Is there "danger" in removing Macintosh HD from my Time Machine as a back up? I want to use Seagate Backup Plus Drive I'm a novice (obviously!), and my Seagate will not back up my computer because it says there is nothing to back-u since my Macintosh HD is in my "Exclude these items from backups" under "Options".  I'm having a little anxiety if I take it off the list -- that I will lose all that is on it.  Call me crazy.  I just need some confirmation since I do not put it on this list so I assume it should be there.
None of the items in the "Exclude these items from backups" will be backed up. Usually only the backup volume (i.e. the Seagate Backup Plus Drive) itself is in the list.

So including Macintosh HD in the above list is counterproductive if you want to backup Macintosh HD.