One definition biological species concept ernst mayr

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One definition: Biological Species Concept Ernst Mayr & Theodore Dobzhansky A species is a group of individuals with the potential to interbreed in their natural environment (a.k.a. a biospecies ) Gene flow between different populations maintains their similarities Gene flow barriers between species = isolation mechanisms Isolation mechanisms may act to prevent fertilization from occurring (= prezygotic ) or to prevent a hybrid from breeding (= postzygotic ) Speciation = origin of new species
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28 Habitat isolation Grassland Forest Will interbreed in captivity Prezygotic isolation mechanisms
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29 Temporal isolation Eastern spotted skunk S. putorius Breeds in late winter Western spotted skunk Spilogale gracilis Breeds in late summer Prezygotic isolation mechanisms
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30 Behavioural isolation Eastern meadowlark Sturnella magna Western meadowlark S. neglecta Different mating songs Prezygotic isolation mechanisms
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31 Columbine, Aquilegia canadensis Pollen/nectar accessible only to hummingbirds Mechanical isolation Prezygotic isolation mechanisms
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32 Even if mating occurs, sperm die before reaching, or cannot fuse with, the ovum Gametic isolation Prezygotic isolation mechanisms In sea urchins, gametes of different species are unable to fuse
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33 Reduced hybrid viability Leopard frogs, Rana spp. Hybrids die before reaching maturity Postzygotic isolation mechanisms
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34 Reduced hybrid fertility Horse Donkey Mule (hybrid) Healthy but sterile Postzygotic isolation mechanisms
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35 Hybrid breakdown Postzygotic isolation mechanisms F2 hybrids of different strains of rice are small and infertile
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36 Morphological species concept Alternative to B.S.C. Species are defined based on arbitrarily selected physical traits Used by Linnaeus Unlike biological species concept, can be used with Asexual species Extinct species (a.k.a. paleontological species concept ) Main disadvantage is that species are defined arbitrarily; no objective criterion is used
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