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Biology 1001 Part 2 - final.pdf

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Biology 1001A
Tom Haffie

Inheritance in Populations Lecture 12 October-22-12 8:59 PM Pre-Lecture 1. strategyto distinguishbetween a phenotypethat results from codominance relative to incomplete dominance Incompletedominance:the effects of recessive alleles can be detected to some extent in heterozygotes White and Red phonotypes in flowers create Pink flowers Codominance:alleles haveapproximatelyequal effects in individuals, making the two alleles equallydetectablein heterozygotes White and Red phenotypes in flowers create spottedflowers with both phenotypes expressed 2. characteristics that identify a pleiotropic allele Pleiotropy:whena single gene effects more than one characteristic Example: Sickle cell disease is caused by a recessive allele of a single gene that affects hemoglobin structure and function. However, the altered hemoglobin protein,the primaryphenotypicchangeof the sickle cell mutation leads to blood vessel blockage,whichcan damage manytissues and organs in the body and thus affect manybody functions, producingwide-ranging symptoms. These are pleiotropiceffects of sickle cell disease 3. conditions underwhich Hardy Weinberg Equilibrium is possible in a population. - The point at whichneither allele frequencies nor genotype frequencieschange in succeeding generations a. No mutations are occurring b. The population is closed to migration from other populations c. The population is infinite in size d. All genotypes in the populationsurvive and reproduceequallywell e. Individuals in the population mate randomlywith respect to genotypes Lecture Clicker Questions: If you mated a pure-breeding black pig with a pure-breeding brown pig what do you think the piglets will look like? A: all black If you cross two of the piglets together what will the resulting offspring look like? A: both black and brownpigs in a 3:1 ratio - Therefor the black allele is dominant If we start with a dominant allele that is common and a recessive allele that is rare, whatwill eventuallyhappen? A: Allele frequencies will not change much Would this changeif there was a large numberof rare recessive allele and a very small number of dominantcommon allele? A: Allele frequencies will not change much In a large population, in the absence of selection,whatinfluencesfuture allele frequencies? A: The starting allele frequencies What if a population contains manyalleles? B (p=0.3) W (q=0.3) and R (r=0.4) How manypossible genotypes are there? A: 6, there will be 3 different types of homozygotes and 3 different types of heterozygotes 1. general pathway of eukaryoticmembrane proteinproduction. - DNA is in the nucleus,the two homologues are in the nucleus - The alleles are transcribed and spliced - The transcripts leave the nucleus and attractribosomes - They are taken to the Endoplasmic Reticulumand are translated by the Endoplasmic Reticulumand - They are taken to the Endoplasmic Reticulumand are translated by the Endoplasmic Reticulumand packaged that go to the Golgi apparatus and then into new vesicles that send the proteins to the cell membrane 2. general physiologyof skin/hair pigmentation. - Pigmentproductionresults from the productionof two types of melanin: black and red - Melaninis produced by melanocytes,packedinto subcellular units called melanosomeswhich are exported - Melanocytes pack melanosomes with melaninand export them to skins cells in order for them to be pigmented - The protein MC1R, a membranereceptor, is activatedwhen cyclic AMP levels are high  High cyclic AMP makes black melanin  In response to hormonesthe cyclic AMP levels can fall and then red melanin is producedinstead 3. characteristics of dominantalleles. - Dominanceoccurs between any two particular alleles at a particular time  WRONG: since the black allele is dominant over brown it will be dominant over red - Dominanceoccurs from the interactionof the gene products - The dominant alleles do not inhibit the recessive allele 4. whichallele in a heterozygoteis dominant,given the biochemicalmechanismof action of allele products. - The allele that is on all the time determines the phenotypeof the individual 5. factors that affect how allele frequencieschangeover time in a population. - The startingallele frequencies in the population - Selective fitness of certainalleles 6. allele frequencies (p and q), given genotypic frequencies. - Given a common dominant allele and a rare recessive allele the frequenciesof the populationwill stay relativelythe same - Given a common recessive allele and a rare dominant allele the frequenciesof the populationwill stay relative the same • Using the product rule of a populations allele frequencies Ex. W (0.6) R (0.4) from males and W (0.6) R (0.4) from females - WW = 0.6 x 0.6 = 0.36 - WR = (0.6 x 0.4) x 2 = 0.48 - RR = 0.4 x 0.4 = 0.16 Using p and q - WW = q^2 - WR = pq - RR = p^2 7. function of variousMC1R alleles. a. The brown allele causes both melaninto be produced b. The black allele is on all the time, cyclic AMP levels are high all the time, it is insensitiveto hormones in the environment c. Heterozygote:some of the black allele and some of the brown allele in the same cell - Causes two different types of MC1R receptors - Even though the brown receptor is off sometimes the black receptor is on all the time • In the case of an additional red allele that is off all the time, in red homozygotes cyclic AMP levels are always low and the cells are alwaysmakingred melanin - Different from the black allele which is alwayson • Red/Black heterozygotes RECALL: black is dominant to brown and brown is dominant to red, an allele is not dominantall the time - The black and red heterozygote looks black - A brown and red heterozygote is brown Selection and Fitness October-24-12 6:55 PM Pre-lecture Genotype: a combinationof genes Allele: a version of a gene 1. Meaning of deme, population, allele frequency, genotype frequency Deme: a local population of a species; in sexual forms, a local interbreeding group a.k.a.- a local population of organisms of one species that interbreed with one another and share a distinct gene pool - Structural features of an environment- a river that individuals cannot cross, or a landslip- reduce effectivedeme size Allele frequencies: the proportion of different alleles in a population Ex. (p=0.7 q=0.3) Genotype frequency: the frequency of a genotype — homozygousrecessive,homozygous dominant, or heterozygous — in a population Ex. (CrCr= 0.45 CrCw= 0.50 CwCw=0.05) - Finding the q and p □ p = 2CrCr + CrCw / 2CrCr + 2CrCw + 2CwCw (0.9 + 0.5) / 2.0 = 0.7 □ q = CrCw + 2CwCw / 2CrCr + 2CrCw + 2CwCw (0.5 + 0.1) / 2.0 = 0.3 2. Allele frequencies in a population, given the genotype frequencies - Allele frequencies do not depend upon dominance or recessiveness(genotype frequency) - Remain essentially unchanged from one generation to the next, provided that mating is random and all genotypes are equally viable 3. Genotype frequencies in the next generation, given the allele frequencies and assuming Hardy- Weinberg equilibrium - By confining our attention to alleles rather than genotypes, we can predict allele and genotype frequencies in future generations - Once Hardy-Weinberg equilibrium is reached the genotype frequencies will remain the same 4. Assumptions of Hardy-Weinberg equilibrium 1. Parents represent a random sample of the gene frequencies in the population 2. Genes segregate normally into gametes (heterozygotesfor any gene pair produce their two kinds of gametesin equal frequencies) 3. Parents are equally fertile (gametes are produced according to the frequency of the parents) 4. The gametes are equally fertile (all have an equal chance of becoming a zygote) 5. The population is very large (all the possible kinds of zygotes will be formed in frequencies determined by the genetic frequencies) 6. Mating between parents is random (not determined by any preferences associated with specific genotypes) 7. Gene frequencies are the same in both male and female parents 8. All genotypes have equal reproductive ability Simply put: 1. Random mating in large populations 2. Equilibrium allele frequencies 3. Absence of gene flow into the population Lecture Clicker Questions: A population of pigs contains 3 MC1R alleles: B (p=0.3) W (q=0.3) R (r=0.4) If this population is in Hardy-Weinberg equilibrium at MC1R what proportion of pigs are genotype WR A: (0.3 x 0.4) x 2 = 0.24 - Multiply by 2 due to the ability to have WR or RW 1. conditions necessary for Hardy-Weinberg equilibrium A large, random-mating population, where mutations are rare enough to be ignored, in the absence of immigration or emigration,and if there is no selection Immigration and emigration: a change in environment 2. whether a population is in HWE, given observed genotype or phenotype frequencies - In HWE all allele and genotype frequencies remain the same, this a condition when evolutionis not happening - P and q are both equal to 0.5 - the population in HWE is: - 25% GG, 50% Gg, 25% gg - 49% GG, 42% Gg, 9% gg - 2 x (rootG^2) x (root g^2) = 42 - 2 x (root49)x (root9)= 42 - p doesn’t always equal q when in HWE - If genotype frequencies can be predicted from allele frequencies, population is in Hardy- Weinberg equilibrium (HWE) at this locus. Allele frequencies will not change while this is true. 3. effect of selection on changes in allele frequency - Strong selection against a dominant allele- frequencies decrease quickly and becomes extinct - Strong selection against a recessiveallele- frequencies decrease much slower and will not becomeextinct - heterozygotescarry both dominant and recessivealleles and will therefor prevent extinction 4. relative vs. absolute fitness Relative Fitness: the average number of surviving progeny of a particular genotype compared with average number of surviving progeny of competing genotypesafter a single generation Absolute Fitness: the ratio between the number of individuals with that genotype after selection to those before selection 5. how to calculate relative fitness - Using absolute fitness as (W) and relative fitness as (w) w=W/Wmax 6. how to quantify strength of selection - The difference in w between different genotypes reflects the strength of selection - By definition the fittest genotype has w=1 and all others w=W/Wmax 7. relationship between dominance/recessivenessof alleles and response to selection. - Strong selection against dominant allele- frequencies decrease quickly and becomes extinct - Strong selection against recessive allele- frequencies decrease much slower and will not becomeextinct - Heterozygotescarry both dominant and recessivealleles and will therefor prevent - Heterozygotescarry both dominant and recessivealleles and will therefor prevent extinction 8. effect of heterozygoteadvantage on genetic variation - Strong selection against homozygotes - Only pigs with high fitness are the heterozygotes - A situation where both alleles are going to be maintained in a population, they will be maintained in the proportion that the heterozygotesare at in the population at a maximum - The population is not evolving but is out of Hardy-Weinberg equilibrium - Allele frequencies are not changing 9. why the amount of genetic variation in a population is important - Selection has important effects on genetic variation 10. different types of selection (stabilizing, directional) and their effect on genetic variation a. Stabilizing selection: intermediatetraits of individuals have greater fitness rather than extremes - Occurs on birth weight, low weight have health problems - Birds could not survive a storm due to specific traits b. Directional selection:one extremeof the distribution has greater fitness and more favourable to selection - Birds have long tails to attract mates, short tailed birds are unattractive (SIZE MATTERS) - Eventually directional selection could become stabilizing selection c. Disruptive selection:either extremesof the distribution have greater fitness - Galapagos island birds, different beak sizes are favoured in different locations due to the availability of food Selection vs. Other Evolutionary Forces October-27-12 12:16 PM Pre-Lecture Polymorphism:the presence of two or more genetic or phenotypic variants in a population 1. difference between Batesian and Mullerian mimicry Batesian Mimicry: a mechanism in which palatable species that mimic distasteful models are protected against predators. - A palatable butterfly mimics an unpalatable butterfly to avoid predators Mullerian Mimicry: beneficial to both species, by enabling predators to learn a single warning pattern that applies to all these potential but distasteful prey. - A commonwarning pattern on butterflies to predators protects both species 2. how the population frequency of a mimic phenotype may affect its fitness - The more frequent the mimic and the less frequent the model, the greater the chances that predators will attack the mimic. - The less frequent the mimic and the more frequent the model, the greater the chances that mimic will be protected. 3. why the same phenotype may be selected against in one environmentbut have a selective advantage in a different environment - Certain environmentsoffer greater protection or an advantage to a certain phenotype which allows it to becomemuch more prosperous than the alternative allele 4. meaning of genetic load and genetic death Genetic Load: the loss in average fitness of individuals in a population because the population carries deleterious alleles or genotypes A.k.a.- In population genetics, genetic load or genetic burden is a measure of the cost of lost alleles due to selection (selectionalload) or mutation (mutational load). Genetic Death: can be expressed as sterility, inability to find a mate, or by any means that reduces reproductiveability including death Lecture 1. effect of various types of selection on amount of variation in a population. There are 3 major modes of selection: Stabilizing: extremelywidespread in large populations, intermediateof the distribution has a higher fitness - Genetic diversity decreases as a population stabilizes on a medium of a particular trait Directional:one extremeof the distribution have higher fitness than everyoneelse - Genetic variation decreases as a population favours an extremeof a particular trait more than another Disruptive: oppositeof stabilizing, either extremesare selectivelyfavoured - Genetic variation increases as a population favours more than one extremeof a particular trait 2. examples of stabilizing, directional, disruptive. - Stabilizing: Babies of a medium weight have the highest rate of survival, stabilizing selection increase the frequency of babies of a medium weight - Directional:Birds with longer tails than others are more attractive to mates, the frequency of long tails increases as birds with short tails are unable to reproduce - Disruptive: The Galapagos Islands birds: birds on some islands had little food available due to small beak size, birds on other islands had little food available due to long beak due to small beak size, birds on other islands had little food available due to long beak size, this increased the frequency of the beak sizes on corresponding islands 3. reasons why directional selection does not removeall genetic variation from a population. - Necessive alleles are always maintained in a population - Not all populations experience directional selectionin the same direction all the time, different phenotypes can be more favourable at different times - The industrial revolutioncreated an environmentwhich increased the frequency of the dark coloured moth - Unpolluted parts created an increased in the frequency of the light coloured moth 4. characteristics, and examples, of frequency dependent selection. a. Negative Frequency-DependenceSelection: i. When the phenotype is rare there is an advantage Ex. Predators search for more profitable prey, the more commonprey will be hunted and eventuallythe rare phenotype will no longer be rare - This is a negative advantage to being rare b. PositiveFrequency-DependenceSelection: i. A selective advantage to having a commonphenotype - Prey will learn to avoid the commonphenotype and the rare allele will be replaced by the commonallele 5. reasons why all living things are not perfectly adapted to their environment. - Limited by available genetic variation Ex. selection may not choose the more favorable allele if it is not available - Limited by dominance relationships - Plays catch-up after environmentchanges Ex. traits represent a compromise(long bird tails can attract mates but have more difficulty flying) - Trade-offs (compromisebetween competing demands) 6. effect of genetic drift on allele frequencies within a population, particularly in the case of bottlenecksetc. Non-Adaptive Evolution a. Genetic Drift: Random fluctuations in expected results, creates a much smaller - Drift strongest in small populations, and populations suddenly becoming small (bottlenecks,founder events) - Decreasesthe amount of genetic variation within a population, the allele frequency of somealleles will increase while others decrease - Outcomedepends on strength of selection, and population size i. Bottleneck:a severe reduction in population size - Creates a reduction in genetic variation - Cheetahs experienced an epidemic resulting in cheetahs being almost genetically identical ii. Founder Effect: a small group of individuals start a population, limiting the populations genetic variation available 7. effect of genetic drift on variations between populations. - Increases the difference among different populations of a species - Some populations would fixate on a certain allele and some population would fixate on another 8. mechanism that explain why mutation is NOT directed toward the needs of the organism. - Mutations are not random, some are more likely than others - A vast majority of DNA is non-coding DNA and therefor more likely to be effected by a mutation  These mutationswill not effect fitness - The majorityof mutations that effect fitness are harmful, there are more ways of - The majorityof mutations that effect fitness are harmful, there are more ways of damaging something than making it better 9. general fitness effects of mutations. - Not a lot of DNA is essential, therefor not a lot of mutations would effect the fitness of an individual - Vast majorityof mutationsthat do effect fitness are harmful - Would not be accurate to say that all mutationsare bad 10. why most mutations that affect fitness are harmful. - There are more ways of breaking something than making it better 11. effect of gene flow on allele frequencies. Gene Flow: can introduce new alleles, often opposes selection  mating of non-local individuals creates unfavourable alleles in the population, opposing selection Ex. Rock-pocketmice: - Some habitat are dark in colour, others are light - The different environmentsselect for different coloured mice - Dark mice have a selective advantage in dark environments 12. characteristics of adaptive vs. non-adaptive mechanismsaffecting allele frequency. a. Adaptive Mechanisms - Stabilizing Selection: medium allele frequency increases - Distributive Selection:one extremeallele frequency increases - Disruptive Selection: morethan one extremeallele frequency increases - Negative Frequency-Dependence: a rare allele frequency will increase - PositiveFrequency-Dependence: a rare allele frequency will decrease b. Non-Adaptive Mechanisms - Genetic Drift: increase the frequency of a particular allele in one population - A random fluctuation in the allele frequency i. Bottleneck:most likely decrease or eliminate the frequency of many alleles and increase the frequency of others ii. Founder Effect: allele frequency would be relative to the founding population, quite small - Gene Flow: increases the frequency of unfavourable alleles 13. how various evolutionaryforces reinforce or oppose one another. - Genetic drift can occur through the bottleneckor founder effect, disruptive selection can increase the genetic variation between the populations of species. - Gene flow can also aid in the increase in genetic variation between populations - Stabilizing and disruptive selection both work to decrease the amount of genetic variation within the population Why Evolution is True October-31-12 8:20 PM Pre-Lecture 1. how Darwin's theory of evolutiondiffered from that proposed by Lamarck Lamarck:two mechanisms fostered evolutionarychange i. Principle of use and disuse: body parts grow in proportion to how much they are used ii. Inheritance of acquired characteristics: changes that an animal acquires during its lifetime are inherited by its offspring Darwin's Theory of Evolution: i. Natural Selection:favourable hereditary traits would becomemore commonin the next generation 2. meaning of catastrophism, gradualism, uniformitarianism Catastrophism:The theory that changes in the earth's crust during geological history have resulted chiefly from sudden violent and unusual events Gradualism: the view that Earth changes slowly over its history Uniformitarianism:The theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes Ex. Volcanic eruptions, erosion etc. 3. difference between relative versus absolute ages of rock formationsand the fossils they contain Relative Ages of Rock Formations:sediments found in any one place form distinctive strata (layers) that usually differ in colour, mineral composition,particle size and thickness. If undisturbed the strata are arranged in order in which they were formed Absolute Age of Rock Formation:radiometric dating using isotopesdecaying at steady rates, rocks containing certain isotopes can be dated using the amount of isotope and the rate of decay 4. principle behind radiometricdating of rock strata - The comparison of the amount of isotope and its rate of decay can give an accurate age of the rock 5. why most living things never form fossils - Living organisms absorb traces of 14C and large quantities of 12C from the environmentand incorporate them into biological molecules. As long as the organism is alive it will continue to absorb 14C, when the organism dies it no longer absorbs 14C, using the ratio of 14C to 12C can determine the fossils age. Lecture 1. types of non-random mating AssortativeMating DisassortativeMating Inbreeding Inbreeding Avoidance 2. effect of non-random mating on HWE Assuming that heterozygotesare distinguishable and intermediatedominance, when a population starts mating assortatively: AA=250 --> 250 AA Aa=500 --> 125 AA, 250 Aa, 125 aa aa=250 --> 250 aa aa=250 --> 250 aa Creating: AA --> 375 Aa --> 250 aa --> 375 This takes the population out of Hardy-Weinberg equilibrium The allele frequencies are the same - not evolutionary 3. characteristics of a scientific theory - Dictionarydefinition of Theory: “an assumption based on limited knowledge… a conjecture” - Scientific definition of Theory: “a coherent set of testable hypothesesthat attemptto explain facts about the natural world” When is something considered true? - An assertion for which there is so much evidence that it would be perverse to deny it - Theories ‘graduate’ to fact-hood after repeated testing fails to falsify them 4. componentsof the theory of evolution 1. Evolution happens - change in allele frequencies in a population, between generations - possibly as a result of selection(adaption evolution, genetic drift due to bottleneck) 2. Most evolutionis gradual - small changes almost imperceptible - accumulate into large changes - drug resistance in bacteria- much faster evolution 3. Speciation happens - all life has evolved from LUCA - over evolutionarytime there were an incredibly high number of speciation events - species divides into two or more different lineages - if it didn’t happen there would be many less species on earth 4. All life is related through commonancestry - all life is related through some commonancestry - MRCA of all life --> LUCA 5. Much of evolutionarychange is caused by selection - Anglar fish, an adaptation to live in a dark environment - most likely natural selection 6. Evolution occurs in populations no within individuals populations change but individuals do no adjust in response to selection 5. evidence for "descent with modification" a. Earth must be old b. Vestigial traits c. Fossil evidence that species change d. Fossil evidence that lineages split (speciate) e. Direct observationof evolution in real time 6. examples of homology a. Structural: Same patterns of bones - only makes sense if they inherited them from a commonancestor b. Developmental:Embryotic development c. Molecular:Genetic code 7. examples of vestigial traits A species of salamanders do not need eyes, why does it have them? - lives in a dark environment - evolvedfrom a salamander that lived in a light environment 8. role of fossil record as evidence for evolution - Dated fossil show the slow evolutionarychanges in species bone structures Why Sex ? November-05-12 2:35 PM Pre- Lecture 1. Relationship between sexual reproduction and genetic variation Recombinationor Genetic Exchange- sections of chromosomescan exchanges material (crossing over)thereby forming different linear arrays of nucleotides - As nucleotide sequences constitute genes , recombinationcan produce different combinationsof genes along a chromosome - Breaking the association between different alleles - Creates an increase in genetic variation 2. Different modes of genetic sex determination - The ratio of X chromosomesto the number of copies of autosomalchromosomes(A) can determine sex. ○ In males the ratio is (X/2A) = 0.5 ○ In females the ratio is (2X/2A) = 1.0 ○ Triploids with an X/A ratio of 0.66 (2X/3A)are intersexes - The time of fertilization ○ The gene that causes testicular feminization syndrome in humans turns XY zygotes into females 3. Different modes of environmentalsex determination - When an individual reverseschromosomedeterminationas a result of sensitivity to agents such as temperatureor hormones 4. Meaning of haplodiploidy - Sex is determined by the fertilization or unfertilization of eggs - Females develop from fertilized eggs and so are diploid, males develop from unfertilized eggs and so are haploid 5. Meaning of hermaphrodite, and whether hermaphroditism is generally rare or commonin plants Hermaphrodite- both male and female organs are found within each individual - Sex determinationdoes not apply to most plants; some 90% of seed plants produce both male and female gametes(hermaphrodites) Lecture Over evolutionarytime, sexual populations usually outlast asexual populations So does this explain the persistence of sex? - Things do not spread simply because the benefit the population - Any individual that started to reproduce asexually would create offspring that would outcompetethe offspring of sexually reproducing individuals 1. relationships among sexual reproduction, meiosis and genetic variability - Sex to a biologist- tied to recombination - Humans are obligatory sexually reproducing animals - However,many animals can reproduce without sex, or can have sex without reproduction - The earliest living things did not reproduce sexually - Meiosis- the process through which sexual reproduction occurs, genetic diversity is created and maintained through this process - Genetic diversity- the creation of new combinationsof alleles - Due to crossing over, independent assortment(not new alleles but new - Due to crossing over, independent assortment(not new alleles but new combinations) - The production of a variety of offspring phenotypes,usually different from each other and from parents 2. mechanismsof asexual reproduction a. Binary fission: a mother cell divides into two identical daughter cells b. Vegetativepropagation: sending runners through the ground and sprouting a new tree from that runner c. In the case of some fish, offspring can develop from the eggs alone but require close contact with male sperm to develop properly, the male sperm has no impact on the chromosomesor genetics of the offspring 3. examples and predictions of size-advantage model of sex change a. Bluestreak Wrasse: all are born as females, can change sex due to size differences, larger fish would be considered moredominant and would change into males, this can occur in a matterof hours b. Clownfish: all are born male and becomefemale when they reach a sufficiently large body size, this creates a better production of eggs 4. distribution of sexual reproduction among all life forms, and particularly among animals - It is almost certain that the first life forms reproduced asexually - The vast majorityof living organisms reproduce asexually (exceptionsbeing most plants and animals) - The vast majorityof animals reproduce sexually 5. costs of sexual reproduction - Finding a mate - Predators threatening the ability to find a mate (frogs sing and attract both predators and mates) - There could already be a mate 6. cost of meiosis - Passing on only half the alleles 7. cost of sons - Females that reproduce asexually would produce offspring that would quickly outcompetethe offspring produced through sexual reproduction 8. "Muller's Ratchet" mutational load explanation for advantage of sexual reproduction - In a species that reproduces asexually there are more ways to accumulate a harmful mutation rather than a beneficial mutation - Asexual lineages will accumulate more and more harmful mutations until the population becomesextinct 9. "Ruby in the Rubbish" hypothesis explanation for advantage of sexual reproduction - “Sir, how wonderful it would be if we were to have a child. It would have your brain and my beauty!” “But what if it were to have my beauty and your brain?” - There could be more deleterious mutations than the parents - Sex continually creates genotypes with fewer (and more!)harmful mutationsthan parental genotypes 10. combination of beneficial mutations for advantage of sexual reproduction - Some small minorityof mutations can be advantageous - Sex speeds up the rate at which beneficial mutations occur in the same individual - In asexual reproduction mutations will competewith one another 11. relationship between extinction rate and sexual reproduction - Probably- almost all of the asexually reproducing animals are of recent evolutionary origin - Rotifer, the only animal that uses asexual reproduction and has been around for a long period of time Sexual Selection November-07-12 11:41 AM Pre-Lecture 1. Meaning of monogamy,polygamy,polygyny, polyandry, promiscuity,lek Monogamy-a situation in which a male and a female form a pair bond for a mating season or, in some cases, for the individuals' reproductive lives Polygamy-either males or females have more than one mating partner Polygyny-a male mates with morethan one female Polyandry- a female mates with morethan one male Promiscuity-a mating system in which individuals do not form close pair bonds, and both males and females mate with morethan one partner Lek- a display ground where males each possess a small territory from which they court attentive females 2. Conditions favouring the evolutionof monogamousversus polygynous mating systems Monogamous - When young require a great deal of care that both parents can provide, monogamy often prevails Polynous - When males have high quality territoriesthat the females are able to raise young on their own in polygyny often prevails 3. Handicap explanation for why females prefer males with extravagant ornaments - Females select mates that are successful- the ones with ornate structures. These structures may impede their locomotion,and their elaborate displays may attract the attention of predators. Femalesselect ornate males because they have survived despite carrying such a handicap. Successful alleles responsible for the ornamental handicap are passed to the female's offspring. 4. Meaning of sexual dimorphism, intersexual selection,intrasexual selection Sexual dimorphism- one gender is larger or more colourful than the other Ex. The developmentof structures used solely for attracting mates or intimidating membersof the same sex Intersexual selection- selection based on the interactions between males and females - Attracting the opposite sex Intrasexual selection- selection based on the interactions between members of the same sex - Intimidating the same sex Lecture 1. “lotteryticket hypothesis” and “red queen hypothesis” to describe the relationship between environmentalstability and benefits of sexual vs. asexual reproduction a. LotteryTicket Hypothesis - The environmentis often changing and unpredictable - A female that has survived to reproductiveage generally has strong genes for survival - In an unchanging environmentthey should make copies of themselves (asexually) to ensure strong survival genes in their offspring - However,if the environmentis changing than offspring may not be equally able to survive as the mother, therefor sexual reproduction, creating diversity is favoured - Some of the offspring may be better suited for a new environment b. Red Queen Hypothesis b. Red Queen Hypothesis - Selection pressure from parasites and harmful mutations, therefor it would benefit the individual to create a diversity of offspring through sexual reproduction, some of which will have a better chance of survival than others - Facilitative sexually- can reproduce sexually and asexually - When the infection rate is high there is a higher rate of sexual reproduction 2. long-term vs. short term advantages to sexual vs. asexual reproduction a. Sexual Reproduction i. Long Term Advantages - Removingharmful mutations,and combining helpful mutations ii. Short Term Advantages - Bet-hedging in a changing environment - Not putting all your eggs in one basket through asexual reproduction and creating offspring that may be unable to survive 3. why sex places different selectiveforces on males vs. females - Males look to attract females and do so through showing off their extravagant ornaments or loud mating calls - With females only mating with sufficiently attractive males this increases the fitness of males with attractive features and decreases the fitness of males with unattractive features 4. relationship between sexual selection and investmentin offspring - Females look to find a mate that will produce offspring that will have a higher survival rate, when an individual has survived through life to a reproductiveage with these deleterious traits it shows that they are likely to have strong genes which will be passed on to offspring 5. role of parasites as an explanation for the persistence of sexual reproduction The Red Queen Hypothesis- when there is a high rate of infection or parasites individuals prefer the production of offspring to be diverse, creating a better chance of survival 6. how sexual selection maintains traits seemingly incompatible with natural selection - Without certain traits to attract a mate an individuals fitness is zero, they produce no offspring - A lack of offspring reduces the frequency of the deleterious traits in a population with respect to sexual selection 7. examples of traits favoured by intra vs. inter sexual selection a. Intrasexual selectivetraits- large body size, horns: to physically competewith other males b. Intersexual selective traits- males competing with one another to win the female 8. why males are more usually competing for access to females (rather than vice versa) - The number of females a male mates with increases his fitness - No matter how many males a female mates with she may only produce a certain number of offspring, therefor she is more interested in increasing the quality of her offspring 9. relationship between parental investmentand which sex is choosy vs. competing - Sex differences in parental investmentand potential fitness determine which sex is choosy, and which sex competesfor a mate - Low investing sex spends more time competingfor the high investing sex - Sperm is cheap - The production of eggs entails a lot of time and energy; large investment 10. what happens (in terms of sexual selection)when both sexes invest heavily in offspring - Generally sexual selection has fashioned high levels of selectivenessin both sexes 11. average vs potential fitness of males vs females - Males and females have about the same average fitness because in moresexually reproducing populations sexual fitness is about 50/50 - More variation in fitness of male reproductivesuccess 12. limiting factors on male vs. female fitness - Females are limited to the number of offspring they can produce - Males are limited by the number of females that they can mate with 13. traits valued in mate choice by human males vs. females - Both sexes in humans undergo strong sexual selection - In long term sexual relationship males are choosy as well as females, this is not the case for males in short term sexual relationships - Physical attractivenessis desired by both sexes - A big driver of attractivenessis symmetry - Someonewho developed symmetrywithstood the demands of development Cooperation and Conflict November-12-12 4:08 PM Pre-Lecture 1. identify the meanings of kin selection, altruism, reciprocal altruism, eusocial Kin Selection- altruistic behaviour to close relatives, allowing them to produce proportionately more surviving copies of the altruist's genes than the altruist might otherwisehave produced on its own - A grey wolf helps his parents raise 4 pups creating 2 copies of his alleles, since all 4 pups share 0.5 alleles (0.5 x 4 = 2) - If the grey wolf had reproduced on its own and only raised 2 pups there would be only one copy of his alleles since he is only passing on 0.5 of his alleles (0.5 x 2 = 1) Altruism- a behavioural phenomenonin which individuals appear to sacrifice their own reproductive success to help other individuals - In the case of the grey wolf exhibiting parental behaviour, this is an example of genetic selfishness and cannot be considered altruistic behaviour Reciprocal altruism- form of altruistic behaviour in which individuals help nonrelatives if they are likely to return the favour in the future - Triver's Hypothesis: reciprocal altruism would be favoured by natural selection as long as individuals that do no reciprocate (cheaters) are denied future aid Eusocial- a form of social organization, observed in some insect species, in which numerous related individuals- a large percentage of them sterile female workers- live and work together in a colonyfor the reproductivebenefit of a single queen and her mate(s) 2. calculate degree of relatedness between two individuals, given the type of relationship (parent- offspring, cousins, etc) Parent-offspring - Each offspring will share 0.25 alleles from either parent Half Siblings - Half siblings share 0.25 alleles from one commonparent Full Siblings - Full siblings share 0.25 alleles from each parent and therefor share 0.25 + 0.25 = 0.5 of their alleles Aunt/Uncle-Niece/Nephew - A niece or nephew shares 1/2 of the alleles from the 0.5 that their parents share = 0.25 First Cousins - First cousins will share 1/2 of the alleles from the 0.25 that a niece/nephew shares with their aunt/uncle = 0.125 of their alleles 3. identify why haplodiploidy can favour high levels of cooperationin social insects - Haplodiploidy produces both diploid and haploid organisms - Offspring that are not produced by the female parent mating are related by 25% where as offspring produced by the female mating are related by 50%  Offspring that receive different alleles from the female parent share only 50% of alleles inherited from the male parent  Offspring that receive the same alleles from the female parent share 50% of alleles from the female parent plus an additional 50% of alleles from the male parent (100%) - This creates an average of workersbeing related by 75%, when there is such a high degree of relatedness offspring devote their lives to caring for each other because one of them, carrying 75% of the alleles may produce enormousnumbers of offspr
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