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01:119:115 (825)
A L L (20)
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GENERAL BIOLOGY Notes (Part 14) - 4.0ed the course!

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Department
Biological Sciences
Course
01:119:115
Professor
A L L
Semester
Fall

Description
Macroevolution 11/19/2013 Speciation Process of one species splitting into two or more species Macroevolution Pattern of evolutionary change above species level Species Kind of organism Biological species concept Most widely accepted definition of “species” in biology Populations whose members have potential to interbreed + produce fertile offspring Do not interbreed w/ members of different species or produce viable, fertile offspring Genetically distinct from other species (not simply based on appearance) Emphasizes reproductive compatibility Reproductive isolating mechanisms Prevent species from interbreeding Biological barriers that interfere w/ interbreeding + productive of viable, fertile offspring Prezygotic barriers or mechanisms Work before mating, preventing fertilization from occurring Postzygotic barriers or mechanisms Work after fertilization has taken place Study figure 24.3 Prezygotic barriers Temporal isolation No genetic exchange occurs b/w 2 overlapping groups b/c reproduce at different times, season or year Habitat isolation No genetic exchange occurs b/w 2 groups in same geographic care b/c live + breed in different habitats in  that area Behavioral isolation No genetic exchange occurs b/w 2 groups in same geographic area b/c each w/ distinct mating signals or  courtship behaviors Mechanical barriers No genetic exchange occurs b/w 2 groups b/c of structural differences in reproductive organs Gametic barriers No genetic exchange occurs b/w 2 groups b/c of molecular + chemical differences in gametes Postzygotic barriers Hybrid inviability Development of embryo does not occur properly; dies before maturity Hybrid sterility Development of embryo occurs after mating/fertilization but offspring is sterile Hybrid breakdown Development of embryo occurs after mating/fertilization but offspring not sterile nd Mating of two hybrids can produce 2  hybrid generation, but it fails to reproduce (defects) Limitation to biological species concept Does not apply to organisms that reproduce asexually (e.g. prokaryotes) Gene flow sometimes occur b/w morphologically + ecologically distinct species Other definitions on species Morphological species concept Organisms classified on visible structural differences Can be subjective Biological species concept Organisms classified on their ecological niche (how they interact w/ environment + species nearby) Phylogenetic species concept Organisms classified on smallest group of individuals sharing a common ancestor Formation of 
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