Since the sixth grade science curriculum focuses on anatomy and physiology, I found these little plushies to be wonderful teaching tools for students who learn best using visuals and manipulatives. Each one comes with a written explanation of what it is, as well as an actual picture of what the real organism looks like! (Note: You might be able to find these cheaper on amazon.com and I do not own this picture.)

 http://www.giantmicrobes.com/us/main/giantmicrobes-originals/