1. According to paragraph 1, why do some organisms have a resting stage during their life cycle? The Role of Diapause Paragraph 1 If conditions within an organism’s environment occasionally or regularly A. To recover from injuries suffered during become harsh, it may be advantageous for an organism to have a resistant stage built into harsh conditions the life cycle. B. To devote all of their energy to a period In such a life history strategy, the organism of growth and reproduction suspends any growth, reproduction, or other C. To wait for local conditions to become activities for a period of time so that they favorable for important life events may occur at a later, more hospitable time. This genetically determined resting stage, D. To prepare to move to a different characterized by the cessation of environment if conditions become harsh development and protein synthesis and suppression of the metabolic rate, is called 2. Why does the author mention “seeds of diapause. Many other kinds of resting stages, the arctic lupine”? with different levels of suppression of physiological activities, are known. Some of A. To argue that members of the pea these resistant stages can be extremely long-family are extremely resistant to cold lived. In one case, seeds of the arctic lupine, a temperatures member of the pea family recovered from ancient lemming burrows in the Arctic, B. To provide information about what germinated in three days even though they ancient lemmings ate during their long were carbon- dated at more than resting periods 10,000years old! C. To provide an example of an organism with a resting stage that has many different levels of suppression of physiological activities. D. To support the claim that some resting stages last an extremely long time 3. According to paragraph 2, why do many seeds require a period of stratification? Paragraph 2 Unfavorable conditions that are relatively predictable probably pose a simpler problem A. To slowly build up a tolerance for lower for organisms than do unpredictable conditions. Adaptations to the regular change and lower temperatures of seasons in the temperate and polar regions B. To guarantee that the seeds grow after may be relatively simple. For example, many seeds require a period of stratification, and not before exposure to low temperatures for some C. To make sure that the seeds can deal minimum period, before they will germinate. with unpredictable conditions This is a simple adaptation to ensure that germination occurs following the winter D. To give the seeds enough time to conditions rather than immediately prior to germinate before winter begins their onset. In contrast, unfavorable conditions that occur unpredictably pose 4. The word “ severity ” in the passage is considerable problems for organisms. In fact, closest in meaning to unpredictability is probably a greater problem A. length than is the severity of the unfavorable B. harshness period. How can organisms cope with the C. unexpectedness unpredictable onset of good or poor D. completeness conditions? 【Paragraph 3】 Many adaptations to this general problem are based on a resting stage that awaits favorable conditions. We will consider two examples from the vertebrates. The first is the red kangaroo. This marsupial inhabits the deserts of central Australia where the onset of rains and the resulting sudden growth of vegetation are extremely unpredictable. Obviously, it is advantageous for a kangaroo female to produce young at a time when plant productivity is sufficient to support her offspring. For such a relatively large mammal, however, gestation (the period of development during pregnancy) is so long that if a female waited to mate and carry the young until after the rains came, the favorable period might be past. The kangaroo’s life history adaptation to this problem involves the use of embryonic diapause during gestation (development in the uterus). 5. According to paragraph 4, all of the following statements are true about the young offspring of the red kangaroo EXCEPT: Paragraph 4 After a 31-day gestation period, the female gives birth to a tiny helpless young typical of marsupials. The newborn crawls into the mother’s pouch and attaches to a teat where A. After birth, a newborn crawls into the it continues to grow and develop. After 235 mother’s pouch where it grows and days it leaves the pouch but remains with the develops. mother and obtains milk from her. Two days B. After a young kangaroo leaves its after giving birth, the female mates again. mother’s pouch, it still needs its mother’s The fertilized egg enters a 204-day period of milk. diapause during which it remains in the uterus but does not attach. It then implants, C. A mother usually gives birth to three and 31 days later, birth of the second young baby kangaroos at the same time. occurs. Note that the first young leaves the pouch at just this time. Again, the female D. A baby kangaroo spends 235 days in mates, fertilization occurs, and another the mother’s pouch after its birth. diapause follows. The eventual result is that at any one time, the female has three young 6. Paragraph 4 supports all of the at various stages of development one in following statements about the red diapause, one in the pouch, and one outside kangaroo of central Australia EXCEPT: the pouch. Among other benefits, this allows her to freeze the development of an embryo A. A female kangaroo mates again shortly during times of drought and food shortage after her newborn enters her pouch. until the offspring in the pouch is able to leave. B. During diapause, a young kangaroo stays in the female’s pouch and growth of a second fertilized egg inside the uterus is delayed. C. A female kangaroo can freeze the development of her young at each stage of their development. D. The adaptation of diapause enables female kangaroos to ensure the survival of their young during periods of environmental stress.
托福阅读真题 The Role of Diapause-练习与答案
