The Nitrogen Cycle Quiz

What percentage of Earth's atmosphere is nitrogen?

• 50%

• 21%

• 92%

• 78%

Answer explanation

78% of Earth's atmosphere is nitrogen, making it the most abundant gas in the atmosphere.

Which of the following is an essential component of DNA, RNA, and proteins?

• Oxygen

• Carbon

• Hydrogen

• Nitrogen

Answer explanation

Nitrogen is an essential component of DNA, RNA, and proteins. It plays a crucial role in their structure and function.

What are the usable forms of nitrogen for plants and animals?

• Nitrates (NO3)

• Both ammonia and nitrates

• Nitrogen gas (N2)

• Ammonia (NH3)

Answer explanation

Plants and animals can use both ammonia and nitrates as forms of nitrogen. These forms provide essential nutrients for growth and development.

What is the first step of the nitrogen cycle?

• Ammonification

• Assimilation

• Nitrogen Fixation

• Nitrification

Answer explanation

The first step of the nitrogen cycle is Nitrogen Fixation, where atmospheric nitrogen is converted into a usable form by nitrogen-fixing bacteria.

Which bacteria convert atmospheric nitrogen (N2) into ammonia (NH4+)?

• Decomposer bacteria

• Denitrifying bacteria

• Nitrifying bacteria

• Nitrogen-fixing bacteria

Answer explanation

Nitrogen-fixing bacteria convert atmospheric nitrogen (N2) into ammonia (NH4+).

What is the process by which plants absorb ammonia or nitrates through their roots to make proteins?

• Nitrogen Fixation

• Assimilation

• Ammonification

• Nitrification

Answer explanation

Plants absorb ammonia or nitrates through their roots to make proteins in a process called assimilation.

What do decomposers like bacteria transform the nitrogen-containing parts of organic matter into?

• Nitrogen gas

• Ammonia

• Carbon

• Oxygen

Answer explanation

Decomposers like bacteria transform the nitrogen-containing parts of organic matter into ammonia, not nitrogen gas, carbon, or oxygen.

Which bacteria convert ammonia into nitrates?

• Nitrifying bacteria

• Denitrifying bacteria

• Nitrogen-fixing bacteria

• Decomposer bacteria

Answer explanation

Nitrifying bacteria convert ammonia into nitrates. They play a crucial role in the nitrogen cycle by oxidizing ammonia to nitrite and then to nitrate.

What is the process by which some bacteria convert nitrates in the soil to nitrogen gas?

• Nitrification

• Nitrogen Fixation

• Denitrification

• Ammonification

Answer explanation

Denitrification is the process where some bacteria convert nitrates in the soil to nitrogen gas. It is the correct choice.

How do fertilizers negatively influence the nitrogen cycle?

• Increase the amount of nitrogen in water environments

• Decrease the amount of oxygen in water environments

• Decrease the amount of nitrogen in water environments

• Increase the amount of oxygen in water environments

Answer explanation

Fertilizers negatively impact the nitrogen cycle by decreasing oxygen in water environments.