End Show Slide 1 of 19 Copyright Pearson Prentice Hall Biology

End Show Slide 2 of 19 Copyright Pearson Prentice Hall 33-2 Controlling Body Temperature

End Show 33-2 Controlling Body Temperature Slide 3 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis How is the control of body temperature important to vertebrate life?

End Show 33-2 Controlling Body Temperature Slide 4 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis The control of body temperature is important for maintaining homeostasis in vertebrates, particularly in habitats where temperature varies widely with time of day and with season.

End Show 33-2 Controlling Body Temperature Slide 5 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis Vertebrates have many ways to control body temperature. All of these incorporate three important features: a source of heat for the body a way to conserve that heat a method of eliminating excess heat when necessary.

End Show 33-2 Controlling Body Temperature Slide 6 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis What is the difference between ectotherms and endotherms?

End Show 33-2 Controlling Body Temperature Slide 7 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis Ectotherms An ectotherm is an animal whose body temperature is mainly determined by the temperature of the environment. Most reptiles, fishes, and amphibians are ectotherms.

End Show 33-2 Controlling Body Temperature Slide 8 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis Ectotherms have relatively low rates of metabolism when they are resting, and their bodies do not generate much heat. When active, an ectotherm’s muscles generate heat, but that heat is lost to the environment fairly easily.

End Show 33-2 Controlling Body Temperature Slide 9 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis Endotherms An endotherm is an animal whose body temperature is controlled from within. Endotherms have relatively high metabolic rates that generate a significant amount of heat, even when they are resting.

End Show 33-2 Controlling Body Temperature Slide 10 of 19 Copyright Pearson Prentice Hall Body Temperature and Homeostasis Birds and mammals are endotherms.

End Show 33-2 Controlling Body Temperature Slide 11 of 19 Copyright Pearson Prentice Hall Comparing Ectotherms and Endotherms Neither endothermy nor ectothermy is superior. Each strategy has advantages in different environments. Endotherms do well in cool weather because they generate and conserve body heat. However, their high metabolic rate requires a lot of fuel.

End Show 33-2 Controlling Body Temperature Slide 12 of 19 Copyright Pearson Prentice Hall Comparing Ecotherms and Endotherms Ectothermic animals need much less food than similarly sized endotherms. In environments where temperatures stay warm and constant, ectothermy is a more energy-efficient strategy.

End Show 33-2 Controlling Body Temperature Slide 13 of 19 Copyright Pearson Prentice Hall Evolution of Temperature Control The first land vertebrates were ectotherms. Modern reptiles are ectotherms, but some dinosaurs may have been endotherms. Scientists are not sure when endothermy evolved. Endothermy may have developed twice: once in the reptile line leading to birds, and once in the line leading to mammals.

End Show - or - Continue to: Click to Launch: Slide 14 of 19 Copyright Pearson Prentice Hall 33-2

End Show Slide 15 of 19 Copyright Pearson Prentice Hall 33-2 The control of body temperature is important for a.maintaining homeostasis. b.marking a territory. c.eliminating wastes. d.delivering oxygen to cells.

End Show Slide 16 of 19 Copyright Pearson Prentice Hall 33-2 Of the following animals, which can maintain a constant internal temperature? a.shark b.elephant c.desert lizard d.frog

End Show Slide 17 of 19 Copyright Pearson Prentice Hall 33-2 Lizards often bask in the sun because they are a.chordates. b.ectotherms. c.endotherms. d.slow moving.

End Show Slide 18 of 19 Copyright Pearson Prentice Hall 33-2 Animals that do not rely on their surroundings to gain or lose body heat are a.fish. b.endotherms. c.ectotherms. d.amphibians.

End Show Slide 19 of 19 Copyright Pearson Prentice Hall 33-2 One disadvantage endotherms have compared to ectotherms is that a.endotherms cannot stay warm in cold weather. b.far more food is required to maintain constant temperature. c.endotherms are more limited in the habitats they can occupy. d.endotherms cannot live in the ocean where the water is too cold.

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