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Species and Speciation

Species and Speciation. BIOL 1407. Biological Species Concept. A group of organisms that can interbreed and produce viable, fertile offspring Photo Credit of Gal á pagos Marine Iguanas: Putneymark, 2008, Wikimedia Commons. Biological Species Concept. Assumes Common characteristics

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Species and Speciation

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  1. Species and Speciation BIOL 1407

  2. Biological Species Concept • A group of organisms that can interbreed and produce viable, fertile offspring • Photo Credit of Galápagos Marine Iguanas: Putneymark, 2008, Wikimedia Commons

  3. Biological Species Concept • Assumes • Common characteristics • Genetically compatible • Interbreed under natural conditions • Sexual Reproduction • Photo Credit of Iguana iguana: Ianare, 2007, Wikimedia Commons

  4. Drawbacks of Biological Species Concept • Cannot be used with exclusively asexual organisms • Prokaryotes • Amoeba & some other protists • Some animals, plants & fungi • Photo Credit of Amoeba proteus: Angel, BIOL 1407 student, fall 2008

  5. Drawbacks: Isolated Populations • How do you test for interbreeding under natural conditions? • Can a deer in Florida interbreed with one in Wisconsin? • Photo Credit of Key Deer: Scott Bauer, 2006, USDA • Photo Credit of Deer Running: Paul Frank, 2006, USFWS

  6. Drawbacks • Can a Great Dane interbreed with a Chihuahua? • Photo Credit: David Shankbone, 2006, Wikimedia Commons

  7. Some species look and behave differently Can interbreed and have viable, fertile offspring Example: coyotes, wolves, dogs Picture Credits: Courtesy of Smithsonian National Zoo @ nationalzoo.si.edu (coyote and wolf); Pam Wolfe (dog) Drawbacks

  8. Drawbacks:Horizontal Gene Transfer • Vertical gene transfer • Parents  offspring • Horizontal gene transfer • Individual  individual • Not parent-offspring • Diagram Credit: Gregorius Pilosus, 2009, Wikimedia Commons

  9. Horizontal Gene Transfer • Can occur between organisms: • Different species • Different kingdoms • Different domains • Diagram Credit: Barth F. Smets, Ph.D., with permission, 2005, Wikimedia Commons

  10. Horizontal Gene Transfer in Bacteria (1) Transformation

  11. Horizontal Gene Transfer in Bacteria (2) Transduction

  12. Horizontal Gene Transfer in Bacteria (3) Conjugation

  13. Horizontal Gene Transfer • E. coli 0157:H7 has picked up Shiga toxin gene from Shigella • Up to 25% genetic difference among E. coli strains • Photo Credit of E. coli 0157:H7: E. H. White, Centers for Disease Control, 1995, Wikimedia Commons

  14. Horizontal Gene Transfer • Normally, 25% genetic diversity  different species • Human and chimp genomes differ by only 1.2% • Photo Credit: Thomas Lersch, 2005, Wikimedia Commons

  15. Drawbacks: Fossil Species • Cannot tell if fossil organisms were capable of interbreeding • Photo Credit of Harlan’s Ground Sloth: Doyle Cross, 2006, UT Memorial Museum

  16. Fossils • Normally can’t compare genes of different fossil species

  17. Morphological Species Concept • Group of individuals that share common characteristics • Used for: • Fossils • Exclusively asexual • Traditional method for sexual organisms • Photo Credit of Orchid: Bernd Haynold, 2004, Wikimedia Commons

  18. Biological Species Concept:Reproductive Isolation • Barriers between species • Prevent viable fertile offspring • Photo Credit (Lesser Bird of Paradise): Roderick Eime, 2005; (Greater Bird of Paradise): Andrea Lawardi, 2008, Wikimedia Commons

  19. Reproductive Isolating Mechanisms • Prezygotic mechanisms • Before fertilization • Postzygotic mechanisms • After fertilization

  20. Prezygotic Mechanisms • Prevents: • Prevent mating from occurring • Prevents gametes from forming a zygote • Photo Credit for Sperm fertilizing an ovum: Wikimedia Commons, 2008

  21. Prezygotic Mechanisms: Temporal Isolation • Isolated by time • May breed: • Different times of day • Different seasons • Different years • Photo Credit: Alan Zomerfeld, 2006, Wikimedia Commons

  22. Temporal Isolation Late Winter Late Summer

  23. Prezygotic Mechanisms: Habitat Isolation • Same geographic area • Different habitats

  24. Prezygotic Mechanisms: Behavioral Isolation • Different courtship rituals • Blue-Footed Booby Video: http://www.youtube.com/watch?v=4MPfTzXEZdY • Photo Credit: Richard001, 2007, Wikimedia Commons

  25. Behavioral IsolationEastern and Western Meadowlarks • Isolated by Songs • Listen to both species (Links to songs are below the picture): • http://www.lewis-clark.org/content/content-article.asp?ArticleID=401

  26. Prezygotic Mechanisms: Mechanical Isolation • Structural differences prevent mating • Example: Genital openings (arrows) not aligned  NoMating

  27. Prezygotic Mechanisms: Gametic Isolation • Sperm cannot fertilize eggs • Very important in aquatic species (broadcast spawners) • Example: Sea Urchins

  28. Postzygotic Mechanisms • Prevents hybrid zygotes from developing into viable, fertile adults • Photo Credit of Zeedonk: Ondrejk, 2004, Wikimedia Commons

  29. Postzygotic Mechanism: Reduced Hybrid Viability • If Sheep and goats mate  Hybrid zygotes • Die before birth. • Photo Credit: Missouri NRCS Photo Gallery

  30. Postzygotic Mechanism: Reduced Hybrid Fertility • Male donkey x Female horse Mule • Mules: • Healthy (viable) • Sterile.

  31. Postzygotic Mechanism: Hybrid Breakdown • First generation hybrids are viable and fertile. • Offspring of hybrids are feeble or sterile.

  32. Speciation • Process of species formation • Two main mechanisms: • Allopatric speciation • Sympatric speciation

  33. Allopatric Speciation Geographic separation •  Genetic exchange • Populations become genetically different • Reproductive isolation

  34. Sympatric Speciation • Populations not geographically separated • Can be due to rapid genetic changes: • Alter morphology • Alter behavior • Alter habitat preferences

  35. Example: Sympatric Speciation • Euhadra snails • Mutation in one gene  Shell spirals in opposite direction • Instant mechanical isolation  Two species

  36. Adaptive Radiation • A common ancestor  Many new species • Relatively rapid • Common in island chains • Isolated • Numerous habitats & resources • Map Credit: M. Minderhoud, 2006, Wikimedia Commons

  37. Galápagos Finches • Ancestral finch from South America  Several finch species • Different diets • Different beak shapes • Different beak sizes

  38. Galápagos Finches

  39. Hawaiian Silverswords • Tarweed arrived from North America ~ 5 mya • Common ancestor  Silverswords • Map Credit: M. Minderhoud, 2006, Wikimedia Commons

  40. Hawaiian Silverswords

  41. The End Unless otherwise specified, all images in this presentation came from: Campbell, et al. 2008. Biology, 8th ed. Pearson Benjamin Cummings.

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