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Messages: 1 - 3 of 3
  • Message 1. 

    Posted by strawberrys (U15494169) on Wednesday, 7th November 2012

    Hey again, what did the earths atmosphere consist of 4.5 billion years ago? I've been asked to describe the main difference between todays atmosphere and the atmosphere 4,5 billion years ago, but i'm a little bit stuck on what exactly to write.

    Oh and 2 more things, are these statements correct?

    -the earths early atmosphere is thought to have been mostly oxygen. - false
    -the development of the ozone layer meant the earths temperature reached a suitable level for complex organisms like us to evolve - false
    -when oxygen started building up the atmosphere, all organisms began to thrive - true

    and are these in the right order? (oldest to newest)

    1: the earth formed there was lots of volcanic activity
    2:the earth cooled down slightly, a thin crust formed
    3:water vapour condensed to form oceans
    4:plant life appeared
    5:the atmosphere is about four-fifths nitrogen and one fifth oxygen
    6: oxygen built up due to photosynthesis and the ozone layer developed
    7: more complex organisms evolved

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  • Message 2

    , in reply to message 1.

    Posted by The Bitesize Science Teacher (U14392404) on Wednesday, 7th November 2012

    These pages describe changes: www.bbc.co.uk/school... and www.bbc.co.uk/school...

    Your order ... I think it's 2,1,3,4,6,7,5

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  • Message 3

    , in reply to message 1.

    Posted by U15495518 (U15495518) on Thursday, 8th November 2012

    Hey again, what did the earths atmosphere consist of 4.5 billion years ago? I've been asked to describe the main difference between todays atmosphere and the atmosphere 4,5 billion years ago, but i'm a little bit stuck on what exactly to write.

    Oh and 2 more things, are these statements correct?

    -the earths early atmosphere is thought to have been mostly oxygen. - false
    -the development of the ozone layer meant the earths temperature reached a suitable level for complex organisms like us to evolve - false
    -when oxygen started building up the atmosphere, all organisms began to thrive - true

    and are these in the right order? (oldest to newest)

    1: the earth formed there was lots of volcanic activity
    2:the earth cooled down slightly, a thin crust formed
    3:water vapour condensed to form oceans
    4:plant life appeared
    5:the atmosphere is about four-fifths nitrogen and one fifth oxygen
    6: oxygen built up due to photosynthesis and the ozone layer developed
    7: more complex organisms evolved  


    Well, the main differance will be that the atmosphere back then was around 70% Co2, with barely any oxygen at all. Plants then grew, did photosynthesis and put more oxygen into the air.

    I'd wait until someone else posts somthing too, just to double-check though.

    As far as I can tell, they're all correct and in the right order, hope you get a good mark!

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