Systematic Biology – Classification of Living Things

Vocabulary flashcards covering the major terms and definitions from the lecture on classification, systematics, and nomenclature of living organisms.

Classification

The process of arranging organisms into groups based on shared similarities.

Linnaean System

Traditional hierarchical classification set up by Carl Linnaeus that groups organisms by basic body structure into divisions and subdivisions.

Scientific Name

Globally accepted, standardized name assigned to a species to avoid confusion caused by common names.

Binomial Nomenclature

Two-part scientific naming system consisting of a genus name and a specific epithet (e.g., Homo sapiens).

Generic Name (Genus)

The first, capitalized word of a scientific name that groups closely related species.

Specific Epithet

The second, lowercase word of a scientific name that identifies a particular species within a genus.

Species (Taxonomy)

Basic unit of classification; members cannot interbreed with other species and are given a binomial name.

Subspecies

Taxonomic rank below species; populations that interbreed with each other but not fully with other subspecies; named with a trinomial (e.g., Canis lupus arctos).

Systematics

Broad science that studies organism diversity and evolutionary relationships, encompassing taxonomy, phylogeny, and nomenclature.

Phylogeny

Evolutionary history and ancestry of a species or taxonomic group.

Monophyletic Group

A common ancestor and all of its descendants; accepted by both systematics and cladistics.

Paraphyletic Group

A common ancestor and some, but not all, of its descendants.

Polyphyletic Group

A group derived from multiple evolutionary ancestors; unsuitable for single taxon placement.

Cladistics

Method within systematics that classifies organisms strictly by recency of common ancestry using shared derived traits.

Cladogram

Diagram that illustrates evolutionary relationships produced by cladistic analysis.

Synapomorphy

Newly evolved, shared derived trait used to define branches in a cladogram.

Plesiomorphy

Ancestral trait shared by all members of a group; not useful for distinguishing close relationships.

Homologous Traits

Features inherited from a common ancestor (e.g., bird and bat forelimbs).

Analogous Traits

Similar features arising from convergent evolution, not common ancestry (e.g., bird wings vs. insect wings).

Outgroup

A taxon outside the study group used to determine which traits are ancestral versus derived.

Domain (Taxonomic Rank)

Highest rank in biological classification, above kingdom; three domains exist: Bacteria, Archaea, Eukarya.

Domain Bacteria

Domain of metabolically diverse, unicellular prokaryotes with peptidoglycan cell walls.

Domain Archaea

Domain of unicellular prokaryotes adapted to extreme conditions; cell walls lack peptidoglycan and membranes have ether-linked lipids.

Domain Eukarya

Domain containing all eukaryotic organisms—protists, fungi, plants, and animals.

Six-Kingdom Classification

System dividing life into Bacteria, Archaea, Protista, Fungi, Plantae, and Animalia.

Kingdom Protista

Paraphyletic group of mostly unicellular eukaryotes; its members do not share a single common ancestor.

Taxonomic Hierarchy

Ordered ranks: Domain, Kingdom, Phylum (Division in plants), Class, Order, Family, Genus, Species.

Order (-ales)

Taxonomic rank below class and above family; names of plant orders typically end in –ales.

Family

Taxonomic rank below order and above genus; groups genera that share a recent common ancestor.

Genus

Taxonomic category below family; first word of a binomial; must be monophyletic, reasonably compact, and distinct.

Species Name (Binomial)

Two-word Latinized name identifying a species; genus capitalized, specific epithet lowercase and both italicized.

Trinomial Name

Three-part scientific name used to identify subspecies.

Nomenclature Codes

Formal sets of rules governing the naming of organisms (e.g., ICZN for animals, botanical code for plants).

International Code of Zoological Nomenclature (ICZN)

Governing code that sets standards for the availability and validity of animal names.

Willi Hennig

German biologist who founded modern cladistics and defined monophyly based on shared derived characteristics.

Synonym (Taxonomy)

Formerly accepted scientific name replaced by a newer, valid name when new information emerges.

Homonym (Taxonomy)

Single scientific name that has been applied to two different taxa; one taxon must be renamed.

Monera

Historical kingdom (now obsolete) that once included all prokaryotes before division into Bacteria and Archaea.

Available Name

Genus or species name published in accordance with nomenclatural codes and therefore valid for use.

Unavailable Name

Name not accepted due to non-conformity with nomenclatural rules, misspelling, or lack of a type species.