Speciation
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Transcript of Speciation
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Speciation
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Speciation• Speciation = formation of new species• Species = group of organisms that breed with
one another and produce fertile offspring in nature (share a common gene pool)
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Speciation can happen in two modes
• Modes of speciation:– Sympatric: new
species develop in same geographic region• Sym= same
– Allopatric: new species develop in separate regions• allo= other
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Isolation isn’t always bad…• As new species evolve, populations become
reproductively isolated from each other: When 2 populations cant breed and produce fertile offspring, resulting in separate gene pools– Behavioral isolation: Capable of breeding, but have
different courtship rituals or behaviors– Geographic isolation: Separate by geographic barriers– Temporal isolation: Reproduce at different times
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Geographic Isolation (allopatric)
• Two populations are separated by geographic barriers. Over time different pressures result in distinct species– Rivers, mountains, bodies of water, glaciers, deserts
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Behavioral Isolation
• Differences in the behavior of two populations prevent mating
• Because there is no gene exchange between populations, evolution occurs
• Behaviors:– Mating rituals– Mate preference– Mate calling
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Behavioral Isolation (sympatric)
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Temporal Isolation (sympatric)
• Two or more populations are separated by the time of year/day that reproduction occurs– Nocturnal vs Diurnal mating– Seasonal mating differences
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Speciation can happen at two different rates
• Gradualism: Evolution occurs slowly, gradually and continuously
• Punctuated Equilibrium: Species remain unchanged for long periods of time. During certain events, species undergo rapid evolution.
• Both of the processes above have likely happened
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Speciation of Darwin’s Finches• Speciation in the Galapagos finches occurred by:
– Founding a new population: A small population of finches migrates to a different island
– Geographic isolation: Finches don’t usually fly over open water, so stayed on own island (separate gene pool)
– Changes in the new population’s gene pool: Adapted to new environment (directional selection) to be more fit
– Reproductive isolation: Differences in phenotypes and mating rituals may turn different finches off to one another
– Ecological competition: Similar finches compete, so individuals that are most different from each other have the highest fitness, because less competition.
– Continued Evolution: Process repeats and over many generations, it produced the 13 different finch species
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