|Image is from Wikimedia Commons under a Creative Commons license|
To begin, I would like to share a bit of a disappointment I have with America's education system. When you are taught science, and biology in particular you are under the assumption that what you are learning is all that there is. No more, no less. Even though the scientific method is taught as part of this, there is no real reference to change. The facts are the facts and you better learn them because otherwise you'll not know anything about biology. As such, for a student such as my younger self, the first time I heard of anything different from that perceived set of facts it was a bit startling. Now, perhaps that was a fault of the particular teachers I had, but the wonder that there is still so much not known about the world is part of the beauty of science. Yes, there are certain things that have been tested and tested and still hold true, but other aspects of science can be anything but concrete.
One example of this uncertainty that still remains in Biology is the classification system, or rather what organism goes in which grouping. Thanks to continued discovery of new species and new knowledge of the organism through DNA testing, things have become a bit of a mess. Not only do scientists disagree as to which classification system is better, but there is work toward completely overhauling some aspects. This includes the proposed complete restructuring of Eukaryotes that would replace the traditional Animal, Plant, Fungi, and Protist with anywhere from five to eight groupings. The restructuring makes since if you know anything about "protists," since the heading really has no meaning other then "stuff that can't be easily placed anywhere else." It's likely that this will filter down to high school level texts rather soon. When I was finishing my undergraduate studies, I tutored for a while and noticed that the basic biology texts already had this system included. Also, if you're curious, the proposed system would place animals under the heading "Opisthokont" along with Fungi and certain protistants. One nice thing about this proposed reorganization is that it wouldn't affect much if any of the lower order groupings such as phyla.
Anyway, back to animal phyla. One common misconception that students currently have about the animal world is that classification is simple and narrow. This is encouraged through the teaching of a simplified version of the classification. In fact, I was rather amused to come across a page that listed only nine animal phyla. Oh boy are there a lot more than nine! In fact, the text we used when I took Invertebrate Zoology listed the following phyla: