Chapter 40 Principles of Animal Form and FunctionHomeostasis- Response to environment varieso Conformer: internal condition change as the external environment changes (40.7)o Regulators: keep internal condition constant even if the environment changeso Sometimes animals do both: shore crab regulates salt- Homeostasis: maintaining most internal conditions within a narrow range in a changing environment- Maintained by negative feedback mechanisms (40.8)- Ex: glucose homeostasis (41.20)Thermoregulation- How bodies lose and get heato Endotherms: heated mostly by metabolism, regulation is physiological and behavioral, mammals and birds do this with a few exceptionso Ectotherms: heated by the environment, regulation is behavioral (40.13), almost all invertebrates, fish and non-bird reptileso Some are partly endotherms: moth ex in booko Some are ectotherms: python voluntarily increasing body temperature during nesting- All animals exchange heat with the environment (40.11)o Radiation: light energyo Evaporation: need a moist surfaceo Conduction: direct contacto Convection: movement through a fluid (air is a fluid)- Adaptations to conserve heato Insulation Feathers and fur trap air (best insulator) Fato Compact body shape: decreases surface area to volume ratioo Circulatory change Vasoconstriction: reduce blood flow at skin surface in extremities to conserve heat for the core body Countercurrent heat exchanges (40.12): reduces heat loss at extremities- Adaptations that lose heato Evaporative heat loss: sweating, panting and bathingo Loss by radiation: increase surface area and vasodilation, elongated limbs or ears- Human physiological control (40.16)o Sensor of heat: hypothalamuso Response: vasoconstriction or dilation; sweating or shiveringo Loss of thermoregulation Too hot: heat exhaustion, leads to heat stroke Too cold: hypothermiao Fever: rise in “set point” (to fight pathogens?), body generates more
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