Question

A source of non-biological oxygen is
A. Photodissociation
B. Photolysis
C. Formation of fats from carbohydrates
D. Both B and C

Answer 1

Oxygen is very important for the survival of all living organisms as it is required by them for respiration. The biogeochemical transitions of oxygen atoms between different oxidation states is called oxygen cycle.

Complete answer: Photosynthesis is the synthesis of carbohydrates or food from sunlight, water and carbon dioxide by the green plants. It is an endergonic and anabolic process in which the light energy is changed into chemical energy by plants. During this process photooxidation or photolysis of water occurs that releases oxygen. It is the biological method of release of oxygen.
In the upper part of the atmosphere called the stratosphere, there is a layer of good ozone that shields us from the ultraviolet radiations of the sun. Bad ozone is formed in the lower atmosphere called the troposphere that harms plants and animals.
UV rays are highly injurious to living organisms as the DNA and proteins of living organisms absorb these rays and break the chemical bonds within these molecules.
Ozone is the product of UV radiations acting on the oxygen molecules. the Uv radiations split apart molecular oxygen into free oxygen atoms. These oxygen atoms combine with the molecular oxygen to form ozone.
In the stratosphere, UV radiation from the sun causes photodissociation of ozone into diatomic oxygen and oxygen atoms that combine to form ozone. This ozone dynamics dissipates the energy of UV as heat. An equilibrium is established between genet=ration and destruction of ozone leading to a steady state concentration of ozone in the stratosphere.

Note: So the stratospheric photodissociation of greenhouse gases like chlorofluorocarbons. HFCs, etc. release chlorine atoms which react with stratospheric ozone releasing non-biological orygen. This oxygen is diatomic and reactive and causes breakdown of the ozone layer.