Biosciences 2 Exam (Ch. 22-24)

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Biosciences 2 Exam (Ch. 22-24) - Quiz

Biology examn based on chapter 22 through 26 on the campbell-reese biology text 8 edition


Questions and Answers
  • 1. 

    1) Catastrophism, meaning the regular occurrence of geological or meteorological disturbances (catastrophes), was Cuvier's attempt to explain the existence of

    • A.

      Evolution

    • B.

      Fossil record

    • C.

      Uniformitarianism

    • D.

      The origin of new species

    • E.

      Natural selection

    Correct Answer
    B. Fossil record
    Explanation
    Catastrophism, as proposed by Cuvier, suggests that geological or meteorological catastrophes occur regularly, which can explain the existence of the fossil record. These catastrophic events would cause mass extinctions, leading to the preservation of fossils in the layers of the Earth's crust. This theory aligns with the observation that different layers of the fossil record contain distinct groups of organisms, indicating that there have been multiple catastrophic events throughout history. Therefore, the correct answer is fossil record.

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  • 2. 

    Which of the events described below agrees with the idea of catastrophism?

    • A.

      The gradual uplift of the Himalayas by the collision of the Australian crustal plate with the Eurasian crustal plate

    • B.

      The formation of the Grand Canyon by the Colorado River over millions of years

    • C.

      The gradual deposition of sediments many kilometers thick on the floors of seas and oceans

    • D.

      The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial body with Earth

    • E.

      The development of the Galapagos Islands from underwater seamounts over millions of years

    Correct Answer
    D. The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial body with Earth
    Explanation
    The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial body with Earth aligns with the idea of catastrophism. Catastrophism is the belief that Earth's geological features and biological changes are primarily caused by sudden, violent events rather than gradual processes. The impact of a large extraterrestrial body causing the extinction of the dinosaurs is a prime example of a catastrophic event that had a significant impact on Earth's history.

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  • 3. 

    What was the prevailing notion prior to the time of Lyell and Darwin?

    • A.

      Earth is a few thousand years old, and populations are unchanging.

    • B.

      Earth is a few thousand years old, and populations gradually change

    • C.

      Earth is millions of years old, and populations rapidly change.

    • D.

      Earth is millions of years old, and populations are unchanging.

    • E.

      Earth is millions of years old, and populations gradually change.

    Correct Answer
    A. Earth is a few thousand years old, and populations are unchanging.
    Explanation
    Prior to the time of Lyell and Darwin, the prevailing notion was that Earth is a few thousand years old, and populations are unchanging. This idea was influenced by religious beliefs and the lack of scientific evidence and understanding about the age of the Earth and the concept of evolution. Lyell's work on geology and Darwin's theory of evolution challenged this prevailing notion and provided evidence for an Earth that is millions of years old and populations that gradually change over time through the process of natural selection.

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  • 4. 

    During a study session about evolution, one of your fellow students remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Which statement is most likely to be helpful in correcting this student's misconception?

    • A.

      Characteristics acquired during an organism's life are generally not passed on through genes.

    • B.

      Spontaneous mutations can result in the appearance of new traits.

    • C.

      Only favorable adaptations have survival value.

    • D.

      Disuse of an organ may lead to its eventual disappearance.

    • E.

      Overproduction of offspring leads to a struggle for survival.

    Correct Answer
    A. Characteristics acquired during an organism's life are generally not passed on through genes.
    Explanation
    The correct answer is "Characteristics acquired during an organism's life are generally not passed on through genes." This statement is most likely to correct the student's misconception because it explains that traits acquired during an individual's lifetime, such as a longer neck from stretching, are not inherited by their offspring. Inheritance is determined by genes, not by acquired characteristics.

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  • 5. 

    Which group is composed entirely of individuals who maintained that species are fixed (i.e., unchanging)?

    • A.

      Linnaeus, Cuvier, and Lamarck

    • B.

      Aristotle, Cuvier, and Lamarck

    • C.

      Lyell, Linnaeus, and Lamarck

    • D.

      Aristotle, Linnaeus, and Cuvier

    • E.

      Hutton, Lyell, and Darwin

    Correct Answer
    D. Aristotle, Linnaeus, and Cuvier
    Explanation
    Aristotle, Linnaeus, and Cuvier are the individuals who maintained that species are fixed (i.e., unchanging). This is evident from their respective contributions to the field of biology. Aristotle, a Greek philosopher, believed in the concept of the "Great Chain of Being" where species were organized in a hierarchical order and were unchanging. Linnaeus, a Swedish botanist, developed the binomial nomenclature system for classifying organisms and also believed in the fixity of species. Cuvier, a French naturalist, was a proponent of catastrophism and believed that species were created in their current form and did not change over time.

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  • 6. 

    Which statement best describes the evolution of pesticide resistance in a population of insects?

    • A.

      Individual members of the population slowly adapt to the presence of the chemical by striving to meet the new challenge.

    • B.

      All insects exposed to the insecticide begin to use a formerly silent gene to make a new enzyme that breaks down the insecticide molecules.

    • C.

      Insects observe the behavior of other insects that survive pesticide application, and adjust their own behaviors to copy those of the survivors.

    • D.

      Offspring of insects that are genetically resistant to the pesticide become more abundant as the susceptible insects die off.

    Correct Answer
    D. Offspring of insects that are genetically resistant to the pesticide become more abundant as the susceptible insects die off.
    Explanation
    The statement that best describes the evolution of pesticide resistance in a population of insects is that the offspring of insects that are genetically resistant to the pesticide become more abundant as the susceptible insects die off. This is because the insects that are genetically resistant to the pesticide are able to survive and reproduce, passing on their resistant traits to their offspring. Over time, the population becomes dominated by these resistant insects, leading to an increase in their abundance.

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  • 7. 

    41) If two modern organisms are distantly related in an evolutionary sense, then one should expect that

    • A.

      They live in very different habitats.

    • B.

      They should share fewer homologous structures than two more closely related organisms.

    • C.

      Their chromosomes should be very similar.

    • D.

      They shared a common ancestor relatively recently.

    • E.

      They should be members of the same genus

    Correct Answer
    B. They should share fewer homologous structures than two more closely related organisms.
    Explanation
    If two modern organisms are distantly related in an evolutionary sense, it means that they have a common ancestor further back in time. As a result, they would have undergone more genetic changes and diverged more from each other. This would lead to fewer similarities in their homologous structures compared to two organisms that are more closely related. Therefore, one should expect that they share fewer homologous structures than two more closely related organisms.

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  • 8. 

    If 3TC resistance is costly for HIV, then which plot (I—IV) best represents the response of a strain of 3TC-resistant HIV over time, if 3TC administration begins at the time indicated by the arrow?

    • A.

      I

    • B.

      II

    • C.

      III

    • D.

      IV

    Correct Answer
    C. III
    Explanation
    Plot III best represents the response of a strain of 3TC-resistant HIV over time. This is because the question states that 3TC resistance is costly for HIV, indicating that the resistant strain will have a disadvantage compared to the non-resistant strain. Plot III shows a decline in the population of the 3TC-resistant strain over time, suggesting that it is not able to survive and reproduce as effectively as the non-resistant strain.

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  • 9. 

    Which of the following pieces of evidence most strongly supports the common origin of all life on Earth?

    • A.

      All organisms require energy.

    • B.

      All organisms use essentially the same genetic code.

    • C.

      All organisms reproduce

    • D.

      All organism show heritable variation

    • E.

      All organisms have undergone eveolution

    Correct Answer
    B. All organisms use essentially the same genetic code.
    Explanation
    The fact that all organisms use essentially the same genetic code strongly supports the common origin of all life on Earth. This indicates that all living beings share a common ancestor and have evolved from a single source. The genetic code is the set of instructions that determine the characteristics and functions of an organism, and the fact that it is universally shared among all living organisms suggests a common evolutionary history. This evidence aligns with the theory of evolution and supports the idea that all life on Earth originated from a single common ancestor.

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  • 10. 

    Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are

    • A.

      Homologous

    • B.

      Examples of convergent evolution

    • C.

      Adaptations to a common environment

    • D.

      A and C only

    • E.

      B and C only

    Correct Answer
    E. B and C only
    Explanation
    The correct answer is B and C only. This is because the dorsal fins and tails of ichthyosaurs and fish are adaptations to a common environment, as they both lived in water. This is an example of convergent evolution, where unrelated species evolve similar traits due to similar environmental pressures. The fact that their closest relatives, terrestrial reptiles, did not have dorsal fins or aquatic tails suggests that these traits evolved independently in ichthyosaurs and fish.

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  • 11. 

    It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that

    • A.

      Island forms and mainland forms descended from common ancestors.

    • B.

      Common environments are inhabited by the same organisms.

    • C.

      The islands were originally part of the continent.

    • D.

      The island forms and mainland forms are converging.

    • E.

      Island forms and mainland forms have identical gene pools.

    Correct Answer
    A. Island forms and mainland forms descended from common ancestors.
    Explanation
    The observation that organisms on islands are different from, but closely related to, similar forms found on the nearest continent suggests that island forms and mainland forms descended from common ancestors. This is because the similarities in genetic traits and characteristics between the two groups indicate a shared ancestry, with the island forms evolving from a population that migrated from the mainland.

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  • 12. 

    The theory of evolution is most accurately described as

    • A.

      An educated guess about how species originate.

    • B.

      One possible explanation, among several scientific alternatives, about how species have come into existence.

    • C.

      An opinion that some scientists hold about how living things change over time.

    • D.

      An overarching explanation, supported by much evidence, for how populations change over time.

    • E.

      An idea about how acquired characteristics are passed on to subsequent generations.

    Correct Answer
    D. An overarching explanation, supported by much evidence, for how populations change over time.
    Explanation
    The theory of evolution is described as an overarching explanation, supported by much evidence, for how populations change over time. This means that it is a comprehensive and widely accepted explanation that is backed by substantial evidence from various scientific fields. It goes beyond being just an educated guess, opinion, or idea, and is considered as the most accurate and well-supported explanation for the changes that occur in populations over time.

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  • 13. 

    Monkeys of South and Central America have prehensile tails, meaning that their tails can be used to grasp objects. The tails of African and Asian monkeys are not prehensile. Which discipline is most likely to provide an evolutionary explanation for how this difference in tails came about?

    • A.

      Aerodynamics

    • B.

      Biogeography

    • C.

      Physiology

    • D.

      Biochemistry

    • E.

      Botany

    Correct Answer
    B. Biogeography
    Explanation
    Biogeography is the most likely discipline to provide an evolutionary explanation for how this difference in tails came about. Biogeography studies the distribution of organisms and their environments, including how different species are distributed across different regions. By studying the geographical distribution of monkeys with prehensile tails in South and Central America and those without prehensile tails in Africa and Asia, biogeographers can analyze the environmental factors and historical events that may have led to the evolution of these different tail characteristics in different regions.

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  • 14. 

    Within a few weeks of treatment with the drug 3TC, a patient's HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?

    • A.

      HIV can change its surface proteins and resist vaccines.

    • B.

      The patient must have become reinfected with 3TC-resistant viruses.

    • C.

      HIV began making drug-resistant versions of reverse transcriptase in response to the drug.

    • D.

      A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.

    • E.

      The drug caused the HIV RNA to change.

    Correct Answer
    D. A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.
    Explanation
    The best explanation for the given scenario is that a few drug-resistant viruses were already present in the patient's HIV population at the beginning of the treatment, and natural selection favored their survival and increased their frequency. This means that these drug-resistant viruses were better able to survive and reproduce in the presence of the drug, leading to the eventual dominance of the 3TC-resistant viruses in the population.

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  • 15. 

    Which of the following is not an observation or inference on which natural selection is based?

    • A.

      There is heritable variation among individuals.

    • B.

      Poorly adapted individuals never produce offspring.

    • C.

      Species produce more offspring than the environment can support.

    • D.

      Individuals whose characteristics are best suited to the environment generally leave more offspring than those whose characteristics are less suited.

    • E.

      Only a fraction of the offspring produced by an individual may survive.

    Correct Answer
    B. Poorly adapted individuals never produce offspring.
    Explanation
    Natural selection is based on the observation and inference that individuals whose characteristics are best suited to the environment generally leave more offspring than those whose characteristics are less suited. This process leads to the accumulation of favorable traits in a population over time. The statement "Poorly adapted individuals never produce offspring" is not an observation or inference on which natural selection is based because it is not always true. While poorly adapted individuals may have lower reproductive success, they can still produce offspring, although their offspring may have reduced fitness.

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  • 16. 

    Which of the following pairs of structures is least likely to represent homology?

    • A.

      The wings of a bat and the arms of a human

    • B.

      The hemoglobin of a baboon and that of a gorilla

    • C.

      The mitochondria of a plant and those of an animal

    • D.

      The wings of a bird and those of an insect

    • E.

      The brain of a cat and that of a dog

    Correct Answer
    D. The wings of a bird and those of an insect
    Explanation
    The wings of a bird and those of an insect are least likely to represent homology because they have different evolutionary origins. Birds belong to the class Aves, while insects belong to the class Insecta. Therefore, their wings have different underlying structures and are not derived from a common ancestor. In contrast, the other options involve structures that are more likely to be homologous because they belong to closely related species or share common ancestry.

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  • 17. 

    Which of the following observations helped Darwin shape his concept of descent with modification?

    • A.

      Species diversity declines farther from the equator.

    • B.

      Fewer species live on islands than on the nearest continents.

    • C.

      Birds can be found on islands located farther from the mainland than the birds' maximum

    • D.

      Earthquakes reshape life by causing mass extinctions.

    • E.

      South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.

    Correct Answer
    E. South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.
    Explanation
    The observation that South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe supports Darwin's concept of descent with modification. This observation suggests that species in a particular region are more closely related to each other than to species in different regions. It implies that species have evolved and adapted to their specific environments over time, leading to the development of distinct characteristics and traits. This observation aligns with Darwin's theory that species change and diversify over generations through the process of natural selection.

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  • 18. 

    Given a population that contains genetic variation, what is the correct sequence of the following events, under the influence of natural selection? 1.   Well-adapted individuals leave more offspring than do poorly adapted individuals. 2.   A change occurs in the environment. 3.   Genetic frequencies within the population change. 4.   Poorly adapted individuals have decreased survivorship.

    • A.

      2 → 4 → 1 → 3

    • B.

      4 → 2 → 1 → 3

    • C.

      4 → 1 → 2 → 3

    • D.

      4 → 2 → 3 → 1

    • E.

      2 → 4 → 3 → 1

    Correct Answer
    A. 2 → 4 → 1 → 3
    Explanation
    The correct sequence of events under the influence of natural selection is as follows: First, a change occurs in the environment (2). This change puts pressure on the individuals in the population, causing poorly adapted individuals to have decreased survivorship (4). Well-adapted individuals, on the other hand, are able to survive and reproduce successfully, leaving more offspring than poorly adapted individuals (1). Over time, this differential reproductive success leads to a change in the genetic frequencies within the population (3). Therefore, the correct sequence is 2 → 4 → 1 → 3.

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  • 19. 

    Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus?

    • A.

      Species are fixed in the form in which they are created.

    • B.

      Populations tend to increase at a faster rate than their food supply normally allows.

    • C.

      Earth changed over the years through a series of catastrophic upheavals.

    • D.

      The environment is responsible for natural selection.

    • E.

      Earth is more than 10,000 years old.

    Correct Answer
    B. Populations tend to increase at a faster rate than their food supply normally allows.
    Explanation
    Darwin learned from the writings of Thomas Malthus that populations tend to increase at a faster rate than their food supply normally allows. Malthus proposed that population growth is limited by the availability of resources, such as food, and that competition for these resources leads to a struggle for existence. Darwin applied this idea to his theory of natural selection, suggesting that individuals with traits that allow them to better compete for limited resources are more likely to survive and reproduce, leading to the evolution of species over time.

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  • 20. 

    Which of these conditions should completely prevent the occurrence of natural selection in a population over time?

    • A.

      All variation between individuals is due only to environmental factors.

    • B.

      The environment is changing at a relatively slow rate.

    • C.

      The population size is large.

    • D.

      The population lives in a habitat where there are no competing species present.

    Correct Answer
    A. All variation between individuals is due only to environmental factors.
    Explanation
    If all variation between individuals is due only to environmental factors, it means that there is no genetic variation in the population. Natural selection relies on genetic variation as it acts on the inherited traits of individuals. Without genetic variation, there would be no differences for natural selection to act upon, and therefore, natural selection would not occur in the population over time.

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  • 21. 

    Which of these is a statement that Darwin would have rejected?

    • A.

      Environmental change plays a role in evolution.

    • B.

      The smallest entity that can evolve is an individual organism

    • C.

      Individuals can acquire new characteristics as they respond to new environments or situations

    • D.

      Inherited variation in a population is a necessary precondition for natural selection to operate.

    • E.

      Populations tend to produce more offspring than the environment can support.

    Correct Answer
    B. The smallest entity that can evolve is an individual organism
    Explanation
    Darwin would have rejected the statement that the smallest entity that can evolve is an individual organism. Darwin's theory of evolution focused on the idea that evolution occurs at the population level, not at the level of individual organisms. He proposed that changes in populations over time, driven by natural selection, lead to the evolution of species. Therefore, Darwin would have disagreed with the idea that evolution can only occur within an individual organism.

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  • 22. 

    Which definition of evolution would have been most foreign to Charles Darwin during his lifetime?

    • A.

      Change in gene frequency in gene pools

    • B.

      Descent with modification

    • C.

      The gradual change of a population's heritable traits over generations

    • D.

      Populations becoming better adapted to their environments over the course of generations

    • E.

      The appearance of new varieties and new species with the passage of time

    Correct Answer
    A. Change in gene frequency in gene pools
    Explanation
    During Charles Darwin's lifetime, the concept of "change in gene frequency in gene pools" would have been most foreign to him. This is because Darwin's theory of evolution primarily focused on the process of "descent with modification," which emphasizes the passing down of traits from one generation to the next. While Darwin did recognize that populations change over time, his understanding was based on the gradual change of a population's heritable traits over generations rather than specifically on changes in gene frequency in gene pools. Additionally, Darwin's theory did not directly address the concept of populations becoming better adapted to their environments or the appearance of new varieties and species.

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  • 23. 

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

    • A.

      23%

    • B.

      46%

    • C.

      54%

    • D.

      92%

    • E.

      There is not enough information to say

    Correct Answer
    C. 54%
    Explanation
    If on average, 46% of the loci in a species' gene pool are heterozygous, it means that the remaining 54% of the loci are homozygous. Therefore, the average homozygosity of the species should be 54%.

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  • 24. 

    Which of these is the smallest unit upon which natural selection directly acts?

    • A.

      A species gene frequency

    • B.

      A population's gene frequency

    • C.

      An individual's genome

    • D.

      An individual's genotype

    • E.

      an individual's phenotype

    Correct Answer
    E. an individual's phenotype
    Explanation
    Natural selection directly acts on an individual's phenotype. Phenotype refers to the observable traits or characteristics of an individual, such as physical appearance or behavior. Natural selection acts on these traits, favoring those that increase an individual's chances of survival and reproduction. This leads to the passing on of advantageous traits to future generations, ultimately shaping the genetic composition of a population.

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  • 25. 

    Which of these evolutionary agents is most consistent at causing populations to become better suited to their environments over the course of generations?

    • A.

      Mutations

    • B.

      Gene flow

    • C.

      Natural selection

    • D.

      Genetic drift

    Correct Answer
    C. Natural selection
    Explanation
    Natural selection is the most consistent evolutionary agent for causing populations to become better suited to their environments over generations. This process involves the differential survival and reproduction of individuals with advantageous traits, leading to the accumulation of beneficial genetic variations in a population. Through natural selection, individuals with traits that enhance their survival and reproductive success are more likely to pass on their genes to the next generation, resulting in an increased frequency of these advantageous traits in the population over time.

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  • 26. 

    Which of these is the smallest unit that natural selection can change?

    • A.

      a species' gene frequency

    • B.

      A population's gene frequency

    • C.

      An individual's genome

    • D.

      An individual's genotype

    • E.

      An individual's phynotype

    Correct Answer
    B. A population's gene frequency
    Explanation
    Natural selection acts on the variation in a population's gene frequency, which refers to the relative abundance of different alleles within a population. This is the smallest unit that natural selection can change because it operates at the level of populations, not individuals. While natural selection can influence individual phenotypes and genotypes, it ultimately acts on the gene frequencies within a population over time. Therefore, a population's gene frequency is the most accurate answer as the smallest unit that natural selection can change.

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  • 27. 

    Which of these variables is likely to undergo the largest change in value as the result of a mutation that introduces a brand-new allele into a population's gene pool at a locus that had formerly been fixed?

    • A.

      Average heterozygosity

    • B.

      Nucleotide variability

    • C.

      Geographic variability

    • D.

      Average number of loci

    Correct Answer
    A. Average heterozygosity
    Explanation
    When a new allele is introduced into a population's gene pool at a locus that had formerly been fixed, it means that there is now genetic variation at that locus. Average heterozygosity measures the proportion of individuals in a population that are heterozygous at a given locus, indicating genetic diversity. Therefore, with the introduction of a new allele, the average heterozygosity is likely to undergo the largest change in value as it reflects the increase in genetic variation caused by the new allele.

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  • 28. 

    Each of the following has a better chance of influencing gene frequencies in small populations than in large populations, but which one most consistently requires a small population as a precondition for its occurrence?

    • A.

      Mutation

    • B.

      Non-random mating

    • C.

      Genetic drift

    • D.

      Natural selection

    • E.

      Gene flow

    Correct Answer
    C. Genetic drift
    Explanation
    Genetic drift is the most consistent factor that requires a small population as a precondition for its occurrence. Genetic drift refers to the random fluctuation of gene frequencies in a population due to chance events. In small populations, chance events can have a greater impact on gene frequencies because there are fewer individuals to contribute to the gene pool. This can lead to the loss or fixation of certain alleles, which can have significant effects on the genetic diversity of the population. In contrast, larger populations are less affected by genetic drift because chance events have a smaller relative impact on the overall gene frequencies.

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  • 29. 

    In modern terminology, diversity is understood to be a result of genetic variation. Sources of variation for evolution include all of the following except

    • A.

      Mistakes in translation of structural genes.

    • B.

      Mistakes in DNA replication.

    • C.

      Translocations and mistakes in meiosis

    • D.

      Recombinations at fertilization

    • E.

      Recombinations by crossing over

    Correct Answer
    A. Mistakes in translation of structural genes.
    Explanation
    Diversity is a result of genetic variation, which is caused by different sources. Mistakes in translation of structural genes refer to errors that occur during the process of protein synthesis, not genetic variation. The other options listed, such as mistakes in DNA replication, translocations and mistakes in meiosis, recombinations at fertilization, and recombinations by crossing over, are all sources of genetic variation that contribute to diversity in populations. Therefore, the correct answer is "mistakes in translation of structural genes" because it does not contribute to genetic variation.

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  • 30. 

    The higher the proportion of loci that are "fixed" in a population, the lower is that population's

    • A.

      Nucleotide variability

    • B.

      Genetic polyploidy

    • C.

      Average heterozygosity

    • D.

      A, B, and C

    • E.

      A and C only

    Correct Answer
    E. A and C only
    Explanation
    The higher the proportion of loci that are "fixed" in a population, the lower is that population's average heterozygosity. This means that there is less genetic diversity in the population, as more loci have the same allele present in all individuals. Nucleotide variability refers to the variation in the DNA sequence, which may or may not be affected by fixed loci. Genetic polyploidy, on the other hand, refers to the presence of multiple sets of chromosomes, which is not directly related to the proportion of fixed loci. Therefore, the correct answers are A and C only.

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  • 31. 

    HIV's genome of RNA includes code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. (answer question 31-33, 35)Which of these represents the treatment option that is most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)?

    • A.

      Using a series of NAs, one at a time, and changed about once a week

    • B.

      Using a single PI, but slowly increasing the dosage over the course of a week

    • C.

      Using high doses of NA and a PI at the same time for a period not to exceed 1 day

    • D.

      Using moderate doses of NA and of two different PI's at the same time for several months

    Correct Answer
    D. Using moderate doses of NA and of two different PI's at the same time for several months
    Explanation
    Using moderate doses of NA and two different PIs at the same time for several months is the treatment option that is most likely to avoid the production of drug-resistant HIV. This is because using a combination of drugs from different classes (NA and PI) targets multiple steps in the viral replication cycle, making it more difficult for the virus to develop resistance. Additionally, using moderate doses and for a longer duration helps maintain effective drug levels in the body, further reducing the likelihood of drug resistance.

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  • 32. 

    Within the body of an HIV-infected individual who is being treated with a single NA, and whose HIV particles are currently vulnerable to this NA, which of these situations can increase the virus' relative fitness?1. mutations resulting in RTs with decreased rates of nucleotide mismatch 2. mutations resulting in RTs with increased rates of nucleotide mismatch 3. mutations resulting in RTs that have proofreading capability

    • A.

      1 only

    • B.

      2 only

    • C.

      3 only

    • D.

      1 and 3

    • E.

      2 and 3

    Correct Answer
    B. 2 only
    Explanation
    Mutations resulting in RTs with increased rates of nucleotide mismatch can increase the virus' relative fitness because it allows the virus to escape the effects of the single NA treatment. The NA targets the reverse transcriptase (RT) enzyme, which is responsible for replicating the virus's genetic material. By increasing the rates of nucleotide mismatch, the virus can introduce errors in its replication process, making it more difficult for the NA to effectively target and inhibit the RT enzyme. This allows the virus to continue replicating and potentially develop resistance to the NA treatment.

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  • 33. 

    HIV has 9 genes in its RNA genome. Every HIV particle contains two RNA molecules, each molecule containing all 9 genes. If, for some reason, the two RNA molecules within a single HIV particle do not have identical sequences, then which of these terms can be applied due to the existence of the non-identical regions?

    • A.

      Homozygous

    • B.

      Gene variability

    • C.

      Nucleotide variability

    • D.

      Average heterozygosity

    • E.

      All except A

    Correct Answer
    E. All except A
    Explanation
    The correct answer is "All except A" because if the two RNA molecules within a single HIV particle do not have identical sequences, it indicates the existence of non-identical regions. This leads to gene variability, nucleotide variability, and average heterozygosity, but not homozygosity, as homozygosity refers to having identical alleles for a particular gene.

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  • 34. 

    A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.(ANSWER QUESTIONS 34, 36-41)What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time?

    • A.

      The population is undergoing genetic drift.

    • B.

      The two phenotypes are about equally adaptive under laboratory conditions.

    • C.

      The genotype AA is lethal.

    • D.

      There has been a high rate of mutation of allele A to allele a

    • E.

      There has been sexual selection favoring allele a

    Correct Answer
    B. The two phenotypes are about equally adaptive under laboratory conditions.
    Explanation
    The most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time is that the two phenotypes (dominant and recessive) are about equally adaptive under laboratory conditions. This means that both phenotypes are able to survive and reproduce at similar rates in the laboratory environment, resulting in a consistent frequency of the recessive trait over generations.

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  • 35. 

    If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true?

    • A.

      There are now fewer genes within the viral particle.

    • B.

      There are now more genes within the viral particle.

    • C.

      A point substitution mutation has occurred in the retroviral genome

    • D.

      The retroviral equivalent of crossing-over has occurred, no doubt resulting in a heightened positive effect

    • E.

      One of the RNA molecules has experienced gene duplication as the result of translocation.

    Correct Answer
    E. One of the RNA molecules has experienced gene duplication as the result of translocation.
  • 36. 

    What is the estimated frequency of allele A in the gene pool?

    • A.

      0.05

    • B.

      0.25

    • C.

      0.50

    • D.

      0.75

    • E.

      1.00

    Correct Answer
    C. 0.50
    Explanation
    The estimated frequency of allele A in the gene pool is 0.50. This means that allele A is present in approximately half of the individuals in the population.

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  • 37. 

    What proportion of the population is probably heterozygous (Aa) for this trait?

    • A.

      0.05

    • B.

      0.25

    • C.

      0.50

    • D.

      0.75

    • E.

      1.00

    Correct Answer
    C. 0.50
    Explanation
    The proportion of the population that is probably heterozygous (Aa) for this trait is 0.50. This means that half of the population is likely to have one dominant allele (A) and one recessive allele (a) for the trait in question.

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  • 38. 

    In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.4. What is the percentage of the population that is homozygous for this allele?

    • A.

      4

    • B.

      16

    • C.

      32

    • D.

      36

    • E.

      40

    Correct Answer
    B. 16
    Explanation
    In a Hardy-Weinberg population, the frequency of the homozygous genotype can be calculated by squaring the frequency of the allele. In this case, the frequency of allele a is 0.4, so the frequency of the homozygous genotype (aa) would be 0.4 squared, which is 0.16. To convert this to a percentage, we multiply by 100, giving us 16%. Therefore, the correct answer is 16.

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  • 39. 

    In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the percentage of the population that is heterozygous for this allele?

    • A.

      90

    • B.

      81

    • C.

      49

    • D.

      18

    • E.

      10

    Correct Answer
    D. 18
    Explanation
    In a Hardy-Weinberg population, the frequency of allele a is given as 0.1. The frequency of allele A can be calculated by subtracting the frequency of allele a from 1, which gives a frequency of 0.9. The percentage of the population that is heterozygous for this allele can be calculated by multiplying the frequencies of both alleles (0.1 x 0.9) and then multiplying the result by 100 to convert it to a percentage. This gives a value of 9%. Therefore, the correct answer is 18.

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  • 40. 

    In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals with Aa genotype?

    • A.

      0.20

    • B.

      0.32

    • C.

      0.42

    • D.

      0.80

    • E.

      Genotype frequency cannot be determined from the information provided.

    Correct Answer
    B. 0.32
    Explanation
    In a Hardy-Weinberg equilibrium, the frequency of individuals with the Aa genotype can be determined using the formula 2pq, where p is the frequency of allele A and q is the frequency of allele a. Since the frequency of allele a is given as 0.2, the frequency of allele A would be 1 - 0.2 = 0.8. Plugging these values into the formula, we get 2 * 0.8 * 0.2 = 0.32, which is the frequency of individuals with the Aa genotype.

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  • 41. 

    You sample a population of butterflies and find that 42% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population?

    • A.

      0.09

    • B.

      0.30

    • C.

      0.49

    • D.

      0.70

    • E.

      Allele frequency cannot be determined from this information.

    Correct Answer
    E. Allele frequency cannot be determined from this information.
    Explanation
    The frequency of the recessive allele cannot be determined from the information given because the percentage of heterozygous individuals does not provide enough information about the frequency of the recessive allele. Heterozygous individuals can have different combinations of alleles, including one dominant and one recessive allele or two different dominant alleles. Therefore, without knowing the genotype frequencies or the number of alleles present in the population, it is not possible to determine the frequency of the recessive allele.

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  • 42. 

    In a hypothetical population of 1,000 people, tests of blood-type genes show that 160 have the genotype AA, 480 have the genotype AB, and 360 have the genotype BB.What is the frequency of the B allele?

    • A.

      0.001

    • B.

      0.002

    • C.

      0.100

    • D.

      0.400

    • E.

      0.600

    Correct Answer
    E. 0.600
    Explanation
    The frequency of the B allele can be calculated by dividing the number of individuals with the BB genotype by the total number of individuals in the population. In this case, there are 360 individuals with the BB genotype out of 1000 individuals in the population. Therefore, the frequency of the B allele is 360/1000 = 0.360.

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  • 43. 

    If there are 4,000 children born to this generation, how many would be expected to have AB blood under the conditions of Hardy-Weinberg equilibrium?

    • A.

      100

    • B.

      960

    • C.

      1,920

    • D.

      2,000

    • E.

      2,400

    Correct Answer
    C. 1,920
  • 44. 

    If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached earlobes when the planet's population reaches 10,000?

    • A.

      100

    • B.

      400

    • C.

      800

    • D.

      1,000

    • E.

      10,000

    Correct Answer
    A. 100
    Explanation
    If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, it means that the population is not evolving and the allele frequencies remain constant from generation to generation. In this case, the frequency of the allele for attached earlobes will remain the same throughout the population. Since the question does not provide any information about the frequency of the allele, it can be assumed that it is a rare trait. Therefore, if the population reaches 10,000, only a small proportion of individuals will have attached earlobes, which is estimated to be around 100 people.

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  • 45. 

    In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All ten of the original colonists had free earlobes, and two were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.Which of these is closest to the allele frequency in the founding population?

    • A.

      0.1 a, 0.9 A

    • B.

      0.2 a, 0.8 A

    • C.

      0.5 a, 0.5 A

    • D.

      0.8 a, 0.2 A

    • E.

      0.4 a, 0.6 A

    Correct Answer
    A. 0.1 a, 0.9 A
    Explanation
    In a population, allele frequency refers to the proportion of a specific allele in relation to all the alleles of that gene. In this scenario, the allele for free earlobes is dominant (A) and the allele for attached earlobes is recessive (a). Since two of the original colonists were heterozygous (Aa) for the trait, the frequency of the recessive allele (a) would be lower. The closest option to reflect this would be 0.1 a, 0.9 A, indicating that the frequency of the recessive allele is 0.1 and the frequency of the dominant allele is 0.9.

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  • 46. 

    If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached earlobes when the planet's population reaches 10,000?

    • A.

      100

    • B.

      400

    • C.

      800

    • D.

      1,000

    • E.

      10,000

    Correct Answer
    A. 100
    Explanation
    Assuming that Hardy-Weinberg equilibrium applies, the frequency of attached earlobes in the population will remain constant over generations. If the answer is 100, it means that the frequency of attached earlobes in the population is 1% (100/10,000). This suggests that 1% of the population will have attached earlobes when the population reaches 10,000.

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  • 47. 

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

    • A.

      Non-random mating.

    • B.

      Geographic isolation.

    • C.

      Genetic drift.

    • D.

      Mutations.

    • E.

      gene flow.

    Correct Answer
    E. gene flow.
    Explanation
    The movement of people on Earth has increased over time, leading to the mixing of different populations and the exchange of genetic material. This process is known as gene flow. As people migrate and interact with individuals from different regions, they introduce new genetic variations into the gene pool of different populations, which can alter the course of human evolution. Therefore, gene flow is the most suitable explanation for how the movement of people has affected human evolution.

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  • 48. 

    Natural selection is most nearly the same as

    • A.

      Diploidy

    • B.

      Non-random mating

    • C.

      Genetic drift

    • D.

      Differential reproductive success

    • E.

      Non-random mating

    Correct Answer
    D. Differential reproductive success
    Explanation
    Differential reproductive success refers to the idea that individuals with certain traits are more successful at reproducing and passing on their genes to the next generation. This process is similar to natural selection, as it involves the selection of certain traits that provide an advantage in survival and reproduction. Natural selection acts on the variation in traits within a population, favoring those that increase an individual's fitness. Similarly, differential reproductive success leads to the accumulation of traits that are advantageous for survival and reproduction over time.

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  • 49. 

    Heterozygote advantage should be most closely linked to which of the following?

    • A.

      Sexual selection

    • B.

      Stabilizing selection

    • C.

      Random selection

    • D.

      Directional selection

    • E.

      Disruptive selection

    Correct Answer
    B. Stabilizing selection
    Explanation
    Heterozygote advantage refers to the situation where individuals with two different alleles for a particular gene have a higher fitness than individuals with either of the two alleles. Stabilizing selection, which favors the average phenotype and reduces phenotypic variation, is most closely linked to heterozygote advantage. This is because when stabilizing selection occurs, individuals with the heterozygous genotype have a higher fitness compared to individuals with homozygous genotypes, as they possess a combination of alleles that provides a selective advantage in the given environment.

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  • 50. 

    Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools?

    • A.

      Phylogenetic

    • B.

      Ecological

    • C.

      Biological

    • D.

      Morphological

    Correct Answer
    C. Biological
    Explanation
    The biological species concept distinguishes two species based on the degree of genetic exchange between their gene pools. According to this concept, two organisms are considered to be of the same species if they are capable of interbreeding and producing fertile offspring. If there is limited or no genetic exchange between two populations, they are considered to be separate species. This concept focuses on reproductive isolation as the primary factor in defining species boundaries.

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  • Mar 22, 2023
    Quiz Edited by
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