原文已被隐藏，你可用 快捷键 - 或点击 显示原文 按钮来查看原文
第1段
1 .<-NARRATOR:-> Listen to a lecture from a biology class.
该句暂无译文！
第2段
1 .<-FEMALE PROFESSOR:-> So, we've been talking about how animals have developed different ways of surviving.
该句暂无译文！
2 .And one way is from having developed special physical characteristics that help protect them from the dangers in their environment.
该句暂无译文！
3 .These are known as protective adaptations, and there are two different kinds.
该句暂无译文！
4 .Some animals have defensive adaptations . . . and that means they protect themselves by having body structures that make it hard for predators to get at them.
该句暂无译文！
5 .And other animals have offensive adaptations,
该句暂无译文！
6 .body structures that keep predators away.
该句暂无译文！
第3段
1 .Alright, let's start with the turtle . . .
该句暂无译文！
2 .it's a good example of an animal with a defensive adaptation.
该句暂无译文！
3 .Since you've probably all seen turtles, you already know that it has a hard shell that covers its back and vital organs.
该句暂无译文！
4 .Its shell is its special physical characteristic
该句暂无译文！
5 .and it's so strong, it won't break or split open, making it very hard for a predator to get at it.
该句暂无译文！
6 .The turtle also has a flexible neck, so it can pull its head down under its shell.
该句暂无译文！
7 .Its legs can also fold up under the shell and provide more protection still.
该句暂无译文！
第4段
1 .Alright, but now let's talk about the porcupine . . .
该句暂无译文！
2 .that's an animal that protects itself with an offensive adaptation by threatening a predator with physical harm.
该句暂无译文！
3 .Um, in case you haven't seen a porcupine recently,
该句暂无译文！
4 .just imagine an animal with a small body that is covered with thousands of long, sharp needle-like quills.
该句暂无译文！
5 .Those quills are its special physical characteristic.
该句暂无译文！
6 .So whenever a predator gets too near . . . when it brushes against the porcupine, these sharp quills come loose and become embedded in the predator's skin.
该句暂无译文！
7 .So predators know enough to stay away because they see the porcupines' threatening quills and they don't want to risk being hurt by them.
该句暂无译文！