Woolly mammoth. Atlantic gray whale. Large lazy lemur. Dodo bird. Silver trout. Baiji white dolphin. Saber-toothed tiger. These are just a few of the many extinct species. All extinct species undergo a process that leads them to extinction. Endangered species are on the verge of extinction due to natural causes and humanity. The number of these species is increasing every year for different reasons, and it is for these reasons that they are becoming endangered. Endangered species are plants or animals that are expected to die within a few years. “Endangered Animal Facts” is an article that teaches its readers general facts about many animals facing extinction. Four main categories of threatened plants and animals include vulnerable species, threatened species, endangered species, and extinct species. Vulnerable species are so numerous that they are at risk (1). Threatened species are in sufficient numbers but are decreasing in their normal environment. Endangered species are on the brink of extinction. Extinct species no longer exist (2). In recent years, thirty-eight known mammal species have been listed as extinct (1). Endangered species are either on the verge of extinction or becoming threatened. In any case, their number is constantly evolving and the aspects are numerous. There are several main reasons why endangered species are on the verge of extinction. Greta Nilsson wrote an article for the encyclopedia on endangered species. In the first part of her essay, she focused on the four main reasons that put plants and animals on the endangered species list: habitat destruction, exotic animal trade, overhunting and competition between natural species. .....corporations have a big impact on the world and are worth saving. Works CitedBloyd, Sunni. Endangered species. San Diego: Lucent Books, 1989. Print. “Endangered Species Act.” National Wildlife Federation. National Wildlife Federation, 2011. Web. October 18, 2011. “Endangered Animal Facts.” » Animal Facts. Np Factsaboutanimals.net, 2008. Web. October 14, 2011. Goodnough, David. Endangered animals of North America. Berkeley Heights, NJ: Enlsow Publishers, 2001. Print. A burning question.Jackson, Peter. Endangered species: elephants. Secaucus, NJ: Chartwell Books, 1990. Print. Klinkenborg, Verlyn. “The last one.” National Geographic Magazine. National Geographic Society, January 2009. Web. October 18, 2011. Kurpis, Lauren. Endangered species. Lauren Kurpis, 2002. The web. October 17, 2011.Nilsson, Greta. “Threatened species”. The World Book Encyclopedia. 2003. Print.