Exam 2

What will happen to DNA sequence variation in the regions of the genome immediately adjacent to an allele undergoing a selective sweep, or strong positive selection? -Decreased variation and high levels of linkage disequilibrium at nearby sites -Increased variation and high levels of linkage disequilibrium at nearby sites -Increased variation and the absence of linkage disequilibrium at nearby sites -Decreased variation and the absence of linkage disequilibrium at nearby sites -No change in local genetic variation

Decreased variation and high levels of linkage disequilibrium at nearby sites

Imagine a population of Galápagos finches that vary for bill size. If the population mean is near the optimum size for eating the seeds found on the island, what would we expect to occur if their main seed resource goes extinct, and another plant with much larger seeds replaces it? -Stabilizing selection maintaining the population average -Disruptive selection increasing phenotypic variance for bill size -Correlational selection between seed size and bill size -Directional selection increasing bill size towards a new optimum -Extinction of the new plant as finches each all its seeds

Directional selection increasing bill size towards a new optimum

Why did industrial melanism in the peppered moth, Biston betularia, help convince researchers that the intensity of natural selection can be very strong? -The dark-colored morph drove the light-colored morph to extinction. -Birds were unable to prey on the moths once they acquired their color adaptations. -The moth population exploded, covering England with moths during the Industrial Revolution. -The dark-colored allele increased in frequency very rapidly in multiple populations and later decreased rapidly after the environment changed. -Natural selection maintained constant proportions of the color alleles in the population, despite rapid environmental change brought about by the Industrial Revolution.

The dark-colored allele increased in frequency very rapidly in multiple populations and later decreased rapidly after the environment changed.

Suppose that gene B occurs in a unicorn population where the frequency of the B1 allele is 0.5 and the frequency of the B2 allele is 0.4. What is the frequency of the B3 allele, assuming that there are only 3 alleles in the population? -The frequency of B3 = 0.1 because 0.5 + 0.4 + B3 = 1. -The frequency of B3 = (0.4)^2 = 0.16 -The frequency of B3 = 0.9 because 0.5 + 0.4 = 0.9 -There is not enough information to determine the frequency of the B3¬ allele.

The frequency of B3 = 0.1 because 0.5 + 0.4 + B3 = 1.

What does the term spq represent?

The product of the selection coefficient and genetic variation

What is standing genetic variation? -When new mutations arise -Variation that occurs after selection -Variation that already exists in a population -When alleles reach an equilibrium of variation

Variation that already exists in a population

Which scenario depicts adaptations incorrectly? -a modified trait in an organism helps it leave behind more descendants -a trait in an organism increases in frequency because of non-random differences in survival and reproduction -a trait evolved that serves a valuable purpose in the environment of those that possess it. -as a trait became modified, its function was also altered - a trait evolved in anticipation of a future environmental change

a trait evolved in anticipated of a future environmental change

Populations of the grasshopper Vandiemenella viatica possess different chromosomal fusions and inversions. Grasshoppers that are heterozygous for different chromosomal rearrangements have reduced fitness. What would you expect to observe if you investigated the genotypes of this population? -New combinations of genes yielding genotypes of greater fitness -Few heterozygotes because of underdominance -Frequency-dependent selection, leading to fluctuations in fitness -Heterozygotes with greater fitness, owing to overdominance -A random assortment of genotypes because of genetic drift

Few heterozygotes because of underdominance

p'= p+∆p

Frequency of the allele (p) in the following generation

Which source of variation is most important to evolution? -genetic change -maternal effect -environmental variance -DNA methylation -Developmental noise

Genetic change

How did light skin color evolve? (2pts) Be sure to include: mode(s) of evolution pressures trade-offs

Light skin color evolved through populations of humans moving up north to cooler temperatures. Cooler temperatures showed less sun so that was less exposure to natural vitamin D. Less exposure to the sun and vitamin D would lead to less necessity for melanocytes. Melanocytes is what gives color to the skin. A trade off of this would be being at risk of skin cancer or other vitamin d deficient diseases.

Which of the followings is not an adaptation? -a trait that appears to have been designed following the engineering principles, like the extendable jaws of snake -a trait that promotes reproduction but does not affect survival, like floral scents -a heritable behavioral trait that does not involve physical morphology, like cooperation -a trait that results in death of the individual exhibiting it but increases that individuals total number of offspring, like the suicidal behavior of male redback spiders after mating -a trait that does not change the probability of survival or reproduction, like the color of cave dwelling fish

-a trait that does not change the probability of survival or reproduction, like the color of cave dwelling fish

Change in allele frequency due to natural selection is greatest when genetic variation is _______ and selection is _______. -.40;2.5 -0.40; 4 -0.30; 4 -0.50; 2.5 -0.50; 4

0.50; 4

Which conditions are required for natural selection to occur? 1. Traits are heritable; offspring resemble parents 2. Traits are coded for by dominant genes 3. Traits are correlated with fitness 4. Populations reproduce sexually -1, 2 and 3 -3 and 4 -2, 3 and 4 -1 and 3 -All the conditions

1 and 3

W= (probability of survival) x (average fecundity)

Absolute fitness

What does the term Wref represent?

Absolute fitness of some reference, usually the most fit allele/individual

w = W1/Wref

Relative fitness

A selective sweep is -Positive selection for a beneficial allele -When an allele spreads through a population to fixation -When an allele fixes in a population by chance -A type of balancing selection

When an allele spreads through a population to fixation

What is pleiotropy? -When many genes contribute to one phenotype - When one gene contributes to multiple phenotypes -When genetic linkage causes evolution of two traits simultaneously -When genetic constraints cause two alleles to trade-off with each other

When one gene contributes to multiple phenotypes

When a population is in Hardy Weinberg equilibrium -all alleles from all gametes are combining randomly -all genotypes are at equal frequencies -the most fit alleles are combining selectively -all alleles are at equal frequencies -the frequencies of beneficial alleles increases by s each generation

all alleles from all gametes are combining randomly

Mutation A. is the raw material for evolution B. generates heritable variation C. is a weak evolutionary force on its own D. A and B E. all of the above

all of the above

Not all traits are adaptations. which statement may also explain the evolution of a particular trait? -it may be a necessary consequence of physics or chemistry -it may have evolved by genetic drift, rather than by natural selection -it may have evolved because it was correlated with another trait that conferred an adaptive advantage -it may be a consequence of phylogenetic history -all of the above

all of the above

p+q=1

allele frequencies

A dairy farmer chooses to mate a male bull only with the female heifers that always make the greatest amount of milk, rather than heifers that produce a small amount of milk. What process is the dairy farmer employing when producing the next generation of calves? -Natural selection -Artificial selection -Sexual selection -Balancing selection

artificial selection

The colors of individuals in a snail population are determined by a single autosomal locus. A1A1 homozygotes are red, A1A2 heterozygotes are pink, and A2A2 homozygotes are white. Relative fitness for each genotype are: wA1A1= 0.5 wA1A2 = 1.0; wA2A2 = 0.75. At equilibrium, -both alleles are equally frequent. -both alleles are maintained in the population, and allele A1 is more common than allele A2. -the population is fixed for allele A2. -the population contains only A1A2 heterozygotes. -both alleles are maintained in the population, and allele A2 is more common than allele A1.

both alleles are maintained in the population, and allele A2 is more common than allele A1.

which of the following does NOT describe how mutations might occur? -change in a single base pair (point mutation, SNP) -change in chromosomes arrangement (structural mutation) -change in response to environment (induced mutation) -change in chromosome number (whole genome duplication)

change in response to environment (induced mutation)

Currently, the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body size is not correlated with risk of hawk predation, although small iguanas can sprint faster than large iguanas. If predators (e.g., cats) that preferentially catch and eat slower iguanas are introduced to the island, iguana body size is likely to ________ in the absence of other factors; the iguanas would then be under ________ selection. -increase; directional -increase; disruptive -decrease; directional -decrease; disruptive -stay the same; stabilizing

decrease; directional

Which of the following is most likely to produce an African butterfly species in the wild whose populations show two strikingly different color patterns? -Artificial selection -Directional selection -Stabilizing selection -Disruptive selection -Sexual selection

disruptive selection

Phenotypic variance that is not due to genetic variance can be attributed to -Environmental variance -dominance -epistasis -pleiotropy -linkage disequilibrium

environmental variance

Phenotypic differences that are not based on DNA sequence differences can be passes from parent to offspring. this phenomenon is called -genotype x environment interaction -maternal effects -epigenetic inheritance -phenotypic plasticity -norm of reaction

epigenetic inheritance

p^2

frequency of the dominant allele in the population

Humans have 23 chromosome pairs. other members of the hominidae, including chimpanzees, gorillas, and organgutans, have 24. what could have caused this difference? -inversions -fusions -deletions -frameshift mutations -backmutation

fusions

If one genotype in a genetically variable population is favored in dry years and a different genotype is favored in wet years, -genetic variation is likely to be maintained. -genetic drift will be a stronger force than selection. -genetic variation is always maintained. -rates of fixation are likely to speed up. -hard selection is likely to occur.

genetic variation is likely to be maintained.

On a trip to the Galápagos (lucky you!) you found that large marine iguanas had higher reproductive success than smaller iguanas. However, the large iguanas were generally in poor body condition because they could not eat enough. You also found that at higher temperatures, large marine iguanas had improved foraging efficiency, allowing them to eat more. Thus, you hypothesized that iguana size will ________ as global climate change increases air and water temperatures in the Galápagos Islands. - increase -decrease -stabilize around the mean body size -remain unchanged (it is not clear that body size increases fitness)

increase

which observation about a population would NOT violate the assumptions of the hardy-weignberg principle? -UV radiation induced new mutations at a high frequency -individuals migrate from nearby population but die prior to breeding -cold tolerance differs by genotype, and the population experiences a frost -inbreeding is present -the population size is smaller than 100 individuals

individuals migrate from nearby populations but die prior to breeding

which statement about natural selection is true? -its the same as evolution -it always results in reduced genetic variation -it can have evolutionary effect only of phenotypic differences are heritable -it acts directly on genotypes -changes in allele frequencies can occur only because of natural selection

it can have an evolutionary effect only if phenotypic differences are heritable

Biological fitness if -the variation in the number of offspring produced as a consequence of competition for mates -any consistent difference in reproductive success among phenotypically different classes of organisms -its survival rate -its average per capita rate of increase in numbers -its physiological condition

its average per capita rate of increase in numbers

Alarm calls by ground squirrels alert other ground squirrels to danger, but they also draw attention to the caller and expose it to increased risk of predation. Such altruistic behavior is best explained by the phenomenon of -selfish genes -group selection -individual selection -kin selection -exaptation

kin selection

Nonrandom associations between alleles at different loci are referred to by which term? -heterozygosity -linkage equilibrium -inbreeding depression -panmictic -linkage disequilibrium

linkage disequilibrium

A change in which variable would NOT change an organism's fitness? -mating success -fertilization success -fecundity -mutation rate -viability

mutation rate

Human sex ratios are close to equal because if one sex becomes rare, it will be at a fitness advantage and increase in frequency in the population until equilibrium at 50:50 is regained. This is an example of -overdominance, or heterozygote advantage. -negative frequency-dependent selection. -positive selection on sex ratio. -underdominance, or heterozygote disadvantage -positive frequency-dependent selection.

negative frequency-dependent selection.

Hardy weinberg equilibrium

p^2+2pq+q^2=1

What are the four processes that drive evolution? -selection, pleitropy, genetic drift, recombination -selection, genetic drift, fitness, geneflow -selection, probability, mutation, segregation of alleles -selection, genetic drift, mutation, gene flow

selection, genetic drift, mutation gene flow

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer or more than this have reduced fitness. Which of the following terms best describes this situation? -artificial selection -directional selection -stabilizing selection -disruptive selection -sexual selection

stabilizing selection

the wings of auks (alcidae), used for swimming, are called an exaptation because -the ancestor, wings were used for flight, but with a little evolution they also function well in water -they are useful, but don't affect fitness -female auks are more attracted to swimming males than flying males -they have a de novo form that was not present in ancestors -individuals that do not use their wings for swimming have lower fitness

the ancestor, wings were used for flight, but with a little evolution they also function well in water

which condition would most likely lead to an increase in the frequency of an altruistic behavior in a population? -groups that differ in terms of altruistic and selfish genotypes have differential reproduction or survival -the altruistic behavior benefits the population -the rate of extinction of the selfish genotype is high -there is a gene flow among populations -the beneficiaries of the behavior are related to the individual performing it

the beneficiaries of the behavior are related to the individual performing it

2pq

the frequency of the heterozygous genotype in the population

q^2

the frequency of the recessive phenotype in a population

which of these is an example of an evolutionary trade-off? -toads with a loud mating call attract more mates. loud mating calls also attract predators -a giraffe has seven neck vertebrae, just like almost all other tetrapods -blue whales lack genetic variation necessary to adapt to other food sources -genetic correlations make it difficult for natural selection of disentangle development of anterior and posterior eyespots on butterfly wings. -changing ocean temperatures select for fish with expanded thermal tolerance, compared to their ancestors.

toads with a loud mating call attract more mates. loud mating calls also attract predators

Which of the following can lead to stabilizing selection? -selection on variance -tradeoffs -linkage disequilibrium -variable selection -realized heritability

trade-offs

recombination and segregation are -ways of mixing alleles in gamete formation -a type of phenotypic covariance -the effect of natural selection on beneficial alleles -major components in calculation a selective sweep

ways of mixing alleles in a gamete formation

when we say that mutation is random, we mean that -we cannot predict which gene copy will undergo a mutation, and environments do not induce adaptive mutations -all loci are equally mutable -the chance that a mutation occurs is influenced by whether or not an organisms is an environment in which that mutation would be advantageous -environmental factors cannot affect mutation rates -all conceivable mutations are equally likely to occur

we cannot predict which gene copy will undergo a mutation, and environments do not induce adaptive mutations

Which equation describes the change in allele frequency in a single generation?

∆p = spq