托福听力中的生物学是托福考试中一个非常频繁的话题，其中共生关系在TPO和真实考试中多次被测试。现在让我们来看看共生关系的三个类别，并补充一些相关的背景知识。下面由新航道的沈阳托福培训小编为您解答！

　　具体可参考TPO 34 L3, TPO48 L3, TPO62 L3

　　1、Parasitism: It is a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Unlike predators, parasites do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts.

　　寄生关系是指一种生物被寄送到另一种生物体内或表面以牺牲另一方而受益的关系。一般来说，寄生物比宿主小，它们不会杀死宿主。寄生物通常是高度系统化的，繁殖速度远高于宿主。

　　2、Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other. Hummingbird drinking from flowers. Pollination is a classic example of mutualism.

　　双赢的合作意味着两个不同物种的生物可以一起受益。例如，花用瑞蚁传粉。瑞蚁从花蜜中吸收营养。

　　3、Commensalism is a class of relationships between two organisms where one organism benefits without affecting the other. It can be compared with mutualism, in which both organisms benefit, and parasitism, where one benefits while the other is harmed. Remoras (sucker fish) benefit from riding on sharks without helping or harming them.

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