GPP and NPP

Question 1

Describe ammonification

2

Answer 1

• saprobionts eat faeces and break down dead material to release ammonia
• forms ammonium ions in soil

Question 2

Describe nitrification

2

Answer 2

• ammonium ions converted to nitrite ions to nitrate ions by nitrifying bacteria
• needs aerated soil thru ploughing

Question 3

Describe nitrogen fixation

Answer 3

• nitrogen gas converted into nitrogen-containing compounds
• free-living nitrogen-fixing bacteria: reduce N gas to ammonia to make aa
• release N rich compounds when die and decay
• mutualistic nitrogen fixing bacteria: live in root nodules gaining carbs and gives aa to plant

Question 4

Describe denitrification

4

Answer 4

• waterlogged soil and low O2 conc
• more anaerobic denitrifying bacteria than aerobic nitrifying bacteria/ N fixing bacteria
• converts nitrates back to N gas so less N rich compounds in soil
• prevent this with ploughing

Question 5

Describe the phosphorous cycle

7

Answer 5

• dissolved phosphate ions in lakes are in rocks thru sedimentation
• dissolve back into lake thru weathering, fertilisers, erosion
• plants absorb phosphate ions into biomass
• animals eat plants and digest phosphate ions into biomass
• excess excreted
• decomposers break down dead material/waste so phosphate ions dissolve back into lakes to make sediment rocks
• some remain in shells/bones as slow to breakdown

Question 6

suggest one way in with an increase in the uptake of phosphate could increase plant growth

(1)

Answer 6

-make ATP/ phospholipids

Question 7

suggest one way in which AMF fungi increasing organic ions mat nenefit from their association with plants?

(1)

Answer 7

-benefits from amino acids or carbs

Question 8

explain why an increase in shoot biomass can be taken as a measurement of net primary productivity

(2)

Answer 8

-represents dry mass
-represents GPP-RL

Question 9

give two examples of bio mols containing Nitrogen that would be removed when a crop is harvested

(2)

Answer 9

-DNA
-RNA

Question 10

The ecologists dried the samples in an oven at 103 degC for 24 hrs.
Describe how the ecologists could have determined whether or not this drying removed all the water from a sample of wood.

(2)

Answer 10

• record mass and reheat
• until constant mass is recorded

Question 11

Suggest how the mass of carbon in the wood of a plantation of trees of a particular species could be estimated

(5)

Answer 11

-calculate mean diameter
- use this to estimate the mean fresh biomass of trees
- use percentage of water content to find dried biomass
- use dried density to calculate the mass of tree
- estimate number of trees in plantation and multiply by mean CO2 content to find total CO2

Question 12

Explain why the scientist sterilised the surfaces of the seeds and grew them in the soil that had been heated to 85 degC for 2 days

(2)

Answer 12

-kill bacteria on seed or in soil
-only fungus has any affect

Question 13

Explain why it was important that the soil contained no mineral ions useful to the plants

(1)

Answer 13

-only type of fertiliser affects growth

Question 14

How does heat-treated fungus added, nitrate fertiliser and fungus added, ammonium fertiliser?

(2)

Answer 14

-only see effect of N/A
-only see effect of fungus

Question 15

Suggest what the scientists should have done during the dryinf process to be sure that all of the water had been removed from the plant samples

(2)

Answer 15

-weigh samples at intervals during drying
-to see if weightings became constant

Question 16

Explain why determination of dry mass was an appropriate method to use in this investigation

(3)

Answer 16

-dry mass measures bio mass
-water content varies
-will effect fresh mass

Question 17

Explain the decrease in gross productivity as the woodland matures

(2)

Answer 17

-less light
-less photosynthesis

Question 18

Explain why biomass shows little increase after 100 years

(2)

Answer 18

-NPP=GPP-RL
-less photosynthesis

Question 19

Describe the role of microorganisms in producing nitrates from the remains of dead organisms

(3)

Answer 19

-saprobionts break down dead material into ammonia
-nitrification
-ammonia into nitrite to nitrate

Question 20

Upwelling often results in high primary productivity in coastal waters. Explain why some of the most productive fishing areas are found in coastal waters.

(2)

Answer 20

-Nitrates used by producers
-more food so more fish reproduce

Question 21

why does freshwater marshes have a
high NPP:GPP and what is the advantage of this?

(2)

Answer 21

-less respiration
-more biomass

Question 22

Why is height not a good way to measure biomass?

(2)

Answer 22

-water gain might affect height
-height might not include roots

Question 23

Other than the thermometer, explain how two features of the calorimeter shown in figure 2 would enable a valid measurement of the total heat energy released.

(2)

Answer 23

-air surrounding acts as insulator so reduces heat loss
-stirrer evely spreads temp so remains constant