Bio Chapter 3

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?

0.42

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.)

2%

Plant species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be

28.

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

A cow that produces a large quantity of milk.

You read about soapberry bugs and select the correct statement describing relative fitness in these individuals.

A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age. Relative fitness is defined by the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals.

What does it mean that organisms have a nearly universal genetic code?

A specific DNA sequence encodes the same information in one species as it would in nearly any other.

Which type of selection tends to increase genetic variation?

Disruptive selection eliminates phenotypes near the average and favors the extreme phenotypes, resulting in increased genetic variation in a population.

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?

Disruptive selection causes both extreme phenotypes (large and small beaks) to be favored over the intermediate phenotypes.

A certain species of salamander was split into two populations by a wide, dry valley, and the populations began to diverge from each other. After a period of time, some members of the two populations began to interbreed in a hybrid zone at the southern end of the valley. Only weak reproductive barriers existed by this time, so the two populations could freely interbreed and re-establish gene flow. This outcome in a hybrid zone is known as _____. See Concept 24.3 (Page 514)

Fusion refers to the weakening of reproductive barriers, allowing the two populations to fuse and remain (or become) one species.

What prevents speciation from occurring in sympatric populations?

Gene flow Gene flow prevents speciation in sympatric populations.

What is the most important factor that holds a gene pool of a species together and prevents speciation? See Concept 24.1 (Page 505)

Gene flow refers to the transfer of alleles among populations. As long as populations are exchanging alleles, speciation is unlikely.

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

Heritability Heritability is the ability of a trait to be passed on to offspring.

Identify the pair of homologous structures.

Maple leaf and oak leaf. The common ancestor of maple and oak trees had leaves, and maple and oak leaves have evolved from that ancestral structure. Homologous structures may be quite similar in structure and function (such as maple and oak leaves) or quite different (such as maple leaves and cactus spines).

Which of the following observations led to Darwin's major inferences? See Concept 22.2 (Page 469)

Members of a population vary in their heritable traits. Although organisms can produce huge numbers of offspring, many of these offspring do not survive.

Which of these is an example of temporal isolation? See Concept 24.1 (Page 505)

One species is nocturnal, and the other species is not. In temporal isolation, two species that breed during different times of the day cannot mix their gametes.

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool. See Concept 23.2 (Page 488)

Sexual reproduction does not change the frequency of alleles in the gene pool.

Select the correct statement describing sympatric speciation.

Sympatric speciation can occur in a single generation.

Within six months of effectively using methicillin to treat S. aureus infections in a community, all new infections were caused by MRSA. How can this result best be explained?

Some drug-resistant bacteria were present at the start of treatment, and natural selection increased their frequency.

Which of the following observations helped Darwin shape his concept of descent with modification?

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

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 causes no change in the average of the population; extreme phenotypes (in this case, large and small babies) become less common.

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?

Stabilizing selection causes no change in the average of the population; extreme phenotypes (large and small lizards) become less common.

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of Staphylococcus aureus, but within two years, methicillin-resistant strains of S. aureus (MRSA) appeared. How did the resistant strains of S. aureus emerge?

Staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common.

Which term is used to describe populations that live close enough to interbreed?

Sympatry describes populations that live close enough to interbreed.

An adaptation is _____. See Concept 22.2 (Page 469)

a trait that gives an organism a reproductive advantage in the current environment

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____. See Concept 23.4 (Page 495)

directional selection The characteristics of the poppies shifted in response to the changed environment.

The evolutionary effects of genetic drift are greatest when _____. See Concept 23.3 (Page 492)

the population size is small Changes in the gene pool of a small population are frequently due to genetic drift.

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is

the reshuffling of alleles in sexual reproduction.

One of the following is NOT a source of genetic variation. See Concept 23.1 (Page 485)

genetic drift Genetic drift can lead to a loss of genetic variation within populations and is therefore not a source of genetic variation.

Allele frequencies in a gene pool may shift randomly and by chance. What is this random shift called?

genetic drift due to chance events that alter allele frequencies.

There are 40 individuals in population 1, all with genotype A1A1, and there are 25 individuals in population 2, all with genotype A2A2. 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 is most likely an example of

genetic drift.

Which of the following is the first step in allopatric speciation? See Concept 24.1 (Page 509)

geographic isolation Allopatric speciation occurs when a population of organisms is geographically separated long enough for significant changes to occur. After a period of time, the populations may no longer be able to interbreed.

According to the punctuated equilibria model,

most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

The original source of all genetic variation is _____. See Concept 23.1 (Page 485)

mutation Mutation is, in itself, very important to evolution because it is the original source of the genetic variation that serves as the raw material for evolution.

Which of the following are causes of evolutionary change?

mutation natural selection genetic drift gene flow

From his observations of organisms in the Galapagos islands, Darwin reasoned that _____. See Concept 22.2 (Page 469)

organisms had adapted to new environments, giving rise to new species

Charles Darwin _____. See Concept 22.2 (Page 469)

proposed natural selection as the mechanism of evolution

The largest unit within which gene flow can readily occur is a

species

Sympatric speciation is _____. See Concept 24.2 (Page 511)

the appearance of a new species in the same area as the parent population It is due to a radical change in the genome.

Hybrid zones provide an opportunity to investigate _____. See Concept 24.3 (Page 514)

the evolution of reproductive isolation

Which of the following is an example of the pattern of evolution? (Overview) See Concept 22.3 (Page 468)

the fossil record of the evolution of modern cetaceans The fossil record contains observable data regarding both the morphological development and biogeographical distribution of early cetaceans.

Generation-to-generation change in the allele frequencies in a population is _____.

microevolution

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

Adaptation An adaptation is a trait that increases an individual's ability to survive in a particular environment.

What happened in the soapberry bug population in central Florida when the bugs began to feed on seeds from the goldenrain tree fruits which are much closer to the fruit surface?

Bugs with shorter beaks had more access to food, allowing them to produce more offspring.

What is the meaning of Darwin's expression "descent with modification"?

Descent with modification refers to evolutionary change over time.

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?

Directional selection drives the average of the population in one direction, in this case, toward longer necks.

How does diploidy help to preserve genetic variation? See Concept 23.4 (Page 498)

It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes. Natural selection tends to decrease genetic variation. Recessive alleles are shielded from natural selection in heterozygotes.

What is true of microevolution? See Concept 23.1 (Page 484)

It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations.

Which of the following statements about natural selection is true?

Natural selection favors individuals that reproduce more than others. Individuals who are better able to survive and reproduce are more likely to be selected for than individuals who don't survive or cannot reproduce.

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data?

Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.

The fruit fly Drosophila melanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from flies collected in the wild in the 1930s (before the widespread use of insecticides) and the 1960s (after 20 years of DDT use). Lab strains established in the 1930s have no alleles for DDT resistance. In lab strains established in the 1960s, the frequency of the DDT-resistance allele is 37%. Which statement is correct?

The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread. As the environment changed with the increased use of DDT, the advantages of the heritable trait of DDT resistance increased. Natural selection has different effects in different environments.

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population? See Concept 23.3 (Page 492)

The founder effect is genetic drift attributable to colonization by a limited number of individuals from a parent population.

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

The two forms interbreed often in nature, and their offspring have good survival and reproduction.

Which statement correctly describes the role of chance in evolution?

The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA. Genetic variation does arise by chance mutations.

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent?

behavioral isolation

Two animals are considered members of different species if they _____. See Concept 24.1 (Page 505)

cannot mate and produce viable, fertile offspring If two individuals cannot interbreed and produce viable, fertile offspring, they are members of different species.

In evolutionary terms, an organism's fitness is measured by its _____. See Concept 23.4 (Page 495)

contribution to the gene pool of the next generation Those organisms with adaptations best suited to the current environment will make the most significant contribution to the next generation.

Natural selection changes allele frequencies because some _______ survive and reproduce more successfully than others.

individuals

A heritable trait is one that

is determined at least in part by genes passed from parents to offspring.

The theory of evolution through natural selection is considered a scientific theory because _____. See Concept 22.3 (Page 475)

it is broad enough in scope to explain many observations it is supported by a massive body of evidence from many disciplines it is general enough to provide many testable hypotheses

What is the only evolutionary mechanism that consistently leads to adaptive evolution? See Concept 23.4 (Page 495)

natural selection Because natural selection has a "sorting" effect, it consistently increases the frequency of alleles that improve the match between an organism and its environment.