation (burning the fat = heat)
o Shivering is an important means of thermogenesis
o Fluffing feathers help retain body heat
Whenever heat is generated by the body it is called thermogenesis
3. Coloration
- Pale colours retain body heat better
o Most northern owl in the world Snowy Owl (white)
o Most northern grouse in the world ptarmigan (white)
o Most northern fox in the world artic fox (white)
Black colors are good for absorbing but release heat quite quickly
Snowshoe Hares gain 27% in the coat’s insulation value by being white
Gloger’s rule animals in the north tend to be paler in coloration then animals in the south and
that’s a means of staying warmed (exception but general rule)
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