Facts101 is your complete guide to Biology of the Invertebrates. In this book, you will learn topics such as The Protists, The Poriferans and Placozoans, Introduction to the Hydrostatic Skeleton, and The Cnidarians plus much more. With key features such as key terms, people and places, Facts101 gives you all the information you need to prepare for your next exam. Our practice tests are specific to the textbook and we have designed tools to make the most of your limited study time.