ACT Science Question of the Day

Predator prey relationships can often influence the survivorship of species. Models are created to better visualize these relationships and their effects on population growths and declines. One way to display this information is to plot the density of the prey population against the number of prey consumed by a certain predator. As seen in Figure 1, three characteristic curves have been observed using this method. Curve Type I curve is the most unrealistic and exists when the number of prey consumed increases in direct proportion to the number of prey, with no limit on consumption. Curve Type II curve is characterized by a trend that shows the number of prey consumed per predator increasing quickly, but as the prey density increases the predators become satiated and the number of prey consumed stabilizes. Curve Type III resembles Type II in that it has an upper limit, but predators consume relatively few prey at lower densities due to various reasons.

Figure 1

When prey exist in low numbers their evasiveness rises. With fewer number of prey in one area they have increased opportunities to hide from predators; furthermore, predators have a decreased ability to create a search image of their prey. A search image is a mental development that dictates a predator's main source of prey through multiple interactions. Which curve in Figure 1 exhibits these characteristics?