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Clemson BIOL 3350 - Darwin and Mendel's Contributions
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BIOL 3350 1st Edition Lecture 7Outline of Last Lecture I. The Effects on Finches of 1976-1978 Drought on Daphne MajorII. Alfred Russel WallaceIII. The History of Evolutionary ThoughtIV. Selection does not have a goalV. Evolution is not intrinsically progressiveOutline of Current Lecture I. Dilemma/Critiques for DarwinII. Castle’s ExperimentIII. Maintenance of variationIV. SpeciationV. The Contributions of MendelVI. The Modern SynthesisCurrent LectureI. Dilemma/Critiques for Darwina. Natural selection is limited in its effectivenessi. Artificial selection reaches a limit at which the trait value can no longer beextendedb. Small differences are not large enoughII. Castle’s Experimenta. Artificial selection on “racing stripe” width in hooded ratsb. Maybe selection modifies the genesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c. Should reach a plataeu if keep selecting for racing striped. Modifying factors were changed due to selection factorse. Continuous range of widthsf. Recombination of multiple genes extends the “limits” of selectiong. Changes can accumulate and you can break plataeuh. The original genes have not changed i. By having this range of variation, some rats were born with original racing stripesj. Selection can work on continuous variations and the original genes have not actually changedIII. Maintenance of variationa. Blending inheritance i. Does not allow for variation among individuals to be maintainedb. Environmental variationi. The environment produces many changes in the geneii. Changes in genes could cause positive effectsc. Survival of mutantsi. Mutants have greater survival most of the timesd. Discrete traits are determined by a single gene and are actually raree. Most traits are determined by the effects of multiple genesi. These polygenic traits show continuous variationIV. Speciationa. Adaptive divergence can result in reproductive isolate between speciesb. Small changes can accumulate when two populations of the same species exist indifferent habitats à if they come back into contact with each other, they may not be able to reproduce with each other anymorec. If barrier is created, the two populations start adapting to their individual habitats and become so different that they are no longer compatible as matesd. Allopatric speciation – speciation that is taking place in geographic isolatione. Speciation can occur even without geographic barrier à limnetic lives in deep part of lake and benthic lives at top in open waterf. They diverged in the presence of one another because they were choosing different sub habitatsg. When it came to mating benthic were too small for limnetic and limnetic were too big for small (the preferred mating with their own sizes)h. Preference for spawning with organism of the same size à this drove speciationi. Sympatric speciation – speciation in the same placej. Punctuated way of evolution – long periods of no change followed by short, rapidburst of evolutionk. Driving force behind evolutionary change is environmental changel. During periods of rapid environmental change (glacial period) à punctuated, rapid changes in evolutionm. Examples of intense natural selection and subsequent rapid evolutioni. Antibiotic resistance – occurs because bacteria are rapidly evolving to become resistantii. Viruses also become resistant to treatmentsiii. Almost all viruses are resistant when it becomes about 20 months of using treatmentiv. This is why a variety of treatments are used in order to prevent viral resistanceV. The Contributions of Mendela. - Mendel solved mechanism of how traits are passed from one generation to another à passed on discretely from parent to offspring (not blended)i. Particulate inheritance of discrete traitsii. Independent assortment and segregation of alleles produce variationb. Experiments done with ground finch show that continuous traits can have very high heritabilityc. This continuous trait is almost entirely due to genetics since the slope of the line is almost 1VI. The Modern Synthesisa. Population geneticsi. Demonstrated that mutation is not an alternative to natural selectionii. Mutation is the raw material upon which natural selection and other forces of evolution actb. Evolution results from small genetic changes that are acted upon by natural selectionc. Process operating within species account for the major, long term features of evolutioni. Small microevolutionary changes are the same mechanisms that are responsible for macroevolutionary changesii. Small changes leads to


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Clemson BIOL 3350 - Darwin and Mendel's Contributions

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