Then again I tend to be wrong when it comes to science.
Yes.
All you need is oxigen. Divers for example breath a mixture of helium and oxigen, because nitrogen becomes toxic at a certain depth (helium also becomes toxic at a certain depth, tho later than nitrogen). But so does 100% oxigen (at about 1.4-1.6 bar).
2) 0% oxigen? Well most people for about 3 minutes. Tho there are plenty of animals like whales that can hold their breath way longer. But if you count cyanobacteria as animals and not as a plant, then that would be it (those are the guys that shifted the atmosphere 2.5 billion years ago) http://en.wikipedia.org/wiki/Cyanobacteria
Yes.
All you need is oxigen. Divers for example breath a mixture of helium and oxigen, because nitrogen becomes toxic at a certain depth (helium also becomes toxic at a certain depth, tho later than nitrogen). But so does 100% oxigen (at about 1.4-1.6 bar).
1) Such an enviroment is only possible in a lab. Not on planets. You might have heard about this thing, it's called fire and it loves oxigen. But in a lab, over a longer period, it would be deadly. (German article: http://www.welt.de/wissenschaft/article889026/Reiner-Sauerstoff-schadet-Herz-und-Hirn.html)
2) 0% oxigen? Well most people for about 3 minutes. Tho there are plenty of animals like whales that can hold their breath way longer. But if you count cyanobacteria as animals and not as a plant, then that would be it (those are the guys that shifted the atmosphere 2.5 billion years ago) http://en.wikipedia.org/wiki/Cyanobacteria
Air consits of: