BIOL 1951 CHAPTER 25 TAXONOMY AND SYSTEMATICS

Taxonomy

the science of naming, classifying, and organizing organisms

Systematics

the study of biological diversity and evolutionary relationships among organisms

Taxon/taxa

a group (or groups) of organisms classified together, like species or genus

Binomial nomenclature

a two-part naming system using genus and species names (e.g., Homo sapiens)

Phylogeny/phylogenetic tree

a diagram showing evolutionary relationships based on ancestry

Anagenesis

evolution where one species slowly changes into a new one without splitting

Cladogenesis

evolution where one species splits into two or more different species

Common ancestor

an earlier organism from which two or more species descended

Node

a branching point on a phylogenetic tree showing a common ancestor

Clade

a group of organisms that includes an ancestor and all its descendants

Monophyletic, paraphyletic, and polyphyletic group

• monophyletic: includes ancestor and all descendants

• paraphyletic: ancestor and some descendants

• Polyphyletic: unrelated species without a common ancestor in the group

Homology

similar traits due to shared ancestry

Cladistics

a method of classifying species based on shared derived traits

Character

a trait or feature used to study evolutionary relationships

Shared ancestral character (symplesiomorphy)

a trait shared with a common ancestor but not unique to the group being studied

Shared derived character (synapomorphy)

a new trait that evolved and is shared only within a specific group

Ingroup vs. outgroup

ingroup: the group being studied

outgroup: a closely related group used for comparison

Parsimony

the simplest explanation with the fewest evolutionary changes is preferred

Molecular clock

a tool that uses genetic changes to estimate the time of evolutionary events

Horizontal gene transfer

the movement of genes between unrelated species, not by inheritance