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TORPOR

|| Outline || Thermoregulation || Torpor || Water Conservation || Size Matters ||

 

DEFINITION: lowering body temperature (TB) below activity temperature.kangaroo rat in torpor

CONCEPT: lowering TB decreases rate of body function (metabolism) due to Van’t Hoff’s Rule – for every 10 degrees C drop in temperature, rates of biochemical reactions (metabolism) slow by half.

TYPES:

  • SEASONAL TORPOR: more than one day
    • In response to coldHIBERNATION
      • Deep: body temperature follows outside temp. to close to freezing.
      • Shallow: body temperature drops only somewhat.
    • In response to heat/drynessSEASONAL ESTIVATION
  • DAILY TORPOR: less than 24 hours
    • In response to coldDAILY TORPOR IN RESPONSE TO COLD
    • In response to heat/drynessDAILY ESTIVATION

ADAPTIVE VALUES:

  • Saves Energy
    • By decreasing temperature difference between body and outside, the rate of heat loss is lowered, thus reducing energy expenditure to replace the lost heat energy.
    • By slowing metabolism, all tissues use less energy.
  • Saves Water
    • By decreasing cutaneous water loss (lower body temperature means lower rate of evaporation out external surface).
    • By decreasing excretory water loss (lower metabolism generates less urine and feces thus less water lost).
    • By decreasing respiratory water loss (fewer breaths per minute and less water lost per breath). Lower metabolism requires slower breathing rate and lower TB means exhaled air is cooler, thus contains less water.