题目内容
（请给出正确答案）
The photosynthesis by ancient microbes is an example of ______.
A．the change of Earth
B．the long history of Earth
C．the life's influences on Earth
D．the power of sunlight
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更多“The photosynthesis by ancient …”相关的问题
The crucial function of photosynthesis in terms of plant needs is______.
A．to form. sugars
B．to preserve water
C．to combine carbon dioxide with water
D．to derive energy from light
The essential function of photosynthesis in terms of plant needs is ______ .
A．to derive energy from light
B．to preserve water
C．to combine carbon dioxide with water
D．to form. sugars
Plants have【C10】______ relations to get what they need to survive. Normal【C11】______ plants can make their own carbohydrates through photosynthesis, but they still need minerals. Most plants have【C12】______ a symbiotic relationship with a【C13】______ network of what are called mycorrhizal fungi, which lies beneath the forest【C14】______ . The fungi help green plants absorb minerals through their roots, and【C15】______ , the plants normally【C16】______ the fungi with sugars, or carbon. With a number of plants sharing the same fungal web, it was perhaps【C17】______ that a few cheaters —dubbed epiparasites-- would evolve to beat the system.【C18】______ , these plants reversed the flow of carbons【C19】______ it into their roots from the fungi【C20】______ releasing it as "payment".
【C1】
A．but
B．if
C．because
D．though
The actual amount of water in the plant at any one time, is only a very small part of what passes through it during its development. The processes of photosynthesis (光合作用), by which carbon dioxide and water are combined in the presence of chlorophyll (叶绿素) and with energy derived from light--to form. sugars, require that carbon dioxide from the air enter the plant. This occurs mainly in the leaf. The leaf surface is not solid but contains great numbers of minute openings, through which the carbon dioxide enters. The same structure that permits the one gas to enter the leaf, however, permits another gas--water vapor to be lost from it. Since carbon dioxide is present in the air only in trace quantities (3 to 4 parts in 10,000 parts of air) and water vapor is near saturation in the air spaces within the leaf (at 80F, saturated air would contain about 186 parts of water vapor in 10,000 parts of air), the total amount of water vapor lost is many times the carbon dioxide intake. Actually because of wind and other factors, the loss of water in proportion to carbon dioxide intake may be even greater. Also, not all of the carbon dioxide that enters the leaf is synthesized into carbohydrates.
A growing plant needs water for all of the following except ______.
A．forming sugars
B．sustaining actively growing parts as well as woody stems
C．absorbing mineral elements
D．taking in carbon dioxide from the air
The actual amount of water in the plant at any one time, however, is only a very small part of what passes through it during its development. The processes of photosynthesis, by which carbon dioxide and water are combined—in the presence of chlorophyll (叶绿素) and with energy derived from light to form. sugars, require that carbon dioxide from the air enter the plant. This occurs mainly in the leaves. The leaf surface is not solid but contains great numbers of minute (细小的) openings, through which the carbon dioxide enters. The same structure that permits the one gas to enter the leaf, however, permits another gas—water vapor to be lost from it. Since carbon dioxide is present in the air only in trace quantities (3 to 4 parts in 10, 000 parts of air) and water vapor is near saturation in the air spaces within the leaf (at 80 F , saturated air would contain about 186 parts of water vapor in 10,000 parts of air), the total amount of water vapor lost is many times the carbon dioxide intake. Actually, because of wind and other factors, the loss of water in proportion to carbon dioxide intake may be even greater than the relative concentrations of the two gases. Also, not all of the carbon dioxide that enters the leaf is synthesized into carbohydrates(碳水化合物).
A growing plant needs water for all of the following except ______.
A．forming simple sugars
B．keeping woody stems
C．keeping green
D．producing carbon dioxide
Why leaves change colors
If you are lucky, you live in one of those parts of the world where Nature has one last fun before settling down into winter's sleep. In those lucky places, as days shorten and temperatures become crisp, the quiet green palette(调色板) of summer leaves is transformed into the vivid autumn palette of reds, oranges, golds, and browns before the leaves fall off the trees. On special years, the colors are truly breathtaking,
How does autumn color happen？
For years, scientists have worked to understand the changes that happen to trees and shrubs in the autumn. Although we don't know all the details, we do know enough to explain the basics and help you to enjoy more fully Nature's multicolored autumn farewell. Three factors influence autumn leaf color-leaf pigments(色素), length of night, and weather, but not quite in the way we think. The timing of color change and leaf fall is primarily regulated by the calendar. That is, the increasing length of night. None of the other environmental in flounces -temperature, rainfall, food supply, and so on—are as unvarying as the steadily increasing length of night during autumn. As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Nature's autumn palette.
Where do autumn colors come from？
-A color palette needs pigments, and there are three types that are involved in autumn color. Chlorophyll(叶绿素),which gives leaves their basic green color. It is necessary for photosynthesis(光合作用), the chemical reaction that enables plants to use sunlight to manufacture sugars for their food.
-Carotenoids(类胡萝卜素), which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils.
-Anthocyanins(花青素), which give color to such familiar things as red apples, grapes, blue berries, cherries, strawberries, and plums. They are water soluble and appear in the watery liquid of leaf cells.
Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.
During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autunm, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.
Certain colors are characteristic of particular species. Oaks turn red, brown, or russet; hickories, golden bronze; aspen and yellow-poplar, golden yellow; dogwood, purplish red. Maples differ species by species: red maple turns brilliant scarlet; sugar maple, orange-red; and black maple, glowing yellow. Leaves of some species such as the elms simply shrink and fall, exhibiting little color.
The timing of the color change also varies by species. Sourwood in southern forests can become vividly colorful in late summer while all other species are still vigorously green. Oaks put on their colors long after other species have already shed their leaves. These differences in timing among species seem to be genetically inherited, for a particular species at the same latitude will show the same coloration in the cool temperatures of high mountains at about the same time as it does in warmer lowlands.
How does weather affect autumn color？
The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is decreasing. Temperature and moisture are the main influences. A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most specta
A．Y
B．N
C．NG
证明在格中如果a≤b≤c，则a∨b=b∧c，(a∧b)∨(b∧c)=(a∨b)∧(a∨c)．
判断字符串a和b是否相等，应当使用( )。
(A)if(a==b) (B)if(a=b)
(C)if(strcpy(a，b)==0) (D)if(strcmp(a，b)==0)
