Chapter 26 Phylogeny and the Tree of LifeClassification and PhylogenyLinnaean classification- Binomial nomenclature for species (scientific name)o Genus (family group) + “specific epithet” (species name)o Felis catus (genus is always capitalized and always written in italics)- Taxonomyo Groups (taxa) are based on similarities and differences But it is very subjective- Linnaeus’s hierarchical classification system is nestedo Groups of lower taxa (species, genus) form higher taxa All species in any taxon share certain featuresPhylogenetic Trees- Phylogeny is the evolutionary history of a species and its relationship to other specieso Shown as a tree (fig 26.4 and 26.5)- Branch point is where lineages diverge- Polytomy is an unresolved pattern of divergence- Sister taxa are the par that shares the most recent common ancestor- Basal taxon is a n old/remnant species that hasn’t changed for a long timeSystematics- Systematics is the overall study of phylogenetic relationships- Based on homologieso Of morphology (26.11)o Of DNA sequences (26.8)- But morphological differences can be much greater than DNA differenceso Adaptive radiation of Hawaiian plants- Taxa and trees should correspond- The goal is a monophyletic taxa (26.10)o Each taxon includes an ancestor and all of its descendants- Paraphyletic is a taxon that leaves out a common descendant- Polyphyletic is a taxon that includes species with different ancestorsSystematicsCladistics- Purpose: Hypothesize phylogeny in the form of a dichotomous tree (2 branches)- Method: Identify characteristics as ancestral or derivedo Create the most “parsimonious” tree based on shared derived characteristics (synapomorphies)- Interpreting cladistic tree (clado=branch)o Clade= all the species on a brancho All species in a clade share homologies The more shared derived characteristics, the closer the relationshipo Infer the sequence of evolutionary events Characteristics shared by all are the earliest in history Unique characteristics are the most recento Trees may be scaled to geological time Look at where the latest common ancestor for the group is.Tree of LifeOlder way of grouping life- 2 kingdom system-Linnaeuso Animals- animals and unicellular motile protozoanso Plants-fungi, bacteria, algae, unicellular organisms- 5 kingdom- Whitakero Monera-bacteria and archaeo Animalso Plantaeo Fungio Protista- Current 3 domain systemo Eukaryao Archaeao BacteriaThere was a common ancestor for ALL life (LUCA)Horizontal gene flow was likely in early organismsMitochondrion develop into chloroplastsSome see the tree with tangled
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