This isn't a question, it's an answer - to my own question. I found the solution just now and it was staring me in the face the whole time. The issue was how to make a shape, like a vertical bar grow higher or lower.
The answer is:
1. Set the Y value of the anchor point so that it is at the bottom of the shape instead of its default location in the center.
2. Next, under "Scale" animate the Y value up and down as needed to grow and shrink the shape vertically.
You wouldn't believe the ugly workarounds I was using to create this effect.