ORIGIN OF SPECIES     Chapter 24
Speciation• Speciation - Origin of  new species• Two models:  – Anagenesis  – Cladogenesis• Micro v. Macro evolution  – Mi...
What is a species?• Hard to define, considers  – Morphology  – Body function  – Biochemistry  – Behavior  – Genetics• Biol...
Biological SpeciesEastern meadowlark (left) and western meadowlark (right) aretwo different species even though they look ...
Barriers toReproduction• Prezygotic –  prevent fertilization• Postzygotic –  prevent viable, fertile  offspring
Example of Behavioral BarrierBehavioral signal (dance, movement, pattern, etc.) is required formating. “Secret password.” ...
Modes of Speciation
Example of Allopatric Speciation    A. harrisi        A. leucurus
Speciation and Geographic Isolation
North American salamander:       A Ring Species
Adaptive Radiation
Long-distance dispersal and adaptive radiation
Sympatric speciation by autopolyploidyPolyploidy – extra sets of chromosomesAutopolyploidy – extra sets of chromosomes der...
AllopolyploidyContribution of two different species to apolyploid hybrid
Models for the tempo of speciation
“Evo-Devo”• Evolutionary Biology meets Development  – Slight genetic divergence can become major    difference between spe...
Allometric GrowthDifferent rates of growth – alter body proportionsduring development
Heterochrony•Different timing•Modification in allometric growth•Example: Salamander feet –    •a - longer time for foot de...
PaedomorphosisAdult stage of species retains juvenile characteristics
Homeotic GenesDetermine placement of body partsExample: Hox genes – position of body parts in animals
Hox mutations and the evolution of vertebrates                                Development of                              ...
Species Selection
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Ch.24 origin of species

  1. 1. ORIGIN OF SPECIES Chapter 24
  2. 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. 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. 4. Biological SpeciesEastern meadowlark (left) and western meadowlark (right) aretwo different species even though they look alike. They arereproductively isolated.
  5. 5. Barriers toReproduction• Prezygotic – prevent fertilization• Postzygotic – prevent viable, fertile offspring
  6. 6. Example of Behavioral BarrierBehavioral signal (dance, movement, pattern, etc.) is required formating. “Secret password.” For fun: search “blue-footed booby” inyoutube.
  7. 7. Modes of Speciation
  8. 8. Example of Allopatric Speciation A. harrisi A. leucurus
  9. 9. Speciation and Geographic Isolation
  10. 10. North American salamander: A Ring Species
  11. 11. Adaptive Radiation
  12. 12. Long-distance dispersal and adaptive radiation
  13. 13. Sympatric speciation by autopolyploidyPolyploidy – extra sets of chromosomesAutopolyploidy – extra sets of chromosomes derived from a single species(failure of meiosis). Ex: 2n becomes 4n and 4n self-fertilizes or mates withother 4ns.
  14. 14. AllopolyploidyContribution of two different species to apolyploid hybrid
  15. 15. Models for the tempo of speciation
  16. 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. 17. Allometric GrowthDifferent rates of growth – alter body proportionsduring development
  18. 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. 19. PaedomorphosisAdult stage of species retains juvenile characteristics
  20. 20. Homeotic GenesDetermine placement of body partsExample: Hox genes – position of body parts in animals
  21. 21. Hox mutations and the evolution of vertebrates Development of backbone Development of jaws and limbs
  22. 22. Species Selection
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