2. What % of the atmosphere is nitrogen? A) do I have to answer? B) 0 % C) 27.56 % D) 75 % E) 79 %

3. a) The placing of leeches on people in the name of medical experimentation b) When bacteria convert nitrogen from one form to another c) When nitrates run into groundwater d) It’s a synonym for nitrogen fixation

4.  A) a word that I can’t pronounce  B) when heterotrophic bacteria break NO3- into N2 or N2O  C) when ammonium is used in small amounts by plants  D) when plants modify NH3 to NH4

5. a) N1 and N2 b) NH4 and NO3- c) Liquid and gaseous d) I have no clue

6.  Name the three major stores of nitrogen.

7. a) Increased deposition of nitrogen from atmospheric sources because of fossil fuel combustion and forest burning b) Livestock ranching c) Increased rates of denitrification d) All of the above

8.  How do animals acquire their nitrogen?

9.  Why is there a nitrogen cycle? Why can’t we just inhale and get our nitrogen fix?