字神帝國英語天地

 今日主題：Plant Thorns Increase When Defense Needed
需要防禦外敵時，植物的刺就會增多

 洪欣老師推薦：托福聽力最好的課外教材：60-Second Science
康康精選托福會考的主題，堅持每天精聽一定會進步的哦!!

 建議方法：
1. 先聽兩三遍 (不看文稿)
2. 再一句一句聽寫 (每句都要聽寫數遍，直到寫出85%以上的字)
3. 最後check文稿，看哪聽不出來，單字沒背過，還是發音不熟。
4. 堅持天天聽，就能每天進步哦。

 MP3音檔：喜歡的同學，幫忙推或按讚哦~~
http://online1.tingclass.net/voaspe/…/20141027sa_science.mp3

 只有音檔怎夠，聽不懂地方，不用怕，康康幫你準備好中英文稿了：

 中英文稿：
Plants thrive all over the planet, despite the fact that many animals love to snack on them. Various hypotheses account for all those plants. One is that predators kill enough plant-eating animals to give vegetation a chance. Another is that plants develop physical and chemical means to defend themselves.
儘管有很多動物喜歡吃植物，但是地球上的植物仍然很繁茂。對這些植物有很多假設性的說法。一種說法是：食肉動物吃掉了食草動物，給植物一個生長的機會。另一種說法是：植物自身形成的物理和化學手段來保護它們自己。

Now researchers have teased out some of these factors in an East African savanna.
現在研究者們已經在東非的熱帶草原找出一些原因。

The impala—an African antelope—eats grasses and trees and is itself eaten by wild dogs and leopards. Impala often munch on a tree called the acacia. Some acacia have thorns, and some don't.
黑斑羚——非洲的一種羚羊——吃草和樹葉，卻野狗和豹子吃掉。黑斑羚經常食用一種金合歡樹，有些金合歡樹有刺，有些則沒有。

The researchers found that the impala—perhaps not surprisingly—prefer thorn-free acacia. Also, the animals avoid woody areas where predators are more likely to hide.
研究者發現黑羚羊——也許並不奇怪——喜歡無刺的金合歡樹。同樣，動物儘量避免樹木較多的地方，因為那裡很有可能隱藏著捕食者。

And as a result, the thorn-free, vulnerable acacia are more plentiful in woody areas with plenty of predators. But the thorny acacia are more numerous on the open savanna, where they need to defend themselves. The study is in the journal Science. [Adam T. Ford et al, Large carnivores make savanna tree communities less thorny]
結果，在林木多的地方，更多的無刺、易受黑羚羊攻擊的的金合歡樹，在肉食動物較多的樹林裡生長。但是有刺的金合歡樹在熱帶草原的空曠地區生長的很多，它們也需要保護自己。這一眼就發現在科學期刊上發表。

The researchers say their findings show that both plant defenses and carnivorous predators help plants thrive. They also say that when humans influence—in part by eliminating large predators—we disrupt longstanding, complex systems. And that we should really try to better understand such systems, and our effects on them.
研究者說他們的發現表明：無論植物的防禦措施還是食肉動物都促進了植物的繁茂。他們還說人類的影響——部分原因是殺死了大型的肉食動物——我們打亂了長期存在的複雜的生態體系。我們應該更好地理解這個草原的生態體系，瞭解我們對草原動植物的影響。