The Nitrogen Cycle

Question 1

Why is the nitrogen cycle important?

Answer 1

The nitrogen cycle is important because it allows animals and plants to find a way to absorb nitrogen as they cannot absorb nitrogen through normal gas exchange.

Question 2

What percentage of the air is made up of nitrogen?

Answer 2

78%

Question 3

Why can’t animals and plants absorb nitrogen through gas exchange?

Answer 3

Nitrogen contains a triple bond that makes it harder to break the compound

Question 4

What do animals and plants mainly need to absorb nitrogen?

Answer 4

Animals and plants mainly need microorganisms to convert nitrogen gas and plant materials substances

Question 5

How do animals nitrogen instead?
How do plants absorb nitrogen?

Answer 5

Animal absorb nitrogen by digesting food and plant materials

Plants absorb nitrogen through active transport in the roots

Question 6

What do plants need nitrogen for? How do plants get this nitrogen?

Answer 6

Plants need nitrogen to manufacture proteins which help in the growth of plants. Plants get their nitrogen from the soil - the nitrate ions are absorbed via active transport

Question 7

What are the four key stages of the nitrogen cycle?

Answer 7

Ammonification
Nitrification
Nitrogen fixation
Denitrification

Question 8

What bacteria is involved with nitrogen fixing? Where can the bacteria be found?

Answer 8

Nitrogen fixing bacteria for example Rhizobium. This bacteria can be found in the root nodules of legumes or can live freely in soil

Question 9

Legumes have nitrogen fixing bacteria in the root nodules. Give some examples of legumes (hint: starts with p, starts with b)

Answer 9

Pea plants and Bean plants

Question 10

What happens in the nitrogen fixing stage?

Answer 10

This is when the nitrogen fixing bacteria convert nitrogen from the air into ammonium ions, in a solution, that can be absorbed by the plants or remain in the soil

Question 11

What bacteria is involved with ammonification?

Answer 11

Saprobionts, a type of composer

Question 12

What happens in the stage of ammonification?

Answer 12

In ammonification, nitrogen compounds from dead organisms/animal waste are turned into ammonia by saprobionts. These go on to form ammonium ions

Question 13

What bacteria is involved with nitrification?

Answer 13

Nitrifying bacteria for example “nitrosomonas and nitrobacter

Question 14

What are the names of the nitrifying bacteria involved in nitrification?

Answer 14

Nitrosomonas and Nitrobacter

Question 15

What happens in the nitrification stage of the nitrogen cycle?

Answer 15

Nitrification involves the conversion of ammonium ions into nitrites and then nitrates. Nitrates can then be directly absorbed by plants

Question 16

What bacteria is involved in dentrification?

Answer 16

Denitrifying bacteria

Question 17

Where do denitrifying bacteria live?

Answer 17

Denitrifying bacteria live in anaerobic conditions for example water logged soil

Question 18

Denitrifying bacteria live in anaerobic conditions. What is a prime example of a living place that fits the description?

Answer 18

Waterlogged soil

Question 19

What happens in the stage denitrification in the nitrogen cycle

Answer 19

Denitrifying bacteria convert nitrates in the soil into nitrogen gas which is returned to the atmosphere.

Question 20

How does nitrogen fixing occur with lightning?

Answer 20

1. The high levels of heat energy produced from lightning can cause chemical reactions in the atmosphere.
2. This leads to nitrogen reacting to oxygen to form nitrous oxide.
3. This nitrous oxide reacts with more oxygen to then dissolve in rain water to form nitric acid.
4. This rain water containing nitric acid adds to the amount of the nitrate in the salt

Question 21

How does nitrogen fixing occur with the ocean?

Answer 21

In the ocean species of blue green algae. known as cyanobacteria, “fix” nitrogen. The blue green algae act as a source of nitrogen for the aquatic animals