Question 1

Scientists have studied, in detail, the evolution of the peppered moth, Biston betularia, over the last two hundred years. The peppered moths rest on tree trunks and are a tempting treat for birds in the area. In the mid -1800's the trees in their England habitat were covered with lichens, which are a light, grayish - green color. Although color variations occurred, the vast majority of the moths were light-colored. Because their light coloration effectively camouflaged them against the lichens-covered trees, they were not as easily seen by birds as darker colored moths. The light colored moths flourished.
The environment changed, as the Industrial Revolution progressed. By 1900, the lichens had died and trees were coated with soot due to the industrial pollution. The lighter colored moths were no longer 'hidden' in their environment, and in fact, were easily seen by their predators. Their numbers dwindled. At the same time, the darker-colored moths flourished because of their ability to hide on the darkened trees.
As environmental standards have been implemented, environmental conditions have shifted, allowing lichens to grow on tree trunks.
a. What type of selection is this?
b. What is the agent of selection?
c. What alleles were favored in the clean environment? The polluted environment?

Accepted Answer

The answer of Scientists have studied, in detail, the evolution...

Question 2

Over the course of millions of years various environments have changed. As grasslands slowly took the place of forests the inhabitants were forced to adapt or they went extinct. During this time period the horse evolved from a small cat sized creature to the size of the modern horses we see today. This is an example of which type of natural selection?

Accepted Answer

The evolution of the horse from a small cat-sized creature to the size of modern horses is an example of directional natural selection. This is because the changing environment favored larger body size which allowed the horses to better adapt and survive in the new grassland habitats.

Question 3

In a population, the allele frequency for red flower color remained at 0.7 and the allele frequency for white flower remained at 0.3 for six generations. This ____ an example of a Hardy-Weinberg equilibrium in that ___________.

Accepted Answer

This is an example of a Hardy-Weinberg equilibrium as the allele frequencies remain constant over time. This scenario assumes no evolution occurred, as the genetic makeup of the population did not change.

Question 4

Natural selection can maintain genetic variation by favoring heterozygous genotypes. In equatorial Africa, the best genotype to have for hemoglobin is heterozygous (HbA / HbS). In the United States of America, there is no advantage to the heterozygous genotype. HbA codes for normal hemoglobin, whereas HbS codes for an abnormal hemoglobin that causes red blood cells to become distorted in shape (sickle cell). Explain why the heterozygous state is advantageous in Africa, but not in the USA. What has happened to the sickle cell allele in Africa? What has happened to the sickle cell allele in the United States?

Accepted Answer

The answer of Natural selection can maintain genetic variation by...

Question 5

Social research indicates that a person is most likely to marry someone from the same village or city, or a high school or college classmate. Therefore, the Hardy-Weinberg equilibrium does not apply well to human populations because

Accepted Answer

The Hardy-Weinberg equilibrium assumes that individuals within a population are mating randomly with respect to genotype, which is not entirely true for human populations. People tend to marry others from their same village or city, or a high school or college classmate. This non-random mating results in certain alleles being more common in a population than predicted by the Hardy-Weinberg equilibrium.

Question 6

Amish populations in Lancaster County, Pennsylvania have high rates of a rare form of dwarfism. The recessive allele that codes for this disorder is found in 1 of 14 individuals in this Amish population, in contrast to 1 in 1,000 in the general population. In Ohio, an Amish population suffers with higher than normal rates of cystic fibrosis and a host of other genetic diseases so rare that some have not yet been named. What factors have caused such severe genetic problems in these two communities?

Accepted Answer

The answer of Amish populations in Lancaster County, Pennsylvania have...

Question 7

Which of the following is required for natural selection to occur in a population?

Accepted Answer

All of the choices are required for natural selection to occur in a population. Without variation in the population, there is no basis for selection. Without inheritance of variation through genetic differences, any selected traits could not be passed on to the next generation. Without differential reproduction, the adaptive traits would not be favored and would not increase in the population. And without the accumulation of adaptive traits, there would be no overall shift in the genetic makeup of the population over time.

Question 8

In the case of the peppered moths in England, when Kettlewell set up cameras to document that more white or black moths were eaten by birds on clean or sooty trees, he was verifying which factor involved in evolution by natural selection?

Accepted Answer

Kettlewell's study verified that some individuals (in this case, the darker moths) were better adapted to the environment (sooty trees) than others (white moths) which is a key aspect of evolution by natural selection. The other choices (A, B, and C) are not directly related to this concept.

Question 9

Define and give an example of assortative mating. Will this affect genotype frequencies? If so, predict how genotype frequencies will be affected in a population if assortative mating persists.

Accepted Answer

The answer of Define and give an example of assortative...

Question 10

The black bellied seed cracker, Pyrenestes, is a West African finch. Within the same geographic region, two subspecies of the finch are found. One subspecies has a large beak, which is efficient at cracking the hard seeds of the sedge, Scleria verrucosa. The other subspecies has a small beak, which is more efficient at eating the soft seeds of the sedge, Scleria goossensii. What type of selection occurred to produce this situation? Explain what a population distribution graph would look like that would depict this type of selection.

Accepted Answer

The answer of The black bellied seed cracker, Pyrenestes, is...

Question 11

The northern elephant seal was hunted almost to extinction during the 18^th and 19^th centuries. Less than 100 seals were left to contribute to the gene pool of their future generations. Since the early 20^th century, the elephant seals have been protected by law in both the U.S. and Mexico. Over 100,000 seals now inhabit the western shores of North America, all related to the small population that survived the slaughter of hunters. Scientists fear the elephant seals may be more susceptible to disease and pollution due to a ______.

Accepted Answer

The bottleneck effect occurs when a population is drastically reduced in size, causing a loss of genetic diversity. As mentioned in the passage, the northern elephant seal population was hunted to near extinction, leaving fewer than 100 seals to contribute to the gene pool of future generations. This would have resulted in a bottleneck effect, and as a result, the elephant seals may be more susceptible to disease and pollution due to reduced genetic diversity. A heterozygous advantage or disruptive selection are not relevant to the situation described in the passage. The founder effect occurs when a small group of individuals establish a new population, but this is not relevant to the current situation since the elephant seals were not establishing a new population, but recovering from a bottleneck event.

Question 12

What is the relative biological fitness of an individual who is heterozygous for sickle-cell disease who lives in Central Illinois vs. an individual who is heterozygous and lives in South Africa?

Accepted Answer

The answer of What is the relative biological fitness of...

Question 13

If early Viking explorers in Greenland and North America had survived and become the main ancestors of early North American settlers, rather than the mixture of immigrants from across Europe and other continents, today there would be a much higher incidence of Nordic traits in the U.S. population. Such a scenario would demonstrate

Accepted Answer

The scenario described demonstrates the Founder Effect, as a small group of Vikings would have established a new population with limited genetic diversity, leading to a higher incidence of their unique traits in descendants. The other options do not fit the scenario as well: gene flow would imply ongoing contact between different populations, the bottleneck effect would require a sudden reduction in population size, genetic drift would suggest random changes in allele frequency, and directional selection implies a shift in the overall characteristics of a population due to environmental factors.

Question 14

A dominant allele is found in a population with a frequency of 0.8. As the environment begins to change, the dominant allele is not favored. Scientists find that the frequency of the dominant allele decreases by half each generation. What are the allele, genotype and phenotype frequencies before and one generation after the population begins to change. Is Hardy-Weinberg equilibrium maintained?

Accepted Answer

The answer of A dominant allele is found in a...

Question 15

While we have seen how natural selection and the use of pesticides can lead to the development of resistant varieties of insects, two economically important flies, the Mediterranean fruit fly (Medfly) and the screwworm fly, can be driven to local extinction by the continuous release of sterile flies of those species. The critical factor is that the female of these species only mates once. But which of the following is/are also necessary for sterile release to work?

Accepted Answer

All of the choices are necessary for sterile release to work. The target species must be just one species, so that the sterile releases can be targeted and effective. The insects must be able to be raised artificially in large numbers, so that sufficient numbers of sterile insects can be released. And the insects to be released must be able to be sterilized with radiation without affecting their ability to attract a mate in the wild, so that they can successfully compete for and mate with wild counterparts.

Question 16

A population was surveyed to determine the percentage of individuals with detached earlobes and attached earlobes. 16% of the population was found to have attached earlobes, a trait coded for by a recessive allele. Calculate the allele, genotype and phenotype frequencies of the population, assuming Hardy-Weinberg equilibrium is maintained.

Accepted Answer

The answer of A population was surveyed to determine the...

Question 17

The difference in temperature preference between two populations of Daphnia water fleas is due to a mutation. The original population prefers temperatures near 20 $\degree$C, while the mutant population prefers temperatures between 25 $\degree$C and 30 $\degree$C. Predict how natural selection might affect the geographical distribution of these two populations.

Accepted Answer

The answer of The difference in temperature preference between two...

Question 18

Hospital data shows that human infants born with an intermediate birth weight have a better chance of survival than those that weigh much less or much more than usual. Larger than normal babies may have a difficult delivery, while smaller than normal babies may not be fully developed. What type of selection is occurring? Is the variability in birth weight in human populations increasing or decreasing? Explain what the normal population distribution would look like on a scale of 1 - 20. Explain what the distribution would look like after many generations and indicate the phenotype selected.

Accepted Answer

The answer of Hospital data shows that human infants born...

Question 19

Explain why male baboons have evolved to be larger than the females of the species?

Accepted Answer

The answer of Explain why male baboons have evolved to...

Question 20

Scientists have studied, in detail, the evolution of the peppered moth, Biston betularia, over the last two hundred years. The peppered moths rest on tree trunks and are a tempting treat for birds in the area. In the mid -1800's the trees in their England habitat were covered with lichens, which are a light, grayish - green color. Although color variations occurred, the vast majority of the moths were light-colored. Because their light coloration effectively camouflaged them against the lichens-covered trees, they were not as easily seen by birds as darker colored moths. The light colored moths flourished.
The environment changed, as the Industrial Revolution progressed. By 1900, the lichens had died and trees were coated with soot due to the industrial pollution. The lighter colored moths were no longer 'hidden' in their environment, and in fact, were easily seen by their predators. Their numbers dwindled. At the same time, the darker-colored moths flourished because of their ability to hide on the darkened trees.
As environmental standards have been implemented, environmental conditions have shifted, allowing lichens to grow on tree trunks.
Describe what the initial normal population curve would look like before pollution. Describe what the population curve would look like after the Industrial Revolution and indicated what phenotype was favored.

Accepted Answer