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Systematics

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Systematics Classifying organisms into groups Why classify? To create the fundamental database of the science Analogy - classification systems for rocks Big ... – PowerPoint PPT presentation

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Title: Systematics


1
Systematics
  • Classifying organisms into groups

2
Why classify?
  • To create the fundamental database of the science
  • Analogy - classification systems for rocks
  • Big difference -
  • Rocks are on a continuum of composition
  • Organisms fall into discrete groups (species)
  • So geological classification tends to be
    graphical and biological is hierarchal

3
http//www.newworldencyclopedia.org/entry /FileHo
minoid_taxonomy_6.png
http//www.geologycafe.com/images/igneous_rocks.jp
g
4
Goals of classification
  • Make morphologic groups
  • This is what Linneaus was trying to do in the
    1700s
  • Represent evolutionary relationships
  • These two goals are not always compatible

5
Schools of classification
  • Traditional taxonomy
  • Phenetics
  • Cladistics

6
Traditional
  • Original goal produce morphologic groups
  • New goal represent evolutionary relationships,
    produce natural groups
  • Find patterns of ancestry
  • Methodology analyze important characters
  • Product evolutionary trees
  • Requires expertise - only an expert recognizes
    the important characters
  • How is it objective?
  • How is it subjective?
  • Challenges convergent evolution

7
Cladistics
  • Goal to construct and test evolutionary
    hypotheses
  • Find sister groups, not ancestry
  • Sister groups are evolutionary related, but it
    makes no statement about descent
  • Methodology analyze derived characters
  • Characters that mark a change from the lineage
    that led to this organism
  • Product cladogram

8
Cladistics, cont.
  • Requires expertise to recognize derived
    characters
  • Challenge blows up some recognized groups

9
Evolutionary tree what are the axes?
http//darwiniana.org/famtree3b.gif
10
Cladograms what are the axes? Why arent they
the same?
http//tolweb.org/tree/ToLimages/ cladogram_parall
el_evo.250a.jpg
https//www.sciencemag.org/content/340/6129/ 12330
62/F1.large.jpg
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