Evolution of Populations

During a study session about evolution, one of your fellow students remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Which statement is most likely to be helpful in correcting this student's misconception?

*Characteristics acquired during an organism's life are generally not passed on through genes. Only favorable adaptations have survival value. Spontaneous mutations can result in the appearance of new traits. Disuse of an organ may lead to its eventual disappearance.

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele? 9.0 0.9 0.49 0.09

.09

Given a population that contains genetic variation, what is the correct sequence of the following events under the influence of natural selection? 1. Well-adapted individuals leave more offspring than do poorly adapted individuals. 2. A change occurs in the environment. 3. Genetic frequencies within the population change. 4. Poorly adapted individuals have decreased survivorship. 2 → 4 → 3 → 1 4 → 2 → 3 → 1 2 → 4 → 1 → 3 4 → 2 → 1 → 3

2 → 4 → 1 → 3

One out of 10,000 babies born in North America is affected by cystic fibrosis, a recessive condition. Assuming that the North American human population is in Hardy-Weinberg equilibrium for this trait, what percentage of the population is heterozygous for this trait? (Remember the equation for a population in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1.) 1% 0.01% 2%

2%

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be _____. 92% 46% 23% 54%

54%

A farmer wishes to develop a strain of high-yield corn that is also resistant to drought. He has the following individuals from the current year's crop: Individual A—Yield: 179 bushels/acre; drought resistance: high Individual B—Yield: 220 bushels/acre; drought resistance: low Individual C—Yield: 185 bushels/acre; drought resistance: medium Individual D—Yield: 140 bushels/acre; drought resistance: high Individual E—Yield: 200 bushels/acre; drought resistance: medium Which of the following crosses would produce the highest corn yield with the highest resistance to drought?

A and E

Which of the following organisms could be produced by artificial selection?

A chimpanzee that communicates through sign language. *A cow that produces a large quantity of milk. A dog that serves as the "eyes" for a blind individual. A rabbit that is housebroken.

The Grants witnessed strong selection during droughts in 1977 and 1985. Compare the two droughts. Select all that apply. Both droughts resulted in changes to food sources that favored the survival of some medium ground finches over others. Both droughts events provided strong natural selection on medium ground finch populations. In both droughts, small-beaked medium ground finches had the highest survival rates. In both droughts, large-beaked medium ground finches had the highest survival rates. SubmitMy AnswersGive Up

Both droughts resulted in changes to food sources that favored the survival of some medium ground finches over others. Both droughts events provided strong natural selection on medium ground finch populations.

Which of these conditions are always true of populations evolving due to natural selection? Condition 1: The population must vary in traits that are heritable. Condition 2: Some heritable traits must increase reproductive success. Condition 3: Individuals pass on most traits that they acquire during their lifetime. Condition 1 only Condition 2 only Conditions 2 and 3 Conditions 1 and 2

Conditions 1 and 2

Different finch species have beaks of different shapes and sizes. What do these beak differences tell us? Different finch beak shapes are evidence that several finch species with different beak types came to the Galápagos Islands from the mainland. Different finch beak shapes are evidence that all Galápagos finches share a common ancestor. Different finch beak shapes are evidence that finch species adapted to different environments over many generations. Different finch beak shapes are evidence that individual birds changed their beaks so that they could feed efficiently.

Different finch beak shapes are evidence that finch species adapted to different environments over many generations.

Which term describes the ability of a trait to be passed on to offspring?

Evolution Adaptation *Heritability Fitness

Which term describes a trait that increases an individual's ability to survive in a particular environment?

Heritability *Adaptation Evolution Fitness

If Darwin had been aware of genes and their typical mode of transmission to subsequent generations, with which statement would he most likely have been in agreement? If an organism acquires new genes by engulfing, or being infected by, another organism, then a new genetic species will result. If an organism's somatic cell genes change during its lifetime, making it more fit, then it will be able to pass these genes on to its offspring. If natural selection can change gene frequency in a population over generations, given enough time and genetic diversity, then natural selection can cause sufficient genetic change to produce new species from old ones. A single mutation in a single gene in a single gamete, if inherited by future generations, will produce a new species.

If natural selection can change gene frequency in a population over generations, given enough time and genetic diversity, then natural selection can cause sufficient genetic change to produce new species from old ones.

The film defines species as populations whose members don't interbreed. What keeps different Galápagos finch species from mating? Select all that apply. Individuals recognize and only respond to songs of their own species. One population eats mostly small, soft seeds and the other population eats mostly large, hard seeds. Geographic isolation and different environments led to changes in traits that affected mating. Males only court females that have a similar beak and similar size.

Individuals recognize and only respond to songs of their own species. Geographic isolation and different environments led to changes in traits that affected mating. Males only court females that have a similar beak and similar size.

Genetic evidence supports which of the following explanations for the presence of 13 different finch species on the Galápagos islands? The 13 species have existed on the Galápagos islands since the islands first formed. Each of the 13 species migrated to the islands at different times over the years. Many years ago, more than 13 different species of birds migrated to the islands. The current 13 finch species are the only species that survived. Many years ago, a small population of a single finch species migrated to the islands and evolved into the current 13 species.

Many years ago, a small population of a single finch species migrated to the islands and evolved into the current 13 species.

In 1977, medium ground finches on Daphne Major experienced a severe drought. The figure shows the beak depths of the initial population before the drought (red bars) and of the drought survivors (black bars). What do the data show? Select all that apply. The most common beak size of the surviving population was 10.3 millimeters. A very small proportion (~5%) of the initial population with this beak size survived. More than one-half of the initial population died during the drought. The most common beak size of the initial population was 8.8 millimeters. A very small proportion (~5%) of the initial population with this beak size survived. Finches with larger beaks had a survival advantage in the 1977 drought.

More than one-half of the initial population died during the drought. The most common beak size of the initial population was 8.8 millimeters. A very small proportion (~5%) of the initial population with this beak size survived. Finches with larger beaks had a survival advantage in the 1977 drought.

In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident? Mutation led to increased genetic variation. Mutation caused the fixation of new alleles. Mutations caused major changes in rodent physiology over time. Mutation caused genetic drift and decreased fitness.

Mutation led to increased genetic variation.

Which of the following statements about natural selection is true?

Natural selection is a process whereby genes are selected randomly for preservation in the next generation. Natural selection occurs in opposition to evolution. *Natural selection favors individuals that reproduce more than others. Natural selection can be used by farmers to generate organisms with desirable traits.

Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus? Technological innovation in agricultural practices will permit exponential growth of the human population into the foreseeable future. The environment is responsible for natural selection. Populations tend to increase at a faster rate than their food supply normally allows. Earth changed over the years through a series of catastrophic upheavals.

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

Which pair of chickens should a farmer breed to produce larger chickens?

Small hen, large rooster Small hen, small rooster Large hen, small rooster *Large hen, large rooster

The top figure shows beak sizes of the 1976 finch population before the drought of 1977 (red bars) and after the drought (black bars). The lower figure shows the beak sizes of the offspring of the drought survivors in 1978. What do these figures tell us? The overall beak depths of the 1978 offspring population are larger the original 1976 population. In 1978, the offspring population is larger than the initial 1976 population before the drought. The finches that survived the drought (black bars) had offspring with much larger beaks. The offspring had a smaller range of beak depths--from smallest to largest--than their parents (black bars).

The overall beak depths of the 1978 offspring population are larger the original 1976 population.

In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following? The number of individuals The value of a particular characteristic; characteristics of an organism can include such traits as size and color. Time

The value of a particular characteristic; characteristics of an organism can include such traits as size and color.

How did the Grants test their hypothesis that differences in birds' songs can keep different species of finches from breeding with one another? They placed stuffed female finches onto branches to see if males would respond. They observed which birds were mating with each other and listened for the songs the birds were singing. They recorded birds singing on the island of Daphne Major to see which type of song was sung more often by each species. They played the songs of medium ground finches and cactus finches through a loudspeaker to see which species responded to each song.

They played the songs of medium ground finches and cactus finches through a loudspeaker to see which species responded to each song.

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 _____. reduce the number of flies that you transfer at each generation transfer only the largest flies cross your flies with flies from another lab change the temperature at which you rear the flies

cross your flies with flies from another lab

Which of the following is the most predictable outcome of increased gene flow between two populations? lower average fitness in both populations higher average fitness in both populations increased genetic difference between the two populations decreased genetic difference between the two populations

decreased genetic difference between the two populations

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today? Disruptive selection Directional selection Stabilizing selection

directional selection

In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. In the United States, the parasite that causes malaria is not present, but African-Americans whose ancestors were from equatorial Africa are present. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa? In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. directional selection; stabilizing selection disruptive selection; stabilizing selection stabilizing selection; disruptive selection directional selection; disruptive selection

directional selection; stabilizing selection

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers? Directional selection Stabilizing selection Disruptive selection

disruptive selection

Which type of selection tends to increase genetic variation? Directional selection Disruptive selection Stabilizing selection

disruptive selection

True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population. True False

false

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population? heterozygote advantage and stabilizing selection founder effect and genetic drift mutation and natural selection population bottleneck and Hardy-Weinberg equilibrium

founder effect and genetic drift

Which of the following must exist in a population before natural selection can act upon that population? genetic variation among individuals variation among individuals caused by environmental factors the population has predators sexual reproduction

genetic variation among individuals

Prior to the work of Lyell and Darwin, the prevailing belief was that Earth is _____.

millions of years old, and populations are unchanging millions of years old, and populations rapidly change a few thousand years old, and populations gradually change *a few thousand years old, and populations are unchanging

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? stabilizing selection sexual selection directional selection disruptive selection

stabilizing selection

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards? Disruptive selection Stabilizing selection Directional selection

stabilizing selection

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies? Stabilizing selection Disruptive selection Directional selection

stabilizing selection

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus, _____. natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency two alleles are present in equal proportions individuals within the population are evolving the allele's frequency should not change from one generation to the next

the allele's frequency should not change from one generation to the next

Soon after the island of Hawaii rose above the sea surface (somewhat less than one million years ago), the evolution of life on this new island should have been most strongly influenced by _____. a genetic bottleneck the founder effect habitat differentiation sexual selection

the founder effect