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Thermit
Joined: 08 Jul 2000
Posts: 3136
Location: Texas |
 Thu Jan 31, 2002 4:54 pm
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BOB B
Joined: 19 Jan 2002
Posts: 307
Location: LINDEN ,TEXAS,CASS |
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Thu Jan 31, 2002 6:20 pm
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......Kinds looks my mother in law a little, Thermit! |
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Thermit
Joined: 08 Jul 2000
Posts: 3136
Location: Texas |
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Thu Jan 31, 2002 7:14 pm
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LOL. hehe, I can see you don't have that 8-ball avatar for nuthin'!!   |
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Catnip57
Joined: 22 Apr 2001
Posts: 596
Location: Central Washington |
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Sat Feb 02, 2002 4:11 am
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Yikes!! Talk about a strange looking creature. When you said salamander I had a totally different image in my mind. Those things look like something out of the prehistoric age. Darn right ugly.  |
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Duncan Kunz
Joined: 19 Oct 2000
Posts: 582
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Mon Feb 04, 2002 5:30 am
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Dear Amber:
I'm not sure which program you are talking about, but an increase in the amount of O2 in the atmosphere (not CO2) during the eras before the dinosaurs (mississipian, pennsylvanian, and permian) would explain how large animals that take in oxygen via spiracles (like insects) could grow to such a large size, e.g., dragonflies with a two-foot wingspread.
Such animals couldn't exist today, because spiracles are a very inefficient way of getting oxygen to the blood. All the innards of the body have to be VERY near the surface to be perfused with oxygen, which is why it works with ants and bees, but not anything much larger.
But with a lot more oxygen in the atmosphere (say, 45% then as opposed to 28% now) you could have much bigger insects who wouldn't die of oxygen deprivation.
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Duncan Kunz / duncankunz@home.com
Mesa AZ / 480-891-2525
[Edited 1 times, lastly by Duncan Kunz on 02-03-2002] |
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amber
Joined: 17 May 2001
Posts: 445
Location: uk |
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Mon Feb 04, 2002 12:11 pm
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Thank you for the reply, Duncan. I should have paid more attention....I think it was on the Discovery channel....Makes you wonder though, how falling levels of O2 may be effecting us? |
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Duncan Kunz
Joined: 19 Oct 2000
Posts: 582
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Mon Feb 04, 2002 4:36 pm
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Amber, you bring up an interesting question when you ask about decreasing levels of oxygen. Let me start by saying that I have done absolutely no research whatsoever on this subject, so all I can give you is my opinion.
A drop from 45% to 28% oxygen is pretty significant, but considering that those home-laundry size insects seem to have died out about 200 million year ago, it would mean that the delta of oxygen percentage (assuming a straight-line drop from 0.45 to 0.2 would be very slow, equating to -0.000000085% per year or minus seventeen ten-thousandths of one percent since the birth of Jesus.
But it probably isn/t a straight-line drop. Most geologists believe that the earth's atmosphere changed from a rducing atmosphere (consisting mostly of methane and ammonia, like on Jupiter and Saturn today) to an oxidizing atmosphere about three thousand million years ago. Now that's a long time, and it probaly has reached an equilibrium by now, but we don't really know for sure -- or at least I don't.
My guess is that the O2 levels stayed pretty much the same over the past ten or twenty million years, since we see the same rate of oxidation in iron-rich minerals back that long.
A more pressing concern to me is the increase or decrease in the smaller amounts of gases like CO2, where the possibility of just a tiny change could have unknown and possible dangerous effects on climate, etc.
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Duncan Kunz / duncankunz@home.com
Mesa AZ / 480-891-2525 |
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BOB B
Joined: 19 Jan 2002
Posts: 307
Location: LINDEN ,TEXAS,CASS |
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Tue Feb 05, 2002 7:36 am
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Duncan is right, the gas CO2 is being created by human activity , and it is the main engine for change in the enviroment today. Products released from the burning of fossil fuels ineveitably increased co2 levels in our atomosphere to the point where artificial regulation of the earths thermal budget is now required........http://wwwpm.larc.nasa.gov/ This is the least of our many worries though! |
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amber
Joined: 17 May 2001
Posts: 445
Location: uk |
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Tue Feb 05, 2002 6:55 pm
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You are blinding me with science, Duncan I think ANY significant change in ANY of the gases in our atmosphere is important. I found this post on the net...it refers to levels found in amber suggesting that our O2 levels were once much higher - you might find it interesting Duncan:
"WHY DID DINOSAURS AND NOT MAMMALS GO EXTINCT?
Hengst has shown that Dinosaurs could not venilate their lungs as easily
as Birds or Mammals (Hengst et al '93, '96).
* Dinosaurs required 40 breaths to fully replace the air in their lungs.
* Mammals and Birds only require 7 breaths to completely replace the air
in their lungs.
* Large Dinosaurs required elevated levels of O2 in the air to
diversify."
-------
Some additional notes:
The paper indicates that the O2 level during the Permian was 14%, 35%
during the Pennsylvanian (and most of the Cretaceous), and is currently 21%.
Barremian 130 mya 28%
Aptian 115 mya 29%
Cenomanian 95 mya 35%
Turonian 88 mya 33%
Judith River Formation 75 mya 35%
Basal Hell Creek 70 mya 35%
Hell Creek (Maastrictian) 68 mya 35%
Top-most Hell Creek 65.2 mya 31%
AFTER K/T Boundary 65 mya 29%
Eocene 50 mya 16%
Miocene 20 mya 14%
NOW NOW 21%
[Edited 2 times, lastly by amber on 02-05-2002] |
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amber
Joined: 17 May 2001
Posts: 445
Location: uk |
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Tue Feb 05, 2002 7:04 pm
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contd.....
"Of course, some recent work (using new techniques) indicates that the O2
levels in amber may have been equal to current levels. If the higher O2
rates ARE CORRECT, then dinosaurs might have grown large simply because
their muscles would allow them to lift more (because they are easily
replenishing their O2).
Subject: Re: extinction by suffocation?!
>There is a really good article on this subject in J. Exp. Biol.
201,1043-1050 (1998),
>Atmospheric Oxygen, Giant Paleozoic Insects And The Evolution Of Aerial
Locomotor
>Performance by Robert Dudley.
>
>Dudley reports that oxygen peaked at 35% at the very end of the
Carboniferous and
>declined precipitously into and through the Permian, with a double minimum
in the
>Jurassic and early Triassic, then rose to another, lower maximum at the end
of the
>Cretaceous and early Tertiary, before declining gradually to the present
day levels.
>It's interesting to note that spontaneous combustion of the biosphere might
be possible
>at 35% oxygen concentration. Wonder where all those coal deposits came
from? Also, the
>higher oxygen partial pressures might allow oxygen and carbon dioxide
exchange in the
>trachea of long-necked animals."
WOW - "spontaneous combustion of the biosphere might
be possible
>at 35% oxygen concentration."
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Duncan Kunz
Joined: 19 Oct 2000
Posts: 582
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Wed Feb 06, 2002 4:06 am
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Well, there goes my straight-line oxygen depletion hypothesis!
But I have an out – I told you I didn’t do any research LOL! And I still haven’t, although I promise I will look up Brother Hengst’s work, because I’ve always been interested in paleontology.
I know that, even in the past ten years, we’ve learned a whole lot more about saurischian physiology than we ever knew, even finding what we’re pretty sure are fossilized hearts(!) which seem to show three chambers, just like birds. If this is valid (and I don’t know whether it is or not), and assuming the same sort of anatomical structure as birds, then dinosaurs ought to be about as efficient respirators as any other critters, all things being equal.
But of course, all things aren’t equal. A critter that’s twice as tall as another weighs four or six times as much, and the ratio of volume to surface area is much greater. Given a really biggie like some of the sauropods, I can see how they’d have to breathe like mad just to keep the blood oxygenating. And if you have a big critter like a sauropod that’s right on the margin of success/failure, then just the smallest drop of ambient oxygen percentage could kill ‘em off.
What really surprises me, though, is that the oxygen level goes up and down and up and down so dramatically. I made an Excel graph (which I don’t know how to upload) of percentage against time, and the levels seem almost random. It’s obvious, given what you say, that there are a bunch of causative factors (that I don’t have a clue about) which result in some very significant changes in levels.
Even more surprising is the relatively small change on either side of the K-T layer, which coincided with the death of the dinosaurs. I mean, over an 800,000-year period which saw the end of the dinosaurs, there was only a two percent drop in the O2 level. Yet maybe that two-percent drop was the straw that broke the camel’s back – at least for the dinosaurs.
This whole thing juse seems to point out that we don’t know diddly about the atmospheric dynamics, and that any change to our atmosphere could be really serious.
Great post, Amber. Now I have a bunch of reading to do.
Regards,
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Duncan Kunz / duncankunz@home.com
Mesa AZ / 480-891-2525 |
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