Speciation - Speciation Allopatric speciation The...

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Speciation Allopatric speciation The divergence of populations into different species by physical isolation of populations in different geographic areas. There are two kinds: vicariance and dispersal. Characteristics of a colonizing population are likely to be different from original species due to founder effects. Allopolyploidy The state of having more than two full sets of chromosomes (polyploidy) due to hybridization between two species. If two aren’t able to combine, they may duplicate separate genes and will make diploid gametes. Only plants are able to do this – example is Tragopogon specis introduced to North America hybridized and formed offspring that became teatraploid and formed new species. Autopolypoloidy The state of having more than two full sets of chromosomes due to a mutation that doubled the chromosome number. Ex: maidenhead ferns, mistake in meiosis in ancestor and created species of tetraploid ferns. They become genetically isolated with incapacity to mate with anyone but themselves. Behavioural isolation This is an example of prezygotic isolation. Ways that males compete for females separate species. Certain rituals ensure there are no mixing, other birds will not react to rituals. Ex: fireflies, they signal each other in a specific way, only the same species respond. Biological species The biological species concept is the definition of a species as a population or group of populations that are reproductively isolated from other groups. Members of a species have the potential to interbreed in nature to produce viable, fertile offspring but cannot produce viable, fertile hybrid offspring with members of other species. This speciation caused by prezygotic and postzygotic isolation. Disadvantages: we cannot use criterion on fossils or those that reproduce asexually.
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This note was uploaded on 09/09/2011 for the course BIO 1130 taught by Professor Fenwick during the Spring '08 term at University of Ottawa.

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Speciation - Speciation Allopatric speciation The...

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