because there's something all amphibians need to raise their young. 因为所有两栖动物养育后代 都需要一样东西

227. Despite the low hit rate,
     虽然命中率低
228. amphibians have survived for over 350 million years.
     但两栖动物已在地球上生存 超过3.5亿年
229. And yet, they never conquered every environment the planet had to offer...
     然而它们并未征服 地球上的每一种环境
230. because there's something all amphibians need to raise their young.
     因为所有两栖动物养育后代 都需要一样东西
231. Water.
     水
232. This is the strawberry dart frog of Costa Rica.
     这是哥斯达黎加的草莓箭毒蛙
233. Her tadpoles are in mortal danger.
     它的蝌蚪危在旦夕

来自《我们星球上的生命 第一季 第三集 Life on Our Planet S01E03 入侵大地》第 230 行