Answers

2015-06-28T18:17:25+05:30
Nice question 
there is about 75% N2 in air


oxygen involves in photosynthesis
trees absorb carbondioxide and release oxygen
our body cells absorb oxygen
nitrogen was made by the world stunning 2 famous microorganisms
pecuria was a kind which transfered nh3 to no3
and the ammonia from ground to nitrogen
also this ammonia came first from volcanic eruptions
also lets take a noble gas
possibly argon
its used in making light bulbs 
we know that
it comes from the ground
its product of beta + ions to form ar(40)+carbon+venadium
it reacts with gama particles to form argon 40 again with vanadium
i hope you are clear and please mark my answer as the best


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2015-06-28T19:36:04+05:30
78% of the eath's atmosphere is composed of nitrogen. It is composed of oxygen in 21%. The other 1% are the other gases such as carbon dioxide, argon, neon etc.Plants realeases oxygen.We realease carbondioxide.The plants take in carbondioxide, we take in Oxygen. The volcanoes on eruptions releases a large of gases such as nitrogen etc.
These are few cases in which gases are added to the atmosphere...
hope this helps u.
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