So basically, it eats then it farts.
Think about that next time you're having a beer or a nice slice of bread. You owe it all to yeast farts.
Btw, yeast and I don't get along in the kitchen. Whenever I try to get yeast to fart itself into a nice loaf of bread, it always laughs at me then goes off to watch tv or something. I have had no success at getting home made bread to rise despite trying several techniques and recipes. Surely it's all the yeast's fault! Damn yeast! ;)