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Speciation

Speciation. 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). Speciation can happen in two modes. Modes of speciation:

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Speciation

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  1. Speciation

  2. 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)

  3. 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

  4. 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

  5. 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

  6. 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

  7. Behavioral Isolation (sympatric)

  8. 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

  9. 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

  10. 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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