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Date May 2017 Marks available 1 Reference code 17M.3.SL.TZ1.13
Level Standard level Paper Paper 3 Time zone Time zone 1
Command term State Question number 13 Adapted from N/A

Question

Reef-building corals are an association between two organisms: coral polyps and Zooxanthellae.

State the relationship between Zooxanthellae and coral reef species.

[1]
a.

Describe the exchange of materials between the coral’s polyps and Zooxanthellae.

[2]
b.

State one limiting factor on Zooxanthellae which affects coral reef formation.

[1]
c.

Markscheme

mutualism

a.

a. polyp is a source of carbon dioxide for the Zooxanthellae 
OR
polyp is a source of ammonia/nitrogen for the Zooxanthellae 

b. Zooxanthellae provide oxygen to the polyp
OR
Zooxanthellae provide sugars/glucose/glycerol/lipids/amino acids to the polyp

b.

light / temperature / salinity / carbon dioxide / pH

c.

Examiners report

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

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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