No, it doesn't, you're right! The webcam app doesn't do sound; the giveaway is that there is no configuration tab for any sound device!
Other applications, such as Skype work fine with the internal mic, but if you want to check your mic is working first, start a terminal and do
then talk a bit, then hit CTRL-C.
and you should hear your voice coming back.
Clean up after the test by doing
as the file you've recorded might be quite big!