Zoology 1 covers the classification system and binomial nomenclature, which are used throughout the 3 zoology texts. It also introduces terms sucah as "extinct" and "habitat." The subsequent texts assume that the student knows these things. You can download and read Lesson 1 of Zoology 1 to learn these concepts (except for extinction), before moving on to Zoology 2 and Zoology 3. Then it really doesn't matteer which order you read the books. This Lesson is available at the bottom of the main page at www.Apologia.com listed under Resources.
Tags: General, Zoology 1, Zoology 2, Zoology 3