gymnospermy

例句：

1. 1. The gymnosperms are the earliest type of plants to have appeared on Earth.
   裸子植物是地球上最早出现的植物类型。
2. 2. Many gymnosperms are now extinct, but their fossils can still be seen in museums.
   许多裸子植物现在已经灭绝，但它们的化石仍然可以在博物馆中看到。
3. 3.Researchers are studying the genetic differences between different species of gymnosperms.
   研究人员正在研究不同物种间裸子植物的遗传差异。