IUCN Red List of Threatened Species
Provided by the World Conservation Union, the IUCN Red List of Threatened Species provides taxonomic, conservation status, and distribution information on animals and plants that have been globally evaluated using the IUCN Red List Categories and Criteria. The main purpose of the IUCN Red List is to catalogue and highlight those taxa that are facing a higher risk of global extinction.
Provided by the United States Department of Agriculture, the PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the United States and its territories. This resource includes a detailed classification hierarchy for most species.
Created by the Association of Biodiversity Information, this site provides access to information on more than 70,000 plants, animals, and ecosystems of the United States, Canada, and Latin America. Entries for organisms provide common name, scientific name, taxonomic hierarchy, distribution, conservation status, ecology and life history information, references, and more. NatureServe includes particularly in-depth coverage for rare and endangered species.
Tree of Life
The Tree of Life Web Project is a collaborative effort of biologists from around the world. The site provides pictures, text, and other information for organisms, living or extinct. Pages also contain hierarchical information in the form of an evolutionary tree of life.