Is there more than one definition of natural selection?

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In fact many genes exhibit a random effect on phenotype, a phenomenon known in genetics as penetrance.

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Just to be clear, penetrance is actually the degree to which a gene controls its phenotypic expression. Crashfrog's example is of a gene with low penetrance. A gene whose phenotype is always expressed in every individual has high penetrance.

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Natural Selection is not Evolution-- R.A. Fisher

I didn't explain it very well; thanks for the correction.

For the frog's benefit, Allopatrik, would you mind explaining what "expression" means? What is being expressed and what is expressing it? I'd like to know if I am wrong that a genetic message”the genotype” is expressed in a protein”the phenotype.”HM

I know what expression is. How about you give the arrogant condescension a rest? Don't misrepresent the discussion. You know that's not the issue under dispute, here. Answer the questions I posed to you in my post.

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I'd like to know if I am wrong that a genetic message”the genotype” is expressed in a protein”the phenotype.

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Most geneticists I'm familiar with refer to the protein as the gene's product, not the phenotype. The phenotype is more properly the result of the protein's activity or function. Example: the enzyme beta-galactosidase is the product of the gene;the phenotype is the specific enzymatic activity on the galactose substrate.

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Natural Selection is not Evolution-- R.A. Fisher

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Maybe I'll change my mind when I finally understand what you're saying, but I cannot at this time see how a differential reproductive success of 0 is always the equivalent of no natural selection taking place. For example, imagine two subpopulations which produce equal numbers of offspring, but that during that particular reproductive season leading up to the equal numbers of offspring that many eggs in both subpopulations were eaten by predators. That's natural selection, even though the differential reproductive success was 0.

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Sorry for jumping in again, but this particular passage interested me.If the relative (I prefer ”relative’ to ”differential’, but that’s just me) reproductive success of one subpopulation is identical to that of the other, than the two subpopulations have identical fitness. Having identical fitness does not mean the absence of natural selection. What it does mean is the allelic frequencies of these subpopulations will change relative to each other randomly, entirely due to genetic drift.Consider the Peppered Moth. It undergoes both bat and bird predation. Under bat predation, both the light and dark genotypes have equal fitness, since bats do not discriminate by moth coloration. One would expect, with no bird predation, to see the frequencies of the two genotypes to drift at random. Under bird predation, however, the fitness of the two genotypes depend on the background coloring of the trees, and one genotypic frequency will increase steadily at the expense of the other, even if bat predation is occurring simultaneously.A

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Natural Selection is not Evolution-- R.A. Fisher

Hey, jump on in, the water's fine. All threads are open to all members. Right, I agree with this. I wonder if this is what Quetzal was saying, but I just couldn't tell?I'm finding this discussion defining natural selection to be an unexpectedly tough slog. We can't seem to get out of our own way. The approach I'm lobbying for is to start with a simple definition from which we elaborate. I proposed that we start with Darwin's definition, but I'm flexible as long as we start simply. I do feel that we're at far too detailed a level since there isn't even agreement that sexual selection is a type of natural selection.--Percy

Ugh, that has to be one of the the sloppiest and least accurate descriptions of the process I have seen which still used all the right terms. DNA isn't transcribed by mRNA but to mRNA by the RNA polymerase. The events you describe as occurring on the way to the ribosome actually occur within the ribosome, the ribosomal machinery is as much a part of the translational machinery as tRNA is not merely some subsequent stage of assembly. tRNA isn't actively translating anything, merely bringing the write amino acids to the site of translation.No doubt once again pointing out your tenuous grasp of molecular biology is only ankle-biting.TTFN,WKP.S. Care to address Message 66 yet?

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I'm finding this discussion defining natural selection to be an unexpectedly tough slog. We can't seem to get out of our own way. The approach I'm lobbying for is to start with a simple definition from which we elaborate. I proposed that we start with Darwin's definition, but I'm flexible as long as we start simply. I do feel that we're at far too detailed a level since there isn't even agreement that sexual selection is a type of natural selection.

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I get that feeling as well. For what it is worth, I tend to consider sexual selection as merely a certain kind of animal behavior, subject to natural selection like everything else. As an example, consider first a population of deer mice living in an open, grassy field. These mice are nocturnal, so they do all of their foraging under the cover of darkness. Now suppose a behavioral variant arises that forages during the day. Such behavior in an open field during the day exposes these mutant mice to predation from diurnal animals, such as hawks. This behavioral variation will be selected against if it raises the risk of predation significantly, and would not be expected to become common in the population. Now consider other kinds of behavior in the same population. Let’s assume females only choose mates who smell ”right’--those who possess a certain pheromone. If we imagine a variant male being born who does not possess the requisite pheromone, it should be easy to see that such variants will not become common in the population.So, what is the difference between the two scenarios? Why would we consider the behavior that affects predation risk qualitatively different from the other, which affects mating success? In both cases we have behavioral variants (or, more properly, the genes underlying the behavior) competing with each other for replicative success. I would argue both scenarios are examples of natural selection in action.AEdited by Allopatrik, : Spelling

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Natural Selection is not Evolution-- R.A. Fisher

Wounded King is a subtle monarch, at least when it comes to helping me get a leg up on those empirical evolutionary “forces.” His Majesty has written:

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“This has to be the stupidest example ever...

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“Ugh, that has to be one of the the sloppiest and least accurate descriptions of the process I have seen . ”

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Sloppy is as sloppy does, even with extra articles. BTW, Wounded King, where exactly were you wounded? A frontal lobe perhaps? You can have your polymerase enzyme argument; it’s perfunctory anyway. But translation does NOT occur in the ribosome; it occurs in the cytoplasm. Transfer RNA serves as an interpreter during translation” and of course enzymes and ATP are involved with that, too. From there the tRNA joins up with a ribosome to build polypeptydes. Time to get down off your throne and get back to school.And as for your Message 66: My point all along has been that nonrandom mating (SS) may possibly occur and eventually affect the course of a population’s evolution without NS necessarily playing a role. I agree that nonrandom mating can be provocative of NS, but it’s not necessarily a turn-key operation. Can you prove to me that SS will always provoke NS? Why does SS have to always be a sub-process of NS? Why couldn’t it be a co-process or even a counter-process?”HM

This is a stupid attack on WK. His comments were about the details of your description of the protein synthesis process. He then pointed out exactly where you were, in his opinion, in error.I suspect that you shouldn't be mouthing off -- for two reasons:
1) it will get you suspended.
2) I think WK actually knows what he is talking about and you will look fooish when he points out (again) where you are wrong.Last warning!

Sexual Selection
Special form of natural selection based on an organism's ability to mate. Some animals possess characteristics that are more attractive to potential mates, such as the distinctive plumage of some male birds. Individuals with such characteristics mate at higher rates than those without, ensuring more next generation offspring will inherit the desirable trait. As generations procreate the desirable trait becomes increasingly common, further boosting the sexual disadvantage for individuals who lack the desired trait.
National GeographicSexual selection: Selection which promotes traits that will increase an organism's success in mating and ensuring that its gametes are successful in fertilization. This is distinct from natural selection which acts simply on traits which influence fecundity and survival.
Natural History Collections: Glossary P-ZSexual selection: A type of natural selection that acts differently on males and females of the same species. Traits involved in mate competition (e.g., canines, flashy peacock tail) are products of sexual selection.
http://web.missouri.edu/~flinnm/courses/mah/glossary.htmThe theory of sexual selection was first proposed by Charles Darwin in his book The Origin of Species, though it was primarily devoted to natural selection. A later work, The Descent of Man and Selection in Relation to Sex dealt with the subject of sexual selection exhaustively, in part because Darwin felt that natural selection alone was unable to account for certain types of apparently non-competitive adaptations, such as the tail of a male peacock.
Sexual selection - WikipediaSince the discipline itself cannot agree whether Sexual Selection is distinct from or is a type of Natural Selection, agreement in this thread is dubious.

Only the Edinburgh site makes a claim that sexual selection is distinct and if you look at the definition it gives for Natural Selection... Sexual selection seems to fit right in with this definition since it clearly influences an organism's chances of reproduction. Edinburgh seem to have treated reproduction and fecundity as the same thing, which they aren't.Be that as it may, I agree that if your definition of NS only encompasses survival and fecundity then you can make a clear case for a distinction. The real question was whether Hoot Mon could make such a case, and he seems to have singularly failed to do so.Even if we can't necessarily agree on a canonical definition of NS or SS we should still be able to agree on the implications of accepting specific definitions.TTFN,WK

Allopatrik, I see your point and mostly agree. But doesn't your point tend to blur the coherent meanings of any categorical distinctions amonst the so-called evolutionary "forces"? (I cringe to use the term “forces,” but I’ll go along with the crowd.)In these threads we have competing arguments running a spectrum of NS meanings. At one end NS is the Final Cause to which all other evolutionary "forces" serve supporting roles (paleo-Darwinism); at the other end NS is merely a Causal Factor that works co-operationally with other evolutionary "forces" (neo-Darwinism).So, I have another question for you. Back in Message 32 I mentioned this observation of counter-processing by two evolutionary geneticists, Hartl & Jones:

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It is apparent from [their studies] that selection tends to eliminate harmful alleles from a population. How, harmful alleles can never be eliminated totally because recurrent mutation of the normal allele continually creates new harmful alleles. These new mutations tend to replenish harmful alleles eliminated by selection. Eventually the population will attain a state of equilibrium in which the new mutations exactly balance the selective eliminations .

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Is it fair for me to extrapolate from this, then, that the "forces" of evolution may be viewed in any of these process-oriented contexts?:1. Independent processes.2. Sub-processes.3. Super-processes.4. Co-processes.5. Counter-processes.I’ve been arguing that all five processes are possible along the course of an evolutionary continuum. What do you think about it?”HM

You have yet to provide anything to cause me to revise my opinion, your example was one where sexual selection and natural selection would cooperate, the exact opposit of what you were trying to demonstrate. If you think it wasn't then explain why. It seems that whenever you get your basic molecular biology wrong it is merely perfunctory. ___
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Oh rly?Please see here, here, here,here, here, here and most of the rest of the internet. Since non-random mating and sexual selection are not the same thing this makes your point rather irrelevant. You may have seen what AZPaul wrote upthread. If you want to define NS narrowly as only selection acting on survival and fecundity then I agree that you can discriminate between NS and SS as forces. Then you need to add in a whole lot of other selective forces which are not sexual, survival or fecundity. I prefer to treat the various element of fecundity, survival, sexual, gametic,viability and whatever other forms of selection act upon heritable genetic chracteristics to influence allele frequencise in subsequent generations as all elements of Natural Selection.TTFN,WK