Spider 4 Spider B Spider C Grasshopper Grasshopper Grasshopper Grasshopper Beetle Herbs Competition for food among herbivorous insects Meadow food web 05.9. Imagine all the Grasshoppers are removed and excluded from a large area of the meadow ecosystem. Which of the following predictions is LEAST likely to occur, according to the diagrams? Spider B will go extinct The Spider C population size will decrease The Beetle population size will increase The diagrams indicate that all of the above are equally likely: Bug Bug
The Correct Answer and Explanation is:
The correct answer is The Beetle population size will increase.
Based on the provided diagrams, if all grasshoppers are removed from the meadow ecosystem, the prediction that is LEAST likely to occur is the extinction of Spider B. Here is a detailed explanation of the ecological dynamics at play.
Analysis of the Food Web
The “Meadow food web” diagram illustrates the predator-prey relationships in this ecosystem. Spiders A, B, and C are predators, while leafhoppers, bugs, grasshoppers, and beetles are herbivores that feed on herbs. The “Competition for food” diagram shows that these four insects compete with each other for the same food source, which the food web identifies as herbs.
Impact on Spider Populations
- Spider B: According to the food web, Spider B preys on both leafhoppers and grasshoppers. If grasshoppers are removed, Spider B loses one of its two food sources. While this would likely cause a decrease in Spider B’s population due to reduced food availability, extinction is an extreme and less probable outcome. Spiders can often survive on alternative prey, so as long as the leafhopper population remains, Spider B has a food source.[1]
- Spider C: Spider C has a more diverse diet, feeding on bugs, grasshoppers, and beetles. The removal of grasshoppers eliminates one of its three food sources. This loss would likely lead to a decrease in the Spider C population, as there is now less available food and more competition for the remaining prey.[2][3] This makes the prediction of a population decrease for Spider C a likely event.
Impact on the Beetle Population
The “Competition for food among herbivorous insects” diagram clearly indicates that beetles and grasshoppers compete for resources. By removing the grasshoppers, a major competitor of the beetle is eliminated.[4][5] This reduction in interspecific competition means that more herbs are available for the beetle population. With an increased food supply, the beetle population is very likely to increase, assuming food is a limiting factor for its growth.
Conclusion
Comparing the three predictions, the extinction of Spider B is the most severe and therefore the least likely to happen. A population decrease is probable, but having an alternative food source makes complete extinction unlikely. In contrast, a decrease in Spider C’s population and an increase in the beetle population are direct and highly probable consequences of removing grasshoppers from the ecosystem. Therefore, the extinction of Spider B is the least likely prediction.
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