AP - A conservation group filed a formal petition Wednesday seeking to list the polar bear as a threatened species under the federal Endangered Species Act, saying global warming could make it extinct by the end of the century.{br}{br}View the Entire Article (http://us.rd.yahoo.com/dailynews/rss/science/*http://story.news.yahoo.com/news?tmpl=story2&u=/ap/20050217/ap_on_sc/polar_bears){br}