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Author | Topic: Question on how Evolution works to produce new characteristics | |||||||||||||||||||||||||||||||||||||||||||
Dr Adequate Member (Idle past 314 days) Posts: 16113 Joined:
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Why would there be any exceptions to blind selection? Natural selection is blind with no direction or purpose. So the exceptions have direction and purpose? No-one said that they were exceptions to natural selection. What you have to remember is that natural selection acts as a force for conservation as well as for change; depending on the circumstances. When a species can be improved on, then natural selection will select for any mutations which improve the species, and we'll see change. But what happens when a species has had millions of years to settle into a stable environmental niche? By that time it will be about as good as it can get, and any change will likely be for the worse. At that point, natural selection won't be able to pick out any favorable new mutations, 'cos there won't be any; its role will be confined to slapping down harmful mutations and keeping the species much the same. Your green frogs are an example. Until the vegetation changed, the role of natural selection would have been to keep them green by slapping down any variants, producing stasis. If an orange-speckled mutant had turned up, it would have been overly conspicuous and would have been gobbled up by the Giant Frog-Eating Grebe: so natural selection would have been a conservative force. When the vegetation changed, an orange-speckled version would have been less conspicuous, and natural selection would have favored change.
My question is coelacanth is not the only species that live in deep water. If the other species have changed, why has it not changed? Your question is based on a misconception: there are other groups that have remained remarkably stable. DrJones just mentioned coelacanths because for some reason creationists are obsessively wrong about this particular group rather than all the others.
N.B: Coelacanths are not a species, but an entire order; and the modern species of coelacanths are not identical with the fossil species.
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RAZD Member (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi Europa,
Why would there be any exceptions to blind selection? Natural selection is blind with no direction or purpose. So the exceptions have direction and purpose? Selection is not blind, it is a filter. Organisms that survive better and reproduce better than their peers will produce more offspring which ends up selecting the features that enable them to survive better and reproduce better. When the ecology is stable this will result in selection for stability, and the only changes will be due to genetic drift. The modern coelacanthe is larger and lives in a different ecology than the fossil ones, so there has been evolution from the fossils to the modern fish. Same for alligators and other examples of species that appear in general to be similar to fossil species.
My question is coelacanth is not the only species that live in deep water. If the other species have changed, why has it not changed? The modern coelacanths do not appear to be a deep water fish, so much as a bottom feeding fish that happens to inhabit the deep water around sea mounts. There are different species found at different sea mounts, rather than one species found in general deep water locations. Excellent website on the coelacanth http://www.dinofish.com/DINOFISH.COM - Weird Bodies Frozen in Time Enjoy. we are limited in our ability to understand
by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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Dr Adequate Member (Idle past 314 days) Posts: 16113 Joined: |
Natural selection is blind with no direction or purpose. I should say that if you're trying to understand evolution, statements like that are more of a hindrance than a help. There's a sense in which it's true, and a sense in which it's thoroughly misleading. The words "blind with no direction or purpose" doesn't really clarify the situation: after all, you could say that of lots of things, like the weather or gravity or chemistry. If anything, you need to understand why it is somewhat less meaningful to describe natural selection in this way than other forces of nature. But rather than think about such quasi-metaphorical descriptions in the first place, it's better to think about what natural selection would actually do in various cases, such as your frogs. Once you can do that, then vaguer and more abstract descriptions of natural selection won't be able to confuse you; and until you can do that, they probably won't help you much either.
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Europa Member (Idle past 4716 days) Posts: 68 Joined: |
No-one said that they were exceptions to natural selection. Then what are they exceptions to? ................................................................. I am no biologist and my knowledge on evolution is pretty basic. I am probably talking more out of common sense. We have some organisms that have not changed very much -- living fossils -- and we have other organisms that have shown remarkable change in a relatively short period of time. If we MUST apply the same theory to explain them both -- evolution -- I think there is something that I do not follow here. And when i ask, you say the living fossils are the exceptions. I thought they were exceptions to natural selection for I could not think of anything else. If they are exceptions because natural selection applies in an exceptional way, when we talk of living fossils, it does not make sense to me. How do you apply the same theory to explain the living fossil and the monkey?
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Europa Member (Idle past 4716 days) Posts: 68 Joined: |
But rather than think about such quasi-metaphorical descriptions in the first place, ... Why not?The 'quasi-metaphorical' terms are not false. They are not projecting anything the way it should not be projected. And I think I fully understand these terms. So why can't I use them?
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Huntard Member (Idle past 2325 days) Posts: 2870 From: Limburg, The Netherlands Joined: |
Europa writes:
Yes. The environmeent of the one species might not have changed much at all (think deep sea creatures for example), while for the other, a radical change in environmet cuased them to change radically as well (lizards being transported to a completely different island with different foodsources develloping a cecal valve).
We have some organisms that have not changed very much -- living fossils -- and we have other organisms that have shown remarkable change in a relatively short period of time. If we MUST apply the same theory to explain them both -- evolution -- I think there is something that I do not follow here. And when i ask, you say the living fossils are the exceptions. I thought they were exceptions to natural selection for I could not think of anything else.
They are exceptions to what we "normally" see.
If they are exceptions because natural selection applies in an exceptional way, when we talk of living fossils, it does not make sense to me.
Well, it doesn't apply any differently. The pressure were simply much less, resulting in far less change than other populations.
How do you apply the same theory to explain the living fossil and the monkey?
The environment, and changes to it, is key.
----- Also, a free tip for you. If you reply to a post it is better to use the "reply" button on the bottom right of the post you are replying to. This will make it easier to track your replies and will also send an e-mail notification to the person you replied to. Edited by Huntard, : Added a free tip!
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Dr Adequate Member (Idle past 314 days) Posts: 16113 Joined:
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Then what are they exceptions to? Many lineages seem either to change or go extinct. Some don't change much or go extinct. This is one of the meanings of the words "living fossils" (it has a number of meanings, none of them very precise).
I am no biologist and my knowledge on evolution is pretty basic. I am probably talking more out of common sense. Common sense will scarcely help you with classes of events which are outside your experience.
We have some organisms that have not changed very much -- living fossils -- and we have other organisms that have shown remarkable change in a relatively short period of time. If we MUST apply the same theory to explain them both -- evolution -- I think there is something that I do not follow here. There is. Consider the theory of gravity as an analogy.
It predicts that a ball placed at point A will descend quickly and to the right, a ball placed at point C will descend more slowly and to the left, and a ball placed at point B will stay where it is. The theory does not predict "balls will move quickly" or "balls will move slowly" or "balls will stay still" or "balls will move to the left" or "balls will move to the right". Rather, it relates the motion of balls (and other objects) to the situation that they're in. The same with the theory of evolution. Think again about your frogs. So long as they're well-camouflaged from predators (green on a green background) natural selection will act to keep them that way --- it's a force for stasis, like gravity operating on the ball at point B. Change the background, and we expect natural selection to favor mutations which make them look more like the new background --- then it's a force for change, like gravity operating on a ball on a slope.
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Dr Adequate Member (Idle past 314 days) Posts: 16113 Joined: |
Why not? The 'quasi-metaphorical' terms are not false. They are not projecting anything the way it should not be projected. I think they do. They're ambiguous. Yes, there's a sense in which natural selection is "blind". There's an equally good sense in which you could call it "all-seeing". Neither of them would be particularly accurate.
And I think I fully understand these terms. I think if you understood what it meant to say that natural selection is "directionless", you wouldn't be so puzzled by "living fossils".
So why can't I use them? You may: I'm just giving you some free advice. It's better to try to understand natural selection, or any other aspect of nature, by thinking carefully about what it actually does.
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Europa Member (Idle past 4716 days) Posts: 68 Joined: |
Yes. The environmeent of the one species might not have changed much at all It is hard to believe that tuataras and other reptiles lived in the same habitat and yet, the tuataras did not change but the other reptiles did.
They are exceptions to what we "normally" see. Okay.But if natural selection is a creative force that is blind, has no purpose or direction, why do some organisms change and some do not? I think there should be no exceptions because NS is BLIND. ............
If you reply to a post it is better to use the "reply" button on the bottom right of the post you are replying to. This will make it easier to track your replies and will also send an e-mail notification to the person you replied to. Makes sense.All my replies appear at the bottom of the page irrespective of the button I clicked. So I did not bother. I probably must have mostly clicked the reply button of the last reply.
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Europa Member (Idle past 4716 days) Posts: 68 Joined: |
"all-seeing?"
This is interesting.Please explain. I'm just giving you some free advice. It's better to try to understand natural selection, or any other aspect of nature, by thinking carefully about what it actually does. Well, thank you very much.I thought that's what I am truing to do.
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Europa Member (Idle past 4716 days) Posts: 68 Joined:
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So long as they're well-camouflaged from predators (green on a green background) natural selection will act to keep them that way --- it's a force for stasis, I think I understood the explanation.Just that it does not make sense to me because we are not talking of organisms from a different planet. The living fossils and the rest of the organisms on this planet have lived and continue to live through more or less similar environmental conditions.They both mutate. Its not that the LFs have a low incidence of mutations. I would think they should both show similar degrees of evolution. But we know they don't. So ... Random mutations and natural selection after all do not adequately explain evolution?
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Huntard Member (Idle past 2325 days) Posts: 2870 From: Limburg, The Netherlands Joined:
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Europa writes:
Then there is of course also the possibilities that they went on to specialize and fill different niches. The tuataras are well enough adapted to survive in their own niche, yet other reptiles found another niche where they could prosper better, and so, adapted to that particular niche. Think about it as lions and zebras, both inhabit the same environment, but fill very different niches.
It is hard to believe that tuataras and other reptiles lived in the same habitat and yet, the tuataras did not change but the other reptiles did. Okay.
It's not really a creative force. Mutation screate the adaptations. Natural selections weeds out the bad ones and allows the beneficial ones to proper.
But if natural selection is a creative force that is blind... ...has no purpose or direction...
The "purpose" of natural selection is to allow the most fit individuals to thrive, the direction is determined by the environment.
why do some organisms change and some do not?
Because some don't need to. They fulfill their particualr niche well enough to not need to change at all to thirve. Some find a differeent niche in the same environment, not yet filled by another organism, and adapt to make full use of that niche. Or sometimes the environment changes rdically, and this force the creature to adapt as well. Or go extinct of vourse, that's always a possibility.
I think there should be no exceptions because NS is BLIND.
I don't agree it's "BLIND",a t least, it can be argued about. Anyway, even if this were the case, then would that not be a perfect explanations on why some things change and some things don't? Afterall, if it's blind, it doesn't know what to act on.
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RAZD Member (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi Europa,
They both mutate. Its not that the LFs have a low incidence of mutations. I would think they should both show similar degrees of evolution. They do, it's just that your expectations of what you should see are incorrect.
But we know they don't. So ... Random mutations and natural selection after all do not adequately explain evolution? The reason that "living fossil" appear not very changed is that natural selection kept them in a fit ecology. If they were not fit they would be extinct eh? Mutations arise randomly and offer opportunities for change. If an organism is not fit to the ecology and some of the mutations offer better fitness then natural selection will increase their proportion in the population. If an organism IS fit and the mutations do not add fitness, then they will all be selected against. Enjoy Enjoy. we are limited in our ability to understand
by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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Dr Adequate Member (Idle past 314 days) Posts: 16113 Joined: |
But if natural selection is a creative force that is blind, has no purpose or direction, why do some organisms change and some do not? I think there should be no exceptions because NS is BLIND. And how come gravity moves some things and not others? I think there should be no exceptions because gravity is DEAF. And has NO SENSE OF SMELL either. --- This is why you should take my advice and think about what natural selection actually does. Trying to think about it in poetic metaphors instead of thinking about the real thing has evidently only confused you. Edited by Dr Adequate, : No reason given.
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Dr Adequate Member (Idle past 314 days) Posts: 16113 Joined: |
I think I understood the explanation. Just that it does not make sense to me Which?
The living fossils and the rest of the organisms on this planet have lived and continue to live through more or less similar environmental conditions. No. Different species live in different environmental niches. Obviously a lamp shell does not live in the same environment as a daisy, nor face the same pressures or challenges, so why should you expect similar rates of evolution?
I would think they should both show similar degrees of evolution. And you are wrong. It depends on the pressures applied. Imagine two islands both with green frogs amongst green leaves. Then your orange-spotted vegetation invades one island but not the other. One bunch of frogs will stay the same, the other will change. Different environmental pressures, different results. This is not a difficult concept.
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