Nitrogen get into the air by lightning strike or fires by certain types of bacteria.
Answer is Translational control.
Gene expression refers to genes being ‘turned on’ and makes protein as product. Protein can be a structural protein, an enzyme or a control molecule. The protein synthesis rate is proportional to the concentration and translational efficiency of its mRNA. Translational control governs the efficiency of mRNA production. Translational control mechanisms are the most determining for final protein levels.
Diploid cells contain 2 sets of the same DNA where as haploid contains one set.....so our normal cells in our body (somatic cells) are diploid however our sex cells(gametic cells) which are the egg of a woman and sperm from a guy are only haploid which means they have only 1 copy of DNA......this is because they fuse with one another and add their DNA together to make a diploid cell
Evolution would be the answer you may be looking for.