BIO 345 Exam 1
Drag each label on the left to the correct description on the right to indicate whether each scenario describes gene sharing or gene duplication. A label may match more than one description, but each description will correspond to only one label.
- An antifreeze protein in Antarctic fishes is encoded by a gene very similar in sequence to the gene that encodes the cellular enzyme sialic acid synthase (SAS): gene duplication - Gelsolin is a protein that regulates the structure of the actin cytoskeleton and participates in signaling pathways promoting programmed cell death: gene sharing - Serum albumin is a protein that transports fatty acids in the bloodstream and catalyzes the oxidation of nitric oxide: gene sharing
homoplasy
- Groups constructed based on this kind of trait are polyphyletic. - a trait that is similar in two or more species but was not present in their most recent common ancestor
Imagine that a new predator has invaded the region of the United States shown on the map. This predator prefers to eat mice (Peromyscus polionotus) with light coats regardless of background color in the environment. Click on the pie chart(s) of the population(s) in which the dark variant of the Mc1R gene could increase in frequency due to selection pressures imposed by this new predator.
- Perdido key mouse - santa rosa island - choctawhatchee beach - st. andrews
Underdominance
- There is a stable equilibrium in which one allele or the other is fixed.
positive frequency-dependent selection
- There is a stable equilibrium in which one allele or the other is fixed.
negative frequency-dependent selection
- There is a stable intermediate allele frequency. - This is a form of balancing selection.
overdominance
- This is a form of balancing selection. - There is a stable intermediate allele frequency.
Drag each statement to the correct box to indicate whether it is true or false regarding the fitness effects of mutations.
- True - Modern molecular techniques allow evolutionary geneticists to estimate the distribution of fitness effects of mutations. - Although mutation is undirected, most mutations that arise are neutral or deleterious. False - Work in Drosophila indicates that the distribution of fitness effects is highly variable across different genetic backgrounds, making it difficult to generalize about the relative frequencies of neutral, harmful, and advantageous mutations. - Given that natural selection can cause adaptive evolution, most mutations must therefore increase fitness.
symplesiomorphy
- a shared ancestral character state - Groups constructed based on this kind of trait are paraphyletic.
Synapomorphy
- a trait that establishes the most recent common ancestor between two taxa - a shared derived character state
Drag the appropriate label on the left to each trait on the right to indicate whether the trait is an adaptation or an exaptation.
- feathers in birds that function in flight: exaptation - cranial sutures that allow skull deformation during live birth in mammals: exaptation - the helmet in treehoppers, which arises via activation of an ancestral developmental pathway that generated wings on the first thoracic segment: exaptation - a focusing eye that evolved from an indented eye cup, which in turn evolved from a simple patch of photosensitive cells: adaptation
In a population of diploid individuals, there are ___ gene copies at any given locus. If this locus is evolving neutrally by ____, we can trace any two of these gene copies back to a common ancestral gene copy that occurred ____ generations ago, on average, and we can trace all of the present gene copies back to an ancestral copy that occurred an average of ____ generations ago. When we trace the ancestry on gene trees using this approach, we say that gene copies ____ to their most recent common ancestor.
1) 2N 2) drift 3) 2N 4) 4N 5) coalesce
In the eighteenth century, _____ noticed that organisms could be arranged into a(n) ____ classification system in which groups of similar organisms are nested within more inclusive groups. In the twentieth century, developed a classification system called ____, which aimed to classify organisms into nested groups that reflect the process of descent with modification from common ancestors.
1) Carolus Linnaeus 2) hierarchical 3) Willi Hennig 4) phylogenetic systematics
Place the following steps in the order they occur during transcription of a eukaryotic protein-coding gene.
1) RNA polymerase binds to the promoter 2) The DNA double helix is unwound 3) RNA polymerase catalyzes the synthesis of an RNA polymer that is complementary to the DNA template strand 4) Introns are removed and exons are spliced together into a molecule of mRNA that can be translated into the amino acid sequence of a protein
If A and B are independent events with the probabilities of a and b respectively, then the probability that both A and B will occur is ___. If A and B are mutually exclusive events, then the probability that A or B will occur is ____, and the probability that both will occur is ____.
1) a × b 2) a + b 3) zero
We can decompose the phenotypic variance of a trait into components related to genetic and environmental variance. The fraction of phenotypic variance due to overall genetic variance is known as the _____ heritability. We can further break down genetic variance into (1) variation associated with ____ interactions among loci, (2) variation associated with _____ interactions between alleles at a locus, and (3) ____ variation associated with independently acting alleles whose phenotypic effects can be summed across loci. The fraction of overall phenotypic variation due to this third type of genetic variation is called the _____ heritability, which provides an indicator of how readily a population can respond to natural selection on the trait in question.
1) broad-sense 2) epistatic 3) dominance 4) additive 5) narrow-sense H2 = VG/VP = VG/(VG + VE).
You are studying the population genetics of wing color in a species of butterfly. Wing color is governed by a single locus with the following correspondence between genotype and phenotype:BB: black wingsBb: gray wingsbb: white wingsDrag the steps below into the correct order to show how you would test whether the population is in Hardy-Weinberg equilibrium at this locus.
1) collect a sample of butterflies and count the number in each phenotypic class 2) divide the number of indiviudals in each phenotypic class by the total number of individuals in the sample to arrive at relative genotype frequencies. Use these values to calculate observed allele frequencies. 3) calculte HW expected gentoype frequencies 4) multiply expected genotype frequencies by the total number of butterflies in the sample to calculate expected numbers of each genotype 5)for each genotypic class, subtract the expected number from the observed number, square that value, and divide the squared value by the exected number for that class. sum these values over all three genotypic classes. 5) compare the chi-square test statistic to the critial value with one degree of freedom
Sometimes the observed heterozygosity of a large population resembles what we would expect in a small population subject to strong genetic drift. These large populations often have a history of size fluctuations or a biased sex ratio. The _____ population size, which dictates the effects of genetic drift on allele frequency change, can be considerably smaller than the _____ population size, which is the total number of individuals in the population. As a consequence of drift, heterozygosity _____ from one generation to the next.
1) effective 2) census 3) decreases
There is no guarantee that natural selection will always generate a perfect fit between organisms and their environments. Even if certain phenotypes confer a survival or reproductive advantage, these traits will increase in frequency in a population only if there is adequate ___ variation underlying phenotypic differences. If there is ___, the genes governing one trait under selection might affect a different trait that is also under selection in such a way that neither trait can be optimized. Geographic variation in selective pressures can also limit ___ to local conditions if there is ____ among populations of the same species.
1) genetic 2) pleiotropy 3) adaptation 4) gene flow
Carolus Linnaeus and Willi Hennig developed classification schemes that were similar in that both generated ____ taxonomies. However, Hennig's approach, called ____, aimed to classify organisms based on their ____, while the Linnaean taxonomy did not.
1) hierarchical 2) phylogenetic systematics 3) evolutionary relationships
The figure depicts a form of founder effect known as _____, in which a small number of individuals at the periphery of a population colonize newly available habitats just outside the previous limits of the species range. Black spruce underwent such a process as glaciers retreated in North America. Plants initially colonize new habitats through ____ dispersal, which occurs over relatively short distances and delivers both nuclear and mitochondrial DNA. Newly established populations also receive genetic material via ____ dispersal, which occurs over much longer distances and in much greater volume but brings only nuclear DNA into the new population. New northern subpopulations of black spruce have ____ genetic diversity at mitochondrial loci than at nuclear loci, which is consistent with a founder event in which the population grew from fewer "mitochondrial DNA migrants" than "nuclear DNA migrants."
1) leading edge expansion 2) seed 3) pollen 4) lower
Downstream guppies are preyed upon by the voracious pike cichlid, which can eat large and small guppies with ease. The only predator of upstream guppies is a small, less voracious fish that can't consume guppies above a certain size. Natural selection in ___ populations has favored female guppies that produce few small broods of large offspring, which quickly grow enough to avoid predation. Although it would presumably confer higher fitness to produce large broods of large offspring, a(n) trade-off between offspring size and number prevents this combination of traits from occurring. Transplantation experiments confirm that this ___ strategy is an adaptation in these guppies to predation pressure.
1) low-predation 2) trade-off 3) life-history
Each line in the graph depicts the ____ for a specific ___ governing number of leaves in the weedy annual plant Persicaria maculosa. This plot shows that any given genotype can produce more than one ___ depending on environmental conditions. If Persicaria plants with the most leaves have the highest fitness in a population, then we expect natural selection to drive ___ to greater frequency at light intensities of 37% and 100% of available sunlight.
1) norm of reaction 2) genotype 3) phenotype 4) different genotypes
A trait governed by multiple loci is called a _____ trait. If the effects of alleles at these loci can simply be summed to predict the phenotype of an individual, we say that the loci show ____ effects. If, however, the phenotypic effects of the alleles at one locus depend on the genotype present at another locus, we say that the loci show ___ effects.
1) polygenic 2) additive 3) epistatic
When the fitness associated with a trait increases as the trait becomes more common in the population, there is ____. When the fitness associated with a trait decreases as the trait becomes more common, there is ____. The figure to the right shows that, regardless of how common each foraging behavior is in the population of Drosophila larvae (as shown along the x axis), rovers always have higher fitness than sitters when there is no resource competition. There is thus ___ on foraging behavior under these conditions. However, when there is resource competition, the fitness associated with each behavioral mode varies with trait frequency. Under resource competition, there is ____ on larval foraging behavior.
1) positive frequency-dependent selection 2) negative frequency-dependent selection 3) frequency-independent selection 4) negative frequency-dependent selection
Expected coalescence time for a new mutation depends on whether the mutation is neutral or under selection. We expect a new mutation under positive selection to go to fixation ___ and thus to have a _____ coalescent time than a neutral mutation. Since balancing selection maintains allelic variation, we expect a new mutation under balancing selection to have a _____ coalescent time than a neutral mutation.
1) rapidly 2) more recent 3) less recent
The evolution of eye position in birds is characterized by a between range of ___ and total ___. Front-facing eyes give owls excellent binocular vision but limit their field of vision to a narrow range. Owls can overcome the effects of this ___ to some extent via the ability to turn their heads almost 180° to look behind themselves.
1) trade-off 2) binocular vision 3) field of vision 4) physical constraint
Point mutations in a DNA sequence in which a purine is replaced by a purine (or a pyrimidine by a pyrimidine) are called ___. These mutations are about twice as common as ____, in which a purine is replaced by a pyrimidine or vice versa. Chromosomal mutations include ____, in which a segment of a chromosome flips 180°. Addition or deletion of entire sets of chromosomes can change the ____ of an organism, which is usually lethal in animals but is common in plants.
1) transitions 2) transversions 3) inversions 4) ploidy
Neotropical treehoppers have elaborate helmets that vary widely among species and perform a camouflaging function. These structures develop via a pathway that generated ____ in an extinct ancestral insect lineage. We thus consider these structures to be ____. We do not see helmets in other living insects because the developmental pathway is ____ in these groups.
1) wings 2) exaptations 3) suppressed
Click on the branch (A, B, C, or D) containing the root of the tree that fits the description below: - Group 1 is paraphyletic. - Groups 2 and 3 are sister clades. - P. diminuta is the sister taxon to the clade consisting of Groups 2 and 3.
A
Mendel's law of segregation describes the pattern whereby which occurs?
Alleles at a single diploid are distributed into haploid gametes
The figure below depicts the results of an experiment designed to estimate the distribution of fitness effects of mutations induced in a viral genome. Fitness values are expressed in comparison to the fitness of the wild-type virus. Which of the following statements is true of these results?
Beneficial mutations were less common than neutral mutations
Drag each statement to the correct box to indicate whether it is true or false of inbreeding.
CORRECT - Inbred populations have higher frequencies of homozygous genotypes than predicted by the Hardy-Weinberg model. - Inbreeding depression often occurs because rare deleterious recessive alleles are more likely to be found in a single individual than when mating is random. - Inbreeding depression occurs when the offspring of genetic relatives have lower fitness than the offspring of unrelated individuals. FALSE - Inbreeding causes deleterious recessive alleles to increase in frequency in a population, which is a key contributor to inbreeding depression. - Inbreeding depression is primarily a consequence of higher mutation rates in the offspring of matings between kin.
Which of the following conclusions can you draw about the evolution of eyes in mollusks based on the phylogeny in the figure?
Correct: - Simple eye morphologies in living animals, like those found in the limpet Patella, serve as models of possible intermediates along the evolutionary trajectory that culminated in complex lensed eyes. Incorrect: - Simple patches of light receptors appeared early in the evolution of mollusks and were replaced by complex eyes with lenses in living lineages. - The simple lensed eye of the snail Murex evolved into the more complex lensed eye of cephalopods like the octopus.
Drag each statement to the correct box to indicate whether or not it provides evidence for epistasis between the Agouti locus and the Mc1R locus in oldfield mice.
EVIDENCE FOR EPISTASIS - Mice with the LL genotype at the Agouti locus differ in coat color depending on their genotype at the Mc1R locus. - Mice with the DL genotype at the Mc1R locus differ in coat color depending on their genotype at the Agouti locus. NOT EVIDENCE FOR EPISTASIS - Mice with the DL genotype at both loci are intermediate in coat color. - Mice with the LL genotype at both loci are the lightest in color, and mice with the DD genotype at both loci are the darkest in color.
Which of the following statements accurately describes how epigenetic effects on gene expression differ from genetic effects?
Epigenetic effects do not involve changes in DNA sequence
Examine the figure below. Drag each statement to the correct box to indicate whether or not it helps explain the different trajectories for favored dominant and recessive alleles under directional selection. p is the frequency of this favored allele.
Explanation - The fitness effects of an advantageous recessive allele are masked in heterozygotes, so such an allele rises in frequency slowly until it is common enough to appear in homozygotes. - The fitness effects of an advantageous dominant allele are present in heterozygotes, so such an allele rises in frequency rapidly when rare. - When an advantageous dominant allele has reached a high frequency, it approaches fixation slowly because the rare recessive allele is found predominantly in heterozygotes. Not an explanation - Dominant alleles are typically advantageous, whereas recessive alleles are typically deleterious.
Drag each item to the correct box to indicate whether or not it is an assumption of the Hardy-Weinberg model.
HW assumption: - There is no mutation or migration. - Population size is effectively infinite. - There is no natural selection. Not HW assumption: - There is assortative mating with respect to the genetic locus in question. - The population reproduces asexually.
Drag each item on the left to the correct answer on the right to indicate whether each process increases, decreases, or does not change allelic variation within a population.
INCREASES - migration - mutation DECREASES - underdominance - directional selection favoring a dominant advantageous allele - directional selection favoring a recessive advantageous allele DOES NOT CHANGE - nonrandom mating - Mendelian inheritance
Why is it important to tetrapod hormonal function that, before aldosterone even evolved, one copy of the duplicated mineralocorticoid receptor (M receptor) lost the ability to bind aldosterone but retained the ability to bind cortisol?
If both versions of the receptor could still bind both hormones, then the appearance of aldosterone would probably have disrupted cortisol signaling.
Drag each process to the correct box to indicate whether it increases or decreases genetic variation within a population.
Increases Variation - migration - balancing selection - mutation Decreases variation - directional selection
Which statement would be true about any trait that is considered an exaptation?
It initially evolved under natural selection for one function and was later co-opted for a new function.
An equilibrium is at a stable point if which of the following is true of the system?
It returns to that point after a small local perturbation
When researchers rediscovered Mendel's work in the late nineteenth and early twentieth centuries, why did his results initially seem incompatible with Darwinian natural selection?
Mendel derived his laws from inheritance patterns of discretely varying traits, whereas Darwin contended that natural selection acted primarily on continuous variation
dominance
One allele masks the phenotypic effects of another allele at the same locus.
Drag each statement below to the correct box to indicate whether it describes overdominance or underdominance for a locus with two alleles, A1 and A2.
Overdominance: - Heterozygotes have the highest fitness among the three genotypes. - There is a stable intermediate (nonzero) equilibrium frequency of the A1 allele. - This is a form of balancing selection. Underdominance: - Heterozygotes have the lowest fitness among the three genotypes. - There is an unstable intermediate (nonzero) equilibrium frequency of the A1 allele.
Drag each item to the correct box to indicate whether or not it is a question that can be answered via population genetics.
Population genetics: - Is the genotype frequency observed in a population at a stable equilibrium? - How are genotype frequencies in an offspring population related to genotype frequencies in the parental population? - How can we mathematically model the evolutionary dynamics of a population in which a genetic locus is under natural selection? Not population genetics: - What proportion of offspring in a family will be heterozygous at a locus? - Is there complete or incomplete dominance at a locus?
Drag each trait to the population in which you expect to find it based on the experiments on guppies in mountain streams of Trinidad and Tobago. Remember that Crenicichla alta is a more voracious predator than Rivulus hartii. A single trait can match one or both populations, but you will not necessarily use every trait.
Predatory (Crenichla alta) - swimming in larger groups - trade-off between offspring size and number - more offspring per brood Predator (Rivulus hartii) - larger offspring - fewer broods of young per season - trade-off between offspring size and number
quantitative genetics
R = h2S, where R is the difference between the mean trait values of the parent and offspring generations, h2 is narrow-sense heritability, and S is the difference in means between the whole parental population and the individuals in that generation that actually produce offspring.
From the crosses shown, why can we conclude that flower color shows particulate inheritance?
Red and white flowers like those in the parental generation appear in the F2
Which of the following statements best describes a hypothesis that could be tested using the method illustrated in the figure below?
Species 2,3, and 4 share the same flower shape because they all inherited that shape from their most recent common ancestor
Drag each statement to the correct box to indicate whether it is true or false of the inheritance pattern for kernel color in winter wheat.
TRUE - All kernels with exactly two alleles denoted by a capital letter are the same color regardless of the loci at which these alleles are found. - The three loci governing kernel color interact additively. FALSE - There are too many loci governing kernel color for inheritance to be consistent with Mendel's laws.
Drag each statement to the correct box to indicate whether it is true or false regarding the evolutionary reversal of antibiotic resistance.
TRUE - Although resistance alleles typically confer a fitness cost in antibiotic-free environments, compensatory mutations that mitigate these costs can arise at other loci. - The frequency of bacterial resistance alleles often declines sharply when the antibiotic is removed from their environment, but resistance is not always lost under drug-free conditions. FALSE - The presence of antibiotics induces resistance, and once a bacterium has switched to a resistant phenotype, it is not reversible because natural selection cannot reduce the frequency of an environmentally determined trait. - Mutations that confer antibiotic resistance are typically advantageous in environments with and without antibiotics, so once these alleles arise, they will always be maintained at high frequencies by natural selection.
Drag each statement to the correct box to indicate whether it is correct or incorrect of allele frequency change under genetic drift.
TRUE - At any given time, the probability that a neutral allele will eventually be fixed in a population equals the frequency of the allele at that time. - In a Wright-Fisher population, genetic drift reduces heterozygosity by an average factor of ½N each generation. - Random fluctuations in allele frequency from one generation to the next are more pronounced in small than in large populations under genetic drift. FALSE - In finite populations, one allele at a neutral locus will eventually be fixed by genetic drift only when the population size is less than 100 individuals. The fixation probability of a new neutral mutation in a diploid population is ½N.
Drag each statement to the correct box to indicate whether it is true or false of genetic drift.
TRUE - Genetic drift is random change in allele frequencies due to sampling effects in finite populations. Essentially, because some individuals no longer contribute alleles to the gene pool, due to random death or other reasons preventing reproduction, genetic drift causes random changes in allele frequencies over generations. - Genetic drift decreases heterozygosity in a population. - Genetic drift causes fluctuation of allele frequencies from one generation to the next in finite populations. FALSE - Genetic drift maintains genetic variation within a finite population. - Genetic drift causes separate populations of the same species to converge on the same allele frequencies over time.
Drag each statement to the correct box to indicate whether it is true or false based on the figure demonstrating the results of a cross between plants that breed true for red flower color and white flower color.
TRUE - If blending inheritance were the explanation for pink-flowered F1 offspring, we would not expect any red- or white-flowered offspring in the F2. - Blending inheritance would pose a problem for the theory of natural selection because it would erode heritable genetic variation in fitness-related traits. FALSE - Only blending inheritance can explain the observation that F1 flowers are pink since red must be dominant to white.
Watch the animation and then identify whether each statement is correct or incorrect of inheritance and evolution in a sexually reproducing diploid population.
TRUE - If two parents are heterozygous at a locus, we know the odds that an individual offspring will have a particular genotype. - We can model population-level change in genotype frequencies without knowing the genotypic compositions of specific families. FALSE - If two parents are heterozygous at a locus, we can say with certainty which parental alleles an individual will inherit. - When two specified gametes come together, there is uncertainty about what genotype will develop.
Drag each statement to the correct box to indicate whether it is true or false.
TRUE - In a natural, diploid population, we expect that genetic drift will be the main driver of allele frequency change when the selective advantage of an allele is much less than ½Ne. - The probability that a new advantageous mutation will rise to fixation via selection depends on the strength of selection. FALSE - Natural selection is the only force that leads to the fixation of advantageous mutations in natural populations, even if it takes a long time.
This graph reports data from a study of twin types and correlation to depression. Consider different types of twin pairs and drag each statement to indicate whether it is correct or incorrect.
TRUE - Monozygotic (MZ) twins are genetically identical, whereas dizygotic twins are as genetically similar as any pair of non-monozygotic full siblings. - Researchers compare correlations between monozygotic and dizygotic twin pairs because both types of pairs likely share similar developmental environments but differ in their genetic similarity. FALSE - Higher correlations for monozygotic than for dizygotic twin pairs support the conclusion that susceptibility to depression is entirely genetically determined. - The lack of a difference in correlation between male-male and male-female dizygotic twin pairs (as shown in the graph above) suggests that all variation in susceptibility to depression is environmental.
Drag each statement to the correct box to indicate whether it is correct or incorrect of heritability.
TRUE - Narrow-sense heritability is the fraction of total phenotypic variation that is due to additive genetic variation. - Heritability is a statistical property of a population under a specific set of environmental conditions, not a general property of a species as a whole. FALSE - If a trait has a nonzero narrow-sense heritability in two separate populations in a species, we can conclude that any difference in mean trait value between the two populations is due to genetic differences between the populations. - Heritability values calculated from laboratory breeding experiments provide the best estimates of heritability for natural populations.
Drag each statement to the correct box to indicate whether it is true or false of the expected long-term consequences of migration from the mainland to the island as shown in the figure to the right. Assume that migration is the only driver of allele frequency change in these populations.
TRUE - On the island, the frequency of A1 will increase and the frequency of A2 will decrease until they converge on the initial mainland values. - The frequencies of A1 and A2 will remain unchanged on the mainland. FALSE - The frequencies of A1 and A2 will change on both the mainland and the island until they attain values halfway between the initial values in the two populations. - On the mainland, the frequency of A1 will decrease and the frequency of A2 will increase until they converge on the initial island values.
Drag each statement to the correct box to indicate whether it is true or false of the results depicted in the graphs below.
TRUE - Reduced heterozygosity in northern elephant seals is consistent with a population bottleneck. - The graph on the right shows that northern elephant seals show some DNA sequence variation even though enzyme electrophoresis revealed no heterozygosity at the loci examined. - Based on these data, it is possible that northern and southern elephant seals differ in their genetic variation because of some factor other than the hunting-induced bottleneck. FALSE - The DNA sequence data shown on the right and the enzyme data shown on the left lead to different conclusions regarding the source of reduced genetic variation in northern elephant seals.
Drag each statement to the correct box to indicate whether it is true or false of the relationship between genealogy and mutation at a neutral locus.
TRUE - The origin of new neutral mutations occurs randomly on branches of a coalescent tree representing the genealogy of the locus. - The origin of new neutral mutations does not affect the branching pattern of a coalescent tree representing the genealogy of the locus. FALSE - The distribution of new neutral mutations on a genealogy determines which gene copies are most likely to leave descendants from one generation to the next.
Drag each statement to the correct box to indicate whether it is true or false of the phenotypic adaptive landscape shown in the figure.
TRUE - There are two combinations of color pattern and reversal behavior associated with high fitness in garter snakes. FALSE - A snake population located on the X in the adaptive landscape would most likely evolve in behavior rather than color pattern under the action of natural selection. - Only natural selection could drive a population of spotted snakes that reverse frequently to evolve into a population of striped snakes that rarely reverse.
The figure depicts adaptive landscapes for bacteria in the presence (A) and absence (B) of antibiotics. The R allele confers resistance to the antibiotic, and the C allele is a compensatory mutation that mitigates the negative fitness effects associated with resistance in the absence of the drug. The vertical axis on each graph represents fitness.Drag each of the following statements to the correct box to indicate whether they are true or false of this adaptive landscape.
TRUE - There is no fitness advantage to the compensatory mutation on a genetic background without resistance. - This adaptive landscape is represented as a genotype space. FALSE - Natural selection will not drive the loss of compensated resistance when antibiotics are present, but it will lead to loss when antibiotics are absent. - Since the RC genotype has the highest fitness when antibiotics are present, we should expect a population to evolve directly from the rc genotype to the RC genotype upon introduction of antibiotics.
Drag each statement to the correct box to indicate whether it is true or false of the mainland-island model of migration illustrated in the figure to the right.
TRUE - We assume random mating in both the mainland population and the island population. - Over time, the island population will reach allele frequencies equal to those found on the mainland. FALSE - Island allele frequencies will reflect a balance between the introduction of mainland alleles by migration and the selective removal of mainland alleles that are deleterious in the island environment. - Allele frequencies will change in both the mainland and island populations until both are in Hardy-Weinberg equilibrium.
Drag each statement to the correct box to indicate whether or not it correctly characterizes the information conveyed by Wright's F-statistic.
TRUE - the probability that the two alleles found in an individual are identical by descent - the extent to which a population is deficient in heterozygotes relative to expectations under random mating FALSE - the mutation rate from advantageous to deleterious alleles at a locus - the rate at which allele frequencies change from one generation to the next as a consequence of inbreeding
Imagine a population in which mutation is the only driver of allele frequency change. Which of the following statements is true for a locus with two alleles and the mutation rates shown in the figure to the right?
The A1 allele will reach an equilibrium frequency of v/(u+v)
epistasis
The phenotype associated with a genotype at one locus depends on the genotype present at another locus.
norm of reaction
The phenotype associated with a genotype depends only on the environment in which the genotype is expressed.
Which of the following statements is true of the chronogram depicted below?
The relationships among the Cypripedioideae, Vanilloideae, and (Orchidoideae + Epidendroideae) are incompletely resolved.
According to the phylogeny below, why do birds have four visual opsins?
They did not lose any of the four ancestral visual opsins, nor did they gain any new ones
According to the phylogeny below, why do New World primates have two visual opsins?
They retained the two opsins present in ancestral mammals and gained no new ones.
Drag each statement to the correct box to indicate whether it is true or false of the phylogenies shown.
True - A group consisting of spoonbills and storks would be paraphyletic under the hypotheses put forth in both trees. - Tree A was constructed based on morphological data, and Tree B was constructed later based on molecular data. We can thus consider Tree B to be a test of the hypothesis posited by Tree A. False - Tree A is based on morphological data, and Tree B is based on DNA-sequence data. Tree B must therefore be true because molecular data accurately reflect phylogenetic relationships. - If we rotate branches around nodes in Tree B, we can see that both trees posit the same relationship between penguins and loons.
Drag each statement to the correct box to indicate whether it is true or false of Mendel's conclusions on flower-color inheritance in pea plants.
True - A purple-flowered plant in the parental generation has only alleles for purple flowers. - Each plant in the F1 generation has alleles for both purple and white flower color. - Some plants with purple flowers in the F2 generation have alleles for white flower color. False - White flowers in the F2 generation must be the consequence of new mutations.
The figure below depicts results from a study by researcher Claudia Bank and her colleagues (Bank et al. 2014) who induced point mutations in the coding region of a heat shock protein (HSP90) in yeast and estimated the distribution of fitness effects at two different temperatures. Drag each statement below to the correct box to indicate whether it is true or false of these results.
True - HSP90 is likely more crucial for fitness at 36°C than at 25°C. - Nonsense mutations tend to fall in the deleterious or lethal peak of the distribution. False - The peak corresponding to neutral mutations is higher at 36°C than at 25°C.
Luria and Delbrück found that resistant colonies of E. coli grew on plates covered with viruses even though the original bacterial culture was phage-sensitive. Drag each of the following statements to the correct box to indicate whether it is true or false of the conclusions Luria and Delbrück drew from their experiments.
True - There was a lot of variation among replicate runs of the experiment in the number of resistant colonies that grew. - The resistant colonies grew from cells in which resistance mutations randomly arose prior to phage exposure. False - The resistant colonies grew from cells in which exposure to phage induced mutations favoring resistance. - Approximately the same number of resistant colonies grew in each replicate of the experiment.
Stick insects are members of the clade that includes Lepidoptera and Diptera in the phylogeny shown. Some stick insects have wings that are useless for flight. Given this information, drag each statement below to the correct box to indicate whether it is true or false.
True - Wings are a vestigial trait in stick insects. - Functionless wings in stick insects are homologous to functional wings in Lepidopterans and Dipterans. False - If we are looking for vestigial wings in other species shown in this tree, we are better off looking in the Zygentoma than in the Myriapoda.
Drag each statement to the correct box to indicate whether it is true or false of variation in mutation rates among human tissues.
True - Cells in the human intestinal epithelium undergo many more cell divisions per generation than human retinal cells, but the mutation rate per cell division is lower in the intestine. - Mutation rates vary among human tissue types. - Mutation rates are lower in the human germ line than in somatic tissues. False - The human intestinal epithelium has a higher mutation rate per cell division than human fibroblasts in culture.
Drag each statement to the correct box to indicate whether it is true or false.
True - It is possible to map traits onto a phylogeny that has been constructed based on other traits. This mapping allows us to infer the timing and order of evolutionary events in a group of related species. - Morphological, behavioral, or DNA sequence data can be used to infer phylogenetic relationships. False - A phylogeny can be used to represent evolutionary relationships among species or genera but not among more inclusive groups of organisms like families or classes.
Drag each statement to the correct box to indicate whether it is true or false based on the phylogeny shown.
True - Limbs are a symplesiomorphy of the tetrapods. - The common ancestor of snakes and lizards most likely had limbs. - Limbs are homologous among different taxa within the tetrapods. False - Limbs are a symplesiomorphy of the clade consisting of fish plus tetrapods. - Limbs are analogous between marsupials and lizards.
Watch the animation and then drag each statement to the correct box to indicate whether it is true or false.
True: - Fish are a paraphyletic group because their most recent common ancestor also gave rise to the tetrapods. False: - The vertebrate tree shown in the animation represents the relationships among taxa within the tetrapod clade as a polytomy. - Various rootings of a phylogeny differ in the direction of time along the tree but not in the groupings of taxa that are monophyletic. - Rotating branches around interior nodes on a particular phylogeny changes our hypotheses about which groups of taxa are monophyletic.
Which of the following statements must be TRUE if we are to consider a trait to be an adaptation? Which statements are FALSE?
True: - The trait must be heritable. - The trait must have evolved due to natural selection on its primary function. False: - The trait must confer a fitness advantage with respect to biotic rather than abiotic environmental conditions.
pleiotropy
Variation at a single gene influences a variation of multiple traits.
If a genotype frequency is at a stable equilibrium in a population, a small perturbation that increases the genotype frequency will be followed by ____ in frequency.
a decrease
additive genetic effects
a genotype-phenotype relationship whereby effects of alleles at different loci sum to generate an individual's phenotype
epistasis
a genotype-phenotype relationship whereby the phenotypic effects of the genotype at one locus depend on the genotype at another locus
Which of the following is true of an adaptive landscape that is represented in genotype space?
a rugged landscape results when single mutations generate large changes in phenotype and fitness
Which of the following conclusions can you draw from the graphs, which depict the results of a long-term artificial experiment on oil content in corn?
additive genetic variation for oil content in corn persisted even after many years of selection
If a genotype frequency is at an unstable equilibrium in a population, a small perturbation that increases the genotype frequency will be followed by ____ in frequency.
an increase
Which phenomenon occurs when genotype frequencies in a population change from one generation to the next?
biological evolution
S
difference between the mean phenotype of the individuals that reproduce in the parental generation and the mean phenotype of the whole parental population
R
difference in mean phenotype between offspring and parent generations
Examine the graphs below. Variation in this trait is governed by 10 additively acting loci, each with two alleles. Which of the following statements best explains why we see trait values outside the original range (between 16 and 18) in the population after selection?
due to increased fitness of individuals with the favored trait value, allele frequencies increase and subsequent generations have genotypes associated with even higher trait values than observed in the original population
Click on the picture of the organism in the figure that meets all four of the following criteria: cannot synthesize aldosterone can synthesize cortisol descends from the lineage in which the M receptor gene was duplicated could bind both hormones with both copies of the receptor
elasmobrachs - Even though aldosterone synthesis did not evolve in elasmobranchs, the receptors in elasmobranchs would have the ability to bind it, because this branch did not experience the mutation that occurred in the branch leading to teleosts and tetrapods.
Phenotypic variation within an inbred line of a model organism is due to what factor?
environmental variation
when mutation is the only process operating to change allele frequencies, the equilibrium frequency of the A1 allele, which we label p*, is equal to ν/(μ + ν). Correspondingly, the equilibrium frequency of the A2 allele is given by q* = μ/(μ + ν). Correspondingly, the equilibrium frequency of the A2 allele is given by q* = μ/(μ + ν). eventually reach an equilibrium value, called p*. At that equilibrium value, the allele frequency p′ in one generation is unchanged from p in the previous generation: p = p′ = p*. Substituting p* for both p and p′ in the first equation above, we get p* = p*(1 − μ) + (1 − p*)ν. With a little bit of algebra we can solve this equation for p*, and when we do, we get p* = ν/(μ + ν). Correspondingly, the equilibrium frequency of the A2 allele is q* = μ/(μ + ν).
equilibrium frequency
h2
fraction of phenotypic variance that is due to additive genetic variance
What is true of evolutionary change within populations depicted on a phenotypic adaptive landscape like the one in the figure?
genetic drift or mutations of large effect can help move a population from a local peak to a higher global peak when natural selection alone cannot Selection drives populations uphill on such an adaptive landscape, so other mechanisms, such as drift in small populations, must come into play if a population must cross a fitness valley to shift to a higher peak.
Imagine a population that starts out with two alleles at a locus with a frequency of A1 = 0.4 and a frequency of A2 = 0.6. Under which of the following scenarios do you expect genetic variation to be maintained after many generations?
heterozygote advantage Heterozygote advantage, or overdominance, is a form of balancing selection, which maintains genetic variation in populations.
You have set up an experimental population consisting entirely of plants that are heterozygous at a locus with two alleles. You allow these individuals to self-fertilize to create the next generation. Assuming that the population conforms to all Hardy-Weinberg assumptions other than random mating, which of the following statements is true of the genetic composition of that next generation?
homozygous gentoypes will occur at a higher frequency than predicted by the HW model
Not all finite populations subject to drift are entirely homozygous for which of the following reasons?
mutation introduces new alleles even as genetic drift erodes genetic diversity
If a genotype frequency is at a neutral equilibrium in a population, a small perturbation that increases the genotype frequency will be followed by ____ in frequency.
no further change
Assume a locus with two alleles such that p is the frequency of A1 and q is the frequency of A2. A1 mutates to A2 at rate μ. The rate of back mutation from A2 to A1 is v. Mutation is the only driver of allele frequency change in the population. Given this information, match each description on the left with the correct term from the equation shown below:q′ = pμ + q(1 - v)
q(1-v): - proportion of A2 alleles that do not mutate to A1 q': - frequency of A2 in the next generation pu: proportion of A1 alleles that mutate to A2
Violation of which Hardy-Weinberg assumption does not, on its own, change allele frequencies in a population from one generation to the next?
random mating
Which of the following statements is true about coalescent time in a Wright-Fisher population?
the coalescent point for all current gene copies in a population is more recent in a small population than in a large population Since the expected coalescent time is 4N generations, a larger population will have a longer coalescent time.
Which of the following conclusions can you draw from the graph below? The calculations that generated this plot assume that the advantageous allele starts at a frequency of 1% in the population. s is the selection coefficient against the deleterious allele.
the effectiveness with which natural selection can fix an advantageous allele depends on population size and the strength of selection
On what basis do we determine whether a trait as an exaptation or an adaptation?
the evolutionary history of the trait and its function(s)
Which of the following statements best describes the expected trajectory of evolutionary change on a phenotypic adaptive landscape when each genetic change has a small phenotypic effect?
the population will slowly climb directly uphill until it reaches the nearest fitness peak
Berthold and Pulido (1994) were interested in whether migratory behavior in the blackcap warbler could respond to natural selection due to climate change. Nocturnal restlessness in the lab is a proxy for migratory behavior in this species. Why did the researchers measure this behavior in both parents and offspring in their study?
the slope of a parent-offspring regression is an estimate of the narrow-sense heritability (h2) for a trait, which must be greater than 0 if a population is to respond to natural selection on that trait
Which of the following statements is true of the gene effects summarized in the table?
the two loci interact epistatically One way to convince yourself of this conclusion is to look at which genotype at one locus has the highest fitness. For the A locus, the fittest genotype depends on which genotype is present at the B locus and vice versa.
Which of the following conclusions can we draw from the figure, which depicts mtDNA types found in northern elephant seals sampled before, during, and after their hunting-induced bottleneck?
there was much more variation in the population before the bottleneck than during or after the bottleneck, indicating that the temporary reduction in population size was responsible for the low levels of genetic diversity in current populations
discrete variation
type of trait distribution in which individuals fall into a few phenotypic categories
polygenic
type of trait governed by multiple loci
