What is the Linnaean System of Taxonomy?

							    What is the Linnaean System of Taxonomy?
• Levels of taxonomy: Kingdom, Phylum (or Division); Class;
     Order; Family; Genus and Species
   – Today, all levels are intended to reflect evolutionary relatedness
   – Developed by Carolus Linnaeus (mid 1700s), a Swedish botanist
• Binomial Nomenclature (Linnaeus, 1758)
   – Each species receives a unique scientific name in Latin (common names
      differ by location and change over time)
       • Latin is a dead language (will not change), and is used internationally
   – Scientific names always two words (Genus species), always underlined or
      italicized (versus longer description in Latin); second name not used alone,
      lower case, often describes location species found or in honor of person
       • Tomato (pre-Linnaeus): Solanum caule inermi herbaceo, foliis pinnatis incises
• Descriptions of Newly Discovered Species
   – Often identified based on their physical structure (Morphological Species
      Concept); taxonomists attempt to include genetic comparisons and
      ecological descriptions also (e.g., habitat)
   – Holotype and Paratypes: first known specimen and subsequent specimens
      described in peer-reviewed scientific journal
Figure 26.3
     How are Phylogenetic Relationships
               Determined?
• Clade: an ancestral species and all of its descendents (a
      “branch on the Tree of Life”)
   – Cladistics: systematic analysis of clades and their relationships to
      other clades; focuses on the evolutionary innovations that define
      branch points in evolution (synapomorphies: shared, derived traits)
       • Parsimony: convergence considered more rare than homology; tree that
               results in fewest number of steps considered most parsimonious
• Techniques
   – Often heavy computer memory requirements for statistical tests
      (bootstrapping, Monte Carlo simulations, tests of monophyly)
       • If multiple trees result with equal significance, relationships remain
                 unresolved (a “bush” or polytomy)
       • Any single resulting tree still considered a hypothesis; best if consistent
                 with other independent evidence (e.g., the fossil record)
   – Character states entered for multiple traits (ex. horns present = 1,
      horns absent = 0); taxa that share more homologies considered
      more closely related; nucleotide or amino acid sequences often
      used (eliminates potential bias in choice of characters)
Figure 26.5
Figures 26.2 and 26.4
Figure 26.10
Figure 26.11
Figures 26.16 and 26.17
Figure 26.6
 The Evolution of Inflation in Pufferfishes




Phylogenetic trees can be produced via DNA comparisons (relatively free from
subjective choices of characters). Behaviors of interest then “mapped” onto tree.
Figure 26.21
Figures 26.22 and 26.23