Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
3 online now:
Newest Member: popoi
Post Volume: Total: 915,817 Year: 3,074/9,624 Month: 919/1,588 Week: 102/223 Day: 13/17 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Question on how Evolution works to produce new characteristics
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 19 of 104 (563768)
06-06-2010 7:22 PM
Reply to: Message 11 by Europa
06-06-2010 5:49 AM


Lamarckism
I am not arguing for the sake of arguing. But ...
The often quoted example of Lamarkism is the elongation of a giraffe's neck. Now, the giraffe did not 'learn' how to have a long neck. But this is Lamarkism.
It's an example of the sort of thing Lamarck was wrong about. But now we know that nature doesn't work that way.
The same with the frogs. There is simply no genetic mechanism which can look at the vegetation, notice that it has orange speckles, figure out that the frogs would be better equipped to survive if they too had orange speckles, figure out what proteins would bring that about, and then change the genes of the frogs to produce those proteins. Even scientists aren't yet smart enough to do that last bit --- the best they could do would be to copy (and splice in) the genes of another species of frog that already had orange speckles.

This message is a reply to:
 Message 11 by Europa, posted 06-06-2010 5:49 AM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 20 of 104 (563776)
06-06-2010 7:42 PM
Reply to: Message 8 by Europa
06-06-2010 5:31 AM


Drift And Selection
If orange speckling, by chance, occurs due to a single mutation on a single frog, will it be capable of making this the dominant trait of the colony over time?
This has been answered, but let's be more precise.
When we do the math, we find that unless a new useful mutation is really awesomely useful, it's more likely than not that the mutation will end up extinct in the population, rather than becoming "fixed".
This may seem counter-intuitive, but the thing is that a new mutation is outnumbered. When (for example) there's just one frog with this useful trait, it can still get eaten by an alligator or die of frogfluenza, whereas it would take a very peculiar set of circumstances to wipe out all the plain frogs but leave the speckled one.
However, precisely because the mechanism behind mutation is blind and random, Nature is not able to say to itself: "OK, I tried that, it didn't work". The same mutation, or another one that produces speckles, can arise again. And again. And again ... until it finally manages to get itself fixed.
So if (a) such mutations are possible at all (b) the species doesn't go extinct, then given long enough we will indeed end up with a population of speckled frogs.

This message is a reply to:
 Message 8 by Europa, posted 06-06-2010 5:31 AM Europa has replied

Replies to this message:
 Message 21 by Europa, posted 06-06-2010 11:19 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 23 of 104 (563838)
06-07-2010 1:38 AM
Reply to: Message 21 by Europa
06-06-2010 11:19 PM


Re: Drift And Selection
If this is so, how do you explain living fossils?
Do they not mutate?
It cannot be that their environment did not change. So, if they mutate and if their environment changes, why are they the same?
Well, a couple of things. First, it is possible for an environment to stay pretty much the same for a long time. Second, most "living fossils" are not just the same as their ancestors.
Even when they look like their ancestors in the fossil record, this is not necessarily the case. If you think about your frogs, you wouldn't be able to tell that they'd evolved: the speckled form would have the same skeletal anatomy as the green ones.
Isn't natural selection a 'creative force?'
Yes and no. The mutations are creative, natural selection is selective.

This message is a reply to:
 Message 21 by Europa, posted 06-06-2010 11:19 PM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 25 of 104 (563848)
06-07-2010 2:51 AM
Reply to: Message 24 by Phage0070
06-07-2010 2:04 AM


If at the time of the invasion of plants they lack any members with orange pigment whatsoever, probably not. It might develop during the takeover ...
... or at any time after.
The frogs might instead be dominated by the quickest variety of frogs that quickly dodge predators ...
But camouflage would still be an adaptive feature, it's not either-or.
Or the frogs that hide on the underside of leaves might win out, or the ones that burrow in the ground or swim in the water.
As I understood it, the question implies that they are better off by being camouflaged against the vegetation.
... in the same sense that none of the frogs have the ability to shoot fire out of their rears and fly through the air as the perfect defense, a new threat isn't necessarily going to wipe them out if they don't develop such a trait.
But it doesn't require that the species will develop the feature or become extinct, just that a speckled frog is better off than a plain one. It's a hypothetical "toy" situation to elucidate the operation of mutation and selection.
Now, we know that frogs are very variable in color.
For my money, given the premises of the question, we would indeed end up with green frogs with orange spots.

This message is a reply to:
 Message 24 by Phage0070, posted 06-07-2010 2:04 AM Phage0070 has replied

Replies to this message:
 Message 26 by Phage0070, posted 06-07-2010 3:52 AM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 27 of 104 (563856)
06-07-2010 4:03 AM
Reply to: Message 26 by Phage0070
06-07-2010 3:52 AM


If the frogs get selected for the nasty or toxic ones surviving longer, they might develop the survival method of being garish and poisonous.
Sure, that would work too. (Though I note that by hypothesis the green frogs have not yet evolved this defense, and are relying on camouflage rather than aposematism as a defense.)
But I think that the point of the question is how to get from one form of camouflage to another.
In that case camouflage might actually be selected against, even though theoretically if they were all camouflaged they would have a higher rate of survival.
I think that that could have been better phrased.
The process doesn't run through what is most effective in theory, it needs to work with what it has.
I didn't mean to imply otherwise.

This message is a reply to:
 Message 26 by Phage0070, posted 06-07-2010 3:52 AM Phage0070 has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 31 of 104 (564012)
06-07-2010 6:56 PM
Reply to: Message 30 by Europa
06-07-2010 5:55 PM


Re: Drift And Selection
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.

This message is a reply to:
 Message 30 by Europa, posted 06-07-2010 5:55 PM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 33 of 104 (564064)
06-08-2010 1:13 AM
Reply to: Message 30 by Europa
06-07-2010 5:55 PM


Metaphors
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.

This message is a reply to:
 Message 30 by Europa, posted 06-07-2010 5:55 PM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 37 of 104 (564075)
06-08-2010 6:29 AM
Reply to: Message 34 by Europa
06-08-2010 5:32 AM


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.

This message is a reply to:
 Message 34 by Europa, posted 06-08-2010 5:32 AM Europa has replied

Replies to this message:
 Message 41 by Europa, posted 06-08-2010 7:02 AM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 38 of 104 (564077)
06-08-2010 6:36 AM
Reply to: Message 35 by Europa
06-08-2010 5:37 AM


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.

This message is a reply to:
 Message 35 by Europa, posted 06-08-2010 5:37 AM Europa has replied

Replies to this message:
 Message 40 by Europa, posted 06-08-2010 6:53 AM Dr Adequate has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 44 of 104 (564093)
06-08-2010 7:38 AM
Reply to: Message 39 by Europa
06-08-2010 6:49 AM


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.

This message is a reply to:
 Message 39 by Europa, posted 06-08-2010 6:49 AM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 45 of 104 (564094)
06-08-2010 7:49 AM
Reply to: Message 41 by Europa
06-08-2010 7:02 AM


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.

This message is a reply to:
 Message 41 by Europa, posted 06-08-2010 7:02 AM Europa has replied

Replies to this message:
 Message 49 by Europa, posted 06-08-2010 7:35 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 46 of 104 (564095)
06-08-2010 8:01 AM
Reply to: Message 39 by Europa
06-08-2010 6:49 AM


Tuataras
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.
But the tuataras did change.
Remember I told you that the term "living fossil" is ambiguous?
Tuataras are called "living fossils" not because they are unchanged from their Mesozoic ancestors, but because they are the last few members of what used to be a larger group --- the Sphenodontia.
(If you killed off all the other primates, humans would then become "living fossils" according to that meaning of the term. But not, of course, in the sense of prolonged morphological stasis.)

This message is a reply to:
 Message 39 by Europa, posted 06-08-2010 6:49 AM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 50 of 104 (564179)
06-08-2010 7:59 PM
Reply to: Message 48 by Europa
06-08-2010 7:22 PM


My question is why the LFs only? And not everything else?
The same reason why only the balls not on slopes don't roll downhill.
To go into more detail, we'd have to look at some specific case of morphological stability.
Edited by Dr Adequate, : No reason given.

This message is a reply to:
 Message 48 by Europa, posted 06-08-2010 7:22 PM Europa has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 51 of 104 (564181)
06-08-2010 8:17 PM
Reply to: Message 49 by Europa
06-08-2010 7:35 PM


You are saying my green froggies will survive as green froggies for 200 million years if their environment remains green and provided everything else is also the same for them.
That is fine. I understand this.
Good.
What I do not understand is if alien plants can invade one island with green frogs and force them to change and ultimately speciate, why would I think the other island with green froggies can be out of reach for such changes?
If you say this island is not invaded by alien plants for another 100 years, that is believable. But when you say for 200 million years, no alien plants invaded that island and that is why the froggies of that island are green, it becomes too much of a stretch.
It's a thought experiment, like your OP (in which, I note, it took "ages" for the alien plants to get round to invading the island). The point is to get you to think about what would happen under those circumstances.
---
Now when we have two very different species living in completely different environmental niches, it is perfectly plausible that one will undergo pressures that will not affect the others. For example, the evolution of flowering plants provided a new set of opportunities for the winged insects, causing a whole cascade of changes; but this momentous event would have had no effect at all on lobsters.

This message is a reply to:
 Message 49 by Europa, posted 06-08-2010 7:35 PM Europa has replied

Replies to this message:
 Message 60 by Europa, posted 06-10-2010 6:15 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 66 of 104 (564488)
06-10-2010 6:25 PM
Reply to: Message 57 by Europa
06-10-2010 6:04 PM


Re: Cyanobacteria -- the ultimate "living fossil"?
Logically, it is also difficult o believe that for one population the environment is more or less the same for millions of years.
Prefacing a remark with the word "logically" does not make it logical; some sort of reasoning is also required.
One thing to bear in mind is that species are mobile (even a plant species, qua species, is mobile by dispersal of its seeds). And this allows species to stay in the same environment even when environmental changes occur. For example, the evidence shows that during Ice Ages, species requiring a temperate climate neither evolved nor went extinct. They just moved south. When the glaciers retreated, they moved back north.
(ABE: I note that you have acknowledged this point in post #60; I began writing this post before you'd posted #60.)
Now Huntard will say this is an argument from incredulity.
Yes.
Edited by Dr Adequate, : No reason given.

This message is a reply to:
 Message 57 by Europa, posted 06-10-2010 6:04 PM Europa has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024