Yes. Admin on OS X *is* Admin - *not* Root, like it is on a Windows box. To do anything serious you have to escalate privileges - either within the GUI (by submitting your password) or at the CLI by using sudo. Much safer than Windows.
This is good on the mini:
Some of the follow-up discussion is good, too.
But don't be misled by the follow-up posts that recommend all sorts of (mostly badly-written) utilities to run the system functions. Do it from the command line:
sudo periodic daily
sudo periodic weekly
sudo periodic monthly
... all it takes. Or pick up Clix - which, unlike the specialist (and frequently AppleScript) utilities people tend to recommend - is a Cocoa interface for Terminal and, as such, infinitely customisable and extensible: