Do I need a battery in a Nikon D7000 Battery grip to use it?

Do I need a battery in a Nikon D7000 Battery grip to be able to use the battery grip?

Ah - it's called a "battery grip".
The MB-D11 is a new design that gives you a couple of options.
#1 - You can put in a second EN-EL15 battery in it, giving your camera extended shooting as you'll have access to the power of two batteries.
#2 - You can remove the EN-EL15 from your camera, and put in into the MB-D11.
#3 - You can use 6 AA Alkaline batteries in the MB-D11. Very handy when your battery dies and you have to find backup power.
http://www.nikonusa.com/...-Pack.html

Most probably. If the battery grip has an protruding end that goes inside the camera's battery compartment then you won't have any other power source except for the one in the battery grip.

Normally when you use the battery grip, you put the battery that came with the camera into the battery grip. You can optionally use a second battery in the grip, or an emergency AA battery tray that comes with the grip in case you run through both batteries (or forget to charge them).

http://www.althephoto.com/concepts/lenses.php