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Allopatric vs. Sympatric Speciation
Episode 920th January 2021 • My AP Biology Thoughts • Hopewell Valley Student Publications Network
00:00:00 00:05:26

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My AP Biology Thoughts

Episode #9

Welcome to My AP Biology Thoughts podcast, my name is Adrienne and I am your host for episode 9 called Unit 7 Evolution: Allopatric vs. Sympatric Speciation. Today we will be discussing the differences between allopatric and sympatric speciation and I will provide examples for each.

Segment 1: Introduction to Allopatric & Sympatric Speciation

  • Speciation: formation of a new species, occurs when a group of organisms isn’t capable of interbreeding and producing viable offspring anymore
  • Allopatric speciation: occurs through geographical isolation like a physical geographic barrier
  • Sympatric speciation: occurs without a geographical barrier
  • Driven by other factors: habitat differentiation and sexual selection. 

Segment 2: Example of Allopatric & Sympatric Speciation

Allopatric speciation

  • Ex. Isthmus of Panama: narrow strip of land that causes a geographical barrier between Caribbean sea and Pacific ocean
  • Two species of porkfish have emerged 

Sympatric speciation: 2 types (prezygotic and postzygotic barriers)

  • Prezygotic barriers: before the sperm and egg
  • Habitat: different times of year organisms reproduce
  • Ex. 2 related frog species, Rona aurora breeds earlier in the year than Roma poyilil making them unavailable for each other 
  • Behavioral: set of certain behaviors that must be executed to reproduce
  • Ex. New Birds of Paradise and Birds of Paradise have different courtship characteristics
  • Mechanical: the sexual parts must fit like a “lock” and “key”
  • Ex. 20 different species of Bush Babies, different sexual parts won’t fit and allow reproduction
  • Gametic isolation: if the gametes are incompatible, the organisms won’t reproduce
  • Ex. Cells of red and purple sea urchins are genetically incompatible, fertilization is impossible
  • Postzygotic barrier: after sperm and egg
  • Inviability: organism dies before reproduction
  • Infertility: organisms can’t form gametes
  • Breakdown: F2 generation doesn’t sexually develop properly
  • Ex. Horses and donkeys produce a mule but it cannot reproduce due to hybridization problems

Segment 3: Digging Deeper Allopatric & Sympatric Speciation

  • Connect to evolution: speciation is a mechanism of evolution, different species emerge because they are not able to mate and reproduce with each other 
  • Ties into evolution because evolution is the change in allelic frequencies over time 
  • Speciation occurs when the gene flow between populations of organisms is stopped
  • Populations diverge over time 
  • Allopatric speciation: different geographic regions have different selective pressures which leads to changes in the gene pool
  • Sympatric speciation: factors such as polyploidy and sexual selection leads to different allelic frequencies
  • Influence certain organisms with certain characteristics and behaviors to mate with each 

Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts, make sure that you visit www.hvspn.com. Thanks for listening!

 Music Credits:

  • "Ice Flow" Kevin MacLeod (incompetech.com)
  • Licensed under Creative Commons: By Attribution 4.0 License
  • http://creativecommons.org/licenses/by/4.0/

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