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Author | Topic: All species are transitional | |||||||||||||||||||||||
robinrohan Inactive Member |
But what I would emphasize is that massive changes to pigmentation (or any other trait) don't require massive changes to the genetic basis of that trait. That, I think, answers my question. I really appreciate your thorough comments on the subject. I didn't pick it all up, but I think I got the gist.
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robinrohan Inactive Member |
The point being made is that whatever criteria you develop, whether based upon morphology or genetics or a combination or something else, they are open to discussion and debate Yes and we are discussing it and debating it. And my point is we want something arbitrary, once you get beyond the first round of generalities. But gene pool isolation is not arbitrary. RAZD and I have already proven that. So we need another one which is more arbitrary. In point of fact, evolution is seamless and we want some definition that will represent that fact more accurately. Gene pool isolation, being datable, will not do. "Turning out pigs for creationists makes me blue and blurry."--Brad McFall
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robinrohan Inactive Member |
To fuss about it at the most detailed level is a waste of time. There is NO "perfect" definition It's very important for political reasons. We must act. We must be able to explain to the people that there are no such things as "kinds." The way to do that is to show the seamlessness of the evolutionary process. You can't do that by defining species as gene pool isolation.
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robinrohan Inactive Member |
I am happy to report, RAZD, that the ancestors of you and me and the cat made it through that terrible time. Due to only one mutation and various subsidiary effects (feedback mechanisms, hormones, and the like), we were able to become heavily speckled enough to keep hidden from the bad guys, and mighty bad they were too. There were many trials yet to come. And through all the horrors of being meals for predators (they found us delicious--we tasted just like chicken), we made it through. And then one bright sunny day, someone had a thought--another puzzling development--and human life began.
All the rest is history--the history of grief. This message has been edited by robinrohan, 10-28-2005 09:35 PM
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robinrohan Inactive Member |
A grief history of time? Very good, RAZD. I'm sitting here with my cat--she likes to get up by the keyboard--and I wonder why we can relate so much to these creatures. The cat turns to me, and I interpret her look: "You old fool; did you not know that we are relatives?" And I thought about all the pain of history. Life is set up such that the only way to survive is to feed upon other life forms. The horror! The horror! (sorry--off-topic). This message has been edited by robinrohan, 10-28-2005 10:25 PM
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robinrohan Inactive Member |
Your choice of this criteria is therefore arbitrary because you can advance no better reasons for using it than other people can advance for other criteria. (In reality, gene pool isolation is a very poor criteria, and we can get into the reasons for that if you're interested. Percy, I did not choose this criteria. On the contrary, I am trying to show that this will not do. What will do is an arbitrary definition, and that is the only one that will do. This message has been edited by robinrohan, 10-29-2005 08:24 PM
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robinrohan Inactive Member |
The different opinions about it represented in this thread are proof that it falls prey to the same exigencies of reality as other criteria. Just because there are different opinons, this does not mean that the definition is arbitrary. It just means that it is a debatable topic.
I'm still getting the sense that your goal is to remove ambiguity from the species classification system. I'm trying to install arbitariness as the only realistic definition. Because if it's not arbitrary, it's not seamless. If it's not seamless, then there are speciation events. I'm arguing that there is no such thing as a speciation event. Under the gene pool isolation definition, there are. In fact, I believe that they are inevitable, always, according to that definition. This message has been edited by robinrohan, 10-30-2005 07:45 PM
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robinrohan Inactive Member |
I don't think so, but I suppose it depends upon how you define it. Point me to your definition of "gene pool isolation". Gene pool isolation occurs when there is no more and cannot be any more gene flow between two groups. In the example, we ended up with 3 groups, unspeckled, lightly speckled, and heavily speckled. The genetic connection between unspeckled and heavily speckled was the lightly speckled. When the last lightly speckled Eutherian died, there was isolation between the other two groups. This happens at a particular moment in time. But that's misleading. If we had a different definition, having to do with morphological change, then we might call the two groups variants or we might call them separate species. It wouldn't matter. The designation is arbitrary. This is more in keeping with the real process of evolution. RAZD mentioned the possibility that later on the members of the 2 groups might start interbreeding again, due to hard times, like some finches he mentioned did. If that happens, then the earlier designation that we had 2 separate species would be seen to be mistaken, according to the definition I'm using.
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robinrohan Inactive Member |
Why do you feel the need for a species classification system based on limited criteria. One might call my reason pedagogical. If you are trying to explain TOE to someone who thought in terms of speciation events (and ultimately of "kinds"), it's much easier to understand the seamlessness of the process if one uses morphological change as the criteria for speciation. It's easy to see that the labelling is arbitrary. It's not at all easy to see if we define it the other way. If you were trying to explain it to someone who didn't know much about it, you would be speaking on a basic level.
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robinrohan Inactive Member |
Anybody got a nice plain definition of "polyploidy"?
I looked it up in a dictionary; unfortunately, I couldn't understand the definition. ABE: Apparently , in these circles, "polyploidy" is an everyday word, like "please" or "thank you." "How was your day, dear?" "Well, it was rather polyploidy, to be frank." "I'm sorry to hear that." "No problem. I'll get over it." That sort of thing. This message has been edited by robinrohan, 11-02-2005 10:35 PM
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robinrohan Inactive Member |
Like having triplets?
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robinrohan Inactive Member |
The discussion was with circumstances where there can be more than two copies of each chromosome in cells Thanks. I'll study it out. "Turning out pigs for creationists makes me blue and blurry."--Brad McFall
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