Exercise 2 is where the rhythm playing gets interesting. This is also where you'll find a few eighth notes mixed in with the sixteenth notes.
Also, be mindful of the sixteenth note rests that you'll see in each bar. For those rests, I'd recommend letting your picking hand fall on the strings to really solidify the silence during each rest. That will help make your rhythm playing sound tighter.
In the second beat of each measure, you'll find what are called "dead notes", which are represented by the "X" markings on the strings. For those notes, you'll simply be muting the strings with both hands while you play them. This will give off a strong percussive sound.