Re: Pressure"?


"Dick" <remdickhm@xxxxxxxxxxxxx> wrote in message
news:kb7lg29mkgiufnk0rp380p277s3du7tuol@xxxxxxxxxx
snip

My understanding is the survivors breed thus maintain their gene pool.

Because the English language does not have a singular pronoun that means
his
or her, people often use the plural pronoun "their" to refer to
individuals.
I just want to make sure you aren't doing so in the above sentence, as the
"gene pool" is the population, not the individual. An individual does not
have a "gene pool" as such. If you mean the population of surviors, then I
apologize.

"Survivors" is plural. However, a population can be one survivor,
right?

No, if there is only one survior, the species is going to go extinct.

In this day and age we have "endangered species" with small
populations. How does your concern about my use of gene pool explain
the use of "pressure" and its implied application to a gene pool?

I just wanted to make sure you understood that "gene pool" refers to the
population, not the individual. While an individual could be thought of as
a collection of genes, the term "gene pool" refers to the pool of genes in
the population.

snip

Again, pressure does not cause more mutations, it simply intensifies the
effect of a mutation on the gene pool.

How does this "pressure" "intensify" the mutation's effect?

It makes it more likely to be a deciding factor in the survival of an
indiviual. If there is less population pressure, a wider set of mutations
can be considered neutral. For example, if there are fewer predators,
mutations favoring flashy colors can become more prevalant. See:
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act2.html


Isn't the environment neutral?

No, the enviroment is not neutral, it's what filters what traits will be
passed on.

It seems to me, neither the
environment nor the mutated organism do any more than interact.

That's all that's needed, for them to interact. The enviorment "decides"
what traits are beneficial. The mutations are random in respect to the
needs of the organism.

Pressure is measured by resistance to movement. In a drought how does
the organism resist?

By either being able to find, or utilize food better than it's competitors.
Remember, the word "pressure" here is more of a metaphor, than an acutal
pressing force.


I gather the word, pressure, has become important in the lexicon for
NS discussions. I am surprised there is not a history how this
"selection" came to be. Pressure would make good sense if we were
discussing Lamarkian mutations.

"pressure" also makes sense in Darwinian usage. Again, you have to
remember that the word "pressure" is used metaphorically. Nothing is
actually pressing on these genes.


DJT


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