Biosciences 2 Exam (Ch. 22-24)

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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?
- Characteristics acquired during an organism's life are generally not passed on through genes.
- Spontaneous mutations can result in the appearance of new traits.
- Only favorable adaptations have survival value.
- Disuse of an organ may lead to its eventual disappearance.
- Overproduction of offspring leads to a struggle for survival.

About This Quiz

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

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2.

Males of one species sing only when its predators are absent; males of another species sing only when its predators are present.
- Behavioral
- Gametic
- Habitat
- Temporal
- Mechanical
Correct Answer

A. Behavioral

Explanation

The correct answer is "behavioral". This is because the behavior of males in one species is influenced by the absence of predators, leading them to sing. On the other hand, the behavior of males in another species is influenced by the presence of predators, leading them to sing. Therefore, the singing behavior of these males is determined by their response to predators, making it a behavioral characteristic.

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3.

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?
- Aerodynamics
- Biogeography
- Physiology
- Biochemistry
- Botany
Correct Answer

A. 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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4.

Which of these evolutionary agents is most consistent at causing populations to become better suited to their environments over the course of generations?
- Mutations
- Gene flow
- Natural selection
- Genetic drift
Correct Answer

A. 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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5.

Which statement best describes the evolution of pesticide resistance in a population of insects?
- Individual members of the population slowly adapt to the presence of the chemical by striving to meet the new challenge.
- All insects exposed to the insecticide begin to use a formerly silent gene to make a new enzyme that breaks down the insecticide molecules.
- Insects observe the behavior of other insects that survive pesticide application, and adjust their own behaviors to copy those of the survivors.
- Offspring of insects that are genetically resistant to the pesticide become more abundant as the susceptible insects die off.
Correct Answer

A. 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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6.

Which of the events described below agrees with the idea of catastrophism?
- The gradual uplift of the Himalayas by the collision of the Australian crustal plate with the Eurasian crustal plate
- The formation of the Grand Canyon by the Colorado River over millions of years
- The gradual deposition of sediments many kilometers thick on the floors of seas and oceans
- The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial body with Earth
- The development of the Galapagos Islands from underwater seamounts over millions of years
Correct Answer

A. 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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7.

What was the prevailing notion prior to the time of Lyell and Darwin?
- Earth is a few thousand years old, and populations are unchanging.
- Earth is a few thousand years old, and populations gradually change
- Earth is millions of years old, and populations rapidly change.
- Earth is millions of years old, and populations are unchanging.
- 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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8.

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be
- 23%
- 46%
- 54%
- 92%
- There is not enough information to say
Correct Answer

A. 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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9.

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.
- 2 → 4 → 1 → 3
- 4 → 2 → 1 → 3
- 4 → 1 → 2 → 3
- 4 → 2 → 3 → 1
- 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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10.

According to the punctuated equilibria model,
- Speciation is usually due to a single mutation
- Most evolution occurs in sympatric populations.
- Most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.
- Natural selection is unimportant as a mechanism of evolution.
- Given enough time, most existing species will branch gradually into new species.
Correct Answer

A. Most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

Explanation

According to the punctuated equilibria model, most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species. This means that speciation is not usually due to a single mutation, but rather a rapid accumulation of unique features. Additionally, it suggests that most evolution occurs in sympatric populations, rather than being driven solely by natural selection. Given enough time, this model also suggests that existing species will gradually branch into new species.

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11.

Which of the following observations helped Darwin shape his concept of descent with modification?
- Species diversity declines farther from the equator.
- Fewer species live on islands than on the nearest continents.
- Birds can be found on islands located farther from the mainland than the birds' maximum
- Earthquakes reshape life by causing mass extinctions.
- South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.
Correct Answer

A. 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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12.

1) Catastrophism, meaning the regular occurrence of geological or meteorological disturbances (catastrophes), was Cuvier's attempt to explain the existence of
- Evolution
- Fossil record
- Uniformitarianism
- The origin of new species
- Natural selection
Correct Answer

A. 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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13.

Which definition of evolution would have been most foreign to Charles Darwin during his lifetime?
- Change in gene frequency in gene pools
- Descent with modification
- The gradual change of a population's heritable traits over generations
- Populations becoming better adapted to their environments over the course of generations
- 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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14.

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?
- Mutation
- Non-random mating
- Genetic drift
- Natural selection
- Gene flow
Correct Answer

A. 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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15.

Natural selection is most nearly the same as
- Diploidy
- Non-random mating
- Genetic drift
- Differential reproductive success
- Non-random mating
Correct Answer

A. 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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16.

A defining characteristic of allopatric speciation is
- The appearance of new species in the midst of old ones.
- Asexually reproducing populations.
- Artificial selection
- Geographic isolation
- Large populations
Correct Answer

A. Geographic isolation

Explanation

Allopatric speciation refers to the formation of new species due to geographic isolation. This means that a population of organisms becomes separated geographically, such as by a mountain range or a body of water, which prevents gene flow between the separated populations. Over time, these isolated populations accumulate genetic differences, leading to the development of new species. Therefore, geographic isolation is a defining characteristic of allopatric speciation.

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17.

41) If two modern organisms are distantly related in an evolutionary sense, then one should expect that
- They live in very different habitats.
- They should share fewer homologous structures than two more closely related organisms.
- Their chromosomes should be very similar.
- They shared a common ancestor relatively recently.
- They should be members of the same genus
Correct Answer

A. 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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18.

Which of the following pieces of evidence most strongly supports the common origin of all life on Earth?
- All organisms require energy.
- All organisms use essentially the same genetic code.
- All organisms reproduce
- All organism show heritable variation
- All organisms have undergone eveolution
Correct Answer

A. 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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19.

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?
- HIV can change its surface proteins and resist vaccines.
- The patient must have become reinfected with 3TC-resistant viruses.
- HIV began making drug-resistant versions of reverse transcriptase in response to the drug.
- A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.
- The drug caused the HIV RNA to change.
Correct Answer

A. 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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20.

Which of the following is not an observation or inference on which natural selection is based?
- There is heritable variation among individuals.
- Poorly adapted individuals never produce offspring.
- Species produce more offspring than the environment can support.
- Individuals whose characteristics are best suited to the environment generally leave more offspring than those whose characteristics are less suited.
- Only a fraction of the offspring produced by an individual may survive.
Correct Answer

A. 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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21.

One species mates at the season when daylight is increasing from 13 hours to 13 hours, 15 minutes; another species mates at the season when daylight is increasing from 14 hours to 14 hours, 15 minutes.
- Behavioral
- Gametic
- Habitat
- Temproal
- Mechanical
Correct Answer

A. Temproal

Explanation

The correct answer is "temporal". This is because the question is discussing the mating behavior of two different species in relation to the duration of daylight. The word "temporal" refers to time or the timing of events, which is relevant in this context as the species mate during specific seasons when daylight is increasing by a certain amount of time.

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22.

The theory of evolution is most accurately described as
- An educated guess about how species originate.
- One possible explanation, among several scientific alternatives, about how species have come into existence.
- An opinion that some scientists hold about how living things change over time.
- An overarching explanation, supported by much evidence, for how populations change over time.
- An idea about how acquired characteristics are passed on to subsequent generations.
Correct Answer

A. 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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23.

The biological species concept is inadequate for grouping
- Plants
- Parasites
- Asexual organisms
- Animals that migrate
- Sympatric populations
Correct Answer

A. Asexual organisms

Explanation

The biological species concept defines a species as a group of organisms that can interbreed and produce fertile offspring. However, this concept is not applicable to asexual organisms, as they reproduce without the need for sexual reproduction or interbreeding. Asexual organisms can reproduce through processes like budding, binary fission, or fragmentation. Therefore, the biological species concept is inadequate for grouping asexual organisms, as it relies on reproductive compatibility, which does not apply to them.

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24.

Which group is composed entirely of individuals who maintained that species are fixed (i.e., unchanging)?
- Linnaeus, Cuvier, and Lamarck
- Aristotle, Cuvier, and Lamarck
- Lyell, Linnaeus, and Lamarck
- Aristotle, Linnaeus, and Cuvier
- Hutton, Lyell, and Darwin
Correct Answer

A. 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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25.

Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus?
- Species are fixed in the form in which they are created.
- Populations tend to increase at a faster rate than their food supply normally allows.
- Earth changed over the years through a series of catastrophic upheavals.
- The environment is responsible for natural selection.
- Earth is more than 10,000 years old.
Correct Answer

A. 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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26.

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?
- 4
- 16
- 32
- 36
- 40
Correct Answer

A. 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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27.

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?
- 0.20
- 0.32
- 0.42
- 0.80
- Genotype frequency cannot be determined from the information provided.
Correct Answer

A. 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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28.

Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing
- Non-random mating.
- Geographic isolation.
- Genetic drift.
- Mutations.
- gene flow.
Correct Answer

A. 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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29.

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?
- I
- II
- III
- IV
Correct Answer

A. 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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30.

Which of these is a statement that Darwin would have rejected?
- Environmental change plays a role in evolution.
- The smallest entity that can evolve is an individual organism
- Individuals can acquire new characteristics as they respond to new environments or situations
- Inherited variation in a population is a necessary precondition for natural selection to operate.
- Populations tend to produce more offspring than the environment can support.
Correct Answer

A. 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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31.

What was the species concept most used by Linnaeus?
- Biological
- Morphological
- Ecological
- Phylogenetic
Correct Answer

A. Morphological

Explanation

Linnaeus, a renowned taxonomist, primarily used the morphological species concept. This concept defines species based on their physical characteristics and appearance. Linnaeus classified organisms based on their observable traits such as size, shape, color, and structure. He believed that species could be distinguished and categorized based on these morphological features. This approach allowed for easier identification and classification of organisms, making it the most widely used species concept during Linnaeus's time.

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32.

Which of the following pairs of structures is least likely to represent homology?
- The wings of a bat and the arms of a human
- The hemoglobin of a baboon and that of a gorilla
- The mitochondria of a plant and those of an animal
- The wings of a bird and those of an insect
- The brain of a cat and that of a dog
Correct Answer

A. 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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33.

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?
- 100
- 400
- 800
- 1,000
- 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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34.

What is the estimated frequency of allele A in the gene pool?
- 0.05
- 0.25
- 0.50
- 0.75
- 1.00
Correct Answer

A. 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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35.

Males of one species are too small to perform amplexus (an action that stimulates ovulation) with females of all other species.
- Behavioral
- Gametic
- Habitat
- Temporal
- Mechanical
Correct Answer

A. Mechanical

Explanation

The correct answer is mechanical. This means that the reason males of one species are unable to perform amplexus with females of other species is because of physical incompatibility or differences in reproductive structures. The mechanical barriers prevent successful mating between different species.

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36.

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
- Island forms and mainland forms descended from common ancestors.
- Common environments are inhabited by the same organisms.
- The islands were originally part of the continent.
- The island forms and mainland forms are converging.
- 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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37.

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?
- Homozygous
- Gene variability
- Nucleotide variability
- Average heterozygosity
- All except A
Correct Answer

A. 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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38.

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?
- 0.001
- 0.002
- 0.100
- 0.400
- 0.600
Correct Answer

A. 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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39.

Species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be
- 12
- 14
- 16
- 28
- 56
Correct Answer

A. 28

Explanation

When two different species combine to form an allopolyploid, the diploid number of the new species is usually the sum of the diploid numbers of the parent species. In this case, species A has a diploid number of 12 and species B has a diploid number of 16. Therefore, when they combine to form species C, the diploid number would be 12 + 16 = 28.

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40.

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?
- The population is undergoing genetic drift.
- The two phenotypes are about equally adaptive under laboratory conditions.
- The genotype AA is lethal.
- There has been a high rate of mutation of allele A to allele a
- There has been sexual selection favoring allele a
Correct Answer

A. 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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41.

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?
- 100
- 960
- 1,920
- 2,000
- 2,400
Correct Answer

A. 1,920
42.

Heterozygote advantage should be most closely linked to which of the following?
- Sexual selection
- Stabilizing selection
- Random selection
- Directional selection
- Disruptive selection
Correct Answer

A. 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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43.

Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools?
- Phylogenetic
- Ecological
- Biological
- Morphological
Correct Answer

A. 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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44.

Which of these is the smallest unit that natural selection can change?
- a species' gene frequency
- A population's gene frequency
- An individual's genome
- An individual's genotype
- An individual's phynotype
Correct Answer

A. 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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45.

What proportion of the population is probably heterozygous (Aa) for this trait?
- 0.05
- 0.25
- 0.50
- 0.75
- 1.00
Correct Answer

A. 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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46.

Rank the following from most general to most specific: 1. gametic isolation 2. reproductive isolating mechanism 3. pollen-stigma incompatibility 4. prezygotic isolating mechanism
- 2, 3, 1, 4
- 2, 4, 1, 3
- 4, 2, 1, 3
- 2, 1, 4, 3
Correct Answer

A. 2, 4, 1, 3

Explanation

The correct answer is 2, 4, 1, 3. The ranking starts with the most general term, which is "reproductive isolating mechanism" (2), followed by "prezygotic isolating mechanism" (4), which is a more specific type of reproductive isolating mechanism. Then, "gametic isolation" (1) is even more specific, referring to the specific mechanism of reproductive isolation involving the incompatibility of gametes. Finally, "pollen-stigma incompatibility" (3) is the most specific term, referring to a specific type of gametic isolation mechanism involving the incompatibility between pollen and stigma.

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47.

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
- Homologous
- Examples of convergent evolution
- Adaptations to a common environment
- A and C only
- B and C only
Correct Answer

A. 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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48.

The origin of a new plant species by hybridization, coupled with accidents during nuclear division, is an example of
- Allopatric speciation.
- Sympatric speciation.
- autopolyploidy
- Habitat selection.
Correct Answer

A. Sympatric speciation.

Explanation

The origin of a new plant species by hybridization, coupled with accidents during nuclear division, is an example of sympatric speciation. Sympatric speciation occurs when a new species arises within the same geographical area as the parent species. In this case, the hybridization event and accidents during nuclear division lead to the formation of a new plant species without the need for geographic isolation. This process allows for the rapid evolution of new species in the same habitat.

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49.

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?
- Average heterozygosity
- Nucleotide variability
- Geographic variability
- 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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The theory of evolution is most accurately described as

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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?

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?

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

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

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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?

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

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

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

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

Rank the following from most general to most specific: 1. gametic isolation 2. reproductive isolating mechanism 3. pollen-stigma incompatibility 4. prezygotic isolating mechanism

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

The origin of a new plant species by hybridization, coupled with accidents during nuclear division, is an example of

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?