Chapter 20: Phylogenies and the History of Life

analogy

(also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path

basal taxon

branch on a phylogenetic tree that has not diverged significantly from the root ancestor

binomial nomenclature

system of two-part scientific names for an organism, which includes genus and species names

branch point

node on a phylogenetic tree where a single lineage splits into distinct new ones

cladistics

system used to organize homologous traits to describe phylogenies

cladograms

visual representations of evolutionary relationships between organisms

class

division of phylum in the taxonomic classification system

eukaryote-first hypothesis

proposal that prokaryotes evolved from eukaryotes

family

division of order in the taxonomic classification system

gene transfer agent (GTA)

bacteriophage-like particle that transfers random genomic segments from one species of prokaryote to another

genome fusion

fusion of two prokaryotic genomes, presumably by endosymbiosis

genus

division of family in the taxonomic classification system; the first part of the binomial scientific name

homology

similarity in characteristics resulting from a shared ancestry

horizontal gene transfer (HGT)

(also, lateral gene transfer) transfer of genes between unrelated species

kingdom

division of domain in the taxonomic classification system

maximum parsimony

applying the simplest, most obvious way with the least number of steps

mitochondria-first hypothesis

proposal that prokaryotes acquired a mitochondrion first, followed by nuclear development

molecular systematics

technique using molecular evidence to identify phylogenetic relationships

monophyletic group

(also, clade) organisms that share a single ancestor

nucleus-first hypothesis

proposal that prokaryotes acquired a nucleus first, and then the mitochondrion

order

division of class in the taxonomic classification system

parsimony

the simplest, most straightforward way of constructing phylogenetic and evolutionary relationships between organisms

phylogenetic tree

diagram used to reflect the evolutionary relationships among organisms or groups of organisms

phylogeny

evolutionary history and relationship of an organism or group of organisms

phylum

(plural: phyla) division of kingdom in the taxonomic classification system

polytomy

branch on a phylogenetic tree with more than two groups or taxa

ring of life

phylogenetic model where all three domains of life evolved from a pool of primitive prokaryotes

rooted

single ancestral lineage on a phylogenetic tree to which all organisms represented in the diagram relate

shared ancestral character

describes a characteristic on a phylogenetic tree that is shared by all organisms on the tree

shared derived character

describes a characteristic on a phylogenetic tree that is shared only by a certain clade of organisms

sister taxa

two lineages that diverged from the same branch point

systematics

field of organizing and classifying organisms based on evolutionary relationships

taxon

(plural: taxa) single level in the taxonomic classification system

taxonomic classification system

hierarchical system of classifying organisms, including the classification of domain, kingdom, phylum, class, order, family, genus, and species

taxonomy

science of classifying organisms

web of life

phylogenetic model that attempts to incorporate the effects of horizontal gene transfer on evolution