L2: The Tree of Life

• What does the medieval view of the scala naturae represent?

  • An ascending stairway of life forms
  • Ranges from lower forms (minerals) to higher forms (God)
  • Each higher being possesses attributes of all lower beings
• What is the title of Linnaeus' work published in 1735?

  Linnaeus’ Kingdom of Animals
• What is the modern Linnaean classification order?

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• What concept from medieval thinking still exists in modern views of evolution?

  The March of Progress towards Homo sapiens
• What did Charles Darwin suggest about species in relation to extinction?

  Extinction is necessary for many species to exist within the same genus
• What does Darwin's diagram of divergence of taxa illustrate?

  Some taxa go extinct while others diverge or remain unbranched
• Who redefined evolution in 1937 and how?


  Theodosius Dobzhansky defined evolution as a change in allele frequency in a gene pool
• What questions can be answered with an understanding of evolution?

  Questions about antibiotic resistance, pesticide resistance, and organism distribution
• What types of evidence can be used to examine lineages?

  Behavioral, ecological, morphological, and molecular evidence
• What traits are useful for constructing phylogenies in whales?

  Homologous traits, derived traits, and apomorphies
• What is homology in the context of evolutionary biology?

  Similarity between traits due to shared ancestry
• How can a fin and a hand be homologous?

  Both can develop through programmed cell death in embryonic development
• What happens to the hindlimb in dolphin embryos?

  The hindlimb develops but is then reabsorbed
• What remains in some whales despite the loss of hindlimbs?

  Pelvic girdles and occasionally small leg bones
• What are synapomorphies in evolutionary biology?

  Derived traits shared by two or more taxa
• What is the significance of synapomorphies in whale evolution?

  • Shared derived characteristics
  • Indicate common ancestry
  • Help in classifying and understanding evolutionary relationships
• What molecular evidence supports the relationship between cetaceans and artiodactyls?

  Comparison of protein sequences and DNA sequences identifies Hippos as the nearest living relative
• What is cladistics in phylogenetic analysis?

  • Classification based on most recent common ancestry
  • Groups organisms by shared derived characteristics (synapomorphies)
  • Depicted as a phylogenetic tree
• What do nodes represent in a phylogenetic tree?

  Branch points that represent common ancestors
• How should one read a phylogenetic tree?

  Read from its nodes, not from the taxa
• What happens when branches rotate around nodes in a phylogenetic tree?

  The label order changes, but the relationships shown by the nodes do not change
• What is a clade in phylogenetics?

  An ancestor and all its descendants
• What defines a monophyletic group in cladistics?

  A clade that comprises an ancestor and all its descendants
• What do phylogenetic trees tell us about evolutionary changes?

  They show the order of changes based on synapomorphies
• Why is the term 'fish' considered problematic in cladistics?

  Because it captures amphibians, mammals, reptiles, and birds as well
• What are autapomorphies in evolutionary biology?

  A derived trait that is unique to a given taxon
• What unique traits do platypuses possess as mammals?

  They lay eggs and have venom glands connected to hollow spurs
• What is horizontal gene transfer (HGT)?

  The sharing of genes between organisms, creating a web of life
• Who sketched the 'Tree of Life' in 1837?

  Charles Darwin