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Phylogeny and the Tree of Life

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Phylogeny and the Tree of Life Chapter 26 BCOR 012 February 4,7, 2011 In a phylogenetic classification, only monophyletic groups are named. If a paraphyletic group ... – PowerPoint PPT presentation

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Title: Phylogeny and the Tree of Life


1
Phylogeny and the Tree of Life
  • Chapter 26
  • BCOR 012
  • February 4,7, 2011

2
Outline for February 4,7 2011
  • Systematics Connecting Classification to
    Phylogeny
  • Systematics, Taxonomy, and Phylogeny
  • Constructing cladograms
  • Phylogenetic Classification
  • Molecular Systematics
  • Parsimony

3
  • Systematics is the study of biological diversity
    in an evolutionary context. It includes
  • speciation
  • taxonomy
  • phylogeny.

4
Taxonomy is the branch of systematics concerned
with naming and classification.
  • Scientific names are binomials
  • Example Acer saccharum
  • - Acer is the genus name - it is a Latin noun
  • - saccharum is the specific epithet - it is a
    Latin
    adjective

Carolus Linnaeus 1707-1778
5
Biological classifications are hierarchical each
taxonomic group is nested within a more inclusive
higher order group.
(Note that only the genus name and specific
epithet are italicized.)
6
Fig. 26-4
Species
Order
Family
Genus
Pantherapardus
Panthera
Felidae
Taxidea taxus
Taxidea
Carnivora
Mustelidae
Lutra lutra
Lutra
Canis latrans
Canidae
Canis
Canis lupus
7
Phylogeny and Classification
Our classifications will come to be, as far as
they can be so made, genealogies. - Charles
Darwin, 1859
8
Phylogeny is the study of the pattern of
divergence history. (as opposed to speciation,
which addresses process.)
Willi Hennig, 1913 - 1976 Founder of
Phylogenetic Systematics (also called
cladistics)
Assembling a phylogeny using cladistics, taxa are
associated on the basis of shared evolutionary
innovations.
9
One of the evolutionary innovations shared by
birds is the feather
Homology, the sharing of an innovation (derived
character) because of its invention in a common
ancestor.
10
Serial Homology of the Lobster
11
Figure 34.4b-c  Chordate segmentation
12
CRUSTACEANS COMPARED - EVOLUTIONARY HOMOLOGY
13
CRUSTACEANS COMPARED EVOLUTIONARY TRANSFORMATION
ROCK CRAB
LOBSTER
14
Fig. 26-8
1
Deletion
2
Insertion
3
4
15
Fig. 26-8a
1
Deletion
2
Insertion
16
Fig. 26-8b
3
4
17
DNA Evolution stable and labile characters
relate to function. Example Homeobox genes,
which govern variation in serial homologs.
18
The homeobox (in the gene) codes for a
homeodomain (in the protein synthesized from the
gene). The homeodomain has a precise
three-dimensional structure related to its
function.
In evolution, the homeodomain is relatively
stable because it has a precise job.
19
Amino acid sequences compared for the homeotic
gene Ubx
insects
arthropods
Dm - Fruitfly Tc - Beetle Jc - Butterfly Ak -
Onycho- phoran
Decides six legs or more
20
(No Transcript)
21
Parsimony
22
Under the principle of parsimony, tree A would
be preferred over B and C as it is one step
shorter.
Ockham's razor. when trying to choose between
multiple competing theories the simplest theory
is probably the best.
23
How to construct a cladogram
  • Choose a study group
  • Choose an appropriate outgroup
  • Compile data matrix
  • Polarize characters
  • Use shared derived characters to associate study
    group taxa and construct the cladogram

24
The outgroup is the group used to polarize
character states in the study group. It should
be the group most closely related (on the basis
of other lines of evidence) to the study group
that is not actually part of the study group.
lancelet
25
How to construct a cladogram
  • Choose a study group
  • Choose an appropriate outgroup
  • Compile data matrix
  • Polarize characters
  • Use shared derived characters to associate study
    group taxa and construct the cladogram

26
The primitive character is the one shared by the
outgroup and some, but not all, of the study
group.
27
How to construct a cladogram
  • Choose a study group
  • Choose an appropriate outgroup
  • Compile data matrix
  • Polarize characters
  • Use shared derived characters to associate study
    group taxa and construct the cladogram

28
(No Transcript)
29
Kinds of Characters
  • Apomorphy - a derived character state
  • Synapomorphy - a shared derived character state
  • Autapomorphy - a derived character state unique
    to one study group member
  • Symplesiomorphy a shared primitive character
    state

30
Cladistic Analysis and Classification Kinds of
Groups
31
A monophyletic group includes a common ancestor
and all of its descendents
Example Reptilia (defined to include birds)
32
A paraphyletic group includes a common ancestor
and some but not all of its descendents
Example Reptilia (defined to exclude birds)
33
A polyphyletic group is a group whose members do
not share a recent common ancestor
Example homeotherms (warm-blooded animals)
34
In a phylogenetic classification, only
monophyletic groups are named. If a
paraphyletic group bears a name, it will be an
informal one (e.g., gymnosperms)
For Phylogenetic Classification, taxa (taxonomic
groups) should be natural groups, that is groups
reflecting phylogeny.
35
The nested relationship of clades is reflected in
the nested relationship of taxa in the resultant
classification. All are monophyletic groups.
36
eukaryotes
EUKARYA
Dinoflagellates
Land plants
Forams
Green algae
Ciliates
Diatoms
Red algae
Amoebas
Cellular slime molds
Euglena
Trypanosomes
Animals
Leishmania
Fungi
Sulfolobus
Green nonsulfur bacteria
Thermophiles
(Mitochondrion)
Spirochetes
Chlamydia
Halophiles
COMMON ANCESTOR OF ALL LIFE
Green sulfur bacteria
BACTERIA
Methanobacterium
Cyanobacteria
both are prokaryotic
(Plastids, including chloroplasts)
ARCHAEA
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