Re: Lizard engines and rat engines

On Fri, 8 Jul 2005 08:21:36 -0400 (EDT), "g" <gillawton@xxxxxxxxxxxxx>
wrote:

>
>"dkomo" <dkomo871@xxxxxxxxxxx> wrote in message
>news:dak4st$eco$1@xxxxxxxxxxxxxxxxxxxxxx
>>g wrote:
>>
>
>>
>> And it jars me to see someone make a statement like this, which to me is
>> akin to ignorance. Elephants have big ears for very *specific* reasons.
>
>???
>> Being so large and living under the blistering sun of the African
>> savannah, African elephants have severe problems with potential
>> overheating. Their ears are an important way of dissipating much of
>> this body heat.
>>
>Let me see if I'm getting this right. If the why of it is that larger
>animals
>have big ears because of their size and the temperature of the climate
>where they live, then giraffes and ostriches have ears that are not as large
>because they are smaller and live in a cooler climate. And Indian elephants
>are smaller and live in a cooler climate, which explains why theirs are
>much smaller. And jackals have larger ears for their body size than
>rinoceroses because they are larger than rinos and live in a hotter climate.
>
>Now that's ...
>
>Uh oh, wait...
>
>No that's not right...
>
>Dang ! For a minute there I almost thought I got it.
>

There is an extensive discussion of this same topic over in
talk.origins, including a rather long post by me about the
comparative and environmental physiology of temperature regulation.
There are a number of advantages and disadvantages to homeothermy
(maintaining a constant body temperature). As is always the case in
biology, there are animals that "choose" one strategy and animals that
choose another. Furthermore, there are many physiological tricks
animals can use to maintain regulate their body temperature. Large
animals tend to have a problem with overheating, the larger the animal
the worse the problem. Large "chunky" animals have a much worse
problem than animals with long, thin elongated body regions,
especially if those regions are not covered in thick, heavy skin and
fur or feathers. Having large ears is just one trick to cool off.
Few organisms use that technique, elephants and rabbits being the two
most common examples. Other organisms have different tricks.

Note: True, rabbits are not particularly large. Nevertheless, they
found that trick to be useful. Evolutionary tricks, like all weird
adaptations, are sporadic in distribution demonstrating independent
evolutionary origin.




.

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