5.4 Nutrient Cycles

Question 1

What cycles have nutrients recycled

Answer 1

Nitrogen and Phosphorus Cycles

Question 2

What is the recylcing of nutrients (phosphorus and nitrogen) dependant on

Answer 2

Bacteria

Question 3

What are saprobionts

Answer 3

• Organisms that decompose dead organic matter
• By secreting digetive enzymes extracellulary
• Hydrolysisng polymers into monomers

Question 4

What is the role of Mycorrihizae

Answer 4

Facilitates the uptake of water and inorganic ions by plants

Question 5

Nitrogen Cycle Stage: Nitrogen gas in atmosphere to ammonia

Answer 5

Nitrogen Fixation

Question 6

Nitrogen Cycle Stage: Ammonia to nitrites then nitrates

Answer 6

Nitrification

Question 7

Nitrogen Cycle Stage: Nitrites then nitrates to nitrogen gas in atmoshpere

Answer 7

Denitrification

Question 8

Nitrogen Cycle Stage: Dead organic matter to amino-acids

Answer 8

Saprobioitc Nutrition

Question 9

Nitrogen Cycle Stage: Amino-acids to ammonia

Answer 9

Ammonification

Question 10

What carries out nitrogen fixation and where

Answer 10

• Nitrogen fixing bacteria
• In soil
• Root nodules of legumes

Question 11

What carries out nitrification and where

Answer 11

Nitrifying bacteria in the soil

Question 12

What carries out denitrification

Answer 12

Denitrifiying bacteria

Question 13

What sort of process is denitrification

Answer 13

Anaerobic

Question 14

What carries out sapreobiotic nutrition

Answer 14

Saprobionts

Question 15

What carries out ammonification

Answer 15

Saprobionts

Question 16

In what conditions does denitfification occur in

Answer 16

Water-logged soil

Question 17

What is the purpose of fertilisers

Answer 17

• Replace minerals lost (nitrates and phosphates) from the soil
• By harvesting plants and removing livestock

Question 18

Point of comparison for natural vs artificial fertilisers

Answer 18

• Natural need to be decomposed by saprobionts, so are longer lasting
• Artificial are absorbed quicker

Question 19

Describe leaching

Answer 19

When mineral ions dissolve in the water from rain, and run-off into watercourses

Question 20

Describe how farmers could increase the productivity of crops

Answer 20

• Fertilisers
• Selective breeding
• Crop rotation, for pest reduction
• Plough the soil to aerate it, reducing denitrification and increasing nitrification

Question 21

Describe the process of eutrophication

Answer 21

• Higher concentration of mineral ions in the water due to leaching
• Rapid algal growth occurs, and an algal bloom, covering the surface of the water
• Algae blocks sunlight, so aquatic plants cannot photosynthesise
• Aquatic plants die
• Saprobionts decompose dead aquatic plants
• This increases the bacterial poppulation, that are respiring aerobically
• Oxygen concentration in water falls
• Causes death of aquatic animals