What does the ozone layer protect and shield the organisms on Earth from?

The ozone layer protects and shields the organisms on Earth from ultraviolet light from the sun. It sits in the stratosphere, around nine miles above the surface of the earth. Basically, ozone molecules in the stratosphere absorb ultraviolet light, an excess of which can be extremely harmful to living things, including plants and animals (the fact that it causes skin cancer is why we should wear sunscreen when exposed to the sun). For many years, scientists warned that certain chemicals containing chlorine atoms, especially CFCs (chlorofluorocarbons) used as propellants in aerosols, were actually eroding the ozone layer by destroying ozone molecules. According to the Environmental Protection Agency (EPA), these problems persist, despite increasing evidence that ozone depletion is causing "holes" over the Antarctic that threaten to expose the planet to dangerous levels of ultraviolet rays from the sun. Ozone depletion, along with climate change, remains among the most serious environmental challenges of the twenty-first century.