Nutrient Cycles- BP

Question 1

stages of the nitrogen cycle

Answer 1

1. nitrogen fixation
2. ammonification
3. nitrification
4. denitrification

Question 2

what happens in nitrogen fixation of the nitrogen cycle?

Answer 2

• nitrogen gas fixed into other compounds by bacteria with a nitrogen fixing ability
• reducing nitrogen gas to ammonia
• ammonia dissolves to form ammonium ions
• nitrogen fixing bacteria live in the root nodules of leguminous plants (this is a mutualistic relationship)

Question 3

what happens in ammonification of the nitrogen cycle?

Answer 3

• This nitrogenous organic material (dead plants, dead animals, waste) is turned into ammonia by saprobionts, which goes on to form ammonium ions.

Question 4

what happens in nitrification of the nitrogen cycle?

Answer 4

• nitrifying bacteria convert ammonia into nitrate ions in an oxidation reaction

Question 5

what happens in denitrification of the nitrogen cycle?

Answer 5

• nitrate ions are converted to nitrogen gas by denitrifying bacteria

Question 6

what happens in the phosphorus cycle?

Answer 6

• weathering releases phosphate ions from rocks into the soil
• plant roots take phosphate ions into the plant
• phosphate ions are passed through the food chain as animals eat the plants and are in turn eaten by other animals
• phosphate ions lost from animals in waste products
• animals die, saprobionts break down the organic compounds, phosphate ions released into soil for assimilation by plants
• saprobionts also release phosphate ions from urine and faeces
• weathering rocks releases phosphate ions into sea, lakes and rivers.
• these are taken up by aquatic producers and passed along the food chain to birds
• waste by birds contains a high proportion of phosphate ions and it returns them back to the soil

Question 7

eutrophication?

Answer 7

• mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers
• large amounts of algae block light from reaching the plants below
• eventually the plants die bc they are unable to photosynthesise enough
• bacteria feed on the dead plant matter
• increased number of bacteria reduce the oxygen concentration in the water by carrying out aerobic respiration
• fish and other aquatic organisms die because there isn’t enough dissolved oxygen

Question 8

why is the nitrogen cycle important?

Answer 8

plants and animals cannot obtain nitrogen through gas exchange
this is because nitrogen has a triple bond