It is helpful to be able to classify life forms. There are many ways that it could be done -- by weight, by color, by habitat, by diet, even alphabetically. But these methods of classification are not useful.

Scientists struggled with the naming issue for a long time. In 1735 Carolus Linnaeus (1707-1778) published his Systema Naturae, which was the beginning of his system of classification. This system is still widely used today.

The system attempted to name living organisms in such a way that their names also reflected their relationships to each other. The biologist started with a large group (the Kingdom) and then worked down to find groups with common characteristics.

The system is hierarchical, working from a large group down to a small and specific kind of organism.

Scientists are working to name living organisms in such a way that their names also reflect their relationships to each other.

Category	What is It?	Example One	Example Two
Kingdom		Animals	Plants
Phylum		Chorodates (have spinal cords)	Flowering Plants
Class		Amphibians	Dicotyledons
Order		Frogs	Rose Family
Family
Genus			Rosa (the flowers)
Species			canina (briar rose)

Cladistics is the study of the relationships of different life forms to each other. It groups together life forms that

• have a common evolutionary history (the same ancestors, though that may have been long ago)
• share (have evolved) unique characteristics that were not present in their distant ancestors