In this chapter, you will read about the system for classifying organisms that was devised by Carolus Linnaeus in the 1700s and how the theory of evolution changed the meaning of classification. You will also find out about how modern methods of studying organisms have led to changes in how organisms are classified.

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 		Chapter Outline

Section 18-1: Finding Order in Diversity
To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner.
In binomial nomenclature, each species is assigned a two-part scientific name.
Linnaeus's system of classification uses seven taxonomic categories. They are—from smallest to largest—species, genus, family, order, class, phylum, and kingdom.

Section 18-2: Modern Evolutionary Classification
Organisms are now grouped into categories that represent lines of evolutionary descent.
The genes of many organisms show important similarities at the molecular level. These similarities can be used as criteria for classification.

Section 18-3: Kingdoms and Domains
The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia.
The three domains are Bacteria, Archaea, and Eukarya.