I. I.Phylogeny and Systematics A. A.Cladistics Analysis of phylogenetic relationships based on shared characters Characters may be primitive or derived Clade = Group of species that includes ancestral species and all descendents Cladogram – Diagram that illustrates evolutionary relationships among clades Outgroup – Used to distinguish primitive from derived characters

I. I.Phylogeny and Systematics B. B.Relationships among Taxa Taxa may be categorized according to how they reflect evolutionary relationships

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I. I.Phylogeny and Systematics C. C.Traits in Classification Establishing relationships among taxa requires careful examination of characters Ancestral characters = plesiomorphies Shared ancestral characters (symplesiomorphies) unite descendants of a single ancestor into a monophyletic clade Ex: Vertebral column in vertebrates Derived characters = apomorphies Shared derived characters = (synapomorphies) unite derived clades and separate them from ancestral clades Ex: Amniote egg and feathers in reptiles/birds and birds

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II. II.Ecology “Ecology” from Greek “Oikos” (house) Interactions among groups of organisms and between organisms and physical environment Includes abiotic and biotic components

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Physiological Behavioral Evolutionary Fig. 52.2