Nitrogen cycle (F25)

Open Ended

In what ways do you think the nitrogen cycle might impact life on Earth?

Multiple Choice

Why is nitrogen considered an essential element for living organisms?

• Because it is a component of DNA, RNA, and proteins

• Because it is the most abundant gas in the atmosphere

• Because it is a source of energy for plants

• Because it is used in respiration

Multiple Choice

Why is most of the nitrogen in the atmosphere unavailable for use by organisms?

• Because it is in the form of N2, which is very stable and not easily broken down by most organisms.

• Because it is toxic to living things.

• Because it is dissolved in water.

• Because it reacts quickly with oxygen.

Open Ended

Explain why plants and animals cannot use nitrogen gas (N2) directly from the atmosphere. What must happen for them to be able to use nitrogen?

Multiple Select

Which of the following are products or steps in the nitrogen cycle?

• Nitrates

• Ammonia

• Nitrites

• All of the above

Open Ended

What is nitrogen fixation and what are the two elements nitrogen combines with during this process?

Multiple Choice

Which of the following is NOT a way nitrogen can be fixed?

• By special bacteria converting N2 to NH3

• By lightning strikes converting N2 to N2O or NO3-

• By plants absorbing N2 directly from the air

• By industrial production turning N2 into NH3

Multiple Choice

What is the main purpose of nitrogen assimilation in plants?

• To absorb nitrates and ammonia and convert them into organic nitrogen

• To release nitrogen gas into the atmosphere

• To decompose dead organisms

• To produce oxygen for animals

Open Ended

Describe how the processes of assimilation and ammonification are connected in the nitrogen cycle.

Open Ended

Explain how the process of ammonification contributes to the nitrogen cycle.

Multiple Choice

Which type of bacteria is responsible for converting nitrate (NO3-) back to atmospheric nitrogen (N2) in the nitrogen cycle?

• Nitrifying bacteria

• Denitrifying bacteria

• Nitrogen-fixing bacteria

• Decomposers

Multiple Select

Which of the following are possible consequences of excess nitrogen fertilizer use as described in the slides?

• Contamination of surface water

• Respiratory distress in infants

• Increased oxygen production

• Cancer in humans

Multiple Choice

Why is nitrogen important for living organisms?

• It is a component of DNA, RNA, and proteins

• It provides energy directly

• It is the main source of oxygen

• It is not required by organisms

Multiple Choice

Which of the following is a consequence of nutrient over-enrichment in surface waters due to extra nitrogen?

• Fish-kills

• Increased oxygen levels

• Reduced plant growth

• Cleaner water