Bio1151 Chapter 24 The Origin of Species
  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.