Chapter 26: Phylogeny and the Tree of Life

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phylogeny

The evolutionary history of a species or a group of species

systematics

A scientific discipline focused on classifying organisms and determining their evolutionary relationships

taxonomy

The scientific study of how living things are classified

binomial

The two part scientific name of a species, consisting of genus and specific epithet. Instituted by Carolus Linnaeus in the 18th century

genus

first part of a binomial name that indicates which species the organism belongs to

taxon

A named taxonomic unit at any given level of classification

phylongenetic tree

A branching diagram that represents the evolutionary history of a group of organisms

PhyloCode

System of classification of organisms based on evolutionary relationships: Only groups that include a common ancestor and all of its descendants are named.

branch point

The two way points that represent the divergence of two evolutionary lineages from a common ancestor

sister taxa

Groups of organisms that share an immediate common ancestor

rooted

Describes a phylogenetic tree that contains a branch point representing the last common ancestor of all taxa in the tree

polytomy

A branch point from which more than two descendant groups emerge

analogy

The similarity between two species that is due to convergent evolution rather than to descent from a common ancestor

homoplasies

Analogous structures or molecular sequence that has evolved independently

molecular systematics

The discipline that uses DNA and other molecular data to determine evolutionary relationships

cladistics

An approach to systematics in which organisms are placed into groups called clades based primarily on common descent

clade

A group of species that includes an ancestral species and all its descendants.

shared ancestral character

A character, shared by members of a particular clade, that originated in an ancestor of the taxon

shared derived characteristic

Evolutionary novelty unique to a particular clade that is not found in their ancestors

outgroup

A species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied.

ingroup

In a cladistic study of evolutionary relationships among taxa of organisms, the group of taxa that is actually being analyzed

maximum parsimony

A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts

maximum likelihood

A principle that states that when considering multiple phylogenetic hypotheses, one should take into account the one that reflects the most likely sequence of evolutionary events, given certain rules about how DNA changes over time

phylogenetic bracketing

An approach in which features shared by two groups of organisms are predicted (by parsimony) to be present in their common ancestor and all of its descendants

orthologous genes

Homologous genes that are found in different species because of speciation

paralogous genes

Homologous genes that are found in the same genome due to gene duplication

molecular clock

A yardstick for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates

neutral theory

The hypothesis that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian natural selection

horizontal gene transfer

A process in which genes are transferred from one genome to another through mechanisms such as exchange of transposable elements and plasmids, viral infection, and perhaps fusions of organisms

monophyletic

Pertaining to a group of taxa that consists of a common ancestor and all its descendants.

paraphyletic

Pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants

polyphyletic

Pertaining to a group of taxa derived from two or more different ancestors

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