RC 4.1

Biologists have advanced two theories to explain

why schooling of fish occurs in so many fish species.

Because schooling is particularly widespread among

species of small fish, both theories assume that

schooling offers the advantage of some protection

from predators.

Proponents of theory A dispute the assumption that

a school of thousands of fish is highly visible.

Experiments have shown that any fish can be seen,

even in very clear water, only within a sphere of 200

meters in diameter. When fish are in a compact group,

the spheres of visibility overlap. Thus the chance of a

predator finding the school is only slightly greater

than the chance of the predator finding a single fish

swimming alone. Schooling is advantageous to the

individual fish because a predator's chance of finding

any particular fish swimming in the school is much

smaller than its chance of finding at least one of the

same group of fish if the fish were dispersed

throughout an area.

However, critics of theory A point out that some

fish form schools even in areas where predators are

abundant and thus little possibility of escaping

detection exists. They argue that the school continues

to be of value to its members even after detection.

They advocate theory B, the "confusion effect," which

can be explained in two different ways.

Sometimes, proponents argue, predators simply

cannot decide which fish to attack. This indecision

supposedly results from a predator's preference for

striking prey that is distinct from the rest of the

school in appearance. In many schools the fish are

almost identical in appearance, making it difficult for a

predator to select one. The second explanation for

the "confusion effect" has to do with the sensory

confusion caused by a large number of prey moving

around the predator. Even if the predator

(40)

makes the decision to attack a particular fish,

the movement of other prey in the school can

be distracting. The predator's difficulty can be

compared to that of a tennis player trying to

hit a tennis ball when two are approaching

simultaneously

1. According to the passage, theory B states that which

of the following is a factor that enables a schooling

fish to escape predators?

(A) The tendency of fish to form compact groups

(B) The movement of other fish within the school

(C) The inability of predators to detect schools

(D) The ability of fish to hide behind one another in

a school

(E) The great speed with which a school can

disperse

2. According to the passage, both theory A and theory B

have been developed to explain how

(A) fish hide from predators by forming schools

(B) forming schools functions to protect fish from

predators

(C) schooling among fish differs from other

protective behaviors

(D) small fish are able to make rapid decisions

(E) small fish are able to survive in an environment

densely populated by large predators

3. According to one explanation of the "confusion

effect," a fish that swims in a school will have greater

advantages for survival if it

(A) tends to be visible for no more than 200 meters

(B) stays near either the front or the rear of a

school

(C) is part of a small school rather than a large

school

(D) is very similar in appearance to the other fish in

the school

(E) is medium-sized

4. The author is primarily concerned with (A) discussing different theories (B) analyzing different techniques (C) defending two hypotheses (D) refuting established beliefs (E) revealing new evidence

Two works published in 1984 demonstrate

contrasting approaches to writing the history of

United States women. Buel and Buel's biography of

Mary Fish (1736–1818) makes little effort to place

her story in the context of recent historiography on

women. Lebsock, meanwhile, attempts not only to

write the history of women in one southern

community, but also to redirect two decades of

historiographical debate as to whether women

gained or lost status in the nineteenth century as

compared with the eighteenth century. Although

both books offer the reader the opportunity to

assess this controversy regarding women's status,

only Lebsock's deals with it directly. She examines

several different aspects of women's status, helping

to refine and resolve the issues. She concludes that

while women gained autonomy in some areas,

especially in the private sphere, they lost it in many

aspects of the economic sphere. More importantly,

she shows that the debate itself depends on frame

of reference: in many respects, women lost power

in relation to men, for example, as certain jobs

(delivering babies, supervising schools) were taken

over by men. Yet women also gained power in

comparison with their previous status, owning a

higher proportion of real estate, for example. In

contrast, Buel and Buel's biography provides ample

raw material for questioning the myth, fostered by

some historians, of a colonial golden age in the

eighteenth century but does not give the reader

much guidance in analyzing the controversy over

women's status.

69. The primary purpose of the passage is to (A) examine two sides of a historiographical debate (B) call into question an author's approach to a historiographical debate (C) examine one author's approach to a historiographical debate (D) discuss two authors' works in relationship to a historiographical debate (E) explain the prevalent perspective on a historiographical debate 70. The author of the passage mentions the supervision of schools primarily in order to (A) remind readers of the role education played in the cultural changes of the nineteenth century in the United States (B) suggest an area in which nineteenth-century American women were relatively free to exercise power (C) provide an example of an occupation for which accurate data about women's participation are difficult to obtain (D) speculate about which occupations were considered suitable for United States women of the nineteenth century (E) illustrate how the answers to questions about women's status depend on particular contexts 71. With which of the following characterizations of Lebsock's contribution to the controversy concerning women's status in the nineteenth-century United States would the author of the passage be most likely to agree? (A) Lebsock has studied women from a formerly neglected region and time period. (B) Lebsock has demonstrated the importance of frame of reference in answering questions about women's status. (C) Lebsock has addressed the controversy by using women's current status as a frame of reference. (D) Lebsock has analyzed statistics about occupations and property that were previously ignored. (E) Lebsock has applied recent historiographical methods to the biography of a nineteenthcentury woman. 72. According to the passage, Lebsock's work differs from Buel and Buel's work in that Lebsock's work (A) uses a large number of primary sources (B) ignores issues of women's legal status (C) refuses to take a position on women's status in the eighteenth century (D) addresses larger historiographical issues (E) fails to provide sufficient material to support its claims 73. The passage suggests that Lebsock believes that compared to nineteenth-century American women, eighteenth-century American women were (A) in many respects less powerful in relation to men (B) more likely to own real estate (C) generally more economically independent (D) more independent in conducting their private lives (E) less likely to work as school superintendents 74. The passage suggests that Buel and Buel's biography of Mary Fish provides evidence for which of the following views of women's history? (A) Women have lost power in relation to men since the colonial era. (B) Women of the colonial era were not as likely to be concerned with their status as were women in the nineteenth century. (C) The colonial era was not as favorable for women as some historians have believed. (D) Women had more economic autonomy in the colonial era than in the nineteenth century. (E) Women's occupations were generally more respected in the colonial era than in the nineteenth century.

It was once believed that the brain was

independent of metabolic processes occurring

elsewhere in the body. In recent studies, however,

we have discovered that the production and release

in brain neurons of the neurotransmitter serotonin

(neurotransmitters are compounds that neurons use

to transmit signals to other cells) depend directly on

the food that the body processes.

Our first studies sought to determine whether

the increase in serotonin observed in rats given

a large injection of the amino acid tryptophan

might also occur after rats ate meals that change

tryptophan levels in the blood. We found that,

immediately after the rats began to eat, parallel

elevations occurred in blood tryptophan, brain

tryptophan, and brain serotonin levels. These

findings suggested that the production and release

of serotonin in brain neurons were normally coupled

with blood-tryptophan increases. In later studies we

found that injecting insulin into a rat's bloodstream

also caused parallel elevations in blood and brain

tryptophan levels and in serotonin levels. We then

decided to see whether the secretion of the animal's

own insulin similarly affected serotonin production.

We gave the rats a carbohydrate-containing meal

that we knew would elicit insulin secretion. As we

had hypothesized, the blood tryptophan level and

the concentrations of tryptophan and of serotonin

in the brain increased after the meal.

Surprisingly, however, when we added a large

amount of protein to the meal, brain tryptophan

and serotonin levels fell. Since protein contains

tryptophan, why should it depress brain tryptophan

levels? The answer lies in the mechanism that

provides blood tryptophan to the brain cells. This

same mechanism also provides the brain cells with

other amino acids found in protein, such as tyrosine

and leucine. The consumption of protein increases

blood concentration of the other amino acids much

more, proportionately, than it does that of tryptophan.

The more protein is in a meal, the lower is the ratio

of the resulting blood-tryptophan concentration to

the concentration of competing amino acids, and

the more slowly is tryptophan provided to the brain.

Thus the more protein in a meal, the less serotonin

subsequently produced and released.

75. Which of the following titles best summarizes the contents of the passage? (A) Neurotransmitters: Their Crucial Function in Cellular Communication (B) Diet and Survival: An Old Relationship Reexamined (C) The Blood Supply and the Brain: A Reciprocal Dependence (D) Amino Acids and Neurotransmitters: The Connection between Serotonin Levels and Tyrosine (E) The Effects of Food Intake on the Production and Release of Serotonin: Some Recent Findings

76. According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with the (A) amount of protein present in a meal (B) concentration of serotonin in the brain before a meal (C) concentration of leucine in the blood rather than with the concentration of tyrosine in the blood after a meal (D) concentration of tryptophan in the brain before a meal (E) number of serotonin-containing neurons 77. According to the passage, when the authors began their first studies, they were aware that (A) they would eventually need to design experiments that involved feeding rats high concentrations of protein (B) tryptophan levels in the blood were difficult to monitor with accuracy (C) serotonin levels increased after rats were fed meals rich in tryptophan (D) there were many neurotransmitters whose production was dependent on metabolic processes elsewhere in the body (E) serotonin levels increased after rats were injected with a large amount of tryptophan

78. According to the passage, one reason that the authors gave rats carbohydrates was to (A) depress the rats' tryptophan levels (B) prevent the rats from contracting diseases (C) cause the rats to produce insulin (D) demonstrate that insulin is the most important substance secreted by the body (E) compare the effect of carbohydrates with the effect of proteins 79. According to the passage, the more protein a rat consumes, the lower will be the (A) ratio of the rat's blood-tryptophan concentration to the amount of serotonin produced and released in the rat's brain (B) ratio of the rat's blood-tryptophan concentration to the concentration in its blood of the other amino acids contained in the protein (C) ratio of the rat's blood-tyrosine concentration to its blood-leucine concentration (D) number of neurotransmitters of any kind that the rat will produce and release (E) number of amino acids the rat's blood will contain

80. The authors' discussion of the "mechanism that provides blood tryptophan to the brain cells" is meant to (A) stimulate further research studies (B) summarize an area of scientific investigation (C) help explain why a particular research finding was obtained (D) provide supporting evidence for a controversial scientific theory (E) refute the conclusions of a previously mentioned research study

81. According to the passage, an injection of insulin was most similar in its effect on rats to an injection of (A) tyrosine (B) leucine (C) blood (D) tryptophan (E) protein

82. It can be inferred from the passage that which of the following would be LEAST likely to be a potential source of aid to a patient who was not adequately producing and releasing serotonin? (A) Meals consisting almost exclusively of protein (B) Meals consisting almost exclusively of carbohydrates (C) Meals that would elicit insulin secretion (D) Meals that had very low concentrations of tyrosine (E) Meals that had very low concentrations of leucine

83. It can be inferred from the passage that the authors initially held which of the following hypotheses about what would happen when they fed large amounts of protein to rats? (A) The rats' brain serotonin levels would not decrease. (B) The rats' brain tryptophan levels would decrease. (C) The rats' tyrosine levels would increase less quickly than would their leucine levels. (D) The rats would produce more insulin. (E) The rats would produce neurotransmitters other than serotonin.