3.5.4 - NUTRIENT CYCLES

Question 1

freshwater marsh soils are normally waterlogged. this creates anaerobic conditions.

use your knowledge of the nitrogen cycle to suggest why these soils contain relatively high concentrations of ammonium compounds and low concentrations of nitrite ions and nitrate ions. (2)

Answer 1

1. less nitrification OR less nitrifying bacteria OR nitrifying bacteria require aerobic conditions
2. less oxidation of ammonium to nitrate and nitrite

Question 2

suggest one way in which an increase in the uptake of phosphate could increase plant growth (1)

Answer 2

used to produce DNA/ATP/phospholipids in cells

Question 3

arbuscular mycorrhiza fungi (AMF) are fungi which grow on, and into the roots of plants. AMF can increase the uptake of inorganic ions such as phosphate.

suggest one way in which AMF may benefit from their association with plants (1)

Answer 3

1. amino acids
2. carbohydrates
3. vitamins

Question 4

upwelling is a process where water moves from deeper parts of the sea to the surface. this water contains a lot of nutrients from the remains of dead organisms.

describe the role of microorganisms in producing nitrates from the remains of dead organisms (3)

Answer 4

1. saprobiotic microorganisms/bacteria/saprobionts breakdown remains into ammonia/ammonium
2. ammonium ions converted into nitrite then into nitrate
3. by nitrifying bacteria/nitrification

Question 5

upwelling is a process where water moves from deeper parts of the sea to the surface. this water contains a lot of nutrients from the remains of dead organisms.

upwelling often results in high primary production in coastal waters.

explain why some of the mostly productive fishing areas are found in coastal waters (2)

Answer 5

1. nitrate/phosphate absorbed by algae/plants/producers
2. more producers/food so more fish move to area/reproduce

Question 6

nitrate from fertiliser applied to crops may enter ponds and lakes.

explain how nitrate may cause the death of fish in fresh water (5)

Answer 6

1. growth of algae creates algal bloom which blocks light
2. reduced photosynthesis so submerged plants die
3. saprobiotic microorganisms/bacteria
4. aerobically respire
5. so less oxygen for fish to respire

Question 7

nitrates and phosphates provide a source of nitrogen and phosphorus for cells.

give a biological molecule that contains: (2)

1. nitrogen
2. phosphorous

Answer 7

1. amino acid/protein/enzyme/DNA/RNA/ATP/NAD
2. DNA/RNA/ATP

Question 8

describe the role of microorganisms in producing nitrates rom the remains of dead organisms (3)

Answer 8

1. saprobiotic bacteria break down remains into ammonia
2. ammonia converted intro nitrite then into nitrate
3. by nitrifying bacteria