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horse

horse. donkey. Speciation. mule. Speciation. Defined : the rise of two or more species from an existing species Species : group of organisms that can interbreed and produce fertile offspring Isolation reduces gene flow Reproductive Geographical Behavioral Temporal

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horse

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  1. horse donkey Speciation mule

  2. Speciation • Defined: the rise of two or more species from an existing species • Species: group of organisms that can interbreed and produce fertile offspring • Isolation reduces gene flow • Reproductive • Geographical • Behavioral • Temporal • Gene pools & frequencies altered

  3. Gene Flow • Defined: Movement of alleles from 1 population to another • Increases variation • Keeps differing populations similar • If gene flow prevented: • No variations exchanged • Populations isolated • Organisms adapt to their own environment

  4. 1) Geographic Isolation • Mountains, rivers, canyons, oceans may separate apopulation • Natural selection allows favorable organisms to survive in different environments • Each population adapts to its isolated environment • Because isolated, no gene flow

  5. Kaibab Squirrel (Grand Canyon)

  6. Founder Effect: 14 Species of Galapagos Finches A B B D D C C

  7. 2) Behavioral Isolation • Although not geographically separated, reproduction is prevented • 1) Different mating rituals • 2) Use of pheromones • No gene flow: differing populations unable to reproduce

  8. 3) Temporal Isolation • Although not geographically separated, reproduction is prevented • 1) Mate at different seasons • 2) Some nocturnal • No gene flow: differing populations unable to reproduce

  9. End Result: Reproductive Isolation • Created as a result of behavioral, geographical, & temporal isolation • No mating between populations (no gene flow) • Two groups unable to reproduce • Sex organs don’t match, rituals don’t attract, physically separated • Final step to becoming different species • Ultimately leads to speciation = the rise of two or more species from one existing species.

  10. Quick Review • New species are created (speciation) when populations become isolated • A changing or new environment greatly affects natural selection

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