The ozone layer in the atmosphere protects living organisms on Earth from harmful ultraviolet (UV) rays from the Sun. It acts as a shield to absorb the UV rays, and keep them from doing damage at the Earth’s surface.

Reference:

Unknown (n.d.) ‘How Ozone protect us’ Retrieved on 11 March, 2015 from http://earth.rice.edu/mtpe/atmo/atmosphere/topics/ozone/o3.html