BIO 2150 Chapter 22 Notes I Types of Selection A Sexual Selection selecting a mate based on looks B Artificial Selection selective breeding of plants and animals by humans C Positive selection natural selection selects against a bad trait D Negative selection natural selection selects against the normal trait E Balancing selection natural selection selects for the middle trait II Factors That Cause Changes in Allele Frequencies A Migration populations moving to different areas B Mutation changing allele frequencies C Genetic drift Random event III Morphospecies Concept A The morphospecies concept says that organisms within a species are morphologically similar and therefore dissimilar from those of other species B In essence this concept says that organisms that look similar reflect genetic similarity C The problems with this concept are 1 Different life stages or sexes of the same species can look like different species 2 Different species can look almost identical IV Biological Species Concept A This concept says that species are groups of actually or potentially interbreeding populations that are reproductively isolated from other B Basically this concept says that the ability to interbreed depends on such groups genetic similarity C The problems with this concept are 1 It is difficult to apply to the real world 2 It can t be applied to asexual or extinct organisms 3 It doesn t account for hybridization in plants 4 It doesn t account for genetic exchange in ring species D Ring Species species that connect two other species through A This says that a new species can appear when two populations within the original species become genetically distant enough that they can t interbreeding V Origin of New Species interbreed B This is called speciation VI Speciation A During a speciation event 1 Gene flow has to be blocked preventing two populations from interbreeding 2 Enough genetic change must occur that the species can t interbreed B Allopatric Speciation depends on geographical separation of the original 1 It can be based on vicariance which is an event that separated the 2 It can be based on dispersal which is the migration of a portion of the population population population 3 Adaptive Radiation Occurs when a species enters an environment with many empty niches C Sympatric Speciation results from blocking gene flow between populations in the same geographical area 1 The populations can be separated by a Disruptive selection b Polyploidy VII Reproductive Isolation A Pre zygotic is when isolation occurs before fertilization B Some examples of pre zygotic isolation are 1 Behavioral 2 Physical 3 Time 4 Space C Post zygotic is when isolation occurs after fertilization D An example of post zygotic isolation is 1 Genetic Incompatibility
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