Groove is arguably the most important currency of the bassist and a solid understanding of rhythm is the way to cultivate it. Different styles of music call for different feels, but all are underpinned by the same rhythms. Reading music is a bit of a lost art but I think that if you can understand how to read a few simple rhythms then you are better placed to work on your sense of timing and your groove.
This video lesson takes you through the main simple rhythms you will need to master as a bass player, and then a few example lines using only one note.
Sixteenth Notes/Semi Quavers
I don't believe that you need to be able to read music to be a great bass player. There are too many brilliant bassists who can't (including Pino Palladino) so it can't be true! I do think, though, that if you can read it opens up many doors for you including the pleasure of self-learning and discovering and being able to play new music. For studying groove, I reckon it's well worth the effort. Once you recognise a few rhythms you'll quickly be able to decipher them.
Be sure to check out the other groove/timing/feel lesson here.