On Mon, 14 Nov 2005 18:27:21 -0700, allen dick <[log in to unmask]> wrote:

>> Variation, selection, adaptation -- it all adds up to evolution.
>
>Not really, if we are simply looking at an expression of genes, rather than
elimination of genes or generation of new ones.

comment:

Evolution on the grand scale is made up of all these smaller parts. Without
variation, no change. Without selection, no adaptation. Here's a bit which
goes into "microevolution" -- which is what we are talking about when we
discuss "natural resistance" -- either in bees or mites, or any other life form.

quote:

Microevolution is evolution on a small scale — within a single population.
That means narrowing our focus to one branch of the tree of life. If you
could zoom in on one branch of the tree of life scale — the insects, for
example — you would see another phylogeny relating all the different insect
lineages. Microevolution is a change in gene frequency in a population and a
population as a group of organisms that share a common gene pool — like all
the individuals of one beetle species living on a particular mountaintop.
There are a few basic ways in which microevolutionary change happens.
Mutation, migration, genetic drift, and natural selection are all processes
that can directly affect gene frequencies in a population.

The environment may impose an external barrier to reproduction, such as a
river or mountain range, between two incipient species but that external
barrier alone will not make them separate, full-fledged species. Allopatry
may start the process off, but the evolution of internal (i.e.,
genetically-based) barriers to gene flow is necessary for speciation to be
complete. If internal barriers to gene flow do not evolve, individuals from
the two parts of the population will freely interbreed if they come back
into contact. Whatever genetic differences may have evolved will disappear
as their genes mix back together.

source:

http://evolution.berkeley.edu/evosite/evo101/IVADefinition.shtml

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