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Chapter 5.6 Speciation and Evolution

Chapter 5.6 Speciation and Evolution. 5.6 Speciation and Evolution. I.) Speciation Formation of new species Species A population of individuals who are reproductively isolated Not capable of breeding with individuals of other species under natural conditions.

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Chapter 5.6 Speciation and Evolution

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  1. Chapter 5.6Speciation and Evolution

  2. 5.6 Speciation and Evolution I.) Speciation • Formation of new species • Species • A population of individuals who are reproductively isolated • Not capable of breeding with individuals of other species under natural conditions

  3. Allopatric speciation – speciation by reproductive isolation • A physical barrier separates a single interbreeding population into 2 or more groups • Groups are isolated from each other • Any mutations that occur in these groups are not shared with other populations • From large to small physical barriers • Mountain ranges, oceans, river channels, canyons, dams, canals

  4. 2. Natural selection works on separated groups independently • Results in inherited differences in the 2 populations • I.e., populations evolve independently • Differences in selective pressures will be greater the more pronounced the environmental differences

  5. 3. In time, accumulated physical and / or behavioral populations are pronounced that groups cannot reproduce with each other • If reunited, individuals of these 2 groups are not sexually compatible • Thus, the formation of two or more distinct species

  6. EXAMPLE: PLANT SPECIATION • A single population splits into distinct breeding populations in a single geographic region • Sudden process • Mutation results in a double # of normal chromosomes • Polyploids • Healthy, vigorous individuals • Reproductively isolated from rest of population • http://bcs.whfreeman.com/thelifewire/content/chp24/2402001.html

  7. II.) Rate of Evolution • Theory of gradualism • Speciation takes place slowly • However, distinct species often appear abruptly in fossil record • Little further change is seen over very long periods of time

  8. Theory of punctuated equilibrium • Proposed by Eldridge and Gould • 3 assertions: • Many species evolve rapidly in evolutionary time • Speciation usually occurs in small isolated populations • Intermediate fossils are rare • After an initial burst of evolution, species are well adapted to their environment • They do not significantly change over long periods of time Dr. Niles Eldridge Dr. Stephen Jay Gould

  9. Gradualism vs. punctuated equilibrium

  10. III.) Macroevolution:Diversificationand Extinction • Earth has experienced an increase in diversity of living things • Interrupted by “extinction” events • Example: Burgass Shale • Canada’s Rocky Mountains • 515 million year old fossils • 120 species • Evidence for divergent evolution • Evolution into many different species

  11. https://www.youtube.com/watch?v=2oKlKmrbLoU Read page 159

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