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endothermy
endothermy in sharks
9
Biology
Undergraduate 4
07/18/2012

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Term
ectothermic
Definition
body temperature is regulated by the extrenal environment
Term
temperature regulation in sharks
Definition
  • ectothermic
  • heat diffuses through body 10x faster than water
  • gills keep blood temps same as environment
  • heat from metabolism is lost through the gills
Term
endothermy in sharks
Definition
  • keep body temp higher than water
  • 7 lamnids: great white, mako, porbeagle, thresher, salmon sharks
  1. whole body
  2. regional
Term
whole body endothermy
Definition
  • elevated temps due to rete mirable
  • blood supply is rerouted so arterioles are next to veins
  • heat diffuses from veins to arterioles
  • counter current exchange
Term
whole body endothermy circulation
Definition
  • routs blood into two cutaneous artries that run along side of body. a cutaneous vein (along artery) brings blood back to the heart
  • heat transfered from venous blood to arterial blood
  • blood travels into muscles though arterial and venous capillaries
Term
white shark
Definition
  • maintains highest temperatures
  • has been measured with body temps as high as 14 C above ambient water temps
Term
regional endothermy
Definition
  • isolated elevated temps
  • eye, brain, and parts of digestive tract
  • same concept as whole body, but on a smaller scale
Term
advantages of endothermy
Definition
  1. increase muscle power
  2. increases sustained swimming
  3. can invade other habitats
  4. more O2 for working tissues 
  5. keeps brain alert in cold water
  6. increased lactate clearence
  7. increased digestive efficiency
Term
disadvantages of endothermy
Definition
  1. high BMR- energetically costly (10x higher compared to similarly sized ectothermic sharks)
  2. aquire more food
  3. population densities are not as high as for ectothermic species due to competition
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