At some universities, undergraduates are involved in research, are included in research group activities, and interact closely with graduate students; i.e., not just in labs or classes with graduate TAs, but in a research context. At these universities, some undergraduates routinely attend department seminars and may participate in professional conferences. At other universities, the undergraduate and graduate populations are more separate, and mix only in labs or classes in which there is a graduate instructor. At these universities, undergraduates don't tend to be as connected to the research activities of the department.
Of course, even in a department in which the overall culture involves separation of grads and undergrads, individual research groups can adopt their own philosophy, but it is easier to integrate grads and undergrads in research activities if there is a culture of interaction, in part because there may be more opportunities, e.g., internship programs and such.
If, as is the case at most universities (I think), there are talented and motivated graduate and undergraduate students, there can be many opportunities for mutually beneficial interactions. I have been fortunate to be associated with a number of such universities.
If, however, there is a discrepancy between the undergraduate and graduate programs in terms of "quality" (a vague term, I know) or attention and resources focused on one program vs. another, opportunities are missed and there may be tensions between various groups within the department. I was recently thinking of one such example of a place with a discrepancy between grad/undergrad programs; hence, this post.
Comparison of the "rank" of a university and its constituent graduate programs reveals numerous examples in which there is a mismatch between the university's overall reputation and that of individual programs. In my own field, although excellent graduate and undergraduate programs commonly coexist at the same institution, it's not difficult to think of prestigious universities with unimpressive graduate programs, and non-prestigious universities with excellent graduate programs.
When I serve on a committee that evaluates some aspects of one of the engineering departments at my university, I commonly see letters from faculty at a particular university from which it would be unthinkable to solicit a letter in my own field. If you believe that any of the various rating schemes mean anything, I am sure you can find a number of such examples by comparing university-as-a-whole rankings vs. doctoral program rankings for particular fields.
These mismatches can create stressful situations, such as in undergraduate labs taught by graduate TAs or in research groups that have both graduate and undergraduate researchers.
Two mismatch scenarios are:
1. The undergraduate program is much stronger than the graduate program in the same department. During my brief association with one such department, there were occasional problems in mid/upper level undergraduate classes when a graduate TA did not have the intellectual ability or authority to make the undergrads feel they were learning anything worthwhile. This transcended teaching ability (or lack thereof) of the TA. For example, in a number of labs, highly motivated and intelligent undergrads were "taught" by a graduate student who would be unlikely to get an A in the course if they were taking it as a student. This was very frustrating for the undergraduates, and I am sure the grad TAs did not feel good about the situation either.
2. The graduate program is significantly stronger than the undergraduate program in the same department. In such programs, graduate students, when they TA, may be contemptuous of the intellectually inferior beings who populate the undergraduate lab courses, creating an unfortunate climate of mutual dislike that is not conducive for learning. Of course there is always the potential for there to be unmotivated students in any class at any level, but if such students dominate the courses for majors, the collision of unmotivated majors with highly focused graduate students (who are also likely to be inexperienced teachers) can be severely unpleasant for all concerned.
I think that departments can overcome these mismatches by promoting an atmosphere of respect at all levels of teaching and learning, by helping TAs become effective teachers, by emphasizing that good teaching is a priority (no matter how brilliant you are at research), and by finding creative ways to integrate graduate and undergraduate programs so as to maximize constructive interactions.
So, how well matched do you think the graduate and undergraduate programs are at your institution (or at places with which you've been associated in the past)? In addition to your assessment of this, an important piece of information is whether you are an undergrad, grad, postdoc, professor, other.