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Speciation

Speciation. The evolution of new species. Species. A group of populations whose individuals have the potential to interbreed and produce fertile offspring in a natural environment . (Ernst Mayr). Liger.

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Speciation

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  1. Speciation • The evolution of new species.

  2. Species • A group of populations whose individuals have the potential to interbreed and produce fertile offspringin a natural environment. (Ernst Mayr)

  3. Liger Result of male lion and female tiger mating in captivity. Offspring are infertile.

  4. Tigon Result of male tiger and female lion mating incaptivity. Offspring are infertile. Separated both geographically and ecologically.

  5. Charles Darwin • Wrote in 1859: “On the Origin of Species by Means of Natural Selection” Two main points: 1. Species were not created in their present form, but evolved from ancestral species. (Descent With Modification) 2. Proposed a mechanism for evolution:NATURAL SELECTION

  6. What are the two driving forces behind speciation?

  7. The biological species concept is based on interfertility rather than physical similarity

  8. Ethnic Groups

  9. Speciation in African Cichlids

  10. Macroevolution vs. Microevolution?

  11. Macroevolution is above the species level. Microevolution is at the species level.

  12. Speciation can take place with or without geographic barriers.

  13. Geographic Isolation • Induced when the ancestral population becomes separated by a geographical barrier. • Example: Grand Canyon ground squirrels

  14. Geographic Isolation Kaibab Squirrel (left) Abert Squirrel (right)

  15. Reproductive Isolating MechanismsGeographic Isolation

  16. Has speciation occurred during geographic isolation?

  17. Insect Eaters

  18. Adaptive Radiation • Emergence of numerous species from a common ancestor introduced to new and diverse environments. • Occurs as a result of DivergentEvolution • Examples: Darwin’s Finches, African Cichlid Fish

  19. Directional selection for beak size in a Galápagos population of the medium ground finch

  20. Reproductive Barriers • Any mechanism that impedes two species from producing fertile and/or hybrid offspring.

  21. Blue-Footed Boobies in the Galapagos Islands Figure 24.3 Courtship ritual as a behavioral barrier between species Behavioral Isolation (Courtship Rituals)

  22. Reproductive Isolating Mechanisms Sciurus carolinensis, the gray squirrel, breeds in July and August Sciurus niger, the fox squirrel breeds in May and June

  23. Bishop’s Pine releases pollen in summer Monterey Pine releases pollen in early spring Temporal Isolation (a specific type of reproductive isolation)

  24. Reproductive Isolating Mechanism • Behavioral Isolation Bluestripe butterflyfish Ornate butterflyfish

  25. Mechanical Isolation

  26. Ensatina eschscholtzii, a ring species, here in the Golden State, an example of reduced hybrid viability and adaptive radiation

  27. White-crowned Sparrowinhabits fields and meadows Ecological Isolation White-throated Sparrowfeeds in dense thickets

  28. A Model for Adaptive Radiation on Island Chains

  29. Hawaiian Silversword Evolved 5 million years ago; 28 endemic species

  30. Different geographic regions, different mammalian “brands” – Eutherian vs. Marsupials Convergent Evolution

  31. Gradualism Punctuated Equilibrium

  32. Interpretations of Speciation • Two theories: 1. Gradualist Model: Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change. (Eldredge and Gould)

  33. Macroevolutionary changes can accumulate through many speciation events.

  34. “Evo-Devo” biologists compare developmental processes of different multicellular organisms Development is intimately connected to evolution because all changes in form come about through changes in development.

  35. Homeotic Genes – any of the master regulatory genes that control overall body plan of animals and plants by controlling the developmental fate of groups of cells The products of one class of homeotic genes called Hox genes provide positional information in an animal embryo.

  36. Hox mutations and the origin of vertebrates

  37. Homologous genes that affect pattern formation in a fruit fly and a mouse

  38. “The amazing diversity of organisms has been produced by a modest number of genes” (Sean Carroll – author of Endless Forms Most Beautiful)

  39. Speciation that occurs in which members are separated from each other is called ____________ isolation. Give an example using either the common name or species names. Speciation that occurs in which members have no barriers between them is called ______________ isolation.

  40. The driving forces behind speciation include: Why is it that all “bad” mutations are not eventually eliminated from populations?

  41. The biggest difference between amphibian eggs and reptilian eggs was the development of the. . . The five groups of vertebrates are: Reptiles can reproduce in three ways. These are:

  42. Name two characteristics • common to almost all members • of the following classes of • animals: • amphibians • reptiles • mammals

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