# PSAT Critical Reading : Understanding the Content of Natural Science Passages

## Example Questions

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

Adapted from “Humming-Birds: As Illustrating the Luxuriance of Tropical Nature” in Tropical Nature, and Other Essays by Alfred Russel Wallace (1878)

The food of hummingbirds has been a matter of much controversy. All the early writers down to Buffon believed that they lived solely on the nectar of flowers, but since that time, every close observer of their habits maintains that they feed largely, and in some cases wholly, on insects. Azara observed them on the La Plata in winter taking insects out of the webs of spiders at a time and place where there were no flowers. Bullock, in Mexico, declares that he saw them catch small butterflies, and that he found many kinds of insects in their stomachs. Waterton made a similar statement. Hundreds and perhaps thousands of specimens have since been dissected by collecting naturalists, and in almost every instance their stomachs have been found full of insects, sometimes, but not generally, mixed with a proportion of honey. Many of them in fact may be seen catching gnats and other small insects just like fly-catchers, sitting on a dead twig over water, darting off for a time in the air, and then returning to the twig. Others come out just at dusk, and remain on the wing, now stationary, now darting about with the greatest rapidity, imitating in a limited space the evolutions of the goatsuckers, and evidently for the same end and purpose. Mr. Gosse also remarks, ” All the hummingbirds have more or less the habit, when in flight, of pausing in the air and throwing the body and tail into rapid and odd contortions. This is most observable in the Polytmus, from the effect that such motions have on the long feathers of the tail. That the object of these quick turns is the capture of insects, I am sure, having watched one thus engaged pretty close to me.”

What evidence does Mr. Gosse have to support the claim that hummingbirds eat insects?

He surmised that they must eat insects because he has never seen one eating flower nectar.

He observed one flailing around in the air and concluded that it was eating insects.

A hummingbird got into his collection of live insects, and soon after, all of his insects were missing.

He read in a reputable scientific journal that they eat insects.

He examined the contents of a hummingbird’s stomach and found many insects in it.

He observed one flailing around in the air and concluded that it was eating insects.

Explanation:

To answer this question, we have to consider the quotation attributed to Mr. Gosse found at the end of the passage:

“Mr. Gosse also remarks, ‘All the hummingbirds have more or less the habit, when in flight, of pausing in the air and throwing the body and tail into rapid and odd contortions. This is most observable in the Polytmus, from the effect that such motions have on the long feathers of the tail. That the object of these quick turns is the capture of insects, I am sure, having watched one thus engaged pretty close to me.’”

He doesn’t mention anything about having a collection of live insects, getting his information from a scientific journal, or dissecting a hummingbird’s stomach, so we can ignore those answer choices. He actively observes a hummingbird and surmises that they eat insects because of that, so the correct answer is “He observed one flailing around in the air and concluded that it was eating insects.”

### Example Question #2 : Identifying And Analyzing Supporting Ideas In Science Passages

Adapted from An Introduction to Astronomy by Forest Ray Moulton (1916 ed.)

It is doubtful if any important scientific idea ever sprang suddenly into the mind of a single man. The great intellectual movements in the world have had long periods of preparation, and often many men were groping for the same truth, without exactly seizing it, before it was fully comprehended.

The foundation on which all science rests is the principle that the universe is orderly, and that all phenomena succeed one another in harmony with invariable laws. Consequently, science was impossible until the truth of this principle was perceived, at least as applied to a limited part of nature.

The phenomena of ordinary observation, as, for example, the weather, depend on such a multitude of factors that it was not easy for men in their primitive state to discover that they occur in harmony with fixed laws. This was the age of superstition, when nature was supposed to be controlled by a great number of capricious gods whose favor could be won by childish ceremonies. Enormous experience was required to dispel such errors and to convince men that the universe is one vast organization whose changes take place in conformity with laws which they can in no way alter.

The actual dawn of science was in prehistoric times, probably in the civilizations that flourished in the valleys of the Nile and the Euphrates. In the very earliest records of these people that have come down to modern times it is found that they were acquainted with many astronomical phenomena and had coherent ideas with respect to the motions of the sun, moon, planets, and stars. It is perfectly clear from their writings that it was from their observations of the heavenly bodies that they first obtained the idea that the universe is not a chaos. Day and night were seen to succeed each other regularly, the moon was found to pass through its phases systematically, the seasons followed one another in order, and in fact the more conspicuous celestial phenomena were observed to occur in an orderly sequence. It is to the glory of astronomy that it first led men to the conclusion that law reigns in the universe.

According to this passage, why were astronomical bodies so important to the emergence of science?

Being above the earth's surface, they seem to encompass the whole of the world.

They exhibit a great deal of regularity.

Their beauty encouraged continuous speculation.

They were once believed to be gods, but by showing that they were not such, humanity was able to believe in scientific thought.

They exhibit a great deal of regularity.

Explanation:

The key sentence for this question is, "It is perfectly clear from their writings that it was from their observations of the heavenly bodies that they first obtained the idea that the universe is not a chaos." The idea is that for prehistoric humanity, the stars and planets likely provided the first example of regularity in our day-to-day experience. Though many of our experiences seem random, the stars do indeed continue in their courses and the sun has its own repeating path. Hence, they began to see that the world had regular patterns—not all is chaos.

### Example Question #11 : Content Of Natural Science Passages

Adapted from “Darwin’s Predecessors” by J. Arthur Thomson in Evolution in Modern Thought (1917 ed.)

In seeking to discover Darwin's relation to his predecessors, it is useful to distinguish the various services which he rendered to the theory of organic evolution.

As everyone knows, the general idea of the doctrine of descent is that the plants and animals of the present day are the lineal descendants of ancestors on the whole somewhat simpler, that these again are descended from yet simpler forms, and so on backwards towards the literal "Protozoa" and "Protophyta" about which we unfortunately know nothing. Now no one supposes that Darwin originated this idea, which in rudiment at least is as old as Aristotle. What Darwin did was to make it current intellectual coin. He gave it a form that commended itself to the scientific and public intelligence of the day, and he won widespread conviction by showing with consummate skill that it was an effective formula to work with, a key which no lock refused. In a scholarly, critical, and preeminently fair-minded way, admitting difficulties and removing them, foreseeing objections and forestalling them, he showed that the doctrine of descent supplied a modal interpretation of how our present-day fauna and flora have come to be.

In the second place, Darwin applied the evolution-idea to particular problems, such as the descent of man, and showed what a powerful tool it is, introducing order into masses of uncorrelated facts, interpreting enigmas both of structure and function, both bodily and mental, and, best of all, stimulating and guiding further investigation. But here again it cannot be claimed that Darwin was original. The problem of the descent or ascent of man, and other particular cases of evolution, had attracted not a few naturalists before Darwin's day, though no one [except Herbert Spencer in the psychological domain (1855)] had come near him in precision and thoroughness of inquiry.

In the third place, Darwin contributed largely to a knowledge of the factors in the evolution-process, especially by his analysis of what occurs in the case of domestic animals and cultivated plants, and by his elaboration of the theory of natural selection, which Alfred Russel Wallace independently stated at the same time, and of which there had been a few previous suggestions of a more or less vague description. It was here that Darwin's originality was greatest, for he revealed to naturalists the many different forms—often very subtle—which natural selection takes, and with the insight of a disciplined scientific imagination he realized what a mighty engine of progress it has been and is.

Based on this passage, what was the role of Herbert Spencer in the history of evolutionary doctrine?

He was the only real source from which Darwin drew his thought.

In many ways, his thought presaged that of Darwin's, predicting several major aspects of Darwin's theories.

His thought had aspects related to evolution as a theme in certain social sciences.

His thought had no major relation to thought pertaining to evolution.

His thought had aspects related to evolution as a theme in certain social sciences.

Explanation:

In the passage, it is said that few naturalists focused on evolution or the descent/ascent of man before Darwin's day. "Naturalists" would be "natural scientists." The parenthetical remark about Spencer makes sure that the reader knows, however, that Spencer did pay attention to it "in the psychological domain." Some argue that he was influential to Darwin, but that is not discussed here. However, we can say that his thought did contain aspects that applied the idea of evolution to certain branches of the social sciences.

### Example Question #1 : Argumentative 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. Why did Mr. Trouvelot bring gypsy moths to Boston? Possible Answers: He wanted to feed them to the birds he kept in his aviary. Mr. Trouvelot did not bring gypsy moths to Boston; he brought them to Yellowstone National Park. He was trying to find a moth that would make cocoons he could sell. He wanted to release them as a scientific experiment. He wanted to use them combat other insect pests that were ruining his crops. Correct answer: He was trying to find a moth that would make cocoons he could sell. Explanation: The second paragraph of the passage tells the story of how Mr. Trouvelot released the gypsy moths, so we should look there for our answer. In it, the author writes that the gypsy moth “was imported at Maiden, Massachusetts, near Boston, by a French entomologist, Mr. Leopold Trouvelot, in 1868 or 69”; this allows us to eliminate the answer “Mr. Trouvelot did not bring gypsy moths to Boston; he brought them to Yellowstone National Park.” The author then explains that Trouvelot “was endeavoring with live specimens to find a moth that would produce a cocoon of commercial value to America.” Therefore, the correct answer is “He was trying to find a moth that would make a cocoon he could sell.” ### Example Question #101 : Passage Meaning And Construction 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.

At the time the passage was written, in which of the following states was the gypsy moth NOT found?

Rhode Island

Massachusetts

New York

New Hampshire

Connecticut

New York

Explanation:

The part of the passage most relevant to this question is found in the last paragraph:

“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.”

We can tell that “New York” is the answer based on this quotation, but one state remains unaccounted for: Massachusetts. Earlier in the passage, we are told that the gypsy moth “was imported at Maiden, Massachusetts, near Boston,” and that “enough escaped to produce progeny that soon became a scourge to the trees of Massachusetts.” We can infer that the gypsy moth is found in Massachusetts at the time the passage was written, especially given that the author writes, “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!” This quotation—especially the author’s use of the transition “Up to this date”—suggests that the gypsy moth remained a problem in Massachusetts at the time the author was writing.

### Example Question #1 : Distinguishing Between Fact And Fiction 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.

How was the underlined view about geocentrism incorrect?

Religions gladly accepted the point and moved on.

Religion had always despised human existence anyway, so this is not much of a change.

The view is actually reflective of the history of thought and does not contradict it.

Many earlier thinkers actually thought the earth was rather insignificant compared with the other celestial bodies.

Many earlier thinkers actually thought the earth was rather insignificant compared with the other celestial bodies.

Explanation:

For this question, the key two sentences are: "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." These state that geocentric thinkers in the ancient and medieval period actually believed that the higher "spheres" of heaven were more important than earth.

### Example Question #101 : Passage Based Questions

"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.

To where are chromosomes moved in the cell during metaphase?

The poles of the cell

Outside of the cell

The center of the cell

The edges of the cell

The center of the cell

Explanation:

Chromosomes are moved to the center of the cell during metaphase. This is supported by the passage in the third paragraph, when it states, "During metaphase, the cell’s chromosomes are moved to the center of the cell."

### Example Question #31 : Drawing Evidence From Natural Science Passages

"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.

How many checkpoints are present in the cell cycle?

Three

Two

Five

Four

Three

Explanation:

There are three checkpoints in the cell cycle. Two are located in interphase, as the passage says in paragraph two: "At the end of each gap phase the cell has to pass two regulatory checkpoints to ensure proper cell growth and environmental conditions." Another checkpoint is present in mitosis, according to paragraph three: "A checkpoint ensures that the chromosomes are aligned on the center and halts the cycle if an error occurs."

### Example Question #161 : Sat Critical Reading

"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, 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, 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.

Which of the following is a characteristic of a cancerous cell?

It prevents other cells from moving past the checkpoints in the cell cycle.

It spends much more time in interphase than do other cells.

Its chromatin does not condense into chromosomes.

It divides uncontrollably.

It divides uncontrollably.

Explanation:

Cancerous cells divide uncontrollably. This information is conveyed in the last paragraph, when the passage says, "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." From this part of the passage, we can tell that a cell "in a state of uncontrolled division" is cancerous.

### Example Question #51 : Identifying And Analyzing Important Details In Natural Science Passages

"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.

During anaphase, chromosomes break apart into __________.

Centromeres

Chromatin

Nuclear membranes

Sister chromatids