BIOL 1902 Lecture 4: October 3 - Lecture 4.docx
Document Summary
Problem with subzero temperatures: water turns to ice and expands. Animals are full of water, so this can kill them. Ectotherms most of their heat is derived from the outside environment. Endotherms control their own body temperature, able to generate heat internally. Main solutions to the cold problem: escape the cold either by leaving = migration or by going dormant, for animals that stay active and deal with the subzero temperatures: Dress for the occasion: mammals stay warn by growing more hair for the winter guard hairs; however hair is more complex than that. Mammals have dense underfur that traps body heat: birds grow bulkier feathers, contour feathers on the outside and down feathers underneath. Animals can also add extra layers on the inside. Two types of fats: subcutaneous fat for insulation = warmth, brown fat is a high efficiency fuel (mammals, not birds)
