Lecture #11 Date _______Lecture #11 Date _______

• Chapter 26 ~ Chapter 26 ~ Phylogeny & Phylogeny & SystematicsSystematics

You Must KnowsYou Must Knows

• The taxonomic categories and how The taxonomic categories and how they indicate relatedness.they indicate relatedness.

• How systematics is used to develop How systematics is used to develop phylogenetic trees.phylogenetic trees.

• The three domains of life including The three domains of life including their similarities and differences.their similarities and differences.

Phylogeny:Phylogeny: the evolutionary history of a speciesthe evolutionary history of a species

• Systematics:Systematics: the study of biological the study of biological diversity in an diversity in an evolutionary contextevolutionary context

• The fossil recordThe fossil record: : the ordered array of the ordered array of fossils, within layers, or fossils, within layers, or strata, of sedimentary rockstrata, of sedimentary rock

• PaleontologistsPaleontologists

The fossil recordThe fossil record

• Sedimentary rockSedimentary rock: rock formed from : rock formed from sand and mud that once settled on the sand and mud that once settled on the bottom of seas, lakes, and marshesbottom of seas, lakes, and marshes

• DatingDating::• 1-1- Relative~ Relative~ geologic time scale; geologic time scale;

sequence of speciessequence of species• 2-2- Absolute~ Absolute~ radiometric dating; age radiometric dating; age

using half-lives of radioactive using half-lives of radioactive isotopesisotopes

BiogeographyBiogeography: : the study of the past and the study of the past and present distribution of speciespresent distribution of species

• PangaeaPangaea-250 mya -250 mya √ Permian extinction√ Permian extinction

• Geographic isolationGeographic isolation-180 mya-180 mya√ African/South √ African/South

American American reptile reptile fossil similarities fossil similarities √ √ Australian marsupialsAustralian marsupials

Mass extinctionMass extinction• PermianPermian (250 (250

million years ago): million years ago): 90% of marine animals; 90% of marine animals; Pangea mergePangea merge

• CretaceousCretaceous (65 (65 million years ago): million years ago): death of dinosaurs, 50% death of dinosaurs, 50% of marine species; low of marine species; low angle cometangle comet

PhylogeneticsPhylogenetics

• The tracing of evolutionary The tracing of evolutionary relationships relationships ((phylogenetic treephylogenetic tree))

• LinnaeusLinnaeus• BinomialBinomial• Genus, specific epithetGenus, specific epithet• Homo sapiensHomo sapiens• Taxon (taxa)Taxon (taxa)

Phylogenetic TreesPhylogenetic Trees• Cladistic AnalysisCladistic Analysis: taxonomic approach

that classifies organisms according to the order in time at which branches arise along a phylogenetic tree (cladogram)

• Clade: each evolutionary branch in a cladogram

• Types:

• 1- Monophyletic1- Monophyletic single ancestor that gives single ancestor that gives rise to all species in that taxon and to no rise to all species in that taxon and to no species in any other taxon; legitimate species in any other taxon; legitimate cladogramcladogram

• 2- Polyphyletic members of a taxa are 2- Polyphyletic members of a taxa are derived from 2 or more ancestral forms not derived from 2 or more ancestral forms not common to all members; does not meet common to all members; does not meet cladistic criterioncladistic criterion

• 3- Paraphyletic lacks the common 3- Paraphyletic lacks the common ancestor that would unite the species; does ancestor that would unite the species; does not meet cladistic criterionnot meet cladistic criterion

Constructing a CladogramConstructing a Cladogram• Sorting homology vs. analogy...Sorting homology vs. analogy...

• HomologyHomology: : likenesses attributed to likenesses attributed to common common ancestryancestry

• AnalogyAnalogy: : likenesses attributed to likenesses attributed to similar similar ecological roles and natural selectionecological roles and natural selection

• Convergent evolutionConvergent evolution: : species from species from different evolutionary branches that different evolutionary branches that

resemble one another due to resemble one another due to similar ecological rolessimilar ecological roles

A CladogramA Cladogram