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MDCAT Biology QUESTION #11284
Question 1
The process by which nitrogen gas (N$_2$) from the atmosphere is converted into ammonia (NH$_3$) by bacteria is called:
  • Nitrification
  • Nitrogen fixation✔️
  • Denitrification
  • Ammonification
Correct Answer Explanation
Nitrogen fixation is the conversion of atmospheric N$_2$ into ammonia by nitrogen-fixing bacteria (e.g., Rhizobium in legume root nodules). Nitrification converts ammonia to nitrite and nitrate. Denitrification returns nitrogen gas to the atmosphere.