左沐熙

各位同学们，为了督促帮助大家持续提升英语能力，培君老师们特意给大家准备了托福每日一包。每天覆盖听说读写内容，坚持完成两周以上，就能见到自己的英语能力不断上涨哟。



1.听写包 答案：

You are pretty close, actually, the caterpillars have a honey gland, an organ that secretes an amino acid and carbohydrate liquid.

The caterpillars secretes the liquid from the honey gland, rather large quantities, enough to feed several ants.
But what makes this relationship obligatory for the caterpillar?
Well, if the ants don’t feed regularly on the liquid from the caterpillar’s honey gland, the gland overloads and gets infected.
The infection will kill the caterpillar and it’ll never reach its final stage of development, becoming a butterfly. John?
OK, I just want to make sure I’m following here, the caterpillar needs the ants or it won’t make it to the stage where it can become a butterfly.
And the ants do this because they get an easy meal out of it, right?
But the ants don’t absolutely need the caterpillar for survival, ‘cause they can get food from other places, right?
So it’s still called mutualism even though it seems like the caterpillar’s getting way more out of it.
Oh, wait, you said they don’t have to equally benefit. Never mind, sorry.
Yes. But there is a type of mutualism where the relationship is necessary for both organisms to survive.
It’s called obligatory mutualism. And we’ll talk about that in the next class.
你已经很接近了，事实上，毛毛虫有一个蜜腺，一种能分泌氨基酸和液态糖的器官。
毛毛虫从蜜腺中分泌出大量液体，足够喂饱好几只蚂蚁。
但是这种关系对毛毛虫来说为什么是强制性的呢？
如果蚂蚁不定期吃掉毛毛虫从蜜腺中分泌出的液体，蜜腺就会负荷过重，受到感染。
这种感染对毛毛虫来说是致命的，它永远也无法成长到进化的最后阶段变成一只蝴蝶了，John，请说？
我只是想确认一下我听懂了，毛毛虫需要蚂蚁，否则就活不到进化成蝴蝶的阶段了。
而蚂蚁这么做是因为它们能从中获得白吃的午餐，对吗？
但是蚂蚁不是绝对需要毛毛虫才能生存啊，因为它们能从其他地方弄到食物，不是吗？
所以这种关系仍被称为互惠共生，即使看起来毛毛虫获得的利益比较多。
啊，等一下，你说过它们得到的不一定是同等的好处，不好意思，忘记我说过的话吧。
是的，但是有一种类型的互惠共生关系对两种生物来说都是生存必需的。
它叫做义务性共生，我们下节课再讲。


2. 阅读包答案：

17世纪时风琴、敲弦琴和拨弦琴成为键盘乐器类的主要成员，这种至高无上的地位一直由它们保持，直到18世纪末被钢琴所取代。

3.写作包 答案：

Jiaozi, or dumpling is a kind of food stuffed with filling inside a wheat wrapper. As a quite traditional food in Northern China, it is very popular among Han Chinese. Jiaozi is absolutely necessary when the Chinese people celebrate the Spring Festival and other festivals. It is said that jiaozi was invented by China's famous ancient doctor Zhang Zhongjing. The reason for naming the food as “jiaozi” is very simple: because “jiaozi” is homophonous to the Chinese phrase “change of year”，which means the transition from the old to the new. As the Spring Festival marks the start of a new year, people choose to eat jiaozi to express their best wishes for the New Year. This tradition has remained unbroken despite the change of times.