Part Eight - Animals: Form and Function 853

40. Physiology, Homeo­stasis, and Temperature Regulation 854

40.1 Why Must Animals Regulate Their Internal Environments? 855 An internal environment makes complex multicellular animals possible 855 Homeostasis requires physiological regulation 856 Physiological systems are made up of cells, tissues, and organs 857 Organs consist of multiple tissues 859 40.2 How Does Temperature Affect Living Systems? 860 Q10 is a measure of temperature sensitivity 860 Animals can acclimatize to a seasonal temperature change 861 40.3 How Do Animals Alter Their Heat Exchange with the Environment? 861 How do endotherms produce so much heat? 861 Ectotherms and endotherms respond differently to changes in temperature 862 Energy budgets reflect adaptations for regulating body temperature 863 Both ectotherms and endotherms control blood flow to the skin 864 Some fish elevate body temperature by conserving metabolic heat 864 Some ectotherms regulate heat production 865 40.4 How Do Mammals Regulate Their Body Temperatures? 866 Basal metabolic rates are correlated with body size and environmental temperature 866 Endotherms respond to cold by producing heat and reducing heat loss 867 Evaporation of water can dissipate heat, but at a cost 868 The vertebrate thermostat uses feedback information 868 Fever helps the body fight infections 869 Turning down the thermostat 870