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BIOLOGY 1M03 (663)
Ben J Evans (235)
Lecture 8

Bio 1M03 Notes lecture 8.odt

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McMaster University
Ben J Evans

Bio1M03 Lecture 8 Last time: • biological species concept • prezygotic barriers, post zygotic brriers • morphological species concept • phylogenetic species concept • allopatric speciation • sympatric speciation via disruptive selection in the soapberry bug Speciation by polyploidization (genome duplication) Comes in two ways: spontaneous duplication, or autopolyploidisation and through interaction with another species, or allopolyploidisation Autopolyploidy Angiosperm plants, eg ferms, developed through autopolyploidisation. EG Maidenhair ferns include diploid (2N)and tetraploid populations. Tetraploids are the offspring of a parent that produced diploid gametes and then self fertilized. Tetraploid (4N) individuals can breed with other tetraploids but not with diploids. Allopolyploidy may occur after two species hybridise. Tetraploid species are generated and these can undergo polyploidisation to generate “octoploid” species. -. can occur due to hybridisation, as pairing of homologous chromosomes require homology. Polyploidy can lead to reproductive isolation. The gametes of a triploid individual rarely contain the same number of each type of chromosome. When gametes combine, offspring almost always have an uneven and dysfunctional number of chromosomes. Genome duplication is an important phenomenon, humans came from a polyploid organism as well. By creating redundancy, we have the potential for crazy things to happen. When isolated populations come into contact When prezygotic isolation does not exist, populations may interbreed to produce hybrids. Gene flow then occurs and may erase distinctions between the two populations. Reinforcement If two populations of re
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