If you'd bothered to read the thing you C&P'd you'd notice that the results Harrison reported couldn't be replicated.
You would also have noticed, if you'd read as much as four sentences into your C&P, that Harrison's experiments weren't on peppered moths.
So what we have here is an experiment not on peppered moths, which no-one could replicate, and the supposed implications of which for peppered moths have been utterly refuted by ... well, all the work ever done on the moths since the 1920s.
But I'm not sure why I bother telling you this. If you're too lazy to read your own posts, I have little hope that you'll make the effort to read mine.
It would appear that the peppered moths are a good example of how natural selection (as currently defined) is protected against in the natural world.
Darker and lighter moths are simply varieties in the available DNA pool and other alleles can exhibit recessive or dominant traits as demonstrated in experiments by Mendel.
Recessive traits which are only exhibited when set criteria are met are nevertheless still available in the DNA source. It might appear as though they have been selected against by observers and a good argument for natural selection. However, when the circumstances change and become favourable these traits will be manifested again. Mendels examples include the return of green and wrinkly recessive traits in subsequent generations.
Natural selection, rather than being defined as "survival of the fittest" might be better viewed as "allele domination under significant environmental and sexual selection pressures".
However, when the circumstances change and become favourable these traits will be manifested again. Mendels examples include the return of green and wrinkly recessive traits in subsequent generations.
I'm not quite sure what you are saying here, and you did not link to any past discussion. Are you suggesting that individual moths are changing their appearance in response to the environmental changes? That is not what Mendel demonstrated.
If instead you are suggesting that the ability to produce a dark (or light colored) moth is present in the population, but is recessive, then you are not expressing an issue with natural selection which is merely a screening process, but with mutation which is a source of diversity.
But again, I don't know which if either of the above is your actual point. Please clarify.
Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
Choose silence of all virtues, for by it you hear other men's imperfections, and conceal your own. George Bernard Shaw
Are you suggesting that individual moths are changing their appearance in response to the environmental changes?
I think your comprehension skills are somewhat lacking. Try re-reading my post.
If instead you are suggesting that the ability to produce a dark (or light colored) moth is present in the population, but is recessive, then you are not expressing an issue with natural selection which is merely a screening process, but with mutation which is a source of diversity.
I have supplied you with two definitions for natural selection. An old darwinian definition "survival of the fittest" and another which I have conjured up myself. I am totally bemused as to how you have chosen to define natural selection, as "screening process" doesn't really tell me anything. Perhaps you would be kind enough to offer your own definition.
And as for mutation, I didn't even mention mutation once in my post. Does mutation have anything to do with this topic?
It would appear that the peppered moths are a good example of how natural selection (as currently defined) is protected against in the natural world.
What does it mean to say that natural selection is protected against the natural world?
Recessive traits which are only exhibited when set criteria are met are nevertheless still available in the DNA source. It might appear as though they have been selected against by observers and a good argument for natural selection. However, when the circumstances change and become favourable these traits will be manifested again. Mendels examples include the return of green and wrinkly recessive traits in subsequent generations.
You first argue that recessive traits only appear to be an example of natural selection, then say that changing circumstances can cause recessive traits to become more common, which is an excellent example of natural selection at work. This apparent contradiction is why your message drew the earlier responses. Also, I don't think anyone considers recessive traits to be an example of natural selection. They are what they are, and natural selection can cause their frequency in a population to rise and fall in reaction to changing circumstances.
Natural selection, rather than being defined as "survival of the fittest" might be better viewed as "allele domination under significant environmental and sexual selection pressures".
"Survival of the fittest" is just a pithy soundbite. Natural selection is more accurately described in the way you just attempted, as varying allele frequencies in a population over time in response to changing environmental pressures.
An old darwinian definition "survival of the fittest"
Actually Darwin did not come up with this term. You actually might want to read something on a subject before you expound on it. It only took me 1 minute to research this phrase.
It was coined by Herbert Spencer who used it in a book after he read Darwin. He was using the term to draw comparisons between his economic theories and Darwins theories. Darwin did use it in the fifth edition of "On the Origin of Species". It was used as a metaphor.
quote: Darwin meant it as a metaphor for "better adapted for immediate, local environment", not the common inference of "in the best physical shape". Hence, it is not a scientific description.
quote:Evolutionary biologists customarily employ the metaphor survival of the fittest, which has a precise meaning in the context of mathematical population genetics, as a shorthand expression when describing evolutionary processes. Yet, outside of the shared interpretative context of evolutionary biology, the same metaphor has been employed to argue that evolutionary theory is fundamentally flawed. Natural Selection, the argument goes, leads to a survival of the fittest. The fittest are those that survive. Ergo, natural selection describes the survival of the survivors. Thus one of the core concepts of evolutionary theory is a tautology. While it is easy to see how such an argument represents a deliberate misunderstanding of evolutionary theory, it also alerts us to some problems inherent to the use of metaphors in science.
Source [aside]You should read this whole article. It is a fascinating look at how metaphors have helped and hindered science.[aside]
Interesting. You see how that research works. Survival of the fittest is not a scientific term and is not the basis of Darwinism. It is a metaphor for Natural Selection.
I apologize to all those offended by the quotes I am using to back up my comments. But it would be impossible to make the argument without the evidence to back them up.
Facts don't lie or have an agenda. Facts are just facts
"God did it" is not an argument. It is an excuse for intellectual laziness.
What does it mean to say that natural selection is protected against the natural world?
Populations and species are protected from the harsh dangers of natural selection. Mendels laws of heridity provide a degree of protection. Where we might believe that certain traits have been wiped of the face of the earth through "survival of the fittest", those attributes can live on, hidden and preserved, within the genome. When more favourable circumstances arise, those traits will re-emerge continuing to offer variety where it appeared lost.
Natural selection is more accurately described in the way you just attempted, as varying allele frequencies in a population over time in response to changing environmental pressures.
I am glad that we can "kind of" agree on this more modern definition of natural selection.
Where we might believe that certain traits have been wiped of the face of the earth through "survival of the fittest", those attributes can live on, hidden and preserved, within the genome.
The operative word there being "can". Even then, I don't think that it can happen in quite the way that you're describing it. A recessive gene can't "hide" simply by dint of it being recessive. If two carriers of the recessive gene mate and produce offspring, it will be expressed. Given that this is a very likely occurrence, it would hardly be hidden.
But what if the allele is so strongly selected against that all of the individuals that carry it are wiped out? What protects against that? Nothing.
It is easy to picture such an example; if an allele that is adapted for water-rich environments is present in just such an environment, it would be beneficial. But if the local environment changed and became arid, that same allele could switch to being strongly deleterious. That could then lead to the allele being wiped out of the gene pool. Meanwhile, members of the same species that lacked that hydro-phile allele would survive. What protects against this? Nothing.
I am glad that we can "kind of" agree on this more modern definition of natural selection.
Actually, I think that you'll find widespread agreement on that one. "Survival of the fittest" was never more than a soundbite and in my opinion it gives a slightly misleading spin on things. "Survival of the best adapted" might be a slightly better way of putting it, or even "survival of the just good enough...".
Natural selection, rather than being defined as "survival of the fittest" might be better viewed as "allele domination under significant environmental and sexual selection pressures".
"Survival of the fittest" is not accurate, it is more "[i]genetic trait survival in those individuals able to live long enough to breed" ... if an organism survives long enough to breed then it is successful in passing its genes.
It would appear that the peppered moths are a good example of how natural selection (as currently defined) is protected against in the natural world.
There is no protection against the natural world - and organism survives to breed or it doesn't. Only the genes in the survivors persist to breed the next generation.
Note that natural selection is not the only mechanism that can remove non-beneficial traits from a gene pool, you can also have stochastic (chance) occurrences, like volcano eruptions, that can wipe out all copies of a specific gene (as well as many individuals without it) in a breeding population. This is called neutral selection, because it isn't related to any traits. It can also remove beneficial traits in a population.
The Peppered moths are one of the examples where natural selection has been observed to occur.
Darker and lighter moths are simply varieties in the available DNA pool ...
This much is correct, and the differences between them account for the shift in their frequency between the two different ecologies, one that selected for dark moths and one that selected for light moths.
... and other alleles can exhibit recessive or dominant traits as demonstrated in experiments by Mendel.
Mendel's experiments dealt with how alleles existing in a population are inherited, with varied effect on individuals due to dominance\recessiveness, and had nothing to do with natural selection -- there was no selection pressure in his experiments.
He also did not know about mutations and how they could introduce new traits or alter existing ones. He did have some slight variation in his experiments where the "Mendel Laws of Inheritance" did not always work. These show up in his statistics. They are, of course, due to mutations in the populations.
Recessive traits which are only exhibited when set criteria are met ... when the circumstances change and become favourable these traits will be manifested again.
Biological reproduction does not happen that way. The expression of different traits in the population via reproduction generally follow the Mendelian principles, they are NOT a response mechanism. IF expressed (ie gg instead of GG, Gg or gG) THEN they are available for selection pressure to act on their expressed traits. Natural selection then determines if the homogeneous recessive can survive to breed or not.
A recessive gene can't "hide" simply by dint of it being recessive. If two carriers of the recessive gene mate and produce offspring, it will be expressed.
Let's use your definition ie "survival of the just good enough". If the environment was so harsh that a particular trait could not even survive long enough to reproduce, then only individuals who are actively expressing that trait would disappear. The unexpressed allele would still linger on in the population at large. These harsh conditions could even continue for thousands or millions of years. In every generation where the allele is expressed, the individual would die.
However, after enough time had passed, circumstances or the environment might change. Individuals who are now expressing the gene may actually survive or even flourish. The example that I am thinking of is the peppered moths.
Sickle Cell mutation and Natural Selection -- new topic?
Hi again Big_Al35,
... If the environment was so harsh that a particular trait could not even survive long enough to reproduce, then only individuals who are actively expressing that trait would disappear. The unexpressed allele would still linger on in the population at large. These harsh conditions could even continue for thousands or millions of years. In every generation where the allele is expressed, the individual would die.
However, after enough time had passed, circumstances or the environment might change. Individuals who are now expressing the gene may actually survive or even flourish. The example that I am thinking of is the peppered moths.
Carrying both copies is usually fatal, carrying one copy is beneficial in an ecology with malaria, where carrying no copies can be fatal.
This is not the case with the peppered moths -- would you like to start a new thread on tht topic (Sickle Cell mutation and Natural Selection)? Then we can discuss how a mutation can change a trait in an individual and then how that trait ca survive in a breeding population.
I suggest a new thread as this one should be near or in summation mode.
™ Version 4.2
(1)
(1)