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In reply to an earlier post on May 19, 2012 10:23:14 AM PDT
Hi Philip,

This isn't really a fight. I think Robert just has a few concepts mixed up. Here are some nice illustrations of the mechanisms of evolution: http://evolution.berkeley.edu/evosite/evo101/IIIBMechanismsofchange.shtml

I hope this makes it clearer in your mind. Cheers.

In reply to an earlier post on May 19, 2012 9:24:32 PM PDT
Re O'Neill, 5-19 6:54 AM: Good post. But I think that any mechanism for fudging the genome will subject the species to natural selection. In particular, genetic drift is a form of mutation: mutation refers to genetic modifications arising from any means.

Duerdoth, immediately following yours, seeks some elaboration in this, particularly as to migration. Now migration does not, in and of itself, cause genetic modification: it merely permits two separated populations to evolve differently. So I would not call migration a form of evolution.

In reply to an earlier post on May 20, 2012 6:41:19 AM PDT
Last edited by the author on May 20, 2012 7:34:42 PM PDT
Hi Robert, By fudging, I assume you mean changing. Most genetic changes to the genome are neutral or nearly neutral; therefore most will not subject the species to any additional selective pressure.

Genetic drift is not a form of mutation. Mutations are changes in the sequence of the genome. Genetic drift is stochastic change in the frequencies of alleles already present in a population. Genetic drift is negatively correlated with population size. Number of mutations in a population is positively correlated with population size.

You are correct that migration does not cause genetic modification of an individual, but migration can alter allele frequencies of populations. It can even introduce new alleles to a population or result in the loss of alleles from a population. Migration and drift actually have opposite effects. Migration tends to make 2 populations more similar, while drift tends to make them more different. If one is evolution, then so is the other.

This is all based on the Hardy Weinberg equilibrium (http://en.wikipedia.org/wiki/Hardy-Weinberg_principle) and all of these mechanisms can be parameterized to demonstrate how they alter the process of evolution. If you want to know more about the effects of each parameter on the frequencies of alleles in a population you can try the program popG which is available for free here: http://evolution.gs.washington.edu/popgen/popg.html

In reply to an earlier post on May 20, 2012 9:34:38 AM PDT
Re O'Neill, above: Thanks. I will be looking into this further.

In reply to an earlier post on May 20, 2012 10:30:59 AM PDT
You are welcome. Cheers.

Posted on May 20, 2012 10:32:39 AM PDT
TKitten7 says:
Hmmmmm.....

In reply to an earlier post on May 20, 2012 10:49:37 AM PDT
Christine M. Janis wrote: "No mesoderm. "
===============================
In an abstract at:

http://www.ncbi.nlm.nih.gov/pubmed/10867759

The author, Seely S., contends that each germ layer pursued its own evolutionary path.

Excerpts:
======
"In effect, the entoderm is the chemist of the body, the mesoderm its architect and engineer, the ectoderm deals with its external affairs. It is proposed that cognitive and reasoning faculties are inherent in every germ layer and when they separate, they all take an equal share. Each performs its complex and multitudinous tasks by virtue of its faculty of conceptual thought, except that the entoderm and mesoderm began to develop that faculty millions of years before the ectoderm."
======================End of Excerpts

My interpretation is that the author considers the evolution of germ layers differently from the evolution of species.

There is still many troubles with placing viruses anywhere on the tree of life, unless that tree is altered to the evolution of DNA and RNA molecules.

Mohamed F. El-Hewie

In reply to an earlier post on May 20, 2012 4:55:02 PM PDT
Hmm. Seely doesn't know that the most internal germ layer is the enDoderm.
Oh, yes. And he's clearly quite bonkers.

In reply to an earlier post on May 21, 2012 5:48:40 AM PDT
Ambulocetus says:
Eric,

lovely exposition. Reading the postings of creationists in tandem with postings like this really makes clear where the knowledge is--and where it isn't.

In reply to an earlier post on May 21, 2012 5:58:53 AM PDT
Thanks Daniel.

In reply to an earlier post on May 21, 2012 6:25:32 AM PDT
drgnslyr says:
This is Islam....This guy is your brain on Islam...any questions?
You are the most undereducated person alive sir, if you are honestly asking any of these questions seriously. You have zero understanding of evolution nor the biological relationships between species. Wow, please stop posting to any educated site from now on, because you just simply make yourself out to look as stupid as you actually are, and that is not good for anyone.

In reply to an earlier post on May 21, 2012 4:47:23 PM PDT
Re dgrnslyr, above: I hope that this is not a new revelation for you. For sheer ignorance, MFEH is hard to beat.

Posted on May 21, 2012 8:15:12 PM PDT
Trolls like MFEH and Kepler are just here seeking attention and to stroke their egos. I suggest ignoring them if you don't like what they write. Replying to them only encourages them.

In reply to an earlier post on May 21, 2012 8:51:34 PM PDT
Re O'Neill, above: I have had both of them on Ignore for quite some time.

In reply to an earlier post on May 22, 2012 11:49:15 AM PDT
zato says:
Robert A. Saunders said: "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."

I can buy this. I guess my question is: do we currently have the technology to point at the specific mutation (the where, when, so on) and analyze it, or are we still at the stage of just being aware that it happened at some point between non-resistance and resistance, but we don't know exactly where or how?

Posted on May 22, 2012 12:00:19 PM PDT
Last edited by the author on May 22, 2012 12:03:56 PM PDT
zato says:
btw everybody, thanks for replying to my posts. I readily admit that I am a layman, and have been confused about evolution and/or adaptation (adaption--or are they different things?) since the professor of a class I took said that pigeons at Disney World had developed the ability to digest buttery popcorn and claimed that it was evolution. This seems like adaptation to me, not evolution. Even I have developed the ability to tolerate new and different kinds of food within my lifetime, and would not consider it evolution but instead as just adapting to a new diet. This is also the reason I am confused about the Lenski experiments because the sample that evolved/adapted to convert the solution itself (I can't remember what exactly it was) into a new source of energy was in some ways just adapting to a new diet. Really, I don't know--just curious.

Anyway, thanks again.

In reply to an earlier post on May 22, 2012 3:55:28 PM PDT
Last edited by the author on May 22, 2012 4:09:40 PM PDT
Hi Zato, we certainly do have the technology to point to specific mutations and analyze their effects; however, this is still somewhat expensive and time consuming. It is easier to simply determine whether a change is genetically determined or not. This is done using a common garden experiment in which the environmental variables are the same, therefore any differences seen over multiple generations are the result of genetic rather than environmental effects (e.g. phenotypic plasticity).

In reply to an earlier post on May 22, 2012 3:59:43 PM PDT
When biologists talk (or write) about adaptation they are using the definition that I presented, not the one that Robert and you are (were) using. Adaptations are genetic changes that are the result of selection over multiple generations, not "modification of a particular organism to respond to environmental conditions". I hope this helps. Cheers.

In reply to an earlier post on May 22, 2012 4:01:39 PM PDT
Last edited by the author on May 22, 2012 4:10:00 PM PDT
zato wrote:
"This seems like adaptation to me, not evolution. "
=====================================
Pigeons developing the ability to digest buttery popcorn in no different from people falling asleep after drinking plenty of highly caffeinated coffee. That is clearly adaptation of neuroreceptors to triggering agents.

The rationale is, however, that after many years of indulging into certain activities, organisms develop new skills that increase their selectability for better survival. An example of such scenario is observed in people who die from alcohol intoxication due to the inactivity of the liver enzymes to metabolize alcohol at the same rate in the population. Some individuals, including myself, cannot metabolize alcohol and would suffer acute intoxication if given the same amount of liquor tolerated by an average drinker.

It is well accepted in pharmacological prescriptions that individuals react differently to the same medications and some develop new reactions that have never been observed before.

Things get more confusing when our own body starts rejecting our own organs as if those organs were foreign antigens. Rheumatic fever is a typical example of how the body immune system attacks the cardiac endocardium after streptococcal sore throat. The bacterial antigen mimics the endocardium cell markers and thus get the T-lympocytes to confuse the cardiac valves for the streptococcal antigen. Meanwhile, many people get the same sore throat infection and never develop rheumatic fever, others do.

Mohamed F. El-Hewie

In reply to an earlier post on May 22, 2012 4:17:10 PM PDT
Last edited by the author on May 22, 2012 4:18:26 PM PDT
"I readily admit that I am a layman, and have been confused about evolution and/or adaptation (adaption--or are they different things?) since the professor of a class I took said that pigeons at Disney World had developed the ability to digest buttery popcorn and claimed that it was evolution."

This is actually a testable hypothesis (if anybody wants to do the research, and/or could get funding to do the same).

The issue here is: have the Disney World pigeons just accommodated their normal physiology, or has this population undergone a mutation that enables them to digest the previously undigestable? (That, of course, is what Lenski's experiments showed, and also the experiments with bacteria now being able to digest nylon.)

But, outside of trying to get the dwindling funds from the National Science Foundation to support genetic laboratory research on pigeons, there is actually a simple test that we could do here to get a handle on things.

That is: do pigeons in other enclosed situations (Disneyland, EuroDisney, any other type of park) also, at least in some cases, become able to digest the buttery popcorn? If "yes" that implies accommodation within the individuals in the local populations. If "no" that implies something special about the pigeons at Disney World, and supports the hypothesis of a retained mutation (i.e., evolution).

Edit. I note that Eric O'Neill (who understands population genetics much better than I) made a similar observation, but perhaps mine spells it out more clearly in layman's terms.

In reply to an earlier post on May 22, 2012 4:19:39 PM PDT
"Some individuals, including myself, cannot metabolize alcohol and would suffer acute intoxication if given the same amount of liquor tolerated by an average drinker. "

Thank goodness I have Eastern European genes on both sides of the family!

In reply to an earlier post on May 22, 2012 6:56:50 PM PDT
Last edited by the author on May 22, 2012 7:06:17 PM PDT
The pigeons example seems a little spurious to me. I did a couple of quick google scholar searches and did not find anything resembling what you describe. I would ask for a citation from your professor. Diet is a funny thing. We can acquire microbes that alter what we are able to digest and that may be what has happened in this case. Adaptation requires that the difference be genetically determined within the genome of the organism. Acquiring a new gut symbiont that allows pigeons to eat buttered popcorn would not be an adaptation of the pigeon. The gut symbionts within the pigeon could have adapted, in which case the adaptation occurred in the symbionts not the pigeons. This later hypothesis (adaptation of gut symbionts) seems more likely to me, than adaption in the pigeons, give the rate of evolution in microbes is much faster than in birds. Can't really be sure though without knowing more details.

In reply to an earlier post on May 22, 2012 8:47:51 PM PDT
Last edited by the author on May 22, 2012 8:54:16 PM PDT
Re Zato, 5-22 11:49 AM: "It depends." In a few cases, we know exactly the evolutionary path taken to reach a certain state. My favorite example of this is human color vision. We see three colors; our simian ancestors could only see two. The coding for the human blue-receptive photosensitive dye is on chromosome 5. Originally, the coding for the red-sensitive dye was on the X chromosome (it still is). Somewhere in our past, this got duplicated, and the new copy got modified by a single-base substitution to be sensitive to green instead of red [1].

But these cases are infrequent. Usually, a multitude of changes are involved in a particular trait, and trying to puzzle out the specific mutations which got us (or any species) from A to B is difficult.

Also see O'Neill, 5-20 6:41 AM for discussion of "adaptation."

1. Thanks to Prof. Janis for sending me Chapter 10 of "Sensing in Nature", which discusses this in considerable detail.

In reply to an earlier post on May 23, 2012 12:49:55 PM PDT
zato says:
In regard to pigeons at Disney World, I guess that the individuals that can produce the enzymes to digest buttery popcorn would be more likely to survive and propagate, as they would have a larger food source; and the pigeons that cannot produce such enzymes are more likely to die off, as their food source would be smaller. In that case, the pigeons with the ability to digest popcorn would eventually completely overtake the population. Would this be an example of the adaption of individuals becoming evolution in a species?

In reply to an earlier post on May 23, 2012 12:54:07 PM PDT
zato says:
Eric, this class was a long time ago, and it wasn't a biology class--it was a western civ class and we were studying Darwin and his ideas. As far as a citation, that I cannot supply--I just assumed that the professor knew what he was talking about.

But the adaptation of the symbionts inside the pigeon, and not the pigeon itself, makes a lot more sense to me. Thanks.
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Discussion in:  Science forum
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Initial post:  May 15, 2012
Latest post:  Jun 7, 2012

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