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Author Topic:   Galapagos finches
NosyNed
Member
Posts: 9006
From: Canada
Joined: 04-04-2003


Message 31 of 104 (84729)
02-09-2004 1:04 PM
Reply to: Message 29 by Tamara
02-09-2004 11:37 AM


So what happens when very different sizes of critters do breed (say by insemination)? Would not nature make adjustments for the discrepancy so that the mother does not just blow up?!
But the biological definition of species involves the behavior in nature. That is, even animals that could successfully breed may not for behavioral or other reasons. If they don't (or don't very often the definition makes them different species.
Are tigers and lions now the same species? They can breed and, I think, produce fertile offspring. However, they tend not to as they don't usually recognize each other as mates. (Of course, they rarely see each other for that matter.)
Would nature make adjustments? I don't know. Do we have a dog breeder present?

This message is a reply to:
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truthlover
Member (Idle past 4136 days)
Posts: 1548
From: Selmer, TN
Joined: 02-12-2003


Message 32 of 104 (84732)
02-09-2004 1:26 PM
Reply to: Message 21 by Tamara
02-09-2004 10:02 AM


Problem with your argument is... if chihuahuas and St. Bernards would not be considered one species "in the wild" then why should Icelanders and Bantus be considered one species? You see that sort of thinking opens up a can of worms. Better leave them all together if they interbreed...
That's not opening a can of worms. The can of worms is opened. That's part of what we've been trying to tell you. It's hard to define species, and when you say, "Well, look how different dogs are, and they're all one species," (which is what you said) you're already pulling from the can of worms. The only reason I see that dogs are all one species is because we bred them. In the wild, I can't see any way they'd not be separate species. Maybe someone can name for me a species that varies in size and appearance as much as dogs do, yet are all considered one species (rather than one genus).
As an example, the European wildcat is regarded to be the ancestor of our domestic cats, yet it is classified as Felis silvestris, while our kitties at home are Felis catus. There is far less difference between those two species than there is between, say, Doberman Pinschers and Cocker Spaniels.
It's a can of worms. Thus, there is absolutely no problem that one person classified the Galapagos finches as 14 species and another reduced it to no less than six (which you need to admit is what was said).

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truthlover
Member (Idle past 4136 days)
Posts: 1548
From: Selmer, TN
Joined: 02-12-2003


Message 33 of 104 (84733)
02-09-2004 1:30 PM
Reply to: Message 29 by Tamara
02-09-2004 11:37 AM


So what happens when very different sizes of critters do breed (say by insemination)?
This is bizarre. What does this have to do with speciation? Obviously, artificial insemination doesn't happen in the wild.

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Tamara
Inactive Member


Message 34 of 104 (84753)
02-09-2004 3:21 PM


Paul, at one time, I read, there were said to be some thirty finch species there. The ornithologist who came up with them said that he could have just made them one species. Once there were I hear 64 species of brown bear, now there is one. I think if you want credibility with us, you gotta come up with something better than a vague definition up for grabs by the splitters.
quote:
Oh and what DOES Wells have to say about "gill slits" ? The structure is there in vertebrate embryos, and it is genuine evidence of evolution even though Wells doesn't like it.
Are you baiting me or something? There are pharyngeal pouches that develop into neck and jaw and adenoids etc in humans. There are no gills and there are no gill slits. The pharyngeal pouches of humans have nothing whatsoever to do with gills. Since I know from personal experience that the notion of gill slits creates powerful images of human embryos have gills, therefore it must be true we were once fishlike. In other words, it is a propaganda item, and I think it’s high time we all started using the proper term. (And no, I am not denying that there are similarities among various critters in embryonic stage.)
As for my bias what would I possibly have to gain by claiming to bias-free? Are you?
quote:
Are tigers and lions now the same species?
NosyNed, why not? What objection do you have to making them merely a separate subspecies?
Wolves and dogs are now, you know
Temp:
quote:
The only reason I see that dogs are all one species is because we bred them. In the wild, I can't see any way they'd not be separate species. Maybe someone can name for me a species that varies in size and appearance as much as dogs do, yet are all considered one species (rather than one genus).
Easy. Humans. And we haven’t bred them. (And please note: dogs and wolves are now the same species, and we have not bred them [wolves] either.)
I agree it’s a can of worms. But as I said, greater rigor would be in the interest of better argumentation.
Re insemination — I was trying to bypass the whole can a st bernard impregnate a chihuahua. I still think it can at least a big male to a small female. Anyway, a side issue.

Replies to this message:
 Message 36 by NosyNed, posted 02-09-2004 3:35 PM Tamara has not replied
 Message 38 by MrHambre, posted 02-09-2004 3:47 PM Tamara has not replied
 Message 44 by PaulK, posted 02-10-2004 2:42 AM Tamara has not replied

  
Tamara
Inactive Member


Message 35 of 104 (84759)
02-09-2004 3:27 PM


Temp, please note that the species of finches have not been reduced to 6. As far as I know, there are still officially 14, at this time.
As for whether Grant meant at least 6 or at most 6, I admit the quote is ambiguous.
[This message has been edited by Tamara, 02-09-2004]

Replies to this message:
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NosyNed
Member
Posts: 9006
From: Canada
Joined: 04-04-2003


Message 36 of 104 (84766)
02-09-2004 3:35 PM
Reply to: Message 34 by Tamara
02-09-2004 3:21 PM


You offer up very few facts in amongst your assertions. It would be nice if you got them right when you did.
... and we have not bred them [wolves] either.)
- is wrong (if you mean breed wolves with dogs).
NosyNed, why not? What objection do you have to making them merely a separate subspecies
So what is your definition of 'species' to replace the rather complex defintions given at the referenced site?
http://www.wordiq.com/cgi-bin/knowledge/lookup.cgi?title=...

This message is a reply to:
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Tamara
Inactive Member


Message 37 of 104 (84770)
02-09-2004 3:43 PM


Nosy, please read with care. Don't just yell wrong! All I said was that Canis lupus (whom we have not bred, per Temp's comment above) and Canis familiaris are now classed as one species.
I will get back to you on the link.
[This message has been edited by Tamara, 02-09-2004]

Replies to this message:
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MrHambre
Member (Idle past 1470 days)
Posts: 1495
From: Framingham, MA, USA
Joined: 06-23-2003


Message 38 of 104 (84774)
02-09-2004 3:47 PM
Reply to: Message 34 by Tamara
02-09-2004 3:21 PM


It's Not About Species
Tamara,
Why are you still claiming there's a need to define 'species'? I told you that in terms of evolutionary theory, such distinctions are useful but arbitrary. Please let me know you understand this point, because the way you continue to harp on the point tells me you don't really get it.
Evolutionary theory claims that chimps and humans descended from a common ancestor. However, it denies that there is a magical point where humans acquired their human-ness and chimpanzees acquired their chimp-ness. There are no magic thresholds that organisms cross that make them a different species. The point of all this is the change itself that we see among the different members of populations, that constitutes evolution's first steps. Call it microevolution or adaptation, but it's evolution nonetheless.

The dark nursery of evolution is very dark indeed.
Brad McFall

This message is a reply to:
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Coragyps
Member (Idle past 812 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 39 of 104 (84778)
02-09-2004 3:54 PM
Reply to: Message 35 by Tamara
02-09-2004 3:27 PM


As for whether Grant meant at least 6 or at most 6, I admit the quote is ambiguous.
In the 1992 paper - Science, vol 256, pp 193-197 - the Grants write, after discussing by name the three species of Geospiza on the island Daphne Major
A parallel study on Genovesa island gave similar estimates of the frequency of hybridization among the three other species in the genus of Darwin's finches.
That's the only mention I can find there of the total number of species. Tamara, PM or email me if you want a copy of the whole paper - copyright laws won't let me post it here.

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Tamara
Inactive Member


Message 40 of 104 (84834)
02-09-2004 7:48 PM


The species link says: Although the current scientific understanding of species suggests there is no principled, black and white way to distinguish between different species in all cases, biologists continue to seek concrete ways to operationalize the idea. One of the most popular biological definitions of species is in terms of reproductive isolation; if two creatures cannot reproduce to produce fertile offspring, then they are in different species. This definition captures a number of intuitive species boundaries, but nonetheless has some problems, however. It has nothing to say about species that reproduce asexually, for example, and it is very difficult to apply to extinct species. Moreover, boundaries between species are often fuzzy: there are examples where members of one population can produce fertile offspring with a second population, and members of the second population can produce fertile offspring with members of a third population, but members of the first and third population cannot produces fertile offspring. Consequently, some people reject this notion of species.
--
When it comes to living birds, the two first objections are not an issue. (No matter how a species is defined, it will not solve the paleontologists’ difficulties.) The third objection I am not familiar with. Does it apply to birds? I think we are not likely to have a useful definition of a species that works for all — plants, unicellulars, everyone. But Dobzhansky’s old definition is a good one, can anyone tell me why it should not be applied to birds?
quote:
Why are you still claiming there's a need to define 'species'? I told you that in terms of evolutionary theory, such distinctions are useful but arbitrary. Please let me know you understand this point, because the way you continue to harp on the point tells me you don't really get it.
MrH: I would prefer if a more rigorous definition were applied, yes. I think it would be more useful. I understand that no such definition can be completely rigorous. Do you understand that if the definition of a species is so diluted that any few minor characteristics can be said to set apart a species then the argument for speciation has virtually no value for the theory of evolution? Trivializing species means trivializing speciation; in other words, all you have then left is an argument that from groups of closely related critters, there arise by selection other groups of closely related critters slightly different from the first group. Animal and plant breeders have known this for millennia, we don’t need science to tell us this.
quote:
There are no magic thresholds that organisms cross that make them a different species.
I am not interested in magic thresholds. I am interested in good argumentation.
Coragyps: I believe that the latter part of that quote is from: Peter R Grant and B. Rosemary Grant, "Speciation and hybridization in island birds", Philosophical Transactions of the Royal Society of London B 351 (1996), pp765-772. I tried looking for it online but no luck. (I emailed you. )

Replies to this message:
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MrHambre
Member (Idle past 1470 days)
Posts: 1495
From: Framingham, MA, USA
Joined: 06-23-2003


Message 41 of 104 (84871)
02-09-2004 11:14 PM
Reply to: Message 40 by Tamara
02-09-2004 7:48 PM


Win a Date with Konrad
Syamsu, is that you?

The dark nursery of evolution is very dark indeed.
Brad McFall

This message is a reply to:
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Tamara
Inactive Member


Message 42 of 104 (84872)
02-09-2004 11:19 PM


Thank you Coragyps!
I was able to access the Science article, and here are the only pertinent stuff to our discussion that I could find:
p 196
"The discovery of superior hybrid fitness over several years suggests that the three study populations of Darwin's finches [on Daphne] are fusing into a single panmictic population, and calls into question their designation as species."
p 197
"Hybridization and fluctuations in relative fitness of hybrids illustrate the challenges to our concept of species that arise from moderately rare but significant events in the real world."

Replies to this message:
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 Message 46 by Coragyps, posted 02-10-2004 8:25 AM Tamara has not replied

  
NosyNed
Member
Posts: 9006
From: Canada
Joined: 04-04-2003


Message 43 of 104 (84878)
02-10-2004 12:14 AM
Reply to: Message 42 by Tamara
02-09-2004 11:19 PM


Clarifying
There are a couple of points being bounced around here.
1) What is a species?
2) Has speciation taken place amoung finchs of the Galopagos?
1) Since speciation is a gradual process in many cases it can be difficult to decide then the line has been crossed. Until there is a reproductive barrier speciation may not be clear. However, for any number of reasons (historical, convenience, genetic) a species may be declared. It is the classic lumper and spliter argument.
2) Given that speciation may start and not complete it is possible, as you sources note, that it could reverse. It seems that the experts who are argueing over this have somewhat fewer species than once upon a time but still more than one.
I don't see why this is such a large issue. Cases like this aren't too surprising and there are lots of cases here a reproductive barrier does occur and full speciation takes place.
For now we have a number of finch species. Only by settling on a defintion and applying that to the populations there with enough data gathered are we going to be satified that we have the 'right' number and be able to know if the number if changing up or down.
(from a previous post)
The third objection I am not familiar with. Does it apply to birds?
Yes it does. The first case of this I heard of I learned about here. There are such a series of gulls around the north pole.

This message is a reply to:
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PaulK
Member
Posts: 17838
Joined: 01-10-2003
Member Rating: 4.1


Message 44 of 104 (84921)
02-10-2004 2:42 AM
Reply to: Message 34 by Tamara
02-09-2004 3:21 PM


SO baiscally you expect me to disagree with the quote you produced and agree with some vague references you produced. And you say that *I* have to come up with something better ?
The simple fact is that there are a number of different definitions of species. NONE of them is entirely adequate. How do you think the Galapogos "finches" were originally classified ?
And no, I'm not "baiting" you over the "gill slits". Here is a structure in vertebrate embryos that is referred to as "gill slits". There are no gills but the "gill slits" are there and that is evidence of evolution. It isn't a propaganda term as you claim - it's just an old term that was coined before people knew better and has stuck. Now *WElls* is propaganda - and your misrepresentations of the Galapagos "finches" is propaganda but the "gill slits' aren't.
Now I may not be bias fee but at least I do make the effort to evaluate the claims of the other side fairly. Unlike you.
Nor do I misrepresent my position as you do :
"I am not here to convince anyone. I am here to make up my mind." (Post 16).
It's obvious that you have made up your mind and you refuse to learn.
"MrH, you make a lot of unwarranted assumption about my point of view. I am not against evolution, or science." (Post 21)
Well it is obvious that you *are* against evolution.
And no, humans do not vary as greatly as dogs.

This message is a reply to:
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Tamara
Inactive Member


Message 45 of 104 (84961)
02-10-2004 8:22 AM


NosyNed, that about sums it up. As I said, the finches would be much more persuasive as an argument if the classification were redone. Better to have two solid species than 14 iffy ones.
Too bad about the gulls... I'm gonna have to rethink my suggestion. Still... it could hold apart from the anomalies... including the marginally fertile hybrids like hinnies.

  
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