Nutrient Cycles

Question 1

what are the four stages of the nutrient cycle

Answer 1

1. Ammonification
2. Nitrification
3. Dentrification
4. Nitrogen fixation

Question 2

what happens in ammonification

Answer 2

microbes known as saprobionts break down organic matter to
ammonia in a two stage process. Firstly, proteins are broken down into amino acidswith the use of extracellular protease enzymes. These are then subsequently brokendown further to remove amino groups with the use of deaminase enzymes.
Saprobionts use the products of decomposition for respiration.

Question 3

what happens in nitrification

Answer 3

nitrifying bacteria convert ammonia to nitrite ions, NO2-, in an oxidation reaction, with a nitrate ion, NO3-, intermediate. Most plants can take in nitrate ions through their roots.

Question 4

what happens in dentrification

Answer 4

nitrate ions, NO3-, are converted to nitrogen gas, N2, by the denitryfing bacteria. This process is wasteful and can be prevented from occurring by soil being well drained and aerated.

Question 5

what happens in nitrogen fixation

Answer 5

nitrogen gas is fixed into other compounds by bacteria with
nitrogen fixing ability. They do so by reducing nitrogen gas to ammonia which subsequently dissolves to form ammonium ions. Nitrogen fixing bacteria live in root
nodules of leguminous plants. The relationship between nitrogen fixing bacteria and the plant is known as mutualistic, as it is beneficial to both organisms

Question 6

where is phosphate released from

Answer 6

sedimentary rocks as a result of weathering, decay of bones, shells and excreta of some birds

Question 7

what is mycorrhizae

Answer 7

• facilitates the uptake of water and inorganic ions in plants
• increase surface area and act as a sponge holding water and minerals
• association between certain types of fungi and roots

Question 8

what is leaching

Answer 8

• mineral ions dissolve in rainwater and are carried from the soil to end up in rivers and lakes
• eutrophication occurs. This
  provides algae in waterways with enough nitrate ions to grow more rapidly than it otherwise would do
• this can block out light from other plants, causing decay and the use of oxygen in the water way
• eventually leads to the death of the ecosystem