Quarian

The Quarian are nomadic, bipedal sapients who must wear environmental suits at all times, as living in the sterile environment of the Flotilla has atrophied their immune systems. Many rumors exist as to their race in fact being cybernetic in nature - a perfect blend of biology and technology that allows them to survive in the vacuum of space for a time.

Trivia

 * Of all the Quarians in existent Mass Effect universe, Tali'Zorah was the only one seen in-game.