Nutrient Cycle Flashcards
The diagram shows part of the nitrogen cycle.
( Diagram to Nitrogen gas - > Ammonium ions - > Nitrates - > back to Nitrogen gas )
( First arrow is label Q second arrow is labelled R and third arrow is labelled P )
Which one of the processes P, Q or R involves nitrification?
- R
The diagram above includes one process in which microorganisms add ammonium ions to soil.
( Diagram to Nitrogen gas - > Ammonium ions - > Nitrates - > back to Nitrogen gas )
( First arrow is label Q second arrow is labelled R and third arrow is labelled P )
Describe another process carried out by microorganisms which adds ammonium ions to soil.
- Amino acids are broken down to ammonium ions
- By saprobionts
Denitrification requires anaerobic conditions.
Ploughing aerates the soil.
Explain how ploughing would affect the fertility of the soil.
- Fertility is increase as more nitrate ions are formed
- Less denitrification
One farming practice used to maintain high crop yields is crop rotation.
This involves growing a different crop each year in the same field.
Suggest two ways in which crop rotation may lead to high crop yields.
- Grow crops with nitrogen fixing bacteria
- Different crops use different minerals
Scientists investigated the effect of a mycorrhizal fungus on the growth of pea plants with a nitrate fertiliser or an ammonium fertiliser.
The fertilisers were identical, except for nitrate
or ammonium.
The scientists took pea seeds and sterilised their surfaces.
They planted the seeds in soil that had been heated to 85 °C for 2 days before use.
The soil was sand that contained no mineral ions useful to the plants.
Explain why the scientists sterilised the surfaces of the seeds and grew them in soil that had been heated to 85 °C for 2 days.
- To kill any bacteria on the surface of the seeds and in the soil
- So only the added fungus has any effect
Explain why it was important that the soil contained no mineral ions useful to the plants.
( Scientists investigated the effect of a mycorrhizal fungus on the growth of pea plants with a nitrate fertiliser or an ammonium fertiliser.
The fertilisers were identical, except for nitrate
or ammonium.
The scientists took pea seeds and sterilised their surfaces.
They planted the seeds in soil that had been heated to 85 °C for 2 days before use.
The soil was sand that contained no mineral ions useful to the plants. )
- So that only nitrates or ammonia affects the growth of the plant
The pea plants were divided into four groups, A, B, C and D.
- Group A – heat-treated mycorrhizal fungus added, nitrate fertiliser
- Group B – mycorrhizal fungus added, nitrate fertiliser
- Group C – heat-treated mycorrhizal fungus added, ammonium fertiliser
- Group D – mycorrhizal fungus added, ammonium fertiliser
The heat-treated fungus had been heated to 120 °C for 1 hour.
Explain how groups A and C act as controls.
- So that the effects of nitrate fertilizer or ammonium fertilizer alone can be seen
- So that the effects of fungus can be seen
After 6 weeks, the scientists removed the plants from the soil and cut the roots from the shoots.
They dried the plant material in an oven at 90 °C for 3 days.
They then determined the mean dry masses of the roots and shoots of each group of pea plants.
Suggest what the scientists should have done during the drying process to be sure that all of the water had been removed from the plant samples.
- Weigh the samples at intervals during the drying process
- To see if the weighings become constant
The scientists’ results are shown in the table below.
Treatment:
A - heat-treated fungus and nitrate fertilizer
B - fungus and nitrate fertilizer
C - heat treated fungus and ammonium fertilizer
D - Fungus and ammonium fertilizer
Mean dry mass / g per plant ( standard deviation ):
Root:
A ) 0.40 ( +- 0.05 )
B ) 1.61 ( +- 0.28 )
C ) 0.34 ( +- 0.03 )
D ) 0.96 ( +- 0.18 )
Shoot:
A ) 1.01 ( +- 0.12 )
B ) 9.81 ( +- 0.33 )
C ) 0.96 ( +- 0.26 )
D ) 4.01 ( +- 0.47 )
What conclusions can be drawn from the data in the table about the following?
The effects of the fungus on growth of the pea plants.
- In B and D, fungus increases the growth of roots and shoots
- However growth is greater with nitrate fertilizer
The scientists’ results are shown in the table below.
Treatment:
A - heat-treated fungus and nitrate fertilizer
B - fungus and nitrate fertilizer
C - heat treated fungus and ammonium fertilizer
D - Fungus and ammonium fertilizer
Mean dry mass / g per plant ( standard deviation ):
Root:
A ) 0.40 ( +- 0.05 )
B ) 1.61 ( +- 0.28 )
C ) 0.34 ( +- 0.03 )
D ) 0.96 ( +- 0.18 )
Shoot:
A ) 1.01 ( +- 0.12 )
B ) 9.81 ( +- 0.33 )
C ) 0.96 ( +- 0.26 )
D ) 4.01 ( +- 0.47 )
What conclusions can be drawn from the data in the table about the following?
The effects of nitrate fertiliser and ammonium fertiliser on growth of the pea plants.
- With heat treated fungus, there is similar dry masses of roots and shoots
- There is probably no significant difference because standard deviations overlap
The scientists determined the dry mass of the roots and shoots separately.
The reason for this was they were interested in the ratio of shoot to root growth of pea plants.
It is the shoot of the pea plant that is harvested for commercial purposes.
Explain why determination of dry mass was an appropriate method to use in this investigation.
- Dry mass measures the increase in organic material
- Water content varies
Which treatment gave the best result in commercial terms?
Justify your answer.
( Treatment:
A - heat-treated fungus and nitrate fertilizer
B - fungus and nitrate fertilizer
C - heat treated fungus and ammonium fertilizer
D - Fungus and ammonium fertilizer
Mean dry mass / g per plant ( standard deviation ):
Root:
A ) 0.40 ( +- 0.05 )
B ) 1.61 ( +- 0.28 )
C ) 0.34 ( +- 0.03 )
D ) 0.96 ( +- 0.18 )
Shoot:
A ) 1.01 ( +- 0.12 )
B ) 9.81 ( +- 0.33 )
C ) 0.96 ( +- 0.26 )
D ) 4.01 ( +- 0.47 ) )
- Fungus with nitrate containing fertilizer ( B ) gave the largest shoot : root ratio
- And the largest dryness of the shoot
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.
Nitrates and phosphates are two of these nutrients.
They provide a source of nitrogen and phosphorus for cells.
Give a biological molecule that contains:
- nitrogen
- phosphorus.
- Amino acids
- 2. DNA
Describe the role of microorganisms in producing nitrates from the remains of dead organisms.
- Saprobiotic bacteria break down remains
- Ammonium ions turn into nitrites which turn into nitrates
- By nitrification
Upwelling often results in high primary productivity in coastal waters.
Explain why some of the most productive fishing areas are found in coastal waters.
- Nitrates are present for the growth of plants
- More food so more fish in the area
