I was curious how life on Earth, or an Earth-like planet, would be effected by changes in the gases which make up our atmosphere.
Assuming there is a similar level of oxygen in an atmosphere, could other gases be reduced or even replaced and still be able to maintain life as we know it?
Not really biology, but if the following could be kept in mind too that would be amazing:
[To give some context, I would like to ask how a sky could be light blue with a purplish hue, which supports some life larger than what we see on Earth, but still capable of supporting life which we find on Earth.
I am assuming a slightly higher percentage of oxygen is needed, but what other gases which are none lethal, but give a purplish hue?]
Thank you to all who take the time to give an answer, very much appreciated!