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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