Practise AP Biology 8.4.A questions by linking carrying capacity, density-dependent limits and resource availability with logistic population growth.
The common wild oat is native to regions of Europe and Asia but is an invasive species in central California grasslands. In California, the common wild oat has almost completely replaced some species of native bunchgrass. Researchers found that aphids, a type of small insect that often carries plant viruses, have a much higher reproductive rate in grasslands that include the common wild oat than in grasslands composed of only native bunchgrass species. Additionally, the viruses carried by the aphids appear to affect only the native bunchgrasses and not the common wild oat. Native bunchgrasses infected by the virus have much higher death rates than do native bunchgrasses that are not infected.
Explain how the addition of the common wild oat affects the number of native bunchgrass plants that can be supported by the California grasslands ecosystem.
Accept one of the following:
- (The addition of the wild oat) limits the resources available (to the native plants), resulting in a decrease (in the population size).
- (The addition of the wild oat) enables the aphid population to increase/increases the exposure to viruses, resulting in a decrease (in the population size of the native bunchgrass).