13_Thermoreg_Osmoreg_&_Excretion

13_Thermoreg_Osmoreg_&_Excretion - Controlling the...

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1 Controlling the Internal Environment © 2006: D. Julian Home Page Regulating vs. conforming Conformers : internal condition follows the external condition. Regulators : internal condition independent of external condition. Most animals are at least partial regulators for a variety of internal conditions (e.g., pH, Po 2 , osmolarity, electrolyte concentrations, and in some cases temperature). However, even strict regulators can maintain the condition only over a limited range. © 2006: D. Julian Tolerance limits An environmental condition outside the tolerance limit will eventually lead to death of the animal. © 2006: D. Julian
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2 Thermoregulation © 2006: D. Julian Thermoregulation Thermoregulation is the maintenance of body temperature within a range that allows cells to operate efficiently. Effect of temperature on activity of representative enzyme 0 25 50 75 100 25 30 35 40 45 50 temperature percent of maximal activity All enzymes have a temperature range over which their activity is maximal. © 2006: D. Julian Ectotherms and endotherms Campbel , Fig. 44.04 Ectothermy : body is warmed mainly by absorbing heat from the environment. (Most invertebrates, fishes, amphibians and reptiles) Endothermy : body is warmed mainly from its own metabolism. (Mammals, birds, some fishes and many insects) © 2006: D. Julian
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3 Regulation of heat exchange by ectotherms Some ectotherms live in environments with stable ambient temperatures and so have stable body temperatures (e.g., fish at the bottom of the ocean, insects and other invertebrates in deep caves, and internal parasites of mammals and birds). Other ectotherms can achieve limited thermoregulation primarily by behavioral responses, such as basking in the sun, moving to warmer or colder locations, and altering blood flow to skin. © 2006: D. Julian “Fever” in ectotherms Iguanas infected with bacteria use behavioral thermoregulation to increase their body temperature above normal. Eckert, Fig. 16-38 When researchers prevented the infected iguanas from causing a behavioral fever, their mortality rate increased. © 2006: D. Julian Endothermy in insects Campbel , Fig. 44.5 Many insects (primarily larger flying insects) produce metabolic heat, thereby allowing flight during cold winter months. © 2006: D. Julian
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4 Endothermy in large, active fishes Some tunas and sharks can maintain a core body temperature 10°C higher than the ambient seawater. The
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13_Thermoreg_Osmoreg_&_Excretion - Controlling the...

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