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Author | Topic: The Definition and Description of a "Transitional" | |||||||||||||||||||||||
arachnophilia Member (Idle past 1375 days) Posts: 9069 From: god's waiting room Joined: |
Let me see if I got this. You're saying then that the transitional species has more information than the present one because it went from being able to live in both enviroments (land - water) to living in only one. Hmmm wasn't information supposed to increase. A cat can walk, jump, swim and climb just like the mudskipper. So i guess a cat is also in a transitional state. i can probably take photograph and draw better than you can. do i have more information than you? these terms are simply preposterious, you should know better. and a cat can walk, jump, and climb BETTER than a mudskipper. but i bet a mudskipper can swim better than a cat.
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coffee_addict Member (Idle past 508 days) Posts: 3645 From: Indianapolis, IN Joined: |
Let me ask you a question. Are proto-mammals transitional enough for you? If you want an example of a proto-mammal, just go to Australia.
Hate world. Revenge soon!
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Darwin Redux Inactive Member |
It's not so much their existence, but rather their definition as 'ancestral' or 'derived' that is more important me thinks.
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NosyNed Member Posts: 9004 From: Canada Joined: |
Please explain that more fully?
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NosyNed Member Posts: 9004 From: Canada Joined: |
We have some threads on "information" in the ID forum I think.
I suggest that you not bring up the concept unless you are prepared to deal with it. Starting with an operational definition. That can be done in the appropriate threads. It seems that everytime someone brings it up it is because they have read some creationist material and not really understood it. You have more of a background than many so you may have a chance of understanding it but there is no hint so far that you do.
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Darwin Redux Inactive Member |
Sure - I'll try my best.
You said in a previous post
quote: It's not so much whether the transitional possesses characters that 'we would associate only with ...', although in most cases we would. The reason that this isn't our exclusive caveat is that we may discuss a character that is present in BOTH A and B. We need more to focus on whether our characters are derived, ie, evolved within that lineage, or whether they are ancestral, ie, inherited by common descent from an ancestor. An example, perhaps, using Archaeopteryx and the theropods/bird relationships. Dromaeosaurids, such as Velociraptor possess a unique, derived character (synapomorphy), and that is axial rotation of the wrist. In Archaeopteryx, this is present also, but as an inherited, ancestral characteristic (plesiomorphy). Archaeopteryxalso possesses feathers. Now, let us for argument's sake say that feathers first appeared in Archaeopteryx (although they didn't, but it just complicates things). Here, they would be a unique, derived characterstic - synapomorphy. Then we examine modern birds. Feathers and rotatable wrists are present as ancestral characters - plesiomorphies. So here we see it is not really pertinent to talk about 'what we now associate only with'. In evolution we don't really do that. What we do is look at which characters are derived (i.e appear in that lineage). Monophyletic clades are defined only be derived characters of the basal group. So, a transitional form can be defined as a lineage that possesses a synapomorphy of a basal lineage as a plesiomorphy, and a plesiomorphy of a descendent lineage as a synapomorphy. Note that this doesn't preclude the descendent lineage also possessing the synapomorphy of the ancestral lineage as well.
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mark24 Member (Idle past 5226 days) Posts: 3857 From: UK Joined: |
Hi Arachnophilia,
this is some nice circular logic here, and it needs to be pointed out. why are feathers not a defining characteristic of a bird? no other animal today has them. do reptiles have them? mammals? amphibians? fish? if you ask any biologist the single most defining feature of a bird what will they say? Feathers are not definining characters of birds because non-birds have feathers. If you ask a biologist who has a knowledge of therapoda, he will probably reply that feathers are not defining characters of birds. Extant birds have feathers & no other extant organisms do, but that's neither here nor there. Extinct non-avians, as identified cladistically, have feathers, ergo; feathers do not define birds in the most inclusive sense.
for something to be partway between a bird and something else, wouldn't it have to feathers? why should that rule out feathers as a defining feature? it is, afterall, what we're looking for. In this case all birds have feathers, but not all non-avians lack them. In other words, feathers evolved before birds. But speaking generally & hypothetically, suppose early birds lacked feathers, so what? It doesn't make them non-birds. What makes them birds are that they are on or above the node on a cladogram called "Aves". Running with this hypothetical, all extant birds which share characters that are exclusive to other organisms are crown group birds, everything else on or above the Aves node are stem group birds. Characters that are common to crown & stem groups are defining characters of clade Aves. A good example of this is the fused pygostyle, ALL extant birds have this, Archy lacks it. If Archy is to be considered a bird (& not all cladograms agree, it is often placed in the next node lower than Aves; Aviala) then it is a stem group bird. In short, there is nothing that cladistically says that all extinct organisms in a clade must have the same characters as all extant members of that clade.
but you can't say it's not a defining characteristic of a bird because the transitional form that led up to birds also had feathers. that just makes no sense. No I didn't. The feathered non-avians are not birds, they are below Aves, furthermore, after the aves/dromaeosaur/troodontid split there was then a sister group that possessed feathers. Ergo if feathered therapods exist that are non-ancestral to Aves, then feathers are not a defining character of birds by definition. Mark There are 10 kinds of people in this world; those that understand binary, & those that don't
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Loudmouth Inactive Member |
quote: Information has nothing to do with it. A transitional form displays characteristics of two different taxonomic categories, in this case fish and amphibians.
quote: If I show you the real fossil will you accept it as a transitional form?
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coffee_addict Member (Idle past 508 days) Posts: 3645 From: Indianapolis, IN Joined: |
Loudmouth writes:
Not very likely, based on his past behavior, but you can try if you want. If I show you the real fossil will you accept it as a transitional form? Hate world. Revenge soon!
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Loudmouth Inactive Member |
quote: Jazz is one of the more congenial creationists around here, so don't jump to conclusions. What I want to avoid is the creationist run-around, which goes as follows: Creo: "There are no transitional forms." Evo: "Yes there are, look at this drawing of a fossil." Creo: "How can I trust a drawing, Haeckal faked his drawings." Evo: "Here is the actual fossil." Creo: "That isn't a real transitional, it is just a different created kind." In the end, the accuracy of the drawing is never really in question, just the definition of what the fossil is. I felt like skipping the second response and go right to the issue at hand.
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coffee_addict Member (Idle past 508 days) Posts: 3645 From: Indianapolis, IN Joined: |
We'll see.
Hate world. Revenge soon!
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Itachi Uchiha Member (Idle past 5646 days) Posts: 272 From: mayaguez, Puerto RIco Joined: |
nosyNed writes: We'll have to start finding pictures. I've seen plenty of them and I'm not interested in pictures but the original fossils. From the Dinosaur to bird link.
[quote]Part reptile, part dinosaur, part bird the creature still fascinates us. If Archaeopteryx is not an evolutionary link, how do creationists explain such a unique organism?[/qs] It's already explained - its an unique organism.Archaeopteryx is a fossil creature with some reptilian and some bird features. Most leading evolutionary paleontologists today would not regard it as a transitional form because it has no transitional structures, and because fossils of true birds have been found in a supposedly earlier geological layer. If you do some more reearch youll find that many evo Paleontologists now believe that this creature was complete bird and not a transitional form. The author of the link says it himself - "Despite all the conflicting data with respect to the linkage between dinosaurs/reptiles and birds, it seems clear that although Archaeopteryx is the best candidate, it is not the link." From the reptile to mammal link I only have one question. How did you get such a god idea that it looked the way that it is in the picture when you only have the skull. I'm getting more of the same in the third link.
NosyNed writes: The only problem I can see you having with the drawings is that you think someone is making them up. Exactly. I dont only think theyre making it up know I apparently know from the links you posted.
NosyNed writes: They are done very carefully indeed from the fossils to allow them to be shown clearly. One thing is to do a reconsruction of the head with the fossil of the head available and it is another thing to reconsruct the whole creature from just the head.
NosyNed writes: Something that is difficult if you don't have the actual fossil in front of you for some of them. We finally agree. I wouldn't say difficult, impossible is more like it. This message has been edited by jazzlover_PR, 11-30-2004 10:46 PM Ponlo todo en las manos de Dios y que se joda el mundo. El principio de la sabiduria es el temor a Jehova
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
The Definition and Description of a "Transitional"
Let me ask you a few questions. First is a chimp different than a human? Aslan is not a Tame Lion
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Itachi Uchiha Member (Idle past 5646 days) Posts: 272 From: mayaguez, Puerto RIco Joined: |
Arachnophilia writes: i can probably take photograph and draw better than you can. do i have more information than you? the ability to draw better than me or the ability of me playing a musical instrument better than you (just an example. i do not know if youre a musician)is developed by practice and not by code in our dna. Anyone of us (assuming no one is disabled) can play an instrument,draw or become an athlete with a little dedication and practice. This message has been edited by jazzlover_PR, 11-30-2004 10:53 PM This message has been edited by jazzlover_PR, 11-30-2004 10:54 PM Yo soy BoriCua Pa Que tu lo Sepas
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Itachi Uchiha Member (Idle past 5646 days) Posts: 272 From: mayaguez, Puerto RIco Joined: |
Lam writes: Let me ask you a question. Are proto-mammals transitional enough for you? If you want an example of a proto-mammal, just go to Australia. Transition between what? Cite a reference that convinces me it is a transition. Ponlo todo en las manos de Dios y que se joda el mundo. El principio de la sabiduria es el temor a Jehova
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