SAT Critical Reading : Passage-Based Questions

Study concepts, example questions & explanations for SAT Critical Reading

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Example Questions

Example Question #1 : Interpreting Literary Devices

Adapted from “Introduced Species That Have Become Pests” in Our Vanishing Wild Life, Its Extermination and Protection by William Temple Hornaday (1913)

The man who successfully transplants or "introduces" into a new habitat any persistent species of living thing assumes a very grave responsibility. Every introduced species is doubtful gravel until panned out. The enormous losses that have been inflicted upon the world through the perpetuation of follies with wild vertebrates and insects would, if added together, be enough to purchase a principality. The most aggravating feature of these follies in transplantation is that never yet have they been made severely punishable. We are just as careless and easygoing on this point as we were about the government of the Yellowstone Park in the days when Howell and other poachers destroyed our first national bison herd, and when caught red-handed—as Howell was, skinning seven Park bison cows—could not be punished for it, because there was no penalty prescribed by any law. Today, there is a way in which any revengeful person could inflict enormous damage on the entire South, at no cost to himself, involve those states in enormous losses and the expenditure of vast sums of money, yet go absolutely unpunished!

The gypsy moth is a case in point. This winged calamity was imported at Maiden, Massachusetts, near Boston, by a French entomologist, Mr. Leopold Trouvelot, in 1868 or 69. History records the fact that the man of science did not purposely set free the pest. He was endeavoring with live specimens to find a moth that would produce a cocoon of commercial value to America, and a sudden gust of wind blew out of his study, through an open window, his living and breeding specimens of the gypsy moth. The moth itself is not bad to look at, but its larvae is a great, overgrown brute with an appetite like a hog. Immediately Mr. Trouvelot sought to recover his specimens, and when he failed to find them all, like a man of real honor, he notified the State authorities of the accident. Every effort was made to recover all the specimens, but enough escaped to produce progeny that soon became a scourge to the trees of Massachusetts. The method of the big, nasty-looking mottled-brown caterpillar was very simple. It devoured the entire foliage of every tree that grew in its sphere of influence.

The gypsy moth spread with alarming rapidity and persistence. In course of time, the state authorities of Massachusetts were forced to begin a relentless war upon it, by poisonous sprays and by fire. It was awful! Up to this date (1912) the New England states and the United States Government service have expended in fighting this pest about $7,680,000!

The spread of this pest has been retarded, but the gypsy moth never will be wholly stamped out. Today it exists in Rhode Island, Connecticut, and New Hampshire, and it is due to reach New York at an early date. It is steadily spreading in three directions from Boston, its original point of departure, and when it strikes the State of New York, we, too, will begin to pay dearly for the Trouvelot experiment.

Which of the following best paraphrases the underlined sentence, “Every introduced species is doubtful gravel until panned out”?

Possible Answers:

An invasive species can cause beneficial effects to its new environment as well as harmful ones.

One should never move a species from its natural environment into a new environment for fear of the consequences.

Species that live underground should be carefully examined before being moved into new environments.

Species that live in gravel are usually harmful when placed in new environments.

One can’t tell whether an introduced species will be helpful or harmful until it is actually introduced.

Correct answer:

One can’t tell whether an introduced species will be helpful or harmful until it is actually introduced.

Explanation:

Here, the author is using figurative language to describe introduced species. He metaphorically calls them “doubtful gravel until [they are] panned out.” Because he’s not speaking literally, this sentence has nothing to do with the ground or gravel itself, so we can eliminate the answer choices “Species that live underground should be carefully examined before being moved into new environments” and “Species that live in gravel are usually harmful when placed in new environments.”

What is the author getting at with his metaphor? Panning rocks and dirt allows miners to separate out valuable minerals from other matter. Think of miners “panning for gold”—it’s the same principle, except here, the author is speaking of it as applying to gravel. By calling the gravel “doubtful,” the author is expressing that you don’t know what you’re going to get with it before you “pan it out” and see if there is anything valuable in it. Applying this thinking to invasive species, the author is therefore saying that “one can’t tell whether an introduced species will be helpful or harmful until it is actually introduced.” 

If you didn’t know what panning gravel was, you could still solve this question by narrowing down your answer choices. For instance, nowhere in the passage are the beneficial effects of introduced species discussed, though the author discusses this in a previous chapter of his book. Because they’re not mentioned in the passage, we can discard the answer choice “An invasive species can cause beneficial effects to its new environment as well as harmful ones.” This is definitely not what the indicated sentence is saying; if we replaced the sentence with this answer choice, the logic of the paragraph wouldn’t make any sense.

As for the remaining answer choice, “One should never move a species from its natural environment into a new environment for fear of the consequences,” it cannot be correct because in the sentence before the one on which this question focuses, the author writes, “The man who successfully transplants or ‘introduces' into a new habitat any persistent species of living thing assumes a very grave responsibility.” Note that he doesn’t say that this should never be done; he just implies that it could go very badly. It wouldn’t make much sense if in the next sentence, the author said this should never be done. It seems more logical that he would have led with that statement, it being the stronger of the two.

Example Question #51 : Natural Science Passages

"The Place of Lesion Studies in Neuroscience" by Samantha Winter (2013)

It’s easy to forget that the study of neuroscience originated from non-normalized, non-statistically appraised methods like lesion studies. It’s equally easy, with the advent of sophisticated technology, to render such a method obsolete. A small group of neuroscientists today make a case for the reinstitution of lesion studies—the study of abnormal brains with damaged regions in order to better understand the brain—into the twenty-first-century cognitive neuroscience realm. Their suggestion is bold, but their argument is justified.

Cognitive neuroscientists advocate for the use of convergent methods. Many of them argue that with the limitations of our existing techniques, convergent evidence is imperative for sound research. If this is the case, why ignore a method that has potential for implying causality in a domain dominated by correlational research? Rather than advocating for a single method, neuroscientists should take their own advice and use convergent techniques. Sound research should combine a variety of techniques to examine both causal relationships and overcome the individual shortcomings of each method through the use of many.

Lesion studies are also significantly more beneficial now than they were in earlier times. Neuroimaging methods have enhanced our understanding of what contributes to the brain problems most often encountered, and more refined experiments have been developed to confirm the findings from the more unreliable lesion studies. This transformation allows lesion studies to be included alongside the other systems as a mechanism for understanding the human brain.

The underlined selection "to render such a method obsolete" most closely means __________.

Possible Answers:

to make lesion studies more important

to question the existence of lesion studies

to make neuroscience the most important field of science

to consider lesion studies outdated

to redesign lesion studies

Correct answer:

to consider lesion studies outdated

Explanation:

The answer is obsolete, because it means outdated or archaic, and the word “method” refers back to the prior sentence, “methods like lesion studies,” thus stating that the some consider these lesion studies outdated. Because of the meaning of the word obsolete, "to make lesion studies more important" is incorrect. This statement does not refer to the field of neuroscience, therefore "to make neuroscience the most important field of science" is incorrect, and there is no consideration in the paper (and certainly not in the first few sentences) that lesions do not exist, just how valuable they are to the field of study – therefore "to question the existence of lesion studies" is incorrect.

Example Question #51 : Science Passages

Adapted from Volume Four of The Natural History of Animals: The Animal Life of the World in Its Various Aspects and Relations by James Richard Ainsworth Davis (1903)

The examples of protective resemblance so far quoted are mostly permanent adaptations to one particular sort of surrounding. There are, however, numerous animals which possess the power of adjusting their color more or less rapidly so as to harmonize with a changing environment.

Some of the best known of these cases are found among those mammals and birds that inhabit countries more or less covered with snow during a part of the year. A good instance is afforded by the Irish or variable hare, which is chiefly found in Ireland and Scotland. In summer, this looks very much like an ordinary hare, though rather grayer in tint and smaller in size, but in winter it becomes white with the exception of the black tips to the ears. Investigations that have been made on the closely allied American hare seem to show that the phenomenon is due to the growth of new hairs of white hue. 

The common stoat is subject to similar color change in the northern parts of its range. In summer it is of a bright reddish brown color with the exception of the under parts, which are yellowish white, and the end of the tail, which is black. But in winter, the entire coat, save only the tip of the tail, becomes white, and in that condition the animal is known as an ermine. A similar example is afforded by the weasel. The seasonal change in the vegetarian Irish hare is purely of protective character, but in such an actively carnivorous creature as a stoat or weasel, it is aggressive as well, rendering the animal inconspicuous to its prey.

The phrase “harmonize with,” underlined in the first paragraph, most closely means __________.

Possible Answers:

systematize

conduct

sing in harmony with

match

parallel

Correct answer:

match

Explanation:

The phrase “harmonize with” appears in this sentence in the first paragraph: “There are, however, numerous animals which possess the power of adjusting their color more or less rapidly so as to harmonize with a changing environment.” While “harmonize with” can mean “sing in harmony with,” this meaning doesn’t make sense in the context of the passage’s sentence. “Parallel,” “systematize,” and “conduct” don’t make sense either—only “match” makes sense, so it is the correct answer.

Example Question #51 : Language In Natural Science Passages

Adapted from “In Mammoth Cave” by John Burroughs (1894)

Some idea of the impression which Mammoth Cave makes upon the senses, irrespective even of sight, may be had from the fact that blind people go there to see it, and are greatly struck with it. I was assured that this is a fact. The blind seem as much impressed by it as those who have their sight. When the guide pauses at a more interesting point, or lights the scene up with a great torch or with small flares, and points out the more striking features, the blind exclaim, "How wonderful! How beautiful!" They can feel it, if they cannot see it. They get some idea of the spaciousness when words are uttered. The voice goes forth in these colossal chambers like a bird. When no word is spoken, the silence is of a kind never experienced on the surface of the earth, it is so profound and abysmal. This, and the absolute darkness, to a sighted person makes him feel as if he were face to face with the primordial nothingness. The objective universe is gone; only the subjective remains; the sense of hearing is inverted, and reports only the murmurs from within. The blind miss much, but much remains to them. The great cave is not merely a spectacle to the eye; it is a wonder to the ear, a strangeness to the smell and to the touch. The body feels the presence of unusual conditions through every pore.

In context, the reference to sound going forth in the “colossal chambers like a bird” conveys a sense of __________.

Possible Answers:

grandeur 

dimness

audacity 

mediocrity

empathy

Correct answer:

grandeur 

Explanation:

The author states that in the Mammoth Cave, “The voice goes forth in these colossal chambers like a bird.” This description highlights the imposing and awesome size of the cave, or in other words, its "grandeur" (impressiveness). "Dimness" doesn't make any sense as an answer choice because while the cave is dark, the sentence in question isn't highlighting that aspect of it. The statement doesn't convey a sense of "mediocrity" (averageness when greater results were expected) either, and "audacity" (gall) and "empathy" (the ability to connect with others on an emotional level) don't relate at all to the statement either.

Example Question #241 : Natural Sciences

Adapted from The Evolutionist at Large by Grant Allen (1881)

I am engaged in watching a brigade of ants out on foraging duty, and intent on securing for the nest three whole segments of a deceased earthworm. They look for all the world like those busy companies one sees in the Egyptian wall paintings, dragging home a huge granite colossus by sheer force of bone and sinew. Every muscle in their tiny bodies is strained to the utmost as they pry themselves laboriously against the great boulders that strew the path, and that are known to our Brobdingnagian intelligence as grains of sand. Besides the workers themselves, a whole battalion of stragglers runs to and fro upon the broad line that leads to the headquarters of the community. The province of these stragglers, who seem so busy doing nothing, probably consists in keeping communications open, and encouraging the sturdy pullers by occasional relays of fresh workmen. I often wish that I could for a while get inside those tiny brains, and see, or rather smell, the world as ants do. For there can be little doubt that to these brave little carnivores here the universe is chiefly known as a collective bundle of odors, simultaneous or consecutive. As our world is mainly a world of visible objects, theirs, I believe, is mainly a world of olfactible things.

In the head of every one of these little creatures is something that we may fairly call a brain. Of course most insects have no real brains; the nerve-substance in their heads is a mere collection of ill-arranged ganglia, directly connected with their organs of sense. Whatever man may be, an earwig at least is a conscious, or rather a semi-conscious, automaton. He has just a few knots of nerve cells in his little pate, each of which leads straight from his dim eye or his vague ear or his indefinite organs of taste; and his muscles obey the promptings of external sensations without possibility of hesitation or consideration, as mechanically as the valve of a steam engine obeys the governor balls. The poor soul's intellect is wholly deficient, and the senses alone make up all that there is of him, subjectively considered. But it is not so with the highest insects. They have something that truly answers to the real brain of men, apes, and dogs, to the cerebral hemispheres and the cerebellum that are superadded in us mammals upon the simple sense-centers of lower creatures. Besides the eye, with its optic nerve and optic perceptive organs—besides the ear, with its similar mechanism—we mammalian lords of creation have a higher and more genuine brain, that collects and compares the information given to the senses, and sends down the appropriate messages to the muscles accordingly. Now, bees and flies and ants have got much the same sort of arrangement, on a smaller scale, within their tiny heads. On top of the little knots that do duty as nerve centers for their eyes and mouths, stand two stalked bits of nervous matter, whose duty is analogous to that of our own brains. And that is why these three sorts of insects think and reason so much more intellectually than beetles or butterflies, and why the larger part of them have organized their domestic arrangements on such an excellent cooperative plan.

We know well enough what forms the main material of thought with bees and flies, and that is visible objects. For you must think about something if you think at all; and you can hardly imagine a contemplative blow-fly setting itself down to reflect, like a Hindu devotee, on the syllable Om, or on the oneness of existence. Abstract ideas are not likely to play a large part in apian consciousness. A bee has a very perfect eye, and with this eye it can see not only form, but also color, as Sir John Lubbock's experiments have shown us. The information that it gets through its eye, coupled with other ideas derived from touch, smell, and taste, no doubt makes up the main thinkable and knowable universe as it reveals itself to the apian intelligence. To ourselves and to bees alike the world is, on the whole, a colored picture, with the notions of distance and solidity thrown in by touch and muscular effort; but sight undoubtedly plays the first part in forming our total conception of things generally.

In the first paragraph, the information about Egyptian wall paintings serves to __________.

Possible Answers:

show the reader that the author is in a desert environment

show that ants have been around for aeons

show that the ants are like slaves

show the reader the author's superior historical knowledge

show that the ants are undertaking a proportionally great task

Correct answer:

show that the ants are undertaking a proportionally great task

Explanation:

The author is comparing the ants' struggle with the earthworm to the movement of monuments, by slaves, in Egyptian wall paintings. The purpose of this is to emphasise how the ants are undertaking a great task proportionally. “Every muscle in their tiny bodies is strained to the utmost as they pry themselves laboriously.”

Example Question #51 : Passage Based Questions

Adapted from Ice-Caves of France and Switzerland by George Forrest Browne (1865)

This account states that the cave is in the county of Thorn, among the lowest spurs of the Carpathians. The entrance, which faces the north, and is exposed to the cold winds from the snowy part of the Carpathian range, is eighteen fathoms high and nine broad; and the cave spreads out laterally, and descends to a point fifty fathoms below the entrance, where it is twenty-six fathoms in breadth, and of irregular height. Beyond this no one had at that time penetrated, on account of the unsafe footing, although many distant echoes were returned by the farther recesses of the cave; indeed, to get even so far as this, much step-cutting was necessary.

When the external frost of winter comes on, the account proceeds, the effect in the cave is the same as if fires had been lighted there: the ice melts, and swarms of flies and bats and hares take refuge in the interior from the severity of the winter. As soon as spring arrives, the warmth of winter disappears from the interior, water exudes from the roof and is converted into ice, while the more abundant supplies which pour down on to the sandy floor are speedily frozen there. In the dog-days, the frost is so intense that a small icicle becomes in one day a huge mass of ice; but a cool day promptly brings a thaw, and the cave is looked upon as a barometer, not merely feeling, but also presaging, the changes of weather. The people of the neighborhood, when employed in field-work, arrange their labour so that the mid-day meal may be taken near the cave, when they either ice the water they have brought with them, or drink the melted ice, which they consider very good for the stomach. It had been calculated that six hundred weekly carts would not be sufficient to keep the cavern free from ice. The ground above the cave is peculiarly rich in grass.

In explanation of these phenomena, Bell threw out the following suggestions, which need no comment. The earth being of itself cold and damp, the external heat of the atmosphere, by partially penetrating into the ground, drives in this native cold to the inner parts of the earth, and makes the cold there more dense. On the other hand, when the external air is cold, it draws forth towards the surface the heat there may be in the inner part of the earth, and thus makes caverns warm. In support and illustration of this view, he states that in the hotter parts of Hungary, when the people wish to cool their wine, they dig a hole two feet deep, and place in it the flagon of wine, and, after filling up the hole again, light a blazing fire upon the surface, which cools the wine as if the flagon had been laid in ice. He also suggests that possibly the cold winds from the Carpathians bring with them imperceptible particles of snow, which reach the water of the cave, and convert it into ice. Further, the rocks of the Carpathians abound in salts, niter, alum, etc., which may, perhaps, mingle with such snowy particles, and produce the ordinary effect of the snow and salt in the artificial production of ice.

In the third paragraph, the information about Bell's hypothesis serves to __________.

Possible Answers:

discredit Bell

explain the phenomenon described in the second paragraph

demonstrate the exponential growth of ice in the cave

demonstrate the habits of the inhabitants of different European nations

vilify the author

Correct answer:

explain the phenomenon described in the second paragraph

Explanation:

The third paragraph is a justification and explanation of the seemingly contradictory phenomenon of the second paragraph. The author is describing how the ice cave is able to retain its cold temperature in summer, as is mentioned in the second paragraph.

Example Question #1 : Identifying And Analyzing Supporting Ideas In Science Passages

Adapted from “Birds in Retreat” in “Animal Defences—Active Defence” in Volume Four of The Natural History of Animals: The Animal Life of the World in Its Various Aspects and Relations by James Richard Ainsworth Davis (1903)

Among the large running birds are forms, like the African ostrich, in which the absence of powers of flight is largely compensated by the specialization of the legs for the purpose of rapid movement on the ground. For straightforward retreat in open country nothing could be more effective; but another kind of adaptation is required in birds like rails, which are deficient in powers of flight, and yet are able to run through thickly-growing vegetation with such rapidity as to commonly elude their enemies. This is rendered possible by the shape of their bodies, which are relatively narrow and flattened from side to side, so as to easily slip between the stems of grasses, rushes, and similar plants. Anyone who has pursued our native land-rail or corn-crake with intent to capture will have noted how extremely difficult it is even to get within sight of a bird of this sort.

Certain birds, unfortunately for themselves, have lost the power of flight without correspondingly increased powers of running, and have paid the penalty of extinction. Such an arrangement, as might be anticipated, was the result of evolution in islands devoid of any predatory ground-animals, and a classic example of it is afforded by the dodo and its allies, birds related to the pigeons. The dodo itself was a large and clumsy-looking species that at one time abounded in the island of Mauritius, which, like oceanic islands generally, possessed no native mammals, while its indigenous reptiles were only represented by lizards. The ubiquitous sailor, however, and the animals (especially swine) which he introduced, brought about the extinction of this helpless bird in less than a century after its first discovery in 1598. Its memory is now only kept green by a few contemporary drawings and descriptions, certain museum remains, and the proverb "as extinct as a dodo.” A similar fate must overtake any organism suddenly exposed to new and unfavorable conditions, if devoid of sufficient plasticity to rapidly accommodate itself to the altered environment.

The purpose of the underlined sentence is __________.

Possible Answers:

to explain how other types of running birds differ from the African ostrich

to introduce a discussion of the land-rail and corn-crake

to suggest that more people hunt land-rails and corn-crakes

to make himself feel better about having never been able to catch a land-rail or corn-crake

to provide an example likely familiar to readers of how effective a running bird’s defenses can be

Correct answer:

to provide an example likely familiar to readers of how effective a running bird’s defenses can be

Explanation:

The underlined sentence appears at the end of the first paragraph and reads, “Anyone who has pursued our native land-rail or corn-crake with intent to capture will have noted how extremely difficult it is even to get within sight of a bird of this sort.”

This is the only sentence in the passage that mentions the land-rail and corn-crake, so “to introduce a discussion of the land-rail and corn-crake” cannot be the correct answer. The author doesn’t tell us that he himself has pursued a land-rail or corn-crake, and while one might infer this, he doesn’t say anything about having failed to catch one, so “to make himself feel better about having never been able to catch a land-rail or corn-crake” doesn’t seem to be the correct answer either. The answer choice “to suggest that more people hunt land-rails and corn-crakes “ cannot be correct, as the author isn’t urging the reader to do anything in this sentence; it is simply conveying information. 

This leaves us with two answer choices: “to explain how other types of running birds differ from the African ostrich” and “to provide an example likely familiar to readers of how effective a running bird’s defenses can be.” While the first of these answer choices may seem correct at first glance, the author isn’t actually mentioning the land-rail and corn-crake to explain how other types of running birds differ from the African ostrich. He does this in a previous sentence. It is more accurate to say that the underlined sentenceprovide[s] an example likely familiar to readers of how effective a running bird’s defenses can be.”

Example Question #1 : Authorial Purpose In Natural Science Passages

Adapted from “Birds in Retreat” in “Animal Defences—Active Defence” in Volume Four of The Natural History of Animals: The Animal Life of the World in Its Various Aspects and Relations by James Richard Ainsworth Davis (1903)

Among the large running birds are forms, like the African ostrich, in which the absence of powers of flight is largely compensated by the specialization of the legs for the purpose of rapid movement on the ground. For straightforward retreat in open country nothing could be more effective; but another kind of adaptation is required in birds like rails, which are deficient in powers of flight, and yet are able to run through thickly-growing vegetation with such rapidity as to commonly elude their enemies. This is rendered possible by the shape of their bodies, which are relatively narrow and flattened from side to side, so as to easily slip between the stems of grasses, rushes, and similar plants. Anyone who has pursued our native land-rail or corn-crake with intent to capture will have noted how extremely difficult it is even to get within sight of a bird of this sort. 

Certain birds, unfortunately for themselves, have lost the power of flight without correspondingly increased powers of running, and have paid the penalty of extinction. Such an arrangement, as might be anticipated, was the result of evolution in islands devoid of any predatory ground-animals, and a classic example of it is afforded by the dodo and its allies, birds related to the pigeons. The dodo itself was a large and clumsy-looking species that at one time abounded in the island of Mauritius, which, like oceanic islands generally, possessed no native mammals, while its indigenous reptiles were only represented by lizards. The ubiquitous sailor, however, and the animals (especially swine) which he introduced, brought about the extinction of this helpless bird in less than a century after its first discovery in 1598. Its memory is now only kept green by a few contemporary drawings and descriptions, certain museum remains, and the proverb "as extinct as a dodo.” A similar fate must overtake any organism suddenly exposed to new and unfavorable conditions, if devoid of sufficient plasticity to rapidly accommodate itself to the altered environment.

The narrator mentions the proverb “as extinct as a dodo” in order to __________.

Possible Answers:

transition to a discussion of the ways in which common sayings reference birds

lament that the dodo was not eliminated sooner

provide an example of what little is left of the dodo in his era

support the idea that the dodo went extinct because of human influence

encourage his readers to use more figurative language

Correct answer:

provide an example of what little is left of the dodo in his era

Explanation:

The author mentions the proverb “as extinct as a dodo” in the second paragraph, when he states, “[The dodo’s] memory is now only kept green by a few contemporary drawings and descriptions, certain museum remains, and the proverb ‘as extinct as a dodo.’” The author is clearly not mentioning the proverb in order to “lament that the dodo was not eliminated sooner”; we can tell this from the rest of the paragraph as well, in that he is saddened that it went extinct at all. The author isn’t urging his readers to do anything, so he can’t be using the proverb to “encourage his readers to use more figurative language.” He doesn’t begin to discuss the ways in which common sayings reference birds after this point, so it doesn’t make any sense to say that he uses the proverb as a transition to such a discussion. This leaves us with two answer choices: that he mentions the proverb to “support the idea that the dodo went extinct because of human influence” and that he does so to “provide an example of what little is left of the dodo in his era.” While this may seem like a somewhat tricky choice, it is important to realize that at this point, the author has made the point that the dodo went extinct due to human influence in an earlier sentence, and this sentence doesn’t mention the reasons why the dodo went extinct at all—it’s talking about what is left over now that the dodo is extinct. This means that the correct answer is that the author mentions this proverb in order to “provide an example of what little is left of the dodo in his era.”

Example Question #2 : Purpose And Effect Of Phrases Or Sentences In Natural Science Passages

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.

In the fourth paragraph, the information about the work of Kolreuter and Gartner serves to __________.

Possible Answers:

support the information about errors in germination given in the previous paragraph

show that the author has researched the subject

argue that further study of the effect of pollen quantity on the rate of fertilisation is necessary

continue a discourse on the most effective methods to rear healthy plants

begin a discussion on the appropriate amounts of pollen needed in the experiment 

Correct answer:

begin a discussion on the appropriate amounts of pollen needed in the experiment 

Explanation:

It should be expected that the author would have researched the subject, so the purpose of the reference cannot be the demonstration of their research. The paragraph begins a discussion on the amount of pollen used and whether it has an adverse impact on seeds produced or plants produced. The work of Kolreuter and Gartner, as stated by the author, concerns the specific amount of pollen needed to fertilize all the ovules, so it allows the author to transition naturally into a new line of discussion.

Example Question #501 : Act Reading

Adapted from Volume Four of The Natural History of Animals: The Animal Life of the World in Its Various Aspects and Relations by James Richard Ainsworth Davis (1903)

The examples of protective resemblance so far quoted are mostly permanent adaptations to one particular sort of surrounding. There are, however, numerous animals which possess the power of adjusting their color more or less rapidly so as to harmonize with a changing environment.

Some of the best known of these cases are found among those mammals and birds that inhabit countries more or less covered with snow during a part of the year. A good instance is afforded by the Irish or variable hare, which is chiefly found in Ireland and Scotland. In summer, this looks very much like an ordinary hare, though rather grayer in tint and smaller in size, but in winter it becomes white with the exception of the black tips to the ears. Investigations that have been made on the closely allied American hare seem to show that the phenomenon is due to the growth of new hairs of white hue. 

The common stoat is subject to similar color change in the northern parts of its range. In summer it is of a bright reddish brown color with the exception of the under parts, which are yellowish white, and the end of the tail, which is black. But in winter, the entire coat, save only the tip of the tail, becomes white, and in that condition the animal is known as an ermine. A similar example is afforded by the weasel. The seasonal change in the vegetarian Irish hare is purely of protective character, but in such an actively carnivorous creature as a stoat or weasel, it is aggressive as well, rendering the animal inconspicuous to its prey.

Why is the American hare mentioned in the passage?

Possible Answers:

It is a predator of the Scottish hare.

It is better at hiding than the Scottish hare.

Scientists have studied it to find out how a hare’s fur changes color.

It is another name for the Scottish hare.

It is a type of hare that does not change color.

Correct answer:

Scientists have studied it to find out how a hare’s fur changes color.

Explanation:

The American hare is mentioned in the last line of the passage’s second paragraph, “Investigations that have been made on the closely allied American hare seem to show that the phenomenon is due to the growth of new hairs of white hue.” Here, the American hare is mentioned because “investigations” “have been made” on it, and those “investigations” “seem to show that the phenomenon is due to” something. We can tell from this context that in these “investigations,” scientists have studied how a hare’s fur changes color, since they are about what “the phenomenon is due to.” This means that “Scientists have studied it to find out how a hare’s fur changes color.” None of the other answer choices are supported by the passage.

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