Biology 202 Chapter 26 Phylogeny And The Tree Of Life Vocabulary

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PHYLOGENY

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the evolutionary history of a species or group of related species

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SYSTEMATICS

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a scientific discipline focused on classifying organisms and determing their evolutionary relationships

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TAXONOMY

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a scientific discipline concerned with naming and classifying the diverse forms of life

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BINOMIAL

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the two-part latinized name of a species, consisting of the genus and specific epithet

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GENUS

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a taxonomic category above the species level, designated by the first word of a species' two-part scientific name

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FAMILY

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in classification, the taxonomic category above genus

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ORDER

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in classification, the taxonomic category about the level of family

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CLASS

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in classification, the taxonomic category above the level of order

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PHYLUM

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in classification, the taxonomic category above class

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KINGDOM

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a taxonomic category, the second broadest after domain

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DOMAIN

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a taxonomic category above the Kingdom level. The three domains are Archaea, Bacteria, and Eukarya

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TAXON

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a named taxanomic unit at any given level of classification

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PHYLOGENETIC TREE

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a branching diagram that represents a hypothesis about the evolutionary history of a group of organisms

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PHYLOCODE

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system of classification of organsims based on evolutionary relationships: Only groups that include a common ancestor and all of its descendents are named

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BRANCH POINT

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the representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor. Most branch points are shown as dichotomies, in which a branch representing the ancestral lineage splits into two branches, one for each of the two descendent taxa

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SISTER TAXA

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groups of organisms that share an immediate common ancestor and hence are each other's closest relatives

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ROOTED

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

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POLYTOMY

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in a phylogenetic tree, a branch point from which more than two descendent taxa emerger. A polytomy indicates that the evolutionary relationships among the descendent taxa are not yet clear

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ANALOGY

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similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait

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HOMOPLASY

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similar structure or molecular sequence that has evolved independently in two species

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MOLECULAR SYSTEMATICS

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a scientific discipline that uses nucleic acids or other molecules in different species to infer evolutionary relationships

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CLADISTICS

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

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CLADE

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a group of species that includes an ancestral species and all of its descendants

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MONOPHYLETIC

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pertaining to a group of taxa that consists of a common ancestor and all its descendents. A monophyletic taxa is equivilent to a clade

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PARAPHYLETIC

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

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POLYPHYLETIC

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

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SHARED DERIVED CHARACTER

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an evolutionary novelty that is unique to a particular clade

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SHARED ANCESTRAL CHARACTER

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a character, shared by members of a particular clade, that originated in an ancestor that is not a member of that clade

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OUTGROUP

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a species or goup of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied. An outgroup is selected so that its members are closely related by not as closely related as any study-group members are to each other

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INGROUP

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a species or group of species whose evolutionary relationships we seek to determine

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MAXIMUM PARSIMONY

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

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MAXIMUM LIKELIHOOD

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

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PHYLOGENETIC BRACKETING

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an approach in which features shared by two groups of organisms are predicted to be present in their common ancestor and all of its descendents

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ORTHOLOGOUS GENES

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homologous genes that are found in different species because of speciation

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PARALOGOUS GENES

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homologous genes that are found in the same genome as a result of gene duplication

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MOLECULAR CLOCK

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a method for estimating the time required for a given amount of evolutionary change based on the observation that some regions of genomes appear to evolve at constant rates

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NEUTRAL THEORY

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

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HORIZONTAL GENE TRANSFER

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the transfer of genes from one genome to another through mechansims such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms