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Author Topic:   Question on how Evolution works to produce new characteristics
Dr Adequate
Member
Posts: 16052
Joined: 07-20-2006
Member Rating: 3.4


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 yet responded

  
Europa
Member (Idle past 2635 days)
Posts: 68
Joined: 06-05-2010


(1)
Message 47 of 104 (564170)
06-08-2010 7:01 PM
Reply to: Message 42 by Huntard
06-08-2010 7:14 AM


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.

Well, well, well.
This is almost like a story now. Not that a story is unacceptable. But that it is not scientific.

Bottom line is ...
We have organism A (a living fossil)
We also have organism B (a regular animal. Say a monkey)

A has not changed for 100 million years.
B's ancestors' lives if traced to 100 million years will show fifteen or more species.

We are asked to explain this.
So we have to do something.

The only rational explanation is to say what you all have been saying: That A's environment did not PROBABLY change that much and that there was no real evolutionary pressure for A to change.

Anything else will not make sense.

Sorry to say this, but the above explanation does not make sense to me.

It's not really a creative force.

If it is not a creative force, how do you explain the existence of human beings form something that started as unicellular organisms?


This message is a reply to:
 Message 42 by Huntard, posted 06-08-2010 7:14 AM Huntard has responded

Replies to this message:
 Message 53 by Huntard, posted 06-09-2010 3:44 AM Europa has responded

    
Europa
Member (Idle past 2635 days)
Posts: 68
Joined: 06-05-2010


Message 48 of 104 (564173)
06-08-2010 7:22 PM
Reply to: Message 43 by RAZD
06-08-2010 7:16 AM


Hi RAZD

The reason that "living fossil" appear not very changed is that natural selection kept them in a fit ecology.

Well, fine.
My question is why the LFs only? And not everything else?

Edited by Europa, : No reason given.


This message is a reply to:
 Message 43 by RAZD, posted 06-08-2010 7:16 AM RAZD has responded

Replies to this message:
 Message 50 by Dr Adequate, posted 06-08-2010 7:59 PM Europa has not yet responded
 Message 52 by RAZD, posted 06-08-2010 9:37 PM Europa has responded

    
Europa
Member (Idle past 2635 days)
Posts: 68
Joined: 06-05-2010


(1)
Message 49 of 104 (564174)
06-08-2010 7:35 PM
Reply to: Message 45 by Dr Adequate
06-08-2010 7:49 AM


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.

Not at all.

The concept is easy to understand. The difficulty lies not in understanding the concept. But to make sense of it.

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.

Suppose we have 2 identical islands with green frogs.

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.


This message is a reply to:
 Message 45 by Dr Adequate, posted 06-08-2010 7:49 AM Dr Adequate has responded

Replies to this message:
 Message 51 by Dr Adequate, posted 06-08-2010 8:17 PM Europa has responded

    
Dr Adequate
Member
Posts: 16052
Joined: 07-20-2006
Member Rating: 3.4


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 yet responded

  
Dr Adequate
Member
Posts: 16052
Joined: 07-20-2006
Member Rating: 3.4


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 responded

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

  
RAZD
Member
Posts: 19665
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.9


Message 52 of 104 (564191)
06-08-2010 9:37 PM
Reply to: Message 48 by Europa
06-08-2010 7:22 PM


Cyanobacteria -- the ultimate "living fossil"?
Hi Europa,

You're trying to think of evolution as a force of nature. It isn't, it is a result of various processes and opportunities.

When we look at Peppered Moths and Galapagos Finches we see evolution -- the change in the frequency of hereditary traits in breeding populations from generation to generation -- and we see that the population swings one way in response to an ecological change and then swing back when the ecology changes back. Why? Because the first population was better fit for the first ecology.

Well, fine.
My question is why the LFs only? And not everything else?

Because every species lives in a different ecology. Different subpopulation of species can live in different ecoclines. This means that different species have different opportunities and thus are affected differently by selection processes.

Let's start with the ultimate "Living Fossil" -- cyanobacteria:

http://www.ucmp.berkeley.edu/bacteria/cyanofr.html

quote:
The cyanobacteria have an extensive fossil record. The oldest known fossils, in fact, are cyanobacteria from Archaean rocks of western Australia, dated 3.5 billion years old. This may be somewhat surprising, since the oldest rocks are only a little older: 3.8 billion years old!

Cyanobacteria are among the easiest microfossils to recognize. Morphologies in the group have remained much the same for billions of years, and they may leave chemical fossils behind as well, in the form of breakdown products from pigments.


http://en.wikipedia.org/wiki/Cyanobacteria

quote:
Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria (Greek: κυανός (kyanós) = blue). They are a significant component of the marine nitrogen cycle and an important primary producer in many areas of the ocean, but are also found in habitats other than the marine environment; in particular cyanobacteria are known to occur in both freshwater,[2] hypersaline inland lakes[3] and in arid areas where they are a major component of biological soil crusts.

Now here we have a bit of a conundrum: we have a fossil organism\species\type that has apparently evolved tremendously - they have apparently evolved into all other forms of life (or certainly a large number of them), AND

we have a fossil organism\species\type that has apparently barely evolved any changes at all from the original ancestral population, AND

they are the same species.

Logically this means that the result is not, cannot be, dependent on the ability of the population of organisms to evolve, but rather on the external factors that affect the opportunities and selection of the populations of organisms for fitness to different ecologies.

Population {A} in ecology {1} has different opportunities for evolving than population {B} in ecology {2} and there will be different selection of the opportunities for fitness provided by the different sets of random mutations in the different populations --- even if they had the same parents.

Going back to the green frogs:

Message 49: Suppose we have 2 identical islands with green frogs.

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?

Both population has the same possibility of evolving traits that would adapt (or preadapt) them to the green\orange ecology BUT:

The population on the green\orange island will have those opportunities for increased fitness to the green\orange ecology selected FOR, while there will be selection AGAINST staying green, resulting in orange speckles or some other adaptation to the different ecology, and ...

... the population on the green\only island will have those opportunities for increased fitness to the green\orange ecology selected AGAINST, while there will be selection FOR staying green ... resulting in no significant change in the green appearance.

You can even have this happen on one island:

Say your invasive orange speckled plant only survives in the upper elevations on the island. The frog population once covered the whole island, and now you have two different ecologies: one similar to the previous ecology for the whole island and one with the new orange speckled plants.

A sub-population of the green frogs can remain the the green\only ecology, while a second sub-population that happens to evolve orange speckles can now take advantage of the orange\green ecology -- an opportunity that is not open to the green only sub-population.

Thus once again you have the apparent conundrum: we have one sub-population that has apparently evolved tremendously - they have apparently evolved into orange speckled frogs, AND

we have a sub-population that has apparently barely evolved any changes at all from the original all green frogs, AND

they are the same species.

Message 47: If it is not a creative force, how do you explain the existence of human beings form something that started as unicellular organisms?

The same way all other species are explained. There is nothing particularly special about human evolution compared to the evolution of any other species, it is the result of the same basic processes.

Evolution is the change in frequency and character of hereditary traits in breeding populations from generation to generation in response to ecological opportunities.

Humans (and many other species) are very badly fit for occupying the ecological niche filled by cyanobacteria, in fact the species best fit for occupying the cyanobacterial niche is cyanobacteria: hence we still have cyanobacteria occupying that niche.

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) • • •

This message is a reply to:
 Message 48 by Europa, posted 06-08-2010 7:22 PM Europa has responded

Replies to this message:
 Message 54 by Dr Jack, posted 06-09-2010 5:22 AM RAZD has responded
 Message 57 by Europa, posted 06-10-2010 6:04 PM RAZD has responded

  
Huntard
Member (Idle past 244 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 53 of 104 (564222)
06-09-2010 3:44 AM
Reply to: Message 47 by Europa
06-08-2010 7:01 PM


Europa writes:

Bottom line is ...
We have organism A (a living fossil)
We also have organism B (a regular animal. Say a monkey)


A living fossil is also a regular animal, there is nothing special about it. And as Dr. Adequate has explained, the term "living fossil" is quite ambiguous.

A has not changed for 100 million years.
B's ancestors' lives if traced to 100 million years will show fifteen or more species.

There is no organism alive today that has not changed in a 100 million years.

We are asked to explain this.
So we have to do something.

It has been explained to you.

The only rational explanation is to say what you all have been saying: That A's environment did not PROBABLY change that much and that there was no real evolutionary pressure for A to change.

Anything else will not make sense.

Sorry to say this, but the above explanation does not make sense to me.


So? That's an argument from incredulity: "This does not make sense to me, therefore it cannot be true!". That's a logical fallacy.

If it is not a creative force, how do you explain the existence of human beings form something that started as unicellular organisms?

Like I said, mutations are the creative force. Natural selection is a filter that keeps what that force creates and is beneficial, and discards what that force creates and is detrimental.
This message is a reply to:
 Message 47 by Europa, posted 06-08-2010 7:01 PM Europa has responded

Replies to this message:
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Dr Jack
Member (Idle past 54 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 54 of 104 (564229)
06-09-2010 5:22 AM
Reply to: Message 52 by RAZD
06-08-2010 9:37 PM


Re: Cyanobacteria -- the ultimate "living fossil"?
Now here we have a bit of a conundrum: we have a fossil organism\species\type that has apparently evolved tremendously - they have apparently evolved into all other forms of life (or certainly a large number of them)

I'm pretty sure this is incorrect. If you look at phylogenies of life, the cyanobacteria group with other cyanobacteria, they're not intermixed with other bacterial groups, and bacteria are quite distinct from archaea and eukarya. So it's generally believed that the Archaea/Bacteria split predates the separation of cyanobacteria from other bacteria.

(If you look at the tree here, all the cyanobacteria are grouped between 4 and 5 O'Clock from Gloebacter and Synechococcus. Note how the root for this group nests with others.)

Edited by Mr Jack, : Added tree of life


This message is a reply to:
 Message 52 by RAZD, posted 06-08-2010 9:37 PM RAZD has responded

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RAZD
Member
Posts: 19665
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.9


Message 55 of 104 (564378)
06-10-2010 7:39 AM
Reply to: Message 54 by Dr Jack
06-09-2010 5:22 AM


Re: Cyanobacteria -- the ultimate "living fossil"?
Hi Mr Jack,

Perhaps. Or perhaps you are confusing the status of modern cyanobacteria with what the status of ancient cyanobacteria would be.

(If you look at the tree here, all the cyanobacteria are grouped between 4 and 5 O'Clock from Gloebacter and Synechococcus. Note how the root for this group nests with others.)

Curiously, you can also make a straight line from original hypothetical ancestor population (at the center) to these modern cyanobacteria, with all else branching off that line.

So it's generally believed that the Archaea/Bacteria split predates the separation of cyanobacteria from other bacteria.

Which would then need to be before 3.5 billion years ago, yet the only evidence is that cyanobacteria existed at that time ... or that the bacteria lineage split off from the cyanobacteria lineage later ...

Enjoy.

Edited by RAZD, : modern


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) • • •

This message is a reply to:
 Message 54 by Dr Jack, posted 06-09-2010 5:22 AM Dr Jack has responded

Replies to this message:
 Message 56 by Dr Jack, posted 06-10-2010 7:52 AM RAZD has responded

  
Dr Jack
Member (Idle past 54 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 56 of 104 (564383)
06-10-2010 7:52 AM
Reply to: Message 55 by RAZD
06-10-2010 7:39 AM


Re: Cyanobacteria -- the ultimate "living fossil"?
Perhaps. Or perhaps you are confusing the status of modern cyanobacteria with what the status of ancient cyanobacteria would be.

No, I'm not.

Curiously, you can also make a straight line from original hypothetical ancestor population (at the center) to these modern cyanobacteria, with all else branching off that line.

Er, no. If cyanobacteria were the stem group for all the rest you'd expect other groups to group within, with some cyanobacteria more closely related to other groups than they are to other cyanobacteria. Consider the reptiles for an example of how this works.

Also the root is not arbitrary. You can't just root a phylogeny anywhere you like.

Which would then need to be before 3.5 billion years ago, yet the only evidence is that cyanobacteria existed at that time ... or that the bacteria lineage split off from the cyanobacteria lineage later ...

Actually there is chemical evidence for Archaea back to 3.8 billion years ago. The evidence for cyanobacteria is more solid because they are involved in stromatolite formation making the preservation of fossils indicating their morphology more likely.

Edited by Mr Jack, : No reason given.


This message is a reply to:
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Replies to this message:
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Europa
Member (Idle past 2635 days)
Posts: 68
Joined: 06-05-2010


(1)
Message 57 of 104 (564475)
06-10-2010 6:04 PM
Reply to: Message 52 by RAZD
06-08-2010 9:37 PM


Re: Cyanobacteria -- the ultimate "living fossil"?
Hi RAZD

Logically this means that the result is not, cannot be, dependent on the ability of the population of organisms to evolve, but rather on the external factors that affect the opportunities and selection of the populations of organisms for fitness to different ecologies.

Logically, it is also difficult o believe that for one population the environment is more or less the same for millions of years. Now Huntard will say this is an argument from incredulity. lol


This message is a reply to:
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Replies to this message:
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 Message 66 by Dr Adequate, posted 06-10-2010 6:25 PM Europa has not yet responded
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Europa
Member (Idle past 2635 days)
Posts: 68
Joined: 06-05-2010


Message 58 of 104 (564477)
06-10-2010 6:08 PM
Reply to: Message 53 by Huntard
06-09-2010 3:44 AM


So? That's an argument from incredulity: "This does not make sense to me, therefore it cannot be true!". That's a logical fallacy.

Is there an argument from credulity too? 'This is the only way it makes sense to me. Therefore this has to be the only explanation.' Will that be a logical fallacy as well?


This message is a reply to:
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Replies to this message:
 Message 59 by Huntard, posted 06-10-2010 6:15 PM Europa has responded

    
Huntard
Member (Idle past 244 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 59 of 104 (564479)
06-10-2010 6:15 PM
Reply to: Message 58 by Europa
06-10-2010 6:08 PM


Europa writes:

Is there an argument from credulity too? 'This is the only way it makes sense to me. Therefore this has to be the only explanation.' Will that be a logical fallacy as well?


Yes.Although this is also an argument from incredulity, what you're actually saying is: "Nothing else makes sense to me, so....".

Sense is a very bad way of determining truth.


This message is a reply to:
 Message 58 by Europa, posted 06-10-2010 6:08 PM Europa has responded

Replies to this message:
 Message 61 by Europa, posted 06-10-2010 6:18 PM Huntard has responded

    
Europa
Member (Idle past 2635 days)
Posts: 68
Joined: 06-05-2010


Message 60 of 104 (564480)
06-10-2010 6:15 PM
Reply to: Message 51 by Dr Adequate
06-08-2010 8:17 PM


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.

Do you guys honestly believe that the environment can remain similar for an organism for 200 million years? I agree that the organism can also move to what environment that suits him. So the environment of an organism is not on a fixed piece of land area.

Still, to believe that an organism managed to live in an unchanging environment for 200 million years, while the others could not do it, is so counter intuitive for me.


This message is a reply to:
 Message 51 by Dr Adequate, posted 06-08-2010 8:17 PM Dr Adequate has responded

Replies to this message:
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