Question 1

Which process in the nitrogen cycle converts atmospheric nitrogen ($$N_2) $$into a form usable by plants?

Accepted Answer

Nitrogen fixation

Question 2

What is the primary role of decomposers such as fungi and bacteria in the nitrogen cycle?

Accepted Answer

They break down organic matter, releasing ammonia ($$NH_3) $$into the soil

Question 3

Which of the following equations correctly represents the process of nitrification?

Accepted Answer

$$NH_4$$^+ \rightarrow $$NO_2$$^- \rightarrow $$NO_3$$^-$$

Question 4

Human activities such as the combustion of fossil fuels primarily affect which aspect of the nitrogen cycle?

Accepted Answer

Increase in nitrogen oxides released into the atmosphere

Question 5

A farmer applies synthetic fertilizers to his crops. Which process is most directly affected by this action?

Accepted Answer

Nitrification

Question 6

Which step in the nitrogen cycle is responsible for returning nitrogen to the atmosphere?

Accepted Answer

Denitrification

Question 7

Plants primarily absorb nitrogen from the soil in which chemical form?

Accepted Answer

$$NO_3$$^-$$

Question 8

Which of the following best describes the process of ammonification?

Accepted Answer

Conversion of organic nitrogen into ammonia ($$NH_3)$$

Question 9

Which group of organisms is primarily responsible for nitrogen fixation in the soil?

Accepted Answer

Nitrogen-fixing bacteria

Question 10

If denitrification rates increase due to changes in soil conditions, what is the most likely consequence for the ecosystem?

Accepted Answer

Decrease in available nitrogen for plants

Question 11

Which of the following is a multi-step process involving both nitrifying and denitrifying bacteria?

Accepted Answer

Conversion of $$NH_4$$^+$$ to NO_3$^-$$ and then $$NO_3$$^-$$ to N_2$

Question 12

Which of the following best explains why excessive use of nitrogen fertilizers can lead to water pollution?

Accepted Answer

Fertilizers increase nitrate ($$NO_3$$^-$$) runoff, causing eutrophication

Question 13

Which chemical reaction represents the process of denitrification?

Accepted Answer

$$NO_3$$^- \rightarrow $$N_2$$

Question 14

In a scenario where soil bacteria are killed by pollution, which process in the nitrogen cycle would be most directly disrupted?

Accepted Answer

Nitrogen fixation

Question 15

Which of the following is NOT a direct result of ammonification?

Accepted Answer

Increase in organic nitrogen in the soil

Question 16

Which process allows plants to incorporate nitrogen into amino acids?

Accepted Answer

Assimilation

Question 17

A soil sample contains high levels of $$NO_2$$^-$$. Which process is most likely occurring at a high rate?

Accepted Answer

Nitrification

Question 18

Which of the following is a consequence of reduced denitrification in agricultural soils?

Accepted Answer

Accumulation of nitrate ($$NO_3$$^-$$) in the soil

Question 19

Which process in the nitrogen cycle is most dependent on anaerobic conditions?

Accepted Answer

Denitrification

Question 20

Which of the following best describes the relationship between plants and nitrogen-fixing bacteria?

Accepted Answer

Bacteria convert atmospheric $$N_2$$ into ammonia ($$NH_3) $$that plants can use

The Nitrogen Cycle: Roles of Bacteria and Biological Processes

Study Guide - Practice Questions