One of my favorite sources of books for our homeschool is Chicago Review Press, and so when I got the idea to write a Zoo guide, I checked their catalog first. An unsolicited commercial- all their For Kids books and the Hands-On History series are excellent sources for creating grade school homeschool courses. Check out their website if you are in the midst of your Summer planning. They have something for nearly every period of history.
I recommend this book in the first unit as an excellent introduction to not only Zoology, but also to zoo careers, in the second part of the book, readers examine the various careers associated with animals including zookeepers and aquarists, veterinarians, researchers, and conservationists. You can use the activities within to supplement all the units in my guide. They have some fun and easy to implement activities including baking an animal cell out of cake mix, making a bird feeder out of a cardboard tube, interviewing a zoologist, and monitoring animal behavior in your own backyard.