Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 115 (8752 total)
Current session began: 
Page Loaded: 05-29-2017 1:52 AM
112 online now:
Dredge, dwise1, Tangle (3 members, 109 visitors)
Chatting now:  Chat room empty
Newest Member: DeliverUsFromEvolution
Post Volume:
Total: 809,178 Year: 13,784/21,208 Month: 3,266/3,605 Week: 52/556 Day: 3/49 Hour: 2/1

Announcements: Reporting debate problems OR discussing moderation actions/inactions


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Prev1
...
4567
8
9Next
Author Topic:   Peter & Rosemary Grant, Darwin's Finches and Evolution
RAZD
Member
Posts: 18478
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.8


(1)
Message 106 of 131 (725978)
05-05-2014 9:42 AM
Reply to: Message 94 by Faith
05-05-2014 4:44 AM


Re: " narrowing down of traits"
Need to say more about "narrowing down of traits" which I didn't grasp at first. You say this isn't happening. But it has to happen in Natural Selection, for instance, where only the adaptive traits are preserved. The ones that didn't work for the environmental situation drop out, are maybe even killed off by a predator. ...

That is how less fit individuals are removed from the breeding population.

... That's a narrowing down of traits isn't it?

Not necessarily. If the population grows by 20% due to reproduction success, but half of those don't make it to breeding age then the population still grows by 10%.

Whether a population grows, shrinks or remains the same size is a function of selection pressure: lower pressure means more survival\reproduction, while higher pressure means less survival\reproduction.

But even the simple case of microevolution by migration of a small number of founders ...

A very confused phrase.

Consider this instead: a population grows and spreads into adjoining ecosystems, some that are marginal for survival and reproduction. Individuals that move into these marginal areas will be under different selection pressure than the parent population, and those that survive to breed will be those individuals more able to take advantage of the resources in that marginal ecosystem. Let's say larger harder seeds, so birds with larger stronger beaks will have an easier surviving than ones with smaller weaker beaks.

... has to lead to the same situation, and a new species could develop from that new population, which really could happen in a short time if it has favorable conditions for long term inbreeding. ...

When does breeding become inbreeding?

What is a new species?

So the daughter population in the marginal ecology develops larger stronger beaks on average than the parent population.

This would be evolution, but not necessarily speciation at this point.

... It's going to develop its own traits that are different from those of the mother population. ...

Depending on the gene flow between the parent population and the population in the adjoining ecosystem. As gene flow decreases more differences will develop, and it is also likely that as more differences develop that gene flow will decrease (individuals from the other population may be less desirable as mates than individuals in their own population)

... If the old traits are low frequency enough their alleles will disappear from the new population altogether. ...

So the traits for small beaks will tend to be eliminated, while the variation around beak size will be the same, just with a larger average beak size in the adjoining population, ... and the variation of beak size in the parent population remains as before.

... This is a "narrowing down of traits" isn't it?

Or an increase in traits overall between both populations, more than existed previously, with room to increase further.

Enjoy.


we are limited in our ability to understand
by our ability to understand
RebelAmerican☆Zen☯Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 94 by Faith, posted 05-05-2014 4:44 AM Faith has responded

Replies to this message:
 Message 107 by NoNukes, posted 05-05-2014 10:34 AM RAZD has acknowledged this reply
 Message 108 by Faith, posted 05-05-2014 3:31 PM RAZD has responded

  
NoNukes
Member
Posts: 9551
From: Central NC USA
Joined: 08-13-2010
Member Rating: 3.1


(3)
Message 107 of 131 (725981)
05-05-2014 10:34 AM
Reply to: Message 106 by RAZD
05-05-2014 9:42 AM


Re: " narrowing down of traits"
Not necessarily. If the population grows by 20% due to reproduction success, but half of those don't make it to breeding age then the population still grows by 10%.

The analogy I've come up with is that Faith is looking down a telescope backwards and ignoring a bunch of stuff. She pictures a final breed that is narrowly defined coming from an initial diverse population and figures that all of those traits not in the final breed are lost.

That may be what dog breeders do. I'm guessing that they neuter, discard, or otherwise eliminate from the stock the dogs that don't look like the ones they want. But in the wild, unless the new traits provide some survival possibility, those 'mistakes' continue to thrive and can drift through either both populations. In the end, it might well be that in the population of dogs, no traits are lost.

For example, humans have traits that were re-integrated from Neanderthals.

And of course as someone else has noted, some new traits provide new opportunities for diversity. Using the given example, a mutation that provides a plume also provides opportunity for colorful plume variations. Or we might look at all of the variations mammals have in their inner ear that only became possible once the structure had evolved.

And of course, there is the fact that if mutation come overcome the loss of diversity from one trait, it is only logical that the same can happen to counteract the loss of diversity from several traits.

Is all of current humanity, 7 billion people less diverse phenotypically and genetically than a hypothetical pairing of Adam and Eve, only 6000 years ago? Or than eight people 4400 years ago? Really?

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I have never met a man so ignorant that I couldn't learn something from him. Galileo Galilei

If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass


This message is a reply to:
 Message 106 by RAZD, posted 05-05-2014 9:42 AM RAZD has acknowledged this reply

    
Faith
Member
Posts: 24846
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 108 of 131 (725990)
05-05-2014 3:31 PM
Reply to: Message 106 by RAZD
05-05-2014 9:42 AM


Re: " narrowing down of traits"

Need to say more about "narrowing down of traits" which I didn't grasp at first. You say this isn't happening. But it has to happen in Natural Selection, for instance, where only the adaptive traits are preserved. The ones that didn't work for the environmental situation drop out, are maybe even killed off by a predator. ...

That is how less fit individuals are removed from the breeding population.

Yes, RAZD, but the point I'm making is that this process brings about the [abe] removal of traits [/abe] along with reduction of genetic diversity I've been focusing on, and if the culling is radical even possibly the complete loss of some alleles from the population, and this loss of genetic diversity is what compromises the ability of the species to vary further [abe] as it continues to evolve [/abe]down the path of variation or speciation, which is the whole thing I'm focusing on here. The very processes that bring about a new species eventually make it impossible for the species to continue to vary.

... That's a narrowing down of traits isn't it?

Not necessarily. If the population grows by 20% due to reproduction success, but half of those don't make it to breeding age then the population still grows by 10%.

If you are still talking about traits that's not at all evident from this statement and you may want to rewrite it, as the size of the population is another subject from the frequency of the traits and their alleles in the population. Their frequency is affected by their selection for fitness if that is in fact in operation, which is the subject here. Again if the selection is severe there may be no alleles left at all except those that underlie the successful traits. (And of course if it's even more severe extinction may be the result.) This is certainly a "narrowing down of traits."

Whether a population grows, shrinks or remains the same size is a function of selection pressure: lower pressure means more survival\reproduction, while higher pressure means less survival\reproduction.

But here again you are talking about population size which is at best incidental in the context of loss of traits and their alleles.

But even the simple case of microevolution by migration of a small number of founders ...

A very confused phrase.

The problem is that we are thinking of different things. There's nothing confused about it in the context of what I'm talking about which is what happens to the TRAITS and their alleles, which is brought about by the reproductive isolation of a small number of individuals, which can be brought about by migration of those individuals or by natural selection of those individuals or even by sexual selection of those individuals within the larger population. The size of the population that develops subsequently is something else.

Consider this instead: a population grows and spreads into adjoining ecosystems, some that are marginal for survival and reproduction. Individuals that move into these marginal areas will be under different selection pressure than the parent population, and those that survive to breed will be those individuals more able to take advantage of the resources in that marginal ecosystem. Let's say larger harder seeds, so birds with larger stronger beaks will have an easier surviving than ones with smaller weaker beaks.

OK, yes, of course, but accepting your scenario my point is how such selection of traits leads to reduced genetic diversity for that population. This is the more severe the more such pressures exist, pressures of natural selection, adaptive requirements for particular beaks and so on. The more pressure, the more culling of the unfit beaks and their alleles, and the less genetic diversity in the population as a whole.

... has to lead to the same situation, and a new species could develop from that new population, which really could happen in a short time if it has favorable conditions for long term inbreeding. ...

When does breeding become inbreeding?

When you have a daughter population that is reproductively isolated it helps to use the term inbreeding to describe the confinement of the genetic possibilities to that gene pool exclusively and the absence of gene flow between the daughter and parent populations. Since speciation is defined as the loss of ability to INTERbreed with the former populations I'm simply looking for ways to keep the different populations conceptually distinct from each other.

What is a new species?

A new population that is separate from other populations of the larger Species that has developed distinct traits of its own that clearly differentiate it from the mother population from which it has diverged, as well as any cousin populations, which happens because of reproductive isolation of the new population, which may be the result of geographic isolation or natural selection etc. Over time this can lead to inability to interbreed with the other populations which is of course where standard evolutionary theory identifies it as a new species.

So the daughter population in the marginal ecology develops larger stronger beaks on average than the parent population.

This would be evolution, but not necessarily speciation at this point.

Yes, and I'm focused on EVOLUTION, which is the change in the character of a new population that occurs through the reproductive isolation of a portion and a number of generations of inbreeding. Speciation as formally understood may or may not occur. Call it a new "subspecies" then.

... It's going to develop its own traits that are different from those of the mother population. ...

As gene flow decreases more differences will develop,

Yes, RAZD, which is a condition I have been emphasizing all along.

and it is also likely that as more differences develop that gene flow will decrease (individuals from the other population may be less desirable as mates than individuals in their own population)

Yes that is very likely to happen also. But the main thing that I want to keep in view here, that is happening in the absence of gene flow and the development of the distinctive traits of the new population, is the decrease in genetic diversity of that population.

... If the old traits are low frequency enough their alleles will disappear from the new population altogether. ...

So the traits for small beaks will tend to be eliminated,

Yes, the small beaks will tend to be eliminated, and the ALLELES for small beaks will tend to be eliminated..

while the variation around beak size will be the same, just with a larger average beak size in the adjoining population, ... and the variation of beak size in the parent population remains as before.

I'm not sure what you mean or if it is true that "the variation around beak size will be the same" or why this would be the case, since if a larger beak has been selected it should eventually become a consistent feature of the new population. And I'm not sure what your point is about the "adjoining population." But I can completely agree that "the variation of beak size in the parent population remains as before" ASSUMING it is appreciably larger in numbers than the daughter population (because if it's not that population too would have appreciably new allele frequencies and also develop some change in its phenotypic presentation)

... This is a "narrowing down of traits" isn't it?

Or an increase in traits overall between both populations, more than existed previously, with room to increase further.

Yes there is always room for the increase in TRAITS, the phenotypic presentation, even more than previously, yes, this is what evolution does, it brings out new traits, but what I keep trying to point out is that it does this WITH RESPECT TO ANY GIVEN POPULATiON by culling the traits that don't fit, so that their alleles disappear from that particular population along with the traits themselves, which is a decrease in genetic diversity, so that any further selection, isolation, culling itself will further reduce that genetic diversity WHILE BRINGING OUT EVEN MORE NEW TRAITS in subsequent daughter populations, so that at every stage you are getting the development of populations characterized by new collections of traits AND the loss of genetic diversity, so that if these processes continue you ultimately reach a point where you can't get further variation of traits because the traits you have at that extremity of the evolving pathway are going to be predominantly or even exclusively homozygous throughout the whole group.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : mostly changes in punctuation, emphasis etc.

Edited by Faith, : to add "or even exclusively" homozygous

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : Punctuation

Edited by Faith, : just keep adding abe:s hoping to improve clarity


This message is a reply to:
 Message 106 by RAZD, posted 05-05-2014 9:42 AM RAZD has responded

Replies to this message:
 Message 109 by RAZD, posted 05-06-2014 11:02 AM Faith has responded
 Message 111 by Dr Adequate, posted 05-06-2014 4:18 PM Faith has responded

    
RAZD
Member
Posts: 18478
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.8


(2)
Message 109 of 131 (726069)
05-06-2014 11:02 AM
Reply to: Message 108 by Faith
05-05-2014 3:31 PM


Re: " narrowing down of traits" and the "expansion of traits"
Yes, RAZD, but the point I'm making is ...

... still wrong.

... that this process brings about the [abe] removal of traits [/abe] along with reduction of genetic diversity I've been focusing on, ...

While ignoring the addition of traits by mutations -- a process you now admit can cause "curly ears" in cats.

... and if the culling is radical even possibly the complete loss of some alleles from the population, ...

Some alleles are probably lost every generation -- ones less able to provide ability to survive and reproduce and certainly new ones that are lethal. The loss of less viable alleles does not cause extinctions.

... and this loss of genetic diversity is what compromises the ability of the species to vary further ...

Which doesn't happen: the amount of mutation is independent of the number of alleles. The amount of new diversity introduced into a breeding population is related to the size of the population. This is why small founding populations have restricted variations in traits at the start, but this still doesn't inhibit new traits from occurring due to mutations.

... as it continues to evolve down the path of variation or speciation, which is the whole thing I'm focusing on here. The very processes that bring about a new species eventually make it impossible for the species to continue to vary.

So you will be relieved to know that this doesn't occur.

If you are still talking about traits that's not at all evident from this statement and you may want to rewrite it, as the size of the population is another subject from the frequency of the traits and their alleles in the population. ...

But here again you are talking about population size which is at best incidental in the context of loss of traits and their alleles.

No Faith, population size is directly related to the degree of diversity available in a breeding population. A small population cannot have as much diversity as a large population.

However, when you divide a breeding population into two isolated breeding populations you do not lose diversity relative to the ecological whole, rather you increase the opportunity for new traits to survive in different ecological space.

... Their frequency is affected by their selection for fitness if that is in fact in operation, which is the subject here. ...

Sadly, for you, this is not a matter of debate, it is a fact that natural selection occurs, it is an observed and documented process, and denial of it is delusional.

The Grants alone have observed and documented natural selection occurring on the Galapagos Islands for 40 years.

... Again if the selection is severe there may be no alleles left at all except those that underlie the successful traits. ...

Which still leaves the population viable with successful survival and reproductive traits as more new traits are added due to mutations.

... (And of course if it's even more severe extinction may be the result.) This is certainly a "narrowing down of traits."

Extinction would be a "narrowing down of traits" ... but the cause of extinction is not the loss of traits, it is the failure to survive and reproduce, natural selection at its most stern implementation, regardless of the diversity of traits in the population.

The problem is that we are thinking of different things. There's nothing confused about it in the context of what I'm talking about which is what happens to the TRAITS and their alleles, which is brought about by the reproductive isolation of a small number of individuals, which can be brought about by migration of those individuals or by natural selection of those individuals or even by sexual selection of those individuals within the larger population. The size of the population that develops subsequently is something else.

Indeed, I am talking about evolution occurring according to the observed and documented processes (scientific facts) of mutations adding new traits and selection removing the less viable traits from the populations

OK, yes, of course, but accepting your scenario my point is how such selection of traits leads to reduced genetic diversity for that population. This is the more severe the more such pressures exist, pressures of natural selection, adaptive requirements for particular beaks and so on. The more pressure, the more culling of the unfit beaks and their alleles, and the less genetic diversity in the population as a whole.

And with pressure for larger stronger beaks we see the survival and reproduction of those with the largest beaks being more pronounced than before, that the average beak size increases, that new even larger beaks survive and reproduce as mutations in that direction that were deleterious before now become beneficial.

The amount of variation in size in a population is typically a normal distribution around the average size. This whole pattern shifts towards larger beaks allowing the opportunity for even larger beaks to survive.

Your thinking is hampered by your false preconceptions.

When you have a daughter population that is reproductively isolated it helps to use the term inbreeding to describe the confinement of the genetic possibilities to that gene pool exclusively and the absence of gene flow between the daughter and parent populations. ...

So you are misusing a word again. Inbreeding is generally considered the mating or breeding of individuals or organisms which are closely related genetically, such as parent, brother, sister, child, such that they share almost all of the same traits.

With your usage every breeding population is "inbreeding" and the term become meaningless.

... Since speciation is defined as the loss of ability to INTERbreed with the former populations I'm simply looking for ways to keep the different populations conceptually distinct from each other.

The actual loss of ability to interbreed does not necessarily occur, what usually happens is that reproductive isolation occurs for any of a number of factors, including plain loss of attraction. Of course the further your daughter populations diverge the greater is the opportunity for inviable offspring to occur, but this can be many generations after interbreeding has ceased.

A new population that is separate from other populations of the larger Species the parent population that has developed distinct traits of its own that clearly differentiate it from the mother population from which it has diverged, as well as any cousin populations , which happens because of reproductive isolation of the new population between the populations, which may be the result of geographic isolation or natural selection etc. Over time this can lead to inability to interbreed with the other populations which is of course where standard evolutionary theory identifies it as a new species.

All that's needed is the loss of interbreeding between populations such that each population evolves without gene flow from the other population/s.

Yes, and I'm focused on EVOLUTION, which is the change in the character of a new population that occurs through the reproductive isolation of a portion and a number of generations of inbreeding. Speciation as formally understood may or may not occur. Call it a new "subspecies" then.

Ah, you are talking about macroevolution ... rather than microevolution.

Tell me Faith, if a whole breeding population moves into a new ecology (or the ecology changes around them) and they develop new frequency distribution of traits plus the new traits from mutations, in response to the opportunities and challenges of the new ecosystem ... the very same process as your daughter population above, but for the whole population (no parent population left behind) ... would that be a new species?

As gene flow decreases more differences will develop,

Yes, RAZD, which is a condition I have been emphasizing all along.

Allow me to rephrase for clarity: As gene flow decreases new differences will develop between populations with restricted gene flow due to more and more new traits not being shared.

Yes that is very likely to happen also. But the main thing that I want to keep in view here, that is happening in the absence of gene flow and the development of the distinctive traits of the new population, is the decrease in genetic diversity of that population.

Which is still wrong on two counts:

(1) as far as the rest of the ecology is concerned it makes no difference whether there is a homogeneous population of diverse individuals or two separated populations with the same overall diversity: total diversity within the ecology has not decreased.

(2) while this process of isolation is going on, new traits are constantly being added and tested by selection within each population -- which will necessarily have different results in isolated population under different selection pressures -- and thus total diversity within the ecology will increased.

Yes, the small beaks will tend to be eliminated, and the ALLELES for small beaks will tend to be eliminated..

And the alleles for larger beaks would tend to increase within the population. New alleles for larger beaks would be selected as they occur.

I'm not sure what you mean or if it is true that "the variation around beak size will be the same" or why this would be the case, since if a larger beak has been selected it should eventually become a consistent feature of the new population. ...

These aren't quantum size jumps Faith, it is a spectrum of sizes, where beaks run from "too big" to "too small" and a fairly large group of "good enough to survive and breed" ... and what changes is the "good enough to survive" size, increasing within the variation already occurring within the population (selection only works on what is available), while providing opportunity for larger beaks to exist than before within the overall population variation.

... But I can completely agree that "the variation of beak size in the parent population remains as before" ASSUMING it is appreciably larger in numbers than the daughter population (because if it's not that population too would have appreciably new allele frequencies and also develop some change in its phenotypic presentation)

Unless caused by catastrophic separation the parent population will tend to be comprised of the individuals most fit to meet the challenges and benefit from the opportunities in the parent ecology, and the individuals less fit will tend to foray into neighboring ecologies. Think of the dark pocket mice moving onto the lava beds while the parent tan mice remain in the desert sands. There is no reason for the frequency of alleles to shift appreciably for the tan mice, but there is for the dark mice.

Yes there is always room for the increase in TRAITS, the phenotypic presentation, even more than previously, yes, this is what evolution does, it brings out new traits, ...

Close. It allows new traits to be positively selected that previously were negatively selected. It allows new traits to arise that did not exist before, building on the mix of traits in the population. Like stepping stones. First you get a plume feather on the head, then it becomes red ...

... but what I keep trying to point out is that it does this WITH RESPECT TO ANY GIVEN POPULATiON by culling the traits that don't fit, ...

Which happens in all populations every generation, it's called natural selection. The other half of evolution is the mutations that provide new variety within the population which is then subject to the next round of selection ... a two-step feedback response system that is repeated in each generation:

Like walking on first one foot and then the next.

... so that their alleles disappear from that particular population along with the traits themselves, ...

A process underway all the time as less viable traits are selected against in favor of new successful traits.

... which is a decrease in genetic diversity, so that any further selection, isolation, culling itself will further reduce that genetic diversity ...

Only as long as you ignore and deny the addition of genetic diversity from new mutations. They may not balance every generation, but they would tend to balance over time as long as the ecology doesn't become lethal (global climate change?).

... WHILE BRINGING OUT EVEN MORE NEW TRAITS in subsequent daughter populations, ...

From new mutations that are selected for their viability at survival and reproduction within the daughter population ecology (which is necessarily different from the parent population ecology).

... so that at every stage you are getting the development of populations characterized by new collections of traits ...

That are viable within the ecology and provide sufficient success at survival and reproduction, a process that occurs in all population in all generations.

... AND the loss of genetic diversity, so that if these processes continue you ultimately reach a point where you can't get further variation of traits because the traits you have at that extremity of the evolving pathway are going to be predominantly or even exclusively homozygous throughout the whole group.

Except for all those new traits from mutations that survived selection in the new ecologies.

Certainly if the new traits cannot keep up with the challenges of the ecologies populations can go extinct, but one can just as easily have the quantity of new traits exceed the needs of the population to survive and breed so that some will be culled by selection, changing the types of diversity involved while leaving the degree of diversity of the population as a whole basically unchanged.

Enjoy


we are limited in our ability to understand
by our ability to understand
RebelAmerican☆Zen☯Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 108 by Faith, posted 05-05-2014 3:31 PM Faith has responded

Replies to this message:
 Message 110 by Faith, posted 05-06-2014 3:46 PM RAZD has responded
 Message 113 by Faith, posted 05-06-2014 5:01 PM RAZD has responded

  
Faith
Member
Posts: 24846
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 110 of 131 (726115)
05-06-2014 3:46 PM
Reply to: Message 109 by RAZD
05-06-2014 11:02 AM


Re: " narrowing down of traits" and the "expansion of traits"
Yes, RAZD, but the point I'm making is ...
... that this process brings about the [abe] removal of traits [/abe] along with reduction of genetic diversity I've been focusing on, ...

While ignoring the addition of traits by mutations -- a process you now admit can cause "curly ears" in cats.

Your post didn't mention mutations so I didn't. That doesn't mean I ignore them, I've responded over and over to the claim that mutations add genetic diversity by assuming for the sake of argument that this occurs and answering accordingly, and the conclusion I keep coming to and trying to demonstrate is that the inevitable trend even WITH mutations is to decrease in or loss of genetic diversity WHEREVER EVOLUTION IS ACTUALLY OCCURRING, evolution meaning selection and isolation processes that lead to the development of a new subspecies or even species, that is, the development of a population-wide divergence in phenotypic character from other populations of the same Species. Any increase in genetic diversity starts with new traits appearing in individuals, which creates a variegated population that may grow in population but remain static as far as evolutionary processes are concerned. These may spread generally in the population over generations of mixing, there may be genetic drift that brings out some change in the overall character of the population, but the rule is that takes selection of traits to begin the processes of evolution, otherwise any new traits remain scattered in individuals throughout the population.

... and if the culling is radical even possibly the complete loss of some alleles from the population, ...

Some alleles are probably lost every generation -- ones less able to provide ability to survive and reproduce and certainly new ones that are lethal. The loss of less viable alleles does not cause extinctions.

Which is a completely different subject. I'm talking about the situation where alleles are lost WITHIN A GIVEN POPULATION because of their lower frequency in the gene pool where new traits are developing based on the higher frequency of other alleles for those traits. This has nothing to do with extinction at all and I said nothing of the sort. The alleles that drop out of a new population are still present in other populations of the Species, they are only dropping out in the population I'm talking about, the one that's evolving. This is also the context in which the decrease in genetic diversity is developing. The context in which these things are happening in my scenario is ALWAYS the given evolving population, the particular evolving pathway as I've called it, NOT THE GREATER POPULATION of the Species. So, to repeat, if within this evolving daughter population the culling of traits and their alleles is severe there can be a complete loss of some alleles from the population.

Here's an overview: There could be a number of daughter populations of the same Species evolving at the same time in different geographic locations. The original population could have had a gray coat, black eyes and bushy tails. One of the daughter populations could have a new set of allele frequencies that brings out a black coat, green eyes and even bushier tails. Another daughter population could have a lighter gray coat, the green eyes of the cousin population and short stubby tails and so on. EACH of these populations, all of the same Species, over a number of generations in reproductive isolation from each other, can develop its own set of traits to the point that it is distinctively recognizable from all the others and may even eventually lose the genetic ability, at least the behavioral inability, to interbreed with the others. Each will have the reduced genetic diversity I'm talking about with respect to the traits that are favored in the other groups, and may even completely lose the alleles for those traits, but they will nevertheless remain in those other groups and proliferate there. THIS CAN ALL COME ABOUT MERELY FROM THE SEXUAL RECOMBINATON OF EXISTING ALLELES, mutation is not required, but even assuming mutation WAS the source of the various traits, the process of evolving a new subpopulaton with new characteristics from the others, HAS TO decrease or eliminate the alleles for characteristics that are not developing in that group OR those characteristics simply won't develop and you won't have your new species or even subspecies. it's not that new species have to develop, it's that IF they develop this is how it has to happen.

... and this loss of genetic diversity is what compromises the ability of the species to vary further ...

Which doesn't happen: the amount of mutation is independent of the number of alleles.

I would refer you back to the example of domestic breeding then, where it certainly can and does happen if an animal is overbred, and the trend even before that situation arises is always more and more loss of genetic diversity, because this HAS to happen IF you are going to get a recognizable set of traits that constitute the breed. If you DON'T lose genetic diversity you don't have a distinctive breed. There cannot be a significant number of alleles in the population for traits OTHER than those that characterize that breed, and where undesired traits do occur the selection of mates for the desired traits continues until the undesired traits simply no longer exist in the gene pool. It may be rare to arrive at the purebred situation of homozygosity for the desired traits, but that is the ideal, all other alleles having disappeared from the gene pool.

Again, to get phenotypic evolution requires genetic culling or decreased genetic diversity. AND IT DOESN"T MATTER IF THE SOURCE OF THE ALLELES IS MUTATION OR NOT: THE UNDESIRED TRAITS STILL HAVE TO DISAPPEAR, and their alleles have to become lower frequency or finally disappear completely, while the desired traits become higher frequency and their alleles may even eventually be the ONLY alleles in the whole population for the desired traits, which is the condition of fixed loci or homozygosity for all those traits, ALL OTHER ALLELES FOR OTHER TRAITS HAVING DISAPPEARED COMPLETELY FROM THE POPULATION.

While this process occurs intentionally in domestic breeding, the same basic genetic situation also has to occur in the wild wherever new species or subspecies develop: formation of new traits depends on reduction or absence of alleles for other traits.

I am of course repeating this because what you are saying denies it though it is obvious and inevitable. Increasing genetic diversity is the opposite of evolution of new species/subspecies so mutations would do nothing but interfere with evolutionary processes. Again, these DEPEND on genetic decrease.

The amount of new diversity introduced into a breeding population is related to the size of the population.

Yes, a static population would acquire more new phenotypes whether the cause is mutation or simple sexual recombination of existing alleles. This is not an EVOLVING population as I'm describing it, and again it's only when some of the traits are selected and reproductively isolated that you start to get the evolution of a new POPULATON with some collection of those traits that changes its look from the mother population.

This is why small founding populations have restricted variations in traits at the start, but this still doesn't inhibit new traits from occurring due to mutations.

Restricted variations at the beginning of a new population are simply based on the holdover of the traits from the original population from which it split. It will still have the look of the original population at that point. New traits don't start to appear for a few generations as new genetic combinations are brought out through sexual recombination -- OR mutations if you insist on that but mutations are NOT necessary to bringing out new phenotypes. It will take a few generations for the new allele frequencies to work through the new population and bring out the high frequency traits while decreasing the low frequency traits and diverging more and more in appearance from the mother population. This WILL occur simply due to the new allele frequencies after a few generations. The population will be growing too as the new phenotypes are appearing, scattered in the population at first, until after many generations of inbreeding in reproductive isolation they are mixed together into a general appearance that differs visibly from the old population. If the founding population was small enough a fixed set of traits may be the final result from which further variation is not possible, or this may take more population splits as in a ring species to get to a final species with the inability to vary further.

... as it continues to evolve down the path of variation or speciation, which is the whole thing I'm focusing on here. The very processes that bring about a new species eventually make it impossible for the species to continue to vary.

So you will be relieved to know that this doesn't occur.

It has to, RAZD, you are not going to get a new breed in domestic programs OR a new species or even subspecies in the wild UNLESS this happens. There's nothing to be "relieved" about. This will happen in any given population that is evolving. The greater population may not be evolving.

I'm going to stop here for now because you aren't getting it and I'm repeating it over and over because you aren't getting it, so you'll either get it from this much repetition or you won't but your post is very long and if there's more to respond to in it I'll come back to it later.

Cheers.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


This message is a reply to:
 Message 109 by RAZD, posted 05-06-2014 11:02 AM RAZD has responded

Replies to this message:
 Message 112 by PaulK, posted 05-06-2014 4:34 PM Faith has not yet responded
 Message 116 by RAZD, posted 05-06-2014 10:36 PM Faith has responded

    
Dr Adequate
Member
Posts: 15929
Joined: 07-20-2006
Member Rating: 3.8


Message 111 of 131 (726122)
05-06-2014 4:18 PM
Reply to: Message 108 by Faith
05-05-2014 3:31 PM


Re: " narrowing down of traits"
Yes, RAZD, but the point I'm making is that this process brings about the [abe] removal of traits [/abe] along with reduction of genetic diversity I've been focusing on, and if the culling is radical even possibly the complete loss of some alleles from the population, and this loss of genetic diversity is what compromises the ability of the species to vary further [abe] as it continues to evolve [/abe]down the path of variation or speciation, which is the whole thing I'm focusing on here. The very processes that bring about a new species eventually make it impossible for the species to continue to vary.

Unless mutation exists. Oh look, it does.

A new population that is separate from other populations of the larger Species that has developed distinct traits of its own that clearly differentiate it from the mother population from which it has diverged, as well as any cousin populations, which happens because of reproductive isolation of the new population, which may be the result of geographic isolation or natural selection etc. Over time this can lead to inability to interbreed with the other populations which is of course where standard evolutionary theory identifies it as a new species.

So, consider the following scenario. A species is homozygous for traits A and B. A breeding pair of the species is marooned on an island by a freak wind. Some years later, an allele A* arises in the new population and replaces A. Then an allele B* arises in the new population and replaces B. The parent population continues as it was. Now if zygotes with the alleles A and B* are inviable, then by definition the new population is a new species (if not it is at least a new variety).

Note that the clade has undergone a net increase in genetic diversity and that neither species has undergone a net reduction in genetic diversity.

Now there are two points in this process where the daughter group loses genetic diversity --- where it goes from a mixed A/A* to an all A* population, and then again where it goes from a mixed B/B* to an all B*. But there is no net loss of diversity in either species.


This message is a reply to:
 Message 108 by Faith, posted 05-05-2014 3:31 PM Faith has responded

Replies to this message:
 Message 117 by Faith, posted 05-07-2014 5:04 AM Dr Adequate has responded

  
PaulK
Member
Posts: 12688
Joined: 01-10-2003
Member Rating: 2.8


Message 112 of 131 (726129)
05-06-2014 4:34 PM
Reply to: Message 110 by Faith
05-06-2014 3:46 PM


Re: " narrowing down of traits" and the "expansion of traits"
quote:

Your post didn't mention mutations so I didn't. That doesn't mean I ignore them, I've responded over and over to the claim that mutations add genetic diversity by assuming for the sake of argument that this occurs and answering accordingly...

Which generally takes the from of finding excuses to ignore them.

quote:

...and the conclusion I keep coming to and trying to demonstrate is that the inevitable trend even WITH mutations is to decrease in or loss of genetic diversity WHEREVER EVOLUTION IS ACTUALLY OCCURRING, evolution meaning selection and isolation processes that lead to the development of a new subspecies or even species, that is, the development of a population-wide divergence in phenotypic character from other populations of the same Species

So you have to invent your own definition of evolution. However, redefining evolution to exclude increases in genetic diversity, doesn't change the fact that you still have to take them into account to have a valid argument. So, even if your definition were correct it's irrelevant. And that is why it is just an excuse. You aren't coming to a conclusion, you'r making excuses to keep to your desired conclusion.

So we're back to the model where there are decreases in genetic diversity during the period of speciation, counterbalanced in successful species be increases in diversity during the period of growing and large populations.

So far your only objection to that happening is that if that were the case something would prevent speciation. But I'm still waiting to find out what it could be. If your position is really the product of thought then why haven't you suggested anything that could do it ? Or even any idea of how it could do it ?


This message is a reply to:
 Message 110 by Faith, posted 05-06-2014 3:46 PM Faith has not yet responded

    
Faith
Member
Posts: 24846
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 113 of 131 (726140)
05-06-2014 5:01 PM
Reply to: Message 109 by RAZD
05-06-2014 11:02 AM


Re: " narrowing down of traits" and the "expansion of traits"
If you are still talking about traits that's not at all evident from this statement and you may want to rewrite it, as the size of the population is another subject from the frequency of the traits and their alleles in the population. ...

But here again you are talking about population size which is at best incidental in the context of loss of traits and their alleles.

No Faith, population size is directly related to the degree of diversity available in a breeding population. A small population cannot have as much diversity as a large population.

OK as a general rule, but large populations are generally not evolving as I keep trying to keep in focus. It is WHEN you get the reduced numbers with the reduced diversity that you get the best examples of evolution of new traits that characterize a new population, which also shows the trend of decreased genetic diversity I'm also trying to keep in focus.

The larger population may be relatively static but you CAN can get the same effect even in a larger population if there is strong genetic drift which favors some traits over others, which is another example of a reproductively isolated group, this one physically within the larger population but genetically unaffected by it. As this new population develops within the larger population it too has to lose genetic diversity AS A GROUP as it acquires a new look that diverges from the greater population. In all cases where evolution is happening by the usual means of selection and isolation that I'm talking about, if you are getting a new subspecies you are also getting reduced genetic diversity. It HAS to happen or you are not getting that new species or subspecies.

[q\s] However, when you divide a breeding population into two isolated breeding populations you do not lose diversity relative to the ecological whole, rather you increase the opportunity for new traits to survive in different ecological space. [/qs]

This may be the case but all I'm talking about is the mechanisms or processes that bring about a divergence in traits between two separate populations, and this is always the same no matter what else is going on. If strong selection pressure occurs you'll get a dramatic development of adaptive traits with a more dramatic loss of the unadaptive traits. It will simply speed up the normal processes.

... Their frequency is affected by their selection for fitness if that is in fact in operation, which is the subject here. ...

Sadly, for you, this is not a matter of debate, it is a fact that natural selection occurs, it is an observed and documented process, and denial of it is delusional.

Sad? I've never denied natural selection, I've only said I think it is far less a factor than it is reputed to be. Which you might like to hear since it only speeds up the processes I'm describing that you don't much like. NS more dramatically demonstrates them than the neutral situation of simple geographic isolation I keep focusing on, because the adaptive characters proliferate more rapidly while the unadaptive die out a lot faster than they would if only low frequency alleles were the cause.

The Grants alone have observed and documented natural selection occurring on the Galapagos Islands for 40 years.

It doesn't matter to me. They may or they may not have. It doesn't affect the point I'm making, and in fact only dramatizes it if it is happening. I just don't think it happens as much as you all think it does, that evolution is going to occur just as well without it.

... Again if the selection is severe there may be no alleles left at all except those that underlie the successful traits. ...

Which still leaves the population viable with successful survival and reproductive traits as more new traits are added due to mutations.

No, this is not happening in this context. What I'm describing is how you get a new species or subspecies. If mutations are added you will lose your species or subspecies. And again it's not that you have to have a new species or subspecies it's just that when one develops it is by losing genetic diversity, not adding it.

And nothing I'm describing necessarily challenges the VIABILITY of a population either. Some species do OK with drastically reduced genetic diversity. However the drastic cases ARE generally more vulnerable of course. And again, conservation principles do make it desirable that the cheetah for instance acquire some new mutations so it won't remain so vulnerable in its genetically depleted condition. However there are plenty of healthy looking cheetahs out there. The elephant seal is also apparently doing extremely well with extreme genetic depletion.

... (And of course if it's even more severe extinction may be the result.) This is certainly a "narrowing down of traits."

Extinction would be a "narrowing down of traits" ... but the cause of extinction is not the loss of traits, it is the failure to survive and reproduce, natural selection at its most stern implementation, regardless of the diversity of traits in the population.

Extinction is just an extreme possibility and of course there are other causes. Paul K said that narrowing of traits doesn't occur down the evolving pathway but of course it does, it has to. Any daughter population represents a selection of traits out of the greater population to become its own characteristic look over time. And I have in mind a population that isn't in a situation that challenges its ability to survive and reproduce. You can get population splits into new geographic areas where there is no real difference in environmental support than the original population had.

The problem is that we are thinking of different things. There's nothing confused about it in the context of what I'm talking about which is what happens to the TRAITS and their alleles, which is brought about by the reproductive isolation of a small number of individuals, which can be brought about by migration of those individuals or by natural selection of those individuals or even by sexual selection of those individuals within the larger population. The size of the population that develops subsequently is something else.

Indeed, I am talking about evolution occurring according to the observed and documented processes (scientific facts) of mutations adding new traits and selection removing the less viable traits from the populations

But that scenario is also covered by the scenario I'm describing. You have your source of traits and then you have the processes that mold or evolve them into a new population. The processes that evolve them, the selection that removes the less viable traits does exactly what I'm describing: it favors the proliferation of the adaptive traits WHILE IT ELIMINATES THE UNADAPTIVE TRAITS, which creates an overall loss of genetic diversity in that population.

I'm stopping again for now.

Edited by Faith, : No reason given.


This message is a reply to:
 Message 109 by RAZD, posted 05-06-2014 11:02 AM RAZD has responded

Replies to this message:
 Message 114 by Dr Adequate, posted 05-06-2014 5:09 PM Faith has not yet responded
 Message 115 by PaulK, posted 05-06-2014 5:57 PM Faith has not yet responded
 Message 119 by RAZD, posted 05-07-2014 7:16 AM Faith has responded

    
Dr Adequate
Member
Posts: 15929
Joined: 07-20-2006
Member Rating: 3.8


Message 114 of 131 (726142)
05-06-2014 5:09 PM
Reply to: Message 113 by Faith
05-06-2014 5:01 PM


Re: " narrowing down of traits" and the "expansion of traits"
But that scenario is also covered by the scenario I'm describing. You have your source of traits and then you have the processes that mold or evolve them into a new population. The processes that evolve them, the selection that removes the less viable traits does exactly what I'm describing: it favors the proliferation of the adaptive traits WHILE IT ELIMINATES THE UNADAPTIVE TRAITS, which creates an overall loss of genetic diversity in that population.

See my previous post.


This message is a reply to:
 Message 113 by Faith, posted 05-06-2014 5:01 PM Faith has not yet responded

  
PaulK
Member
Posts: 12688
Joined: 01-10-2003
Member Rating: 2.8


(1)
Message 115 of 131 (726152)
05-06-2014 5:57 PM
Reply to: Message 113 by Faith
05-06-2014 5:01 PM


Re: " narrowing down of traits" and the "expansion of traits"
quote:

Paul K said that narrowing of traits doesn't occur down the evolving pathway but of course it does, it has to. Any daughter population represents a selection of traits out of the greater population to become its own characteristic look over time.

Let's make it absolutely clear. I do NOT argue that there are no periods when genetic diversity of a particular population decreases. I HAVE argued that successful species regain genetic diversity during their periods of expanding and large populations, so that for these species - and their successful descendants - genetic diversity follows a cyclical pattern of decrease and increase.

And your current objections are that we should ignore the periods of increase because you don't count it as evolution - which is both false and fallacious - or that something would stop speciation in such cases without suggesting anything at all plausible that might do so.

So where is your case ? An excuse for only looking at decreases and ignoring increases isn't a valid argument. Nor is the assertion that SOMETHING will somehow make things come out the way you want. But those are what you offer.

And that is why anybody who THINKS about your argument will see that you don't really have one - just an assumption poorly hidden by excuses.

Edited by PaulK, : Trivial corrections


This message is a reply to:
 Message 113 by Faith, posted 05-06-2014 5:01 PM Faith has not yet responded

    
RAZD
Member
Posts: 18478
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.8


(1)
Message 116 of 131 (726181)
05-06-2014 10:36 PM
Reply to: Message 110 by Faith
05-06-2014 3:46 PM


The simpler explanation: biological evolution
This is getting waaay too long, so rather than attempt to reply to your repeated points I am going to take desperate measures and lay out how biological evolution explains the diversity we see around us. I've broken it into a couple of sections so you may want to review each independently.

Biological Evolution

(1) The process of evolution involves changes in the composition of hereditary traits, and changes to the frequency of their distributions within breeding populations from generation to generation, in response to ecological challenges and opportunities.

This is sometimes called microevolution, however this is the process through which all species evolve and all evolution occurs at the breeding population level.

Mutations and mixing existing hereditary traits in different combinations (ie for eyes and ears) can cause changes in the composition of hereditary traits for individuals in a breeding population, but not all mutations do so (many are in non-hereditary areas). In addition there are many different kinds of mutations and they have different effects (from small to large), especially if they affect the developmental process of an organism.

Natural Selection and Neutral Drift can cause changes in the frequency distribution of hereditary traits within a breeding population, but they are not the only mechanisms known that does so. Selection processes act on the expressed genes of individual organisms, the phenotype, so bundles of genetic mutations are selected rather than individual genes, and this means that some non-lethal less viable mutations can be preserved. The more an individual organism reproduces the more it is likely to pass on bundles of genes and mutations to the next generation, increasing the selection of those genes.

The ecological challenges and opportunities change when the environment changes, when the breeding population evolves, when other organisms within the ecology evolve, when migrations change the mixture of organisms within the ecology, and when a breeding population immigrates into a new ecology. These changes can result in different survival and reproductive challenges and opportunities, affecting selection pressure, perhaps causing speciation, perhaps causing extinction.

This is a two-step feedback response system that is repeated in each generation:

Like walking on first one foot and then the next.

Mutations of hereditary traits have been observed to occur, and thus this aspect of evolution is an observed, known objective fact, rather than an untested hypothesis.

Different mixing of existing hereditary traits (ie Mendelian inheritance patterns) have been observed to occur, and thus this aspect of evolution is an observed, known objective fact, rather than an untested hypothesis.

Natural selection has been observed to occur, along with the observed alteration in the distribution of hereditary traits within breeding populations, and thus this aspect of evolution is an observed, known objective fact, and not an untested hypothesis

Neutral drift has been observed to occur, along with the observed alteration in the distribution of hereditary traits within breeding populations, and thus this aspect of evolution is an observed, known objective fact, and not an untested hypothesis.

Thus the process of evolution is an observed, known objective fact, and not an untested hypothesis.

This is basic simple biological evolution as observed in the world around us.


Phyletic Change\Speciation

If we look at the continued effects of evolution over many generations, the accumulation of changes from generation to generation may become sufficient for individuals to develop combinations of traits that are observably different from the ancestral parent population. This lineal change within species is sometimes called phyletic change in species , or phyletic speciation . This is also sometimes called arbitrary speciation in that the place to draw a line between linearly evolved genealogical populations is subjective, and because the definition of species in general is tentative and sometimes arbitrary.

If phyletic speciation was all that occurred, then all life would be one species, readily sharing DNA via horizontal transfer (asexual) and interbreeding (sexual) and various combinations. This is not the case, however, because there is a second process that results in multiple species and increases the diversity of life.


Divergent Speciation

(2) The process of divergent speciation involves the division of a parent population into two or more reproductively isolated daughter populations, which then are free to (micro) evolve independently of each other.

The reduction or loss of interbreeding (gene flow, sharing of mutations) between the sub-populations results in different evolutionary responses within the separated sub-populations, each then responds independently to their different ecological challenges and opportunities, and this leads to divergence of hereditary traits between the subpopulations and the frequency of their distributions within the sub-populations.

Over generations phyletic change occurs in these populations, the responses to different ecologies accumulate into differences between the hereditary traits available within each of the daughter populations, and when these differences have reached a critical level, such that interbreeding no longer occurs, then the formation of new species is deemed to have occurred. After this has occurred each daughter population microevolves independently of the other/s. These are often called speciation events because the development of species is not arbitrary in this process.

If we looked at each branch linearly, while ignoring the sister population, they would show phyletic change in species (accumulation of evolutionary changes over many generations), and this shows that the same basic processes of evolution within breeding populations are involved in each branch.


Nested Hierarchies

An additional observable result of speciation events, however, is a branching of the genealogical history for the species involved, where two or more offspring daughter species are each independently descended from the same common pool of the ancestor parent species. At this point a clade has been formed, consisting of the common ancestor species and all of their descendants.

With multiple speciation events, a pattern is formed that looks like a branching bush or tree: the tree of descent from common ancestor populations. Each branching point is a node for a clade of the parent species at the node point and all their descendants, and with multiple speciation events we see a pattern form of clades branching from parent ancestor species and nesting within larger clades branching from older parent ancestor species.

Where A, B, C and G represent speciation events and the common ancestor populations of a clade that includes the common ancestor species and all their descendants: C and below form a clade that is part of the B clade, B and below form a clade that is also part of the A clade; G and below also form a clade that is also part of the A clade, but the G clade is not part of the B clade.

The process of forming a nested hierarchy by descent of new species from common ancestor populations, via the combination of phyletic change in species and divergent speciation, and resulting in an increase in the diversity of life, is called macroevolution in biology. This is often confusing to people, because there is no additional mechanism of evolution involved, rather this is just the result of looking at evolution over many generations and the effects of spreading into different ecologies.


Now your argument is basically that species run out of variation the more they evolve, having to discard alleles\traits in the process (the basis of the traits is genetic, but selection is on the phenotype).

Even with mutations you argue -- if I have it right -- that the rate of loss is greater than the rate of gain:

It has to, RAZD, you are not going to get a new breed in domestic programs OR a new species or even subspecies in the wild UNLESS this happens. ... This will happen in any given population that is evolving. ...

And you don't get a new species without mutations introducing new traits that are foreign to the parent population. That is what allows species to take advantage of different ecologies, and that increases diversity.

Every individual in every generation has new mutations, thus no matter how small a population is, there is still new variations, new traits. They may be small -- longer fur, larger beak, different color, etc. What is important is that they will be different, and those differences can add up to make a difference in different ecologies.

This has been observed. Not all species survive, but enough to carry on. There have been times of mass extinction, but life has rebounded with new diversity after each one.

Enjoy.


we are limited in our ability to understand
by our ability to understand
RebelAmerican☆Zen☯Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 110 by Faith, posted 05-06-2014 3:46 PM Faith has responded

Replies to this message:
 Message 118 by Faith, posted 05-07-2014 6:25 AM RAZD has responded

  
Faith
Member
Posts: 24846
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 117 of 131 (726224)
05-07-2014 5:04 AM
Reply to: Message 111 by Dr Adequate
05-06-2014 4:18 PM


Re: " narrowing down of traits"
The very processes that bring about a new species eventually make it impossible for the species to continue to vary.

Unless mutation exists. Oh look, it does.

Look at what? The cheetah and the elephant seal could wait a long time before they get any beneficial mutations to alter their condition of genetic depletion, and they'll have to get them in those particular genes that have become homozygous too, which narrows the probability rather drastically.

One thing that has to be said about this mutation Solution To All Problems of Evolution is that you all say that getting a beneficial mutation doesn't happen very often, so assuming you do have a new species with little to no ability to vary further, it's going to stay that same species for a long time before mutations come along to change it.

So, consider the following scenario. A species is homozygous for traits A and B. A breeding pair of the species is marooned on an island by a freak wind. Some years later, an allele A* arises in the new population and replaces A. Then an allele B* arises in the new population and replaces B. The parent population continues as it was. Now if zygotes with the alleles A and B* are inviable, then by definition the new population is a new species (if not it is at least a new variety).

Note that the clade has undergone a net increase in genetic diversity and that neither species has undergone a net reduction in genetic diversity.

Now there are two points in this process where the daughter group loses genetic diversity --- where it goes from a mixed A/A* to an all A* population, and then again where it goes from a mixed B/B* to an all B*. But there is no net loss of diversity in either species.

This strikes me as totally nonsensical but let me try to work my way through it anyway.

So, consider the following scenario. A species is homozygous for traits A and B. A breeding pair of the species is marooned on an island by a freak wind. Some years later, an allele A* arises in the new population and replaces A. Then an allele B* arises in the new population and replaces B. The parent population continues as it was. Now if zygotes with the alleles A and B* are inviable, then by definition the new population is a new species (if not it is at least a new variety).

First should I assume you are talking about a sexually reproducing animal? I have the question because according to dwise the term "variety" is supposed to apply to plants. But a "breeding pair" must be animals and I'm happy to have the term "variety" available.

Second, if you have only one breeding pair isolated on this island it's only going to be a few generations before a lot more than traits A and B are homozygous, they should be close to clones of each other very soon.

Third, as I say above even you guys don't expect to get viable new alleles from mutations except very very rarely. Which is why the cheetah and the elephant seal are waiting and may go on waiting for thousands of years. So getting a new species from a single mutation as you are describing is highly unlikely, let alone two new species.

Fourth, nyou've only described the appearance of two mutations in two individuals, you haven't said anything about how species would have come about from this. So are you simply assuming this happened? One new population characterized by the allele A* and later another new population of B* or something like that?

If so I'll attempt to play along. You get this new allele A* in an individual. That individual mates with an A, which is all that's available, and let's say A* is dominant so you're going to get three A* phenotypes and one A. Over some generations there should be a healthy proportion of A*s in the population, a quarter of them homozygous. On the other hand, if all those with the A* got lost in another part of the island then all this would be going on in this isolated daughter population alone and it would come to look like A* while the parent population would stay A. But if it spreads IN the parent population, over some generations the A* is going to be expressed there in large numbers along with the As.

Then an allele B* arises in the new population and replaces B. The parent population continues as it was. Now if zygotes with the alleles A and B* are inviable, then by definition the new population is a new species (if not it is at least a new variety).

Later a B becomes B* in a single individual "in the new population," so I guess you mean in the main population which now has a good mix of A and A* traits.

Now if zygotes with the alleles A and B* are inviable, then by definition the new population is a new species (if not it is at least a new variety).

This is getting too complicated. You can get this combination of A and B* in zygotes in matings between a lot of different individuals in the population, except B and B*s with A*A*s where the zygotes would presumably always be viable, but you will also get B with A and B with A* and B* with A* which would produce viable zygotes, out of those same matings where you are getting the inviable zygotes.

So I don't see how you get a species out of any of this. I guess I have to give up because I'm not following you.

Note that the clade has undergone a net increase in genetic diversity and that neither species has undergone a net reduction in genetic diversity.

Yes I gather you are trying to prove something about a species being defined by inability to produce offspring, but I don't see that this has to be the case in your scenario, as I describe above. You aren't going to get offspring from a particular combination of alleles but the same individuals would produce other combinations which would be viable.

But none of this answers what I've been saying about the conditions under which genetic diversity is reduced which involves the formation of a reproductively isolated population, and when that happens it's never just one trait that is involved, but many traits will undergo changes due to new allele frequencies, and over time acquire distincft phenotypic divergence from the original group. And that's the situation in which there will be the trend to reduced genetic diversity.

But in your scenario you've got a single breeding pair as the founders so you've already got homozygosity for all or most of its traits within a few generations anyway which is a HUGE loss of genetic diversity even from that original pair.

And again beneficial mutations simply don't occur frequently enough to make a difference in such a situation.

Now there are two points in this process where the daughter group loses genetic diversity --- where it goes from a mixed A/A* to an all A* population, and then again where it goes from a mixed B/B* to an all B*. But there is no net loss of diversity in either species.

Since your scenario broke down long before this, this doesn't clarify anything. How are your daughter populations going to get to the all A* or all B* situation? Yes that situation would be a reduction in genetic diversity all right but I don't see any path of variation in this scenario that explains anything.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


This message is a reply to:
 Message 111 by Dr Adequate, posted 05-06-2014 4:18 PM Dr Adequate has responded

Replies to this message:
 Message 126 by Dr Adequate, posted 05-07-2014 9:36 AM Faith has responded

    
Faith
Member
Posts: 24846
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 118 of 131 (726225)
05-07-2014 6:25 AM
Reply to: Message 116 by RAZD
05-06-2014 10:36 PM


"the simpler explanation" still requires reduction in genetic diversity
This is also too lengthy and too complicated, RAZD, but I'll see what I can do with it.

Biological Evolution

(1) The process of evolution involves changes in the composition of hereditary traits ....

Which occur regularly simply with ordinary sexual recombination in any population where the genetic diversity is fairly high. That is, hereditary traits are based on allele combinations and these get shuffled with each new sexual recombination event.

and changes to the frequency of their distributions within breeding populations from generation to generation,

which isn't going to happen to any noticeable extent without selection or isolation, which is what brings about new allele frequencies. This CAN happen entirely within a large population with genetic drift though, a subpopulation having reproductive isolation from random factors that change the allele frequencies for that breeding group within the larger group.

in response to ecological challenges and opportunities.

which may exist and be important, but even without these those changes in traits and distribution occur simply from the change in allele frequencies that comes about even from completely random isolation of a relatively small number of individuals out of the larger population. The mixing of new allele frequencies is all it takes to develop a new subspecies.

This isolation of a relatively small number is also what happens when you do have ecological challenges and opportunities -- the adaptive individuals will thrive in the new environment, the less adaptive ones will eventually disappear from the population and the mixing of the new allele frequencies that are in this case determined by the adaptive pressures will also eventually develop a new subspecies.

This is sometimes called microevolution, however this is the process through which all species evolve and all evolution occurs at the breeding population level.

OK

Mutations and mixing existing hereditary traits in different combinations (ie for eyes and ears) can cause changes in the composition of hereditary traits for individuals in a breeding population,

So can simple sexual recombination of preexisting alleles.

but not all mutations do so (many are in non-hereditary areas).

And in fact this is why mutations are not likely to play much of a role in varying a population. They don't occur very often in "hereditary areas" as you put it, and then when they do they aren't necessarily viable or beneficial. There is a very very low probability of getting a mutation that would contribute a viable new allele.

In addition there are many different kinds of mutations and they have different effects (from small to large), especially if they affect the developmental process of an organism.

All of which also decreases the likelihood of mutations contributing anything viable.

Natural Selection and Neutral Drift can cause changes in the frequency distribution of hereditary traits within a breeding population, but they are not the only mechanisms known that does so. Selection processes act on the expressed genes of individual organisms, the phenotype, so bundles of genetic mutations are selected rather than individual genes, and this means that some non-lethal less viable mutations can be preserved. The more an individual organism reproduces the more it is likely to pass on bundles of genes and mutations to the next generation, increasing the selection of those genes.

Natural Selection and Neutral Drift can cause changes in the frequency distribution of hereditary traits within a breeding population, but they are not the only mechanisms known that does so.

So does simple migration or the accidental geographic and reproductive isolation of a portion of the larger population. And all these mechanisms change “the frequency of distribution of hereditary traits within a breeding population” by bring about new allele frequencies in the new population, which is the natural result of the smaller number of individuals that are the founders of the new population. Neutral drift reproductively isolates a small number of individuals within the larger population, and natural selection reproductively isolates the adaptively selected individuals from the larger population.

Selection processes act on the expressed genes of individual organisms, the phenotype, so bundles of genetic mutations are selected rather than individual genes,

Or as I’ve been putting it, bundles of traits and their alleles, since you don’t get populations developing from a single trait but from a mixture of new traits brought about by new allele frequencies.

and this means that some non-lethal less viable mutations can be preserved. The more an individual organism reproduces the more it is likely to pass on bundles of genes and mutations to the next generation, increasing the selection of those genes.

Yes, or just bundles of traits and their alleles however originally formed

The ecological challenges and opportunities change when the environment changes, when the breeding population evolves, when other organisms within the ecology evolve, when migrations change the mixture of organisms within the ecology, and when a breeding population immigrates into a new ecology. These changes can result in different survival and reproductive challenges and opportunities, affecting selection pressure, perhaps causing speciation, perhaps causing extinction.

So far this is all very similar to what I’ve been describing except you make it all hinge on the environmental pressures whereas I’m saying the changes also come about just by simple neutral random isolation of traits and their alleles, then being mixed by ordinary sexual recombination.

And ALL these scenarios require the reduction of genetic diversity to bring out the new traits.

I think I'll stop here for now.


This message is a reply to:
 Message 116 by RAZD, posted 05-06-2014 10:36 PM RAZD has responded

Replies to this message:
 Message 121 by RAZD, posted 05-07-2014 8:35 AM Faith has not yet responded

    
RAZD
Member
Posts: 18478
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.8


(1)
Message 119 of 131 (726227)
05-07-2014 7:16 AM
Reply to: Message 113 by Faith
05-06-2014 5:01 PM


Re: " narrowing down of traits" and the "expansion of traits"
OK as a general rule, but large populations are generally not evolving as I keep trying to keep in focus. ...

Except that they are. All populations are evolving, it is a continual process.

... It is WHEN you get the reduced numbers with the reduced diversity that you get the best examples of evolution of new traits ...

I think you are confusing populations in stable ecologies where evolution centers on the most fit for that ecology (creating an apparent stasis) with a lack of evolution: mutation and selection still occur. Neutral traits still arise that add variations within the population, and new trait still occur, but selection for the most fit individuals for survival and reproduction will act against changing the population once it has reached a relative equilibrium fitness.

The larger population may be relatively static but you CAN can get the same effect even in a larger population if there is strong genetic drift which favors some traits over others, ...

Genetic drift doesn't come in flavors nor does it favor some traits over others -- it is stochastic - chance - and it is more noticeable in small populations than large ones. It is one mechanism for how neutral traits spread in populations

This may be the case but all I'm talking about is the mechanisms or processes that bring about a divergence in traits between two separate populations, and this is always the same no matter what else is going on. If strong selection pressure occurs you'll get a dramatic development of adaptive traits with a more dramatic loss of the unadaptive traits. It will simply speed up the normal processes.

What brings about divergence is the appearance of new traits that allow the daughter populations to take better advantage of the opportunities in different ecologies -- a gain in diversity for the total population as well as a gain available resources.

Sad? I've never denied natural selection, I've only said I think it is far less a factor than it is reputed to be. Which you might like to hear since it only speeds up the processes I'm describing that you don't much like. NS more dramatically demonstrates them than the neutral situation of simple geographic isolation I keep focusing on, because the adaptive characters proliferate more rapidly while the unadaptive die out a lot faster than they would if only low frequency alleles were the cause.

It doesn't matter to me. They may or they may not have. It doesn't affect the point I'm making, and in fact only dramatizes it if it is happening. I just don't think it happens as much as you all think it does, that evolution is going to occur just as well without it.

Yes sad, because you insist on being totally ignorant of how evolution works. Let me show you this picture once more:

Evolution is a two-step feedback response system that is repeated in each generation, like walking on first one foot and then the next. It is rather difficult to walk across the country if you don't use both legs.

In every generation there are individuals that do not survive to breed. That is selection.

No, this is not happening in this context. What I'm describing is how you get a new species or subspecies. ...

Except that you aren't. You don't understand the process well enough to describe it.

... If mutations are added you will lose your species or subspecies. ...

Bizarre. Do you think mutations are some kind of infection?

Except that mutations are what cause new traits that allow a daughter population to diverge from the parent population as they take advantage of different opportunities in different ecologies. They are what cause the new species/subspecies/varieties to diverge from the parent population.

... And again it's not that you have to have a new species or subspecies it's just that when one develops it is by losing genetic diversity, not adding it.

Which curiously is a statement at odds with the facts.

... You have your source of traits and then you have the processes that mold or evolve them into a new population. ...

Again, you do not understand the process. Mutations change traits randomly, natural selection favors those traits that provide better survival and reproduction. When a species moves into a marginal ecology (or the ecology changes) there will be different traits selected in response to the opportunities and challenges of that ecology.

In other words, Faith, natural selection picks the traits best suited in the population for the population, natural selection "molds" the population ...

... The processes that evolve them, the selection that removes the less viable traits does exactly what I'm describing: it favors the proliferation of the adaptive traits WHILE IT ELIMINATES THE UNADAPTIVE TRAITS, which creates an overall loss of genetic diversity in that population.

In favor of new traits that are better suited for survival and reproduction in the new ecology. Ones that enable the population to survive and grow.

I'm stopping again for now.

Read Message 116. Again. ... and try for comprehension instead of denial. It is lengthy and it may seem complicated to you, but it describes how evolution actually works.

Enjoy.

Edited by RAZD, : ..


we are limited in our ability to understand
by our ability to understand
RebelAmerican☆Zen☯Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 113 by Faith, posted 05-06-2014 5:01 PM Faith has responded

Replies to this message:
 Message 120 by Faith, posted 05-07-2014 7:32 AM RAZD has responded

  
Faith
Member
Posts: 24846
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 120 of 131 (726228)
05-07-2014 7:32 AM
Reply to: Message 119 by RAZD
05-07-2014 7:16 AM


Re: " narrowing down of traits" and the "expansion of traits"
OK as a general rule, but large populations are generally not evolving as I keep trying to keep in focus. ...

Except that they are. All populations are evolving, it is a continual process.

Yeah yeah yeah but this is an academic point because they aren't actively involving as a selected or isolated smaller population is, as new allele frequencies are making a difference in every generation as new traits are bring brought out and blended into the whole population so that it clearly diverges phenotypically from the former population. You are getting something new all the time as it were in these more actively evolving populations, until they reach a point after many generations where it's all blended into their new appearance and behavior and really LOOKS like a new species.

The level of evolution that is going on in the larger static population where all its alleles have already been mixed through and all you are getting is occasional individual variations popping up here and there, is negligible by comparison.

... It is WHEN you get the reduced numbers with the reduced diversity that you get the best examples of evolution of new traits ...

I think you are confusing populations in stable ecologies where evolution centers on the most fit for that ecology (creating an apparent stasis) with a lack of evolution: mutation and selection still occur.

This may be another situation where the same description would apply, but all I mean is that it isn't ACTIVELY evolving because there is nothing happening to bring that about. Mutation would be going on supposedly but all that would do is cause various novel traits to pop up in individuals now and then (which I think is going to happen without mutations anyway), and selection is NOT going on because that's what brings about the active evolution I'm talking about.

Neutral traits still arise that add variations within the population, and new trait still occur, but selection for the most fit individuals for survival and reproduction will act against changing the population once it has reached a relative equilibrium fitness.

Fine, all that does is describe the same situation I'm describing where ACTIVE evolution isn't occurring.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


This message is a reply to:
 Message 119 by RAZD, posted 05-07-2014 7:16 AM RAZD has responded

Replies to this message:
 Message 122 by NoNukes, posted 05-07-2014 8:41 AM Faith has not yet responded
 Message 124 by RAZD, posted 05-07-2014 9:07 AM Faith has not yet responded

    
Prev1
...
4567
8
9Next
Newer Topic | Older Topic
Jump to:


Copyright 2001-2015 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2017