ACT Reading : Identifying and Analyzing Main Ideas in Natural Science Passages

Study concepts, example questions & explanations for ACT Reading

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Example Questions

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Example Question #1 : Analyzing Argumentative Claims, Bias, And Support In Natural 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.

Which of the following is the best image for the author’s view of the universe?

Possible Answers:

It is the source of the greatest of all marvels, particularly life itself.

Its highest beauties are found in the stars.

It is a structured whole.

It is relatively ordered chaos.

None of the other answers

Correct answer:

It is a structured whole.

Explanation:

Sometimes, the answer to a question can be found in a single sentence. In the case of this question, the answer is found in the very last sentence: "It is to the glory of astronomy that it first led men to the conclusion that law reigns in the universe." If law reigns in the universe, this means that it is an orderly whole, not deviating from its law-like course of events. This is the best answer among those provided.

Example Question #1 : Understanding Main Ideas 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 best states the main idea of this passage?

Possible Answers:

Flightless birds sometimes develop strong running abilities, but if they don’t, they may be threatened with extinction.

The extinction of the dodo can be traced to human causes.

Flightless birds adapt to their particular surroundings.

Birds employ a variety of defenses for avoiding predators.

The African ostrich’s strong leg muscles makes it well adapted to its environment.

Correct answer:

Flightless birds sometimes develop strong running abilities, but if they don’t, they may be threatened with extinction.

Explanation:

When asked to identify a passage’s main idea, it is important to pick out an answer choice to which all of the paragraphs can relate, but that is not too broad in including things that the passage does not discuss. Considering if each of the answer choices falls into one or another of these categories can help you narrow down your choices. For instance, “Birds employ a variety of defenses for avoiding predators” is far too broad to accurately describer this passage’s main idea. The author only discusses flightless birds, not all birds. “Flightless birds adapt to their particular surroundings” cannot be correct either, as the first paragraph discusses this, but the second paragraph discusses a flightless bird that did not adapt to its surroundings. Since the second paragraph can’t relate to this answer, it can’t be the main idea of the entire passage. Two of the remaining answer choices can be discarded due to their being too detailed: “The African ostrich’s strong leg muscles makes it well adapted to its environment” and “The extinction of the dodo can be traced to human causes.” While the first of these choices is stated in the first paragraph and the second is stated in the second paragraph, neither relates to the other paragraph, or even adequately summarizes the entire paragraph in which it appears. This leaves us with one answer choice, the correct one: “Flightless birds sometimes develop strong running abilities, but if they don’t, they may be threatened with extinction.” Each of the two paragraphs can relate to this answer choice, but it doesn’t include things that the passage doesn’t discuss.

Example Question #1 : 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 best states the main idea of this passage?

Possible Answers:

Eider down is valuable as a source of bedding, leading to its collection from ducks.

The extinction of the Labrador duck can be traced to a definite cause.

The Icelandic people collect eider down in an efficient and reasonable way.

Natural resources are precious.

The North American and Icelandic methods of collecting eider down have had vastly different consequences. 

Correct answer:

The North American and Icelandic methods of collecting eider down have had vastly different consequences. 

Explanation:

Questions that ask about a passage’s main idea need to encompass each of the topics it discusses while not describing them in a way that is too broad. We can ignore any answer choices that only describe parts of the passage—here, “Eider down is valuable as a source of bedding, leading to its collection from ducks,” “The extinction of the Labrador duck can be traced to a definite cause,” and “The Icelandic people collect eider down in an efficient and reasonable way.” This leaves us with “Natural resources are precious,” which is far too broad to accurately describe the passage’s main idea, and the correct answer, “The North American and Icelandic methods of collecting eider down have had vastly different consequences.”

Example Question #1 : 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.

What can we say, in general, about the interpretations that have been offered for the effects of Copernicus’ discoveries?

Possible Answers:

They have been abused for tyrannical purposes by many parties.

They have unlocked a number of themes that were long hidden by the powers of religion and authoritarian regimes.

They have been used more according to the disposition of their interpreters than in accord with the reality of the facts.

They have provided the grounds for a fruitful dialogue between religion and science.

None of the other answers

Correct answer:

They have been used more according to the disposition of their interpreters than in accord with the reality of the facts.

Explanation:

While the passage does catalogue two different worldviews that emerged from Copernicus' findings, it ultimately stresses the point that such outlooks are both limited because of their adherents' biases. Neither of them really reads the history or even the general images correctly. It seems that each one uses the findings as an occasion for strengthening his or her outlook on reality, whatever that might be.

Example Question #21 : Identifying And Analyzing Main Ideas 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.

Why is the "Copernican revolution" of the human sciences contrary to the literal sense of Copernicus' findings?

Possible Answers:

Copernicus' findings were scientific in contrast to nebulous humanistic aims.

Copernicus' findings were focused on a new external "center," drawing attention away from the immediate center experienced in day-to-day life.

Copernicus' scientific aims immediately prove the fact that the human person is merely a speck on a rock in a large universe.

None of the other answers

Copernicus' findings aim only at disproving a former worldview, not finding new data around a new center of experience.

Correct answer:

Copernicus' findings were focused on a new external "center," drawing attention away from the immediate center experienced in day-to-day life.

Explanation:

The key sentence for this question is: "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." To start looking at the sun as the center requires us to "look outward" in a new way, not paying attention to our particular earth-bound viewpoint. However, the "Copernican revolution" centered on humanity does just the opposite. It turns the gaze "inward," quite different from the literal sense of Copernicus' findings.

Example Question #12 : Inference About The Author

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.

How does the author feel about Howell?

Possible Answers:

The author agrees with Howell that invasive species are often problematic.

The author thinks that Howell made a great mistake in releasing Gypsy moths into the United States.

The author greatly dislikes Howell for his audacious disrespect for nature.

The author is annoyed by Howell’s insistence that invasive species do not cause significant problems.

The author likes Howell because he helped identify a problem with the consequences available for environmental disruptors.

Correct answer:

The author greatly dislikes Howell for his audacious disrespect for nature.

Explanation:

Let’s look at the part of the first paragraph in which the author brings up Howell, paying attention to why he does so:

“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.”

In mentioning Howell, the author is providing an example supporting his argument that harsher legal penalties are necessary for those who harm the environment. The author describes Howell as a “poacher” who “destroyed our first national bison herd” and was “caught red-handed.” From this, we can tell that the best answer choice is “the author greatly dislikes Howell for his audacious disrespect for nature.” 

One of the other answer choices attempts to get you to confuse Howell with Mr. Trouvelot, who released the gypsy moths—don’t fall for that! Check the passage if you are worried at all about confusing the two so you can avoid pitfall answers like that one.

Example Question #231 : Passage Based Questions

"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 primary goal of this passage is __________.

Possible Answers:

To convince readers that lesion studies are more effective than all other neuroscience studies and to present the opinion that lesion studies are valuable and should be used in combination with other techniques

To discuss the specific limitations of all neuroscience methods

To present the opinion that lesion studies are valuable and should be used in combination with other techniques

To argue against the use of lesion studies

To provide the reader with a thorough understanding of the terms “correlational” and “causational”

Correct answer:

To present the opinion that lesion studies are valuable and should be used in combination with other techniques

Explanation:

While "to convince readers that lesion studies are more effective than all other neuroscience studies and to present the opinion that lesion studies are valuable and should be used in combination with other techniques" may seem correct at first, on close inspection, the passage indicates that lesion studies should be used in convergence with other methods and does not directly discuss the effectiveness of lesion studies in comparison with other methods. "To discuss the specific limitations of all neuroscience methods" is incorrect because no specific limitations are cited. "To provide the reader with a thorough understanding of the terms 'correlational' and 'causational'" may seem like a viable option because the passage does address these concepts, but they are not the core tenet of the passage. "To present the opinion that lesion studies are valuable and should be used in combination with other techniques" is correct because the passage repeatedly comments on the use of convergent techniques, including lesion studies, to better understand the brain.

 

Example Question #1 : Identifying And Analyzing Main Idea And Theme In 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.

Which of the following best expresses the main idea of the passage?

Possible Answers:

All animals that live in a changing environment change color.

The Scottish hare changes its fur color.

Animals like the stoat, the weasel, and the Irish hare are better adapted to changing environments than to unchanging ones.

Increased defense is the only reason for an animal to change its fur color.

Certain animals change their fur color to be better predators or better at hiding.

Correct answer:

Certain animals change their fur color to be better predators or better at hiding.

Explanation:

When answering questions about the main idea of a passage, it’s important to pick out an answer choice to which each paragraph relates, but one that isn’t too broad. Some of the answer choices to this question are too specific: “The Scottish hare changes its fur color” is, and we can tell because the first paragraph doesn’t say anything about the Scottish hare, and the third paragraph only mentions it in its last line. “Increased defense is the only reason for an animal to change its fur color” should get your attention due to its use of the word “only”—did we hear anything in the passage about color-changing adaptations being used “only” for defense? No, we heard the opposite, in the passage’s last line: “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 language may be a bit dense here, but what the passage is saying is that the hare uses its color-changing adaptation for defense, but stoats and weasels use it for being better predators and sneaking up on their prey—definitely not a defensive use. Similarly, “All animals that live in a changing environment change color” is making a strong statement due to its use of the word “all.” The passage gives us a few examples of animals that change that live in a changing environment and change their color, but this isn’t enough for us to assume that all animals that live in changing environments act this way. 

Example Question #161 : Content Of Natural Science Passages

Adapted from "Taking a Second Look: An Analysis of Genetic Markers in Species Relatedness" by Joseph Ritchie (2014)

Phylogenetics is the study of genetic composition in various species and is used by evolutionary biologists to investigate similarities in the molecular sequences of proteins in varying organisms. The amino acid sequences that build proteins are used to construct mathmatical matrices that aid in determining evolutionary ties through the investigation of percentage similarities. The study of these matrices helps to expose evolutionary relationships between species that may not have the same overt characteristics.

Species adapt and evolve based on the pressures that exist in their environment. Climate, food source, and habitat availability are only a few factors that act on species adaptation. These stressors can alter the physical characteristics of organisms. This divergence in evolution has made it difficult to determine the interrelatedness of organisms by analyzing their physical characteristics alone.

For instance, looking only at physical characteristics, the ghost bat resembles a pigeon more than a spider monkey; however, phylogenetics has found that the amino acid sequences that construct the beta hemoglobin molecules of bats are twenty percent more similar to those of mammalian primates than those of birds. This helps reject the assumption that common physical characteristics between species are all that is needed to determine relatedness. 

The differences produced by divergent evolution observed in the forest-dwelling, arboreal spider monkey and the nocturnal, airborne ghost bat can be reconciled through homology. Homologous characteristics are anatomical traits that are similar in two or more different species. For instance, the bone structure of a spider monkey’s wrist and fingers greatly resembles that of a bat’s wing or even a whale’s fin. These similarities are reinforced by phylogenetic evidence that supports the idea that physically dissimilar species can be evolutionarily related through anatomical and genetic similarities.

The central idea of this passage is best described by which of the following statements?

Possible Answers:

Despite differences in physical appearance, genetic similarities can aid in determining species relatedness and evolutionary histories.

Genetic analysis is the only method of studying evolutionary ties and species relatedness.

Understanding divergent evolution is necessary for understanding species relatedness.

Phylogenetics is a relatively new area of study and has yet to yield supported conclusions on evolutionary histories.

Correct answer:

Despite differences in physical appearance, genetic similarities can aid in determining species relatedness and evolutionary histories.

Explanation:

This is the correct answer because it is the only statement that is supported by the passage. The passage introduces the field of phylogenetics and the need to explore evolution beyond simple examination of physical characteristics. It does not state which field of study is better or correct. It simply states that they compliment the same cause: the study of relatedness. The other choices are unsupported opinions. The answer choice about divergent evolution is incorrect because while the passage's fourth paragraph is about divergent evolution, the entire passage encompasses many more topics.

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