Nutrient Cycling

Question 1

What 3 things do ecosystems require to remain sustainable?

Answer 1

1) Continuous energy supply (i.e: light)
2) Nutrient cycling
3) Recycling of waste

Question 2

What is a biochemical cycle

Answer 2

the cycling of nutrients via biological, geological and chemical pathways

Question 3

Name 3 examples of biochemical cycles

Answer 3

Any from: 
•	Carbon - (carbon cycle)
•	Nitrogen - (nitrogen cycle)
•	Oxygen - (oxygen cycle)
•	Phosphorus - (phosphorus cycle)
•	Sulphur	 - (sulphur cycle) 
•	Water - (hydrological cycle)

Question 4

Which 4 gases make up 96% of cells?

Answer 4

Carbon
Oxygen
Hydrogen
Nitrogen

Question 5

Which are the 2 main types of biochemical cycles?

Answer 5

Gaseous

Sedimentary

Question 6

Which 4 biochemical cycles are gaseous?

Answer 6

Carbon
Oxygen
Sulphur
Nitrogen

Question 7

Which 4 biochemical cycles are sedimentary?

Answer 7

Phosphorus
Potassium
Calcium
Iron

Question 8

What 2 phases are involved in sedimentary cycles?

Answer 8

Solution phase - where weathering releases minerals from parent rocks, that dissolve as salts in the sea
Rock phase - These salts are deposited out as sediment and rock in shallow seas

Question 9

What % of the atmosphere is nitrogen?

Answer 9

80%

Question 10

Why is nitrogen in the atmosphere difficult for plants to use?

Answer 10

Because most is locked up as N2(g) which cannot be used

Question 11

Why is nitrogen important for life forms?

Answer 11

It is critical for DNA, protein, chlorophyll and ATP

Question 12

which 4 sources do plants obtain nitrogen from?

Answer 12

1) Nitrate fertilisers, ammonia or manure in soil
2) Decomposing organic matter
3) Nitrogen fixation during natural processes like lightening
4) Biological Nitrogen Fixation (BNF)

Question 13

What 4 transformations does Nitrogen undergo during the nitrogen cycle?

Answer 13

1) Biological nitrogen fixation
2) Nitrification
3) Denitrification
4) Ammonification

Question 14

Name 2 ways nitrogen can exist organically

Answer 14

Amino acids

Nucleic acid

Question 15

Name 2 ways nitrogen can exist inorganically

Answer 15

Ammonia

Nitrate

Question 16

Which type of enzyme is needed for BNF?

Answer 16

nitrogenase enzymes

Question 17

Name 3 bacteria that nitrogenase enzymes can be found in

Answer 17

1) Aquatic cyanobacteria
2) free-living soil bacteria - i.e: Azobacter
3) Symbiotic bacteria in association with legume plants - i.e: Rhizobium

Question 18

What do nitrogenase enzyme containing bacteria do to nitrogen in BNF?

Answer 18

They convert nitrogen to ammonia (so it becomes fixed)

Question 19

Which type of bacteria is most important in biological nitrogen fixation?

Answer 19

Symbiotic bacteria

Question 20

What is nitrification?

Answer 20

The conversion of ammonia to nitrate

Question 21

Is biological nitrogen fixation an anaerobic or aerobic process?

Answer 21

Anaerobic - enzymes don’t need oxygen

Question 22

Is nitrification an anaerobic or aerobic process?

Answer 22

Aerobic - does require oxygen

Question 23

What are the 2 steps in nitrification?

Answer 23

1) ammonia oxidation

2) nitrite oxidation

Question 24

Which type of bacteria converts ammonia ions to nitrite in nitrification?

Answer 24

nitrosomonas bacteria

Question 25

Which type of bacteria converts nitrite to nitrate in the second stage of nitrification ?

Answer 25

Nitrobacteria

Question 26

Where does ammonia come from?

Answer 26

Fish waste and urine
decaying plant matter
Excess fish food
Fertilizers

Question 27

Briefly describe the process of nitrification

Answer 27

nitrosomonas bacteria consume ammonia ions and convert it into nitrite. Then nitrobacteria consume the nitrite and convert it into nitrate

Question 28

What is denitrification?

Answer 28

When nitrate is converted into nitrogen gas and returned to the atmosphere

Question 29

Is denitrification an anaerobic or aerobic process?

Answer 29

Anaerobic - no O2 needed

Question 30

Where does denitrification occur?

Answer 30

In soil, sediment, anoxic zones of lakes and oceans

Question 31

Why is denitrification important?

Answer 31

Reduces the risk of water causing pollution - i.e: algal blooms

Question 32

What is ammonification?

Answer 32

When ammonia is produced through organism waste or decaying dead matter

Question 33

How does ammonification release nitrogen into the ecosystem?

Answer 33

Decomposers (fungi and bacteria) break down organic matter, releasing nitrogen from DNA and amino acids as ammonia

Question 34

What is the organic form of nitrogen?

Answer 34

Ammonia

Question 35

What type of nitrogen fixation converts more nitrogen to ammonia than the whole biosphere?

Answer 35

Industrial fixation

Question 36

What is the main impact of fertilisers on ecosystems?

Answer 36

Eutrophication

Question 37

Briefly describe how eutrophication is problematic

Answer 37

Excess nitrogen from fertilisers seep into ground water.
Heavy rain runs it into rivers and streams.
Nitrogen causes rapid growth of algae.
When algae dies, it decreases dissolved O2 levels in water causing mass mortality of aquatic organisms

Question 38

Briefly describe the 4 steps of the carbon cycle

Answer 38

1) Carbon enters atmosphere as CO2 from RESPIRATION and COMBUSTION
2) CO2 is used up in photosynthesis
3) Consumers feed on plants, passing carbon up the food chain.
4) Animals die, decomposers break down organic matter, releasing CO2 by respiration

Question 39

Name 2 fossil fuels

Answer 39

Oil
Coal
Methane?

Question 40

How does burning fossil fuels release carbon?

Answer 40

Carbon is sometimes trapped in dead organisms.
These organisms fossilise in rock.
When burned, the carbon is released along with water and energy.
The carbon is returned back to the atmosphere by CO2

Question 41

what is Rhizobium

Answer 41

soil bacteria that fix nitrogen - found in legume roots

Question 42

what is Azotobacter

Answer 42

A free-living soil bacteria that fixes nitrogen