QUIZ 1. Which process least affects nitrogen fixation on earth in modern times? a. Cyanobacteria b. Symbiotic nitrogen-fixers c. Fossil fuel burning d. Lightning strikes Answer: d. Each of these is a major way that nitrogen fixation occurs; however, lightning strikes play a minor role in this process. 2. What molecule gets made by nitrogen-fixing bacteria? a. Nitrate b. Nitrite c. Ammonium d. N2 Answer: c. Nitrogen-fixing bacteria get N2 from the atmosphere and make ammonium out of it in the process. 3. Which nitrogen cycle process contributes to greenhouse gases? a. Denitrification b. Nitrogen fixation c. Nitrogen mineralization d. Nitrification Answer: a. Denitrification takes the NO3 and turns it ultimately back into N2 gas. This process has intermediaries such as N2O gas, which is a greenhouse gas that contributes to global warming. It ultimately means that all of the burning of fossil fuels and the use of nitrogencontaining fertilizer is contributing to the N2O getting into the atmosphere.
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