GENEVA (AP) -- Polar bears and hippos are among more than 16,000 species of animals and plants threatened with global extinction, the World Conservation Union said today. According to the Swiss-based conservation group, known by its acronym IUCN, the number of species classified as being in serious danger of extinction rose from about 15,500 in its previous "Red List" report, published in 2004. The list includes one in three amphibians, a quarter of the world's mammals and coniferous trees, and one in eight birds, according to a preview of the 2006 Red List. The full report is published later this...