Exam only covers class, phylum, kingdom and domain. Taxon = general name for group at any level. Linnaean classification and phylogeny can differ from each other. Phylogeny = groups with common ancestor and all descendants. Smallest set of organism that can be distinguishes on a phylogenetic tree. Hypothesis about evolutionary relationships (common ancestor but different species) Rooted tree = represent most recent common ancestor of all taxa on tree. Basal taxon = the branch that diverges early and originates near the common ancestor (fewest branches) Branch point = divergence of 2 species from a common ancestor. Sister taxa = 2 taxa share immediate common ancestor. Polytomy = more than 2 groups among from one branch. Common ancestor and some, but not all, descendent. Cladistics = groups organisms by common descent or ancestry. A clade = a group which includes ancestral species and all descendent. Homology (homologous) = derived from a common ancestor.