What are the two forms of oxygen found in the atmosphere? What is their importance?

(N/A) The two forms of oxygen found in the atmosphere are:
$1$. $O_2$ (Diatomic Oxygen): It is essential for the process of respiration in living organisms and is also required for combustion (burning) of fuels.
$2$. $O_3$ (Ozone): It is found in the upper atmosphere (stratosphere) and acts as a protective shield by absorbing harmful ultraviolet $(UV)$ radiations from the Sun,preventing them from reaching the Earth's surface.