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Thread: My problem with estimate of Dinosaur extinction

  1. #1 My problem with estimate of Dinosaur extinction 
    Forum Professor WVBIG's Avatar
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    I have a problem with the estimate of 65,000,000 years ago for the Dinosaur extinction. Numerous other animals have been around for longer than that. Wouldn't the extinction of the top predator throw the whole system oyt of balance & have a rippling out effect on the rest of the animals?


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    Forum Cosmic Wizard spuriousmonkey's Avatar
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    You don't consider a mass extinction event a rippling out effect, and why do you think dinosaurs were only top predators?


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    WYSIWYG Moderator marnixR's Avatar
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    anyhow, what does the timing of the extinction event have to do with the mechanism that caused it ?
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    Time Lord Paleoichneum's Avatar
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    The evidence of the extinction is very clear, and the total restructuring of the food-webs is very clear in the Paleocene and Eocene stratas. What restructuring is not sown may I ask?
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    Forum Freshman LordKelvin's Avatar
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    Quote Originally Posted by WVBIG View Post
    I have a problem with the estimate of 65,000,000 years ago for the Dinosaur extinction.
    What does this have to do with your question?

    Quote Originally Posted by WVBIG View Post
    Numerous other animals have been around for longer than that. Wouldn't the extinction of the top predator throw the whole system oyt of balance & have a rippling out effect on the rest of the animals?
    It actually did. Mammalian explosion was probably just one of the many consequences.
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    Forum Professor WVBIG's Avatar
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    Quote Originally Posted by LordKelvin View Post
    Quote Originally Posted by WVBIG View Post
    I have a problem with the estimate of 65,000,000 years ago for the Dinosaur extinction.
    What does this have to do with your question?

    Quote Originally Posted by WVBIG View Post
    Numerous other animals have been around for longer than that. Wouldn't the extinction of the top predator throw the whole system oyt of balance & have a rippling out effect on the rest of the animals?
    It actually did. Mammalian explosion was probably just one of the many consequences.
    Yes I know it cleared the way for the Mammalian explosion. But how do you explain the survival of those species who were around at that time?
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    Time Lord Paleoichneum's Avatar
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    Generalist features, location in relation to the event, size, and a large chunk of luck. Or are you thinking of specific groups?
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    And also, mammals were blessed by god... Yeah ! <IMG class=inlineimg title=Shocked alt="" src="http://www.thescienceforum.com/images/smilies/icon_eek.gif" border=0 smilieid="19"><BR><BR>More seriously, the fact that mammals AND birds AND small lizards, snakes, all smaller sizes terrestrial animals survived is not probably due to random. There seems to be a pattern of survival which by the way was similar during the permian. Opportunist, easy to hide and protect themselves in holes, burrows, caves. Maybe it has also something to do with faster metabolism i.e. shorter live durations i.e. shorter reproductive cycles.
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    Also, being restricted to life on land... crocodiles and the majority of the fish species survived. And the Loch Ness monster
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    Forum Cosmic Wizard spuriousmonkey's Avatar
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    a major group of dinosaurs also survived and they are still one of the most common warmblooded species around: the birds.
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    Forum Radioactive Isotope skeptic's Avatar
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    The smallest true cretaceous dinosaur (excluding the birds) was turkey size. It appears that all large land animals died out, or almost all, thus eliminating the dinosaurs. Small mammals and birds managed to survive - possibly because they were able to access food supplies that would not have supported a larger one. From those small survivors, all modern land animals evolved.
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    Forum Professor WVBIG's Avatar
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    Quote Originally Posted by spoonman View Post
    Also, being restricted to life on land... crocodiles and the majority of the fish species survived. And the Loch Ness monster
    The Crocodillians was what I was wondering about
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  14. #13  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Quote Originally Posted by WVBIG View Post
    Quote Originally Posted by spoonman View Post
    Also, being restricted to life on land... crocodiles and the majority of the fish species survived. And the Loch Ness monster
    The Crocodillians was what I was wondering about
    crocodile lineage survived.
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    Time Lord Paleoichneum's Avatar
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    one of the keys to the crocodylomorph survival was location, the northern and southern poles were temperate with little to no below freezing days so the species living there were able to pass through the K-T event.
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  16. #15  
    Forum Professor WVBIG's Avatar
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    But how? They were part of the food chain
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  17. #16  
    Time Lord Paleoichneum's Avatar
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    everything is part of one food web or another, so Im not sure what your point is. They are mostly going to be feeding on fish, amphibians, turtles and things like that
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

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    WYSIWYG Moderator marnixR's Avatar
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    i think WVBIG's issue is that if the food web collapsed, why didn't all species go to the same early grave ?
    what makes the exceptions stand out ?

    my answer to that is that species which can go without food for long periods of time (e.g. hibernation or aestivation) could have an advantage, as could species that are small enough so that crumbs off the table still represent sufficient food to survive
    it also helps to be a generalist rather than a specialist feeder so that you can get whatever food comes your way

    i believe there is also some evidence that freshwater environments were less affected than terrestrial and marine ones, but i could be wrong there
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    Marnix
    Your theory is incomplete. Lots of small mammals and birds survived, and they require lots of food. To keep a warm blooded body going, with small size ( which equals a high surface area to volume ratio and subsequent heat loss), needs heaps of food per kg of body weight.

    Crocodiles and some other reptiles may have survived due to low food needs per kg of body weight, but not the mammals and birds.

    My personal theory goes like this. Following the major asteroid impact, and fires that came with it, the world's skies were filled with smoke and dust, causing photosynthetic organisms to die and rot. Forests fell. Large herbivores died due to lack of food. Their predators died due to lack of prey. However, stored organic matter was still there in the form of decaying vegetation, and especially in the soil. Tiny soil living animals like earthworms and insects lived on using this food source. Small mammals and birds which could eat those worms and insects lived on. Eventually seeds germinated and a new set of trees and grasses grew. By then, all the larger animals were gone.
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  20. #19  
    WYSIWYG Moderator marnixR's Avatar
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    Quote Originally Posted by skeptic View Post
    Marnix
    Your theory is incomplete. Lots of small mammals and birds survived, and they require lots of food. To keep a warm blooded body going, with small size ( which equals a high surface area to volume ratio and subsequent heat loss), needs heaps of food per kg of body weight.
    that's as may be but the individual portions, even though they need to be kept up at very regular intervals, are far smaller than what goes as a square meal for a dinosaur weighing several tonnes
    in addition, and echoing what you said, small mammals and birds these days often feed on seeds and insects of which there is more likely a suitable if not plenty supply

    in short, small animals are more likely to get a sufficient food source (even if this means a large amount in comparison to their size) + because of their reproduction rates are more likely to recover from a population crash as well

    [edit for an afterthought]

    so what i'm trying to say in a roundabout way is that the absolute quantity needed by an organism is important when resources are limited - whether that's achieved through hibernation / aestivation or just needing small portions because you're small is immaterial

    [/edit]
    Last edited by marnixR; September 17th, 2011 at 08:18 AM.
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