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Biology: 04 - Ecology > The Nitrogen Cycle - Stages > Flashcards

The Nitrogen Cycle - Stages Flashcards

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1
Q

What do living things need the element nitrogen to make?

4

A

Proteins

DNA

RNA

Other biomolecules

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2
Q

What is the chemical formula for nitrogen gas?

A

N2

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3
Q

What percentage of the air is made up of nitrogen gas?

A

79%

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4
Q

Why can’t the nitrogen gas in air be used by organisms?

A

Because it is inert or unreactive and cannot be used by plants and animals

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5
Q

Define nitrogen fixation.

A

Nitrogen fixation is the conversion of nitrogen gas into ammonia (NH3), ammonium (NH4+) or nitrate (NO3-)

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6
Q

What is the formula for ammonia?

A

NH3

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7
Q

What is the formula for ammonium?

A

NH4+

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8
Q

What is the formula for nitrate?

A

NO3-

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9
Q

What is nitrogen fixation carried out by?

4

A

Volcanic action

Lightning

Industrial processes

By nitrogen-fixing bacteria

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10
Q

Where can nitrogen-fixing bacteria be found?

2

A

They can be found free in the soil

They may be associated with the roots of certain plants

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11
Q

Some nitrogen-fixing bacteria may be associated with the roots of certain plants, where exactly are they found.

A

They live in nodules (swellings) on the roots of a group of plants called legumes,

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12
Q

Some nitrogen-fixing bacteria live in nodules on the roots of what group of plants?

A

Legumes

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13
Q

Where do nitrogen-fixing bacteria live in legumes?

A

In nodules on the roots

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14
Q

Give four examples of legumes which have nitrogen-fixing bacteria living in nodules on their roots.

A

Clover

Soya beans

Peas

Beans

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15
Q

Is nitrogen-fixation an aerobic or anaerobic process?

A

Nitrogen fixation is an anaerobic process

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16
Q

Nitrogen fixation is an anaerobic process, what does this mean?

A

This means it does not require oxygen

17
Q

Nitrogen-fixation is an anaerobic process, how is it adapted for this process.

A

The nodules on roots allow the nitrogen-fixing bacteria to escape from oxygen

18
Q

How can the relationship between the nitrogen-fixing bacteria and the legume be described?

A

It can be described as a form of symbiosis

19
Q

Describe the symbiotic relationship between the nitrogen-fixing bacteria and the legume.

A

The bacteria get food and the plant gets nitrates (this is technically mutualism)

20
Q

What are nitrates converted into?

A

They are converted into plant and animal protein, DNA and RNA

21
Q

What organisms bring about decomposition?

A

Bacteria and fungi of decay

22
Q

What do bacteria and fungi of decay cause the decomposition of?

A

The decomposition of dead organisms

23
Q

Where are bacteria and fungi of decay mostly found?

A

They are mostly found in the soil

24
Q

What is released when bacteria and fungi of decay decompose dead organisms?

A

These organisms release nitrogenous compounds such as ammonia (NH3) into the soil

25
Q

Define nitrification.

A

Nitrification is the conversion of ammonia and ammonium (NH4+) compounds to nitrite and then to nitrate

26
Q

What carries out nitrification?

A

Nitrifying bacteria

27
Q

Where are nitrifying bacteria found?

A

They are found in the soil

28
Q

How do nitrifying bacteria get their food?

A

They are chemosynthetic, i.e. they make their own food (normally in darkness in the soil) using energy from chemical reactions

29
Q

What happens to some of the nitrate made by nitrifying bacteria?

A

Some of the nitrate formed in the soil is absorbed and used by plants

30
Q

Define denitrification.

A

Denitrification is the conversion of nitrates to nitrogen gas

31
Q

What carried out denitrification?

A

Denitrifying bacteria

32
Q

Where are denitrifying bacteria found?

A

In the soil

33
Q

Are denitrifying bacteria aerobic or anaerobic?

A

They are anaerobic

34
Q

Where is the preferred place for denitrifying bacteria to live?

A

Swampy soil or deep down in the soil where water collects to produce anaerobic conditions

35
Q

Why do denitrifying bacteria like living deep down in the soil?

A

As water collects here to produce anaerobic conditions

36
Q

List the stages of the nitrogen cycle.

6

A
  1. Describe the need for the nitrogen cycle
  2. Nitrogen fixation
  3. Decomposition
  4. Nitrification
  5. Plants absorb nitrate
  6. Denitrification

Biology: 04 - Ecology (29 decks)

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