Unit 4: Mechanisms of Evolution Extras  Study Guide

Chapter 24 The Origin of Species Review
  1. A species is a group of organisms whose members can interbreed in nature and produce offspring under natural conditions.
  2. Reproductive can prevent interbreeding and result in reproductive .
    • Prezygotic barriers prevent the formation of , and include , , , , and isolation.
    • Postzygotic barriers prevent the from developing into a fertile adult, and include reduced hybrid , reduced hybrid , and hybrid .
  3. Speciation can occur by ("Other Country") speciation, or by speciation.
    • Sympatric speciation may also result from
      • chromosomal changes such as that leads to reproductive isolation.
      • selection that leads to nonrandom mating.
  4. Some isolation barriers may weaken over time and result in and allow two species to merge into one.
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