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Bio 1001 Final Exam Outcomes.docx

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Biology 1001A
Tom Haffie

Bio 1001 Final Exam Outcomes Lecture 12 – Inheritance in Populations  Strategy to distinguish between a phenotype that results from codominance relative to incomplete dominance o Incomplete dominance occurs when effects of recessive alleles can be detected to some extent in heterozygotes (red + white =pink) o Codominance occurs when effect of different alleles are equally detectable in heterozygotes (red + white = spotted) o Cannot distinguish in inheritance patterns, they are the same  Characteristics that identify a pleiotropic allele o When two or more characters are affected by a single gene  Conditions under which Hardy-Weinberg Equilibrium is possible in a population o Genetic equilibrium (allele and genotype frequencies do no change) occurs when: no mutations, no gene flow, large population size, no selection, and random mating o Evolution is not occuring under these conditions  General pathway of eukaryotic membrane protein production o DNA is transcribed in nucleus  ribosomes transport transcripts to ER  ER translates  proteins are packaged into vesicles to the Golgi complex  send protein to cell membrane  General physiology of skin / hair pigmentation o Pigment production is determined by melanocytes that produce melanin  melanosomes that exported into cells o Two kinds of melanin – black VS red & yellow, brown is produced by the mixture of the two  Characteristics of dominant alleles o Mask effects of recessive alleles and determine phenotype o An allele is not always dominant all the time, depends on other  Which allele in a heterozygote is dominant, given biochemical mechanism of action of allele products o Happens due to interaction of the gene products  Factors that affect how allele frequencies change over time in a population o No selection = allele frequencies do not change o Diploidy, dominance / recessive relation, inheritance are not in themselves sufficient to drive changes in allele frequencies  Allele frequencies (p and q), given genotypic frequencies o p + 2pq + q = does not have to be 50/50  Function of various MC1R alleles o Membrane receptor that produce black melanin if there are high cyclic AMP levels and red during low levels (due to hormones) o B allele (always on), W allele, R allele (always off) Lecture 13 – Selection & Fitness  Meaning of deme, population, allele frequency, genotype frequency o Deme: local population of organisms of one species that interbreed with one another and share distinct gene pool o Population: group of potentially interbreeding organisms o Allele Frequency: proportion of different alleles within a population o Genotype Frequency: frequency of genetic constitutions within a population  Allele frequencies in a population, given the genotype frequencies o Frequency of genotypes: f(pp) = p , f(pq) = 2pq, f(qq) = q 2  Genotype frequencies in the next generation, given the allele frequencies and assuming Hardy-Weinberg equilibrium o If population is at genetic equilibrium of locus p and q, predicted frequency are p , 2pq, q 2  Assumptions of the Hardy-Weinberg equilibrium o No evolutionary forces, genes on separate chromosomes, at least 2 alleles, large effective population size, and no inbreeding  Conditions necessary for Hardy-Weinberg equilibrium o Large population, random mating, no gene flow or selection  Whether a population is in HWE, given observed genotype or phenotype frequencies o Compare actual observed frequency with predicted HWE frequency o If they are not equal, population may be evolving  Effect on selection on changes in allele frequency o Can cause genotypic frequencies in a population change as one genotype is weeded out, brings population out of HWE  Relative VS absolute fitness o Relative Fitness (w): fitness of genotype relative to other genotypes in a population, predicts genotype change o Absolute Fitness (W): number of offspring / survival rates / lifespan…etc produced by a certain genotype  How to calculate relative fitness o w = W / W MAX o Fittest genotype = 1, range between 0 – 1  How to quantify strength of selection o Greater the difference in between other genotypes, stronger the selection and faster the evolution  Relationship between dominance / recessiveness of alleles and response to selection o Selected against (dominant)  disappear from population, quickly weeded out o Selection for (dominant)  spreads quickly but never reaches 1 o Selected against (recessive)  remain at low frequencies indefinitely, masked by dominant in heterozygotes o Selected for (recessive)  takes a while to spread but may completely outcompete dominant partner  Effect of heterozygote advantage on genetic variation o Increases number of heterozygotes in population, does not weed out homozygotes o Selection is occurring (population is out of HWE) but no evolution  Why amount of genetic variation in a population is important o Raw material for evolution to occur, without it there can be no adaption to a changing environment o Inbreeding Depression: offspring of close relatives tend to have low fitness since deleterious recessive alleles are more likely to combine in offspring  Different types of selection (stabilizing, directional) and their effect on genetic variation o Vast majority of traits exhibit continuous quantitative variation o Stabilizing: extreme phenotypes are selected against, reducing amount of variation (most common) o Directional: extreme phenotype is selected for, shifts mean of population in that direction, eventually becomes stabilizing o Disruptive: extreme phenotype on either side of the distribution, intermediates selected against, splitting distribution in two Lecture 14 – Selection VS Other Evolutionary Forces  Difference between Batesian and Mullerian mimicry o Batesian: palatable species mimic distasteful models are protected against predators (frequency-dependent) o Mullerian: mimicry between different species benefits both, predator learns warning pattern that applies to all potential distasteful prey  How population frequency of a mimic phenotype may affect its fitness o Batesian  more frequent the mimic and less frequent the model, the greater chance the predators will attack the mimic o Mullerian  rare conspicuous warning patterns on unpalatable individuals offer little protection  Why same phenotype may be selected against in one environment but have a selective advantage in different environment o Population sufficiently widespread enough may maintain a variety of genotypes, each of which is superior in a particular habitat  Meaning of genetic load and genetic death o Genetic Load: extent to which population departs from optimal genotype o Genetic Death: loss of some individuals through any means that reduces reproductive ability o Population with a relatively high genetic load may find an environment where previously detrimental alleles may benefit survival  Effect of various types of selection on amount of variation in a population o Stabilizing selection causes less variation o Not all population experience directional selection over the same time o Selective environments may change and cause disruptive selection  Examples of stabilizing, directional, disruptive o Stabilizing – birth weight in babies o Directional – long tail lengths in widow birds o Disruptive – big / small beaks in finches  Reasons why directional selection does not remove all genetic variation from a population o Natural selection can‟t predict future, adaptations are environment- specific  Characteristics and examples of frequency dependent selection o Negative frequency-dependent (advantage of rarity) – predators hunt most common but the forms will eventually switch o Balancing selection, both alleles will be maintained o Positive frequency-dependent – advantage to most common form will cause allele to replace other alleles in population  Reasons why all living things are not perfectly adapted to their environment o Environment is constantly changing o Selection doesn‟t choose most perfect allele, constrained by available genetic variation, not the only evolutionary force o Traits represent a compromise between competing demands, limited by dominance relationships (can‟t weed out recessive)  Effect of genetic drift on allele frequencies within a population, particularly in the case of bottlenecks…etc o Genetic drift occurs whenever population size is less than infinite o Random unpredictable changes in allele frequency due to sampling error  Effect of genetic drift on variations between populations o Drift oppose selection and outcome depends on strength of selection and population size, reduces variation  Mechanism that explains why mutation is NOT directed toward the needs of the organism o Mutations are always occurring, not just because selective forces change, selection increases mutation frequency  General fitness effects of mutations o Most mutations are neutral, but ones that affect fitness are mostly harmful  Why most mutations that affect fitness are harmful o Easier to break something than to make it better with random fix  Effect of gene flow on allele frequencies o Introduces new alleles to population, often opposes selection o Prevents local population from becoming perfectly adapted  Characteristics of adaptive VS non-adaptive mechanism affecting allele frequency o Selection – only form of adaptive, increase fitness by removing harmful alleles and increase beneficial o Genetic drift, mutation, gene flow – non adaptive, random and oppose selection but cause population to go out of HWE  How various evolutionary forces reinforce or oppose one another o Mutations provide genetic variation for adaptive evolution o Genetic drift reduces variation within a population but increase it between populations, gene flow balances allele frequencies Lecture 15 – Why Evolution is True  How Darwin‟s theory of evolution differed from that proposed by Lamarck o Lamarck proposed metaphysical perfecting principle caused organisms to become better suited to environments o Inheritance of acquired characteristics stated that changes an animal acquired during its lifetime are inherited by offspring o Darwin proposed variations in hereditary traits enable some individuals to survive and reproduce while those that lacked favourable traits would die, leaving few offspring o Evolutionary change occurs in groups rather than individuals  Meaning of catastrophism, gradualism, uniformitarianism o Catastrophism: theory that reasons abrupt changes between geological strata marked dramatic shifts in ancient environments o Gradualism: view that Earth changed slowly over its history under the influence of continuous processes acting over long periods of time o Uniformitarianism: processes that shaped Earth‟s surface over long periods of time are the same as the processes observed today  Difference between relative VS absolute ages of rock formations and the fossils they contain o Relative ages – sediments found in any one place form different strata which are arranged with the youngest layers on top, sequence of fossils from high to low reveal relative age o Absolute ages – radiometric dating uses isotopes  Principle behind radiometric dating of rock strata o Amounts of isotopes can be measured and rates of decay are known, limited by half life of isoto14 o Living organisms maintain levels of C in bodies as soon as they die  Why most living things never form fossils o Soft remains are consumed / decomposed, sediments do not accumulate, absence of skeletons  Types of non-random mating o Inbreeding VS inbreeding avoidance o Assortative VS disassortative  Effect of non-random mating on HWE and evolution o Random mating is requirement for HWE o If a population mates assortatively, evolution will not occur, reduces amount of heterozygotes o If a population mates non-randomly, genotype frequencies change  Characteristics of a scientific theory o Coherent set of testable hypothesis that attempt to explain facts about the natural world o Must be able to be tested and to be proven false  Components of theory of evolution o Evolution happens gradually in populations, speciation happens o All life is related through common ancestry o Much of evolutionary change is caused by selection  Evidence for “descent with modification” o Evidence for common descent in form of homologies and intermediates in fossil record  Examples of homology and why they support idea of evolution o Any similarity between two species, not explainable by shared function / environment, reflects shared ancestry  Examples of vestigial traits and why they support idea of evolution o Vestigial traits only make sense in evolution o Genes can be duplicated and take on new function, but can also be duplicated to lose function / disabled  Role of fossil record as evidence for evolution o Descent – transitional forms link related groups, modification – fossil evidence of change Lecture 16 – Why Sex?  Relationship between sexual reproduction and genetic variation o Recombination produces different combinations of genes along a chromosome o Production of genetic variation is one of the hypothesis for persistence of sexual reproduction and allows population to adapt  Different modes of genetic sex determination o Particular genes are located on chromosomes are associated with sex determination o Sex can also be affected by autosomal genes or gender potential exists at time of fertilization  Different modes of environmental sex determination o Penis fencing in flatworms, temperature-dependent, hormones  Meaning of haplodiploidy o Mode of sex determination in which males develop from unfertilized haploid eggs and females develop from fertilized diploid eggs  Meaning of hermaphrodite, whether it is generally rare / common in plants o Having both female and male function, 90% of plants  Relationships among sexual reproduction, meiosis and genetic variability o Recombination in meiosis, crossing over, independent assortment creates genetic diversity  Mechanisms of asexual reproduction o Binary Fission: mother cell divides and gives rise to two genetically identical daughter cells o Vegetative Propagation: plant sends out runner to create clones  Examples and predictions of size-advantage model of sex change o Relationship between body size and fitness is different between males and females o Protandry: male to female sex change  Distribution of sexual reproduction among all life forms, and particularly among animals o Sexually reproducing organisms may be dioecious or monoecious o Dioecious: male and female functions are housed in different individuals o Monoecious: male and female functions are found in the same individual o Sequential monoecy means an organism can switch from male to female  Cost of sexual reproduction o Cost of finding a mate, courtship, mating  Cost of meiosis o Only pass half your alleles to offspring, dilute genome  Cost of sons o “Evolutionary dead end”, does not allow the maximum to be produced  “Muller‟s Ratchet” mutational load explanation for advantage of sexual reproduction o Asexual lineages accumulate harmful mutations o No way to get rid of harmful mutations, sex continually reforms genotypes  “Ruby in the Rubbish” hypothesis explanation for advantage of sexual reproduction o Does not increase average fitness, but increases amount of variation in fitness among offspring  Combination of beneficial mutations for advantage of sexual reproduction o Sex speeds up rate at which beneficial mutations occur in the same individual (speed of evolution is faster) o There‟s no way to combine beneficial mutations in an asexually reproducing population  Relationship between extinction rate and sexual reproduction o Sex speeds up evolution rate by discarding harmful mutations and combining beneficial ones, thus reducing extinction rate  Does sex for the good of the species explain its persistence? o Traits do not spread “for the good of the species” (or the group, or the population…) Lecture 17 – Sexual Selection  Meaning of monogamy, polygamy, polygyny, polyandry, promiscuity, lek o Monogamy: male and female form a pair for mating season or life o Polygamy: male and females have more than one active pair bond o Polygyny: one male has more than one female pair bond o Polyandry: one female has more than one male pair bond o Promiscuity: male and females have no pair bonds beyond mating time o Lek: congregation of displaying males where females come to mate  Conditions favouring the evolution of monogamous VS polygynous mating systems o Monogamy is favoured when young require a great deal of care from both parents o Polygyny is prevalent among mammals since females make larger investment, males are more sperm donor / protector  Handicap explanation for why females prefer males with extravagant ornaments o Features signal male quality and genetic makeup, as well large territories o Females select males who are more successful despite carrying such a handicap since they survived  Meaning of sexual dimorphism, intersexual selection, intrasexual selection o Sexual Dimorphism: differences in appearance of male / female o Intersexual Selection: based on interaction between males and females o Intrasexual Selection: based on interactions between members of the same sex  “Lottery Ticket Hypothesis” and “Red Queen Hypothesis” to describe relationship between environmental stability and benefits of sexual VS asexual reproduction o LTH: sex in unpredictable environment benefits individual, produces diversity in offspring – maximize chances that offspring will survive o RQH: sex is favoured when environment is continually evolving, benefits individual to produce variety of genotypes to better protect them  Long term VS short term advantages to sexual VS asexual reproduction o Long-term advantage – sexual reproduction speeds up evolution o Short-term advantage – genetically diverse, some offspring will survive  Why sex places different selective forces on males VS females o Sexual dimorphism and traits that reduce survival are due to sexual selection, must compete to gain access to opposite sex  Relationship between sexual selection and investment in offspring o Heavy-investment is under selection pressure to choose most fit individual while least-investment is under pressure to gain access to the most number of mates to create most offspring  Roles of parasites as an explanation for the persistence of sexual reproduction o Host must evolve faster than parasites to fight them o Sexual reproduction is advantage when parasites are a major selective force in environment  How sexual selection maintains traits seemingly incompatible with natural selection o Adaptations to maximize mating success to produce more offspring o Increases fitness, lifespan doesn‟t matter  Examples of traits favoured by intra VS intersexual selection o Intra – horns, large body size, tusks o Inter – bright colours, long tails, songs  Why males are more usually competing for access to females (rather than vice versa) o Sperm is cheap and easy to produce, while eggs are energetically costly (anisogamy = unequal gamete size) o Females are limited by the number of offspring they can produce and care they can provide  Relationship between parental investment and which sex is choosy VS competing o Sex differences in parental investment and potential fitness determines who is choosy and who competes o High investing sex becomes limiting resource for low investing sex  What happens (in terms of sexual selection) when both sexes invest heavily in offspring o Selection pressure favouring monogamy with both sexes facing equal selection pressure and both sexes being pick
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