General Biology

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

Allele frequencies can be altered by __________.

In the Hardy-Weinberg equation, p² represents __________.

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.

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?

In the equation for Hardy-Weinberg equilibrium, 1 represents __________.

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 what percentage of people are carriers?

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?

Assume a population in Hardy-Weinberg equilibrium 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?

Which of the following sets of conditions is required for Hardy-Weinberg equilibrium?

How does natural selection fashion organisms?

Consider a gene that exists in two allelic forms in a simple Mendelian dominant/recessive pair. 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, __________.

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2? a. 0.7 b. 0.49 c. 0.42 d. 0.21

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from a. genetic drift. b. gene flow. c.nonrandom mating. d. directional selection.

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus? a. gene variability=0%; number of alleles=0 b. gene variability=0%; number of alleles=1 c. gene variability=0%; number of alleles=2 d. gene variability>0%; number of alleles=2

In a population of 2500, how many babies would you expect to have cystic fibrosis, a homozygous recessive condition, if the frequency of the dominant allele is 0.9 and the population is at Hardy–Weinberg equilibrium? a. 0.9×2500=2250 b. 2×0.9×0.1×2500=450 c. 0.9×0.1×2500=225 d. 0.1x0.1x2500=25

In what sense is the Hardy–Weinberg principle a null hypothesis?

Determine what is incorrect in the following statement: Red deer mutated their genes so that they could have larger antlers to compete for mates.

In humans, albinism is caused by loss-of-function mutations in genes involved in the synthesis of melanin, the dark pigment in skin. Only people homozygous for a loss-of-function allele (genotype aa) have the albino phenotype. In Americans of northern European ancestry, albino individuals are present at a frequency of about 1 in 10,000 (or 0.0001). Assuming that genotypes are in Hardy–Weinberg equilibrium, what is the predicted frequency of Caucasians in the United States who carry a single allele for albinism?

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?

Stabilizing selection __________.

Which of the following mechanisms can form entirely new alleles?

Sexual recombination includes the shuffling of chromosomes in __________ and fertilization.

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

Which of the following would seem to be an example of neutral variation?

What is the importance of neutral variation in evolution?

__________ and __________ generate variation, whereas __________ results in an adaptation to the environment.

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 __________.

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 __________.

Which of the following scenarios would most likely result in the microevolution of a population of humans?

Which of the following is the best example of gene flow?

Which of the following most accurately measures an organism's fitness?

The lethal genetic disorder Tay-Sachs disease occurs in individuals with two copies of a recessive allele of the responsible gene. Which of the following statements is true?

Antibiotic resistance in bacteria is an example of which of the following?

For several years, scientists have warned doctors of the danger of overprescribing antibiotics such as penicillin. Scientists are concerned because __________.

A population of squirrels is preyed on 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?

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 __________.

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

Selection that acts over evolutionary time to preserve traits that increase an individual's ability to mate is known as __________.

Which statement below is true about sexual selection?

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

The heritable differences among organisms are a result of                   . a. differences in their DNA; b. mutation; c. differences in alleles; d. A and B are correct; e. A, B, and C are correct

The risks faced by small populations include                   . a. erosion of genetic variability through genetic drift; b. decreased fitness of individuals as a result of inbreeding; c. increased risk of experiencing natural disasters; d. A and B are correct; e. A, B, and C are correct

Describe three ways that evolution can occur via genetic drift.

Antibiotic resistance is becoming common among organisms that cause a variety of human diseases. All of the following strategies help reduce the risk of antibiotic resistance evolving in a susceptible bacterial population except                   . a. using antibiotics only when appropriate, for bacterial infections that are not clearing up naturally; b. using the drugs as directed, taking all the antibiotic over the course of days prescribed; c. using more than one antibiotic at a time for difficult-to-treat organisms; d. preventing natural selection by reducing the amount of evolution the organisms can perform; e. reducing the use of antibiotics in non–health-care settings, such as agriculture

Ivory from elephant tusks is a valuable commodity on the world market. As a result, male African elephants with large tusks have been heavily hunted for the past few centuries. Today, male elephants have significantly shorter tusks at full adulthood than male elephants in the early 1900s. This is an example of                   . a. diversifying selection; b. stabilizing selection; c. directional selection; d. chance; e. more than one of the above is correct

No two people are genetically identical, except for identical twins. The main source of genetic variation among humans is a. new mutations that occurred in the preceding generation. b. genetic drift. c. the reshuffling of alleles in sexual reproduction. d. environmental effects.

Natural selection changes allele frequencies because some _________ survive and reproduce better than others. a. alleles b. loci c. species d. individuals

The largest unit within which gene flow can readily occur is a a. population. b. species. c. genus. d. hybrid.

Suppose you were studying several species of monkeys. In one, males never helped females raise offspring. In another, males provided just as much parental care as females except for actually carrying the fetus during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?

In the 1700s and 1800s, royalty in Europe often married their close relatives; furthermore, recessive genetic diseases such as hemophilia showed up much more often among royals than in the general population. Explain the likely connection.

Why isn’t inbreeding considered an evolutionary process? a. It does not change genotype frequencies. b. It does not change allele frequencies. c. It does not occur often enough to be important in evolution. d. It does not violate the assumptions of the Hardy–Weinberg principle.

Draw a small concept map showing how selection, genetic drift, gene flow, and mutation relate to genetic variation.

Why is genetic drift aptly named? Select True or False for each statement. T/F It causes allele frequencies to drift up or down randomly. T/F It occurs when alleles from one population drift into another. T/F It occurs when mutations drift into a genome.

Evaluate this statement: Gene flow increases the genetic divergence of populations.

Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest? Toucans can eat fruits with large seeds because their large bills can open wide. Most other birds in the same forest can only eat small seeds. Ecologist Mauro Galetti and his colleagues measured the seed sizes of palms in forest fragments with and without toucans. The graphs show two of the forest populations they studied. What is the take-home message of the data?

Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest? Toucans disperse seeds of key forest species such as juçara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. If there are no toucans, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why? a. increase (due to increased genetic drift) b. decrease (due to decreased gene flow) c. decrease (due to decreased mutation rate) d. decrease (due to decreased natural selection)

True or false? Gene flow can either increase or decrease the average fitness of a population. Explain.