『新东方在线托福听力』为托福考生准备了ETS托福TPO/【学术讲座】#18听力练习：What does the subject mentioned by the professor?原文题目答案解析，TPO/【学术讲座】#18听力原文范文音频翻译。

托福TPO/【学术讲座】#18听力原文What does the subject mentioned by the professor?【新东方在线】

According to the professor, how have household products changed?

What does the professor say about the treatment of waste water?

What does the subject mentioned by the professor?

Listen to a talk on environmental conservation.Let’s talk the environmental issue that has to do with how common household products have changed. More and more products contain bacterial killing chemicals these days. These antibacterial chemicals aren’t just in product like soap. They are in all sorts of household cleaners and toothpaste. And if you think about it for second you will realize that most of those chemicals just end up going down the drain. But you are probably thinking that all that stuff go through a treatment plan that removes chemicals, right? After all that’s what happens to stuff that goes down the drain. Well, waste water is treated, but that doesn’t usually remove all the chemicals in it. The chemicals left in the treated water get into the aquatic environment. That is into the rivers, and streams where plants and fish and other animals live. Now to find out the affect of antibacterial chemicals on fresh water ecosystems, a study was done with algae, which are tiny plant like organisms. Different spices algae were taken to a lab and the expose to just a few antibacterial chemicals found in the streams. And guess what? In the experiment, the overall gross of algae and the number of spices dropped. This is not good and here is why. Algae are the base of the aquatic of food chain, which means that other organisms depend on them for food. So if the chemicals kill algae at the bottom of the food chain, the whole system is being disrupted.

Listen to a talk on environmental conservation.

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