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Date Created: 09/06/15
Tuesday September 1 2015 Week 2 Notes Hardy Weinberg Equation 1 Terms Gene a specific DNA sequence that codes for a protein or may regulate the expression of other genes or function may be unknown Locus a particular LOCATION on chromosome gene Allele one of multiple forms of a gene 2 Chromosomes two copies of each Genotype Homozygous Heterozygous PP and aa Bb Polymorphic for a given trait when there are 2 or more types WITHIN A POPULATION vs MONOMORPHIC population can be genetically polymorphic and PHENOTYPICALLY polymorphic A trait is often determined by 10 s or 100 s of loci many genes polygenic traits most behaviors human skin color at least 8 loci height LOTS OF VARIATION Tuesday September 1 2015 When no evolution is occurring for a particular gene we expect genotype frequencies to follow the HardyWeinberg Equation the equation predicts the genotype frequencies in a population when NO evolution is occurring These assumptions are being made mo mutation no gene flow no natural selection extremely large population size random mating HardyWeinberg Equation Example A diploid plant species where flower is controlled by a single gene This gene had to alleles Cr and Cw Plant exhibits incomplete dominance Take every allele in the population 2 from each plant and put them into a bin the population s gene pool for that locus Probability of Cr and Cr sperm PxPp2 8x864 64 percent Tuesday September 1 2015 Probabilty if a Cw egg and a Cw sperm qxqq2 2x204 4 percent Probability of Cr egg Cw sperm pxq pq 08x02 16 Probablity of Cw egg Cr sperm qxp qp 2 x816 pqqp 161632 So 32 percent of the plants will be heterozygotes pink flowers if random mating occurs Red Flower Pink Flower White Flower 64 32 4 1 technically 100 use this to determine if are right or wrong Formula for given two alleles at a locus with frequencies p and q pq1 p22pqq21 Tuesday September 1 2015 Macroevolution Micro vs Macroevolution Along an evolutionary continuum A microevolution small changes eg allele frequencies within a population shorter time B macroevolution bigger changes eg morphological changes longer time Microevolution mutation genetic drift gene flow natural selection changes in aee or genotype frequencies Macroevolution speciation extinction human origin changes in physical appearance Tuesday September 1 2015 tree of life common origins of species Macroevolution eg SPECIATION when 2 pops become genetically different enough that can t be interbreed eg EXTINCTION when no genotype in a species survives lndividuals CAANOT evolve Methicillinresistant Staphylococcus aureus MRSA as new antibiotics introduced repeatedly select for resistant bacteria aeles for resistance and other traits that increase spread for lethality also increase Soapberry bugs traditionally fed on native balloon vine then started feeding on introduced godenrain tree Homoogysimilarity resulting from common ancestry Homologous structures similar structures in organisms inherited from a common ancestor Does evolution lead to increasing complexity Not really oss of digestive system in parasites and host oss of wings in insect parasites 5 Tuesday September 1 2015 fish to mammals is one more complex the oldest fossils are LESS complex than more recent fossils vestigial traits ancestral Baggage an odd trait that makes sense if new species arise from ild app and not if each species is newly formed perfect at origin an unused and incomplete version of a trait seen in similar organisms Examples of vestigial traits a structure starts to form in fetus but is reabsorbed before being used outer 2 toes in horse fetus are usually reabsorbed Baleen whales lack teeth as adults yet they are present in fetus and extinct ones Some bones forms as separate units then fuse EX bird tail and wing finger bones nonfunctional anthers male part in female flowers located where pollen can t get out Ear Wiggling in some humans sexual and reproductive behavior in asexual app EX some lizards hind limb bones that are too small to walk with Primitive Snakes some ancestral fossil snakes have a pelvic girdle and functional legs outside the nbcage Tuesday September 1 2015 COMPLEX requires more information to describe Examples of vestigial traits con t vestigial genes DNA sequences that largely match functioning genes in other species but no longer work due to mutations Ex crocodile ice fish white blooded fishes they have no red blood cells BUT have remnants of DNA sequence fro red blood cells Evolutionary Trees depict trees of evolutionary relationship among taxa singular taxon Determining evolutionary relationships making phylogenies A generally more similar organisms are more closely related B Types of evidence 1 DNA RNA ProteinTraits 2 compares fossils and living organisms 3 development adults juveniles embryos EX neck grooves in embryos of fish frogs birds humans Determining evolutionary relationships Potential complication when using similarity There are 2 explanations for 2 organisms having same trait Both have because Tuesday September 1 2015 1 A common ancestor had trait The traits are HOMOLOGOUS 2 They evolved the trait independently EX no comm ancestor had it The traits are analogous EX insects do not have bones birds do and results form convergent evolution 4 ways to distinguish descent versus convergence 1 if traits develop from different structures probably convergence 2 if trait not under selection probably same vis descent but not if trait is under the same section pressure in both organisms probably same due to convergent evolution 3 if similar traits are very complex probably similar due to descent 4 look at many traits EX we conclude wings of birds bats pterosaur are analogous because DNA and many other physical traits suggest the following phylogeny Fossils physical remains and traces of organisms from the past most species that ever lived are now EXTINCT 1 of species fossilize not all found evoution includes extinction by definition Continental drift continents rest on plates that move helps explain where fossils are found and when they occurred Timeline prokaryotes350 million eukaryotes2 million vertebrates 05 million amphibian 35 million reptile 310 million mammal 200 million modern humans 000015 150000 yrs Determining Fossil Age 1 relative age of sedimentary rock deeperoder Tuesday September 1 2015 when older layers have been pushed above younger can be detected 2 ABSOLUTE AGE by radiometric dating 40 different isotopes used Confirmed ages previously determined by geologists using relative aging and other methods Translational fossils Tuesday September 1 2015 in between major groups have characters of both groups gradualism to punctuated equilibrium Which would make it more likely we can find transitional fossils gradualism Misconception Evolution is just a theory theory has different definitions in science and in general everyday use saying evolution is just a theory is an equivocation misleading use of a word that has multiple meanings Definitions of theory General use an untested idea what scientists call a hypothesis other scientific theories gravity atomic theory matter is composed of atoms copernican theory earth orbits around the sun germ theory infectious diseases are caused by microorganisms 1O Tuesday September 1 2015 Misconception evolution is random mutations are random and variations in traits may be random But natural selection is explicitly systematic nonrandom But evolution is NOT goaloriented evoution and species do not have an end point in mind What is favored by natural selection at one point in time may be selected again at a layer time EX Darwin s finches on the Galapagos There are some random process that occur in evolution eg genetic drift genetic bottlenecks founder effects 11 12 Tuesday September 1 2015 13 Tuesday September 1 2015
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