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Author Topic:   How do you define the word Evolution?
New Cat's Eye
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Posts: 11176
From: near St. Louis
Joined: 01-27-2005
Member Rating: 1.7


Message 31 of 70 (260569)
11-17-2005 12:46 PM
Reply to: Message 29 by U can call me Cookie
11-17-2005 1:32 AM


Re: Is a mutation evolution?
The point to make, however, is that mutation is not the be-all and end-all of evolution.

Yes, that definition was not complete, i mean, it was not the whole definition.

The occurrence of a new allele in a population (thro' mutation in one individual) would, technically, change the allele frequencies of that gene in the population; albeit to the tiniest extent.

Yes, I guess technically, mutation is evolution; its just on an idividual level (but individuals don't evolve). The problem is that it totally leaves out the other half of evolution, natural selection. But, if one considers genetic drift to be evolution, couldn't one consider a mutation to be genetic drift on the individual level? I'm not sure.


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bkelly
Inactive Member


Message 32 of 70 (260670)
11-17-2005 5:45 PM
Reply to: Message 31 by New Cat's Eye
11-17-2005 12:46 PM


Yes, I guess technically, mutation is evolution; its justRe: Is a mutation evolution?
cs writes:

Yes, I guess technically, mutation is evolution; its just on an idividual level (but individuals don't evolve).

Agreed, but I feel the need to split a hair. In sexually reproducing entities (animal, plant, and anything else) the point of evolution is conception. The parent’s DNA combine in new and unique ways to produce an offspring. With one exception that I know of, after conception, there can be no further evolution of that individual.

Question, how is asexual evolution manifested?


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 Message 31 by New Cat's Eye, posted 11-17-2005 12:46 PM New Cat's Eye has responded

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 Message 33 by New Cat's Eye, posted 11-17-2005 6:10 PM bkelly has responded

  
New Cat's Eye
Member
Posts: 11176
From: near St. Louis
Joined: 01-27-2005
Member Rating: 1.7


Message 33 of 70 (260676)
11-17-2005 6:10 PM
Reply to: Message 32 by bkelly
11-17-2005 5:45 PM


Re: Is a mutation evolution?
In sexually reproducing entities (animal, plant, and anything else) the point of evolution is conception.

Conception is the point of mutation, not evolution. Multiple mutations results in variation of the population, not every individual is the same but some of them are. You can use statistics to calculate the probability that an individual will be of a certain variation. When selection causes a variation to be more or less favorable, the probability that an individual will be of that variation changes. It is this change in that probability that is defined as evolution. You can quantize the evolutionary change down to the individual level, but then that change will fall into a different definition…mutation.

...after conception, there can be no further evolution of that individual.

You gotta stop thinking of evolution on the individual level.

Question, how is asexual evolution manifested?

I don’t really know, but my guess would be that mutation occurs during the anaphase of mitosis. I don’t think there’s any recombination in mitosis so I’d have to research that and don’t have the time.


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bkelly
Inactive Member


Message 34 of 70 (260716)
11-17-2005 8:24 PM
Reply to: Message 33 by New Cat's Eye
11-17-2005 6:10 PM


Re: Is a mutation evolution?
re: You gotta stop thinking of evolution on the individual level.

No, not only do I not gotta*, I should not. Evolution on a large scale is nothing but the composition of evolution of the individuals one at a time. You did not provide an adequate answer to my example of green eyes and blue eyes.

Because that is what I was taught in a 100 level college biology course on evolution.

That says why you believe, but it provides no evidence, justification, or substance.

Given my example of green eyes in a blue eyed population, at what point do we have the transition from mutation to evolution? Why do you pick that point?

Mutation is evolution. If the mutant dies without decendants, then that particular path of evolution failed. But it did meet the definition of evolution.

* Gotta is terrible english, but I will use it for effect

edited to fix typo

This message has been edited by bkelly, 11-17-2005 08:25 PM


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crashfrog
Inactive Member


Message 35 of 70 (260744)
11-17-2005 9:21 PM
Reply to: Message 34 by bkelly
11-17-2005 8:24 PM


Re: Is a mutation evolution?
Evolution on a large scale is nothing but the composition of evolution of the individuals one at a time.

Individuals do not evolve. Individuals are born with mutations; they either reproduce or they do not.

Evolution, which is a change in allele frequencies in a population, cannot be meaningfully said to occur to individuals.

Given my example of green eyes in a blue eyed population, at what point do we have the transition from mutation to evolution? Why do you pick that point?

For the individual, it's a mutation. For the population, it's evolution.


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 Message 34 by bkelly, posted 11-17-2005 8:24 PM bkelly has responded

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 Message 36 by bkelly, posted 11-18-2005 8:12 AM crashfrog has responded

  
bkelly
Inactive Member


Message 36 of 70 (260860)
11-18-2005 8:12 AM
Reply to: Message 35 by crashfrog
11-17-2005 9:21 PM


another problems of definition
Hello Crash,
When I put together your response with that from Catholic Scientist
I figured out that we, no, I, have a defintiion problem. Here is how I see this now.

The individulal entity does not exist until the union of sperm and egg is complete. CS referred to the anaphase of mitosis and that is real close. The imprecision is that mitosis occurs in every cell division. I am referring to the process in which the sperm and egg combine their genetic material to become one living entity. Anaphase does not occur until that combination is complete and the first cell division is in progress. I did some searches but did not find the correct description.

I found a nice animation here: http://www.cellsalive.com/mitosis.htm
The DNA duplication appears to occur during interphase, but the site does not go into that very deeply.

According to this site: http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html
During anaphase the chromosomes separate at the kinetochores (as I understand this, where the chromosomes are tied together causing the X shape) but it does not clearly say where or when the chromosomes reconstruct after the split.

More to the point, neither site presents the point where sperm and egg combine for produce the first complete set of chromosomes for the individual.

So, you guys are right, an individual does not evolve. But the act or event of evolution occurs on an individual level during the process of conception. The same could be said for mutation, an individual does not mutate, the mutation occurs during the creation of the individual.


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Replies to this message:
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crashfrog
Inactive Member


Message 37 of 70 (260893)
11-18-2005 9:49 AM
Reply to: Message 36 by bkelly
11-18-2005 8:12 AM


Re: another problems of definition
During anaphase the chromosomes separate at the kinetochores (as I understand this, where the chromosomes are tied together causing the X shape) but it does not clearly say where or when the chromosomes reconstruct after the split.

Well, they don't. They never reconstruct. The two copies of each chromosome are forever seperated by the division of the cell.

The same could be said for mutation, an individual does not mutate, the mutation occurs during the creation of the individual.

To be most pedantic, the mutation is actually occuring during meiosis, the cellular division process that produces the haploid genetics of gametes.


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 Message 36 by bkelly, posted 11-18-2005 8:12 AM bkelly has responded

Replies to this message:
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bkelly
Inactive Member


Message 38 of 70 (260912)
11-18-2005 10:46 AM
Reply to: Message 37 by crashfrog
11-18-2005 9:49 AM


Re: another problems of definition
chuckle, I think we have another definition problem.

re: Well, they don't. They never reconstruct.

That depends on how we define reconstruct. Lets see if I have this right. The chromosomes split into two pieces. From each of these two pieces (really each piece seems to be multiple pieces, but the term piece refering to each complete half of the DNA should suffice) the entire and correct dna sequence can be constructed. Since the DNA was once whole, reconstruct is appropriate. After the split, each of the two pieces gathers together the bits and pieces it needs to "reconstruct" its other half and becomes whole again. At the end of this phase, there are two complete copies of the DNA of one cell. These two copies go their separate ways and become two cells.

re: To be most pedantic, the mutation is actually occuring during meiosis, the cellular division process that produces the haploid genetics of gametes.

I agree but don't think that is pedantic at all. Meiosis is composed of a series of smaller operatioins. I am looking further down into meiosis and into those smaller operations. What is the name of the step where the separated stands of DNA gather together the parts needed to make itself whole again.

And back to one of my earlier points, what is the name of the process when the half DNA of the sperm and the half DNA of the egg (each formed my mitosis) combine together to complete conception?


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 Message 37 by crashfrog, posted 11-18-2005 9:49 AM crashfrog has responded

Replies to this message:
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Percy
Member
Posts: 15490
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.5


Message 39 of 70 (260932)
11-18-2005 11:43 AM
Reply to: Message 38 by bkelly
11-18-2005 10:46 AM


Re: another problems of definition
Edited to fix misremembered definitions of mitosis and meiosis.

bkelly writes:

That depends on how we define reconstruct. Lets see if I have this right.

If I understand you correctly, I'm pretty sure you have this wrong. It looks like you're confusing the two halves of a chromosome pair with the two halves of the DNA double helix. You've got the formation of gametes (haploid sexual reproductive cells or meiosis) mixed up with mitosis (cell division). It looks this way to me because you go on to say:

The chromosomes split into two pieces. From each of these two pieces (really each piece seems to be multiple pieces, but the term piece refering to each complete half of the DNA should suffice) the entire and correct dna sequence can be constructed.

Sperm and egg are haploid cells, meaning they only have half the full chromosome complement. For humans, instead of having 23 chromosome pairs like all other cells, sperm and egg have only 23 individual chromosomes. A haploid cell is created during meiosis by selecting only one chromosome from each pair.

Every chromosome is a lengthy and tightly coiled strand of DNA. During mitosis every chromosome (all 46 in humans) has it's DNA split down the middle, and each half goes to one of the two cells created by the division. These DNA halves are used as templates to rebuild copies of the original DNA strands. These rebuilt strands form the chromosomes (again, 46 in humans) which then gather back together into the chromosome pairs (23 in humans).

--Percy

This message has been edited by Percy, 11-18-2005 12:43 PM


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New Cat's Eye
Member
Posts: 11176
From: near St. Louis
Joined: 01-27-2005
Member Rating: 1.7


Message 40 of 70 (260946)
11-18-2005 12:25 PM
Reply to: Message 36 by bkelly
11-18-2005 8:12 AM


Re: another problems of definition
The individulal entity does not exist until the union of sperm and egg is complete. CS referred to the anaphase of mitosis and that is real close.

I think you're confused or misusing some words.

Mitosis is for asexualy reproduction. With a sperm and egg its meiosis.


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crashfrog
Inactive Member


Message 41 of 70 (260963)
11-18-2005 1:29 PM
Reply to: Message 38 by bkelly
11-18-2005 10:46 AM


Re: another problems of definition
That depends on how we define reconstruct. Lets see if I have this right. The chromosomes split into two pieces. From each of these two pieces (really each piece seems to be multiple pieces, but the term piece refering to each complete half of the DNA should suffice) the entire and correct dna sequence can be constructed. Since the DNA was once whole, reconstruct is appropriate.

Ok so far, the term you're looking for is "replication"; both strands of the DNA molecule are seperated from each other by enzymes and are used as templates to attach complimentary nucelotides; the end result is two copies of the same molecule, where before you had one. This occurs during prophase of mitosis.

At the end of this phase, there are two complete copies of the DNA of one cell. These two copies go their separate ways and become two cells.

So far, so good. Your wording earlier confused me; I thought you were referring to the "reconstruction" of the paired chromosomal copies that seperate in telophase of mitosis.

What is the name of the step where the separated stands of DNA gather together the parts needed to make itself whole again.

That's still prophase; to correct your misapprehension about the process of DNA replication, the separation of strands and the development of the complimentary strand occur in one pass along the chromosome, simultaneously. They're not seperate steps in mitosis/meiosis.

And back to one of my earlier points, what is the name of the process when the half DNA of the sperm and the half DNA of the egg (each formed my mitosis) combine together to complete conception?

That is conception. Again, to correct what appears to be your misapprehension, gametes do not contain "half DNA"; they contain full chromosomes with complete double-helix DNA. They simply contain half of the chromosomes of a normal somatic cell.

During conception, chromosomes from the egg and from the sperm combine in the egg and a nucelus forms around them, but the chromosomes do not physically attach to each other or anything, they don't combine in the way that one strand of DNA is combined with its compliment to form one chromosome.

All that happens is that the 23 chromosomes from the sperm are dumped in with the 23 from the egg, and a nuclear membrane forms around them.


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crashfrog
Inactive Member


Message 42 of 70 (260967)
11-18-2005 1:38 PM
Reply to: Message 39 by Percy
11-18-2005 11:43 AM


Re: another problems of definition
During mitosis every chromosome (all 46 in humans) has it's DNA split down the middle, and each half goes to one of the two cells created by the division. These DNA halves are used as templates to rebuild copies of the original DNA strands.

I think you've got it backwards, or else I do. My information indicates that chromosome replication occurs first, during prophase; and then the duplicate chromosome pairs are pulled to different ends of the elongating cell, and then cytokinesis occurs and the cell is divided into two.

The reason I think it happens this way is because DNA helix seperation and nucleotide replication occur in the same pass. My guess is that it would be very dangerous to the cell to have an uncomplimented DNA strand floating along; those open pyramidines and purines will probably bond to anything, and lead to lots of errors if you try to go back and run a polymerase along the strand to generate its compliment.


This message is a reply to:
 Message 39 by Percy, posted 11-18-2005 11:43 AM Percy has responded

Replies to this message:
 Message 43 by Percy, posted 11-18-2005 1:47 PM crashfrog has responded

  
Percy
Member
Posts: 15490
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.5


Message 43 of 70 (260970)
11-18-2005 1:47 PM
Reply to: Message 42 by crashfrog
11-18-2005 1:38 PM


Re: another problems of definition
You're very likely right, or at least more right than me. Hopefully I was able to make clear to bkelly that's he's confusing mitosis and meiosis, whatever be the detailed specifics.

--Percy


This message is a reply to:
 Message 42 by crashfrog, posted 11-18-2005 1:38 PM crashfrog has responded

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crashfrog
Inactive Member


Message 44 of 70 (260972)
11-18-2005 1:54 PM
Reply to: Message 43 by Percy
11-18-2005 1:47 PM


Re: another problems of definition
Part of the problem here is the confusing fact that, in your average animal cell, you've got pairs of things at every level - paired strands of DNA that seperate for replication, pairs of replicated chromosomes that line up for metotic seperation, and complimentary pairs of chromosomes 1 through 23, each one of the pair from one of two parents.

Understanding how many "normal" pairs, and pairs of what, exist in a baseline cell and how many pairs, and pairs of pairs, you have during different phases of different kinds of cell divison is very confusing indeed. I have to draw little pictures to keep it straight.


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bkelly
Inactive Member


Message 45 of 70 (261636)
11-20-2005 7:21 PM


Haven't given up
I am looking for some sites that explicitly cover the fusion of the oocyte and sperm. My searching techniques seem to be sorely lacking.

Just the same, I have not given up on this thread. Just searching for more info. If you have any help, please reply.


  
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