ABSTRACT
The role of stratospheric ozone as fi l ter of harmful ultraviolet (adiation (tNR) is " Iell known. The development of ozone in the stratosphere ( see Fig. 1 1 . 1 ) occurred originally as a byproduct of other biogeochemical changes. Water-based plants began producing o;qgen VIa photosynthesis - and eve [-Itually waste gas spilkd over into the atmos phere. Incoming UVR from the sun chemically converted some of the oxygen in the upper atmosphere to ozone. Oxygen in the lower atmosphere allowed the development
aerobic and mane in upper C1tJl1ospbc:re acted �l S filter to provide protection harmful UVR [2J . The �cene was set for the development of land-based life.
