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  • 1. ORIGIN OF SPECIES Chapter 24
  • 2. Speciation
    • Speciation - Origin of new species
    • Two models:
      • Anagenesis
      • Cladogenesis
    • Micro v. Macro evolution
      • Micro – changes within a population/ species
      • Macro – origin of new species, genera, etc.
  • 3. What is a species?
    • Hard to define, considers
      • Morphology
      • Body function
      • Biochemistry
      • Behavior
      • Genetics
    • Biological species
      • Reproductive isolation
      • Can produce viable, fertile offspring
  • 4. Biological Species Eastern meadowlark (left) and western meadowlark (right) are two different species even though they look alike. They are reproductively isolated.
  • 5. Barriers to Reproduction
    • Prezygotic – prevent fertilization
    • Postzygotic – prevent viable, fertile offspring
  • 6. Example of Behavioral Barrier Behavioral signal (dance, movement, pattern, etc.) is required for mating. “Secret password.” For fun: search “blue-footed booby” in youtube.
  • 7. Modes of Speciation
  • 8. Example of Allopatric Speciation A. harrisi A. leucurus
  • 9. Speciation and Geographic Isolation
  • 10. North American salamander: A Ring Species
  • 11. Adaptive Radiation
  • 12. Long-distance dispersal and adaptive radiation
  • 13. Sympatric speciation by autopolyploidy Polyploidy – extra sets of chromosomes Autopolyploidy – extra sets of chromosomes derived from a single species (failure of meiosis). Ex: 2n becomes 4n and 4n self-fertilizes or mates with other 4ns.
  • 14. Allopolyploidy Contribution of two different species to a polyploid hybrid
  • 15. Models for the tempo of speciation
  • 16. “ Evo-Devo”
    • Evolutionary Biology meets Development
      • Slight genetic divergence can become major difference between species
    • Genes that involve
      • Rate of development
      • Timing
      • Spatial patterns
    • Keywords involved
      • Allometric growth
      • Heterochrony
      • Paedomorphosis
      • Homeotic genes
  • 17. Allometric Growth Different rates of growth – alter body proportions during development
  • 18. Heterochrony
    • Different timing
    • Modification in allometric growth
    • Example: Salamander feet –
      • a - longer time for foot development – longer digits and less webbing
      • b – less time for foot development – shorter digits, more webbing – adaptation for gripping tree
  • 19. Paedomorphosis Adult stage of species retains juvenile characteristics
  • 20. Homeotic Genes Determine placement of body parts Example: Hox genes – position of body parts in animals
  • 21. Hox mutations and the evolution of vertebrates Development of backbone Development of jaws and limbs
  • 22. Species Selection