AP Biology Questions on the Nitrogen Cycle with Answers

📚 Quick Study Guide

• 🌍 Nitrogen Fixation: 🦠 Conversion of atmospheric nitrogen ($N_2$) into ammonia ($NH_3$) or ammonium ($NH_4^+$) by bacteria.
• 🌱 Ammonification: 🍂 Decomposition of organic matter releases ammonia ($NH_3$).
• 🧪 Nitrification: ⚗️ Two-step process: First, bacteria convert ammonia ($NH_3$) to nitrite ($NO_2^-$). Second, different bacteria convert nitrite ($NO_2^-$) to nitrate ($NO_3^-$).
• 🌳 Assimilation: 🥬 Plants absorb ammonium ($NH_4^+$) and nitrate ($NO_3^-$) through their roots and incorporate them into organic molecules (proteins, nucleic acids).
• 🔥 Denitrification: 💨 Conversion of nitrate ($NO_3^-$) back into atmospheric nitrogen ($N_2$) by bacteria in anaerobic conditions.
• 💧 Key Players: 🔑 Bacteria play the most crucial roles in all steps of the nitrogen cycle.
• ⚡ Human Impact: 💥 Excessive use of fertilizers can disrupt the nitrogen cycle, leading to environmental problems.

Practice Quiz

1. Which of the following processes converts atmospheric nitrogen into ammonia?
   1. A. Denitrification
   2. B. Nitrification
   3. C. Nitrogen Fixation
   4. D. Assimilation
2. Which type of bacteria is primarily responsible for converting ammonia into nitrite?
   1. A. Denitrifying bacteria
   2. B. Nitrogen-fixing bacteria
   3. C. Nitrosomonas bacteria
   4. D. Pseudomonas bacteria
3. What is the role of plants in the nitrogen cycle?
   1. A. To release nitrogen gas into the atmosphere
   2. B. To convert nitrate into nitrite
   3. C. To assimilate ammonia and nitrate into organic compounds
   4. D. To decompose organic matter
4. Under what conditions does denitrification primarily occur?
   1. A. Aerobic conditions
   2. B. Anaerobic conditions
   3. C. High temperature conditions
   4. D. Low pH conditions
5. Which of the following is the final product of nitrification?
   1. A. Ammonia
   2. B. Nitrite
   3. C. Nitrate
   4. D. Nitrogen gas
6. Decomposers contribute to the nitrogen cycle through which process?
   1. A. Nitrogen fixation
   2. B. Ammonification
   3. C. Nitrification
   4. D. Denitrification
7. What is the main environmental impact of excessive fertilizer use on the nitrogen cycle?
   1. A. Decreased plant growth
   2. B. Increased atmospheric nitrogen
   3. C. Disruption of the nitrogen cycle and water pollution
   4. D. Enhanced denitrification