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Initial post: May 15, 2012 4:30:47 PM PDT
zato says:
Is there any empirical evidence of the preservation of random mutation by natural selection?

In reply to an earlier post on May 15, 2012 6:31:45 PM PDT
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In reply to an earlier post on May 15, 2012 9:09:25 PM PDT
A. Whitney says:
Have you heard of bacteria that have become resistant to antibiotics?
The ones that mutate to have a better chance against antibiotics survive and breed and become more resistant generation by generation. It's a perfect example. And it takes a very short time.

In reply to an earlier post on May 15, 2012 11:09:26 PM PDT
Re original post: Of course there is. A mutation is, by definition, heritable. And natural selection will pick and choose those that work -- and those that don't.

One of my favorite examples is the evolution of color vision in the human eye. Most animals, including primates, have bi-color vision, but humans have tri-color, which arose as follows: One of the photosensitive dyes (blue-sensitive) is encoded on chromosome 5. In most animals, the (only) other one (red-sensitive) is on the X chromosome. At some point in our evolutionary history, this gene got doubled (it happens occasionally), and subsequently the copy was modified by a single-base substitution to be sensitive to a shorter wavelength (green).

Posted on May 16, 2012 1:25:51 PM PDT
Last edited by the author on May 16, 2012 1:26:05 PM PDT
Rev. Otter says:
my favorite mutation is on the MC1R-gene, because it gave us redheads.

"In the United States, approximately 25 percent of the population are carrying the mutated Melanocortin 1 Receptor that causes red hair."
http://en.wikipedia.org/wiki/Melanocortin_1_receptor

In reply to an earlier post on May 16, 2012 1:41:28 PM PDT
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In reply to an earlier post on May 16, 2012 5:53:20 PM PDT
"You are also not questioning why trees could not dream of developing brains and running away from the monkeys that eat up the figs and palms without seeking permission from the mother tree."

No mesoderm.

In reply to an earlier post on May 16, 2012 6:39:02 PM PDT
zato says:
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In reply to an earlier post on May 16, 2012 6:41:31 PM PDT
zato says:
Robert, do we actually have the physical evidence that indicates when and where this modification occurred? Or is it just assumed that humans once had bi-color vision?

In reply to an earlier post on May 16, 2012 7:44:38 PM PDT
Try this: http://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment

In reply to an earlier post on May 16, 2012 7:45:30 PM PDT
"In this instance, how do we know that this isn't merely adaptation?"

I don't think you understand what adaptation is. The "preservation of random mutation by natural selection" is adaptation.

In reply to an earlier post on May 17, 2012 4:24:31 PM PDT
zato says:
So adaptation is considered evolution, even though adaptation is not heritable?

In reply to an earlier post on May 17, 2012 4:32:30 PM PDT
zato says:
Michael, thank for the link. I read it and it seems to be a pretty good explanation of the experiment.

Posted on May 17, 2012 5:08:24 PM PDT
Last edited by the author on May 17, 2012 5:09:02 PM PDT
Julian says:
The bacteria that survive the antibiotics do not do so because they are exposed and change to fight the antibiotics. They survive because a random mutation changed how the part of them that is affected by the antibiotics functions. The mutation is there before the antibiotics and allows them to survive and pass it on.

In reply to an earlier post on May 17, 2012 6:41:55 PM PDT
Adaptations are heritable. You need to look up the word "adaptation". You can start here: http://en.wikipedia.org/wiki/Adaptation

In reply to an earlier post on May 18, 2012 9:07:47 AM PDT
"So adaptation is considered evolution, even though adaptation is not heritable?"

1. Organisms reproduce
2. Those offspring are slightly different from their parents
3. Some of those differences could convey a survival advantage
4. Those with that advantage are more likely to successfully reproduce
5. Those that reproduce are likely to pass on those differences to the next generation
6. Those differences are now more well-represented in the population

Lather... rinse... repeat, and we have the pattern of change known as "evolution".

In reply to an earlier post on May 18, 2012 9:33:13 AM PDT
Re zato, 5-16 6:39 PM: Adaptation refers to modification of a particular organism to respond to environmental conditions. Mutation refers to modification of its descendants. In the case of bacteria, their lifetime is short, and the observed modifications clearly outlast the lifetime of individual organisms. So it is clearly NOT simply adaptation.

In reply to an earlier post on May 18, 2012 9:38:52 AM PDT
Re zato, 5-16 6:41 PM: "... when and where this modification [for color vision] occurred?" Not precisely, but good inferences can be drawn by comparison of the evolution of animals that have it with that of ones that don't. Since it appears in some organisms other than humans, it clearly developed in our primate ancestors.

In reply to an earlier post on May 18, 2012 9:40:48 AM PDT
Re zato, 5-16 7:45 PM, to O'Neill: O'Neill's definition of adaptation is wrong. See my preceding post on this subject.

In reply to an earlier post on May 18, 2012 9:50:58 AM PDT
ErikR says:
I think it's also important to point out that genetic changes do not necessarily have to provide a survival advantage. They just have to NOT provide a survival disadvantage. This is important when discussing how evolutionary changes happen in geographically isolated populations.

In reply to an earlier post on May 18, 2012 10:08:41 AM PDT
Good point...

In reply to an earlier post on May 18, 2012 1:47:26 PM PDT
Last edited by the author on May 18, 2012 1:51:08 PM PDT
Hi Robert, I am afraid you are mistaken. Adaptation does not "refer to modification of a particular organism to respond to environmental conditions." You are thinking of acclimation (a.k.a. Acclimatization). Adaptation is a change in a population's allele frequencies as a response to selection.

In reply to an earlier post on May 18, 2012 10:29:02 PM PDT
Re O'Neill, above: Your definition of "adaptation", which you got from Wikipedia, is a variant usage -- indistinguishable from evolution. I avoid using this word because of its potential ambiguity.

In reply to an earlier post on May 19, 2012 6:54:56 AM PDT
Hi Robert, I did not get my definition of adaptation from Wikipedia. I get mine from the primary literature and text books on the subject. I direct people to the wiki definition because it is consistent with my these sources and often provides links to them.

Adaptation is not "indistinguishable from evolution". Evolution encompasses several mechanisms including adaptation, genetic drift, mutation, and migration; the later three are non-adaptive mechanisms of evolution. So it is actually quite easy to distinguish between evolution and adaptation. Adaptation is only the evolutionary change that results from natural or sexual selection.

In reply to an earlier post on May 19, 2012 8:00:26 AM PDT
Eric and Robert,
It matters not to me who wins your fight but I would appreciate some illustrations of the different aspects of evolution/adaptation you are both describing, in particular adaptation and *migration*.

I could then become clearer in my own mind and, if asked, act as referee. (Joking)
Thanks.
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Discussion in:  Science forum
Participants:  22
Total posts:  95
Initial post:  May 15, 2012
Latest post:  Jun 7, 2012

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