RT water and heat retention in theory and life

[Д.А, <lantan@list.ru>]

There was discussion about respiratory turbinates some years ago, but
it apparently missed (AFAIK) some very important points.

Here's some theory to start with.

For water vapour to condense, its pressure should be higher that
*saturated vapour pressure* at given point of temperation.
Depencity is close to being exponential. So for water retention
an organism needs to have RTs to be significantly cooler than air
(does it?) Ergo, at ambient low temperatures (like -5 deg C)
there is no way to stop water loss, as organism can't let its RTs
to cool for so low temperatures. It is well known that many mammals
do quite fine at such temperatures.

Take a glass and bring it to your nose. Exhausted air will produce
consended water drops on glass surface. (After doing that several
times glass, of course, will be heaten up and you water won't condense
on it). Well, how is it? This does mean that exhausted air has much higher
vapour pressure than saturated pressure at temperature of ambient air.
This is slightly inconsistent with Ruben's theory. Seems like mammals
still lose water even when ambient T is about 22 deg C.

Water production. Dinosaurs probably did not eat dry food. About 60%
by mass (or even more) of their food was water. An animal needs to
breathe if, and only if, it has metabolized some of its food and needs
to remove carbon dioxide and add oxygen to its blood. Dry matter
(carbohydrates, protein, fat) produces water, carbon dioxide and
(in case of protein) nitrogen in some form (uric acid, ammonium, etc.)
What happens with water? The water (which was 60%) is now free.
Animal does not need to metabolise it, so it is available for other
uses.

In typical mammals: small amount of water goes with fecal masses.
Through skin and lungs and most goes with urination.
Note that water expenses due to nitrogen excretion are not linked
to temperature in any way.

Why most animals need so much water? Because water is cheap in most
environments, that is.

Well compare two almost identical animals, one endothermic and other
one ectothermic at same temperature, about 36 deg C. Ectotherms
typically have metabolic speed of about 1/4 of endotherm of same size
(provided that ectotherm is as warm as endotherm).
An ectotherm has major disadvantange that water loss through skin
is same in both animals (as T is the same), but relative to metabolism
water loss is a lot higher in ectotherm.
Reptiles cope with that having thicker skin than mammals.
So they have water retention.

When endotherm spends water to cool itself, it is not significant if
water is lost though respiration or other sweating.

At extreme high metabolic rates RTs shrink in size in order to allow
higher respiration rates (ah well, why extreme, even in case of human
running at 3 m/s). IRONIC: RTs CANNOT SERVE AS WATER RETENTION
ORGANS WHEN RESPIRATION RATES ARE HIGH! But is it true.
Unfortunately, air is not filtered as well in this case...
Organism is _a lot more_ vunvenerable to poisons and infections
present in air. [The nature's wisdom: she knew that we mammals would
live up to creation of civilization and pollution of environment with
various chemicals, and gave us RTs to protect us. She knew dinosaurs
woudn't, so dinosaurs do not have them. Hehe. ]

Well... someone linked that RTs help heat retention and through that
promote endothermy.
I did a lot of physical activity (like running distances like 5--40 km)
at temperatures as low as -25 deg C and as high as +30 deg C.
At temperatures at -25 deg C, human can overheat if wearing
heavy clothes. THIS MEANS THAT BODY GAINS MORE HEAT THROUGH METABOLISM
THAN IT LOSES THROUGH RESPIRATION. (UNLESS YOU'RE AMPHIBIAN AND BREATHE
THROUGH YOUR SKIN). Most mammals have sweat glands.
If respiratory heat loss is not overhelming at
T diffs (lung-ambient) about 50 deg C, why should it
be for reptile for which T diff is hardly over 3?

Mammals are plainly not designed to save water. Rather reverse.
And it is very likely that early dinosaurs have been quite adapted to
dry climates (Pangea).
Also, when endotherm spends water to cool itself, it is not significant if
water is lost though respiration or other sweating.

When endotherm spends water to cool itself, it is not significant if
water is lost though respiration or other sweating.

WELL... LET'S ESTIMATE WATER LOSS/WATER GAIN RATIO.
We will assume that ambient air is totally dry, and exhaled air
is totally saturated with water vapour, and has 4% (by volume) of
carbon dioxide. Pick a temperature that lungs have (e.g. 35 deg C).
Take a table (like one in wikipedia) and find saturated vapour pressure.
Remember simple chemical formulae. Simple arithmetic. How is extra
water dumped?

I haven't heard warning from doctors about possible dehydratation in
case of using medicines that make nasal passages to extend.

NOTE.
For mammals (specially starving) water is needed for urination in
big quantities because of product of nitrogen metabolism is urea.
This has nothing do to with endothermy.

Conclusions
1. It is true that in some points ectotherms have less prone to water loss.
2. In other situations, endotherms should have less to worry about
 water retention.
3. It wasn't explained how RTs help to conserve water.
4. It wasn't demostrated that RTs actually do it.
5. It wasn't shown that water loss is significant.
6. It wasn't explained how RTs help to conserve heat.
7. Respiratory heat loss could be an advantage as well as drawback.
8. It wasn't shown that their presence/absence has to do with endothermy.
9. Without any RTs, heat production is greater that respiratory heat loss
   and water production is about same as respiratory water loss.
10. The above does not mean that dinosaurs were ectothermic or
   endothermic. This only means that Ruben's claims about
   RTs - endothermy are soundless
11. Reasons why do people like Ruben et al. write such 
 (no theory basis, no practise basis) is beyound my
 ability to explain. Please do someone!