thermoregulation

• Endotherms are warm blooded - heat is generated by internal metabolic activity 
• Ectotherms are cold blooded - heat is obtained by external heat sources. 
• ectotherms are more vulnerable when temperatures are low because they lack energy to escape danger. 
• Ectotherms control body temperature by exposing themselves to the sun, taking shelter and gaining warmth from ground or making adjustments when temperature is too high. 
• Endotherms use behaviours to control body temperature and have physiological features to maintain core temperatures. 
• Endotherm thermoregulation:

  • Vasodilation 
  • Sweating - latent heat of vaporisation 
  • Panting in animals with fur - evaporation from tongues
  • Lowering of body hair
  • Behaviour - sheltering in shade 
• Endotherm thermoregulation (cold):

  • Vasoconstriction 
  • Shivering 
  • Piloerection - hair 
  • Increased metabolic rate - increasing respiration 
  • Decreased sweating 
  • Behaviour - sheltering, basking in sun 
• Vasoconstriction:

  • Smooth muscle contraction of arterioles decrease the size of the lumen. Less blood flows close to the surface of skin - blood flows through vessels deeper in epidermis. Less heat is lost by radiation. Nerve impulses from the hypothalamus trigger vasoconstriction. 
• Vasodilation:

  • Smooth muscle contraction of arterioles increase the size of the lumen. More blood flows close to the skin surface and more heat is lost by radiation. 
• Blood has a small temperature range because water has a high specific heat capacity. 
• Endotherm advantages:

  • Wide range of habitats and day times 
• Endotherm disadvantage:

  • Use more energy in thermoregulation 
  • Eat more frequently 

   
• Ectotherm advantage:

  • losses less energy in thermoregulation 
  • Less need to eat 
• Ectotherm disadvantage:

  • Limited habitats 
  • More vulnerable at certain day times and seasons.