Obviously Earth's atmosphere is just fine for life it, but is there a possibility of one composed of gases that would make life have an easier time living? If yes, what would it consist of?
I have a rough idea of something along those lines:
-1.5 atm pressure- with denser atmosphere, flying creatures should have easier time staying afloat
-around 30% Oxygen concentration- below 0,5 bars of partial pressure, so that humans won't get intoxinated, but still would be able to breathe more efficiently
-Carbon Dioxide concentration between 0,5% and 0,1%- to let plants generate more energy via photosynthesis
-higher concentrations of water vapour- due to higher temparature and atmospheric density, more water vapour could "fit in", allowing moisture to get transported further inland than on Earth