Nutrient cycles (13)

Question 1

What are the 5 stages of the phosphorus cycle?

Answer 1

1) weathering
2) runoff
3) assimilation
4) decomposition
5) uplift

Question 2

What are the 2 reasons why the phosphorus cycle is a slow process?

Answer 2

• phosphorus has no gas phase so there is no atmospheric cycle
• most phosphorus is stored as phosphate (Po43-) in rocks

Question 3

What happens in weathering and runoff?

Answer 3

phosphate compounds from sedimentary rocks leach into surface water and soil

Question 4

What are 2 reasons why phosphorus is significant in organisms?

Answer 4

• plants convert inorganic phosphate into biological molecules
• phosphorus is passed to consumers via feeding

Question 5

What are 3 biological molecules that phosphate can be converted into?

Answer 5

DNA
ATP
NADP

Question 6

What happens in the uplift stage?

Answer 6

sedimentary layers from oceans are brought up to land over many years

Question 7

What is sedimentary layers from oceans formed from?

Answer 7

the bodies of aquatic organisms

Question 8

What speeds up uplift?

Answer 8

mining

Question 9

Why can’t organisms used nitrogen directly from the atmosphere?

Answer 9

very stable due to strong covalent triple bond

Question 10

What are the 4 stages of the nitrogen cycle?

Answer 10

1) nitrogen fixation
2) nitrification
3) ammonification
4) dentrification

Question 11

What is the purpose of using fertilisers?

Answer 11

to increase gross productivity for higher yield

Question 12

What are 2 advantages of aerobic conditions?

Answer 12

• uses oxygen so nitrogenase works
• provides ATP for reaction

Question 13

What happens during nitrogen fixation?

Answer 13

mutualistic nitrogen-fixing bacteria in modules of legumes use nitrogenase to reduce nitrogen into ammonia

Question 14

What are 3 ways to reduce the risk of eutrophication?

Answer 14

• sewage treatment marshes on farms
• pumping nutrient-enriched sediment out of water
• using phosphate-free detergent

Question 15

What happens during ammonification?

Answer 15

saprobionts break down proteins by feeding on and decomposing waste, this causes ammonia to be released and dissolve in water in the soil to form ammonium ions

Question 16

What happens during nitrification?

Answer 16

saprobionts convert ammonium ions into nitrite using oxygen, and then nitrite into nitrate using oxygen

Question 17

What is the equation for the conversion of ammonium ions into nitrite?

Answer 17

2NH4- + 3O2 > 2NO2- + 2H2O + 4H+

Question 18

What is the equation for the conversion of nitrite into nitrate?

Answer 18

2NO2- + O2 > 2NO3-

Question 19

What is the significance of nitrogen to living organisms?

Answer 19

plant roots uptake nitrates via active transport and use them to make biological molecules

Question 20

What are 3 biological molecules that nitrogen can be converted into?

Answer 20

amino acids
NAD/NADP
nucleic acids

Question 21

What happens during dentrification?

Answer 21

anaerobic denitrifying bacteria convert nitrate back into nitrogen

Question 22

What is the relationship between plant and fungus called?

Answer 22

symbiotic relationship

Question 23

What type of fungus is associated with plants?

Answer 23

mycorrhizae

Question 24

How do plants benefit from a relationship with fungus?

Answer 24

fungus increases surface area of root system and increases uptake of water and mineral ions

Question 25

How does fungus benefit from a relationship with plants?

Answer 25

provides access to sucrose

Question 26

What are 3 advantages of planting different crops on the same field each year?

Answer 26

+ nitrogen-fixing crops make soil more fertile by increasing soil nitrate content
+ different crops have different pathogens
+ different crops use different proportions of certain ions

Question 27

What are the 2 types of fertiliser?

Answer 27

organic
inorganic

Question 28

What is an organic fertiliser made from?

Answer 28

decaying organic matter and animal waste

Question 29

What is an inorganic fertiliser made from?

Answer 29

minerals from rocks usually containing nitrogen, phosphorus and potassium

Question 30

What are 2 issues that fertilisers can cause?

Answer 30

leaching
eutrophication

Question 31

What happens during leaching?

Answer 31

nitrates dissolve in rainwater and runoff into water sources

Question 32

What is meant by eutrophication?

Answer 32

when a water source becomes putrid as a result of algal bloom

Question 33

What are the 4 stages of eutrophication?

Answer 33

1) aquatic plants grow exponentially as nitrate level isn’t a limiting factor
2) algal bloom on water surface prevents light from reaching bottom and plants die
3) oxygen levels decrease as aerobic saprobionts increase to decay dead matter, so fish die
4) anaerobic organisms reproduce exponentially and produce toxic waste, making water putrid