Chapter 57.4, Problem 1CS

Core Skill: Modeling The goal of this modeling challenge is to use your understanding of top-down control to construct a simple bar graph that predicts the relative abundances of plants and herbivores under three different conditions: plants alone, plant plus herbivores, and plants plus herbivores and carnivores that prey on the herbivores.

Modeling Challenge: Let’s assume that a group of plants, herbivores, and carnivores that feed on those herbivores, are subject to top-down control. An ecologist studies the relative numbers of plants in three different areas of the same size. In one area, both the herbivores and carnivores have been removed. In a second area, only the carnivores have been removed. In a third area, the plants, herbivores, and carnivores are all present. Draw a series of bar graphs that predict the relative population sizes of the plant and herbivore populations in these three different areas. The y-axis should be labeled “Relative population size,” and three pairs of bars, one pair for each of the three areas, should appear along the x-axis. Within each pair of bars, the left bar should indicate the size of the plant population and the right bar should show the size of the herbivore population. Note: The y-axis does not need to have numbers on it; the goal is to predict the relative population sizes, not the actual numbers.