task4题目 Reading Part:

　　Relict Behavior

　　In general, animals act in ways that help them to survive within their specific habitats. However, sometimes an animal species may display a behavior that no longer serves a clear purpose. The original purpose for the behavior may have disappeared long ago, even thousands of years before. These behaviors, known as relict behaviors, were useful to the animal when the species’ habitat was different; but now, because of changed conditions, the behavior no longer serves its original purpose. Left over from an earlier time, the behavior remains as a relict, or remnant, long after the environmental circumstance that influenced its evolution has vanished.

　　Listening Part:

　　Now listen to part of a lecture in a biology class.

　　Ok, uh, so a good ex ample of this, found right there in North America, is something an animal called the American Pronghorn does. Prong Horns, as you may know, are a kind of deer-like animal, they live out in the open grassy plains, somewhat in the middle of America, and they are super fast. Pronghorns are, in fact, noted for being the fastest animal in the western hemisphere. Once a Pronghorn starts running, zoom!

　　None of its present predators, like the bobcat or the coyote can even hope to catch up with it. It’s off in a flash! Ok, so why then do Pronghorns run so fast? That’s the question.

　　Well, it turns out that quite a long time ago, I’m talking tens of thousands of years, things on the grassy plains used to be very different for the Pronghorns, because back then, lions used to live on the plains, chasing and preying upon the Pronghorns, and lions, of course, are a very swift-moving mammal, much faster than the bobcat or coyote or other predators you’d find on the plains today.

　　But, now, however, lions are all extinct in North America, they’re no longer predator of the Pronghorn. Tens of thousands of years ago, though, the lions were there chasing the Pronghorns. So back then, the Pronghorn’s speed was critical to its survival.

　　Question:

　　Using the example of the pronghorn and lion, explain the concept of a relict behavior.

　　答案解析：

　　1.Reading key

　　Term: Relict Behavior

　　Definition: Relict Behavior are animal behaviors that don’t serve it’s original purpose anymore because of the change of conditions.

　　2.Listening key

　　Example:

　　(2.1) pronghorn runs so fast that none of its present day predators like coyotes stand a chance of catching them when they run off

　　(2.2) This behavior originated from the past.

　　(2.3) Pronghorns needed to run from fast running predators in the past like lions who was much faster runners compare to coyotes.

　　(2.4) Although lions are all extinct in North America

　　(2.5) Pronghorn kept this fast running behavior although it isn’t necessary for it’s survival anymore