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Phylogeny and Systematics in Taxonomy

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Collect data on each species' morphology or gene sequences ... Gibbons, orangutan, gorilla, two chimpanzees. Hominidae = humans ... – PowerPoint PPT presentation

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Title: Phylogeny and Systematics in Taxonomy


1
Phylogeny and Systematics in Taxonomy
  • BIOL 100
  • 10 September 2009

2
Inferring Phylogeny
  • Choose set of species
  • Collect data on each species morphology or gene
    sequences
  • Use data to find a tree representing likely
    evolutionary history of relationships (
    phylogeny)

3
Parsimony
  • Concept that the simplest solution to a question
    is the most probable
  • Phylogenetic tree favored is the one that would
    require the least evolutionary change

4
Fig 19.7 p. 407
5
Fig 15.1 p. 300
6
Clade
  • Any complete set of the descendants of a common
    ancestor
  • May or may not be named as a taxon (genus,
    family, suborder, etc.)

7
HANDOUTMeylan 1987
8
Monophyletic vs. Paraphyletic
  • Monophyletic Group
  • Taxon that includes all descendants of a common
    ancestor
  • Paraphyletic Group
  • Taxon that includes some, but not all,
    descendants of a common ancestor
  • Ex Group
  • Taxon of same Linnaean rank as a paraphyletic
    taxon, whose recognition renders that taxon
    paraphyletic

9
Pongidae and HominidaeFig 15.1 p. 300
  • Pongidae great apes
  • Gibbons, orangutan, gorilla, two chimpanzees
  • Hominidae humans
  • Pongidae is paraphyletic due to exclusion of
    hominids

10
Evolutionary Taxonomy vs. Cladistics
  • Evolutionary Taxonomy is old-school way of
    thinking
  • Permits paraphyly when ex group is distinguished
    by exceptional divergence
  • Cladistic school was begun by entomologist Willi
    Hennig (1950, 1966)
  • No paraphyly allowed
  • All species within a taxon must be each others
    closest relatives

11
Splitting or Lumping?How a Cladist Fixes
Paraphyly
  • Splitting Divide up paraphyletic taxon into
    monophyletic taxa of same rank as ex group
  • Lumping Join paraphyletic taxon with its ex
    group as one taxon
  • Use name that has priority

12
Pongidae and HominidaeFig 15.1 p. 300
  • Splitting Pongidae becomes four separate
    families
  • Lumping Combine pongids and hominids in one
    family

13
Bony Fishes (Osteichthyes) and Four-legged
Vertebrates (Tetrapoda)
Fig. 24.2 p. 497
  • Paraphyletic Class Osteichthyes
  • Ex group terrestrial vertebrates (classes
    Amphibia, Reptilia, Aves, Mammalia)
  • Split?
  • Lump?

14
Reptiles and Birds
Fig. 24.16 p. 507
  • Paraphyletic Class Reptilia
  • Ex group Class Aves
  • Split?
  • Lump?

15
The Six Kingdoms
  • Monera (single kingdom of prokaryotic bacteria)
    was paraphyletic
  • Protista is paraphyleticnext to be split up?
  • Are the three domains each monophyletic?

Fig. 19.6 p. 404
16
HANDOUT Fixing the Paraphyly of ProtistaTen
Eukaryote Kingdoms? (Lipscomb 1985)
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