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Date May 2019 Marks available 3 Reference code 19M.3.SL.TZ1.10
Level Standard level Paper Paper 3 Time zone Time zone 1
Command term Compare and contrast Question number 10 Adapted from N/A

Question

Torre Guaceto is a marine protected area which covers over 22 km2 of the Adriatic Sea in south-eastern Italy. The diagram shows a food chain within this area.

The data refers to the numbers of these three species inside the marine protected area, where fishing is limited, and outside the marine protected area, where fishing is allowed.

[Source: data provided by The Science of Marine Reserves Project (PISCO), based on Guidetti 2006 Ecological Applications]

State the trophic level of the sea urchin.

[1]
a.

Compare and contrast the community structure within and outside the marine protected area.

[3]
b.

With respect to this food chain, outline what is meant by a keystone species.

[3]
c.

Markscheme

herbivore/primary consumer ✔

Do not accept second trophic level

a.

compare:

a. all three species present in both
OR
richness is the same ✔

b. sea urchin numbers highest in both
OR
sea bream density less than sea urchin density in both ✔ Allow converse answer

c. all species numbers are affected by fishing ✔

contrast:

d. sea urchin population is greater outside the marine protected area ✔

e. reduction in sea bream/sea grass percent cover outside the marine protected area ✔

f. less species evenness outside the marine protected area ✔

b.

a. keystone species have a disproportionate effect on the biological community ✔ 

b. removal of the sea bream «due to fishing» ✔

c. results in more sea urchins ✔

d. which significantly reduce the producers/seagrass ✔

Do not accept first trophic level for mpd

c.

Examiners report

Primary consumer was frequently stated and second trophic level also seen, although not credited as the syllabus demands the former term.

a.

There were nearly always at least two differences between the areas described but much less often a comparison, so three marks were not often awarded. Some candidates gave explanations rather than following the command term.

b.

The syllabus definition of a keystone species was not often given, so alternative wording had to be judged on merit. The keystone species was not always recognized as the sea bream, but if it was, three marks were easily achieved.

c.

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.2 Communities and ecosystems
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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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