question about disciplinary norms regarding prerogatives of rank

Two general questions about statistical and moral norms governing rank.

1. Among tenure-track and tenured faculty, to what extent does having a higher rank typically give one greater control over teaching assignments?
2. To what extent should having a higher rank give one greater control over teaching assignments?

For example, is it normal for all ranks to typically teach the same distribution of upper and lower level courses? Or is it normal for Fulls to teach whatever they want, even if this means some of them only teach upper level courses while Associates and Assistants are required to teach freshmen and sophomore general education courses? Are there any good arguments for the norms being one way or the other? 

I genuinely have no idea what the answers to the above are, and as a result think I don't really know the commonly accepted meaning of the terms "Full," "Associate," and "Assistant" as applied to job titles, e.g.

1. To what extent is it the job of Assistant Professors to assist higher ranked professors? 
2. To what extent is being an "Associate Professor" like what retail stores mean when they call non-management employees "associates." 

I'm not being sarcastic by asking these questions. The answers would be extremely helpful information, if only so that I know what I'm saying when I say that I am an Associate Professor.*

[*Full disclosure: I was a "K-Mart Associate" for three years and am so confident in the meaning of that term that I have in fact co-written with my wife two (unpublished) work-place comedies which go far towards explaining the meaning of the term. Even though I've worked four times longer in academia at this point, I couldn't begin to imagine penning an academic comedy without resolving basic questions such as the above. I guess I'd also have to find academia comedic, and that's a much dicier sell than it was in the glory days of Kingsley Amis or even David Lodge's early novels. Ah well, at least we've got Merle Haggard, even with the goofy instrumental solos still a pure thing in this fallen world.]