Practice Exam

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1) In a Hardy-Weinberg population with two alleles that show complete dominance, the frequency of the recessive allele is 0.4. What percentage of the population has a homozygous genotype?
A) 36 B) 4 C) 40 D) 16 E) 52

E) 52
p2 +q2=.52

2) Which of the various species concepts distinguishes two species based on whether genes are exchanged between their gene pools?
A) phylogenetic B) morphological C) biological D) ecological

C) biological

Several closely related firefly species in the same genus are found in a wooded area in the Apalachian mountains. The species remain distinct by reproductive barriers. In each case, match the various descriptions of fireflies below with the appropriate reproductive barrier listed.
3) One species lives close to the ground; another species lives in treetops.
A) temporal
B) gametic
C) mechanical
D) habitat
E) behavioral

D) habitat

Several closely related firefly species in the same genus are found in a wooded area in the Apalachian mountains. The species remain distinct by reproductive barriers. In each case, match the various descriptions of fireflies below with the appropriate reproductive barrier listed.
4) Males of several different species choose mates based on different flash frequencies.
A) behavioral
B) habitat
C) gametic
D) mechanical
E) Temporal

A) behavioral

Several closely related firefly species in the same genus are found in a wooded area in the Apalachian mountains. The species remain distinct by reproductive barriers. In each case, match the various descriptions of fireflies below with the appropriate reproductive barrier listed.
5) One species flashes at dusk, and another only flashes once darkness has completely fallen.
A) habitat
B) gametic
C) mechanical
D) temporal
E) temporal

D) temporal

6) 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) A and B

7) 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) Gene flow between the two populations is extensive.

8) A field mouse population has a gene with two alleles, F and f. Seventy percent of the gametes produced in the population contain the F allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the mice carry both F and f?
A) 0.42
B) 0.7
C) 0.49
D) 0.21
E) 0.09

A) 0.42

9) 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) genetic drift.

10) 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) the sources of genetic variations among individuals

11) 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 best help you determine whether the similarity reflected homology as opposed to convergent evolution?
A) Both species reproduce sexually.
B) The two species live at great distance from each other.
C) The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical.
D) Both species are well adapted to their particular environments.
E) The sizes of the structures in adult members of both species are similar in size.

C) The two species share many proteins in common, and the nucleotide

13) 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) All new alleles are the result of nucleotide differences.

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.

D) All three of these.

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).
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) All three of these

16) Which of these naturalists synthesized a concept of natural selection independently of Darwin?
A) Charles Lyell
B) John Henslow
C) Alfred Wallace
D) Thomas Malthus
E) Gregor Mendel

C) Alfred Wallace

17) Plants with smooth leaves and plants with extremely hirsute (hairy) leaves are observed in roughly equal numbers within a population of begonias in a Costa Rican rainforest, with other leaf phenotypes being rare. Which of the following terms best explains this?
A) sexual selection
B) artificial selection
C) disruptive selection
D) directional selection
E) stabilizing selection

C) disruptive selection

18) You sample a population of great blue herons in Hardy-Weinberg equilibrium and find that 64% exhibit the dominant phenotype for feather color, a trait that is determined by a single gene. What is the frequency of the dominant allele in this population?
A) 0.64
B) 0.36
C) 0.8
D) 0.4
E) Allele frequency cannot be determined from this information.

D) 0.4

19) 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) Both (A)and (C)

20) Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating _____.
A) the bottleneck effect.
B) stabilizing selection.
C) disruptive selection.
D) frequency-dependent selection.
E) neutral variation.

B) stabilizing selection.

21) You have before you an assortment of fossil crabs that colleagues from around the world sent you and now you must assign these to separate species. Which species concept will you use?
A) ecological
B) biological
C) sympatric
D) morphological

D) morphological

22) A city's parks were intensively treated with "Weed-B-Gone" in the 1950's in an effort to eradicate dandelions. The number of dandelions in the parks was immediately greatly reduced. Each year thereafter, the city's parks were again treated with Weed-B-Gone, but the dandelions gradually increased in number until 15 years later they were almost as abundant as they were when the weed-control program was begun. Which statement below best explains these observations?
A) Dandelions from the surrounding countryside moved in and replaced those killed by Weed-B-Gone.
B) The few dandelion plants that survived the initial treatment developed antibodies in response to the
chemical and passed this ability on to their offspring.
C) Weed-B-Gone caused new mutations in to occur in the surviving dandelions and this allowed them
and thier offspring to survive.
D) Weed-B-Gone killed susceptible dandelions but a few resistant survivors reproduced and their
offspring gradually repopulated the parks.
E) All of the above

D) Weed-B-Gone killed susceptible dandelions but a few resistant survivors reproduced and their
offspring gradually repopulated the parks.

23) Which of these is the smallest unit that natural selection can change?
A) a population's gene frequency
B) a species' gene frequency
C) an individual's genome
D) an individual's phenotype
E) an individual's genotype

A) a population's gene frequency

24) Which of the following observations helped Darwin shape his concept of descent with modification?
A) Species diversity declines farther from the equator.
B) Earthquakes reshape life by causing mass extinctions.
C) South American temperate plants are more similar to the tropical plants of South America than to the
temperate plants of Europe.
D) Fewer species live on islands than on the nearest continents.
E) Birds can be found on islands located farther from the mainland than the birds' maximum nonstop flight distance.

C) South American temperate plants are more similar to the tropical plants of South America than to the
temperate plants of Europe.

25) Which group is composed entirely of individuals who maintained that species are fixed (i.e., unchanging)?
A) Linnaeus, Cuvier, and Lamarck
B) Lyell, Linnaeus, and Lamarck
C) Aristotle, Linnaeus, and Cuvier
D) Hutton, Lyell, and Darwin
E) Aristotle, Cuvier, and Lamarck

C) Aristotle, Linnaeus, and Cuvier

26) 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) A, B, and C

27) Mules are relatively long-lived and hardy organisms that cannot, generally speaking, successful produce gametes by meiosis. Consequently, which statement about mules is true?
A) Mutations cannot occur in their genomes.
B) When two mules interbreed, genetic recombination cannot occur by meiotic crossing over, but only by
the act of fertilization.
C) Their offspring have less genetic variation than the parents.
D) If crossing-over happens in mules, then it must be limited to prophase of mitosis.
E) They have a relative evolutionary fitness of zero.

E) They have a relative evolutionary fitness of zero.

28) Which of the following pairs of structures is least likely to represent homology?
A) The hemoglobin of a baboon and that of a gorilla
B) The wings of a bird and those of an insect
C) The wings of a bat and the arms of a human
D) The brain of a cat and that of a dog
E) All of the above represent homology.

B) The wings of a bird and those of an insect

You are studying three populations of birds. Population A has ten birds, of which one is brown (a recessive trait) and nine are red. Population B has 100 birds, of which ten are brown. Population C has 30 birds, and three of them are brown.
29) In which population is the frequency of the allele for brown feathers highest? A) Population A.
B) Population B.
C) Population C.
D) They are all the same.
E) It is impossible to tell from the information given.

D) They are all the same.

31) In three-lined skinks, a gene controls stripe width such that B = broad stripes and b = narrow stripes. In an isolated patch of woods, there are 36 skinks with braod stripes and 64 skinks with narrow stripes. Assuming Hardy-Weinberg equilibrium, what is the value of the recessive allele for this population?
A) 0.36 B) 0.60 C) 0.75 D) 0.80 E) 0.64

D) 0.80

32) In North America, there is a progresive decrease in ear length among populations of cottontail rabbits from the south to the north of their range. This is an example of _____.
A) a cline.
B) a bottleneck.
C) genetic drift.
D) geographic variation.
E) relative fitness.

A) a cline.

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.

A) frequency-dependent selection

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.
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.

B) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time.

35) Two pirates and three Polynesian beauties are shipwrecked on a previously uninhabited island. All five had brown eyes, but only one person carried the recessive allele for blue eyes (let's assume eye color is a case of one gene and complete dominance). What are the frequencies of the dominant (B) and recessive (b) allele in this island popualtion?
A) B = 0.8; b = 0.2
B) B = 0.9; b = 0.1
C) B = 0.1; b = 0.9
D) B = 0.2; b= 0.8
E) It cannot be determined from the information given.

B) B = 0.9; b = 0.1

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

D) intersexual selection.

37) Natural selection is based on all of the following except _____.
A) individuals who survive longer tend to leave more offspring than those who die young.
B) populations tend to produce more individuals than the environment can support.
C) the best-adapted individuals tend to leave the most offspring.
D) genetic variation exists within populations.
E) individuals adapt to their environments and, thereby, evolve.

E) individuals adapt to their environments and, thereby, evolve.

38) 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) cross your flies with flies from another lab.

39) If, on average, 46% of the loci in a spopulation's gene pool are heterozygous, then the average homozygosity of the population should be _____.
A) 54% B) 46% C) 92% D) 23%
E) There is not enough information to say.

A) 54%

40) In a human population that is in Hardy-Weinberg equilibrium, the frequency of the IA allele is 0.4
and the frequency of the IB allele is 0.5. All possible ABO blood genotypes are present in the population. What is the frequency of individuals with Type A blood?
A) 0.08 B) 0.16 C) 0.20 D) 0.24 E) 0.50

D) 0.24

41) 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) sympatric speciation, habitat differentiat

42) A defining characteristic of allopatric speciation is _____.
A) asexually reproducing populations.
B) large populations.
C) geographic isolation.
D) artificial selection.
E) the appearance of new species in the midst of old ones.

C) geographic isolation.

43) Darwin's mechanism of natural selection required long time spans in order to modify species. From whom did Darwin get the concept of Earth's ancient age?
A) Thomas Malthus
B) John Henslow
C) Georges Cuvier
D) Charles Lyell
E) Alfred Wallace

D) Charles Lyell

44) Gene flow is a concept best used to describe an exchange between _____.
A) males and females.
B) species.
C) populations.
D) individuals.
E) generations.

C) populations.

45) Which of Darwin's ideas had the strongest connection to Darwin having read Malthus's essay on human population growth?
A) Descent with modification
B) The ability of related species to be conceptualized in "tree thinking"
C) Variation among individuals in a population
D) That the ancestors of the Galapagos finches had come from the South American mainland
E) Struggle for existence

E) Struggle for existence

46) 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) natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

47) Two species of guinea hens belonging to the same genus occasionally mate, but the offspring fail to develop and hatch. What is the mechanism for keeping the two species separate?
A) the postzygotic barrier called hybrid breakdown
B) adaptation
C) gametic isolation
D) the postzygotic barrier called hybrid inviability
E) the prezygotic barrier called hybrid sterility

D) the postzygotic barrier called hybrid inviability

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