At UIUC, we get many more, and much better, domestic grad school applications now than in previous years. (International applicants are more complicated. Yay 9/11.) Good grades are a MINIMUM requirement for admission now. Most incoming grad students already have some research experience; some of them even have publications. That was not true five years ago.
. From 1point 3acres bbs
When grad applications arrive, one of our department secretaries sorts them roughly into three equal piles -- MAYBE, PROBABLY NOT, and NO -- based almost entirely on GPA, weighted by the quality of the school, and GREs. (Penn has a very good program, so this works in your favor.) The committee looks at the MAYBE pile, and if there's still space, maybe the top of the PROBABLY NOT pile. If a student's GPA is under 3.0, it's very likely that no one on the committee will even look at their application. (This is a bit of an oversimplification.)
...UNLESS they're rescued by someone on the faculty. (后面的略了，因为是小概率事件 undefined ）