Re: Re: Warm/Cool/Cold blood

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>Could someone explain to an ignorant lay person what "gigantothermy" is?
>(Sounds like something Godzilla would beat up in a Japanese movie :)

Gojira tai Gigantosurumi?  Hmm, maybe...

Anyway, gigantothermy (sometimes called inertial homeothermy) is the ability
to maintain constant, relatively "high" blood temperature du to size alone,
rather than some internal cellular mechanism.  This is due to basic
principles of geometry. If you double an objects length, its surface area
goes up by squares, and the volume by cubes.  Thus, the larger an animal
gets, the lower its surface-to-volume ratio becomes.  Because this ratio
goes down, it becomes relatively more difficult to dump internal heat
generated by any mechanism (digestion, motor muscles, etc.).  The heat is
essentially "trapped" in the body, reducing or eliminating the dependance of
the animal on external heat sources.  Thus, a gigantotherm can have a
metabolism based on internal heat sources, but without requiring the greater
amounts of food that true endotherms need.

Hope that helps.

>
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>Thanks
>
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Thomas R. HOLTZ
Vertebrate Paleontologist, Dept. of Geology
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Phone:301-405-4084