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Thread: Ok you Mathamaticians!

  1. #17

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    It's a bit off-topic, but I have to asnwer:

    Quote Originally Posted by [b
    Quote[/b] ]And yet scientists insist that it was a meteor impact that caused massive global cooling which killed them off yet left crocodiles, turtles, snakes, lizards, frogs, toads and salamanders (i.e. all the cold-blooded creatures) more or less untouched. Now explain that one to me?!?
    Well, the idea is that the cold was a minor second problem, while the big issue was dust choking out the light and impeding photosynthesis. That would mean less plants, which would mean less herbivores, which means less carnivores, with the big things and the warm-blooded things (since both large size and high metabolism increase food requirements) being the first to starve.

    Also, it's technically inaccurate to say that ectotherms survived unscatched; many species of crocodylians and other reptiles perished, including the pterosaurs and marine reptiles. They just didn't get screwed nearly as badly as the dinosaurs did.

    There is, of course, still debate. Other alternatives include Bakker's theory, volcanic eruptions, or disease. It's complciated by the fact we've never directly witnessed a large asteroid strike on a rocky planet, thus must rely on historical evidence to infer the effects. Hopefully if that situation changes, it'll involve the moon or some rocky planet other than Earth.

    Quote Originally Posted by [b
    Quote[/b] ]Would that have something to do with smaller critters having more time to adapt / evolve than the larger ones?
    In part, yes. Big animals have some advantages (efficent metabolism and walking, protection from small predators, mass-based inertial effects for temperature, salinity, etc,), but suffer the dual problems of long generation time and small numbers. In 100 years, there are only about 8 or so generations of elephants, while there are 100 or more of mice, meaning that if natural selection is working on both, the mice will respond sooner (this is why bacertia and viri are so problematic; they evovle on a scale of weeks, while we take centuries to evolve resistance to them). Also, if a disaster kills 50% of the population, there are still several thousand mice, who can breed and repopulate, and the chances of valuable alleles being permanently lost because the animal carrying them died are minimal, as arre inbreeding effects. In contrast, there's probably only a handful of elephants left after the 50% loss, meaning that rare alleles were likely lost (reducing genetic diversity) and that inbreeding will become a factor in the future (which is very, very bad for a species survival).

    Mokele
    \"With malleus aforethought, mammals got an earful of their ancestor's jaw.\"
    --J. Burns, on the evolution of auditory ossicles.

  2. #18
    Tropical Fish Enthusiast jimscott's Avatar
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    I've read that cockroaches will outlive us all. I'd be willing to bet that bacteria and viruses will outlive the cockroaches.

    Here's wonderfuly poor logic: Cats have green eyes. My wife has green eyes. Therefore, my wife is a cat. Or... does that mean that I am married to a bazillion green-eyed cats? Yeah, P->Q, does not mean that Q->P!

  3. #19
    nepenthes_ak's Avatar
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    jim stay out of those interspecies relation ships!!

    Thanks, I understand it better now, thanks, Im just waiting for it to be graded to see how I did... illl let you all know

  4. #20

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    I love this thread!
    Droserae will inherit the earth.

  5. #21
    N=R* fs fp ne fl fi fc L Pyro's Avatar
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    Quote Originally Posted by [b
    Quote[/b] (Mokele @ July 20 2006,10:32)]
    Hey Mokele,

    Quote Originally Posted by [b
    Quote[/b] ]Well, the idea is that the cold was a minor second problem, while the big issue was dust choking out the light and impeding photosynthesis. That would mean less plants, which would mean less herbivores, which means less carnivores...
    When you hear it discussed it is most always put forth as the mother of all "Nuclear Winter" situations and I think most people feel that way, even the scientists. And yes it would be the double play of the dust cooling and blotting out the sun that would be the cause but I still don't buy it. Look at it this way, if you upset the lowest level of the food web then ALL the upper levels will feel it. KNock out the plants and yes you knock out the herbivores but not just the big one, you lose all the little ones too, like insects. You lose the insects and you lose the food supply for the smaller mammals and herps. You lose the small mammals and herps you lose the food for the larger mamals and herps... Ad infinitum. So again, why did the herps and smaller critters come out less scathed than the dinos??

    Quote Originally Posted by [b
    Quote[/b] ]with the big things and the warm-blooded things (since both large size and high metabolism increase food requirements) being the first to starve
    Actually that is not fully correct, there is not a linear increas in size and food intake. In fact most smaller warm bloods have to eat more than their own mass to maintain their body heat because their small size means they radiate the heat faster.

    Quote Originally Posted by [b
    Quote[/b] ]Also, it's technically inaccurate to say that ectotherms survived unscatched; many species of crocodylians and other reptiles perished, including the pterosaurs and marine reptiles. They just didn't get screwed nearly as badly as the dinosaurs did.
    I never said unscathed I said "more or less untouched" which is pretty accurate. Yes, some crocodiliads died off, but not all. Yes the pterosaurs died off however, 1) they were also considered to be warm blooded and 2) I group them in with the dinos as far as the extiction talk goes so they are on that side of the equation for me. As for the marine reptiles, data nowadays seems to indicate that they were dying off long before the meteor hit so while it might have done them in they were already on the way out.

    Quote Originally Posted by [b
    Quote[/b] ]There is, of course, still debate. Other alternatives include Bakker's theory, volcanic eruptions, or disease.
    Bakker's theory is the disease theory (unless he has come up with something new) and AFAIC the volcano theory is just slant on the meteor theory, lots of ash and smoke...

    Quote Originally Posted by [b
    Quote[/b] ]It's complciated by the fact we've never directly witnessed a large asteroid strike on a rocky planet, thus must rely on historical evidence to infer the effects. Hopefully if that situation changes, it'll involve the moon or some rocky planet other than Earth.
    I'll agree that it is complicated but I still thenk that people jump to "smoking gun" too soon.
    'My love was science- specifically biology and, more specifically, when placed in a common jar, which of two organisms would devour the other.'

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  6. #22

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    Quote Originally Posted by [b
    Quote[/b] ]When you hear it discussed it is most always put forth as the mother of all "Nuclear Winter" situations and I think most people feel that way, even the scientists. And yes it would be the double play of the dust cooling and blotting out the sun that would be the cause but I still don't buy it.
    Well, first, you must remember that the Alvarez paper (proposing the asteriod impact) was proposed before Bakker's theories of endothermy.

    Secondly, we do know that there was a big impact event around the right time, and such events would likely cause a nuclear winter effect. The real question is more whether this is what killed them off or not.

    Quote Originally Posted by [b
    Quote[/b] ]Look at it this way, if you upset the lowest level of the food web then ALL the upper levels will feel it. KNock out the plants and yes you knock out the herbivores but not just the big one, you lose all the little ones too, like insects. You lose the insects and you lose the food supply for the smaller mammals and herps. You lose the small mammals and herps you lose the food for the larger mamals and herps... Ad infinitum. So again, why did the herps and smaller critters come out less scathed than the dinos??
    Because the producers were not eliminated, just impeded. Some plants, as you no doubt know, can work with low light levels and cool temperatures. This would create an impediment to all subsequent trophic levels, with only those organisms who can manage to fulfill their dietary requirements surviving. Thus the animals with the lowest dietary requirements survive, those with the highest die.

    Quote Originally Posted by [b
    Quote[/b] ]Actually that is not fully correct, there is not a linear increas in size and food intake. In fact most smaller warm bloods have to eat more than their own mass to maintain their body heat because their small size means they radiate the heat faster.
    I never said it was linear, only that it increases with both size and metabolism. Trust me, I am more than aware of allometry and biological scaling; it's a large part of what I do.

    Also, it doesn't matter to my point. Small animals need *proportionally* more food, but not on an absolute scale. A mouse needs more food than a lizard, and an elephant needs more than a mouse. Sure, it's not linear, but all that matters is that big things, warm things, and especially big warm things, need a *LOT* of food.

    Quote Originally Posted by [b
    Quote[/b] ]I'll agree that it is complicated but I still thenk that people jump to "smoking gun" too soon
    I strongly suspect there's less consensus in the scientific community than the media makes out.

    Nevermind, this is paleontlogy, the field that gave us the quote "Consensus is established one funeral at a time". I'm amazed they can reach a consensus on where to have meetings.

    Mokele
    \"With malleus aforethought, mammals got an earful of their ancestor's jaw.\"
    --J. Burns, on the evolution of auditory ossicles.

  7. #23
    herenorthere's Avatar
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    The problem with the asteroid hypothesis is that it's a photogenic, high school textbook kind of explanation like saying the US Civil War happened because shots were fired at Fort Sumter or that the Great Depression happened because of Black Thursday. The world is a complicated place.
    Bruce in CT

    Madness is something rare in individuals but in groups, parties, peoples, ages it is the rule. Friedrich Nietzsche

  8. #24
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    Mokele wrote:
    Quote Originally Posted by [b
    Quote[/b] ]Nevermind, this is paleontlogy, the field that gave us the quote "Consensus is established one funeral at a time". I'm amazed they can reach a consensus on where to have meetings.
    Hmmmm - how do you really feel??
    All the best,
    Ron
    You must do the thing you think you cannot do. --- Eleanor Roosevelt

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