It used to be as easy as animal, vegetable, and mineral. My fifth-grade daughter was assigned some homework for the weekend. She had to illustrate the Five Kingdoms. The Five Kingdoms? Well, there's Munchkin Land, the Emerald City, Winki Country... "No, Mom, you know, Animals, Plants, Fungi, Monderans..." What? Monderans?
When I was her age, all life was divided into the plant kingdom and the animal kingdom. Since then, discoveries have strained the definition of a plant or an animal. There are things that just don't fit. As soon as we think we've got it figured out and create new definitions, along comes another lifeform that doesn't fit the new taxonomy, either. Since when is fungi not a plant? I looked up taxonomy at Wikipedia, and found this image by Peter Halasz. Things have changed a bit since I was in school. I thought kingdoms were at the top of the taxonomy tree. I understand "life", to separate it from non-living things, but "domain" is a new one to me, and for good reason -it was introduced in 1990. The resulting six kingdoms have yet to make it to my child's elementary school.
Update: My child got an A on her poster, since she could demonstrate an understanding of the material better than the other students!
Update 5/26/11: The child featured in this article scored high enough to get into an advanced placement science class when she starts high school this fall!