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The Origin of Species

The Origin of Species. AP Biology Crosby High School. Reproductive Isolation. Prezygotic Barriers: Habitat Isolation: Parasites in different hosts Behavioral Isolation: Generally courtship rituals Temporal Isolation: Different time, day, season, or year

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The Origin of Species

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  1. The Origin of Species AP Biology Crosby High School

  2. Reproductive Isolation • Prezygotic Barriers: • Habitat Isolation: Parasites in different hosts • Behavioral Isolation: Generally courtship rituals • Temporal Isolation: Different time, day, season, or year • Mechanical Isolation: Square peg, round hole • Gametic Isolation: Gamete recognition doesn’t match

  3. Reproductive Isolation (cont.) • Postzygotic Barriers: • Reduced Hybrid Viability: Embryo may abort due to genetic incompatibility • Reduced Hybrid Fertility: Hybrid can not backbreed due to sterility • Hybrid Breakdown: May produce one generation of viable and fertile offspring, but future generations are not

  4. Classifying a Species • Biological Species: emphasizes reproductive isolation • Ecological Species: Species defined by ecological niche • Pluralistic Species: Reproductive or niche • Morphological Species: Unique set of structural features • Geneological Species: Unique genetic history

  5. Allopatric Speciation • Conditions • Separated by a geographical feature • Changes must prevent interbreeding • Ring Species • California Salamanders more distant to the south • Adaptive Radiation • Diversely adapted species from common ancestor

  6. Evolution of Reproductive Barriers • Prezygotic: • Two populations of D. melanogaster • Starch vs. Maltose for generations • Maltose females only breed with maltose males

  7. Sympatric Speciation • Polyploid Speciation in Plants • 2n  4n • 4n can self pollinate or mate with other 4n • Oats, cotton, potatoes, tabacco, wheat • Sympatric Speciation in Animals • Pundamilia pundamilia vs. Pundamilia nyererei • Normal light vs. monochromatic orange

  8. Evolutionary Time “Although each species must have passed through numerous transitional stages, it is probable that the periods during which each underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition.” -Charles Darwin

  9. Punctuated Equilibrium • Evolution occurs so rapidly that there is no fossil record

  10. Eye Development • Pigmented Cells • Eyecup • Pinhole camera-type • Eye w/ Primitive lens • Complex Camera-type

  11. Exaptations • Develop for one purpose, but later end up serving another • Birds • Honeycombed bones • Original: light for agility • Present: light for flight • Feathers • Original: Display for mating • Present: flight

  12. Evo - Devo • Allometric Growth: Growth rates create proportioning for each species • Heterochrony: Evolutionary change in rate or timing of developmental events • Paedomorphosis: Rate of reproductive development accelerates compared to somatic • Homeotic genes: Determine placement and spatial organization of body parts • Hox genes

  13. Evolutionary Trends • Evolution is not goal oriented • Horse Evolution • Equus is only surviving genus of the tree • Not all adaptive radiations lead to same result • Parahippus: Grazers • Miohippus: Browsers • Species Selection: Species that endure the longest and reproduce the most set the trend for macroevolution

  14. Equus Evolution

  15. Sympatric Speciation

  16. Ring Species

  17. Adaptive Radiation

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