Nitrogen Cycle

Question 1

Flows

Answer 1

Fixation
Nitrification
Denitrification
Feeding
-absorption
-assimilation
-consumption
Absorption
Excretion
Death and Decomposition

Question 2

Stores

Answer 2

Biotic:
Organism

Abiotic:
Soil
Fossil Fuels
Atmosphere
Water Bodies

Question 3

Fixation

Answer 3

-Atmospheric nitrogen (N2) is made available to plants.
-Nitrogen-fixing bacteria
1.Bacteria in soil
2.Bacteria in root nodules (symbiosis with plant, nitrates for sugars)
3.Cyanobacteria in soil or water
4.Lightning - causing oxidation of N which is then washed into the soil
5.Industrial HARBER process. N2+H2 under pressure w iron catalyst =ammonium. Making fertilisers.

Question 4

Nitrification

Answer 4

-Nitrifying bacteria
-Bacteria convert ammonium to nitrites
-Bacteria convert nitrites (NO2-) to nitrates (nitrobacter)
-Absorbed by root nodules

Question 5

Denitrification

Answer 5

-Denitrifying bacteria in waterlogged, anaerobic conditions turn ammonium, nitrate and nitrite ions to nitrogen gas.

Question 6

In What Forms in Nitrogen Available to Plants

Answer 6

Ammonium, NH4+
Nitrates, NO3-

Question 7

Decomposition

Answer 7

More nitrogen than fixation.
Decomposers (worms, fungi and bacteria) break down proteins producing ammonium ions, nitrite ions and nitrate ions for plants to recycle.

Question 8

Assimilation

Answer 8

Organisms turn nitrogen into more complex molecules.
Protein synthesis - nitrogen compounds to amino acids which join to form proteins.
Nucleotides (building blocks of DNA) contain nitrogen.

Question 9

Human Impact

Answer 9

Removal of plants and animals takes nitrogen from the cycle which is then lost to sea via sewage.

Add through fertilisers or by planting legumes (bacteria in root-nodules).

Waterlogged allows denitrification.
Excess rainwater washes nitrates into water bodies - leaching and eutrophication.