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Date November 2018 Marks available 2 Reference code 18N.1.SL.TZ0.5
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Describe Question number 5 Adapted from N/A

Question

Figure 9(a): Fact file on beaver’s role in the ecosystem

© International Baccalaureate Organization 2018

 

Figure 9(b): The succession of ecosystems caused when a beaver dam is built across a river

With reference to Figures 9(a) and 9(b), describe one abiotic change and one biotic change in a beaver meadow community undergoing succession.

Markscheme

This question requires “Resource Booklet - Nov 2018 SL paper 1”, available under the "your tests" tab > supplemental materials.

Biotic [1 max]:
increase in small bushes followed by trees / reforestation / plant diversity increases;
increase in (mammal) species more adapted to forests;
increase in animal diversity / increase in predation due to greater animal diversity;

Abiotic [1 max]:
reduction in soil moisture (as water is taken up by trees);
reduction in soil nitrogen / reduction in soil nutrients;
reduction in light penetration;
reduced temperature ranges due to greater shade in day;
increased humidity due to transpiration by trees/water channel/creation of river;

Do not accept only “change in vegetation/creation of new vegetation area”.
Do not accept “increase in water turbidity” as meadow is not a water body.

Examiners report

Very few candidates correctly described changes in two suitable factors. Most candidates described changes linked to a river system that was being dammed rather than a beaver meadow undergoing succession. Some students did not know the difference between biotic and abiotic factors.

Syllabus sections

Topic 2: Ecosystems and ecology » 2.1 Species and populations
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Topic 2: Ecosystems and ecology

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