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Q46 - Grazing Intensity, Root Competition, and Sex Ratio in Poa Grass

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

The dioecious perennial Poa grass coexists with Stipa grass in the steppes. The former is highly preferred by domestic and wild herbivores, while the latter is relatively unpalatable. Scientists grew Poa plants at different distances from Stipa plants, with or without a root barrier, at different grazing levels, and then recorded the growth of Poa plants. In another experiment, they recorded the density of Poa male and female plants under different grazing levels.

Figure 1. Figure 1.

Figure 2. Figure 2.

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

A. Distance to the less palatable Stipa neighbours affects the Poa biomass of females and males at the ungrazed site.
B. Plants at the moderate grazing site, whether male or female, generally perform better near Stipa tussocks than far from them, demonstrating a positive effect of Stipa canopies on both genders.
C. There is a strong below-ground competition between Poa females and Stipa neighbours at the ungrazed site.
D. Population sex ratio drift between female and male bias is influenced by domestic grazing intensity.
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Question reproduced from IBO 2016, Theoretical Paper A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)