Modern Taxonomy Reflects Evolutionary History

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Modern Taxonomy Reflects Evolutionary History

• Section 15.4

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Taxonomy

• Identification, naming, classification of
  species
• Common names dont always work well, because they
  have different meanings in different areas.
• For example, a tortoise might be called a gopher
  in Florida, but in Kansas, "gopher" might refer
  to either a ground squirrel or a pocket gopher.
• Goals
• assign universal scientific name to each known
  species.
• Place groups of species into larger groups of
  related species.

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Linnean System of Classification

• Swedish botanist Carolus Linnaeus
• System has 2 main characteristics
• 2 part latin name for each species (binomial).
  The 1st part is the Genus name, the 2nd part is
  the species name.
• Genus is capitalized, species is lower case
• The whole name is in italics
• Ex. African lion (Panthera leo)
• Hierarchy of species into broader and broader
  groups
• KPCOFGS or SGFOCPK
• Lg ? Sm Sm? Lg

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• Phylogenic Trees (Cladograms)

• In a phylogenetic tree, each branch point
  represents a common ancestor of the species above
  that point. In this diagram, the branches are
  labeled to reinforce how taxonomy reflects the
  branching pattern of evolution.

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• Homologous structures are one of the best clues
  to assess how closely organisms are related.
• Not all similar structures are inherited from a
  common ancestor.
• Convergent evolution is a process in which
  unrelated species from similar environments have
  adaptations that seem very similar.
• Similar adaptations that result from convergent
  evolution are called analogous structures.
• For example, the wings of insects and those of
  birds are analogous, not homologous, flight
  equipmentthey evolved independently. And, they
  are built from entirely different structures.
  There is no evidence that insects and birds
  shared a common winged ancestor.

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Cladistics

• This cladogram shows how derived characters can
  be used to identify clades among certain
  vertebrates (animals with backbones). All the
  species shown here share a common ancestor that
  had a backbone. (Each clade is actually defined
  by several derived characters, not just one.)

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• The key rule in cladistics is that all of the
  organisms of a particular clade must share
  homologous structures that do not occur outside
  the clade.
• These unique features that unite the organisms as
  a clade are called derived characters.
• A phylogenetic diagram that specifies the derived
  characters of clades is called a cladogram.
• For example, compare the animals in the cladogram
  in Figure 15-30. The horse, wolf, leopard, and
  house cat all have hair. This derived character
  unites a clade that doesn't include the turtle.

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Comparing Classification Schemes

• Two- and Three-Kingdom Schemes - Linnaeus divided
  all known forms of life between the plant and
  animal kingdoms.
• A Five-Kingdom Scheme
• Three Domains - This newer scheme recognizes
  three basic groups two domains of
  prokaryotesthe Bacteria and the Archaeaand one
  domain of eukaryotes, the Eukarya.

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• For many years, most biologists classified
  organisms according to a five-kingdom system.
  Based on molecular data, however, many biologists
  now prefer a three-domain classification. Within
  each domain there are multiple kingdoms (only
  listed here for Eukarya).