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Date November 2018 Marks available 1 Reference code 18N.3.SL.TZ0.15
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term State Question number 15 Adapted from N/A

Question

When water rises above a certain temperature, coral bleaching may occur. The coral expels Zooxanthellae algae living in its tissues, leaving the coral a white colour. The graph shows how the water temperature is changing in the coral reefs surrounding the Cayman Islands.

State the trend in temperatures from 1982 to 2014. 

[1]
a.

Deduce the effect of bleaching on corals. 

[4]
b.

Markscheme

«overall» water temperature increasing
OR
the range of fluctuations increases ✔

Do not accept the trend is fluctuating

a.

a. the coral and the algae have a symbiotic/mutualistic relationship
OR
two different organisms live together and depend on each other ✔

b. algae expelled from coral/relationship broken ✔

c. coral produces carbon dioxide from respiration ✔

d. the algae use the carbon dioxide to carry out photosynthesis/produce nutrients ✔

e. without the nutrients from the algae the coral are liable to starve ✔

f. coral dies/is susceptible to disease ✔

 

Do not accept effects on species other than coral

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.1 Species and communities
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Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics)
Option C: Ecology and conservation

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