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Classification and phylogeny. 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). Classification and phylogeny. Concepts and terms Why to study phylogeny

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  • 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).
classification and phylogeny1
Classification and phylogeny
  • Concepts and terms
  • Why to study phylogeny
  • Constructing phylogentic tree (cladogram)
  • Classification
  • MacClade
concepts and terms
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

concepts and terms1
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

why to study phylogeny
Why to study phylogeny
  • Helps to deal with practical problems
  • Supply us with evolutionary information about -organisms


-when they evolved and their sequence

-how many time they evolved (happened)

-related species

constructing cladogram
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)

constructing cladogram1
Constructing Cladogram

Sister groups

Sister groups







Short antennae

Large size

Eye spots on elytra

Modified anal glands

constructing cladogram2
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

constructing cladogram3
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

constructing cladogram4
Constructing Cladogram




constructing cladogram5
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

  • 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
what to do
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)
exercise 1
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