BISC208 Lecture Notes - Lecture 2: Sympatric Speciation, Allopatric Speciation, Allele Frequency
16 May 2016
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5/16/2016 5:21:00 AM
• The biological species concept
• Members of the same species:
• Interbreed in nature
• Produce viable and fertile offspring
• Cannot produce viable offspring with other species
• If organisms from two sexually reproducing populations do not fulfill these
criteria, these are reproductively isolated.
• Reproductive isolation: individuals from different populations of the same species
cannot produce viable offspring
• Pre-zygotic barriers:
o Spatial or temporal divergence
o Behavioral avoidance
o Mechanical and gametic isolation
• Post-zygotic barriers:
o Reduced hybrid viability
o Hybrid sterility
• Speciation event: part of a population becomes genetically isolated
• Phylogenetic species concept: genetics used to determine whether populations share a
common ancestor, called a monophyletic group or clade
• Morphological species concept: considers traits of species, even when highly divergent
individuals can interbreed
• Ecological species concept: information about an organism’s niche to distinguish
between species
• Domestication and artificial selection can lead to considerable morphological diversity
within the same species.
• Allopatric speciation: speciation following geographic separation
• Sympatric speciation: speciation within the same geographic region
• Fusion:
• Reinforcement
• Controversial:
• Polyploidy: the failure of chromosomes to separate during meiosis
• Sexual selection: differential mate choice
• Habitat differentiation: small-scale geographic segregation
• Reproductive isolation:
• Key to sympatric speciation
• Assertive mating-non random mating
The Biological Species Concept
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