1. led to geneticists' skepticism of the role of or need for natural selection
2. evolution by mutation versus evolution by natural selection

1. no inheritance of acquired characteristics
2. continuous variation has the same basis as Mendelian variation
3. variation within and among populations has a genetic basis
4. geographic variation is adaptive
5. hidden variation within natural populations is likely to be plentiful
6. species are not fixed types but variable populations that are reproductively isolated

1. All populations contain genetic variation that arises from random mutation and recombination
2. Populations evolve by changes in gene frequency via genetic drift, migration, mutation and natural selection
3. Phenotypic changes are gradual
4. Diversification of all life comes about by speciation
5. Genetic divergence of great magnitude can give rise to higher taxa

1. Part 1: full development of a mathematical theory of evolution within populations
   G. Hardy and W. Weinberg (1908) independently develop the mathematical models for evolution of populations
   1. S. Wright (1918, 1931) begins development of mathematical theory of the effects of evolutionary forces; publishes article: Evolution in Mendelian populations. Genetics 16:97-159.
   2. R.A. Fisher (1932) The Genetical Theory of Natural Selection establishes natural selection as the primary cause of evolutionary change
   3. J.B.S. Haldane (1932) The Causes of Evolution explains how evolutionary forces interact
2. Part 2:
   1. T. Dobzhansky (1937) Genetics and the Origin of Species - centerpiece of the New Synthesis
   2. E. Mayr (1942) Systematics and the Origin of Species documents extensive geographic variation
   3. G.G. Simpson (1944, 1953) Tempo and Mode in Evolution and The Major Forces of Evolution tied paleontological evidence to evolutionary theory
   4. J. Huxley (1942) Evolution and the Modern Synthesis
   5. G.L. Stebbins (1950) Variation and Evolution in Plants

1. perfection of forms
   1. observed variation in form is inconsequential
   2. no evolution of forms is possible (necessary) for perfect forms
   3. perfect forms are eternal; no extinction could be possible for any but imperfect forms
2. "Scala Naturae" or the Great Chain of Being
   1. continuum of forms (no gaps) from the inanimate ----> plants ----> animals ----> humans ----> angels
   2. no change; permanence
   3. fixity
3. philosophy later adopted by Christian church and gained wide influence in western thought

1. John Ray (1691): The wisdom of God manifested in the works of creation
2. Karl Linné (Carolus Linnaeus) published Systema Naturae (1735) and Species Plantarum (1753) "ad majorem Dei gloriam" (for the greater glorification of God)
   1. binomial nomenclature (two-name naming system)
   2. species name consists of
      1. generic (genus) name, e.g., Drosophila, Pisum
      2. specific epithet, e.g., canescens, sapiens
         1. Homo sapiens, Drosophila melanogaster, Pisum sativum
3. Speciation
   1. hybridization
   2. instant speciation
      1. chromosomal mutation
      2. polyploidy
   3. gradual speciation
      1. sympatric
      2. allopatric
         1. division of range
         2. isolation of colony
      3. parapatric
         1. Parapatric speciation involves a hybrid zone between two adjacent populations (this is not the same as the hybrid zone found after allopatric speciation and secondary contact)
            1. different allele(s) favored in each population
            2. width of hybrid zone proportional to s/h, where s is the standard deviation of the distance organisms disperse and h is the selection against heterozygotes
   4. observed instances of speciation
   5. mass extinction / adaptive radiation
4. Reproductive isolating mechanisms
   1. one view

                        premating
      
      1. potential mates do not meet                
      
        spatial (geographic, habitat)	isolation              
        temporal (seasonal, time of day) isolation
      
      2. potential mates meet but do not mate	      
      
        behavioral (courtship) isolation
      
                        postmating
      
      1. mating (copulation) attempted but no sperm transfer occurs
      
        mechanical isolation
      
      2. sperm transfer occurs but egg is not fertilized
      
        gametic mortality
      
      3. egg is fertilized but zygote dies
      
        hybrid (F1) mortality
      
      4. zygote grows but hybrid has reduced viability
      
        hybrid (F1) inviability
      
      5. zygote grows but hybrid is completely sterile
      
        hybrid (F1) sterility
      
      6. zygote grows but hybrid is partially sterile
      
        hybrid (F2) breakdown
      

   2. another view

                        prezygotic
      
      1. potential mates do not meet
      
        spatial (geographic, habitat) isolation
        temporal (seasonal, time of day) isolation
      
      2. potential mates meet but do not mate
      
        behavioral (courtship) isolation
      
      3. mating (copulation) attempted but no sperm transfer occurs
      
        mechanical isolation
      
      4. sperm transfer occurs but egg is not fertilized
      
        gametic mortality
      
                        postzygotic
      
      1. egg is fertilized but zygote dies
      
        hybrid (F1) mortality
      
      2. zygote grows but hybrid has reduced viability
      
        hybrid (F1) inviability
      
      3. zygote grows but hybrid is completely sterile
      
        hybrid (F1) sterility
      
      4. zygote grows but hybrid is partially sterile
      
        hybrid (F2) breakdown
      

This is not intended to be an exhaustive transcript of everything discussed in class; however, major topics not listed here will not be covered on the exam. It is intended as a guide to help in your preparation for the exam. When in doubt about the details, look first to your class notes, then check out the index at the back of your textbook(s).

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