Week 4 Notes
Week 4 Notes 81463 - BIOL 3030 - 001
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This 6 page Class Notes was uploaded by Abigail Towe on Wednesday September 16, 2015. The Class Notes belongs to 81463 - BIOL 3030 - 001 at Clemson University taught by Richard W. Blob in Fall 2015. Since its upload, it has received 63 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.
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Date Created: 09/16/15
Evolutionary Biology Biol 3550 Week 4 Lecture Outline Review 0 selection does NOT have a goal 0 the environment favors certain traits I example finches in drought a thicker beak is favored 0 Evolution is not intrinsically progressive 0 many simple forms have stayed virtually unchanged for hundreds of millions of years 0 some complex forms have become extinct 0 some complex forms have become simpler O increasingly diversity of life on Earth I Ancestral Free living mite need microscope to see them 0 parasitic skin mite O free living dust mite Merger of Darwin amp Mendel I Dilemmas amp Critiques of Darwin s Theory A Stability and effectiveness of change 1 Natural selection is too limited 2 Small differences are not large enough 3 W Castle s experiments on hooded rats 9 arti cial selection on racing stripe width in hooded rats b recombination through backcrossing to control line wild type allowed for new phenotype with wider stripe to evolve c multiple genes were responsible for variation in stripe width d continuous range of widths e recombinations of multiple genes extends the limits of selection f ends up increasing width over time i after getting a really wide stripe he then bred them with the narrower stripe B Maintenance of variation 1 Why was concept of blending inheritance a problem a Blending Inheritance Fleeming J enkin 1867 does not allow for variation among individuals to be maintained 2 Why was concept of that most variation was the result of environmental variation a problem a also during this time it was thought that most variation was thought to be environmentally induced i negates the idea that Darwin had of passing variation from parenting to offspring How can it be parent to offspring if it s affected by environment 3 Poor survival of mutants a mutants were thought to arise so infrequently that their establishment and evolution into new species was impossible Continuous variation results from the inheritance of discrete genes 0 Discrete traits like pea coat color which are determined by a single gene are actually rare 0 most traits are determined by the effects of multiple genes 0 these polygenic traits show continuous variation 4 Polygenic traits a Corolla length in tobacco b depending on number of genes different numbers of phenotypes were predicted c one gene 3 phenotypes d two genes 5 phenotypes e if Mendelian model works the parental phenotypes should reappear through selective breeding f east selectively bred for both short and long corolla lengths g by generation 5 the length was nearly same as parents C Natural selection could not explain speciation l Speciation via allopatric adaptive divergence a relationship of divergence to speciation i no mechanisms that promote speciation were known such as reproductive isolation ii adaptive divergence can result in reproductive isolation between species iii reproductive isolation can evolve as a by product of adaptive divergence in geographic isolation 2 Sympatric speciation via assortative mating Benthic and limnetic threespine sticklebacks O benthic mainly eats invertebrates large body and few short gill rakers O Limnetic primary eats plankton small body and many long gill rakers lab experiments show that there is size assorted mating large mates with large D Observed punctuational change over time 1 Rapid evolutionary change has been observed a short period of rapid change followed by long periods of stasis b natural selection should result in gradual continual change c we now know natural selection can result in very rapid evolutionary change as well as long periods of stasis i this is because natural selection changes in populations where the environment changes ii changes in the environment drives the changes 2 Example of intense natural selection and subsequent rapid evolution a micro examples antibiotic resistances antiviral resistance b macro example escape ability in Trinidadian guppies i guppies in streams 1 moved them to streams in high predation and low 2 within 20 years guppies from high predation populations had much higher survival rate when placed in enclosure with a predator 3 F2 generation from high predation population raised in predator free enclosures also had greater escape ability when placed with a predator 4 escape ability is a rapidly acquired heritable trait 11 Contributions of Mendel A Mechanism of heritability mendel solved the heritability problem 1 Discrete traits 1 particular inheritance of discrete traits 2 Independent assortment amp segregation 1 independent assortment and segregation of alleles produce variation 1 not all variation is dependent solely on mutation B Problems Mendel did not solve 1 Inheritance of continuous traits Mendel s laws were based on discrete variation b much variation in natural populations is continuous c thought that environment not heredity controlled eXpression of continuous variation d continuous traits can have really high heritability values 2 Example beak depth in ground finches III The Modern Synthesis A Population genetics a developed in the 1930s early 1950s b shows that mutation is not an alternative to natural selection c actually creates lots of variability d mutation is the raw material on which natural selection and other forces of evolution actually act B Genetics amp Natural Selection combined a evolution results from small gneetic changes that are acted upon by natural selection b process operating within species account for the major long term features of evolution i microevolutionary forces are responsible for macroevolutionary change origin of species ii anagenesis leads to cladogenesis 1 both speciation C Restating Darwin s Postulates in genetic terms 1 Individuals within species are variable 0 due to mutation creating new alleles O recombination shuf ing existing alleles into new combinations 2 certain of these variants are passed on to offspring alleles are passed on unchanged from parents to offspring 3in every generartion more offpsinrg are produced than can survive 4 differences exist in survival and reproductive rates among individuals 0 individuals who contribute more offspring to the next generation are those with alleles or allelic combinations that produce traits that are best adapted for the particular environmental features encountered 0 therefore those alleles that favor survivability and reproduction will increase in frequency in the next generation D Evolution is a genetic process a evolutionary change is the change in allele frequencies from one generation to the next in a biological population b evolutionary change occurs by means of natural selection when alleles associated with higher fitness increase in frequency from one generation to the next IV Stuart et al 2014 A Elements of a scientific paper B Discussion of results
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