Phylogeny & Phylogeny & SystematicsSystematics

Chapter 25Chapter 25

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

Systematics: the study of Systematics: the study of biological diversity in an biological diversity in an evolutionary contextevolutionary contextAnalytical approachAnalytical approachFocuses on morphological, Focuses on morphological, biochemical and molecular biochemical and molecular resemblancesresemblances

Constructing a Constructing a Phylogeny: Phylogeny:

The fossil record: the The fossil record: the ordered array of fossil, ordered array of fossil, within layers (strata) within layers (strata) of sedimentary rockof sedimentary rock

Constructing a Constructing a Phylogeny: Phylogeny:

Sedimentary rock(?)Sedimentary rock(?):: Richest source of fossilsRichest source of fossils Lake Turkana Boy(1984)Lake Turkana Boy(1984)

The fossil recordThe fossil record

Limitations?Limitations?

The fossil recordThe fossil record

Morphological and Morphological and Molecular Homologies:Molecular Homologies:HomologiesHomologies= similarities do = similarities do to shared ancestry to shared ancestry

Constructing a Constructing a Phylogeny:Phylogeny:

Homology vs. analogyHomology vs. analogy Convergent(independent) Convergent(independent)

evolution vs shared ancestryevolution vs shared ancestry Similar environmental pressures can Similar environmental pressures can

produce analogous adaptations in produce analogous adaptations in organisms from different lineagesorganisms from different lineages

Some more challenges: Some more challenges:

The tracing of evolutionary The tracing of evolutionary relationships (relationships (phylogenetic phylogenetic treetree))

Linnaeus(taxonomy)Linnaeus(taxonomy)Binomial NomenclatureBinomial Nomenclature

PhylogeneticsPhylogenetics

Binomial NomenclatureBinomial Nomenclature--two part naming systemtwo part naming system First partFirst part: genus(genera): genus(genera) Second partSecond part: species(specific : species(specific

epithet)epithet)

PhylogeneticsPhylogenetics

Hierarchical Hierarchical Classification: Classification:

1. Domain1. Domain 2. Kingdom2. Kingdom 3. Phylum3. Phylum 4. Class4. Class 5. Order5. Order 6. Family6. Family 7. Genus7. Genus 8. Specie8. Speciess

Hierarchical Hierarchical ClassificationClassification

11. . EukaryaEukarya 2. Animalia2. Animalia 3. Chordata3. Chordata 4. Mammalia4. Mammalia 5. Primate5. Primate 6. Homidae6. Homidae 7. 7. HomoHomo 8. sapiens8. sapiens

Example: Example:

Classification is reflected in the Classification is reflected in the

branching of the branching of the phylogenic phylogenic treestrees Evolutionary relationships are Evolutionary relationships are

traced between some of the traced between some of the taxataxa

What is the connection between What is the connection between classification and phylogeny: classification and phylogeny:

Cladograms: diagrams that show patterns of shared characteristicsClade: a group of species that includes an anestral species and all its descendants.

Phylogenetic Phylogenetic systematics:systematics:

Cladistics: the analysis of how species may be grouped into clades

Phylogenetic TreesPhylogenetic Trees

Monophyletic- single Monophyletic- single ancestor that gives rise to ancestor that gives rise to all species in that taxon and all species in that taxon and to no species in any other to no species in any other taxontaxon The only valid clade(cladogram)The only valid clade(cladogram)

Valid vs. non valid Valid vs. non valid cladesclades

Paraphyletic- lacks Paraphyletic- lacks information about some information about some speciesspecies Consists of an ancestral species Consists of an ancestral species

but not all descendantsbut not all descendants Not validNot valid

Valid vs. non valid Valid vs. non valid cladesclades

Polyphyletic-grouping of Polyphyletic-grouping of several species that lack a several species that lack a common ancestorcommon ancestorNot validNot valid

Valid vs. non valid Valid vs. non valid cladesclades

{{A CladogramA Cladogram

http://ccl.northwestern.edu/simevolution/obonu/http://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swfcladograms/Open-This-File.swf

http://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swf