托福阅读背景知识：水藻(Seaweed)

　　针对这道托福考题，新东方富亦聪老师来为大家普及一下关于水藻的背景知识，这样有助于考生在面对这类题目时方便作答，同时富亦聪老师也为您指导解答这类题目的小技巧。

　　托福阅读真题再现：

　　Characteristics of seaweed plants

　　海草

　　第一段大概就在说这个海里面的东东和陆地植物有点不一样，但还是有叶绿素的，貌似还有其他神马的。。

　　第二段有图， 就讲这些东东要领队在在诸如石头啊什么的东西上面。说他们的类似于stem一类的东西可以达到35metres，(这里有题)还说因为这种植物不需要通过根部transportation，从ground里面吸收营养和水分，所以这个根部roots和一般的陆地植物根部不一样的(有题，问为什么他们不一样，有个选项是：因为他们不需要像leaves一样有运送水分和营养的功能，还有个选项说这个植物不需要ground的水分和营养)。。

　　第三段讲如果植物遇到storm的话，他们貌似会抓得更紧(有题：问遇到storm的时候这个哪门)。然后又讲说这个植物在某种情况下会die。

　　第四段说这个植物在海里的情况，说有三种颜色：green, blue, 和red。说是按深浅来的，只要在某Z的区域内，阳光都能照到，然后都可以活。

　　第五段讲这种植物可以给很多生物提供shelter。然后可以作为很多动物的food，还有一个功能，我也记不清了。然后下面有一道题问下列哪个不是这个植物可以为其他生物做的(有个选项貌似说是提供construction materials。我就选的这个。)题目：

　　海草为什么会被 植物学家特别划分出来?因为它有叶绿素会进行光合作用;为什么storm有可能造成海草死亡，因为它的根脱落。

　　海草跟陆上植物叶子或根作用有何不同?海草的叶子不储存水分(不确定)。

　　海草的根不吸收水份及营养。

　　新东方富亦聪解析如何解答这类考题：

　　本文主旨明确，结构清晰，围绕seaweed展开陈述。每段首句为topic sentence的可能性较高。做题时需注意记录笔记，对于结构化阅读及最后一题的解答有很大好处。

　　水藻(Seaweed)相关背景：

　　Seaweed, any red, green, or brown marine¹ algae² that grow on seashores. They are anchored to the sea bottom or to some solid structure by rootlike holdfasts that perform the sole function of attachment³ and do not extract nutrients⁴ as do the roots of higher plants.

　　Seaweeds often form dense⁵ growths on rocky shores or accumulations in shallow water. Many show a well-established zonation along the margins⁶ of the seas, where the depth of the water is 50 metres (about 165 feet) or less. The types of seaweed growing near the high-water mark, where plants are often exposed to air, differ from those growing at lower levels, where there is little or no exposure. Fucus, Macrocystis, Nereocystis, and Laminaria are widely distributed in colder zones and are absent from tropical waters.

　　Brown algae commonly found as seaweeds include kelps and Fucus. Among the kelps are the largest algae; certain species of Macrocystis and Nereocystis of the Pacific and Antarctic regions exceed 33 metres (100 feet) in length. Laminaria, another kelp, is abundant along both Pacific and Atlantic coasts. Gulfweed (Sargassum;) is common as free-floating masses in the Gulf⁷ Stream and the Sargasso Sea.

　　Red alga seaweeds include dulse (Rhodymenia), Gelidium, Chondrus, and laver (Porphyra). Various species of Chondrus (see Irish moss) carpet the lower half of the zone exposed at low tide along rocky coasts of the Atlantic.

　　Ulva species, commonly called sea lettuce⁸, are among the relatively⁹ few green algal seaweeds.

　　Structure

　　Seaweeds' appearance somewhat resembles non-arboreal terrestrial plants.

　　· thallus: the algal body

　　· lamina or blade: a flattened¹⁰ structure that is somewhat leaf-like· sorus: a spore¹¹ cluster

　　· on Fucus, air bladder: a floatation-assisting organ on the blade· on kelp, float: a floatation-assisting organ between the lamina and stipe· stipe: a stem-like structure, may be absent· holdfast: a specialized¹² basal structure providing attachment to a surface, often a rock or another alga· haptera: a finger-like extension of the holdfast anchoring to a benthic substrateThe stipe and blade are collectively known as the frond¹³.

　　Ecology

　　Two specific environmental requirements dominate seaweed ecology. These are the presence of seawater (or at least brackish¹⁴ water) and the presence of light sufficient to drive photosynthesis¹⁵. Another common requirement is a firm attachment point. As a result, seaweeds most commonly inhabit the littoral¹⁶ zone and within that zone more frequently on rocky shores than on sand or shingle¹⁷. Seaweeds occupy a wide range of ecological¹⁸ niches²⁰. The highest elevation²¹ is only wetted by the tops of sea spray, the lowest is several meters deep. In some areas, littoral seaweeds can extend several miles out to sea. The limiting factor in such cases is sunlight availability. The deepest living seaweeds are some species of red algae.

　　A number of species such as Sargassum have adapted to a fully²² planktonic²³ niche¹⁹ and are free-floating, depending on gas-filled sacs to maintain an acceptable depth.

　　Others have adapted to live in tidal rock pools. In this habitat seaweeds must withstand rapidly changing temperature andsalinity and even occasional drying.

 

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