章节大纲

  • 常规

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  • 干燥气候

    Two types of cacti from North and South America illustrating similar adaptations to dry climates.

     

    How do plants that evolved in different places end up being so similar?
    ::在不同地方进化的植物 怎么会变得如此相似呢?

    Organisms evolve to fit the conditions they are in. There are only so many ways to minimize the use of  water . Plants in arid climates evolve very similar structures to lessen water use. They also have structures to protect themselves from the  . The cactus on the right is from South America. The cactus on the left is from North America. These plants are just one of many examples of organisms evolving under very similar conditions and turning out to be very similar.
    ::生物进化到符合它们所处的条件。只有如此多的方法可以最大限度地减少水的使用。干旱气候中的植物会形成非常相似的结构来减少水的使用。它们也有保护自己免受水使用的结构。右边的仙人掌来自南美洲。左边的仙人掌来自北美。这些植物只是许多在非常相似的条件下进化并变得非常相似的有机体的例子之一。

    Dry Climates
    ::干旱气候

    Dry climates receive very little rainfall. They also have high rates of  evaporation . This makes them even drier.
    ::干旱气候的降雨量很少,蒸发率也很高,因此更干燥。

    Deserts
    ::荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒 荒

    The driest climates are  deserts . Most occur between about 15° and 30°  . This is where dry air sinks to the surface in the global   cells. Deserts receive less than 25 centimeters (10 inches) of  rain  per  year . They may be covered with  sand dunes  or be home to sparse but hardy plants. With few  , many deserts have hot days and cool nights.
    ::最干燥的气候是沙漠,大多发生在约15°至30°之间。干燥的空气从这里沉入全球细胞的表层,沙漠每年降雨量不到25厘米(10英寸),可能有沙丘覆盖,或者有稀有但坚硬的植物居住。只有很少的沙漠,许多沙漠有炎热的天气和凉爽的夜晚。

    Two desert landscapes: one with plants and the other mostly barren with rocks.

     

    Some deserts receive a small amount of rain during the winter and again during the summer. This is enough to keep plants alive as in the left photo. Some deserts receive very little rain or rain only one season a year. These deserts have few plants as in the right photo.
    ::有些沙漠在冬季和夏季都得到少量雨水,这足以维持植物与左照片中的植物一样的存活。有些沙漠每年只得到很少的雨水或一季的雨水。这些沙漠只有很少的植物,而正确的照片中只有很少的植物。

    Steppes
    ::中继数

    Other dry climates get a little more  . They are called  steppes . These regions have short grasses and low bushes ( Figure   ). Steppes occur at higher latitudes than deserts. They are dry because they are in continental interiors or rain shadows.
    ::其他干燥的气候则多一些。它们被称为草原。这些区域有短草和低灌木(图)。草原出现在比沙漠高的纬度地区。它们干燥,因为它们位于大陆内地或雨影中。

    A Mongolian steppe landscape featuring rolling hills and short grasses under a cloudy sky.

     

    A steppe in Mongolia.
    ::蒙古的一只大草原

     

     

    Science Friday: Superbloom: How Death Valley Springs to Life
    ::科学星期五:超级大爆炸:死亡谷的春天如何给生命带来生命

    A massive seed bank of desert wildflowers lies beneath Death  Valley . This video by  Science  Friday shows that when heavy winter rains soak deep into the  soil , these hidden wonders spring to life, in an event called a “superbloom”.
    ::沙漠野花的庞大种子库位于死亡谷下方。 科学周五的录像显示,当冬季暴雨淹没在土壤深处时,这些隐藏的奇事在被称为“超级大爆炸”的事件中,会给生命带来春天。

     

    Summary
    ::摘要

    • Deserts receive very little rainfall. They are often home to very unusual and well adapted plants.
      ::沙漠得到的降雨量很少,它们往往居住着非常不寻常和适应性强的植物。
    • Steppes receive more rain than deserts. They are higher and have grasses and scrub.
      ::草原的降雨量比沙漠还要大,它们更高,有草和洗涤剂。
    • Plants adapt to local conditions. If conditions are the same but the plants are far apart, they may still be very similar.
      ::植物适应当地条件,如果条件相同,但植物相距很远,它们可能仍然非常相似。

    Review
     ::回顾

    1. What is the reason that an arid desert has so little rainfall?
      ::干旱沙漠降雨量如此少的原因何在?
    1. What is the reason that a steppe has so little rainfall?
      ::草原降雨量这么少的原因是什么?
    1. What is the difference between a desert and a steppe in vegetation?
      ::沙漠和草原之间有什么区别?
    1. What adaptations do arid climate zone plants have to the dry conditions?
      ::干旱气候区植物对干旱条件有什么适应措施?