A question about evolution

That is two possibilities. The other is beneficial. But NONE of those make any sense except when considered through the filter of Natural Selection.The beautiful thing about the TOE is it explains all of that.Those changes that are most harmful are selected out. The neutral and beneficial changes are passed on.As the filter changes, many of those that were harmful or neutral may turn out to be beneficial.The whole process described in the TOE assures that the progression from pond scum to man is not just possible, but almost inevitable. LOLWell it is a good thing that no one but the IDists and Biblical Creationists say ("Just saying that macroevolution is a magnification of microevolution doesn't make it so.") that then.Really. It IS plain as day unless you shut your eyes.Macro is just an accumulation of micro changes. Nothing more.

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Aslan is not a Tame Lion

A sub-specie. Think of what you would produce if you crossed a Calico and a Tabby. Would you get a new specie? No.

How so? It seems to me that the definitions are being supplied by the question.If they can so easily merge then it seems ridiculous to assert that they were ever seperate in an evolutionary sense. They're no more seperate populations, and evolution is no more occuring, than if I take all the brown-eyed people over here for ten minutes and then bring them back to the group. What seperation existed between these two groups was illusory and temporal, not a meaningful period of genetic seperation relevant to an evolutionary question. If they weren't part of the original population, they aren't part of the new one. If it was two seperate populations in the beginning then it doesn't make any sense to treat them as two seperate populations throughout, and in that case, there's still no evolution because the populations haven't been in proximity long enough for any gene flow to occur. Either they're a population throughout, or they're two seperate populations throughout. There's no description of any kind of mating activity and it doesn't make sense to treat two groups of the same species as two populations "merging" into one just because they came within geographic proximity. Still no evolution, because they're not part of the same population now. There's absolutely no indication of any gene flow between members of these two groups in the timeframe of the question. They're apparently different allotypes of the same species in momentary geographical proximity. The fact that they're in proximity to each other is meaningless, evolutionarily speaking.I think your problem is that you're treating the populations as real things, rather than seeing that it's the individual birds who are real, and that you don't suddenly join another individual's species simply because you're standing next to them. You don't suddenly become an African-American just because you moved to Harlem.

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In the wise words of Jerry Maguire, "Show me the money."

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"Tell me you didn't sign anything.... Because I'm still kind of moved by your, 'My word is stronger than oak,' speech." -Jerry Maguire

"Specie" is money. "Species" is the term for a reproductive community of organisms. It's its own plural. This is not the merging of two populations because calicos and tabbys are part of the same population - Felis sylvestris catus.

You totally misunderstood the question.

I was under the impression that the birds were all the same species and that they were divided into two populations. Then the two populations were merged and selected against by the storm. The percentage of the alleles was different after the merger and selection. We can't redefine populations? Does the most basic definition of evolution include the flow of genes? Can't allele frequencies change without gene flow when some individuals die?

How? Just by proximity? That doesn't make any sense. How are they any suddenly part of the same gene pool simply because their members are standing next to each other? To suit our own arbitrary purpose? No, I don't think we can. Species has a definition, gene pool already means something, and I don't think allele frequencies change just because two birds are suddenly flying next to each other. Only if those individuals were part of the gene pool. For that to be the case, gene flow had to be occuring between those individuals and the other individuals in the gene pool.My point is pretty simple - either the new birds were always part of the gene pool, or else they're not a part of it at all. They don't just become part of the pool simply by physical proximity to other individuals. Otherwise you'd be a zebra every time you went to the zoo.

It seems that by definition that's exactly what happened: So, by definition, because the population of bb birds had to migrate to that area, they would then be considered part of a joint population with the aa birds.

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And the Ignorant shall fall to the Squirrels - Chip 2:54

Yes just by proximity and without any gene flow. We draw the lines for the populations. If we move the line or if they cross the line then the population changes. Then how are populations defined?Its all reletive to what you want to be talking about. All of the dogs in Bob's backyard, all the dogs in Missouri, all the dogs in the U.S., all the dogs on the planet. They are all the same species regardless of where we draw the lines, but we can still draw them and talk about them as different populations.The allele frequency of the dogs in Bob's backyard could change and that population could be said to have evolved. This has also affected the population of dogs in Missouri, which has also evolved. But what about the population of dog's in Ted's backyard. They haven't had any changes in their allele frequency, but they can also be included in the Missouri population, which has.Is there a term for the situation where the allele frequency changes because of the population definitions?You're being defensive and avoiding answering an honest question that I would like to learn the answer to. It doesn't always have to be an argument, well, apparently with you it does Depends on the definition of the population. Oh, I think they do. That's retarded, it doesn't change my species, it changes the population I belong to. I would become a part of the population of people at the zoo, not some new species altogether

They were reproductively isolated from one another. Let us say some short range migratory birds are blown off course. Most of them die, and the survivors are forced to ground on a remote volcanic island.No other members of their species arrive and it stays that way for 10,000 years. This population of geographically isolated birds has 100% frequency of a certain allele - and they are effectively reprodctively isolated since they can't physically get to the other birds without a storm to blow them that way (and vice versa)After 10,000 years another ragtag group of birds gets to the island. They alter the allele frequencies. The question in the OP throws in a bit of selection too. This new allele seems a bit better at weathering certain types of storm. Yes - and demes have their own definition - geographically isolated populations. This island population has next to zero gene flow with the mainland variety. They are following their own evolutionary path, with a very rare (or even unique) allele making it in from elsewhere. It is likely they will eventually drift to the point of speciation (much like Darwin's finches).The question then is: has evolution occurred if the allele frequencies of a deme change, but the allele frequencies of the entire potential reproductive community hasn't?I say it is evolution, because one of the driving factors behind evolution is reduction in gene flow from sections of a population which allows the sections of the species to evolve in different directions leading to diversity. They were all part of a potential gene pool (much like lions and tigers are part of a potential gene pool), however there is some isolation between them (due to geography) which hinders gene flow. They can produce viable offspring if/when they come in contact.As can the birds, they are isolated but could reproduce if only there wasn't some barrier between them (unlike humans and zebras (though I've never personally tested this)). Migration into otherwise isolated populations is defintely part of evolution - and is one of the wonders of sexual recombination.Demes can evolve. I contend that demes can evolve due to sexual migrants inserting an occasional new allele (or just increasing the frequency of certain alleles) thus increasing the deme's diversity.

Then we can control evolution with our minds, just by marks on paper.That's incoherent to me. The question is not about what we consider a population, the question asks about whether or not evolution happened, where evolution is a change in allele frequencies as a result of random mutation and natural selection.I don't see any mutation or selection in the example. The storm isn't a selective force in the context of the question (though storms certainly could select certain traits over others.) So we can discount evolution right there. "Melding" populations - that is, us redrawing the lines - isn't a selective force either.There's no change in allele frequencies due to selection here. There may not be a change in frequencies at all - under 2 of the three reasonable interpretations of the situation, there's no reason to consider a shift in allele frequencies. There's simply a shift in our perception. That's not evolution; that's basically a Jedi mind trick.Just because you can imagine a map where south is at the top doesn't change the orientation of the Earth. Just because you can imagine a line that moves to encompass these new individuals doesn't mean that the individuals have, in any objective way, become part of the population. Until they're involved in gene flow with the larger population they're irrelevant to it, except as part of the environment that might be involved in selection (i.e. as competition for food or mates.) Yeah. "Bullshit."No, seriously. I'm not aware of any term for that, and it would be incoherent for there to be one. That's not the evolution of a species; it's just humans changing their mental models. It's no more significant to the physical reality of the species than it is when species names get changed. It's just humans changing marks on paper, not a reflection of a changing physical reality. By gene flow. A species represents a reproductive community. If these new individuals aren't reproducing with the old ones, they're not a part of the population - any more than you become part of the anthill when you step on it. But you're already involved with gene flow with the people at the zoo. Perhaps some of your distant relatives are there. If your family has long-term ties to the community, that's certainly the case.So the fact that you went to the zoo doesn't change the allele frequencies of any population; you were already a part of the population that is here at the zoo before you came. Evolution doesn't happen simply because you walk into the room and change the "allele frequencies" represented by the population in the room. That simply doesn't make any sense. It doesn't make any sense to draw a boundary there.Similarly, it doesn't make any sense to draw a boundary between the aa individuals who were over here and the bb individuals who were over there, unless that boundary represents a species-defining lack of interfertility. Even if we want to consider these two populations as re-combining proto-incipient subspecies, they don't actually become part of the same population until they start mating and there's gene flow between them. Until then, they're just in physical proximity.Evolution doesn't happen just because birds get close to each other. That doesn't make any sense! Maybe after the storm, the bb individuals go on their merry way, so there never was any gene flow between them. What possible basis would we have then for concluding that they were ever part of the same population, the same species? That we should consider their alleles as a sum rather than in seperate domains? None whatsoever. So why on Earth does it make any sense to try to do that now, well before we have any indication that such an approach would even make sense?Edited by crashfrog, : No reason given.

We don't know that. We don't even know they're the same species. All we know is that two flocks met each other and came into physical proximity right before a storm.That strikes me as a pretty flimsy basis to conclude that there's a sudden introduction of a bunch of new alleles. We have absolutely no indication that any gene flow between the two groups has occured or will occur. If no gene flow ever happens then the bb individuals were never a part of the same gene pool as the aa individuals. That's a great new word that I didn't know. Thank you very much. That's what I've been saying all along, if we assume they're the same species (as the question implies but does not state.) Sure. But the introduction of new alleles doesn't happen until mating season. Until then we're looking at two seperate demes, physically superimposed. No more significant than walking into a room. If they do mate, we might retroactively describe the migration event as the instant when the two populations became one.But if they don't ever mate, then it doesn't make any sense to refer to the migration event as the joining of anything. Does that make sense?

Heh - if we want to be over literal about it. It would render the structure of the question unnecessary. We could just say: Some guy walks into a room full of dogs, is this evolution? To even ask the question is absurd. No probs, I don't use it often enough - but I like it nevertheless. Perhaps. However, I think that would be perhaps looking at the question too literally. When the animals migrated into a population, it is implied by the word population that they formed a reproductive community.Unless the new birds were too old to reproduce (have already been effectively selected out), then evolution is taking place. Some new alleles are now present in the deme's pool which are subject to selection. The new birds may never get to mate (their allele might be strongly selected against in the environment), but it would still be evolution.Since the answer to the question is 'Yes', we can safely make the assumptions that they meant this. Without the context we'd have to list our assumptions. It certainly does make sense, I just don't completely agree. It's a minor technical point, of course, but what else can otherwise like minded people find to disagree on?

Yes we can, by our definition of evolution. This certainly doesn’t affect what is actually physically occurring but our models might change the representation of the occurrence by the way we have defined the model. Yes, but we do it nonetheless, even if it is just in the hypothetical.On a global scale, all species are constantly evolving (although there might be exceptions, I dunno). What we can do though, is define smaller populations, or sub-populations, of the global population of a species. We can use these to ”zoom-in’ on specific groups to observe what modification and selection they are experiencing. These sub-populations may or may not be having changes in their allele frequencies. A small group of some species might be in stasis while the species on a global scale is not. When we zoom back out, the small group that was not evolving becomes part of the larger group that is evolving. On a global scale, not all sub-populations have gene flow with each other. Can they not be a part of the same population for that species as a whole, on a global scale? Why does you example talk of two different species when exemplifying two populations of the same species? I can never become a part of the ant population but it is possible for the new individuals to flow genes with the old ones.If populations are defined by gene flow alone, then for some species, there cannot be a global population because they are unable to have gene flow with member ”across the globe’. If one sub-population of that species has a selective force that changes the allele frequency, then only a fraction of that species is evolving? The species, as a whole, is evolving too, yes? What about the sub-population across the globe, have they not evolved? Even if we consider them a part of the whole species?I’m not trying to prove you wrong or argue, I’m trying to better understand some of the concepts and definitions involved in evolution. Not if the zoo is in Australia. Well if you define the population to include me then of course the population doesn’t change by me joining it. The question was for a population that didn’t already include me. See, I think that we could say, WRT the population in the room, evolution has occurred when I walk into the room, because the allele frequency has changed. That sub-population has had a change in its allele frequency. Now, this really doesn’t offer us anything useful in the real world, but it seems to fit the definitions. I realize that doesn’t make sense but I don’t realize where my misunderstanding begins and the faults in the definitions end.I think that I’m using too simple a definition of ”evolution’. But I think that is too strict of a definition because of the generation to generation part. If a selective pressure eliminates a bunch of alleles of a single generation, hasn’t that population evolved, by definition? Its defined here over successive generations as well. Is that really the current accepted definition? If so, then if a selective pressure eliminates a bunch of alleles of a single generation, that species has not evolved until the next generation is born. But then, generation for some species is not defined well enough to determine when evolution has actually occurred.Now I’m starting to confuse myself and I’m getting sick and tired of typing. Time to hit the submit button.