[NAEP] Classification is one of the "softer" areas of "hard" science

[Dawn Wiseman]

What is the differences between plants and animals? What counts as a planet?

Science isn't always cut and dry. We humans have a love for 
classifying everything we can see, but there's a lot of discussion 
about how we should do it. As an example, witness the past week's 
debate at the International Astronomical Union in the Czech Republic. 
Leading astronomers from all over were trying to figure out what 
exactly constitutes a planet.

The newly agreed upon definition,  "a celestial body that is in orbit 
around the sun, has sufficient mass for its self-gravity to overcome 
rigid body forces so that it assumes a ... nearly round shape, and 
has cleared the neighborhood around its orbit," disqualifies Pluto 
because its oblong orbit overlaps with Neptune's. So, as of this 
morning, Pluto, which has been a planet since  it was discovered in 
1930, is now a minor or dwarf planet, along with the asteroid Ceres, 
and 2003 UB313, an icy object slightly larger than Pluto nicknamed 
"Xena."

CNN
http://edition.cnn.com/2006/TECH/space/08/24/pluto.ap/index.html

NASA
http://spaceweather.com

Planetary classifications aren't the only contentious sorting system 
in science. Biological classification is a hotbed of debate. Those in 
my age group will remember being taught a variation of Linnaean 
classification with the divisions of Kingdom, Phylum, Class, Order, 
Family, Genus, Species. There were five kingdoms, each divided over 
and over again into trees that led to various individual species. 
These days, biologist (generally) agree that largest groupings are 
Domains with branches that reflect Darwin's view of evolutionary 
common descent. The 3 domains are Bacteria, Archaea (single 
celled-organisms lacking nuclei) and Eucarya (complex or multi-celled 
organisms).

Below are some articles regarding debates in biology about classification

American Scientist
http://www.americanscientist.org/template/AssetDetail/assetid/44520

Principles of classification
http://anthro.palomar.edu/animal/animal_2.htm

For comparison purposes, the Inuit have a classification system for 
organisms which is different from either of the above "biological" 
approaches. The Inuit system is based on practical characteristics 
(appearance, behaviour, and relevance to the people) that provides an 
accurate and revealing portrait of the web of Arctic life.

Inuit Taxonomy
http://www.arctic.uoguelph.ca/cpl/Traditional/traditional/taxonomyintro.htm

Note, the image is clickable.