Punctuated Equilibrium and Stasis
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11-08-2011, 06:08 PM
RE: Punctuated Equilibrium and Stasis
(11-08-2011 11:34 AM)BadKnees Wrote:  
(11-08-2011 11:24 AM)TheBeardedDude Wrote:  That is an intriguing concept but I do not know of any specific examples of such. I assume what your asking is there a population that is so large that it segregates itself by some method thus driving evolutionary change? If so humans would be a good example. Before international travel remixed our populations we had a lot of variation that was the result of tribal segregation. These different groups and tribes left Africa and colonized other areas. Geography and climate were important drivers for evolution in this case so it is not strictly what you were asking for.

Yes, that's the gist of it if I'm reading you correctly. Humans are too messy a species (what with our artificial travel capabilities) to demonstrate this effectively though. I was thinking slow moving or small ground animal without the need for large territorial hunting grounds or the like. Perhaps some insect species or even a micro-organism?

There are species of birds and insects that segregate based on location on a tree.

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12-08-2011, 09:46 AM (This post was last modified: 12-08-2011 09:55 AM by BadKnees.)
RE: Punctuated Equilibrium and Stasis
(11-08-2011 06:08 PM)TheBeardedDude Wrote:  There are species of birds and insects that segregate based on location on a tree.

Not really what I'm getting at, I think. Let me try to present a theoretical example:
Imagine an insect that is slow-moving, non-flying, quickly reproduces, requires little territory to survive and is short-lived. Imagine a population of these insects in an environment with no natural enemies and no geographical barriers with an abundance of food. We would expect the population to grow quickly, taking up more and more physical space as they did so. Eventually the physical space occupied by the population would exceed the distance that one of the creatures could traverse in its lifespan. At some point beyond that size, is it conceivable that the the population itself could act as its own geographical barrier, such that a mutation occurring initially at one edge of the population could spread like a ring species, treating the main body of the population as a barrier?
(I made an image illustrating this, but can't seem to figure out how to post it yet.)
Well, I got it to attach at least--hopefully you can view it.


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13-08-2011, 12:34 PM
RE: Punctuated Equilibrium and Stasis
(12-08-2011 09:46 AM)BadKnees Wrote:  
(11-08-2011 06:08 PM)TheBeardedDude Wrote:  There are species of birds and insects that segregate based on location on a tree.

Not really what I'm getting at, I think. Let me try to present a theoretical example:
Imagine an insect that is slow-moving, non-flying, quickly reproduces, requires little territory to survive and is short-lived. Imagine a population of these insects in an environment with no natural enemies and no geographical barriers with an abundance of food. We would expect the population to grow quickly, taking up more and more physical space as they did so. Eventually the physical space occupied by the population would exceed the distance that one of the creatures could traverse in its lifespan. At some point beyond that size, is it conceivable that the the population itself could act as its own geographical barrier, such that a mutation occurring initially at one edge of the population could spread like a ring species, treating the main body of the population as a barrier?
(I made an image illustrating this, but can't seem to figure out how to post it yet.)
Well, I got it to attach at least--hopefully you can view it.

In this scenario no evolutionary change would occur. Mutations can cause variation and change but back-mutations would keep the mutations in check. Ergo even this population needs some physical force to aid in driving evolutionary change. The gene pool would be to well mixed to allow for mutations alone to cause evolution. Now if the isolation were to cause segregation based on type, color or family then this is a more feasible scenario. But they would have to avoid reproduction with other family/color/types in order for evolution to cause any change. Without any physical or biological barriers though they would merely be variations on a theme. Life the different races of men or the different breeds of dog. We are variable and even within small communities there is some natural segregation but any gene flow across these barriers would prevent evolution from separating the populations into new species.

Ever heard of the Hardy-Weinberg Principle? They conceptualized what would be necessary for a population to NOT evolve. (http://en.wikipedia.org/wiki/Hardy-Weinberg_principle) Check that out and see if it helps.

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13-08-2011, 07:14 PM
RE: Punctuated Equilibrium and Stasis
(13-08-2011 12:34 PM)TheBeardedDude Wrote:  In this scenario no evolutionary change would occur. Mutations can cause variation and change but back-mutations would keep the mutations in check. Ergo even this population needs some physical force to aid in driving evolutionary change. The gene pool would be to well mixed to allow for mutations alone to cause evolution. Now if the isolation were to cause segregation based on type, color or family then this is a more feasible scenario. But they would have to avoid reproduction with other family/color/types in order for evolution to cause any change. Without any physical or biological barriers though they would merely be variations on a theme. Life the different races of men or the different breeds of dog. We are variable and even within small communities there is some natural segregation but any gene flow across these barriers would prevent evolution from separating the populations into new species.
Yes, now I think I see where I went wrong. I was thinking in terms of single mutation, but describing it in terms of speciation, which obviously would require more than one mutation event separated from the main gene pool of the population. What I illustrate may be possible in terms of a single allele mutation series but would never result in a new species for the reasons you state. Is that a correct interpretation?

(13-08-2011 12:34 PM)TheBeardedDude Wrote:  Ever heard of the Hardy-Weinberg Principle? They conceptualized what would be necessary for a population to NOT evolve. (http://en.wikipedia.org/wiki/Hardy-Weinberg_principle) Check that out and see if it helps.
I had not heard of it (although looking back through the thread I see this is not the first mention of it here.) I think I have the general idea of it now--although the specifics of it will require more study on my part. Learnin new stuff! Thanks, TheBeardedDude.
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15-08-2011, 12:12 PM (This post was last modified: 15-08-2011 12:13 PM by TheBeardedDude.)
RE: Punctuated Equilibrium and Stasis
(13-08-2011 07:14 PM)BadKnees Wrote:  
(13-08-2011 12:34 PM)TheBeardedDude Wrote:  In this scenario no evolutionary change would occur. Mutations can cause variation and change but back-mutations would keep the mutations in check. Ergo even this population needs some physical force to aid in driving evolutionary change. The gene pool would be to well mixed to allow for mutations alone to cause evolution. Now if the isolation were to cause segregation based on type, color or family then this is a more feasible scenario. But they would have to avoid reproduction with other family/color/types in order for evolution to cause any change. Without any physical or biological barriers though they would merely be variations on a theme. Life the different races of men or the different breeds of dog. We are variable and even within small communities there is some natural segregation but any gene flow across these barriers would prevent evolution from separating the populations into new species.
Yes, now I think I see where I went wrong. I was thinking in terms of single mutation, but describing it in terms of speciation, which obviously would require more than one mutation event separated from the main gene pool of the population. What I illustrate may be possible in terms of a single allele mutation series but would never result in a new species for the reasons you state. Is that a correct interpretation?

(13-08-2011 12:34 PM)TheBeardedDude Wrote:  Ever heard of the Hardy-Weinberg Principle? They conceptualized what would be necessary for a population to NOT evolve. (http://en.wikipedia.org/wiki/Hardy-Weinberg_principle) Check that out and see if it helps.
I had not heard of it (although looking back through the thread I see this is not the first mention of it here.) I think I have the general idea of it now--although the specifics of it will require more study on my part. Learnin new stuff! Thanks, TheBeardedDude.

I think you get the gist of it. Evolutionary biologists would call changes in allele frequencies evolution but it is not the same as speciation. Microevolution plus multiple generations (ergo a lot of time) generates new species.
(15-08-2011 12:12 PM)TheBeardedDude Wrote:  
(13-08-2011 07:14 PM)BadKnees Wrote:  
(13-08-2011 12:34 PM)TheBeardedDude Wrote:  In this scenario no evolutionary change would occur. Mutations can cause variation and change but back-mutations would keep the mutations in check. Ergo even this population needs some physical force to aid in driving evolutionary change. The gene pool would be to well mixed to allow for mutations alone to cause evolution. Now if the isolation were to cause segregation based on type, color or family then this is a more feasible scenario. But they would have to avoid reproduction with other family/color/types in order for evolution to cause any change. Without any physical or biological barriers though they would merely be variations on a theme. Life the different races of men or the different breeds of dog. We are variable and even within small communities there is some natural segregation but any gene flow across these barriers would prevent evolution from separating the populations into new species.
Yes, now I think I see where I went wrong. I was thinking in terms of single mutation, but describing it in terms of speciation, which obviously would require more than one mutation event separated from the main gene pool of the population. What I illustrate may be possible in terms of a single allele mutation series but would never result in a new species for the reasons you state. Is that a correct interpretation?

(13-08-2011 12:34 PM)TheBeardedDude Wrote:  Ever heard of the Hardy-Weinberg Principle? They conceptualized what would be necessary for a population to NOT evolve. (http://en.wikipedia.org/wiki/Hardy-Weinberg_principle) Check that out and see if it helps.
I had not heard of it (although looking back through the thread I see this is not the first mention of it here.) I think I have the general idea of it now--although the specifics of it will require more study on my part. Learnin new stuff! Thanks, TheBeardedDude.

I think you get the gist of it. Evolutionary biologists would call changes in allele frequencies evolution but it is not the same as speciation. Microevolution plus multiple generations (ergo a lot of time) generates new species.

And I love learning new stuff. That is why I love this forum. Quite a diversity of topics to discuss!

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12-11-2011, 08:22 AM
RE: Punctuated Equilibrium and Stasis
I just found a blog post that reminded me of this topic here. It's about an article in Nature in 2009 called "Global patterns of speciation and diversity".

To quote the blog author: "...this was a computer model, but the results showed how diverse species can arise from the arrangement of organisms across an area without any influence from geographical barriers or even natural selection. Over generations, the genetic distance between organisms in different regions increases, the study noted. Organisms spontaneously form groups that can no longer mate resulting in a patchwork of species across the area. Thus the number of species increases rapidly until it reaches a relatively steady state."

This was over 2 years ago now, don't know if the results have been duplicated or refuted. Has anyone here read the article and/or know anything more about this line of questioning since the publication of the article?
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24-09-2012, 01:03 AM
RE: Punctuated Equilibrium and Stasis
I think you guys are thinking more about Gould and Elderidge who wrote about punctuated equilibrium theory. Weinberg is in there somewhere on a more biologically genetic level, however, the main theory of evolution that was posed at the beginning of this thread has more to do with Gould and Elderidge. I would suggest you read a collegial paper by Monalie C. Saylo, Cheryl C. Escoton, and Micah M. Saylo titled Punctuated Equilibrium vs. Phyletic Gradualism. This paper explains the process nicely.
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24-09-2012, 05:13 AM
RE: Punctuated Equilibrium and Stasis
(24-09-2012 01:03 AM)hika-chi Wrote:  I think you guys are thinking more about Gould and Elderidge who wrote about punctuated equilibrium theory. Weinberg is in there somewhere on a more biologically genetic level, however, the main theory of evolution that was posed at the beginning of this thread has more to do with Gould and Elderidge. I would suggest you read a collegial paper by Monalie C. Saylo, Cheryl C. Escoton, and Micah M. Saylo titled Punctuated Equilibrium vs. Phyletic Gradualism. This paper explains the process nicely.

Welcome to the forum.

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