陜西 呂 品

科學家們發(fā)現(xiàn)，波西多尼亞水生植物很有可能是地球上最大的植物，這項新發(fā)現(xiàn)能使公眾更關(guān)注生態(tài)問題。

主題語境：自然生態(tài) 篇幅：345詞 建議用時：7分鐘

1Scientists have discovered what they believe is the world's largest plant, an underwater field of sea grass that stretches for112miles(180kilometers)off the west coast of Australia.The sea grass plant is believed to be around 4,500 years old.

2Sea grass grows together in thick fields,known as meadows. Sea grass meadows help clean the ocean's water. They also provide food and shelter for many sea creatures. The climate crisis and water pollution are threatening sea grass meadows in many places around the world. But the huge sea grass meadow in Shark Bay,off the coast of Western Australia,seems to be doing very well.It's a kind of sea grass called Posidonia Australis,and it has spread widely all through Shark Bay.

3Scientists from the University of Western Australia and Flinders University wanted to study the sea grass, so they took samples from 10 different parts of this huge meadow.Many plants create new plants by growing flowers and spreading seeds. The DNA of the plants that grow from these seeds is slightly different from the DNA of the plants that the seeds came from. By comparing the DNA from their samples, the scientists hoped to get an idea of how many different sea grass plants there were in the meadow.

4What they learned shocked them—all of the grass samples had almost exactly the same DNA.That meant that they were all just one plant—one big sea grass plant spreading out over 77 square miles (200 square kilometers). This makes it the largest known plant in the world by far.

5Instead of spreading with flowers and seeds, the Shark Bay sea grass spreads by cloning itself. As its roots spread out under the sea floor, new plants shoot up from those roots.The sea grass in Shark Bay is also unusual in another way.It's a“polyploid(多倍體)”.Usually, an organism has two parents, and gets half of its DNA from each. But polyploid organisms have all of the DNA from both parents,meaning they have twice as much DNA.

Reading Check

Language Study

Ⅰ.Difficult sentences in the text

1. Scientists have discovered what they believe is the world's largest plant, an underwater field of sea grass that stretches for 112 miles (180 kilometers) off the west coast of

Australia.科學家們發(fā)現(xiàn)了一種他們認為是世界上最大的植物，一片位于澳大利亞西海岸外綿延112英里(180千米)的海草。

【點石成金】本句中，what they believe...plant 是discovered 的賓語從句，an underwater field of sea grass that stretches for 112 miles (180 kilometers) off the west coast of

Australia是the world's largest plant的同位語。

2. What they learned shocked them—all of the grass samples had almost exactly the same DNA.他們所了解到的情況震驚了他們——所有海草樣本的DNA幾乎完全相同。

【點石成金】這是一個主從復合句，主句的謂語動詞是shocked；What they learned是主語從句，What 引導主語從句并且在從句中作learned 的賓語。句中，all of the grass samples had almost exactly the same DNA 是對前面內(nèi)容的進一步的解釋說明。

Ⅱ.Text-centered chunks

provide...for 為……提供

be slightly different from 略微不同于……

spread out 散開；分散

instead of 代替；而不是

shoot up 迅速成長；迅速增加