Two Peas in a Bucket: Photography Course

In an effort to improve my photography skills and learn how to use our DSLR correctly, I am taking the Two Peas in a Bucket photography course.  I've tried reading, Understanding Exposure, which is how Jarod learned.  However, I find it easier to do the courses since they are more hands on.  I figured I would post each lesson here, to hold myself to doing it each week. 
This weeks lesson was on aperture, which is basically how much light you allow through the lens.  When you have the lens wide open the background will be blurred behind your focal point.  The less the lens is open the more in focus your background will be.

I used and f-stop of 1.8 on the first photo.  The second was a f-stop of 8.0.  And the last photo was an       f-stop of 22.0.  I did all of this with our 50mm lens.