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horse

horse. donkey. Speciation. mule. Speciation. Defined : evolution of a new species Species : group of organisms that can interbreed and produce fertile offspring Factors that lead to evolution Natural Selection Gene flow Mutations Sexual selection Genetic drift. Gene Flow.

ashely-freeman
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horse

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  1. horse donkey Speciation mule

  2. Speciation • Defined: evolution of a new species • Species: group of organisms that can interbreed and produce fertile offspring • Factors that lead to evolution • Natural Selection • Gene flow • Mutations • Sexual selection • Genetic drift

  3. Gene Flow • Defined: Movement of alleles from 1 population to another • With gene flow: • At first: Increases variations in a population (new genes introduced) • Over time: Populations appear more similar (genes mix together) • Without gene flow • No variations exchanged • Organisms adapt to their own environment • New species develop

  4. Genetic Drift • Defined: Changes in gene pool due to chance (not natural selection) • More likely in smaller populations • Ex: Natural disaster • Pre-forest fire (left picture): Blue is more advantageous • Post-forest fire (right picture): Due to more red survivors, red has the advantage to reproduce • Survival unrelated to adaptations

  5. Geographic Isolation • Mountains, rivers, canyons, oceans may separate apopulation • Gene flow stopped • Each population adapts to its isolated environment • Over time, genetic differences prevent reproduction (new species)

  6. Kaibab Squirrel (Grand Canyon)

  7. 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. 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 • Occurs as a result of behavioral, geographical, & temporal isolation • No mating = no gene flow • Two groups unable to reproduce • Sex organs don’t match • rituals don’t attract • physically separated • New species created

  10. Kobe Kuiz • What is speciation? • What leads to speciation? • What is gene flow? • What happens if gene flow is prevented? • How are temporal, behavioral, and geographic isolation different? • How are temporal, behavioral, and geographic isolation similar?

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