Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How oxygen came on earth?

  1. Apr 24, 2009 #1
    organic evolution took place in the absence of oxygen....if so, how oxygen came on earth??
     
  2. jcsd
  3. Apr 24, 2009 #2

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    With the evolution of organisms able to carry out photosynthesis they began converting carbon dioxide to oxygen and using the carbon. Further chemical and biological processes produce hydrocarbons taking hydrogen from water and yielding up net oxygen (usually again as CO2 which is again converted via photosynthesis). The oxygen was always there but in the form of CO2, H2O and mineral oxides.

    You must distinguish the absence of free oxygen from the absence of oxygen in general.
     
  4. Apr 25, 2009 #3
    many micro-organisms produce poisonous substances to kill their competitors. (think of peroxide).
     
  5. Apr 25, 2009 #4

    russ_watters

    User Avatar

    Staff: Mentor

    I don't think oxygen was produced as a defense mechanism, but rather as a waste product.
     
  6. Apr 25, 2009 #5

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    Careful about ascribing intent to the initial genetic advance. The microbes didn't choose to produce oxygen nor were they conscious of effect so the "why" of it shouldn't be debated at this level. The oxygen was a byproduct of an advantageous process and also a toxic substance so its production also made oxygen tolerance an advantageous trait. Both together also had the advantage of poisoning competitors more than selves. It is clear such a genetic innovation is a one way street and almost all organisms either adapted or died off... and so here we are.
     
  7. Nov 21, 2010 #6
    How was it possible for organisms such as plants or microbes to introduce oxygen to the earth if their DNA template, from which all of their biological features come, contains oxygen? DNA consists of many nucleotides, which contain oxygen ,that are linked on the outer rim of the DNA through the use of phosphate groups, which also contain oxygen. So, if the number one important molecule needed for the survival and procreation of plants and microbes contains oxygen, I'm curious as to how microbes or plants introduced oxygen as a novel agent to the earth. :smile:
     
  8. Nov 22, 2010 #7

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    You are confusing free oxygen, O2, with oxygen in general. There was plenty of oxygen in the early Earth's atmosphere in the form of CO2 and other compounds, plenty of of oxygen in the early Earth's oceans in the form of H2O, and plenty of oxygen in the early Earth's crust in the form of many oxygenated compounds.
     
  9. Nov 22, 2010 #8
    oxygen is oxygen whether it is incorporated into molecules within the atmosphere or water in the oceans...perhaps the original question was addressing diatomic oxygen as opposed to oxygen as a novel agent on earth. My apologies if so. As long as no one is under the assumption that microbes or plants introduced oxygen on an oxygen-less planet. =]
     
  10. Nov 22, 2010 #9

    russ_watters

    User Avatar

    Staff: Mentor

    That was answered in posts #2 and #4: There always was oxygen on earth, just not in the form of O2.
     
  11. Nov 22, 2010 #10
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook