Chapter 25 - Chapter25LectureOutline Introduction...

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Chapter 25 Lecture Outline Introduction Let Sleeping Bears Lie A. Animals survive fluctuations in the external environment because they have internal, homeostatic controls. 1. Thermoregulation is the control of internal temperature within narrow limits. 2. Osmoregulation is control of the concentration of water and dissolved solutes. 3. Excretion is the disposal of nitrogen-containing wastes. B. Animals vary in the ways they control body temperature. 1. The concept of cold-blooded and warm-blooded animals is better replaced by the terms ectothermic and endothermic because these terms focus on the processes animals use to control body heat. 2. Endotherms derive most of their body heat from their own metabolism. This group includes mammals, birds, some reptiles and fish. 3. Ectotherms warm themselves by absorbing heat from the surrounding environment. This group includes most invertebrates, fishes, reptiles, amphibians, and other birds. 4. Some animals hibernate during the winter, and their body temperature may drop as much as 30 8 C. 5. Bears do not hibernate but instead go dormant and maintain body temperatures only a few degrees below their normal temperature. 6. Bears have several adaptations that allow a state of dormancy such as: a. Change in eating habits prior to dormancy to increase weight and store the excess energy as fat. b. Reduced blood flow to the extremities. c. Fetal position during dormant sleep. d. Dense fur and fat for excellent insulation. e. No eating, expelling waste, or urinating during the dormant state. C. This chapter covers the homeostatic control mechanisms of thermoregulation, osmoregulation, and excretion. I. Thermoregulation Module 25.1 Heat is gained or lost in four ways. A. An animal can exchange heat with the environment in four ways; any or all can happen at the same time (Figure 25.1). 1. Conduction is the direct transfer of heat between surfaces in contact. 2. Convection is the transfer of heat from air or liquid moving past a surface. 3. Radiation, the emission of electromagnetic energy, can transfer heat between two bodies not in contact.
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4. Evaporative cooling is the loss of heat from a surface of liquid as the liquid is transformed into gas. B. In each mechanism, heat is conducted from an area of higher temperature to one of lower temperature. Module 25.2 Thermoregulation involves adaptations that balance heat gain and loss. Preview: Thermoreceptors (Module 29.3). A. Each species has an optimal internal temperature range. There are five categories of thermoregulation in which most animals can be placed. B. Metabolic heat production: A change in the metabolic rate induced by altered hormonal levels is common among mammals and birds during cold weather. Movement and shivering are methods used to increase internal temperatures (Figure 25.2A). C.
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This note was uploaded on 03/10/2011 for the course BIOL 10 taught by Professor Kite during the Spring '11 term at Laney College.

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Chapter 25 - Chapter25LectureOutline Introduction...

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