McGraw Hill
Arthropods
Are spiders related to crabs? Study the order of arthropods with a reading selection about animal diversity. It provides details about each class within the order, as well as vivid pictures and explanatory charts.
BiologyWise
Biology Wise: Classification of Animals
The classification system for animals is explained and examples given. Includes suggestions for how to teach the system to younger students and how to create a classification chart of the animal kingdom.
The Franklin Institute
The Franklin Institute: Living Things Families
What do centipedes and crabs have in common? What's so special about a backbone? Check this site out from The Franklin Institute if you are interested in biology and classification.
BiologyWise
Biology Wise: Classification and Characteristics of Rotifers
Outlines the classification hierarchy of the phylum Rotifera and describes their characteristics and anatomy. Rotifera have survived for up to 80 million years and continue to play an important role in ecological systems.
Other
The Domains and Kingdoms of Life
This site is a description of the history behind the 5 Kingdom system suggested by Robert Whittaker. An extensive list of resources is included.