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Faith  Suspended Member (Idle past 1475 days) Posts: 35298 From: Nevada, USA Joined: |
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Author | Topic: Natural Limitation to Evolutionary Processes (2/14/05) | |||||||||||||||||||||||||||||||||||||||
DBlevins Member (Idle past 3806 days) Posts: 652 From: Puyallup, WA. Joined: |
Not "can" cause a reduction, but natural selection ALWAYS causes a reduction in variation by selecting some types at the expense of others.
and
None of these processes increase variability to say the least, but an increase in variability would seem to me to be THE engine to drive "macroevolution" if it is really possible. Natural selection does NOT ALWAYS cause a reduction in variation because hidden variation is ALWAYS present in continuously varrying traits. Natural selection can INCREASE variation. How about an example of how this can come about, eh? Suppose you have an environment that favors larger beaks in birds. We'll let + equal the gene for large beaks and - as the gene for small beaks. Because deeper beaks is determined by genes at many loci, a population of even large beaked birds + have some small beak genes -. Now when the birds with the smallest beaks die, alleles for the small beaks are removed from the breeding popuation. This may increase the frequency of the + gene at every loci, but because even the larger beaked birds have some - alleles, variation still remains. Reproduction shuffles these genes within the population and because + genes are more common, individuals in future generations will have more + alleles. Because the more + genes you have the deeper your beak, the population will show a shift to larger beaks, and the new generations biggest beaks will be bigger than the previous generation. If this continues the same thing happens again. The individuals with the biggest beaks will have beaks even larger than the previous generation. As you can see you have MORE variation. This process can even be reversed. An example I have seen used is an experiment on oil content within seeds. The experiment conducted on corn showed that oil content could be increased, after 80 generations, beyond the initial oil content of 4-6%. The researchers were also able to reverse the process and select for low oil content instead. This showed that selection could INCREASE the initial range of variation.(From Boyd and Silk, ibid, p. 74 with the citing found in the url below) Evolution: Online course And finally, where do you think our domestic dogs have come from? If they come from wolves and we SELECTED traits then of course you should be able to see that we do have MORE dog breeds and MORE variation in this species.
It is hidden variation that is selected FOR in many situations of natural selection... It is EXPRESSED variation that is selected for. Hidden variation is later expressed through reproduction/recombination.
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PaulK Member Posts: 17828 Joined: Member Rating: 2.6 |
You certainly indicated that the formulatiosn of evolution you had seen excluded mutation. And claimed that "umpteen" sources did so. Yet the only one you named did not do so, and also included an essay which explicitly did include mutation - and which you certanly should have read.
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Faith  Suspended Member (Idle past 1475 days) Posts: 35298 From: Nevada, USA Joined: |
quote: I'm sorry I'm not taking time to think anything through carefully as I'm trying to do too many things at once, so if I misunderstand I'll have to get back to it later. I'm talking about decreased VARIABILITY, not variation. New variations through selection processes decrease variability. With the elimination of the - alleles the VARIABILITY is decreased. Yes lots and lots and lots of VARIATION, all accompanied by less and less VARIABILITY. And yes about the "hidden" variations I said it wrong. It can't be selected until it is expressed.
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crashfrog Member (Idle past 1498 days) Posts: 19762 From: Silver Spring, MD Joined: |
I'm talking about decreased VARIABILITY, not variation. Well, that's news to me, at least. Shifting the goalposts, are we?
New variations through selection processes decrease variability. No, they don't. Why would it? Mutation happens; the only thing that can restrict that are specific traits that confer resistance to mutation. Expanding variation itself does nothing to restrict mutation rates; mutation rates are density-independant. Selection does not reduce the likelyhood of mutations, contrary to your assertion.
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crashfrog Member (Idle past 1498 days) Posts: 19762 From: Silver Spring, MD Joined: |
As I've asked before, is there simply no more idea in anyone's mind at all of a BUILT-IN set of genetic variables that combine in sexual selection and define a species, and upon which all the selective processes work? No, because there's no mechanism for it. Diploid organisms have at most two alleles per gene; haploid organisms have only one allele per gene. There's simply not enough room in the genome for the sort of restricted recombination that you're proposing.
Flood theory assumes an enormous pre-existing built-in set of genetic variables For which there's no room in an organism's genetics. So right there we can falsify flood "theory".
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DBlevins Member (Idle past 3806 days) Posts: 652 From: Puyallup, WA. Joined: |
I apologize if I misunderstood what you were saying. It seemed to me that you were talking about variation. Specifically a reduction in variation due to genetic drift/ NS.
I do think I percieve what you are saying and perhaps a misunderstanding about alleles that you might have. In your first post you talked about a reduction in alleles:
Migration out of a population leaves both the remaining populations genetically reduced. This is what happened with Darwin's Galapagos turtles. They are both likely to develop traits peculiar to themselves from their reduced allotment of alleles... This is infact not the case. There is no genetic reduction, or reduced allotment of alleles, as if they are somehow reduced. Instead there is a shift in the frequency of alleles by selection working on the expressed alleles. This may or may not cause a reduction in the "FREQUENCY" of an allele, but that is because the frequency of a selected allele is increased. So if we see in our finches with small beaks that they are selected against, we still have a population of larger beaked birds that may have the small beak alleles. In the case of a drastic reduction, such as a bottleneck the allele frequency may shift so much that the allele for small beaks doesn't exist in the population, but the number of alleles for that trait are still there, they may all be large beak alleles. To express this visually, suppose you have a population of birds that vary in beak size according to expressed alleles, as shown below (with - allele for small beaks and + allel for larger beaks). Now remember we are talking about continuouly varrying traits or multiple alleles affect a trait (such as height in humans.) (numbers in parenthesis show hypothetical population) (5) (11) (20) (30) (21) (10) (3)-- -- -- -+ -+ -+ ++ -- -- -+ -+ -+ ++ ++ -- -+ -+ -+ ++ ++ ++ Now if some selection pressure caused the smallest beaked birds to die off you still have - genes in all but the largest beaked birds. There was no "reduction" in the alleles that affect beak size but a reduction in the FREQUENCY of the - allele. This I think is the misperception you have about some reduction. As far as there being a reduction in variability. Variability is the "ability" to vary. What is stopping a mutation to act on or change one of the alleles, even if they were all + alleles? If a mutation acts or changes one of these alleles it will remain hidden and reshuffled among the population if it isn't detrimental to the reproduction of the species UNTIL selective forces act in such a way that this NOVEL ALLELE becomes expressed. This novel allele may or may not help the species to survive. This message has been edited by DBlevins, 02-17-2005 19:09 AM
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inkorrekt Member (Idle past 6112 days) Posts: 382 From: Westminster,CO, USA Joined: |
Faith, I have been reading all your posts. However, those who attack you have done everything they could do to prove that you are wrong. In spite of all they had written, they have not proved anything. Kind refers to different species. No question about this. When you look at all the animal kingdom, there is an ecological interdependence of various species. Survival of the fittest theory cannot explain this. The only explanation can be that the Intelligent designer knew everything and He brought everything into existence all at one time. There cannot be any other explanation. Any other explanation does not make any sense to me.
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NosyNed Member Posts: 9004 From: Canada Joined: |
Kind refers to different species. No question about this. Thank you, inkorrect. You just destroyed the creationists (and Faith's) arguments against macroevolution. Thanks for being on our side.
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Coragyps Member (Idle past 765 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
There cannot be any other explanation. Any other explanation does not make any sense to me. Think about what you wrote here, Ink. Are those two sentences necessarily tied together?
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kuresu Member (Idle past 2544 days) Posts: 2544 From: boulder, colorado Joined: |
this may have been mentioned, but . . .
what Paulk was calling a normal event would be the extinction of the cheetah. We severely reduced their numbers, and had no conservation programs stepped in, they would have been hunted to extinction. Even if there was no hunting but no conservation program, the cheetah would have died off. But not entirely becasue of a decrease in genetic variation, but becasue there are too few scattered in too few locales to bring their population back up without our help. If they ever have high numbers again, I would not be surprised to find increased genetic variation. when you say that the cheetah reduction in variation is the inexorable trend that should destroy evolution you missed his point.
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kuresu Member (Idle past 2544 days) Posts: 2544 From: boulder, colorado Joined: |
As far as I know, that sort of symbiotic relationship is very important to ecology and evolution includes it. When Darwin was at Madagascar, he noticed a plant with the nectary eleven inches inside of the flower. The only way to get ot it would be to have a beak eleven inches or a proboscis eleven inches, and it turned out that their is a moth with such a probosicis. Survival of the fittest is within a species--though who produce the most offspring are said to be better fit. This is because organisms produce more offspring than the habitat can support, leading to a competition for resources. Since producing sperm or egg takes a good deal of energy and time, those who can outcompete others for resources will invariable produce more offspring, passing on those advantageous (and non-advantageous) traits of the parents. Since the moth with an eleven inch probosis can get the food, he will pass on his genes. What was once a mutation is now the norm. Oh, and have you ever heard of co-evolution? It's pretty much what I just explained.
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mark24 Member (Idle past 5226 days) Posts: 3857 From: UK Joined: |
inkorrekt,
The only explanation can be that the Intelligent designer knew everything and He brought everything into existence all at one time. Directly contradicting the biblical creation account. Give yourself a medal!
Kind refers to different species. Forget giving yourself a medal, Dawkins himself would be proud to present you the VC for this. I suspect you'll be in receipt of more than one Purple Heart's before your fellow creo's have finished with you! Mark There are 10 kinds of people in this world; those that understand binary, & those that don't
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inkorrekt Member (Idle past 6112 days) Posts: 382 From: Westminster,CO, USA Joined: |
Oh, and have you ever heard of co-evolution? It's pretty much what I just explained
Alright. Let us assume that mutation and macro and microevolution really occur. In the evolutionary scale, man is the current existing species at the top level. What will man become if these processes continue? Edited by inkorrekt, : to make more meanigful post
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Belfry Member (Idle past 5116 days) Posts: 177 From: Ocala, FL Joined: |
Inkorrekt writes:
By what measure?
In the evolutionary scale, man is the current existing species at the top level.
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ramoss Member (Idle past 643 days) Posts: 3228 Joined: |
Define 'top level'???
We are the species that are the most technological, yes, but does that mean 'top level'?? It has not been established that either techology or intelligence is a good long term survivial technique. After all, our species has only been around less that 200,000 years, and our technology has only been about 12,000 years or so. The cockroach seems to be much more robust in surviviablity.
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