Nutrient Cycles

Question 1

what happens in ammonification?

Answer 1

• saprobionts break down organic matter to ammonia
• saprobionts use the products of decomposition for respiration

Question 2

what happens in nitrification?

Answer 2

• nitrifying bacteria convert ammonia to nitrate ions (NO3-) in an oxidation reaction with a nitrite ion (NO2-) intermediate
• nitrate ions can be taken up by plants through their roots

Question 3

what happens in denitrification?

Answer 3

• nitrate ions are converted into nitrogen gas by denitrifying bacteria
• occurs in anaerobic conditions and can be prevented by aerating and draining soil

Question 4

what happens in nitrogen fixation?

Answer 4

• nitrogen gas is converted into other compounds by nitrogen fixing bacteria
• nitrogen fixing bacteria live in root nodules of leguminous plants
• the relationship between nitrogen fixing bacteria and the plant is mutualistic

Question 5

where is phosphorus released from?

Answer 5

• plants can take in PO43- (phosphate ions) from the soil
• phosphate is released from sedimentary rocks from weathering, and through the decay of bones, shells and excretion from some birds

Question 6

what are mycorrhizae?

Answer 6

• help facilitate uptake of water and inorganic ions by plants
• increase surface area and act as a sponge holding water and minerals
• plants can resist drought better and take up inorganic ions more easily

Question 7

what is leaching?

Answer 7

• mineral ions dissolve in rainwater and are carried from soil to end up in rivers and lakes

Question 8

what is eutrophication?

Answer 8

• occurs as a result of leaching
• algae in water have enough nitrate ions to grown more rapidly
• algae blocks light from other plants causing decay and decrease of oxygen in water
• leads to death of the ecosystem (fish etc.)