Oxygen: A Necessary Evil

Inorganic Evolution:

Astrophysics/Particle Physics states that the journey of existence started from Plasma state of matter to sub-atomic particle to the atom of lowest atomic number (say one proton & one electron, i.e. Hydrogen).

Then it was the turn of inorganic evolution, gradually atoms of higher atomic number came into existence .... elements formed, and then their compounds ....

(reference: picture #1)

Inorganic Evolution Evident:

This is evident from the periodic table of chemical elements (1896 Dimitri Mendeleev) in which the elements are arranged by order of atomic number in such a way that the periodic properties ( chemical periodicity) of the elements are made clear.

In 1914 Rutherford .... transmuted a Nitrogen atom into an Oxygen atom for the first time.

Organic Evolution:

When 'Primordial Soup' ( no Nucleus, no Cell Membrane as such) of some simple organic compounds gained just few characteristics of life (nutrition as growing in size and reproduction as dividing into two), .... in the environment of Hydrogen (as Oxygen was not found). It was all a reducing environment ( opposite to oxidizing of Oxygen).

(reference: picture #3)

Age-Old 'Vedic' Observation (from India):

One of the oldest recorded human observation is made evident in the book 'Rig Veda' ( 5-6 thousand years BC) about the nature of these primordial life forms and their reducing environment.

(reference: picture #2)

Oxygen:

In the further course of inorganic evolution, oxygen came to exist and the whole scenario of organic evolution changed... as oxygen being highly reactive.. due to oxidizing behavior (having only 2 electrons in outermost orbit, it has great binding affinity with all); and soon primitive life forms learned to live with this unwanted oxidizing guest of their environment by burning ( getting oxidized) some part of their cellular body to get rid of it.

They gradually developed some organelle , later to Mitochondria in their cell and stored those emitted energy in molecular form (ATP) for later use for their further biological activity.

That was the beginning of an environment of oxidative respiration, that is what we have today, changing the the course of life development of the life forms there on ....

(reference: picture #4,5,6,7)

Conclusion:

Oxygen is not a friend. It oxidizes, burns the part of cell...or rather silently a killer factor..
But ever since through our evolutionary history, life forms have adopted to this evil factor..

Related blog post links:

http://sciencedoing.blogspot.in/2013/05/oxidative-stress-strain-as-predisposing.html
http://sciencedoing.blogspot.in/2013/05/dark-oxidants-super-oxides-in-depth-of.html

http://sciencedoing.blogspot.in/2012/09/free-radicals-cause-and-concern.html