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Bettawrekonize -> RE: Nested Hierarchy violations? (8/27/2007 1:24:03 AM)
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ORIGINAL: Quasar6 They can classify them closer to birds. 'Closer'? I think we need a diagram of the nested heirachy. ----------------Common ancestor ---------------/ --------------/\ Mammals - Reptiles -------------/--\ ------------/----\ -----------/\-----\ ----------/--\----/\ Reptiles - Aves (birds) ---------/----\---\-\ --------/\-----\---\-\ -------/--\-----\---\-\ ------/----\-----\---\-\ -----/\-----\-----\---\-\ ---B--*----*-----*---R-A Bats (B) have features from the animals marked with a Star (*) (other mammals), and even some remnants from reptiles (like all mammals have), but they have no features from Aves (A). A bat with features would still have to be related to the Star (*) animals, but somehow it would also have to be related to Aves. Try to achieve that: it's impossible. There is no way it can break off of the Ave line and also break off of the mammal line... which is why bats with feathers don't exist. They can restructure the hierarchy like this (in fact, they seemed to have done this in the case of bats). ----------------Common ancestor ---------------/\Mammals - Reptiles --------------/\-\ -------------/--\-\ ------------/----\-\ -----------/\-----\-\ ----------/--\-----\-\ Reptiles - Aves (birds) ---------/----\-----\-\ --------/\-----\-----\-\ -------/--\-----\-----\-\ ------/----\-----\-----\-\ -----/\-----\-----\-----\-\ ---B--*----*-----*----R-A It could be speculated that other groups lost their feathers. In the article about bats, horses, and cows they found a violation in the previous hierarchy so they arbitrarily re - arrange the hierarchy quote:
Okada and his colleagues looked at genetic mutations caused by retroposons, lengths of DNA that can copy themselves into RNA and then reverse-copy themselves back into DNA at a different location on a chromosome. Closely related species share more of these mutations than more distant relatives. The analysis by Okada's team forces a rethink of the relationships of many mammalian orders, which are currently classified by morphological and nuclear DNA sequence data. "We need to look at fossils from a new point of view, because there must have been a common ancestor of bats, horses and dogs," Okada says. http://www.newscientist.com/channel/life/genetics/mg19025575.600-bats-and-horses-get-strangely-chummy.html Protists have been very difficult to classify for many years because they have characteristics in common with the kingdoms animalia, plantae, and fungi. So what did they do to solve the problem? They arbitrarily created a new kingdom; protista. In fact, to explain the violation in the hierarchy, in the Endosymbiont Hypothesis, Lynn Margulis speculates (based on practically no evidence whatsoever) that the first protists were formed by a symbiosis relationship among many prokaryotes. According to this unsupported hypothesis, these prokaryotes lived within another moneran as endosymbionts. The endosymbionts and their host cell became a team and benefited from one another. The endosymbionts eventually lost their independence and created the organelles in eukaryotic cells (such phenomena has never been observed, it is only speculated). Also, there is nothing stopping them from creating new phylums to solve discrepancies or just pushing the branches / divergences higher up in hierarchy.
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