LECTURE 11: Temperature Regulation

• Thermoregulation is a homeostatic process that maintains an internal

  body temperature despite changes in external conditions.
• Radiation - heat transfer through electromagnetic waves
• Convection - heat transfer through fluid (air or liquid)
• Conduction - heat transfer between two objects by direct contact
• Evaporation - heat transfer through change of water from liquid to gas
• Animals have to maintain an internal environment for normal cellular functions
• Poikilothermy - a state of variable body temperature as observed in amphibians, reptiles and fishes
• Homeothermy - a state of constant body temperature as observed in mammals and birds
• Poikilothermy and Homeothermy - terms used by zoologists
• Ectothermy and Endothermy - terms preferred by physiologists
• Ectothermy - a state of variable body temperature as observed in amphibians, reptiles and fishes
• Endothermy - a state of constant body temperature as observed in mammals and birds
• Behavioural adjustments

  ๏ used by some ectotherms to regulate body temperature

  ✓ E.g. Some seek environment where the temperature is favourable to them
• Metabolic adjustments

  • most ectotherms can adjust their metabolic rate to the existing temperature

  • allows intensity of their metabolism to stay the same in varying environmental temperature
• Endotherms maintain constant body temperature through balance between heat production and heat loss
• heat production - can be through oxidation of food (catabolism), basal cellular metabolism, muscular contraction
• heat loss - can be through conduction, convection, evaporation, and radiation
• mainly live burrowed in the ground (fossorial)
• active at night (nocturnal)
• Harris’s antelope squirrel - both fossorial and nocturnal
• Desert coyote

  ✓stays out of the sun during the day by burrowing in the ground

  ✓comes out to huntfood at night
• Arabian sand gazelle

  • shrinks its liver and heart so it will breathe less often
• glossy fur - an excellent insulator as it reflects sunlight
• hump at the back - has fat reserves (e.g. in camels, bison)
• concentrating urine and releasing dry feces as a means of conserving water (e.g. in elands)
• Daily torpor - adaptive hypothermia
• hibernation - prolonged and controlled state of dormancy
• Bears, raccoons, and opossums enter a prolonged sleep called torpor, which is not a true hibernation