听力文本

Most rivers drain into the sea, but some end their journey in vast lakes.
大部分河流都汇入大海，可有些河流的终点却是大型湖泊
Worldwide, lakes hold 20 times more fresh water than all the rivers.
全球湖泊淡水储量比江河多20倍
The East African Rift Valley holds three of the world's largest, Malawi, Tanganyika and Victoria.
东非大裂谷内有着3个世界上最大的淡水湖，马拉维湖、坦噶尼喀湖以及维多利亚湖。
Lake Malawi, the smallest of the three, is still bigger than Wales.
马拉维湖是这3个湖泊中最小的，却仍比威尔士还要大
Its tropical waters teem with more fish species than any other lake.
生活在这个热带湖泊里的鱼类比其它湖泊都要丰富

There are 850 different cichlids alone,
这里有850多种不同的慈鲷
all of which evolved from just one single ancestor isolated here thousands of years ago.
它们都是从一个数千年前即被隔绝在此的祖先进化而来的
These two-metre wide craters are fish-made.
这些2米宽的土丘是鱼儿们的杰作
Fastidiously maintained by the males, these bowers are courtship arenas.
雄鱼一丝不苟地维护着坑巢，因为这里正是求爱的场所
Cichlids are caring parents. Brooding young in the mouth is a very effective way of protecting them.
慈鲷是尽心尽职的父母。它们将鱼苗含在嘴里，这是一种保护它们的有效方法。

词汇解析

1.drain into 流入
Agricultural fertilizers often drain into aquatic ecosystems and spur a frenzy of growth.
通常，农业化肥流入水生生态系统，促使生物急速的生长。

2.teem with 富于；充满
This newspaper teems with misprints.
这份报纸满是印刷错误。

3.evolve from 由…进化
At this time science only perceives perhaps the earliest changes in DNA that are beginning to evolve from 2 to 12 strands.
此时，科学家可能只觉察到DNA里最早期的变化，它们开始从2股进化到12股。

视频及简介

淡水是我们最宝贵的资源，它决定了地球上生命的分布。同河流一起，从高高的山峰一路而降，直向大海，观看壮观的瀑布，在大峡谷里飞翔，在世界上最深的湖泊的冰雪下面探索野生的生命，见证动物行为的独特的、生动的一面：水獭和泽鳄将一决胜负。