Hi samcdkey - do you mean that with the 'terminator' mutation in operation - selection, drift and flow would lead to polymorphism rather than evolution?
Evolution of mutation!
- Thread starter John Connellan
- Start date
There are many polymorphisms with no known functional consequences.
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.
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?
Ophiolite
Valued Senior Member
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.
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.
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.
John Connellan
Valued Senior Member
Well that was one of the conditions in the OP wasn't it? It is a "what if..." question.
Only in a rapidly (evolutionarily speaking) changing environment.
By preventing other mutations. I will agree that this in itself, however, is highly improbable.
Perhaps learned behaviour will allow some adaptation in changing environments
John Connellan
Valued Senior Member
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?
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?
John Connellan
Valued Senior Member
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
)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: 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: 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.
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.)
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.)
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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