Ch 16 - Practice Test

In a very small population of birds, assume 5 out of 20 alleles are the type that codes for blue feathers. What is the allele frequency of the "blue feather allele" in this population?

0.25

According to the Hardy-Weinberg principle, if 75% of the alleles in the gene pool are A1 and 25% are A2, what is the proportion of individuals with genotype A1A2 in this population?

0.375

According to the mathematical equation used in the Hardy-Weinberg principle, if the alleles for a certain trait in a population are A1 and A2, then the proportion of individuals with the genotype ________ is represented by 2pq.

A1 A2

A new predator is introduced to an area that can feed on any millipedes shorter than 200 millimeters. No millipedes that live in that area are longer than 15 millimeters. What will happen?

All millipedes will be potential prey

Based on the information shown in the figure, what do you predict the fourth generation will look like?

All the hamsters will be tan.

Which of the following is most likely to experience genetic drift? A) A population of bears that is growing by thousands of individuals each year B) A population of endangered birds that includes only five individuals C) A species of insect that occurs all across North America D) A plant species that has spread to many different habitats all around the world E) A population of common rodents that includes millions of individuals

B) A population of endangered birds that includes only five individuals

Which of the following mutations would increase evolutionary fitness? A) One that removes other alleles from the population B) One that increases the frequency of successful reproduction C) One that increases the birth weight of offspring while decreasing the number of offspring D) One that attracts more potential mates without increasing the frequency of reproduction E) One that increases the life span of the organism

B) One that increases the frequency of successful reproduction

Which of the following can be measured to estimate an organism's evolutionary fitness? A) The number of gametes it produces over its lifetime B) The number of offspring it produces over its lifetime that survive to breed C) The size of its offspring D) The number of eggs it produces over its lifetime E) The number of offspring it produces over its lifetime

B) The number of offspring it produces over its lifetime that survive to breed

Explain why new mutations appear frequently in bacterial populations but infrequently in human populations.

Bacterial populations reproduce rapidly and can produce hundreds of generations in much less time than it takes humans to produce a single generation. So, you can observe new mutations among bacteria before humans even have a next generation.

If two or more phenotypes in a population are both favored by selection, what is happening?

Balanced polymorphism

Which of the following is an example of assortative mating? A) A female lizard chooses to mate with the first male she encounters. B) A female sheep chooses a mate because he has previously mated with many females. C) A female mouse chooses a mate because he is the same color that she is. D) A dominant male elephant mates with most females in a group, excluding other males from mating with the females. E) A female sparrow chooses a mate because he attracts her by singing a different species' song.

C) A female mouse chooses a mate because he is the same color that she is.

Which trait is the best example of an adaptation? A) A new mutation that confers Tay-Sachs disease in humans B) A mutation resulting in weak branches in a species of tree that lives in windy regions C) A mutation resulting in a heat-resistant enzyme in a bacterium living in a hot spring D) A longer tongue in an insect-eating mammal that feeds on insects that live in shallow burrows E) A shorter neck in a giraffe that lives in an area with many rival males and tall trees

C) A mutation resulting in a heat-resistant enzyme in a bacterium living in a hot spring

As predator and prey species acquire new adaptations to help them survive the constant "arms race" between them, what evolutionary phenomenon is occurring?

Coevolution

Within a large population, if no mutations occur, no migration occurs, all matings are random, and each individual has an equal chance of reproducing, which of the following will probably happen? A) Natural selection will occur at the normal rate for that species. B) Extinction will result. C) A bottleneck will occur. D) No evolution will occur. E) A change in allele frequency will lead to rapid evolution.

D) No evolution will occur.

Which of the following can evolve? A) Genes B) Individuals C) Communities D) Populations

D) Populations

If the tallest and shortest individuals of a population of humans do not survive and reproduce as well as the individuals of "average" height, which type of selection would most likely result? A) Disruptive selection B) Directional selection C) Artificial selection D) Stabilizing selection

D) Stabilizing selection

Explain how disruptive selection could lead to the development of two species from one original founding population.

Disruptive selection favors the extreme phenotypes of a population. Over time, this could lead to organisms so different that they are no longer able to reproduce with each other.

Suppose that the only remaining population of a certain reptile species lives on an African mountain and that there is no migration out of this large but isolated population. Which of the following describes the most likely future of this reptile population? A) The population will survive only as long as the environment remains constant. B) Evolution will promptly cease. C) The population will go extinct after a few generations because of inbreeding. D) The bottleneck effect will cause major evolutionary changes in the isolated population. E) Evolution will continue because of mutations, assortative mating, and genetic drift.

E) Evolution will continue because of mutations, assortative mating, and genetic drift.

What causes evolutionary change in a small population?

Evolutionary change in small populations can result from genetic drift, random mutations, and natural selection.

A bird comes in a range of phenotypes, from white through gray to black. Disruptive selection favors the gray phenotype.

False

Environmental change causes the heritable variations in individuals that natural selection acts upon.

False

Genetic drift is more common in large populations than in small populations.

False

In a population, the most common phenotype represents the dominant allele.

False

In a single family, the parents have brown eyes but all five of their children have green eyes. This is an example of evolution.

False

Natural selection causes genetic changes in an individual.

False

The use of antibiotics caused the mutation that produced methicillin-resistant Staphylococcus aureus (MRSA).

False

Imagine that two men and two women settle on an uninhabited island, no new settlers arrive, and nobody leaves the island for many generations. All four of the settlers have brown eyes, but one of the men carries a recessive gene for blue eyes. Eye color has no effect on fitness. If the percentage of blue-eyed individuals on the island increases from 0% to 25%, what is the probable cause?

Genetic drift

Which of the following can cause evolutionary change in a small population?

Genetic drift

Which of the following occurs due to chance events that change the allele frequencies in small populations?

Genetic drift

Zoos often loan animals to other zoos for breeding purposes. From an evolutionary standpoint, what is the benefit?

It increases the genetic diversity of the zoo's population.

Which of the following can affect a small, endangered population so severely that it goes extinct?

Lost alleles and/or low genetic diversity

Evolution occurs in ________.

Populations

When a species lives in a constant environment for a long time, the "average type" of individual may have the best chance of surviving and producing the most offspring. What type of selection is occurring?

Stabilizing

In one butterfly species, the colors of individuals range from white to black, with many shades of gray in between. If the butterflies in a mountain population become more and more similar in color over several generations (e.g., if most butterflies are the same shade of gray), what kind of evolutionary force is likely acting on the population?

Stabilizing selection

Which of the following phenomena favors individuals with average phenotypes over those with extreme phenotypes?

Stabilizing selection

How does the founder effect influence the frequency of alleles in a population?

The alleles carried by the founding population are the only alleles available in the population unless mutation occurs or new individuals migrate to the area. If an allele is not present in the founding population, subsequent generations will not display that trait. For example, if all individuals shipwrecked on an island were blood type O (a recessive trait), all of their descendants would be type O.

A young male baboon leaves the troop that he was born in and joins a small neighboring troop of small baboons. He quickly rises to become a dominant male. From an evolutionary point of view, what important process has occurred?

The bottleneck effect

A city was intensively sprayed with the chemical DDT to control houseflies. The number of houseflies was immediately greatly reduced. Each year thereafter, the city was sprayed again, but the flies gradually increased in numbers until 10 years later when they were as abundant as they were before the control program began. Provide an evolutionary explanation of what happened.

The few flies that happened to be born with a genetic resistance to DDT survived and then passed this resistance on to their offspring. Subsequent generations of flies were less and less affected by DDT, and natural selection resulted in a population resistant to the chemical that could proliferate even when DDT was applied.

Despite causing a life-threatening disease, the sickle-cell allele in some areas of Africa has remained in high frequency in those populations because it protects against malaria. In the United States, malaria was eradicated shortly before World War II by eliminating the mosquito that spreads the disease. What is likely to happen to the frequency of the sickle-cell allele in African Americans living in the United States?

The frequency of the sickle-cell allele will decrease.

Evolutionary adaptations are not always the "best" solution to a problem. Explain how the long necks of giraffes can be both advantageous and disadvantageous.

The long neck provides an advantage to males when battling for dominance and feeding on the leaves of tall trees. However, when drinking water from a pool, the giraffe is in a very awkward position and at a disadvantage because it is vulnerable to attack by predators.

The fish in a certain population average 10 millimeters in length. Imagine that a population of predatory birds arrives in the area, but they cannot eat fish longer than 15 millimeters. After a decade, if the fish average 14 millimeters in length, what probably happened?

The longer fish survived and produced more offspring than shorter fish.

Explain how a recessive trait can be the most frequent phenotype in a population.

The population's environment can drive directional selection, which could favor the organisms expressing the recessive trait while removing the dominant phenotype from the gene pool

What conditions are necessary for a population to be at equilibrium?

There can be no mutations, no gene flow, only random matings, no natural selection, and a large population.

Gene flow results when new individuals migrate into an area and join the breeding population there.

True

Natural selection causes genetic changes in populations.

True

Organisms that have the greatest reproductive success are considered the most evolutionarily fit.

True

Evolution can be defined as

a change in the genetic makeup of a population over time.

Imagine a population of monkeys in South America whose habitat has been reduced to the point where only 20 individuals survive. This is an example of

a population bottleneck

The extreme loss of genetic diversity that has occurred in cheetah populations due to overhunting is the result of

a population bottleneck

Evolution by natural selection is

a process that occurs as a result of differences in fitness.

The nonliving components of an environment, such as weather and water availability, are

abiotic components

A population is defined as

all individuals of the same species located in a given geographic region

The gene pool for a particular population is made up of

all the genes that occur in the population

In the population shown in the figure, what is the most common fur color allele in this population?

allele b

In an equilibrium population

allele frequencies do not change

Multidrug-resistant bacteria

are becoming more widespread

A population that maintains several different phenotypes of the same trait displays ________.

balanced polymorphism

When natural selection tends to split a population into two phenotypic groups, it is called

balanced polymorphism

In some butterfly populations, there are equal frequencies of alleles that code for black and yellow coloration. This is an example of

balanced polymorphism.

A bacterial allele that provides resistance to the antibiotic streptomycin is

beneficial to the cell in the presence of streptomycin.

In hamsters, the dominant allele B codes for a black coat and the recessive allele b codes for a tan coat. In the population shown in the figure above, what is the most frequent phenotype?

black coat

Mutations

can be helpful, neutral, or harmful to individuals

Gene flow

can spread certain alleles throughout a species.

Populations of organisms are constantly evolving, which means that they are always

changing

The change in one population driven by a change in an associated population is called

coevolution

When different species closely interact for an extended period of time and develop new adaptations in response to each other, it is called

coevolution

When one species evolves a new phenotypic feature and another species evolves new adaptations in response, it is called

coevolution

Suppose a small population of deer is introduced to an island. All of the original males have 6 to 10 points on their antlers, and the average male has 8 points. After several generations, if most males have antlers with 10 points and no males have 6 points, the population has undergone ________ selection.

directional

A population of hummingbirds with a variety of beak sizes finds a new food source in a plant that has a long trumpet flower with nectar at the bottom of the trumpet. Over time, these hummingbirds develop longer beaks. This is an example of

directional selection

In central Africa, the frequency of the sickle-cell allele has remained stable over the years because the allele protects against malaria. In the United States, malaria was eradicated by eliminating the mosquito that spreads the disease. The decreasing frequency of the sickle-cell allele in African Americans since malaria was eliminated in the United States is an example of

directional selection

Suppose a population of mostly sand-colored crabs migrates from a sand beach to a pebble beach and evolves a darker, speckled coloration that closely resembles the pebble beach. This is an example of

directional selection

In a certain species of salmon, some adult males are extremely large whereas other adult males are very small, compared to the females. There are no intermediate-sized adult males in the population. This is probably the result of

disruptive selection

A flock of birds with various beak sizes migrates to a new island where their traditional food is not available. However, there are plants that produce a variety of large nuts, which can be eaten by birds with the largest beaks, and plants that produce a variety of small, soft seeds, which can be eaten by birds with the smallest beaks. Over time, this population divides into two species with large and small beaks. This is an example of

disruptive selection.

Evolution can be defined as change in ________ in a population.

frequency of alleles

The net migration of alleles into or out of a population from neighboring populations is called

gene flow

Suppose a new mutation that improves metabolic efficiency is lost from a small population of mammals living in a region of seasonal food scarcity after a hurricane eliminates half the mammal population. This is an example of

genetic drift

The process by which allele frequencies are altered in a small population due to chance is called

genetic drift

Having greater evolutionary fitness means

having more offspring.

Individuals who have one dominant allele and one recessive allele for a trait are referred to as ________.

heterozygotes or heterozygous

A population of plants comes in two flower colors: blue and white. Crossing two blue-flowered plants produces mostly blue-flowering offspring and some white-flowering offspring. Crossing two white-flowered plants produces only white-flowering offspring. This indicates that the white-flowering plants are

homozygous recessive for the flower color allele.

A population with ________ is at risk for extinction.

limited genetic variability

Antibiotic resistance is a result of ________ in bacteria.

natural selection

Bright coloration in birds makes them stand out to predators. In female birds that sit on the nest, bright coloration is rare. This is likely the result of

natural selection

In the context of evolution, equilibrium means

no change in allele frequency

The interaction of genes and environment produces a specific

phenotype

Natural selection selects for or against certain

phenotypes

Habitat loss, natural catastrophes, and/or excessive harvesting of a species often result in

population bottlenecks

Natural selection acts on individual phenotypes to affect the evolution of ________.

populations

A population carries two alleles for a trait in which T is dominant and t is recessive. In the Hardy-Weinberg equation, 2pq represents the

proportion of heterozygous individuals

A population carries two alleles for a trait in which T is dominant and t is recessive. In the Hardy-Weinberg equation, p2 represents the

proportion of homozygous dominant individuals.

A population carries two alleles for a trait in which T is dominant and t is recessive. In the Hardy-Weinberg equation, q2 represents the

proportion of homozygous recessive individuals.

Mutations are important because they

provide variation that can result in evolutionary change.

The allele frequency of a population is the

relative proportion of a given allele in that population

Inbreeding is defined as

sexual reproduction among closely related individuals.

Female finches, which do not sing, often choose to mate with males that sing a specific, elaborate song. This is an example of

sexual selection

Male fish that display a bright blue color attract more mates as well as more predators. Maintaining that blue gene in the population is an example of

sexual selection

Members of one gender influence allele frequencies in a population by choosing mates according to some conspicuous feature in the other gender in the process called

sexual selection

The bright coloration of male birds is often the result of

sexual selection

The elaborate courtship displays common among animals are the result of

sexual selection

The male peacock's beautiful tail is really a trade-off between

sexual selection and natural selection

Imagine that a mutation for red eye color becomes very common in a population of flies because female flies in this population prefer to mate with red-eyed males. This is an example of

sexual selection.

Evolution by genetic drift is most obvious in

small populations

The type of selection most likely to act on a well-adapted population in a relatively constant environment is

stabilizing

The 30,000 elephant seals alive today are genetically very similar due to

the bottleneck effect

Imagine that one of the original four mice that escape from a research lab is blind due to a genetic defect. If the escaped mouse breeds and most of the mice born in subsequent generations are blind from birth, this is most likely a case of

the founder effect

Shrews have been documented to travel across frozen lakes and establish populations on previously uninhabited islands. The low level of genetic diversity in the new populations is the result of

the founder effect

The Pennsylvania Amish have a very high frequency of an unusual allele that results in short arms and legs and extra fingers. This high frequency is thought to be the result of

the founder effect

In general, each species of fruit fly in the Hawaiian archipelago is restricted to a single island. One hypothesis to explain this pattern is that new species formed after a small number of flies colonized each new island. This mechanism of speciation is called

the founder effect.

Genetic drift results in a change in allele frequencies because

the population size is so small that chance occurrences can alter allele frequencies.