Ozone is made of three oxygen atoms its formula is O3

It formed in the upper atmosphere from the break up of water (H2O) in the secondary atmosphere

It is critically important to life on the earth surface because it absorbs Ultra Violet energy BEFORE it can get to the surface of the earth.

Before the ozone layer developed, the only place that organisms could live was deep in the oceans where the water protected them from the UV energy. When the Ozone layer developed the OZONE absorbed the UV so organisms could live closer to the surface.

Living close to the surface allowed organisms to develop the ability to use sunlight for energy. The began to use photosynthesis.

Early plant-like organisms began to use photosynthesis and to make OXYGEN (O2) which began to build up in the atmosphere changing the composition to the level of oxygen (21%) that we see today.

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