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ORIGINAL: Jhud

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"Critical to the survival of the organism" is not required for selection. Selection only requires the characteristic to be passed on to more offspring. Survival of the organism often desirable to accomplish the task of passing on the characteristic to more offspring and the environment the organism finds itself does not need to be different or change. Though a changing environment is often a pivotal moment that selects against organisms that lack the characteristic of interest.

Funny, you seem to be saying here that in order for a characteristic to be selected, it need not actually be … selected. Ah, the mysteries of the amazingly vague notion of evolution.

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No, you simply misunderstand what I say.. Frequently I might add.
You are equating "Critical to the survival of the organism" as the only mechanism for selection.
"Critical to the survival of the organism" is a subset of possible mechanisms for selection.

Suppose a specific mayfly acquires a mutation that doubles the number of viable eggs. The specific mayfly still has an amazingly short lifespan, each of its offspring also survive or die at the same rate as normal mayflies, but because this mutation leads to twice as many offspring, then it is selected for by sheer numerical advantage compared to mayflies without the mutation. Each individual adult mayfly dies just as quickly.

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ORIGINAL: Jhud

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No, you simply misunderstand what I say.. Frequently I might add.
You are equating "Critical to the survival of the organism" as the only mechanism for selection.
"Critical to the survival of the organism" is a subset of possible mechanisms for selection.

Suppose a specific mayfly acquires a mutation that doubles the number of viable eggs. The specific mayfly still has an amazingly short lifespan, each of its offspring also survive or die at the same rate as normal mayflies, but because this mutation leads to twice as many offspring, then it is selected for by sheer numerical advantage compared to mayflies without the mutation. Each individual adult mayfly dies just as quickly.

Well then that ability would quite obviously be critical to the survival of the mutated mayfly, and thus be selected...

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ORIGINAL: Jhud

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Right. That is the natural range of neutral variation that exists in any population. But when a variation offers any advantage, however slight, it is selectable. It doesn't have to be something significant or obvious.

Well, of course any genetically expressed characteristic of an organism is 'selectable', I think the larger question, "under what circumstances is a particular genetically expressed characteristic selected and come to typify and organism". I would say generally the answer in this case is, "that characteristic which becomes critical to the survival of the organism in the particular environment it finds itself."

And I would further suggest that those circumstances wherein one particular characteristic is critical are rare indeed.

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No, the specific mutated mayfly would die on schedule in less than a day just like unmutated mayflies..

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Swan42 beat me to it. No, for a character trait to become a fixed trait of the species, it is not necessary that it be critical to the survival of the organism. Just a bit better for survival and/or surviving progeny than what it replaced.

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ORIGINAL: Jhud

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Swan42 beat me to it. No, for a character trait to become a fixed trait of the species, it is not necessary that it be critical to the survival of the organism. Just a bit better for survival and/or surviving progeny than what it replaced.

Actually, I don't think it would then become 'fixed'; it would simply exist as one of a number of possible variations that exist within a population organisms.

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I mean, sickle cell isn't even a 'fixed' variation, despite the neccesity of it in certain circumstances.

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ORIGINAL: Jhud

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No, the specific mutated mayfly would die on schedule in less than a day just like unmutated mayflies..

How does that negate what I just said? Obviously, the increased propogation of 'mutated' mayflies is crtical to their success over the ordinary sort - if it wasn't there wouldn't be a change.

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No, that would mean either that the trait is neutral and not being selected or that the selection factor is changing before the trait is fully fixed.

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Special case. Not a good example. Outside of malaria-prone areas, you might note, the lack of sickle cell is fixed.

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It wouldn't negate it if we were using the same definition of "organism".

http://en.wikipedia.org/wiki/Organism
In biology, an organism is an individual living system (such as animal, plant, fungus or micro-organism).

I'm using the definition above, it now appears to me you are using "organism" as synonymous with "species".
Organism != Species.

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ORIGINAL: Jhud

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No, that would mean either that the trait is neutral and not being selected or that the selection factor is changing before the trait is fully fixed.

Exactly; because it wouldn't be critical to an organisms survival.

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Special case. Not a good example. Outside of malaria-prone areas, you might note, the lack of sickle cell is fixed.

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ORIGINAL: Jhud

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It wouldn't negate it if we were using the same definition of "organism".

http://en.wikipedia.org/wiki/Organism
In biology, an organism is an individual living system (such as animal, plant, fungus or micro-organism).

I'm using the definition above, it now appears to me you are using "organism" as synonymous with "species".
Organism != Species.

I didn't even use the word organism in the quote you just responded to.

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ORIGINAL: swan42

Just 3 people in the world have this ability.

http://www.cnn.com/2008/HEALTH/conditions/05/07/miraculous.memory/index.html