Macbook won't recognize mixer or mic

I have a 2,26 Ghz Intel Core 2 Duo Macbook, which has one port for audio input and output.

I have a small 4-channel mixer and a nice microphone I used to use together on my old Powerbook to record with Garageband. That computer had two inputs.

Now with the macbook I've

a) plugged the mixer and mic in

b) selected "use audio port for: sound input" in system sound preferences.

I see no sound level in the sound prefs, no activity, i.e. no bars appear when I make noise in front of the mic.

Unsurprisingly there's no option for the mixer in garageband input options, only built-in ones.

Has anyone else had this problem? Know how to fix it? It's kinda weird seeing as I never had this problem with my old computer, and this should work. I've done everything right.