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Date November 2017 Marks available 6 Reference code 17N.3.HL.TZ0.18
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Discuss Question number 18 Adapted from N/A

Question

Discuss the causes and consequences of eutrophication.

Markscheme

causes:

a. excess nutrients/nitrates/phosphates in an aquatic system

b. natural runoff from soil/erosion/weathering of rocks

c. runoff of fertilizers «from agricultural land/golf courses»

d. partially treated sewage/animal waste discharged into waterways

consequences: [4 max]

e. algal blooms

f. blocks light for photosynthetic organisms

g. dead organisms sink to bottom of water and decompose

h. decomposers/microorganisms increase BOD/use oxygen

i. oxygen/DO availability for other organisms decreases

j. decrease in biodiversity/disappearance of organisms

OWTTE

[Max 6 Marks]

Examiners report

[N/A]

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Additional higher level topics) » C.6 Nitrogen and phosphorus cycles
Option C: Ecology and conservation » Option C: Ecology and conservation (Additional higher level topics)
Option C: Ecology and conservation

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