Final answer:
Island ecosystems are vulnerable to invasive species due to limited biodiversity, lack of evolutionary defenses, and human activities.
Step-by-step explanation:
Island ecosystems are vulnerable to invasive species for several reasons. Firstly, islands often have unique and fragile ecosystems with limited biodiversity, making them more susceptible to disruptions caused by invasive species. Additionally, islands are typically isolated, which means that the native species have not evolved defenses against invasive species that are not found on the mainland. Lastly, human activities, such as trade and travel, can introduce invasive species to islands, as seen in the case of the accidental introduction of the brown tree snake to Guam.