Biosciences 2 Exam (Ch. 22-24)

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.

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.

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.

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.

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.

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.

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.

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%.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The correct answer is species. Gene flow refers to the transfer of genetic material from one population to another. Within a species, individuals can freely interbreed and exchange genetic information, leading to gene flow. However, gene flow between different species is limited or nonexistent due to reproductive barriers, such as differences in mating behaviors, anatomy, or genetic incompatibilities. Therefore, the largest unit within which gene flow can readily occur is a species.

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.

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.

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.

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.

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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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.

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.