Account for the following `:`
Ozone layer is necessary for life.

Explanation

At high altitudes to the atmosphere consists of a layer of ozone ( `O_(3)`) which acts as an umbrella or shield for harmful UV radiations. It protects us from harmful effect such as skin cancer. UV radiation can convert molecular oxygen into ozone.
`O_(2(g)) overset( UV)(rarr) O_((g))+ O_((g))`
`O_((g)) +O_(2(g)) overset(UV)(rarr) O_(3(g))`