Exam 16: How Populations Evolve

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?

If the Hardy-Weinberg equilibrium is met,what is the net effect?

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

The northern elephant seal was hunted almost to extinction during the 18th and 19th centuries.Less than 100 seals were left to contribute to the gene pool of their future generations.Since the early 20th 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

Which genotype is most likely to survive in a region of the world that contains malaria?

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,there is no advantage to the heterozygous genotype.HbA codes for normal hemoglobin,whereas HbS codes for 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 United States.What has happened to the sickle-cell allele in Africa? What has happened to the sickle-cell allele in the United States?

Which statement is NOT true about the founder effect?

At the beginning of a research project on egg laying in seagulls,a researcher noted that the birds laid an average of 7-9 eggs per clutch.After studying the population for 15 generations,the researcher noted that the birds were now laying 3-4 eggs per clutch.What type of natural selection is occurring in the population of gulls?

You have been studying a newly discovered species of lemur.You have established that sexual selection has been a powerful force in the evolution of this species and it is clear that female choice plays an important role in determining which males procure mates.After many hours of observation and data collection,you find that females prefer males that are more proficient at collecting sap and fruit.You should conclude that your data strongly supports the good genes hypothesis.

You are employed by the Natural History Museum of Chicago as a wildlife biologist.You recently completed an expedition to Indonesia where you discovered a new and very colorful species of beetle.Based on observations,you hypothesize that sexual selection may be playing a role in the evolution of this species.Which of the following observations would support your hypothesis?

Which of the following would change the allele frequencies of a population?

Define and give an example of assortative mating.Will this affect genotype frequencies?

British land snails are an example of disruptive selection.In the grassy fields,the light-banded snails escape bird predators.In the darker forest,the dark snails survive and the light-banded snails are eaten.The different colored snails have the opportunity to interact and breed across the British landscape.Why doesn't this "disruptive selection" eventually lead to two separate species?

Which of the following statements about natural selection are true? Select all that apply.

The recessive allele for sickle cell anemia is more prevalent in regions of Africa where malaria is prevalent,than it is in regions where there is no malaria.This is due to

A certain species of butterfly varies in color from white to dark blue.The birds found in the same area feed on the white or lightly colored butterflies,leaving butterflies that are darkly colored.This is an example of what type of selection?

The founder effect is an example of genetic drift in which rare alleles occur at a higher frequency in a population isolated from the general population.

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-1800s 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 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 soot-covered trees. 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?

The bottleneck effect is thought to be responsible for the loss of genetic variability in certain populations.

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 ________.