The Aquarium Nitrogen Cycle

Multiple Choice

What percentage of Earth's atmosphere is made up of nitrogen gas (N₂)?

• 21%

• 78%

• 50%

• 10%

Multiple Choice

Which of the following is NOT a component that nitrogen is a key part of?

• Amino acids

• Proteins

• DNA

• Carbohydrates

Multiple Choice

Which nitrogen compound is least toxic but harmful in high amounts?

• Ammonia (NH₃)

• Nitrite (NO₂⁻)

• Nitrate (NO₃⁻)

• Hydrogen (H₂)

Fill in the Blanks

The nitrogen cycle is a vital biogeochemical process that describes how nitrogen moves through Earth's ecosystems. The steps of the nitrogen cycle include:

1. Nitrogen Fixation: The cycle begins with nitrogen fixation, where atmospheric

(N₂) is converted into biologically usable forms like ammonia (NH₃) by nitrogen-fixing bacteria in soil or root nodules of legumes, or through lightning strikes.

Fill in the Blanks

The nitrogen cycle is a vital biogeochemical process that describes how nitrogen moves through Earth's ecosystems. The steps of the nitrogen cycle include:

2.

: Plants absorb the fixed nitrogen compounds through their roots and incorporate them into organic compounds like amino acids and nucleic acids, which are then consumed by animals and other organisms.

Fill in the Blanks

The nitrogen cycle is a vital biogeochemical process that describes how nitrogen moves through Earth's ecosystems. The steps of the nitrogen cycle include:

3. Ammonification: When plants and animals die or produce waste, decomposers break down the organic nitrogen compounds, releasing

(NH₃) back into the environment.

Fill in the Blanks

The nitrogen cycle is a vital biogeochemical process that describes how nitrogen moves through Earth's ecosystems. The steps of the nitrogen cycle include:

4. Nitrification: Nitrifying bacteria in the soil convert ammonia first into nitrites (NO₂⁻) and then into

(NO₃⁻), which are forms of nitrogen that plants can readily use.

Fill in the Blanks

The nitrogen cycle is a vital biogeochemical process that describes how nitrogen moves through Earth's ecosystems. The steps of the nitrogen cycle include:

5.

: Under anaerobic conditions, denitrifying bacteria convert nitrates back into atmospheric nitrogen (N₂), completing the cycle and returning nitrogen to the atmosphere.

Multiple Choice

What is the process of establishing biological filtration in an aquarium called?

• Cycling

• Filtering

• Cleaning

• Aerating

Multiple Choice

What substances are quickly consumed during the cycling process in an aquarium?

• Oxygen and carbon dioxide

• Ammonia and nitrites

• Salt and sugar

• Chlorine and fluoride

Multiple Choice

How long can it take to complete the cycling process when establishing a new tank?

• Days or weeks

• Weeks or months

• Hours or days

• Months or years

Multiple Choice

What can speed up the cycling process in an aquarium?

• Adding nitrifying bacteria

• Increasing water temperature

• Reducing light exposure

• Adding more fish

Multiple Choice

How can bacterial growth be encouraged in an aquarium?

• By adding more fish

• By providing surfaces to live on

• By reducing water changes

• By increasing light exposure

Open Ended

Summarize the process of maintaining safe nitrogen levels in a fish tank.