Alien Invaders
Non-native species animals can throw off entire ecosystems.
PHOTOS: Asian Carp and Other Alien Animal Invaders
A northern snakehead fish swims in a tank at the Academy of Natural Sciences April 28, 2005 in Philadelphia, Pennsylvania. Richard Horwitz, a senior biologist with the Academy of Natural Sciences and his team caught 15 northern snakehead, whose scientific name is Channa Argus, in FDR Park two days ago. The northern snakehead can grow to several feet in size, crawl on land for short distances, and is native to Asia and Africa. Scientists fear the fish, with its voracious appetite, can destroy or severely harm the ecosystem. (William Thomas Cain/Getty Images)
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