Systematics and Taxonomy
Core concepts
Understand taxonomy as the theory and practice of classification, and systematics as classification plus evolutionary relationships. Know the Linnaean hierarchy (domain, kingdom, phylum, class, order, family, genus, species), binomial nomenclature rules (genus capitalized, species lowercase, both italicized or underlined, author and year where relevant), and the type concept. Distinguish phenetics (overall similarity), cladistics (shared derived characters, synapomorphies), and evolutionary taxonomy. Be fluent with monophyly, paraphyly, and polyphyly; homologous versus analogous structures; and the species concepts (biological, morphological, phylogenetic, ecological). Know the International Code of Zoological Nomenclature principles: priority, homonymy, and the rule that the first valid name prevails.
Common traps
A group sharing only ancestral traits is not a clade. Warm-bloodedness in birds and mammals is convergent, not homologous. The biological species concept fails for asexual organisms and fossils. Do not italicize higher taxa. Priority applies from the publication date of the valid description, not the discovery date.
Worked example
Rule of thumb: to test monophyly, remove one member and see whether the remainder still shares a unique common ancestor that excludes nothing else. If removing a single group makes the rest paraphyletic, the original grouping was paraphyletic - as with traditional Reptilia excluding birds.