Practice Exams

Fossil evidence indicates that horses have gradually increased in size over geologic time

-directional selection

Pathogenic bacteria found in many hospitals are antibiotic resistant

-directional selection

A certain species of land snail exists as either a cream color or a solid brown color. Intermediate individuals are relatively rare

-disruptive selection

Brightly colored peacocks mate more frequently than do drab peacocks

-sexual selection

The average birth weight for human babies is about 3 kg

-stabilizing selection

The allele for red flower color (R) in garden peas shows complete dominance over the allele for white flower color(r) at the same locus. In a population of peas you count 32 white flowered individuals and 168 red flowered plants. -What fraction of the red flowered plants is heterozygous?

0.57

In peas, a gene shows incomplete dominance for flower color such that RR = purple, Rr = pink, and r = white. In an isolated pea patch, a killing frost takes the population out of H/W equilibrium and leaves only 36 plants with white flowers, 7 with pink flowers, and 14 with purple flowers. What is the frequency of the recessive allele in the surviving population population?

0.69

Each of the phenomena listed below might (or might not) result in a violation of the assumptions required to maintain Hardy-Weinberg equilibrium. For each one, provide the letter for the Hardy-Weinberg assumption that it violates. Phenomenon 1.___ Gene Flow 2.___Population bottleneck 3.___Heterozygote advantage 4.___Inbreeding Hardy-Weinberg Assumptions A. the population is large B. there is no mutation C. there is no migration D. mating is at random E. all genotypes survive and reproduce equally well (no natural selection)

1.C 2.A 3.E 4.D

In a Hardy-Weinberg population with two alleles, T and t, that are in equilibrium, the frequency of the allele "t" is 0.7. What is the percentage of the population that is homozygous for this allele?

49

Which statement best describes how the evolution of pesticide resistance occurs in a population of insects?

A number of genetically resistant pesticide survivors reproduce. The next generation of insects contains more genes from the survivors than it does from susceptible individuals.

A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 36% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. 18) What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time? A) The two phenotypes are about equally adaptive under laboratory conditions. B) The genotype AA is lethal. C) There has been sexual selection favoring allele a. D) The population is undergoing genetic drift. E) There has been a high rate of mutation of allele A to allele a.

A) The two phenotypes are about equally adaptive under laboratory conditions

Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. Which information would shed the most light on whether these structures are homologous or whether they are, instead, the result of convergent evolution? A) The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical. B) Both species are well adapted to their particular environments. C) The sizes of the structures in adult members of both species are similar in size. D) Both species reproduce sexually. E) The two species live at great distance from each other.

A) The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical.

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of _______.

A) frequency-dependent selection.

Who was the naturalist who developed an hypothesis of evolution by natural selection independently of Darwin?

Alfred Wallace

Which of the following is most likely to have been produced by sexual selection? A) bright colors of female flowers B) camouflage coloration in animals C) a male lion's mane D) different sizes of male and female pinecones E) the ability of desert animals to concentrate their urine

C) a male lion's mane

Cattle breeders have improved the quality of meat over the years by which process? A) directional selection B) artificial selection C) stabilizing selection D) A and B E) A and C

D) A and B

Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, these bones having developed from the same embryonic tissues. How do biologists interpret these similarities? A) by proposing that humans, bats, and dolphins share a common ancestor B) by the principle of convergent evolution C) by identifying the bones as being homologous D) A and C only E) A, B, and C

D) A and C only

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. What would need to be true for pest eradication efforts to have been successful in the long run? A) DDT application should have been continual. B) All habitats should have received applications of DDT at about the same time. C) Larger doses of DDT should have been applied. D) All individual insects should have possessed genomes that made them susceptible to DDT. E) The frequency of DDT application should have been higher.

D) All individual insects should have possessed genomes that made them susceptible to DDT.

Which of the following statements best summarizes evolution as it is viewed today? A) It represents the result of selection for acquired characteristics. B) It is synonymous with the process of gene flow. C) It is the descent of humans from the present-day great apes. D) It is the differential survival and reproduction of the most fit phenotypes. E) It is goal-directed.

D) It is the differential survival and reproduction of the most fit phenotypes

All of the following are criteria for maintaining Hardy-Weinberg equilibrium involving two alleles except ____. A) there should be no natural selection. B) matings must be random. C) gene flow from other populations must be zero. D) populations must be large. E) the frequency of all genotypes must be equal.

E) the frequency of all genotypes must be equal.

Which of the following would be most likely to cause genetic drift? A. a spontaneous change in chromosome number in a population B. movement of individuals from one population to another C. the production of more offspring by brighter colored individuals D. a tendency of individuals to prefer to mate with their relatives E. the initiation of a new population by a small number of individuals

E. the initiation of a new population by a small number of individuals

The inheritance of acquired characteristics was a major component of the evolutionary hypothesis proposed by whom?

Lamarck

During drought years on the Galapagos, small, easily eaten seeds become rare leaving only large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, then what should one expect to result from natural selection?

More small-beaked birds dying than the larger-beaked birds. The offspring produced in subsequent generations have a higher percentage of birds with large beaks.

Which of the following represents an idea Darwin took from the writings of Thomas Malthus?

Populations tend to increase at a faster rate than their food supply.

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. That the actual forelimbs of these mammals do not seem to be optimally arranged is because _____. A) natural selection is generally limited to modifying structures that were present in previous generations and in previous species. B) though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design. C) natural selection operates in ways that are beyond the capability of the human mind to comprehend. D) in many cases, phenotype is not merely determined by genotype, but by the environment as well. E) natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time.

a

Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven it? A) sympatric speciation, habitat differentiation B) sympatric speciation, allopolyploidy C) sympatric speciation, sexual selection D) allopatric speciation, ecological isolation E) allopatric speciation, behavioral isolation

a

The existence of two or more distinct phenotypic forms in a species is known as ____. A. a population bottleneck B. stabilizing selection C. heterozygote advantage D. polymorphism E. directional selection

a

The allele frequency at a flower color locus in a population of alpine plants changes when a landslide kills most of the individuals in the population. This is an example of _______.

a bottleneck effect

Batesian mimicry is when _______.

a palatable species mimics an inedible species

The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA in attacking bacteriophages. 33) The outcome of the conflict between bacteria and bacteriophage at any point in time results from _____. A) frequency-dependent selection. B) heterozygote advantage. C) stabilizing selection. D) genetic variation being preserved by diploidy. E) neutral variation. 34) Over the course of evolutionary time, what should occur? A) Methylated DNA should become fixed in the gene pools of bacterial species. B) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time. C) Nonmethylated DNA should become fixed in the gene pools of bacteriophages. D) Methylated DNA should become fixed in the gene pools of bacteriophages. E) Both A and B are correct.

a,b

A recent trend seen in many plant species that are most susceptible to global warming is an increase in the number of tiny white hairs on leaves to increase leaf reflectivity and help cool leaves. This trend is an example of _____. A. a cline B. directional selection C. disruptive selection D. inheritance of acquired characteristics E. Bergman's rule

b

Body size in a species of gray mice shows clinal variation from north to south with northern mice having a larger phenotype than southern mice. If the clinal variation is due to genetic rather than environmental causes, then if I move a pregnant female from Boston to Tallahassee and allow her to give birth and raise her offspring here, how would I expect her offspring to compare to native mice born and bred here in Tallahassee? A. The Boston offspring will have a similar body size to Tallahassee mice. B. The Boston offspring will have a larger body size to Tallahassee mice. C. The Boston offspring will have a smaller body size to Tallahassee mice. D. The transplant study cannot work because the northern and southern populations cannot interbreed. E. The Boston mice will thoroughly embarrass the Yankees and go on to clobber to Colorado Rockies.

b

By itself (i.e., not necessarily Hardy-Weinberg equilibrium) the equation p + q = 1 tells us ____. A. the frequencies of alleles in a population are not changed by random mating B. the sum of the frequencies of two alternate alleles at a gene locus must total 1.0 C. genotype frequencies can be calculated if allele frequencies are known D. there are only two possible genotypes in a population E. a population that does not conform to this equation is evolving

b

In Batesian mimicry, the fitness of the ______. A. palatable mimic is highest when the model species exists in low frequency B. palatable mimic is highest when the mimic exists in low frequency C. distasteful mimic is highest when the model species exists in low frequency D. distasteful mimic is highest when the mimic exists in low frequency E. none of the above

b

About which of these did Darwin have a poor understanding? A) that much of the variation between individuals in a population is inherited B) the factors that cause individuals in populations to struggle for survival C) the sources of genetic variations among individuals D) that individuals in a population exhibit a good deal of variation E) how a beneficial trait becomes more common in a population over the course of generations

c

Frogs are able to migrate freely among four ponds that are found close together in a section of the Apalachicola National Forest south of Tallahassee. Over time you would expect to see: A. frogs in some ponds better adapted overall than frogs in other ponds B. the pond-populations evolving into two or more separate species of frogs C. similar allele frequencies among pond-populations D. at least one pond-population going extinct E. none of the above

c

There are 25 individuals in population 1, all of which have genotype RR, and there are 15 individuals in population 2, all of genotype rr. Assume that these populations are located far from one another and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is mostly likely an example of _____. (read & think carefully!) A) directional selection. B) gene flow. C) genetic drift. D) discrete variation. E) disruptive selection.

c

Which of the following factors would not contribute to allopatric speciation? A) The isolated population is exposed to different selection pressures than the ancestral population. B) A population becomes geographically isolated from the parent population. C) Gene flow between the two populations is extensive. D) The separated population is small, and genetic drift occurs. E) Different mutations begin to distinguish the gene pools of the separated populations.

c

Which statement about variation among individuals of a species is true? A) All genetic variation produces phenotypic variation. B) All nucleotide variability results in neutral variation. C) All new alleles are the result of nucleotide differences. D) All geographic variation results from the existence of clines. E) All phenotypic variation is the result of genotypic variation.

c

Which of the following would be an example of macroevolution? A) evolution of polymorphism in Papilio dardanus, with each morph mimicking a different protected butterfly B) evolution of antibiotic resistance in a strain of E. coli C) evolution of modern humans, Homo sapiens, from australopithecine ancestors D) replacement of a melanin-poor morph by a melanin-rich morph over many generations under conditions of increased UV exposure E) evolution of insecticide resistance in populations of insect pests treated through the years with DDT

c) evolution of modern humans, Homo sapiens, from australopithecine ancestors

In Australia, sugar gliders are small marsupial mammals that glide from tree to tree. In North America, flying squirrels are placental mammals that also glide from tree to tree. The similarities in morphology and lifestyle exhibited by these two types of animals are most likely the result of ________.

convergent evolution

All of the following would tend to maintain balanced polymorphism in a population except _____. A. disruptive selection B. frequency-dependent selection C. heterozygote advantage D. directional selection E. none of the above

d

Several mice from Alabama with dark fur color float down the Apalachicola River on a tree branch and join a large population of mice in Florida in which nearly all the mice are light- colored. What mechanism of evolution does this scenario illustrate? A. a founder event B. a population bottleneck C. epistasis D. gene flow E. directional selection

d

Sexual dimorphism is most often a result of _____. A) artificial selection. B) pansexual selection. C) intrasexual selection. D) intersexual selection. E) stabilizing selection.

d

Sexual selection will ____. A. increase the size of individuals B. result in individuals better adapted to a particular environment C. result in a relative fitness (w) more than 1 D. select for traits that enhance an individual's chance of mating E. all of the above

d

The higher the proportion of loci that are "fixed" in a population, the lower is that population's _____. A) nucleotide variability. B) average heterozygosity. C) diploidy. D) A and B E) A, B, and C

d

Which of the following scenarios would most likely cause a population to evolve via genetic drift? A. a spontaneous change in the chromosome number in a population B. movement of individuals back and forth between neighboring populations C. negative assortative mating D. the initiation of a new population by a small number of individuals E. when the rarest phenotype in a population has the highest fitness

d

A population of giant hissing cockroaches from Madagascar are pretty evenly divided among two strikingly different color patterns: very dark brown and very light golden. _____

disruptive selection

In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birds' diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the male's feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal). 14) During breeding season, female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation? A) Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations. B) Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations. C) There should be directional selection for bright red feathers in males. D) All three of these. E) Only B and C. 15) Which of the following terms are appropriately applied to the situation described in the previous question? A) Mate choice B) Sexual selection C) Intersexual selection D) All three of these E) Only B and C

d,d

14. Farm-raised turkeys have been bred to now have disproportionately much more breast meat than wild turkeys. _____ 15. The pesticide malathion was once widely used but is now ineffective for mosquito control, as it fails to kill off these insects like it once used to. _____

directional selection

If the frequency of a particular allele that is present in a small, isolated population of fiddler crabs decreases due to an oil spill that leaves even fewer crabs bearing this allele, then what has occurred? A) genetic drift B) a bottleneck C) microevolution D) A and B only E) A, B, and C

e

In a hypothetical population's gene pool, an autosomal gene, which had previously been fixed, undergoes a mutation that introduces a new allele, one inherited according to incomplete dominance. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations? (read and think carefully!) A) The proportions of both types of homozygote should decrease. B) The proportion of the population that is heterozygous at this locus should remain constant. C) The population's average heterozygosity should increase. D) Both (A)and (B) E) Both (A)and (C)

e

The forelimbs of modern vertebrates such as a human, a bird, and a bat provide a nice example of _____. A. the inheritance of acquired characteristics B. the idea that ontogeny recapitulates phylogeny C. convergent evolution D. vestigial organs E. descent with modification from a common ancestor

e

Which of the following serve to introduce and/or maintain genetic variation in populations despite the trend for natural selection to increase the frequency only of the fittest individuals? A. epistasis B. mutation C. crossing over during meiosis D. A and B only E. A, B and C

e

You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to _____. A) transfer only the largest flies. B) shock the flies with a brief treatment of heat or cold to make them more hardy. C) reduce the number of flies that you transfer at each generation. D) change the temperature at which you rear the flies. E) cross your flies with flies from another lab.

e

Laboratory studies have shown that male fruit flies that exhibit uncommon courtship behaviors father more offspring because females prefer to mate with them. When these same behaviors are common in a population, males exhibiting them are no longer preferred. This scenario describes _____.

frequency-dependent selection

Through time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing _______.

gene flow

The correct sequence from the most to the least comprehensive of the taxonomic levels listed here is

kingdom, phylum, class, order, family, genus, and species.

If a phenotypic polymorphism lacks a genetic component, then

natural selection cannot act upon it to make a population better adapted over the course of generations.

Male guppies with the flashiest longest fins mate more frequently than males with less showy fins. _____

sexual selection

The classic study of industrial melanism in the peppered moth

showed that natural selection could change gene frequencies

In a large, sexually reproducing population, the frequency of an allele changes from 0.6 to 0.2. From this change, one can most logically assume that, in this environment, ________.

the allele reduces fitness.

The Darwinian fitness of an individual is measured by ________.

the number of its offspring that survive to reproduce.