Surface temperatures between 40 and -40 C allow liquid water. Earth is only known planet with abundant O2 atmosphere.
Atmosphere protects earth from UV, meteorites, solar wind.
Eat 3x per day, can survive without food for 40 days. Drink 6x per day, can survive without water for 7 days. Breathe 22,000x per day, can go without air for 3-5 min. There are 1022 molecules in every breath of air.