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The Limit of Evolution?

Discussion of everything related to the Theory of Evolution.

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The Limit of Evolution?

Postby Ultrashogun » Tue May 16, 2006 5:45 pm

Ok I would like to describe a line of thought I had today based on some assumptions, I would like everybodys opinion on whether the asumptions or the conclusion are wrong.

A)Independantly of external mutagens mutations in organism occure randomly.

B)Because mutations happen at random the rate of mutations can be seen as linear, you can approximate that one mutation manifests itself in the population every 10 million years(as an example).

C)There are meccanisms which reduce the rate of mutation (example exonuclease)

D)The rate of mutations which positively manifest themselves in "mutation prevention meccanisms" is also at random, 1/x of all mutations affect these meccanisms.

E)A consequence of mutations over a long term is evolution, a species undergoes a certain amount of mutations which manfest themselves due to assisting in the adaptation of that species and after some time we say that there is another species.

Conclusion :

If the rate of manifestation of mutations is constant and so is the rate of manifestation of mutations which slow the rate of mutations by a certain factor, then the overall process of evolution can be graphed as a hyperbole with an asymptote, evolution eventually reaches a limit.
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Postby Doc44 » Wed May 17, 2006 12:33 am

In theory maybe yes. But using humans as an example, consider:

46 chromosomes consisting of paried molecules

length of chromosomes

the different types of mutations that can occur, breakage, translocation, etc

how many permentations are possible for the sequence arrangement of the dna molecules....(((a bunch))).

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and I don't mean grapes.
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Postby mith » Wed May 17, 2006 2:20 pm

hyperbole with an asymptote???
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Postby Ultrashogun » Wed May 17, 2006 4:45 pm

mithrilhack wrote:hyperbole with an asymptote???


Yeah, what dont you understand?
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Postby 2810712 » Tue May 30, 2006 3:41 pm

yeah interesting!
You are talking about the no. of mutations existing in a gene that occured untill that time vs time right? or it can be Y-axis number of "existing" mutants of a gene [alleles of a gene] versus time X-axis.
if this is the plot you are refering to then the probability that a gene will manifest itself into an antimutation gene due to any random mutation is very less.
the plot u r refering to can be- or Total no. of alleles of all the genes versus time, here u can use ur antimutation gene thing with more strength. But the need to reduce mutation is also to be considered. Thus the no. of antimutation genges might remain the same. Their efficiencies may also differ! so if their efficiency is increasing in the evolution while keeping the total no. same the net mutation rate will still decrease. & vice versa.

The mutants are not just being dumped but may be replacing each others, so total no. of existing mutants is not just the fuction of mutation rate, but the replacement rate should also be considered...along with the efficiencies of the antimute genes

Still many neglect this, rate of mutation may vary as per the cell & gene environment change, [ of both intracellular origin & extracellular origin].To have the same mutation after some years [ u said 10million] needs that gene to be conserved for that much years , which is very less probable.
You can very rarely have the same gene [mutant] returned to you in the evolution. & even if the gene reappears as a mutation, it might not survive.
& as the surviving abilities of different mutants vary differently with time their existance/survival is not necessarily the similar pattern.

Still thinking. Thanks for such a nice topic.



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Postby AstusAleator » Mon Jun 05, 2006 9:39 am

Do your antimutation factors prevent random or non-random (mutagenic) mutations? If they prevent non-random then your assumption is wrong.
Also, your conclusion is not stated correctly. You say "If the rate of manifestation of mutations is constant..." which makes it hypothetical, rather than being based on your assumption. Of course I took it to mean "If the rate of manisfestation of mutations is held constant...". In that form it makes more sense.
You're also assuming that antimutation factors can have a cumulative effect on one's genome, ie the more the merrier. I don't know enough specifics to refute that, but I don't think that's the case.
Finally, you exclude mutagens in your assumption a, but then include them again in e and your conclusion by talking about adaptation and evolution. Adaptation is driven by environment, both abiotic and biotic. One's environment includes such things as mutagens.
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Postby KJ1 » Fri Jun 16, 2006 2:32 pm

Hey,

If I understand your argument correctly, then you're saying that anti-mutator alleles should slowly be introduced into a population, via either drift or selection, so eventually there will be negligible mutation.


It's a nice idea, but there's problems with either of these methods of introduction.

Firstly, in a finite population, mutator alleles will also be introduced by drift, likely faster than anti-mutators are introduced by drift.

Secondly, it might seem intuitive for selection to get rid of mutators, but they can be beneficial in certain circumstances. As the chap above me says, adaptation is all about the environment. In a completely stable environment, mutation rate might well diminish to a very low value. In reality, the environment is always changing, and in a changing environment, then producing mutations more quickly can result in producing new beneficial mutations before anyone else. (As an extreme, imagine a species with no mutation at all. It will have no natural variation for coping with different environments, so when the environment changes sufficiently, it will die). Thus there is a balance in the mutation rate between avoiding deleterious (bad) mutations and allowing a certain degree of flexibility for natural selection to work on.

If you're interested in this, look up some information on the role of bacterial mutator strains in evolution, I think you'll find it really illuminating. :)
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Postby majik1213 » Sat Jul 01, 2006 7:24 pm

Ok I would like to describe a line of thought I had today based on some assumptions, I would like everybodys opinion on whether the asumptions or the conclusion are wrong.

A)Independantly of external mutagens mutations in organism occure randomly.

^Change to say: A)Independent of external, radndomly occurring mutagens, mutations in organism occur randomly.

B)Because mutations occur randomly, the rate of mutations can be seen as linear, you can approximate that one mutation manifests itself in the population every 10 million years(as an example).

^This assumption has a weak premise upon which the antecendent is derived. The fact that some mutations occur randomly does not suggest any conclusions regarding the rate of mutation.

C)There are mechanism that reduce the rate of mutation (example exonuclease)

^Exonuclease repairs mutations that have occurred, so I would say that exonuclease is not an example of a mechanism that reduces the rate of mutation but that it is an example, rather, of a mechanism that reduces the rate of manifest mutations.

D)The rate of mutations which positively manifest themselves in "mutation prevention meccanisms" is also at random, 1/x of all mutations affect these meccanisms.

E)A consequence of mutations over a long term is evolution, a species undergoes a certain amount of mutations which manfest themselves due to assisting in the adaptation of that species and after some time we say that there is another species.

^The phrase "long term" is subjective; evolution has been demonstrated to occur in as little as 20 years, and scientists have found records that indicate examples of evolutionary processes taking ~1 million years.
What consitutes a unique species is not what you wrote. In fact, scientists have debated for many years what constitutes a unique species. Currently, we use molecular evidence to create phylas and trees of descent.

Conclusion :

If the rate of manifestation of mutations is constant and so is the rate of manifestation of mutations which slow the rate of mutations by a certain factor, then the overall process of evolution can be graphed as a hyperbole with an asymptote, evolution eventually reaches a limit.

^I disagree. There are factors a biologist must take into account when considering manifestation of a mutation and whether it leads to evolution. One such consideration is Hardy-Weinberg equilibrium. Whether a population is in Hardy-Weinberg equilibrium will affect the surviving percentages. Populations not in this equilibrium will produce offspring that are naturally fit, and the rate of evolution towards species best fit for the conditions will increase relative to the rate of evolution for a population in HW equilibrium (which, if i'm not mistaken, should, over a sufficient amount of time, tend to zero).
Basically, what I'm trying to say is that evolution, in a laboratory setting, can reach a limit, but in the real world, where conditions are changing, evolution won't reach a limit because populations are hardly in HW equilibrium.
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Postby shyan » Thu Jul 20, 2006 4:18 am

umm....wow. i cant wait till i start college..then mabey ill understand what is being said here.

is there any place on the web i can go that will explain all of this to me...in laymans terms?
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