chapter13

Which of the following list of assumptions was part of Charles Darwin's theory of natural selection?

1. Organisms vary in heritable ways.2. Some traits improve the survival and reproduction of individuals who possess them.3. Populations produce more offspring than their environment can support, so individual organisms must compete for limited resources.4. Earth and its life are very old.

In a certain group of African people, 4% are born with sickle-cell disease (homozygous recessive). In this case, only homozygous recessive individuals have sickle-cell disease. Heterozygous individuals not only don't have sickle-cell disease, they are resistant to malaria. If this group is in Hardy-Weinberg equilibrium, what percentage of the population is heterozygous and resistant to malaria?

32%

In the normal course of evolution and adaptation, what is the most likely way for wings to develop in a tetrapod (four-limbed organism)?

The forelimbs (or possibly hind limbs) will be used for the new purpose of flight. This new function will arise through many gradual steps, and there will be aspects of the wing that reflect its history and are not perfectly suited for flight.

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.

Consider a hypothetical insect population of 100 individuals. Two equally represented alleles (A and a) exist for a particular gene. Which scenario is an example of microevolution in this population?

The population is exposed to a toxin that kills individuals with the A allele. After exposure to the toxin the population has 25 surviving individuals, and 95% of them have the aa genotype.

Blue poppies native to China are grown at a plant-breeding center in California, where those with the thickest leaves survive and reproduce best in the drier climate. This evolutionary adaptation of the poppies to their new environment is due to _____.

directional 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 evolution of populations due to chance is

genetic drift.

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

has more effect on the evolution of a small population.

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

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

microevolution

Genetic drift is _____.

more likely to have an impact on small populations

The original source of all genetic variation is _____.

mutation

Genetic variation in a population of animals or plants depends mainly on which of the following?

sexual recombination

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

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.

Part complete Which genotype relative to the sickle-cell allele has the greatest reproductive success in regions where malaria is a common disease?

the heterozygous genotype

If whales evolved from land-dwelling mammals, one would expect the fossil record to include intermediate forms, creatures more whale-like than land-dwelling mammals yet still possessing hind limbs and a pelvis lacking in modern whales. Such intermediates are termed __________.

transitional forms

Imagine that four people are infected with HIV from a common source (an infected blood sample). Initially, the patients' HIV populations are genetically identical. By the time they develop full-blown AIDS, how would the viral populations of the four patients compare?

Each patient's viral population would be unique, specifically adapted to deal with—and overcome—his or her unique immune system responses.

Suppose that, with regard to a particular gene with two alleles, A and a, we know that 60% of the alleles in the gene pool of a particular large population are A. We observe this population for five generations, during which we know that no mutation, selection, or migration has occurred. After this period, the frequency of the a allele is expected to be _____

0.4

Approximately one out of every 2,500 Caucasians in the United States is born with the recessive genetic disorder cystic fibrosis. According to the Hardy-Weinberg equilibrium equation, approximately how many people are carriers?

1 in 25

Of the scenarios below, which represents the occurrence of evolution at its smallest scale?

A pesticide spray is heavily used on a particular farm. Initially it kills 98% of the grasshoppers on contact. Over several generations, the local grasshopper population becomes resistant to the pesticide through inheritance of resistance alleles. Other nearby grasshopper populations do not change in any noticeable way.

How are adaptations beneficial to organisms?

Adaptations help organisms survive and reproduce in a particular environment.

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.

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.

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.

As proposed by Darwin, what sorts of traits are favored by natural selection?

Heritable traits that help individuals survive and reproduce more successfully than others in the same population.

Which example below presents a misconception about how antibiotic resistance develops?

Individual bacteria and viruses become immune to antibiotics after they are exposed to them. Eventually the antibiotics are useless.

Natural selection and evolution are two terms that are sometimes confused, even by freshman biology students. What is the relation between natural selection and evolution?

Natural selection is one of several mechanisms of evolution.

Which of the following is a misconception regarding natural selection?

Natural selection progressively refines organisms' adaptations, eventually leading to perfection.

Sometimes critics charge that evolution is based on mere speculation because it cannot be directly observed or experimentally induced. Is this true of evolution by natural selection?

No. Natural selection changes the traits of some organisms quite quickly, in ways that are clearly adaptive. Scientists have documented such changes in thousands of studies.

The human immune system cannot effectively suppress the HIV virus on its own. What key feature of HIV makes it so hard to beat?

The HIV virus has an extremely high rate of mutation.

A population of small fish lives in a lake with a sandy bottom. The major predator of these fish is a wading bird that hunts by sight. Most of the fish are light sandy brown, but about 10% are mottled. The color pattern is heritable. A construction company dumps a load of gravel in the bottom of the lake, giving it a mottled appearance. Which of these statements presents the most accurate prediction?

The proportion of mottled fish will increase over time.

Sickle-cell disease is a debilitating disease that results from being homozygous recessive for the "sickle-cell allele" of a hemoglobin gene. Why is the allele present and even common in many human populations?

The sickle-cell allele confers malaria resistance to heterozygotes. In some regions where malaria is common, heterozygotes have an advantage over both homozygotes, and their reproductive success maintains the recessive allele at a high frequency in the population.

Which of the following is true of homologous structures?

They are structurally similar due to inheritance from a common ancestor.

Natural selection is best described as _____.

a filtering process that fine-tunes the traits of populations by sorting among existing, randomly produced variations

HIV has become an important source of mortality for humans. If AIDS persists as a major factor for humans for many generations in the future, natural selection theory predicts that _____.

any heritable traits that help humans survive and reproduce in the presence of AIDS should become more frequent over time