3.5.4 Nutrient Cycles Flashcards

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1
Q

In which form do plants need nitrogen?

A

Most organisms can not use nitrogen gas so they must secure their nitrogen in its fixed form

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2
Q

What are the fixed forms of nitrogen?

A

Nitrate ions: NO3 (2- charge)
Ammonia: NH3
Ammonium: NH4 (+1 charge)

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3
Q

What are the four nitrogen processes? (No explanation)

A

Nitrogen fixation
Decomposition
Nitfrification
Dentrification

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4
Q

What is nitrogen fixation?

A

Forming fixed compounds from nitrogen gas

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5
Q

What is decomposition it terms of the nitrogen cycle?

A

The breaking down of compounds into ammonia

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6
Q

What is nitrification?

A

The oxidation of ammonia into nitrates

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7
Q

What is dentrification?

A

The reducing of nitrates into nitrogen gas

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8
Q

What is biological fixation?

A

Fixation by microbes

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9
Q

What is atmospheric fixation?

A

Fixation by lightning where the energy combines with oxygen

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10
Q

What is industrial fixation?

A

Fixing of nitrogen during the Haber process

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11
Q

What is Rhizobium?

A

A symbiotic bacteria which fixes nitrogen and takes sugars produced by the plant
Contains an enzyme called nitrogenase that converts nitrogen and hydrogen to ammonia

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12
Q

How do animals secure their nitrogen?

A

From plants through feeding

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13
Q

What is responsible for decomposition in the nitrogen cycle?

A

Microorganisms

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14
Q

What are the types of nitrifying bacteria?

A

Genus Nitrosomes: oxidises NH3 to nitrites

Genus Nitrobacter: oxidises nitrites to nitrates

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15
Q

Out of the phosphorous and nitrous cycles, which is faster?

A

Nitrous

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16
Q

What are the effects of a low concentration of phosphorous?

A

It reduces plant growth and slows soil microbial growth

17
Q

Are soil microorganisms sinks or sources in terms of the phosphorous cycle?

A

They can act as both

18
Q

How can fertiliser run-off damage local water sources?

A
Large amounts of phosphate lead to growth of algea
Algea die quickly
Decomposers break it down
These microorganisms use a lot of oxygen
Oxygen levels decrease in the water
Other organisms die
19
Q

How do animals absorb phosphates?

A

By eating plants or plant-eating animals
When animals die, phosphates return to the soil or oceans during decomposition
Then phosphorous ends up in sediments or rock formations
Seabirds eat phosphorous-containing fish

20
Q

What is mineralisation?

A

When organic phosphorous compounds are mineralised by a wide range of organisms

21
Q

What is assimilation?

A

When microorganisms assimilate phosphorous which enters in the composition of several macromolecules in the cell
Some microorganisms can store phosphorous in special granules

22
Q

What is the solubility of phosphorous controlled by?

A

The pH and the presence of Ca / Mg / Fe / Al ions

23
Q

What are natural fertilisers?

A

Materials derived from animal parts or residues

e.g. manure, seaweed and compost

24
Q

What are artificial fertilisers?

A

Man - made fertilisers

25
Q

Why are fertilisers needed?

A

To achieve the high crop yields demanded by developed worlds

26
Q

What do fertilisers contain?

A

Minerals, such as nitrogen, potassium and phosphorous

27
Q

What is the function of nitrogen in fertilisers?

A

Increases the plant’s capacity to produce new stems / flowers / fruit
Increases the speed of growth

28
Q

What is the function of phosphorous in fertilisers?

A

Helps plants to produce oils and starch which is helpful for forming large and strong root systems
Helps the plant to develop chlorophyll which allows more photosynthesis

29
Q

What is the function of potassium in fertilisers?

A

Aids in the building of protein
Fights off diseases
Essential for photosynthesis

30
Q

How are artificial fertilisers different from natural fertilisers?

A

Artificial fertilisers add nutrients to the plant whereas natural fertilisers feed the microorganisms and the plant

31
Q

What is groundwater contamination?

A

Nitrogen fertilisers break down into nitrates and easily travel through the soil
This creates an accumulative effect
This increases plant life which takes up a lot of oxygen and starves fish and crustaceans

32
Q

What is the effect of repeated fertiliser on soil?

A

Reduces the fertility of the soil, making it barren after time

33
Q

What is the process of eutrophication?

A

Excess nutrients enter waterways
Nutrients promote plant growth
An algae bloom occurs
Algae die and are decomposed by bacteria
The decomposition of algae requires oxygen
This causes a drop in oxygen levels
Therefore fish and other aquatic life die

34
Q

What are acidifying processes?

A

The addition of nitrogen
Loss of nitrogen due to leaching or run - off
Production of organic acids from decaying matter
Removal of alkaline products such as hay

35
Q

What is leeching?

A

The process of water carrying away soluble material when the upper layer of the soil does not absorb all the water

36
Q

What happens when leaching removes too much nitrate from the soil?

A

The pH drops too far and becomes overly acidic

37
Q

What does soil acidity alter?

A

Soil microbes

38
Q

What is the effect of a high salt content in the soil?

A

It limits the ability of seeds to germinate so controlled leaching can reduce salt content

39
Q

What is the process of acidification?

A

Acidification limits plant species
Which leads to weaker root systems
Which leads to erosion
The wind then removes more topsoil