普通高中课程标准实验教科书 英语选修9 Unit 4 Reading task

　　1 Before you read the text, glance quickly through it and answer these questions.

　　1 What's the topic of the text?

　　2 What three plants are featured?

　　3 What do the photos show you?

　　4 What three animal pollinators are featured?

　　CO- EVOLUTION

　　Some plants, like the examples given below, depend on a single species of pollinator to make its seeds. Likewise, many pollinators rely on one plant species to provide all the food for their young. The kind of evolution where two species have become totally dependent on each other is called co-evolution.

　　The Yucca (丝兰)

　　The yucca moth is the only animal that is the right size and shape to pollinate yucca flowers. The female moths lay their eggs in the yucca flowers. In the process, pollen sticks to the moths that then carry the pollen to another flower. The moths' caterpillars (毛虫 ) eat some of the developing yucca seeds. Although the plant loses a few seeds to the caterpillars, the moths' visits to the yucca flowers ensure pollination.

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