Nutrient cycles Flashcards

1
Q

Name 4 substances that animal cells require a source of nitrogen to make.

A

DNA and RNA
Amino acids and Proteins
NAD and NADH
ATP

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2
Q

What is nitrogen fixation?

A

Nitrogen gas is converted into ammonia/nitrate

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3
Q

Name the bacteria that carry out nitrogen fixation

A

Nitrogen fixing bacteria

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4
Q

Where are nitrogen fixing bacteria found?

A

Free in the soil
In root nodules of legumes

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5
Q

What does the term symbiotic relationship mean?

A

Two organisms of different species interact

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6
Q

What does the term mutualistic relationship mean?

A

Two organisms of different species interact.
Both organisms benefit from the relationship

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7
Q

Give the main benefit

A

Nitrogen fixing bacteria - gain protection in the nodule and a source of organic substances from the plant
Plant gains a source of ammonium/nitrate ions

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8
Q

What is ammonification?

A

Formation of ammonium ions from organic material (eg urea, faeces, dead organisms)

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9
Q

Name the organisms that cause ammonification

A

Saprobiontic bacteria

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10
Q

What is nitrification?

A

Conversion of ammonium ions into nitrites and then nitrates

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11
Q

Name the organisms that cause nitrification

A

Nitrifying bacteria

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12
Q

What is denitrification?

A

Conversion of nitrates in the soil into nitrogen gas

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13
Q

Why does dentification take place in waterlogged soils

A

Denitrifying bacteria require anaerobic conditions.
No air pockets in the soil when saturated with water

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14
Q

Name 4 biological molecules that contain phosphate

A

Phospholipids
DNA
RNA
ATP

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15
Q

How do phosphates get into the soil

A

Weathering of rocks containing phosphate minerals

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16
Q

Describe how phosphates or nitrates can get into water bodies

A

Dissolve in rain water
Leached/run off into the water body

17
Q

Name the process that causes the death of fish in water containing lots of phosphates and nitrates

A

Eutrophication

18
Q

Describe how the presence of nitrates/phosphates cause the death of fish

A

Leached into water body
Causes increased growth of algae (algal bloom)
As lack of nitrates and phosphate was a factor limiting their growth
Blocks light so less photosynthesis of plants which causes death of plants
Increase in number of decomposers/bacteria
Increased respiration by bacteria
Reduces oxygen content of water
Anaerobic bacteria increase, releasing toxin into water
Fish die

19
Q

Outline the role of mycorrhizae

A

Mutualistic relationship between plants and fungus
Increases the surface area for absorption of minerals and water by roots.

20
Q

Give 3 benefits of planting a different crop in the same field each year

A

Nitrogen fixing crops increase soil nitrate content
Different crops have different pathogen
Different crops removed different proportions of ions

21
Q

Why do farmers add fertiliser to their fields?

A

Increase primary productivity
More minerals for plant growth

22
Q

What is an organic fertiliser?

A

Derived from living organisms
eg manure, slurry

23
Q

What is an inorganic fertiliser?

A

Manufactured fertiliser
Ammonium nitrate

24
Q

Why are organic fertiliser better than inorganic fertilisers?

A

Minerals released at a slower rate
Minerals available for longer
Less likely to be leached from the soil
Improves soil structure

25
Q

Why are inorganic fertilisers better than organic fertilisers?

A

Control proportion of nitrates, phosphates and potassium added to the soil