The similarity of oxygen and ozone.

Both O2 and O3 are reactive, and O2 gas contains 21% of the atmosphere and is the form in which most eukaryotic organisms depend on metabolism. Ozone is found mainly at high altitudes and is essential for protecting the biosphere by absorbing ionizing ultraviolet radiation before it reaches the earth.

Both of them consist only of oxygen atoms, are gases at room temperature, interact with UV-215 and more energetic radiation, dissolve well in water, and are strong oxidants.