2017托福阅读生物类真题
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How Plants and Animals Arrived in the Hawaiian Islands
Scientists have attempted to explain how living things that are not native to the Hawaiian Islands were able to reach the islands from distant places. The way in which birds reached the Hawaiian Islands is obvious enough. Some of the plants that probably came with them had seeds that readily attached to feathers, about 7 percent of the Hawaiian nonendemic (nonnative) seed plants probably arrived in this way. The Hawaiian insects, too, arrived by air. Entomologists have used airplanes and ships to trail fine nets over the Pacific at different heights and have trapped a variety of insects, most of which, as would be expected, are light-bodied. These types also predominate in the Hawaiian Islands (an indication of their airborne arrival), although heavier dragonflies, sphinx moths, and butterflies are also found there.
The influence of the winds in providing colonists is shown by the fact that, although flowering plants are far more common than ferns in the world as a whole, their diversity in Hawaii is more evenly balanced: 225 immigrant flowering plants and 135 immigrant ferns. The relatively greater success of the ferns is probably due to the fact that their spores (reproductive structures) are much smaller and lighter than the seeds of flowering plants. Of the nonendemic seed plants of the Hawaiian Islands, about 7.5 percent almost certainly arrived carried by the wind, while another 30.5 percent have small seeds (up to three millimeters in diameter) and thus may also have arrived this way.
One of the most interesting plants that probably arrived as a wind-borne seed is the tree Metrosideros. It is unusual because its seeds are relatively tiny, and this has allowed it to become widely dispersed through the Pacific islands. It is able to form forests on lowland lava with virtually no soil—a great advantage on a volcanic island. Metrosideros shows great variability in its appearance in different environments, from a large tree in the wet rain forest, to a shrub on windswept ridges, to as little as 15 centimeters high in peatlands, and it is therefore the dominant tree of the Hawaiian forest. The different forms are not distinct species, and intermediates are found where two different types are adjacent to one another.
Probably the single most important method of entry of seed plants to the Hawaiian Islands has been as seeds within the digestive systems of birds that have eaten their fruit (e.g. blueberry, sandalwood), about 37 percent of the nonendemic seed plants of the islands probably arrived in this way. Significantly, many plants that succeeded in reaching the islands are those that, unlike the rest of their families, bear fleshy fruits instead of dry seeds, such as the species of mint, lily, and nightshade found in Hawaii.
Dispersed by sea accounts for only about 5 percent of the nonendemic Hawaiian seed plants. As well as the widespread coconut, the islands also contain Scaevola toccata, this shrub has white, buoyant fruits and forms dense hedges along the edge of the beach. Another seaborne migrant is Erythrina, most species of this plant have buoyant, beanlike seeds. On Hawaii, after its arrival on the beach, Erythrina was unusual in adapting to an island environment, and a new endemic species, the coral tree E sandwichensis, has evolved on the island. Unlike those of its ancestors, the seeds of the coral tree do no float—an example of the loss of its dispersal mechanism often characteristic of an island species.
The successful colonists of the Hawaiian Islands are the exceptions, many groups, both plants and animals, have failed to reach the islands by natural processes. There are no truly freshwater fish and no native amphibians, reptiles, or mammals (except for one species of bat), while 21 orders of insect are completely absent. As might be expected, most of these are types that seem in general to have very limited powers of dispersal. For example, the ants, which are an important part of the insect fauna in other tropical parts of the world, were originally absent. They have, however, since been introduced by humans, and 36 different species have now established themselves and filled their usual dominant role in insect faunas. This proves that the obstacle was reaching the islands, not the nature of the Hawaiian environment.
Paragraph 1
Scientists have attempted to explain how living things that are not native to the Hawaiian Islands were able to reach the islands from distant places. The way in which birds reached the Hawaiian Islands is obvious enough. Some of the plants that probably came with them had seeds that readily attached to feathers, about 7 percent of the Hawaiian nonendemic (nonnative) seed plants probably arrived in this way. The Hawaiian insects, too, arrived by air. Entomologists have used airplanes and ships to trail fine nets over the Pacific at different heights and have trapped a variety of insects, most of which, as would be expected, are light-bodied. These types also predominate in the Hawaiian Islands (an indication of their airborne arrival), although heavier dragonflies, sphinx moths, and butterflies are also found there.
1. The word "obvious" in the passage is closest in meaning to
¡ unusual
¡ natural
¡ clear
¡ simple
2. According to paragraph 1, how are dragonflies, sphinx moths, and butterflies different from other insects in Hawaii?
¡ They are heavier.
¡ They are native to Hawaii.
¡ They fly at much higher levels above the land.
¡ They were brought to the islands by birds.
Paragraph 2
The influence of the winds in providing colonists is shown by the fact that, although flowering plants are far more common than ferns in the world as a whole, their diversity in Hawaii is more evenly balanced: 225 immigrant flowering plants and 135 immigrant ferns. The relatively greater success of the ferns is probably due to the fact that their spores (reproductive structures) are much smaller and lighter than the seeds of flowering plants. Of the nonendemic seed plants of the Hawaiian Islands, about 7.5 percent almost certainly arrived carried by the wind, while another 30.5 percent have small seeds (up to three millimeters in diameter) and thus may also have arrived this way.
3. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
¡ In the world as a whole, flowering plants are much more common than ferns, but in Hawaii the opposite is true.
¡ A wide variety of plants, including 225 flowering plants and 135 ferns, were probably brought to Hawaii by wind.
¡ Ferns are well suited to the windy conditions in Hawaii, as demonstrated by their high diversity compared to flowering plants.
¡ Hawaii has a higher proportion of ferns to flowering plants than the world as a whole because many of its colonists arrived by wind.
4. According to paragraph 2, Hawaiian plants whose seeds are no more than 3 millimeters in diameter
¡ are more likely to be flowering plants than ferns
¡ make up about 7.5 percent of all nonendemic plants on the islands
¡ make up the majority of seed-bearing plants on the islands
¡ may have been transported to the islands by wind
Paragraph 3
One of the most interesting plants that probably arrived as a wind-borne seed is the tree Metrosideros. It is unusual because its seeds are relatively tiny, and this has allowed it to become widely dispersed through the Pacific islands. It is able to form forests on lowland lava with virtually no soil—a great advantage on a volcanic island. Metrosideros shows great variability in its appearance in different environments, from a large tree in the wet rain forest, to a shrub on windswept ridges, to as little as 15 centimeters high in peatlands, and it is therefore the dominant tree of the Hawaiian forest. The different forms are not distinct species, and intermediates are found where two different types are adjacent to one another.
5. According to paragraph 3, all of the following are true of the tree Metrosideros EXCEPT:
¡ It has very small seeds that were probably brought to the islands by wind.
¡ It needs almost no soil to grow.
¡ It has evolved into at least three distinct species since reaching the islands.
¡ It adapts its size to fit environmental conditions.
6. The phrase "adjacent to" in the passage is closest in meaning to
¡ next to
¡ mixed with
¡ competing with
¡ related to
Paragraph 4
Probably the single most important method of entry of seed plants to the Hawaiian Islands has been as seeds within the digestive systems of birds that have eaten their fruit (e.g. blueberry, sandalwood), about 37 percent of the nonendemic seed plants of the islands probably arrived in this way. Significantly, many plants that succeeded in reaching the islands are those that, unlike the rest of their families, bear fleshy fruits instead of dry seeds, such as the species of mint, lily, and nightshade found in Hawaii.
7. In paragraph 4, what point is the author making about the particular species of mint, lily and nightshade found in Hawaii?
¡ These species have close relatives that, because they produce dry seeds, are unable to grow in the Hawaiian Islands.
¡ If these species did not produce edible fruits, they probably would not have succeeded in reaching the islands.
¡ These species, in addition to Hawaii’s blueberry and sandalwood, provide further examples of fruiting plants that now grow in Hawaii but that are not native to the islands.
¡ These species have close relatives in the Hawaiian Islands that are able to attract birds without producing fleshy fruit.
Paragraph 5
Dispersed by sea accounts for only about 5 percent of the nonendemic Hawaiian seed plants. As well as the widespread coconut, the islands also contain Scaevola toccata, this shrub has white, buoyant fruits and forms dense hedges along the edge of the beach. Another seaborne migrant is Erythrina, most species of this plant have buoyant, beanlike seeds. On Hawaii, after its arrival on the beach, Erythrina was unusual in adapting to an island environment, and a new endemic species, the coral tree E sandwichensis, has evolved on the island. Unlike those of its ancestors, the seeds of the coral tree do no float—an example of the loss of its dispersal mechanism often characteristic of an island species.
8. The word "widespread" in the passage is closest in meaning to
¡ impressive
¡ common
¡ adaptable
¡ hardy
9. The word "dense" in the passage is closest in meaning to
¡ long
¡ tall
¡ beautiful
¡ thick
10. According to paragraph 5, which of the following plants does NOT have seeds that float?
¡ Scaevola toccala
¡ E sandwichensis
¡ Erythrina
¡ Coconut
Paragraph 6
The successful colonists of the Hawaiian Islands are the exceptions, many groups, both plants and animals, have failed to reach the islands by natural processes. There are no truly freshwater fish and no native amphibians, reptiles, or mammals (except for one species of bat), while 21 orders of insect are completely absent. As might be expected, most of these are types that seem in general to have very limited powers of dispersal. For example, the ants, which are an important part of the insect fauna in other tropical parts of the world, were originally absent. They have, however, since been introduced by humans, and 36 different species have now established themselves and filled their usual dominant role in insect faunas. This proves that the obstacle was reaching the islands, not the nature of the Hawaiian environment.
11. Which of the following can be inferred from paragraph 6 about the animals currently on the Hawaiian Islands?
¡ Except one species of bat, all of the amphibians, reptiles, and mammals on the islands were introduced by people.
¡ Except for one species of bat, there are no amphibians, reptiles, or mammals on the islands
¡ Except for one species of bat, none of the amphibians, reptiles, or mammals on the islands have spread to other islands.
¡ Except for one species of bat, all of the amphibians, reptiles, and mammals on the islands died out after people arrived.
12. Why does the author provide the information that a number of species of ants “have now established themselves and filled their usual dominant role in insect faunas”?
¡ To demonstrate that species introduced by humans often disrupt the island ecosystem by replacing endemic species
¡ To provide an example of some of the most successful colonists of the Hawaiian Islands
¡ To support the claim that many types of organisms are absent from Hawaii because they could not get there, not because they are unsuited to its environment
¡ To argue that ants have better powers of dispersal than the 21 orders of insects that are absent from the islands
Paragraph 1
Scientists have attempted to explain how living things that are not native to the Hawaiian Islands were able to reach the islands from distant places. The way in which birds reached the Hawaiian Islands is obvious enough. ■Some of the plants that probably came with them had seeds that readily attached to feathers, about 7 percent of the Hawaiian nonendemic (nonnative) seed plants probably arrived in this way. ■The Hawaiian insects, too, arrived by air. ■Entomologists have used airplanes and ships to trail fine nets over the Pacific at different heights and have trapped a variety of insects, most of which, as would be expected, are light-bodied. ■These types also predominate in the Hawaiian Islands (an indication of their airborne arrival), although heavier dragonflies, sphinx moths, and butterflies are also found there.
13. Look at the four squares [■] that indicate where the following sentence can be added to the passage.
Flying over from the American mainland or from other Pacific Islands, they often brought additional colonists with them.
Where would the sentence best fit?
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Drag your choices to the spaces where they belong. To review the passage, click on View Text.
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