Exam 2

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

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

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

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

All of the following are examples of adaptations EXCEPT A heritable behavioral trait that does not involve physical morphology, like cooperation A trait that does not change the probability of survival or reproduction, like the color of cave-dwelling fish A trait that promotes reproduction but does not affect survival, like floral scents A trait that results in death of the individual exhibiting it but increases that individual's 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

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

Absolute fitness

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

When one gene has multiple phenotypic effects

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

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

p+q=1

allele frequencies

Quantitative traits (select all) are affected by many, sometimes thousands of loci follow a normal distribution show complex patterns of inheritance are continuous are not affected by environmental variance are affected by environmental variance follow mendelian inheritance patterns are not subject to evolution

are affected by many, sometimes thousands of loci Follow a normal distribution show complex patterns of inheritance are continuous are affected by environmental variance

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)

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

Fixation of an allele by natural selection depends on: (select all) average age of reproduction survival past reproduction average lifespan of the population dominance effects frequency of the beneficial allele selection coefficient

dominance effects frequency of the beneficial allele selection coefficient

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

environmental variance

p^2

frequency of the dominant allele in the population

Each of the following would be a violation of Hardy-Weinberg equilibrium EXCEPT -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

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

linkage disequilibrium

Which of the following makes a phenotypic distribution more normal? (select all) less dominance less genetic variance more genetic variance less environmental variance more environmental variance more dominance

more genetic variance more environmental variance

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.

The colors of individuals in a snail population are determined by a single autosomal locus. A1A1homozygotes 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. This locus demonstrates overdominance . At equilibrium the population contains only A1A2 heterozygotes. overdominance the population contains only A1A2 heterozygotes. both alleles are maintained in the polymorphic equilibrium

overdominance both alleles are maintained in the polymeric equilibrium

Which of the following maintains genetic variation? (select all) overdominance disruptive selection frequency-dependent selection positive selection stabilizing selection balancing selection

overdominance frequency-dependent selection balancing selection

Hardy weinberg equilibrium

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

Birds evolved from theropod dinosaurs. Pre-avian theropod dinosaurs had feathers, used for insulation (and possibly mating displays). Modern birds also have feathers, of course, that are used in flight. Pre-avian dinosaurs were not capable of flight. Feathers in pre-avian dinosaurs and modern birds are an example of preadaptation/ exaptation adaptation standing genetic variation genetic constraints

preadaptation/ exaptation

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

Which of the following decreases genetic variation? (select all) stabilizing selection directional selection overdominance disruptive selection balancing selection underdominance

stabilizing selection directional selection under dominance

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

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