Individuals of the roughly 2,000 species in the family Lampyridae include those insects capable of producing bioluminescent light through a specific metabolic process. Though commonly referred to as fireflies or lightning bugs, these idiosyncratic creatures are more accurately categorized as winged beetles. Like their amphibian predators, most fireflies are crepuscular and are thus largely reliant on their bioluminescence to attract mates, find food, and warn predators of their potential poisonousness. Fireflies are known not to be desirable prey animals for most predators due to the presence of potentially harmful substances in their blood and bitter taste. During their larval stage, bioluminescence serves as the primary defense mechanism to fend off those predators. The diet of most fireflies includes a mixture of nectar, pollen, fireflies, and other insects. It has been shown that different species of fireflies exhibit unique bioluminescence patterns when attracting mates. For example, males of the species P. pyralis (the state insect of Tennessee) use flashing patterns during courtship to attract potential mates. If a female elects to mate with the male, she will respond by reciprocating with a flash of her own. However, the males must beware, as females of other species such as P. pensylvanica can mimic these patterns to deceive, attract, and eat the males.

The biochemical reaction by which fireflies produce light occurs inside a specialized organ in their lower abdomen. This light-emitting organ utilizes the molecule luciferin, which is responsible for the production of visible light. In the presence of oxygen, magnesium ions, and the energy-rich molecule adenosine triphosphate (ATP), the enzyme luciferase converts luciferin into oxyluciferin, which emits light due to being in an electronically excited state. Upon emitting light, oxyluciferin is recycled and reconverted to luciferin so the process may continue. As with any biochemical process, the rate and capacity for bioluminescence in fireflies is dictated by the concentration of inputs as well as the rate at which byproducts are recycled. Scientists still do not fully understand how fireflies are able to produce bioluminescence with upwards of 80-90% energy efficiency. In comparison, the average incandescent light bulbs and LED lights emit only about 10% and 20% of their total electrical energy input as light, respectively. Since the first law of thermodynamics states that the total energy of the universe is constant and energy can neither be created nor destroyed, heat is the major byproduct in the reactions mentioned above.

To further study the interaction of firefly luciferase with its substrate, a student designs an experiment testing the rate at which the molecules involved are recycled. The student gathers 100 fireflies and separates them randomly into five equal experimental groups. Group A is not given any treatment and each subsequent group of fireflies is administered increasing concentrations of luciferin. Each group of fireflies is then released into separate pitch-black rooms that mimic the fireflies’ natural habitat. These rooms also contain light meters that measure the intensity of light emitted by the group of 20 fireflies as a whole. The results of this experiment are shown in Table 1.

Table 1

Which group of fireflies exhibited the most bioluminescent activity?

Individuals of the roughly 2,000 species in the family Lampyridae include those insects capable of producing bioluminescent light through a specific metabolic process. Though commonly referred to as fireflies or lightning bugs, these idiosyncratic creatures are more accurately categorized as winged beetles. Like their amphibian predators, most fireflies are crepuscular and are thus largely reliant on their bioluminescence to attract mates, find food, and warn predators of their potential poisonousness. Fireflies are known not to be desirable prey animals for most predators due to the presence of potentially harmful substances in their blood and bitter taste. During their larval stage, bioluminescence serves as the primary defense mechanism to fend off those predators. The diet of most fireflies includes a mixture of nectar, pollen, fireflies, and other insects. It has been shown that different species of fireflies exhibit unique bioluminescence patterns when attracting mates. For example, males of the species P. pyralis (the state insect of Tennessee) use flashing patterns during courtship to attract potential mates. If a female elects to mate with the male, she will respond by reciprocating with a flash of her own. However, the males must beware, as females of other species such as P. pensylvanica can mimic these patterns to deceive, attract, and eat the males.

The biochemical reaction by which fireflies produce light occurs inside a specialized organ in their lower abdomen. This light-emitting organ utilizes the molecule luciferin, which is responsible for the production of visible light. In the presence of oxygen, magnesium ions, and the energy-rich molecule adenosine triphosphate (ATP), the enzyme luciferase converts luciferin into oxyluciferin, which emits light due to being in an electronically excited state. Upon emitting light, oxyluciferin is recycled and reconverted to luciferin so the process may continue. As with any biochemical process, the rate and capacity for bioluminescence in fireflies is dictated by the concentration of inputs as well as the rate at which byproducts are recycled. Scientists still do not fully understand how fireflies are able to produce bioluminescence with upwards of 80-90% energy efficiency. In comparison, the average incandescent light bulbs and LED lights emit only about 10% and 20% of their total electrical energy input as light, respectively. Since the first law of thermodynamics states that the total energy of the universe is constant and energy can neither be created nor destroyed, heat is the major byproduct in the reactions mentioned above.

To further study the interaction of firefly luciferase with its substrate, a student designs an experiment testing the rate at which the molecules involved are recycled. The student gathers 100 fireflies and separates them randomly into five equal experimental groups. Group A is not given any treatment and each subsequent group of fireflies is administered increasing concentrations of luciferin. Each group of fireflies is then released into separate pitch-black rooms that mimic the fireflies’ natural habitat. These rooms also contain light meters that measure the intensity of light emitted by the group of 20 fireflies as a whole. The results of this experiment are shown in Table 1.

Table 1

How many more lumens did the brightest group produce than the group administered twice that dose of luciferase?

Individuals of the roughly 2,000 species in the family Lampyridae include those insects capable of producing bioluminescent light through a specific metabolic process. Though commonly referred to as fireflies or lightning bugs, these idiosyncratic creatures are more accurately categorized as winged beetles. Like their amphibian predators, most fireflies are crepuscular and are thus largely reliant on their bioluminescence to attract mates, find food, and warn predators of their potential poisonousness. Fireflies are known not to be desirable prey animals for most predators due to the presence of potentially harmful substances in their blood and bitter taste. During their larval stage, bioluminescence serves as the primary defense mechanism to fend off those predators. The diet of most fireflies includes a mixture of nectar, pollen, fireflies, and other insects. It has been shown that different species of fireflies exhibit unique bioluminescence patterns when attracting mates. For example, males of the species P. pyralis (the state insect of Tennessee) use flashing patterns during courtship to attract potential mates. If a female elects to mate with the male, she will respond by reciprocating with a flash of her own. However, the males must beware, as females of other species such as P. pensylvanica can mimic these patterns to deceive, attract, and eat the males.

The biochemical reaction by which fireflies produce light occurs inside a specialized organ in their lower abdomen. This light-emitting organ utilizes the molecule luciferin, which is responsible for the production of visible light. In the presence of oxygen, magnesium ions, and the energy-rich molecule adenosine triphosphate (ATP), the enzyme luciferase converts luciferin into oxyluciferin, which emits light due to being in an electronically excited state. Upon emitting light, oxyluciferin is recycled and reconverted to luciferin so the process may continue. As with any biochemical process, the rate and capacity for bioluminescence in fireflies is dictated by the concentration of inputs as well as the rate at which byproducts are recycled. Scientists still do not fully understand how fireflies are able to produce bioluminescence with upwards of 80-90% energy efficiency. In comparison, the average incandescent light bulbs and LED lights emit only about 10% and 20% of their total electrical energy input as light, respectively. Since the first law of thermodynamics states that the total energy of the universe is constant and energy can neither be created nor destroyed, heat is the major byproduct in the reactions mentioned above.

To further study the interaction of firefly luciferase with its substrate, a student designs an experiment testing the rate at which the molecules involved are recycled. The student gathers 100 fireflies and separates them randomly into five equal experimental groups. Group A is not given any treatment and each subsequent group of fireflies is administered increasing concentrations of luciferin. Each group of fireflies is then released into separate pitch-black rooms that mimic the fireflies’ natural habitat. These rooms also contain light meters that measure the intensity of light emitted by the group of 20 fireflies as a whole. The results of this experiment are shown in Table 1.

Table 1

The scientists who conducted the aforementioned experiment decided to add another group of 20 fireflies, Group F, which was administered 0.25 mmol luciferase. Which of the following would be the expected luminosity of this new group?

Adapted from The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom by Charles Darwin (1876)

As it is impossible to exclude such minute pollen-carrying insects as Thrips, flowers which it was intended to fertilise with their own pollen may sometimes have been afterwards crossed with pollen brought by these insects from another flower on the same plant; but as we shall hereafter see, a cross of this kind does not produce any effect, or at most only a slight one. When two or more plants were placed near one another under the same net, as was often done, there is some real though not great danger of the flowers which were believed to be self-fertilised being afterwards crossed with pollen brought by Thrips from a distinct plant. I have said that the danger is not great because I have often found that plants which are self-sterile, unless aided by insects, remained sterile when several plants of the same species were placed under the same net. If, however, the flowers which had been presumably self-fertilised by me were in any case afterwards crossed by Thrips with pollen brought from a distinct plant, crossed seedlings would have been included amongst the self-fertilised; but it should be especially observed that this occurrence would tend to diminish and not to increase any superiority in average height, fertility, etc., of the crossed over the self-fertilised plants.

As the flowers which were crossed were never castrated, it is probable or even almost certain that I sometimes failed to cross-fertilise them effectually, and that they were afterwards spontaneously self-fertilised. This would have been most likely to occur with dichogamous species, for without much care it is not easy to perceive whether their stigmas are ready to be fertilised when the anthers open. But in all cases, as the flowers were protected from wind, rain, and the access of insects, any pollen placed by me on the stigmatic surface whilst it was immature, would generally have remained there until the stigma was mature; and the flowers would then have been crossed as was intended. Nevertheless, it is highly probable that self-fertilised seedlings have sometimes by this means got included amongst the crossed seedlings. The effect would be, as in the former case, not to exaggerate but to diminish any average superiority of the crossed over the self-fertilised plants.

Errors arising from the two causes just named, and from others,—such as some of the seeds not having been thoroughly ripened, though care was taken to avoid this error—the sickness or unperceived injury of any of the plants,—will have been to a large extent eliminated, in those cases in which many crossed and self-fertilised plants were measured and an average struck. Some of these causes of error will also have been eliminated by the seeds having been allowed to germinate on bare damp sand, and being planted in pairs; for it is not likely that ill-matured and well-matured, or diseased and healthy seeds, would germinate at exactly the same time. The same result will have been gained in the several cases in which only a few of the tallest, finest, and healthiest plants on each side of the pots were measured.

Kolreuter and Gartner have proved that with some plants several, even as many as from fifty to sixty, pollen-grains are necessary for the fertilisation of all the ovules in the ovarium. Naudin also found in the case of Mirabilis that if only one or two of its very large pollen-grains were placed on the stigma, the plants raised from such seeds were dwarfed. I was therefore careful to give an amply sufficient supply of pollen, and generally covered the stigma with it; but I did not take any special pains to place exactly the same amount on the stigmas of the self-fertilised and crossed flowers. After having acted in this manner during two seasons, I remembered that Gartner thought, though without any direct evidence, that an excess of pollen was perhaps injurious. It was therefore necessary to ascertain whether the fertility of the flowers was affected by applying a rather small and an extremely large quantity of pollen to the stigma. Accordingly a very small mass of pollen-grains was placed on one side of the large stigma in sixty-four flowers of Ipomoea purpurea, and a great mass of pollen over the whole surface of the stigma in sixty-four other flowers. In order to vary the experiment, half the flowers of both lots were on plants produced from self-fertilised seeds, and the other half on plants from crossed seeds. The sixty-four flowers with an excess of pollen yielded sixty-one capsules; and excluding four capsules, each of which contained only a single poor seed, the remainder contained on an average 5.07 seeds per capsule. The sixty-four flowers with only a little pollen placed on one side of the stigma yielded sixty-three capsules, and excluding one from the same cause as before, the remainder contained on an average 5.129 seeds. So that the flowers fertilised with little pollen yielded rather more capsules and seeds than did those fertilised with an excess; but the difference is too slight to be of any significance. On the other hand, the seeds produced by the flowers with an excess of pollen were a little heavier of the two; for 170 of them weighed 79.67 grains, whilst 170 seeds from the flowers with very little pollen weighed 79.20 grains. Both lots of seeds having been placed on damp sand presented no difference in their rate of germination. We may therefore conclude that my experiments were not affected by any slight difference in the amount of pollen used; a sufficiency having been employed in all cases.

The word "dichogamous", as used in the second paragraph, most nearly means

Passage adapted from The Confidence-Man: His Masquerade by Herman Melville (1857)

At sunrise on a first of April, there appeared suddenly a man in cream-colors at the water-side in the city of St. Louis.

His cheek was fair, his chin downy, his hair flaxen, his hat a white fur one, with a long fleecy nap. He had neither trunk, valise, carpet-bag, nor parcel. No porter followed him. He was unaccompanied by friends. From the shrugged shoulders, titters, whispers, wonderings of the crowd, it was plain that he was, in the extremest sense of the word, a stranger.

In the same moment with his advent, he stepped aboard the favorite steamer Fidèle, on the point of starting for New Orleans. Stared at, but unsaluted, with the air of one neither courting nor shunning regard, but evenly pursuing the path of duty, lead it through solitudes or cities, he held on his way along the lower deck until he chanced to come to a placard nigh the captain's office, offering a reward for the capture of a mysterious impostor, supposed to have recently arrived from the East; quite an original genius in his vocation, as would appear, though wherein his originality consisted was not clearly given; but what purported to be a careful description of his person followed.

As if it had been a theatre-bill, crowds were gathered about the announcement, and among them certain chevaliers, whose eyes, it was plain, were on the capitals, or, at least, earnestly seeking sight of them from behind intervening coats; but as for their fingers, they were enveloped in some myth; though, during a chance interval, one of these chevaliers somewhat showed his hand in purchasing from another chevalier, ex-officio a peddler of money-belts, one of his popular safe-guards, while another peddler, who was still another versatile chevalier, hawked, in the thick of the throng, the lives of Measan, the bandit of Ohio, Murrel, the pirate of the Mississippi, and the brothers Harpe, the Thugs of the Green River country, in Kentucky—creatures, with others of the sort, one and all exterminated at the time, and for the most part, like the hunted generations of wolves in the same regions, leaving comparatively few successors; which would seem cause for unalloyed gratulation, and is such to all except those who think that in new countries, where the wolves are killed off, the foxes increase.

Pausing at this spot, the stranger so far succeeded in threading his way, as at last to plant himself just beside the placard, when, producing a small slate and tracing some words upon it, he held it up before him on a level with the placard, so that they who read the one might read the other. The words were these:—

"Charity thinketh no evil.”

What is the best evidence of the narrator's tone, as assessed in the preceding question?

Passage adapted from The Confidence-Man: His Masquerade by Herman Melville (1857)

At sunrise on a first of April, there appeared suddenly a man in cream-colors at the water-side in the city of St. Louis.

His cheek was fair, his chin downy, his hair flaxen, his hat a white fur one, with a long fleecy nap. He had neither trunk, valise, carpet-bag, nor parcel. No porter followed him. He was unaccompanied by friends. From the shrugged shoulders, titters, whispers, wonderings of the crowd, it was plain that he was, in the extremest sense of the word, a stranger.

In the same moment with his advent, he stepped aboard the favorite steamer Fidèle, on the point of starting for New Orleans. Stared at, but unsaluted, with the air of one neither courting nor shunning regard, but evenly pursuing the path of duty, lead it through solitudes or cities, he held on his way along the lower deck until he chanced to come to a placard nigh the captain's office, offering a reward for the capture of a mysterious impostor, supposed to have recently arrived from the East; quite an original genius in his vocation, as would appear, though wherein his originality consisted was not clearly given; but what purported to be a careful description of his person followed.

As if it had been a theatre-bill, crowds were gathered about the announcement, and among them certain chevaliers, whose eyes, it was plain, were on the capitals, or, at least, earnestly seeking sight of them from behind intervening coats; but as for their fingers, they were enveloped in some myth; though, during a chance interval, one of these chevaliers somewhat showed his hand in purchasing from another chevalier, ex-officio a peddler of money-belts, one of his popular safe-guards, while another peddler, who was still another versatile chevalier, hawked, in the thick of the throng, the lives of Measan, the bandit of Ohio, Murrel, the pirate of the Mississippi, and the brothers Harpe, the Thugs of the Green River country, in Kentucky—creatures, with others of the sort, one and all exterminated at the time, and for the most part, like the hunted generations of wolves in the same regions, leaving comparatively few successors; which would seem cause for unalloyed gratulation, and is such to all except those who think that in new countries, where the wolves are killed off, the foxes increase.

Pausing at this spot, the stranger so far succeeded in threading his way, as at last to plant himself just beside the placard, when, producing a small slate and tracing some words upon it, he held it up before him on a level with the placard, so that they who read the one might read the other. The words were these:—

"Charity thinketh no evil.”

Based on the way it is used in the passage, which of the following is the meaning of the underlined phrase “ex-officio” in the third paragraph?

Passage adapted from The Confidence-Man: His Masquerade by Herman Melville (1857)

At sunrise on a first of April, there appeared suddenly a man in cream-colors at the water-side in the city of St. Louis.

His cheek was fair, his chin downy, his hair flaxen, his hat a white fur one, with a long fleecy nap. He had neither trunk, valise, carpet-bag, nor parcel. No porter followed him. He was unaccompanied by friends. From the shrugged shoulders, titters, whispers, wonderings of the crowd, it was plain that he was, in the extremest sense of the word, a stranger.

In the same moment with his advent, he stepped aboard the favorite steamer Fidèle, on the point of starting for New Orleans. Stared at, but unsaluted, with the air of one neither courting nor shunning regard, but evenly pursuing the path of duty, lead it through solitudes or cities, he held on his way along the lower deck until he chanced to come to a placard nigh the captain's office, offering a reward for the capture of a mysterious impostor, supposed to have recently arrived from the East; quite an original genius in his vocation, as would appear, though wherein his originality consisted was not clearly given; but what purported to be a careful description of his person followed.

As if it had been a theatre-bill, crowds were gathered about the announcement, and among them certain chevaliers, whose eyes, it was plain, were on the capitals, or, at least, earnestly seeking sight of them from behind intervening coats; but as for their fingers, they were enveloped in some myth; though, during a chance interval, one of these chevaliers somewhat showed his hand in purchasing from another chevalier, ex-officio a peddler of money-belts, one of his popular safe-guards, while another peddler, who was still another versatile chevalier, hawked, in the thick of the throng, the lives of Measan, the bandit of Ohio, Murrel, the pirate of the Mississippi, and the brothers Harpe, the Thugs of the Green River country, in Kentucky—creatures, with others of the sort, one and all exterminated at the time, and for the most part, like the hunted generations of wolves in the same regions, leaving comparatively few successors; which would seem cause for unalloyed gratulation, and is such to all except those who think that in new countries, where the wolves are killed off, the foxes increase.

Pausing at this spot, the stranger so far succeeded in threading his way, as at last to plant himself just beside the placard, when, producing a small slate and tracing some words upon it, he held it up before him on a level with the placard, so that they who read the one might read the other. The words were these:—

"Charity thinketh no evil.”

What is the purpose of the underlined sentence?

Passage adapted from The Confidence-Man: His Masquerade by Herman Melville (1857)

At sunrise on a first of April, there appeared suddenly a man in cream-colors at the water-side in the city of St. Louis.

His cheek was fair, his chin downy, his hair flaxen, his hat a white fur one, with a long fleecy nap. He had neither trunk, valise, carpet-bag, nor parcel. No porter followed him. He was unaccompanied by friends. From the shrugged shoulders, titters, whispers, wonderings of the crowd, it was plain that he was, in the extremest sense of the word, a stranger.

In the same moment with his advent, he stepped aboard the favorite steamer Fidèle, on the point of starting for New Orleans. Stared at, but unsaluted, with the air of one neither courting nor shunning regard, but evenly pursuing the path of duty, lead it through solitudes or cities, he held on his way along the lower deck until he chanced to come to a placard nigh the captain's office, offering a reward for the capture of a mysterious impostor, supposed to have recently arrived from the East; quite an original genius in his vocation, as would appear, though wherein his originality consisted was not clearly given; but what purported to be a careful description of his person followed.

As if it had been a theatre-bill, crowds were gathered about the announcement, and among them certain chevaliers, whose eyes, it was plain, were on the capitals, or, at least, earnestly seeking sight of them from behind intervening coats; but as for their fingers, they were enveloped in some myth; though, during a chance interval, one of these chevaliers somewhat showed his hand in purchasing from another chevalier, ex-officio a peddler of money-belts, one of his popular safe-guards, while another peddler, who was still another versatile chevalier, hawked, in the thick of the throng, the lives of Measan, the bandit of Ohio, Murrel, the pirate of the Mississippi, and the brothers Harpe, the Thugs of the Green River country, in Kentucky—creatures, with others of the sort, one and all exterminated at the time, and for the most part, like the hunted generations of wolves in the same regions, leaving comparatively few successors; which would seem cause for unalloyed gratulation, and is such to all except those who think that in new countries, where the wolves are killed off, the foxes increase.

Pausing at this spot, the stranger so far succeeded in threading his way, as at last to plant himself just beside the placard, when, producing a small slate and tracing some words upon it, he held it up before him on a level with the placard, so that they who read the one might read the other. The words were these:—

"Charity thinketh no evil.”

The steamship in the passage is traveling from __________ to __________.

Gentrification is a social phenomenon that is characterized by community developments that, at times, displace lower income residents and small businesses. This process is often characterized by urban renewal or urban planning projects that are initiated by increased interest in a particular community. For example, low-income artisans such as artists and musicians may move into a lower income urban sector and utilize their talents to enhance its aesthetics. These early gentrifiers increase the community’s appearance and desirability, which attracts the attention of others who wish to further develop the area. Once urban development begins, it is common for these areas to experience an influx in wealthier inhabitants, which are often accompanied by upper-class business enterprises and increased property values. Once the gentrification process has reached this point, some of the earlier inhabitants or locals of the area may not be able to afford the increased cost of living in the community. This may result in population migration out of the community. As a result, the area’s social demographics change, which may be accompanied by conflict and controversy between immigrating and emigrating groups. A case study in Chicago’s Hyde Park will help to illustrate this process.

In the wake of WWII, labor-hungry war industries coupled with white out-migration (“white flight”) from Chicago’s inner city to the suburbs resulted in a dramatic shift in the city’s racial demographics between the years 1920 to 1950. In the early 1900s, the migration of southern blacks to Chicago’s south side south of 55^th Street created what became known as the Black Belt. This shift in racial demographics resulted in an increase of Chicago’s black population, from only 4 percent of the city’s population in 1920 to 23 percent in 1960. 

In the early 1950’s, the traditional Cottage Grove Avenue barrier that separated the Hyde Park-Kenwood area from the Black Belt was traversed by further black migrations, which resulted—in part—from the demolition of the nearby Lake Meadows Housing Development. The University of Chicago used political power to revitalize neighborhood areas that had deteriorated due to the construction of low-income housing developments nearby. Specifically, they sought to keep public housing out of the neighborhoods surrounding the University. The creation of the citizen-oriented Hyde Park-Kenwood Community Conference (HPKCC) in 1949 and the University of Chicago’s establishment of the Southeast Chicago Commission (SECC) in 1952 resulted in the implementation of a plan disguised as urban renewal, which attempted to slow the racial transformation of the area. In 1958, the Chicago City Council approved the Hyde Park-Kenwood Renewal Plan that racially segregated the area. The University sought to maintain a compatible environment for its operations and to preserve the racial homogeneity of the community; thus, the University, through the SECC, attempted to create an economically upgraded and predominantly white neighborhood. In other words, if the racial composition of the area could not be maintained, then upgraded class and socioeconomic statuses could prevent demographic changes by making it unaffordable to lower income groups. It is important to note that this contention and “renewal” of Hyde Park’s racial structure was not contained within this time span between the post war period and the Civil Rights Era in the 1960s. The 1970s brought similar racial strife and tension to Hyde Park in the wake of gentrifying forces.

A group of researchers observed gentrification in the Chicago suburbs. These researchers paid close attention to neighborhoods that were described as “up and coming.” They decided to use census data to look at two factors in these regions: population and median home values between the years of 2010 and 2015. The researchers planned to observe the changes contained in four census tracts: 8412, 6706, 6715, and 7107. The researchers hypothesized that they would observe population out-migrations and increased property values in areas that have been gentrified. The results of this data were tabulated in the following two figures.

Figure 1: Changes in population of observed census tracts between 2000 and 2015.

Figure 2: Changes in median home value of observed census tracts between 2000 and 2015.

Early in the nineteenth century, scientists sought to understand the differences in the earth’s flora and fauna from their archeological ancestors. The prevailing view at the time was that the differences between current and previous species were unremarkable deviations from their Platonic ideal forms. This theory hinged upon the ideals of the religious-based “created kinds” theory, which stated that individuals of today are the direct descendants of the organisms that were present at the earth’s creation. They were the result of an intelligent designer and have remained relatively unchanged from their conception. Proponents of the created kinds theory believed that unseen geological and astrological forces slowly altered organisms throughout time; furthermore, they postulated that these minor alterations could explain the differences between organisms—past and present. Other scientists of the same period and similar mindset theorized that organisms had the ability to change within their lifetimes and pass on traits to their offspring efficiently and quickly through a single generation (i.e. rapid evolution).

Charles Darwin and other biologists, such as Alfred Wallace, were not greatly influenced by these views and hypotheses. Their propositions stated that species evolve over many generations, due to the selective pressures of their given environments. This evolution could result in the generation of divergent traits, as well as speciation and separation from the original ancestral species. The concept that organisms were not finite or present since creation was very controversial to the scientists of the period. Opponents of Darwin’s theorizations saw such an idea as unsupportable, while others perceived this novel concept as heretical and fanatical.

Darwin set out to find support for his theory. This evidentiary quest led to the collection of data and observations that formed Darwin’s most notable work: On the Origins of Species by Means of Natural Selection. Darwin’s theory was influenced by archeological discoveries of species, which appeared to have vastly different physiological appearances from present-day organisms. This discovery led Darwin to decide to sail around the world on a Royal Navy ship named the H.M.S. Beagle. During his travels, he was taken to the Pacific islands of the Galapagos archipelago. The volcanic islands followed a patterned distribution on either side of the Equator. The landscapes of each island varied, with vastly different observable flora and fauna.

Through scientific observations, Darwin noticed subtle variations of finches on different islands. Finches are a type of passerine. Almost half of all bird species can be described as passerines. Among other characteristics, the most notable feature of passerines is the structure of their feet: three toes face forward and one toe faces back, which enables improved perching abilities. Darwin noticed that some Galapagos finches had large hard beaks, while others had slender beaks. He hypothesized that the beaks were differentiated from island to island. After careful study, Darwin noticed that the beaks seemed to match the food source on each island. The large beaks were specialized for breaking open hard-shelled nuts, while the slender beaks were specialized for eating certain fruits that were abundant. Darwin hypothesized that an ancestral species of finch landed on the islands, and over generations they became adapted to the locally abundant food sources. In this way, Darwin believed that particular beak size was a trait that was selected for by particular environments. In other words, finches with beaks best suited for foraging of nutrients were able to survive and pass on their genetics and subsequent traits (i.e. beak size); however, those without these particular traits suffered from an evolutionary disadvantage and were likely to die off before engaging in a successful reproductive event and produce offspring. These observations formed the basis of Darwin's theory of natural selection.

Over time, Darwin compiled multiple instances of natural selection and incorporated discoveries made by archeologists and physiologists. He surmised that species evolve over time due to the selective pressures of their respective habitats. These events occur slowly over many generations. Each species selects for advantageous traits among its members. Over time, traits selected as advantageous by environmental pressures and stressors become commonplace in the species. This niche-forming process specializes species by rewarding those with traits most suitable for reproductive success. These traits may progress into speciation of the original species, which results in the eventual development of an entirely new species. Darwin’s theory was met with opposition at the time of its publication, and the theory of evolution remains a controversial topic in several arenas of debate.

Which of the following best describes the purpose of the underlined paragraph?