Allopatric vs. Sympatric Speciation and Hybrid Zones Flashcards Preview

AP Biology 2014 > Allopatric vs. Sympatric Speciation and Hybrid Zones > Flashcards

Flashcards in Allopatric vs. Sympatric Speciation and Hybrid Zones Deck (10):
1

Speciation

- the orgin of new species

- at the focal point of of evolutionary theory

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Allopatric speciation 


- Geographically separate populations may evolve independently through mutation, natural selection, and genetic drift

- Gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations

- even if contact is restored between populations, interbreeding is prevented

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Sympatric Speciation 

- a reproductive barrier isolates a subset of a population without geographic separation from the species

- occurs when gene flow is reduced

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What are the three ways in which gene flow is reduced? 

o    polyploidy- presence of extra sets of chromosomes due to accidents during cell division (more common in plants than animals- cotton, potatoes)
o    habitat differentiation- sympatric speciation can also result from the appearance of new ecological niches (North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees)
o    sexual selection- natural selection arising through preference by one sex for certain characteristic in individuals of theother sex (sexual selection for mates of different colors has likely contributed to the speciation in cichlid fish in lake Victoria)

 

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Sympatric vs. Allopatric Speciation

- allopatric- population geographically divided

- sympatric- reproductive barrier isolates population

- both give rise to new species that cannot interbreed

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Hybrid

- the offspring of crosses between different species

- for example: a mule is the offspring of a male donkey and a female horse

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Hybrid zone

- a region in which members of different species mate and produce hybrids

- can occur when adjacent species meet

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What are the possible outcomes when closely related species meet in a hybrid zone?

- strengthening of reproductive barrier

- weakening of reproductive barrier

- continued formation of hybrid individuals

 

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9

Polyploidy 

o   the presence of extra sets of chromosomes due to accidents during cell division (more common in plants than animas- cotton, potatoes)

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10

Habitat differentiation

- the appearance of new ecological niches (North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees)