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Unformatted text preview: Lecture 29: Thermoregulation 40.2 Feedback Control Loops Maintain the Internal Environment in Many Animals Regulating and Conforming- regulator : uses internal control mechanisms to regulate internal change in the face of external fluctuation- conformer : allows its internal condition to conform to external changes in the variable-could conform to environment for some aspects, (ie: temp) but regulate others (ie: solute concentration) Homeostasis-homeostasis: internal balance Mechanisms of Homeostasis-keep aspects to a set point-fluctuations in the variable above or below serve as the stimulus -a receptor or sensor detects stimulus and triggers a response , physiological activity that helps return the variable to the set point Feedback Loops in Homeostasis-homeostasis relies largely on negative feedback: a response that reduces the stimulus-homeostasis reduces but doesnt eliminate changes in the internal environment-additional fluctuation occurs if a variable has a normal range (upper and lower limit) rather than a single set point-positive feed back do not contribute to homeostasis because it triggers mechanisms that amplify rather than diminish the simulus Alterations in Homeostasis- regulated changes : when set points and normal ranges for homeostasis changes- accilimatization : process by which an animal adjusts to changes in its external environment 40.3 Homeostatic Processes for Thermoregulation Involve Form, Function, and Behavior thermoregulation : process by which animals maintain an internal temperature within a tolerable range Endothermy and Ectothermy- endothermic : warmed mostly by heat generated by metabolism (birds and mammals)- ectothermic : gain most of the heat from external sources (amphibians, lizards, snakes, turtles, fish, invert)-endotherms: animals that are mainly endothermicectotherms: mainly ectothermic-endotherms can survive in environments that ectotherms cannot-ectotherms need to consume much less food than endotherms of equal size and ecotherms can usually tolerate larger fluctuations in their internal temperatures-many ectotherms adjust temperature by behavioral means (seeking out shade) Variation in Body Temperature- poikilotherm : animal whose body temperature varies with its environment - homeotherm : constant body temperature-no fixed relationship between the source of heat and the stability of body temperature (ie: many ectothermic fish inhabit waters with stable temperatures and their temps vary less than that of endotherms) Balancing Heat Loss and Gain-exchanges heat by 4 physical processes 1- radiation : emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between objects that are not in direct contact (lizard absorbs heat radiating from sun) 2- evaporation : removal of heat from the surface of a liquid that is losing some of its molecules as gas. Evaporation of water from a lizards moist surfaces that are exposed to the environment-strong cooling effect...
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- Fall '10