Chapter 21: The Evolution of Populations

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted

How did Mendel's model of inheritance help explain Darwin's theory of natural selection?

by proposing a mechanism of how organisms could transmit discrete, heritable units to offspring

How can genetic variation at the whole gene level (gene variability) be quantified?

by the average percentage of loci that are heterozygous

Which process in sexual reproduction results in diversity at the nucleotide level?

chromosome crossover

Which of the following describes a mechanism for generating more genes?

duplication

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus,

the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change

The frequency of a disease is 30/1000. This is a disease that follows a dominant/recessive pattern of inheritance on one gene (where the only affected individuals are all homozygous recessive). What is the frequency of the disease genotype q2?

3%

In a population of 200 seagulls, dark brown feathers are dominant to having only white feathers. If 160 of the 200 seagulls have brown feathers, what is the frequency of seagulls that are homozygous dominant?

31%

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele?

0.09

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?

0.80

Phenylketonuria (PKU) is a birth defect that causes an amino acid called phenylalanine to build up in the body. The frequency of individuals born in a population with PKU is q 2. There is one PKU (q 2) birth per 10,000 births. The frequency of the recessive allele for PKU in this population is q = 0.01. The frequency of the dominant allele in this population is p = 1 −− q = 0.99. What is the frequency of carriers (2pq) in this population?

2%

In a population of 200 mice, brown fur is dominant to gray fur. If 120 of the 200 mice have brown fur, what is the frequency of mice that are heterozygous?

46%

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be

54%

Which statement about variation is true?

All new alleles are the result of nucleotide variability

Anopheles mosquitoes, which carry the malaria parasite, cannot live above elevations of 5,900 feet. In addition, oxygen availability decreases with higher altitude. Consider a hypothetical human population that is adapted to life on the slopes of Mt. Kilimanjaro in Tanzania, a country in equatorial Africa. Mt. Kilimanjaro's base is about 2,600 feet above sea level, and its peak is 19,341 feet above sea level. If the incidence of the sickle-cell allele in the population is plotted against altitude (feet above sea level), which of the following distributions is most likely, assuming little migration of people up or down the mountain?

B

Blue light is a portion of the visible spectrum that penetrates deep into bodies of water. Ultraviolet (UV) light, though, can penetrate even deeper. A gene within a population of marine fish that inhabits depths from 500 m to 1,000 m has an allele for a photopigment that is sensitive to UV light and another allele for a photopigment that is sensitive to blue light. Which of the graphs in the figure best depicts the predicted distribution of these alleles within a population if the fish that carry these alleles prefer to locate themselves where they can see best?

B

Which of the following is correct about genetic variation?

It must be present in a population before natural selection can act upon the population

Recent research investigating variation in human height have found that a variety of genes at different loci, as well as early nutrition, especially that of the mother during gestation (the period of time during development of a fetus) and childhood years, influence height. Given this information, which of the following is correct?

Phenotypes are usually the result of a combination of genes as influenced by the environment

Why don't similar genotypes always produce the same phenotype?

Phenotypes can vary depending upon environment

Imagine you predict a particular frequency for a genotype, based upon detailed knowledge of that genotype frequency in population "X" of a species. Then, using the Hardy-Weinberg model, you find that the observed genotype frequency in a different population, named "Y" of the same species, is not significantly different from what you predicted/expected based on population "X."Which of the following should you conclude?

The particular gene of interest is not undergoing any mechanisms of evolution

The Hardy-Weinberg equation p2 + 2pq + q2 = 1 allows you to calculate

genotype frequencies

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because

heterozygotes have two alleles

In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because

heterozygotes have two alleles

It is estimated by a wide body of scientists that in recent decades we have begun another mass extinction event on Earth. Amphibians in particular have been in decline, sometimes due to climate change, and they therefore provide a possible early sign of dramatic biodiversity change to come. With respect to climate change and natural selection acting upon a population of one species of frog in a tropical rain forest, mutations of DNA sequences of the frog genome that are inherited by offspring

may have no effect at all, be beneficial, or be harmful

Which of the following consistently improves the degree to which organisms are well suited for life in their environment?

natural selection

When using the Hardy-Weinberg equilibrium model, we assume that

natural selection is not occurring

A mutation that is neither harmful nor beneficial is termed a

silent mutation

Which of the following represents the treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)?

using moderate doses of NA and two different PIs at the same time for several months

When evolution occurred on the Galápagos Islands, the finch beaks

varied in size across the population and sometimes conferred benefits in feeding, survivorship, and reproduction that were passed down to surviving offspring

What is a population in biology?

when a group of individuals of the same species live in the same area and interbreed