Forum:Storyline help, please!

I'm going through my second play of Bioshock and I have some story questions. Simple curiosity. I was reading up that Fontaine controlled the ADAM. If this was the case, then how did Ryan make plasmids (they say "by Ryan Industries") if Plasmids are made of ADAM. Also, with the Little Sisters, I understand the sea slug part at that the Sisters regurgitate ADAM. But, in this wiki it says that they feed on the dead. Why is that? Is that in the game? Also, they were later controlled by Ryan? Who makes them go out and get ADAM from the dead people, and why do they do that? If anyone answers this, I would be most appreciative.