Chapter 44 Notes - Chapter 44 Notes Homeostasis-the ability...

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Chapter 44 Notes Homeostasis -the ability of animals to regulate their internal environment. Thermoregulation -how animals maintain internal temperature within a tolerable range. Osmoregulation -how animals regulate solute balance and the gain or loss of water. Excretion -how animals get rid of the nitrogen-containing waste products of metabolism. An Overview of Homeostasis Regulating and conforming are the two extremes in how animals cope with environmental fluctuations. Animal said to be regulator if it uses mechanisms in homeostasis to moderate internal change in the face of external fluctuations. In contrast, animals that live in relatively stable environments are known as conformers. Conformers allow some conditions within their bodies to vary with certain external changes. Conforming and regulating= extremes and no organisms are perfect regulators or conformers. A species may conform in one situation and regulate in another. Regulation requires expenditure of energy. Homeostasis balances an animal’s gain versus losses for energy and materials. Animals=open systems (must exchange energy/materials with environments). Rates of gains and losses must be closely matched over time. Animal’s inputs only exceed outputs when there’s a net increase in organic matter due to growth or reproduction. Homeostasis can be viewed as set of budgets of gains/losses. Regulation of Body Temperature Biochemical and physiological processes are very sensitive to changes in temperature. Rates of most enzyme- mediated reactions increase by factors of 2-3 for every 10 ° C increase. This is known as the Q10 Effect. These thermal effects influence animal function and performance. Four physical processes account for heat gain or loss. An organism exchanges heat by four physical processes called conduction, convection, radiation, and evaporation. Conduction is the direct transfer of heat between molecules of objects in direct contact with each other. Heat is always conducted from an object of higher temperature to one of lower temperature. Convection is the transfer of heat by the movement air or liquid past a surface. Example is when a breeze contributes to heat loss from the surface of an animal with dry skin. The “wind-chill factor” compounds the harshness of low temperatures by increasing the rate of heat transfer. Radiation is the emission of electromagnetic waves by all objects warmer than absolute zero. It can transfer heat between objects that aren’t in direct contact. Evaporation is the removal of heat from the surface of liquid that’s losing some of its molecules as gas. Ectotherms have body temperatures close to environmental temperature; endotherms can use metabolic heat to keep body temperature warmer than their surroundings. An
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This note was uploaded on 05/31/2011 for the course BIO 120 taught by Professor Throgerson during the Winter '08 term at Grand Valley State University.

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Chapter 44 Notes - Chapter 44 Notes Homeostasis-the ability...

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