CLASSIFICATION: The process and practice of describing, defining and ranking taxa within a hierarchical series of groups; permits organizing and ordering knowledge about organisms, and creates a simplified language for conveying information about order in the diversity of life. In biology, we use the Linnean classification hierarchy (Kingdom, Phylum, Class, Order, Family, Genus, Species).

Kingdom Phylum Class Order Family Genus species

Kingdom Metazoa Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo species sapiens Binomen (scientific name) in “binomial” or “binominal” nomenclature

Class Mammalia Subclass Infraclass Cohort Superorder Order Primates Suborder Anthropoidea Infraorder Superfamily Hominoidea Family Hominidae Subfamily Tribe Subtribe Genus Homo Subgenus species sapiens subspecies G.G. Simpson, 1945

Systematics: The field of biology that deals with the diversity of living organisms, usually divided into the two subdisciplines of taxonomy and phylogenetics. Taxonomy: The science of describing, naming, and classifying (grouping) organisms. Taxon (plural: taxa): Any named group of organisms (not necessarily a clade). A subspecies respresents a "taxon," as does every hierarchical level up to Kingdom. Phylogenetics: The field of biology that deals with the relationships between organisms, including the discovery of these relationships and the study of the causes behind these patterns.

Phylogeny: The evolutionary relationships among organisms; the patterns of lineage branching produced by the evolutionary history of organisms.

time

Terminal node (terminal) (=interior branch) Outgroups

Most Recent Common Ancestor of B+C MRCA of A+B+C MRCA of N+A+B+C “basal” to the ingroup

ABCD A B C D A A B B C C D D

ABCDABCD

ABCDABCD

Types of “trees” DENDROGRAM: A branching diagram with nodes and branches. PHYLOGENETIC TREE or CLADOGRAM: A dendrogram representing the genealogic relationships between taxa with ancestry and relative time implied. ABCD

Types of “trees” DENDROGRAM: A branching diagram with nodes and branches. PHYLOGENETIC TREE or CLADOGRAM: A dendrogram representing the genealogic relationships between taxa with ancestry and relative time implied. EVOLUTIONARY TREE: A phylogenetic tree that includes a time axis and (generally) all members, living and extinct.

Types of “trees” PHYLOGRAM: A tree with branch lengths drawn to represent the degree of genetic (or other) divergence. A B C D scale=10%

Monophyly (monophyletic) monophyletic group (monophyly): A group of organisms/taxa that includes ALL known descendants of that group's common ancestor (including the common ancestor). Monophyletic groups (clades) are grouped by shared derived characters (synapomorphies) not present in earlier ancestors or other groups. Monophyletic groups are also called "natural" groups. Mammalia is an example of a monophyletic group.

Monophyly (monophyletic) clade: A monophyletic or “natural” group. subclade: A clade nested within a larger, more inclusive clade. clade subclade

Monophyly (monophyletic) paraphyletic group (paraphyly): An artificial group of organisms/taxa that includes some, but NOT ALL, of the descendants of a common ancestor. Paraphyletic groups are typically recognized by the sharing of primitive (plesiomorphic) characters. Reptiles are an example of a paraphyletic group. A "grade" is also, by definition, paraphyletic. Paraphyly (paraphyletic)

Monophyly (monophyletic) grade: An artifical (non-monophyletic) taxon, frequently paraphyletic and sometimes polyphyletic. Grades are supposed to represent some level of evolutionary progress. Paraphyly (paraphyletic) grade

Monophyly (monophyletic) Paraphyly (paraphyletic) Polyphyly (polyphyletic) polyphyletic group (polyphyly): An artificial group of organisms/taxa derived from two or more independent, distinct ancestral taxa. The common ancestor, and many closely related taxa, are excluded from the group. Polyphyletic groups are generally recognized by superficial similarities resulting from convergence that do not reflect close evolutionary relationships.

Monophyly (monophyletic) Paraphyly (paraphyletic) Polyphyly (polyphyletic)

AnapsidaDiapsida SynapsidaSaurapsida Turtles Lizards & snakes Crocodiles Dinosaurs & birds Mammals & reptile-like mammals Amniota -evolution of cleidoic (shelled) egg; ca. 350 mya Amphibians -ca. 320 mya

Why do we care? 1.Meaningful classifications.

Why do we care? 1.Meaningful classifications. 2.Need pattern (=phylogeny) to study process (evolution, biogeography, etc.).

Why do we care? 1.Meaningful classifications. 2.Need pattern (=phylogeny) to study process (evolution, biogeography, etc.). 3.The “comparative method”

Why do we care? 1.Meaningful classifications. 2.Need pattern (=phylogeny) to study process (evolution, biogeography, etc.). 3.The “comparative method” 4.Predict properties of organisms

“cheetahlike cat” † Miracinonyx N. America Pleistocene