Ch. 26: Phylogenetic Classification zTracing the evolutionary history of a species: phylogeny (phylogenetic tree) zLinnaeus zBinomial system yGenus, species xHomo sapiens zTaxonomy- study of classification of living things. zHigher Taxa- groupings above Genus and Species

Linking Classification and Phylogeny zSystematists depict evolutionary relationships yIn branching phylogenetic trees Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Panthera Mephitis Lutra Canis FelidaeMustelidaeCanidae Carnivora Order Family Genus Species

zEach branch point yRepresents the divergence of two species Leopard Domestic cat Common ancestor

z“Deeper” branch points yRepresent progressively greater amounts of divergence Leopard Domestic cat Common ancestor Wolf

Phylogenetic Trees zEvolutionary systematics: Classifying organisms according to the order at which branches arise along a phylogenetic tree zClassical vs. Cladistic zCladogram: Branching trees that display derived traits: new features zClade: each evolutionary branch in a cladogram

A valid clade is monophyletic zSignifying that it consists of the ancestor species and all its descendants (a)Monophyletic. In this tree, grouping 1, consisting of the seven species B–H, is a monophyletic group, or clade. A monophyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics. Grouping 1 D C E G F B A J I K H

Outgroups zSystematists use a method called outgroup comparison yTo differentiate between shared derived and shared primitive characteristics

zAs a basis of comparison we need to designate an outgroup ywhich is a species or group of species that is closely related to the ingroup, the various species we are studying zOutgroup comparison yIs based on the assumption that homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

The outgroup comparison zEnables us to focus on just those characters that were derived at the various branch points in the evolution of a clade Salamander TAXA Turtle Leopard Tuna Lamprey Lancelet (outgroup) Hair Amniotic (shelled) egg Four walking legs Hinged jaws Vertebral column (backbone) Leopard Hair Amniotic egg Four walking legs Hinged jaws Vertebral column Turtle Salamander Tuna Lamprey Lancelet (outgroup) (a)Character table. A 0 indicates that a character is shared with the outgroup; a 1 indicates that a character has shifted. (b)Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny. CHARACTERS

A Cladogram

Maximum Parsimony and Maximum Likelihood zSystematists yCan never be sure of finding the single best tree in a large data set yNarrow the possibilities by applying the principles of maximum parsimony and maximum likelihood

zAmong phylogenetic hypotheses yThe most parsimonious tree is the one that requires the fewest evolutionary events to have occurred in the form of shared derived characters

zApplying parsimony to a problem in molecular systematics Human Mushroom Tulip 40% 0 30% 0 Human Mushroom Tulip (a) Percentage differences between sequences 0

Applying parsimony to a problem in molecular systematics Tree 1: More likely (b) Comparison of possible trees Tree 2: Less likely 15% 5% 15% 20% 5% 10% 15% 25%

The Universal Tree of Life zThe tree of life yIs divided into three great clades called domains: Bacteria, Archaea, and Eukarya zThe early history of these domains is not yet clear BacteriaEukaryaArchaea 4Symbiosis of chloroplast ancestor with ancestor of green plants 3Symbiosis of mitochondrial ancestor with ancestor of eukaryotes 2Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells 1Last common ancestor of all living things Billion years ago Origin of life

The Major Lineages of Life Three Domains of Life 1) Eubacteria 2) Archeabacteria 3) Eukarya Kingdom Classifications: Monera/ Prokaryotes: 1) Eubacteria 2)Archeabacteria Eukaryotes: 3) Protista 4) Fungi 5) Plantae 6) Animalia