An interval in music is the distance between two musical notes. Every single thing you ever play on bass is built from them so you'd better learn them!
This video lesson follows on from a recent one where I went through the intervals up to the octave:
How To Name Intervals On Bass (Plus Application/Tips/Tricks)
Scroll down for the various downloads.
Bass Guitar Extended Intervals
Here's a D Dorian mode. Notice how the notes go up the alphabet consecutively. But, when you stack a chord in thirds, you spell out the scale in a vertical manor. Very interesting results occur from playing using different combinations of scale (horizontal) and chord/arpeggio tones (vertical).

You can do this with any chord and scale.
Playing these ideas over drones allows your ear to recognise the intervals, paving the way to strengthen one of your most important assets.
Download twelve free drones here and give it a go.
D Dorian Scale, Chord, And Intervals
More lessons on intervals:
Harmonising The Natural Minor Scale: Play Bass Lines, Chords & Solos!
Create Bass Lines With Only FOUR Arpeggios