For your poster you can use information from websites as well. Make sure to use websites that come from scientific organizations, appropriate governmental units, or academic departments. Here are a few suggested places to begin.
The University of Michigan's Museum of Zoology provides an online database of animal natural history, distribution, classification, and conservation biology. In addition to thousands of species accounts, there are descriptions of levels of organization at the phyla, class, order, and family level.
"The Tree of Life Web Project (ToL) is a collaborative effort of biologists from around the world. On more than 9000 World Wide Web pages, the project provides information about the diversity of organisms on Earth, their evolutionary history (phylogeny), and characteristics."
This represents "an ambitious project to organize and make available via the Internet virtually all information about life present on Earth. At its heart lies a series of Web sites—one for each of the approximately 1.8 million known species. Each site is constantly evolving and features dynamically synthesized content ranging from historical literature and biological descriptions to stunning images, videos and distribution maps."
Courtesy of Alan Vernon; located at