> This in fact happens. We can even, in many cases, parse out what those
> *where*, sometimes by finding those extra structures still intact in
> other species.

More to the point, biological structures can *change purpose* too.

> And you are dead wrong on the later, evolution **keeps**
> masses of junk, whether it produces a benefit or not.

That too. The human genome has half a dozen broken copies of the globin 
gene, for example. (Plus 4 (?) similar but not identical copies that 
actually work.)

> The single cell do not, in general, contain mitochondria.

False.

Note carefully that "single-celled organisms" covers a vast variety of 
life forms, only some of which are closely related. Many of these 
contain mitochondria, and many do not. The fact that they are 
unicellular does not correlate particularly well with the presence of 
absence of mitochondria.

The distinction you're looking for is between eukaryotes and non-eukaryotes.

> Their genetics are often **far** more streamlined, because
> they can't afford to carry junk around, which doesn't do anything, for
> the reason you describe. It costs resources. Having a sort of "power
> plant" in the cell, whose genetics are 100% geared at producing excess
> amounts of energy, over what is absolutely needed by themselves, allows
> the rest of the genome, in the main cell, to be very sloppy in its
> operations, copying, cleanup, etc. Anything with such an internal power
> plant can afford to keep lots of stuff that does nothing at all, and
> only gets rid of things that are actively defective, usually not by
> deletion, but just by shutting them off, so they do nothing. This allows
> for what, in a single cell, would be egregious errors, such as making an
> exact copy of a sequence, then later having that sequence get mangled
> into a unique function. Its way harder to manage that if you can't
> afford extra copies lying around, where your energy input is drastically
> damaged, if you allow such a copy to happen.

I'm not sure I actually agree with this assessment.

> Most of
> their "changes" are, as a result, point mutation/deletion/addition, not
> the copy of whole sequences.

You got a citation for that?

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