them well enough to skilfully justify not using them. Phenetics was an attempt to determine the relationships of organisms through a measure of overall similarity, making no distinction between plesiomorphies (shared ancestral traits) and apomorphies (derived traits). From the late-20th century onwards, it was superseded by cladistics, which rejects plesiomorphies in attempting to resolve the phylogeny of Earth's various organisms through time. systematists generally make extensive use of molecular biology and of computer programs to study organisms. Taxonomic characters Taxonomic characters are the taxonomic attributes that can be used to provide the evidence from which relationships (the phylogeny) between taxa are inferred. Kinds of taxonomic characters include: Morphological characters General external morphology Special structures (e.g. genitalia) Internal morphology (anatomy) Embryology Karyology and other cytological factors Physiological characters Metabolic factors Body secretions Genic sterility factors Molecular characters Immunological distance Electrophoretic differences Amino acid sequences of proteins DNA hybridization DNA and RNA sequences Restriction endonuclease analyses Other molecular differences Behavioral characters Courtship and other ethological isolating mechanisms Other behavior patterns Ecological characters Habit and habitats Food Seasonal variations Parasites and hosts Geographic characters General biogeographic distribution patterns Sympatric-allopatric relationship of populations See also Cladistics – a methodology in systematics Evolutionary systematics – a school of systematics Global biodiversity Phenetics – a methodology in systematics that does not infer phylogeny Phylogeny – the historical relationships between lineages of organism 16S ribosomal RNA – an intensively studied nucleic acid that has been useful in phylogenetics Phylogenetic comparative methods – use of evolutionary trees in other studies, such as biodiversity, comparative biology. adaptation, or evolutionary mechanisms References Notes Further reading Brower, Andrew V. Z. and Randall T. Schuh. 2021. Biological Systematics: Principles and Applications, 3rd edn. Simpson, Michael G. 2005. Plant Systematics. Wiley, Edward O. and Bruce S. Lieberman. 2011. "Phylogenetics: Theory and Practice of Phylogenetic Systematics, 2nd edn." External links Society of Australian Systematic Biologists Society of Systematic Biologists The Willi Hennig Society Evolutionary biology Biological classification