Ch 23

In the context of populations, how do we define evolution? ( Overview)

  Evolution is a change in a population's allelic frequencies over generations

Evolution is the tendency for some individuals in a population to leave more offspring than othersEvolution is the way in which sexual reproduction can rapidly spread advantageous traits throughout a populationEvolution is the explanation for how organic molecules formed from inorganic molecules.

Evolution is always caused by natural selection.

Which of the following mechanisms can alter allele frequencies? ( Overview)

  genetic drift

natural selection

gene flow

all of the above

none of the above

Which example below correctly describes average heterozygosity? ( Concept 23.1)

  Average heterozygosity refers to the number of individuals in a population that are heterozygous for a certain trait.Average heterozygosity is measured by comparing the nucleotide sequences of DNA samples, and then averaging the data from the comparison.Average heterozygosity is usually less than the average difference between nucleotide sequences.Average heterozygosity refers to the average percentage of loci that are heterozygous in a population.Average heterozygosity is measured by looking at changes in karyotypes.

The human genome consists of approximately 3 billion base pairs. If humans typically differ from one another by about 3 million base pairs, what is the nucleotide variability of Homo sapiens? (

Concept 23.1)

  10%

1%

50%

3%

0.1%

Which example below would most likely be a cline? ( Concept 23.1)

  Individuals who are heterozygotic for the sickle-cell disease allele have a greater resistance to malaria.Rabbits that live in colder regions tend to have smaller ears than rabbits of the same species that live in warmer regions.Male bowerbirds decorate stations to attract females.

Cows are selectively bred to gain a higher milk yield.

Seals have flippers that make them great swimmers but make their movements on rocks and land very cumbersome.

New alleles originate from _____. ( Concept 23.1)

  natural selection

genetic drift

sexual recombination

the environment

mutation

Sexual recombination includes the shuffling of chromosomes in _____ and fertilization. ( Concept 23.1)

  mitosis

genetic drift

natural selection

mutation

meiosis

Which type of mutation plays the most important role in increasing the number of genes in the gene pool? ( Concept 23.2)

  Mutations are so rare that there are no mutations that can have such an important effect.

duplication

point mutation

rearrangement of gene loci

changes in nucleotide sequence

In a large population of randomly breeding organisms, the frequency of a recessive allele is initially 0.3. There is no migration and no selection. Humans enter this ecosystem and selectively hunt individuals showing the dominant trait. When the gene frequency is reexamined at the end of the year, _____. ( Concept 23.2)

  the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go up, and the frequency of the homozygous recessives will remain the samethe frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will remain the same, and the frequency of the homozygous recessives will go upthe frequency of the homozygous dominants will go up, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go downthe frequency of the homozygous dominants will go up, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go upthe frequency of the individuals who express the dominant phenotype will go down and the frequency of homozygous recessive individuals will go up

In the Hardy-Weinberg equation, p2 represents _____. ( Concept 23.2)

  the total alleles in the gene pool

the frequency of heterozygous dominant individuals in the population

the frequency of homozygous recessive individuals in the population

all of the possible phenotypes in the gene pool

the expected frequency of homozygous dominant individuals in the population

In a large population of bonobos, the frequency of the recessive allele is initially 0.1. There is no migration and no selection. What is the frequency of the dominant allele? Assume that there are two alleles of this gene. ( Concept 23.2)

  10%

20%

50%

90%

99%

In a population in Hardy-Weinberg equilibrium, 1% of the individuals in a population show the

recessive trait of a certain characteristic. In this situation, what is the value of p? ( Concept 23.2)

  99%

0.81

0.9

0.18

The answer cannot be determined from the information given.

In the equation for Hardy-Weinberg equilibrium, 1 represents _____. ( Concept 23.2)

  the sum of the frequencies of the genotypes for a particular gene locus

the frequency of heterozygous individuals in the populations

the frequency of homozygous recessive individuals in the population

all the possible phenotypes in the population

the frequency of homozygous dominant individuals in the population

Approximately 1 out of every 2,500 Caucasians in the United States is born with the recessive disease cystic fibrosis. According to the Hardy-Weinberg equilibrium equation, approximately how many people are carriers? ( Concept 23.2)

  about 1 in 50

about 96 in 100

about 1 in 25

about 1 in 10

none of the above

In a certain group of African people, 4% are born with sickle-cell disease (homozygous recessive). If this group is in Hardy-Weinberg equilibrium, what percentage of the group has the selective advantage of being more resistant to malaria (heterozygous) than those individuals who are homozygous for normal hemoglobin or for sickle-cell disease? ( Concept 23.2)

  2%

4%

8%

16%

32%

Assume a population in Hardy-Weinberg equilibrium for a character trait with these genotypic frequencies: AA = 0.25, Aa = 0.50, and aa = 0.25. If you remove all the homozygous dominants and allow the remaining population to reproduce (again under Hardy-Weinberg conditions), what will be the frequency of homozygous dominants in the next generation? ( Concept 23.2)

  0

0.11

0.22

0.44

0.50

Which of the following sets of conditions is required for Hardy-Weinberg equilibrium? ( Concept 23.2)

  a large population, no mutations, and natural selection

a large population, random mutations, and no migration of alleles in or out of the population

no mutations, sexual selection, and no natural selection

random mating, no natural selection, and a large population

random mating, a small population, and no mutations

_____ and _____ generate variation, while _____ results in an adaptation to the environment. ( Concept 23.2)

  Genetic drift; natural selection; mutation

Mutation; sexual recombination; natural selection

Overproduction of offspring; mutation; sexual recombination

Natural selection; mutation; sexual recombination

Sexual recombination; natural selection; overproduction

A population of 15 birds inhabits a fairly new island. Ten of the birds are dark brown and five of them are light brown. By chance, two of the dark brown birds and three of the light brown birds die before producing any offspring. All of the birds in the next generation are dark brown. This change in phenotypic frequency can be attributed to _____. ( Concept 23.3)

  natural selection

genetic drift

gene flow

disruptive selection

a cline

An earthquake hits a small island. All but a small group of closely related lizards are eliminated, and the survivors spread out over the island. This is an instance of _____. ( Concept 23.3)

  founder effect

bottleneck effect

gene flow

mutation

nonrandom mating

Which of the following scenarios would most likely result in the microevolution of a population of humans? ( Concept 23.3)

  Only random mating takes place among all the people that reproduce in North America.

A colony of humans on the moon is isolated from Earth.

The incidence of skin cancer in adults over age 40 rises significantly.

Hundreds of thousands of people are killed in a natural disaster.

Both random mating and an increase in middle-aged skin cancer occur.

Which of the following is the best example of gene flow? ( Concept 23.3)

  A small population of humans colonizes a newly formed island.

Genes are shuffled by the crossing over of chromosomes during meiosis.

An earthquake results in the formation of a canyon, splitting a population of toads apart.

Wind blows pollen from one population of plants to another and cross-fertilization occurs.

All the mutations in a population were neutral.

Which of the following most accurately measures an organism's fitness? ( Concept 23.4)

  how strong the organism is when pitted against others of its species

its mutation rate

how many fertile offspring it produces

its ability to withstand environmental extremes

how much food it is able to make or obtain

Antibiotic resistance in bacteria is an example of which of the following? ( Concept 23.4)

  stabilizing selection

directional selection

disruptive selection

Hardy-Weinberg equilibrium

macroevolution

For several years, scientists have warned doctors of the danger of overprescribing antibiotics such as penicillin. Scientists are concerned because _____. ( Concept 23.4)

  humans will become tolerant to the effects of drugs

the organisms that produce many of the antibiotics are overexploited and could become extinctstrains of microorganisms that are resistant to these drugs will be selected for

the drugs will be metabolized more quickly by our bodies, decreasing their effectiveness

none of the above

A population of squirrels is preyed upon by small hawks. The smaller squirrels can escape into burrows. The larger squirrels can fight off the hawks. After several generations, the squirrels in the area tend to be very small or very large. What process is responsible for this outcome? ( Concept 23.4)

  stabilizing selection

directional selection

disruptive selection

balancing selection

Hardy-Weinberg equilibrium

Stabilizing selection _____. ( Concept 23.4)

  favors intermediate variants in a population

prevents mutations from occurring

occurs when some individuals migrate to an area with different environmental conditions

can take place only in species exhibiting sexual dimorphism

occurs only in plants

Birds with average-size wings survived a severe storm more successfully than other birds in the same population with longer or shorter wings. If severe storms occur regularly, then over time, one should expect these storms to bring about _____. ( Concept 23.4)

  the bottleneck effect

stabilizing selection

artificial selection

gene flow

disruptive selection

Tay-Sachs disease, which is lethal, results from having the homozygous recessive condition of the responsible gene. Which one of the following statements is true? ( Concept 23.4)

  Because homozygous recessive individuals die, the recessive allele will eventually be lost from the population.Only homozygous dominant individuals will be able to survive and reproduce.

Heterozygous individuals will survive and may pass the recessive allele on to their offspring.

In the heterozygous condition, the dominant allele will overcome the recessive allele and only the dominant allele will be passed on to offspring.Homozygous dominant individuals will be more likely to reproduce than heterozygous individuals.

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population? ( Concept 23.4)

  balancing selection

neutral variation

heterozygote advantage

stabilizing selection

relative fitness

Which of the following would seem to be an example of neutral variation? ( Concept 23.4)

  homozygosity of the cheetah population

polymorphism of the Gálapagos finches

founder effect

human fingerprints

moth coloration

What is the importance of neutral variation in evolution? ( Concept 23.4)

  DNA forensics relies on neutral variation among humans.

Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change.Relative frequencies of neutral variations are controlled by natural selection.

Neutral variation is usually removed from the population by natural selection because it does not confer an advantage in the current environment.Many mutations are silent and do not affect the amino acid that is coded for.

Selection that acts over evolutionary time to preserve traits that increase an individual's ability to mate is known as _____. ( Concept 23.4)

  directional selection

disruptive selection

stabilizing selection

sexual selection

balancing selection

Which statement below is true about sexual selection? ( Concept 23.4)

  Intrasexual selection leads to the death of most unfit males in combat.

Showy secondary sexual characteristics cannot be explained because they break all of the rules of natural selection.In most vertebrates, females court the males.

There is no evidence that intrasexual selection takes place between females.

Sexual selection can result in sexual dimorphism-marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction.

How does natural selection fashion organisms? ( Concept 23.4)

  The best traits for the current environment arise in the population and are selected for.

Brand new body plans arise often, giving natural selection many new possibilities to work with.Chance and the environment interact with natural selection, so that the best available traits are selected for.Sexual selection acts to make organisms better adapted to their environments.

Neutral traits are often selected for because they will eventually produce alleles that confer an advantage.

A number of mosquito populations today are resistant to insecticides that were once quite effective. Biologists think that insecticide resistance evolved in mosquitoes because _____. ( Concept 23.4)

  individual mosquitoes built up an immunity to an insecticide after being exposed to it

mosquitoes needed to develop insecticide resistance to survive after the insecticide was used

a few mosquitoes were probably resistant to the insecticide before it was ever used, and these individuals were more likely to survive and reproducemosquitoes attempted to adapt to their environment

a new allele developed in response to the insecticide that provided future generations the benefit of resistance