Answer:
Around 600 million years ago, a thin ozone layer formed that was capable of protecting life from harmful wavelengths of UV radiation (wavelengths between 200-300 nm). ... In the Silurian, around 420 million years ago, ozone levels were high enough to allow for organisms to survive on land, without any shielding from water.
Step-by-step explanation:
Around 600 million years ago, a thin ozone layer formed that was capable of protecting life from harmful wavelengths of UV radiation (wavelengths between 200-300 nm). ... In the Silurian, around 420 million years ago, ozone levels were high enough to allow for organisms to survive on land, without any shielding from water.