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Speciation • Defined: evolution of a new species • Species: group of organisms that can interbreed and produce fertile offspring • Isolation reduces gene flow – Reproductive – Geographical – Behavioral – Temporal • Gene pools & frequencies altered 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 More Sun and Rain Less Sun and Less Rain Gene Flow 1) Geographic Isolation • Mountains, rivers, canyons, oceans may separate a population – Natural selection allows favorable organisms to survive in different environments • Each population adapts to its isolated environment • Because isolated, no gene flow Founder Effect: 14 Species of Galapagos Finches 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 3) Temporal Isolation • Although not geographically separated, reproduction is prevented – 1) Mate at different seasons – 2) Some noctural • No gene flow: differing populations unable to reproduce 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 • Species: group of organisms that can interbreed and produce fertile offspring Quick Review • New species are created (speciation) when populations become isolated • A changing or new environment greatly affects natural selection • I love the Far Side!