DP Biology (first assessment 2025)

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Question 19M.2.SL.TZ1.b

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.2.SL.TZ1.b
Level SL Paper 2 Time zone TZ1
Command term Outline Question number b Adapted from N/A
b.
[Maximum mark: 2]
19M.2.SL.TZ1.b

Outline the relationship between Zooxanthellae and reef-building coral reef species.

[2]

Markscheme

a. a symbiotic/mutualistic relationship ✔

b. Zooxanthellae obtain shelter/habitat/exposure to light ✔

c. coral obtains energy/food through photosynthesis of the Zooxanthellae ✔

Examiners report

This was a well-answered question with many candidates knowing the term symbiosis or mutualism. Protection provided by coral was often stated but the role of Zooxanthellae in providing nutrients from photosynthesis was less often seen.

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