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Author | Topic: On Transitional Species (SUMMATION MESSAGES ONLY) | ||||||||||||||||||||||||||||||||
New Cat's Eye Inactive Member |
To be recognised as a 'Transitional Species' surely an organism would have to show traits of a pre-existing species AND of a post-existing or contempory species. Do you have an example of an organism that doesn't fit this criteria? Every species has traits from a pre-existing species and the species after it will have traits from it too so....
Since one could, theoretically, have a species that represents a change from an older form to a contempory form then there might be some species living today which could be viewed as transitional. Lets take a look.
I don't mean to imply that those species are closely related or anything. But just looking at their form, the hippo, sea lion, and manatee all look like steps along the path from land mammal to sea mammal. Could we count those as transitionals?
I'm evening starting to think that pre-existing or contempory would be closer to the mark -- all three species could coincide in time and yet be related in a 'transitional species' sense.
Like my examples above? Edited by Catholic Scientist, : No reason given.
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New Cat's Eye Inactive Member |
What was kind-of the point!?
My post was interrogative...
Do I have to wait another coupla years for a reply?
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New Cat's Eye Inactive Member |
You're weird...
Which somewhat elaborated the point that (I think) I was attempting to make -- i.e. that any species could, in some respect, be considered a transitional one. I guess the most confusing part, then, is why you posted this:
quote:
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New Cat's Eye Inactive Member |
Oh, okay, I think I understand what you are saying now. But, I do think you're wrong.
You're using the word "transitional" in a colloquial sense, but there is an accepted usage of the word "transitional" by evolutionary biologists when referring to specific species and how they relate within the evolutionary lines. I think you'd be more accurate to use the word "intermediate".
Dead-ends/extinctions are not transitional ... so not every organism can be considered to be involved in transitional species. I agree with you on dead-ends but not on extinctions. Tiktaalik is a transitional that is extinct.
However, all extant species could be considered transitional except that we don't know into what yet. Could be, I suppose, but should be I do not. The better word here would be "intermediate".
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New Cat's Eye Inactive Member |
The platypus is a transitional species because it has a mixture of characteristics from mammals and reptiles. From wiki:
quote:
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New Cat's Eye Inactive Member |
Also, the transitional nature of a species has nothing to do with ancestry. It only has to do with the morphology of the species. Ancestry is a conclusion derived separately from the transitional nature of the species. My link did have this to say:
quote: I would argue that "close" is completely arbitrary. At what point is a species too distant from the common ancestor to no longer be considered transitional? Is the "distance" even really a focus of the determination of a transitional or not? I'm under the impression that its about forms and whether they have been uniquely derived or not. Take a hypothetical transition from a fish fin to a foot. Changes to the shape of the fin would be intermediates until it has enough uniquely derived traits that it can be considered a foot and then those species with that proto-foot are the transitional ones. The earlier ones where the shape was just changing are intermediates that don't really count as transitionals. Amirite?
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New Cat's Eye Inactive Member |
I'm just trying to figure out the proper usage of the word but you seem to be focused on something else and its confusing me so I'm just gonna say thanks and stop pursuing this.
So... Thanks.
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New Cat's Eye Inactive Member |
I'll give it one more try and see if it helps. Well I'm not gonna not reply
For all intents and purposes the terms transitional and intermediate are one in the same. I realize that's just an idiomatic phrase, but I would say that they are not the same for all purposes. Specifically, the purpose of studying evolutionary biology and the relationships between species that are or are not consider in a transition from one morphological feature to another. Further, there are distinctions between the terms used in that purpose that are important enough to maintain and not "grey out", so to speak.
When these terms are put together with the theory of evolution then you can also include evolutionary distance. In this respect there is a tendency to label species close to the common ancestor as transitional and those further away as intermediate. However, it is an arbitrary line just as there is an arbitrary line between being short and tall. They are all shades of grey, if you will. I agree that you can do this, but I don't find it particularly useful. Plus, I don't think the distinction is based solely on distance from the ancestor but also includes the morphologies, themselves.
The proper usage of transitional is in relation to the observations, which is what I was trying to stress. When I realized you had a different aim here than me, and that we're not really in much disagreement, is when I figured it wasn't worth pursuing any further. But there does seem to be enough disagreement to keep typing to you.
You don't observe evolutionary distance, that is the conclusion from analysing the observations. You observe the morphology. Therefore, a transitional fossil must be described in terms of direct observations that are independent of theory. Does that make sense? It does, and I don't disagree with that. But I do think there is enough distinction between intermediate and transitional to keep them as seperately defined, at least for some purposes. That's what I was trying to exemplify with the 'fin-to-foot' hypothetical.
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New Cat's Eye Inactive Member |
I see what you mean about 'extinctions' ... I would think there are huge numbers of extinct transitionals You're welcome
I chose the word 'could' very carefully. quote:
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