The Phosphorus Cycle

Question 1

What are the three reservoirs of phosphorus

Answer 1

• Plants and animals (biosohere)
• Sediments and rocks (lithosphere)
• Water (hydrosphere)

Question 2

Why is phosphorus often a limiting factor in plant growth

Answer 2

Quantities of phosphorus in soil is usually small

Question 3

What form of phosphorus is in the biosphere

Answer 3

Phosphate ions are absorbed by plants which are then eaten by animals

Question 4

What form of phosphorus is in the lithosphere

Answer 4

Present in phosphate rocks and sediments

Question 5

What form of phosphorus is in the hydrosphere

Answer 5

Phosphate ions in solution in water which is good for plants

Question 6

What form of phosphorus is in the atmosphere

Answer 6

There is no atmospheric reserve of phosphorus which means the cycling of phosphorus is slower

Question 7

What is the process of absorption of roots

Answer 7

Plants absorb phosphate ions in solution for metabolic processes.

Question 8

What is the process of food chain transfer

Answer 8

Plants absorb phosphate from the soil and then are consumed by animals who are consumed by predators

Question 9

What is the process of decomposition

Answer 9

Living organisms die and microbes breakdown the phosphorylated proteins in DOM and release phosphates into the soil.

Question 10

What is the process of sedimentation

Answer 10

Organisms that die containing phosphorus become incorporated into sediments, planktonic organisms that die and sink to the ocean floor settle and form rocks that contain phosphorus

Question 11

What is the process of mountain building (uplift)

Answer 11

Phosphorus in marine sediments may not become available until plate tectonics uplift the rocks from the deep to the surface forming mountain ranges

Question 12

What is the process of weathering and erosion

Answer 12

Uplifted rocks weathered and eroded and releases phosphates

Question 13

What are the two human activities that affect the phosphorus cycle

Answer 13

• Mining of phosphate rocks
• Fertiliser use

Question 14

How does mining phosphate rocks impact the phosphorus cycle

Answer 14

Accelerates movement of phosphorus into oceans

Question 15

How does fertiliser use impact the phosphorus cycle

Answer 15

• Mobilises phosphorus compounds into the environment in more soluble forms
• Increases crop production but causes eutrophication

Question 16

What are 3 examples of how the phosphorus cycle can be sustainably managed

Answer 16

• Use natural fertilisers
• Leave crop waste and dead organic matter to return phosphates
• Manipulate crops, so they they can efficiently absorb phosphate