ECOL 182R Evolution 2 Lecture: Other Mechanisms
ECOL 182R Evolution 2 Lecture: Other Mechanisms ECOL 182R
U of M
Popular in Introductory Biology II
Popular in Science
This 11 page One Day of Notes was uploaded by Jenna Pimentel on Friday January 23, 2015. The One Day of Notes belongs to ECOL 182R at University of Arizona taught by Bonine, Hunter, Martinez in Spring2015. Since its upload, it has received 103 views. For similar materials see Introductory Biology II in Science at University of Arizona.
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12115 Today he I Mechanisms of evolution A Examples of natural selection Evolution B Genetic drift C Gene ow a Change In D Mutation frequency overtime in a population of organisms 1 2 Popma on a group of potentially interbreeding individuals ofthe same species usually in the same geographic area Allele a form ofa gene Examples A cat sh of same speCIes In a gIven lake Allele frequency proportion ofthat allele in a particular The bighorn sheep in the Catalina Mountains population Were locally extinct but reintroduced recently 3 4 A E coli bacteria in your stomach M N Example ABO blood type proteins in humans The Gene P l are encoded by a gene with 3 alleles IA IB and lo IA and II3 alleles are codominant 0 allele is recessive Diploid Individuals have 2 copies of gene Genotype Blood Type IA A or IAIO A Genotypes IAIB AB for gene X IBIB orIBIO B H I A e es are lol0 0 X1 X2 X3 When allele frequency approaches 1 it becomes fixed when it approaches 0 it becomes extinctc Three examples of what could happen with an allele over time Which ones show evolution 1 Allele xed Proportion 5 r Alleles of a I Type X1 I O Generations Evolution occurs when allele frequencies change 7 12115 Four mechanisms of evolution A Natural Selection B Genetic Drift C Gene Flow D Mutation A Natural Selection REVIEW 1 individuals in a population vary in some trait 2 at least some variation is geneticallybased 3 certain genotypes produce more surviving offspring than others 4 differences in reproduction are due to an agent of selection Classic example of natural selection Moth rests on tree branches during day Matches lichencovered tree surface Pepper moth Biston betularia vPollution during Industrial Revoluti onin m En gland killed lichens anddeposlted black spot on trees 1 A dark morph appeared in 1848 which matched sooty surface Dark and light morphs have different alleles in a single gene 1 Frequency of Dark 075 Allele 05 025 0 1875 1900 1925 1950 Year 1 5o Dark morph allele increased in frequency to gt95 by 1950 Graph byJ Bronstein C Parus major Agent of selection is m insectfeeding bird Birds nd fewer ofthe cryptic form 12115 Data for Manchester Engbnd Frequency of Dark Morph 0 I I I I n I L I I 1950 1960 1970 1980 1990 2000 year Frequency ofdark morph declined in 1980 s and 1990 s after sulfur dioxide DOllUl39On was reduced and lichens returned Summarizing the case for natural selection for pepper moth coloration 1 individuals in a population vary in some trait Moths vary in color pattern 2 at least some variation is geneticallybased Dark and light morphs encoded by different alleles 3 certain genotypes reproduce more than others Dark genotype reproduced more 18481950 light genotype reproduced more in 1980 s and 1990 s 4 differences in reproduction are due to an agent of selection Predation by birds is agent of selection We know humans can be agents of natural selection intentionally eg arti cial selection and unintentionally eg humans had a role in industrial melanism Another example of humaninfluenced evolution resistance to antibiotics V V V What s evolving bacteria What is the agent of selection tOXlI Where are bacteria encountering in the agent of selection What is the result antibiotic reSl What should we be doing differently using bacteria to 15 lt s 1uman body stance w Humanin uenced selection 1 Bacteria and plants evolve resistance to antibiotics and herbicides EVOLUTION OF RESISTANCE TO ANTIBIOTICS AND HERBICIDES Antibiotic or Year Resistance herbicide deployed observed Antibiotics Sulfonamides 19305 19405 Penicillin 1943 1946 Streptomycin 1943 1959 Chloramphenicol 1947 1959 Tetracycline 1948 1953 Erythromycin 1952 1988 Vancomycin 1956 1988 Methicillin 1960 1961 Ampicillin 1961 1973 Cephalosporins 19605 late 19605 Herbicides 24 D 1945 1954 Dalapon 1953 1962 Atrazine 1958 1968 Picloram 1963 1988 Trifluralin 1963 1988 Triallate 1964 1987 Diclofop 1980 1987 What are the agents of selection displace probiotics finishing antibiotic course before taking another HIV resistance todrugsa public health concern worldwide Currently 8 million people on antiretroviral drugs as many as 24 million untreated Public health of cials trying to increase scope 0ftreatment while encouraging new drug development and preventing widespread resistance that would lead to anotherAlDS epidemic WWW 3 Ovis canadensis trophy male Humanin uenced selection 2 Bighorn sheep become smaller Large trophy male 12115 A 015 a gt U E E Small Taken U 5 Random 5 39 I45 x Taken 9 quotfquot K9 0 0 l 1 Large Taken 015 l l l l 0 1 2 3 4 I Generation I I L Gill nets catch sh ofa particular snze arge 53929 nets SGleCl for llSh thatgrow more slowly and are smaller as adults 20 Small male quot Ovscanadensi8male Large males more attractive Why might that be true to predators C What is the agent of selection Humans 19 V Humanin uenced selection 1 Industrial melanism in pepper moths 2 Resistance to antibiotics in bacteria 3 Evolution of virulence in viruses uHV 4 Resistance to herbicides by weedy plants 5 Resistance to pesticides by insects 6 Reduction in sh size due to gill nets All involve genetic changes in populations 21 So far we ve had lots of examples of evolution by natural selection Can we have evolution without natural selection Yes Q 22 Four evolutionary processes affect allele frequency A Natural Selection B Genetic Drift C Gene Flow D Mutation B Genetic Drift random changes in allele frequency from one generation to the next 24 W W4 12115 A hypothetical exampleYou are a timetraveller that s discovered a village ofVikings in which all individuals have red hair How The second generatlon mlght lock llke thls39 could this have occurred by drift Imagine a snapshot ofthe founders ofthe village originally looked like this You determine I the second generation allele frequencies are A 01 and a09 Assume there are two alleles for hair color A for brown halr COl0r and a for red The a allele is recessive so redheads are Now 99 ofthe second generation couples are either aa aa and heterozygotes Aa or AA homozygotes have brown hair homozygotes or brown haired heterozygotes Aa Initial allele frequency isA 03 and ao7 91 ofthe rst By chance no offspring ofthe second generation couples have generation couples are either red haired aa homozygotes or brown brown hair haired heterozygotes Aa All ofthese can produce redhaired offspring By chance most offspring have red hair 25 26 The third generation looks like this ReSUItS Of computer SlmUIatlons 4 v 1 39 l Iva Sin a g z populations g K are m 37 Population size 20 susceptible to E V V You determine the third generation allele frequencies are A 00 loss and O 4 Q 1 2 Se 2 a and a10 xation of Generation 1 The a allele has become fixed 100 and the A allele has allelesquot lt ecome lOSl39 At this point unless new Vikings arrive this village a will produce nothing but redheads Why do YOU ac thinkthis is E 39 Key the red hair allele became xed by chance This is genetic true 0 A dr39 39 27 Less to fixate on 0 s I I 2 28 Generation Genetic Drift in Galapagos Turtles 7 Galapagos Pm Islands arCIIEEEHOVQsa a Santia 0 fBartolome39 To rt0Ises Fernandina Floreana EsBa o Tortoises on Alcedo Volcano Alcedo population numbers ca 4000 individuals low genetlc varlablllty OfAlcedO tortOlses due to severe population bottleneck DNA f39ngerpr39nt39ng indicates that gt90 of individuals descended from ONE female probably caused by volcanic eruption 3100000 years ago 30 29 WWW5 A population bottleneck is genetic drift It s like shaking a few beans from a jar by chance you may get more of one type even ifthe starting frequency is 50 12115 Class experiment in effect of size of bottleneck on loss ofdiversity White and black beans are equally common so each color allele frequency is 05 3 beans 6 beans All All All All black Mixed white Total black Mixed white Total 0125 r075 0125 10 00156 6969 00156 10 7 t i l i 32 Q K 2 Cheetah and prairie chicken populations also experienced population bottlenecks Alleles for many genes lost reduced genetic variation Both species are endangered 33 Why does reduced genetic variation threaten populations Without genetic variation population cannot adapt when environment changes Population may even go extinct 34 Genetic drift can cause signi cant evolutionary change BUT Genetic drift does NOT make organisms adapted to their environment Just one process will do that That process is Natural selection W V Four evolutionary processes affect allele frequency A Natural Selection B Genetic Drift C Gene Flow D Mutation 36 WWW6 12115 c Gene Flow SnowGeese Gene flow can counter local effects of natural transfer of alleles from one 39 v SEIECtion o ulation to another quot p p X Example A 2nd lizard speCIes has white morph In Usually involves movement of i If the White sand dunes 39nd39V39duals39 Blue morph White morph But brown genotypes disperse frequently from twin19 scrub into white dunes pzw Sceloporus undulatus Il A llPopulation I quot quot quotI a allele for white color here shown moving from Pop Ito Pop II in snow geese 37 38 D Mutation Four EVOlUthnary processes affect allele alteration ofa gene that gives rise to new allele frequency Usually involves change in DNA sequence A Natural Selection B Genetic Drift DNA t 1t 3 TACACCGAGGGCCAATT 39 C Gene Flow sjggdae D Mutation u pointquot mutation one nucleotide change 39 Ifyou haven t taken 181 review DNA in Text 40 Some Drosophila behavior mutants Mutations 639 etheraQOQO Rare per gene but common per genome kdn knockdown Pei perlOd Drosophila fruit fly mutation rates fru fruitless qtc quick to court spin spinster sk stuck ca 10395 per gene per generation ca 1 per genome per generation generated in laboratory using radiation or chemical mutagens 41 42 7 Mutations 1 rarely generate novel traits 2 usually change pre existing traits 3 usually deleterious But 4 footed ducks Meet Stumpy 43 12115 quotmalevolentquotC BUT I Ultimately mutations 39 germ cells are ultimately the source of almost all genetic variation in a population Germ Cells Reproductive cells which go on to form the next generation Whyjust germ cells IN OTHER WORDS Without mutation evolution would eventually grind to a halt 44 Drosophila head with legs instead of antennae Stumpy who learned to walk anyway 45 Sceloporus undulatus Aspidascelisinornata Holbrookia maculata In the White Sand Dunes of New Mexico there are actually THREE species of lizards with white morphs Natural selection for white crypsis believed to have occurred separately in each species 46 39 39 maculata In each species white morph is caused by a lossoffunction mutation in a gene coding for melacortin 1 receptor protein Extracellular melacortin 1 receptor Mclr Transmembrane lntracellular 47 r l J l a 391 39 39 quot quot quot maculata HISZOSTYR THR17o ILE VAL 68 ILE Extracellular Transmembrane 39 membranes of cells making pigment in uences what color pigment cell makes Three different amino acid changes in Mc1r indicating mutations at three different positions in DNA coding sequence 48 8 12115 Do you get it Do you get it Ofthe 4 processes natural selection genetic drift gene ow and mutation which process What two evolutionary processes were required es to see the increase in the number ofwhite lizards in Sand Dunes 1 Mutation 2 Natural selection a Tend to reduce genetic variation Genetic drift b Tend to increase genetic variation Gene flOW mutation c Make the organism more adapted to its C environment Natural selection 49 50 Do you get it What kind ofvariation in a trait is required for evolution to occur Example inheritedgenetic variation What kind ofvariation in a trait will NOT result i evolution Example It Not all variation is geneticallybased some is environmentallybased Environmentallybased variatio 51 52 Leaves of a white oak Quercus alba Andrew Frank and Andrew are brothers Frank lifts weights at the gym all the time Andrew doesn t Will Frank have children with bigger muscles than Andrew will Grown In sun Why or why not environmentallybased C E Ifthere is a population of exercisers eg Spartans ofancient Example Of enVlronmentaHY39based V3 rlatlon Greece will their offspring be stronger than those in a Another exa mple Population of Philosophers Why or why not environmentallybased 53 54 cactus flower able to store water for a long period of time WWW9 Average height of a man in the Netherlands imagesta mm 1850 5 ft 4 12 inches Why the difference Can a trait be in uenced by both a genes and environment 2009 5 ft 11 quotinches 55 genetic basis 12115 10 I Mechanisms of evolution A Examples of natural selection B Genetic drift C Gene flow D Mutation Key concepts 1 Understand how the four mechanisms of evolution natural selection genetic drift gene flow and mutation cause evolution how they increase or decrease variation in populations and think about how they might interact in populations Natural selection makes organism more adapted to environ ent likely to survive to reproduce Genetic drift tends to reduce genetic variation through Gene flow tends to reduce genetic variation throu 39 Mutation tends to increase genetic variatip eck reaction ation reaction changes in DNA coding 2 Understandbe able to define Evolution a change in allele fre Population a group of ot 39 Allele a form of a gen Allele frequency proportio of that allele in a particular population Genetic drift random cha sin allele frequency from one generation to the next Allele fixation when an allele frequency reaches 1 Population bottleneck one way to get genetic drift may by chance get more of one organism even if it starts with 50 Gene flow transfer of alleles from one population to another Mutation alteration of a gene that gives rise to a new allele Mutagen toxins that cause mutations Germ cells reproductive cells of an organism Environmentally based variation a variation in a trait that will not result in evolution over time in a population of organisms interbreeding individuals of the same species