Notes 3: Analyze Patterns and Phylogenetic Trees

• Purpose of studying Evidence of Evolution


  To understand if species share common ancestry

  
• Evidence for evolution


  • Fossil evidence
  • Embryological development
  • Homologous structures
  • Analogous structures
  • Vestigial organs/structures
• Fossil evidence


  • Record of the history of organisms, which includes transitional fossils, indicating a link between extinct and living species
• Embryological development


  • Embryos of different species that develop similarly early on show evidence of common ancestry
• Homologous structures


  • Species sharing similar structures with different functions show evidence of common ancestry. The greater the number of shared structures, the more closely those species are related
• Analogous structures


  • Species that have different structures, but similar function evolved this way due to similar environments and NOT common ancestry
• Vestigial organs/structures


  • Structures with little or no function to the organism, which are remnants of structures that had important functions in ancestors of the species
• Speciation


  Forming of a new species by evolution from pre-existing species
• Divergent evolution speciation


  • A number of different species arise from one common ancestor. New environments caused them to evolve to be different
• Convergent evolution speciation


  • Unrelated species evolve similar characteristics because they live in similar environments and NOT because they have a common ancestor
• Phylogeny


  Evolutionary history of a species or group of related species
• Phylogenetic trees


  • Diagrams that scientists use to organize the research and patterns they find while studying evidence for evolution
• Phylogenetic trees


  • Help scientists predict the evolutionary relationships of organisms
  • Organized using evidence AND taxonomy (naming system)
  • Constructed to make the simplest relationships
  • Classifies organisms into major taxa (groups) based on evolutionary relationships
  • Classifies species in the order in which they descended from a common ancestry using physical characteristics
  • Can show order of species divergence from the common ancestor and some even more specifically show time of divergence

  
• What you can learn from a phylogenetic tree


  • Which groups are most closely related
  • Which groups are least closely related
  • Which group diverged first (longest ago)

  
• How to read phylogenetic trees

  • Speciation: branching of a family tree
  • Extinction: loss of one of the branches
  • Start reading from the "trunk," which represents a common ancestor that all organisms on the tree evolved from
  • Each node represents a more recent common ancestor

  
• They do NOT show that A → B → C → D
• They also do NOT show that A > B > C, etc