Q28 - Fruit Availability and Fish Diet Niche in Amazon Floodplains

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

Within a single year, the Amazon floodplain forests have a high-water (HW) and a low-water (LW) season with a high and low fruit production, respectively. Fruit consumption is widespread among Amazonean fishes, and the relationships between fish diet and fruit production have been explained by three hypotheses H1-H3 (Fig.). Two species of fish (Brycon falcatus and Myloplus asterias) were studied in detail. Three hypotheses (H1-H3) explain how food niche breadth and overlap among fish species (Y) respond to seasonal changes in fruit availability (X).

Figure 1. Figure 1.

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

A. Fact: Diet overlap among fish increased from 28% to 95% from low-resource to high-resource season: This relationship is best explained by H1

B. Fact: B. falcatus was, at first, observed not to change its food niche, when food became more plentiful, but then at higher food availability it became increasingly selective: This relationship is best explained by a combination of H1 and H3

C. Fact: Some fish had a constant food niche throughout the year, irrespectively of fruit availability: This is best explained by H1

D. Fact: During HW, M. asterias had a fruit-dominated diet, but switched to leaves instead of fruit in the LW season: This is best explained by H2

← Previous: Q27 Next: Q29 →

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)