Topic 7:Phosphorous Cycle

Question 1

Where is there not a store of phosphorous?

Answer 1

No gaseous reservoir

Question 2

Importance of phosphorous

Answer 2

Component of bones,ATP,DNA,RNA, cell membranes and proteins

Question 3

4 main processes of the phosphorous cycle

Answer 3

Decomposition
Absorption by roots
Sedimentation
Mountain building and weathering

Question 4

Decomposition as a process in the phosphorus cycle

Answer 4

The breakdown of phosphorylated proteins in dead organic matter releases phosphates that are often made more soluble by soil microbes so they can be absorbed by plants

Question 5

Absorption by roots as a process of the phosphorous cycle

Answer 5

Plant roots absorb the phosphates they will use in metabolic processes
They aren’t effective at this so have a symbiotic relationship with mycorrhizal fungi which have extensive networks of fungal hyphae in the soil, so increase the surface area for phosphate absorption

Question 6

Sedimentation as a process in the phosphorus cycle

Answer 6

The phosphorous in organisms that die are incorporated into sediments so they aren’t available to other organisms
E.g. planktonic organisms sink to ocean floor when they die

Question 7

Mountain building and weathering as processes in the phosphorous cycle

Answer 7

Processes that mobilise phosphorus and make it available to living organisms are slow
The phosphorous in marine sediments may not become available til continental drift forms new mountains and rock weathering releases phosphates

Question 8

2 human impacts on the phosphorous cycle

Answer 8

Mining of phosphate rocks
Fertiliser use

Question 9

Mining of phosphate rocks

Answer 9

Most is mined as calcium phosphate and treated to produce ammonia phosphate which is more soluble
In the past, large accumulations of bird droppings were exploited e.g. Peru

Question 10

Fertiliser use

Answer 10

The use mobilises phosphorous compounds into the environment in more soluble forms.
This can increase crop production but also contribute to eutrophication

Question 11

How can the phosphorous cycle be sustainably managed?

Answer 11

Compensating for phosphate losses by mining rock phosphates is unsustainable
Crop breeding programmes can increase the efficiency of phosphate absorption by crops
Biological wastes can be used as fertilisers