Non-native species is a term commonly used to refer to plants and animals introduced into a foreign environment primarily by humanity intentionally or accidentally. Such exotic invaders die because they fail to adapt to the introduced ecosystem, implying that they involve domestication. However, some thrive to the point of dominating their new ecosystem and spreading rapidly and widely. These types of invaders do not have their own native predators and over time take control of the ecosystem from native species (David and Sweeney 53). The term invasive can also refer to introduced species and diseases. To date, approximately 50,000 non-native species have been introduced into the United States. Non-native species can be defined as invasive if they pose a danger to ecological systems. Introduced species that need to be cared for by humans to thrive are known as ornamental plants. In addition to human activities, non-native species can be introduced through climate change due to natural selection by which new organisms are established that can survive. Continental drift is another factor known to contribute to the presence of non-native species. However, these are slow processes and the most common is human activity. In past centuries, immigration has taken place globally, moving humans to extremely distant destinations, where their movements have led to the transportation of plants and other organisms to entirely new environments, far from their native ecosystem. To protect these ecosystems, native species, and the U.S. economy, respective authorities have devised regulatory measures designed to control the introduction of new foreign species by humans. Invasive species face extremely severe measures despite...... half of paper ......häuser, 2005. PrintMolnar, L., Rebecca L. Revenga, G . & Mark, D. Assessment of the global threat of invasive species to marine biodiversity. Frontiers of ecology and the environment. 6.9 (2008): 485–92 Richardson, D. M. Fifty years of ecological invasion: the legacy of Charles Elton. Chichester, West Sussex: Wiley-Blackwell, 2011. Print.Roman, J. and John A. Lost paradox: genetic diversity and aquatic invasion success. Trends in Ecology and Evolution 22.9 (2007): 454-64. Venner, Marie. Control of invasive species: a summary of highway practice. Washington, DC: Transportation Research Board, National Research Council, 2006. Print. The Regulation of Live Animal Imports into the United States: Wildlife Defenders. Herpetological Society of New England, Inc. 2005-2014. Network. March 9 2013.