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Phylogeny and Systematics

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... Genus & species Leopard = Panthera pardus African Lion = Panthera leo Hierarchical classification system Taxon = a group at any level (plural,taxa ... – PowerPoint PPT presentation

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Title: Phylogeny and Systematics


1
Phylogeny and Systematics
  • Order out of chaos

2
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

3
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

4
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

5
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

6
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
7
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8
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
9
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.

10
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11
How the dinosaurs died out
12
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

13
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14
SYSTEMATICS
  • The study of biological diversity in an
    evolutionary context

15
Carolus Linnaeus, or Carl Linné, 1707-1778,
Swedish botanist.
http//www.english.upenn.edu/jlynch/Frank/People/
linnaeus.html
16
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)

17
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18
Domains
19
Diversity of Systems
20
CLADISTICS
  • A Taxonomic Approach To Classification

21
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

22
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)
23
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.
24
Phylogeny Inferred From
  • Morphological data (comparative anatomy)
  • Fossil data
  • DNA
  • Proteins
  • Embryology (embryo fetal development)

25
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
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