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Q26 - Indirect Effects of Introduced Arctic Foxes on Island Vegetation

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Ecology

The Aleutians Islands west of Alaska are rich in sea birds. The Arctic Fox was not originally present here, but was introduced as a fur game- animal and is now present on many islands. The fox decimates sea bird populations severely. Indirect effects of foxes on island vegetation were compared on islands with and without foxes (Fig.). Mean values for parameters sampled on fox-infested islands (red, left-hand bars) and fox-free islands (blue, right-hand bars). I, view of the plant community on an island; II, logarithm10 of density of breeding sea birds; III, total soil Phosphor; and IV, relative abundance of grasses, shrubs, non-grass herbs, mosses, and others.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. The study is based on the assumption that sea bird-derived nutrients are distributed all over an island
B. The presence of foxes on an island changes the vegetation from grassland to tundra- shrubland
C. Diversity and number of major plant groups are reduced in islands with fox populations
D. The ecological changes on islands with fox introduction represent exclusively top-down processes
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Question reproduced from IBO 2015, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)