ORIGIN OF SPECIES Chapter 24
Speciation <ul><li>Speciation  - Origin of new species </li></ul><ul><li>Two models: </li></ul><ul><ul><li>Anagenesis </li...
What is a species? <ul><li>Hard to define, considers </li></ul><ul><ul><li>Morphology </li></ul></ul><ul><ul><li>Body func...
Biological Species Eastern meadowlark (left) and western meadowlark (right) are two different species even though they loo...
Barriers to Reproduction <ul><li>Prezygotic  –  prevent fertilization </li></ul><ul><li>Postzygotic  – prevent viable, fer...
Example of Behavioral Barrier Behavioral signal (dance, movement, pattern, etc.) is required for mating.  “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 autopolyploidy Polyploidy  – extra sets of chromosomes Autopolyploidy  – extra sets of chromosomes...
Allopolyploidy Contribution of two  different  species to a polyploid hybrid
Models for the tempo of speciation
“ Evo-Devo” <ul><li>Evolutionary Biology  meets  Development </li></ul><ul><ul><li>Slight genetic divergence can become ma...
Allometric Growth Different rates of growth – alter body proportions during development
Heterochrony <ul><li>Different timing </li></ul><ul><li>Modification in allometric growth </li></ul><ul><li>Example:  Sala...
Paedomorphosis Adult stage of species retains juvenile characteristics
Homeotic Genes Determine placement of body parts Example:  Hox  genes – position of body parts in animals
Hox  mutations and the evolution of vertebrates Development of backbone Development of jaws and limbs
Species Selection
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Ch.24 origin of species

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Ch.24 origin of species

  1. 1. ORIGIN OF SPECIES Chapter 24
  2. 2. Speciation <ul><li>Speciation - Origin of new species </li></ul><ul><li>Two models: </li></ul><ul><ul><li>Anagenesis </li></ul></ul><ul><ul><li>Cladogenesis </li></ul></ul><ul><li>Micro v. Macro evolution </li></ul><ul><ul><li>Micro – changes within a population/ species </li></ul></ul><ul><ul><li>Macro – origin of new species, genera, etc. </li></ul></ul>
  3. 3. What is a species? <ul><li>Hard to define, considers </li></ul><ul><ul><li>Morphology </li></ul></ul><ul><ul><li>Body function </li></ul></ul><ul><ul><li>Biochemistry </li></ul></ul><ul><ul><li>Behavior </li></ul></ul><ul><ul><li>Genetics </li></ul></ul><ul><li>Biological species </li></ul><ul><ul><li>Reproductive isolation </li></ul></ul><ul><ul><li>Can produce viable, fertile offspring </li></ul></ul>
  4. 4. Biological Species Eastern meadowlark (left) and western meadowlark (right) are two different species even though they look alike. They are reproductively isolated.
  5. 5. Barriers to Reproduction <ul><li>Prezygotic – prevent fertilization </li></ul><ul><li>Postzygotic – prevent viable, fertile offspring </li></ul>
  6. 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. 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 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. 14. Allopolyploidy Contribution of two different species to a polyploid hybrid
  15. 15. Models for the tempo of speciation
  16. 16. “ Evo-Devo” <ul><li>Evolutionary Biology meets Development </li></ul><ul><ul><li>Slight genetic divergence can become major difference between species </li></ul></ul><ul><li>Genes that involve </li></ul><ul><ul><li>Rate of development </li></ul></ul><ul><ul><li>Timing </li></ul></ul><ul><ul><li>Spatial patterns </li></ul></ul><ul><li>Keywords involved </li></ul><ul><ul><li>Allometric growth </li></ul></ul><ul><ul><li>Heterochrony </li></ul></ul><ul><ul><li>Paedomorphosis </li></ul></ul><ul><ul><li>Homeotic genes </li></ul></ul>
  17. 17. Allometric Growth Different rates of growth – alter body proportions during development
  18. 18. Heterochrony <ul><li>Different timing </li></ul><ul><li>Modification in allometric growth </li></ul><ul><li>Example: Salamander feet – </li></ul><ul><ul><li>a - longer time for foot development – longer digits and less webbing </li></ul></ul><ul><ul><li>b – less time for foot development – shorter digits, more webbing – adaptation for gripping tree </li></ul></ul>
  19. 19. Paedomorphosis Adult stage of species retains juvenile characteristics
  20. 20. Homeotic Genes Determine placement of body parts Example: 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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