This title explores the role of zebra mussels in introduced environments, how humans helped spread the species, the threats they pose to ecosystems, and efforts being taken to manage them. This book also includes a table of contents, two infographics, informative sidebars, a "That's Amazing!" special feature, quiz questions, a glossary, additional resources, and an index. This Focus Readers title is at the Navigator level, aligned to reading levels of grades 3-5 and interest levels of grades 4-7.