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Author Topic:   Peter & Rosemary Grant, Darwin's Finches and Evolution
Faith
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Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 87 of 131 (725889)
05-03-2014 1:48 AM
Reply to: Message 84 by NoNukes
05-03-2014 1:35 AM


Re: Beneficial mutations and other facts
You get a curly ear, you get some more curly ears, that's enough for your "grouping." But it's not enough for what I've been trying to get across. Your grouping has to become an isolated inbreeding group over many generations to be what I'm talking about. The smaller number of individuals is going to create a gene pool of new allele frequencies for starters but those have to get worked through the whole population, and THAT is where the reduced genetic diversity shows up.

If that happens with your "grouping" then you will have a new breed or subspecies with the reduced genetic diversity that is inevitable to that formation. Your curly-eared wolves are at best the first stage of the process I'm talking about.

You really are just playing with words and missing the whole point.


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 88 of 131 (725890)
05-03-2014 5:01 AM
Reply to: Message 86 by NoNukes
05-03-2014 1:46 AM


I hope this is clarifying
And of course if a population of wolves having the curly ear and all of the wolves other variations gets isolated from the other wolves, then at that point they are necessarily less diverse than all of the wolves together, but nothing then prevents new mutations from generating spots, or bobbed tails, or an enhanced sense of smell etc. In time the grouping might be just as diverse as the original pool, and that is regardless of the fact that the new group lacks a gene for pointy ears.

You said I didn't acknowledge that you'd characterized my argument and dealt with it. I don't remember my answer to this but apparently it didn't suffice for you. So OK I'll try again.

And of course if a population of wolves having the curly ear and all of the wolves other variations gets isolated from the other wolves, then at that point they are necessarily less diverse than all of the wolves together,

Yes this is the crux of my argument. The curly ears that exist in individuals within the larger population do add to the phenotypic and genetic diversity of that population, but when they are isolated that is when what I'm talking about starts to happen. This is where you get new allele frequencies and the reduction of genetic diversity I've been talking about that inevitably accompanies the development of a new population-wide set of characteristics. This is where the formation of new species starts. (It COULD start within the greater population if for some reason the curly-eared individuals selected each other exclusively as mates too, just to say that.) This is, as I've said many times, THE situation I've been talking about and I'm not talking about any other such as the one you are now proposing. You can certainly get increased diversity within a larger population, both phenotypic (whether through mutation or simply new combinations of preexisting alleles) and genetic (assuming mutation really is a viable source of alleles) but this, as I've said many times, is not what I'm talking about and it doesn't affect what I'm talking about. What I'm talking about begins ONLY when you get a reproductively isolated daughter population that develops its own peculiar characteristics over time, such as the daughter species in a ring species formation. Really I HAVE answered this already in the last few posts although you keep saying I haven't.

but nothing then prevents new mutations from generating spots, or bobbed tails, or an enhanced sense of smell etc. In time the grouping might be just as diverse as the original pool, and that is regardless of the fact that the new group lacks a gene for pointy ears.

Leaving aside whether this really occurs, this is not evolution/microevolution. I'm only talking about what brings about microevolution. Some form of "selection" has to happen for that to come about, some form of reproductive isolation. In your scenario you'll have a motley population with individuals here and there that have spots or bobbed tails or that enhanced sense of smell and so on, but you won't have a whole population that is characterized by any of those traits unto itself, which would be a new subspecies, UNTIL the individuals with the particular traits get selected/isolated and inbred over generations. Your diverse group is not evolving in other words, it takes the selection or isolation of a portion of it to start the processes of evolution rolling. If it's just a population of wolves with curly ears for starters, OK, but if isolated that population is going to have a new set of allele frequencies because it's appreciably smaller than the parent population, and while the allele for the curly ears would be very high frequency in such a population, the allele for pointy ears would be rare to nonexistent, and over generations of inbreeding would become nonexistent anyway, because low-frequency alleles tend to eventually die out.

Meanwhile there is really no such thing as the evolution of a single trait in a new population. All the traits in the individuals have new allele frequencies in the population, all of them are subject to new expressions in this new population. Some of the dominant characteristics of the parent population could be completely overshadowed by a whole new set of characteristics in the daughter population, an entirely new look as it were.

You said in the case of Darwin's finches a species was defined by the single trait of beak type and yes they are defined that way but that wouldn't be the only characteristic of the finch to be different from the other finches, because evolution varies many traits as a package, the whole animal gets its own new look shared by the rest of the members of its clan. I was looking at pictures of some of the different types of finches, nut eaters, berry eaters, insect eaters etc., but it's hard to tell size differences, body-build differences etc from the pictures in order to make comparisons with each other, and just at a skim-through, I didn't identify any clear markings and other characteristics that differentiate them consistently either, but I might if I spent more time at it. Or it may be that there is enough gene flow to prevent a really distinct type from developing.

Again, you are focusing on what brings about increase in genetic and phenotypic diversity, but when this is occurring evolution (population-level change) is not occurring.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 92 of 131 (725962)
05-05-2014 3:46 AM
Reply to: Message 90 by PaulK
05-03-2014 5:20 AM


Re: I hope this is clarifying
I do think that anyone who thinks THROUGH what I'm saying should come to see it as I do. What happens to the genetic increases is hard to describe clearly. I might be able to illustrate it but I don't think that would be particularly clear either. But let me try to describe what I'm seeing.

So you have a population of some species in the wild, say a fairly large number, say pack or herd animals so we can count on them all breeding together and not isolating themselves in families like the rabbits discussed some time back.

So what is happening in this population? Genetic changes are occurring from time to time. You attribute these to mutations, I attribute them to simple sexual recombination of existing alleles. Of course I'm sure you include this in your scenario too, we are merely disagreeing about the source of the genetic material.

So these genetic changes are occurring. Say they ARE mutations in single individuals. How many of these occur in the germ cells? Anyway it's only those that will get passed on of course. And only the neutral and the "beneficial" ones if we assume the bad ones will be selected out. And as you've all pretty much agreed, this can take a very long time. If mutations could save the cheetah it will be a very long time if they can hold out that long. Anyway...

So after a generation or two the genetic changes start to show up in the phenotype as the offspring and the offspring's offspring mate together. Or maybe even in the first generation if the genetic change is dominant.

OK so far? What would you correct?

So now we could have different genetic changes here and there in the population showing up in a few individuals here and there after a couple generations or so.

Different traits. A slightly different pattern of markings, of texture or color of fur, of length of tail, of shape of facial features, of ears, probably not anything really dramatic just differences here and there in the population.

Anything to object to so far?

If there is genetic drift that appreciably favors one or more of these new traits those will start appearing in the population in greater numbers. If the drift is very strong they night even come to characterize the population as a whole. I think the usual idea is that this should take a very long time. I tend to think in terms of a relatively small number of generations myself, fifty being a lot.

Any problem with that?

OR, if a part of the population gets lost and ends up in a new part of the forest and sets up housekeeping there, no longer with any reproductive contact with the old population, and continues on there breeding only among themselves, growing their population and so on, what I'm saying is that whatever genetic material they brought with them in greater frequency than that expressed in the old population will now come to characterize this new population. Say longer tails, a white diamond-shaped splotch over the nose, a lavender tinge to the coat, and shorter stature. All this built from the mutations that came with the individuals that formed the new population.

Now what I'm saying is that this is the basis for a new species or subspecies, this change in allele frequencies that comes about with the isolation of a small number of individuals from the greater population. As this new group inbreeds for many generations the new traits should begin to develop a characteristic look in the population at large, a new species.

Is there a problem with this scenario?

What I'm ALSO saying of course that in the development of this new species alleles for traits from the old species or any traits that are not those favored by greater frequency in the new population, will start to disappear from the population and if low frequency enough to begin with, may drop out altogether. At this point there is no new genetic input, there is only what was brought over from the old population, unfavored alleles are starting to disappear, which is the loss of genetic variability I'm talking about, and some of the high frequency alleles may soon be homozygous or fixed loci even through the entire population. (If enough of this happens for enough of the characteristic traits it seems to me that a genetic inability to breed with the former population could develop simply from this fact, but there can be many reasons for an inability to interbreed to develop between cousin populations of course).

If the original number of founders of the new population was quite small I would expect the change in allele frequencies to be dramatic enough to change the look of the new population rather rapidly, the unfavored alleles dropping out faster, and the inability to interbreed with the former population could develop very fast too, maybe even in a matter of a dozen generations or so, but give it fifty. It should show significantly decreased genetic variability from the former population by this point. The population should be sufficiently different from as well as unable to interbreed with the former population to earn it the label New Species.

Problems with this scenario?

Now at this point the idea here seems to be that mutations will just keep multiplying and prove me wrong about a genetic decrease that spells the end of evolution.

SO, what should happen at this point is what happened in the first part of this account: Mutations will be popping up in the new population just as they did in the original population. Over time some will be expressed in various individuals scattered throughout the population. If there is genetic drift some of the new traits could even come to change the overall look of the population. This is a form of evolution too as it involves a selection of sorts that changes allele frequencies, only within the population rather than by physical isolation. And then yes you will be getting even a population wide change. And again if a small number split off the other scenario will also develop that could ultimately lead to another New Species. If the mutations really do keep increasing the genetic diversity as you say. (ABE: Which again I'm allowing only for the sake of argument because I think sexual recombination of the existing genetic material explains it all quite well, mutations in fact add nothing but problems, and in any case it's clear any beneficial mutations that might arise and confer a valuable trait to the population are a very rare occurrence. /ABE)

AND there could be Natural Selection involved too, in the first phase or the second. But NS is simply a more drastic way of reducing genetic diversity by STRONGLY favoring a particular trait or set of traits so that the competing traits very rapidly die out. Any strong environmental pressure to adaptation to a particular kind of food or protection against a predator or anything along those lines would just exaggerate the tendencies I'm describing here. If hunters killed off as high a percentage of these creatures as they did the elephant seal, a really dramatic case of natural selection that the creature couldn't survive at all without intervention, then you'd see really dramatic decrease in genetic diversity even if the population was healthy enough to increase in numbers as the elephant seal did.

So back to the increase in diversity. Just go back to the original scenario. That increase has to be cut down IF the population is to evolve a new set of characteristics AS A POPULATION, and this is also what happens in genetic drift, it's simply another way this happens. Otherwise you'll have a nicely variegated population, perhaps millions of individuals with a very wide variety of traits among them.

Now you seem to want to call THAT situation "evolution" too which of course only muddies up the point I'm trying to make.

Are you REALLY saying MACROevolution doesn't depend on the formation of distinctively new populations, but that the normal variation from generation to generation without there being any sort of isolation or selection acting on it, would ultimately lead to MACROEVOLUTION just as well as the formation of distinctly different whole populations would?

Now I can't see how. I can see how you get new species but that requires the reduction in genetic diversity no matter how much you increase that diversity here and there. If it isn't reduced you aren't going to get a distinct new species. And if you don't get a distinct new species but only a very variegated large population I don't see how you are getting the kind of microevolution that Darwin identified in his finches and turtles and so on, and of course since to get this distinctive new population requires loss of genetic diversity end of evolution.

You've said I haven't sufficiently explained how the increases in genetic diversity don't answer my argument and I hope I've made it somewhat clearer.

I think YOU need to explain how you get new species without this reduction in genetic diversity. Of course you theoretically get new individual traits from the ongoing mutations, but unless they are selected or isolated so they can proliferate as a new population you aren't getting the kind of change that evolution is defined by.

Edited by Faith, : change wrong punctuation

Edited by Faith, : No reason given.

Edited by Faith, : add the ABE

Edited by Faith, : No reason given.


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 93 of 131 (725963)
05-05-2014 4:16 AM
Reply to: Message 89 by PaulK
05-03-2014 5:09 AM


Re: Beneficial mutations and other facts
The evolution of birds shows some problems with your argument, Faith.
Some traits aren't fixed. Size is the easy example. While a species has a relatively narrow range of size, the difference between a wren and an ostrich is huge. And there have been birds bigger, still.

But where have I said anything to imply it's fixed? AND remember I'm arguing from an assumption of separately created Kinds, so I don't necessarily assume a wren and an ostrich are genetically related. But if they happen to be, size is something I WOULD expect to vary dramatically in the original population from which they diverged.

Some traits open up a range of new possibilities. You can't have plumage patterns without plumage, there,s a huge range of shapes and colours and patterns. And the range of bill sizes and shapes is dependent on having a bill. Again, lots of new diversity.

Same answer as above. I'm assuming such a huge range of differences in plumage, bill size and shape and so on, it's the stuff from which microevolution is made, it's the stuff that makes the different birds in a ring species of birds. I don't believe that plumage or bills evolved from some other species of course, but even if they did it would be by the same methods I'm describing here.

And traits can be lost. A number of different lineages have lost the ability to fly. Penguins are adapted for swimming, ostriches and similar birds are too large for efficient muscle-powered flight.

And of course I've been talking about populations eliminating alleles haven't I? Alleles are the basis for traits, aren't they? So if the birds do happen all to be genetically related which may or may not be the case, this would be how all those differences came about. (ABE: if small wing size is favored in the daughter population -- simply by the luck of the draw in a population split --, the genetic material/alleles for wings large enough for flying would drop out. There's no reason why an ostrich couldn't fly but it would need enormous wings and those didn't make it into its gene pool /ABE).

There's no continuous narrowing down of traits, new variation is always coming in.

But focus on what happens when you have a new population based on a smallish number of founding individuals. Think about what the change in allele frequencies means. You are getting higher frequencies of some alleles for some versions of some traits than those in the original population, so you are getting new traits in the new population [[[ABE: I mean new traits in enough numbers to become CHARACTERISTIC of the new population /ABE] after some generations of inbreeding, and you are getting lower frequencies of the alleles for the different forms of those same traits in the old population and if low enough they drop out altogether. I wouldn't describe this as a "narrowing down of traits."

And I've tried to explain in that last post how you simply would never get anything you could call a New Species IF new variation did keep coming in and changing the whole population. Of course you will get new traits continuing to pop up in INDIVIDUALS within the population assuming there are still alleles for those traits in the mix [[ABE forgot here you are assuming mutations instead, but that works too/ABE]=, but unless they change the character of the whole population you are not getting a new species.

And at this point I've asked how you can have evolution if you are NOT getting new species. Which is something you are all claiming.

I know that you don't believe all this, but that isn't an argument. Nor is assuming that it couldn't happen. You need reasons why it can't. And we've been waiting for you to supply those for years.

I think I've done a lot more than assert my belief and assumption and hope that last post makes it even clearer. I've been giving reasons all along it seems to me.

Edited by Faith, : add comma

Edited by Faith, : add ABE about wing size for penguins and ostriches

Edited by Faith, : add phrase simply by the luck of the draw

Edited by Faith, : add ABEs: new traits enuf numbers to become characteristic...and "forgot you are assuming mutations...


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 94 of 131 (725964)
05-05-2014 4:44 AM
Reply to: Message 93 by Faith
05-05-2014 4:16 AM


" 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's a narrowing down of traits isn't it?

But even the simple case of microevolution by migration of a small number of founders 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. It's going to develop its own traits that are different from those of the mother population. If the old traits are low frequency enough their alleles will disappear from the new population altogether. This is a "narrowing down of traits" isn't it?

Edited by Faith, : No reason given.


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 98 of 131 (725968)
05-05-2014 7:55 AM
Reply to: Message 97 by PaulK
05-05-2014 5:31 AM


Re: " narrowing down of traits"
All I can answer right now is this:

My first of the last three posts was to describe the accumulation of mutations in a basically static population, which makes for a variegated population that grows in numbers but doesn't evolve into a new species. You say I keep avoiding this, no I'm describing it and have been describing it all along. A static variegated populatuon is all you get with increases, you don't get new species. (Micro)evolving into a new (sub)species requires the selection and isolation processes which leads down the line to reduced genetic diversity.

If each new species then acquires mutations as did the first population you'll get the same variegated static population and the same scenario repeated ad infinitum over and over, you won't get evolution, just expanding populations with unique traits held by individuals but not dispersed in the whole group. They get dispersed only when there is some kind of selection mechanism or isolation, then you get a particular new trait or set of traits spreading throughout the whole population.

So you keep expanding and contracting down the line, you are not getting evolution. That's if mutations play any kind of significant role at all and even then that's just a generous concession to the best possible scenario in that case. Every time you have speciation you have something that interferes with it, and that presumably can keep on going indefinitely, there is no real speciation happening.

But if mutations don'


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 99 of 131 (725969)
05-05-2014 7:55 AM
Reply to: Message 97 by PaulK
05-05-2014 5:31 AM


Re: " narrowing down of traits"
All I can answer right now is this:

My first of the last three posts was to describe the accumulation of mutations in a basically static population, which makes for a variegated population that grows in numbers but doesn't evolve into a new species. You say I keep avoiding this, no I'm describing it and have been describing it all along. A static variegated populatuon is all you get with increases, you don't get new species. (Micro)evolving into a new (sub)species requires the selection and isolation processes which leads down the line to reduced genetic diversity.

If each new species then acquires mutations as did the first population you'll get the same variegated static population and the same scenario repeated ad infinitum over and over, you won't get evolution, just expanding populations with unique traits held by individuals but not dispersed in the whole group. They get dispersed only when there is some kind of selection mechanism or isolation, then you get a particular new trait or set of traits spreading throughout the whole population.

So you keep expanding and contracting down the line, you are not getting evolution. That's if mutations play any kind of significant role at all and even then that's just a generous concession to the best possible scenario in that case. Every time you have speciation you have something that interferes with it, and that presumably can keep on going indefinitely, there is no real speciation happening.

But if mutations don't play any significant role, and it is all powered by sexual recombination then you WILL run out of genetic diversity down a line of evolving species.


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 103 of 131 (725973)
05-05-2014 8:28 AM
Reply to: Message 101 by RAZD
05-05-2014 8:18 AM


Re: what is macroevolution Faith?
Fitness as an adaptive mechanism is just an article of faith, in reality there is hardly any struggle in the Darwinian sense to adapt. Just another tenet of the theory assumed as fact without evidence. There are certainly some striking adaptations but they can just as easily be the right beak finding the right food as the available food determining the right beak.

ABE: That is, microevolution is a natural process that happens with sexual recombination and will produce new subspecies simply from reproductive isolation of a limited number of individuals, without any struggle at all. Microevolution I mean sexual recombination will evolve various beak types as a matter of course. If there is food in the vicinity that a particular beak handles particularly well it will gravitate to that food even if food for all the other kinds of beaks is present too. Then the offspring that inherit the same beak, also choosing that kind of food, will develop more distinctive versions of that beak type. It doesn't have to be this scenario where the food determines how the beak evolves. /ABE

As for what is macroevolution: I define it functionally as the point at which microevolution so decreases genetic diversity that no further evolution is possible.

However, here's another attempt: It's whatever CAN vary in the given genome of the species, its peculiar traits and the genes for those traits with their various alleles. No variation is possible outside those built-in design limits.

ABE: Sorry, I'm tired. I mean microevolution is whatever can vary and anything beyond that would be macroevolution but it can'

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


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
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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


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

  
Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


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
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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


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: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


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

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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


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

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Faith
Member
Posts: 33872
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.2


Message 130 of 131 (726268)
05-07-2014 1:47 PM
Reply to: Message 126 by Dr Adequate
05-07-2014 9:36 AM


Re: " narrowing down of traits"
I read it as replacing A in the individual. Your whole scenario was hard to follow, sorry if I got that wrong.

This message is a reply to:
 Message 126 by Dr Adequate, posted 05-07-2014 9:36 AM Dr Adequate has responded

Replies to this message:
 Message 131 by Dr Adequate, posted 05-07-2014 5:45 PM Faith has not yet responded

  
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