Where does our breathing oxygen O2 come from ? New 2020 in 1min 28s Eng...

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Where does our breathing oxygen O2 come from ? 1min 28s English-Français
Oxygen O2 production has always been attributed to vegetation. But in deserts, there are not enough plants to provide respiratory oxygen to humans and animals, which also release carbon dioxide CO2.
Next, the oceans and seas do not provide oxygen, but they dissolve. oxygen dissolves in water.
Now where does this 21% oxygen from the air come from?
My answer is that all the oxygen necessary for the life of humans, animals and plants comes from the decomposition of ozone by the action of ultraviolet solar rays. In reality the dioxide molecules rain down, they descend slowly because they are slightly heavier than air and feed the lower atmosphere.
Plants release oxygen, but in the form of atoms lighter than air and which escape at altitude to supply the ozone layer. The pressure and temperature conditions in the lower atmosphere do not allow these atoms to associate or combine with air molecules such as O2 molecules which are stable. and which do not accept it or with the nitrogen molecules which have an inertia to react. So he has to go up.
Thank you