RC- Exercise 6
All of the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots, stems, leaves, and fruits? The answer is that only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time. This is accomplished by a complex system of chemical messengers that in plants include hormones and other regulatory molecules. Five major hormones have been identified: auxin, abscisic acid, cytokinin, ethylene, and gibberellin. Studies of plants have now identified a new class of regulatory molecules called oligosaccharins.
Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops. Auxin, for instance, stimulates the rate of cell elongation, causes shoots to grow up and roots to grow down, and inhibits the growth of lateral shoots. Auxin also causes the plant to develop a vascular system, to form lateral roots, and to produce ethylene.
The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones. Such a hierarchy may also exist in plants. Oligosaccharins are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharins. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.
Based on the Passage, answer the following questions:
1. According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because
(A) it is not known exactly what functions the hormones perform
(B) each hormone has various effects on plants
(C) none of the hormones can function without the others
(D) each hormone has different effects on different kinds of plants
(E) each hormone works on only a small subset of a cell’s genes at any particular time
2. the passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?
(a) plant cell walls
(b) the complement of genes in each plant cell
(c) a subset of a plant cell’s gene complement
(d) the five major hormones
(e) the oligosaccharins
3. the passage suggests that which of the following is a function likely to be performed by an oligosaccharin?
(a) to stimulate a particular plant cell to become part of a plant’s root system
(b) to stimulate the walls of a particular cell to produce other oligosaccharins
(c) to activate enzymes that release specific chemical messengers from plant cell walls
(d) to duplicate the gene complement in a particular plant cell
(e) to produce multiple effects on a particular subsystem of plant cells
4. the author mentions specific effects that auxin has on plant development in order to illustrate the
(a) point that some of the effects of plant hormones can be harmful
(b) way in which hormones are produced by plants
(c) hierarchical nature of the functioning of plant hormones
(d) differences among the best-known plant hormones
(e) concept of pleiotropy as it is exhibited by plant hormones
5. according to the passage, which of the following best describes a function performed by oligosaccharin?
(a) regulating the daily functioning of a plant’s cells
(b) interacting with one another to produce different chemicals
(c) releasing specific chemical messengers from a plant’s cell walls
(d) producing the hormones that cause plant cells to differentiate to perform different functions
(e) influencing the development of a plant’s cells by controlling the expression of the cells’ genes
6. the passage suggests that, unlike the pleiotropic hormones, oligosaccharin could be used effectively to
(a) trace the passage of chemicals through the walls of cells
(b) pinpoint functions of other plant hormones
(c) artificially control specific aspects of the development of crops
(d) alter the complement of genes in the cells of plants
(e) alter the effects of the five major hormones on plant development
Two recent publications offer different assessments of the career of the famous British nurse Florence Nightingale. A book by Anne Summers seeks to debunk the idealizations and present a reality at odds with Nightingale’s heroic reputation. According to Summers Nightingale’s importance during the Crimean War has been exaggerated: not until near the war’s end did she become supervisor of the female nurses. Additionally, Summers writes that the contribution of the nurses to the relief of the wounded was at best marginal. The prevailing problems of military medicine were caused by army organizational practices, and the addition of a few nurses to the medical staff could be no more than symbolic. Nightingale’s place in the national pantheon, Summers asserts, is largely due to the propagandistic efforts of contemporary newspaper reporters.
By contrast, the editors of a new volume of Nightingale’s letters view Nightingale as a person who significantly influenced not only her own age but also subsequent generations. They highlight her ongoing efforts to reform sanitary conditions after the war. For example, when she learned that peacetime living conditions in British barracks were so horrible that the death rate of enlisted men far exceeded that of neighboring civilian populations, she succeeded in persuading the government to establish a Royal Commission on the Health of the Army. She used sums raised through public contributions to found a nurses’ training hospital in London. Even in administrative matters, the editors assert her practical intelligence was formidable: as recently as 1947 the British Army’s medical services were still using the cost-accounting system she had devised in the 1860’s.
I believe that the evidence of her letters supports continued respect for Nightingale’s brilliance and creativity. When counseling a village schoolmaster to encourage children to use their faculties of observation she sounds like a modern educator. Her insistence on classifying the problems of the needy in order to devise appropriate treatments is similar to the approach of modern social workers. In sum, although Nightingale may not have achieved all other goals during the Crimean War, her breadth of vision and ability to realize ambitious projects have earned her an eminent place among the ranks of social pioneers.
Based on the Passage, answer the following questions:
7. The passage is primarily concerned with evaluating
(A) the importance of Florence Nightingale’s innovations in the field of nursing
(B) contrasting approaches to the writing of historical biography
(C) contradictory accounts of Florence Nightingale’s historical significance
(D) the quality of health care in nineteenth-century England
(E) the effect of the Crimean War on developments in the field of health care
8. According to the passage, the editors of Nightingale’s letters credit her with contributing to which of the following?
(A) Improvement of the survival rate for soldiers in British Army hospitals during the Crimean War
(B) The development of a nurses’ training curriculum that was far in advance of its day
(C) The increase in the number of women doctors practicing in British Army hospitals
(D) Establishment of the first facility for training nurses at a major British university
(E) The creation of an organization for monitoring the peacetime living conditions of British soldiers
9. The passage suggests which of the following about Nightingale’s relationship with the British public of her day?
(A) She was highly respected, her projects receiving popular and governmental support.
(B) She encountered resistance both from the army establishment and the general public.
(C) She was supported by the working classes and opposed by the wealthier classes.
(D) She was supported by the military establishment but had to fight the governmental bureaucracy.
(E) After initially being received with enthusiasm, she was quickly forgotten.
10. The passage suggests which of the following about sanitary conditions in Britain after the Crimean War?
(A) While not ideal, they were superior to those in other parts of the world.
(B) Compared with conditions before the war, they had deteriorated.
(C) They were more advanced in rural areas than in the urban centers.
(D) They were worse in military camps than in the neighboring civilian populations.
(E) They were uniformly crude and unsatisfactory throughout England.
11. With which of the following statements regarding the differing interpretations of Nightingale’s importance would the author most likely agree?
(A) Summers misunderstood both the importance of Nightingale’s achievements during the Crimean War and her subsequent influence on British policy.
(B) The editors of Nightingale’s letters made some valid points about her practical achievements but they still exaggerated her influence on subsequent generations.
(C) Although Summers’ account of Nightingale’s role in the Crimean War may be accurate, she ignored evidence of Nightingale’s subsequent achievement that suggests that her reputation as an eminent social reformer is well deserved.
(D) The editors of Nightingale’s letters mistakenly propagated the outdated idealization of Nightingale that only impedes attempts to arrive at a balanced assessment of her true role.
(E) The evidence of Nightingale’s letters supports Summers’ conclusions both about Nightingale’s activities and about her influence.
12. Which of the following is an assumption underlying the author’s assessment of Nightingale’s creativity?
(A) Educational philosophy in Nightingale’s day did not normally emphasize developing children’s ability to observe.
(B) Nightingale was the first to notice the poor living conditions in British military barracks in peacetime.
(C) No educator before Nightingale had thought to enlist the help of village schoolmasters in introducing new teaching techniques.
(D) Until Nightingale began her work, there was no concept of organized help for the needy in nineteenth-century Britain.
(E) The British army’s medical services had no cost- accounting system until Nightingale devised one in the 1860’s.
13. In the last paragraph, the author is primarily concerned with
(A) summarizing the arguments about Nightingale presented in the first two paragraphs
(B) refuting the view of Nightingale’s career presented in the preceding paragraph
(C) analyzing the weaknesses of the evidence presented elsewhere in the passage
(D) citing evidence to support a view of Nightingale’s career
(E) correcting a factual error occurring in one of the works under review