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Author Topic:   Question on how Evolution works to produce new characteristics
Asking
Junior Member (Idle past 2990 days)
Posts: 19
Joined: 05-19-2010


Message 16 of 104 (563660)
06-06-2010 10:51 AM
Reply to: Message 1 by Europa
06-05-2010 10:24 PM


Just to break your question down in a few points

Initially

1) Frogs are all green
2) Flora is all green

After

a) Frogs are all green
b) Flora is mixed colour

Ok the first problem with your question is that that not said what the selective pressure is (though I'm assuming that its predation) because without some form of selective pressure that operates on colour there is no reason why any particular colour will be favoured by seleciton. Genes are only conserved when there is a selective pressure weeding out mutations (Neutral mutation aside which have no effect on a genes function) so its likely that (Assuming a mutation in the genes that control the frogs colour aren't also involved in something that would prove fatal if a mutated) that there may be some variation in colour already unless there was predation.

For you're question we'll need to make a few assumptions

  1. There is predation and that predator hunts by colour vision
  2. The genes responsible for frog skin colour:
    1. produce different colours following mutation
    2. are not linked to something else in the frog that if changed via mutation would be fatal.
  3. There is sufficient time for the neccesary mutation to take place. Extinction is the alternative if a species is unable to evolve quickly enough to keep up with environmental change.

For what you propose to happen a frog would need to have a mutation in the genes that controls its skin colour which results in it being slighty better camouflaged than others of its kind. The result being that this individual has a greated chance of surviving predation and therefore reproducing and passing its genes on. Depending on how great an advantage this mutation gives an individual will affect how quickly it spread through the population but I understand that beneficial mutations can become common in a population very quickly. There may be further mutations within the population which in turn make individuals slightly more better camouflaged and the same process happens again.

Assuming that the assumptions I made above are met then yes the island would be dominated by the speckled (Or more likely whatever the mutation resulted in) skin. Evolution has no forsight and therefore doesn't decide what will be the best camouflage. It simply selects the best at surviving in a given population and by doing so ensures the genes that gave them that advantage get passed on.

In my opinion extinction would be the most likely outcome if its an issue of predation. Just look at the effect which alien predators have had on Australian fauna in a short period of time.

Edited by Asking, : Forgot to mention nuetral mutations

Edited by Admin, : Fix list to use dBCodes.


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AZPaul3
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Posts: 3477
From: Phoenix
Joined: 11-06-2006


(1)
Message 17 of 104 (563661)
06-06-2010 11:10 AM
Reply to: Message 1 by Europa
06-05-2010 10:24 PM


Can someone explain to me how evolution will work to make the frogs survive?

No. We can speculate on what might happen to the population, but since evolution is not pre-ordained or goal oriented there is no direction in which to say how it "will" solve this problem.

I like Asking's treatment in message 16.

However, camouflage (or extinction) may not be what happens. There are a whole host of other probabilities within biological systems. The same kind of scenario as skin color may involve skin taste or poison instead. So a bunch of bright green easy to see froggies survive in the open because predators learn to avoid them.

They may, for all evolution cares, mutate into froggie equivalents to pink elephants and fly away on Dumbo ears (though I wouldn't count this one as very highly probable).

The point being, no one can say what will happen. All we can say is that since the environment is dramatically changing, the species will change (in some unpredictable way) or die.


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RAZD
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Message 18 of 104 (563766)
06-06-2010 7:06 PM
Reply to: Message 1 by Europa
06-05-2010 10:24 PM


Hi Europa and welcome to the fray,

I am confused about all the information on evolution, creation and intelligent design. Hence I joined this forum to post this question.

An excellent approach, let's see if we can help out.

Let me add to what others have said, with attention to some details:

But there is not a single orange speckled frog so far in this island population.

Evolution does not occur on demand, mutations are not produced to fit changing ecologies, but are random events.

Message 5 ... will it not be a response to a 'felt need'?

There is no "felt need" as there is no mechanism to feel it. Selection operates on traits existing in a population, and mutation is a random event that may provide a beneficial trait, a deleterious trait, or a neutral trait in the descendents.

Lamarkism

(Lmarkism?)
Message 8 1. Why do you say this -- orange speckling -- isn't Lamarkism?
Message 11 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.

Well first it isn't an acquired trait so it doesn't fit his (best known) theory\model of inheritance of acquired traits. Another of his (less well known) theories was that the environment drove changes:

http://en.wikipedia.org/wiki/Lamarck#Lamarckian_Evolution

quote:
... that the environment gives rise to changes in animals. He cited examples of blindness in moles, the presence of teeth in mammals and the absence of teeth in birds as evidence of this principle.

Both of these processes have been falsified. In the example of the giraffe, we have a growing giraffe that stretches it's neck, and much like you or can excercise and build muscles, or loosen joints to stretch, this giraffe becomes able to reach further that previously.

In order to pass on this trait to it's offspring, there needs to be a mechanism that takes this acquired trait and somehow transfers it into the DNA of its sex reproduction cells. There is no such mechanism known.

I am confused about all the information on evolution, creation and intelligent design.

Curiously, you have asked more about Lamarkism than about any of these, so perhaps we need to clarify what each is first:

Evolution

Evolution is the change in the frequency and character of hereditary traits in breeding populations from generation to generation in response to ecological opportunities. The change in the frequency of the hereditary traits occurs through natural selection, genetic drift, and some other mechanisms. The change in the character of hereditary traits occurs through random mutations, mutations that cause deleterious, neutral or beneficial alterations to the alleles. Natural selection is the differential success of individuals to survive and breed against the background of the changing ecological opportunities: what is fit (all green) in one ecology (all green) many not be fit (all green) in a different ecology (mixed green and orange).

Evolution predicts that either:

(a) the selection pressure will cause the all green frogs to go extinct, or

(b) the selection pressure will still allow all green frogs to survive, but in reduced numbers compared to the all green environment, or

(c) a mutation will arise that enable the frogs with the mutation to survive and breed better than their all green cousins, or

(d) a population of frogs from the same source as the orange vegetation would invade the ecology and become predominate due to their previous adaptation to the orange vegetation (their expansion into this area being previously prevented by the all green frogs being better adapted to the all green ecology).

Note that (c) can occur after (b) or during the time it is taking for (a) to occur, as neither would be likely to occur overnight.

The mutation could be for brown or dark skin to blend into shadows, the mutation could be for the frogs to become nocturnal and spend days in hiding, the mutation could be for the frog to become poisonous to the predator, or the mutation could be for colored spots that appear to the predator as similar to the orange/green ecology.

Note that there are frogs that exhibit each of these traits.

Evolution further predicts that, should a beneficial mutation occur, that the distribution of it within the population will be according to common ancestry from the frog with the initial mutation/s.

Creation

As far as I know, the various concepts of creation are that organisms are created as they are. If we consider that this creation is ongoing, then we have concerns about why it wasn't finished and why such changes keep happening. This seems to fall in the "Intelligent Design" concept of an ongoing process.

The major problem is that this concept makes no predictions about changes to any organisms, rather it predicts a lack of change (or the initial product was imperfect).

There is no reason for the frogs to change.

Intelligent Design

If such changes as the (all green) ecology to the (mixed green & orange) ecology were done as part of some intelligent grand scheme, and the changes to the frogs to be orange speckled were also part of that same grand scheme, then we would expect that the changes would occur randomly across the populations of both plant and frog with no hereditary relationship.

If the frogs were "redesigned" for the altered ecology, then the changes should be across the board in the whole frog population, and should result in the best possible fitness to the ecology.

There is no reason for the changes to the frog population to lag behind the changes to the ecology.

Message 8 2. 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? Is this how evolution works? I mean by the chance mutation of a favourable trait on a single organism?

Yes ... IF (a) the selection pressure does not cause extinction first and (b) if the selection pressure is sever enough to depress the reproduction and survival of the all green frogs relative to ones with any orange speckling.

If half the offspring of the initial frog have orange speckling and half of the remaining offspring are subject to predation, then after one generation of frogs there would be twice the number of orange speckled frogs than all green frogs from that one individual.

Also look at the Peppered Moth changes in response to altered ecology.

Peppered Moths and Natural Selection

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This message is a reply to:
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Dr Adequate
Member
Posts: 16055
Joined: 07-20-2006
Member Rating: 3.1


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.


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Dr Adequate
Member
Posts: 16055
Joined: 07-20-2006
Member Rating: 3.1


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:
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Europa
Member (Idle past 2639 days)
Posts: 68
Joined: 06-05-2010


(1)
Message 21 of 104 (563826)
06-06-2010 11:19 PM
Reply to: Message 20 by Dr Adequate
06-06-2010 7:42 PM


Re: Drift And Selection
Thanks guys for your input. I am enjoying this.

Dr Adequate has summed it up. So I will take one of his statements.

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.

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?

Isn't natural selection a 'creative force?'


This message is a reply to:
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Replies to this message:
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DrJones*
Member
Posts: 1739
From: Edmonton, Alberta, Canada
Joined: 08-19-2004
Member Rating: 2.4


Message 22 of 104 (563835)
06-07-2010 1:11 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?

Why must their enviroment change? And to head off any mention of the coelocanth, the current species is not found in the fossil record.


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Dr Adequate
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Posts: 16055
Joined: 07-20-2006
Member Rating: 3.1


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.


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Phage0070
Inactive Member


(1)
Message 24 of 104 (563841)
06-07-2010 2:04 AM
Reply to: Message 1 by Europa
06-05-2010 10:24 PM


Europa writes:

Will orange speckled frogs be the dominant variety of frogs in this island at a later time?

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 but it is very unlikely.

The frogs might instead be dominated by the quickest variety of frogs that quickly dodge predators, rather than those that sit still and hide. 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. Orange skin pigment isn't the only trait at work here; 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.


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Dr Adequate
Member
Posts: 16055
Joined: 07-20-2006
Member Rating: 3.1


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.


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Phage0070
Inactive Member


Message 26 of 104 (563855)
06-07-2010 3:52 AM
Reply to: Message 25 by Dr Adequate
06-07-2010 2:51 AM


Dr Adequate writes:

As I understood it, the question implies that they are better off by being camouflaged against the vegetation.
...
For my money, given the premises of the question, we would indeed end up with green frogs with orange spots.

And that is where you go wrong. Evolution isn't concerned with what they are better off being, it doesn't work that way. If the frogs get selected for the nasty or toxic ones surviving longer, they might develop the survival method of being garish and poisonous. 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.

The process doesn't run through what is most effective in theory, it needs to work with what it has.


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Dr Adequate
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Posts: 16055
Joined: 07-20-2006
Member Rating: 3.1


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.


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Dr Jack
Member (Idle past 57 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 28 of 104 (563862)
06-07-2010 5:13 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?

Firstly, recognise that living fossils are the exception, not the rule. Secondly, note that living fossils are not identical to their fossil relatives, merely similar and, finally, recognise that the evidence suggests that living fossils are genetically quite different from their ancestors suggesting that they have mutated but stablising selection has kept their phenotypes consistent.

It cannot be that their environment did not change. So, if they mutate and if their environment changes, why are they the same?

Why can't their environment have been unchanging? Or, more saliently, why can't the aspects of it relevant it their survival have been unchanging? Remember, as well, that environments are not spatially unvarying, species can move to areas that continue to match the environment they are fit for as well as adapting to their current environment.


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Taq
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Posts: 7594
Joined: 03-06-2009
Member Rating: 3.4


Message 29 of 104 (563985)
06-07-2010 4:15 PM
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?

Last I checked, fossils are dead.

If you have time, do some reading on "fitness peak". In this model a species becomes more adapted to a specific environment over time. The longer this occurs the more fit the species becomes. At a certain point they reach a peak where very few changes will increase their fitness. This results in a population that just doesn't change much, even if the rate of mutation is the same. In this situation, the number of deleterious mutations will be much greater than the number of beneficial mutations so selection tends to be negative.

One example is the coelacanth which has many features in common with it's distant ancestors. This fish is found in very deep waters (>200m if memory serves). These environments do not vary by more than a few degrees each year and are very, very stable. Chances are that this coelacanth species has changed very little over the last 60 million years since it moved to these deeper waters (most known fossil coelacanth species were from shallow water environments).


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Europa
Member (Idle past 2639 days)
Posts: 68
Joined: 06-05-2010


(1)
Message 30 of 104 (564000)
06-07-2010 5:55 PM
Reply to: Message 29 by Taq
06-07-2010 4:15 PM


Re: Drift And Selection
Thanks Dr Adequate for the pictures.

Firstly, recognise that living fossils are the exception, not the rule.

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?

Last I checked, fossils are dead.

You must have seen them before some were resurrected.

Chances are that this coelacanth species has changed very little over the last 60 million years since it moved to these deeper waters.

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?

Edited by Europa, : No reason given.


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