TPO62听力Lecture4原文+MP3+题目+答案下载

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TPO62听力Lecture4原文+MP3+题目+答案下载

TPO62听力Lecture4原文：

Listen to part of a lecture in an ecology class.

Termites, insect order Isoptera. Hard to think of them as more than just pests that want to eat your house, but I think you’ll be surprised at how interesting they are and how important they are to the ecosystem.

Now what do you already know about them?

They eat wood, lots of it.

Right, to be more specific, they eat dead wood, like dead trees in forests and plant litter. Their consumption of wood is like, you can think of this like recycling. Termites are recycling that litter back into soil. Their major source of nutrition comes from cellulose, the main chemical ingredient of wood and the cell walls of other plants, leaves, grasses, etc.

Now cellulose is a complex sugar. And most termites can’t actually digest it because they don’t have the right enzyme to metabolize it, to release its nutritional benefit.Now that would be a problem, but they have a special relationship with protozoa and bacteria that actually live in their digestive system.

Inside?

Yes. It’s these microscopic organisms that break down the cellulose for the termites. They’d starve without them.

A good example of…Symbiosis. Two different kinds of organisms live together so it’s good for one or both of them.Good. What else is interesting? Termites are social. They live in colonies like ants or bees. Now about the colonies. Each termite colony is founded by a male and female pair that mate and produce more termites. The termites in the colony come in several types called castes. There’s the reproductive pair, the workers that gather food to feed the colony, and soldiers that defend the colony against predators, like ants.And they communicate by?

Dancing? Like the dances bees do?

You are not too far off. Every colony has its own distinct smell, a scent that other termites within their colony recognize. If a worker finds a new food source, it secretes a trail of scent that others can follow to locate the food.

And scent plays an important role in helping soldiers defend the colony against predators. If they detect an unfamiliar scent, well, let’s say an ant is lurking around, well, the ant has a distinct smell. As soon as soldiers detect this ant’s scent, it’s a warning. They shift into an aggressive mode, ready to start defending their colony.

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