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Author Topic:   Natural Selection - not natural?
Loudmouth
Inactive Member


Message 46 of 62 (132432)
08-10-2004 4:35 PM
Reply to: Message 45 by mike the wiz
08-10-2004 3:29 PM


quote:
I think I have your drift - that evolution is observed through a change in gene pool, and survival of fittest = time not necessarily the *bingo* but in this instance, because of diversity - time *is* what it has taken to produce you and I. So I can see now that you and I may take time like the mountain, but if a change is seen = evolution. Yhis is the vagueness of the wiz-layman. How close am I?
We may have taken time like mountains, but so did every other species alive today, including bacteria. This kind of goes against the way most people think, but bacteria are the most highly evolved organisms in a sense. This is because they have been evolving for the longest period of time, some 3.5 billion years. But overall, you got it. Evolution=plate tectonics and diversity=different mountain ranges. Biodiversity is the result of long periods of evolution. Evolution happens in every generation, speciation happens after thousands of generations (or around there anyway), and the combination of these two and time results in the wonderful myriad of organisms we see today.
On a side note, where your questions sufficiently answered in regards to the quotes in your OP?

This message is a reply to:
 Message 45 by mike the wiz, posted 08-10-2004 3:29 PM mike the wiz has replied

Replies to this message:
 Message 49 by mike the wiz, posted 08-10-2004 6:05 PM Loudmouth has replied

  
pink sasquatch
Member (Idle past 6104 days)
Posts: 1567
Joined: 06-10-2004


Message 47 of 62 (132455)
08-10-2004 5:50 PM
Reply to: Message 43 by Wounded King
08-10-2004 1:30 PM


not so fast (snails)
WK- My favorite example, in part because speciation was essentially observed by the researchers, and thus serves as a counter to the "no one has ever seen a new species form" argument:
Evolution: single-gene speciation by left-right reversal.
Ueshima R, Asami T. Nature. 2003 Oct 16;425(6959):679.
The researchers witnessed a speciation event in a closed population they were studying, a single gene mutation changed the shell pattern of a snail, and the constraints of the new shell shape prevent the snails with the two types of shells from aligning their genitals to mate. But, the old-shelled snails could mate with the old-shelled, and the new-shelled could mate with other new-shelled snails. Thus snails with the shell-changing mutation are incapable of "interbreeding" with the ones without the mutation - even if they are sitting next to each other in the same pond - thus reproductive isolation.
Truthfully I'm not sure if the snail species' sex determination includes hermaphroditism, but I'm quite sure it does not include self-fertilization.
In any case, the reproductive isolation here did not proceed by changes in sex determination, but rather by pre-mating-based isolation.
There was also the Drosophilia work from a year or two ago that showed a single gene can be responsible for reproductive isolation - thus it logically follows that changes to a single gene can result in reproductive isolation (changes and isolation which could potentially occur acutely and sympatrically as opposed to mechanisms involving chronic geographic isolation...)
Also, as a side note - I just added a comment on a recent study regarding your "Evolution in the absence of selective pressure" thread:
http://EvC Forum: Evolution in the absence of selective pressures -->EvC Forum: Evolution in the absence of selective pressures
I be interested in any comments you might have...

This message is a reply to:
 Message 43 by Wounded King, posted 08-10-2004 1:30 PM Wounded King has replied

Replies to this message:
 Message 55 by Wounded King, posted 08-11-2004 7:49 AM pink sasquatch has replied

  
pink sasquatch
Member (Idle past 6104 days)
Posts: 1567
Joined: 06-10-2004


Message 48 of 62 (132460)
08-10-2004 6:00 PM
Reply to: Message 44 by mike the wiz
08-10-2004 3:13 PM


Re: definitions, again...
Am I being oversensitive? I don't think so... and perhaps you didn't state directly that I was dishonest, but when you respond to comments with "no one is honest here," I include myself in that.
Most of my confusion was why you didn't try to clarify your point in a reasonable manner, and instead started throwing "creo" and "evo" labels around...
This is because I know from previous interactions that you are normally much more articulate than the messages in this thread reveal, so when I see you write things like...
mike writes:
I said that I can do sily talk, and proseeded to do so... Infact if you dig into my babble and between the lines...
...I have trouble determining if you are arguing in good faith or not.
In any case, no grudge at all, just passing frustration...
What was the question again?

This message is a reply to:
 Message 44 by mike the wiz, posted 08-10-2004 3:13 PM mike the wiz has replied

Replies to this message:
 Message 50 by mike the wiz, posted 08-10-2004 6:08 PM pink sasquatch has replied

  
mike the wiz
Member
Posts: 4755
From: u.k
Joined: 05-24-2003


Message 49 of 62 (132461)
08-10-2004 6:05 PM
Reply to: Message 46 by Loudmouth
08-10-2004 4:35 PM


On a side note, where your questions sufficiently answered in regards to the quotes in your OP?
Yes. The two quotes struck me as "odd" or vague. The "developed" and "undeveloped" seemed like some kind of hogwash talk. I mean, I didn't see what the creationist was getting at.
Thanks for the information.
Evolution happens in every generation, speciation happens after thousands of generations (or around there anyway),
The area I don't get a lil is speciation. I must research more about it if I'm a good boy.

This message is a reply to:
 Message 46 by Loudmouth, posted 08-10-2004 4:35 PM Loudmouth has replied

Replies to this message:
 Message 51 by Loudmouth, posted 08-10-2004 6:20 PM mike the wiz has replied

  
mike the wiz
Member
Posts: 4755
From: u.k
Joined: 05-24-2003


Message 50 of 62 (132462)
08-10-2004 6:08 PM
Reply to: Message 48 by pink sasquatch
08-10-2004 6:00 PM


Re: definitions, again...
I got the questions answered.
Am I being oversensitive? I don't think so... and perhaps you didn't state directly that I was dishonest, but when you respond to comments with "no one is honest here,"
Well, Don't take it personally though. I guess I took it as dishonest that we should start this whole "define thing, else or kind" and then you say I'm off-topic. Sheesh.
Anyway - have you been an infidel? Or are you talking about previous discussions we've had at this site?

This message is a reply to:
 Message 48 by pink sasquatch, posted 08-10-2004 6:00 PM pink sasquatch has replied

Replies to this message:
 Message 54 by pink sasquatch, posted 08-10-2004 7:08 PM mike the wiz has replied

  
Loudmouth
Inactive Member


Message 51 of 62 (132470)
08-10-2004 6:20 PM
Reply to: Message 49 by mike the wiz
08-10-2004 6:05 PM


quote:
The area I don't get a lil is speciation. I must research more about it if I'm a good boy.
Boiled down, speciation is the production of two populations from one population. The definition of population is a group of interbreeding organisms. Within science, being in two different species does not prevent fertile offspring. Instead, species is a term for two populations that DON'T interbreed, but forced interbreeding may still result in fertile offspring. "Species" is a description of how organisms reproduce, not if they can interbreed.
The mechanisms of speciation are varied, but all of these mechanisms deal with how the population becomes separated into two or more sub-populations. A quick example, I remember reading a paper where bird coloration caused a slight separation within a species because of mate preference. Some of the female birds liked the new coloration of the new male birds. Other examples deal with exploitation of new food sources or geographic isolation, such as rats being moved to an island. I might be able to dig up some tutorials tutorials or primers if you feel interested (and if I do you owe me one ).

This message is a reply to:
 Message 49 by mike the wiz, posted 08-10-2004 6:05 PM mike the wiz has replied

Replies to this message:
 Message 52 by mike the wiz, posted 08-10-2004 6:32 PM Loudmouth has not replied

  
mike the wiz
Member
Posts: 4755
From: u.k
Joined: 05-24-2003


Message 52 of 62 (132474)
08-10-2004 6:32 PM
Reply to: Message 51 by Loudmouth
08-10-2004 6:20 PM


Since I'll be re-reading this post, I think it best if I refrain from any further brain-bashing tonight.
Boiled down, speciation is the production of two populations from one population.
That don't breed with one another? (Don't laugh) But that first paragraph just Bradifies me.
Instead, species is a term for two populations that DON'T interbreed, but forced interbreeding may still result in fertile offspring.
Okay - are you trying to frazzle my brain?

This message is a reply to:
 Message 51 by Loudmouth, posted 08-10-2004 6:20 PM Loudmouth has not replied

  
mike the wiz
Member
Posts: 4755
From: u.k
Joined: 05-24-2003


Message 53 of 62 (132477)
08-10-2004 6:35 PM


I think I get it now.
Look what I found while looking up a definition "To breed with another kind or species; hybridize."
ROFL.

  
pink sasquatch
Member (Idle past 6104 days)
Posts: 1567
Joined: 06-10-2004


Message 54 of 62 (132498)
08-10-2004 7:08 PM
Reply to: Message 50 by mike the wiz
08-10-2004 6:08 PM


Re: definitions, again...
Just in this forum - I think one of our discussions involved one of those "increases in complexity/genetic info" threads.
Also, when I brought up the other thread, I wasn't calling your comments off-topic - I was just trying to provide a resource for the concepts I thought you were talking about... If you have any interest RAZD did provide a link above.
________________________
Anyways:
One clarification on a comment of Loudmouth's - while generally it does take a long time for speciation to occur (thousands of years), it can take much longer, or on the other hand, can happen in a single generation (I cite an example above in this thread).
If you are still having a problem with the species "don't" vs. "can't" interbreed concept, here is an example that might help:
Crickets find mates using song recognition - a male cricket plays a song (determined by genetics), which the female recognizes (also determined by genetics).
If you have a field full of different cricket species, they only breed within species, because they base their mating upon these songs. In a way, female crickets do not "hear" male crickets of another species as possible mates. Some cricket species have compatible genitalia and other reproductive biology, so they "could" reproduce if the song barrier wasn't in place.
Now if you take a male and a female cricket from two different species as described above, and put them in a small terrarium, occasionally they will mate despite the song barrier. Also, artificial fertilization of sorts can be used to produce hybrids in the lab.
However, these two species essentially "don't" hybridize in the wild, hence the distinction between species.
Hopefully that clarifies rather than confuses.
(The next step is testing the hypothesis that mutation of the genes underlying song production or choice in these crickets is sufficient to allow a subset of crickets with the mutation to become reproductively isolated from the rest of the population... thus resulting in speciation.)

This message is a reply to:
 Message 50 by mike the wiz, posted 08-10-2004 6:08 PM mike the wiz has replied

Replies to this message:
 Message 57 by mike the wiz, posted 08-11-2004 7:16 PM pink sasquatch has replied

  
Wounded King
Member (Idle past 114 days)
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 55 of 62 (132720)
08-11-2004 7:49 AM
Reply to: Message 47 by pink sasquatch
08-10-2004 5:50 PM


Re: not so fast (snails)
I wondered if it was the snails. You should be very careful what you present because this paper doesn't actually neccessarily document an observed instance of speciation.
If all you require is that some of the offspring of a particular generation exhibit pre-mating isolation then by that criteria you have shown speciation to have occurred but the subsequent generation still produced a number of dextral snails so it is a fairly weak example.
The paper suggests very persuasively that this system will quickly lead to chiral fixation in a small population but they don't actually follow their experimental population to either two homozygote populations with opposing chiral fixations or a population with chiral fixation opposing that of the source population, although these might well have resulted from a longer study.
This is a very neat paper and it makes a very good argument but it does not document a speciation event. It may have produced speciation, in as much as two populations of homozygotes for the distinct alleles, after subsequent generations, but this is not documented in the paper.
Your explanation left out another very important feature of this particular mutation, which is that the chiral phenotype is determined by the mothers genotype rather than the offsprings. It is arguably only due to this 'delayed inheritance' that there is the possibility for this single gene speciation to occur.
If the fly gene you are thinking of is the Nup96/98 gene in the nature paper
Adaptive evolution drives divergence of a hybrid inviability gene between two species of Drosophila
DAVEN C. PRESGRAVES*, LAKSHMI BALAGOPALAN, SUSAN M. ABMAYR & H. ALLEN ORR*
Nature 423, 715 - 719 (12 June 2003)
then it does show that they identify gene which can account for reproductive isolation but it does not do so alone, there are neccessary differences between the D. simulans and D. melanogaster X chromosomes which result in the hybrid lethality.
This paper does not therefore support the argument that changes in a single gene can cause speciation/RI. But maybe you were thinking of a different paper.
Changes in a single gene can result in reproductive isolation but as far as we know only in rather unusual situations such as the 'delayed inheritance' seen in the snail example, otherwise there is the usual problems of what the mutant is going to breed with, unless the mutation occurs in a selfing population or there being a significant number of the specific mutation occurring within overlapping generations.
TTFN,
WK
p.s. I saw your post in the other thread, but thanks for the heads up.
This message has been edited by Wounded King, 08-11-2004 06:57 AM

This message is a reply to:
 Message 47 by pink sasquatch, posted 08-10-2004 5:50 PM pink sasquatch has replied

Replies to this message:
 Message 56 by pink sasquatch, posted 08-11-2004 3:24 PM Wounded King has replied

  
pink sasquatch
Member (Idle past 6104 days)
Posts: 1567
Joined: 06-10-2004


Message 56 of 62 (132886)
08-11-2004 3:24 PM
Reply to: Message 55 by Wounded King
08-11-2004 7:49 AM


Re: not so fast (snails)
It has been a while since I've read the snail paper, and I was using a rather simple reproductive-isolation-based definition. Yet, I don't think that the study is quite as weak as your comments make it out to be.
The fact that a subsequent generation pro duced both chiralities of shells doesn't necessarily weaken the single-gene-speciation event (though it does make my comment that speciation occurred in a single generation an exaggeration). True, the published work only followed the population for two o r three generations, but (I think) they showed that the mutation was already on a trend towards fixation. Hopefully, the researchers have continued to follow this population and will publish on it again.
Also, the mode of "delayed inheritance" should not weaken the example in any way. I also do not see why it is "arguably only" due to the delayed inheritance that speciation might proceed via this mutation's effects - perhaps more likely than "Mendelian" inheritance, but not "only". Given the numb er of o ffspring in a single snail brood(term?), homozygous sibs (likely) from het X het parentage would be reproductively isolated with heterozygous and wild-type sibs...
In any case, you are correct that I should not overstate the case on this one, but I think it remains a n example that many non-scientists can wrap their minds around, as opposed to many others involving single-celled organisms that would be seen as inconsequential...rrr
This message has been edited by pink sasquatch, 08-11-2004 02:27 PM

This message is a reply to:
 Message 55 by Wounded King, posted 08-11-2004 7:49 AM Wounded King has replied

Replies to this message:
 Message 60 by Wounded King, posted 08-12-2004 8:15 AM pink sasquatch has replied

  
mike the wiz
Member
Posts: 4755
From: u.k
Joined: 05-24-2003


Message 57 of 62 (132978)
08-11-2004 7:16 PM
Reply to: Message 54 by pink sasquatch
08-10-2004 7:08 PM


Re: definitions, again...
Thanks Pinky.
If you are still having a problem with the species "don't" vs. "can't" interbreed concept
So is that really all there is to it then? The "don't" aspect?
Loudmouth said that a population is a group that interbreeds.
He then said that two groups that don't interbreed? I just got a bit confused.
Thanks for the example.
Is a population simply defined by what they look like then? Am I confusing myself?

This message is a reply to:
 Message 54 by pink sasquatch, posted 08-10-2004 7:08 PM pink sasquatch has replied

Replies to this message:
 Message 58 by Loudmouth, posted 08-11-2004 7:25 PM mike the wiz has not replied
 Message 59 by pink sasquatch, posted 08-11-2004 7:33 PM mike the wiz has not replied

  
Loudmouth
Inactive Member


Message 58 of 62 (132990)
08-11-2004 7:25 PM
Reply to: Message 57 by mike the wiz
08-11-2004 7:16 PM


Re: definitions, again...
quote:
Is a population simply defined by what they look like then?
Populations tend to be homogenous because there is gene flow throughout the population. Think of it as currency. When a mint gives out a ten pound note in London, what is stopping it from staying in London? Nothing. It moves freely within the UK. However, it does not flow freely into France. There is a barrier that keeps the ten pound note out of France, and therefore the Euro and the Pound are separate "populations". (I am assuming that the UK is still using the pound). Therefore, this ten pound note will flow from person to person with ease within the UK, but where it starts (London) has little bearing on where it will stop.
This is why populations tend to look alike, because of the genetic "economy". Populations are not determined by what they look like directly, but by the "economy" that they follow. Looking alike is a consequence of being an breeding population.

This message is a reply to:
 Message 57 by mike the wiz, posted 08-11-2004 7:16 PM mike the wiz has not replied

  
pink sasquatch
Member (Idle past 6104 days)
Posts: 1567
Joined: 06-10-2004


Message 59 of 62 (132999)
08-11-2004 7:33 PM
Reply to: Message 57 by mike the wiz
08-11-2004 7:16 PM


Re: definitions, again...
Perhaps this will be helpful:
Individuals in a population interbreed with others within their own population, but not with individuals in another population.
Another complication to the definitions is that rare hybridization events (breeding of individuals from two different species) in the wild do not necessarily destroy the species boundary - think 1% or less interbreeding between two species populations...

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Wounded King
Member (Idle past 114 days)
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 60 of 62 (133134)
08-12-2004 8:15 AM
Reply to: Message 56 by pink sasquatch
08-11-2004 3:24 PM


Re: not so fast (snails)
Yet, I don't think that the study is quite as weak as your comments make it out to be.
I don't think the study is weak at all. I just think that some of the statements you made aren't really backed up by the study is all.
but (I think) they showed that the mutation was already on a trend towards fixation. Hopefully, the researchers have continued to follow this population and will publish on it again.
The trend in the paper was towards fixation of the dextral chirality, which was the same as the population the originial parent came from and would not therefore be an example of speciation. If the sinsitral chirality went to fixation or two populations with fixation of the differing alleles were produced then you would arguably have had an observed speciation event.
I also do not see why it is "arguably only" due to the delayed inheritance that speciation might proceed via this mutation's effects - perhaps more likely than "Mendelian" inheritance, but not "only".
Actually I've been thinking about this and I think I was wrong, all you need is a recessive gene and a large enough number of offspring to ensure a couple of homozygotes capable of mating, and not worrying too much about inbreeding perhaps, but in this case you would need the homozygote phenotype to present in the homozygote rather than in its progeny so you could ensure that you would only get homozygote to homozygote mating. In fact this would be a much more successful way to produce a reproductively isolated population as you would have immediate fixation of the reccessive allele in the homozygotes and their offspring. This mechanism would actually produce your single generation speciation event, I don't think this has ever been observed however.
homozygous sibs (likely) from het X het parentage would be reproductively isolated with heterozygous and wild-type sibs...
But they wouldn't. Since the maternal genotype determines the shell chirality all the offspring of a het mother would have the dextral shell chirality and be able to interbreed. Some of the next generation of offspring from the sinistral homozygote mothers would have sinistral shell chirality and be reproductively isolated, but they would not neccessarily be homozygous themselves so their offspring could still have the dextral chirality.
TTFN,
WK

This message is a reply to:
 Message 56 by pink sasquatch, posted 08-11-2004 3:24 PM pink sasquatch has replied

Replies to this message:
 Message 61 by pink sasquatch, posted 08-12-2004 3:22 PM Wounded King has replied

  
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