题型：阅读理解 题类：常考题 难易度：普通
辽宁省六校协作体2018-2019学年高一下学期英语期中考试试卷
Living in the wild can be hard. Finding food and staying safe aren't easy. Each day, animals try to survive in their habitats. Not all animals get by on their own. Some animals form a close partnership with other kinds of animals. These pairings are called symbiotic(共生的)relationships.
In a symbiotic relationship, the animals depend on each other. One animal helps the other meet its needs. Sounds good, right? Not always. Some animals are not very kind to their partners. In some cases, one animal meets its needs but hurts its partner. Take ticks(扁虱), for example. These insects suck blood to live. To get blood, they attach themselves to other kinds of animals. Ticks can pass germs(细菌)that cause disease instead of helping their hosts.
In other relationships, animals don't treat their partners so poorly. Both animals benefit from living with the other animal.
Small animals called cleaner shrimps(清洁虾)have found a way of helping fish. As their name suggests, the shrimps clean the fish. They hang out at what scientists call a cleaning station. A fish stops by. Then a shrimp climbs onto the fish and even steps into the fish's mouth. The shrimp uses its tiny claws to pick stuff off the fish's body. That can include dead skin and tiny pieces of food that can hurt the fish. The fish gets a nice cleaning. The shrimp enjoys a tasty meal of fish trash.
Small birds called plovers(灰斑)are also in the cleaning business. They have big customers-crocodiles. Crocodiles have long noses filled with sharp teeth. Cleaning them is funny. When a crocodile opens its mouth, the plover hops right in. It lets the plover eat small, harmful animals attached to the crocodile's teeth. The plover gets an easy meal while the crocodile gets clean teeth.
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