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A-level Biology > 5B - Nutrient cycles > Flashcards

5B - Nutrient cycles Flashcards

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1
Q

What 2 nutrient cycles do we need to know?

A

Nitrogen cycle and phosphorus cycle.

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2
Q

What two things have an important role in nutrient recycling?

A

Bacteria and fungi

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3
Q

What is a natural ecosystem?

A

One that hasn’t been changed by human activity.

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4
Q

How are nutrients recycled in a natural ecosystem?

A

Through food webs.

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5
Q

What often disrupts the recycling of nutrients through food webs in a natural ecosystem?

A

Human activity

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6
Q

Why are fungi and bacteria important in food webs?

A

Because many are saprobionts (a type of decomposer) - they feed on the remains of dead plants and animals and on their waste products (faeces, urine), breaking them down. This allows important chemical elements in the remains to be recycled.

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7
Q

How do saprobionts get their nutrients?

A

They secrete enzymes and digest their food externally, then absorb the nutrients they need.

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8
Q

What is it called when saprobionts digest their food externally?

A

Extracellular digestion.

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9
Q

What is extracellular digestion?

A

When saprobionts digest their food externally.

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10
Q

What happens during the process of extracellular digestion in saprobionts?

A

Organic molecules are broken down into inorganic ions.

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11
Q

What is obtaining nutrients from dead organic matter using extracellular digestion known as?

A

Saprobiontic nutrition.

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12
Q

What is saprobiontic nutrition?

A

Obtaining nutrients from dead organic matter using extracellular digestion.

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13
Q

What are mycorrhizae?

A

Associations/symbiotic relationships between fungi and the roots of plants.

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14
Q

What are the symbiotic/mutualistic relationships between fungi and the roots of plants known as?

A

Mycorrhizae.

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15
Q

What are mycorrhizae made up of?

A

Fungi and the roots of plants.

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16
Q

What are the fungi in mycorrhizae like?

A

Made up of long, thin strands called hyphae, which connects to the plant’s roots.

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17
Q

How do mycorrhizae help plants?

A

The fungi have hyphae which connect to the plant’s roots, greatly increasing the SA of the plant’s root system, helping the plant to absorb ions from the soil that are usually scarce (e.g. phosphorus). Hyphae also increase the uptake of water by the plant.

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18
Q

Why is the relationship between the plant and fungi mutualistic?

A

The plant gets water and nutrients and the fungi obtains organic compounds such as glucose.

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19
Q

What does the nitrogen cycle show?

A

How nitrogen is recycled in ecosystems.

How nitrogen is converted into a usable form and then passed on between different living organisms and the non-living environment.

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20
Q

Why do plants and animals need nitrogen?

A

To make proteins and nucleic acids (DNA and RNA).

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21
Q

How much of the atmosphere is made up of nitrogen gas?

A

About 78%.

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22
Q

Can plants and animals use nitrogen in its atmospheric/gaseous form?

A

No

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23
Q

What do plants and animals need for them to use the nitrogen gas from the atmosphere?

A

They need bacteria to convert it into nitrogen-containing compounds first.

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24
Q

What does the nitrogen cycle include?

A

Food chains (nitrogen is passed on when organisms are eaten), and four different processes that involve bacteria - nitrogen fixation, ammonification, nitrification and dentrification.

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25
Q

Nitrogen fixation

A

Nitrogen gas –> ammonium ions

Carried out by:

1) Lightening.
2) Nitrogen fixing bacteria - mutualistic bacteria that live inside root nodules of leguminous plants and free living nitrogen fixing bacteria in the soil.

^Mutualistic because bacteria provide plant with nitrates and the plant provides them with carbohydrates.

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26
Q

Nitrogen gas –> ammonium ions

A

Nitrogen fixation

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27
Q

Ammonification

A

Saprobionts break down dead organisms and release the nitrogen contained as ammonia which goes on to form ammonium ions.

Nitrogen-containing compounds –> decomposers –> ammonium.

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28
Q

Nitrogen-containing compounds –> decomposers –> ammonium

A

Ammonification

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29
Q

Nitrification

A

Ammonium ions –> nitrite ions.
Nitrite ions –> nitrate ions.

Nitrifying bacteria.

Oxidation process - oxygen must be present.

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30
Q

Ammonium ions –> nitrite ions.

Nitrite ions –> nitrate ions.

A

Nitrification

31
Q

Dentrification

A

Nitrates in soil –> nitrogen gas.

Anaerobic conditions (e.g. waterlogged soil).

Denitrifying bacteria.

32
Q

Nitrates in soil –> nitrogen gas.

A

Dentrification

33
Q

Does waterlogged soil have high or low levels of oxygen?

A

Low levels.

34
Q

What is ammonification?

A

The production of ammonium ions from ammonia-containing compounds.

35
Q

What is nitrification?

A

The production of nitrate ions from ammonium ions.

36
Q

What is nitrogen fixation?

A

The process by which nitrogen gas is converted to nitrogen-containing compounds.

37
Q

What is dentrification?

A

The process by which nitrates are converted into nitrogen gas.

38
Q

Oxidation

A

The gain of oxygen.

39
Q

What do saprobionts do in the nitrogen cycle?

A

Break down dead organisms and release the nitrogen contained as ammonia which goes on to form ammonium ions.

40
Q

What organism is present in ammonification?

A

Saprobionts.

41
Q

What process are saprobionts in in the nitrogen cycle?

A

Ammonification.

42
Q

What is nitrification carried out by?

A

Nitrifying bacteria.

43
Q

What type of process is nitrification?

A

Oxidation - oxygen must be present.

44
Q

What organism is nitrogen fixation carried out by?

A

Nitrogen fixing bacteria:

  • Mutualistic bacteria inside root nodules of leguminous plants.
  • Free-living nitrogen fixing bacteria in the soil.
45
Q

What process are nitrifying bacteria in in the nitrogen cycle?

A

Nitrification.

46
Q

What organism is dentrification carried out by?

A

Denitrifying bacteria.

47
Q

What conditions does denitrification require?

A

Anaerobic conditions (e.g. waterlogged soil).

48
Q

What process are denitrifying in in the nitrogen cycle?

A

Denitrification

49
Q

What process are nitrogen fixing bacteria

in in the nitrogen cycle?

A

Nitrogen fixation.

50
Q

How is phosphorus passed through the food web?

A

In the phosphorus cycle.

51
Q

Why do plants and animals need phosphorus?

A

To make biological molecules such as phospholipids (which make up cell membranes), DNA and ATP.

52
Q

Where is phosphorus found?

A

In rocks and dissolved in the oceans in the form of phosphate ions.

53
Q

What does assimilated mean in the phosphorus cycle?

A

Phosphate ions dissolved in water in the soil can be assimilated (absorbed and then used to make more complex molecules) by plant and other producers.

54
Q

What does the phosphorus cycle show?

A

How phosphorus is passed through an ecosystem.

55
Q

Where is the origin of phosphate ions?

A

The sea.

56
Q

How are phosphate ions brought to the surface?

A

By the geographical uplifting of rocks. Weathering helps them to be dissolved and so available for absorption.

57
Q

How are phosphate ions in plants transferred into phosphate ions in animals?

A

Feeding and digestion.

58
Q

What does feeding and digestion do in the phosphorus cycle?

A

Phosphate ions in plants –> phosphate ions in animals.

59
Q

How are phosphate ions in animals transferred into dissolved phosphate ions in oceans, lakes, and soils?

A

Excretion.

60
Q

What does excretion do in the phosphorus cycle?

A

Phosphate ions in animals –> dissolved phosphate in oceans, lakes, and soils.

61
Q

How are dissolved phosphate ions in oceans, lakes, and soils transferred into phosphate ions in plants?

A

Assimilation (or absorption).

62
Q

What does assimilation do in the phosphorus cycle?

A

Dissolved phosphate ions in oceans, lakes, and soils –> phosphate ions in plants.

63
Q

How are dissolved phosphate ions in oceans, lakes, and soils transferred into phosphates in rocks?

A

sedimentation

64
Q

How are phosphate ions in wastes and remains transferred into dissolved phosphate ions in oceans, lakes, and soils?

A

decomposition (or erosion)

65
Q

How are phosphates in rocks transferred into dissolved phosphate ions in oceans, lakes, and soils?

A

Erosion and use of fertilisers.

66
Q

What does sedimentation do in the phosphorus cycle?

A

Dissolved phosphate ions in oceans, lakes, and soils –> phosphates in rocks.

67
Q

What does decomposition do in the phosphorus cycle?

A

Phosphate ions in wastes and remains –> dissolved phosphate ions in oceans, lakes, and soils.

68
Q

What does erosion and use of fertilisers do in the phosphorus cycle?

A

Phosphates in rocks –> dissolved phosphate ions in oceans, lakes, and soils.

69
Q

What happens in the phosphorus cycle?

A

1) Phosphate ions in rocks are released into soil by weathering.
2) Phosphate ions are taken into the plants through the roots. Mycorrhizae greatly increase the rate at which phosphorus can be assimilated.
3) Phosphate ions are transferred through the food chain as animals eat the plants and are in turn eaten by other animals.
4) Phosphate ions are lost from the animals in waste products.
5) When plants and animals die, saprobionts are involved in breaking down the organic compounds, releasing phosphate ions into the soil for assimilation by plants. These microorganisms also release the phosphate ions from urine and faeces.
6) Weathering of rocks also releases phosphate ions into seas, lakes and rivers. This is taken up by aquatic producers, such as algae, and passed along the food chain to birds.
7) The waste produced by seabirds is known as guano and contains a high proportion of phosphate ions. Guano returns a significant amount of phosphate ions to soils (particularly in coastal areas). It is often used as a natural fertiliser.

70
Q

What is guano?

A

The waste produced by sea birds.

71
Q

What does guano contain?

A

A large amount of phosphate ions.

72
Q

Why is guano good?

A

It contains a high proportion of phosphate ions. Guano returns a significant amount of phosphate ions to soils (particularly in coastal areas). It is often used as a natural fertiliser.

73
Q

What can guano be used as?

A

A natural fertiliser.

74
Q

How are phosphate ions transferred from the sea to the land?

A

The waste produced by seabirds is known as guano and contains a high proportion of phosphate ions. Guano returns a significant amount of phosphate ions to soils (particularly in coastal areas). It is often used as a natural fertiliser.

A-level Biology (42 decks)

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