How did the formation of an ozone layer affect life near Earth’s surface?

The formation of the ozone layer during the Precambrian was a critical development for the evolution and expansion of life on Earth. By screening out lethal levels of ultraviolet (UV) radiation—specifically UVB radiation—this atmospheric shield protected living organisms from the damaging effects of the Sun’s rays.123

Before this protective layer existed, the intense ultraviolet radiation reaching the surface would have been hazardous or fatal to most life-forms. As oxygen levels in the atmosphere increased due to the metabolic activity of early organisms, ozone began to accumulate in the stratosphere. This transition allowed marine plants and animals to evolve and eventually facilitated the migration of life-forms from the safety of the oceans onto land.2415

Without this protective barrier, the high-energy radiation would continue to pose a significant threat to ecosystems and the food chain by damaging biological materials and DNA. Consequently, the ozone layer is considered essential for the survival and diversification of life on Earth's surface.1342