Ch. 18: Classification and Taxonomy
The goal of biologists who classify organisms is to construct a tree of life that shows how all organisms are related to one another.
18.1 Finding Order in Diversity
In binomial nomenclature, each species is assigned a two-part scientific name. The goal of systematics is to organize living things into groups that have biological meaning. Over time, Linnaeus’s original classification system expanded to include seven hierarchical taxa: species, genus, family, order, class, phylum, and kingdom.
18.2 Modern Evolutionary Classification
The goal of phylogenetic systematics, or evolutionary classification, is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences. A cladogram links groups of organisms by showing how evolutionary lines, or lineages, branched off from common ancestors. In general, the more derived genetic characters two species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary terms.
18.3 Building the Tree of Life
The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia. The tree of life shows current hypotheses regarding evolutionary relationships among the taxa within the three domains of life