Chapter 40 Principles of Animal Form and Function Homeostasis Response to environment varies o Conformer internal condition change as the external environment changes 40 7 o Regulators keep internal condition constant even if the environment changes o 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 heat o Endotherms heated mostly by metabolism regulation is physiological and behavioral mammals and birds do this with a few exceptions o Ectotherms heated by the environment regulation is behavioral 40 13 almost all invertebrates fish and non bird reptiles o Some are partly endotherms moth ex in book o Some are ectotherms python voluntarily increasing body temperature during nesting All animals exchange heat with the environment 40 11 o Radiation light energy o Evaporation need a moist surface o Conduction direct contact o Convection movement through a fluid air is a fluid Adaptations to conserve heat o Insulation Feathers and fur trap air best insulator Fat o Compact body shape decreases surface area to volume ratio o 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 heat o Evaporative heat loss sweating panting and bathing o Loss by radiation increase surface area and vasodilation elongated limbs or ears Human physiological control 40 16 o Sensor of heat hypothalamus o Response vasoconstriction or dilation sweating or shivering o Loss of thermoregulation Too hot heat exhaustion leads to heat stroke Too cold hypothermia o Fever rise in set point to fight pathogens body generates more heat
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