乍一说起外来生物,大家不一定很熟悉,可它与我们的日常生活密不可分。比如,红薯来自爪哇,玉米来自墨西哥,向日葵来自美洲,烟草来自巴西,橡胶来自东南亚,黄瓜、葫芦原产于印度,甜菜、莴苣原产于地中海,植物园里的奇花异草,动物园里的陌生脸孔……然而,“请来”的和“不请自来” At first glance alien life, we are not necessarily familiar, but it and our daily life are inseparable. For example, sweet potato from Java, corn from Mexico, sunflower from the Americas, tobacco from Brazil, rubber from Southeast Asia, cucumber, gourd native to India, sugar beet, lettuce native to the Mediterranean, Botanic Garden exotic flowers, zoo stranger Face ... However, “Please come” and “Unsolicited”