I just noticed that theres apparently less than 1% CO2 in the atmosphere and yet there appears to be life forms that breathe CO2. I realize plants arent tap dancing but im still impressed by the small % that s able to do the job for them.Are there creatures that currenly breathe methane(microbes?) and if the earth had lets say 9% methane in the atmoshere for the past 600 million years could this be enough for animal like life forms to breathe methane?