【单选题】在自然状态下,某一桦树林中出现了云杉树苗,云杉长大后,高度超过桦树林。桦树不如云杉耐阴,而逐渐减少,最终形成以云杉为主的树林,这种现象是
【简答题】玉米螟俗称玉米钻心虫。属()目、()科,是世界性害虫。
【判断题】玉米螟俗称玉米钻心虫。属鳞翅目.螟蛾科,是世界性害虫。( )
【单选题】In the DNA double strand, the strand that guides the synthesis of RNA is called
【单选题】In the DNA double strand, the strand that guides the synthesis of RNA is called ( )