Bio 102 Notes Chapter 26 PDF

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26 (pg. 550-559, 566-567) Monday, October 5, 2020 10:06 PM

Definitions: -Phylogeny: evolutionary history of a species or group of species. -Systematics: discipline focused on classifying organisms and determining their evolutionary relationships. -taxonomy: how organisms are named and classified. -binomial: two-part format of the scientific name. • First part of a binomial is the name of the genus to which the species belongs. • The second part, called the specific epithet, is unique for each species within the genus. -genus: a taxonomic category above the species level, designated by the first word of a species' two-part scientific name. -taxon: the named taxonomic unit at any level of the hierarchy. -Phylogenetic tree: The evolutionary history of a group of organisms can be represented in this branching diagram. -Sister taxa: groups of organisms that share an immediate common ancestor that is not shared by any other group. • Ex: Chimps and humans -rooted: describing a phylogenetic tree that contains a branch point representing the most recent common ancestor of all taxa in the tree. -basal taxon: in a specified group of organisms, a taxon whose evolutionary lineage diverged early in the history of the group. -homologies: phenotypic and genetic similarities due to shared ancestry. -Cladistics: common ancestry is the primary criterion used to classify organisms. • Using this methodology, biologists attempt to place species into groups called clades, each of which includes an ancestral species and all of its descendants. • Clades, like taxonomic categories of the Linnean System, are nested within larger clades. -Monophyletic: pertaining to a group of taxa that consists of a group of common ancestor and all of its descendants. A monophyletic taxon is equivalent to a clade. • Paraphyletic: pertaining to a group of taxa that consist of a common ancestor and some, but not all, of its descendants. ~In this particular group the most recent common ancestor of all members of the group is part of the group. • Polyphyletic: pertaining to a group of taxa that includes distantly related organisms but does not include their most recent common ancestor. ~In this particular group the most recent common ancestor of all members of the group is not part of the group. ^^^FIG. 26.10^^^ -Shared ancestral character: a character that originated in an ancestor of the taxon. -Shared derived character: an evolutionary novelty unique to a clade. • Ex: hair in mammals. Hair is a character shared by all mammals but not found in their ancestors. -Outgroup: Species or group of species from an evolutionary lineage that is closely related to but not part of the group of species that we are studying (the ingroup) -Horizontal gene transfer: 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 (as when a host and its endosymbiont become a single organism)

Notes: -The taxonomic system named after Linnaeus, the Linnaean System, places related genera in the same family, families into orders, orders into classes, classes into phyla, phyla into kingdoms, and kingdoms into domains. -A potential source of confusion in constructing a phylogeny is similarity between organisms that is due to convergent evolution (Analogy), rather than to shared ancestry (homology). • A clue to distinguishing between homology and analogy is the complexity of the characters being compared. The more elements that are similar in two complex structures, the more likely it is that the structures evolved from a common ancestor. • Also, if genes in two organisms share many portions of their nucleotide sequences, it is likely that the genes are homologous. -(regarding cladistics) A taxon is equivalent to a clade only if its monophyletic. -Look at (pg. 559) Inferring Phylogenies Using Derived Characters -First two kingdoms of classification: Plants (kingdom plantae) and Animals (kingdom animalia) -5 present-day kingdoms: Monera (prokaryotes), Protista ( a diverse kingdom consisting mostly of unicellular organisms), Plantae, Fungi, and Animalia. -The three domains (taxonomic level higher than kingdoms): • Bacteria ~contains most of the currently known prokaryotes • Archaea ~consists of a diverse group of prokaryotic organisms that inhibit a wide variety of environments. • Eukarya ~consists of all the organisms that have cells containing true nuclei...