Chapter 10 Outline

Temperature and Heat

  • BOX 10.1 Global Warming

Heat Transfer between Animals and Their Environments

  • Conduction and convection: Convection is intrinsically faster
  • Evaporation: The change of water from liquid to gas carries much heat away
  • Thermal radiation permits widely spaced objects to exchange heat at the speed of light

Poikilothermy (Ectothermy)

  • Poikilotherms often exert behavioral control over their body temperatures
  • Poikilotherms must be able to function over a range of body temperatures
  • Poikilotherms respond physiologically to their environments in all three major time frames
  • Acute responses: Metabolic rate is an approximately exponential function of body temperature
  • Chronic responses: Acclimation often blunts metabolic responses to temperature
  • The rate–temperature relations and thermal limits of individuals: Ecological decline occurs at milder temperatures than the temperatures that are lethal
  • Evolutionary changes: Species are often specialized to live at their respective body temperatures
  • Temperature and heat matter because they affect the functional states of molecules, as well as the rates of processes
  • Poikilotherms threatened with freezing: They may survive by preventing freezing or by tolerating it
  • BOX 10.2 Evolutionary Genomics: The Genes  for Antifreeze Proteins Are Descended from  Genes for Other Functional Proteins

Homeothermy in Mammals and Birds

  • BOX 10.3 Thermoregulatory Control, Fever, and Behavioral Fever
  • Metabolic rate rises in cold and hot environments because of the costs of homeothermy
  • The shape of the metabolism–temperature curve depends on fundamental heat-exchange principles
  • Homeothermy is metabolically expensive
  • Insulation is modulated by adjustments of the pelage or plumage, blood flow, and posture
  • Heat production is increased below thermoneutrality by shivering and nonshivering thermogenesis
  • Regional heterothermy: In cold environments, allowing some tissues to cool can have advantages
  • Countercurrent heat exchange permits selective restriction of heat flow to appendages
  • Mammals and birds in hot environments: Their first lines of defense are often not evaporative
  • Active evaporative cooling is the ultimate line of defense against overheating
  • Mammals and birds acclimatize to winter and summer
  • Evolutionary changes: Species are often specialized to live in their respective climates
  • Mammals and birds sometimes escape the demands of homeothermy by hibernation, torpor, or related processes
  • Human thermoregulation

Warm-Bodied Fish

Endothermy and Homeothermy in Insects

  • The insects that thermoregulate during flight require certain flight-muscle temperatures to fly
  • Solitary insects employ diverse mechanisms of thermoregulation
  • Colonies of social bees and wasps often display sophisticated thermoregulation

Coda

  • BOX 10.4 Warm Flowers
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