Your graduate work was on bacterial evolution, but now you're lecturing to 200 freshmen on primate social life. You've taught Kant for twenty years, but now you're team-teaching a new course on "Ethics and the Internet." The personality theorist retired and wasn't replaced, so now you, the neuroscientist, have to teach the "Sexual Identity" course. Everyone in academia knows it and no one likes to admit it: faculty often have to teach courses in areas they don't know very well. The challenges are even greater when students don't share your cultural background, lifestyle, or assumptions...
Your graduate work was on bacterial evolution, but now you're lecturing to 200 freshmen on primate social life. You've taught Kant for twenty years...