ACT Reading : Drawing Inferences from Natural Science Passages

Study concepts, example questions & explanations for ACT Reading

varsity tutors app store varsity tutors android store varsity tutors amazon store varsity tutors ibooks store

Example Questions

Example Question #1 : Making Inferences 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.

Which of the following can we infer based on the passage?

Possible Answers:

The land-rail and corn-crake are not well adapted to running through tall grass.

Lizards were a predator of dodos.

If predatory ground-animals had lived on Mauritius, the dodo would have probably evolved to fly or run.

Ostriches would likely be as effective at running away from predators in tall grass as in open country.

If sailors had visited Mauritius sooner, dodos might still be alive today.

Correct answer:

If predatory ground-animals had lived on Mauritius, the dodo would have probably evolved to fly or run.

Explanation:

This may seem like a tricky question, but let’s consider each of the answer choices individually:

“If sailors had visited Mauritius sooner, dodos might still be alive today.”: The passage doesn’t support this assertion at all. Since the arrival of sailors on New Zealand is identified as the cause of the dodo’s extinction, it doesn’t make sense that the dodo would have survived if the sailors would have arrived earlier; it would probably have gone extinct sooner, based on the passage’s logic.

 “Ostriches would likely be as effective at running away from predators in tall grass as in open country.”: The passage specific disproves this when it says of ostriches and their running abilities, “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 suggests that ostriches are better adapted to surviving in open country than in areas covered by tall grass.

“The land-rail and corn-crake are not well adapted to running through tall grass.”: The passage disproves this answer choice when it describes the ability of rails to run through tall grass: “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.” After this sentence, the author mentions land-rails and corn-crakes’ abilities to evade hunters, so we can assume that these birds are well adapted to running through tall grass.

“Lizards were a predator of dodos.”: This can’t be true, because the passage tells us that “The dodo . . . 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.” Given that when animals that preyed on the dodo were introduced to Mauritius, the dodo went extinct, we can assume that since the lizards and dodos coexisted before this point, the lizards did not prey on the dodos. If this were true, the dodos would likely have learned to run or fly away, which they did not.

This brings us to the remaining answer choice, the correct one: “If predatory ground-animals had lived on Mauritius, the dodo would have probably evolved to fly or run.” The author attributes the dodo’s extinction to the fact that it did not have to adapt and defend itself from any predators before humans introduced new species on Mauritius. From this, we can infer that if those species had been present, the dodo would have learned to fly, or, like the ostrich and the rail, would have learned to run to defend itself.

Example Question #1 : Making Predictions Based On Narrative Science Passages

Adapted from “Feathers of Sea Birds and Wild Fowl for Bedding” from The Utility of Birds by Edward Forbush (ed. 1922)

In the colder countries of the world, the feathers and down of waterfowl have been in great demand for centuries as filling for beds and pillows. Such feathers are perfect non-conductors of heat, and beds, pillows, or coverlets filled with them represent the acme of comfort and durability. The early settlers of New England saved for such purposes the feathers and down from the thousands of wild-fowl which they killed, but as the population increased in numbers, the quantity thus furnished was insufficient, and the people sought a larger supply in the vast colonies of ducks and geese along the Labrador coast. 

The manner in which the feathers and down were obtained, unlike the method practiced in Iceland, did not tend to conserve and protect the source of supply. In Iceland, the people have continued to receive for many years a considerable income by collecting eider down, but there they do not “kill the goose that lays the golden eggs.” Ducks line their nests with down plucked from their own breasts and that of the eider is particularly valuable for bedding. In Iceland, these birds are so carefully protected that they have become as tame and unsuspicious as domestic fowls In North America. Where they are constantly hunted they often conceal their nests in the midst of weeds or bushes, but in Iceland, they make their nests and deposit their eggs in holes dug for them in the sod. A supply of the ducks is maintained so that the people derive from them an annual income.

In North America, quite a different policy was pursued. The demand for feathers became so great in the New England colonies about the middle of the eighteenth century that vessels were fitted out there for the coast of Labrador for the express purpose of securing the feathers and down of wild fowl. Eider down having become valuable and these ducks being in the habit of congregating by thousands on barren islands of the Labrador coast, the birds became the victims of the ships’ crews. As the ducks molt all their primary feathers at once in July or August and are then quite incapable of flight and the young birds are unable to fly until well grown, the hunters were able to surround the helpless birds, drive them together, and kill them with clubs. Otis says that millions of wildfowl were thus destroyed and that in a few years their haunts were so broken up by this wholesale slaughter and their numbers were so diminished that feather voyages became unprofitable and were given up. 

This practice, followed by the almost continual egging, clubbing, shooting, etc. by Labrador fishermen, may have been a chief factor in the extinction of the Labrador duck, that species of supposed restricted breeding range. No doubt had the eider duck been restricted in its breeding range to the islands of Labrador, it also would have been exterminated long ago.

Which of the following would you LEAST expect to be discussed elsewhere in the book from which this passage was taken?

Possible Answers:

The practice of sending messages by carrier pigeon

Falconry

The use of tropical birds’ feathers as hat decorations

The raising of chickens for their eggs

The types of birds encountered by the first Antarctic explorers

Correct answer:

The types of birds encountered by the first Antarctic explorers

Explanation:

The passage describes how humans use the eider down produced by eider ducks as a commodity for its insulating properties. Given this focus, along with the title of the book from which the passage is taken, The Utility of Birds, we can assume that other topics discussed in the books would deal with ways in which birds are useful to humans. “The use of tropical birds’ feathers as hat decorations,” “the raising of chickens for their eggs,” “falconry,” and “the practice of sending messages by carrier pigeon” all deal with ways in which birds are useful to humans, but “The types of birds encountered by the first Antarctic explorers” does not relate to how birds are useful to humans, so it would be least likely to be discussed elsewhere in a book called The Utility of Birds and is the correct answer.

Example Question #2 : Making Predictions Based On Narrative Science Passages

Adapted from “Feathers of Sea Birds and Wild Fowl for Bedding” from The Utility of Birds by Edward Forbush (ed. 1922)

In the colder countries of the world, the feathers and down of waterfowl have been in great demand for centuries as filling for beds and pillows. Such feathers are perfect non-conductors of heat, and beds, pillows, or coverlets filled with them represent the acme of comfort and durability. The early settlers of New England saved for such purposes the feathers and down from the thousands of wild-fowl which they killed, but as the population increased in numbers, the quantity thus furnished was insufficient, and the people sought a larger supply in the vast colonies of ducks and geese along the Labrador coast. 

The manner in which the feathers and down were obtained, unlike the method practiced in Iceland, did not tend to conserve and protect the source of supply. In Iceland, the people have continued to receive for many years a considerable income by collecting eider down, but there they do not “kill the goose that lays the golden eggs.” Ducks line their nests with down plucked from their own breasts and that of the eider is particularly valuable for bedding. In Iceland, these birds are so carefully protected that they have become as tame and unsuspicious as domestic fowls In North America. Where they are constantly hunted they often conceal their nests in the midst of weeds or bushes, but in Iceland, they make their nests and deposit their eggs in holes dug for them in the sod. A supply of the ducks is maintained so that the people derive from them an annual income.

In North America, quite a different policy was pursued. The demand for feathers became so great in the New England colonies about the middle of the eighteenth century that vessels were fitted out there for the coast of Labrador for the express purpose of securing the feathers and down of wild fowl. Eider down having become valuable and these ducks being in the habit of congregating by thousands on barren islands of the Labrador coast, the birds became the victims of the ships’ crews. As the ducks molt all their primary feathers at once in July or August and are then quite incapable of flight and the young birds are unable to fly until well grown, the hunters were able to surround the helpless birds, drive them together, and kill them with clubs. Otis says that millions of wildfowl were thus destroyed and that in a few years their haunts were so broken up by this wholesale slaughter and their numbers were so diminished that feather voyages became unprofitable and were given up. 

This practice, followed by the almost continual egging, clubbing, shooting, etc. by Labrador fishermen, may have been a chief factor in the extinction of the Labrador duck, that species of supposed restricted breeding range. No doubt had the eider duck been restricted in its breeding range to the islands of Labrador, it also would have been exterminated long ago.

Which of the following most likely happened after the Labrador feather voyages were no longer organized?

Possible Answers:

The price of eider down in North America plummeted.

North Americans imported eider down from Iceland.

A population of the Labrador duck was reestablished.

The quality of bedding in North America became preferable to that found in Iceland.

Eider down began to be used for other purposes in North America.

Correct answer:

North Americans imported eider down from Iceland.

Explanation:

The first paragraph tells us that the Labrador feather voyages were organized to keep up with an increased demand for eider down caused by an increased North American population. The passage doesn’t mention any alternative sources of eider down being used after the Labrador feather voyages were no longer organized. Therefore, we can eliminate the answer choice “The price of eider down in North America plummeted” since if eider down became more rare, its price would likely have gone up, not down. We can also eliminate the answer choice “Eider down began to be used for other purposes in North America” as this is not suggested in the passage at all and would require more information to be supported. “The quality of bedding in North America became preferable to that found in Iceland” cannot be correct either, as in the first paragraph, the author claims that eider down makes the best bedding, and if eider down becomes rare in North America, it’s not likely that the quality of North American bedding will exceed that of bedding made in Iceland, where eider down is assumed to be more available. “A population of the Labrador duck was reestablished.” cannot be the correct answer because the passage tells us that the Labrador duck went extinct, and if a species is extinct, there are no living members left from which populations of it could be reestablished. This leaves us with one answer, the correct one: “North American populations had to import eider down from Iceland.” This makes sense, as if less eider down were available in North America but there was still a desire for it, it would be likely to be imported from elsewhere in the world.

Example Question #41 : Extrapolating From The Text In Natural Science Passages

"Interpreting the Copernican Revolution" by Matthew Minerd (2014)

The expressions of one discipline can often alter the way that other subjects understand themselves. Among such cases are numbered the investigations of Nicolaus Copernicus. Copernicus is best known for his views concerning heliocentrism, a view which eventually obliterated many aspects of the ancient/medieval worldview, at least from the standpoint of physical science. It had always been the natural view of mankind that the earth stood at the center of the universe, a fixed point in reference to the rest of the visible bodies. The sun, stars, and planets all rotated around the earth.

With time, this viewpoint became one of the major reference points for modern life. It provided a provocative image that was used—and often abused—by many people for various purposes. For those who wished to weaken the control of religion on mankind, it was said that the heliocentric outlook proved man’s insignificance. In contrast with earlier geocentrism, heliocentrism was said to show that man is not the center of the universe. He is merely one small being in the midst of a large cosmos. However, others wished to use the “Copernican Revolution” in a very different manner. These thinkers wanted to show that there was another “recentering” that had to happen. Once upon a time, we talked about the world. Now, however, it was necessary to talk of man as the central reference point. Just as the solar system was “centered” on the sun, so too should the sciences be centered on the human person.

However, both of these approaches are fraught with problems. Those who wished to undermine the religious mindset rather misunderstood the former outlook on the solar system. The earlier geocentric mindset did not believe that the earth was the most important body in the heavens. Instead, many ancient and medieval thinkers believed that the highest “sphere” above the earth was the most important being in the physical universe. Likewise, the so-called “Copernican Revolution” in physics was different from the one applied to the human person. Copernicus’ revolution showed that the human point of view was not the center, whereas the later forms of “Copernican revolution” wished to show just the opposite.

Of course, there are many complexities in the history of such important changes in scientific outlook. Nevertheless, it is fascinating to see the wide-reaching effects of such discoveries, even when they have numerous, ambiguous effects.

Which of the following would likely be most interesting to those who believe the underlined sentence?

Possible Answers:

None of the other answers

The chemical basis for human emotions

Evolution of primates into man

Human culture

Human anatomy

Correct answer:

Human culture

Explanation:

The group noted in the underlined sentence has an interest in the human person precisely taken as a human person. That is, they are interested in the unique characteristics of human life. All of the incorrect answers consider something that is not necessarily unique to human life (though they do involve human beings). The other subjects are more like applications of chemistry and biology to the human person. However, human culture is unique to the human person. Therefore, it would most likely interest these people quite a bit.

Example Question #161 : Science Passages

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.

Based on the first paragraph, the author would be most likely to support __________.

Possible Answers:

a law severely punishing those who introduce invasive species that damage the environment

introducing damaging invasive species to the South

keeping bison out of Yellowstone National Park

an effort to catalogue the exact amount of money invasive species have cost the United States

granting Howell clemency for his actions

Correct answer:

a law severely punishing those who introduce invasive species that damage the environment

Explanation:

One of the author’s main points in the first paragraph is that harsher legal repercussions are needed for those who release damaging invasive species into the United States. This is clear when the author writes, “The most aggravating feature of these follies in transplantation is that never yet have they been made severely punishable.” Thus, we can infer that the author would be most likely to support “a law severely punishing those who introduce invasive species that damage the environment.” Though the author does discuss the potential for someone to introduce invasive species to the South, he is not in favor of this, and he clearly doesn’t want to grant Howell clemency for his actions. (Furthermore, “clemency” somewhat implies that Howell has been charged with a crime, and the author explains that this isn’t the case.) 

The author does state, “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,” and we can therefore assume that he might support cataloguing the amount of money invasive species have cost the United States. However, this inference requires a much larger logical leap than does the one that the author would support harsher legal punishments for those who introduce damaging invasive species, making “a law severely punishing those who introduce invasive species that damage the environment” the best answer. If you’re unsure when picking between answers to an inference question, it’s usually a good idea to see which one is more relevant to the passage’s topic and has the most evidence supporting it.

Example Question #171 : Science

dapted 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.

If the author were to learn that the gypsy moth could be efficiently repelled from trees by coating them with a cheap, natural substance, he would likely feel __________.

Possible Answers:

unsurprised

pessimistic

anxious

exuberant

horrified

Correct answer:

exuberant

Explanation:

Throughout the passage, the author makes it apparent that he feels that the gypsy moth is a very damaging invasive species that causes a lot of problems in the United States. He calls it a “winged calamity” and, in the third paragraph, describes how it spread:

“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!”

From this paragraph, we can tell that if the author were to learn that the gypsy moth could be efficiently stopped from damaging trees, he would be most likely to feel “exuberant,” or excited and happy. Nothing in the passage supports any of the other answers.

Example Question #101 : Content Of 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 author would most likely agree with which of the following statements?

Possible Answers:

It is important to eliminate old methods and techniques to avoid being archaic in all fields.

The best research uses a number of techniques to understand a concept.

The study of abnormality should be the primary focus of all research.

Neuroscience is the most important branch of science.

Scientific research should receive more financial support.

Correct answer:

The best research uses a number of techniques to understand a concept.

Explanation:

The main argument of this passage is that numerous techniques should serve to compliment each other and produce the best results. Presumably, the author’s opinion in neuroscience would likely apply to research overall. The author argues against "it is important to eliminate old methods and techniques to avoid being archaic in all fields hh. Scientific research should receive more financial support." There is no indication that financial support has any contribution to the author’s argument, therefore "scientific research should receive more financial support" is incorrect. Finally, "the study of abnormality should be the primary focus of all research" is incorrect because the support of lesion studies in this passage is not derived from a desire to study abnormality, but to understand regular functioning using a method that assesses abnormal functioning.

Example Question #201 : Natural Sciences

"The Cell Cycle" by Joseph Ritchie (2014)

The process by which cells divide and multiply is known as the cell cycle. This cycle consists of two main phases: interphase and mitosis. Each phase consists of a series of clearly defined and observable steps. At the conclusion of the cycle, each parent cell produces two genetically identical daughter cells that may also replicate by proceeding through the cell cycle.

Roughly ninety percent of the cell cycle is spent in interphase. Interphase is comprised of three main steps: the first gap phase, the synthesis phase (also called "S phase"), and the second gap phase. The initial gap phase is a period of cellular preparation in which the cell increases in size and readies itself for DNA synthesis. In the synthesis phase, or S phase, DNA replication occurs, so that when the cell divides, each daughter cell will have the DNA necessary to function properly. In the second gap phase, the cell grows in size and prepares for cellular division in the mitotic phase. At the end of each gap phase, the cell has to pass a regulatory checkpoint to ensure that nothing is going wrong. If anything has gone wrong, the checkpoints stop the cell from proceeding through the cell cycle any further.

The next part of the cell cycle is mitosis. Mitosis is a form of cell division and is broken down into five distinct phases. During prophase, the genetic material contained in the cell’s chromatin condenses into distinct chromosomes. Prometaphase is marked by the breakdown of the cell’s nuclear envelope and the formation of centrosomes at the poles of the cell. During metaphase, the cell’s chromosomes are moved to the center of the cell. A checkpoint ensures that the chromosomes are properly aligned on the center and halts the cell cycle if any errors have occurred. In anaphase, chromosomes break apart at their center, or centromere, and sister chromatids move to opposite ends of the cell. Lastly, telophase and cytokinesis occur as nuclear membranes form to physically divide the cell into two new daughter cells. Chromosomes also unwind into loose chromatin during this part of mitosis. Cytokinesis is defined as the division of the each cell’s cytoplasm and organelles. At the conclusion of the cell cycle, two genetically identical daughter cells have formed.

The cell cycle operates by a series of checkpoints and external cues. This system of checks enables the cell to enter a state of dormancy known as the gap zero phase when conditions or other factors inhibit the cell cycle. Conversely, unregulated and uncontrolled cellular division can occur under certain circumstances. A cell in a state of uncontrolled division is known to be cancerous. Lastly, cells have the ability to mediate their own death by way of apoptosis if certain genetic or physical abnormalities exist. The cell cycle is a complex process that enables cells to replicate and proliferate under a stringent set of checks and balances that produce healthy and viable daughter cells that are each able to perform the process in the future.

About how much time does a cell spend undergoing mitosis in the cell cycle?

Possible Answers:

Fifty percent

Fifteen percent

Ten percent

Twenty-five percent

Correct answer:

Ten percent

Explanation:

At the beginning of the second paragraph, the passage says, "Roughly ninety percent of the cell cycle is spent in interphase." Based on this information, and the fact that we are told that the cell cycle consists of "two main phases: interphase and mitosis," we can thus infer that about ten percent of a cell's time in the cell cycle is spent undergoing mitosis.

Example Question #21 : Reading Comprehension

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.

What can we infer preceded this paragraph?

Possible Answers:

Descriptions of animals that have not adapted to their environments

Descriptions of animals that hunt other animals efficiently by camouflaging themselves

Descriptions of animals that defend themselves by looking like things in a stable environment

Descriptions of changing environments

Descriptions of animals that defend themselves by looking like things in a changing environment

Correct answer:

Descriptions of animals that defend themselves by looking like things in a stable environment

Explanation:

In order to infer what likely “preceded,” or came before, this passage, we should take at what the passage is talking about right when it starts. The passage’s first sentence says, “The examples of protective resemblance so far quoted are mostly permanent adaptations to one particular sort of surrounding.” The “so far quoted” means so far said or provided and tells us that the writer has been talking about “examples of protective resemblance.” This means that the writer most likely discussed “animals that defend themselves by looking like things in a stable environment” in the part of the book that comes right before the passage.

Example Question #11 : Making Inferences In Natural 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.

Based on the passage, what can we infer about the weasel?

Possible Answers:

Like the Irish hare, has been the subject of investigations.

Like the stoat, it also changes its coat color.

Like the Irish hare, it has grey fur in the summer.

Like the stoat, it also lives in burrows.

Like the stoat, it has claws.

Correct answer:

Like the stoat, it also changes its coat color.

Explanation:

The weasel is mentioned in two places in the passage, both in the passage’s last paragraph, both reproduced here:

“But in winter, the entire coat [of the stoat], 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.”

What does the passage tell us about the weasel? Well, we can infer that it is in some way like the stoat, because the passage says “A similar example is afforded by the weasel” right after describing how the stoat’s fur changes color. We are also told that it is carnivorous, but this is not an inference we have to make, and it doesn’t relate to any of the answer choices. The best answer choice is “Like the stoat, it also changes its coat color.” This captures the specific similarity between the stoat and weasel being discussed when the author writes, “A similar example is afforded by the weasel.”

Learning Tools by Varsity Tutors