Chapter 13

The recessive allele of a gene causes cystic fibrosis. For this gene among Caucasians, p = 0.98. If a Caucasian population is in Hardy-Weinberg equilibrium with respect to this gene, what proportion of babies is born homozygous recessive and therefore suffers cystic fibrosis?

(0.02)2 = 0.0004

When Charles Darwin set sail on the HMS Beagle, what did he and most of his contemporary scientists think about the origin of species?

Most scientists, including Darwin, thought each species was specially created by God in its present form and did not change over time. -Special creation was the prevailing idea of the time. Darwin, like most other scientists, began his journey believing species were unchanging and specially created by God.

Which of the following is a misconception regarding natural selection?

Natural selection progressively refines organisms' adaptations, eventually leading to perfection. -This is a misconception. Natural selection is not "progressive" toward a fixed goal. Instead, it tracks a changing environment. In addition, natural selection cannot produce perfection, partly because adaptations often involve compromises.

Which of the following statements regarding natural selection is false?

Natural selection starts with the creation of new alleles that are directed toward improving an organism's fitness.

Which condition would disturb the Hardy-Weinberg equilibrium and cause the gene pool to change?

Several homozygous recessive individuals leave the population -Gene flow can alter allele frequencies in the population.

A news article discussing the evolution of domestic dogs from wolves included this statement: "On its way from pack-hunting carnivore to fireside companion, dogs learned to loveor at least live onwheat, rice, barley, corn, and potatoes." What is a more scientifically accurate way to state what happened with dogs?

Some wolves may have had variants in their digestion that allowed them to eat wheat, rice, barley, corn, and potatoes and so were able to survive with humans.

Darwin and Wallace independently arrived at the same conclusion that species change over time. Which observations supported their conclusions?

The bony shells of armadillos resembled fossilized shells from the extinct Glyptodon. Mockingbirds from different Galapagos islands had subtle, consistent differences. Birdwing butterflies were found throughout the Malay archipelago, but species differed slightly from island to island. The fossilized remains of giant sloths were similar to the smaller, living sloths Darwin encountered. Tortoises from different Galapagos islands have distinct shells. Bird families clustered geographically: cockatoos in the Malay Archipelago and Australia, macaws and hummingbirds in the Americas. -The resemblance between species and the variations among distant species led both Darwin and Wallace to conclude that species change over time.

Which observations led Darwin to establish a relationship between extinct and living animals?

The bony shells of armadillos resembled the shells of ancient Glyptodon fossils. The fossilized remains of giant sloths were found in places where smaller sloths now live. -Darwin puzzled over why he found fossils of extinct animals in places where he found similar, living animals. Eventually, these observations supported his idea that today's species descend from older, extinct species.

Which of the following is true of homologous structures?

They are structurally similar due to inheritance from a common ancestor. -Even though they may serve different functions, they maintain the same underlying structure inherited from a common ancestor.

Who developed a theory of evolution almost identical to Darwin's?

Wallace

Mutations are always __________.

a change in an individual's DNA -Mutations are rare genetic changes that can be neutral, beneficial, or detrimental depending on an individual's circumstances. A dark-color fur mutation is good for a rock pocket mouse living on black lava and bad for one living in the sandy desert

The change in curves in the graph represents

a shift in the range of genetic variation in a population of mice.

In natural selection, _____ determine which phenotypes are successful.

current conditions in the local environment -Natural selection occurs through an interaction between the environment and the variability inherent among individual organisms making up a population.

Color is an inherited trait in beetles. If brown beetles move into a population from a nearby island, which of the following statements is correct?

Gene flow causes the frequency of the brown allele to increase. -Gene flow occurs when individuals move into or out of a population, changing the allele frequencies in the population. In this case, new brown beetles in the population cause the frequency of the brown allele to increase.

Remember that color is an inherited trait in beetles. Which of the following is an example of natural selection?

Green beetles leave more offspring than brown beetles because they are better at finding food. -Natural selection occurs when organisms with one inherited trait survive and reproduce more than organisms with other traits.

Which of the following statements best describes the true nature of natural selection?

Heritable traits that promote reproduction become more frequent in a population from one generation to the next.

When dark-colored fur gives mice a 1% competitive advantage and 1% of the population begins with dark fur, in about 1000 years, 95% of the population will have dark fur. Which of the following statements is true?

If dark-colored rock pocket mice had a competitive advantage of 0.1%, it would take longer for 95% of the population to have dark fur. -A small evolutionary advantage can lead to large changes in a population. The larger the advantage, the faster the changes occur.

By what means has the overuse of antibiotics in medicine and agriculture lead to the current global problem of antibiotic resistance?

Indiscriminant use of antibiotics selects for resistant bacteria and increases their numbers. -Thus, the ultimate result of the overuse of an antibiotic is increased survival and reproduction of bacteria that are resistant to that antibiotic.

If a population is in Hardy-Weinberg equilibrium and remains in equilibrium, which of the following will be true?

Individuals survive and reproduce equally well regardless of their genotype. -Absence of selection is a condition of Hardy-Weinberg equilibrium.

What did Wallace conclude from observing that the bones in manatee flippers look similar to the bones in a human arm and hand?

Manatees' arm and finger bones are evidence that manatees share a common ancestor with land mammals. -For Wallace, the unnecessary arm and finger bones in manatee flippers show that they descended from an ancestor with arms. These vestigial structures are evidence that every species is a modified form of an older species.

Which statement reflects a possible weakness of the fossil record?

Many species probably did not die in the right place at the right time to be captured in fossils, and many fossils will never by found by paleontologists. -The fossil record is a spotty collection of past life-forms, and scientists have unearthed and described only a tiny fraction of the fossils that exist on Earth.

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

how many fertile offspring it produces -This is a direct measure of relative fitness: the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. The fittest individuals in the context of evolution are those that produce the largest number of viable, fertile offspring and thus pass on the most genes to the next generation.

Mate-attracting features such as the bright plumage of a male peacock result from

intersexual selection.

The smallest unit that can evolve is a _____.

population -Populations evolve as individuals with different genotypes live and die, causing changes in the gene pool..

In artificial selection, humans provide the selective pressure for species to change and shape the evolution of various breeds. What provides the selective pressure in natural selection?

the environment -The organisms best adapted to a particular environment have the greatest reproductive success.

If color is an inherited trait in beetles, and birds are more likely to eat brown beetles than green beetles,

the frequency of the green allele will increase -If birds are more likely to eat brown beetles than green beetles, then green beetles will survive and reproduce more than brown beetles. This causes the frequency of the green allele to increase.

Blue-footed boobies have webbed feet and are comically clumsy when they walk on land. Evolutionary scientists view these feet as

the outcome of a trade-off: Webbed feet perform poorly on land but are very helpful in diving for food.

Organisms that possess homologous structures probably __________.

share a common ancestor that also had this structure -Homology refers to similarity attributable to common ancestry. Homologous structures, both anatomical and molecular, can be used to determine the branching sequence of an evolutionary tree. Some homologous characters, such as the genetic code, are shared by all species because they date to the deep ancestral past. In contrast, characters that evolved more recently are shared only within smaller groups of organisms.

Members of the same population __________.

share a common gene pool -In studying evolution at the population level, biologists focus on the gene pool, which consists of all copies of every type of allele at every locus in all members of the population.

The core theme of biology, which explains both the unity and diversity of life, is

evolution

The evolution of populations due to chance is

genetic drift -Genetic drift describes the evolution of a population due to chance.

In a population with brown and green alleles for color, genetic drift

has more effect on the evolution of a small population. -Genetic drift affects the evolution of small populations more than it affects the evolution of large populations.

After his journey on the HMS Beagle, Darwin made this now-famous sketch in his notebook. Which ideas does it represent?

Species descend from other species just as naturally as children come from parents. All species are linked to one another by common ancestry. All species are connected to one another in a "family tree." -Darwin's simple drawing shows his thinking: any species can give rise to new species with different features. This is what Darwin described as "descent with modification."

Which of the following statements regarding the currently available fossil record is false?

The currently available fossil record shows that the first life-forms were eukaryotes.

According to this figure, which pair of organisms shares the most recent common ancestor?

lizards and ostriches

Which of the following terms represents the frequency of heterozygotes in a population that is in Hardy-Weinberg equilibrium?

2pq

What usually occurs during intersexual selection?

A member of one sex usually chooses his or her mate based on cues that exhibit good genes. -In some cases, female birds choose their mates based on elaborate physical or behavioral displays to woo females.

Why did dark-colored rock pocket mice first appear in a population of light-colored rock pocket mice?

they have a genetic mutation that affects their fur color. -The rock pocket mice that Dr. Nachman catches in the film have a mutation in a gene that leads to the dark fur color.

Darwin and Wallace made independent observations in different parts of the world. Which statements are true?

Both collected huge numbers of specimens and realized that individuals vary within species. Both observed slightly different species on nearby islands and concluded that species could change over time. Both witnessed nature up close and realized it was a battlefield with massive casualties. -Darwin and Wallace observed similar fact patterns in nature and came to the same explanation about the origin of species.

Why was Darwin's acceptance of an ancient, continuously changing Earth so important in his development of his ideas about evolution?

Darwin hypothesized that species changed gradually, over long spans of time, in response to diverse and changing habitats. -Darwin recognized that descendants of a common ancestor adapted to a diversity of habitats through natural selection. To produce current life-forms, this process required a great deal of time within a dynamic Earth environment.

Lyell's book Principles of Geology, which Darwin read on board the HMS Beagle, argued in favor of which of the following concepts?

Earth's surface is shaped by natural forces that act gradually and are still acting.

Genetic differences between populations tend to be reduced by

Gene flow

Why do dark-colored rock pocket mice on dark lava flows have white bellies?

There is no selection for dark bellies by visual predators. -The color of a rock pocket mouse's belly is not visible to a predator and therefore is not under strong selection pressure.

The forelimbs of humans, cats, and bats have a number of detailed similarities in their construction. What best explains these similarities?

The forelimbs are similar because all of these organisms inherited the basic forelimb design from a common ancestor. -This is a prime example of the concept of homologous features-features that are similar due to shared ancestry.

Which best describes the fossil record?

The fossil record is the highly ordered sequence in which fossils are found in layers of sedimentary rock. -The order is most apparent when we look at the "big picture" of the appearance of life-forms over long periods of Earth's history.

Brown-eye genes are dominant over blue-eye genes. What is the best explanation for the fact that all the blue-eye alleles have not disappeared in the human population?

The population is likely in Hardy-Weinberg equilibrium for that locus.

Certain bacterial strains have traits that allow them to resist the effects of antibiotic drugs. How do the resistance traits arise in a bacterial population, and under what circumstances will the resistance traits be most common?

The resistance traits are produced by chance mutations and are present to varying degrees in most bacterial populations. Resistance traits will be most prevalent, however, in bacteria that are chronically exposed to antibiotic drugs. -This is a prime example of natural selection in action. The resistance traits arise by chance, but current conditions can systematically favor their success; this is a big problem for public health.

As Wallace traveled the Malay Archipelago, he noticed that western islands had placental mammals, like monkeys. Eastern islands had marsupial mammals, like kangaroos. How did Wallace explain this distribution?

The western islands were once connected to Asia and the eastern islands had been connected to Australia. The islands had never been connected to each other. -Different kinds of animals were restricted to different regions because species come from pre-existing, nearby species. Because the western islands were once all connected, they would have the same species, which are also found in the mainland in Asia. The eastern islands were once also all connects and had the same species, which are also found in Australia.

All known organisms use genetic information to produce protein molecules via the same genetic code. This finding strongly supports the hypothesis that __________.

all organisms are descended from one or a few common ancestors -A common genetic code provides strong evidence that all life is related.

The frequency of a particular lethal recessive allele in a population is 0.02. Given this information, calculate the percentage of individuals who are carriers of the lethal recessive allele.

approximately 4% -Because you know the frequency of the recessive allele is 0.02, you can determine the frequency of the dominant allele: 1 - 0.02 = 0.98. Thus, 0.982 + 2(0.98)(0.02) + 0.022 = 1. Solving for 2pq will give you the frequency of approximately 0.04, or 4%.

Broccoli, cabbages, and Brussels sprouts all descend from the same wild mustard and can still interbreed. These varieties were produced by

artificial selection.

A large population of mice is isolated on an island. There are two varieties of the mice, brown and gray. Their fur colors closely match the gray rock outcrops and brown soils of the island. Hawks are their main predators. This situation most likely reflects the outcome of __________.

disruptive natural selection -The hawks will catch the mice they see best in each environment, favoring the maintenance of two different morphs in a patchy environment.

When they were first sold, certain insecticides were highly effective in killing mosquitoes. Today, dozens of mosquito generations later, a much smaller proportion of these insects die when sprayed with the same chemicals. Fewer insects are killed today because __________.

many mosquitoes today are descendants of mosquitoes with insecticide-resistant characteristics -Individuals whose characteristics give them the greatest chances of survival, such as pesticide resistance, are likely to leave more offspring than are more poorly adapted individuals. This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over the generations.

Sexual recombination occurs when chromosomes are shuffled in __________ and fertilization.

meiosis -Crossing over and independent assortment of chromosomes contribute to diversity due to sexual reproduction by producing diverse gamete types.

What is the term for a change in the relative frequencies of alleles in a population over several generations?

microevolution -Microevolution is a generation-to-generation change in allele frequencies within a population.

Genetic drift is __________.

more likely to have an impact on small populations -Genetic drift represents chance events and is therefore more likely to have a significant impact on smaller populations.

The ultimate source of all new alleles is

mutation

Imagine that you are studying a very large population of moths that is isolated from gene flow. A single gene controls wing color. Half of the moths have white-spotted wings (genotype WW or Ww), and half of the moths have plain brown wings (ww). There are no new mutations, individuals mate randomly, and there is no natural selection on wing color. How will p, the frequency of the dominant allele, change over time?

p will neither increase nor decrease; it will remain more or less constant under the conditions described.