Changing the aperture in M on Canon DSLR's?

I'm a Nikon user and was wondering how Canon has their exposure controls. In Nikon entry level bodies there's a dial for shutter speed and for aperture you hold on to a button and adjust it with the dial. On entry level Canon bodies I believe it's the same thing. On Nikon prosumer bodies there are 2 dials one for each. I never used prosumer Canon's, but I see in pictures there's only one dial but I don't see a Av button. Or maybe there's?

Added (1). I think I found out how it is on prosumer canon bodies. I think it's the big circle that is the d-pad on entry level bodies.

Hold down the Av button while rolling the scroll wheel on my EOS450D