Something Newly learned:
Reading the the few pages in the book and watching videos, I have been doing extra research on how to teach this concept without stepping on toes or offending parents or students. I think that possibly a letter/email needs to go out to parents (checked by the principal/superintendent) that posts the Iowa Standards and what needs to be covered in the unit so that parents feel comfortable and prepared for what will be taught to their children.
That evolution is an ongoing science and that natural selection acts on organisms so that they can survive the change. This is not a quick process but it is an important process that occurs in nature.
After reading online articles, most of them read that this is a concept that is not taught in school because of religious or cultural objectives. There is a conflict with religious beliefs that cause parents not to want teachers to teach their children and that teachers don't want to offend parents/students so they just skip the unit.