User Tag List

Informational! Informational!:  0
Likes Likes:  0
Page 4 of 5 FirstFirst 12345 LastLast
Results 25 to 32 of 38

Thread: Ok you Mathamaticians!

  1. #25

    Join Date
    Nov 2003
    Location
    Singapore
    Posts
    1,453
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [b
    Quote[/b] (jimscott @ July 20 2006,9:53)]Would that have something to do with smaller critters having more time to adapt / evolve than the larger ones?
    Quote Originally Posted by [b
    Quote[/b] ]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??
    Since we've already gone from math to dinosaurs, I wanted to drag this dead quotes back up. 'The weather' thing always means something else.

    Think what Jim meant was that the 'smaller critters' (e.g. worms, bugs...raccoons) could adapt more easily as they lived more generally. I mean, for example, while the larger creatures (i.e. dinos) were more specialized (i.e. some were strictly carnivorous, eating only one type of meat - fussy is the word). While the smaller critters, they could feed off anything, be it plant or meat, and perhaps a larger range of primary food sources (algae, plankton...) as well. So when 'nuclear winter' hits and a source of food is wiped out, the animals that can switch habitat, diets, would be the survivors.

    You guys would have probably discussed this to death already, but thought I'd just throw an interesting point in. Plus, I am in no mood for logic, so excuse me if I appear to be doodling and dozing off.

  2. #26

    Join Date
    Apr 2006
    Location
    Cincinnati, OH
    Posts
    427
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [b
    Quote[/b] ]The problem with the asteroid hypothesis is that it's a photogenic
    Definitely. The view the public has of paleo is pretty off, thanks to the media's presentation of the most photogenic theories. For instance, we have one, and only one, find that *might* support pack hunting by dromaeosaurs ("raptors"), though they might also have been scavenging, while we actually have a fossil of a velociraptor and protoceratops locked in combat (likely a sand dune collapsed on top of them) and it's just one of each. (Also, I heard though the grapevine of a yet-unpublished trackway showing a solitary dromaeosaur.) But the media gets things into their heads, and because it's 'sexy' and sells, they parrot it endlessly.

    Quote Originally Posted by [b
    Quote[/b] ]Hmmmm - how do you really feel??
    hehehe. I'm just rather cynical, and a fellow student I worked with used to do paleo, so she clued me in on all the metaphorical dirt.

    Quote Originally Posted by [b
    Quote[/b] ]Think what Jim meant was that the 'smaller critters' (e.g. worms, bugs...raccoons) could adapt more easily as they lived more generally. I mean, for example, while the larger creatures (i.e. dinos) were more specialized (i.e. some were strictly carnivorous, eating only one type of meat - fussy is the word). While the smaller critters, they could feed off anything, be it plant or meat, and perhaps a larger range of primary food sources (algae, plankton...) as well. So when 'nuclear winter' hits and a source of food is wiped out, the animals that can switch habitat, diets, would be the survivors.
    Actually, AFAIK, there's no real tendency for big animals to be either specialists or generalists. Plenty of large animals will eat anything they can stuff in their mouths (wolves, lions, crocodiles, elephants, bison), while others are specialist (anteaters, gharials, cheetahs, sperm whales). Similarly, there are generalist small animals (anoles, rodents, roaches, pond turtles, sparrows) and specialists (hummingbirds, snail-eating-snakes, woodpeckers, etc).

    While specialists would be hurt more, I'm not aware of specialists vs generalists being more common at either end of the size range. If anything, I'd think that big animals would be more likely to be generalists, since they can't afford to be picky if they're going to feed that huge body.

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

  3. #27
    N=R* fs fp ne fl fi fc L Pyro's Avatar
    Join Date
    Aug 2001
    Location
    Maryland
    Posts
    4,844
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [b
    Quote[/b] ]Well, first, you must remember that the Alvarez paper (proposing the asteriod impact) was proposed before Bakker's theories of endothermy.
    Yes, I knew/know that. Does not make much of a difference to me. I mean, if everyone can gladly accept the challenge to the idea of cold blooded dinos then why can they not think to challenge the impact when things start to look a little fishy??

    Quote Originally Posted by [b
    Quote[/b] ]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.
    I would not say we know but I grok your point. However, there are a bunch of different ways to both interpret and explain the data and that again brings me to the critisizm of jumping to the "smoking gun" and totally discarding everything else.

    Quote Originally Posted by [b
    Quote[/b] ]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.
    It still does not jive because there would have been dinos that were just as/more maleable/generalist than the small mammals and herps. We are not talking species or genus level extinction here, a global event like an impact is not going to hit selectivly.

    Quote Originally Posted by [b
    Quote[/b] ]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.
    I offer my apologies for misinterpreting.

    Quote Originally Posted by [b
    Quote[/b] ]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.
    But not all dinos were big. And some crocodyliads (that made it through) were quite large. And then there is the scavenger aspect, with all those dead bodies scavengers must have had a ton of food so why didn't T rex (assuming you accept the theory that he was a scavenger [which I am not saying I do or do not, just throwing it out as part of the argument]) make it through?

    Quote Originally Posted by [b
    Quote[/b] ]I strongly suspect there's less consensus in the scientific community than the media makes out.
    I would concur but even in the literature it is pretty slanted.
    'My love was science- specifically biology and, more specifically, when placed in a common jar, which of two organisms would devour the other.'

    See You Space Cowboy

    actagggcagtgatatcccattggtacatggcaaattagcctcatgat
    Hagerstown, Maryland

    --
    actagggcagtgatatcccattggtacatggcaaattagcctcatgat

  4. #28

    Join Date
    Nov 2003
    Location
    Singapore
    Posts
    1,453
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [b
    Quote[/b] (Mokele @ July 22 2006,3:20)]Actually, AFAIK, there's no real tendency for big animals to be either specialists or generalists. Plenty of large animals will eat anything they can stuff in their mouths (wolves, lions, crocodiles, elephants, bison), while others are specialist (anteaters, gharials, cheetahs, sperm whales). Similarly, there are generalist small animals (anoles, rodents, roaches, pond turtles, sparrows) and specialists (hummingbirds, snail-eating-snakes, woodpeckers, etc).

    While specialists would be hurt more, I'm not aware of specialists vs generalists being more common at either end of the size range. If anything, I'd think that big animals would be more likely to be generalists, since they can't afford to be picky if they're going to feed that huge body.

    Mokele
    True, but if not that, then why do all the small critters survive over the big ones (not that all do, but the large ones always seem to go quickly) when there is a mass extinction?

    I doubt that large animals could become generalists, really. Just imagine, a T-rex trying to swallow a roach? C'mon!

    Joking...

  5. #29

    Join Date
    Apr 2006
    Location
    Cincinnati, OH
    Posts
    427
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [b
    Quote[/b] ]I mean, if everyone can gladly accept the challenge to the idea of cold blooded dinos then why can they not think to challenge the impact when things start to look a little fishy??
    The fact that there are other theories out there indicates that the impact theory *is* being challenged.

    Quote Originally Posted by [b
    Quote[/b] ]I would not say we know but I grok your point. However, there are a bunch of different ways to both interpret and explain the data and that again brings me to the critisizm of jumping to the "smoking gun" and totally discarding everything else.
    Well, we do know: we've got a worldwide iridium layer and a giant crater off the Yucatan. Something big definitely did hit, the question is what happened when it did.

    Also, while not everything else is being discarded, I must admit to having a strong affinity for the impact hypothesis, simply as a matter of scale. Disease, famine, climate change, all of these happened regularly during the reign of the dinosaurs. And they were doing well, all the way up until 65 mya (the supposed 'decline' is due to paucity of fossil deposits from that time; a series in Alberta that shows from 10 my prior all the way to the extinction shows no decline). Then, all of sudden, one of the most successful vertebrate lineages ever almost completely dies out, leaving only birds behind. All of them, the world over, large and small, along with other successful groups of the time, such as marine reptiles and pterosaurs. I have a hard time believing anything less that a collosal catastrophe could have such a sudden effect.

    Maybe there were other factors, maybe it worked differently from how we think, but the fact remains that they were doing fine until they vanished in a geological instant, accompanied by a huge crater and a lot of iridium dust.

    Quote Originally Posted by [b
    Quote[/b] ]It still does not jive because there would have been dinos that were just as/more maleable/generalist than the small mammals and herps. We are not talking species or genus level extinction here, a global event like an impact is not going to hit selectivly.
    It's not the generality, it's the *amount* of food. Specialists may have been more boned that generalists, but either way, a dinosaur that needs 5 kg of meat a day is a lot worse off than a crocodile that needs 5 kg of meat a month.

    If there's less food, and everyone's fighting for it, the ones who will suffer the most will be those who need the most.

    Look at the predictions that makes: you survive if you need little food because you either a) have a low metabolism or b) are small (even a small endotherm). Now look at what lived: herps (which, as we know, can survive a *long* time between meals, even large ones), small mammals (they eat more than a small lizard, but not as much as a large mammal or large dinosaur),and small dinosaurs survived (now known as birds).

    The real puzzle, from what I can see, is the extinction of the large marine reptiles. Given that they seem to have been denizens of the warm shallows, it's very possible their food web simply collapsed due to insufficient light and/or warmth for phytoplankton; given that ammonites, belmenites, and reef-building rudist clams all went extinct at the time, it's certainly a reasonable proposition.

    Quote Originally Posted by [b
    Quote[/b] ]But not all dinos were big.
    Exactly, and the little ones lived on. Flight was probably a big bonus, allowing them to scour huge areas for food.

    Quote Originally Posted by [b
    Quote[/b] ]And some crocodyliads (that made it through) were quite large.
    The truly huge ones, Deinosuchus, died. Modern-sized crocs are surprisingly economical: they can survive for a year on only a dozen or so kg of meat, especially if they brumate/hibernate for a portion of the year. They're also so long-lived that the loss of younger animals wouldn't have hurt them as badly.

    Quote Originally Posted by [b
    Quote[/b] ]And then there is the scavenger aspect, with all those dead bodies scavengers must have had a ton of food so why didn't T rex (assuming you accept the theory that he was a scavenger [which I am not saying I do or do not, just throwing it out as part of the argument]) make it through?
    Dead bodies rot fast, though. Firstly, you've got just about every predator around out for a free meal (because even predators won't turn away a free meal). Anything that can't be eaten in a few days is too rotten. As populations drop, so do the numbers of bodies, so more predators fight over fewer and fewer corpses.

    There's also the fact that a dead body can only have as many nutrients as the live animal. If the animal starved to death, it's gonna have no fat reserves left, little remaining muscles (as the body will break those down for food when starving), and not much glycogen left in the liver. It's gonna be little but skin, bones, and organ meats. That's still something, especially to a starving theropod, but it's not exactly the bounty that you'd get from carrion from healthier animals (weird as it is to call a corpse healthy; disease and such rarely strips the body to nothing before death like starvation does).

    Quote Originally Posted by [b
    Quote[/b] ]True, but if not that, then why do all the small critters survive over the big ones (not that all do, but the large ones always seem to go quickly) when there is a mass extinction?
    Not always; trilobites, toothed birds, and other small animals died too.

    However, as noted above, big animals need more food. As noted in prior posts, big animals also have smaller populations and longer generation times, leading to slower evolutionary responses.

    Quote Originally Posted by [b
    Quote[/b] ]I doubt that large animals could become generalists, really. Just imagine, a T-rex trying to swallow a roach? C'mon!
    Well, specialist vs generalist is always size-based; what could the animal eat vs. what does it eat. False gavials are *huge* crocodilians, known to top 16 feet, thus should be able to eat just about anything, yet they've evolved into a specialist fish-eater niche.

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

  6. #30
    nepenthes_ak's Avatar
    Join Date
    Mar 2006
    Location
    Spring Feild Ohio
    Posts
    3,116
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    oh yea back to the point, I got a satasfactory on my assignment, thanks guys!

  7. #31
    N=R* fs fp ne fl fi fc L Pyro's Avatar
    Join Date
    Aug 2001
    Location
    Maryland
    Posts
    4,844
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Hey Mokele,

    Before I go on I just want to say that I really am enjoying this discussion with you. It is nice to be able to go talk with someone who does not just parrot "but it is what the experts thing so it must be true". So I thank you.

    Quote Originally Posted by [b
    Quote[/b] ]The fact that there are other theories out there indicates that the impact theory *is* being challenged.
    I take your point but I counter that unless you are really interested in it all you never really hear the other theories. Ask the Average Joe on the street and they will say it was the meteor. Period. End of discussion. You don't really have anyone making public noise about the other theories. To drag T-rex back into it, there is not Horner to the Bakker.

    Quote Originally Posted by [b
    Quote[/b] ]Well, we do know: we've got a worldwide iridium layer and a giant crater off the Yucatan. Something big definitely did hit, the question is what happened when it did.
    I am not saying nothing hit, I am sure something did. I am just saying that it was not THE cause. There are some inconsistancies in the iridium layer and, as I noted before, there are different ways to both interpret and explain the data: Meteors are not the sole source of iridium, the layer could be the result of concentration deposition, etc.

    Quote Originally Posted by [b
    Quote[/b] ]Disease, famine, climate change, all of these happened regularly during the reign of the dinosaurs. And they were doing well, all the way up until 65 mya (the supposed 'decline' is due to paucity of fossil deposits from that time; a series in Alberta that shows from 10 my prior all the way to the extinction shows no decline). Then, all of sudden, one of the most successful vertebrate lineages ever almost completely dies out, leaving only birds behind. All of them, the world over, large and small, along with other successful groups of the time, such as marine reptiles and pterosaurs. I have a hard time believing anything less that a collosal catastrophe could have such a sudden effect.
    Yes, disease, famine and climate change all probably happened regulary but they also were (like today) more "isolated" incidences. But at the time of the extinction you had massive global changes. You had basically every continent connected again after long isolation. You had global weather changes. Oceans were cut off from one another so currents and convection flows were disrupted. In concert it would be seriously disruptive.

    Quote Originally Posted by [b
    Quote[/b] ]It's not the generality, it's the *amount* of food. Specialists may have been more boned that generalists, but either way, a dinosaur that needs 5 kg of meat a day is a lot worse off than a crocodile that needs 5 kg of meat a month.
    Quite true. However a dino that eats 1kg should be at least an equal match to a small mammal that eats 1kg. So why then didn't the small dinos pull through?

    Quote Originally Posted by [b
    Quote[/b] ]Look at the predictions that makes: you survive if you need little food because you either a) have a low metabolism or b) are small (even a small endotherm). Now look at what lived: herps (which, as we know, can survive a *long* time between meals, even large ones), small mammals (they eat more than a small lizard, but not as much as a large mammal or large dinosaur),and small dinosaurs survived (now known as birds).
    Some small dinos survived as birds. However, not all the small dinos were of the same lineage that would evolve up to be birds. So why did they die?

    Quote Originally Posted by [b
    Quote[/b] ]The real puzzle, from what I can see, is the extinction of the large marine reptiles. Given that they seem to have been denizens of the warm shallows, it's very possible their food web simply collapsed due to insufficient light and/or warmth for phytoplankton; given that ammonites, belmenites, and reef-building rudist clams all went extinct at the time, it's certainly a reasonable proposition.
    Yes it is reasonable. However it is just as reasonable to propose that a disruption of the ocean dynamic upset the balance at the lowest level. There are always alternatives.

    Quote Originally Posted by [b
    Quote[/b] ]Exactly, and the little ones lived on. Flight was probably a big bonus, allowing them to scour huge areas for food.
    But as I noted, not all small dinos were of the lineage that would become bird. So what happened to them? Why didn't they make it? And I do agree about flight being an advantage, not only does it allow you to cover large area in search of food but it also offers a great escape from diseased areas. Or, the flipside, it is great for colonizing new areas and bringing with you something nasty that the locals don't know about.

    Quote Originally Posted by [b
    Quote[/b] ]The truly huge ones, Deinosuchus, died. Modern-sized crocs are surprisingly economical: they can survive for a year on only a dozen or so kg of meat, especially if they brumate/hibernate for a portion of the year. They're also so long-lived that the loss of younger animals wouldn't have hurt them as badly.
    Yes, Deinosuchus died off, but IIRC he actually came after the dinos left, early in the age of mammals (or maybe I am thinking of another of the megacrocs.) Still, the point I was making was that some, not all, large crocs did make it through. And I will grant that modern-sized crocs are surprisingly economical but you still don't see them inhabiting areas like costal New England, hibernation or not. Global cooling from a dust layer would have been pretty hard on them.

    Quote Originally Posted by [b
    Quote[/b] ]Dead bodies rot fast, though. Firstly, you've got just about every predator around out for a free meal (because even predators won't turn away a free meal). Anything that can't be eaten in a few days is too rotten. As populations drop, so do the numbers of bodies, so more predators fight over fewer and fewer corpses.
    It was a semi-rhetorical question anyways but... Yes, bodies rot fast but not everything would drop at the same time so there would be a constant (albeit deminishing) supply. And when you are talking about global death then even that diminishing supply is still pretty good sized. A small scavenger species could be quite happy and stable under those conditions.
    'My love was science- specifically biology and, more specifically, when placed in a common jar, which of two organisms would devour the other.'

    See You Space Cowboy

    actagggcagtgatatcccattggtacatggcaaattagcctcatgat
    Hagerstown, Maryland

    --
    actagggcagtgatatcccattggtacatggcaaattagcctcatgat

  8. #32

    Join Date
    Apr 2006
    Location
    Cincinnati, OH
    Posts
    427
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [b
    Quote[/b] ]I take your point but I counter that unless you are really interested in it all you never really hear the other theories. Ask the Average Joe on the street and they will say it was the meteor. Period. End of discussion. You don't really have anyone making public noise about the other theories. To drag T-rex back into it, there is not Horner to the Bakker.
    True, but the average joe also seems to be willing to believe that grass juice cures cancer, that seasons are caused by the earth getting closer and farther from the sun, and that said planet is 10,000 years old. With such an abysmal state of science education, I think the public's perception of the KT extinction is the *least* of our worries, and definitely not something to reproach the scientific community on.

    Quote Originally Posted by [b
    Quote[/b] ]I am just saying that it was not THE cause. There are some inconsistancies in the iridium layer and, as I noted before, there are different ways to both interpret and explain the data: Meteors are not the sole source of iridium, the layer could be the result of concentration deposition, etc.
    I'm pretty sure it's not the *only* cause, but it's certainly a major player. As for other sources of Iridium, what can explain a worldwide deposition or a usually rare element in both terrestrial and aquatic habitats. Major volcanic eruption, maybe, but that puts us back into the "big explosion" category with the ensuring climatic effects, even if the cause is terrestrial.

    Quote Originally Posted by [b
    Quote[/b] ]Yes, disease, famine and climate change all probably happened regulary but they also were (like today) more "isolated" incidences. But at the time of the extinction you had massive global changes. You had basically every continent connected again after long isolation. You had global weather changes. Oceans were cut off from one another so currents and convection flows were disrupted. In concert it would be seriously disruptive.
    Actually, the landmasses weren't all connected at the time:
    Page showing map of earth 66 MYA

    In fact, if you look at the map on the same site of 94 MYA, you don't see much difference, except that South America and Africa were a bit farther apart. Certainly nothing suggestive of massive, worldwide climatic disruptions.

    Quote Originally Posted by [b
    Quote[/b] ]Quite true. However a dino that eats 1kg should be at least an equal match to a small mammal that eats 1kg. So why then didn't the small dinos pull through?
    Were there any non-avain dinosaur species at the time that were small enough for this to be relevant? Maybe some of the small ornithischians, but even those were pretty sizable, and a lot bigger than the mouse-sized mammals and crow-sized birds they were competing with. Most of the truly small dinosaurs I can think of are from eras before this, or are proto-birds.

    Quote Originally Posted by [b
    Quote[/b] ]There are always alternatives.
    Hence my cynical comment about how contentious paleontology can be; we can think of alternatives, but without a time machine, all we can do is amass post-hoc evidence. With enough explaining, any amount of post-hoc evidence can be dismissed or turned to another theory. As a historical science, paleontology is essentially denied the most powerful tool of science, direct experimentation. Hence the ceaseless arguements.

    Quote Originally Posted by [b
    Quote[/b] ]Yes, Deinosuchus died off, but IIRC he actually came after the dinos left, early in the age of mammals (or maybe I am thinking of another of the megacrocs.)
    Well, several lineages have produced huge crocs (and some sizable phytosaurs, too), both before and after. Deinosuchus was from before, probably died during the KT extinction (we think; the fossil record for the big D is very poor). The next big croc wasn't until the Miocene, some 40 MY later, namely Purussaurus.

    Quote Originally Posted by [b
    Quote[/b] ]Still, the point I was making was that some, not all, large crocs did make it through. And I will grant that modern-sized crocs are surprisingly economical but you still don't see them inhabiting areas like costal New England, hibernation or not. Global cooling from a dust layer would have been pretty hard on them.
    Actually, gators have ranged into NC and VA in modern times, and can hibernate quite well; it's possible the ancestor of modern crocs could do likewise.

    Quote Originally Posted by [b
    Quote[/b] ]Yes, bodies rot fast but not everything would drop at the same time so there would be a constant (albeit deminishing) supply. And when you are talking about global death then even that diminishing supply is still pretty good sized. A small scavenger species could be quite happy and stable under those conditions.
    Yep, note the *small* part. That actually does wonders for explaining mammals and birds. The former are very small, thus have low requirements. The latter, though they have higher metabolisms than, well, anything, can fly, thus covering huge areas, allowing them to last longer in the diminishing supply as both the number of bodies decreased and the space between them increased.



    Ok, I've been doing some digging, and I've found several mentions of the value in the literature that nothing over 25 kg survived on land. However, inconveniently, none of these mentions, reliable as they seem to be, actually give citations of articles in the scientific literature. It's late for me, so I'll look into it more later, but it seems that there is an upper size limit for all taxa, even crocs. If there were no non-avian dinosaurs bellow that size, it would explain with only the avain lineage survived. Like I said, I'll do more digging (pun intended).

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

Page 4 of 5 FirstFirst 12345 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •