The Nitrogen Cycle

Question 1

Describe the process of ammonification

Answer 1

• ammonification is when nitrogen compounds (proteins) from dead organisms are turned into ammonium compounds (ammonium ions) by decomposers
• animal waste (urine and faeces) also contains nitrogen compounds which are also turned into ammonium by decomposers

Question 2

Describe the process of nitrification

Answer 2

• nitrification is when ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants
• nitrosomonas bacteria change ammonium ions into nitrites
• nitrobacter bacteria change nitrites into nitrates

Question 3

Describe the process of denitrification

Answer 3

• denitrification is when nitrates in the soil are converted into nitrogen gas by denitrifying bacteria
• they use nitrates in the soil to carry out respiration and produce nitrogen gas and nitrous oxide
• this happens in anaerobic conditions such as waterlogged soils

Question 4

Describe the process of nitrogen fixation

Answer 4

• nitrogen fixation is when nitrogen gas in the atmosphere is turned into ammonia by a bacteria called rhizobium
• rhizobium is found inside root nodules of leguminous plants e.g. peas, beans
• they from a mutualistic relationship with the plants as they provide the plant with nitrogen compounds and the plant provides them with carbohydrates e.g. glucose