题目：
Submerged Plant Life:Surviving Underwater
Whereas a land plant expends a great deal of energy on the production of roots that can forage in the soil for vital water supplies, an aquatic plant is surrounded by water. All of the adaptations associated with drought resistance in land plants (small, inrolled or leathery leaves, stout cylindrical stems, and so on)are not needed in the water. Water is also a denser medium than air, and this means that plants find it easier to support their leafy canopies without resort to tough stems and branches. There is no equivalent to woody trunks among aquatic plants. Water supports the plants, and those parts that need to be at, or close to, the surface can be provided with air-filled flotation structures.
Hardened, woody materials are, therefore, uncommon in submerged aquatic plants. They are sometimes needed for the protection of seeds, especially if these are likely to become trapped in mud or desiccated (dried out) for long periods or if they are adapted to pass through the gut of an animal and survive to enjoy the consequences of wider dispersal. For support purposes, however, the natural buoyancy of the water is adequate.
The supply of elements needed by a plant for constructing its component parts is also freely available. Whereas a land plant gains most of its elements (with the obvious exception of carbon) from roots embedded in the soil and often relies on microbes around those roots to liberate nutrients from organic matter and clay particles, aquatic plants are constantly bathed in nutrient solution. Sometimes that nutrient solution is very dilute in vital elements, and the plant needs to be adept at concentrating them.
Roots in submerged aquatic plants have some absorptive function, but this need not be restricted to the substrate (materials at the bottom of a marine habitat). In the Canadian pondweed and in the bulbous rush, for example, stems proliferate and produce dense bunches of roots at specific growth points (nodes). The roots contain no chlorophyll, so they do not photosynthesize, but they absorb elements from the water and, if they extend down to the basal mud, they also serve to anchor the plant, thus preventing its being washed away in the flow of water.
Photosynthesis requires a supply of light (from which energy is trapped) and carbon dioxide, which is used as a source of carbon for the building of sugars and complex organic molecules. Photosynthesis under water is perfectly possible as long as these two resources are available. Light is absorbed by water, but in the shallow- water bodies included in the definition of wetlands, this does not deplete the resource significantly. If, however, the water contains suspended particles of material (either inorganic or organic), light is absorbed more effectively and may be in short supply even in a shallow- water body. When this occurs, submerged aquatic plants can exist only close to the surface, or they may be replaced by aquatics with floating leaves, such as the water lilies, or by plants with their entire body floating in a mat. Water lilies, with their tuberous stems in the substrate and their leaf blades on the surface, are limited in the depth of water they can occupy by the length of the leaf stalk that needs to be developed to link these stems to the floating leaves. They seldom occupy water bodies deeper than 12 feet (3.7 meters).
The availability of carbon in the water depends on its being dissolved from the atmosphere or, alternatively, on the supply of calcium (or magnesium) carbonate from rocks. Carbon dioxide is also generated by the plant and animal respiration in the water, and by the decay processes taking place mainly in the organic-rich substrates on the bottom. Dissolved carbon dioxide, like dissolved oxygen, does not diffuse as rapidly in water as it does in air, so, at any given time, its availability will depend on how rapidly the aquatic plants use up the supply in their photosynthetic activities and how quickly it is replenished. At night, when no photosynthesis takes place, carbon builds up in the water, but in the daytime, when the plants are actively photosynthesizing, it may become locally scarce, forcing plants to compete for the limited supply.
1
Whereas a land plant expends a great deal of energy on the production of roots that can forage in the soil for vital water supplies, an aquatic plant is surrounded by water. All of the adaptations associated with drought resistance in land plants (small, inrolled or leathery leaves, stout cylindrical stems, and so on)are not needed in the water. Water is also a denser medium than air, and this means that plants find it easier to support their leafy canopies without resort to tough stems and branches. There is no equivalent to woody trunks among aquatic plants. Water supports the plants, and those parts that need to be at, or close to, the surface can be provided with air-filled flotation structures.
which of the following provides structural support for the parts of an aquatic plant?
Factual Information Questions事实信息题
AHardened stems
BA floating root system
CThe surrounding water
DAir moving across the water’s surface
2
Hardened, woody materials are, therefore, uncommon in submerged aquatic plants. They are sometimes needed for the protection of seeds, especially if these are likely to become trapped in mud or desiccated (dried out) for long periods or if they are adapted to pass through the gut of an animal and survive to enjoy the consequences of wider dispersal. For support purposes, however, the natural buoyancy of the water is adequate.
According to paragraph 2. woody materials are useful for protecting seeds from all of the following risks EXCEPT
Negative Factual Information Questions否定事实信息题
Adrying out for a long time
Bgetting stuck in the mud
Cpassing through an animal’s digestive system
Dbecoming submerged for long periods of time
3
The supply of elements needed by a plant for constructing its component parts is also freely available. Whereas a land plant gains most of its elements (with the obvious exception of carbon) from roots embedded in the soil and often relies on microbes around those roots to liberate nutrients from organic matter and clay particles, aquatic plants are constantly bathed in nutrient solution. Sometimes that nutrient solution is very dilute in vital elements, and the plant needs to be adept at concentrating them.
The word “obvious” in the passage is closest in meaning to
Vocabulary Questions词汇题
Apossible
Bsole
Cimportant
Dclear
4
The supply of elements needed by a plant for constructing its component parts is also freely available. Whereas a land plant gains most of its elements (with the obvious exception of carbon) from roots embedded in the soil and often relies on microbes around those roots to liberate nutrients from organic matter and clay particles, aquatic plants are constantly bathed in nutrient solution. Sometimes that nutrient solution is very dilute in vital elements, and the plant needs to be adept at concentrating them.
The word “adept” in the passage is closest in meaning to
Vocabulary Questions词汇题
Askilled
Baccurate
Cflexible
Dthorough
5
Roots in submerged aquatic plants have some absorptive function, but this need not be restricted to the substrate (materials at the bottom of a marine habitat). In the Canadian pondweed and in the bulbous rush, for example, stems proliferate and produce dense bunches of roots at specific growth points (nodes). The roots contain no chlorophyll, so they do not photosynthesize, but they absorb elements from the water and, if they extend down to the basal mud, they also serve to anchor the plant, thus preventing its being washed away in the flow of water.
According to paragraph 4, which of the following is NOT true of the roots of the Canadian pondweed and bulbous rush?
Negative Factual Information Questions否定事实信息题
AThey grow off of certain points along their stems.
BThey help to hold the plant in place.
CThey take in floating nutrients
DThey absorb materials from the basal mud
6
Photosynthesis requires a supply of light (from which energy is trapped) and carbon dioxide, which is used as a source of carbon for the building of sugars and complex organic molecules. Photosynthesis under water is perfectly possible as long as these two resources are available. Light is absorbed by water, but in the shallow- water bodies included in the definition of wetlands, this does not deplete the resource significantly. If, however, the water contains suspended particles of material (either inorganic or organic), light is absorbed more effectively and may be in short supply even in a shallow- water body. When this occurs, submerged aquatic plants can exist only close to the surface, or they may be replaced by aquatics with floating leaves, such as the water lilies, or by plants with their entire body floating in a mat. Water lilies, with their tuberous stems in the substrate and their leaf blades on the surface, are limited in the depth of water they can occupy by the length of the leaf stalk that needs to be developed to link these stems to the floating leaves. They seldom occupy water bodies deeper than 12 feet (3.7 meters).
The author discusses “suspended particles of material” in order to
Rhetorical Purpose Questions修辞目的题
Aexplain why photosynthesis is necessary under water
Bidentify a condition that requires submerged aquatic plants to adapt to limited light
Ccontrast the need for light in water lilies with the light needs other plants that have floating leaves
Ddescribe a part of the process by which photosynthesis produces sugars and other complex organic molecules
7
Photosynthesis requires a supply of light (from which energy is trapped) and carbon dioxide, which is used as a source of carbon for the building of sugars and complex organic molecules. Photosynthesis under water is perfectly possible as long as these two resources are available. Light is absorbed by water, but in the shallow- water bodies included in the definition of wetlands, this does not deplete the resource significantly. If, however, the water contains suspended particles of material (either inorganic or organic), light is absorbed more effectively and may be in short supply even in a shallow- water body. When this occurs, submerged aquatic plants can exist only close to the surface, or they may be replaced by aquatics with floating leaves, such as the water lilies, or by plants with their entire body floating in a mat. Water lilies, with their tuberous stems in the substrate and their leaf blades on the surface, are limited in the depth of water they can occupy by the length of the leaf stalk that needs to be developed to link these stems to the floating leaves. They seldom occupy water bodies deeper than 12 feet (3.7 meters).
According to paragraph 5, floating leaves allow a water lily to do which of the following?
Factual Information Questions事实信息题
AConvert sugars into complex organic molecules for photosynthesis
BObtain needed light that is unavailable below the water’s surface
COccupy deep waters rather than shallow-water bodies
DGrow tuberous stems that are very long
8
The availability of carbon in the water depends on its being dissolved from the atmosphere or, alternatively, on the supply of calcium (or magnesium) carbonate from rocks. Carbon dioxide is also generated by the plant and animal respiration in the water, and by the decay processes taking place mainly in the organic-rich substrates on the bottom. Dissolved carbon dioxide, like dissolved oxygen, does not diffuse as rapidly in water as it does in air, so, at any given time, its availability will depend on how rapidly the aquatic plants use up the supply in their photosynthetic activities and how quickly it is replenished. At night, when no photosynthesis takes place, carbon builds up in the water, but in the daytime, when the plants are actively photosynthesizing, it may become locally scarce, forcing plants to compete for the limited supply.
Which of the following can be inferred from paragraph 6 about carbon dioxide at night?
Inference Questions推理题
AIt comes primarily from plants that are photosynthesizing.
Bit is present less at night than it is during the day.
C it is mainly produced by nighttime decay in the substrate.
Dit builds up at night because it is not being used as it is during the day.
9
Photosynthesis requires a supply of light (from which energy is trapped) and carbon dioxide, which is used as a source of carbon for the building of sugars and complex organic molecules. [■]Photosynthesis under water is perfectly possible as long as these two resources are available. [■]Light is absorbed by water, but in the shallow- water bodies included in the definition of wetlands, this does not deplete the resource significantly. [■]If, however, the water contains suspended particles of material (either inorganic or organic), light is absorbed more effectively and may be in short supply even in a shallow- water body. [■]When this occurs, submerged aquatic plants can exist only close to the surface, or they may be replaced by aquatics with floating leaves, such as the water lilies, or by plants with their entire body floating in a mat. Water lilies, with their tuberous stems in the substrate and their leaf blades on the surface, are limited in the depth of water they can occupy by the length of the leaf stalk that needs to be developed to link these stems to the floating leaves. They seldom occupy water bodies deeper than 12 feet (3.7 meters).
Look at the four squares [■] that indicate where the following sentence could be added to the passage
Whether there is enough light in a particular body of Water depends on some key characteristics of that bodyInsert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Aquatic plants have different adaptations than do land plants because of the special properties of aquatic environments.
Prose Summary Questions概要小结题
Select 3 answers
AHard and woody materials are common in land plants but are mostly unnecessary in aquatic plants, except for protecting seeds.
BNutrients and other elements are freely available in the water and an absorbed by roots, but light may be less available in certain aquatic environments.
CEven in aquatic environments with plenty of light and carbon dioxide, photosynthesis is not possible if the water is too deep.
DPlants that extend all the way down to the muddy aquatic floor are better able to preserve their seeds and ensure widespread dispersal.
EThe Canadian pondweed and bulbous rush have leaves floating on the surface of the water in order to enhance photosynthesis.
FSome aquatic plants must have leaves close to the surface in order to absorb enough light and carbon dioxide that may be in limited supply.
