Microevolution (my lab and mastering)

A heritable trait is one that

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

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.

A biologist observes that a particular plant species is found in a forest but not in a nearby meadow. She hypothesizes that the plants could grow in the meadow but are not found there because their seeds have yet to land in the meadow. Which of the following would be the most appropriate way to scientifically evaluate this hypothesis?

scattering seeds in several areas of the meadow and observing whether they start to grow

An adaptation is __________.

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

Which of the following is an observation or inference on which natural selection is based?

Species produce more offspring than the environment can support.

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

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

Hypothesize why the percentage of mosquitoes resistant to DDT rose rapidly.

The rapid rise in the percentage of mosquitoes resistant to DDT was most likely caused by natural selection in which mosquitoes resistant to DDT could survive and reproduce, while other mosquitoes could not.

Suggest an explanation for the global spread of DDT resistance.

In India−where DDT resistance first appeared−natural selection would cause the frequency of resistant mosquitoes to natural selection over time. If resistant mosquitoes then migrated from India (for example, transported by wind or in planes, trains, or ships) to other parts of the world, the frequency of DDT resistance there would natural selection.

over time. If resistant mosquitoes then migrated from India (for example, transported by wind or in planes, trains, or ships) to other parts of the world, the frequency of DDT resistance there would increase.

Honeypot ants (genus Myrmecocystus) can store liquid food inside their expandable abdomens. Consider other ants you are familiar with, and list how a honeypot ant exemplifies three key features of life: adaptation, unity, and diversity?

The honeypot ants share many of the characteristics found in other ants. It is an example of unity.

Their unique abdomen is a result of descent with modification. It is an example of diversity.

The expandable abdomen of the honeypot ants allows them to store food when it is available. It is an example of adaptation.

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.

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

There is no selection for dark bellies by visual predators.

Mutations are always __________.

a change in an individual's DNA

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.

What does Dr. Carroll mean when he says, "while mutation is random, natural selection is not"?

Mutations for advantageous traits are more likely to be passed on to the next generation.

Natural selection acts on traits.

Natural selection favors some mutations.

In the lab, Nachman examined dark mice from two different populations living hundreds of miles apart. The mice looked nearly identical. Their dark color was caused by two different genes. What does this tell you?

Under very similar conditions, natural selection can favor very similar adaptations.

Dark fur color evolved independently on each lava flow.

There are at least two genes involved in creating dark mouse fur.

Two completely different mutations in two separate genes can generate the same phenotype.

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

Descent with modification refers to evolutionary change over time.

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.

Soapberry bugs use needlelike "beaks" to feed on seeds within the fruits of various plants. Bugs feed most successfully when their beak length matches the size of the fruit on which they are feeding. For 25 years, populations of soapberry bugs in central Florida have been feeding on small goldenrain tree fruits that were introduced to the area, rather than on the larger native balloon vine fruits that serve as food for other soapberry bug populations. Beak lengths of soapberry bugs are variable, but the average beak length is shorter in soapberry bug populations that feed on goldenrain tree fruits than in populations that feed on balloon vine fruits, as shown in the graph. How does natural selection act on beak length in soapberry bug populations?

The action of natural selection on beak length in soapberry bug populations varies with the 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.

Varieties of Staphylococcus aureus that are resistant to the drug methicillin __________.

already existed in the population before methicillin was developed

were strongly selected for as methicillin became widely used to treat bacterial infections

Suppose that a gene for coat color in mice has two alleles, B and b, where B is completely dominant and encodes a black coat color, and b is recessive and encodes a brown coat color. A mouse that is heterozygous has genotype _____, and its phenotype is _____.

Bb; black

The original source of all genetic variation is __________.

mutation

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

the reshuffling of alleles in sexual reproduction.

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if __________ is the only process acting on the gene pool.

random mating

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%

The evolutionary effects of genetic drift are greatest when __________.

the population size is small

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?

founder effect

One population of a species has 25 individuals, all with genotype AA; a second population of this species has 40 individuals, all with genotype aa. Assume that these populations live far apart but in similar environmental conditions. Based on this information, the observed genetic variation most likely resulted from

genetic drift

How may mutation, natural selection, genetic drift, and gene flow have affected populations that colonized the lake?

Natural selection would cause evolutionary change in animal populations that colonize a new environment as its conditions differ from those found in their home.

Genetic drift would probably change allele frequencies because only few colonists reach new environments, and so the size of the population would be very small initially.

Over time, mutations and ongoing gene flow would introduce new alleles into the populations; some of these alleles would be favored by selection.

In the beetles described in the animation, there were two alleles for color, brown and green. Suppose that you discover a very small population of these beetles, consisting of the individuals shown below. How can you calculate the frequency of each allele in this population?

1. To calculate the frequency of the brown allele, count the number of brown alleles and divide by the total number of alleles in this population.

2. In this beetle population, the number of brown alleles is 8.

3. In this beetle population, the total number of alleles is 20.

4. The frequency of the brown allele in this beetle population is 0.4.

5. The frequency of the green allele in this beetle population is 0.6.

The three major mechanisms of evolution differ in how they work, and as a result often have different effects on a population. Review your understanding of natural selection, genetic drift, and gene flow by sorting the statements below into the correct bins.

natural selection

- consistently causes a population to become better adapted to its environment

- a result of differential success in reproduction

- cannot cause a harmful allele to become more common

genetic drift

- can result from the founder effect

- can result from the bottleneck effect

- causes allele frequencies to fluctuate randomly

gene flow

- can introduce new alleles into a population's gene pool

- a result of the movement of fertile individuals or their gametes

Populations evolve for many reasons. Suppose there is a population of plants that have either purple flowers or white flowers, and the allele for purple flowers is dominant. This means that plants with two purple alleles have purple flowers. Plants with one purple allele and one white allele also have purple flowers. Only plants with two white alleles have white flowers.

For each event or condition described below, answer the following questions.

Which mechanism of evolution is at work?

How does this event affect the population's gene pool? Do the frequencies of the two alleles change, and if so, how?

https://quizlet.com/cdn-cgi/image/f=auto,fit=cover,h=200,onerror=redirect,w=240/https://o.quizlet.com/LlJIPfSIaDsWmtakBV-Veg.png

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

genetic drift

Which type of selection tends to increase genetic variation?

Disruptive selection

Submit

In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following?

The value of a particular characteristic; characteristics of an organism can include such traits as size and color.

True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.

False

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

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

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

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

In evolutionary terms, an organism's relative fitness is measured by its __________.

contribution to the gene pool of the next generation

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 __________.

directional selection

What is the only evolutionary mechanism that consistently leads to adaptive evolution?

natural selection

How is the process of evolution revealed by the imperfections of living organisms?

Organisms inherit a basic form from their ancestors, and that form is modified by natural selection over time. This form is usually not perfect.

Imperfections in organisms result from a variety of other constraints, such as a lack of genetic variation for the trait.

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.