•Narrator: Now listen to two students discussing the letter.

•Woman: So what do you think of that letter?

•Man: Well, it might sound like a good idea，

•but I really don't think it's gonna have any of the benefits that the letter writer says it will.

•Woman: So you don't agree with it？

•Man: Nope. If anything, it's going to hurt our relationship with our town.

•I mean forcing students to volunteer,

•it's gonna make them see it as a chore, a nuisance,

•and so they're not gonna to put their hearts into it,

•which is gonna make the university look bad.

•Woman: You are saying that students doing volunteer work in town will be unenthusiastic and...

•Man: Right. It'll be obvious they don't want to be there.

•That's sure not going to make things better,

•you know, in terms of how were regarded by people in the local community.

•Woman: But maybe students would learn to like it.

•Man: I really doubt it. The whole idea that this is gonna to encourage students to do more volunteering in the future is just ridiculous.

•A lot of students are likely to come away from the experience with negative feelings about it.

•Woman: Yeah, especially if their studies suffer from being forced to spend time away from them.

•Man: All the students I know already complain about not having enough time as it is.

•So this extra work is going to be a bad experience,

•hardly inspiration for them to pursue more volunteer work after they graduate.

•Narrator: Now listen to part of a lecture on this topic in a Business class.

•Professor: For example, I used to work for a corporation that was having trouble with workers being absent a lot.

•To help address this problem,

•they hired a consultant,

•who began by interviewing a lot of the workers and getting to know more about them.

•She also researched other aspects of the company,

•such as the types of eating facilities and health services it offered.

•And what the consultant discovered was that many of the employees were missing work

•not for an obvious, simple reason, like, say, lack of motivation,

•but because of health problems.

•Health problems that were the result of, or at least made worse by the combination of factors,

•such as poor eating habits and lack of exercise.

•The consultant concluded that since the company didn't offer exercise opportunities or healthy meals,

•that this indirectly contributed to the workers' poor health.

•The consultant proposed building a gym within the company office building for employees to use to exercise,

•and also to offer a more nutritious menu in the cafeteria, which the company did.

•But it took a while.

•And after a year or so,

•after the company had time to construct a gym and revise its cafeteria menu,

•attendance began to improve, and continued to improve until it was no longer a problem.

•Narrator: Listen to part of a lecture from a Biology class.

•Professor: Most animals, including humans,

•follow biological cycles that are 24 hours long.

•Now what determines these 24-hour cycles?

•Do animals have something like a 24-hour clock inside them?

•Or our biological cycles determined by external factors,

•like the alternation of daylight and darkness?

•Well, research suggests that the answer is somewhere in between.

•Animals do have an internal clock,

•but external cues are important too.

•Take flying squirrels, flying squirrels are nocturnal.

•They are active during the night and sleep during the day.

•But in an experiment,

•some of these squirrels were kept in constant darkness.

•They were not exposed to any daylight for about a month.

•Now did the squirrels continue to follow regular cycles of activity?

•Actually they did.

•They continued to have regular patterns of sleeping and waking.

•This indicates that animals do have an internal clock which regulates their activity cycles.

•But the internal clock is not precisely 24 hours long.

•Instead of following 24-hour cycles,

•the squirrels followed cycles that were about half an hour shorter than that.

•So every day they woke up a little bit earlier.

•Without external cues,

•without sunlight to fine-tune their internal clocks,

•the squirrels' biological cycles drifted.

•So what happened when the squirrels were exposed to daylight again?

•Well, after a month of darkness,

•a month of waking up half an hour earlier each day,

•the squirrels' activity cycle had shifted a lot.

•So at first, their schedules didn't match up with a normal day.

•They weren't active during the nighttime as flying squirrels usually are, instead,

•they were waking up in the middle of the day.

•But after a while, the squirrel cycles began to change.

•Gradually, external cues,

•the cycle of light and darkness adjusted their internal clocks.

•So eventually they were brought back into a normal 24-hour schedule.