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IB Biology > C.6 The nitrogen and phosphorus cycles > Flashcards

C.6 The nitrogen and phosphorus cycles Flashcards

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1
Q

What is the nitrogen cycle?

A

The biogeochemical cycle where nitrogen is converted into various chemical forms

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2
Q

What is unable to be used by plants and animals?

A

Nitrogen

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3
Q

What does chemoautotrophic bacteria convert nitrogen into?

A

Compounds that can be assimilated by plants and animals

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4
Q

What are the four components of the nitrogen cycle?

A

Nitrogen fixation
Ammonification
Nitrification
Dénitrification

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5
Q

What is the first stage of the nitrogen cycle?

A

Nitrogen fixation

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6
Q

What is nitrogen fixation?

A

The conversion of inert nitrogen gas into ammonia

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7
Q

What catalyses the conversion of nitrogen into ammonia?

A

The enzyme nitrogenase

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8
Q

What produces nitrogenase?

A

Nitrogen-fixing bacteria in the soil

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9
Q

When does ammonia become ammonium?

A

When mixed with water

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10
Q

What does Rhizobium supply ammonia to plants in exchange for?

A

Carbohydrates

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11
Q

How can ammonia be produced from organic sources of nitrogen?

A

When broken down by decomposers

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12
Q

In ammonification, what happens as a plant or animal decays?

A

Saprotrophs will decompose organic materials to produce ammonia

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13
Q

What does ammonification release?

A

Ammonium ions into the soil which can be absorbed by plants

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14
Q

What is nitrification?

A

The conversion of ammonium ions into nitrites and nitrates by nitrifying bacteria in the soil

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15
Q

What converts ammonium ions into nitrites?

A

Nitrosomonas

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16
Q

What do nitrobacters convert?

A

The nitrites into nitrates

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17
Q

What do nitrosomonas and nitrobacter reactions require?

A

Oxygen

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18
Q

If the reaction needs oxygen, what must the soil be?

A

Well aerated to ensure a rich supply of nitrites and nitrates

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19
Q

Why do nitrates and nitrites function as a predominant source of nitrogen for plants?

A

As they are easier for plants to assimilate

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20
Q

What is dentrification?

A

A chemical reduction process that converts nitrates into nitrogen gas

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21
Q

What carries out dentrification?

A

Denitrifying bacteria

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22
Q

When does denitrification occur?

A

In the absence of oxygen

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23
Q

What can be used instead of oxygen as an electron acceptor during cellular respiration?

A

Nitrates

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24
Q

When will nitrates be used during cellular respiration instead of oxygen?

A

In oxygen poor condition

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25
Q

What is reduced when nitrates are used instead of oxygen?

A

The availability of nitrates to plants

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26
Q

When does waterlogging occur?

A

When the soil becomes inundated with water through flooding or irrigation with poor drainage

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27
Q

How does waterlogging impact the nitrogen cycle?

A

By reducing the levels of nitrates and nitrites in the soil

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28
Q

Through which process does waterlogged soil lose nitrates and nitrites?

A

Denitrification and leaching

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29
Q

Where will there be a build up of water when rainfall exceeds evaporation?

A

Within porous soil

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30
Q

What happens as water drains downwards through the soil?

A

Soluble minerals are removed with it

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31
Q

What does continual leaching do to the upper layers of soil?

A

Impoverishes them

32
Q

What does the continual leaching do to the lower bedrock?

A

Concentrates dissolved minerals in the lower bedrock

33
Q

Where is leaching most common?

A

In highly porous soils

34
Q

Where is leaching least common?

A

In textured soils

35
Q

What does a reduction in nitrogen availability within the soil mean for plants?

A

That they are unable to access sufficient quantities of nitrogen from the soil via their roots

36
Q

How are insectivorous plants able to obtain nitrogen in low nutrient environments?

A

By feeding on invertebrates

37
Q

What is an example of an insectivorous plant?

A

Venus fly trap

38
Q

What happens when the insect is trapped in the plant?

A

Digestive enzymes are released that allow it to absorb nutrients from the insect

39
Q

How are insectivorous plants baited to attract insects?

A

By nectar

40
Q

What does the phosphorus cycle show?

A

How different forms of phosphorus are transitioned within the environment

41
Q

What do certain rocks contain high levels of?

A

Phosphate

42
Q

Where can the phosphate released from rocks end up?

A

Into the soil and water

43
Q

How do rocks that contain phosphate lose it to the soil and water?

A

Chemical weathering

44
Q

Why do organisms require phosphates?

A

To synthesise nucleic acids, membranes and ATP

45
Q

When are phosphates returned to the soil?

A

Upon the decomposition of plant and animal remains

46
Q

What does the phosphorous cycle not include?

A

A gaseous component

47
Q

Why is the rate of turnover in the phosphorus cycle much lower than other cycles?

A

Because it doesn’t have a gaseous component

48
Q

What are the two rates which are slower due to the fact there is no gaseous component in the phosphorus cycle?

A

Rate or turnover and replenishment

49
Q

How can phosphates be removed from the lithosphere?

A

Via mining

50
Q

What can phosphates be converted into?

A

Phosphate based fertilisers

51
Q

Why is turning phosphate into fertilisers good?

A

It allows phosphates that otherwise remain inaccessible in buried rock to become available for plant use

52
Q

Why are fertilisers good for plants?

A

It increases their productivity by increasing plant access to phosphate

53
Q

What happens to the phosphates that comprise part of the plants biomass when the crops are harvested?

A

They are lost from the phosphorus cycle

54
Q

What does using fertiliser in one site cause in another?

A

The depletion of phosphorus reserves

55
Q

What is the continued production of phosphate based fertilisers depleting?

A

Global phosphorus reserves

56
Q

What is contradictory about the demand for fertiliser but turnover in the phosphorus cycle?

A

Demand for fertiliser is high but turnover in the phosphorus cycle is low

57
Q

What are phosphate minerals classed as?

A

Non-renewable resource

58
Q

When is it predicted for phosphates to become severely restricted?

A

Within 50 - 100 years

59
Q

What is the problem with the possible future restriction of phosphates?

A

It would greatly limit the crop yield

60
Q

What is eutophication?

A

The enrichment of an ecosystem with chemical nutrients

61
Q

In eutrophication, how can nutrients be introduced?

A

Via leaching from soil by rainfall or released as part of sewage

62
Q

Where is eutrophication common?

A

Around agriculture lands where using fertilisers are prevalent

63
Q

What happens when there is an increase in nutrient supplies within waterways?

A

An algal bloom occurs but then they die. There is an increase in decomposers which results in increased oxygen demand by bacteria. Saprotrophs consume all available oxygen cleaning out the water supply. It also reduces oxygen production by seaweed

64
Q

What will stress the survival of marine organisms in eutrophication?

A

The reduced oxygen production of seaweeds

65
Q

What can eutrophication potentially lead to within the ecosystem?

A

A reduction in biodiversity

66
Q

What is the bulk of soil made up of?

A

A mixture of organic matter, rock and mineral particles

67
Q

What does the relative proportion of components of soil determine?

A

Soil type

68
Q

What can soil testing kits be used to identify ?

A

Nutrients
Soil ph
texture
water content

69
Q

How do soil testing kits test for nutrients?

A

Chemical reagents produce colour changes when testing for N, P and K

70
Q

How do soil testing kits test for soil pH?

A

Colour changes can be used to identify the acidity or alkalinity of a soil sample

71
Q

How can soil testing kits test for texture?

A

Soil can be separated into layers according to particle size

72
Q

How can soil testing kits test for water content?

A

Electrical meters can determine water quantities based on the soils capacity to transmit an electrical current

73
Q

Why do gardeners and farmers need to test their soil for the different components?

A

To determine the viability of the soil for planting purposes

74
Q
A
75
Q

Why do nitrates and nitrites function as a predominant source of nitrogen for plants?

A

IB Biology (57 decks)

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