Phylogeny and Systematics

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Phylogeny and Systematics

• Order out of chaos

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Phylogeny
The evolutionary history of a species or group of
species

• Phylon tribe
• Genesis origin
• The evolutionary history of a species or a group
  of related species
• Part of the science of Systematics
• Systematics ecompasses phylogeny and taxonomy

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Fossils

• Form in sedimentary rocks
• Hard parts such as shell, bone, or teeth
• Hardened by mineralization
• Soft parts replaced by mineralization becoming
  stone
• Molds or casts of decayed organisms
• Preservation in amber, ice, tar

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Relative Dating

• Younger sediments are on top of older ones
• Index fossils are widespread and reliable ones
• Rock layers provide a relative age for fossils
  in the layers

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Geological Time Scale

• Four eras Precambrian, Paleozoic, Mesozoic, and
  Cenozoic
• Boundaries between eras correspond to mass
  extinctions
• Eras are subdivided into Periods
• Periods are subdivided into Epochs

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Absolute Dating

• Ages given in year quantities
• Ratio of Carbon-12 to Carbon-14
• Carbon-14 decays to Nitrogen-14
• Half-life of C-14 is 5,730 years
• U-238 has a half-life of 4.5 billion years
• L-amino acids convert to D forms over time
• Racemization clock is temperature sensitive

Click here to see a half life simulation
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Types of Radioactive Decay

• Alpha decay Helium nucleus ejected
• Beta decay Electron or positron ejected
• Gamma decay Gamma photon emitted

Read more about radioactive decay
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Continental Drift

• Major geographic factor in evolution
• Continents move about on the Earths surface
• Continents merged as Pangea 250 mya.
• Pangea begins to break up 180 mya.

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How the dinosaurs died out
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Mass Extinctions

• Mass extinctions are followed by diversification
  of survivors
• Extinctions are inevitable in a changing world
• Permian extinction 95 of marine animals became
  extinct in less than 5 million yrs.
• Cretaceous extinction separates Mesozoic and
  Cenozoic eras 65 mya
• Impact hypothesis

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SYSTEMATICS

• The study of biological diversity in an
  evolutionary context

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Carolus Linnaeus, or Carl Linné, 1707-1778,
Swedish botanist.
http//www.english.upenn.edu/jlynch/Frank/People/
linnaeus.html
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Taxonomy

• The naming and classification of organisms
• Formalized by Carolus Linnaeus(1707-78)
• Binomial nomenclature Genus species
• Leopard Panthera pardus
• African Lion Panthera leo
• Hierarchical classification system
• Taxon a group at any level (plural,taxa)

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Domains
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Diversity of Systems
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CLADISTICS

• A Taxonomic Approach To Classification

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Cladistics

• Phylogenetic approach to classification
• Based on dichotomous (2-way) branching
• Branches show new species budding from a common
  ancestor
• Branching symbolizes historical chronology
• Each branch is called a clade
• Clades consist of an ancestral species and all of
  its descendants Monophyletic

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Examine groups for common ancestors. Branches
should bifurcate (split in two).
Taxon one consists of an ancestral species and
all of its descendents
Taxon 2 includes some, but not all of As
descendents
Taxon 3 lacks a common ancestor. Two ancestors
for one group (D,E,G,H)
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Cladistic Analysis
Clades are defined by their shared-derived
characters The outgoup (Lancelet) and ingroup
share characters that were present in the common
ancestor. The ingoup is defined by the presence
of a vertebral column.
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Phylogeny Inferred From

• Morphological data (comparative anatomy)
• Fossil data
• DNA
• Proteins
• Embryology (embryo fetal development)

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Molecular Clocks

• Rely on genomic regions that evolve at a fairly
  constant rate
• Must be referenced to fossil records to provide
  accuracy
• Difficult to relate to absolute time