This set of 2 video based web-quests is perfect for introducing students to invasive species. These activities could be used as a general introduction (instead of notes), an an activity for early finishers or given as sub-work (I have used them for all 3!) and can be assigned together or separately, as needed.
The first video web-quest uses Ted-Ed's "The Threat of Invasive Species" and has 10 questions to get students thinking about "what are invasive species?"
The second video web-quest uses How Stuff Works "5 Extremely Invasive Species" and has 15 questions about specific species and their effects on ecosystems.