Is bitcoin the only entrance to buying other coins? I am totally newbie and looking into buying some other coins such as Megacoin and Quark with my bank account. After some research, I found that the only way to buy those coins seems to be buying them with Bitcoin.

Are there ways for me to directly buy other coins?
You can find coin exchange who sell those alt coins, see at MtGox or BTC-e
other ways to get alt coin such as Megacoin and Quark is by mining that coin