2.2 - The Nitrogen Cycle

Question 1

Where is the largest store of nitrogen located?

Answer 1

In the atmosphere, where it exists as N2

Question 2

What are some other major nitrogen stores other than the atmosphere?

Answer 2

Oceans and organic matter in soil.

Question 3

What are some minor nitrogen stores?

Answer 3

Terrestrial ecosystems, living organisms, lakes and marshes.

Question 4

How much of earth’s atmosphere is nitrogen?

Answer 4

78%, but most organisms cannot use it.

Question 5

What are the three processes of the nitrogen cycle?

Answer 5

Nitrogen fixation, nitrification, uptake.

Question 6

What is nitrogen fixation?

Answer 6

The process when nitrogen gas is converted into compounds that contain nitrate or ammonium. Which are usable by plants.

Question 7

Name the three ways nitrogen fixation occurs?

Answer 7

The atmosphere, in the soil and in water bodies

Question 8

What happens in atmospheric nitrogen fixation?

Answer 8

Nitrogen gas is converted into nitrate and other nitrate containing compounds by lightning. Nitrogen reacts with oxygen using the energy provided by the lightning discharge of static electricity. The nitrogen compounds enter the ecosystems in the rainfall.

Question 9

What happens in nitrogen fixation in soil?

Answer 9

Nitrogen gas gets converted into ammonium by bacteria during the decomposition process.

Question 10

How does nitrogen fixation occur in water?

Answer 10

Aquatic species (ex. Cyanobacteria) fix nitrogen into ammonium.

Question 11

What are nitrogen fixing bacteria?

Answer 11

Bacteria that convert convert nitrogen gas into ammonium during decomposition.

Question 12

What is nitrification?

Answer 12

When ammonium is converted into nitrate. There are two stages.

Question 13

What are nitrifying bacteria?

Answer 13

Soil bacteria involved in two stages of nitrification.

Question 14

What are the two stages of nitrification?

Answer 14

1. Certain nitrifying bacteria species convert ammonium into nitrite.
2. Different nitrifying bacteria species convert nitrite into nitrate.

Question 15

What is uptake?

Answer 15

When nitrate are taken up by plants by their roots and are incorporated into plant proteins.

Question 16

What is denitrification?

Answer 16

The process where nitrogen is returned to the atmosphere.

Question 17

What are denitrifying bacteria?

Answer 17

Bacteria that convert bacteria nitrate back into nitrogen gas.

Question 18

In what form is nitrogen returned to the atmosphere?

Answer 18

As ammonium

Question 19

What happens to excess nitrate and ammonium that isn’t used in uptake?

Answer 19

They mix with rainwater and are washed from the soil mixing in with streams and water. They may later settle at the bottom of the ocean, lake stream, etc in sediments. These sediments will layer form rock.

Question 20

What are some human activities that change the nitrogen cycle?

Answer 20

Clearing forests and grasslands, fossil fuel combustion in power plants, burning fossil fuels using vehicle, and using chemical fertilizers.

Question 21

When did the use of chemical fertilizers begin?

Answer 21

In the 1800s

Question 22

What is leaching?

Answer 22

The removal by water of substances that have dissolved into the moist soil.

Question 23

What is eutrophication?

Answer 23

The process by which excess nutrients result in increased plant production and decay.

Question 24

Why is nitrogen so important to living things?

Answer 24

It is an important component of DNA and proteins, which are essential for the life processes that occur inside of cells.