[Orgmode] declaring items as implicit TODO entries

[Nick]

Hi,

I have an .org file I currently use as a TODO list.  Everything below a certain
level (currently 3) is a TODO item (of some sort).

Is there a way to tell org-mode to assume any item below this level is by
default a TODO item, such that the agenda view displays all of them which aren't
explicitly marked as DONE?

Thanks,

N