Statement-I says Ozone is essential for biotic life. While ground-level ozone is harmful, the ozone layer in the stratosphere is crucial for life on Earth. Statement-II clarifies the essential role: The ozone layer protects the earth's surface from high energy radiation (specifically, most of the sun's harmful ultraviolet (UV) radiation). Without this protection, UV radiation would reach the surface in levels that would cause severe harm to DNA, leading to increased rates of skin cancer, eye damage, and harm to plant and animal life.