Classification and phylogeny

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Classification and phylogeny
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Announcements

• Assignment from lab 1 is due today in lab
• Assignment for lab 2 include p23,24,27,28 and
  MacClade exercise (do it on data from exercise 2).

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Classification and phylogeny

• Concepts and terms
• Why to study phylogeny
• Constructing phylogentic tree (cladogram)
• Classification
• MacClade

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Concepts and terms

• Phylogeny.
• evolutionary history of a group of organisms
  (taxa)
• Systematics
• study biological diversity of organisms and
  their evolution
• Phylogenetic tree (Cladogram, dendrogram,
  phylogram).
• phylogeny of a group of organisms portrayed in
  a tree

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Concepts and terms

• Classification
• attaching names to organisms and group of
  organisms that may or may not reflect their
  phylogeny
• Homology
• similarity b/c of having a common origin
• Analogy
• similarity b/c of having a common function

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Why to study phylogeny

• Helps to deal with practical problems
• Supply us with evolutionary information about
  -organisms
• -traits
• -when they evolved and their sequence
• -how many time they evolved (happened)
• -related species

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Constructing Cladogram

• Cladogram in P 15 P18
• Derived character (1)
• derived (arose) within a group lineage
• Ancestral character
• trait found in common ancestor (0)
• Outgroup
• closely related but outside of the group of
  interest
• Tree length
• sum of the number of evolutionary steps
  (events)

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Constructing Cladogram
Sister groups
Sister groups
B
A
C
Other beetles
dimples
Short antennae
Large size
Eye spots on elytra
Modified anal glands
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Constructing Cladogram

• Topology
• branching pattern of a phylogenetic tree
• Characters conflicts due to homoplasy (trait
  evolved more than once) or evolutionary reversal
• Cladistic approach (evolutionary path) and
  Maximum parsimony method (p 18)
• minimum number of steps to generate the
  phylogenetic tree

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Constructing Cladogram

• P 17
• Monophyletic (clade)
• common ancestor with all its descendants
• Paraphyletic
• common ancestor with some but not all its
  descendants
• polyphyletic
• unconnected species

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Constructing Cladogram
Paraphyletic
Monophyletic
polyphyletic
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Constructing Cladogram

• Good character is
• 1-Variable between species but not within a
  species
• 2-Easily measured and unambiguous
• 3-Shared derived characters is the key for a
  cladogram
• Example page 23

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Classification

• Taxonomy grouping and classification of
  organisms
• Binominal or linnaean system ( E.coli )
• Species group of organisms reproductively
  isolated from others
• Genus group of related species
• Other categories (kingdom, phylum, class, order,
  family, genus, species) and any of this is called
  taxon

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What to do

• Look for the homologous shared derived character
  that you can use to construct a clade
• Try more than one tree shape until you get the
  most parsimonious
• Try different topologies (straw model)

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Exercise 1
Characters or traits 1-head shape 2-head
width 3-tip point 4-head notch 5-spiral
thread 6-shank width 7-tight spiral
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MacClade