- Discover ways in which alien species inadvertently travel.
- Explore the means by which exotic invaders spread after entering ecosystems.
- Trace the foreign or domestic origins of nonnative animals and plants.
Students do a card-matching activity to learn how human activities accidentally transport invasive species into ecosystems. Pairs or groups explore in greater depth the introduction and spread of an individual animal or plant.
They may penetrate natural or political borders stowed away in the ballast water of ships, afloat on rafts of marine debris, by drifting down artificial waterways, escaping from ornamental gardens and croplands, hitching rides with outdoor enthusiasts, or being "set free" from human homes. Wherever they go, however they get there, these accidental tourists can count on people to give them an unintended lift.
Most alien species cannot last long outside their native habitats. But, those that survive can multiply fast and spread from one region to another through the forces of nature and with human help. Without the natural predators, competitors, and diseases they left behind in their homelands, they have an unfair advantage over native species, and their populations can explode.
- Divide the students into small groups. Give each group a set of "X-Files" - unidentified alien invader pictures and description cards.
- Have the students look briefly at the cards. They should work cooperatively to match each picture with its corresponding description card.
- Confirm the correct matches as a class, in accordance with the following answer key: 1) Atlantic salmon, 2) brown spruce longhorn beetle, 3) bullfrog, 4) dead man's fingers, 5) domestic cat, 6) green crab, 7) leafy spurge, 8) spiny water flea
- Then, discuss ways in which invasive species are transported from one ecosystem to another and how they spread once they have arrived.
- Ask individuals to research in depth the introduction and spread of another invasive animal or plant. More examples of accidental transplants include: the clubbed tunicate, Dutch elm disease, Eurasian water-milfoil, flowering-rush, house mouse, Norway rat, round goby, ruffe, rusty cray-fish, sea lamprey, spotted knapweed, wild boar, and zebra mussel.
- Students should then share their research findings with the class in a written or oral report. Alternatively, ask them to draw each invader and describe (briefly and without naming the species) how it was transplanted on a separate sheet. Turn these "X-files" into new sets of cards to be copied and distributed among small groups for another round of the matching activity described above.
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