Obviously, environments change over time, predators change, climates shift etc etc. Because of this, mutation (along with NS) allows living organisms to adapt over time and become more efficient at surviving in their environment. Suppose there was a mutation which stopped any further genetic mutations. At face value it looks advantageous because mutations on their own are only errors in the replication system of life. This final mutation has made replication error free and quite efficient.

Now, as we know, any individuals with these genes would not last long in environments there has been over the past couple of billion years on earth as the environment has changed quite rapidly. Thus, mutations have ALWAYS occurred in ALL species there have ever been before those we are living amongst today. Suppose however, there was actually no significant change to the environment for the next 500 million years. Would a chance mutation like the one mentioned above enable that gene to spread in a population over time? Perhaps it would eventually completely eliminate the genes of organisms that have error-prone DNA.
Would this be the end of evolution?

Hi John, there are some interesting topics in your thread....could we define the term 'NS' please? Thank you.

NS - natural selection

Perhaps in the circumstances you mention 'biological' evolution would be affected - but many of the factors that select for fitness are now cultural rather than biological (in my opinion).

IMO, death and reproduction are facets of adaptation to a changing environment. If we ever discovered life in a completely stable environment (from abiogenisis to today), then I doubt that death from 'natural causes' or reproduction would exist.

On the opposite end of that sepctrum, I'd say yes to the OP; if you took life that evolved in a changing environment, and placed it into a stable environment, then there would be no driving force behind evolution, and population changes would, given enough time, cease.
I also think, that as an extention to this, healing would improve, lifespans of the individual would increase, and reproduction would eventually become detrimental to an individual's survival.

This already happened. Not perfectly, but there is a mechanism to mitigate mutations in some vital areas and allow it on others. Such a mechanism would survive, since it prevents disadvantageous mutations. There is still room for natural variation, evolution does not depend solely on mutations for variation.

There's always drift.

There is still room for natural variation, evolution does not depend solely on mutations for variation.

Can u give an example of that?

Cats through domestication have multicolored fur. In nature, they tend towards a striped pattern for disguise, or all black for night hunting.

Dark moths were selected for in the pollution of the Industrial Revolution now the lighter allele is more commonly expressed.

New evidence suggests this may not be true.

I see what u mean Spider goat. There is still room for Natural Selection essentially?

What I'm saying is, with a very very stable environment, all phenotypes will probably converge through selection until there is nothing left to select.

Actually, the environment serves to keep a degree of uniformity in a gene pool, but it always retains the capacity for variation. Species should be much less stable than they are, which is probably why under rapidly varying conditions, rapid evolution is possible.

Cats through domestication have multicolored fur. In nature, they tend towards a striped pattern for disguise, or all black for night hunting.Both examples are caused by mutations. Different selective pressures.

I guess. What is the difference between a mutation and a variation?

"Suppose there was a mutation which stopped any further genetic mutations."

I think this is a problem as not all mutations are under genetic loci of control; also the mutation would need other mutations to stop mutations as there are many types of mutation and DNA can repair itself.

I still think evolution would chug along due to NS even if this mutation(s) were successful?

Dark moths were selected for in the pollution of the Industrial Revolution now the lighter allele is more commonly expressed.

sadly, you have been let down by the biological field on this one. The moths in question do not hang out on the sides of trees, and certainly not during the day. The study was poorly designed to the point of uselessness.

There is enough good evidence for evolution; this example and the embryo woodcuts need to be excised from biological education ASAP to remove the biggest tools anti-evolutionists can use.

http://pondside.uchicago.edu/ceb/Majerus_review.pdf

Excellent - many thanks for bringing me up-to-date with this. I will now revise my opinions based on this information.
I think any anti-evolutionists should note that I am making this revision on the best current evidence.

"Suppose there was a mutation which stopped any further genetic mutations."

I think this is a problem as not all mutations are under genetic loci of control; also the mutation would need other mutations to stop mutations as there are many types of mutation and DNA can repair itself.

I still think evolution would chug along due to NS even if this mutation(s) were successful?

That's contradictory. If there was a mutation that stopped any further mutations then NS could not continue because NS depends on mutations. Further, the mutation would not stop any further mutations, per se; it would just be a climax mutation. Couldn't happen. Mutations are not under genetic loci control; they change the genetic loci and the genetic loci control. Two different aspects of genetics: the loci (the genome) and the genetic regulation of it. You're wording it like this said mutation would be an infectious virus.

I apologise if it appears that I have contradicted myself - please allow me to clarify my terms: What I mean by a genetic loci of control (re:above) is that the mutations are caused by faults in the replication of DNA (random errors); as opposed to mutations caused in a specific manner by viruses, chemicals or radiation.
This is the basis of the position that if hypothetically a mutation stopped any further genetic mutations - viruses, chemicals or radiation could still cause mutations as these are not under a genetic loci of control.
NS would continue at a population level due to: Selection, drift and gene flow.
Also mutations that offer no advantage are often selected against.

Look forward to learning more about this fascinating topic...

Sounds like you're attempting to distinguish between a polymorphism and a mutation.

Hi samcdkey - do you mean that with the 'terminator' mutation in operation - selection, drift and flow would lead to polymorphism rather than evolution?

Polymorphisms (different morphs) arise from mutations and are a form of evolution. Some are maintained; others cannot persist because there is no evolutionary advantage to the mutation.

Polymorphisms (different morphs) arise from mutations and are a form of evolution. Some are maintained; others cannot persist because there is no evolutionary advantage to the mutation.

There are many polymorphisms with no known functional consequences.

But this does not mean that they are not functional...

But this does not mean that they are not functional...

No it does not.

In fact even a polymorphism that appears to be functional, in the absence of a known functional consequence directly related to that change in allele, may merely be a biomarker that represents an change in a related/allied genomic region

So returning to the criticism of my point: Do you think that the conditions (posed in the initial post) would lead to an increase in polymorphisms rather then true evolution?
Personally I think true evolution would still continue given a large enough initial population...although I am open to debate on this.

So returning to the criticism of my point: Do you think that the conditions (posed in the initial post) would lead to an increase in polymorphisms rather then true evolution?
Personally I think true evolution would still continue given a large enough initial population...although I am open to debate on this.

Evolution is random, natural selection occurs through environmental pressures.
Environment is not a constant. A mutation which stops other mutations(which sounds wildly improbable, how could any mutation prevent the natural effects of environment and aging on the genes) is one that leads to extinction of the species.

You don't need a significant change in environment to cause pressures. Its a slow gradual process.

Exactly samcdkey I agree - and this is why initially I said that evolution would continue even if such a 'terminator' gene existed. Evolution is not predicated on mutation, other factors are involved. I think Valich had some criticism of my position (or terminology)?

Punctuated evolution is not gradual. Polymorphisms are mutations whether or not they are functional. Functional for what? If the polymorph mutations are advantageous adaptations that benefit the organism's survival and reproductive fitness they will prevail, else they will serve no purpose for fitness and will not prevail. The foundation of evolutionary change lies in adaptative mutations. Evolution is predicated on mutations. I do not understand why you think otherwise. What is evolution to you? New polymorphs arise from new mutations.

What about genetic drift, selection and gene flow....are these not also required for evolution, Valich?

While I tremulously await the flood of quotations (sans thought) from valich addressing the pertinent issues raised by zebablefish let us consider Lingula. This delightful brachipod, dating from the Cambrian and still with us to day in much the same environmental niche, is held up as a classic example of a 'living fossil', supposedly unchanged from the day its remote ancestor first suspended its lopophore from its brachidium.

But look more closely and we find all is not as it seems.
For example:
Lingula is often considered a "living-fossil" based on its supposed lengthy morphological conservatism owing to its absence of evolution, and its remarkable survival for more than 550 M.Y. This conclusion is based on the typical apparently unchanged "linguliform" shape of the shell. However the taxa of the family Lingulidae show morphological evolutionary changes despite the fact that the group appears panchronic among the Recent Brachiopoda. Consequently, traditional opinion that Lingula is a "living-fossil" should be rejected. Diagnoses of the Family Lingulidae and of its three genera are herewith emended.
Source: http://paleopolis.rediris.es/cg/CG2003_L01_CCE/index.html

At the root of this I believe th OP's question is flawed: environments cannot remain unchanged. The present is the key to the past, not a padlock upon it.

The foundation of evolutionary change lies in adaptative mutations.

Fallacy.
If evolutionary change required adaptive mutations then the most complicated structures evolutionarily derived would be impossible.
If evolutionary change required adaptive mutations, then the creationists would be right about the complexity of the eyeball proving that a creator had a hand in the whole affair.

Look up exaptation, Mr. Magoo.

Environment is not a constant.

Well that was one of the conditions in the OP wasn't it? It is a "what if..." question.


A mutation which stops other mutations is one that leads to extinction of the species.

Only in a rapidly (evolutionarily speaking) changing environment.


(which sounds wildly improbable, how could any mutation prevent the natural effects of environment and aging on the genes)

By preventing other mutations. I will agree that this in itself, however, is highly improbable.


You don't need a significant change in environment to cause pressures. Its a slow gradual process.

Perhaps learned behaviour will allow some adaptation in changing environments

zenbabelfish, I have to agree that Natural Selection can occur without new mutations leading to a change in the frequency of genes in a pool with changing conditions. However, evolution itself requires the formation of new genes every now and again especially in the formation of new species etc.
If I am not mistaken?

Hi John, I agree in general but have we not yet observed a large gene pool where mutation does not happen? This would disprove the null hypothesis making the OP a valid hypothetical scenario...anything else would be a resort to Lamarckism.
However I still think that the OP scenario is paradoxical in that the organism is part of the environment so if the environment is totally homoeostatic no evolution could take place in any circumstances with or without mutation.

Interesting thread. What do you think?

However I still think that the OP scenario is paradoxical in that the organism is part of the environment so if the environment is totally homoeostatic no evolution could take place in any circumstances with or without mutation.

Interesting thread. What do you think?

If the only thing that caused evolution was changing external environments, then that statement would be true. However, I'm far too tired now to think about it. I shall return tomorrow to discuss further. (It's half one local time and I'm working early tomorrow :eek: :( )

Fact: Mutations create variation in the gene pool, and the less favorable deleterious mutations are removed from the gene pool by natural selection, while more favorable beneficial advantageous ones accumulate resulting in evolutionary change.

Fact: Natural Selection occurs in a population when heretible traits, traits that came about from mutations, become more common in a population over time. In this way the population's characteristics change as a result of natural selection. A change in the characteristics in a population over time is evolution.

A trait mutation that increases the fitness of the individual in an evironment is an adaptation - fitness being measured in the number of offspring produced. By repeating this process of passing on that advantageous heritable trait mutation over many generations it accumulates in the population and favors that trait mutation and evolution occurs. The only way the phenotype can express new advantageous traits that counter environmental changes that give it an advantage to adapt is for genetic mutations to alter the genotype so that the new phenotypic adaptation is expressed. This novel advantageous mutation in the population increases over time and this is called evolution.

Exaptation is simply a change in function of a trait with environmental change of an earlier adaptation that originally developed as a result of a random mutation that accumulated in the population. The trait in question original arose from a mutation. It's function changed in accordance with the environment. I use my legs to walk, but when thrown into the water I find they they are equally adapted to help me swim. No evolution occurs.

"Mutations within genes, migration between populations, and the reshuffling of genes during sexual reproduction creates variation in organisms. While a certain random component, known as genetic drift, is involved, the variation is also acted on by natural selection, in which organisms which happen to have combinations of traits that help them to survive and reproduce more than others in the population will, on average, have more offspring, passing more copies of these beneficial traits on to the next generation. This leads to advantageous traits becoming more common in each generation, while disadvantageous traits become rarer. Given enough time, this passive process can result in varied adaptations to changing environmental conditions. Genetic variation arises due to random mutations that occur at a certain rate in the genomes of all organisms. Mutations are permanent, transmissible changes to the genetic material of a cell, and can be caused by: "copying errors" in the genetic material during cell division; by exposure to radiation, chemicals, or viruses. In multicellular organisms, mutations can be subdivided into germline mutations that occur in the gametes and thus can be passed on to progeny, and somatic mutations that can lead to the malfunction or death of a cell and can cause cancer. Mutations that are not affected by natural selection are called neutral mutations. Their frequency in the population is governed by mutation rate, genetic drift and selective pressure on linked alleles." Wiki

Fact: Mutations create variation in the gene pool, and the less favorable deleterious mutations are removed from the gene pool by natural selection, while more favorable beneficial advantageous ones accumulate resulting in evolutionary change.


Fact: Just because a mutation isn't favorable, doesn't mean it is unfavorable. Doesn't mean it is removed from the gene pool by selection. Thus, it becomes a nonadaptive trait.


Exaptation is simply a change in function of a trait with environmental change of an earlier adaptation that originally developed as a result of a random mutation that accumulated in the population. The trait in question original arose from a mutation. It's function changed in accordance with the environment. I use my legs to walk, but when thrown into the water I find they they are equally adapted to help me swim. No evolution occurs.

Ah.
So. Wings aren't an example of evolution then.
Ok.

Anyway.
Something to further your 'lifelong learning'.

Gould's Spandrels of San Marcos.

http://www.aaas.org/spp/dser/03_Areas/evolution/perspectives/Gould_Lewontin_1979.shtml

(I expect you to start quoting liberally from this landmark paper and further to pretend that you had been in possession of the knowledge contained within all along. I also expect you to not realize there's a wall in front of your face you're about to walk into.)

Fact: Just because a mutation isn't favorable, doesn't mean it is unfavorable. Doesn't mean it is removed from the gene pool by selection. Thus, it becomes a nonadaptive trait.

So. Wings aren't an example of evolution then.

Most all mutations are neutral mutations that simply collect in the genome and make up a large part of it.

I think for the purposes of subject addressed on this forum we should consider evolution as the adaptative heriditable traits that change over the global dispersion of a species or genus rather than just the population, because of how interconnected species in the world are today (imports/exports, hybridization, artificial selection). A given global population of species has only a finite set of alleles that can be exchanged, thus a finite set of traits. The only way left to change a trait would be through allele variations that arise in the crossovers that occur during meiosis, but much more importantly, mutations. You're not going to get a Homo sapien from a chimpanzee without genetic mutations. I think all speciation can be attributed to mutations, while adaptations within a given species can occur from allele transfer and variations that occur from this

With regard to wings, again they had to evolve from mutations. Wings evolved separately in different species at least four times through convergent evolution. The reptilian Pterosaurs (228-65 mya) were the first vertebrates to evolve wings that were structured appropriately enough to used for flight. They were highly modified compared to its reptilian ancestors and pterosaurs also evolved a keeled breastbone for the attachment of stronger flight muscles. They had no feathers but had hair, similar but not homologous to mammalian hair. They were also quadrupeds with a distinctive four-toed hind foot and three-toed front foot. They are thought to have evolved from Scleromochlus or Sharovipteryx, both of which had webs of skin from long hind legs to their bodies or tails, but could not fly. Quite different from wings. This suggests a 'ground-up' evolution of flight or even a route that evolved by gliding from cliffs. The wings that eventually enabled true flight are thought to have evolved this way. http://en.wikipedia.org/wiki/Pterosaur

Most all mutations are neutral mutations that simply collect in the genome and make up a large part of it.

Yeah.
That's what I said.
And contradicts with what you said earlier.

True to form, Valich.
True to form.

Sorry I posted this on the 'Do Bacteria Communicate' thread but strangely it is equally applicable in both - some kind of polymorphism?

I would also refer to the American Fire Ant Solenopsis invicta, a colony is described by Wilson (2001) as: "an assembly of workers so tightly knit around the mother queen as to act as a single, well-coordinated entity."
The expressed products of the Gp-9 gene act as a mechanism in the control pathways of social behaviour affecting the level of colony queen:worker ratio (Ridley 2001). A female ant either becomes a queen, soldier or worker depending on the food and chemical stimuli received as a larva; however sometimes alates are produced that fly off to start new colonies.

I introduce this to enquire if there are similar mechanism in bacteria, and if so, whether the equivalent of 'alates' are produced.

I guess I'm looking at the idea that in a stable environment without mutation evolution would continue through polymorphism and allometry and the establishment of new populations.

Polymorph: Poly means "many," morph, as in morphology, means the shape and appearance of an organism. In other words, it is the phenotype expression of the genotype. The only way that new morphs can arise is through an alteration or change in the genotype.

Allometry refers to the disproportionate change in body size compared to an individual component or feature, such as a limb size or heart rate, etc. Normally this refers to comparisons made in developmental biology.

New populations arise on their own without any need for mutations, new polymorphs that arise from mutations, or allometry.

Evolution is a process. Polymorphisms are states of being. Allometry refers to disproportionate developments. What are you trying to say?

If in our hypothetical OP ecological system there is no mutation due to a gene would it be possible that through polymorphism 'alates' would create new populations?

Also I would describe: evolution as the regenerative and dynamic momentum of genetic information through space and time; polymorphisms as the existence within a species of different forms of individuals or the occurrence of different forms of the same individual at different times of life; and allometry as the study of relative growth, or disproportion in size relative to standard growth.

Again, you first talk as if polymorphism is a process, then state that it is an existence of different forms at different times. yes, this is why it is so commonly used in developmental biology. That's contradictory. And then: "Regenerative and dynamic momentum of genetic information"? Did you get this from the aliens landing at Area 54?

Again, you first talk as if polymorphism is a process, then state that it is an existence of different forms at different times. yes, this is why it is so commonly used in developmental biology. That's contradictory. And then: "Regenerative and dynamic momentum of genetic information"? Did you get this from the aliens landing at Area 54?

No - I perceive the movement of information moving through space and time in the form of genes and their material expression. Ditto memes - although in this instance information is moving through space and time in the form of culture. 'Reproduction' of information is achieved biologically and culturally; this is a dynamic process with momentum.
Its not from Area54 but is a basis for understanding evolution that I have developed myself from meta-analysis of the leading thinkers in the field. I'm just being honest - I could be picky about your definitions too...where did they come from? Area Wikipedia?

Regarding polymorphism: the reference is in Henderson's Biological Dictionary. I don't recognise the contradiction you suggest.
In the hypothetical OP: alates, allometric variants of polymorphism, are phenotypically-expressed due to a steady environment. This is important as as alates (or their equivalents should they exist) leave the parent population to start new populations.
If a 'terminator' gene stops mutation then maybe evolution will continue along another vector...I think I'm making reasonable points in a forum debate about an unprecedented hypothetical scenario.

I think you are, too.

What are "allometric variations of polymorphism" and how do they occur? I already told you what the standard definition of allometry is. And a polymorphism is a variant trait that already exists in a population, caused by the different alleles within the population. Some are advantageous: some are deleterious. Whether one polymorph becomes more dominant than another depends on the environmental pressures that select for it. This is not evolution: this is a change in allele frequency. This is a very basic standard definition accepted throughout the field of biology by everyone that you cannot change. Else you cannot communicate.

Mutations can occur during allometry that can change the phenotype. There are genes that express the phenotype; and also genes that regulate the developmental expression of the phenotype. This is why morphology is conserved in embryo replication amongst various heirarchical species in the phylum: genetic conservation within the genome.

the terminology being used is non-standard, but if I've been reading the posts right, he's extending the normal terms to work through a time-line as well as within a temporal snapshot of a given population.

So I've been interpreting the posts as "looking at the progression of different traits both within a population and over time." this seems to include not only a single population, but also the branch-off that occur when individuals take thier oddities to a new group, or start a new group themselves.

zenbabelfish, tell me if I'm mis-representing your position.

http://en.wikipedia.org/wiki/Allometry
http://en.wikipedia.org/wiki/Polymorphism_%28biology%29

the terminology being used "here" is non-standard. We talk about polymorphs over an extended time-line until those characteristics evolve into a different form resulting in a genetic change, by mutations or cross-overs. Black hair today was black hair 50 million years ago. Evolution does not progress through blending like taking a crayon and rubbing it darker. There has to be a genetic change that changes the genotype to express the different new phenotype. The article that you are citing on Wikipedia is one that I wrote.

This is not evolution: this is a change in allele frequency. Evolution is defined, rightly or wrongly, as a change in allele frequency, you great lump of mutton.


The article that you are citing on Wikipedia is one that I wrote.Then it should contain a very large warning sign. If you don't even know how to define evolution you have no business on this site pontificating as if you were learned in the matters.
You arrogance remains only outpaced by your gross ignorance. A deadly combination.

Is there a definition of evolution you prefer Ophilolite?

I view a quality definition of evolution to be somewhat akin to a definition of life: a potentially valuable, but thus far unattainable goal. But like life I know what evolution is when I see it.
And where I saw it, in detail and delight, was in the fossil record. Since you can't see alleles in a fossil, for me evolution is about changes in form. Sure these reflect genotype, but they are not genotype.
So my working definition of evolution is 'change in the character of a population that likely reflects a change in genotype'.

One definition of evolution that is commonly used today is simply a change in allele frequency in a population. However, I do not care for this definition because it does not lead to new speciation. In the classic example with peppered moths in England, the allele frequency caused adaptation for black wings against the pollution but the allele frequency was reverted back to lighter gray-colored wings as is seen today. The end result: no change. No evolution. Allele frequency change alone, i.e., various polymorphs, does not result in evolution.

I view a quality definition of evolution to be somewhat akin to a definition of life: a potentially valuable, but thus far unattainable goal. But like life I know what evolution is when I see it.
And where I saw it, in detail and delight, was in the fossil record. Since you can't see alleles in a fossil, for me evolution is about changes in form. Sure these reflect genotype, but they are not genotype.
So my working definition of evolution is 'change in the character of a population that likely reflects a change in genotype'.

I'm terribly biased towards change of form myself. That's because I am a developmental biologist. Nothing makes sense to me but change of forms. Of course I have to keep in mind some of the physiological changes that are also present in evolution but don't manifest themselves in 'visible' form. And there is evolution of behaviour of course, but form is the king.

long live the king of evolution.

valich: please see my post from page one of this thread, and come up with a different example.

http://www.sciforums.com/showpost.php?p=1281023&postcount=16


Change in allele frequency in a population certainly can lead to speciation. If a population splits due to geographical or other reasons, the net genetic change between the to groups can lead to speciation - this has been seen in the lab, and has been seen in nature. Introduction of new mutations allows the "change in allele frequency" to not only be limited to shifts within the genetic pool, but to wholsale phenotype changes.

Your rationale is not clear and is unarticulated. Your allusion to mutations is confusing because allele frequency can and does change without mutations. Miniature Fox Terriers, Pinschers and Schnauzers are smaller than their standard-sized breeds, and Pomeranians come in black, blue, tan, chocolate, chocolate, cream, orange, red and sable - all caused by different alleles, not mutations. They're still the same species. Where does allele frequency alone lead to new species where they can no longer interbreed?


Majerus concludes, reasonably, that all we can deduce from this story is that it is a case of rapid evolution, probably involving pollution and bird predation...claiming that the true story is likely to be more complex and therefore more interesting.

What can one make of all this? Majerus concludes with the usual call for more research...There are many studies more appropriate for use in the classroom, including the classic work of Peter and Rosemary Grant on beak-size evolution in Galapagos finches.

Your rationale is not clear and is unarticulated. Your allusion to mutations is confusing because allele frequency can and does change without mutations. Miniature Fox Terriers, Pinschers and Schnauzers are smaller than their standard-sized breeds, and Pomeranians come in black, blue, tan, chocolate, chocolate, cream, orange, red and sable - all caused by different alleles, not mutations. They're still the same species. Where does allele frequency alone lead to new species where they can no longer interbreed?
Don't be so obtuse. Nowhere in river-wind's post did he state that a change in allele frequency alone lead to speciation.

Mutation leads to different alleles. Different alleles change allelic frequency. If an allele doesn't mutate, how does it change?