Lec 28 - BIS2B Fall 2009 (Keen) Lecture 28 . Speciation III...

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Unformatted text preview: BIS2B Fall 2009 (Keen) Lecture 28 . Speciation III 16 November Examples of speciation; hybridization and ring species Students should be able to: Give examples of alloparatric, parapatric and sympatric speciation including relevant forms of reproductive isolation and situations that favor positive assortative mating Explain how hybrid zones and ring species arise Discuss ways in which hybrid zones and ring species pose problems for biological pigeon-holes (species descriptions) Q. In fishes, males and females release gametes into the water together. Suppose two closely related fishes occur in the same place and gametic isolation normally keeps the species from cross-fertilization. After gametic isolation fails, what could still keep the two lineages apart? a) spatial isolation b) hybrid inviability c) mechanical isolation d) behavioral isolation e) ecological isolation Cladograms Cladogenesis is the process of speciation or lineage splitting Cladograms are visual representations of proposed ancestor-descendant relationships. Species A Species B Species C most recent common ancestor MRCA sister taxa discuss branch order and time Cladograms are hypotheses about the sequence of evolution You will be taught how cladograms are constructed in BIS 2C. In essence, shared features that were inherited from a common ancestor indicate patterns of relationship: Homologous characters An homologous character is a character inherited from a common ancestor. If we see the same feature in two lineages, the feature might have been inherited from a common ancestor or it might have evolved independently. An homoplasious character is one that was not inherited from a common ancestor; it evolved independently. When/where did the characteristic beak evolve?...
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This note was uploaded on 04/21/2010 for the course BIS 2C BIS 2C taught by Professor Rizzo during the Winter '09 term at UC Davis.

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Lec 28 - BIS2B Fall 2009 (Keen) Lecture 28 . Speciation III...

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