AP Environmental Science Flashcards: The Nitrogen Cycle

What this deck covers

This deck focuses on The Nitrogen Cycle, giving you a quick way to review the definitions, rules, and examples that matter most for AP Environmental Science.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Identify the process that converts atmospheric nitrogen into ammonia.

Answer: Nitrogen fixation. Breaks the strong triple bond in $N_2$ to create bioavailable forms.

Flashcard 2: Name one impact of industrial nitrogen fixation.

Answer: Increased crop yields. Synthetic fertilizers dramatically boost agricultural productivity.

Flashcard 3: What is the chemical formula for ammonia?

Answer: $NH_3$. Product of nitrogen fixation with one nitrogen and three hydrogens.

Flashcard 4: What is the main function of nitrogen-fixing bacteria in root nodules?

Answer: Convert $N_2$ to ammonia. Use nitrogenase to break triple bonds in atmospheric nitrogen.

Flashcard 5: What is the main reservoir of nitrogen in the nitrogen cycle?

Answer: The atmosphere. Contains 78% of Earth's nitrogen in unreactive $N_2$ form.

Flashcard 6: Which process involves the conversion of nitrates back to nitrogen gas?

Answer: Denitrification. Anaerobic bacteria reduce nitrates, completing the nitrogen cycle.

Flashcard 7: Identify one environmental issue caused by excess nitrogen from agriculture.

Answer: Water pollution. Runoff causes eutrophication and groundwater contamination.

Flashcard 8: What is the primary impact of nitrogen oxides in the atmosphere?

Answer: Acid rain formation. Nitrogen oxides react with water to form nitric acid.

Flashcard 9: What is the main form of nitrogen found in fertilizers?

Answer: Ammonium nitrate. Common synthetic fertilizer providing readily available nitrogen.

Flashcard 10: Identify the form of nitrogen that plants can directly absorb and use.

Answer: Nitrates ($NO_3^-$). Most oxidized and soluble form readily absorbed by plant roots.

Flashcard 11: What is the chemical formula for nitrous oxide?

Answer: $N_2O$. Two nitrogen atoms bonded to one oxygen atom.

Flashcard 12: Identify the process that converts nitrates to nitrogen gas in waterlogged soils.

Answer: Denitrification. Occurs in oxygen-poor conditions like wetlands and sediments.

Flashcard 13: Which soil bacteria convert ammonia into nitrites?

Answer: Nitrifying bacteria. First step in two-stage nitrification process.

Flashcard 14: What is the primary impact of nitrogen oxides in the atmosphere?

Answer: Acid rain formation. Nitrogen oxides react with water to form nitric acid.

Flashcard 15: What is the main form of nitrogen found in fertilizers?

Answer: Ammonium nitrate. Common synthetic fertilizer providing readily available nitrogen.

Flashcard 16: What is the chemical formula for nitrous oxide?

Answer: $N_2O$. Two nitrogen atoms bonded to one oxygen atom.

Flashcard 17: What is the impact of nitrogen on the atmosphere when released as a pollutant?

Answer: Contributes to smog. Nitrogen oxides contribute to photochemical air pollution.

Flashcard 18: Identify the nitrogen compound that plants primarily absorb from soil.

Answer: Nitrates ($NO_3^-$). Highly soluble and mobile form preferred by most plants.

Flashcard 19: What is the impact of nitrogen on the atmosphere when released as a pollutant?

Answer: Contributes to smog. Nitrogen oxides contribute to photochemical air pollution.

Flashcard 20: Name the process that involves the conversion of ammonium to nitrite.

Answer: Nitrification. First oxidation step in the two-stage nitrification process.

Flashcard 21: Identify the nitrogen compound that contributes to greenhouse gas emissions.

Answer: Nitrous oxide ($N_2O$). Potent greenhouse gas with 300 times warming potential of $CO_2$.

Flashcard 22: What process converts organic nitrogen in dead organisms to ammonia?

Answer: Ammonification. Decomposition releases ammonia from organic nitrogen compounds.

Flashcard 23: What type of bacteria is responsible for converting nitrites to nitrates?

Answer: Nitrifying bacteria. Complete the nitrification process by oxidizing nitrites.

Flashcard 24: Name the process by which ammonia is converted to nitrites and nitrates.

Answer: Nitrification. Two-step oxidation process performed by soil bacteria.

Flashcard 25: Which process releases ammonium ions from organic matter?

Answer: Ammonification. Bacterial decomposition converts organic nitrogen to inorganic forms.

Flashcard 26: What is the process called when plants uptake nitrates from the soil?

Answer: Assimilation. Plants absorb nitrogen compounds through their root systems.

Flashcard 27: Identify the process that converts nitrates to nitrogen gas in waterlogged soils.

Answer: Denitrification. Occurs in oxygen-poor conditions like wetlands and sediments.

Flashcard 28: Identify the key enzyme used by bacteria to fix nitrogen.

Answer: Nitrogenase. Catalyzes the energy-intensive conversion of $N_2$ to $NH_3$.

Flashcard 29: Which process in the nitrogen cycle is anaerobic?

Answer: Denitrification. Requires oxygen-free environment for bacteria to function.

Flashcard 30: State the role of lightning in the nitrogen cycle.

Answer: Nitrogen fixation. High energy electrical discharge breaks $N_2$ bonds naturally.

Flashcard 31: What is the main function of nitrogen-fixing bacteria in root nodules?

Answer: Convert $N_2$ to ammonia. Use nitrogenase to break triple bonds in atmospheric nitrogen.

Flashcard 32: What is the process called when plants uptake nitrates from the soil?

Answer: Assimilation. Plants absorb nitrogen compounds through their root systems.

Flashcard 33: Identify the key enzyme used by bacteria to fix nitrogen.

Answer: Nitrogenase. Catalyzes the energy-intensive conversion of $N_2$ to $NH_3$.

Flashcard 34: State the role of legumes in the nitrogen cycle.

Answer: Host nitrogen-fixing bacteria. Provide shelter and nutrients for nitrogen-fixing bacteria.

Flashcard 35: Identify one environmental issue caused by excess nitrogen from agriculture.

Answer: Water pollution. Runoff causes eutrophication and groundwater contamination.

Flashcard 36: Which organism type is crucial for the nitrogen cycle in aquatic systems?

Answer: Cyanobacteria. Blue-green algae that fix nitrogen in marine environments.

Flashcard 37: Identify the nitrogen compound that plants primarily absorb from soil.

Answer: Nitrates ($NO_3^-$). Highly soluble and mobile form preferred by most plants.

Flashcard 38: Identify the process that bacteria use to convert ammonia into nitrite.

Answer: Nitrification. First step in nitrification where ammonia becomes nitrite.

Flashcard 39: Which gas is released during the process of denitrification?

Answer: Nitrogen gas ($N_2$). Returns nitrogen to atmosphere, completing the cycle.

Flashcard 40: What organisms primarily perform nitrogen fixation?

Answer: Nitrogen-fixing bacteria. Contain nitrogenase enzyme that converts $N_2$ to $NH_3$.

Flashcard 41: Identify the product when nitrogen gas is fixed by bacteria.

Answer: Ammonia ($NH_3$). Direct product of nitrogen fixation by bacterial nitrogenase.

Flashcard 42: Name one impact of industrial nitrogen fixation.

Answer: Increased crop yields. Synthetic fertilizers dramatically boost agricultural productivity.

Flashcard 43: Name the process by which ammonia is converted to nitrites and nitrates.

Answer: Nitrification. Two-step oxidation process performed by soil bacteria.

Flashcard 44: What is the chemical formula for nitrite?

Answer: $NO_2^-$. Intermediate form with one nitrogen and two oxygen atoms.

Flashcard 45: What is the main consequence of excess nitrogen in aquatic systems?

Answer: Eutrophication. Excess nitrogen causes algal blooms and oxygen depletion.

Flashcard 46: State the role of legumes in the nitrogen cycle.

Answer: Host nitrogen-fixing bacteria. Provide shelter and nutrients for nitrogen-fixing bacteria.

Flashcard 47: What is the main reservoir of nitrogen in the nitrogen cycle?

Answer: The atmosphere. Contains 78% of Earth's nitrogen in unreactive $N_2$ form.

Flashcard 48: What is the final product of the denitrification process?

Answer: Nitrogen gas ($N_2$). Completes the nitrogen cycle by returning to atmosphere.

Flashcard 49: Which soil bacteria convert ammonia into nitrites?

Answer: Nitrifying bacteria. First step in two-stage nitrification process.

Flashcard 50: What organisms primarily perform nitrogen fixation?

Answer: Nitrogen-fixing bacteria. Contain nitrogenase enzyme that converts $N_2$ to $NH_3$.

Flashcard 51: What is the first step in the nitrogen cycle that involves atmospheric nitrogen?

Answer: Nitrogen fixation. Converts inert atmospheric $N_2$ into reactive compounds.

Flashcard 52: Identify the process that converts atmospheric nitrogen into ammonia.

Answer: Nitrogen fixation. Breaks the strong triple bond in $N_2$ to create bioavailable forms.

Flashcard 53: Which organism type is crucial for the nitrogen cycle in aquatic systems?

Answer: Cyanobacteria. Blue-green algae that fix nitrogen in marine environments.

Flashcard 54: State the effect of nitrogen on plant growth.

Answer: Promotes growth. Essential nutrient for protein synthesis and chlorophyll production.

Flashcard 55: Which process in the nitrogen cycle is anaerobic?

Answer: Denitrification. Requires oxygen-free environment for bacteria to function.

Flashcard 56: What process converts organic nitrogen in dead organisms to ammonia?

Answer: Ammonification. Decomposition releases ammonia from organic nitrogen compounds.

Flashcard 57: Which process releases ammonium ions from organic matter?

Answer: Ammonification. Bacterial decomposition converts organic nitrogen to inorganic forms.

Flashcard 58: Which process involves the conversion of nitrates back to nitrogen gas?

Answer: Denitrification. Anaerobic bacteria reduce nitrates, completing the nitrogen cycle.

Flashcard 59: What is the chemical formula for ammonia?

Answer: $NH_3$. Product of nitrogen fixation with one nitrogen and three hydrogens.

Flashcard 60: Identify the form of nitrogen that plants can directly absorb and use.

Answer: Nitrates ($NO_3^-$). Most oxidized and soluble form readily absorbed by plant roots.

Flashcard 61: Name the symbiotic relationship between legumes and nitrogen-fixing bacteria.

Answer: Mutualism. Both organisms benefit from the nitrogen-fixing relationship.

Flashcard 62: State the chemical formula for nitrate.

Answer: $NO_3^-$. One nitrogen atom with three oxygen atoms and negative charge.

Flashcard 63: Which gas is released during the process of denitrification?

Answer: Nitrogen gas ($N_2$). Returns nitrogen to atmosphere, completing the cycle.

Flashcard 64: State the role of lightning in the nitrogen cycle.

Answer: Nitrogen fixation. High energy electrical discharge breaks $N_2$ bonds naturally.

Flashcard 65: Identify the process that bacteria use to convert ammonia into nitrite.

Answer: Nitrification. First step in nitrification where ammonia becomes nitrite.

Flashcard 66: What is the chemical formula for nitrite?

Answer: $NO_2^-$. Intermediate form with one nitrogen and two oxygen atoms.

Flashcard 67: What is the role of decomposers in the nitrogen cycle?

Answer: Ammonification. Break down proteins and nucleic acids, releasing ammonia.

Flashcard 68: What is the main consequence of excess nitrogen in aquatic systems?

Answer: Eutrophication. Excess nitrogen causes algal blooms and oxygen depletion.

Flashcard 69: What type of bacteria is responsible for converting nitrites to nitrates?

Answer: Nitrifying bacteria. Complete the nitrification process by oxidizing nitrites.

Flashcard 70: Which human activity contributes significantly to nitrogen fixation?

Answer: Fertilizer production. Industrial Haber-Bosch process creates synthetic nitrogen compounds.

Flashcard 71: Which human activity contributes significantly to nitrogen fixation?

Answer: Fertilizer production. Industrial Haber-Bosch process creates synthetic nitrogen compounds.

Flashcard 72: Name the symbiotic relationship between legumes and nitrogen-fixing bacteria.

Answer: Mutualism. Both organisms benefit from the nitrogen-fixing relationship.

Flashcard 73: What is the first step in the nitrogen cycle that involves atmospheric nitrogen?

Answer: Nitrogen fixation. Converts inert atmospheric $N_2$ into reactive compounds.

Flashcard 74: Name the process that involves the conversion of ammonium to nitrite.

Answer: Nitrification. First oxidation step in the two-stage nitrification process.

Flashcard 75: What is the final product of the denitrification process?

Answer: Nitrogen gas ($N_2$). Completes the nitrogen cycle by returning to atmosphere.

Flashcard 76: Identify the product when nitrogen gas is fixed by bacteria.

Answer: Ammonia ($NH_3$). Direct product of nitrogen fixation by bacterial nitrogenase.

Flashcard 77: What is the role of decomposers in the nitrogen cycle?

Answer: Ammonification. Break down proteins and nucleic acids, releasing ammonia.

Flashcard 78: State the chemical formula for nitrate.

Answer: $NO_3^-$. One nitrogen atom with three oxygen atoms and negative charge.

Flashcard 79: Identify the nitrogen compound that contributes to greenhouse gas emissions.

Answer: Nitrous oxide ($N_2O$). Potent greenhouse gas with 300 times warming potential of $CO_2$.

Flashcard 80: State the effect of nitrogen on plant growth.

Answer: Promotes growth. Essential nutrient for protein synthesis and chlorophyll production.