Re: Evolution of Bird Feather and Aerofoil

On Wed, 19 Sep 2007 20:30:56 -0000, UC <uraniumcommittee@xxxxxxxxx>
wrote:

On Sep 19, 4:24 pm, r norman <r_s_norman@xxxxxxxxxxxx> wrote:
On Wed, 19 Sep 2007 19:32:28 -0000, UC <uraniumcommit...@xxxxxxxxx>
wrote:



On Sep 19, 12:55 pm, r norman <r_s_norman@xxxxxxxxxxxx> wrote:
On Wed, 19 Sep 2007 09:12:21 -0700, John Harshman

<jharshman.diespam...@xxxxxxxxxxx> wrote:
r norman wrote:

On Wed, 19 Sep 2007 15:07:39 -0000, UC <uraniumcommit...@xxxxxxxxx>
wrote:

On Sep 19, 10:22 am, Augray <aug...@xxxxxxxxxxxx> wrote:

On Wed, 19 Sep 2007 13:03:59 -0000, UC <uraniumcommit...@xxxxxxxxx>
wrote in
<uranium-1190207039.524377.63...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> :

On Sep 19, 8:38 am, Augray <aug...@xxxxxxxxxxxx> wrote:

On Tue, 18 Sep 2007 17:58:12 -0700, UC <uraniumcommit...@xxxxxxxxx>
wrote in
<uranium-1190163492.498010.293...@xxxxxxxxxxxxxxxxxxxxxxxxxxx> :

On Sep 18, 8:37 pm, Augray <aug...@xxxxxxxxxxxx> wrote:

On Tue, 18 Sep 2007 14:16:54 -0000, UC <uraniumcommit...@xxxxxxxxx>
wrote in <uranium-1190125014.226665.29...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
:

On Sep 18, 10:05 am, Augray <aug...@xxxxxxxxxxxx> wrote:

On Mon, 17 Sep 2007 18:58:22 -0000, UC <uraniumcommit...@xxxxxxxxx>
wrote in
<uranium-1190055502.185699.137...@xxxxxxxxxxxxxxxxxxxxxxxxxxx> :

On Sep 17, 2:43 pm, r norman <r_s_norman@xxxxxxxxxxxx> wrote:

On Mon, 17 Sep 2007 17:37:59 -0000, UC <uraniumcommit...@xxxxxxxxx>
wrote:

On Sep 17, 1:30 pm, Arkalen <skiz...@xxxxxxxxx> wrote:

Using minimal scientific knowledge, have I just annihilated UC's
argument that hot-bloodedness evolved because the first mammals and
birds were small ? Answer : why yes, I believe I have !

Do you know what surface to volume ratio means? Are you aware that the
smallest Mammalia have the fastest metabolisms and heart rates, and
shortest life span? The largest dinos were not warm-blooded and could
not have been.

You (UC) know nothing about animal physiology or about animal
evolution or about dinosaurs. Arkalen is right. You are wrong.

See Fortey, page 221.

Fortey doesn't claim that the largest dinosaurs couldn't have been
"warm-blooded". You are singularly unreliable as a source for what
others believe.

"Would it have been possible to stuff sufficient food through the head
of Seismosaurus or Diplodocus to stoke up a furnace sufficient heat
thirty to fifty tons? And how much should a tyrannosaur eat to stay
alive?"

Life, page 222

Where does it say that "The largest dinos were not warm-blooded and
could not have been"?-

That is a summary of what he said, you ***-faced baboon.

No, it wasn't. How does Fortey's supposed incredulity demonstrate that
the largest dinosaurs couldn't have been endothermic?

How would they get enough food through their small heads to support
homeothermy?

Is the amount of food required substantially different from the amount
required to support poikilothermy?

I would think so.

You haven't read a word I write, have you? I told you that such a
large animal would have a warm core temperature anyway, so that the
food requirement to sustain true homeothermy would not be
substantially different! You agreed that such a large animal would be
a passive inertial endotherm. The addition of regulation to the warm
temperature, that is, homeothermy, poses very little increase to the
metabolic rate.

I think you need to explain the difference between homeothermy and
endothermy to him explicitly, as well as the difference between passive
and active endothermy. Not that it would do any good.

It won't do UC any good, but there is a minuscule chance that there
are actually some other people here reading this nonproductive
exchange and some of them might appreciate the distinctions.

The deprecated terms "warm-blooded" and "cold-blooded" are not
meaningful because "cold-blooded" animals in warm environments may
have warmer blood than "warm-blooded" animals. There are functional
terms to replace them. Unfortunately, these have their own baggage of
historical usage they carry around with them. Nonetheless, here are
modern terms and their uses.

A 'homeotherm' regulates its body temperature so that it stays
reasonably constant. A 'poikilotherm' allows its body temperature to
vary. There are subcategories like 'regional homeotherm' that
regulates most of the body but allows other parts to vary. Many birds
standing in cold water, for example, allow their feet to cool. A
'temporal homeotherm' regulates its temperature some of the time but
not all of the time. Some small hummingbirds, for example, regulate
their temperature during the day but allow it to drop at night.

An 'endotherm' has a body temperature that depends primarily on
metabolically produced heat. An 'ectotherm' has a body temperature
that depends primarily on the environment. There are 'homeothermic
ectotherms', many larger lizards for example, that regulate their
temperature with behavior, selecting environments of the appropriate
temperature; basking in the sun when cool and seeking shade when hot.

Birds and mammals are 'endothermic homeotherms' (or 'homeothermic
endotherms') because we regulate our body temperature at a high level
which we maintain ordinarily by means of metabolically produced heat.
As a side issue, if we have no particular 'use' or 'need' for a high
metabolic rate in terms of being physically active, doing external
work, or actively synthesizing more body parts but still are too cold,
we have to find some way of running our metabolism in idle, "wasting"
energy by producing only heat. There are two ways to do this. One is
to run our muscles uselessly back and forth, using energy but doing
nothing useful in exchange. This is shivering. The second is to find
some way of burning glucose without producing ATP, that is, without
getting anything useful out of it. This is 'futile metabolism' also
called 'non-shivering thermogenesis'.

Very large animals have a very high heat capacity. That is, it takes
a lot of heat movement to change their temperature significantly. As
a result, they tend to have relatively constant temperatures simply
because it is very difficult to change their temperature quickly. That
is called 'inertial homeothermy' and is passive; the animal doesn't
have to do anything to make it happen. This is in contrast to active
homeothermy, where the animal has to control heat production
(metabolism) and heat loss (conduction, convection, radiation, and
evaporation) to regulate its temperature. To a great extent, control
of heat loss alone can do the job. In this case, there is no
metabolic cost of homeothermy except the trivial cost of adjusting
your posture, fluffing up or sleeking down your fur or feathers, and
allowing or preventing a heavy flow of warm blood to the skin.

Another factor to consider is the variation in metabolic rate with
temperature. All biochemical reactions run faster when warm so the
metabolic rate increases with body temperature. Of course
homeotherms regulate their temperature so this is not a factor.
However a very large poikilotherm (non-regulator) has a large body
producing a lot of metabolic heat but relatively small surface area to
dissipate the heat. As a result, it tends to retain heat and its core
stays relatively warm, whether it 'likes' it or not, whether it
'wants to' or not. Given that a very large animal will ordinarily
have a relatively high body temperature (endothermy), the additional
metabolic cost of adding regulation (homeothermy) to the package is
minimal.

Finally, to correct a common misperception, I should add that ALL
animals, indeed all organisms, produce metabolic heat. The difference
between "warm-blooded" and "cold-blooded" (between homeothermic
endotherms and poikilothermic ectotherms) is that the former retains
the heat to keep its body warm while the latter allows (or can't
prevent) the heat from quickly escaping to the environment.,

That leaves the question of what category the dinosaurs belong to.
There have been many types of dinosaur spread over a very long period
of evolutionary history (and continuing with one branch to the
present). Different members of the group may have used different
mechanisms and belong to different thermal categories. Of course,
only indirect evidence can be used to establish the thermal
characteristics of extinct animal types. I leave the answer of this
question to the paleontologists who investigate exactly this type of
thing. My reading of the literature indicates that it is generally
accepted that most of the dinosaurs were endothermic with good
evidence of homeothermy.

The need for the largest animals to regulate their temperature
(especially against cold) is minimal, I think we all could agree. The
question is then did the smaller dinos (of whatever era) resemble
birds in that regard. I think the consensus is 'yes'.

John Harshman is the bird guy here, but my impression is that the
subgroup of dinosaurs that we call 'birds' evolved from ancestors that
were already homeothermic endotherms.


Exactly. That does not mean, however, that other groups of large
species were.

The argument that any particular dinosaur is homeothermic made on the
basis of evidence, not on speculation. The only speculation is that
one particular species (or other group) closely related or derived
from another that has hard evidence of homeothermy and that seems to
have similar morphological features is also homeothermic.

There is no shortage of speculative material about dinosaurs,
especially in the popular literature. (Note: your source is included
in that category, as is "Scientific American" and "Science News" and
all the press releases you see.) Some of this is good stuff, some is
not and you have to evaluate it carefully. Real evidence is published
in the primary scientific literature.

.