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Questions 42-52 are based on the following passage and supplementary material.
This passage is adapted from Laura Kiesel,"Invasive Plants May Adapt to Climate Change Better than Native Species."©2014 by American Institute of Biological Sciences.
The purple loosestrife(Lythrum salicaria) —an invasive wetlands plant that was introduced to North America some 50 years ago—has become the bane of conservationists who have struggled to keep it under control. The plant has crowded out cover species, such as cattails, and harmed native biodiversity in the United States and Canada.
Evolutionary biologist and University of Toronto professor Spencer Barrett wanted to challenge the assumption that invasive plants thrived in their new habitats without internally changing their characteristics. To accomplish this, he and postdoctoral fellow Robert Colautti, of the University of British Columbia, planted purple loosestrife in different regions in North America to determine whether and how the plants adapted to distinct climates. Specifically, they transplanted
purple loosestrife from Virginia to Timmins, Ontario, and vice versa in what is known as a common garden experiment.
"The common garden experiment is an invaluable tool for understanding how the functioning of an organism’s genes is influenced by its environment and how this...interaction ultimately affects growth, development, survival, and reproduction in nature, says Colautti.
What Barrett and Colautti found was surprising: purple loosestrife tended to produce fewer fruits the further away it was from its original introduction site. That was not all. Compared with the plants transplanted to Timmins from the south, the local purple loosestrife in Timmins bloomed 20 days earlier in the spring and remained small and, in doing so,maximized seed production in the shorter growing season. These local plants also yielded up 35 to 37 times as many fruits as the southern plant grown at the same location. In contrast, the northern Ontario plants that were grown in Virginia averaged only a quarter of the seeds of the locally adapted loosestrife because of their earlier flowering when they were still very small.
Barrett and Colautti concluded that the purple loosestrife’s adaptations to different climates through changes in size and flowering times were just as important as the lack of natural pests in determining their ability to thrive. In addition, the plant was found not only to have adapted to a drastically different climate as it migrated but to have evolved this ability in a matter of mere decades.
Colautti notes that the purple loosestrife found in North America contains far more genetic
variability than the purple loosestrife indigenous to Europe, Asia, Africa, and parts of Australia, which suggests that there were multiple introductions of 55 the plant from different continents to the eastern seaboard of the United States. This counters the idea of parallel introductions, which would suggest that the purple loosestrife plants that thrive in northern,
Canada may have been introduced from a northern climate，such as in Scandinavia, whereas those in Virginia may have been introduced from a warmer climate. Instead, the populations likely reproduced with each other, thereby maximizing their genetic variability. Barrett believes that it is the plant’s identity as an outbreeder, or a plant that sexually reproduces with others in its species as opposed to cloning itself, that contributes to its resilience in new climates.
“Purple loosestrife plants are adapting because they have a lot of genetic variability," says Barrett. “More genetic variation allows for more opportunities for natural selection, which enabled the plant’s northward migration.”
Elizabeth Wolkovich, assistant professor in organismic and evolutionary biology at Harvard University, has conducted research comparing different temperature-dependent shifts in invasive plants. She believes that Barrett and Colautti’s studies support the phenological flexibility model of plant invasions. This model suggests that species that can shift their phenologies (how they respond to cues in seasonal and climatic changes) will be very successful invaders as the climate changes.
“Species that tend to be moved around a lot may increase their genetic diversity at any particular site, which could make them more locally adapted...and, therefore, better able to exploit climate change and its earlier growing season than
native species," says Wolkovich.
Mean Fruit Production of Local and Transplanted Purple Loosestrife Plant Populations
Adapted from Robert I. Colautti and Spencer C.H. Barrett," Rapid Adaptation to Climate Facilitates Range Expansion of an Invasive Plant//©2013 by American Association for the Advancement of Science.
42 In describing purple loosestrife as the “bane”(line 4)of conservationists, the author most likely meansthat purple loosestrife
A)destroys ecosystems wherever it is introduced.
B)creates a need for conservationists all acrossNorth America.
C)presents a significant challenge forconservationists.
D)serves as an important symbol toconservationists.
43 The passage suggests that if plants from any North American population of purple loosestrife were transplanted in equal numbers to both a nearby location and a distant one the plants in the nearby location would likely be
A)less invasive than the plants in the distantlocation.
B)more prolific than the plants in the distantlocation.
C)smaller in size than the plants in the distantlocation.
D)earlier blooming than the plants in the distantlocation.
44 Which choice provides the best evidence for the answer to the previous question?
A)Lines 8-12(“Evolutionary...characteristics”)
B)Lines 12-17(“To accomplish...climates”)
C)Lines 27-29 (“What...site”)
D)Lines 42-46(“Barrett…thrive”)
45 It can reasonably be inferred from the passage that the differences noted in the common garden experiment between plants originally from the northern site and plants originally from the southern site result from
A)mutations in subsequent generations after theplants were transplanted to experiment sites
B)an absence of interbreeding among the variousNorth American varieties of purple loosestrife
C)the transplanting of unrepresentatively weakspecimens of southern plants to the northernsite.
D)adaptations undergone by purple loosestrifesince its introduction to North America,
46 Which choice provides the best evidence for the answer to the previous question?
A)Lines 17-20("Specifically...experiment")
B)Lines 37 41("In contrast...small")
C)Lines 46-49("In addition...decades")
D)Lines 56-61("This...climate")
47 The main purpose of the information about Wolkkovich’s research is to
A)offer expert corroboration through repeatingthe findings reported by Barrett and Colautti.
B)demonstrate how Barrett and Colautti’s workconforms with another theory.
C)challenge Barrett and Colautti’s interpretationof the data linking fruit production in invasiveplants to seasonal and climatic changes.
D)revise Barrett and Colautti’s hypothesis aboutthe adaptability of invasive plants.
48 In the eighth paragraph(lines73-82), the focus of the passage shifts from
A) a discussion specific to purple loosestrife to amore general discussion about invasive plants.
B) an analysis of purple loosestrife productivity in different locations to an analysis of it in a single location.
C) a summary of a research study of purple loosestrife to a summary of a follow-up study conducted by another researcher.
D) a description of the general nature of invasive plants to a description of the local and transplanted populations of a specific species.
49 As used in line 86, “exploit” most nearly means
A)promote.
B)utilize.
C)abuse.
D)impose.
50 According to the graph, which statement about mean fruit production from seeds collected at the midrange site is true?
A)Plants grown from midrange seeds were moreproductive when transplanted to the northernsite than when transplanted to the southern site.
B)Plants grown from midrange seeds producedthe same amount of fruit when transplanted tothe northern site as when transplanted to thesouthern site.
C)Plants grown from midrange seeds producedapproximately 3,000 fruits when raised in themidrange site.
D) Plants grown from midrange seeds were moreproductive at each of the three sites than plantsgrown from any other seeds.
51 Which choice states a relationship between local and transplanted purple loosestrife that is indicated by the graph?
A)In the northern site, transplants from thesouthern site showed a higher mean fruitproduction than the local plants did.
B)In the southern site, transplants from the midrange site had a higher mean fruitproduction than the local plants did.
C)The range in mean fruit production of all threevarieties was smaller for the northern site thanfor the other sites.
D)Plants grown from seeds collected from thesouthern site produced the same mean numberof fruits at the northern site as the local plantsdid.
52 Taken together, the passage and the graph support which conclusion about purple loosestrife?
A)Purple loosestrife shows greater variation inmean fruit production from year to year inVirginia than it does in Newmarket.
B)The amount of fruit produced by purpleloosestrife in North America each year exceedsthat of purple loosestrife on all other continentscombined.
C)The total fruit production of North Americanpurple loosestrife increases every year as theplants adapt more completelyto theirsurroundings.
D)The mean fruit production of North Americanpurple loosestrife is lower in climates withshort growing seasons than in climates withlong growing seasons.
答案：42-52 CBCDC BBBCC D
2017年11月SAT北美真题原文及答案