15 The Curious Case of the Peppered Moth-Mid

The Curious Case of the Peppered Moth FOCUS Question What caused the peppered moth population to change color twice?

是什么导致桦尺蠖种群的颜色发生了两次变化?

Different Colors When you think of certain animals, a specific color may come to mind Red for a cardinal. Orange for a tiger. However, some species have more than one color that can appear in their population. Most black bears, for example, have an all-black coat of fur. But did you know that not all black bears are black? They can also be brown, cinnamon, or even blond. Other animals also show this kind of variation. A jaguar can have a typical spotted yellow coat or be almost entirely black. Even monarch butterflies, normally orange, are sometimes white instead. These different color types are called morphs.

不同的颜色当你想到某些动物时，一个特定的颜色可能会出现在脑海里，红色代表红衣主教。 橙色代表老虎。然而，有些物种在种群中可以出现不止一种颜色。 例如，大多数黑熊都有一身全黑的皮毛。 但是你知道不是所有的黑熊都是黑色的吗? 它们也可以是棕色、肉桂色，甚至是金色。 其他动物也表现出这种变异。 美洲虎有典型的带斑点的黄色皮毛，也有几乎全黑的皮毛。 即使是帝王蝶，通常是橙色的，有时也会变成白色。 这些不同的颜色类型被称为变体。

The Peppered Moth Some species of moths have morphs. One famous example is the peppered moth. This night-flying moth is found in Europe, North America, and many parts of Asia, including Russia and China. The peppered moth comes in two morphs—white and black. The white morph is the typical one, making up about 99 percent of the population. That is why it is called typica. Typica peppered moths look as if someone sprinkled pepper over their white wings and backs. This pattern camouflages the white moths on the trees where they rest during the daytime. They blend in with the light-colored lichen that grows on the trees.

有些种类的飞蛾有变种。 一个著名的例子是胡椒蛾。 这种夜间飞蛾分布在欧洲、北美和亚洲许多地区，包括俄罗斯和中国。 胡椒蛾有两种变种——白色和黑色。 白色变种是典型的变种，约占人口的99%。 这就是为什么它被称为典型。 典型的胡椒飞蛾看起来就像有人在它们白色的翅膀和背部撒了胡椒。 这种图案可以伪装白蛾在白天休息的地方。 它们与长在树上的浅色地衣融为一体。

The Moth's Morph Blending in is a good thing for peppered moths since moths are an important food source for birds. But birds have a hard time finding the white moths because they are camouflaged. The black morph is easier to see against the lighter trees. Many of the black peppered moths are eaten before they can reproduce. That is why there are fewer of them. Only 1 percent of the individuals in the species are black morphs. The black morph remained rare in the population for thousands of years. But in the late 1700s, something changed. That's when the case of the peppered moth became curious. Word Wise The root word in carbonaria— carbon—comes from the Latin word carbo, which means "charcoal" or "coal."

混在一起对胡椒蛾来说是件好事，因为飞蛾是鸟类重要的食物来源。 但鸟类很难找到白飞蛾，因为它们伪装了。 在浅色树木的衬托下，黑色的变种更容易被看到。 许多黑胡椒蛾在繁殖之前就被吃掉了。 这就是为什么他们很少。 该物种中只有1%的个体是黑色变种。 数千年来，黑色变种在人群中仍然很少见。 但在18世纪末，情况发生了变化。 从那时起，胡椒蛾的情况变得很奇怪。 carbonaria的词根carbon来自拉丁语carbo，意思是“木炭”或“煤”。

Pollution From 1780 to 1830, the urban areas of Great Britain went through a large transformation. Factories and homes in big cities like London and Manchester stopped using wood as their main form of fuel. Instead, they used coal to power steam engines, furnaces, and fireplaces. This time in history became known as the Industrial Revolution. Coal was a plentiful and cheaper source of fuel. But burning it came at a cost. Chimneys belched black fumes—produced by burning coal—into the air. Wind carried the smoke away from cities. The countryside was soon covered in a blanket of black soot.

从1780年到1830年，英国的城市地区经历了巨大的变化。 伦敦和曼彻斯特等大城市的工厂和家庭不再使用木材作为主要燃料。 相反，他们用煤来驱动蒸汽机、熔炉和壁炉。 历史上的这一时期被称为工业革命。 煤是一种丰富而廉价的燃料来源。 但焚烧它是有代价的。 烟囱向空中喷出燃烧煤产生的黑色烟雾。 风把烟从城市吹走了。 乡村很快就被一层黑烟灰覆盖了。

Suddenly Seen The black soot covered forests and stuck to tree trunks and branches. A toxic gas in the soot, called sulphur dioxide, killed off the light-colored lichens growing on the trees. As a result, the trees turned very dark. The darkened trees were not an ideal place for white peppered moths. Before the pollution, those moths had blended in with the light color of lichens (see page 3). But now they stuck out noticeably against the darkened bark. Think About It Predict how the darkened trees affected the peppered moth population. Then read on to discover the answer.

黑色的烟灰覆盖了森林，粘在树干和树枝上。 煤烟中的有毒气体叫做二氧化硫，杀死了生长在树上的浅色地衣。 结果，树变得很黑。 黑暗的树木并不是白胡椒蛾的理想场所。 在污染之前，这些蛾子已经和浅色的地衣混在一起了(见第3页)。 但现在，它们在黝黑的树皮下显得格外显眼。 想想看，预测一下变暗的树木是如何影响桦尺蠖种群的。 接着往下读，找到答案吧。