Genetic Variation

Concept: Inbreeding and Sexual Selection

8m

Concept: Directional, Stabilizing, and Disruptive Seleciton

3m

Concept: Balancing Selection and Gene Flow

6m

Concept: Genetic Drift

4m

Related Topics

Genetic Variation Additional Practice Problems

Single nucleotide polymorphisms

A. are often found in humans

B. are rarely found in humans

C. arise from gene duplications

D. arise from transposons

E. are only found in open reading frames

Watch Solution

Which definition of evolution is correct and complete?

A. Evolution is the survival of the fittest over generations.

B. Evolution is the change in fitness of a species.

C. Evolution is the change in allele frequencies of a population over generations.

D. Evolution is natural selection within species.

Watch Solution

Can genetic drift lead to adaptations? Why or why not?

Watch Solution

Describe the two ways the genetic variation is increased through meiosis and indicate during which stage of meiosis the process occur. 

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Which of the following is false?

A. If a genetic disease reduces fertility and the allele that causes the disease offers no other advantage, the allele will likely eventually disappear, due to natural selection.

B. Natural selection does not favor individuals who are homozygous for the sickle-cell allele, because these individuals typically die before they are old enough to reproduce.

C. Individuals who are heterozygous HbA/HbS are protected from malaria, and this is why sickle-cell disease persists in wetter, mosquito-ridden regions in Africa.

D. In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HbA).


Watch Solution

After malaria is cured, the frequency of the HbS allele should decrease in regions with lots of mosquitoes because:

A. People will not die from sickle-cell disease in these regions.

B. Having one copy of the HbS allele will no longer be advantageous in these regions.

C. Natural selection will no longer act on the HbS allele at all in these regions.

D. All alleles associated with genetic diseases eventually disappear.

Watch Solution

The only source of new alleles in species is _________.

A. mitosis

B. mutation

C. speciation

D. genetic drift

E. sexual reproduction

Watch Solution

Identify the three major events/processes that result in genetic variation between parents and offspring.

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Refer to the figure below. Which description of the gene pool shown is correct?

a. Size of gene pool = 30

b. Frequency of X1= 0.80

c. Population size = 60

d. Frequency of X1X3 = 0.10

e. Number of genes = 2

Watch Solution

One spring, a dust storm blankets the usually green garden where a species of fraggles forage for food in gray dust. Under these conditions, the green fraggles become very visible to the Gorgs, monstrous beasts who tend the gardens and try to kill fraggles to protect their crops. The gray fraggles, however, now blend into the dusty background and find that they can easily steal radishes without detection. How might this affect microevolution in this population of fraggles?

a. the gray fraggles will likely become a new species over time

b. the proportion of the gray fraggles will increase in the population over time

c. green fraggles learn to forage at night to escape detection

d. green fraggles have more offspring per litter to compensate for their higher mortality

e. green fraggles reproduce more often to compensate for their higher mortality

Watch Solution

A population ecologist observes that the surface area of leaves in a species of dandelion growing in a desert is much smaller compared to the larger surface area of leaves of the same species growing in areas that receive greater rainfall. She gathers seeds from individual plants growing at both low and high rainfall locations, plants them in a uniform environment in a greenhouse, and measures the leaf area of the new plants. All of her experimentally grown plants grow to have similar leaf surface areas. From this she concludes that _____.

a. leaf surface area is not an adaptive trait that promotes fitness

b. the variation she originally observed was due to genetic differences

c. the variation she originally observed was due to disruptive selection

d. the variation she originally observed was an example of non-genetic environmental influence

e. stabilizing selection was responsible for leaf-area differences in the parent plants

Watch Solution

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of _______ selection.

a. frequency-dependent

b. sexual

c. disruptive

d. balancing

e. stabilizing

Watch Solution

Which of the following is most likely to have been produced by sexual selection?

a. camouflage coloration in animals

b. a male lion's mane

c. different sizes of male and female pinecones

d. the ability of desert animals to concentrate their urine

Watch Solution

Cattle breeders have improved the quality of meat over the years by which process?

a. directional selection

b. artificial selection

c. stabilizing selection

d. A and B

e. A and C

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Through time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing _______.

a. nonrandom reproduction

b. genetic drift

c. geographic isolation

d. gene flow

e. mutations.

Watch Solution

Crickets living high on a mountain have a high frequency of alleles for cold tolerance. Storms frequently blow crickets off the mountain down to lower elevations where they mate with crickets lacking the cold tolerant alleles, thus increasing the allele frequency in the low elevation population. This is an example of

a. genetic drift

b. gene flow

c. mutation

d. sexual selection

Watch Solution

In the sage grouse males congregate at areas called leks. Females visit leks and move around, observing the displays of different males. Eventually each female will stop and mate with one of the males, perhaps at a second visit. This is an example of?

a. directional selection

b. stabilizing selection

c. disruptive selection

d. intersexual selection

e. intrasexual selection

Watch Solution

Which type of evolutionary force can maintain genetic variation?

a. directional selection  

b. stabilizing selection   

c. genetic drift

d. mutation     

 

Watch Solution

Which of the following is a correct definition of gene flow (migration)?

a. random change in allele frequency over time

b. movement of alleles between populations

c. changes in allele frequency over time

d. changes in genotype frequency

e. accidental changes in DNA structure

Watch Solution

In crossbill birds the beaks have a specialized shape to allow the crossbills to extract pine seeds out of cones. Crossbills in one forest feed on two different pine species. For one kind of cone a long thin beak is most efficient while in the other type of cone a short thick beak is most efficient. What evolutionary force is likely happening on beak shape?

a. disruptive selection                    

b. genetic drift

c. gene flow

d. intrasexual selection

e. frequency dependent selection

Watch Solution

Without genetic diversity, a population might more easily fall victim to parasites and pathogens. 

a. True

b. False

Watch Solution

The North American bison was hunted to near extinction in the 1800s, and has since recovered, but with decreased genetic diversity. This is an example of: 

a.  Founder effect

b.  A bottleneck

c.  Natural selection

d.  Increased mutation rate

e.  Gene flow

Watch Solution

The few ancestors of the Galapagos finches who colonized the islands would be an example of: 

a.  A bottleneck

b.  Natural selection

c.  Increased mutation rate

d.  Gene flow

e.  Founder effect

Watch Solution

The bottleneck effect: 

a.  Occurs when many members of a population die, resulting in a great loss of genetic diversity

b.  Occurs when many members of a population reproduce causing too much genetic diversity within the population

c.  Occurs when small groups of individuals leave their home population and establish new settlements, mating only among themselves

d.  Occurs when large groups of individuals leave their home population and establish new settlements, mating only among themselves

Watch Solution

The founder effect: 

a.  Occurs when large groups of individuals leave their home population and establish new settlements, mating only among themselves

b.  Occurs when small groups of individuals leave their home population and establish new settlements, mating only among themselves

c.  Occurs when many members of a population die, resulting in a great loss of genetic diversity

d.  Occurs when many members of a population reproduce causing too much genetic diversity within the population

Watch Solution

A male peacock has enormous tail feathers that it uses in mating displays to attract females. While the tail feathers are an advantage in mating, what is the potential disadvantage of these feathers to the male? 

a.  The feathers require a lot of energy to produce

b.  Bright feathers make males less susceptible to predation

c.  The feathers make the male more attractive to other males

d.  There are no disadvantages to having large tail feathers

e.  The large tail feathers would make it easier to fly

Watch Solution

Alleles conferring red plumage to cardinal males are common because red plumage: 

a.  Makes males less susceptible to predation

b.  Is helpful in attracting prey

c.  Is preferred by female cardinals in choosing a mate

d.  Allows male cardinals to easily identify each other

e.  Is an example of genetic drift

Watch Solution

Carriers of cystic fibrosis have some protection against intestinal infections such as cholera. However, people with two copies of the cystic fibrosis allele develop a life-threatening disease. The mutant allele is very common in people of northern European descent because of: 

a.  Disruptive selection

b.  Directional selection

c.  Artificial selection

d.  Sexual selection

e.  Stabilizing selection

Watch Solution

Ancestors of the Galapagos finches had two different types of seeds to eat on some islands. Some seeds were very small, and required small beaks to handle, other seeds were very large and required large strong beaks to crack. This led to ____ among the Galapagos finches. 

a.  Directional selection

b.  Stabilizing selection

c.  Disruptive selection

d.  Artificial selection

e.  Sexual selection

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Ancestors of giraffes with shorter necks could not reach branches high up in trees for food. This led to ____ for longer necked giraffes. 

a.  Stabilizing selection

b.  Disruptive selection

c.  Artificial selection

d.  Sexual selection

e.  Directional selection

Watch Solution

Babies that are at a low birth weight are more likely to have health problems, while women will have difficulty delivering babies with high birth weight. Together this leads to ______ for babies of average birth weight. 

a.  Stabilizing selection

b.  Disruptive selection

c.  Directional selection

d.  Artificial selection

 

Watch Solution

One concern of conservation biologists is that endangered species will have low genetic diversity due to a small population size. Why is this a concern? 

a.  Because individuals in small populations acquire mutations more slowly than those in large populations

b.  Because sexual selection is stronger in small populations

c.  Because if a disease occurs in the population there may not be organisms with resistant alleles

 

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Sexually dimorphic features do not include: 

a.  Colored plumage

b.  Intelligence

c.  Antlers

d.  Body size

e.  None are sexually dimorphic features

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The fact that individuals whose red blood cells break down more rapidly in an area where malaria is more prevalent have a better chance of reaching reproductive age is known as: 

a.  Heterozygote advantage

b.  Homozygote advantage

c.  Polygenic inheritance

d.  Heterozygote disadvantage

e.  Pleiotropy

Watch Solution

"Balanced polymorphism" means that: 

a.  Many genes that affect the same trait persist indefinitely in a population

b.  Multiple alleles of a gene persist indefinitely in a population

c.  Only a dominant and recessive allele exist for each trait in a population

d.  Many traits persist in a population that are controlled by only a single allele

e.  None of the above are correct

Watch Solution

The three types of natural selection are: 

a.  Directional selection, convergent selection, and disruptive selection

b.  Directional selection, artificial selection, and convergent selection

c.  Disruptive selection, stabilizing selection, and normalizing selection

d.  Disruptive selection, stabilizing selection, and artificial selection

e.  Directional selection, disruptive selection, and stabilizing selection

Watch Solution

The mode of natural selection in which extreme phenotypes are less fit than the optimal intermediate phenotype is: 

a.  Directive selection

b.  Disruptive selection

c.  Stabilizing selection

d.  Artificial selection

e.  Convergent selection

Watch Solution

The mode of natural selection in which two or more extreme phenotypes are fitter than the intermediate phenotype is: 

a.  Directive selection

b.  Stabilizing selection

c.  Disruptive selection

d.  Artificial selection

e.  Convergent selection

Watch Solution

The mode of natural selection in which one extreme phenotype is fittest and the environment selects against the others is: 

a.  Directional selection

b.  Disruptive selection

c.  Stabilizing selection

d.  Artificial selection

e.  Convergent selection

Watch Solution

The entire collection of genes and their alleles is a population's: 

a.  Genotype

b.  Phenotype

c.  Dominant traits

d.  Recessive traits

e.  Gene pool

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