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Re: Warm-blooded debate



Dinogeorge@aol.com wrote:

> They >can< be proved to be endothermic or whatever. Just >measure their body
> temperatures< and chart your measurements over several diurnal periods.
> 
> If you cannot do this, then you cannot >prove< endo/ecto/whateverothermy, or
> confirm whether your speculations about endo/ecto/whateverothermy are
> correct.

Even if you can do this, what does this really tell you?  Will give you
"proof" one way or the other?  No.  Say you measure the temperature of a
large sauropod.  Its temperature will not change greatly over several
days simply due to its large size.  It will certainly change less than
your average camel and will almost assuredly be as warm.  Is the
sauropod thus proven to be endothermic?  No, at least not in the sense
that most people mean when they talk about endothermy, albeit most
people throw these terms around without any real understanding of what
it means as GSPaul and several others on the list have pointed out
numerous times.  Is the camel ectothermic because it varies its
temperature so much more so than most endotherms and because it receives
so much of its heat from its environment?  I don't think may people
would seriously consider that, it would after still maintain its
temperature in much cooler periods than is often found in its native
lands.
        Another example:  the big leatherback sea turtles.  They maintain their
core body temperatures even in frigid waters at a constant temperature,
right about where we keep ours normally.  Are they then endotherms? 
Wel...depends on your definition of endothermy.  They maintain a
constant temperature like mammals, but their metabolic rate is pretty
sluggish, so they tend to be called whatever the person favors,
ectotherms for the Spotilas of the world and endotherms for the Bakkers
of the world, and partial endotherms for the fencesitters.
        Here's a good curve for you.  There are algal mats growing the the
polar regions that keep the waters underneath them at a balmy 70
degrees.  What are they?  What about bacteria or Monerans which are too
small to effectively regulate their temperature over environment effects
regardless of what they might want.  Are they endotherms if they try and
fail or ectotherms because they can't possibly succeed?
        Ok, I admit the last examples were really stretching the point. 
However, they do illustrate my meaning.  This is of course that body
temperature does not mean diddly squat in regards to whether or not
animals are endothermic, ectothermic, heterothermic, or
whateverthermic.  So measuring their body temperatures will NOT prove
anything.  What is important here is metabolic rate, and most
importantly, basal metabolic rate.  How much energy do they need to
power their system AND how much control do they have of this.  They are
ectotherms if they don't have much control over this, they are
endotherms if they can.  Even this statement is overgeneral and false if
looked at closely.  After all, both ectotherms and endotherms have some
metabolic control done by behavior.  Ectotherms require behavioral
controls more than endotherms however.  Both snakes and mice like to sun
themselves on cold mornings, but which one literally can't get going to
any great degree without it?
        Anyway, metabolism is far more complicated than most people want to
consider, the human need to pigeonhole things.  Nothing in biology will
ever be decided as simply as taking their temperature.

Just for the record, I tend to think that no dinosaur, was average
reptilian level ectothermic, especially the sauropods which in my view
pretty much had to be what most would call endotherms, but I do not
think they had mammalian type or avian level metabolisms.

Joe Daniel