Hey there!
1.) Without the atmosphere, average temperature on Earth would be freezing! Below zero to be exact!
2.) The atmosphere protects us and animals from dangerous radiation from the Sun. Ultraviolet radiation is basically invisible rays of energy created by the sun.
3.) Also, the atmosphere provides oxygen for humans and animals to breathe and C02 (Carbon dioxide) for plants.
4.) And lastly, the atmosphere protects us from objects coming towards the earth.
Hope this helps!