hce_isu
110年
英文
第 36 題
📖 題組：
Reading 2 Compared to the atmosphere, soil is a place where temperature fluctuations are small and slow. Consequently, soil animals are generally intolerant to sudden temperature changes and may not function well over a very wide range. That’s why leaving bare earth exposed to the hot summer sun often slows plant growth and why many thoughtful composters either put down a thin mulch in summer or try to rapidly establish a cooling leaf canopy to shade raised beds. Except for a few microorganisms, soil animals breathe oxygen just like other living things and so are dependent on an adequate air supply. Where soil is airless due to compaction, poor drainage, or large proportions of very fine clay, soil animals are few in number. The soil environment is generally quite moist, and even when the soil seems dry, the relative humidity of soil air usually approaches 100 percent. Soil animals consequently have not developed the ability to conserve their body moisture and are speedily killed by dry conditions. When faced with desiccation, they retreat deeper into the soil if there is oxygen and pore spaces large enough to move about. So we see another reason why a thin mulch that preserves surface moisture can greatly increase the beneficial population of soil animals. Some single-cell animals and roundworms are capable of surviving stress by encysting themselves, forming a little “seed” that preserves their genetic material and enough food to reactivate it, coming back to life when conditions improve. These cysts may endure long periods of severe freezing and sometimes temperatures of over 150 degrees Fahrenheit. Inhabitants of leaf litter reside close to the surface and so must be able to experience exposure to dryer air and light for short times without damage. These are called primary decomposers. They spend most of their time chewing on the thick reserve of moist leaves contacting the forest floor. Primary decomposers are unable to digest the entire leaf. They extract only the easily-assimilated substances from their food: proteins, sugars and other simple carbohydrates and fats. Cellulose and lignin are the two substances that make up the hard, permanent, and woody parts of plants; these materials cannot be digested by most soil animals. Interestingly, there are a few larvae whose digestive tract contains cellulose-decomposing bacteria but these larvae have little overall effect. By the time the primary decomposers are finished, the leaves have been mechanically disintegrated and thoroughly moistened, worked over, chewed to tiny pieces and converted into minuscule bits of moist excrement still containing active digestive enzymes. Many of the bacteria and fungi that were present on the leaf surfaces have passed through this initial digestion process alive or as spores waiting and ready to activate. Digestive wastes of primary decomposers are thoroughly inoculated with microorganisms that can consume cellulose and lignin. Even though it looks broken down, it has not yet fully decomposed. It does have a water-retentive, granular structure that facilitates the presence of air and moisture throughout the mass creating perfect conditions for microbial digestion to proceed. Both secondary and primary decomposers are necessary to complete the composting process.
Reading 2 Compared to the atmosphere, soil is a place where temperature fluctuations are small and slow. Consequently, soil animals are generally intolerant to sudden temperature changes and may not function well over a very wide range. That’s why leaving bare earth exposed to the hot summer sun often slows plant growth and why many thoughtful composters either put down a thin mulch in summer or try to rapidly establish a cooling leaf canopy to shade raised beds. Except for a few microorganisms, soil animals breathe oxygen just like other living things and so are dependent on an adequate air supply. Where soil is airless due to compaction, poor drainage, or large proportions of very fine clay, soil animals are few in number. The soil environment is generally quite moist, and even when the soil seems dry, the relative humidity of soil air usually approaches 100 percent. Soil animals consequently have not developed the ability to conserve their body moisture and are speedily killed by dry conditions. When faced with desiccation, they retreat deeper into the soil if there is oxygen and pore spaces large enough to move about. So we see another reason why a thin mulch that preserves surface moisture can greatly increase the beneficial population of soil animals. Some single-cell animals and roundworms are capable of surviving stress by encysting themselves, forming a little “seed” that preserves their genetic material and enough food to reactivate it, coming back to life when conditions improve. These cysts may endure long periods of severe freezing and sometimes temperatures of over 150 degrees Fahrenheit. Inhabitants of leaf litter reside close to the surface and so must be able to experience exposure to dryer air and light for short times without damage. These are called primary decomposers. They spend most of their time chewing on the thick reserve of moist leaves contacting the forest floor. Primary decomposers are unable to digest the entire leaf. They extract only the easily-assimilated substances from their food: proteins, sugars and other simple carbohydrates and fats. Cellulose and lignin are the two substances that make up the hard, permanent, and woody parts of plants; these materials cannot be digested by most soil animals. Interestingly, there are a few larvae whose digestive tract contains cellulose-decomposing bacteria but these larvae have little overall effect. By the time the primary decomposers are finished, the leaves have been mechanically disintegrated and thoroughly moistened, worked over, chewed to tiny pieces and converted into minuscule bits of moist excrement still containing active digestive enzymes. Many of the bacteria and fungi that were present on the leaf surfaces have passed through this initial digestion process alive or as spores waiting and ready to activate. Digestive wastes of primary decomposers are thoroughly inoculated with microorganisms that can consume cellulose and lignin. Even though it looks broken down, it has not yet fully decomposed. It does have a water-retentive, granular structure that facilitates the presence of air and moisture throughout the mass creating perfect conditions for microbial digestion to proceed. Both secondary and primary decomposers are necessary to complete the composting process.
According to the reading, which of the following is true about primary decomposers?
- A Most of them are unable to digest cellulose and lignin.
- B Most have a digestive tract that contains cellulose-decomposing bacteria.
- C They can encyst themselves to camouflage.
- D They desiccate leaves, creating mulch.
思路引導 VIP
請回頭看看文中提到的纖維素（cellulose）和木質素（lignin），文章說大多數的土壤動物「能夠」還是「不能夠」消化這些強韌的植物組織呢？而在提到那些消化道裡有特殊細菌的幼蟲時，文章用的量詞是「大多數（most）」還是「極少數（a few）」？
🤖
AI 詳解
AI 專屬家教
太棒了！你能準確定位文中細節並做出正確判斷，代表你對科普長文的資訊擷取能力非常紮實。這題的核心考點在於對**初級分解者（Primary decomposers）**消化特性的理解。
初級分解者的消化限制
文章第三段明確指出，初級分解者只能吸收食物中容易同化的物質，如蛋白質、糖類和脂肪。而植物木質化部分的主要成分——纖維素（cellulose）與木質素（lignin），對大多數（most）土壤動物來說是無法消化的。雖然文中提到「極少數」幼蟲體內有能分解纖維素的細菌，但那只是例外，因此選項 (A) 的敘述完全符合文本原意。
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